Opposed Piston Engines - Evolution, Use, and Future Applications 978-0-7680-3477-6, 978-0-7680-1800-4

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Jean-Pierre Pirault Martin Flint

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EAE -=International Warrendale, Pa.

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mAE -=International

400 Commonwealth Drive Warrendale, PA 15096-0001 USA E-mail: [email protected] Phone: 877-606-7323 (inside USA and Canada) 724-776-4970 (outside USA) Fax: 724-776-1615

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Copyright 0 2010

SAE International. All rights reserved.

No part of this publication may be reproduced, stored in a retrieval system, distributed, or transmitted, in any form or by any means without the prior written permission of SAE.

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Library of Congress Cataloging-in-PublicationData

Pirault. Jean-Pierre. Opposed piston engines: evolution, use. and future applications / Jean-Pierre Pirault and Martin Flint. p. cm. Includes bibliographical references and index. ISBN 978-0-7680-1800-4 1. Opposed piston engines. I. Flint, Martin. 11. Title. TJ7792P57 2010 62 1.43--dc22

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ISBN 978-0-7680-1800-4 SAE Order No. R-378

2009035632

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zy zyxwvuts C 0 NTENTS

OPPOSED PISTON ENGINES: EVOLUTION. USE. AND FUTURE APPLICATIONS

................................................................ Foreward ............................................................... Acknowledgments ....................................................... Contents

v

ix

xi

Accuracy and Representation..............................................

.. xu

Introduction to Opposed Piston Engines .........................

1

Chapter 1

............................................ Rationales for OP Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Issues Facing OP Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1 Introduction

1

1.2

1

1.3

........................... Current Relevance of OP Engines ......................... Summary.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.4 Types of Opposed Piston Engine 1.5 1.6

1.7

Chapter 2

History of Opposed Piston Engines

............................................ Pre 1900 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1900-1945 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Post1945 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 15 15

17 17

2.2

17

2.4 2.5

Aeronautical Opposed Piston Engines

..........................

........................................... Junkers Jumo 205 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Junkers Jumo 207B2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diesel Air., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22 41 52

55

3.1 Introduction

55

3.2

55

3.3 3.4

3.5 References

Chapter 4

7

2.1 Background

2.3

Chapter 3

.............................

5

............................................

Automotive Opposed Piston Engines

..........................

.......................................... Valveless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trojan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

102 119

125

127

4.1 Introduction

127

4.2

127

4.3

132 V

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Opposed Piston Engines: Evolution. Use. and Future Applications

................................................. Rootes Commer TS3 and TS4 . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.4 MAP

138

4.5

142

4.6 Opposed Piston Opposed Cylinder “OPOCTM”Engine ..................................... 4.7 References

Chapter 5

179

5.1 Introduction

179

5.2

.......................................... Leyland L60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rolls Royce K60 and K60T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

179

...................................... References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

203

5.4 Kharkiv Morozov

220

5.5

222

Marine Opposed Piston Engines

..............................

223

6.1 Introduction

223

6.2 Doxford

.......................................... ..............................................

223

6.3 Napier Deltic

263

6.4

.......................................... The American Marc 10 Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . Vincent Marine Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

305

6.5 6.6

Chapter 7

177

.............................

Military Opposed Piston Engines

5.3

Chapter 6

............................................

170

Auxiliary Power Opposed Piston Engine

.......................

317 329 333

....................... 333 Coventry Climax H30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Fairbanks Morse Model 38 OP Engine .................... 346 Sulzer Brothers ZG Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 English Electric Fullagar Q and R Series . . . . . . . . . . . . . . . . . .402 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

7.1 Auxiliary Power Unit Introduction 7.2 7.3 7.4 7.5 7.6

Chapter 8

.............................

417

..........................................

417

8.2 Fairbanks Morse Diamond Experimental OP Submarine Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

417

Unusual Opposed Piston Engines 8.1 Introduction

vi

..................................... References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.3 Africar OP Engine

419

8.4

430

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Contents

Chapter 9

Opposed Piston Research. Concepts and Prototypes

.............431

. . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . .. . . . . . . 431 . Research Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .431

9.1 Introduction 9.2

9.3 Research Engines: Sulzer Brothers G Series OPEngines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .434 9.4 Fuel-to-Air Mixing and Combustion in Opposed Piston Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .446 9.5 Wallace Research into Highly Boosted TS3 Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .460 9.6 Variable Compression Ratio Rootes TS3 OP Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .462 9.7 Rolls-Royce Double Bank Rocking Beam "H12" OP Engine Concept . . . . . . . . . . . . . . . . . . . . . . . . . 467 9.8 Rolls-Royce Double Three Inline Multifuel Engine . . . . . . . . . . 472 9.9 Arrnstrong Whitworth Swing Beam Engine . . . . . . . . . . . . . . . . 478 9.10 Advanced OP Engine Diesel Demonstrator

. . . . . . . . . . . . . . . . 506

9.11 Opposed Piston Gas Exchange and Charging Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .508 9.12 References

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .516 .

Chapter 10 Opposed Piston Applications and the Future 10.1 Introduction

....................519

. . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . .. . . . . . . 519

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520 10.3 Unmanned Aerial Vehicle Engines, 8 kW . . . . . . . . . . . . . . . . . . 522 10.4 Unmanned Aerial Vehicle Engine. 80 kW . . . . . . . . . . . . . . . . . 527 10.2 Utility Engine

10.5 Heavy Duty Truck Engine. 400 kW . . . . . . . . . . . . . . . . . . . . . . . 529 10.6 Enabling Technology

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534

10.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .539 10.8 References

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .540 .

.......................................................... 541 Index ................................................................. 545 About the Authors ...................................................... 629 Abbreviations

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zyxwvutsr Chapter 1

INTRODUCTION TO OPPOSED PISTON ENGINES 1.1 Introduction

The two-stroke, gas-fueled, opposed piston (OP) engine probably first appeared in public use in Germany around 1878 (Ref. l.l),engineered by Wittig. Opposed piston engines are characterized by pairs of pistons operating in a single cylinder, eliminating the need for cylinder heads. Gas exchange for two-stroke versions is handled by piston-controlled ports in the cylinder walls. While the OP concept is applicable to two- and four-stroke diesel engines, highcompression-ratio four-stroke applications require a half-engine-speed sleeve valve cylinder, or rotating valve, to achieve the required frequency of inlet and exhaust events. However, the famous Gobron Brille racing engine, circa 1900, was a four-stroke engine that used poppet valves located in the housing at the center of the cylinder liner. Most OP engines operated on a two-stroke cycle, probably for simplicity, and almost all have been compression ignition diesel engines, as OP engines were intended to achieve high thermal efficiency as well as high power density, Opposed piston engines began to be used commercially around 1900 for numerous land, marine, and aviation purposes. Although OP units are still used in 2009 in the United States, United Kingdom, Russia, India, Iran, and some Arabian Gulf states, their use has greatly decreased due to issues with emissions and particulates, notably oil-derived particles. In spite of this decline, the OP engine has set many of the existing standards for

power-to-weight ratio, dynamic refinement, fuel tolerance, package space, fuel efficiency, and manufacturing simplicity, For these reasons, the OP concept remains viable for certain applications that require outstanding power and package density, simplicity, and reliability, such as aviation and certain military transport requirements.

1.2 Rationales for OP Engines As should become apparent from subsequent chapters, OP engines evolved because of their ease of manufacture, excellent balance (even in single-cylinder form), and competitive performance and fuel efficiency relative to comparable four-stroke engines. The development period around 1890 generated all these aspects, which remain advantages to this day for naturally aspirated engines. With the progressive development of the OP engine from 1900 to 1970, other significant advantages also emerged, which became important for specific applications. Among these advantages were cutting-edge specific output, high specific torque, very high power density, and very high power-tobulk ratio, which were always qualities of well-developed OP engines regardless the field of application. Other OP two-stroke advantages, compared to the four-stroke engine, were relatively low heat-to-coolant ratios (enabling smaller radiators for heat rejection), high reliability and low maintenance, relative ease of servicing, excellent multifuel tolerance, low injection pressures, and simple fuel injection nozzles.

1

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Opposed Piston Engines: Evolution, Use, and Future Applications Simple and solid reasons for these OP engine advantages exist, as will be outlined. As evidence of the more tangible claims, Figs. 1.1 and 1.2 show the relative specific outputs per unit displacement and per unit weight of OP engines versus fourstroke diesels from 1900 to 2005. The figures show that the OP engine held a clear advantage until the four-stroke engine fully adopted turbocharging. Fig. 1.3 plots the leading trends for brake thermal efficiency (BTE) for OP and four-stroke engines, again indicating that the OP met or exceeded the four-stroke for naturally aspirated operation. Heat rejection, always difficult to measure empirically, is compared on an “available data” basis in Table 1.1. This data confirms that the OP has exceptionally low heat-to-coolant ratio, but high heat-to-exhaust ratio, as is common

with most two-strokes at full load (Ref. 1.2). Comparisons of power-to-bulk ratio (Fig. 1.4), exclusive of radiators or intercoolers, also indicate competitive or better values for the OP engines versus their four-stroke counterparts.

Cost comparisons are frequently difficult to arrange on an equitable basis, especially when comparing somewhat specialized OP two-stroke engines to the relatively high-volume four-stroke. However, as we will show in later chapters, one advantage of the OP engine is that it has a low part count, for five main reasons: A single liner services two pistons. In many cases, a single injector serviced two pistons. There are no cylinder heads. There is no valve-train.

Fig. 1.1 Historical Trend of Specific Outputs (kW/L) of Two- and Four-Stroke Diesel Engines

Introduction to Opposed Piston Engines

Fig. 1.2 Historical Trend of Power Density Specific Output (kW/kg) of Two- and FourStroke Diesel Engines

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Fig. 1.3 Historical Trend of Brake Thermal Efficiency of Two- and Four-Stroke Diesel Engines

3

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Opposed Piston Engines: Evolution, Use, and Future Applications % Fuel Energy to Coolant

Rated Power Four-Stroke

Coolant

I Exhaust I Inter-cooling I Other I Total

I I

22 16

2

I

100

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I I I I

27

20

3

100

I I I I

Table 1.1 Heat Rejection Data for Two- and Four-Stroke Engines

Overall there are lower material costs for all major OP castings because of the smaller displacement of the OP versus the four-stroke, at equivalent power levels. The OP cranktrain drive system is probably not a significant additional cost versus a single double-length crankshaft and gear train necessary for a four-stroke engine, and the auxiliary drives and cov-

ers of an OP engine are comparable to those of an equivalently powered fourstroke. However, the OP engine, as with other non-crankcase scavenged twostroke engines, needs a scavenge blower, which were not manufactured in high production volumes. This blower, therefore, represents an additional cost for the OP versus the four-stroke. The assembly of the OP engine, however, is simpler

Fig. 1.4 Historical Trend of Power Bulk Density (kW/dm3) of Two- and Four-Stroke Diesel Engines

Introduction to Opposed Piston Engines than the four-stroke, due to the absence of the valve train. Therefore, on a somewhat subjective valuation basis, the OP engine is likely to offer a lower cost for a given power requirement.

scavenge periods. The use of special ring coatings for improved boundary lubrication and reduced scuffing was probably promoted by high-output OP engines, as well as other boosted two-stroke engines.

Having described the advantages of the OP engine, what were the disadvantages and what caused its demise?

In addition to the more difficult lubrication for the ring faces due to lack of load reversal and the higher thermal loading, the port traversing by the rings subjects them to local bending and distortion that does not occur in a four-stroke engine. Rings would usually be pegged and be larger in section than four-stroke rings. Special attention would be given to port edges, progressive port opening profiles, and port bars to alleviate the local loading on the rings. Several engines, particularly those that operated on a substantially constant rating for extended times, such as marine, stationary, and aircraft engines, adopted the gapless “fire r i n g instead of the conventional gapped outward tension ring. These fire rings were typically five to ten times the height of the conventional ring, had an L-section to ensure a large downward seating force, and were sized to expand, at rated power, to a very close clearance with the cylinder bore. A demountable piston crown was necessary to fit the fire ring to the piston. A successful fire ring effectively reduced gas pressure on the first and second conventional compression rings so that friction was reduced. On the one hand, for starting and part load, the gapless fire ring is not effective and the first compression ring behaves normally. The fire rings were substantially more robust than conventional rings due to their greater height and absence of “free-ends.’’ On the other hand, they required a thinner sec-

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1.3 Issues Facing OP Engines

As a two-stroke engine, the OP configuration has many of the traditional two-stroke challenges. However, wellestablished solutions do exist.

The lack of load reversal on the piston, rings, and connecting rod (conrod), led to the usual lubrication issues for the small-end bushes and piston-pin bosses and to scuffing problems on the top ring. These problems were usually fixed by using special features to distribute oil to the areas subject to unidirectional loading, e.g., spreader grooves in small-end bushes, bushed piston-pin bosses with lubrication grooves, and a plentiful supply of oil to all critical areas to cool as well as to lubricate. Some designs attempted to reduce the heat flow into the ring pack by having partially insulated piston crowns. Smallend and pin bosses could take advantage of the “palm bearing arrangement, which enables a larger and more favorable distribution of the small-end and piston-pin areas. Top rings might adopt an asymmetric or barrel-face piston ring profile to help generate oil films, and sometimes adopted asymmetric ring sections so that the ring was subject to flexure during the alternate high-cylinder pressure and

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Opposed Piston Engines: Evolution, Use, and Future Applications tion to provide some radial compliance. Some OP engines adopted “gapped” fire rings in order to obtain the advantages of the more robust fire ring but to avoid the starting issues of a gapless ring.

The contiguous firing of the two-stroke, the relative high swirl required by compression ignition combustion, and the absence of a long cooling induction stroke resulted in high thermal loading of the piston crown and liner, particularly that of the exhaust piston. Two approaches were taken to solve this problem-to attempt to insulate the piston crown by using air gaps between the crown and piston skirt or to provide extensive forced cooling of the crown. The cylinder liner, arguably the “lungs” of the engine, usually had very controlled high-velocity cooling along its length, particularly in the combustion zone, and was invariably made from high-quality steel or iron. One of the downsides to the OP engine, it could also be justifiably argued, was that some prominent production OP applications were not entirely durable, or required relatively high maintenance, as discussed in Chapters 3,5, and 6 (Jumo 205E, Leyland L60, and Napier Deltic, respectively). There are several responses to this criticism. First and most importantly, all three engines were undersized for their applications and therefore were operating at overrated conditions. Second, the engines were so advanced for their time in terms of specific output, power-to-bulk ratio, and power-to-weight ratio versus any other diesel, that it is surprising there were not more problems with these engines. Third, the development periods for these engines were remarkably short while their technol-

6

ogy was pioneering, and their applications, such as major military vehicles, railway locomotives, and aircraft, had high public visibility and potential liability.

Side injection, as is necessary with an OP engine, is probably also viewed as a major negative feature versus the conventional cylinder head central injection trend that allows symmetry of sprays and fuel-to-air mixing. This “symmetrical combustion” practice is a modern direct injection design standard, and is considered a cornerstone for low NOx and particulate emissions. Some OP engines adopted either dual or quadruple sprays per cylinder in attempts to reduce the fuel-to-air mixing asymmetry. Certainly dual injectors, with one on each side of the cylinder, make good sense, but even this is unlikely to match the fuel-to-air symmetry of the center cylinder injector location. Additionally, as the f d diameter of the cylinder bore is available, wall wetting, other than near the injector location with the outer diameter of the piston crown, should not be an issue for the modern OP engine. Current injection systems, with their very high injection pressure capability, and the possibility of having a nozzle with several different hole sizes and asymmetrical plume trajectories, should also offer a ready and production-feasible means of addressing some of the OP fuel-to-air mixing challenges. While torsional vibration of interlinked crankshaft systems of OP engines is undoubtedly a concern, and possibly compounded by the phase difference of the exhaust- and air-crankshafts, it is an issue that can be analyzed and fixed prior to final design and almost certainly cannot be viewed as any more serious

Introduction to Opposed Piston Engines an issue than the torsional vibration of a much longer four-stroke crankshaft with twice the number of cylinders. Mechanical integrity and wear of the piston rings, which have to pass over the port bars, and the durability of the long liner of the OP engine, particularly the exhaust port bars, are issues that have faced almost every new OP engine. In some cases, particularly for very highly rated and lightweight engines, they have remained service problems for many years. The pistonported, two-stroke situation of a piston ring with unidirectional load, which passes over port bars, is never likely to match the substantially more favorable situation of reverse-loaded rings that pass over an uninterrupted liner surface, as in the poppetvalve four-stroke. However, modern steel piston rings with their extremely hard and ultra-low friction coatings, modern liner surface preparation methods, and synthetic oils and additives can certainly contribute significantly to improving the two-stroke ring-and-liner situation. Careful and close radial support and cooling of the OP liner will also reduce the “panting,” differential expansion, and waterside cavitation erosion problems that afflicted some OP engines. Due attention to stress raisers around the injector and location holes in the critical center section of the liner will also help reduce the tendency for liner fatigue cracking. The weakest link of the OP engine was, and probably remains, the oil consumption issue, which is a fundamental characteristic of piston-ported liners and sleevevalve engines, both two- and four-stroke. Quite apart from the added running and maintenance costs of oil consumption, and

the obvious emission implications of oil carryover into the exhaust, there were frequent examples of gross oil deposits onto houses and gardens from the exhaust of OP engines used for locomotives, or onto clotheslines from airborne OP engines. While modern blowby oil separators and liner plateau honing techniques provide some reduction of oil lost through the liner and ports, the oil consumption of a linerported engine is expected to remain an order of magnitude greater than that of the equivalently powered poppet-valve engine. Yet the 17 L/cylinder Fairbanks Morse OP engine is sold in significant numbers for stationary and marine power applications and has a reported oil consumption of 0.07% of engine fuel consumption. This can be as good as four-stroke full-load diesel oil consumption, where oil consumptions are typically -0.1-0.2% of fuel consumption, although there are engines with lower oil consumption. In spite of these issues and challenges, the OP engine remains a compelling choice for certain applications that currently have unconstrained emission levels. Given the advancement of catalyst technology for diesel and two-stroke engines and the possibility of very low ash lubricants and special additives, a wider field of application for OP engines may also eventually occur.

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1.4 Types of OP Engines

Before beginning a historical review of the OP engine, the various types of OP engine are briefly outlined. Essentially, five types exist, with many variants, amounting to approximately 13-15 embodiments, as illustrated in Fig. 1.5.

Opposed Piston Engines: Evolution, Use, and Future Applications

Fig. 1.5 Hierarchy of Opposed Piston Engines

8

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Introduction to Opposed Piston Engines The main types are described in Sections 1.4.1-1.4.5.

1.4.1 Crankless OP Engines Crankless OP engines are better known as “free piston” engines; the pistons are usually arranged in a single cylinder with the combustion space between them. The noncombustion side of the pistons is connected to some type of pneumatic spring or bounce chamber (Fig. 1.6),which returns the pistons to their inner dead center (IDC) after combustion and expansion. In the arrangement shown, compressed air would be used to start the pistons, which would have to be “parked” appropriately after shutdown. The bounce pistons would also need occasional air replenishment to maintain their minimum pressure levels. Free-piston engines (Ref. 1.3) were initially used in the 1930s as the gas generator portion of turbo-compound systems where all the useful output was via a turbine for marine, power generation, and locomotive applications.More recently, smaller freepiston OP engines have been developed for small combined heat and power units, either with internal or external combustion (Stirling cycle). The noncombustion side of the pistons drives linear electrical generators and/or hydraulic pumps (Ref. 1.4). The crankless OP, or free-piston, engines are not detailed further in this book, as they are a subject in themselves.

1.4.2 Single-Crank OP Engines There are essentially two types of single-crank OP engines, namely, the Wittig three-throw crankshafts and the “folded” crankshaft, or “rocking beam” arrangements.

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Opposed Piston Engines: Evolution, Use, and Future Applications

Key 1.6

1

Injectors

3

Air piston

3a

Air piston bounce chamber

3b

Scavenge pump

3c

Scavenge ports

4

Exhaust piston

4a

Exhaust piston bounce chamber

4b

Scavenge pump

4c

Exhaust ports

5

Power turbine

6

Compressor

7

1.4.2.1 Three-Throw Single-Crank OP Engines

External load

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Fig. 1.6 Free-Piston Engine

Cylinder

2

The first successful OP engines, developed around 1878, used a single threethrow crankshaft (Fig. 1.7) in which long side connecting rods, phased at 180”to the central connecting rod, drove the “outer” piston through a bridge connection, Meanwhile, the central connecting rod drove the “inner” piston. The stroke of the outer crank throws could be selected to offset any difference in reciprocating mass between the outer and inner pistons. The outer piston, which was usually an air piston, could also carry a scavenge pump piston. This single-crank arrangement, usually attributed to Wittig of Germany, had several benefits. First, all gas and inertia loads were contained by the moving parts and the cylinder liner, resulting in almost no transmission of these loads, other than the torque reaction forces, to the engine frame or main bearing. This allowed rela-

Airchest

tively lightweight or lightly stressed engine crankcases, which were a major benefit in the early days of engine castings and during the period when engines operated with exposed moving parts. This could also be a major opportunity in the future with modern composite materials for very high power-to-weight ratio applications. However, the three throws result in a longer crank than other equivalent-displacement single-cylinder OP engine arrangements.

The Doxford engine (Chapter 6) and the CLM (Compagnie Lilloise des Moteurs), were also two successful production examples of single-crank OP engines, the former being in the order of 180 L/cylinder and the latter 0.7 L/cylinder. 1.4.2.2 “Folded” Cranktrain Arrangements

Use of substantial pivoted levers, known as “rockers” or “rocking beams,” in combination with an articulated joint (Fig. 1.8) allows the two pistons to be

Introduction to Opposed Piston Engines connected to a single crankshaft. This arrangement is sometimes referred to a “folded cranktrain” OP engine, and may date from a patent by Hunter, c1896. The rockers, which are subject to large bending loads, are usually supported on very substantial rocker shafts that must be cross-linked by stiff and strong tensile elements such as crossbolts.

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As with the single-crank arrangement, the loads are carried entirely by the cranktrain and the rocker shaft crossbolts. This enables a relatively light crankcase with very lightly loaded crankshaft main bearings, because the loads from each pistonand-cranktrain mechanism balance each other. Production examples of these were the Rootes TS3 (1956-1972), and the Sulzer ZG series (1936-1945).

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Fig. 1.7 Single-Crank, Wittig-Type OP Arrangement [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

zyx zy

Comparing the package volume of the double-crank arrangement, i.e., Junkers Jumo, Leyland L60, and Rolls Royce K60 types (Chapters 3 and 5 ) , with a Rolls Royce Double Bank H (Chapter 9) folded-crank arrangement, and assuming the same cubic capacity and power, the Double Bank H configuration offers approximately 50% reduction in package volume. The Double Bank H arrangement provides one of the best bulk density packages, with perhaps the exception of the Barrel engine configuration. (Ref. 1.5)

1.4.3 Twin-Crankshaft Arrangements

Twin-crankshaft arrangements for OP engines (Fig. 1.9) were suggested around 1881 by T. H. Lucas, but only came into wide use after 1910, enabling substantially more compact inline arrangements than the single-crankshaft configurations. The twin crankshafts can be linked by spur

zyxwvuts

Fig. 1.8 “Folded” Cranktrain-Type OP Arrangement [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

11

zyxwvutsrq zyxwvuts

Opposed Piston Engines: Evolution, Use, and Future Applications

zyxwv

Fig. 1.9 Twin-Crankshaft, Lucas-Type Arrangement [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

gears, bevel gears and lay-shafts, or chain drives. Production examples of the twincrank arrangement, such as the Junkers Jumo family of engines, the Fairbanks Morse 38D, the Rolls Royce K60, the Leyland L60, and the Coventry Climax H30 are described in Chapters 3, 5, and 7. Ignoring the method of scavenge air supply, comparisons of the basic height and length of the single- and twin-crank arrangements indicate that the singlecrank layout is 15%lower in height, but is approximately 250% longer than the twin-crankshaft arrangement for the same displacement. This comparison is on the basis of these heights and lengths as a ratio of their bore dimensions. While the selection of either of these arrangements for an application is dependent on the functional requirements, the single-crank

layout will tend to be less favorable, due to adverse torsion vibration characteristics, than the twin-crank configuration. The new opposed piston-opposed cylinder (OPOC”) configuration (Chapter 5), however, does help reduce the length disadvantage of the single-crank arrangement for a given engine displacement.

1.4.4 Multiple-Crankshaft OP Engine

Arrangements Multiple-crankshaft OP engine arrangements could be viewed as a subset of twocrankshaft systems, as they essentially use multiples of the twin-crankshaft systems arranged in various geometric forms, such as triangle, square, or star. The triangular arrangement gave rise to the Napier Deltic (Chapter 6) with three crankshafts, and the square form was the basis of the

Introduction to Opposed Piston Engines

zyxw zyxwvutsr zyxwv

Fig. 1.10 Multiple-Crankshaft OP Engine Type: Jumo 223 [Reproduced courtesy of Horst Zo eller, Germany]

Jumo 223 four-crankshaft arrangements (Ref. 1.6) as seen in Fig. 1.10.

ants were largely based on two types-the single- and twin-crank versions.

1.4.5 “Rotary” OP Arrangements

1.4.6 Barrel Cam Engines

A rotary OP engine may seem improbable, but various versions have appeared, such as the Mukherjee, Tshudi, Kauertz, and Omega (Ref. 1.7), the Maier (Ref. 1.8), and more recently the Leggat Rotary Oscillatory Mechanism or ROM, (Fig. 1.11, Ref. 1.8). In rotary form, the pistons, which are somewhat like paddle blades, oscillate about a central output shaft while the whole assembly is contained in a cylindrical housing that holds the combustion and gas-exchange systems. In some cases, the pistons orbit as well as oscillate and can perform either two- or four-stroke cycles with the appropriate ports.

Barrel Cam opposed piston engines are usually arranged with the cylinders parallel to the crankshaft axis and the pistons engaging with a cylindrical cam track, which forms part of the crankshaft. Lack of space prevents any review of these very compact engines.

Chapter 2 provides a historical review of many of the OP engine variants of the above types, although the most widely used vari-

1.5 Current Relevance of OP Engines Why bother to consider OP engines when the current four-stroke almost completely dominates all engine applications other than the very largest marine engines? Even the remaining two-stroke applications, such as chainsaws, hand-held equipment, and marine outboard engines, are giving way to lightweight four-strokes, mainly because of emission legislation and because two-stroke engines are per-

zyxwvutsrq

Opposed Piston Engines: Evolution, Use, and Future Applications

zyxwv zyxwv

Fig. 1.1 1 Rotary Oscillating-Type OP Engine: Leggat ROM [Reproduced courtesy of

Applied Enginge Technologj Ltd., United Kingdom] ceived by some to be “polluting” regardless of their actual emission capacity. While the four-stroke engine will continue to be the internal combustion engine of choice for most applications, even for the very small engines of chainsaws and small scooters, there are several reasons to consider OP engines as alternatives for various transport applications. These applications are briefly mentioned here and covered in more depth in Chapter 10, which examines future possibilities of the OP engine. First, diesel OP engines are very well suited for fixed-wing light aircraft and helicopter engines, where power-to-weight ratio, power-to-bulk ratio, fuel efficiency, and

safety are important requirements. Second, the OP power-to-weight ratio and power-to-bulk ratio advantages are ideal for lightweight ground vehicles that need to be air transportable because they are used for emergency and special situations. Third, the requirements of combined heat-and-power (CHP) units are well suited to OP engines. Fourth, OP engines may be a more cost effective route to -45% BTE (excluding compounding) than the current very highly boosted four-stroke engine at post 2010 emission levels. The main issues for the OP engine in this scenario are oil consumption, hydrocarbons, particulate emissions, and efficiency at high boost. The fifth potential application is for the rotary oscillatory types of opposed piston units to be used

Introduction to Opposed Piston Engines

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compactness and high delivery frequency.

1.2 The High Speed Internal Combustion Engine, H. R. Ricardo and J. Hempson,

Some of these OP applications are discussed

Blackie & Son Ltd.

further in Chapter 10.

1.3 Present State e+ Future Outlook of the Free Piston Engine, R. Huber, ASME #58,

in compressors and expanders due to their

1.6 Summary OP engines have been very successful in many applications, as will be detailed in the following chapters, which chart the development of the OP engine from 1890 to 2009, while Chapter 10 looks at their

GTP-9.

zy

1.4 Hot Air and Caloric Stirling Engines, Vol. 1, Beale Free Piston Engine, p. 192, Robert Sier, ISBN #09526417.

1.5 New Light Weight Power Plants for Post War Airplanes, K. L. Herrmann, pub.

SAE Nov. 9,1944.

zyxwvutsr

future potential.

1.6 Junker Aircraft and Engines, Anthony L. Kay, Putnam, ISBN 0-85177-985-9.

1.7 References

1.7 'The Wankel Engine, Design Development Applications, 1971, pp. 501-510, Jan

1.1 The History of the Opposed Piston

P. Norbye, Bailey Brothers & Swinfen Ltd. ISBN 561-00137-5.

Marine Oil Engine, W. Kerr Wilson, pub.

The Institute of Marine Engineers. Trans. 1946, Fig. 27, p. 192.

1.8 Rotary Oscillatory Engine, (www. AETGB.com), ROM page.

15

zyxw

zyxwvutsr Chapter 2

HISTORY OF OPPOSED PISTON ENGINES 2.1 Background

At the start of internal combustion engine development (1850-1900) the emphasis was on single-cylinder engines, with two- and four-stroke variants offering a trade-off in simplicity versus higher efficiency. The opposed piston (OP) concept initially offered an attractive means of achieving a substantially dynamically balanced single-cylinder engine that eliminated the need for cylinder-head joints and the challenges of manufacturing a monolithic cylinder head-cylinder barrel. The “double” stroke gave another significant advantage-the possibility of large-cylinder displacements with smallcylinder bores, reducing the gas loads on the crankshafts. During the period from 1850 to 1910, engine development was addressing not only the issues of two- or four-stroke cycles, and balancing and optimizing multicylinder configurations, but also the question of fuel types and method of fuel preparation. For industrial power generation, the use of gas byproducts from industrial processes, or town “lighting” gas was preferred, while mobile engine applications used fossil fuels such as low-boiling-point gasoline and heavier distillate oils. The latter “diesel” fuels were initially introduced into the pressurized cylinder using air-blast injection, but this eventually (1915-1925) gave way to wet fuel injection only. This reduced the considerable parasitic losses associated with provision of the compressed air and eventually improved combustion

by eliminating the cooling effects of the air blast on the evaporative phase of the injected fuel.

Opposed piston engine history can be divided into three main periods-pre1900,1900-1945, and post 1945. A few of the numerous early contributors to the development of the opposed piston engine are reviewed in this chapter, while those engines that saw extended production after 1930 are described in greater detail in subsequent chapters.

2.2 Pre 1900 2.2.1 Gilles and Wittig Gilles of Cologne constructed an OP single-cylinder engine in 1874 (Fig. 2.1, Ref. 2.1), with one piston linked to a crankshaft and the other being a free piston. The descent of the crank-driven piston induced a fresh charge from a cam-actuated inlet port approximately mid-cylinder. The charge then ignited partway through the expansion of the crank-driven piston. The subsequent pressure rise further drove the cranklinked piston and displaced the free piston toward its end stop, where the free piston was retained by a clutch until it was released to drive out the exhaust products. A considerable number of these engines were built, but were not really commercially successful as the engine was neither economical nor a match for the Otto four-stroke engine of 1876. Wittig of the Hannoversche Maschinenbau- Aktiengesellschaft probably pro-

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Opposed Piston Engines: Evolution, Use, and Future Applications

zyxwvutsrq zy

Fig. 2.1 Gilles Free-Piston Gas Engine, 1874 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

Fig. 2.2 Wittig Gas Engine, 1878 [Reproduced courtesy of lMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

duced the first OP engine where both pistons were crank driven (Fig. 2 . 2 ) . He introduced the classic three-throw crank with the center throw linked to the inner piston, and the outboard throws, phased at 180" to the center throw, being linked via long side conrods to the outer piston. Inlet and exhaust ports were located at the midliner area and were operated on a four-stroke basis. A patented claim of the system was that the use of an open-ended cylinder allowed easier access for air cooling of the inner cylinder walls. A significant advantage of the Wittig concept was the cancellation of forces acting on the main bearings, as two-piston systems produce essentially equal and opposite net gas and inertia forces. This enabled

relatively narrow main bearings, allowing adequate space for the side connecting rods that drove the outer piston.

zyxwvu zy 2.2.2 T. H. Lucas

Use of two crankshafts for an OP engine is probably attributable to T.H. Lucas (United Kingdom, ~ 1 8 8 1 )The . upper driving crankshaft (Fig. 2.3) had a large flywheel, while the lower shaft had various gearing arrangements enabling it to move in a prescribed manner relative to the upper crankshaft, thereby controlling the relative piston motion. The Lucas engine operated on a two-stroke cycle, with the upper piston at its inner dead center just prior to ignition, and the lower piston at its outer dead center. After igni-

History of Opposed Piston Engines

zyxwvu zyxwvu

Fig. 2.3 Lucas Gas Engine, 1881 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

tion, the upper piston moved outward, while the lower piston remained essentially stationary until it was required to provide exhaust of the burned products. After displacement of the exhaust products, both pistons moved downwards, with the lower piston moving more rapidly than the upper piston, enabling an induction period. The exhaust port was in the upper half of the cylinder, while the inlet port was in the lower half of the cylinder. No scavenging occurred in the traditional two-stroke sense, and induction was achieved by positive displacement of the pistons, which is unique for a two-stroke.

ing their dead centers simultaneously, a variation that facilitated starting. The cranks also had unequal strokes. The Robson concept was close in principle to the famous Oechelhaeuser and Doxford arrangements that would be developed in Sunderland 20 years later.

2.2.4 Oechelhaeuser and Junkers In October 1888, Hugo Junkers, as his first post university appointment, joined Oechelhaeuser’s Deutsche Continental Gasgesellschaft at Dessau, later becoming a partner. The two engineers subsequently formed Versuchsstation fur Gasmotoren (Gas Engine Research Institute) at Dessau. In 1892 they produced a practical breakthrough with their two-stroke OP gas engine (Fig. 2.4). This engine used the three-throw, Wittig-type crank with side rods to crossheads that were connected via a pair of side connecting rods

zyxwvut zyxwvutsr

2.2.3 Robson

In 1890, Robson of Sunderland, United Kingdom, suggested a variant of the Wittig engine in which the cranks were arranged to avoid both pistons reach-

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Opposed Piston Engines: Evolution, Use, and Future Applications

zyxw zyxwvuts

Fig. 2.4 Oechelhaeuser and Junkers Gas Engine, 1892 [Reproduced courtesy of IMarEST; London, United Kingdom]

to the outer air piston; the pair of rods acted on the piston via a rocking beam. The same piston rods also passed through a double-acting air pump on one side of the cylinder, providing scavenge air, and a double-acting gas pump on the other side of the cylinder, supplying the gas to the cylinder at 10-12 bar. The gas was injected at the joining center section of the liners, while inlet and exhaust ports were at the extreme ends of the liner, which was divided into two barrels joined by the center section that also contained the gas injector. The operational cycle was classically two-stroke, i.e., ignition when both pistons were close to their inner dead centers, expansion when both pistons were moving toward their outer dead centers, then exhaust port "blowdown," followed by inlet port opening and cylinder scavenging before and after outer dead center, with fresh air from the auxiliary double-acting air pumps, and finally compression with both pistons moving back to their inner dead centers. Phasing of the crank throws was stated to be 180" or substantially 180", and the

inventors claimed the possibility of the same or different diameters and strokes for each piston. This reliable arrangement was probably the forerunner of the Doxford marine engines mentioned earlier, but with the outer piston controlling the scavenge ports, and the inner piston controlling the exhaust ports.

Output of the -3 1 L engine was 84.3 kW at 160 rpm, for a BMEP of 10 bar and an imep of approximately 13 bar; mechanical efficiency was therefore 77%. This was, and still is, an astounding performance. The compression pressure was 18.6 bar and maximum firing pressure 66 bar. Fuel consumption was 40% lower than for a contemporary four-stroke! In 1896 Oechelhaeuser derived an interesting variant of the engine (Fig. 2.5) that had a larger diameter tandem gas pump mounted above the outer exhaust piston, and a set of gas induction ports located below the air ports. Both pistons were designed to overrun the exhaust and scavenge ports, helping to create a depression

History of Opposed Piston Engines that further assisted the induction of the gas. Air for the engine was supplied from a stationary source that also supplied air to a local blast furnace. The exact rationale for this engine is not entirely clear, as it was designed to use blast furnace gas with only 20% of the calorific value of that used in the 1892 engine. This explains why a larger gas pumping cylinder was necessary, but the reversion to low-pressure induction of the gas with open exhaust ports, versus high-pressure injection, is surprising. Nevertheless, Deutsche Kraft Gesellschaft manufactured these variant engines in modular single-cylinder form for use with blast furnace waste gas with bore sizes of 480 mm and combined strokes of 1600 mm, producing -3.4 bar BMEP at 135 rpm; powers ranged from 225 kW to 1100 kW according to the number of cylinders. Engines of this type operated in German ironworks until around 1910. Oechelhaeuser and Junkers parted company in 1893. However, Oechelhaeuser subsequently pursued an academic career

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at the Technical High School of Danzig, of which he was eventually appointed headmaster, a position he retained until his death in 1923.

2.2.5 Summary of Pre 1900 OP Developments

The pre 1900 development period of the OP engine saw mention or introduction of many of the key features of the modern OP engine, notably two- or four-stroke options, use of long stroke and bore, paired crankshaft drives, single threethrow crankshaft with long conrods linking to the outer piston, phasing of the two pistons at other than the obvious 180°, use of each piston to individually control the inlet and exhaust ports for two-stroke variants, use of unequal strokes, and fuelling at the center of the liner.

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During that time, the key advantages of the OP engines versus their competitors appear to be simplicity, balance, absence of the then-problematic cylinder head joint, and relatively light mechanical loading of the crankshafts due to the

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Fig. 2.5 Oechelhaeuser Gas Engine, 1896 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

21

zyxwvutsrq zyxwvuts

Opposed Piston Engines: Evolution, Use, and Future Applications possibility of large engine capacities with low bore-to-stroke ratios. The effect of the rapid gas expansion in the “two directions” following the retreating pistons from top dead center (TDC) was also a benefit in terms of mixing the air with the fuel and turbulence generation.

OP engines substantially improved the efficiency of two-strokes, bringing them somewhat closer to the highly efficient four-stroke. Contemporary two-stroke engines achieved 14-26% Brake Thermal Efficiency (BTE) with Mechanical Efficiencies (ME) of 75%, representing Indicated Thermal Efficiencies (ITE) of 35-37.5%, while four-stroke engines of the time achieved 14-32% BTE with typical ME of 70%, representing ITE of 20-39%. The OP engines raised two-stroke efficiencies to 28-32%, rivaling the four-strokes, with a simpler manufacturing construction. Some of the early OP engines are listed in Table 2.1, which charts the performance of OP engines from 1900 to 1945.

2.3 1900-1945 Whereas the pre 1900 period had been a successful exploratory phase for OP engines using various types of town or industrial gases as fuels, the first 14 years after 1900 saw many practical stationary and marine applications with diesel fuel, with varying degrees of success. After the hiatus in new engine development during World War I, at least four major OP engine products, in land, marine, and air applications in France, the United States, the United Kingdom, and Germany began during this time. Some of the contributors to the practi-

cal advancement of the OP engine in the early 1900s are discussed here.

2.3.1 R. Lucas Motor Vehicle Engine The Lucas engine (Fig. 2.6) was, in many conceptual aspects, a forerunner of the Fairbanks Morse railway, stationary, and marine engines manufactured in the United States from the 1940s until the present, although the Lucas engine was only for motor vehicle use. In the Lucas engine, two contra-rotating crankshafts were used, geared together via bevel gears on a lay-shaft that ran parallel to the cylinder axis. This same shaft was used for the output to the clutch and gearbox. Air was inducted into the crankcase as the pistons moved toward each other, and was then displaced to the cylinder as the pistons moved to their outer dead centers via transfer ports in the liner. It is apparent from the drawing of the engine that Lucas appreciated the importance of the crankcase compression pressure, as the crankcase volume is minimized and fully cylindrical crankwebs were used. A variant of the Lucas engine is shown in Fig. 2.7 and Fig. 2.8 and is in the United Kingdom Science Museum. This engine type was also called the “Valveless”engine and was installed in the “Valveless” car (Chapter 4). One feature of this variant was offsets between the cylinder and crank axes, apparently to reduce side thrust. An engine of this type was reported to deliver 29.8 kW from 3.87 L displacement at 1750 rpm, with a configuration of 133 mm bore x 140 mm stroke (x 2); this corresponds to a BMEP of 2.62 bar, with spark-ignited carbureted gasoline.

History of Opposed Piston Engines

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Fig. 2.6 R. Lucas Opposed Piston Engine, 1901 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 5 8 No. 9/10 1946.1

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Fig. 2.7 Variant of R. Lucas Folded-Cylinder Opposed Piston Engine [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 5 8 No. 9/10 1946.1

Fig. 2.8 R. Lucas Valveless Car Engine,l910 [Reproduced courtesy of Science Museum, Kensington, United Kingdom]

zyxwvutsrq zyxw

Opposed Piston Engines: Evolution, Use, and Future Applications

Date

Bore (mm)

HalfStroke (mm>

Oechelhaeuser & Junkers

1892

200

500

1

Oechelhaeuser Gas

1898

480

800

1

290

2 24

Beardmore & Oechelhaeuser

1906

610

762

1

445

298

1908

1067

1

2316

1911

450

2

286

Opposed Piston Engines

I Beardmore &Oechelhaeuser I I Junkers Oil I

I I

1295 450

Swept

ql #

I I

Junkers Oil

633

Fullagar, South Shore

267

Doxford Oil. Air ini.

I Fullagar, Spennymore I Doxford Oil, Admiralty I EE Fullagar “Q” Type

500

I I I

1917

457

1918

370

1920

356

750

I I I

686 360 406

295

I I I

6

1350

1

77

4

323

3

5

8

92

6

19

I I I I I

I I I

1295 746 933 410 351 1492 298 680

Doxford Doxford Junkers 223 (Sly Sulzer 6 6 3 2 Series

320

400

Junkers 224 (Sly Doxford Junkers 205E

160

Junkers 207C

105 90

I Sulzer 8G18 Series I Leyland L60

I I

1946

180

1959

117.5

160

I I I

120 225 146

I I I

I I I

56 2052 522

Coventry Climax H30 Commer TS3DC-215 Commer TS4D-287 Napier Deltic

I Rolls Royce K60 I Rolls Royce K60T I Fairbanks Morse 38D-lh

85.73

I

I I I

1968

130.2

1988

87.3

1988

87.3

2003

206.4

Morozov 6DT-2

2006

OPOC (predicted)

2006

5 184.2

I I I

91.4 91.4 254

I I I

18

88

6

7

6

7

12

204

I I

I I I

(*spark ignition exceptions) Table 2.1 Performance Parameters of Two-stroke Opposed Piston Diesel Engines

149 2760 156 205 3617

History of Opposed Piston Engines BMEP (bar)

I I

47 200

BTE

Weight

(kg)

Power/ L (kW/L) 1.88

3.44

0.77

6.1 8

0.67

7.14

I I I

29

I I

* 7.82

21,382

184.5

Volume (m9

Power/ Volume (kW/ms)

7.04

5.9

I I I

Power/ Weight (kW/kg)

3.59

360

6.42

250

5.05

I I I

32

I 112,000 I I 87,500

31.6

I

0.56

I

0.019

138.5

0.013

I

11

I

1.1

I

108

0.008

I

6

I

2.1

I

0.005 0.01 2

38.8

E 3000

8.84

1250

5.86

1000

12.1

2400

6.87

I I I

2370

4.1 5

38,700

48.36

51.53 0.077

4.74

0.012 1.83

I I I

36 39.5 36.65

I I I

26.94

909

3.37

0.809

2128

0.61

0.026

9000

9.98

0.228

3100

1.26

0.168

0.42

0.061

44.2

I I I

92 206 415

I I I

8.93

I I I

3750

3.8

3750

5

1000

10.64

36.44 35.83 40.1

27.48

29.84

0.79

71 59

34.5

I I I

22.4

27.72

0.46 38.22

I I I

12.21

I I I

14.3

0.386

757

0.76

0.206

794

0.76

0.258

20,454

47.5

1-

0.89

0.177

31.26

I I I

207 272 76

I I I

23.76 31.22 17.73

I I I

54.95

1.85

25

zy

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Opposed Piston Engines: Evolution, Use, and Future Applications

zyxwvutsr

Fig. 2.9 Junkers Gas Engine, 1901 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

2.3.2 Junkers Tandem Engine

Hugo Junkers created a gas heating appliance firm in Dessau (Germany) in 1895, and two years later took the engineering chair at Aachen University, where he subsequently established a heat engine research laboratory.

In 1901, the Junkers Co. of Dessau produced a tandem OP engine (Fig. 2.9) in which the inner piston of the inner cylinder and the outer piston of the outer cylinder were connected to the center throw of the crank, while the outer piston of the inner cylinder and the inner piston of the outer cylinder and the doubleacting air pumps were connected to the two outer throws of the crankshaft via rocking beams. Firing occurred during each 180", or two impulses per revolution, allowing the compression work in each cylinder to be supplied by the other cylinder, and eliminating any transfer of energy for compression work through the crankshaft. All side connecting rods were also in tension.

2.3.3 Beardmore-Oechelhaeuser

William Beardmore & Co. Ltd. were licensed to build Oechelhaeuser OP engines from 1904 to1910. Beardmore introduced several important features such as locating the oil scraper rings on the cylinder bore, which allowed the piston skirt to overrun the cylinder bore (Fig. 2.10). This substantially reduced the height of the beam driving the outer piston and the overall height of the engine. The more compact Beardmore arrangement reduced the length of the scavenge air connections between the air pump and the cylinder, reducing pumping losses and the need to have extended-height transfer ports to compensate for volumetric efficiency losses due to pulsations in the long air pipes of the traditional Oechelhaeuser design. A further height reduction was achieved by driving the air pump directly from the crankshaft (Fig. 2.1l),which lowered the height by 35% compared to the original Oechelhaeuser engine. These changes enabled significant reductions in

History of Opposed Piston Engines

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Fig. 2.10 Beardmore-Oechelhaeuser Gas Engines, 1904-1 910 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

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Fig. 2.1 1 Beardmore-Oechelhaeuser Gas Engines, 1904-1 910 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

inertia load, and therefore enabled higher engine speeds. Fluid-compressed steel was also used for the connecting rods and the built-up crankshaft, which further reduced the mass of moving parts. Typical outputs were 300-1800 kW per cylinder at 90-130 rpm, and bore and strokes varied from 600 mm bore x 760 mm stroke (x 2) to 1067 mm bore x 1295 mm stroke (x 2). BTEs were typically 29%, with MEs of 85%. Contemporary two- and four-stroke brake efficiencies were 23-32%.

2.3.4 Fullagar Gas Engine Hugh Francis Fullagar graduated from Cambridge University and focused his initial efforts on steam turbines with C. A. Parsons & Co. Ltd., later performing some pioneering consulting work with gas turbines. Material limitations with gas turbines led Fullagar to internal combustion engines, where he introduced several significant improvements in OP packaging and weight reduction. Using paired cylinders with diagonal cross rods (Fig. 2.12), he linked crossheads on the small end of one inner piston with a crosshead on the outer piston of the adjacent cylinder, which eliminated the paired side connecting rods of the Junkers design and

zyxwv

It is notable, however, that these engines did suffer side connecting rod fractures due to the rigid cross beam connection between the two side connecting rods, unlike the Junkers pivoted-beam arrangement.

zyxwvutsrq zyxwvuts

Opposed Piston Engines: Evolution, Use, and Future Applications

were substantial and had to overhang the cylinder bore at each end.

The Fullagar paired crankshaft arrangement (Fig. 2.13) used double diameter pistons in the cylinder that were driven by the cross rods; these effectively provide a crosshead arrangement that was simpler than that of the single-crank arrangement of Fig. 2.12. Several Fullagar gas engines were built for power generation, the first by W. H. Allen of Bedford in 1913 for use at Newcastle Electricity Supply Company’s South Shore Station (Gateshead). This engine had a 305 m m bore x 457 mm (x 2) stroke for each cylinder, and was rated at 410 kW at 250 rpm, i.e., 7.4 bar BMEP, and was connected to an Allen 525V dynamo. Features included a full engine enclosure, oil-cooled pistons, pressure feeding of all principal bearings, and a Roots blower for the scavenge air. Mechanical efficiency and BTEs were apparently 80% and 30%, respectively, and the engine weighed 21.5 tons including the flywheel, or 53.3 kg/kW.

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Fig. 2.1 2 Fullagar Gas Engine, 1909 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

reduced the crankshaft to a two-throw arrangement for two cylinders, compared to a three-throw arrangement for a single cylinder as with the Junkers. The distance between cylinder centers was also appreciably reduced and the arrangement produced two firing pulses per revolution. Of course, these arrangements needed a source of air, such as reciprocating pumps, centrifugal compressor, or Roots type blowers, and the piston crossheads

Mechanically,the engine behaved reliably, but its performance at certain speeds was marred by wave action in the charging and

Fig. 2.1 3 Fullagar Gas Engine, 1909 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

28

History of Opposed Piston Engines

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Fig. 2.14 Fullagar Gas Engine, 1915 to 1917 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

exhaust systems, reducing the volumetric efficiency at those points to only 25% of that at adjacent satisfactory operating speeds. This deficiency was rectified by modifications to the gas exchange system. The relatively high cost of the town gas fuel used for this engine rendered the engine economically unfeasible and it was dismantled. Bellis and Morcombe built a second engine with three paired cylinders (Fig. 2.14). It had a 457 mm bore x 686 mm

(x 2) stroke for each cylinder, and was rated at 1,492 kW at 185 rpm, i.e., 7.2 bar BMEP, and was directly coupled to a 1250 kVA dynamo, to be used in the Weardale Power Station at Spennymore, United Kingdom. The crossheads, attached to the lower piston skirts in the region of the connecting rod small-end, and those attached to the upper pistons that are orthogonal to the small-end crossheads, are visible in Fig. 2.14. It is presumed that the cross rods were manually set on each

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Opposed Piston Engines: Evolution, Use, and Future Applications cylinder pair with adjusting nuts pulling on part-spherical washers, ensuring purely tensile loads in the rods. Scavenge air was supplied by an electrically driven turboblower.

Although Fullagar died tragically in 1916 after a relatively short but dynamic and fruitful contribution to heat engine technology, his assistants, Robert Price Kerr and Arnold Riley, pursued the exploitation of his engine arrangements by successfully commissioning the Weardale engine so that it continued power production until 1937. At that time, the electrical generating frequency was changed from 40 to 50 Hz, and it was decided not to incur the costs of modifying the dynamo and turboblower, and so the engine was decommissioned. Other Fullagar engines were developed for both light duty and marine applications. Also, the Balanced Engine Syndicate launched a two-cylinder 57 mm bore x 86 mm stroke (x 2) unit for automotive applications, in which the upper crossheads drove scavenge air pump pistons. This worked well and they had encouraging test results, but the company was closed before any production or sales occurred. Cammell Laird Co. Ltd., the Scottish shipbuilders, built three experimental direct injection Fullagar engines with the following specifications: 343 mm bore x 381 mm stroke (x 2), for merchant ships 292 mm bore x 305 mm stroke (x 2), for submarines 152 mm bore x 165 mm stroke (x 2), for aircraft

The two-cylinder 292 mm bore engine passed endurance tests at a rating of 224 kW at 360 rpm, and in its eightcylinder form would have been the same height as the single-piston engine it replaced, but 1.5 m shorter.

At least 18 marine engines were put into service in the 1920s,the largest with four cylinders, a 584 mm bore x 914 mm stroke (x 2), and a rating of 2014 kW at 86 rpm, i.e., 7.2 bar, with MEs and BTEs of 80% and 33%,respectively,with air injection. The smallest engine was a 373 kW four-cylinder unit fitted to the MV Fullagar around 1920. The English Electric Company began experimenting with the Fullagar concepts in 1920, and in 1931 began commercial applications of their Fullagar “Q” and “R” products for stationary and power station requirements, as noted in Section 2.3.7 and Chapter 7. Some 115 Q and R engines, with direct injection, covering the displacement range of 80.8-205 L/ cylinder and power ranges of 1462261 1 kW (1960-3500 bhp) were made and remained in service with high BTEs for 15 years without serious faults. These Q and R engines were finely engineered and noted for their simplicity, robustness, efficiency, and longevity. They were usually supplied as “turnkey” products with power generation machines and all supporting control and electrical systems.

2.3.5 Hugo Junkers Civil-lngenieur, Junkers und Compagnie, and Jukra Oil Engines In 1912, Professor Junkers relinquished his chair at Aachen University to allow him to concentrate on his laboratory, which he moved to Dessau in 1914 to be closer to his industrial activities-manufacture of heat-

History of Opposed Piston Engines ing systems, engines, and airplanes. Junkers operated commercially under several company names including Hugo Junkers Civil-Ingenieur, Junkers und Compagnie, Junkers Motorenbau, and Jukra, the original company he started in 1892. The first oil engines, which were derived from the Junkers and Oechelhaeuser gas engines and used air injection, entered production in 1908 with a bore of 200 mm x 400 mm stroke (x 2), operating at 200 rpm. A tandem cylinder was added in 1910. Gebruder Klein of Dalbruch (Westphalia) built several larger versions of this architecture with dimensions of 450 mm bore x 450 mm stroke (x 2) for each

cylinder, which were rated at 746 kW at 180 rpm, i.e., 5.79 bar BMEP. These engines were horizontal and had exhaust systems almost as large as the base engine. A three-cylinder vertical marine version (Fig. 2.15) with side-mounted scavenge pumps and air compressors was fitted to a Hamburg-American Line twin screw cargo ship, but was problematic and required a very tall engine room. The height, length, and open construction of the engine posed difficulties in achieving adequate frame stiffness and caused serious vibration issues. The engines were eventually replaced by steam machinery.

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This experience led Junkers back to the single-cylinder per three crank throw engine

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Fig. 2.1 5 Junkers Tandem Opposed Piston Diesel Engine, 1910 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

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Opposed Piston Engines: Evolution, Use, and Future Applications configuration (Fig. 2.1 1) and two, fourcylinder engines were built by J. Frerichs of Hamburg in 1912 and fitted to a twinscrew oil tanker of the Petroleum Steamship Company (Fig. 2.16). The engines had a 440 mm bore x 520 mm stroke (x 2) for each cylinder, and were rated at 993 kW at 150 rpm, i.e., 6.3 bar BMEP. Although these engines were more practical than the tandem arrangements, they also experienced difficultiesthat eventually led to their replacement by steam power.

The failure of these Junkers marine engines is attributed to a combination of very long multicylinder crankshaft arrangements, and the inability of shipyards in Germany at that time to manufacture precision parts for diesel engines. This is in contrast to United Kingdom shipyard experience, where similar Doxford engines were being built and successfully operated.

Junkers aero engine development began in the 191Os, and quickly moved from the single crankshafthhree-throw arrangement to the twin crankshaft configuration, probably because of the concern with the speed capability of the side connecting rods and the greater flexibility of drives with the twin crankshafts. The first engine was the horizontally arranged, six-cylinder, spark-ignited, gasolinefuelled Fo2 engine with 110 mm bore x 150 mm stroke (x 2), delivering 280 kW at 1800rpmfrom17.1L,i.e.,5.5barBMEP. The engine used a rotary blower instead of the previously used piston air pumps. Fo2s saw aerial service toward the end of WWI. The Fo2 was followed by the Mo3, a four-cylinder diesel with 130 mm bore x 180 mm stroke (x 2) with a power output of 76.8 kW at 1288 rpm from 19.12 L. All of these engines were eventually destroyed under the conditions imposed by the Treaty of Versailles in 1918.

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Fig. 2.1 6 Junkers Opposed Piston Diesel Engine, 191 2 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

32

History of Opposed Piston Engines In 1923, Junkers Motorenbau GmbH was established to manufacture both four- and two-stroke aero engines. The first diesel engine airplane flights in 1929 used a six-cylinder Fo4, which was derived from the Fo2 but was now vertical and had a centrifugal air pump instead of the rotary pump. Although Beardmore and Maybach diesels had already been used for airships, where weight was a lesser issue, the Fo4 pioneered the power density (0.7 kW/kg at take-off power) capability of a diesel for airplane use. A series of developments followed (Ref. 2.2) with major changes to bore, stroke, and piston configurations, resulting in the Jumo 4 engine of 552 kW take-off power at 1800 rpm from 28.6 L, a power density of 0.74 kW/kg. The Jumo 4 was later renamed the Jumo 204. In the early 1930s, Hugo Junkers sold the Junkers Civil-Ingenieur and Jukra

companies, which manufactured only stationary engines, to concentrate on the aero engine business. An evolutionary commercial aviation period followed from 1932 to1939, in conjunction with Deutsche Lufthansa, in which reliable short-, medium-, and long-distance air travel was established in central Europe and across south Atlantic routes to South America. During this period, the Jumo 205, 206, 207, 208, 209, and 218 engines evolved, of which the 205 and 207 entered production. The 205 was the first engine for commercial applications, while the 207 was used in high-altitude applications in the Luftwaffe. During WWII, forty-eight piston versions of the Jumo family were derived, designated as the Jumo 223, with banks of four cylinders/ four crankshafts and eight cylinders per bank (Fig. 2.17), all spark ignited.

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Fig. 2.1 7 Junkers Four-Crank Opposed Piston Diesel Engine-Jumo 223 [Reproduced courtesy of IMarE (now IMarEST) Transactions Vol. 58 No. 9/10 1946.1

33

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Opposed Piston Engines: Evolution, Use, and Future Applications The Jumo 205 and 207 engines are described in detail in Chapter 3. Versions of these engines were sold outside of Germany and some were built under license in the United Kingdom by Napier and in France by CLM prior to WWII.

2.3.6 Doxford After some discouraging experimentation with ported and valved two-strokes, work on an OP engine began in Sunderland in 1910 at the Doxford Engine Works, led by Karl Otto Keller, who was born in Switzerland in 1877 and ended his days in 1942 in Sunderland. Doxford was attracted to the three-throw-side connecting rod concept as the tensile loads were concentrated in the running gear of the engine, which could be made from relatively well controlled, fully machined steel parts while the cast-iron crankcase remained relatively unloaded. Started in 1913, the first experimental Doxford engine with a 500 mm bore x 750 mm stroke (x 2) used two air-assisted fuel injection valves arranged on opposite sides of the cylinder, and had the injector axes slightly tangential to the cylinder bore, with the injectors spaced some 50 mm apart and slits for the nozzle apertures. This arrangement gave two sheets of fuel aerosol, with the bulk of the compressed air at TDC contained between the two sheets. This air charge was drawn through the fuel cloud as the pistons moved away from IDC. By 1914, this engine was operating for up to 12 hours at overload conditions of 7.24 bar BMEP at 150 rpm, corresponding to a cylinder output of 520 kW, with ME and BTE of 75% and 31%, respectively. It was

noted that this engine could run at very low speeds, e.g., 30 rpm, with air-blast injection pressures of only 20 bar, in contrast to other air-blast injection engines that experienced poor combustion under these conditions. This is probably attributable to a combination of the extremely low surface-area-to-volume ratio of the OP engines, the use of a piston construction that resulted in crown surface temperatures of -5OO”C, and the fuel-and-air mixing system.

World War One intervened in the development of this engine, but some experimental work was pursued on a submarine engine with a 370 mm bore and 390 mm inlet stroke and 330 mm exhaust stroke. The United Kingdom Admiralty acquired this engine, obtaining a rating of 298 kW at 360 rpm, i.e., 6.4 bar BMEP-approximately four times the output of contemporary engines. Attempts to move to “fuel only” direct injection had been underway with other commercial engine builders in Europe for many years. In the United Kingdom, Vickers of Newcastle successfully developed a common rail injection system in 1910 that used an accumulator to maintain fuel pressure. Apart from the mechanical development of the injection system, considerable in-cylinder fuel spray, combustion developments, and engine compression optimization were simultaneously required. The end results, which started to appear in engines in 1916, gave a substantial improvement in ME, e.g., 75% increasing to 82%, and a corresponding increase in BTE. Indicated efficiency did not initially increase, as direct injection required an earlier start

Next Page

History of Opposed Piston Engines

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Fig. 2.1 8 Early Doxford Engine, 1921 [Reproduced courtesy of Tyne & Wear Museum, Newcastle on Tyne, United Kingdom]

of injection compared to air injection to enable adequate time for fuel evaporation. The first commercial Doxford marine engine (Fig. 2.18) was commissioned in trials in 1921 and five of these engine types were commissioned from 1919 to 1924, with relatively trouble-free operation. Table 2.1 shows that engine power was 504 kwlcylinder, with speeds between 86 and 185 rpm, while ITEs of 48% were achieved, with BTE of up to 37%. Unequal stroke engines were introduced in 1926, and fully welded crankcases went into service in 1933. Air delivery ratios were also gradually reduced from 130%to 120% of engine displacement, resulting in

an increase in exhaust temperature from -320°C to 375°C. After WWII, Doxford engines would operate with delivery ratios of only 1:1. Experiments with exhaust waste heat recovery began in 1929, generating approximately 0.6 kg of steam per kW of engine power. Steam pressure was typically 8-9 bar with the flue gas leaving at 200"C, and the steam was used to power all engine fluid pumps and seawater pumps. The remaining exhaust gas energy was eventually used to drive the steering gear, to generate electricity, and to provide hot water. A small auxiliary oil-fired boiler was used for occasions when the xvutsroigeaPN

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zyxwvutsr Chapter 3

AERONAUTICAL OPPOSED PISTON ENGINES 3.1 Introduction

The high risk and liability for aeronautical power units is largely why there are very few successful commercial piston engine applications in this field. Also the relatively lower power-to-weight ratio of compression ignition engines versus their spark ignition counterparts effectively reduces this chapter to a review of two basic OP engines: the six-cylinder Junkers Jumo 205 (and its 207 derivative of the 1930-1945 era), and the current twocylinder light aircraft Diesel Air engine. Opposed piston aeronautical engines not detailed in this chapter include the Jumo 204, a larger displacement predecessor of the 205 that was not pursued commercially; the French Salmson SH18 Diesel Twin Row radial engine with folded cyl-

inders (Fig. 3.1, Ref. 3.1); and the OPOC' engine derivatives (Chapter 4) that will see future production for both military and commercial applications.

While there have been many aeronautical diesel engines through the years (Table 3.1), few have been OP engines. It is only since 2000 that several converted automotive four-cylinder four-stroke OP engines have joined the list of diesels that have been successfully used for aeronautical purposes.

3.2 Junkers Jurno 205 3.2.1 Introduction The Junkers Jumo 205, which was one of the Jumo 204-209 family, was a renowned engine in pre WWII civil aviation. It was also used militarily in limited numbers by

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Fig. 3.1 French Salmson Diesel H18 2 Row Radial with Folded Cylinders [Reproduced courtesy of Pitman Publishing Corp., Chicago, United States]

55

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Name

Origin

Cyl.

Config.

Disp. (L)

Takeoff Power (kW

Junkers Fo4 Junkers 204 NaDier Culverin Zbrojovka ZV-350 Deschampes V3050 Junkers 205E Junkers 207B Salmson SH18 Zbroiovka Z O O 260-B Zorch ZO-01A Zorch ZO-o2A General Atomics GAP Teledvne Diesel Air Wil ksch Delta Hawk Beardmore Tornado Ill CleQet 9A CleQet 9 C FIAT AN1 Guiberson A980 Guiberson A91 8M Jalbert Loire 6 Mercedes Benz OF-2 Packard DR980 Rolls Rovce Condor B M W Lanova 1 1 4 V 4 Bristol Phoenix Cleget 14F 01 Cleaet 16H Coatalen 12Vrs 2 Guiberson A 1020 Jalbert Loire 16H Mercedes Benz DB602 SMASR 305 Thielert T AE 125 Thielert T AE 4

GER GER UK CZECH USA GER GER FR CZECH GER GER USA USA UK UK USA UK FR FR IT USA USA FR GER USA UK GER UK FR FR FR USA FR GER FR GER GER

5 6 6 9 12 6 6 18 9 4 4 3 4 2 3 4 8 9 9 6 9 9 6 12 9 12 9 9 14 16 12 9 16 16 4 4 8

OP OP OP R IV OP OP 2-R R R R L L OP L V L R R L R R IL V R V R R R2 V V R H V B I V

30.79 28.6 28.6 15.25 50.51 16.62 16.62 29.53 13.53 2.66 5.33 1.9 3.9 1.81 1.8 3.3 84.1 13.23 20.31 16.62 16.1 15.05 13.26 53.88 16.1 34.54 27.73 28.75 34.5 81.42 36.06 16.73 27.68 88.5 5 1.7 4

74 6 574 581 261 895 522 74 6 485 231 112 220 112 149 74.6 89.5 112 485 112 26 1 164 157 201 175 597 179 373 485 474 701 1492 448 254 448 597 172 101 257

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Table 3.1 Performance Data of Aeronautical Diesel Piston Engines

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Aeronautical 0lpposed Piston Engines

57

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Opposed Piston Engines: Evolution, Use, and Future Applications No.

Engine Series

I Jumo 204 A, B, C I Jumo 5 A, B, C I Jumo 205 A, B, C

Jumo 207 B, C

Jumo 208 A, B

I Jumo 223A I Jumo 224

I

I

1928

6

120

2x210

28.5

16.6

1931

6

120

2x210

28.5

16.6

1931

6

120

2x210

28.5

1932

6

105

2x160

16.6

1933

6

1940

6

105

2x160

16.6

18

2.24

1.27

6

105

2x160

16.6

17

2.05

1.32

I I

105

130

I I

2x160

2x160

I I

16.6

25.5

I I

1.7

1.68

17

1.46

1.51

17

1.53

1.32

17

17

I

1.94

I

I

1.32

I

1940

6

1939

6

105

2x160

16.6

18

2.17

1.37

1942

6

105

2x160

16.6

18

2.17

1.48

1944

6

110

2x160

18.2

18

2.17

1.25

1939

6

130

2x160

25.5

17

1.06

1.44

1940

24

1943

24

I

80 110

I

the Luftwaffe, before and during WWII, and it subsequentlyinfluenced the Russian Kharkiv Morozov battle tank engines manufactured by Kharkiv Morozov Machine Building Design Bureau, and at least four other post WWII military engines. The Jumo 205 was the only diesel engine used in regular aircraft service in significant quantities worldwide. It set many long distance records, and historically remains the most efficient piston aero engine in aviation. The Jumo 205 power ratings ranged from 373 kW at 2200 rpm [see Table 3.2 for the versions using the gear-driven centrifugal blower (CB) (Fig. 3.2)], to 735 kW at 2800 rpm for the turbocharged (TC) versions (Fig. 3.2), corresponding to -25 kW/L

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2x120

2x160

Table 3.2 Jumo Engine Series Data, 1932-1 945

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Jumo 205E

I Jumo 206

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28.95

I

17

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2.37

I

1.37

73

and -29 kW/L for the CB and TC versions respectively, all rpm speeds referring to the crankshaft speed. The bulk of this chapter’smaterial, which focuses on the “E”version of the Jumo 205, is drawn from the original Investigation Report (number 96/1) of an investigation carried out by Sir W. G. Armstrong Whitworth & Company (Engineers) Ltd (Ref. 3.2) for the United Kingdom Admiralty Engineering Laboratory in 1944. Further data, images, and help were provided by Luftfahrt Archiv-Hafner (Ref. 3.3).

zyxwv After WWII, the Armstrong Whitworth premises were occupied by the newly formed British Internal Combustion Engine Research Association (BICERA),

Aeronautical Opposed Piston Engines

which republished the original report as “Red Report” No. 46/2 in 1946 for its United Kingdom members (Ref. 3.4). Additional material was obtained from inspection of Jumo engines at the British Science Museum (Swindon), the Royal Air Force Museum (Cosford), the Junkers Museum (Dessau, Germany), and correspondence with C. F. Taylor (Ref. 3.5). Original factory information on Jumo engines is scarce as the Junkers works at Dessau were destroyed after WWII and the knowledge base transferred to the Soviet Union.

some large marine engines, sometimes in collaboration with Oechelhaeuser, Hugo Junkers applied his skills to aero engines using a two-crankshaft arrangement instead of the single-crank, three-throw Wittig system to achieve OP operation. The Wittig arrangement results in a relatively long crankshaft and a comparatively large empty crankcase, which is not an issue for stationary engines, but at the time seemed unacceptable for high power-to-weight ratio applications. Some concerns about the integrity of the outer piston cross pin and the rotational speed capability of the Wittig system at high piston speeds may also have been an issue, although similar

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3.2.2 Background

Following years of experimenting and producing stationary gas engines and

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 3.2 General View of Jumo 205E [Reproduced courtesy of RAF Museum, Cosford, Shropshire, United Kingdom]

Wittig architecture is now being used for the patented OPOCTb' engine (Chapter 4). Due to prevailing difficulties with liquid diesel fuel injection, gasoline fuelling was used to meet the urgent need for airplane engines in WWI, which eventually led to the horizontal six-cylinder Junkers Fo2 spark ignition (SI) engines (110 mm bore x 150 mm stroke [x 21, 17.1 L that delivered -280 kW), and finally to the use of a rotary blower for scavenge air, moving away from the piston-type compressors that were initially fitted. A V12 OP cylinder version, using three crankshafts,had also been designed, but all work on these projects was terminated and existing engines destroyed under the rules of the Treaty of Versailles.

Work on Junkers Fo3, the Fo2's diesel successor, began in 1924, leading to a vertical five-cylinder with 140 mm bore x 210 mm stroke (x 2) of 32.33 L with a centrifugal blower instead of the rotary compressor. By 1926, this engine was showing more than 600 kW at relatively modest crankshaft speeds of 1200 rpm. A six-cylinder Fo4 version followed (Table 3.2) with inherently better balance, a reduced bore of 120 mm, giving a displacement of 28.6 L, and with compressed air starting. A version of this engine started its airworthiness tests in 1929 with a successful 360 km flight from Dessau southwest to Cologne. Further development and debugging of the Fo4 led to the Jumo 4,

Aeronautical Opposed Piston Engines with a takeoff power of 530 kW at 1800 rpm, which was raised to 552 kW (6.46 bar brake mean effective pressure [BMEP])by 1932 with the Jumo 204, a renamed version of the Jumo 4. The name “Jumo”was from Junkers Motorenwerke AG, the original name of Hugo Junkers’engine manufacturing division. In addition to a weight reduction to 750 kg, the performance of the Jumo 204 was significantly enhanced, and durability improved, with a combination of an insulated piston crown that reduced heat losses and heat flow into the piston and rings, and the use of a tall, gapless but flexible, L-shaped “fire” ring. The fire ring was carefully sized and developed so that it expanded to give a controlled running clearance with the cylinder bore. Its L shape ensured a firm seating, and the height and gapless features increased robustness and reduced ring fractures. Eight-hour flights were performed with the Jumo 204, and the engine started regular international intercity services with Lufthansa, along Berlin- Amsterdam, Berlin-Prague, and other continental European intercity routes. The gear drive on the front of the engine allowed some flexibility in selection of the propeller-drive ratio, although each location required a torsional isolator to decouple the airscrew from engine vibration. These different propellerdrive arrangements, with other minor changes, led to the A, B, and C designations of the Jumo 204. Junkers considered the power-to-weight ratio and power density of the Jumo 204 to be too low for military applications and began to design a reduced-stroke engine that would enable higher rotational speeds, and therefore more power. This

became the Jumo 5, and was eventually renamed the 205. It improved the powerto-weight ratio from 0.74 kW1kg for the 204 to 0.86 kW1kg for the 205, with specific power rising from 19 kW1L to 27 kWIL for a rotational speed increase of -600 rpm, or approximately 30%. Originally, the Jumo 205 was known as the Jumo 5A, 5B, and 5C with airscrew speed reductions of 0.613,0.602, and 0.724 relative to the crankshaft. Unlike the later 20% the airscrew drive of the early 205s was from the center gear of the timing drive at the front of the engine. The Jumo 205 was followed by 206-208 versions, with various features as listed in Table 3.2. Perhaps the most significant version was the turbocharged 207, which had no production applications, although the Luftwaffe experimented with it at high altitudes.

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3.2.3 Jumo 5/205 Family

Approval of the Jumo 205-type engine was received in December 1933 and trials were performed in a Focke-Wulf A17 Mowe passenger aircraft. The 205A, 205B, 205C, series 1-3, of 1934 had minor improvements over the 5A-C versions. The Jumo 205C was the first production version; a series 4 version adopted Glycol cooling and had a takeoff power of -450 kW. A 205D version followed with 656 kW takeoff power; this series was built under license by Napier and named the “Culverin” in the United Kingdom. Construction Lilloise de Moteurs (CLM) in France also had licenses to manufacture.

At 373 kW-rated cruise power and 448 kW takeoff power, the 205E was a downrated version of the 205D, probably aimed

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Opposed Piston Engines: Evolution, Use, and Future Applications at improving reliability. The 205G soon followed, which at 5 15 kW had even more takeoff power but it was not put into production.

3.2.4 General Architecture The Junkers Jumo 205 family of engines was based on a vertical liquid-cooled light-alloy cylinder arrangement (Fig. 3.3, Fig. 3.4, Fig. 3.5, and Fig. 3.6, which are of a Jumo 205D) with an upper “exhaust” crankshaft linked to the exhaust pistons and the lower “air” crankshaft controlling the inlet pistons. A geared centrifugal blower driven from the rear of the air crankshaft supplied scavenge air, while a torsionally damped

and isolated gear meshing directly to the exhaust crankshaft drove the airscrew. A set of five spur gears linked the exhaust and air crankshafts at the front of the engine; the center of these gears drove two camshafts through two spur gears that were located on each side of the engine, the cams driving the individual fuel injection pumps for each cylinder. A single shaft at the rear of the air crank drove the coolant pump and the lubricating oil pressure and scavenge, with each of the two low-pressure fuel pump systems driven off the rear end of each camshaft. The two inlet manifolds, which were cast integral with the cylinder block, had their entries on the rear face of the crankcase.

Key 3.3 2

Closing plate for propeller drive

3

Oil filter casing

16 Oil drain plug 17 Oilfilter 18 Closing plug for oil gallery 27

Oil jets for gear train

28 Wing nut for oil filter cap Gear shaft bolts 48 Connection vent for oil bypass

39

52

Fuel lift pump

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Fig. 3.3 Front View of Engine [Reproduced courtesy of Luftfahrt-Archiv Hafner, Germany]

62

Aeronautical Opposed Piston Engines Key 3.4 4

Coolant outlet

8

Coolant drain

9

Oil inlet connection

10

Oil outlet connection

14 Connection for upper crankshaft pressure gauge 19 Crankcase core plug 20

Injector pump drive fork

23 Air intakes 25

Linkage for fuel injection pump adjustment

30 Starter flange 31

Generator flange

32

Half engine speed drive

34 Coolant drain plugs 35

Coolant entry connection

36 Fuel inlet connection 45

Idle regulator

46

Governor pump

47

Governor drive

49

Upper crankshaft oil bleed outlet

Fig. 3.4 Rear View of Engine [Reproduced courtesy o f Luftfahrt-Archiv Hafner, Germany]

connecting with the twin outlets of the centrifugal blower. Two exhaust manifolds were bolted one on each side of the crankcase, connecting to the exhaust, or to the dual-entry exhaust turbine in the case of the Jumo 207B2. Pressure-charged versions had the turbocharger located at the rear of the engine, above the crankshaftdriven centrifugal compressor; the air was intercooled after the second compressor. In this arrangement, the air was delivered to a massive intercooler with twelve outletssix on each side of the engine-into the scavenge port air chests. Cylinder bore and stroke (x 2) sizes varied according to the engine series number (see Table 3.2). Dry engine weight of the

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205E engine, which forms the basis for most of this chapter, was 520 kg, resulting in a 0.854 kW/kg specific output for the 448 kW takeoff rating, with a cruising power of 373 kW.

3.2.5 Key Features

3.2.5.1 Crankcase and Main Bearings

The crankcase (Fig. 3.7) was an aluminumsilicon alloy casting consisting of six cylinder tunnels, each of approximately 700 mm length and approximately 123 mm internal diameter at the sealing lands. There were seven main bearing housings at the upper and lower ends of the crankcase, each containing two thick aluminum shells that held the steel-backed coppedlead bearings.

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Opposed Piston Engines: Evolution, Use, and Future Applications

Key 3.5

1

Engine mounting flanges

40

Injection pumps

5

Connection for coolant thermometer

41

Main oil pressure regulating valve

6

Coolant flow inlet connection

42

Oil filter for scavenge blower

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24

Exhaust manifold flanges

44

Filter for governor

29

Connection for air manifold pressure gauge

53

Oil pressure vent

33

Connection for hand priming of oil circuit

54

Fuel filter

37

Coolant return pipes

Fig. 3.5 Right-Hand View of Engine [Reproduced courtesy of Luftfahrt-Archiv Hafner, Germany]

The aluminum shells were supported and clamped by a two-bolt, forged-steel main bearing cap. The use of the removable thick aluminum shells allowed the main bearings and supporting cap to overhang the cylinder bore, allowing piston withdrawal. The main bearing stud axes projected onto the mean wall circumference of the cylinder tunnels, which formed the main load path through the crankcase for the resultant forces on the crankshaft. The bearing studs were extremely long and waisted for stress management. The bearing caps had a shal-

low spherical facing around the stud holes, and the loads from the tightening nuts were applied via a distance piece that was spherically ended. Upper and lower crankcase faces offered flat sealing surfaces, on which can be seen fourteen 20 mm-diameter drain holes that connected the upper crankcase to the lower to allow oil return to the scavenge pumps. Crankshaft end thrust was taken by number seven main bearing, which was flanged, bearing against ground faces on

Aeronautical Opposed Piston Engines

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Connection for coolant thermometer

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Coolant flow inlet connection

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Entrance to lubrication connection for remote thermometer

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Fuel pump connections

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12 Connection from oil gallery to oil tank 13 Connection for oil blower oil gallery

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Adjustment for governor

15 Connection for lower crankshaft pressure gauge 21 Connection for fuel pressure gauge

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54 Fuel filter

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Fuel vent pip

Fig. 3.6 Left Hand View of Engine [Reproduced courtesy of Luftfahrt-Archiv Hafner, Germany]

web number 14 and the rear flange of each crankshaft. The general crankcase had a wall thickness of 5 mm, and was made of “Silumin,”an aluminum alloy consisting of Si 11.75%, Cu 2.08%, Mg 1.03%, Ni 1.26%, Mn 0.63%, Fe 0.80%, and Zn 0.40%.

Three cast depressions in the front face of the crankcase accommodated the three meshing transfer and timing gears and their spigots, which were a press fit into the crankcase. Flat sealing lands on either side of the front face were for mounting the gear case.

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Fig. 3.7 Sectional View of Crankcase [Reproduced courtesy of Luftfahrt-Archiv Hafner, Germany]

Fuel-injection camshafts were housed in tunnels that each had seven cambearing supports. The camshaft was fed into the tunnel from the front face of the crankcase. Each cam drove a rocker via a rolling element bearing that was pivoted on a plain bush fitted to individual pump covers, fixed by four bolts to each side of the crankcase, with each cover containing the helically controlled pump plunger.

The rear face of the crankcase had a triangular mounting flange for the centrifugal blower/oil-and-water pump module. This flange extended from the centerline of the air crankshaft rear main bearing to the entry flanges of the inlet manifolds. The crankcase/cylinder block had a cast coolant-flow entry manifold (Fig. 3.5, Fig. 3.6) on each side of the cylinder block below the inlet manifolds. Each coolant manifold had six sealed holes

indicating the location of the water jacket core plugs, through which the coolant flowed equally up and around each cylinder. The coolant flow rose through a series of horizontal divisions in each cylinder tunnel. Coolant flow in each cylinder tunnel therefore began below the air port belt, via four cored holes, to a space above the air port belt, then through helical passages enclosed by a corset fitted to the center section of the cylinder liner on either side of the injectors. The flow entered the nine fabricated cooling channels (Fig. 3.8) in the exhaust port bars and then passed through four cored holes into the final horizontal division, which was essentially the entry into the water outlet manifold on each side of the engine. Each of these coolant return manifolds was “stitched” to the cylinder block face by approximately fifty fixing bolts.

Aeronautical Opposed Piston Engines bearings (Fig. 3.3) that were coaxial with bearings in the front face of the crankcase. The bearings supported the meshing gear with the exhaust crankshaft and also formed the propeller-shaft bearing system. The front crankcase face contained eight drilled holes, approximately equidistant, that served to return oil to the lower crankcase cover, which served as a sump. The upper cover (Fig. 3.7) was a relatively simple half-cylindrical casting with semicircular ends that had internal and external ribbing. The lower sump was similar to the upper sump, except that its rear end connected with the coolant and oil pump drives. However, functionally, the lower sump (Fig. 3.7) performed the additional tasks of transferring oil from the rear pressure-oil pump to the nose of the crankshaft via a cored gallery running the length of the engine, and of filtering collected oil via scavenge pump suction points at the front and rear ends of the engine. The sump had windage trays to keep oil away from the crankshaft and to help drain the oil to either end of the engine.

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Fig. 3.8 Sectional of the Liner Showing Cooling Arrangements [Reproduced courtesy of Luftfahrt-Archiv Hafner, Germany]

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The engine was supported on four mounting pads on each vertical side of the crankcase. Since the pads were at almost the four corners of each crankcase side, a variety of installations were possible. 3.2.5.2 Crankcase Covers

The crankcase (Fig. 3.7) was closed by the front cover and the upper and lower sump covers; the sealing flanges of the latter two being on the centerline of each crankshaft. All three covers were of magnesium alloy. The front cover completed the timing case for the crank-to-crank gear train, providing the timing gears with support

Two sealing caps (not apparent in Fig. 3.3) containing the quills that supplied the oil to the nose of the crankshafts were located at the front-end junction of the timing cover with the two sump covers. Typical external bolt pitch was 38 mm with the sumps each secured by about 40 bolts, while the front covers had about 26 bolts each. 3.2.5.3 Liner

The Jumo liner was the best contender for the pike de resistance of all the components of the engine in terms of design, materials, finish, and its contribution to engine performance and durability. The

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Opposed Piston Engines: Evolution, Use, and Future Applications

Fig. 3.9 Cylinder Liner Drawing [Reproduced courtesy of Sir WG. Armstrong Whitworth & Company (Engineers) Ltd., United Kingdom]

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Aeronautical Opposed Piston Engines alloy steel liner (Fig. 3.9) was 676 mm in length, i.e., 2.1 x total stroke, of 2 mm nominal wall thickness, 109 mm nominal outer diameter and locally -123 mm at the sealing land outer diameters, of which there were six sets, two on each side of the inlet and exhaust ports, and one at each end, leaving -86 mm of liner uncooled at each end to support the piston skirts at ODC.

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Each sealing belt consisted of a pair of synthetic rubber O-rings except for the lower exhaust port sealing belt that had a single O-ring. This single seal was necessary because of the greater exhaust port height compared to the air port height. The paired seals had an intermediate groove that was connected to the outside of the crankcase by a "tell-tale" hole, providing evidence of any coolant leaks past the O-ring seals. Liners had a 120 mm-diameter threaded end, allowing a large flange nut to be tightened against the crankcase sump flange to position the liner, leaving the other end free to expand. Coolant sealing was therefore dependent on the O-ring seals, quite unlike the Sulzer ZG and G types, post WWII Rootes TS3, Rolls Royce K60, and Leyland L60 engines. However, the Napier Deltic and Climax H30, which also used a light alloy crankcase, adopted a similar O-ring sealing strategy as well as considerable interference fit. This topic is discussed in some detail in Chapter 6. Cadmium plating was used on the liner outer surface, except in the central helically splined region that was chromium plated to reduce the effects of cavitation erosion. The central section of the liner had 36 machined helical slots covering 55% of piston travel, the helix making 50% turn over

this distance. The periphery of the helical slots was effectively sealed by a 4.63 mm wall spring-steel sleeve, or "corset," that was a light interference fit on the helical splines. The corset had four holes to allow fitting of the water-cooled injectors (Fig. 3.10). The nine exhaust port bars had 2 x 5 mm helical grooves on their outer diameter that, in combination with a drive fit between the sealing sleeve and liner, with matching port shapes to the liner exhaust ports, formed the coolant transfer passages. The air ports (Fig. 3.1 1) consisted of four rows, the outer two rows having 30 drilled 7 mm-diameter holes, and the inner two rows having a unique angle of incidence with the cylinder center line of 12". Two parallelogram-shaped ports that extended over the height of the outer two rows of air ports provided 10.65%of the air port flow area. These ports also served as inspection ports to examine the piston ring condition. Total inlet port flow area was 4% of the total engine-stroke area, and the inlet port height was 7.3% of the total stroke. As can be seen in details of the Jumo ports (Fig. 3.9), they were at the upper level of two-stroke scavenge ports, and this was probably a reflection of the design intended for a high-output aero engine, with high mean piston speeds such as 11.73 m/s. Timing of the air ports was opening 53" before outer dead center (BODC) relative to the exhaust crank, and closing was 71" after outer dead center (AODC). The net exhaust lead of 15" (Fig. 3.12) is on the low side of two-stroke engines having similar piston speeds. The exhaust ports (Fig. 3.13) consisted of eight parallelogram-shaped

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Fig. 3.10 Injector Hole and Coolant Details (Sections II and Ill on Fig. 3.9) [Reproduced courtesy of Sir WG. Armstrong Whitworth & Company (Engineers) Ltd,, United Kingdom]

(27 m m x 41 mm) apertures, providing a total flow area of 6% of the total engine stroke area, and the exhaust port height was -1 1% of the total stroke. Timing of the exhaust ports was opening 68" BODC relative to the exhaust crank, closing 68" AODC relative to the exhaust crank (Fig. 3.12)

Each of the nine exhaust port bars had a 2 m m x 5 m m helical groove on its outer diameter. The grooves were sealed by a second corset that was seam welded around each port so the entire coolant flow for the cylinder was forced to cool the port bars. Very strict quality checks were vital to check these critical welds

Fig. 3.1 1 Inlet Port Details (Sections I, V, and VI on Fig. 3.9) [Reproduced courtesy of Sir W G. Armstrong Whitworth & Company (Engineers) Ltd., United Kingdom]

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Fig. 3.1 2 Juno 205E Piston Travel and Port Openings

and the durability development of these welds must have posed many challenges. The air ports provided a swirl effect relative to engine speed. The reduced angle of

incidence of the lower air ports promoted more radial flow towards the center of the cylinder where exhaust gases tended to collect because the upper swirl ports forced the higher density clean air to the

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Fig. 3.13 Exhaust Port Details (Sections IV and VII on Fig. 3.9) [Reproduced courtesy of Sir W G. Armstrong Whitworth & Company (Engineers) Ltd,, United Kingdom]

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zyxwvutsr Chapter 4

AUTOMOTIVE OPPOSED PISTON ENGINES 4.1 Introduction

Successful automotive applications of both gasoline and diesel OP engines are limited to the French Gobron-Brille car engine (Fig. 4.1 and Fig. 4.2) ofthe 1900-1910 era; the iconic Rootes Tillings Steven (TS3) light-medium duty truck engine, which was very popular in the United Kingdom from 1954 to 1970; and the Junkers SA/SB series and CLM LC2 truck engines of the 1920s to1930s. Various types of the Ukrainian Kharkiv Morozov OP diesel engines (see Chapter 5) are also thought to be in use in the Ukraine and Russia. The TS3 may have been inspired by the French Manufacture clArmes de Paris (MAP) tractor engine, which had a relatively short commercial life because of premature failures. The MAP may itself have been inspired by the Sulzer ZG engine family (Chapter 7).

The Valveless and Trojan OP engines from the United Kingdom offered simplicity for early low-cost passenger car spark ignition engines and had many innovative features. The much smaller but famous Austrian Puch motorcycle engine may have been inspired by these early parallel-cylinder OP power units. The recent OP opposed cylinder (OPOCTM) and EcoMotor engines are intended for medium and heavy duty military and commercial automotive applications, and aviation use.

4.2 Valveless 4.2.1 Introduction The Valveless Car Company Ltd. opened for business in 1911 in central London, manufacturing customized ‘‘Fifteen Horsepower” luxury vehicles that used a gasoline-fueled, two-cylinder “valve-

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Fig. 4.1 Gobron-Brille Engine Cross Section [Reproduced courtesy of The Automobile, Feb. 19901

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Fig. 4.2 Gobron-Brille Engine Installed in Automobile. 1907

less” two-stroke engine, based on a patent by Ralph Lucas. Much was made in the company’s advertising of the simplicity of the engine with “Only six working parts providing the same work as a four cylinder engine and the silence and smoothness of six” (Ref. 4.1). The engine was an opposed piston engine with parallel cylinders, of the type described in Chapter 2, Section 2.3.1. Rolling chassis with drivelines (Fig. 4.3) were supplied at a base price of €3 15; the “four seated Limousine” body option was an additional €160, while the sevenseated version was an additional €180. A “cape hood, with side curtains” was offered for an additional €16, 10 shillings, and a triple-folding windscreen cost €12, 12 shillings.

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piston phase lead over the air piston. The latter controlled a transfer port in the liner that was connected to the lower crankcase that, in turn, was connected to the air intake. The motion of both pistons resulted in a conventional crankcase induction and compression system. The carburetor was connected to the transfer port (left-hand side [LHS] of Fig. 4.4) in the liner that was connected to the lower crankcase, which in turn was connected to the air intake so that minimal fuel entered the crankcase. A cylindrical throttle barrel, located in the transfer passage (Fig. 4.5), controlled the engine power. The fuel control was from a differential pressure diaphragm-controlled needle that traversed the transfer port and engaged in a main jet connected to the float chamber, also shown in Fig. 4.5.

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4.2.2 Description

The twin cylinders were driven by two parallel crankshafts (Fig. 4.4), which were directly geared together with an exhaust-

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A single spark plug, located at the junction of the cylinder head and the air liner (LHS of Fig. 4.4), fired the mixture. The

Automotive Opposed Piston Engines

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Fig. 4.3 Chassis for Valveless Car Company with Twin-Cylinder Engine and Four-Speed Driveline [Reproduced courtesy of Science Museum, Kensington, United Kingdom]

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Fig. 4.4 View on Sectioned Liner, Showing Water Jacket, Spark Plug Hole, Transfer Port, and Carburetor

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Fig. 4.5 Section through Carburetor Diaphragm Valve with Fuel-Metering Needle, and Barrel Throttle-Valve in Transfer Port

ignition system was powered by a magneto. The cylinders and cylinder head were a single copper casting with closing plates on the top of the cylinder head and at the rear of the cylinders (Fig. 4.6). Auxiliaries, notably the large-diameter water pump, the fan, a lubricator pump, and possibly the magneto, were all driven from a cross shaft (Fig. 4.6) that connected with the output of the flywheel via a skew drive. These auxiliaries were mounted on a cross frame that also supported an outrigger bearing for the flywheel. Six or seven outlets can be seen be seen from the lubricator pump (Fig. 4.7), with two outlets feeding the cylinder liners, and possibly four outlets feeding the main rolling element bearings supporting the two crankshafts. While all the bearings,

including those of the cross shaft, appear to have been of the rolling element type, it is not clear how these other bearings, or the skew drives, obtained their lubrication. It is possible they were regularly greased, although grease nipples are not evident from the remaining hardware. Aluminum alloy was used for the crankcase, cross frame, cross shaft housing, and most of the auxiliary casings.

4.2.3 Performance

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Although advertised as a “15 hp” engine, the 3.9 L-displacement engine claimed to deliver “25 hp” at a normal running speed of 800 rpm, equivalent to 3.58 bar BMEP. Some versions could produce 40 hp (2.62 bar BMEP) at 1750 rpm. The driveable engine speed range was 150 to 2300 rpm, the latter representing 10 m/s piston speed.

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Automotive Opposed Piston Engines

Fig. 4.6 View on Drive Side of Engine, with Flywheel, Cross Shaft, Fan, Magneto, Lubricator, and Coolant Pump Drives

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Fig. 4.7 Side View of Engine Showing Lubricant Distribution Pump, Coolant Impeller Outlet, Carburetor Diaphragm, and Float Chamber

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Opposed Piston Engines: Evolution, Use, and Future Applications 4.2.4 Manufacture

The production output and life of the Valveless Car Company is not known. Certainly the style of the vehicle shown in Fig. 4.8 is very reminiscent of those used to transport British troops to the Western Front in northern France during WWI. As for the engine, it is delightfully simple, beautifully engineered, and well arranged for ease of maintenance. A surviving example can be seen, by request, at the Science Museum, West Kensington, London, United Kingdom.

4.3 Trojan 4.3.1 Introduction “Trojan” is a name that symbolizes unconventional approach, resourcefulness, and durability. Leslie Hayward Hounsfield, an enterprising engineer, adopted the Trojan name for his fledgling motor vehicle company in 1913 when he registered his first light duty and utilitarian vehicle prototype. It certainly was an unconventional

vehicle and engine. WWI intervened in his plans, but by 1920, Hounsfield had further evolved his vehicle and in some ways aimed it to be the Model T of the United Kingdom. Although Trojan was a small business, using premises in south London, Hounsfield succeeded in persuading the Leyland Motor Company, a substantial commercial vehicle manufacturer in the United Kingdom, to take a license for his novel vehicle and engine and therefore to compete in the light duty motorcar business. Hounsfield became chief engineer of Trojan products at Kingston, south of London, where approximately seventeen thousand Trojans were made from 1923 to 1929, all using an unusual four-piston, spark-ignited, two-cycle, OP engine. Light duty utilitarian car competition was intense in the United Kingdom from 1920 to 1939,with the major manufacturers slashing prices and introducing frequent “facelift” and sporting models, much as is done today. Leyland decided to withdraw from this market in 1928 and concentrate

Fig. 4.8 Seven Seater Limousine produced by the Valveless Car Company, 191 1 [Reproduced courtesy of Science Museum, Kensington, United Kingdom]

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Automotive Opposed Piston Engines on the company’s traditional commercial vehicle business, relinquishing the Trojan license, and reclaiming the manufacturing site. In 1929, Hounsfield moved to Croydon, also in south London, and continued manufacturing until 1964. The post WWII years were relatively successful for Trojan with their utility van and people carrier, effectively an early version of a “multipurpose vehicle” (MPV). The original fourpiston, two-cycle OP engine was modified with charging pistons in the early 1940s and continued in use until the mid 1950s when it was replaced by a Perkins diesel. The Trojan OP engine is briefly reviewed because it was probably the first production “duplex” OP engine with a claim of only seven moving parts, and it had several distinctive features. Additionally, it was probably the first automotive OP engine application. Trojan information is drawn from Ref. 4.2 and Ref. 4.3.

had its own closed sump volume (Fig. 4.12 and Fig. 4.13) that was connected to the carburetor by a long induction port, which dispensed a -251 mixture of gasoline (petrol) and oil, traditionally known as “petroil.”Crankcase compression of each pair of pistons, which had the typical OP “exhaust l e a d phase angle between them, resulted in compression of the charge and eventual displacement to above the “inlet piston” via a transfer port (Fig. 4.10). Combustion was initiated with a spark plug located on the inlet side of the cylinder head, and propagated via an aperture in the cylinder head combustion-chamber wall, effectively connecting the volumes above the inlet and exhaust pistons. The exhaust port, with the phase angle advance of the exhaust piston, opened first and closed first, thus offering a degree of supercharge. Trojan engineers claimed the dividing wall in the combustion chamber improved scavenging and combustion. The Trojan was therefore an early and advanced OP version of Dugald Clark‘s crankcase compression two-stroke engine.

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4.3.2 Description

The bore and stroke of the initial fourpiston Trojan OP engine (Fig. 4.9) were 64 m m x 121 mm (x 2), giving a stated cylinder displacement of 1.488 L, although this displacement is lower than the product of the bore and stroke, presumably due to the unique offset geometry of the crankshaft centerline and connecting rods relative to the parallel cylinders. Later engines had an increased displacement of 1.527 L.

One distinctive feature was the parallel cylinder bores (Fig. 4.10) linking pairs of pistons mounted on a split “tuning fork” style connecting rod (Fig. 4.1 I), and a cylinder head and combustion chamber bridging the parallel bores. Each pair of cylinders

Light-load combustion stability was clearly an issue in these early Trojans, as the transfer port was fitted with a flame trap of gauze to prevent backfire flames entering the carburetor. The Trojan service manual warns against trying to save gasoline by using the throttle too little, as lean mixtures under these conditions resulted in a very slow burn that persisted until the transfer port reopened, the flame then attempting to propagate into the crankcase. The long length and small section of the connecting rods (Fig. 4.1 1) clearly made them very flexible and the service manual mentions that the connecting rod shanks

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Fig. 4.9 Sectional Sketch of Trojan Four-Piston Duplex OP Engine, with Inlet Port on LHS through Center of Cylinder Head, Exhaust on Underside [Reproduced courtesy of Trojan Museum Trust, Oxfordshire, United Kingdom]

Automotive Opposed Piston Engines

Key 4.10

1 Configuration of the cylinders 2 Carbureted air entering vacuous crankcase. When compression complete, spark ignites charge. 3 Compressed charge in crankcase about to enter cylinder through transfer port. Combustion complete, burnt gases escaping through exhaust port. The new charge about to enter the cylinder and replace the volume of the burnt gases.

4 Transfer from crankcase to cylinders complete, and compression in cylinders about to commence.

Fig. 4.10 Schematic Layout and Operating Cycle of Trojan Engine, Also Showing Partial Separating Wall in Combustion Space [Reproduced courtesy of Trojan Museum Trust, Oxfordshire, United Kingdom]

Fig. 4.1 1 Trojan Double Connecting Rod, with White Metal Bearings and Pinch Bolts for Big- and Small-Ends [Reproduced courtesy of Trojan Museum Trust, Oxfordshire, United Kingdom]

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Opposed Piston Engines: Evolution, Use, and Future Applications may be appropriately bent to address undue wear on the white metal big-end bearings! One might also imagine that the connecting rods may have flexed during every full-load firing cycle, attenuating the higher cylinder pressures and returning the energy by spring recovery, less efficiently, at a later point in the cycle, in a dynamic form of peak cylinder-pressure control. A second feature of the Trojan engine was its ingenious lubrication system (Fig. 4.12 and Fig. 4.13) that took advantage of the split crankcase and cyclic pressure differences to pump oil, which had drained from the petroil and collected in a small sump in each crankcase half, and then from that sump to the divided internal galleries of the crankshaft in the other half of the engine. The crankshaft main journals had

drillings S and S1 that were timed to match oil feed holes R and R1 in the crankcase, so that the pressure differential between the two crankcase halves resulted in oil being transferred along interconnecting pipes to small reservoirs in connection with the oil feed holes R and R1. The crankshafts had internal galleries to conduct the oil to the big-end white metal bearings by both the differential crankcase pressure and centrifugal force in the oil drillings. Later crankshafts that used rolling element big-end bearings dispensed with the internal crankshaft galleries, conducting the oil from the main journal to the bigend on the outer surface of the crankwebs, possibly in surface grooves. The crankcase pressure differentials were also used to act on annular grooves X and W (Fig. 4.13) so that these were always subject to a depres-

Fig. 4.1 2 First Part Section through Early Trojan Divided Crankcase and Crankshaft, with Individual Oil Sumps, Cross-Pumping Oil System, and Sediment Drain Plugs [Reproduced courtesy of Trojan Museum Trust, Oxfordshire, United Kingdom]

Automotive Opposed Piston Engines

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Fig. 4.1 3 Second Part Section through Early Trojan Divided Crankcase and Crankshaft, with Vacuum-Based Oil Drains to Seal Crankshaft [Reproduced courtesy of Trojan Museum Trust, Oxfordshire, United Kingdom]

sion, forming a natural oil seal and oil return system. The interconnecting pipes of this lubrication system were arranged in a “figure of eight” configuration to ensure that flow reversals were avoided. This can be seen in Fig. 4.12 and Fig. 4.13. Sediment and dirt were allowed to collect in the bottom of the individual crankcase sumps and would be pushed by the cyclic crankcase pressure past check valves into cleanable galleries, fitted with inspection plugs. To ensure satisfactory cold operation of the lubrication system, exhaust gases were circulated against the oil sump surfaces. The engine was water-cooled with a natural convection water circulation system and had a battery-powered ignition system.

and high speeds, respectively. Hill climbing of the early Trojan vehicles was described as outstanding, although maximum speed was limited to -35 mph (56 kph). Fuel consumption was claimed to be 40 mpg, or 7.06 L/100 km, with1000 mpg for the oil. Advertisements claimed that the Trojan vehicle was more economical than the normal wear and tear on shoes and socks associated with walking, an early and interesting comment on carbon footprint philosophy.

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4.3.3 Performance and Fuel Economy

The Trojan engines claimed a flat -7.5 kW power curve from 400 to 1200 rpm, corresponding to 7.2 and 2.4 bar BMEP at low

4.3.4 Applications

The early Trojan vehicles, such as the Utility of 1924 (Fig. 4.14), were almost as unique as the Trojan engines in that they used a “punt” or bathtub box construction instead of the traditional ladder frame for the chassis, thus providing considerable rigidity and passenger safety. Solid tires were also used to avoid punctures, and

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Fig. 4.1 4 Trojan Utility Vehicle, 1925 [Reproduced courtesy of Trojan Museum Trust, Oxfordshire, United Kingdom]

the suspension was claimed to provide a very smooth ride on rough surfaces. The engine was mounted horizontally and transversely under the driver’s seat, in spite of the front-mounted radiator, and the drive from the epicyclic gearbox to the solid axle was via duplex chain. The basic price in 1924 was 4 1 5 7 , approximately $200 at 2009 exchange rates.

with plenty of floor space and access to the rear through double doors. This was a vehicle that was well ahead of its time.

After the termination of Leyland’s participation, Trojan introduced the RE (car, not van) that initially received many customer complaints, probably due to lack of development. This vehicle used the four-piston OP engine in a vertical position, mounted in the rear of the car, and remained in small production until 1935. The post WWII one-ton Trojan van (Fig. 4.15) was a very practical vehicle. Sometimes it served as a small bus and was even sold domestically as a people carrier

4.4 MAP

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4.3.5 Heritage

There is an active Trojan Heritage Society (Ref. 4.2), and working four-piston OP engines can seen at rallies in the United Kingdom.

4.4.1 Introduction Much of the French manufacturing industry was requisitioned during WWII by Germany to support the German war effort, and therefore became a target for Allied bombing. In spite of the war damage, French industry quickly revived post WWII to support the regeneration of commerce, in particular the transport and agricultural sectors, which were vital

Automotive Opposed Piston Engines

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Fig. 4.1 5 Fleet of Trojan One-Ton Vans Belonging to Edinburgh Corporation (Scotland) in front of Fettes College, 1955 [Reproduced courtesy of Trojan Museum Trust, Oxfordshire, United Kingdom]

aspects for the recovery of the country after the dire war years.

Manufacture d’Armes de Paris (MAP) began in 1947 to manufacture a family of folded-cranktrain diesel OP engines with two, three, and four cylinders for automotive, marine, and agricultural applications. The architecture of the engine was a forerunner of the Rootes Commer TS3 engine, and possibly was derived from the Sulzer ZG series. There were plans for the MAP engine to be manufactured under license by Russell Newbery & Co. Ltd. of Dagenham, but this did not occur, possibly because of reliability difficulties of the MAP engine in the French home market. The MAP had a short commercial life because of mechanical problems, but made a name for itself in car racing and record breaking. The limited information available on the MAP is drawn from Ref. 4.4 and Ref. 4.5.

4.4.2 Description

The bore and stroke of the MAP OP engine (Fig. 4.16) were 88 mm x 102 mm (x 2) (which is remarkably close to the 82.55 mm x 101.6 mm [x 21 of the later Rootes Commer TS3), giving cylinder displacement of 1.25 L. Two- and fourcylinder engines were made, all with nominal compression ratios of 16:l.

Water cooling was used, with a fan and dynamo driven by a vee-belt from the crankshaft pulley, Inlet and exhaust manifolds were on the upper face of the engine. The Roots scavenge blower, which operated at a maximum of -0.35 g bar delivery pressure, was mounted on the front of the engine and driven by a cross shaft, the other end of which possibly drove the fuel injection pump. A page from the service manual (Fig. 4.17 and Ref. 4.5) indicates that the connecting rods had forked small-ends that engaged

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Fig. 4.1 6 MAP Cranktrain and Liners (Ref. 4.3.2), Showing Built-up Crankshaft [Reproduced courtesy of Transport World, Nov, 19491

Fig. 4.1 7 View of MAP Two-Cylinder 2.5 L OP Engine, Showing Exploded View of Liner, Rocker, and Crank [Reproduced courtesy of Arnoud Payet, France]

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Automotive Opposed Piston Engines with the rocker pins of the large lever rockers. The piston (wrist) pins were solidly bolted into a palm end of the piston link that engaged via a forked end with the upper joint of the lever rocker. The pistons had five rings, with the top ring resembling a fire ring. Below this were two compression rings and two scraper rings at the outer end of the piston.

expected for this size of engine. The builtup crankshaft is even more unlikely to structurally tolerate torsional vibrations and is not well suited to sustaining the bending forces of the cranktrain, because of the difficulty of achieving adequate overlap between the press-fit crankpin and the adjacent webs and main bearings.

4.4.3 Performance, Weight, and Bulk The cast iron wet liner had single rows of scavenge and exhaust ports and had deep slots to accommodate the rocker swing. The high tension crossbolts penetrated through the rocker fulcrum trunnion on each side of the engine and were secured by nuts. The bolts were not of the two-piece arrangement, as used in the Rootes TS3. The pistons had heat-resistant crowns but were oil cooled. Surprisingly, the crankshaft was built up, at least for the two-cylinder engine, with rolling element bearings supporting the two main journals, lead-bronze-steel-backed shell bearings for the connecting rod big-ends, and helically grooved bushes in the piston bosses. Some service manuals indicate that a floating pin was used in the forked end of the connecting rod, while others indicate that the forked ends of the connecting rod were split and the pin was held by two pinch bolts. The crankshaft and bearing arrangements for the four-cylinder MAP engines also seem to have used built-up crankshafts and only three rolling element bearings. While rolling element bearings are feasible in terms of the almost negligible bearing loads with the folded crankshaft OP engine, they will not dampen or tolerate any torsional excitation that would be

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Performance of both the two- and fourcylinder MAP engines was competitive for that period with peak BMEPs of 5.6 bar at 1500 rpm and 5.9 bar at 1600 rpm for the respective engines, while peak powers were -45 kW and -90 kW respectively at 2000 rpm, corresponding to -5.4 bar BMEP, suggesting an untuned engine. The specific fuel consumption at rated power was -241 g/kWh. Dry engine weights of fully dressed engines, including flywheels, were 352 kg and 555 kg for the two- and four-cylinder engines, giving power-to-weight ratios of 0.127 kW/ kg and 0.161 kW/kg, respectively.

4.4.4 Applications

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Sales brochures indicate the use of the two-cylinder engines in tractors, and maybe some marine and truck applications with the 5 L four-cylinder versions. However, the MAP made its fame with a four-cylinder power unit for a recordbreaking Delahaye racing vehicle in 1949, setting 50 km and 50 mile speeds of 178 kph and 179 kph (112 mph), 100 km and 100 mile records at 179.79 kph and 182.04 kph, among other records. Fuel economy during these speed records was about 24 mpg, equivalent to 11.5 L / l O O km.A 5 L, 101 kW MAP engine-equipped vehicle

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Opposed Piston Engines: Evolution, Use, and Future Applications was also entered for the Le Mans 24-hour race in 1952 (Fig. 4.18 and Fig. 4.19), but retired after six hours. The MAP engine seemed to be well accepted, with approximately 5000 engines in use by 1950, but its reputation was irreparably damaged by crankshaft and rocker failures. Almost certainly the MAP engine would have significantly influenced the Rootes TS3, but the latter developed significantly higher performance than the MAP and had a very successful reputation for ruggedness and durability. It is interesting to remember that Rootes TS3 eventually sourced crankcase castings from Usines Mktallurgiques in France.

4.5 Rootes Cornrner TS3 and TS4 4.5.1 Introduction The concept of a two-stroke diesel engine for light-medium duty trucks was popular in mid-Europe both before and after WWII. Various companies, including Saurer and Sulzer in Switzerland;Foden and Ford Motor Company in the United Kingdom; MAP in France; Sudwerke, Krauss-Maffei, and Atlas in Germany; and Graf and Sift in Austria (Ref. 4.6), experimented with uniflow and loop-scavenge configurations. Professor Hans List of Anstalt fiir VerbrennungskraftmaschinenList (AVL) was known to have consulted on two-stroke truck engines between 1945 and 1960, and some notable two-stroke diesel engines emerged in the United States, Germany, France, and the United Kingdom.

truck chassis with the “Rootes Diesel” TS3 two-stroke, folded-crankshaft, three-cylinder opposed piston diesel engine. The combination became an iconic vehicle and engine and remained in production and service until 1974, when Rootes’ new owners, the Chrysler Corporation of the United States, decided that their new U.K. truck division should use outsourced four-stroke diesel engines, in spite of the development of a four-cylinder version (TS4) of the TS3. The “TS” designation stood for Tillings Stevens, an innovative and leading specialist vehicle manufacturer that had been absorbed into the Rootes Group. Tillings Stevens was based in Maidstone (Kent, United Kingdom), some 200 km from the main Rootes plant in Coventry. From its early days, the TS3 found favor with medium duty vehicle manufacturers for both truck and coach applications. The TS3 engine, in conjunction with the Junkers Jumo 205E, became the inspiration and workhorse of the U.K. Fighting Vehicle Research and Development Establishment (FVRDE), leading to the H30/K60/L60 opposed piston engine “family” used in British military vehicles through the early twenty-first century, and described in Chapters 5 and 7.

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In 1954, the U.K. Rootes Group introduced the new seven-ton, medium duty

The TS3 was undoubtedly inspired largely by the Sulzer ZG series (Chapter 7) that was initiated in 1936 for rail traction, marine, and stationary use. It had cylinder sizes of -0.7-1.5 L, but operated to only -1300 rpm, in contrast to the 2400 rpm rated speed of the TS3. The architecture of the French MAP engine mentioned previously, almost certainly also influenced the design of the Rootes TS3.

Next Page

Automotive Opposed Piston Engines

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Fig. 4.1 8 Four-Cylinder 5L MAP Engine Installation in Delahaye Prior to 1952 Le Mans 24-Hour Race, Showing Fuel Pump [Reproduced courtesy of Arnoud Payet, France]

Fig. 4.1 9 Four-Cylinder 5L MAP Engine Installation in Delahaye prior to 1952 Le Mans 24-Hour Race, Showing Transverse-Mounted Scavenge Blower at Front of Vehicle [Reproduced courtesy of Arnoud Payet, France]

143 xvutsroigeaP

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zyxwvutsr Chapter 5

MILlTARY 0 PPOS ED PISTO N EN G I N ES 5.1 Introduction

While many countries have used and continue to use OP engines for military applications, battle tank engines (Table 5.1) have moved mainly to four-stroke engines after various experiences with OP engines, particularily in the United Kingdom. This chapter focuses on three land-based engines-the United Kingdom Leyland L60 battle tank power unit, the smaller Rolls Royce K60 power unit for armored personnel carriers, and the Ukrainian Kharkiv Morozov 6TD battle tank engine. These engines are still in use, forty years after their introduction. The common element between the United Kingdom L60 and K60 engines was the desire for multifuel capability. The engines can use -50 cetane diesel, a United States JP-4 (jet propulsion fuel type 4) type fuel known as AVTAG in the United Kingdom, a -74 Research Octane Number (RON) gasoline with 0.4 cc/L tetra-ethyl lead (TEL), -80 RON gasoline with 0.8 cc/L TEL, and regular and premium grade United Kingdom and northwestern European gasoline fuels, typically having 2.2-2.6 cc/L TEL, and Reid vapor pressures to 0.83 bar. The United Kingdom military laboratories of the era concluded that the ability to operate on this wide range of fuels would be best addressed by using combustion chambers and cylinder bore-to-stroke ratios with minimal surface area-to-volume ratio, and with the combustion chamber surface temperatures at the highest safe-maximum limit possible with piston materials.

Military OP engine applications discussed in other chapters are the Napier Deltic (Chapter 6), the Junkers Jumo 205 (Chapter 3), the Jumo 207 (Chapter 3), the Coventry Climax H30 (Chapter 7), the Fairbanks Morse 38D% (Chapter 7), the Fairbanks Morse Diamond engine (Chapter 9), and the OPOC'" modular engine (Chapter 4). Some military OP engines from Rolls Royce are briefly described in Chapter 9, as is the AED OP development mule. Among the ground-based engines not included, because of limited information, are the Renault OP engine for the AMX battle tank, used by the French army from 1960 to 1980, and other smaller Morozov engines used for light-, medium-, and heavy-duty military trucks in Russia and the Ukraine.

5.2 Leyland L60 5.2.1 Introduction The Leyland L60 OP engine was the United Kingdom's main battle tank engine from 1960 to 1990, and was one of a family of three military OP engines that also included the Coventry Climax H30 three-cylinder engine of 0.993 L displacement and the Rolls Royce sixcylinder K60 of 6.57 L displacement. The United Kingdom military planners, understanding that multfuel capability was a requirement in the post WWII European situation, adopted the OP two-stroke configuration because it offered:

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Opposed Piston Engines: Evolution, Use, and Future Applications Country

China

Germany

Israel

X I 50-960

M B883

AVDS 1790-9A

4

4

4

Norinco

MTU

Continental

Main Tank Application

T80

Leopard 3

Mer kava-3

Rated Power (kW)

71 6.

1119

895

Rated Speed (rpm)

2200

3000

2400

Engine Ref. Two- or Four- Stroke Manufacturer

I Displacement (L)

I

Number of Cylinders

34.6

I

27.4

I

29.3

12

12

12

Configuration

v-90”

v-90”

v-90”

Engine weight (kg)

1600

1800

2223

Engine Box Volume (m3)

1.2

1.3

3.1

Specific Power (kW/L)

20.7

40.8

30.6

I PowerIWeight (kW/kg) PowerIBulk (kW1L) Estimated bsfc (25:l AFR)(g/kWh) Estimated bsfc (30: 1AFR)(a/kWh) BMEP at rated Power

I

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Cooling (L = liquid, A = Air)

0.45

I

0.62

I

0.40

0.58

0.85

0.29

25 1

252

NA

209

210

NA

11.3

16.3

15.3

L

L

A

I

Table 5.1 Comparative Data for Battle Tank Engines

Minimal top dead center (TDC) surface area-to-volume ratio with acceptable bore-to-stroke ratio, Possibilities of a lenticular, or “clamshell,” combustion chamber with minimal surface area-to-volume ratio, A well “insulated combustion chamber, Ease of generated high swirl, Use of minimum numbers of nozzle holes, thus reducing the fuel injection pressure and fuel filtration requirements, Mechanical simplicity.

These points were reinforced by tests of the Jumo 205 (Chapter 3) and the very successful existing Rootes Tilling Stevens TS3 (Chapter 4) commercial vehicle engine, which was the subject of various military, industrial, and academic investigations. But battlefield functionality requirements of the L60 led to an engine layout that was very different from the Jumo 205 or the TS3 layouts.

Military Opposed Piston Engines Japan

Ukraine

I

V-92S2

CV12

I

6-TD2

2

I

4

4

I

2

I

26.1

I

16.3

I

I I

United

10ZG

I

II

Russia

I

zy

I

Mitsubishi T-90s I

IAZ I

I I

21.5

I

38.9

I

* v-900

v-900

12

6

V-60'

Horizontal OP

I

19.2

I

I I

I

0.50

I

0.73

0.48

I

I

17.9

L

5.2.2 Engine Specification

I

I I

0.76

12.7

L

I

I I

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The L60, with bore x stroke of 117.5 mm x 146 mm (x 2), had a specific output of 27.5 kW/L. This was commendable for its era, bearing in mind that current turbocharged (TC) four-stroke truck engines typically only achieve 27 kW/L in turbocharged form, albeit with a very clean exhaust (low emission), which was not the case for the L60. The L60 rating was similar to the takeoff power rating of the Jumo. The bore-to-stroke ratio of 0.8 was significantly

higher than the 0.66 of the Jumo 205E, and was probably related to the tighter package requirements of power units for ground vehicles. Power-to-package volume of the L60 was 330 kW/m3,very similar to the 340 kW/m3of the Jumo 205E, and powerto-weight ratio was approximately 0.2 kW/ kg with the full power pack, i.e., -20% of the 0.86 kW/kg value of the Jumo 205E. As will be seen, the main reasons for these differences were the choice of materials for the main engine castings and the very dif-

181

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Opposed Piston Engines: Evolution, Use, and Future Applications ferent level of auxiliaries required by these two engines.

5.2.3 General Architecture The constructional similarities of the Jumo and the L60 (Fig. 5.1 and Fig. 5.2) were essentially in the use of a single-piece crankcase casting and the adoption of a five-spur gear drive (Fig. 5.3) between the two crankshafts (Ref. 5.1 and Ref. 5.2). Like the Jumo, the main output drive was on the gear next to one of the crankshafts, though in the case of the L60 the gear was next to the lower crankshaft and there was no torsional isolator on this gear. Otherwise, there was little similarity between the L60 and the Jumo. Whereas the Jumo grouped its oil, fuel, coolant, and scavenge pumps in a modular unit at the rear face of the engine, the L60 had an additional six pumps, a very large

positive displacement blower, and a battery of fuel and lubricating oil filters and heat exchangers that were distributed on the sides of the engine. These auxiliaries tripled the width of the L60 engine relative to the base crankcase width. The single-unit twelve-plunger fuel pump (Fig. 5.4, Fig. 5.5, and Fig. 5.6) was also very prominent on the L60 compared to the 12 standalone pump units on the Jumo.

The flywheel or “nodal” driven end of the engine, in addition to having the five-spur gear drive between the crankshafts, had another two spur gears providing drives along the engine’s sides, while the front end of the engine had a seven-spur gear drive, again for the auxiliaries on the sides of the engine. These drives are elaborated in Section 5.2.4.7.

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Fig. 5.1 Longitudinal Section of L60 Base Engine [Reproduced courtesy of FVRDE Symposium on Multi-Fuel, Nov. 1959, United Kindgom]

Military Opposed Piston Engines

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Fig. 5.2 Part Sectioned L60 Engine with Air Chest Removed to Show Liners [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

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Fig. 5.3 Spur Gear Drive between Crankshafts at Driven End of Engine [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

183

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Opposed Piston Engines: Evolution, Use, and Future Applications

Fig. 5.4 Left-Hand View of Fully Dressed L60 Engine, with Radiator Horizontal [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

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Fig. 5.5 Diagram of Left Side of L60 Engine, without Radiator [Reproduced courtesy of FVRDE Symposium on Multi-Fuel, Nov. 1959, United Kindgom]

184

Military Opposed Piston Engines

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Fig. 5.6 Fuel Pump with 12 Outlets and Hydraulic Governor [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

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The exhaust manifolds on the left side of the engine are more visible (Fig. 5.2 and Fig. 5 . 5 ) , in spite of the heat shield and heat exchanger, than those on the right side of the engine, as are some of the 12 injectors, below the exhaust manifold. The second coolant-outlet manifold and its thermostat are above the exhaust manifold, symmetrical with that on the right side of the engine (Fig. 5.5). The fuel pump and hydraulic governor are driven from the free-end gear train via a short driveshaft visible on the middle left-hand side of Fig. 5.4 and Fig. 5.5, while the coolant pump with its vertical entry spout, which was a twin to the other coolant pump, was driven from the rear gear train shown on the right side of Fig. 5.4 and Fig. 5.5. At a lower level, the front gear train shown on the left side of Fig. 5.4 and Fig. 5.5, provided a drive for a generator of up to - 190 mm diameter, or -4.3 kW maximum. A hydraulic starter motor, used when the battery charge was inadequate, was connected to a hydraulic

source powered by a Coventry Climax H30 auxiliary opposed piston engine (see Chapter 7).

As viewed from the driven end of the engine, the right side of the engine (Fig. 5.7 and Fig. 5.8) was dominated by the Roots blower driven from the free end (front) gear case (Fig. 5.9) and delivered directly to the air ports, three voluminous lubricating oil filters, and two fuel filters. Tucked around these were the oil pressure and scavenge pumps (again driven from the very prominent front gear case), one of the twin coolant pumps driven from the rear spur gear set, the electric starter motor, and a myriad of water and oil connections with a coolant-and-oil heat exchanger. The two exhaust manifolds are barely visible behind the filters and heat shields, their outlets exiting to the top left side of Fig. 5.7, and the cylinder liner locators are also obscured by the blower and coolant pump. Part of the coolant

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 5.7 Right-Hand View of Fully Dressed L60 Engine [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

outlet manifold, with its thermostat, is visible above the fuel filters, and the rightside engine mount is visible towards the bottom left side of Fig. 5.7. Each crank-

shaft carries a large inertia disc, mounted at the free end. These are torsional tuning inertias. The main flywheel is on the output drive gear (Fig. 5.1).

Fig. 5.8 Diagram of Right Side of L60 Engine, without Radiator [Reproduced courtesy of FVRDE Symposium on Multi-Fuel, Nov. 1959, United Kindgom]

186

Military Opposed Piston Engines

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Fig. 5.9 Transverse Section of L60 Engine, with Scavenge Blower and Oil Pumps on Right-Hand Side (RHS) [Reproduced courtesy of FVRDE Symposium on Multi-Fuel, Nov, 1959, United Kindgom]

The engine had its own low- and highpressure hydraulic pumps that were driven directly from the rear end of the exhaust crankshaft, and from the first intermediate gear meshing with the exhaust crankshaft (Fig. 5.1 and Fig. 5.5).

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ence was superficial and primarily due to the particular auxiliary package needed for battle tank propulsion units. The base engine architecture of the L60 was the same as most other OP engines.

5.2.4 Key Features By bolting the principal flywheel to the first gear in mesh with the gear on the rear of the air crankshaft, the engine compactness was considerably enhanced. This arrangement avoided the usual flywheel overhang associated with flywheels attached directly to crankshafts. Dry basic engine weight was 2045 kg, and 2676 kg in its full power-pack form. The firing order was 1,6, 2,4,3, 5. While externally the L60 was very different to any previous OP engine, this differ-

5.2.4.1 Crankcase and Main Bearings

The L60 crankcase (Fig. 5.10) was a singlepiece grey iron casting containing the six cylinder tunnels (Fig. 5.1), each of approximately 620 mm in length and 147 mm internal diameter locally to take the liner sealing lands. By using a substantially stiffer crankshaft compared to the Jumo 205E, the L60 avoided the use of thick overhanging aluminum shells to support the steelbacked copper/lead bearings. As with most heavy duty engines with cylinder bore

-

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 5.10 View of Left-Hand Side of Crankcase, Showing Scavenge Port Chest and Injector Apertures [Reproduced courtesy of m i Technology Group, Leyland, United Kingdom]

sizes in excess of 90 mm, each main bearing cap was secured by four main bearing studs. The axes of the inner pair of these main bearing studs were on the mean wall “circumference” of the cylinder tunnels, which formed the main load path for the resultant forces on the crankshaft. The main bearing caps (Fig. 5.9) were triangulated in section, the outer stud bosses being only half the height of the inner stud bosses, enabling a more compact sump profile. The stud engagement into the cylinder block was approximately 45 mm, or three x stud diameter. Upper and lower crankcase faces were stepped to provide main bearing cap location, the outer flange offering flat sealing surfaces. Blow-by and oil drains were provided by the front and rear covers.

A large polygon-shaped steel faceplate (Fig. 5.11) was bolted to the front face of the crankcase, forming the rear face of the front auxiliary drive casing and carrying the mountings for the oil pump, blower, injection pump, and generator drives (Fig. 5.9). A similar large polygon-shaped steel faceplate (Fig. 5.12), was bolted to the driven face of the crankcase, with an extended portion towards the lower half of the engine, forming the backplate for the rear timing drive and auxiliary mounting cover. This backplate had mounting points for five timing and auxiliary drive gears and the two starter motors and water pumps mounted on the front side of the flange.

Military Opposed Piston Engines The crankcase/cylinder block had a coolantflow manifold above the entry to the scavenge port belt (Fig. 5.10), and was supplied with coolant from the twin coolant pumps via bolt-on manifolds on each side of the cylinder block. The coolant flow manifolds, with their six entry ports on each side of the cylinder block, were connected to the six cylinder tunnels, each of which was divided into six segments along the height of the liner. The coolant flowed equally up and around each cylinder, rising through a series of horizontal divisions in each cylinder tunnel. Coolant flow in each cylinder tunnel (Fig. 5.1) therefore, began above the scavenge port belt, continued to a gallery surrounding the inner dead center (IDC) position of the lower two compression rings of the air piston, then into the coolant gallery surrounding the injectors and IDC combustion volume. meflow in this was helical due to the grooved cooling slots

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zyxwv Fig. 5.1 1 Front-End Auxiliary Gear Train [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

Fig. 5.1 2 Rear-End Auxiliary Gear Train [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

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Opposed Piston Engines: Evolution, Use, and Future Applications in the liner. Coolant flow then entered the gallery surrounding the IDC position of the lower two compression rings of the exhaust pistons before passing over a cored gallery surrounding the exhaust ports and the main exhaust collector into each runner of the exhaust manifold. A large collector gallery above the exhaust ports fed the coolant flow into coolant-return manifolds on each side of the engine, each regulated by a thermostat (Fig. 5.5, Fig. 5.8, and Fig. 5 .9) that was located approximately in line with number 2 cylinder from the front (free end) of the engine. Two main lubricating oil supply galleries can be seen on the left-hand side in Fig. 5.9, each located at approximately the same level as the ends of the cylinder liner and emerging on the front and rear faces of the cylinder block. Oil entered these drillings from the full-flow filters

via two external oil pipes-one relatively short pipe to the upper oil gallery, and a substantially longer oil pipe to the lower gallery (Fig. 5.13). 5.2.4.2 Crankcase Covers

The L60 had eight major crankcase covers: upper cover, lower cover, three at the front, and three at the rear. Both front and rear covers were large and “sewn” to the crankcase with multiple bolts, and each pair was stiffened with a steel stiffening plate. The lower front cover (Fig. 5.7 and Fig. 5.8) contained the free-end auxiliary gears that drove the scavenge blower, oil pumps, and generator, and was connected to the hydraulic starter. The upper, narrower section of the front cover acted mainly as an oil return and blow-by path for oil emerging from the exhaust crankshaft. The same oil provided lubrication for the gear train.

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Fig. 5.13 Isometric of L60 Showing Oil and Coolant Flow Paths [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

Military Opposed Piston Engines The rear nodal drive cover (Fig. 5.5) was of a more constant depth as the rear gear train extended from the air to exhaust crankshafts and had mounting flanges, or cavities, for the twin coolant pumps, the low- and high-pressure hydraulic pumps, and the twin vee-belt drive pulleys. The rear cover engaged with a similarly shaped steel flange plate that formed one half of the bearing carriers for the gear train (Fig. 5.13). The other bearing supports were in the rear cover. The electric starter motor and coolant pumps were mounted off this plate. The upper rear cover, which bolted directly to the rear of the block, also provided an oil return from the upper sump to the rear gear train, and also was a blow-by vent. The upper cover was a relatively simple half-cylindrical casting with semicircular closed ends and internal ribbing (Fig. 5.1). The lower cover, also a half-cylindrical casting with a semicircular closure at the free end, had a cast gallery on the blower side (Fig. 5.13). This gallery was connected at the front of the cover to the oil scavenge pumps that were mounted below the blower. The lower cover was fitted internally, at its lowest point, with a splash plate to contain the oil prior to entry into the scavenge gallery.

Fig. 5.14 L60 Liner with Helical Coolant Flow Slots [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

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5.2.4.3 Cylinder Liner

The high-grade cast-iron cylinder liner (Fig. 5.14) was -616 mm in length, or 2.1 x total stroke, of 4.5-5.0 m m nominal wall thickness, approximately 127 mm nominal outer diameter and locally about 147 mm at the sealing land outer diameters, of which there were five sets, one each side of the exhaust port belt, one at

each end of the liner (one of these serving also to seal the lower edge of the air plenum at entry to the inlet ports), and one at the upper edge of the inlet port. This left 137 m m of liner “uncooled” below the air ports to support the piston skirt at outer dead center (ODC). Instead of using elastomer O-ring seals as the Jumo 205E did, each sealing belt had a cast sprung lip, as exemplified on the TS3 engine that preceded the L60. The cylinder liner sealing lands and the cor-

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Opposed Piston Engines: Evolution, Use, and Future Applications responding female bores in the crankcase had progressively larger diameters from one end of the liner to the other, allowing easier insertion of the liner.

The central section of the liner had approximately 20 cast helical slots covering -48% of piston travel, the helix making approximately a quarter turn over this distance. This portion was also chrome plated to reduce cavitation damage. The helical slots were effectively sealed on their outer diameter by the crankcase walls. Liners for later engines were distinguished by a thicker section at the very center of the liner, which was introduced to reduce the tendency for cylinder cracking from the injector holes due to vibration of the liners. The cylinder liner was located by the flanged plug, which was a close sealing fit on the noninjector side of the liner. These plugs are visible in Fig. 5.9, above the right-hand air chest. Connecting rod shank accommodating slots were at each end of the cylinder liner, which were thought to be one of the sources for oil consumption, but were necessary in order to minimize the engine height. Each liner had eight exhaust and eight scavenge ports. The overall exhaust lead was 25.25" crank angle (CA) (Fig. 5.15), of which 12" was from the exhaust crankshaft phasing relative to the air crankshaft. The exhaust ports opened at -1 11" after inner dead center (AIDC) relative to the exhaust crankshaft. The scavenge ports opened 136" AIDC relative to the exhaust crankshaft. The liner bores were prefinished with carbide impregnation prior to honing, using the famed "Laystall" process.

192

5.2.4.4 Crankshaft

Both six-throw crankshafts were machined from billets of chrome molybdenum steel forgings, were heat treated, and nitrided. Crankpins and main journals were 65% and 88%, respectively, of the cylinder bore diameter. These values were more typical of the bearing sizes of naturally aspirated four-stroke truck engines. This robust sizing of the crankpins and main journals eliminated the need for overhanging main bearings, in contrast to the Jumo 205E main bearing support inserts. Crankpins were supplied with oil from their adjacent main journal, which received oil from the main bearing oil groove. The relatively large cylinder centers of -145 mm, or 1.38 x bore diameter, compared to typical modern automotive values of < 1.1 x bore, also allowed the generous crankshaft proportions. Twelve balance weights were used for rotational balance of the main bearing inertia loads. Main bearings and thrust washers were of the "thinwall" steelbacked aluminum tintype. 5.2.4.5 Connecting Rod and Bearings

The heat-treated alloy-steel connecting rods (Fig. 5.9 and Fig. 5.16), with a length/crank radius of 3.3, had a classical H-section shank with two fixing nutsand-bolts for the straight split big-end cap. The rod was drilled from the big- to small-end, the outer radius of which was machined to match the radius of the oil collector cap fitted to the underside of the piston (Fig. 5.9). Aluminum-tin thinwall bearing shells were fitted to the connecting rod big-ends.

Military Opposed Piston Engines

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Fig. 5.15 Timing Diagram for Ports and Fuel Injection [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

Helical grooves were used in the lower half of the small-end bearing to distribute the oil arriving from the connecting shank drilling. 5.2.4.6 Piston and Rings

Overall piston length (Fig. 5.17) was 1.140 x half stroke, with the portion above the wrist pin axis occupying 56% of the half stroke. Heat losses to the piston, rings, coolant, and oil were minimized by the two-piece piston construction (Fig. 5.16 and Fig.

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5.17). The semilenticular nickel cast iron crown-and-flame plate had oil circulation grooves on its underside. The crown/ flame plate spigotted into an upper bore of the main cast iron piston body, which was tinplated. The crown element carried a tall, pegged, gapped ‘‘I? sectioned cast-iron fire ring that sat on a rectangular compression ring. Two other pegged single taper-sided compression rings were in the piston crown. A stepped port sealing ring and a slotted oil control ring were fitted near the base of the piston skirt.

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 5.1 6 L60 Connecting Rod, Piston, and Rings [Reproduced courtesy of mi Technology Group, Leyland, United King do m]

Fig. 5.17 Section through L60 Liner, Piston, and Injector [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

The crown was secured to the skirt by four very short bolts that engaged with relatively short threads in the underside of the crown, A seal was used between the piston crown and skirt to prevent any oil loss at this joint. Two shallow grooves on the periphery of the piston crown accommodated the two iniector dumes.

small-end and took some of the residual oil from the small-end groove to the under-crown piston area. The springloaded oil cap was fixed by several set bolts into the top face of the piston body, between the wrist pin bosses.

A fully floating hollow steel wrist pin, of length equivalent to 88% cylinder bore, was located by fully circular end caps. The piston bosses had bronze inserts. A spring-loaded oil cap (Fig. 5.9), located in the underside of the main piston body, rode on the oscillating outer radius of the

5.2.4.7 Gear Train

As noted in Section 5.2.3, the L60 had a nodal-drive gear train (Fig. 5.3 and Fig. 5.1 l),which connected the two crankshafts and drove auxiliaries and a freeend gear train (Fig. 5.12) that drove the front-end auxiliaries.

The nodal-drive gear train (Fig. 5.3) had seven spur gears, three of which were

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Military Opposed Piston Engines idlers. The small idler, in mesh with the air crankshaft gear, was the main output gear carrying the flywheel and starter ring, operating at 1.249:l crankshaft speed. The center gear was in mesh with the coolant pump drives on the left and right side. The main intercrank gears were “straddle mounted,” i.e., supported on both sides by rolling element bearings-on the engine side in hardened bearing cups rigidly located on the steel carrier plate, and on the flywheel side by similar hardened cups press-fitted into the rear gear case cover. The free-end auxiliary gear train (Fig. 5.12) also had seven spur gears of which two were idlers. Like the driven end gears, most of these were straddle-mounted in rolling element bearings. On the right side, as viewed from the free end, the idler drove a small pinion of a high-speed generator on its lower side. On the upper side, the idler meshed to provide crankshaft speed to the fuel injection pump. On the left side, the other idler drove the pinion for the oil scavenge and pressure pumps. The upper pinion provided the drive to the Roots scavenge blower.

scavenge blower. A relatively small portion of this flow was diverted to a separate centrifugal “bypass”filter, and then returned to the lower cover through a large external pipe at the front of the engine. The main triple element filters provided filtration for particle sizes above - 10 microns diameter, while the centrifugal filter removed the much finer particles, probably down to -1 micron. It was these finer particles that tended to produce wear of lubricated elements such as the bearings, piston rings, and piston skirt. Although the centrifugal filter only filtered a small portion of the main flow from the oil pressure pump, all of the sump oil was passed through this centrifugal filter, probably in less than an hour. Thus all the engine oil was repeatedly passed through this very effective filtration system. The three element filters, which handled the coarser particles and debris, were linked by a common outlet rail. The filtered flow at the rear of this rail was taken by an external pipe to the main oil gallery for the air crankshaft and to the cooling fan hydraulic hub motors, while the filtered oil from the front of the rail was supplied through a shorter external pipe to the main oil gallery for the exhaust crankshaft. A very small quantity of oil, from the pressure oil pump, was diverted before reaching the element filters and sent by two small external pipes to lubricate the front and rear bearings of the Roots-type scavenge pump. Excess oil flow from the oil pressure pump was routed directly back to the external oil tank.

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5.2.4.8 Oil Pump and lubrication System

A dry sump system (Fig. 5.13) was used on the L60 to cope with the wide range of pitch and yaw inclinations experienced by a battle tank, and also because the compressed engine height did not allow for an “internal” dry sump in the lower engine cover. At oil temperatures below llO”C, oil (indicated in Fig. 5.13) from the pressure pump (Fig. 5.8, bottom right-hand corner) first traveled to the element filters, bypassing the substantial oil cooler located below the

The oil gallery supplying the exhaust crankshaft also supplied oil via jets to the upper two timing gears at the rear of the engine. The oil gallery supplying the air crankshaft

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Opposed Piston Engines: Evolution, Use, and Future Applications supplied the injector pump and the lower three timing gears at the driven end and the gears at the free end of the engine. Both crankshafts and piston sets received oil from the main galleries via individual drillings to the main bearing oil grooves that connected with oil grooves in the connecting rod big-end bearings. Oil from the big-end bearings then travelled along central drillings in the connecting rod shanks to the slipper bearing on top of the small-end of each connecting rod, and then to the under-crown cooling of the pistons. Both ends of each crankshaft were drilled with squirt holes to lubricate the attached gears.

Above 110°C oil pressure pump-delivery temperatures, a thermostatic valve diverted the oil through an external connection to the oil cooler (Fig. 5.18), which rejoined the main oil routing to the oil filters at its outlet.

All oil within the crankcase returned to the lower sump cover via the front cover, rear cover, one external drain from the upper crankcase, two external drains from the scavenge blower, an external drain from the centrifugal filter, and a return line from the fan hydraulic-hub motors at the driven end of the engine. This draining oil was routed by a longitudinal gallery in the lower cover connecting to two short external transfer pipes to the oil scavenge pumps, which then

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Fig. 5.1 8 Underside View at Driven End Showing Sump, Twin Oil Coolers, and Hydraulic Pump for Powering Fans [Reproduced courtesy of mi Technology Group, Leyland, United King do m]

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returned the oil through an external pipe to the de-aerator and oil tank.

The oil pressure pump, driven from the free-end gear train (Fig. 5.9), was a paired spur-gear set. The twin scavenge pumps were formed from three meshing gears, also driven from the same gear as the pressure pump. Delivery flow was 4.5 L/s at 4 bar pressure. The oil cooler (Fig. 5.18) was of the multitube type. The oil flowed through a cluster of small-diameter aluminum tubes that passed through the bulk of the coolant in the cooler.

After circulating around the cylinder liners through the engine cooling system, the coolant flow was passed through each open thermostat, which was located at the high point on each coolant outlet manifold to the left- and right-hand radiators (Fig. 5.20), each with its own 560 mmdiameter fan. Each thermostat also had steam vents to the header tank of each radiator. Various types of thermostats have evolved during the life of the L60. The radiators in Fig. 5.20, shown in a “maintenance” position, could be rotated to a horizontal position for installation in the vehicle (as shown in Fig. 5.4). The cooling system was designed to operate in 50” C ambient temperature and included coolant flow to and from the auxiliary H30 engine (Chapter 7), which provided the drive for the major hydraulic pumps powering the turret and gun movements, as well as providing an auxiliary hydraulic start fluid for the L60 engine in case of low battery voltage.

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A separate reservoir and circuit was provided for the hydraulic governor of the fuel injection pump. The governor used a dedicated lubricant. 5.2.4.9 Coolant Pump and Circuit

The two major cooling fans, mounted at the sides ofthe engine (Fig. 5.19), were driven by hydraulic hub motors, also visible in Fig. 5.20, in the center of each fan. The motors were supplied by pressurized hydraulic fluid from a pump mounted at the driven end of the exhaust crankshaft (Fig. 5.1). The two coolant pumps (Fig. 5.2), driven from the rear gear train, each separately received coolant from the radiator outlets and the bypass flow from each thermostat located on the coolant outlet manifold (Fig. 5.5 and Fig. 5.8). The coolant pumps delivered their flow to the coolant inlet manifold on each side of the engine, to the gearbox oil cooler on the left side of the engine (viewed from the driven end), and the engine oil cooler on the right side of the engine.

5.2.4.10 Air Delivery System

Air delivery was from a Roots-type, twinrotor, positive-displacement blower that was fixed by studs and dowelling to the cast inlet manifold on the right side of the engine (Fig. 5.7, Fig. 5.8, and Fig. 5.9) and was driven from the front gear train at 1.667 x engine speed by a compliant coupling. Each cast-aluminum rotor had three straight lobes that contra-rotated by a pair of spur gears at the driven end of the blower, i.e., adjacent to the free-end gear train of the engine. These gears were mounted to chrome molybdenum steel shafts that were cast into each rotor. The

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Opposed Piston Engines: Evolution, Use, and Future Applications

Fig. 5.1 9 L60 Engine with Cooling Pack Ready for Installation [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

Fig. 5.20 L60 Engine with Cooling Pack Elevated for Maintenance [Reproduced courtesy of mi Technology Group, Leyland, United Kingdom]

Military Opposed Piston Engines shaft protruded at either end of the rotors and was supported by a pair of ball races at the driven end and a pair of cylindrical element rolling element bearings at the free end. There were five elements to the aluminum blower casing-two end covers to allow inspection of the bearings, two bearing carriers (each with iron inserts to prevent thermal bearing relaxation), and the main rotor casing that was heavily ribbed to reduce panel vibration and noise from the sharp pressure waves that occur during the backflow compression of the air. The main air entry was via a large racetrackshaped port on the outside face of the blower casing (Fig. 5.7) that was angled diagonally relative to the rotor axes in order to attenuate some of the noise effects, both in terms of noise initiation and noise reflection into the induction system upstream of the blower. Pressurized lubrication was provided independently to the driven end gears and bearings, and the free end bearings, via two external oil pipes. Separate drains came from the driven- and free-end blower covers. Air sealing of the rotors was accomplished with longitudinal raised sealing strips in the main rotor casing and cylindrical piston ring seals around each rotor at the rotor ends. Great care was taken to avoid oil ingress into the air delivery to the engine, as lubricating oil has very high cetane quality and would auto-ignite within the cylinders and generate run-on of the engine. Gases accumulating in the end covers of the scavenge blower were

vented via external pipes to the main engine breather system. Maximum air delivery was 1.06 m3/sec at a delivery pressure of 0.48 bar gauge, absorbing about 75 kW of engine power. 5.2.4.11 Air and Exhaust Manifolds

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The air chest (Fig. 5.2 and Fig. 5.9) was a rectangular section, open, aluminum casting that bolted to the cylinder block casting around the inlet ports. The outside of the manifold had a large flange to which the outlet port of the Roots scavenge blower was bolted. On the other side of the cylinder block (Fig. 5.9) was a slightly more compact cast-aluminum air chest to ensure even distribution of the air between the cylinders. The exhaust gas exited via a pair of threeinto-one cast-iron log-type manifolds (Fig. 5.5, Fig. 5.7, Fig. 5.8, and Fig. 5.9) on each side of the engine. The front manifold had a connecting section that ran parallel to and above the rear manifold. The rear manifold had a much shorter connecting section to bring it to the rearconnecting flange with the exhaust system. There were therefore six cast pieces for the whole exhaust manifold assembly, and the cast manifold material would probably have been of a high silicon/ molybdenum iron to withstand the high exhaust temperatures. 5.2.4.12 Fuel Injection System, Auxiliary Start Injectors, and Starting Equipment

Twelve pump outlets (Fig. 5.5 and Fig. 5.6) distinguished the inline CAV jerk pump of the L60, supplying the twin injector/ cylinder arrangement on the left side of the engine. The twin injectors were phased

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Opposed Piston Engines: Evolution, Use, and Future Applications by 10" crankshaft timing, with the second injector of the pair, (injector 4), firing first into cylinder 2. The pump was driven from the gear train at the flywheel end of the engine, via a steel coupling that had some compliance to tolerate installation misalignment. The pump was controlled by an all-speed hydraulic governor mounted on the end of the pump (Fig. 5.6). Fuel arrived at the center of the body of the fuel pump from the element filters and was distributed via a longitudinal gallery to all the plunger entry ports. The plungers and cam bearings also received oil from the engine lubricating circuit, which enabled these components to tolerate gasoline fuel types that had very low lubricity. The plungers were distinguished by having reverse helixes, which resulted in the injection system having a variable start of injection with load, but a fixed end of injection, with little inherent speed advance or retard. With the fuel rack closed, there was 6" crankshaft timing and injection retard, versus the full-load injection timing. Each injector had a single-hole nozzle and the injectors were located in holders (Fig. 5.17) at approximately 45" included angles (Fig. 5.10) to each other, and targeted off the cylinder center and in different planes so as to capture as much of the air as possible without spray plume interference. All injectors and the pump had return lines that joined the main recirculation flow to the fuel tank.

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For extreme conditions of -35"C, two alcohol-start pilot injectors were located in the scavenge air chest, on either side of the scavenge pump connection to the air chest. These injectors sprayed highly volatile alcohols, such as ether, into the scavenge air to ensure adequate vaporization time for compression ignition. It is thought that these start injectors were manually operated.

A 150 mm-diameter electrical starter motor enabled starts down to - 17°C. A hydraulic starter motor was also supplied for starting below - 17°C. This hydraulic starter motor was supplied with hydraulic fluid from the slave H30 engine (Chapter 7). 5.2.4.13 Engine Mounting

The front of the L60 was supported by a three-point mounting system located approximately on the roll axis. At the free end, there was a single trunnion above the gear train with a radial rubber bush. The driven end had spherical rubber elements in a trunnion on either side of the engine (Fig. 5.2).

5.2.5 Performance 5.2.5.1 BMEP, Power, Fuel Consumption, and Boost Pressure

Maximum torque of the L60 was 1923 N.m at 1900 rpm with maximum power of 518 kW at 2810 rpm governed speed (Fig. 5.21), corresponding to 27.3 kW/L. This is a creditable value for a naturally aspirated diesel engine and similar to the specific output of the Rolls Royce K60 engine, though the latter achieved the same rating at -400 rpm lower engine speed. Peak BMEP was 6.87 bar (Fig. 5.21) with a 0.5-0.8 bar drop on either side of peak torque speed. Best xvutsroigeaPN

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zyxwvutsr Chapter 6

MARINE OPPOSED PISTON ENGINES 6.1 Introduction

The OP engines discussed in this chapter range from the 7 kW American Marc outboard marine power unit of 1955, to the -3000 kW 18-cylinder Napier Deltic that has remained in service in United Kingdom naval vessels since 1955, to the 15,000 kW cathedral-style Doxford marine engines.

Other OP engines that had marine applications that are mentioned in other chapters are the Sulzer ZG type (Chapter 7), the Sulzer G type (Chapter 9), the Fairbanks Morse 38D8 (Chapter 7), and the Fairbanks Morse Diamond engine (Chapter 8). Some marine OP engines that are not included, due to either book size limits or inadequate material, are the Burmeister and Wain (B&W) engines, the Harland and Wolf 0s engines (licensed from B&W), and OP engines made for French submarines post WWII, possibly by Chantiers d’Atlantique.

6.2 Doxford 6.2.1 Introduction William Doxford began engineering work in 1840. From very humble beginnings, he created one of the largest United Kingdom shipyards, which, from 1925 to 1965, developed what was probably one of the most globally renowned directdrive marine engines. These “cathedral” engines (Fig. 6. l), which were simply called “Doxfords,”were successful derivatives of the early Oechelhaeuser engines and were initially licensed from Junkers.

Junkers themselves had pursued marine applications (see Chapter 2) but had not been successful, perhaps because of a lack of marine engine experience. As can be seen from Fig. 6.1 and Fig. 6.2, Doxfords followed the Gilles and Wittig-type configuration of three-throw crankshafts per cylinder, though Doxford was eventually forced to adopt a more compact crankshaft arrangement in order to mitigate packaging and torsional vibration issues.

At the height of its success, Doxford and its licensees were manufacturing approximately 70 engines a year-more than 400 MWIyear, with engine power rising from 504 kwlcylinder in 1919 to 1865 kwlcylinder in 1978. Doxford engines were known for their high power output, competitive fuel efficiency, simplicity, robustness, and balance versus single piston-plus-cylinder twostroke engines. The demise of Doxford can probably be traced to a reluctance to adopt key technologies such as turbocharging, and, perhaps more importantly,post WWII shortsightedness in refusing licenses to German, Italian, and Japanese engine manufacturers. These factors were compounded by an overall United Kingdom industrial malaise from 1960 to 1980 that arose from both poor industrial relations and the simultaneous rundown of the United Kingdom shipbuilding industry, bearing in mind that Doxford’s owners were shipbuilders as well as marine engine suppliers. Ironically, the coup de grAce for Doxford was probably the

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Opposed Piston Engines: Evolution, Use, and Future Applications result of a pan-European agreement to limit shipbuilding, made at a time when Doxford had an encouraging order book.

from the Doxford archives (Ref. 6.6 and Ref. 6.8), and considerable help from John Jordan, a retired Doxford engineer.

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The material in this chapter, which focuses primarily on the P- and J-type engines, is drawn from several excellent technical papers by Doxford engineers (Refs. 6.1, 6.2,6.3,6.4,6.5, and 6.7), information

6.2.2 Brief Histor"

6.2.2.1 Pre and Post WWI and the 1920s

After initial experimentation with several engine alternatives, gas fueling, and air-

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Fig. 6.1 Side Elevation of Doxford 580 mm Bore, 1 160 mm Upper Stroke, and 1 160 mm Lower Stroke, 1921 [Reproduced courtesy of V n e & Wear Archives Service, Newcastle upon Vne, United Kingdom]

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Fig. 6.2 Front Elevation of Doxford 580 mm Bore, 116 0 mm Upper Stroke, and 1 160 mm Lower stroke, 1921 [Reproduced courtesy of V n e & Wear Archives Service, Newcastle upon Vne, United Kingdom]

Marine Opposed-Piston Engines injection diesel engines, Doxford adopted liquid-only fuel injection and the OP configuration in 1919 with a 504 kW/cylinder (Table 6.1) engine operating at 77 rpm that was later successfully fitted into the Swedish motor ship Yngaren. Five of these engines were built and successfully installed in merchant ships. The power of these early Doxford OP engines

outstripped competing two- and fourstroke units.

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zyxwvut Early engines (Fig. 6.2) had two fan spray injectors located in the 25 m m wall thickness liner that was cooled by distilled water, in contrast to the usual practice of direct seawater cooling. Cast iron pistons were constructed with an outer shell

7 Comment

I

Prototype

Balanced Engine

+ Welded Structure

I

Economy Engine

Dominion Monarch

Trawler Engine

No Scavenge Pumps

I

"P" Type

1965

1865

760

520+1660

9

119

0.219

1971

1865

590

420+990

4

300

0.201

1978

1350

580

340+890

3

220

0.201

Table 6.1 Summary of Doxford Engine Development History

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22 5

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Opposed Piston Engines: Evolution, Use, and Future Applications carrying the piston rings. This arrangement was quickly replaced by steel piston heads with spherical dishes that formed the combustion space. The scavenging air for these four-cylinder engines was from double-acting piston pumps mounted in the middle of the engine. Unlike later engines, the fuel injectors were located in substantially offset planes. Design of a fully balanced engine began in 1926, which led to the use of differential strokes and reciprocating masses. The clamshell-type combustion chamber shape was also introduced about this time. Other United Kingdom shipyards showed interest in the Doxford design and built Doxford-configured engines on a royalty basis. However, torsional vibration problems were experienced, which was traced to the revised firing order necessary for a balanced engine. Vibration detuning of these balanced engines was achieved by replacing the driven end flywheel with smaller flywheels fixed to the driven- and free ends of the crankshaft. The balanced Doxford engine was adopted for the four-screw luxury liner Bermuda in 1928, marking a milestone for Doxford.

gated in 1921 for auxiliary power units, but they were not commercially fruitful, mainly because the competitor’s fourstroke medium-speed engine was too well established in these smaller bore sizes.

There was, however, one very different small Doxford engine. United States-based Sun Shipbuilding and Engineering Corporation, a licensee of Doxford Engines, in 1925 built a twin-bank Sun Doxford OP engine (Fig. 6.3) that had two rows of 13-inch (330.2 mm) bore cylinders arranged on a common bedplate, each with its own crankshaft driving a separate propeller. The stroke was 22 inches (558.8 mm) lower x 17 inches (431.8mm) upper, which combined was 39 inches (990.6 mm), with 4.97 bar Brake Mean Effective Pressure (BMEP) and rated at 560 kW per shaft at 200 rpm. The columns and entablature were of cast aluminum alloy. This was one of the first engines to have a differential stroke and was built for the motor yacht MV Sialia, which belonged to Henry Ford. The vessel continued to operate under different owners until well after WWII. No other engines were built to this design.

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Some smaller lower-power engines of 200-274 kW/cylinder with -400 mm cylinder bore, a combined stroke of 1300 mm, and three cylinders were developed in the late 1920s, potentially for land as well as marine use. The scavenge pump of these engines was driven by a lever mechanism attached to the center cylinder crosshead, and the oil and coolant reciprocating pumps were driven from the scavenge pump rod. These were not the smallest Doxfords, as some -200 mm bore twin-cylinder engines were investi-

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However, Sun did produce air compressors and generating sets (Fig. 6.4) down to -75 kW (100 bhp) using the Doxford OP architecture.

In response to ship-owner demands, Doxford made considerable efforts, with some success, to operate its engines on heavy “bunkers”-type oil, as was used to fire boilers. The main enablers were to centrifugally separate any solid or semisolid elements in the bunker fuel, and to dilute the liquid residue with the usual, lighter, diesel fuel.

Marine Opposed-Piston Engines

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Fig. 6.3 Sun Doxford Twin-Bank Engine for Henry Ford's Vessel MV Sialia, 1925 [Reproduced courtesy of John Jordan, Sunderland, United Kingdom]

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Fig. 6.4 Sun Doxford Two-Cylinder Generator Engine, Approx. 1925 [Reproduced courtesy of John Jordan, Sunderland, United Kingdom]

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Opposed Piston Engines: Evolution, Use, and Future Applications The Doxford engine had certain advantages over rivals in this context. First, the engine scavenging system was the “uniflow” type, compared to other engines that had loop- or cross-scavenging, making for a more efficient gas exchange process. Second, the fuel injection system was operated on the common-rail principle, which meant that fuel injection pressures were at optimum at all times regardless of engine speed. Third, after the first few engines were built, which had equal stroke for upper and lower pistons, the upper stroke was reduced in order to achieve perfect balance. By the end of the 1920s, Doxford had many United Kingdom licensees (Ref. 6.1), but the Sun Shipbuilding and Drydock Company (Pennsylvania, United States) and Lindholmen Motala AB of Gothenburg (Sweden) were the only two nonBritish licensees. 6.2.2.2 Developments in the 1930s

In spite of the depression of the early 1930s, four main developments in Doxford engine technology took place prior to WWII. First, welded “crankcases”were introduced in 1933, reducing production costs and deadweight of the smaller engines by 25%. Welding was later extended to the bedplates and the ‘‘entablature‘‘-the structure above the main vertical columns and adjacent to the main bearings that supported the liners and gas exchange system. Second, Doxford developed an economy engine to compete against the tramp steamers that conducted local coastal trading, which had been less affected by

22 8

the world depression than intercontinental trade. These Doxford “Economy” ships and engines, with a bore of 520 mm and combined stroke of 880 + 1200 mm, produced 448 kwitrlcylinder at 115 rpm and were relatively frugal in terms of fuel and oil usage. A typical daily ration for these 9400 tonne vessels was 6.5 tonnes of fuel and 30 Liters of lubricating oil for a ship speed of -10.5 knots. With a bunker capacity of 790 tonnes, a range of 48,000 km was feasible.

Third, making use of steam technology, Doxford introduced “Economizers”that were effectivelybottoming cycles using exhaust waste heat, capable of delivering 0.6 kg of steam per kW of engine power at pressures of about 10 bar and temperatures of -350°C. Doxford maximized the exhaust temperatures to -375°C by minimizing the scavenge-air delivery ratios from contemporary values of 1.6:1 to values as low as 1:1. These economy engines had brake specific fuel consumption (bsfc)of -212 g/kWh, or 40% brake Brake Thermal Efficiency (BTE), excluding the bottoming cycles. Fourth, five-cylinder engines were introduced in 1935 with outputs of 448 kW/ cylinder for a 560 mm bore and combined strokes of 700 + 980 mm. These were derived from the Economy engines and this architecture was used for 725 mm bore engines to produce 970 kW/ cylinder. Four of these engines were fitted to the liner Dominion Monarch in 1939, making it the most powerful ship in the British merchant fleet at that time. This success led to other contracts from the New Zealand Shipping Co. Ltd., Federal Line Ltd., Port Line, Prince Line Ltd., Silver Line Ltd., and many more who fitted either single- or twin-screw arrangements

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to many of their vessels, including passenger cargo vessels. 6.2.2.3 WWll and Postwar Years

As can be seen in Fig. 6.5, many Doxford engines were made during the war years as the engine compactness offered a favorable cargo space compared with steamships and avoided the telltale smoke they emitted. The United Kingdom merchant fleet had been rather slow to adapt to diesel engines, and Doxford was among the leaders in diesel applications. Ironically, Doxford’s wartime engine production was limited by the United Kingdom’s ability to manufacture the heavy “dogleg” crank elements, which traditionally had been provided by German and Czechoslovakian foundries. Doxford was quite relaxed with licensees, and Sun Shipbuilding experimented with

various alternatives to the traditional piston-type scavenge pumps, trying chain-driven rotary pumps and also electrically driven scavenge pumps. Geared installations were made in 1941, with twin engines running at -180 rpm connected to the propeller shaft.

Resumption of peace saw rapid rebuilding of the world’s merchant fleets and Doxford production rose sharply (Fig. 6.6) in the late 1940s and early 1950s. However in 1953- 1954, Doxford management refused licenses to German, Japanese, Polish, and Yugoslavian engine builders, which was probably an early sign of their end, perhaps reflecting the “Great Britain” cultural and industrial mentality of that era. The 1950-1970 period saw Doxford adopting proprietary injectors from CAV to operate from the traditional Doxford common-rail injection system, with accu-

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Fig. 6.5 Doxford Engines Pre 1945 [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 6.6 Doxford Engines Post 1945 [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

mulators acting as the “common rail,” to maintain pressure during injection. The company introduced a new starting system that was simpler, lighter, and cheaper and finally accepted turbocharging, although probably too late to significantly change Doxford’s fate. Doxford-turbocharged engines eventually stopped using enginedriven scavenge pumps and relied on external compressed air supply for light load operation, but some years after Sulzer and B&W had already done so.

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During this period, the main technical issues tended to be with the crankshaft limitations of the engine, which were largely due to the length effects of the three-throw crank-plus-cylinder arrangement.

6.2.2.4 The Final Years: 1960-1980

Doxford engineers Percy Jackson and John G. Gunn, along with their research team, developed the P-type engine with a 670 mm

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bore to address some of the crankshaft flexibility issues. They reduced the upper stroke and eliminated the self-aligning “spherical” main bearings, which stiffened the overall crankshaft to reduce torsional, axial, and bending vibrations. However, it became apparent that the shipping demands of that era needed much more power. Larger cylinder bores were necessary, which led to the J-type engines of 1965 with 760 mm bore and combined strokes of 520 + 1660 mm. The J-type was significant because its larger cylinder bore used a crankshaft in which the crankwebs were also the main journals, allowing shorter and stiffer crankshafts. This concept had been proposed in 1931 by K. 0.Keller, one of the great Doxford leaders, and versions were already in use in the Maybach engines but with rolling element bearings. By this time, Sulzer, B&W, and MAN had highly optimized their single-piston

Marine Opposed-Piston Engines engines and probably had simpler bearing and maintenance requirements. To compete, in 1971 Doxford developed the smaller geared “Seahorse” engine range with 580 mm bore and 420 + 990 mm combined stroke, operating at 300 rpm with a power rating of 1865 kwlcylinder-the same as the J-type, but significantly more compact. During this period, shipping tankers were becoming extremely large (some in excess of 400,000 tonnes). These vessels needed very large power units to drive them even at moderate speeds such as 15 knots. Doxford designed the Seahorse engine to be a small high-powered engine that could be fitted into this type of vessel in multiples, giving them a high level of redundancy. They could be operated as geared units or as electrical generators. The same engine could also generate electricity on land where required. The engines would have been produced in four- to seven-cylinder units, 10,000 to 17,500 bhp (7460 to 13,055 kW) shaft power. This was a brave move by Doxford, but was too late-no Seahorses were sold. The remaining Doxford engines manufactured between 1971 and 1981 were the J-type, mainly because they cost less than the geared, higher-speed Seahorses. On a final and ironic historical note, Doxford Engines eventually became part of the nationalized British Shipbuilding Group (BSG).The United Kingdom government of the time agreed that BSG would be drastically reduced in size in accordance with a little-known European agreement. Other European countries were also supposed to reduce shipbuilding, but did not

implement the agreement as rigorously as the United Kingdom. Doxford, as part of BSG, was one of the main casualties. Ironically, at the time of closure, Doxford had more orders on its books than it had had for many decades. A number of the orders were redirected to licensees as approximately 80% were for overseas customers.

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6.2.3 General Arrangement and Specification of J-Type Doxford Engines Front and side elevations (Fig. 6.7) of the “new” 1964 Doxford J-type engine show a ‘‘cathedray-type marine structure for a 760 mm bore engine with a combined stroke of 520 + 1660 mm. Scavenge air ports were operated by the lower piston with the longer stroke, and the exhaust ports were operated by the upper piston with only -3 1% of the air piston stroke.

The crankshaft was a more compact arrangement of the original Wittig concept with the side connecting rods driven from crankpins between the main bearings and the crankwebs of the center crankpin. Both air/scavenge and exhaust pistons were driven by extremely long connecting and piston rods connected to crossheads guided by an engine frame that was quite minimal by marine standards. The lower piston, which was oil-cooled on all J engines, was essentially a crowdhead and ring carrier, as the piston rod and its scavenge air seal, or “gland,” enabled the piston to be used without a skirt for either side thrust or scavenge port control. However, the exhaust piston was skirted in order to avoid exhaust gas heating of the liner and the piston skirt above the exhaust piston crown. A transverse beam connected the side rods to the exhaust

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Fig. 6.7 Front and Side Elevations of Doxford J9, 760 x (1 850 + 500) [Reproduced courtesy of Mercator Media Ltd, “Motor Ship, ” Hampshire, United Kingdom]

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Marine Opposed-Piston Engines piston, which was water-cooled. Cooling water was supplied via telescopic pipes attached to the transverse beam, into and out of drilled passages in the piston rod and crownlhead. The J-type engines were turbocharged, using compressed air for starting, and had no scavenge pumps. The complete gas exchange system was mounted above the level of the scavenge air diaphragm seal, with the exhaust system running longitudinally (Fig. 6.7) on transverse beams adjacent to the exhaust piston. The camshaft, driving the fuel timing valves for the common-rail fuel system, was mounted slightly below the fuel injectors, which were located at about 24% of the combined stroke from the outer dead center (ODC) position of the exhaust piston crown. Chain drive was used for the camshaft and the common-rail fuel pumps.

The cylinder liner of the first series of J-type engines consisted of three partsthe exhaust portion, the air portion, and the “combustion chamber” that carried injectors, relief valve and power indicator takeoff, and air starting valve.

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Later versions of the J-type as well as the Seahorse engine had one-piece liners fitted with cooling holes drilled parallel to the liner axis to provide the most efficient removal of heat from the combustion section, which removed the need for a separate combustion belt. The holes were drilled around the valve pockets and were at the closest point possible to the bore. This simplified the liner assembly as well as liner installation into the entablature. These long drilled holes in the onepiece cylinder liner (Fig. 6.8) moved the coolant toward the outer edge of the liner combustion space for both upper and lower parts of the liner. It therefore

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Fig. 6.8 Cross Section through Combustion Space Showing Valve Pockets and Longitudinal Coolant Drillings [Reproduced courtesy of John Jordan, Sunderland, United Kingdom]

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Opposed Piston Engines: Evolution, Use, and Future Applications maintained uniform heat stress over the hottest part of the liner.

As with all Doxford engines of the J-type, the scavenge ports were arranged to increase the swirl of the scavenge air in the cylinder liner to a critical point that allowed fuel to remain airborne rather than impinging on the liner, which reduced wear and thermal loading. The crankshaft, the air-piston rod, and the bedplate to scavenge gland occupied approximately 59% of the overall engine height, with the liner and exhaust piston occupying the remaining 41%.

Cylinder-to-cylinder pitch was 1740 mm, which was -2.29 x cylinder bore. Overall engine height (Fig. 6.7) was 11.5 m, and overall length for the nine-cylinder version was 18 m, averaging 2 m span per cylinder, indicating that the Doxford was very compact at both free and driven ends.

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The nine-cylinder version of the J-type engine had a 1 hour rating of 17,389 kW (-23,300 bhp) at 121 rpm with a -39% BTE.

6.2.4 Key Features of Engine Components

The engine structure essentially consisted of a lower horizontal bedplate, which formed the base of the engine and contained the crankshaft. This was linked by vertical columns to the “entablature,” which was the upper horizontal structure of the engine. The entablature secured the upper end of the columns, formed the air receiver, and carried the liners and upper engine structure. 6.2.4.1 Bedplate

Welded steel bedplates (Fig. 6.9) were partially open structures made from two parallel horizontal box-section longitudinal beams. The beams were joined at each main

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Fig. 6.9 Doxford 76J6 Engine Bedplate and Crankshaft [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

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Marine Opposed-Piston Engines bearing location by a transverse structure forming the lower main bearing supports to which were fitted thinwall steel-shell bearings with a thin Babbitt lining. The upper cap contained a solid Babbitt bearing, cast into the cap, which was secured from the topside by two studs. These main bearings should have only had to cope with the deadweight of the crankshaft and cranktrain, which nevertheless was appreciable, because gas and inertia loads should have been independently balanced. The bottom of the bedplate was essentially flat so that it could be mounted on the main fuel tank in the well of the ship. For engines with more than six cylinders, the bedplate was made in two sections that were bolted together as shown in Fig. 6.9. An independent thrust block was mounted to the bedplate floor to take crankshaft thrust from a flange at the driven end.

beams of the bedplate at each main bearing bridgehead and bolted at their upper ends to the entablature. In addition to supporting the liners and the upper engine structure, the four vertical columns formed the crosshead guides (Fig. 6.7) for both the center connecting and piston rod, and the two outer connecting and piston rods, which have the shorter stroke of the exhaust piston. The entablature was a substantially deep (approximately 70% of full stroke, 1.5m for the 760 mm bore engine) box-section structure that was bolted on its lower surface to the upper ends of the support columns, while its upper surface supported each liner and water jacket at approximately their mid-height. The liner-to-entablature connection was a horizontal flange fitted to the water jacket of each liner. The scavenge air chest was also contained in the lower portion of the entablature.

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6.2.4.2 Main Frame and Entablature

While the main frame (Fig. 6.7) was substantial, its role was primarily to carry the deadweight of the liners, turbocharger, camshaft, injection pumps, lubricators, and exhaust system, as well as handling the crosshead loads. All dynamic and gas loads were carried solely by the dynamic parts, as explained in Chapter 1. This was a very important advantage of the Doxford, as it effectively enabled a relatively lightweight main frame structure, unlike single-piston engines where the crankcase had to support the gas and inertia loads as well as the crosshead loads. Two pairs of hollow steel columns (Fig. 6.7) were bolted on the longitudinal

On earlier J-type engines, alignment of the liner to the running gear was quite difficult as the liner was rigidly set in the entablature framework. This meant guide setup for the cylinder bores had to be very accurate. For later designs where the liner had some “float”within the entablature structure, it was a relatively easy task to set the liner according to the position of the crosshead guides. After the liner was positioned, circular locating pads were welded to the entablature top near to the cylinder jacket flange. The clearance between the pads and the machined flange of the cylinder jacket were stamped with the set clearances. A new liner could then be easily installed and set to the same position as the original.

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Opposed Piston Engines: Evolution, Use, and Future Applications 6.2.4.3 Crankshaft and Connecting Rods

Partial built-up construction was an almost inevitable consequence of the huge length and size of the Doxford crankshafts. Two cast-steel crank elements were used, the first incorporating center throw and crankwebs, the second containing an outer throw, a web, and a main bearing (Fig. 6.10). Crankshafts for nine- or ten-cylinder engines were manufactured in two parts and joined by a coupling after the fifth cylinder. A nine-cylinder, J-type engine crankshaft weighed approximately 128 tons, which was claimed to be comparable to those of single-piston two-stroke engines.

Side and center steel connecting rods (Fig. 6.1 1 and Fig. 6.12) were similar in architecture and consisted of a big-end cap, a big-end upper half, an essentially cylindrical shank, and a pair of upper and lower small-end bearing carriers. Drillings went from the big-end, through the shank, connected to the small-end bearings, and brought oil from a central groove in the big-end shell bearings. Connecting rod lengths were typically greater than 3.1 m for the 520 + 1660 m m stroke, giving a length-to-throw ratio of 3.7:l. Torsional vibration frequencies were inevitably a challenge for earlier Doxfords as they increased their cylinder count from four to nine cylinders. As noted

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Fig. 6.10 Comparison of LB and J Engine Crankshaft and Main Bearing Journals [Reproduced courtesy of V n e & Wear Archives Service, Newcastle upon Vne, United Kingdom]

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Fig. 6.1 1 Doxford J-Type Side Connecting Rod Elevations and Sections [Reproduced courtesy of Mercator Media Ltd. "Motor Ship," Hampshire, United Kingdom]

Fig. 6.1 2 Arrangement of the Doxford Engine Running Gear [Reproduced courtesy of Mercator Media Ltd. "Motor Ship," Hampshire, United Kingdom]

earlier, Doxford initially addressed these issues by splitting the flywheel inertia into two smaller inertias, one at each end of the engine.

a rectangular palm end to the piston rod with four fixings (Fig. 6.14 and Fig. 6.15).

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6.2.4.4 Crosshead, Piston Rods, Pistons, and Crossbeam

Both side and center crossheads were similarly arranged, with the crosshead pin either connecting directly to the piston rod through a threaded joint (Fig. 6.13) (in the case of the side rods), or connecting via

Earlier J-type engines had center crosshead bearings with a centrally placed pad bearing. Adjustment was always difficult due to the deflection of the beam under various loads. This arrangement was replaced on later engines with a composite crosshead bearing as shown in Fig. 6.16.

All three crossheads were rectangular prismatic steel sections that engaged in

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Fig. 6.1 3 Sectional Isometric View and Side Elevation of Doxford J-Type Side Rod Crosshead and Upper Conrod Upper Bearing Assembly [Reproduced courtesy of Mercator Media Ltd. “Motor Ship, ” Hampshire, United Kingdom]

crosshead guides bolted to the vertical columns and were supplied with pressurized oil. The bearings in the side connecting rod were lubricated by oil fed to the main

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bearings and through drillings in the crankshaft to the side big-end bearing. The top-end bearing of the side running gear was lubricated by oil passing around the big-end bearing and through a passage in the rod.

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Fig. 6.14 Sectional Isometric View and Side Elevation of Doxford J-Type Center Rod Crosshead and Upper Connecting Rod (Conrod) Upper Bearing Assembly [Reproduced courtesy of Mercator Media Ltd. "Motor Ship," Hampshire, United Kingdom]

The center crosshead was composite with a crosshead bracket that held three telescopic pipes. The outer two were the oil-cooling supply pipes to the lower air piston that were supplied by a main supply manifold within the crankcase into and out of the telescopic pipes, which operated within standpipes welded in the entablature. The center crosshead bearing oil was supplied from a separate oil manifold that was part of the upper structure of the entablature assembly. Oil was fed to

a valve assembly mounted on to the top of the center standpipe. The valve assembly housed a semi-nonreturn valve, which, when in operation, allowed full flow in the downward or suction mode of the telescopic pipe; on the pumping stroke the semi-nonreturn valve was lifted, partially closing holes in the unit. This process effectively increased the operating pressure of the crosshead oil from a supply pressure of 2.5 bar (37 lb/in*) to approximately 25 bar (375 lb/in2),deliv-

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Opposed Piston Engines: Evolution, Use, and Future Applications

bottom-end bearing. Further drillings were arranged to pass oil at high pressure to the center crosshead guide faces. Unlike the older J-type engines, the center crosshead guide operated on what were termed the ‘Xstern pads” by virtue of the high oil pressure pressing on the main face of the guide or backside. The oil pressure held the crosshead guide in that position throughout its stroke without suffering any tilting as the crosshead passed over inner dead center (IDC). This action greatly improved the piston’s operation in the cylinder, reducing any tendency for piston scuffing by keeping it parallel with the bore of the liner throughout its stroke. It also improved the method of vertically aligning the piston and liner. This improvement was coupled to the arrangement of the one-piece liner.

Pistons had forged-steel crowns (or heads) (Fig. 6.17) with four compression rings; a deep cast-iron bearing (or rubbing ring); and one combined oil scraper, spreader, and compression ring at the lower end of the crown. The piston crowns were attached to the palm ends of both the upper and lower piston rods. Coolant passages were contained in the forged heads (or crowns) as well as the palm ends of the piston rods. The piston crown assemblies were bolted towards their center such that the periphery of the crown was free to expand radially. The circumferential cast iron bearing band, fitted to the piston crown, was lightly pressed into its groove and caulked in position. This bearing ring increased the wear resistance of the piston crown against the cylinder bore. Overall, air piston height was -18% of the lower piston stroke.

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Fig. 6.1 5 Doxford J-Type Engine Center Crosshead Arrangement for a 58JS Engine. (Both 76- and 67-Bore Engines were of similar design.) [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

ering high-pressure oil to the crosshead bearing (Fig. 6.16) exactly when and where it was most required. In addition to providing high-pressure oil to the crosshead bearing, the lubricating oil valve assembly also supplied the

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The exhaust piston length was typically 1.5 x exhaust stroke, had a forged-steel

Marine Opposed-Piston Engines

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Fig. 6.1 6 Doxford J-Type Engine Crosshead Lubricating System [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

crown (Fig. 6.18) similar to the lower piston, and was bolted to the piston rod and cast iron skirt assembly. Coolant temperature rise through the piston was typically ll"C, with coolant entering at 67°C.

Wear rate could be checked without lifting pistons as gaps could be measured by access through the entablature space when the engine was turned to allow the piston head to be seen through the scavenge ports.

All piston rings were designed to have their butts inwardly turned to prevent scuffing and breaking during the bedding-in period. They were also very carefully tested by compressing the ring in a jig to the bore size and measuring the diametral load when the ring gap was at its working position.

The piston-rod shanks of the lower piston and the upper piston skirt were both sealed by scraper boxes. The lower scraper box prevented scavenge air, products of combustion, and used cylinder lubricating oil from entering the crankcase, and prevented lubricating oil from the crankcase entering the scavenge space. The upper piston scraper box prevented the products of combustion and used cylinder oil leaking into the atmosphere.

Ring grooves were hard-chromeplated on the load bearing surfaces; this process reduced ring wear to negligible proportions.

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Opposed Piston Engines: Evolution, Use, and Future Applications

water jacket and contained the necessary ports for the fuel injectors, air start valves, indicator, and relief valves. The cast circumferential ribs in the water jacket ensured two complete circulations of the coolant while passing through the combustion chamber section. Upper and lower liners were independently bolted to the combustion chamber, with copper seals at the joint faces, so that each liner could be removed for repair. Coolant was transferred externally between the two liner and combustion chamber water jackets, so that the copper seals were “dr$ ensuring that no coolant could enter the combustion chamber.

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Later J-type engines had one-piece liners that simplified and improved the cooling method and whole assembly process. The cooling surface around the combustion area (Fig. 6.19 and Fig. 6.22) was formed by a large number of holes

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Fig. 6.1 7 Doxford J-Type Air Piston, Rod, and Scraper Box [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

6.2.4.5 Liner, Combustion Chamber, and Cooling System

On earlier J-type engines, separate upper and lower liners (Fig 6.19 and Fig. 6.20) were relatively thin cast-iron sections. Each was contained in a steel water jacket with internal ribbing/coolant passages to provide radial stiffness and to guide the coolant flow circumferentially. As Fig. 6.21 shows, the internal cooling ribs were a series of parallel, turned collars on the outer bore of the cylinder, with a break in each collar to allow the flow to move upwards. The combustion chamber was a steel casting with its own

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Fig. 6.1 8 Doxford J-Type Exhaust Piston, Skirt, and TransverseBeam [Reproduced courtesy of Mercator Media Ltd, “Motor Ship, “ Hampshire, United Kingdom]

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Fig. 6.1 9 Doxford J-Type One-Piece Cylinder Liner for 58JS Engine Constant Pressure Turbocharged [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

Fig. 6.20 Section through Doxford P- and J-Type Lower and Upper Liners and Combustion Chamber Assembly, with Coolant Jackets and Exhaust Belt [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

drilled at an angle to the vertical axis of the liner. This arrangement produced a fully machined cooling water surface closer to the combustion side of the liner than was possible by other means. The portion of the liner casting outside the cooling holes acted as a "strongback" to carry gas pressure stresses, while thermal stresses were kept low by the intensive cooling effect due to the small distance between gas and water faces.

in a swirling motion. The swirl radius was carefully controlled to ensure that combustion products did not excessively centrifuge. The multihole pattern of fuel injection was also designed to widely distribute the fuel in the combustion chamber and cylinder bore, avoiding impingement, and distributed the thermal stresses within the piston heads and liner.

The lower (or scavenge) section was fitted with an aluminum vane (Fig. 6.23) that assisted and directed scavenge air

The fuel injectors, air start valve, indicator, and relief valves were fixed directly into the combustion chamber flame face, avoiding external clamping systems. As can be

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 6.21 Doxford J- and P-Type Upper Liner with Exhaust Ports, Showing Cooling Grooves, before Placement of Coolant Jacket and Exhaust Belt [Reproduced courtesy of John Jordan, Sunderland, United Kingdom]

Fig. 6.22 Isometric View/Section of Later P- and J-Type Single-Piece Liner and Jacket Assembly [Reproduced courtesy of Tyne & Wear Archives Service, Newcastle upon Tyne, United Kingdom]

seen in Fig. 6.8 and Fig. 6.24 the multihole injectors were diametrically opposed. Doxford-type lubricators metered oil directly onto the cylinder bore at eight points (Fig. 6.25 and Fig. 6.26) on each liner (see Section 6.2.4.7). Peak liner flame-face temperatures (Fig. 6.27) were measured by traversing thermocouples (9.31 bar BMEP/120 rpm) at 240-250°C on the air and exhaust piston liners at the IDC positions of the top rings, and 240°C at the ODC position of the exhaust top ring. Fig. 6.23 Scavenge Ports with Aluminum Swirl Vanes [Reproduced courtesy of John Jordan, Sunderland, United Kingdom]

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6.2.4.6 Exhaust Belt Gases from the d ~ a u sPorts t (Fig. 6.20 and Fig. 6.22) exited via a water-cooled,

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Chapter 7

AUXILIARY POWER OPPOSED PISTON ENGINES 7.1 Auxiliary Power Unit Introduction

Opposed piston engines have been used for auxiliary power units (APUs) primarily because of their compactness, robustness, and ease of maintenance. Examples in this chapter include the -20 kW three-cylinder Coventry Climax H30 with a 55 mm cylinder bore, the 4- to 12-cylinder Fairbanks Morse 38D81/, the Sulzer ZG, and the -2500 kW Fullagar engines that remained in continual service for some 20 years. Nine-cylinder versions of the Napier Deltic OP engines were used as APUs in United Kingdom minesweepers, and the 18-cylinder version (Chapter 6) was also considered for land-based APU use. A smaller OPOC” engine (Chapter 4) is now being offered as a “briefcase” style APU of 2-5 kW, and Golle Motor AG (Dresden, Germany) is working on a 20 kW combined heat and power unit.

7.2 Coventry Climax H30 7.2.1 Introduction The three-cylinder Coventry Climax H30 engine was part of the United Kingdom terrestrial military engine OP “family” from 1957 to 2005, which consisted of the H30 three-cylinder auxiliary power unit (APU) of 995 cc, the Rolls-Royce six-cylinder K60 of -6.57 L displacement (Chapter 5), and the 19 L Leyland six-cylinder L60 battle tank engine (Chapter 5). The common element among these three engines was the multifuel capability covering -50 cetane diesel, United States JP4-type fuel (known as AVTAG in the

United Kingdom), a -74 Research Octane Number (RON) leaded gasoline with 1.8 cc/Imp. gallon tetra ethyl lead (TEL), -80 RON leaded gasoline, and regular- and premium-grade United Kingdom and northwestern European gasoline fuels of 1960- 1980.

As noted in Chapter 5, the United Kingdom military strategy of that era concluded that the ability to operate on this wide range of fuels would be best addressed by using opposed piston engine configurations, bore-to-stroke ratios with minimal combustion chamber surfacearea-to-volume ratio, and combustion chamber surface temperatures at the highest safe maximum values. These points were reinforced by the United Kingdom’s military tests of the Jumo 205 (Chapter 3), and of the United Kingdom Rootes Tilling Stevens TS3 (Chapter 4) commercial vehicle engine that was in large-scale medium duty truck use in the United Kingdom during that era. Compared to the K60 and L60 members of its “family” and most other OP engines, the H30 was very small, because its function was primarily that of a steady speed auxiliary power unit of 10 kW continuous output. However, the H30 functional requirements were substantially more complex than a 10 kW rating suggests. The H30 had to deliver -28 kW for cold starting of the Leyland L60 engine (Chapter 5), with unaided cold starts to -27”C, and ether-assisted starts at -40°C. The H30 had to share the L60 coolant system and provided warming for the L60 under

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Opposed Piston Engines: Evolution, Use, and Future Applications cold starts. The H30 design was controlled by a military committee that required the engine to be fundamentally capable of installation on both sides of existing and future United Kingdom battle tanks. Most remarkably for that era, and even today, the H30 was distinguished by the smallest bore size used for a production direct-injection diesel engine-55 mm diameter. This probably still remains true at the time of publishing. Coventry Climax Engines (CCE), part of the Coventry Climax Group based in Coventry (United Kingdom), were engine manufacturers famed for their Grand Prix Formula 1 engines of 1960- 1970, and also for their lightweight industrial engines that were used for fire fighting water pumps, and fork lift trucks. Pre WWII and WWII CCE engines were used in tractors, lifeboats, radar units, and various marine applications. Ernest Shackelton’ssnow tractors for the Antartic expedition in 1913 were powered by CCE engines. The H30 was CCE’s second two-stroke engine; the first was the small “KF”four-cylinder 1750 cc uniflow with poppet exhaust valves. The KF engine was designed by Sir W. G. Armstrong Whitworth & Co. (Engineers) Ltd. (AW) for CCE, and was used for special naval applications, including as an APU in the United Kingdom Royal Yacht of post WWII. Work on the H30 was preceded by tests on the “H.OP”single-cylinderwith a bore of -50 mm. Design of the H30 started in 1957 with the first prototype operational by 1959. Information for the H30 was derived partly from AW internal reports (Ref. 7.l), which worked with CCE and addressed

the design aspects of production issues; from Stan Suckling of CCE, who was the engineer finally responsible for the H30; and from the military Royal Electrical and Mechanical Engineers (REME) service manuals (Ref. 7.2). H30 engine development was handled entirely by CCE.

Apart from its slave role as an auxiliary for the L60 battle tank engine, the H30 was also used to power various drives on the United Kingdom Tracked Rapier mobile anti-aircraft defense system. It was partly re-engineered for this purpose, in particular having its own coolant tank and sump. H30 engines were sent to power the launch system for the United States’ Blue Water missile system, but this program was subsequently canceled.

7.2.2 Engine Specification The H30 had an approximate specific output of 27.8 kW/L at 3000 rpm, although with unacceptable smoke. This was, and remains, an exceptionally high performance level for an APU, bearing in mind that current four-stroke diesel APUs typically achieve 15 kW/L in naturally aspirated form. With a bore of 55 mm and a stroke of 69.85 mm (x 2), the H30 bore-to-stroke ratio of 0.79 was typical for the K60 and L60 OP family, and was probably dictated by the tight space requirements of military ground vehicles. Power-to-package volume of the H30 was 0.06 kW/dm3. This very low value was primarily attributed to the very large endmounted electrical generator. It would seem that in these installations there was more space along the length of the engine axis than at the sides of the engine. Power-to-weight ratio of the H30 MklOA

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Auxiliary Power Opposed Piston Engines (light-alloy crankcase) was 0.09 kW/kg. This low value again was attributed to the large auxiliaries attached to the engine.

engine, with the scavenge blower driven from the (lower) exhaust crankshaft, the main hydraulic pump from the (upper) air crankshaft, the 10 kW DC generator driven from the center gear of the set of five inter-crankshaft gears, and the lubrication and fuel injection pumps driven from a meshing spur gear with the driven end of the exhaust crankshaft. The coolant pump was driven directly from the free end of the exhaust crankshaft.

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Engine compression ratio was 21:l for cold starting with low cetane and forecourt octane gasolines and, as mentioned earlier, ether-assist was available for very low temperature starts.

7.2.3 General Architecture

The three-cylinder H30 (Fig. 7.1, Fig. 7.2, and Fig. 7.3) initially used a singlepiece, cast iron crankcase casting and the classical five-spur gear drive between the two crankshafts, as per the K60, L60, and Junkers Jumo 205. Most output drives were initially at the driving end of the

The right side of the engine (Fig. 7.4), as viewed from the driven end of the engine, was almost completely masked by driven systems and dress items, most notably the oil and injector pumps along the bottom of the engine and the electrical generator and

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Fig. 7.1 Longitudinal Section of H30 Base Engine [Reproduced courtesy of Sir WG. Armstrong Whitworth & Company (Engineers) Ltd., United Kingdom]

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Fig. 7.2 Transverse Section of H30 Base Engine [Reproduced courtesy of Sir WG. Armstrong Whitworth & Company (Engineers) Ltd,, United Kingdom]

main hydraulic pump (not fitted in Fig. 7.4 photograph) overhanging the driven end. The coolant thermostat with its elbow connection is visible at the upper free end of the engine. Part of the longitudinal air chest is just visible below the very large element oil and fuel filters. These filters were relocated for later Challenger battle tank applications due to space limitations with the bulkier Rolls-Royce V12 four-stroke engine. The Roots scavenge blower is recognizable by its air inlet hose, below the oil pumps at the driving end of the engine, and the only sign of the coolant pump at the free end of the engine is the water inlet blanking plug

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below the governor at the end of the fuel injector pump. The left-hand exhaust manifold is barely discernable (Fig. 7.4) between the end of the oil pumps and the start of the fuel injection pump, although the righthand side of the exhaust manifold can be seen leading to the upswept exhaust pipe. The left-hand side of the engine (Fig. 7.5) had far fewer items, with the left-hand exhaust manifold clearly visible and the delivery from the scavenge blower via the outlet manifold to the air inlet manifold taking prominence. Also visible is the aperture for the electrical start

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Fig. 7.3 Three-Quarter View of H30 engine [Reproduced courtesy of Jersey Aviation Ltd., Jersey, United Kingdom]

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Fig. 7.4 Right-Hand View of Fully Dressed H30 Engine [Reproduced courtesy of Jersey Aviation Ltd., Jersey, United Kingdom]

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Fig. 7.5 Left-Hand View of Fully Dressed H30 Engine [Reproduced courtesy of Jersey Aviation Ltd,, Jersey, United Kingdom]

motor mounted at the top of the engine and linked to the driven-end gear train by a countershaft. In fact, however, this arrangement was not used. Instead the 24V starter engaged directly with the flywheel of the exhaust crankshaft.

engine also had a rigid attached support frame (visible in Fig. 7.4 and Fig. 7.5) to enable easy stillaging. For Chieftain and Challenger battle tank applications, the H30 was held on its left side (as viewed from the driven end) to a sidewall of the tank. This arrangement also enabled removal and replacement of the H30 in -45 minutes.

Although the H30 applications in the Vickers Chieftain battle tank were arranged to use the coolant system of the main Leyland L60 engine, the APU engine had its own coolant pump and its own lubrication system. Versions of the H30 for the British Aerospace Engineering (BAE) Rapier missile launcher were engineered to use an oil tank located under the engine in the form of a fabricated reservoir, bolted to the underside of the lower crankcase cover (Fig. 7.2).

Though the H30 had the common elements of the two-crank OP engine configuration, it was distinguished by dress items that increased its package volume by some 600% versus the base engine package volume, a statistic that is probably unique for any application.

Mounting of the engine was primarily by two mounts at mid-engine height at the front and rear of the engine, although the

The initial H30 crankcase (Fig. 7.2) was a single-piece grey iron casting that contained the three cylinder tunnels, each

7.2.4Key Features

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7.2.4.1 Crankcase and Main Bearings

Auxiliary Power Opposed Piston Engines of approximately 260 m m length (-3.7 x half total stroke) and -80 mm internal diameter locally to take the liner sealing lands. Cylinder center distance was 100 mm, or 1.82 x cylinder bore. This very large value is a reflection of the proportionally large, but entirely normal, liner thickness versus the very small cylinder bore. The main bearing stud load paths were connected by triangulated buttressed sections to the crankcase scantlings. Overall crankcase length was -335 m m (-6.1 x cylinder bore diameter) and overall crankcase height, from sump face to sump face, was -434 mm, i.e., 6.2 x stroke. The rear face (driving end) of the cylinder block was locally thickened to carry the three spigots for the intermediate gears. Both main oil galleries were on the right side of the engine (as viewed from the driven end).

(Mark 7A) of the H30 that was redesigned by AW and CCE reversed the location of the exhaust and air ports to the positions shown in Fig. 7.4 and Fig. 7.5 (Mark 10A version). This change to the upper location of the air ports was made because of oil ingress into the air ports when they were in the lower position, although both the K60 and L60 engines had the air ports in the lower position, as did the Junkers Jumo 205E, the Sulzer G series, and the Fairbanks Morse 38D81/. The “inverted port configuration was introduced on the MklO engines in combination with a move from cast iron to aluminum alloy for the crankcase (Fig. 7.6, Fig. 7.7, and Fig. 7.8). The aluminum alloy was used mainly because of casting quality issues with the foundry supplying the iron castings. A steel tube was cast into the aluminum crankcase to form the main oil gallery,

The crankcase/cylinder block had a coolant flow gallery above the inlet ports, which in later prototype and production versions would become the exhaust ports, supplied with coolant from the coolant pump via a coolant-cored passage in the front of the cylinder block. The coolant gallery was connected to the three cylinder tunnels, each of which was divided into four segments along the height of the liner, so that the coolant flowed equally up and around each cylinder. The coolant flow rose through a series of horizontal divisions in each cylinder tunnel.

The introduction of the light alloy crankcase reduced the dry engine weight from approximately 3 14 kg to 267 kg, a 15% reduction.

-

It should be noted that Fig. 7.2 represents the design of the original prototype, designed by Sir W. G. Armstrong Whitworth & Co., with the exhaust ports in the upper cylinder and the air ports in the lower cylinder. The production version

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7.2.4.2 Crankcase Covers

There were three major crankcase covers-upper sump, lower sump, and driven end covers (Fig. 7.7). Both upper and lower sump covers were semicylindrical and relatively close fitting to their respective crankshafts, with large overhangs at the driven end to accommodate the two flywheels. 7.2.4.3 Liners

The iron liners (Fig. 7.8 and Fig. 7.9) were approximately 300 mm in length, or -2.2 x total stroke, with the United Kingdom spring seal as used on the Rootes TS3, the

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Opposed Piston Engines: Evolution, Use, and Future Applications

Fig. 7.6 H30 MklO Light Alloy Crankcase [Reproduced courtesy of Jersey Aviation Ltd., Jersey, United Kingdom]

Fig. 7.7 H30 MklO Light Alloy Crankcase, Top, and Driving End Cover [Reproduced courtesy of Jersey Aviation Ltd., Jersey, United Kingdom]

Fig. 7.8 Layout of H30 Key Components [Reproduced courtesy of Jersey Aviation Ltd., Jersey, United Kingdom]

Auxiliary Power Opposed Piston Engines with the L60, and also partly due to air entrainment in the system arising from difficulties in bleeding the complex coolant system.

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The spheroidal graphite liner material composition was approximately 0.3% carbon, 1% silicon, 0.9% manganese, and 2.5% phosphorus and of 300 Brine11 hardness. The functional bore was mechanically impregnated with silicon carbide by the Laystall treatment and honing process. This made the cylinder bore surface very resistant to wear. The Laystall process was frequently used on cylinder bores subjected to arduous duty.

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Fig. 7.9 View of Liner as Fitted to MklO [Reproduced courtesy of Jersey Aviation Ltd., Jersey, United Kingdom]

Rolls-Royce K60, and the Leyland L60. But the spring seal was changed to O-ring sealing when the change was made from cast iron to aluminum cylinder block material. There were eight tangential flow air ports of approximately 8% of the total stroke and eight exhaust ports that expanded radially through the liner thickness. The center section of the liner had eight coolant channels to guide the flow and increase the coolant velocity. Development problems occurred with liner cracking in the main combustion area from the threaded hole for the liner location plug that was opposite the injector, but these were solved by deleting the location plug and hole. Some of the liner cracking problems were caused by the unusual thermal cycling of the H30 due to its shared coolant circuit

Part of the oil consumption issue of the H30 was traced to the slots at the extremity of the liners used to provide clearance for the connecting rod movement, which allowed oil splash to bypass the oil control ring onto the piston skirt. These slots were minimized in the MklOA version and helped to reduce the oil consumption.

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The sealing lands of the liner were approximately 77.5 mm outer diameter, or 1.41 x the nominal bore diameter. 7.2.4.4 Pistons and Rings

Two-piece pistons (Fig. 7.10, with fire ring incorrectly fitted in fourth ring position) were used, with a crown bolted from the underside of the skirt. The bolt pulled against a Belleville washer. The material for the crown portion was heat-resisting Nimonic steel, while that for the skirt was iron with 3% carbon, 1-2.5% silicon, 0.7-1.5% manganese, 0.45% chromium, 0.45% molybdenum, and low levels of sulphur and phosphorus. Piston length was 82.75 mm (1.18 x half-stroke) with about

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Opposed Piston Engines: Evolution, Use, and Future Applications

was believed to have operated between 320°C and 400°C without scuffing or collapse up to 5.2 bar BMEP. Below the fire ring were two double taper-faced stepped compression rings. At the skirt bottom there was a single-piece oil control ring and above that a low-tension compression ring to resist air or exhaust pressure leaks into the crankcase. This compression ring had a Napier oil scraper feature.

All rings were pegged by a small dowel into the back of each ring, except for the oil control ring that was pegged at the ring gap. A significant portion of the rubbing face of the fire ring had a large molybdenum-sprayed inlay to reduce scuffing. This inlay was generally successful and was also used on the Leyland L60 engine. The fire ring was also distinguished by a cutout on its upper periphery, necessary to reduce fuel impingement, that matched the fuel spray trench in the piston crown.

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Fig. 7.10 H30 MklO Piston Assembly [Reproduced courtesy of Jersey Aviation Ltd., Jersey, United Kingdom]

60% of the piston length above the wrist pin axis. The seating face of the crown on the skirt was arranged to provide a substantial air gap on the underside of the crown, for insulation purposes-to maximize the crown surface temperature. Piston crown center temperatures, without oil cooling, were reported to be approximately 600"C, and 550°C behind the fire ring. Subsequent use of oil cooling and redesign of the piston crown and fire ring significantly reduced these temperatures, extending ring life and improving the piston pin and pin boss conditions. Five piston rings were used, all effectively located in the skirt portion of the assembly. The fire ring, which was gapped and pegged and approximately 10 mm tall, was held between the crown and the skirt and

The split of the piston assembly at the seating face of the fire ring did give cause for concern regarding susceptibility of the crown to skirt gas-sealing integrity. This was not a serious issue for the H30, but it was a major development task on the Leyland L60 engine. A most unusual feature of the H30 OP engine was the deep piston bowl and also the relatively deep and wide spray approach trench from the outer piston diameter to the inner bowl diameter. This design was implemented, with high air swirl, to reduce wall wetting of both the piston crown and the cylinder bore. The H30 presumably operated with a fuel-toair mixing system that was much closer

Auxiliary Power Opposed Piston Engines to traditional deep-bowl direct-injection diesels than any other OP engine, which usually had relatively shallow “open” piston bowls. The derivation of this deep-bowl, highswirl combustion system was inspired by the combustion development performed on the American Marc (Chapter 6), which indicated that cylinder bore wall wetting in small bore engines could be alleviated by high swirl.

was nitrided steel, but unhardened and without balance masses (Fig. 7.11 and Fig. 7.8). Crankshaft lubrication was by individual feeds from the main oil galleries into the crankcase half grooves of each main bearing, and from these a single drilling to each crankpin.

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The main oil galleries for the lower and upper crankshafts were on the injector pump side of the crankcase (Fig. 7.2) and were each formed by a cast-in steel tube, as previously mentioned.

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The fully floating nitrided steel wrist pin was approximately 24 mm-diameter x 45 mm, i.e., -44% of the bore diameter, and was located by two circular spring-steel end caps. 7.2.4.5 Crankshafts and Connecting Rods

The crankpin and main journal diameters were -67% and 95% of the cylinder bore diameter, respectively, the crankshaft

7.2.4.6 Coolant Pump and Circuit

The cooling circuit of the H30 was a simplified version of that used in the Rolls-Royce K60 and Leyland L60. Coolant from the pump was circulated to a bottom gallery in the crankcase, below the exhaust port belt, traveling through crankcase drillings in each cylinder tunnel to the coolant volume above the exhaust ports, and then the

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Fig. 7.1 1 H30 Crankshaft [Reproduced courtesy of Jersey Aviation Ltd,, Jersey, United Kingdom]

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Opposed Piston Engines: Evolution, Use, and Future Applications flow channels (Fig. 7.9) around the center portion of the liner, adjacent to the injector location, and through a second set of crankcase drillings past the inlet ports. The flows were collected in an upper gallery linking all three cylinder tunnels and emerged on the right-hand side towards the free end of the engine (viewed from the driven end, Fig. 7.4). From here they were taken to the main cooling system of the L60 by thermostat and outlet pipe. As noted earlier, the coolant pump was connected directly to the free end of the exhaust crankshaft by a coupling. H30 applications for the British Aerospace (BAE) Rapier missile launcher had their own radiator. 7.2.4.7 Air Delivery System and Inlet Manifold

Air delivery was from a Roots-type twolobe positive displacement blower that was mounted on the driving end gear casing and driven through a spur gear drive by the exhaust crankshaft. Air entered the scavenge blower on the right side of the engine (see air hose leading to bottom left of Fig. 7.4, and bottom right of Fig. 7.5) from the cylindrical air cleaner at the free end of the engine and was delivered on the left side of the engine by a rectangular section pipe to a rectangular section inlet manifold (Fig. 7.5) that bolted to the left-side air chest. A similar air chest was on the right side, also visible in Fig. 7.2, although this figure reflects the original air chest position and not that finally adopted on the Mark 10A version. Blower delivery at 2000 engine rpm was approximately 47.23 L/s (100 ft3/min.), which was equivalent to a delivery ratio of 1.43:l

7.2.4.8 Inlet and Exhaust Manifolds

The exhaust gases emerged via three-intoone, cast iron, log-type manifolds on each side of the engine (just visible in Fig. 7.4 and Fig. 7.5). The exit flanges of the manifolds were at the free end of the engine. The inlet manifolds were compact lightalloy rectangular box structures (Fig. 7.5 and Fig. 7.2). 7.2.4.9 Fuel Injection System and Auxiliary Start Injectors

A Lucas CAV ‘‘AXtype inline threeplunger pump supplied the fuel to the three injectors via fuel lines on the right side of the engine. The pump plungers and camshaft bearings were connected by external pipes to the engine lubrication system so these elements were lubricated adequately with engine oil for use with low lubricity fuels, such as various grades of gasoline. Fuel leakage from the plungers was collected in a separate gallery and returned to the fuel tank to avoid oil dilution. Static injection advance was 30” before top dead center (BTDC) from 800 rpm idle to 2000 rpm governed speed. An additional 6” advance was added if it was necessary to drive the hydraulic pump at 3000 rpm, which was accomplished by a special advance mechanism in the drive to the pump. An automated injection advance device was introduced on the MklO engine with the light alloy crankcase and “inverted” manifold system.

7.2.5 Performance and Development From limited available performance data, the H30 engine was rated at 17.2 kW at 2000 rpm but was capable of 20 kW at

Auxiliary Power Opposed Piston Engines 2300 rpm, corresponding to 6 bar brake mean effective pressure (BMEP), though at this load (Fig. 7.12) the brake specific fuel consumption (bsfc) had increased to -292 glkWh (approximately 29% Brake Thermal Efficiency [BTE]).Best BTE at 2000 rpm was approximately 33% at 4.5 bar BMEP, or -256 glkWh. For more power to drive the hydraulic starter motor, the engine could be operated at 3000 rpm with an output of 27.6 kW. Smoke was very high when the engine was operated at these ratings, however. Apart from the oil consumption problem that prompted the inversion of the inlet and exhaust manifold and porting, the main development issues were piston crown loosening, some piston crown burning, liner sealing, fire ring optimization, and fuel impingement on the cylinder bore. As noted earlier, the last problem was mitigated by using the deep piston bowl (Section 7.2.3.4) with a fuel spray contain-

ment trench on the piston crown from the injector tip to the edge of the piston bowl.

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The fire ring problems, which were broadly experienced also on the Leyland L60 and the Rolls-Royce K60, were frequently a result of supplier quality issues, which were due to financial strictures of the holding company of the piston and piston ring suppliers.

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7.2.6 Applications, Manufacturing, and Engineers

The H30 was initially only used in conjunction with the Leyland L60 tank engine. For these applications, the little H30 would be operated for hours continuously and relatively quietly, providing electrical power for the tank crew, while the main engine would be shut down in “waiting mode.” Mark 10-Mark 17 versions were used to power the mobile British Aerospace Rapier surface-to-air missile launcher.

Fig. 7.1 2 Coventry Climax H30 Fuel Consumption and Brake Power at 2000 rpm

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Opposed Piston Engines: Evolution, Use, and Future Applications The mounting of the auxiliaries for these engines required considerable re-engineering of the drives.

Engines were initially manufactured at Coventry in the United Kingdom Midlands at the Friars Lane factory, then at the Quinton Road location. A total of -2900 engines were made from 1964 to 1995. With the demise of the Coventry Climax group, however, the maintenance of existing H30 engines was transferred to Horstmann Defense Systems at Bath in Somerset. Currently H30 engine maintenance is taken care of by Aviation Jersey Ltd.. H30 units were also tested and used in military applications in India, Iran, and Jordan, usually with special modifications to suit the particular vehicle installations. All of the design of the H30 engine, from conception to production, and any production changes, was handled by AW. Key engineers overseeing the design and development of the H30 engine at AW were John “Jim”Smith and later John Edwards, while Stan Suckling of CCE was mainly responsible for the development and production aspects at Coventry, and subsequently for maintenance of the H30 by Horstmann Defense Systems at Bath. Today this responsibility is handled by Headley Griffiths and his team at Aviation Jersey Ltd. in Jersey. The H30 enjoyed a good reputation for reliability, both in the Chieftain and Challenger battle tanks and the Rapier missile launcher applications. Field problems were usually due to incorrect maintenance or supplier quality issues. The H30 was eventually replaced by an

“off-the-shelf” four-stroke engine that had a reputation for overheating and was not as well regarded as the H30, which had become firmly established with tank crews and the supporting REME service and maintenance engineers.

7.3 Fairbanks Morse Model 38 OP Engine 7.3.1 Introduction Fairbanks Morse (FM) began developing its first OP engines in 1933 with two engines, a six-cylinder of 127 x 152.4 (x 2) (-5 in. x 6 in. [x 21) delivering -224 kW at 1200 rpm, and the other an eight-cylinder of 203.2 x 254 (x 2) (8 in. x 10 in. [x 21) delivering -895 kW at 720 rpm. The eight-cylinder engine formed the basis of the subsequent 38D8%, which was still manufactured in 2009. In 1934, the United States Navy instigated a competition for engines to power its future submarines and while FM did not enter this contest, the United States Navy ordered eight 8-cylinder engines for the two submarines USS Plunger (SS179) and USS Pollack (SSlSO). Fairbanks Morse also supplied some smaller OP engines for auxiliary drives in the same submarines. The 38D8 was upgraded to a 206.375 bore. This engine was known as the 3 8 D M due to the % inch bore increase. Cylinder count increased to nine and ten cylinders, which delivered about 1194 kW at 720 rpm, or 5.7 bar BMEP. Approximately 700 of these ten-cylinder engines were supplied for United States submarines in WWII, and a further 1700 for surface vessels. At one stage during the WWII Battle of the Atlantic crisis, engines were manufactured at the rate

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Auxiliary Power Opposed Piston Engines of one per day for a considerable period. After WWII, a 12-cylinder version was made, and another smaller engine (171.45 x 203.2 [x 21) with rated speed at 1500 rpm delivering 996 kW, or 5.3 bar BMEP. The smaller engine was discontinued, but the 38DM persisted with many variants, including “turboboosted,” turbocharged, spark-ignited natural gas, and dual-fueled engines using a small diesel micropilot to ignite the natural gas, known as “Enviro-Design@,”A summary of variants and outputs is shown in Table 7.1 At the time of printing, applications include power generation, gas compressor drives, chillers, pump drives, and “distributed

generation”-combined heat and power, as well as surface marine use. As one of the few current production OP engines, the 38D8% range is unique in terms of the blower drive, intercrank drive, manufacturing methods, range of applications, and a production longevity in excess of 75 years with essentially unchanged fundamental base engine design.

This chapter mainly reviews the tencylinder, blower-scavenged diesel engine in its early form, but also includes material on the other cylinder configurations, combustion systems, and current performance levels.

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No. of Cylinders

Max kW1 cyl at 900 rpm

Blower Scavenged

38D8-1/8

6,8,10,12

164.1

234

34.8

Turboblower

38TD8-1/8

6,9,12

287.2

222

38.1

Turbocharged

38ETD8-1/8

6,9,12

301.4

21 1

40.1

Blower Scavenged

38D8-1/8

6,8,10,12

164.1

246

34.34

Turboblower

38TD8-1/8

6,9,12

287.2

221.4

38.25

Turbocharged Enviro-Design@

38ETD8-1/8

6,9,12

301.4

21 3

39.8

Fairbanks Morse Type

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bsfc (glkwh)

BTE (%)

I Spark Ignited (Natural Gas):

I

Blower Scavenged

38D8-1/8

6,8,10,(12)

185,(178)

NA

-34.4

Turboblower

38TD8-118

6,8,10,12

225.7

NA

-36.4

Turbocharged (density and cal. value estimated)

38ETD8-1/8

6,8,10,12

246.2

NA

-37.2

Table 7.1 Summary of Fairbanks Morse Engine Types, Performance, and BTE

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Opposed Piston Engines: Evolution, Use, and Future Applications Material for this chapter is drawn from the Fairbanks Morse centennial book (Ref. 7.3), Fairbanks Morse sales data from 2000 model year (Ref. 7.4), and an SAE paper (Ref. 7.5). With these sources of information spanning more than fifty years of the engine in production, there is inevitably a composite nature to the description of the 3 8 D M engine that has changed in detail over the years. Reference is also made to “upper” and “lower” crankshafts with respect to the air and exhaust crankshafts. This is in keeping with Fairbanks Morse terminology.

7.3.2 General Architecture Distinctive features of the 38D8% engine (Fig. 7.13) are its clean, uncluttered, planar appearance, the end-mounted scavenge blower driven by the upper air crankshaft, the spiral bevel gear/lay-shaft intercrank drive, and the fabricated steel crankcase construction.

Emphasis on low height and narrow width for both submarine and locomotive applications influenced the placement of the auxiliaries on the 38D8%. All drives were mounted at the free- and driven ends (Fig. 7.14) of the engine, like the Junkers Jumo 5. However, the 1.829 m (6 ft) distance between crankshaft centers probably discouraged using spur gears to phase the crankshafts because of the effect of tolerances on gear noise and backlash control, while the spiral bevel gear and driveshaft, as per the original T.H. Lucas engine concept (Chapter 2, Section 2.2.2), were a neat and practical solution to spanning the distance with only four gears. Early prototype engines did use chain and spur gear intercrank drives, but these were abandoned in favor of the bevel/shaft drive arrangement. Hans Davids, Heinrich Schneider, Percy C. Brooks, James W. Owen, and Anker K. Antonsen were prime inventors listed in various patents regarding the drives,

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Fig. 7.1 3 General View of Engine [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

Auxiliary Power Opposed Piston Engines reversing system, and fabricated crankcase structure (United States Patents 2,054,232, 2,244,323, 2,245,810, 2,246,857, 2,341,981,

and 2,292,104, between 1933 and 1944). The fuel lift, and the oil and coolant pumps are driven from the free end of the lower (exhaust) crankshaft, and the pendulum damper is located in the same drive. Like the Junkers Jumo 205 (Chapter 3), camshafts are on either side of the engine. These shafts are driven from the rear of the upper crankshaft by a triplex chain with a tensioner. Each camshaft drives individual high-pressure plunger/barrel pumps, connected to a single injector on the same side of the engine. Each cylinder, therefore, has two injectors. All high-pressure fuel pumps on each side of the engine are connected to a control rod. These two rods

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are linked at the free end of the engine to a Woodward mechanical-hydraulic type of governor, which is driven from the free end of the lower crankshaft by three sets of bevel gears in a “ Z shaft configuration, arranged to minimize vibration from the lower crankshaft into the governor. Each cylinder is also provided with air-starting check valves and excess pressure valves. Visually (Fig. 7.13), the 38D8% has rectilinear lines with the part-cylindrical upper crankcase cover running from front to rear. Both inlet and exhaust manifolds are effectively built into the cylinder block and are, therefore, almost out of sight. The two longitudinal sides are covered with a multiplicity of inspection and safety covers.

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Fig. 7.14 Crankcase [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

34 9

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Opposed Piston Engines: Evolution, Use, and Future Applications

7.3.3 Key Features

7.3.3.1 Crankcase and Main Bearings

The 3 8 D M crankcase (Fig. 7.14) is probably the earliest example of “box girder” engine crankcase construction, consisting of a combination of fabricated steel plates (essentially in either horizontal or vertical planes) welded to a series of vertical forgings for the main tensile loadcarrying members between the upper and lower main bearings. The longitudinal and transverse sections (Fig. 7.15 and

Fig. 7.16) show the vertical 10 mm-thick (3/8 in.) load-carrying forged-steel panels linking the main bearing carriers, each of which has a “flying buttress” to the outer crankcase walls. There are no thread tappings into the forgings, as studs were avoided by using nuts and bolts (Fig. 7.16) to secure the main bearing caps.

Six horizontal decks, or partial decks, (Fig. 7.14, Fig. 7.15, Fig. 7.16, and Fig. 7.17) run the length of the engine (excepting the front and rear drive protrusions). Four

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Fig. 7.1 5 Longitudinal Rear Section [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

350

Auxiliary Power Opposed Piston Engines

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Fig. 7.1 6 Transverse Section [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

of the decks are bored to take the vertical liner and waterjacket housings. The bottom partial deck 1 forms the sump flange and is just above the main bearing cap split line, as it is welded to the lower end of the forged vertical main bearing load panel. Decks 1 and 2 form a rigid box section in combination with the large lower

transverse buttresses of the vertical loadcarrying panel. Each cylinder has its own cooling jacket that has three sequential elements-the exhaust manifold waterjacket, a lower cylinder cooling module, and the main waterjacket between ports. The lower cooling module, an interference fit with the outer diameter of the lower end of the

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 7.1 7 Longitudinal Front Section [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

liner, is bolted to the upper surface of deck 2, which is reinforced locally around the liner containment diameter. Decks 2 and 3 are open at their outer edges, forming two longitudinal galleries that accommodate the water-cooled fabricated exhaust manifolds on each side of the engine. Decks 3 and 4 form windowed galleries on either side of the engine containing the injectors, air start valves, relief valves, and injector control rods. Each cylinder bay has windows on each side of the engine to access the aforementioned components in these two galleries. Decks 4 and 5 contain

the inverted vertical injection pumps and the galleries connecting with the inlet ports and the longitudinal scavenge air manifold on each side of the crankcase. Each manifold has six access windows. The inner portion of Deck 5, just inboard of the injector pumps, is stepped to form containment for the upper end of the liner, which is bolted to the deck by four studs and nuts or cap screws. Decks 5 and 6 form the upper, rigid, box section in combination with the large upper transverse buttresses of the vertical load-carrying panel. The cam bearing carriers, which

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Auxiliary Power Opposed Piston Engines are part of the forged vertical structural panel, are contained between these two decks. Deck 6 also provides the upper cover flange and is located just below the upper main bearing split line. The crankcase structure, therefore, consists of four substantially closed box sections of -885 mm width x 300-480 mm height, and two open box sections for the exhaust manifolds. All box sections are stabilized between the vertical load bearing panels located at 305 mm (12 in.) pitch along the length of the engine. The cylinder waterjacket elements are not a load bearing part of the crankcase structure.

The waterjacket is very compact, formed almost entirely by the combination of the outer sleeves and liners with 20 discrete pipe connections (in the case of the ten-cylinder engines) to the waterjacket surrounding the exhaust manifold. The pressurized lubricating oil is supplied from the oil pump and filter by a system of external longitudinal main conduits, with individual feed pipes to each main

The bevel gear drives (Fig. 7.14 and Fig. 7.18) are housed in a vertical compartment that has extensions of Decks 2 and 4. The bearing supports for the two sections of the vertical shaft are bolted to these deck extensions. The bevel gear compartment has a similar vertical load-carrying panel, with upper and lower main bearing carriers that support the lower crankshaft extension for the output connection, and the drive to the scavenge blower. Another vertical compartment at the front of the engine contains the camshaft drive, the crankshaft pendulum damper, the drives to the governor, and the oil pump. These drives also power the coolant pumps that are mounted outside the crankcase. After welding, sandblasting, crack detection, and rectification, the crankcase is annealed for stress relief. The lower sump flange also serves for mounting and installing the engine, which is frequently on a skid or “1”-section rails.

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Fig. 7.1 8 Gear Drive [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

3 53

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zyxwvutsr Chapter 8

UNUSUAL OPPOSED PISTON ENGINES 8.1 Introduction

Based on the description of OP engine types listed in Chapters 1 and 2, this chapter could have been very large and could have incorporated engines such the Napier Deltic (Chapter 6). Clearly there were difficulties in selecting only two engines for review. The chosen two, the Fairbanks Morse Diamond and Africar engines, were selected because they have distinctly different fundamental or detailed architectures in comparison to the majority of OP engines seen in the last 100 years. Some brief comments follow about engines that might have been included in this chapter, if space and time had permitted. The Telcon Stella is one such engine, with a shared combustion space and three cylinders that come to a focal point. It deserves a more careful review and comparison to other OP configurations. Folded-crank OP configurations with double-ended pistons providing both power and scavenge air delivery, as exemplified by various concepts such as the Southwest Research Institute’s “Witzky”proposal (Chapter 2), raise interesting questions about the high-speed integrity of the additional linkages and piston architecture. Also in this category is the Thiokol Dynastar. The barrel-cam and rotary-oscillatory OP engines, such as the Leggat ROM (Chapter I), clearly offer package and refinement advantages, but their drivelines need careful scrutiny for mechanical feasibility, integrity, and sensitivity to clearances and tolerances.

8.2 Fairbanks Morse Diamond Experimental OP Submarine Engine 8.2.1 Introduction

During WWII, Fairbanks Morse and Company (FM), who were already supplying the 38D OP engine for United States Navy submarines (Chapter 7), were commissioned to build a 24-cylinder, 3000 bhp (2238 kW) OP engine in a narrow “diamond” or parallelogram configuration (Ref. 8.1). The total cylinder displacement was 61.74 L (3767 in3)with a 133.35 mm bore (5.25 in.) and a 184.15 mm stroke (7.25 in.) x (2). The engine was destined for submarine applications.

8.2.2 Description of Engine Fairbanks Morse selected a cylinder size that was 75% of the 38D cylinder displacement, while the piston speed of the diamond engine at 1500 rpm was 8.89 m/s, or 188%that of the 38D at 720 rpm. The major axis of the diamond was vertical (Fig. 8.1) with a crankshaft at each corner of the diamond’s axes, linked through a herringbone gear train to the output shaft in the center of the diamond. There was one idler to each side crankshaft and bottom crankshaft, and three idlers to the upper crankshaft and camshaft drives. The crankshafts and polished fork-and-blade connecting rods were of forged steel and the lubrication system provided gallery cooling for the pistons. The pistons were of a cast iron outer shell for the crown, ring carrier, and skirt, which fitted an inner aluminum-alloy wrist pin carrier. Twin camshafts were fitted each side of the horizontal axis of the diamond to drive the fuel pumps of each bank. A

417

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 8.1 Layout of Fairbanks Morse Four-Crankshaft Diamond OP Engine [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

single, multihole injector was fitted per cylinder. Air from two voluminous intake silencers was supplied to twin centrifugal blowers mounted at the driven end of the engine and powered by the nodal drive gear train. The air was delivered to a chest in the center cavity of the diamond and supplied four air muffs around the scavenge ports. The exhaust ports of each cylinder emptied to muffs fitted to the cylinder liners, each of which was connected to a tubular water-cooled exhaust manifold. The steel

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liners had lozenge-shapedparallelogram ports and were chrome-plated and fitted with either steel or aluminum waterjackets. The crankcases were steel fabrications, and the engine was mounted, with six vibration isolators, on a steel base that also served as an oil sump. Fig. 8.2 shows the crankcase undergoing rigidity and displacement tests in relation to the numerous studies designed to predict the torsional vibration characteristics of the complex cranktrain. Reference 8.1 notes that 6000 man hours

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were spent on the torsional vibration calculations alone.

8.2.3 Performance

Testing of the engine (Fig. 8.3) demonstrated 3000 bhp at 1500 rpm with a best Brake Thermal Efficiency (BTE) of -33% (Fig. 8.4) and peak exhaust temperatures of 450°C. Two major problems, wear and port carbonizing, remained unresolved when the project was terminated at the end of WWII.

8.3 Africar OP Engine 8.3.1 Introduction Some 25 years ago in the United Kingdom, Tony Howarth embarked on the Africar project (Ref. 8.2), which generated three prototype concept cars designed for simple manufacture and functional robustness. Howarth’s vision was that the

cars could be manufactured and used in developing countries with minimum industrialization, such as some of the emerging African nations. A key feature of the vehicles was the use of an all-wood body, with simple doors and glazing, on a chassis and suspension that were derived from the iconic Citroen 2 CV. Howarth and his team subsequently drove the three relatively undeveloped prototypes, using Citroen 2 CV air-cooled, four-stroke, twocylinder engines, from the Arctic Circle to the Equator (Ref. 8.2), encountering many adventures and some breakdowns. However the vehicles were generally successful and proved that a lightweight vehicle with soft and long suspension travel, and frontwheel drive, is well suited to coping with deep snow or mud, and sufficiently light to be manhandled if necessary.

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Fig. 8.2 Diamond OP Engine Crankcase Undergoing Displacement Checks [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

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Fig. 8.3 Diamond OP Engine with Intake Silencers Leading to Twin-Centrifugal Scavenge Blowers [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

Fig. 8.4 bsfc vs. BMEP at 1500 rpm, with 3000 bhp Max Power [Reproduced courtesy of Fairbanks Morse, Beloit, United States]

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Unusual Opposed Piston Engines It was intended that the Africar should eventually have a dedicated engine. Howarth selected a three-cylinder, air-cooled, opposed piston engine for this role, and Bonner Engineering of Shoreham-by-Sea (Sussex, United Kingdom) was commissioned to design and produce two prototypes. The long-term intention was for the Africar engine to be a diesel, but for short-term expediency, a carbureted, spark-ignition (SI) version was produced. The project was conducted on a shoestring budget and so minimal records of the engine exist, but these were made available by Bill Bonner Ltd. and colleagues Tony Palmer and Brian Mann, who jointly designed and supervised the manufacture and assembly of the prototype engine. The Africar engine is of a unique OP configuration, reflecting some lateral and original

thinking on OP engine architecture. This is one reason it was included in this book.

8.3.2 Engine Configuration 8.3.2.1 General Arrangement

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The 2 L, three-cylinder engine (Fig. 8.5 and Fig. 8.6) of -75 mm bore x 75 mm (x 2 ) stroke was of a twin-crankshaft arrangement, linked by five helical gears at the driven (nodal) end. The cylinders were horizontal and air-cooled, the scavenge air was supplied by a Wade Roots blower connected to a single choke carburetor (Fig. 8.6). The scavenge blower, which was driven by a helical gear from the gear train, was mounted above the cylinders and connected to the three inlet air port “muffs,” or sealing rings, by a three-branch castaluminum-alloy inlet manifold (Fig. 8.6). The entries to the air ports were on the

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Fig. 8.5 Three-Quarter Driven End View of Africar Engine Showing Blower, Alternator, Ignition Drive, Open Front Bell Housing [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

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Fig. 8.6 Three-Quarter Free End View Of Africar Engine, Showing Crankcase And Transverse Covers Fitted, Supercharger and Inlet Manifold, Oil Return Drillings [Reproduced courtesy of Bonner Engineering Ltd,, Shoreham, United Kingdom]

upper side of the engine and liners (Fig. 8.7), with the exits from the exhaust ports on the underside of the engine and liner, connecting to a single outlet exhaust pipe.

entry to the cooling fan was by an aperture in the rear bell housing, which was never manufactured, so that the air was simply drawn into the open fan vanes.

The air-cooled liners (Fig. 8.8) essentially floated between two crankcase halves, which were connected transversely by eight crossbolts (Fig. 8.7), and longitudinally by the free end and driven end covers (Fig. 8.9), which also formed the front side of the gear case.

A dry-sump system was used. Gear-type oil pressure and two scavenge pumps were driven from the extreme lower end of the gear casing on the centerline of the engine. The pressure pump supplied oil to each crankcase by drillings in the front face of the gear casing. The main gallery in each crankcase distributed the oil to a groove in each main bearing carrier. Oil spillage was drained to the front casing and sucked to the scavenge pump.

The light flywheel, visible in Fig. 8.10, was fitted with vanes to provide a cooling fan. The fan delivered air from the rectangular aperture in the rear casing (Fig. 8.9) to the central engine air-cooling chest containing the liners, which had a closing plate on the upper side of the engine (Fig. 8.1 l),but was open to the atmosphere on the lower side, where the air exited. Air

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The ignition distributor (Fig. 8.5) was also driven from the gear train. There was one spark plug per cylinder, though the liner (Fig. 8.11) was machined for two spark plugs.

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Fig. 8.7 View on Top of Engine, Showing Inlet Port Entry Cones, Crossbolts with Nuts Acting As Flange Abutment [Reproduced courtesy of Bonner Engineering Ltd,, Shoreham, United Kingdom]

Fig. 8.8 Cast Iron Liners, Showing Ports and Port Channels for Muff Installation [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

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Fig. 8.9 Three-Quarter Free End Engine View (Front Full PTO, Right-Hand Side (RHS) Crank, Cooling Air Entry, and Manifolding) [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

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Fig. 8.10 Three-Quarter, Driven End View of Engine on Testbed, Showing Oil Filter, Distributor, Riveted Top Cover, Assembled Gear Casing, and Front Bell Housing [Reproduced courtesy of Bonner Engineering Ltd,, Shoreham, United Kingdom]

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Fig. 8.1 1 Notional Sectional View of Engine through Liner And Crankcases, Only Upper Spark Plug Used [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

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The main drive of the engine could be taken either from the flywheel, or via a drive shaft that ran along the centerline of the engine emerging on the center ring on the front cover (Fig. 8.9).

8.3.3 Key Features of Africar Engine 8.3.3.1 Cylinder liners

The fully turned cast iron liners (Fig. 8.8) were of 334 m m length (2.23 x full stroke) with six milled radial inflow ports and six radial-flow exhaust ports. Presumably the engine had very low or no inlet air swirl. Inlet and exhaust port areas were -38% and -37% of cylinder bore area, and had very large port heights of 8.2% and 11.3% of full stroke, respectively. Each cylinder liner was secured by a flange on its left-hand side to the lefthand side crankcase with six bolts. The right-hand side of the liner was effectively free to expand in a close fitting bore in the right-hand side crankcase. Air-cooling of the cylinder liner was by 32 fins of 4 m m pitch and outer diameter equal to -118 mm, or 1.57 x cylinder bore. The fins were trimmed to -107 mm

along the crankshaft axis to enable an inter-cylinder center distance of 115 mm (1.53 x cylinder bore).

Inlet and exhaust ports were each contained in cylindrical channels, formed by two turned flanges (Fig. 8.11).

8.3.3.2 Air and Exhaust Port Muffs

Air and exhaust were conducted to and from the ports via cylindrical “muffs,” which were shrink-fitted to the cylindrical channels on the liner. Figure 8.12 shows the details of the inlet ring muff. Each scavenge port muff consisted of a stainless-steel peripheral annular channel welded to a stainless steel entry cone that engaged with one runner outlet of the inlet manifold, with an O-ring seal. The exhaust port muffs were similar, but the exit cone had a two-bolt plain flange to clamp to a corresponding flange on the exhaust pipe branch.

8.3.3.3 Crankcase

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The crankcase consisted of four separate LM 25 aluminum-alloy castings-the

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 8.1 2 Drawing of Inlet Ring Muff Details [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

front transverse casing; the two longitudinal main bearing carriers, between which the liners fitted; and the front portion of the driven end gear casing. Brian Mann’s sketch (Fig. 8.13) shows the notional arrangement, although this layout shows a central “combustion block” intended to connect “half cylinder liners,” which was not used. Figure 8.14 is another sketch showing the bolting arrangements and central combustion chamber.

A sectional drawing (Fig. 8.15) shows the actual crossbolting principle. The studs were only pretensioned at either end, with the central portion of the stud remaining unloaded until the firing and crankcase thermal expansion loads were applied.

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The photograph in Fig. 8.7, if examined carefully, shows the upper cross studs above the cylinder liners.

This arrangement contained the firing loads entirely in the crankcase elements and crossbolts. The cylinder liner was free to expand and not subject to axial loads.

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The two crankcase halves were also bolted axially to the front transverse casing and the driven end gear casing, again shown notionally in Fig. 8.13 and in the photograph in Fig. 8.7. 8.3.3.4 Covers

The crankcase was closed by three cast-aluminum-alloy covers-the front

Unusual Opposed Piston Engines

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Fig. 8.13 Isometric Sketch of Exploded View of Africar Crankcases and Central Combustion Chamber Block, Not Used on Actual Engine [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

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Fig. 8.14 Sectional Sketch of Notional Arrangement with Central Combustion Chamber Block, Not Used on Actual Engine [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

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Fig. 8.1 5 Diagrammatic View of Africar Crankcase Clamping Arrangement [Reproduced courtesy of Bonner Engineering Ltd., Shoreham, United Kingdom]

transverse cover, the two side covers for the crankcases, and the upper lightweight fabricated chest cover (Fig. 8.1l), which contained the cooling air. 8.3.3.5 Cranktrain and Gear Train

Each three-throw steel crankshaft, machined from solid, was counterbalanced for rotational forces only and was drilled from the main journals to the crankpins. The crankpin and main journal diameters were -60% and -67%, respectively, of the cylinder bore diameter. The two crankshafts were linked by a torsionally tuned spur gear train at the driven end. This gear train also provided the drives for the blower, the distributor, oil pumps, an alternator and additional drives for later developments, such as vacuum pumps, steering pumps, and hydraulic pumps. The torsional detuning, which shifted natural frequencies below 600 rpm, was achieved by a multiple compression-spring coupling between the rear flange of the crankshaft and the driven face of the connecting gear, The springs were arranged in a similar pattern to the torsion springs of a clutch.

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Surprisingly, no phase angle was used between the two crankshafts. Connecting rod length-to-radius ratio (L/R) was -3.47. No special measures were adopted for the small-end, the diameter of which was only 25% of the cylinder bore diameter. This was possibly rather small for a two-stroke, although the initial engine at 10:1 nominal compression ratio, and spark-ignited, would have had modest peak-firing pressures. These would have been offset by the inertia forces of the piston and connecting rod. The engine was intended for speeds from 1000-6000 rpm. Machined from solid aluminum-alloy, pistons were used with two compression and two oil scrapers. The piston was uncooled. Lubrication arrangements can be seen in Fig. 8.16

8.3.3 Outcome and Comment

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One engine was installed on the testbed (Fig. 8.10) and operated briefly before the engine and the other parts were transferred to Tony Howarth. The fate of the engines is unknown.

Unusual Opposed Piston Engines

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Fig. 8.16 Lubrication Circuit [Reproduced courtesy of Bonner Engineering Ltd,, Shoreham, United Kingdom]

The authors estimate that the Africar engine would have delivered approximately 143 N.m peak torque (4.5 bar Brake Mean Effective Pressure [BMEP]) at fairly low speeds, such as 2000-3000 rpm, and peak power would have been - 100 kW (5 bar BMEP) at -6000 rpm. This would have been remarkable at that period in comparison to four-stroke engines of that era. However, the spark-ignition fuel economy and hydrocarbon emissions would not have been tolerable, especially without any scavenge port lap. The Africar engine really should have been a diesel engine, but it was a sound policy to have debugged the engine as an SI engine before moving to the more challenging diesel application. The Africar engine would definitely have benefited (particularly as an SI engine) from an advance phasing of the exhaust crankshaft and from the use of a smaller cylinder bore to help burn rate. The single-sided ignition and lack of air motion are also

unlikely to have achieved adequate combustion burn rate for either satisfactory part- or full-load operation. Some slight angling of the inlet and exhaust ports and use of a pair of spark plugs (top mounted and with -90" included angle relative to the plane of the cylinder bore), plus some mild swirl-break features on the piston crown, would probably have been a better starting point than the simple cylindrical combustion chamber.

While the general engine configuration is at first sight simple and attractive, particularly with regard to enabling the air-cooled liners to freely expand and to avoid any axial forces, a question of torsional rigidity of the assembled crankcase arises, especially without structural top- or under-covers. Additionally, the center section of the crossbolts would have experienced very high cyclic loading in comparison to a preloaded bolt with a supporting compression member. This raises the question of bolt fatigue life, as well as the issue of natural frequencies of

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Opposed Piston Engines: Evolution, Use, and Future Applications transverse vibration of the crankcases on the relatively flexible crossbolts.

Similar questions can be raised about one of the earlier Africar engine concepts (Fig. 8.17), which proposed a three-piece liner, as per Doxford (Chapter 6), but the center “combustion section” was compressed by two-piece crossbolts, as shown in the lower scrap view. Other concepts, using an outer aluminum-alloy structural casting shrink-fitted to a steel sleeve, would have put the outer casting into axial compression while allowing the steel sleeve to theoretically avoid axial loading, though this is an unlikely outcome.

The Africar engine demonstrates what could be achieved by capable and brave engineers who were given an unusual challenge relative to their four-stroke background, and all realized on a very modest budget. There is much to learn from this unique arrangement of an OP engine.

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8.4 References

8.1 “The Napier Deltic,” by Ernest Chat-

terton, paper read at the SAE Transactions Vol. 64, pp. 422-424, U.S., 1956.

8.2 Africar, by Anthony Howarth, Chan-

nel Four Book, printed William Hollins Plc, Glasgow, ISBN 1-870427-00-9, 1987.

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Fig. 8.17 Isometric Sketch of Notional Arrangement with Central Combustion Chamber Block [Reproduced courtesy of Bonner Engineering Ltd,, Shoreham, United Kingdom]

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Chapter 9

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OPPOSED PISTON RESEARCH, CONCEPTS, AND PROTOTYPES 9.1 Introduction

This is a large chapter as OP engines have frequently been near the front of research into alternative engine configurations.

The chapter covers the pioneering work by Sulzer into high-pressure charging of its G-type OP engines (1938-1945) that reached 17.7bar brake mean effective pressure (BMEP).Two other remarkable pieces of research work, conducted in 1965 by Wallace and Timoney on the folded-crank Rootes TS3 engine, are then summarized. Two paper-study military engine concepts, one derived from the folded-crank configuration and the other a two-crank arrangement, are also reviewed. Detailed design and experimental information is provided for the ingenious Armstrong Whitworth Swing Beam OP engine, which was claimed to eliminate diesel knock without the use of fumigation, late injection, or very high fuelinjection pressures. The recent Advanced Engines Development Corporation (AED) engine, which is a fast, neat, and economical means of configuring an OP engine for experimental purposes, is briefly outlined. The chapter also reviews some experimental and predictive aspects of injection and combustion in OP engines. Many engines and concepts are omitted, mainly due to lack of space, but of particular note is the turbocharging work of Don Tryhorn at British Internal Combustion Engine Research Association (BICERA) (Ref. 9.1), performed on a Leyland L60

engine, and the cold starting and experimental work by CAV Ltd. (Ref. 9.2 and Ref. 9.3) on various United Kingdom military OP engines.

9.2 Research Background 9.2.1 Research Post WWII research into OP arrangements and prototypes began in 1946 in the United Soviet Socialist Republic, the United States, and in France, with probably the most diverse and in-depth work being done in the United Kingdom, as witnessed by the number of subsequent production applications. The main directions and motivation for this work were the desire for multifuel capability and easier cold starting, as both aspects were important to military engineers of the time. Defunct, or existing production OP engines, were used as “mules” to investigate various aspects of engine behavior.

9.2.2 Research in the United Kingdom and Ireland Professor F. J. Wallace (United Kingdom) (Ref. 9.4) and S. G. Timoney (Ireland) (Ref. 9.5) independently explored variable compression ratios and high boost using TS3 engines, or derived arrangements, as reported later in Section 9.5. Wallace demonstrated 16 bar BMEP at boost pressure ratios of 3:1 and Brake Thermal Efficiences (BTEs) of up to 42% with peak cylinder pressures of 124 bar. Timoney (see Section 9.6), as part of his doctorate,

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Opposed Piston Engines: Evolution, Use, and Future Applications designed and fabricated a 63.5 mm bore x 70 mm (x 2) stroke single-cylinder research engine, based on the TS3 crank-androcker configuration,but with the facility to dynamically alter the compression ratio by rotating the pivot points of the rockers on eccentrics. Air was supplied by a Roots blower that could either be driven electrically or from the engine crankshaft. The engine was initially run carbureted and with spark ignition to check the general functionality and then was switched to a -30 bar pintle-port nozzle, which was connected to either 80 Research Octane Number (RON) gasoline or 50 cetane diesel. The engine allowed smooth transitions from spark ignition (SI) gasoline to compression ignition (CI) diesel by adjusting the compression ratio (CR) from 8 to 12.5:1, andvice versa. With premixed gasoline at 8:l CR, 10.9 bar BMEP was achieved at 2400 rpm with spark ignition, and 5.8 bar BMEP was realized in CI form with injection timings of -15-20" before inner dead center (BIDC). Timoney continued to explore the reasons for the shortfall in CI performance. Rolls-Royce and Sir W. G. Armstrong Whitworth (Engineers) Ltd. performed considerable concept design work from 1960 to 1975 in the United Kingdom in the search for higher power-density arrangements for military tank applications. Some of these arrangements are shown in Chapters 5 and 7. Some interesting and pioneering development work is also outlined in Sections 9.9 and 9.1 1.

Lux of the United States Army TankAutomotive Center proposed a variable compression ratio (VCR) OP engine compounded with a turbine (Ref. 9.6). This conceptual OP engine (Fig. 9.1) was a derivative of a folded-crankshaft arrangement in which the power pistons are extended beyond the link joint to provide compressor pistons, and are of a larger displacement than the power piston. The proposed VCR was by rotation of eccentrics on the rocker shafts, similar to the Timoney engine. The authors proposed boost pressure ratios of 3:l and compression ratios to suit fuel type and the peak cylinder pressure limit of the engine, suggested as 120 bar. Projected bulk density was -0.7 kW/dm3and projected power density was 0.55 kW/kg.

Further research work in the United States includes the development of the micro-pilot prechamber-based version of the Fairbanks Morse engine for dual-fuel operation, i.e., natural gas ignited by less than 2% fuel mass of injected diesel, now sold extensively in the United States. The Engine Research Center of the University of Madison, Wisconsin, has investigated, using various experimental and predictive techniques, the combustion behavior of OP engines, in particular the spray and bulk swirl characteristics for optimizing fuel-to-air mixing for best air utilization and minimal smoke. The OPOCTnlengine (Chapter 4) must also count as a significant research project, much of this work being performed in the United States.

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9.2.3 Research in the United States 9.2.3.1 SwRI-Witzky Engine-Research

9.2.3.2 OPOCTM Engine

In 1965, Witzky and Meriwether of Southwest Research Institute (SwRI) and

A fairly recent concept, the Opposed Piston Opposed Cylinder (OPOCTM) engine

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Opposed Piston Research, Concepts, and Prototypes

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Fig. 9.1 Cross Section of Southwest Research Institute-Witzky Engine [Reproduced courtesy of SAE International, United States]

(Chapter 4, Ref. 9.7) consists of a pair of 180" opposed cylinders linked by a sixthrow crankshaft-essentially a horizontal coupling of two of the three-throw OechelhaeuserlJunkers engines (Chapter 2, Fig. 2.2 and Fig. 2.5). The OPOCTMengine has also arranged, for balance reasons, to have different air- and exhaust-piston strokes, and the inner pistons consist of an air piston of one cylinder and the exhaust piston of the other cylinder. The balanced loadingas exemplified in all single-crank, threethrow OP engines, such as the Doxford (Chapter 2, Fig. 2.18), Compagnie Lilloise des Moteurs (CLM) LC2 (Chapter 2, Fig. 2.23), and Junkers SA9 (Chapter 2, Fig. 2.24)-enables minimal main bearings and minimal crankcase scantlings, as all tensile loads are carried in the six connecting rods.

United States military ground vehicles, as well as some commercial applications. Power densities of greater than 1.645 kW1L at 3800 rpm are predicted, with power density greater than 1.05 kW1L. Specific power is 90.8 kW1L with predicted best BTE of 41.70%. At only 400 m m in height, the engine is very compact vertically, but is long and very wide and most suited to under-floor positioning in vehicles. Cylinders are added via a clutch system between each six-throw crankshaft unit.

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The OPOCT" concept is intended as a flat horizontal power unit for future

In 2008, EcoMotorT", a United States manufacturing company, is looking at various OP engine commercial applications, including the OPOCThT arrangement.

9.2.4 Summary Research Work

While the first half of the twentieth century was certainly the formative

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Opposed Piston Engines: Evolution, Use, and Future Applications period for OP engines with some limited volume applications by Junkers, CLM, Doxford, and Sulzer, the second half of the century has seen more production applications, with some enduring OP examples such as the Doxford, Napier Deltic, Fairbanks Morse, and some complex military automotive applications, such as the Leyland L60 and the Rolls-Royce K60. However, the Jumo 205E probably remains the icon for OP engines because of its power-to-weight ratio and brake thermal efficiency, although the Doxford, which remained substantially unchanged from 1930 to 1965, was arguably more enduring, famed for its reliability, and higher achieved BTEs than the Jumo. The twentieth century also saw a great diversity of OP engine arrangements, most of which offered relatively simple manufacturing requirements relative to poppet-valve engines, and potentially lower product cost per unit power. The lower cost potential never materialized, however, due to the absence of a low-cost scavenge pump and the relatively low manufacturing volumes. As with other two-stroke engines, emissions (particularly in terms of oil carryover and the oxygen-rich exhaust) have been the nemesis of OP engines, except for special applications that have emissions exemption. The rising cost of fuel, while only part of the expensive operational costs of fixed-wing light aircraft and helicopter propulsion, has prompted more interest in diesel engines. The Diesel Air engine and OPOCTMconcepts could be harbingers of a small OP engine renaissance.

9.3 Research Engines: Sulzer Brothers G Series OP Engines 9.3.1 Introduction

Ever since the production application of large two-stroke diesel engines for marine and stationary power plants, Sulzer Brothers of Winterthur, Switzerland, has engaged in research to identify practical solutions for high specific output and efficiency. The period from 1935 to 1955 was particularly active. During these years, Sulzer Brothers explored the application of turbocharging and high-pressure charging to two-stroke diesels, and investigated turbo-compounding in several forms including the use of free-piston engines. Much of this work was performed on OP engines of various types. The arrival of Dr. Curt Retschy as Head of Research at Sulzer Brothers may well have prompted both the intense effort to boost the performance of the two-stroke diesel as well as re-introducing the OP engine format. Retschy, born in Hanover (Germany), had been a collaborator of Professor Junkers, working on various OP engines and eventually the Jumo diesel series, and then assisting the French engine manufacturer CLM with its various Junkers licenses.

9.3.2 Two-Stroke, Turbocharging Issues Exhaust turbocharging of internal combustion engines had been pioneered by Alfred J. Buchi in association with Brown Boveri in 1920, when Buchi was employed by Sulzer Brothers, before he set up the Buchi Syndicate in 1926. Sulzer Brothers was inevitably geographically close to and drawn to this new technology for pressure charging engines.

Opposed Piston Research, Concepts, and Prototypes Pressure charging of two-stroke engines has always posed certain challenges, which may be broadly listed as follows: While the exhaust back pressure must rise in accordance with intake boost pressure to avoid excessive short circuiting of the fresh charge, there must also be the required pressure drop from scavenge to exhaust ports to purge and charge the cylinder. The pressurecharged four-stroke is not as sensitive to scavenge pressure as the two-stroke. The extra scavenging air, which was typically 40% in excess of the cylinder displacement, adds to the flow requirement of the turbocharger, which in any case has to be higher for a two-stroke versus a four-stroke, to meet the added firing frequency requirement. The two-stroke turbocharger mass-flowto-pressure ratio requirements are therefore more demanding than the four-stroke requirements. The thermal loading of the two-stroke cylinder components is higher than that of an equivalently powered fourstroke because the two-stroke does not have the additional induction stroke that enables internal “air cooling” of the cylinder. Pressure charging increases the thermal loading, which is always a particular concern for engine researchers. Two-stroke engines always need positively displaced air for starting and light loads. This may not always be feasible with turbocharging when the exhaust energy is inadequate. It was against this background that Retschy and Sulzer Brothers commenced work in 1935 to substantially

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increase the pressure-charging levels applied to two-stroke engines, and to identify practical limits and optimal benefit levels of boost pressure and exhaust energy recovery.

9.3.3 Sulzer Categorization of Pressure Charging levels

As early as 1912, Sulzer Brothers had evolved an “extra charging process that enabled a small amount of higher density air to be pumped into the cylinders of twostroke engines after the primary scavenge and exhaust ports had been closed (Ref. 9.8 and Ref. 9.9). This involved the use of supplementary higher-pressure (1.2- 1.4 bar) compressors and provided 10-30% increase in BMEP, and was adopted in production on Sulzer Brothers engines and by other licensees.

By 1936, Sulzer Brothers categorized the following three possible types or levels of pressure charging: “Extra Charging,” as already described, but with additional crank-driven compressors capable of achieving 1.7 bar (abs) boost pressure. “High Supercharging,” in which mechanically coupled compressors provided up to 5.0 bar (abs) boost pressure, giving a very high exhaust flow. The exhaust energy would be partially recovered by an exhaust turbine that was mechanically coupled to the engine crankshaft. In more general terms, this corresponded to “turbo-compounding.” “Power Gas Process,” in which the engine power was devoted primarily to providing compressed air for the engine reciprocator, which became essentially a gas generator for an exhaust turbine,

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Opposed Piston Engines: Evolution, Use, and Future Applications coupled to the external load but only linked by the exhaust gases to the base reciprocator.

Initially using one of the larger ZG-type OP engines (Chapter 7), and then moving to the twin-crankshaft type OP engine, Sulzer Brothers systematically explored the relationship of compressor, engine, and turbine, finally evolving turbo-compound design concepts from 1942 to 1947.

9.3.4 Preliminary Research Between 1936 andl940, Sulzer Brothers (Ref. 9.10) conducted several series of tests demonstrating that raising the scavenge pressure to 2.0 bar effectively doubled the BMEP of two-stroke OP engines to 12 bar at speeds of 750 rpm. Further increasing the scavenge pressure to 3.0 bar (abs) resulted in -14.5 bar BMEP at 750 rpm, while at 6.0 bar scavenge pressure the engine could be tuned to give a smokeless 17.6 bar BMEP The nonlinear response of the BMEP scavenge air pressure was undoubtedly because the Sulzer engineers were using increasing air-to-fuel ratios with increasing boost in order to limit the thermal loading. The compression ratio of the engine would undoubtedly have been reduced significantly to maintain structurally acceptable peak cylinder pressures, and special measures, such as heater plugs, were taken to preheat the incoming air in order to ensure cold starting. As the scavenge pressure was raised, an increasing amount of engine power was required to produce the compressed air. From the nominal value of -6% engine brake power to produce “ambient” scav-

43 6

enging, 2.0 bar (abs) scavenge pressure required -25% engine brake power, while 5-6 bar scavenge pressure necessitated the whole engine power to drive the compressor. The exhaust energy was rising continuously with the increasing scavenge pressure, especially as the compression ratio of the engine was reduced to maintain acceptable peak cylinder pressures. At 5-6 bar scavenge pressure, the exhaust turbine was generating all the useful work. So the engine was only driving the compressor and acting as a gas generator to the turbine.

9.3.5 High Supercharging with 4ZGA19 Engine A four-cylinder, ZG-type engine (Chapter 7) of 190 x 300 (x 2) proportions with after-cooling and a geared turbine was tested at up to 2.0 bar (abs) scavenge air pressure from its own reciprocating compressors, achieving a nominal smoke-free power output of 1022 kW at 750 rpm (Fig. 9.2, plotted versus propeller law power requirement), corresponding to 12.0 bar BMEP, with a bsfc of 212 g/ kWh (39.7% BTE). This was achieved in 1940 and the 4ZGA19 engine (Fig. 9.3) was then used to develop components for operation at this rating that could be sustained for one hour continuously, proving that a 100% increase of the usual two-stroke “naturally aspirated performance could be durably sustained. However, the 4ZGA19 engine was never put into production.

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By 1939, several years after Retschy’s arrival at Winterthur, Sulzer Brothers moved away from the horizontal, foldedcrankshaft OP engine arrangement to a

Opposed Piston Research, Concepts, and Prototypes

Fig. 9.2 Performance Parameters for 4ZGA19 Engine Following Propeller Law Demand

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Fig. 9.3 4ZGA19 Engine on Pressure-Charging Test with Turbine at Winterthur, 1940 [Reproduced courtesy of Wartsila (Switzerland) Ltd., Switzerland]

437

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Opposed Piston Engines: Evolution, Use, and Future Applications vertical, twin-crankshaft OP configuration, known as the “G” series. Reasons for this change included some concerns about the number of joints with the folded-crankshaft arrangements; twin crankshafts were considered dynamically stiffer. Additionally, vertical packaging may have been considered to be better suited than horizontal arrangements for large marine and railway applications.

In the United States from 1933 to 1940, Fairbanks Morse (FM) was developing the vertical twin-crankshaft OP engine 38D (Chapter 7) for marine, submarine, and rail applications. ALCO, FM’s competitor in the United States market, was a Sulzer Brothers licensee and this may have influenced Sulzer Brothers’ vision of future markets, especially as the United States Navy was seeking suppliers for submarine engines at that time.

9.3.6 High Supercharging with 618 Engine The G18 series, of 180 x 225 (x 2) bore and stroke, was developed with a smaller 1G12 unit and later built in six- and eight-cylinder forms with various types of pressure charging. Four spur gears linked the two crankshafts with the drive being taken from the lower shaft. Fuel pumps were driven in pairs by camshafts either side of the engine, in a similar arrangement to the Jumo 205, and each pump was connected to two injectors on each side of the cylinder. In addition to the single-cylinder G-type, four experimental multicylinder G series engines were built and tested. The first was the six-cylinder 6G18 (1941-1945), followed by a rebuild with a stiffer crank-

43 8

case. An eight-cylinder 8G18 was derived (1946-1949) from the 6G18, and a second unit was built in the same period for ALCO.

9.3.6.1 General Arrangement

Scavenge and pressure-charging air of the 6G18 (Fig. 9.4 and Fig. 9.5) were supplied by two turbocompressor units lying horizontally on the top of the engines. The high-pressure turbocompressor operated at 13,300 rpm, while the low-pressure unit ran at 8878 rpm, with a rated engine speed of 850 rpm. The compressors were of the axial-flow type with a total of 23 compression stages and with intercooling between low- and high-pressure stages. Both turbines were three-stage axial expander arrangements. The horizontal turbocompressor layout allowed gearing through slipping clutches and quill shafts to the primary gear drive at the front of the engine so that the engines could be started via the geared turbocompressors, which then became self-sustaining. Considerable expertise was gained at Sulzer Brothers in vibration isolation between the cyclic torque impulses of the OP engine and the geared connections to the turbocompressors. Gears were mounted on multiple radial leaf springs to center hubs to provide isolation by compliance. This must have required considerable engineering to avoid resonances in the leaf-spring systems. For experimental purposes, the 6G18 engine could be readily switched from single-stage to dual-stage turbocharging by adding or removing the high-pressure turbine and compressor. As peak cylinder pressures were limited to 100 bar with the G18 engines, starting aids included glow

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Opposed Piston Research, Concepts, and Prototypes

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Fig. 9.4 8G18 engine [Reproduced courtesy of Wartsila (Switzerland) Ltd., Switzerland]

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Fig. 9.5 8G18 Engine Concept with Mechanically Coupled Two-Stage Turbocharger [Reproduced courtesy of Wartsila (Switzerland) Ltd., Switzerland]

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Opposed Piston Engines: Evolution, Use, and Future Applications plugs and an oil burner that preheated the scavenge air, though the latter was only required for the 6 bar scavenge pressures. 9.3.6.2 Performance

Reported test results (1942-1945) at 2 bar scavenge pressure for the 68.7 L 6G18 were 1164 kW at 850 rpm (11.8 bar BMEP) with a specific fuel consumption of 232 g/kWh (-36.5% BTE). This relatively disappointing fuel consumption was attributed to the low compression ratio. At 6.6 bar absolute scavenge pressure, power at 850 rpm was 1745.6 kW, corresponding to a power-toweight ratio of 0.19 kW/kg and 17.68 bar BMEP Overall, it seems that the very high pressure boosting did not yield acceptable full- or part-load fuel economy, or satisfactory part-load operation. The use of very high air-to-fuel ratios to ensure controlled component temperatures, with the corresponding requirement of high scavenge flows, with typically 40% flow-to-exhaust ratio, was probably a major contributing factor for the relatively disappointing full-load fuel consumptions. The reduced compression ratios that were required to avoid high full-load cylinder pressures were the cause of the poor part-load fuel efficiencies, although this was not stated by Sulzer Brothers. The achieved BMEP was remarkable, even by present-day standards, especially as these ratings appeared to be continuously sustainable. 9.3.6.3 Construction Details

Operation of the 8G18 engines seems not to have been trouble-free, as there were issues with pistons, piston rings, and thermal cracking of the liners; 1492 kW was achieved, but this was only 80% of the target power.

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A cast 11% silicon/aluminium cylinder barrel, mounted on cast crankcases, was initially used for the 6G18 tests, but was replaced in 1945 with a fully steel construction like the Fairbanks Morse 38D arrangements.

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An eight-cylinder G18 version, using an all-welded steel crankcase, was built in 1946; many panels used 4 mm steel. This engine was used for research until 1952. A similar engine was built by Alcoa under license in 1946 and transferred to the United States Navy in 1947, but no further information is available. These engines (Fig. 9.4) had a vertical turbocompressor that was approximately 70% of the engine height and driven at the front of the engine, next to the geared drive between the crankshafts. Final output drive was taken by a cardan shaft beneath the turbocompressor. The turbocompressor was connected to the engine crankshaft by a hydraulic coupling, a first set of spur gears, a bevel gear, and a second set of spur gears, while the turbocompressor appears to have been supported by two rolling element bearings plus a double tapered rolling element bearing to take thrust. The turbine appears to have had two expansion stages, one axial at -245 mm-diameter and one radial at 185 mm-diameter, operating at an overall pressure of 2.53 bar. The compressor had eleven axial stages beginning at -330 mm-diameter and reducing to 265 mm-diameter, providing a scavenge pressure of 2.94 bar. Intercooling was not used.

Various conceptual arrangements of the turbo-compound system, such as that shown in Fig. 9.5, can be found in the Sulzer Brothers’ archives. This arrangement, dated approximately 1941 and covered by

Opposed Piston Research, Concepts, and Prototypes Swiss patent #206797, had opposed reciprocating compressors driven at one end of the engine. These pumps had a displacement of approximately 1.36 x engine displacement. The crankshaft gear drive end had an exhaust turbine coupled through a pair of reduction spur gears to the intermediate idler next to the exhaust crankshaft. Other conceptual arrangements featured individual-piston, double-acting scavenge pumps with their connecting rods linked to the lower piston connecting rods and arranged in a vee-bank bolted to the lower half of the crankcase An interesting view of what might be the 6G18 engine (Fig. 9.5) shows possibly two turbochargers lying horizontally on top of the base engine with the turbine drive at the flywheel end of the engine, with a horizontally split compressor casing from midway to the front of the engine. The air delivery from the visible compressor is along a vertical lagged stack pipe with a tapered and lagged horizontal air manifold. Exhaust gases are collected in the upper lagged manifold with expansion joints, leading to multiple pipe routes into the near-side exhaust turbine, and then into the second turbine stage on the far side of the engine. What appears to be an intercooler is sited above the turbochargers, feeding the air into the compressor midway along the engine. 9.3.6.4 618 Design Architecture

Cylinder pitch was 1.4 x cylinder bore, which is compact for a twin-crankshaft OP engine.

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The forged-steel crankshafts had bored main journals and crankpins, with main journal and crankpin diameters of 66% and 63% cylinder bore diameter, respectively, and bearing length-to-diameter ratios (L/D) of 0.4 and 0.47, respectively Pistons were of the rotating body type sitting on an internal armature that connected with a spherical-ended connecting rod. Four compression rings were used, possibly one air ring, and either one or two oil control rings. There were four injectors per cylinder, supplied by cam-driven pumps mounted on the side of the engine. The engine external dimensions were 3.575 m length x 2.343 m height x 1.192 m width, equivalent to 19.86 x bore, 10.41 x stroke, and 6.62 x bore, respectively. For one hour continuous target rating of 2052 kW at 1000 rpm, bulk density was 0.206 kW/L, with engine weight of 9000 kg yielding a power-to-weight ratio of 0.23 kW/kg; specific power was 22.37 kW/L, which would have been a very impressive achievement not only then, but now.

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The base engine had liners of length 4.18 x engine stroke, with exhaust and inlet ports having heights equivalent to 27% and 24% of engine stroke. Length-toradius ratios (L/R) for the exhaust and air connecting were 4.6 and 3.5 respectively.

A list of the various ZG- and G-type OP research engines is shown in Table 9.1. 9.3.6.5 Application Studies

The G-type engines spawned many application possibilities, some of which are listed below (Ref. 9.9): A 6624 of 240 x 300 x 2 for a Canadian single-screw ship installation project, delivering 1119 kW at 700 rpm, using positive-displacement scavenge pumps at

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Opposed Piston Engines: Evolution, Use, and Future Applications “ambient”pressure. In 1942, a nine-cylinder version operating at 2.5 atmospheres scavenge pressure was proposed, with a target power of 3730 kW at 750 rpm, with a power-to-weight ratio of -0.18 kW/kg. A supercharged 8G2 1, delivering 1940 kW (2600 bhp) at 565 rpm was considered for a 10,000 bhp merchant ship. A 9G18 delivering 2611 kW (3500 bhp) at 1000 rpm was needed for a peak rating of a stationary power plant. For a rail traction application, a 16G18, based on a geared twin-bank vertical (“H”) arrangement, would have delivered 3170 kW (4250 bhp) at 928 rpm with a one-hour rating of 3580 kW (4800 bhp) at 1000 rpm. Scavenge pressure would have been 2.0 atmospheres absolute. This engine would have had a power-to-weight ratio of 0.1 kW/kg and a bulk density of 0.123 kW/L. A three-crankshaft, vee-form 12G12 would have given 1492 kW (2000 bhp) at 1500 rpm with a scavenge pressure of 3.0 atmospheres absolute.

One hundred and forty-four 8G12 engines, arranged to drive 72 generators, were proposed for a diesel electric ship installation requiring 149,200 kW (200,000 shp). Boost pressure would have been 6 atmospheres absolute. Eight 9G18 engines, each rated at 2372 kW (3180 bhp) at 1030 rpm, would have powered a 1000-ton displacement destroyer in 1943, via hydraulic couplings to quadruple input gearboxes. These engines were of the type shown in Fig. 9.4 with vertical turbochargers. Several other similar arrangements were considered for similar and larger destroyers.

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1 1 Build Date

Sulzer Ref.

Bore (mm)

1936

1ZG14

140 190 120

I

1941

I

6G18

180 180 320

I 1946 I

8G18

180

These application studies generated various ideas for cylinder configurations, including the H and vee arrangements, many of which were the subject of patent applications.

9.3.7 632 Series Encouraged by the high specific output of the lightly pressure-charged (-2.0 bar abs) ZG14 and G18 engines, Sulzer Brothers

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Stroke (mm)

Power/ cyl. (kw>

BMEP (bar)

rpm

220x2

119.4

13.7

750

4

96

300x 2

264.5

12.3

750

2.25

96

150x2

100.7

11.8

1500

2

122

225x2

I

194

I

11.8

I

850

Scavenge Maximum Pres. Pres. (bar) (bar)

I

I

101

225x2

290.9

17.68

850

6.6

-

400x2

497.3

10.4

440

2

81

225x 2

I

233.1

I

12.1

I

1000

I

Table 9.1 Some Sulzer Opposed Piston Research Engines, 1936-1 949

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2

2.5

I

101

zy zyxwvu Opposed Piston Research, Concepts, and Prototypes

began working on a 6632x 400mm (x 2) marine engine running at 440 rpm with a 4:lgear for a propeller-shaft speed of 110 rpm for merchant ships. Testing began in July 1943 and continued until 1947,covering the full range of operational modesambient scavenged, turbo-compounded and pressure-charged with multiple positive-displacement pumps, and turbocompounded and pressure-charged with a single positive-displacement pump. In contrast to the other G-type engines, the G32 had horizontal cylinders (Fig. 9.6)to facilitate the engine coupling to the gearbox or propeller shaft and to provide easier maintenance. The vertical versions of the G series may have been considered to have

an excessively high output power takeoff point, but Fig. 9.4indicates satisfactory air crankshaft height, as was also used with the Fairbanks Morse 38D8% OP engines. On the other hand, multiple-engine installations were more difficult with the horizontal OP engine configurations.

Crankshaft center distance was 2.74m with the output from the center gear (Fig. 9.6)to a Maag reduction/combining gearbox, while engine length was 6.645m, with a height of 2.02m above the propeller centerline. The engine was fully reversible.

9.3.8 General Arrangement

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As can be seen from Fig. 9.7,initially the scavenged air was supplied by double-

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Fig. 9.6 Sulzer Horizontal Turbo-Compounded 6 6 3 2 and Maag Reduction Gearbox at Driven End, Winterthur Testbed, 1943-1 947 [Reproduced courtesy of Wartsila (Switzerland) L td., Switzerland]

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 9.7 8G18-Type Engine Concept with Reciprocating Pumps [Reproduced courtesy of Wartsila (Switzerland) Ltd., Switzerland]

acting piston pumps driven off the air-side shaft, and mounted vertically above the crankshaft; these pumps, with 510 mm bore x 303.4 mm stroke, had a theoretical displacement of 1.93 x the engine displacement, enabling a scavenge pressure of 1.7 bar (abs). Streamline plate-type reed valves, as used on the ZG-type engines and the smaller G types, controlled the airflow direction.

For turbo-compounding, an additional 400 mm bore double-acting, reciprocating scavenge pump was mounted above each existing scavenge pump, providing a total scavenge pump displacement of -3.44 x engine displacement. This was simplified to a single large-bore pump of 590 mm x 303.4 mm in 1945, giving a theoretical scavenge ratio of 2.23 x engine displacement.

For scavenge pressures of -1.7 bar (abs), a turbocharger with eight axial compression stages and a single exhaust axial turbine was connected in series with the reciprocating compressors, providing a scavenge pressure capability of 2.3 bar (abs). Turbocharger speed was 7500 rpm, or 17.05 x engine rated speed, and connection to the main inter-crankshaft gear train was via a twostage reduction spur gear set and a hydraulic coupling. For reversing, the exhaust gases bypassed the turbine with a butterfly valve and a shutoff valve. Several patents (Ref. 9.1 1) covered these arrangements.

Four injectors fueled each cylinder, supplied from two pumps actuated by a camshaft, driven from the gear next to the exhaust crankshaft, and mounted on the upper crankcase surface.

-

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9.3.9 Performance

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With ambient scavenging, the rated BMEP was 6.52 bar, corresponding to 2014 kW (2700 bhp) at 500 rpm, or a mean piston speed of 6.67 mls, with 222 g1kWh brake specific fuel consumption (bsfc)(38% BTE) at full load. Peak cylinder pressure was 69-71 bar.

Opposed Piston Research, Concepts, and Prototypes In the second stage of development in late 1943, with 2-2.3 bar (abs) scavenge pressure from the combined effects of a turbocharger and the reciprocating pumps, BMEP rose to 10.54 bar, or 2984 kW (4000 bhp) at 440 rpm and full load bsfc of 219 g/kWh, i.e., -38.8% BTE. Compression pressures were 58-59 bar with firing pressures of 93-95 bar. In the third stage, during 1944, all scavenge air was supplied by mechanically driven reciprocating pumps to sustain the engine power at 2984 kW, with all exhaust energy driving the exhaust turbine connected via the two-step reduction gear into the inter-crankshaft drive. Engine BTE was 39% fuel energy. In the fourth and final development stage, the 590 m m bore x 303.4 m m stroke reciprocating pumps replaced the twostage reciprocating pumps, and the 2984 kW was maintained with a bsfc of 218 g/kWh. This finally selected, positive-displacementpump-only arrangement for scavenge air, with all exhaust energy to the turbine, was favored by Sulzer Brothers as it ensured fast transient response to load changes and reversing, which was not always feasible when the scavenge air depended partly on the generation of exhaust energy, as was the case with turbocharging.

Fig. 9.6, while the fuel pumps were located on the right-hand side (RHS) of the engine, as viewed from the Maag gearbox. The scavenge pistons are driven by a three-bar link, connected to a crosshead, from the air-side connecting rod.

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9.3.11 Summary Other than the relatively limited volumes of the ZG-type engines, Sulzer Brothers did not put into production other two-stroke opposed piston engines, in spite of a wide range of prototype arrangements (Fig. 9.8). Table 9.1 lists the range of OP engines from 1936 to 1949. Post 1950 Sulzer Brothers’ engine products remained the slow-running cathedral-type trunk-piston twostrokes, or medium-speed four-strokes, and turbocharging was used rather than mechanical turbo-compounding. It is perhaps puzzling that Sulzer Brothers did not capitalize on the remarkable specific power and bulk density of their OP engines. The lack of commercialization of the two-stroke OP engines for large slowrunning applications was probably associated with the difficulties of packaging and maintenance of a twin-crankshaft system. For medium-speed engines, Sulzer Brothers may have concluded that while high specific outputs were certainly achievable with modest scavenge pressures, brake thermal efficiencies in excess of 40% fuel energy were difficult to achieve because the parasitic burden of the scavenge air became too significant above 2.0 bar (abs) boost pressure,

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9.3.10 Construction Details

The gas exchange of the 6632 was distinguished by positive-displacement scavenge pumps on the left-hand side (LHS) of the engine. The six piston-rod crosshead guides can be seen protruding from the compressor cylinders in

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Figure 9.8 Transverse Cross Section of 8G18 [Reproduced courtesy of Wartsila (Switzerland) L td,, Switzerland]

with the turbochargers then available in 1945-1950. Mechanical turbo-compounding or gas generatorhurbine power output was also not pursued due to the relatively low turbine efficiencies associated with the limited turbine expansion ratios available with the relatively small turbocharger units. Fuel efficiencies therefore rarely exceeded 39% of fuel energy. Other manufacturers had different views, and turbocharged OP two-stroke medium-speed engines still remain in production. Wright entered production with its mechanically turbo-compounded spark-ignition Cyclone engine for civil aviation in 1953.

9.4 Fuel-to-Air Mixing and Combustion in Opposed Piston Engines 9.4.1 Differences between Central- and Side-

Injection The fuel-to-air mixing processes of OP engines differ from the “central injection”

446

of high-speed direct-injection (HSDI) engines in several ways: Fuel enters from the periphery (“side injection”) of the cylinder and must traverse the cylinder diameter. Impingement of fuel on the piston crown and liner were almost inevitable with the relatively low-pressure injection systems that had a minimal number of nozzle holes. With relatively high levels of impingement, fuel mixing by evaporation from liner and piston surfaces will be significant and will clearly vary markedly between starting and warmed operation. Fuel must avoid the relatively lowvelocity central air core of the cylinder, where mixing is poor, in contrast to the fuel plumes of a central-injection system where the jets move outward from a quiescent zone to increasingly higher swirl velocities. Use of a central piston promontory to displace the air from the quiescent center core, as frequently used in

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Opposed Piston Research, Concepts, and Prototypes HSDI engines with central injection, is more difficult to implement in the OP engine because fuel impingement on this promontory would mix relatively slowly due to the low air motion at the center of the cylinder. Also, such a promontory could only be used on the exhaust piston as it would seriously influence the scavenging if used on the air piston. The uniflow and cylinder wall ports of the OP engine enable high swirl generation without the need for squish and a deep center bowl to accelerate the swirl, as used in fourstroke HSDIs. The momentum of the fuel with side injection inevitably augments or reduces the air swirl, depending on whether the injection is “against” the swirl, or “ w i t h the swirl. With central injection and radial fuel movement, any swirl tends to bend the spray plumes, so that cylindrical swirl is not unduly reduced by the fuel momentum. The subsequent combustion of the OP engine is very much a consequence of this very asymmetric combustionsystem geometry and mixing process, which is generally substantially more heterogeneous than that of central injection, probably leading to very different NOx, smoke and particulate behavior.

9.4.2 Visual Study of Fuel Spray and Combustion in Rootes TS3 Engine, 1968

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A Rootes TS3 single folded-cranktrain engine (Chapters 4 and 9) was modified by removal of the side covers (Fig. 9.9) and placement of quartz optical crowns on each piston of the central cylinder (Ref. 9.11). Photographs of the movement of the fuel and combustion were made using Schlieren photography (Fig. 9.10) with a color filter and Fastex very high-speed framing camera. Experiments were performed to examine the effects of injector nozzle, injection timing, spray direction, air swirl, gasoline, diesel fuels, and boost pressure (load) variants. The optical access (Fig. 9.1 1, Ref. 9.1 1) enabled the spray plume evolution to be viewed, as well as the combustion initiation point and the “cloudiness” of the subsequent combustion. The engine was motored at 1000 rpm, the piston was lubricated by oil jets, and air was supplied from a large compressor. Fuel (75 mm3/stroke)was injected, corresponding to trapped air-to-fuel ratios of 20.3:l. Several cycles of injection and combustion could be captured before the windows clouded. As the trapped compression ratio was only 12.7:l due to the configuration of the quartz piston crowns, versus the 16:l of the standard engine, the scavenge air was heated to 80°C to achieve the same compression temperatures as the standard engine. The pressure drop across the ports in most of the tests was -0.3 bar, corresponding approximately to the naturally aspirated full load condition at 1000 rpm, resulting in an end-ofcompression swirl ratio of - l 2 : l , which

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In spite of little published information on the fuel-to-air mixing characteristics of OP engines, some aspects of the OP fuel spray, mixing, and combustion behavior are reviewed, based on historical and current work.

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 9.9 View of TS3 Center Cylinder with Sump Covers Removed for Optical Access [Reproduced courtesy of C.A. Vandervell (now Delphi), Acton, United Kingdom]

was the estimated swirl of the TS3 engine at 1000 rpm. The standard TS3 injection timing with diesel fuel was 20" before inner dead center (BIDC), and the standard nozzle was a single

0.58 mm-diameter x 1 mm-length hole injecting at 15" offset from the cylinder radius, with a counterclockwise direction of swirl (Fig. 9.12, Fig. 9.13, Fig. 9.14, and Fig. 9.15). With a nozzle-

Fig. 9.10 Schematic Diagram of Optical System for TS3 Engine

448

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Opposed Piston Research, Concepts, and Prototypes

Fig. 9.1 1 Quartz Widow Arrangements in TS3 Pistons

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opening pressure drop of - 150 bar, engine output could not be monitored as there were only several firing cycles. Results of some of the experiments are summarized in the following sections. 9.4.2.1 Effect of Injection Timing

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The interpretations of the Schlieren photographs (Fig. 9.12,9.13, 9.14, and 9.15) show that the spray plume, with a spray direction of 15", was deflected increasingly toward the cylinder bore with retarded injections (-0-10" BIDC), and combustion occurred closer to the nozzle tip with late injection. All injection timings caused impingement on the cylinder bore, some -65 mm from the nozzle tip. With injection timings of 30-40" BIDC, ignition started in the impingement zone, which is relatively rich and poorly mixed, resulting in slow and smoky burning. Ignition delay increased from 11" to 27" (Fig. 9.16) for an injection timing advance of 20" BIDC to 40" BIDC.

The rate of spray-tip penetration (Fig. 9.17) increased significantly with increasing injection advance, primarily due to the reduced charge density at earlier injection timings. At 20" BIDC injection timing, the time for spray impingement was 0.9 ms (5" crank angle [CAI), versus 0.5 ms (3"CA) at 40" BIDC injection timing.

9.4.2.2 Effect of Spray Direction

Spray direction changes indicated that spraying against the swirl ("upstream" injection, a = 0 to -15" direction) resulted in 18% higher initial rates of pressure rise, 36% increase in peak rates of heat release, and 18% higher peak pressures (Fig. 9.18) for a spray direction change of +15" to -15". However, the main phase of burning was slower with upstream injection versus downstream injection. These characteristics were attributed to an initial increase in mixing with the contraflow of fuel and air with

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 9.1 2 Impression of TS3 Fuel Plume at 1000 rpm, 0" BlDC Dynamic Start of Injection (Sol), 1 x 0.58 mm D x 1 mm L Nozzle, 12:l Counterclockwise Swirl at Top Dead Center (TDC), 0.35 Bar Inlet Charge Pressure [Reproduced courtesy of C.A. Vandervell (now Delphi), Acton, United Kingdom]

Fig. 9.13 As 9.1 2, 10" BlDC Dynamic Sol, X marks first ignition location [Reproduced courtesy of C.A. Vandervell (now Delphi), Acton, United Kingdom]

Fig. 9.14 As 9.1 2, 20" BlDC Dynamic SO1 [Reproduced courtesy of C.A. Vandervell (now Delphi), Acton, United Kingdom]

Fig. 9.15 As 9.1 2, 30" and 40" BlDC Dynamic Sol [Reproduced courtesy of C.A. Vandervell (now Delphi), Acton, United Kingdom]

450

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Opposed Piston Research, Concepts, and Prototypes

Fig. 9.1 6 TS3 Ignition Delay and Effective Compression Ratio vs. SO1 Timing

Fig. 9.1 7 Observed Spray-Tip Penetration vs. SO1 Timing

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Opposed Piston Engines: Evolution, Use, and Future Applications increasingly upstream injection angles, but the fuel spray momentum eventually reduced the air swirl momentum so that fuel-to-air mixing was impaired in the main burning phase. The spray plume also became more diffuse, i.e., less penetrating and larger in diameter, with upstream spray and combustion severely deteriorated. What appeared to be considerable brown clouds of soot that did not clear were observed in the two to three combustion cycles captured by the combustion photography. Spray penetration (Fig. 9.19) was much reduced with upstream spray. A two-hole nozzle (0.42 mm-diameter x 1 mm-length) with increased downstream spray direction (a = 15" and 30") followed the previous trends of lower rate of pressure rise and more favorable combustion with increasing downstream injection direction.

9.4.2.3 Effect of Nozzle Variants

The single-hole nozzle diameter was varied from 0.58 mm to 0.8 mm, maintaining the length at 1 mm, and a 0.58 mm-diameter x 0.4 mm-length nozzle was evaluated, all at the a = 15" spray direction, although injection pressure varied from the baseline values according to the nozzle hole size, making it difficult to clearly identify trend effects. For the 0.4 to 0.58 mm hole diameter increase, the injection period and pressure decreased for the same 75 mm three-stroke fuel delivery, as might be expected. Further increase in the nozzle diameter resulted in a lengthening of the injection period due to falling injection pressures, which eventually resulted in multiple injections for the 0.7 and 0.8 mm-diameter holes. The larger hole sizes generally increased penetration (Fig. 9.20), even with the reduced pressure, but

Fig. 9.1 8 Rate of Pressure Rise and Peak Cylinder Pressure vs. Spray Direction

452

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Next Page

Opposed Piston Research, Concepts, and Prototypes

Fig. 9.19 Observed Spray-Tip Penetration vs. Spray Angle

Fig. 9.20 Observed Spray-Tip Penetration vs. Nozzle Diameter

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Chapter 10

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OPPOSED PISTON ENGINE APPLICATIONS AND THE FUTURE 10.1 Introduction

The four-stroke engine is supreme in almost all fields of application, mainly because of its capability for low emissions, but also due to its excellent fuel efficiency, robustness in terms of ease of starting and combustion stability, and mechanical durability. So why bother to consider the two-stroke OP engine? One reason for considering OP engines is that these engines may offer solutions to challenges facing the internal combustion engine in certain applications. Given the dominant position of the four-stroke, any potential role for the OP engine would have to show compelling advantages, when both the four-stroke and two-stroke OP engines are compared equitably. For example, for the same emissions and performance, what are the relative fuel efficiencies,weights, package volume and costs of the two engine types? This chapter proposes a simplified answer to these questions for the following power unit applications: 32 kW utility engine 8 kW and 80 kW Unmanned Aerial

Vehicle (UAV) 400 kW heavy duty (HD) truck These engine applications have been selected because each has particular challenges and is not associated with massive annual production volumes with enormous investment requirements, as is the case for light duty (LD) passenger car engines. In fact, small OP engines would have more cost benefits for LD vehicle

applications than for HD trucks, as both cost and selling price are more important in the LD segment than the HD market. However, the time scale for introducing new technology is probably much longer in the LD than the HD fields, partly because the investment and market risks are greater in the LD than HD fields. Therefore, an OP application for LD vehicles was not considered for these reasons.

The important question of future emission compliance of the two-stroke OP engine is addressed at the end of this chapter. The comparisons between two- and fourstroke engines are based on combinations of historical and contemporary performance data, with predicted cost, weight, and sizing. Sizing comparison is restricted to the base engine, and does not address the fully dressed engine, which is broadly similar for both engine types, except in the case where the two-stroke OP engine uses a low-pressure or positive-displacement scavenge blower. Weight comparisons are made for the major engine systems that consist of at least 80% of the engine weight, and do not include smaller items such as gaskets, fixings, pipe work, brackets, blow-by system, and sensors. Dress items, other than starter and alternators, are also excluded. The cost comparison compares the same items used in the weight comparison and is based on 2007 material costs with an

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Opposed Piston Engines: Evolution, Use, and Future Applications allowance for machining and assembly costs in the Western world.

10.2 Utility Engine Reliability and cost are probably the most important aspects for a utility engine. Though two-stroke engines tend to have been renowned for piston ring issues, many examples of extremely long service and reliable two-stroke engines exist, without histories of ring failures. Additionally, the two-stroke avoids any valve train issues and is generally easier to service, and the OP engine is easier to inspect in service than the four-stroke engine. So it therefore becomes primarily a question of cost between the four-stroke and two-stroke utility engine. Utility engines cover a large range of applications from several horsepower to approximately 50 kW. Beyond that power, the “utility”applications tend to become specific, such as power generation, combined heat and power, or gas pumping. Arbitrarily, the comparison between two- and fourstroke utility engines is made at a 32 kW (43 bhp) rating, which is typically achieved with a naturally aspirated, 2 L, four-stroke engine at 2800 rpm. The assumed four-stroke is an inline, four-cylinder engine, with overhead valve configuration (Fig. 10.1 and Fig. 10.2). The two-stroke OP engine is assumed to be a single-crankshaft (Wittig type, see Chapter 2, Section 2.2.1, Fig. 2.2), with scavenge air provided by a piston pump attached to the outer piston, as used on the Junkers, HK, and CLM of the 1930s (see Chapter 2, Fig. 2.22, Fig. 2.23, and Fig. 2.24). A single injector per cylinder is assumed, based on cost saving, but clearly at the

expense of air utilization and performance. This arrangement results in a tall and long two-stroke engine (Fig. 10.1, Fig. 10.2, Fig. 10.3, and Fig. 10.4).

As can be seen from Table 10.1 and by calculation, even at an assumed fairly modest performance of 5.5 bar BMEP for the twostroke, the OP engine offers a 41.7% reduction in engine displacement, 35% specific weight reduction, and 19.6%cost advantage versus the four-stroke engine, while the specific bulk of the two-stroke OP engine is -15% lower than that of the four-stroke engine. A more compact two-stroke OP engine would be possible with some type of rotating scavenge pump, such as a Roots blower as exemplified by the Coventry Climax H30, but this would result in a similar or higher cost than the four-stroke, mainly due to the high cost of the Roots blower. The breakdown of cost and weight (Fig. 10.5 and Fig. 10.6) indicates that the absence of the cylinder head and valve train and a lighter flywheel are the main weight advantages for the two-stroke. The crankcase of the single-crank arrangement is particularly long due to the series packaging of the side connecting rods on either side of the cylinder bore and ports. In terms of cost, the advantages of the OP two-stroke are in the lack of cylinder head and valve train, and also in the reduced fuel injection and electronic control equipment requirements. Outlines (shown dotted) of the allowable space for the induction and exhaust silencing and aftertreatment are shown in Figs. 10.1- 10.4, indicating considerably more space is available within the engine profile for the two-stroke engine.

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Opposed Piston Engine Applications and the Future

Fig. 10.1 Four-Stroke, Four-Cylinder Diesel, Side View

Fig. 10.2 Four-Stroke, Four-Cylinder Diesel, Front View

Fig. 10.3 Two-Stroke, Two-Cylinder Diesel, Side View

Fig. 10.4 Two-Stroke, Two-Cylinder Diesel, Front View

52 1

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Opposed Piston Engines: Evolution, Use, and Future Applications Engine Type

Four-Stroke

Two-Stroke

lnline 4

OP 2

kW

32

32

rPm

2800

2800

Water-cooled

I Bore(mm)

I

86

I

68

Stroke (mm)

92

2 x 85.8

Cylinders or Rotors

4

2

Displacement (L)

2.1 37

1.246

Estimated BMEP (bar)

6.41

5.5

I Estimated Weight (kg) L x H x W(mm)

I

174

I

113

I

400x650~500 360x735~420

zyxwvutsrq 130

111

Estimated Cost ($US @ 500 units per year)

2306

1853

kW/L Displacement

14.97

25.68

kW/L Bulk

0.25

0.29

0.18

0.28

Estimated Bulk (L)

kW/kg

I

Table 10.1 Four- and Two-Stroke 32 k W Engines, Parameters

Another potential benefit of the two-stroke OP engine is that it rejects substantially more heat per given quantity of exhaust than the four-stroke engine, and substantially less per given quantity of coolant. This is a major advantage for combined heat and power applications, as the heat exchangers for the two-stroke would be significantly smaller than those for the four-stroke.

10.3 Unmanned Aerial Vehicle Engine, 8 kW Opposed Piston engines are well suited for diesel applications for fixed-wing light aircraft and helicopter engines, where power-to-weight ratio, powerto-bulk ratio, fuel efficiency, simplicity, and safety are compelling advantages. As has been shown with Diesel Air and

OPOC'" engines (Chapters 3 and 4), aviation opportunities for OP engines are being pursued in at least two publicized instances. Aviation applications are inevitably very demanding functionally, as well as challenging from product liability and customer confidence standpoints. The last two points are daunting for an engine manufacturer as any hint of liability due to an aircraft incident is likely to be fatal for the engine manufacturing company, even if the cause of the accident is unrelated to the engine, such as operator error, failure of the fuel supply system, or freak we ather. Prudence therefore suggests that manufacturers should take lower-risk routes

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Opposed Piston Engine Applications and the Future

Fig. 10.5 Four- and Two-Stroke 32 kW Engines, Weight Comparison

Fig. 10.6 Four- and Two-Stroke 32 kW Engines, Cost Comparison

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Opposed Piston Engines: Evolution, Use, and Future Applications to develop new aviation engines before launching into the very sensitive aviation field. Nevertheless, future transport requirements forecast a strong growth for both fixed- and rotating-wing aircraft with requirements of 100-500 kW per engine, which seems to be a field that is not well suited to turbo-machinery in terms of cost or fuel efficiency.

A softer entry into the aviation field is to address the growing market requirements of large unmanned aerial vehicles (UAV), powered gliders, and the aircraft segment between larger microlights and light aircraft, sometimes referred to as ultralight aircraft. While these are safer market segments in terms of liability,they are very price sensitive and not as demanding in fuel efficiency or power-to-weight ratio as the larger aircraft. However, the large UAV, used for photo and video reconnaissance,both military and commercial, and requiring 50-80 kW, is a field where long flight, high power-to-weight ratio, low bulk, and high payload are extremely important requirements, and this may be a lower-risk starting opportunity for the OP diesel engine. Unmanned aerial vehicle engines in the 1-100 kW power range are becoming an

increasingly important niche market. Applications are beginning to move from purely military to civilian such as coast guard and highway surveillance, and certain types of logistics. Currently, the engine is used mainly to drive the propeller, but there is an increasing demand for some electricalpower generation. Below 40 kW, power requirements are usually met by two-stroke engines, although modern four-stroke engines using rotary valves (Ref. 10.1) are making inroads into this segment. The rotary Wankel engine (Ref. 10.2) has established itself in the 40-75 kW segment with one- and two-rotor versions and electronic port-injected fueling systems. Use of dieseltype fuels, such as JP8, is an increasing requirement and has been met with both premixed spark-ignited and compressionignition combustion systems (Ref. 10.3). Both 8 kW and 80 kW applications for OP engines have been considered for UAVs, because of the simplicity, cost, powerto-weight ratio, and power-to-bulk ratio advantages. In the 8 kW application, the baseline is assumed to be a simultaneously firing Boxer two-stroke (Fig. 10.7 and Fig. 10.8)of loop scavenge configuration, sparkignited, with either one or two carburetors. The twin-ignition, two-stroke OP engine

Fig. 10.7 Two-Stroke Boxer 8 kW Two-Cylinder, Front View

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Opposed Piston Engine Applications and the Future

Fig. 10.8 Two-Stroke Boxer 8 kW Two-Cylinder, Plan View

(Fig. 10.9 and Fig. 10.10) is assumed to be a crankcase-scavenged,twin-crankshaft arrangement with the center propeller driven by a tooth belt, which also links the crankshafts. Twin carburetors may be necessary for the OP engine to avoid unfavorable pulsation or long fuel transport effects of a single carburetor. The same bore, stroke, and BMEP are assumed for both the boxer and OP two-strokes,with a mean piston speed of 10.5 m/s at 8000 rpm. As can be seen from Table 10.2, there is little difference in estimated power-to-weight ratio and unit cost of the Boxer and the OP

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engines, though the OP engine does offer a 14%better power-to-bulk ratio over the Boxer version due to its reduced width. Additional advantages for the OP engine not listed in the table would be better fuel consumption and power-to-weight ratio due to the more favorable port timings and scavenging of the OP engine, though the magnitude of each of these is beyond the scope of simple estimates. One issue for the OP would be the question of the small out-of-balanceprimary forces arising from the phasing of the two crankshafts. This might require isolation absorption for some applications.

Fig. 10.9 Two-Stroke OP 8 k W One-Cylinder, Front View

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52 5

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Opposed Piston Engines: Evolution, Use, and Future Applications

Fig. 10.10 Two-Stroke O P 8 kW One-Cylinder, Plan View

Boxer

OP

2-s

2-s

kW

8

8

rPm

8000

8000

40

40

39.78

2 39.78

2

1

0.1

0.1

Engine Type Air-Cooled

Bore (mm) Stroke (mm) Cylinders or Rotors Displacement (L)

I Predicted BMEP (bar).

I

12

I

6

7.17

6.84

320 x 70 x 70

280 x 70 x 70

Estimated Bulk (L)

1.57

1.37

Estimated Cost ($US @ 500 units per year)

1086

1027

kW/L (Displacement)

80

80

kW/L (Bulk)

5.1

5.83

kW/kg

1.12

1.17

Estimated Weight (kg) L x H x W(mm)

I $US/kW

I

136

Table 10.2 Boxer and OP 8 kW UAV Engines, Parameters

52 6

I

128

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Opposed Piston Engine Applications and the Future The breakdown of cost and weight (Fig. 10.11 and Fig. 10.12) indicates the significant tradeoffs are between two crankshafts, crankcases, cylinder heads, exhaust, and carburetors. In summary, at less than 10 kW, the OP offers a base engine package advantage, but the routing of exhaust systems, location of the carburetors, the potential reliability risks of the belt drive of the OP engine, and the potentially easier cooling of the Boxer engine may favor the Boxer. There does not appear to be a very compelling advantage for the OP engine for this application, other than the relative ease of dieselization of the OP engine versus the Boxer two-stroke.

10.4 Unmanned Aerial Vehicle Engine, 80 kW Currently, twin-rotor, water-cooled Wankel rotary engines, using electronic

port-fuel injection (EFI), dominate the 80 kW (about 108 bhp) UAV market, using AVGAS and 92RON fuels. The spark-ignited OP engine alternative, sized for 80 kW, is assumed to have three water-cooled cylinders and bore x stroke has been set at 65 x 57.4 (x 2) in order to enable 7000 rpm with moderate piston speeds of 13.4 m/s.

Relative profiles of a 700 cc Wankel (Fig. 10.13 and Fig. 10.14) and a 1143 cc OP engine (Fig. 10.15 and Fig. 10.16) show the OP engine to have a very wide and narrow profile in contrast to the Wankel engine, but the OP engine is some 20% shorter than the Wankel engine. Overall, this leads to a 4: 1 bulk advantage (Table 10.3) for the OP engine over the Wankel engine. The weight of both engines is similar at -52 kg in a partially dressed state.

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System System Cost Comparison for Boxer and OP UAV Engines (IOOcc, 2 piston, 8kW @8000rpm, SI JPS Carburetted)

System

Fig. 10.11 Boxer and OP UAV Engines, Cost Comparison

527

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Opposed Piston Engines: Evolution, Use, and Future Applications

Weight Comparison of Major Systems for Boxer & OP UAV (IOOcc, 2 piston, 8kW @8000rpm, SI JP8 Carburetted)

Fig. 10.12 Boxer and O P UAV Engines, Weight Comparison

Engine Type

Wankel

OP

80

80

Water-cooled kW

Irm I Bore(mm) I Stroke (mm)

I I I

8000

Cylinders or Rotors

I I I

7000 65 2 x 57.4

2

3

Displacement (L)

0.7

1.143

BMEP

17.1

6.0

Estimated Weight (kg)

53

49

500 x 450 x 250

400 x 120 x 420

L x H x W (mm)

I Estimated Bulk (L) I I Estimated Cost ($US @ 500 units per annum) I

56

?

I I

20

?

k W I L Displacement

114

70

k W I L Bulk

1.42

4

1.5

1.6

?

?

kWIkg $USlkW Table 10.3 Wankel and OP 80 k W Engines, Parameters

52 8

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Opposed Piston Engine Applications and the Future The cost of the three-cylinder OP engine, with full electronic EFI and digital-ignition control, is estimated to be $5000 at 500 units per annum. This compares to an estimated Wankel engine cost of $6500 at the same production volume as the OP engine.

are already in use. For United States 2010 compliance, -70% NOx after-treatment will be required, as is already being applied to European trucks with selective catalytic reduction (SCR) systems. Various types of

It is also estimated that an OP sparkignited engine with a delivery ratio of unity would have a bsfc of 298 g/kWh (28% BTE) in comparison to the 329 g/ kWh (25% BTE) of the Wankel. This would give the OP a corresponding range advantage Both engines would have similar torque fluctuation levels and dynamic balance. So the prime advantage of the OP engine over the Wankel engine in this 80 kW UAV application would be a large reduction in frontal area, which would lead to further fuel consumption advantages for the OP engine.

Fig. 10.13 Wankel 80 kW, 0.7 L, TwoRotor, Front View

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10.5 Heavy Duty Truck Engine, 400 kW

10.5.1 The Current Four-Stroke Truck Engine

Almost all current heavy duty (HD) truck engines are of the inline, six-cylinder, fourstroke configurations, with displacements above 12 L, typically 15-16 L. The full-load thermal efficiencies of these engines are usually of the order of 43-39% from peak torque speed of 1200 rpm to peak power speed of 2200 rpm. The corresponding full-load BMEPs are of the order of 22- 17 bar. These high efficiencies are achieved at full-load engine-out NOx levels of less than 0.5 g/kWh for United States 2007 on-road compliance, with -30% full-load exhaust-gas recirculation (EGR) and therefore boost pressure levels of 3 bar gauge. Oxidation and particulate traps

Fig.lO.14 Wankel 80 kW, 0.7 L, TwoRotor, Side View

Fig. 10.15 Two-Stroke 80 kW, 1. I 4 L, Three-Cylinder OP, Front View

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Opposed Piston Engines: Evolution, Use, and Future Applications

Fig. 10.16 Two-Stroke 80 kW, 1.14 L, Three-Cylinder OP, Plan View

overhead camshaft (OHC) valve train have been adopted for most HD engines, and many use nodal drives for the gear trains. Typical overall sizes (Fig. 10.17 and Fig. 10.18) are almost cuboid with 1.2 m length x 1.2 m height x 0.9 m width, without inclusion of after-treatment. In spite of increasingly stringent exhaust emission requirements for HD engines, thermal efficiencies of these four-stroke engines can be expected to rise to greater than 45% in the next decade, mainly due to turbocompounding. 10.5.2 Proposed OP Two-Stroke Truck Engine

The heavy duty truck market would at first sight seem to be an unsuitable opportunity for the OP engine with its known particulate and oil-consumption difficulties.

530

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However, some staunch four-stroke truck engineers are now talking of “rethinking the diesel” to meet the post-2010 emission challenges that are expected. Uncertainty exists of what is required to break the apparently endless spiral of increased engine and after-treatment complexity, reduced engine efficiency, very large increases in heat rejection, cylinder pressures in excess of 200 bar, and very large product cost increases. While the urea/SCR after-treatment approach does enable the continued development of thermal efficiency towards 45% BTE and beyond, the urea is an expense that can be equated to approximately 2-4 percentage points loss of BTE or added running costs, and adds to the service bill. So what could the OP engine offer to this severely emission-constrained scenario?

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Opposed Piston Engine Applications and the Future

Fig. 10.17 Four-Stroke 400 kW, 16 L, Six-Cylinder Diesel, Side View

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First, for a given power requirement, a very modestly turbocharged OP engine would only need to deliver 10-12 bar BMEP to match the 20-24 bar BMEP of the fourstroke. Twelve bar BMEP is well within the capabilities of a mildly turbocharged OP engine, as demonstrated by the Fairbanks Morse 38D8%engine. As the two-stroke OP would be operating at a significantly lower BMEP than the four-stroke, (12 vs. 24 bar), a significantlyhigher level of EGR would be possible with the two-stroke OP for a given boost level or maximum cylinder pressures (PmJ limit. For example, United States HD 2007 engines are typically operating at 25% cooled EGR, 4 bar absolute boost pressure, and peak cylinder pressures of 180-200 bar at maximum torque equivalent to 21 bar BMEP* equivalent two-stroke could operate, combustion permitting, with 10% EGR at this power rating, with a predicted two-stroke NOx level that is 60% lower than that of the four-stroke, and a P, that is 30% lower for the two-

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Fig, 10.18 Four-stroke 400 kW, 16 L, SixCylinder Diesel, Front View

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Opposed Piston Engines: Evolution, Use, and Future Applications stroke; these predictions (from an established combustion and NOx model) assume the same geometric compression ratio for both engine types. The difference in NOx is primarily due to the lower maximum bulk gas temperatures of the two-stroke because of the lower boost pressure and temperature. These predictions are based on the assumption of similar air-to-fuel ratio gradients and combustion behavior for the two- and four-stroke engines. Though these are unlikely combustion assumptions in that the side injection of the two-stroke OP has different and larger air-to-fuel ratio gradients than the symmetrical central injection of the four-stroke, it is felt that modern injection systems will be able to realize greatly improved air-to-fuel ratio gradients with side injection. Some of this work has already been reported with the OPOC'" engine (Ref. 10.3).It is therefore assumed that a modern side-injection system will be able to approach, though probably not fully achieve, the in-cylinder NOx and particulate levels of a central-injection combustion system at similar levels of BMEP, and therefore the two-stroke will have at least 40% lower in-cylinder NOx than the four-stroke at the same torque. It is difficult to comment on the smoke and particulates of the OP engine, other than to reference the relatively good characteristics of the Fairbanks Morse 38D8% engines with respect to these pollutants. The emission price to pay for use of the OP engine for low NOx would be burning of the two-stroke carryover oil in an oxidation catalyst. Judging by hearsay of production two-stroke engines, oil consumption could amount to 1% of fuel consumption at rated power, but modern

oil additives and low ash lubricants should enable this to be reduced to well below 1% of the rated-power fuel consumption. Modestly boosted BMEP levels (Table 10.4)for a 12 L three-cylinder engine were assumed from previous and current OP engine performance (Chapters 4,7, and 9) for a speed range of 800- 1800 rpm. This speed reduction was an attempt to trade off the power advantage of the two-stroke for fuel efficiency and reduced pumping losses. Typical OP bore-to-stroke ratios of 0.83 were assumed, which were in fact very similar to those of the HD four-stroke, and bore spacings of 1.4 x cylinder bore were assumed for the OP engines, though lower values may be achievable with modern cylinder liners (Table 10.4).Twin exhaust and intake manifolds are also assumed for the OP (as per most previous OP engines) with a twin-crankshaft configuration because of the need for high cranktrain stiffness at the relatively high cylinder-pressurerequirements for HD engines versus other applications. The gear train linking the crankshafts would be sited at the driven (flywheel) end (Fig. 10.19 and Fig. 10.20) and would also be used to drive many of the auxiliaries that do not need to be belt-driven. The turbocharger, linked to the manifolds on each side of the engine, would be sited at the rear of the engine, above the flywheel housing. Both two- and four-stroke engines are assumed to have similar common-rail injection systems, operating at the same injection pressure levels.

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532

10.5.3 HD Package, Weight, and Cost Comparisons

The resultant three-cylinder OP engine package can be seen to be approximately

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Opposed Piston Engine Applications and the Future Engine Type

Four-Stroke

Two-Stroke

lnline 6

3 cyl

kW

400

400

rPm

2200

1800

Water-cooled

I Bore(mm)

I

140

I

I

128

Stroke (mm)

178

2 x 155

Displacement (L)

16

12

Predicted BMEP (bar).

13.27

11.13

Estimated Weight (kg)

1,425

945

1.2 x 1.2 x 0.9

0.6 x 1.2 x 0.54

1296

389

11,713

10,314

25

35.93

kW/L (Bulk)

0.31

1.03

kW/kg

0.28

0.42

$USlkW

29.28

25.79

LxHxW(m) Estimated Bulk (L) Estimated Cost ($US @ 500 units per year) kW/L (Displacement)

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Table 10.4 Four- and Two-Stroke Heavy-Duty Truck Engines, Parameters

the same height as the four-stroke, but with 50-60% reduced width and length, mainly due to the half-cylinder count of the two-stroke and the substantially narrower gear train. Weight (Fig. 10.21) and cost (Fig. 10.22) comparisons indicate that the two-stroke OP engine could be approximately 34% lighter than the equivalent-performance four-stroke, and cost 12%less. The disparity in the weight and cost comparisons is due to the following assumptions: The two-stroke OP engine is assumed to need a significantly larger turbocharger with electrical assist to enable starting and therefore avoiding the need for a scavenge blower; the turbocharger

cost is therefore doubled for the twostroke relative to the four-stroke. Both two- and four-stroke configurations require a similar level of fuel injection, drive, and auxiliary complexity. Both engines require similar engine management systems because of the equivalent injector count. More complex exhaust manifolds and EGR systems may be required for the two-stroke OP engine versus the fourstroke, because of the twin-manifold configuration of the two-stroke OP engine and the necessary pressure differential across the ports of the two-stroke engine.

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Outlines (shown dotted) of the required oxidation, particulate traps, and NOx

533

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Opposed Piston Engines: Evolution, Use, and Future Applications

zyx zy

Fig. 10.19 Two-Stroke 400 kW, 12 L, Three-Cylinder Diesel, Side View

Fig. 10.20 Two-Stroke 400 kW, 12 L, Three-Cylinder Diesel, Front View

after-treatment volumes are shown notionally in Fig. 10.17 through Fig. 10.20, further emphasizing the potential package space advantage for the OP engine. In this context, it is assumed that the OP two-stroke engine will have a substantiallY larger Oxidation requirement to handle the burning of the increased lubrication oil carryover.

future OP engine. Two particular technology developments and opportunities-the electrically assisted turbocharger and variable compression ratio Piston (VCR)-have added advantages for the two-stroke OP engine versus the four-stroke*

10.6 Enabling Technology The modern OP engine would benefit from all the component improvements that have contributed to the success of today's four-stroke engine. The improvements to piston ring, cylinder liner and lubricant, turbocharging, and fuel-injectiontechnologies would be particularly important for the

Electrically assisted turbochargers (Fig. 10.23), as exemplified by the eCtTM (Ref, 10.3) from EcoMotors International Inc., offer a means of avoiding the need for positive-displacement scavenge blowers to start and idle two-stroke engines. " In this particular example of the ect'", a 2.5 kW 14 V permanent-magnet (PM) motor/generator is located between the compressor and turbine wheels, with external oil-feed to the bearings and liquid-cooling of the PM housing and

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Opposed Piston Engine Applications and the Future

Fig. 10.21 Four- and Two-Stroke, 400 kW, Truck Diesel Engines, Weight Comparison

Fig. 10.22 Four- and Two-Stroke, 400 kW, Truck Diesel Engines, Cost Comparison

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Opposed Piston Engines: Evolution, Use, and Future Applications

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Fig. 10.23 Electrically Controlled Turbocharger ectTMEngine from EcoMotors International Inc. [Reproduced courtesy of Advanced Propulsion Technologies Inc., California, United States]

bearing supports. These types of turbochargers also enable power assist of the compressor for helping with fast upload transients. They can absorb excessive turbine power through the PM generator, and can facilitate control of the boost pressure levels to specific targets.

Variable Compression ratio (VCR) piston (Fig. 10.24) technology, developed primarily for heavy duty diesel four-stroke engines to enable higher outputs for limiting peak-cylinder pressures, almost went into production after 30,000 hrs of single- and multi-cylinder development with the Teledyne Continental Motors AVCR 1360 Battle Tank engine (Ref. 10.4, Ref. 10.5, and Ref. 10.6). However, improvements in materials and structures in 1980 enabled adequately high outputs without the need for VCR. The VCR technology used by British Internal Combustion Engine Research

536

Association (BICERA), Teledyne Continental, and subsequently Daimler Bend Mahle, typically used two-piece pistons (Fig. 10.25, Ref. 10.7, and Fig. 10.26, Ref. 10.8) with upper- and lower-hydraulic chambers supplied by oil through the connecting rod. Pressure within these chambers was controlled by check valves. On reaching the controlling cylinder pressure during the compression or expansion stroke, a relief valve in the upper chamber dumped oil into the crankcase and allowed the outer piston skirt and crown to move “downward” toward the wrist pin, thus relieving the cylinder pressure. On the next exhaust stroke, the inertia force on the moveable outer piston skirt and crown “lifted this moving part relative to the anchored wrist pin carrier, thus increasing the upper chamber volume and allowing oil to enter it from the connecting rod. This process was repeated each inertia stroke, typically with 0.17 mm piston

zy

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Opposed Piston Engine Applications and the Future

Key 10.24 1

Outer piston shell

2

Inner piston body and wrist pin carrier

3

Upper chamber

4

Lower chamber

5

Oil feed from engine lube oil system

6

Slipper collector

7

Oil supply chamber to valves 8 and 9

8

Upper chamber admission valve

9

Lower chamber admission valve

10

Lower chamber orifice

11

Upper chamber pressure relief valve

Fig. 10.24 Teledyne Continental Four-Stroke Variable Compression Ratio Piston [Reproduced courtesy of SAE International, United States]

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Key 10.25 1

Check valve to

2

Upper chamber

3

Check valve to lower chamber

4 5

Orifice

6

Outer piston

Pressure relief valve

7

Inner piston

8

Wrist pin

9

Buffer ring

10

Lower chamber

zyxw 11 Upper chamber

1 2 Valve mounting housing

Fig. 10.25 Daimler Benz/Mahle Four-Stroke Variable Compression Ratio Piston [Reproduced courtesy of SAE International, United States]

537

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Opposed Piston Engines: Evolution, Use, and Future Applications

Key 10.26

zyx zyxw

1

Upper chamber

4

Pressure relief valve

2

Lower chamber

5

Dumpvalve

3

Upper and lower chamber check valves

6

Lower chamber orifice

Fig. 10.26 BlCERl Lightweight Four-Stroke Variable Compression Ratio Piston [Reproduced courtesy of SAE International, United States]

movement per inertia stroke, so that the outer piston recovered its original position and higher compression ratio, assuming that the cylinder pressure on the compression and firing strokes had not exceeded the designed pressure limit of the system. Thus the outer piston shell could be imagined to be moving incrementally “up” or “down” according to the inertia and gas forces, depending on the load and speed of the engine. The two-stroke VCR piston has a different arrangement (Fig. 10.27,Ref. 10.9, and Fig. 10.28, Ref. 10.10)with only the upper hydraulic chamber and a pressure relief valve, similar to the four-stroke VCR system, as the two-stroke engine experiences only net downward forces at low to moderate engine speeds. In this twostroke VCR case, oil is transferred from the connecting rod oil passage into an intermediate accumulator volume during the expansion stroke, by virtue of the inertia forces on the oil column. After BDC, the oil pressure in the accumulator volume

538

can exceed that in the principle hydraulic chamber, and the moveable piston crown and skirt can be progressively pumped “upward,”cycle by cycle, again depending on the engine speed and cylinder pressure, and the scavenge air pressure during the scavenge period.

To ensure control of the cylinder pressure, each cylinder of a four-stroke engine must have a VCR piston, whereas an OP engine only requires one piston per cylinder. There are advantages and disadvantages of locating the VCR function in either the air or exhaust piston of an OP engine. Locating the VCR in the air piston would almost certainly require an arrangement in which the moveable element is within the fixed peripheral crown part (Fig. 10.27), so that the scavenging flow behavior is always with a fixed outer piston crown profile. Whereas the fourstroke piston VCR was highly developed, there is no evidence that any two-stroke piston VCR systems have been successfully made and operated. Nevertheless,

zy

zyxw

Opposed Piston Engine Applications and the Future

zyxwvuts zyxwvu

Fig. 10.27 Two-Stroke VCR, Vertical Section on Wrist Pin Axis and Plan Section through Valves [Reproduced courtesy of Dr. J. Mansfield, Phaphos, Cyprus]

Fig. 10.28 Two-Stroke VCR, Vertical Section across Wrist Pin Axis and Scrap View of Pumping Valve [Reproduced courtesy of Dr. J. Mansfield, Phaphos, Cyprus]

piston VCR would further enhance the power-to-weight ratio and output capability of the OP two-stroke engine, particularly with high levels of EGR as required in heavy duty engine applications.

So, for engines operating for substantial periods at f d load, VCR mainly offers a means of operating at reduced peak pressures to enable more lightweight structures. In the case of engines mainly operating at part-load with occasional full load requirements, such as power units for light duty transport vehicles and fixed-wing aircraft, the VCR piston offers increased power for a given engine structure, as well as improved part-load fuel efficiency,

VCR, therefore, offers means of improving full-load engine output and part-load fuel efficiency, in the latter case through the use of the higher compression ratios at light load. However, test work and predictions indicate that full-load BTE decreases with VCR, mainly because the engine operates with lower compression ratio at full load, and this disadvantage more than offsets the benefit of the higher mechanical efficiency of the engine at the reduced compression ratio and higher full loads.

10.7 Summary This speculative chapter uses simplified analyses and comparisons to make preliminary investigations of the potential of the OP engine for specific applica-

zyxwvutsrq zyxwvuts

Opposed Piston Engines: Evolution, Use, and Future Applications tions. Chapter 1 outlined some of the technical challenges and opportunities facing the OP engine. In the main, these challenges are relatively low risk for the suggested UAV and light-aircraft applications of OP engines, but represent higher risks for engines governed by emission and high durability requirements, such as the utility and HD engine applications. In spite of these emission challenges, new OP designs and developments from Achates Power Inc. and Golle Motor AG (Ref. 10.11, Ref. 10.12, and Ref. 10.13) appeared in 2006-2008 for CHP applications, using technologies to isolate the ports and pistons from crankcase oil splash. While the advent of the Diesel Air, OPOCT”, and Baker OPTD (Ref. 10.14) engines go some way to support the propositions of this chapter, OP engines and their possible renaissance remain very much the dreams and aspirations of a few enthusiasts. More serious considerations of the OP engine potential require a much wider appreciation of this type of engine, which is unlikely due to the risk-aversion predilection of current times, the comfort of “staying with the pack” and not moving out of “comfort zones.” It may also be that the powertrain world has too many other challenges with CO, reduction, fuel cost crises, hybrids, electrification, and new fuels. Moving away from the dependable four-stroke may be deemed an unnecessary risk amid these pressing challenges. However, it is frequently the case that radical improvements require a paradigm shift in thinking and design while maintaining known manufacturing methods, and

that technology shifts are more likely to be driven by smaller, emerging manufacturers, rather than the established product leaders.

zyxwv

10.8 References

10.1 Rotating Cylinder Valve 4-Stroke Engine: A Practical Alternative, by Keith Lawes, (RCV Engines), SAE 2002-32-1828. 10.2 www.uavenginesltd.co.uk. 10.3 www.ecomotors.org. 10.4 A Variable Compression Ratio Engine Development, by W. A. Wallace and F. B. Lux, SAE Paper 762A. 10.5 Recent Developments in Variable Compression Ratio Engines, by J. C. Basiletti and E. F. Blackburne, SAE Paper 660344,1966. 10.6 AVCR 1360-2 High Specific Output Variable Compression Ratio Diesel Engine, by J. R. Grundy, L. R. Kiley, and E. A. Brevick, SAE Paper 760051,1976. 10.7 Development of Pistons with Variable Compression Height for Increasing Efficiency and Specific Power Output of Combustion Engines, by F. G. Wirbeleit, K. Binder, and D. Gwinner. SAE Paper 900229. 10.8 BICERI Patent GB2110791 B. 10.9 BICERA Patent GB902707. 10.10 BICERA Patent GB1032523. 10.11 United States patent pub.# US2007/0215093 A1.Internal Combustion engine with Hypocycloidal Drive and Generator Apparatus. 10.12 United States patent pub.# US2008/0163848 Al. Opposed Piston Engine with Piston Compliance. 10.13 www,gollemotor,ag. 10.14 www.bakerengineeringinc. com.

zyxwvutsr zyxw zyxwvuts Abbreviations

Terminology

Acronym

Adiabatic Efficiency

AFR Al Al D C AODC

I Air-to-Fuel Ratio

I BODC

Meaning

Unit

Actual temperature change of a process versus the theoretical temperature change with no heat transfer

O/O

I Mass ratio of air to fuel

I

Auto lanition

Self igniting, usually due to heating

After Inner Dead Center

Position of piston in the cylinder between IDC and O D C

0

After Outer Dead Center

Position of piston in the cylinder between ODC and IDC

0

Position of piston in the cylinder between ODC and IDC

0

Position of piston in the cylinder between IDC and O D C

0

Before Inner Dead Center Before Outer Dead Center Bore

x

Stroke ( x 2)

I

Usual method of expressing OP engine bore and stroke

BSN

Bosch Smoke Number

Measures the amount of soot in a specified volume of exhaust aas

BTE

Brake Thermal Effic iencv

Work from combustion, acting at flywheel, as O/o fuel enerav

BMEP

Brake Mean Effective Pressure

Brake power of an engine at a particular operating condition expressed in an average pressure acting on the pistons on every working cycle

bsfc

Brake Specific Fuel Consumption

Fuel weight expressed in time rate per unit of power at the engine flywheel

Bulk Density

Power of engine divided by space volume occupied bv engine

mm

O/O

bar

g/kWh kW/L or kW/dm3

Capacity per Cvlinder Capacitv in L for each engine cvlinder

Llcvl

CHP

Combined Heat and Power

kW

CI

Compression Ignition

Combustion commenced by auto ignition

Fuel Cetane number

Measure of ease of auto-ignition

Compression Ratio (geometric)

Ratio of cylinder volumes at O D C to IDC

Compression Ratio (effective)

Ratio of cylinder volumes at final port closina to IDC

Compressor Work

The work expended by the crankshaft in

I moving the scavenge pump

kW

541

zyxwvutsrq

Opposed Piston Engines: Evolution, Use, and Future Applications

I

I

Numerical approximation to the solution of mathematical models of fluid flow and heat transfer

Crank Angle

Usually referenced to IDC, exhaust piston

Direct Injection

Direct injection of fuel into the cylinder

Exhaust Gas Recirculation

Portion of the exhaust gases recirculated to the intake- usually expressed (approximately) as a mass percentage of C 0 2 in the intake relative to C 0 2 in the exhaust

Exhaust Port Closing

Usually expressed in crankshaft degrees before I D C of the exhaust piston

EPo

FIE

I

IDC

ITE imep

I

IVO

0

0

Exhaust Port Opening Usually expressed in crankshaft degrees after I D C of the exhaust piston

I

Exhaust Valve Closing Crank angle at which exhaust valve closes either before or after O D C Exhaust Valve Opening

Crank angle at which exhaust valve opens either before or after O D C

Expansion Ratio

Ratio of expansion cylinder volumes at O D C to I D C

I o I

I ozyx I 0

Fuel Injection Equipment Friction

Difference between indicated and brake power

kW

Friction Mean Effective Pressure

Usually measured by motoring and specified in bar

bar

I Fuel Consumption I

zyxw

CFD

cI

Computational Fluid Dynamics

I

Fuel consumption of a land vehicle

zyx I L/100 km I

Inner Dead Centre

Piston at highest position in cylinder

Indirect Injection

Fuel injection outside the cylinder

Indicated Thermal Efficiency

Work from combustion, acting on piston, as O/o of fuel energy

Indicated Mean Effective Pressure

Cylinder power of an engine at a particular operating condition expressed in an average pressure acting on the pistons on every working cycle

Intake Valve Closing

Crank angle at which inlet valve closes either before or after O D C

0

Intake Valve Opening

Crank angle at which inlet valve opens either before or after O D C

0

O/O

bar

zyxwvutsr zyxwvutsr zyxw Abbreviations

Acronym LHS L/ R

Terminology

Meaning

Length-t o- Radius ratio

Usually the connecting rod center distance divided bv the crank radius

Mechanical Efficiencv

Bhp divided bv Ihp

Meaawatts

Measure of larae powers

NA

Naturally Aspirated

Engine air intake at atmospheric pressure

N Ox

Oxides of Nitrogen

N O and NO- emissions

OP

Opposed Piston Engine

Each cylinder has two pistons that approach to form a common clearance volume or combustion space at inner dead center (IDC)

ODC

Outer Dead Center

Piston at lowest position in cylinder

Power Densitv

Power output per engine weight

ME MW

Unit

Left-Hand Side

RHS

Right-Hand Side

r Pm

Revolutions per Minute

shp

I Ship Horsepower

Number of revolutions of a shaft in one minute

VO

1 bar

kW1kg rlmi n

zyxwv

I Power delivered to the propeller of a ship I

kW

SI

Spark Ignition

Combustion ignited bv a spark

sol

Start of Injection

Position before or after TDC for start of fuel injection.

Specific Power

Power per engine capacity

kW/L

Specific Weight

Engine weight per engine output

kg1kW

VCR

Variable Compression A technology to adjust internal Ratio combustion engine cylinder compression ratios while engine is running.

VPN

Vickers Pyramid Number

0

A penetration-type hardness test using a square-based pyramid made of diamond

543

INDEX

Index Terms

Links

2.33 L ADM OP engine

505

3-D prediction of air and fuel motion

456

3ZG9 connecting link

389

3ZG9 fulcrum rocker

387

3ZG9 liner

390

6.0 bar scavenge pressure

436

8Q Fullagar engine and alternator

413

32 kW utility engine

519

38D8 engine

348

45% BTE and beyond

530

400 kW heavy duty truck engine

529

A Achates Power Inc

540

Achterberg, Fritz

102

106

Admiralty Engineering Laboratory

58

Advanced Demonstrator Module (ADM)

506

Advanced Engines Development Corporation (AED) Africar OP engine

431

506

50

419

2 L three-cylinder, spark-ignition, OP engine air and exhaust port muffs

50 425

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Africar OP engine (Cont.) carbureted, spark-ignition (SI)

421

covers

422

426

crankcase

422

425

crankcase clamping arrangement

428

cranktrain and gear train

428

critique of

428

cylinder liners

425

vs. Fairbanks Morse

417

features

425

view of

51

ahead/astern air starting lever Air Airship Industries air and exhaust manifolds

428

429

426

421

255 50 199

291

498

10

63

80

183

192

199

206

213

235

336

344

391

398

472

489

498

510

514

18

175

355

422

425

See also manifolds airborne parachutable generating set air chest

air cooling

329

435 air delivery system Coventry Climax H30

344

Fairbanks Morse Model 38 OP Engine

363

Junkers Jumo

80

Leyland L60

197

Rolls Royce K60 and K60T

213

Rootes Commer TS3 and TS4 airflow

156 123

214

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms air manifolds

Links 83

98

114

199

268

291

295

336

352

395

441

498

air receivers

234

477

air starting and control system

254

See also air and exhaust manifolds

air-to-fuel ratio

40

93

115

118

158

160

221

291

297

373

436

440

447

454

459

461

467

506

532

152

199

305

260

ALCO

438

all speed hydraulic governor

200

all-welded steel crankcase

440

aluminum alloys iron alloy

75

Silumin alloy

65

aluminum-shelled boat

42

aluminum engines American Marc 10 Engine

175

485

305

aluminum parts air chest

199

blower casing

199

castings

46

83

339

430

43

88

122

152

273

339

425

485

cylinder barrels

173

268

440

cylinder block

341

entry vane ring

111

liners

273

main bearing carriers

173

main bearings

192

oil coolers

197

crankcase

pistons

76

114

276

428

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

aluminum parts (Cont.) rotors

197

scavenge section

243

shells

63

187

192

skirts

154

172

277

thrust washers

192

waterjackets

418

wrist pin carrier

417

aluminum silicon bore

174

aluminum vs. iron

390

Amal side-draft carburetor

325

209

American Marc (Manufacture and Research Co.) American Marc 10 engine

305 305

about

305

accessory drives

315

applications

315

combustion chamber for unit injector

313

combustion chambers for pump-line nozzle system

314

connecting rods

309

cooling system

312

crankshafts

309

cranktrain, gear train, and pistons

309

cylinder block and crankcase

307

gear train and power takeoff

310

general arrangement

305

generator sets of 0.5-2.5 kW

315

injection and combustion system lubrication system

312 311

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

American Marc 10 engine (Cont.) marine outboard 7 kW

316

pistons

310

ports

307

scavenge air

309

summary

317

systems and components

307

American Marc outboard marine power unit

223

AMX battle tank

179

Antonsen, Anker K.

348

Artic Circle to the Equator

419

auto ignition

373

379

automotive engines Armstrong Whitworth

478

480

crankshaft development

75

192

cylinder development

75

211

diesel

47

480

55

491

306

four-cylinder, four-stroke OP engine Gobron-Brille engine

127

MAP OP engine

139

multicylinder SBE

492

497

498

500

52

127

170

432

433

457

510

46

478

480

482

498

127

133

30

141

130

182

194

205

210

219

221

269

279

281

306

320

335

346

348

467

471

472

476

507

226

333

OPOC™ engine

swing beam engine (SBE) Trojan OP engine two-cylinder engine auxiliaries

532 auxiliary power units (APUs)

176

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

auxiliary start injectors

199

AVGAS and 92RON fuels

527

344

aviation. See also unmanned aerial vehicle (UAV) applications

522

Cyclone engine for civil

446

Deutsche Lufthansa diesel engines for early OP engine use for fuel types for Junkers Jumo 205 in civil

33

100

265 1 160 55

most efficient piston aero engine in OPOC™ engine for

58 127

Aviation Jersey

46

346

Avtur

44

213

AW Swing Beam Engine (SBE)

480

517

axial turbine

290

444

216

B Baker OPTD

540

balance weights

192

Barlow, Ben

304

barrel engine

11

battery powered ignition

275

356

386

137

Bauman State Technical University Beardmore-Oechelhaeuser

456 26

Beardmore-Oechelhaeuser gas engine

227

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

bearings. See also main bearings; rolling element bearings big end

75

135

136

176

196

236

238

309

357

386

bottom end

240

cam

200

352

89

283

344

361

153

156

172

192

196

211

368

488

67

151

187

209

212

camshaft connecting rod

crankcase

361 crankpin

487

crankshaft

109

141

246

274

486

crosshead

237

238

239

240

405

end

156

199

end-to-end

78

front blower

156

fulcrum

387

large end

384

485

491

28

78

112

130

155

361

534

63

136

154

187

209

212

274

outrigger

130

156

pivot

488

radial

368

rear

195

rocker shaft

465

roller

112

388

shell

141

154

235

236

410

25

155

198

236

257

lubrication

materials for

small end

387 split

386 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

bearings. See also main bearings; rolling element bearings (Cont.) swing beam

486

tail

275

thrust

357

360

97

195

wear on Bellis and Morcombe Benson, R. S. bevel gears

29 508 12

22

270

281

282

286

348

349

353

357

58

385

386

387

389

390

392

431

480

536

504

506

440 BICERA (British Internal Combustion Engine Research Association)

performance evaluation

395

teardown and test report of a 3ZG9 engine

381

VCR pistons for the air pistons

478

BICERI (British Internal Combustion Engine Research Institute) “Convel” blower

480 484

designed K60 variable compression ratio piston

216

light weight four-stroke variable compression ratio piston Bill Bonner Ltd Birmingham University

538 421 40

Blair, G. P.

508

Blencoe, Few, and Picken

508

518

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Blohm and Voss BV222

103

HA 139

100

Jumo 205C

100

blowby oil separator

106

7

180

blowdown

20

169

514

515

bolts

62

67

80

83

84

97

122

151

157

190

210

230

303

307

323

350

359

386

395

425

66

75

192

211

357

363

410

pinch

135

141

set

150

194

213

268

269

468 See also crossbolts cap

122

fixing

154

spring-loaded

76

through

50

209

272

273

Bonner Engineering, Ltd.

50

421

boost pressure

40

97

103

106

115

118

172

200

221

297

299

400

431

435

442

445

447

454

460

464

467

505

529

531

532

536 Bosch Smoke Number (BSN)

457

bottoming cycles

228

459

Boxer and OP UAV Engine cost comparison

527

engine parameters

526

two-stroke 8 kW two-cylinder

524

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Boxer and OP UAV Engine (Cont.) two-stroke OP 8 kW twocylinder weight comparison Boyle, Bob brake thermal efficiency (BTE)

525 528 305 2

3

14

22

34

41

45

52

59

72

96

100

109

123

158

159

160

163

175

176

201

216

217

228

234

255

266

269

345

347

374

376

398

400

402

413

419

433

434

436

440

444

457

460

462

466

497

500

504

511

513

539

Brico Alloy 31

168

Brinell hardness

72

341

338

344

265

302

British Aerospace Engineering (BAE) Rapier missile launcher British Class 55 Locomotives

303

British Internal Combustion Engine Research Association (BICERA). See BICERA British Science Museum

59

British Shipbuilding Group (BSG)

231

Brivadium liner

153

168

Brooks, Percy C.

348

379

Brown, A.

165

Brown Boveri

434

BSN (Bosch Smoke Number)

457

459

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Buchi Syndicate

434

Biihrer, Fritz

401

built-up crankshaft

27

140

bulk swirl

85

175

432

459

473

493 Burmeister &Wain (B&W) engines Butler, John Francis

223 263

C camera

447

Cammell Laird Co. Ltd.

38

camshaft

64

89

247

254

270

273

275

349

353

360

368

384

417

354

390

See also bearings, camshaft C. A. Parsons & Co. Ltd. cardan shaft

27 400

440

vs. aluminum

339

341

availability

354

load capacity

388

cast iron 390

cast-iron parts bearing band

240

belt

245

Bravidium liner

153

castings

486

46

crankcase

335

408

crankshaft

54

356

407

crowdflame plate

193

exhaust manifold

199

344

76

193

191

210

242

425

485

494

fire ring liners

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

cast-iron parts (Cont.) muff

245

pistons

154

157

rings

76

491

skirts

241

wet liner

141

cast sprunglip

153

191

7

532

534

7

69

272

cavitation erosion resistance

69

272

center pivot

83

411

catalyst technology

193

388

cathedral style marine engines 15,000 kW Doxford

223

derivatives of the early Oechelhaeuser engines J-Type Doxford engines

223 231

manufacture, personalities, and heritage side-injection simulations

258 456

Sulzer trunk-piston twostroke

445

CAV AA type in-line three plunger pump

344

injector/nozzles

248

jerk pump

199

NN type in-line pump

213

rotary DPA pump

156

cavitation erosion

central output gear via quill shafts

269

central telescopic pipe

246

centrifugal by-pass filter

195

213

centrifugally spun cast iron liner

210

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

417

Index Terms

Links

Centurion (tank)

201

cetane

100

159

162

179

333

335

432

500

12

155

157

229

233

354

360

336

338

370

394

400

360

486

chain drives

Challenger battle tank

199

charge cooled CT18-42K engines

269

Chatterton, Ernest

266

check valves

137

349

411

536

201

202

Chieftain 56 ton battle tank

346

chrome molybdenum steel forgings

192

chromium high-nickel, high-chromium steel

154

nickel

113

Nimonic steel

341

plated

211

69

Chrysler Corporation clamshell

48

165

175

188

491

506

220

clamshell-shaped combustion dish

486

Clark, Dugald

133

Clay, Tommy

165

CLM (Compagnie Lilloise des Moteur) LC2 automotive engine

40

balanced loading

433

truck engine

127

clutch

17

Coffman starter

88

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

combined heat and power

22

combustion chamber

80

Commer QX 7 ton vehicle

161

QX 8 Bulk-Flo truck fitted with TS3 common rail

145 82

Compagnie Lilloise des Moteurs (CLM). See CLM compression ignition

1

6

55

176

200

251

377

432

459

465

481

524

compression ratio

84

compressor

10

15

28

31

40

60

63

89

106

110

111

112

113

114

118

123

153

156

176

221

226

266

272

284

286

289

290

291

304

347

365

379

413

432

435

436

438

440

441

444

445

447

461

462

463

466

472

477

484

506

510

511

512

514

534

536 connecting rod

149

Conqueror (tank)

201

conrod

157

constant velocity

175

Convel (Constant Velocity) blower

497

coolant flow

221

coolant flow manifolds

400

coolant flowrate

428

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

coolant pump

433

coolant system

79

107

109

201

333

338

520

533

comparisons

519

525

532

engine

519

and fuel efficiency

524

of labor

520

ofmaterial

519

OP engine advantage

520

predicted

519

and reliability

520

running

530

and safety

519

of UAVs

520

and weight

520

527

533

46

179

390

110

156

202

272

345

480

481

504

520

341

440

69

157

cost compared to four-stroke engines

Coventry Climax Engines (CCE)

334

Climax H30 auxiliary

185

Climax H30 engine

Cox, Robert

404

Coy, Eric

165

cracking air belt belly

486

cylinder barrel

504

cylinder liner

192

fatigue

7

crankcase Africar OP engine alloy

425 63

al-welded steel

440

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

crankcase (Cont.) aluminum

130

152

305

88

122

152

260

273

339

425

485

67

151

186

212

273

361

468

102

135

142

167

221

34

335

408

cast-iron parts

335

408

clamping arrangement

427

cooling

209

crankcase and liner

408

crankcase and main bearings

187

crankcase pressure differentials

136

dimensions

205

151

209

426

aluminum parts

bearings

casting cast-iron

43

88

339

485

43

350

339

English Electric Fullagar Q and R Series exhaust gas leakage

408 342

451

350

364

Fairbanks Morse (FM) Model 38 OP Engine Leyland L60 engine loads

lubrication

and main bearings

187 64

137

496

505

67

196

209

241

276

343

354

401

536

540

63

149

187

209

338

408

525

350 operation

63

77

scavenged

352

354

single-crank

520

single piece casting

182

320

split

50

136

208

steel

38

348

440

507

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

crankcase (Cont.) structural Sulzer Brothers ZG series

65

259

482

394

sump

69

venting

77

vibration

209

430

volume

22

welded

35

38

228

440

crankcase covers

67

152

190

209

321

339

354

395

72

75

78

143

151

482

484

494

73

75

154

192

211

276

343

356

384

386

428

441

487

73

153

211

356

384

211

356

383

6

46

62

66

72

75

77

80

107

187

192

195

206

212

335

348

368

372

443

and bearings

109

141

273

and bedplate

407

crankcase pressure crankcase pressure differentials crankpins

diameter

main journal overlap crankshaft air

built-up and connecting rods contra-rotating

22 136

27

140

236

275

343

486

22

coupled

267

exhaust

62

67

74

78

85

87

92

107

122

153

187

191

195

197

198

208

212

335

338

340

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

crankshaft exhaust (Cont.) 344

349

354

441

444

473

failures

47

folded

9

48

141

437

438

481

13

33

418

four half-throw

487

interlinked

6

multiple

12

paired

21

parallel

128

power distribution between

371

single

11

371

429

432

435

28

32

37

47

404

153

192

213

275

12

60

277

442

9

123

223

223

230

491

11

32

47

421

436

438

441

445

472

490

525

532

18

45

52

59

130

194

205

221

525

527

22

73

75

136

153

211

230

235

356

381

11

50

141

150

151

167

211

268

422

426

429

472

crosshead guides

236

238

408

410

445

crown/flame plate

76

193

520 single-throw six-throw

487 72 438

three three-throw torsional vibration twin

two

crankwebs

crossbolts

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Culver, Bob

42

Culverin

39

56

61

264

265

209

271

339

304 cumulative heat release Cutlass

454 39

cyclic torque

267

438

cylinder bank

42

265

alloy

267

273

aluminum

273

341

casting

391

472

cast-iron

241

cooling

66

Culverin

265

277

cylinder block

iron

45

liners

90

rigidity

189

154

363

cylinder bore clearance contact face

5

61

493

Coventry Climax H30 engine

333

cylinder-to-cylinder pitch

234

diameter

DI diesel

6

73

76

114

151

153

192

211

234

279

343

360

384

387

428

435

441

491

63

153

172

179

194

211

226

235

268

273

339

429

441

449

506

505

dimensions, ratios and distance

532 dummy

493

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

cylinder bore (Cont.) fire rings

5

fuel distribution

243

fuel impingement

345

heavy duty engines

187

high-power engines

230

injector axes

34

J-type engines

230

low-power engines

226

main bearings on

64

oil lubrication

244

oil scraper rings

123

parallel

133

small

17

stroke ratio to Tillings Steven TS3 engine wall wetting cylinder flow coefficient cylinder jacket flange cylinder liner

449

472

339

343

243

409

429

179 44 342 73 235 68

3ZG9 liner

390

Africar OP engine

425

aluminum parts

273

bore spacing

532

Bravidium liner

153

168

cast-iron parts

141

153

191

210

242

354

390

425

485

494

6

66

78

197

201

211

233

cracking

192

341

440

504

Deltic

272

centrifugally spun cast iron cooling

210

eight exhausts and eight scavenge ports

192

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

cylinder liner (Cont.) elements of

19

221

233

247

504

130

157

362

418

English Electric Fullagar Q and R Series exhaust system

408 55 486

Fairbanks Morse (FM) Model 38 OP Engine

354

fully assembled cylinder liner and combustion chamber Gobron-Brille

245 1

with helical coolant flow slots

191

loads on

10

modern

532

Rolls Royce H12

469

SBE

482

scavenge air

234

sealing

19

steel

122

Sulzer Brothers ZG series

390

wet liner

141

wet-steel

272

534

221

cylinder pressures in excess of 200 bar

530

D Davids, Hans

318

379

Davison, C.H. “Bill”

297

300

de-aerator and oil tank

197

Delahaye four-cylinder 5L MAP engine

143

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Delahaye (Cont.) racing vehicle c1949 delivery ratio

141 35

72

95

228

289

290

291

297

307

309

320

344

363

391

398

402

485

493

500

504

506

529

276

280

288

296

50

51

55

119

434

diesel ignition

101

373

Diesel RK

456

Deltic Heritage Archives

264

Deltic Series engines

266

Deltic triangular configuration and phase angles Detroit Diesel Corporation

277 506

Deutsche Continental Gasgesellschaft Deutsche Kraft Gesellschaft

19 21

Deutsche Versuchanstalt fur Luftfahrt

99

diametral interference at each sealing land

153

diamond or parallelogram configuration Diesel air engine

differential swirl system (U.S. patent 2170020) direct injection

417

72 6

30

34

37

93

334

343

446

456

481

493

498

503

510

D. Napier & Son Ltd (DNS)

38

43

364

DNS (D. Napier & Son Ltd) Sabre

39

double-acting air pumps

20

double-acting gas pumps

20

441

444

double-acting piston pumps

226

double-acting scavenge pumps

411

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

double bank rocking beam H8 and H10

468

H12

467

double sided Keystone compression rings

277

downstream

449

455

456

495

223

226

228

374

422

Doxford fuel injection timing valve

250

HP fuel spill valve

250

P-type

230

pulse turbocharger

253

simplified common rail fuel injection system turbo-charged engines Doxford, William

247 230 34

Doxford Engine Friends Association

263

Doxford engines development history

225

early (ca. 1921)

35

first experimental

34

marine

32

parameter development

36

single-crank OP engines

10

Sun Doxford

226

226

Doxford engines J-type port areas and timing

257

starting air system

252

turbo charging system

251

turbo charging systemconstant pressure

254

Doxford engines P-type

244

263

drive shaft with vernier splines

275

dry sump lubrication system

269

507

dry sump system

195

209

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

dual fuel engines

38

347

dual fuel injectors

373

375

365

373

377

dual fuel versions (Enviro Design)

374

dual injectors

6

38

221

223

durability

7

61

67

71

90

97

132

142

168

368

466

490

503

519

540

467

470

489

control

489

490

cylindrical

484

fulcrum

490

491

rockers on

432

465

rotation

432

E eccentrics

EcoMotors International, Inc.

170

173

EcoMotors M100 engine

171

173

economizers

228

Edwards, John

346

EFI and digital ignition control

529

eight exhausts and eight scavenge ports

192

480

534

536

506

517

electrically controlled turbochargers (ECTs)

175

536

39

519

emissions. See also NOx; smoke compliance four-stroke vs. two stroke

510

injectors and

457

legislation oil carryover OPOC engine particulate post 2010 challenges price of

13

48

7

434

176

459

1

6

14

530

14

532

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

emissions. See also NOx; smoke (Cont.) scenarios

530

smoke

170

split scavenge system

510

TS3 and

508

unconstrained

158

175

484

491

end pivot engine concept Africar OP Engine

430

Rootes Commer TS3 and TS4

166

Southwest Research Institute PTC T.H. Lucas Engine Research Center English Electric (EE) Company English Electric Diesels Ltd.

48 348 432 60 264

English Electric Fullagar Q and R Series about

402

applications, manufacture, and engineers

414

cooling system

413

crankcase and liner

408

crankshaft and bedplate

407

engines manufactured

415

fuel pump, injectors, governor, and air starter

411

Fullagar concept

404

general arrangement

406

performance, fuel efficiency, and power density

413

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

English Electric Fullagar Q and R Series (Cont.) pistons, crossheads, slippers, tie bars, and connecting rods scavenge pistons and ports entablature

409 410 235

See also main frame and entablature Enviro-Design

347

Erskine, Mark

168

Everton, George

165

exhaust energy exhaust lead

exhaust manifold

exhaust manifold coolant jacket

370

373

377

365

435

445

508

69

107

133

171

192

251

273

391

38

63

80

90

103

110

139

145

151

156

185

190

199

206

208

270

272

285

290

296

300

302

312

320

324

325

336

344

345

349

352

362

367

377

395

413

418

441

461

472

476

498

533

351

362

418

exhaust port blowdown

20

exhaust ports

10

18

20

70

72

89

122

134

141

145

171

190

192

210

231

244

272

285

307

339

341

343

354

356

383

390

391

395

411

418

422

425

429

435

461

478

494

495

497

498

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

exhaust ports (Cont.) bars

7

66

69

90

122

273

309

355

362

472

151

191

245

251

272

343

362

199

213

339

507 belt

vs. high precision injection

21

location

18

175

muffs

418

425

seal

209

sealing belt

69

sealing lands

210

390

exhaust temperatures

35

95

199

228

255

363

377

386

419

467

500

514

354

418

465

exhaust turbo-charging of internal combustion engines

343

Experimental Station for Gas Engines at Dessau extra charging

19 435

F fabrication

166

259

Fairbanks Morse (FM) Diamond Experimental OP submarine engine OP diesel engine (ca. 1930) OP engine

417 38 7

37

Fairbanks Morse (FM) Model 38 OP Engine 38D8⅛ engine 38D engine about

346 223

339

12

38

531

346 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Fairbanks Morse (FM) Model 38 OP Engine (Cont.) air delivery system

363

applications

379

connecting rod and bearings

357

cooling

367

crankcase and main bearings

350

crankcase covers

364

crankshaft

356

diesel

374

dual-fuel engines

373

dual-fuel versions (EnviroDesign)

377

engine performance

374

exhaust manifold

362

fuel injection system

371

gear train and drives

360

general architecture

348

heat balance

377

inlet manifold

362

key features

350

liner

354

lubrication

368

personalities/leaders

379

piston and rings

359

power distribution between crankshafts

371

spark ignited gas engine version

372

spark ignited versions

375

starting air system

370

Faraday Centre

403

Farnworth, John

203

fatigue

7

97

429

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Fighting Vehicle Research and Development Establishment (FVRDE) fire ring

142 76

122

182

205

14

434

522

flywheel

131

373

514

flywheel scavenge pump (FSP)

514 9

48

141

437

438

481

10

139

151

33

418

17

5 363

five-spur gear drive

193

388

fixed wing light aircraft and helicopter engines

folded crankshafts

folded cranktrain

432

435

401

447

49

101

434

7

170

172

216

468

488

490

504

187

195

274

7

20

76

93

97

98

101

114

117

123

141

158

160

170

187

200

214

217

221

228

251

255

345

368

396

464 folded cylinder opposed piston engine French Salmson Diesel H18

55

Ralph Lucas

23

four crankshafts Fox, Uffa

13 317

free piston engines

9

French Salmson diesel H18 2 row radial with folded cylinders Frerichs, J. friction

55 32

514 front gear train fuel consumption

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

fuel consumption (Cont.)

fuel efficiency

440

444

484

493

511

525

529

532

561

1

14

37

52

93

100

114

118

216

223

355

373

396

402

413

440

446

480

497

507

510

519

522

524

532

447

455

457

539 fuel feed system

79

213

fuel impingement

342

345

459

493

fuel injection nozzle

1

85

247

460

fuel injection system

83

156

199

213

228

247

344

371

459

461

79

114

143

151

155

160

174

185

200

249

275

360

393

397

411

455

467

470

and camshaft

393

417

chain drive

155

233

common rail

233

electrical

165

fuel injection

213

gear drive

208

fuel pump

high pressure inline

497

83

349

157

205

lift

79

low pressure

62

mechanical

120

multiple

248

plunger

182

reverse operation

157

rotary

120

206

371

251

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

fuel spray pattern

85

fuel spray penetration prediction fuel-to-air mixing

455 6

218

432

446

452

160

179

507 fuel tolerance

1

160

17

42

158

200

432

455

145

150

bearings

387

491

505

eccentrics

490

excessive load

472

levers

155

381

386

391

pins

386

388

pivot points

484

489

rockers

141

386

387

394

settings

500

shaft

485

505

fulcrum points

155

383

395

482

485

487

489

505

506

1510

27

30

402

333

406

fuel types

fulcrum

Fullagar, Hugh Francis Fullagar arrangement vs. Wittig concept

405

Fullagar engines

30

6-R

408

SQ

413

EE

414

gas engine

413

Q Type

411

scavenge air

413

414

fully assembled cylinder liner and combustion chamber

245

fully balanced engine

226

fusible plug measurements

277

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

G gallery cooling

417

Garner, Bill

165

Gas Engine Research Institute gas exchange

gas exchange process gas generator gas loads

19 1

13

29

52

106

110

170

216

228

233

445

460

472

475

477

485

504

508

228

514

9

40

435

446

17

150

235

491

179

333

159

179

gasoline 74 RON (research octane number) 80 RON (research octane number) aircraft needs

60

Avatur mix

216

delay period

455

diesel mixture

165

engine efficiency

213

European

179

forecourt octane

335

fuel pump

213

fuel types

200

grades of

344

impingement

455

injection

455

leaded

333

lean mixtures effect

133

low boiling point

432

333

509

17

low-grade

165

lubricity

165

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

505

Index Terms

Links

gasoline (Cont.) military engines

218

MT 80

44

multifuel mix

42

Navy use

265

octane

159

petroil

133

pressurization

165

recreational engines

317

Rolls Royce R Series engine

203

spark-ignition engines

22

32

39

101

303

432

457

459

243

374

22

47

138

197

212

267

269

271

442

445

52

58

83

151

208

267

363

384

393

spray penetration

455

utility engines

317

gas pressures Gasterstädt, Johannes gearbox

gear drives

165

5 101

bevel

353

helical

360

spur

182

205

335

344

gear train

4

74

76

119

152

185

189

194

212

421

470

472

532

auxiliary

189

495

bearing carrier for

181

vs. chain drive

155

crank-to-crank

60

driven end

243

338

and drives

360

free end

185

187

197

front

185

197

274

201

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

gear train (Cont.) herringbone intercrankshaft

417 76

120

144

nodal

194

212

418

530

rear

185

191

197

269

spur

80

428

gear type oil pressure

422

geometry combustion system

447

crankshaft centerline

133

injectors

457

piston bowl

457

rockers

154

SBE

505

shallow domes

85

turbocharger

510

514

Gerlach, Manfred

72

102

German WWII E boat Giles and Wittig

401

265 17

Giles and Wittig three-throw system Gilles of Cologne

223 17

Glover, Stephen

510

glow plug

395

Gobron-Brille engine

127

507

advanced demonstrator module ADM configuration design Golby, R

506 1 165

Golle Motor AG Griffiths, Headley

52

333

540

346

gudgeon pin bosses. See wrist pin bosses gudgeon pins. See wrist pins This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms Gunn, John George

Links 230

259

263

H Hardy, James Albert

259

Harland and Wolf OS engines

223

Harrington Bodied Coach

160

164

heat balance at high thermal efficiency

463

typical data

377

heat rejection

1

heat removal

277

heat resisting Nimonic steel

341

41

481

464

heat to coolant

1

266

heat to exhaust

2

462

heat to oil

530

464

heavy duty engine

93

187

539

368

384

421

89

192

271

6

243

504

180

447

helical bars

496

helical gears

360

helical grooves

69

helical passage

66

helical ports/porting

493

helical rotors

365

helical slots

69

helical splines

69

Hepworth & Grandage

167

high pressure oil circuit

240

high supercharging

435

with 4ZGA19 Engine

436

with G18 Engine

438

high swirl high swirl generation

495

Honeychrome finished by the Van der Horst electroplating process horizontal and air-cooled

272 421

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

horizontal cylinders

443

Horstmann Defense Systems

46

Hounsfield, Leslie Hayward

132

Howarth, Anthony “Tony”

419

421

hydraulic chambers

536

538

hydraulic coupling

440

442

hydraulic dynamometer

345

395

hydraulic governor

185

197

200

213

349

hydraulic hub motors

195

hydraulic paddlewheel

87

9

45

157

191

197

205

335

344

428

446

46

185

200

345

hydraulic piston servo system hydraulic pumps

hydraulic starter motors hydraulic systems hydraulic transmission

346

428

444

465

466 49

I Iconic Citröen 2 CV

419

ignition. See also compression ignition; spark ignition battery powered

137

digital control

529

Fo2

60

magneto powered

130

of NG

374

stability

503

ignition cell

372

373

See also prechamber ignition coil

372

383

ignition delay

449

451

454

457

ignition timing

18

20

449

454

457

243

342

345

446

455

459

493

499

impingement

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

indicated thermal efficiencies (ITE)

22

34

413

10

80

151

306

465

injection period

46

452

454

injector pump

90

196

275

352

374

411

inertia loads

192

235

335

342

injectors air

320

air distribution

247

447

auxiliary start

199

344

control bar

92

diesel

373

Doxford

229

dual

6

38

dual fuel

373

375

elements

90

and fuel pump gas

221

223

192

244

497 20

gasoline

456

geometry

457

holes

liner

95

97

175

494

504

507

6

7

34

66

122

185

189

226

233

243

247

272

344

372

393

475

486

494

506

70

84

114

200

248

253

371

90

liner holes location

210

micro-pilot

373

multifuel

373

nozzles

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

213

Index Terms

Links

injectors (Cont.) per cylinder

2

50

371

520

pilot

200

plumes

199

pumps per

38

83

271

349

459

473

63

replacement

247

return lines

200

simulation

445

sleeve

494

sprays

360

374

twin

199

275

456

69

355

373

62

66

78

80

106

114

156

197

269

272

286

336

344

349

354

362

421

425

514

41

180

157

162

watercooled inlet manifold

insulated combustion chamber insulated two piece piston

461

154

iron. See also cast iron alloy

75

austenitic

359

276

cylinder block

48

cylinder liner

6

dry-liner cylinders

320

grey

187

high-duty

391

inserts

199

liners

339

malleable

499

nodular

354

pistons

486

499

skirts

341

410

spheroidal graphite (SG)

149

153

486

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

465

Index Terms

Links

iron. See also cast iron (Cont.) sump

321

Irving, Phil

318

J Jackson, Percy

230

JP8 (fuel)

119

170

524

J-type Doxford Engines vs. Wittig concept J-type engines

231 224

Jukra (company)

30

33

Junkers, Hugo

19

26

61

101

Junkers Co. of Dessau

30

33

59

55

61

100

26

Junkers engines Fo3

62

gas (ca.1901) HK

262 39

175

520

Ju86P-1

102

105

Jumo 4

33

60

61

348

33

38

264

304

Jumo 205C

61

99

Jumo 205E

6

60

90

93

99

103

106

142

158

181

187

191

205

209

214

216

220

268

272

273

339

434

584

38

63

72

See also Junkers engine, Jumo 204 Jumo 5 See also under Junkers engines, Jumo 205 series Jumo 204

Jumo 207

103

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Junkers engines (Cont.) Jumo 223

13

OP diesel (ca. 1912)

32

SA9

40

series data

58

tandem OP diesel (ca. 1910)

31

Junkers Motorenbau and Jukra

31

Junkers Motorenbau GmbH

19

30

33

433

31

33

102 Junkers Museum

59

102

Junkers two-crankshaft arrangement vs. Wittig threethrow system Junkers und Compagnie

59 31

K Kadenacy, Michel

40

Kadenacy principle

158

Kadenacy technology

480

480

Kauertz OP engine

13

Keller, Karl Otto

34

230

Kerr, Robert Price

38

402

50

119

179

102

220

259

Kharkiv Morozov 6TD-1 1200hp Battle Tank engine 6TD-2 engine data about

221 49

Kharkiv Morozov Machine Building Design Bureau

50

Kimber, Graham

145

Kitchen, Don

145

Klein, Gebrüder

31

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

61

87

Index Terms

Links

Krupp Combined Opposed Free Piston Engine and Hydraulic Transmission Kuleshov, Andrey

49 456

L L60 turbocharged version (Sundance)

201

204

Laystall process

192

341

leaded bronze

465

leaded tetra-ethyl

179

Leggat Rotary Oscillatory Mechanism (ROM)

13

14

417

Leyland Commercial Vehicle Museum

169

Leyland L60 engine

45

about

179

air and exhaust manifolds

199

air delivery system

197

BMEP, power, fuel consumption, and boost pressure

200

cold start

333

connecting rods and bearings

192

coolant pump and circuit

197

crankcase and main bearings

187

crankcase covers

190

crankshaft

192

cylinder liner

191

dry sump system

209

engine specification

181

experimental conversion

511

features

191

fire ring

345

five spur gear drive

205

338

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Leyland L60 engine (Cont.) fuel injection system, auxiliary start injectors, and starting equipment

199

gear train

194

general architecture

182

history and applications

201

oil pump and lubrication system

195

O-ring seal

341

performance

199

pistons and rings

193

port belts

272

research work

433

sprayed rings

342

turbocharger

431

lifeboat

42

334

liner with helical coolant flow slots

191

Linford (British Patent # 1500 of 1879)

380

List, Hans

142

517

518

9

37

348

locomotive applications locomotives British Class 55

264

OP engine potential

6

379

loop scavenge configuration

52

142

lower horizontal bedplate

266

524

234

low pressure fuel circulating pump

271

low pressure oil metering pump L-shaped cast iron fire ring Africar

282 76 491

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms lubricating oil

filters pressure pressure relief valves pumps

Links 75

112

190

241

247

354

182

185

67

209

363

77

245

131

325

199

206 74

lubricating oil circuit

78

lubricating oil pump

77

Lucas, Ralph folded cylinder opposed piston engine

23

motor vehicle engine

22

opposed piston engine 1901

23

Valveless Car Company Ltd. design valveless car engine

127 23

Lucas, T.H. engine concept

348

gas engine 1881

19

Lucas engine design

18

twin-crankshaft arrangements for OP engines

11

Lucas CAV “AA” type inline three plunger pump Lux, Floyd B.

344 432

M Maag reduction gearbox

443

Mägerle, Gebrüder

401

magneto powered ignition

130

Maier rotary OP engine

13

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

228

Index Terms main bearings

main frame and entablature

Links 11

18

63

64

72

78

100

141

149

150

153

187

192

209

211

213

228

230

231

235

246

268

274

283

320

323

338

350

354

368

384

386

405

407

433

487

498

226

228

233

239

241

72

75

136

141

153

192

211

230

276

311

343

356

384

408

428

92

156

395

185

189

197

325

262 main journal

441 manifolds

80

See also air and exhaust manifolds; air manifolds; exhaust manifold; inlet manifold air temperature

115

bifurcated

175

common

413

coolant

66 489

entry

66

external

274

induction

320

324

62

532

intake inverted

344

log-type

199

main supply

239

oil

291

344

239

246

274

outlet

66

185

197

plugs

90

336

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

27

Index Terms

Links

manifolds (Cont.) return

190

twin

533

Mann, Brian

421

426

47

127

41

47

42

138

Manufacture dArmes de Paris (MAP) MAP engine about applications

138

141

141

crankshaft and bearing arrangements

141

crankshaft and rocker failures

142

four-cylinder 5 L

143

performance

141

reliability difficulties

139

as Rootes TS3 influence

142

marine engines

13

20

22

30

35

41

43

45

49

52

59

223

344

347

401

402

434

438

443

456

95

113

115

289

299

435

461

511

20

22

28

93

95

251

255

289

299

413

472

539

medium speed

226

264

445

446

Meriwether, R. F.

432

micro-pilot injectors

373

mass flow

mechanical efficiencies (ME)

military. See also Coventry, Climax H30; DNS (D. Napier &Son Ltd.); Fairbanks Morse (FM) Model 38 OP Engine; Napier Deltic; Rolls Royce This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

military. See also Coventry (Cont.) K60 & K60T; Rolls Royce, Double Bank H; Rolls Royce, Double Three In-Line Multi-fuel Engine; under Kharkiv-Morozov aircraft

38

99

101

317

applications

41

49

61

165

175

179

295

305

346

432

220

333

524 Armstrong Whitworth

480

automotive applications

434

automotive type engines

139

battlefield fuels

305

Bedford truck

165

BMEP

175

CAV Ltd.

431

Deltic engines

44

engine philosophy

45

fuel types effects

158

future engines

160

gasoline engines for ground vehicles

39

333

160

218

433

Junkers

61

99

101

Leyland L60

45

142

165

lifeboat

42

317

logistics

39

multi-fuel engines

44

165

431

OPOC™ engines

55

127

170

431

460

Rootes Commer TS3 engine

48

142

Rootes Commer TS4 engine

168

research

Soviet Union needs tank applications

49

165

180

179

432

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

military. See also Coventry (Cont.) testbed data

158

tests

333

transport requirements UAV

160

1 170

176

U.K. policy

44

179

U.S. Army needs

48

vehicles, major

26

modular displacement clutches

175

Morozov, Alexander

220

motorcycles

42

127

motor torpedo boats (MTB)

43

265

MPV, early version

524

317

318

133

Mukherjee

13

multicylinder

17

32

266

309

438

484

485

492

497

498

503

536

179

multicylinder swing beam engine

498

multifuel capability

20

42

44

170

203

208

333

431

criteria

165

engines

472

injectors

373

needs

168

operation

165

tolerance

1

multiple crankshafts Murray, George

12 304

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

N Napier Culverin

39

56

61

265

268

270

273

276

304 Napier Deltic 18-11B scavenge blower about

287 42

air and exhaust manifolds

291

auxiliary drives

279

breather system

284

British Railway applications

302

cam carriers

274

control system

292

cooling system and pumps

284

crankcases and bearings

273

263

crankshafts and connecting rods CT18-42K engine

275 43

267

CT18-42K turbo-assisted blower with charge cooling

290

cylinder blocks

271

cylinder liners

272

design rationale

266

engineering department

300

engineers and heritage

303

engine weights for T18K

296

features, components, and systems

271

fuel injection system

291

fuel system

291

general architecture

268

general specification

267

high-pressure system

282

history

265

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Napier Deltic (Cont.) lubrication circuit

282

maintainability

295

manufacture and applications

300

manufacture and refurbishment

300

marine applications

265

O-ring seals

69

performance

296

phasing gears

277

301

phasing gears and auxiliary drives

277

pistons

276

pumps and nozzles

292

reduced-pressure system

283

scavenge blower, turbocharger, and drive

286

scavenge system and circuit

284

starting

295

T18-37K turbo-assisted blower trailing pump

290 284

turbo assisted blower with charge cooling Napier Lion

43 38

265

295

211

275

276

343

44

152

155

182

191

194

206

210

212

418

421

530

93

119

199

302

348

481

503

Napier Power Heritage Trust

304

Nelson, Henry

304

Nimonic steel

341

nitrided

192

NO

500

nodal drive

noise

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms NOx

Links 6

52

373

447

482

500

529

531

179

333

59

506

nozzle diameter

452

nozzle variants, effect of

452

460

O octane 74-RON (research octane number)

179

333

159

160

80-RON (research octane number) 92-RON

527

forecourt

335

high

372

low-grade

165

Oechelhaeuser and Doxford arrangements

19

Oechelhaeuser and Junkers two-stroke OP gas engine

19

31

Oechelhaeuser gas engine ADM configuration

506

Doxfords as derivatives of

223

OPOC™ engine

433

variant of Oechelhauser, Wilhelm von

20 20

21

7

537

35

226

oil. See also lubricating oil; oil consumption; oil control ring; oil for crankcase internals use; oil piston cooling; oil pressure; oil pumps; oil scavenge pumps; oil temperatures additives boilers

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

432

Index Terms

Links

oil. See also lubricating oil; oil (Cont.) bunker type carryover

226 7

109

434

532

characteristics

396

compressor

250

convection

277

cooler

195

296

5

38

76

122

141

154

157

212

239

342

cooling

497 deposits dispensers

7 411

distillate

17

emissions

1

engines

312

31

fillers

146

168

324

354

films

5

141

153

488

505

filters

121

145

168

182

185

195

206

209

213

218

279

283

296

321

324

336

423

211

377

156

195

108

284

heat exchanger heat losses heavy

185 76

193

176

hydraulic

49

208

112

154

447

507

93

371

petroil

133

136

pressurized

155

scraper ring

122

seals

137

seawater pollution

302

jets

mist

separators

7

106

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

284

Index Terms

Links

oil. See also lubricating oil; oil (Cont.) sludge galley

75

strainers

210

sumps

137

synthetic

384

411

419

197

283

306

7

tankers

32

tanks

77

195

311

329

turboblower

284

water cooler

156

oil consumption

oil control ring

7

14

97

122

192

201

341

345

368

460

481

493

495

530

532

193

341

410

441

491

493

504

oil convection “cocktail shaker”

539

oil flow rate

361

oil for crankcase internal use

oil piston cooling

67

75

110

113

136

153

190

192

209

211

236

241

274

276

311

367

408

422

28

38

78

109

141

157

300

322

361

368

383

401

oil pressure in accumulator

538

checks

90

circuit

77

engine speed and

462

levels

368

lines

311

positioning

240

213

408

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

oil pressure (Cont.) pumps

reduced

62

67

77

107

120

185

195

206

213

279

286

382

422

66

67

75

77

83

90

108

156

175

187

190

195

213

336

353

361

367

384

428

486

208

213

383

oil pumps

498 oil scavenge pumps

191

196

206

oil temperatures

195

408

497

Omega

13

OPOC™ (opposed piston opposed cylinder) engines about

170

basic data

172

combustion system

175

connecting rods

170

crankshaft

173

172

electrically controlled turbochargers (ECT)

175

features

170

performance

175

pistons

170

pumps

175

summary

176

opposed piston gas exchange and charging systems

509

optical access

447

optical testing

90

447

OP two-stroke truck engine

142

530

Ørbeck, Dr. Fin

263

455

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

orifice dimensions

292

experiments

313

plate

92

singe

313

twin

313

outer connecting rods

172

Owen, James W.

348

Owinett, Reg

165

313

497

379

P paired cylinders with diagonal cross rods Palmer, Tony parachuted lifeboat scheme

27 421 42

317

parallel crankshafts

128

parallel cylinder OP engines

127

133

405

17

216

363

parasitic losses

472

507

514 Paxman

43

264

300

peak cylinder pressure

75

97

118

136

157

160

218

371

386

431

436

438

452

460

465

467

482

505

507

531

5

76

193

212

342

493

495

536 pegged/pegging

Pelton wheel assisted turbocharger

466

Pelton wheel cups in regenerative side wall blower

497

Pemberton, Cyril

165

pendulum damper

349

353

357

penetration

292

449

451

43

304

Penwarden, Mr.

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

petroil

133

136

phasing gear casing

270

283

284

292

296

Philips, A. J.

219

piston cooling

109

156

246

257

282

357

361

462

467

410

piston crown cast-iron

193

ceramic

481

compression rings

193

491

76

122

342

342

345

429

6

313

391

447

exhaust

231

233

fixed

538

forged steel

290

fuel spray trench

342

injector plumes

194

inspection

291

240

290

388

273

277

342

cooled demountable design/redesign dimensions

manufactured

5

345

89

moveable

5

oil returns

368

outer

276

quartz

447

seals

194

shape

360

spray impingement

446

steel

172

211

410

507

34

70

402

492

temperatures

tests

538

455

314

thermal loading thermally isolated

6 482

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

piston crown (Cont.) uncooled

76

wall wetting

342

wear resistance

240

piston link

piston ported

141

381

387

488

491

505

7

481

484

486

piston rings air

291

carbonization

97

313

cast-iron parts

76

491

compression

212

491

design

241

Fairbanks Morse (FM) Model 38 OP Engine five

359 342

heat losses

76

193

211

improvements

69

122

534

195

247

leakage lubrication

520

113 5

problems

440

re-use of

97

99

Rootes Commer TS3 and TS4

154

seals

199

suppliers

345

swing beam engine (SBE)

491

temperatures

273

three

311

Vincent Marine Engine

322

wear piston rods

491

492

7

89

216

20

154

156

166

231

233

237

240

320

322

388

411

445

461

469

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms piston skirt

exhaust

Links 6

22

69

76

97

122

153

191

193

195

210

231

276

309

341

390

491

493

97

242

245

267

function of

311

iron

410

lower

29

outer

536

upper

241

piston speed BMEP at diamond OP engines

36 417

exhaust lead

69

high

59

high mean

69

rate

295

391

130

144

203

258

295

478

525

527

Piston-Turbine Compound (PTC)

48

pivoted lever. See rocker plain bearing

410

poppet valve air injector

295

poppet valves port areas and timing

port bars

1

9

257

266

299

355

392

425

494

508

5

7

66

69

70

90

122

209

210

273

285

309

355

362

391

472

493

507

66

151

156

209

213

391

port belts air

272 aperture

151

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

port belts (Cont.) exhaust

151

191

245

251

145

151

486

272

343 inlet

80

scavenge

189

sealed by sprung lands

272

volume

211

495

70

391

port muff

120

425

port pressure drop

454

port timing

107

108

153

251

273

322

324

356

495

525

182

197

205

344

398

519

534

175

306

441

443

445

port details

496

positive displacement compressor

514

flywheel scavenge pump (FSP)

514

of pistons

19

process

514

Roots-type twin two-lobe rotor blower scavenge blowers

scavenge pumps

197

514 timed compressor for scavenging post 2010 emission challenges power gas process prechamber

514 14

530

435 38

372

434

sale

128

138

519

1323

sensitivity

524

uncompetitve in

307 77

229

269

price

propeller shaft

67 443

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

281

Index Terms

Links

P-type engines

225

230

244

263

Purdy, William

259

52

87

120

150

155

166

206

213

269

273

279

282

284

286

288

291

303

438

160

164

Q quill shaft

QX12 tractor unit-Carrimore Transporter

R RAF museum at Hendon

60

Rapier mobile anti-aircraft defense system

334

338

344

rate of heat release

449

454

507

rate of pressure rise

449

452

455

503

Razleytsev (Professor)

456

rear gear train

185

191

197

269

receivers, air

234

477

reed valves

175

391

393

395

444

regenerative sidewall blower

484

497

Reid vapor pressures

160

179

78

206

233

242

271

283

293

352

354

361

relief valves

536 Research Institute’s “Witzky” proposal

417

432

Retschy, Curt

434

Riley, Arnold

30

402

ring gap

241

342

Robinson, Ralph

203

Robson concept

19

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

rocker arms

83

cam drive

66

154

381

154

155

covers

168

eccentrics

465

failures

142

folded-lever

380

forgings

154

geometry

154

lever

141

145

149

380

386

394

11

47

151

388

141

154

pivoted

83

411

removal

388

shaft bearing

465

swing

141

TS3 engine

155

loads pin

rocker fulcrum trunnion rocker shaft

fulcrum

167

153

157

141 11

150

153

168

432

465

467

472

479

386

395

66

75

83

130

136

141

195

199

230

279

288

290

306

309

311

371

390

440

490

505

rocking beam. See rocker rolling element bearings

Rolls Royce Distributed Generation Systems (Crewe)

203

Distributed Generation Systems (Powerfield) double bank H

301 11

467

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Rolls Royce (Cont.) double three in-line multifuel engine Rolls Royce K60 and K60T

472 11

44

46

151

179

179

333

432

334 about

44

air delivery system

213

applications

218

203

combustion system and peak cylinder pressure

218

connecting rod and bearings

211

coolant pump and circuit

213

crankcase and main bearings

209

crankcase covers

209

crankshaft

211

engine specification

203

features

209

fuel feed system

213

fuel injection system

213

gear train

212

general architecture

205

heritage

219

in-service experience

218

liner

210

manufacture

218

oil pump and lubrication system

213

performance

214

piston and rings

211

RON (research octane number)

159

160

527 Rootes Commer TS3 and TS4 about

142

air delivery system

156

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Rootes Commer TS3 and TS4 (Cont.) applications

160

commercial applications

160

connecting rod and bearings

153

coolant pump and circuit

156

crankcase and main bearings

149

crankcase covers

152

crankshaft

153

development

157

drives

155

engine specification

144

engine types and development

156

engine types and ratings

157

features

149

fuel injection system

156

general architecture

145

heritage

169

liner

153

manifolds

156

manufacturing

166

military applications

165

oil pump and lubrication system

156

performance

158

personalities

165

piston and rings

154

rocker lever and rocker

154

TS3 engine

TS4 engine Roots blowers

47

219

272

431

447

466

468

473

28

38

44

50

139

169

185

195

197

199

206

214

216

336

344

354

360

363

365

421

166

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Roots blowers (Cont.)

Roots pump

432

461

466

500

510

520

157

229

472

484

195

rotary OP engine

13

rotary pump

33

Royal Aircraft Establishment Royal Air Force Museum

103 59

Royal Electrical and Mechanical Engineers (REME)

334

Royal Navy ‘Dark’ and the Norwegian Navy ‘Nasty’ Class patrol boats Russell Newbery & Co. Ltd.

265 47

139

S Sammons, Herbert

304

scavenge-air delivery ratios

228

307

320

scavenge air pressure

213

250

255

400

436

44

144

168

269

267

269

213

538 scavenge blowers

4 533

centrifugal

120

coolant

206

and front auxiliaries

269

gas seals

212

lubrication

190

196

251

254

mechanical efficiencies (ME) mechanically driven

43

positive displacement

519

quill drives

156

Roots

139

195

43

266

turbo-assisted

534

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

scavenge blowers (Cont.) Wade scavenge efficiency scavenge period scavenge port belt scavenge ports air chest

151

213

72

93

391

398

5

25

508

538

20

69

192

206

231

65

175

435

189

with aluminum

244

American Marc engines

355

Diamond OP Engines

425

429

Doxford engines

234

241

Fairbanks Morse (FM) engines

418

multi-fuel SBE

459

Sulzer engines

395

scavenge pressure

201

258

364

400

440

442

444

466

441

444

scavenge pumps American Marc engine

306

blow-by

78

capacity

108

cost

434

dimensions

391

double-acting

411

Doxford engines

226

effectiveness

108

efficiency

398

electrically driven

229

engine driven

232

flow

416

269

282

410

413

77

flywheel scavenge pump (FSP)

514

Fullagar engines

405

gear type

284

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

scavenge pumps (Cont.) Jumo engine

182

L60 engine

185

mechanically driven

257

oil

64

67

77

108

120

191

196

206

208

213

286

422

391

398

and one-way valves

391

per cylinder

514

piston

10

ratio

229

144

reciprocating

31

444

redundancy

107

rocker lever

386

400

Roots blower

195

520

rotary

500

scavenge pump piston

10

391

Sulzer 3ZG9 engine

391

Sulzer Brothers ZG series

391

Sulzer engine

441

TSE engine

191

twin

197

scavenge ratio

73

95

97

355

363

410

444

461

464

507

Schlieren photography

447

448

456

Schneider, Heinrich

348

379

Schweitzer, Paul H.

508

447

Schweizerische Lokomotiv-und Maschinen Fabrik (SLM) Seahorse engine range sealing lands

380 225

231

233

263

63

65

89

122

153

187

191

209

210

273

339

341

355

390

494

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms sealing land outer diameters

Links 69

153

191

276

310

210

354

47

404

390 Seaman, H.W.

165

seawater pumps

35

servo system

465

seven-spur gear drive

182

Sexton, Walter

219

Shackelton, Ernest

334

silicon aluminum

273

Simms “Mini-Mech” pump

485

simulation

456

single camshaft

247

single carburetor

530

single crankshafts

11

514

32

37

520 single cylinder, single crankshaft

39

single fuel injection

66

411

444

single fuel system

79

80

83

233

246

371

373

393

395

438

156

200

213

240

452

454

456

497

78

368

single hole nozzle type injector

single injectors

221

single lubrication

77

single O-ring seals

62

single piece crankcase casting

182

single sided ignition

417

single up ratio

338

77

Sir Armstrong-Whitworth (Engineers) Company Ltd

39

46

58

68

70

71

77

59

83

85

86

89

92

95

97

125

334

338

339

432

478

480

483

484

486

494

495

499

500

514

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms sleeves

Links 69

111

276

353

355

411

430

494

498

504

76

410

93

95

123

160

170

207

229

395

398

432

436

447

455

457

459

467

493

500

507

532

507 small bore size (65 mm)

504

small-end bushes (helically grooved)

5

Smethwick Drop Forgings

167

Smith, Graham

219

Smith, John “Jim”

346

smoke

534 snow tractors

334

soot

452

Soul, David

119

454

Southwest Research Institute PTC engine

48

spark assist

473

479

spark ignited gas engine

101

371

503

39

50

55

100

127

130

250

365

371

421

429

432

446

473

503

510

514

149

356

465

spark ignition

spheroidal graphite (SG) castiron splash plate

191

split carburetor

510

spray direction, effect of

449

spray tip penetration

440

451

453

spur gear drives

182

183

205

344

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms spur gears

squish

starting/cold starts

Links 44

62

76

108

123

155

182

194

206

212

348

428

440

85

175

276

360

447

505

507

213

431

436

481

ahead/astern air starting lever

255

air starting and control system auxiliary start injectors Coffman starter

254 199

344

88

cold starts/starting

175

Doxford engines J-type

252

333

English Electric Fullagar Q and R Series

411

fuel injection system, auxiliary start injectors, and starting equipment hydraulic starter motors

199 46

injectors

199

Leyland L60 engine

199

Napier Deltic

295

starter motors

345

starting air system

370

Sulzer 3ZG9 engine

395

swing beam engine (SBE)

503

temperatures

335

Vincent Marine Engine

327

185

200

333

395

steel alloy

availability of

69

113

141

153

187

192

197

211

250

257

273

288

310

354

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

steel (Cont.) bearing parts

63

64

209

235

354

384

386

242

339

343

324

bed plates

234

bolts

386

carrier plate

195

cast/castings

236

check valves

411

connecting rod

153

167

192

211

309

357

410

417

38

348

354

418

167

211

236

383

407

441

507

211

240

388

410

6

67

69

122

268

272

320

418

350

354

coupling

200

crankcase

34

236

440 crankshaft

crosshead

237

crowns

172 507

cylinder liner

end caps

212

exhaust manifolds

362

faceplate

188

fire ring

154

flange plate

191

212

fluid-compressed

27

forged

88

153

276

356

383

407

gears

310

heat resistant

122

main bearing cheese

88

main oil galleries

386

Nimonic

341

nitrided

275

343

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

steel (Cont.) piston heads piston ring

226 7

plates

350

pressed

156

ring carrier

507

ring pack

493

507

rocker shaft

155

167

Siemans Martin

410

sleeve (corset)

69

spill valve

430

250

spring

84

343

411

stainless

80

312

325

418

thrust washers

274

turbine casing

290

water jacket

240

366

wrist pins

194

343

stepped port sealing ring

193

Stransky, Heinz

165

425

submarines Diamond Experimental OP Engine

417

Fairbanks Morse engines

346

French navy

223

Fullagar engines

38

German WWII E boat

265

OP diesels

379

U.S. Navy

346

USS Plunger (SS179)

346

USS Pollack (SS180)

346

Suckling, Stan

334

346

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Sulzer about

40

fuel efficiency and scavenging air demand

118

horizontal turbo compounded

443

Metco metal sprayed coating

174

two-stroke exhaust turbocompounding.

119

Sulzer 3ZG9 engine characteristics

383

connecting link

388

connecting rod

386

crankcase and covers

394

crankshaft

47

cylinder liner

390

cylinder range

381

fuel pump

393

fulcrum rocker

386

general arrangement

381

manifold

395

pistons

388

scavenge pump

391

starting

395

Sulzer 6GA18

41

Sulzer Brothers

40

383

Sulzer Brothers G32 series about

442

construction details

445

general arrangement

43

performance

444

summary

445

Sulzer Brothers G series about

434

application studies

441

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Sulzer Brothers G series (Cont.) construction details

440

design architecture

441

general arrangement

438

high supercharging with 4ZGA19 engine

436

high supercharging with G18 engine

438

performance

440

preliminary research

436

Sulzer categorization of pressure charging levels

435

two-stroke, turbocharging issues

434

Sulzer Brothers ZG series about

380

connecting link

388

connecting rod

386

crankcase and covers

394

crankshaft

383

cylinder liner

390

fuel pumps and camshaft

393

fulcrum rocker

386

general description of 3ZG9 engine

381

manifolds

395

piston

388

scavenge pump and one-way valves sump

391 137

149

152

156

188 See also dry sump system capacity crankcase

156 69

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

173

Index Terms

Links

sump (Cont.) large

119

lower

67

77

113

174

209

339

353

470

78

113

136

195

368

409

411

114

191

339

454

oil drainage/collection

small

136

upper

67

108

354 Sundance

201

204

226

228

107

175

400

464

491

Sun Shipbuilding and Engineering Corporation of USA supercharging Swindon, Wiltshire, England swing beam

59 457

See also fulcrum points air-side

485

bearings

486

cold start

503

connections

482

durability

503

exhaust-side

485

forces on

480

lever ratio

488

link geometry

505

loads on

491

NOx emissons

500

performance

500

stiffness

401

495

505

variable compression ratio (VCR)

46

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

196

Index Terms swing beam engine (SBE)

Links 480

about

481

air and exhaust manifolds

498

air supply and blower

497

BMEP and BTE

500

charge motion

495

cold start and durability

503

combustion chamber

493

compression rings

491

coolant and oil pumps

498

481

crankshaft and connecting rods

486

development results

504

fulcrum points

489

general arrangement

484

injector and fuel pump

497

liner and ports

494

liner cooling

497

link geometry and engine proportions market strategy

505 482

multicylinder swing beam engine

498

NOx emissions

500

oil control rings

493

performance testing

500

personalities

506

pistons and rings

491

ports

494

refinement

500

specification

484

stiffness and inertia

491

swing beam engine technical concept

482

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

swing beam engine (SBE) (Cont.) swing beams and pivot bearings

488

technical concept

482

swirl

71

85

175

234

325

372

391

429

446

452

455

459

495

497

504

507

510

See also bulk swirl; high swirl generation; swirl ratio differential swirl system high swirl TDC swirl ratio swirl ratio

72 6

243

504

447

454

457

493

374

454

497

454 218 510

SwRI PTC engine symmetrical combustion

48

49

6

T T18-37K turbo assisted blower

43

Tank Automotive Research and Development Engineering Centre (TARDEC)

170

506

Tattersall, Norman

203

222

Telcon Stella engine

417

temperatures. See also exhaust temperatures air

44

115

511 ambient

197

boost

532

bottoming cycle

228

bulk gas

632

combustion chamber surface

178

333

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

temperatures. See also exhaust temperatures (Cont.) component

440

compression

447

481

503

coolant

241

270

487

crown

34

70

277

342

492

373

455

497

gradient

456

land

277

liner

244

247

low/cold start

335

395

oil

195

408

operating

457

462

piston

455

ring

76

templug

493

thermal loading

497

277

342

491

493

5

40

110

116

234

399

402

435

481

165

167

thermostatically controlled heat exchanger

270

thermostatic valve

196

thinwall bearing shells

192

Thiokol Dynastar engine

417

Tillings Stevens

142

Tillings Steven TS3. See Rootes Commer TS3 and TS4 timed positive displacement compressor for scavenging

514

Timoney, engine

432

Timoney, Seamus G.

431

high-output OP diesel engines with asymptotic torque curves

457

new concept in traction power plants

462

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

Timoney, Seamus G. (Cont.) oil-driven Pelton wheel– assisted turbocharger system shortfall in CI performance

466 432

variable compression ratio actuator system torsional vibration

torsional vibration problems transfer port transient response trapped air-fuel ratio

458

467

6

12

141

221

223

226

230

236

263

267

418

460

491

498

22

26

128

133

445

466

93

447

454

461

480

498

504

226 534

Trojan OP engine about

132

applications

137

description

133

early low-cost passenger car spark ignition engines

127

four piston duplex

134

heritage

138

Leyland Motor Company

132

manufacturing period (ca. 1923-1929) performance and fuel economy Tryhorn, Don

132 137 431 514

TS3 engine. See also Rootes Commer TS3 and TS4 about

460

experiments

461

results

462

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

506

Index Terms

Links

TS4 engine

142

144

146

152

163

165

167

218

187

209

437

159

See also Rootes Commer TS3 and TS4 Tshudi rotary OP engine Tuftriding

13 168

tunnel camshaft

78

coolant

78

cylinder

63

66

88

338

343

468

260

422

436

liner

89

151

main bearing main bolt turbine

88 211 9 536

design

438

444

446

460

elements of

110

112

270

272

510

equipment driven by

112

267

466

60

63

106

251

267

365

400

435

441

445

111

118

221

251

255

260

436

444

462

exhaust

fuel

165

gas

27

operating conditions

steam

27

turbine compounding

432

turbo-blower scavenging system

366

turbocharged K60T

216

turbocharged uniflow twostroke engines

36

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms turbochargers

Links 41

63

118

120

175

216

221

235

253

365

435

439

444

468

472

476

481

506

510

514

401

443

446

11

32

47

151

421

436

438

441

445

472

480

525

532

275

456

459

473

182

194

205

276

341

536

532 turbo-compounding

118

twin cartridge oil filters

213

twin coolant pumps

185

twin-crankshaft arrangements for OP engines twin crankshafts

11

twin ignition

524

twin injectors

199

two crankshafts Africar OP engine

428

balance

525

Coventry Climax H30

335

design tradeoffs

527

Junker aero design Kharkov-Morozov 6-TD2

59 224

Leyland L60

45

origin of

18

propeller drive

52

rolling element bearings

130

Sulzer 618

438

T. H. Lucas engines

18

two injector plumes

194

two piece pistons

211

two-stage pressure charging

106

two-stage turbocharging

434

510

two-stroke 400 kW 12L three cylinder diesel

534

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

two-stroke NOx level which is 60% lower than the fourstroke

531

two-stroke variable compression ratio piston

534

U uniflow ports

447

unmanned aerial vehicle (UAV)

540

8 kW

512

519

526

80 kW

519

524

527

349 kW

176

applications

170

176

529

cost comparison

527

weight comparison

528

120

199

upper piston scraper box upstream of blower

527

241 83

upstream of inlet pipe

395

upstream spray direction

449

urea/SCR after-treatment

530

452

U.S. Army Tank Automotive Research and Development Engineering Center (TARDEC)

170

U.S. Blue Water missile system

334

Usines Metallurgiques

142

432

506

167

U.S. Navy aluminum engine

440

engine competition

346

Fairbanks Morse engines

346

359

438

FM 38D OP engine for submarines Nasty PTF

417 266

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

U.S. patent 2170020 (differential swirl system) utility engines 32 KW air-cooled

72 520 519 50

V Valveless Car Company Ltd

127

Vandervell Thinwall lead bronze bearings with lead-indium coatings

274

variable compression ratio (VCR)

48

431

457

534

536

46

48

481

491

OP engine Rootes TS3

462

piston

216

swing beam

465

481

216

431

462

534

536

46

variable compression ratio (VCR) mechanism

variable speed

465

VCR system for folded cranktrain OP engine

464

VCR technology used by BICERA

536

vee

442

Vendaco porting system

307

Vendaco scavenge system

308

Versuchsstation fur Gasmotoren (Gas Engine Research Institute)

19

Vessey, Alan

305

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms vibration

Links 31

66

85

93

192

263

264

438

481

496

583 See also torsional vibration axial

230

bending

230

dampers for

269

detuning

226

isolators for

263

473

52

199

minimization/reduction

349

487

transverse

201

430

418

Vincent Airborne Life Raft Engine

42

Vincent HRD Co. Ltd.

42

Vincent Marine Engine

42

about

317

applications

328

coolant pump and circuit

324

crankcase, liners, main bearings, and covers

320

crankshafts, connecting rods, and bearings

323

engine specification

319

features

320

fuel and ignition systems

325

general architecture and operating sequence

320

induction and exhaust manifold

325

liners

322

lubrication circuit

324

performance

328

pistons, rings, and wrist pins

322

starting and drives

327

viscosity

395

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms

Links

visual study of fuel spray about

447

effect of boost pressure

454

effect of injection timing

449

effect of nozzle variants

452

effect of spray direction

449

fuel spray penetration prediction

455

general conclusions from experiments

455

W W12 Napier Lion Wade Blower Wade Roots blower

38 156 47

421

Wade scavenge blower

151

213

Wallace, Frank I.

431

457

460

462

342

454

456

118

472

506

69

355

373

139

225

38

66

78

104

129

149

174

235

242

259

Wallace research about

460

experiments

461

results

462

wall wetting

6

504

Wankel engine BTE rating

529

cost of

529

one and two rotor versions

524

vs. OP engines

527

parameters

528

waste gate

113

water-cooled exhaust manifolds

418

water-cooled injectors water cooling waterjacket

272 This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

Index Terms water pump

Links 66

74

77

79

130

145

151

156

188

334

361

384

weight and cost comparisons

532

welded steel bedplates

234

W. H. Allen Son & Co. Ltd.

413

William Beardmore & Co. Ltd.

26

Willshaw, Harry

165

Wilson, William Kerr

263

Wittig

1

Wittig and Giles

17

Wittig concept

18

vs. J-Type Doxford Engines Wittig single-crank OP engine variant

231 9

19

19

Wittig three-throw system vs. Junkers two-crankshaft arrangement

59

Witzky engine

417

Witzky, J. E.

432

Woodward, Henry

506

Woodward governor

349

wrist pin bosses

194

wrist pins

432

433

498

76

122

154

193

211

276

342

359

388

410

417

488

491

536

539

This p a g e ha s b e e n re fo rma tte d b y Kno ve l to p ro vid e e a sie r na vig a tio n.

About the Authors Jean-Pierre Pirault worked in the R&D laboratories of plain bearing manufacturer Vandervell Products, moved to Ricardo, Ford Motor Company, Jaguar, and AVL. He is now with Powertrain Technology Ltd, an engine consultancy in the south of England. Martin Flint is a Chartered Mechanical Engineer and a Fellow of the Institution of Mechanical Engineers. He trained as an indentured apprentice at AEC, Southall, Middlesex, United Kingdom, who were designers and manufacturers of commercial vehicles and diesel engines. During his career he has worked for Deutz AG (both in Germany and Canada), BICERI, Perkins, Rolls Royce, and Ricardo, experiencing most aspects of manufacture, design, R&D and engine testing. This book was prompted by a casual phone call between the authors about a colleague who was clearing his garage of boxes of old technical papers prior to moving. The colleague had worked in engine R&D for most of his professional career and had preserved old engine documentation that was due to be destroyed because of its age and lack of use, some of it covering some well known but defunct opposed piston (OP) engines. Both authors felt the need to continue and add to the preservation begun by their colleague and have been saving the data onto compact discs. This book is intended as a more active form of preservation for one particular topic-the Opposed Piston (OP) engine.