Methanol: A Sustainable Transport Fuel for CI Engines (Energy, Environment, and Sustainability) 981161279X, 9789811612794

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Energy, Environment, and Sustainability Series Editor: Avinash Kumar Agarwal

Avinash Kumar Agarwal · Hardikk Valera · Martin Pexa · Jakub Čedík Editors

Methanol A Sustainable Transport Fuel for CI Engines

Energy, Environment, and Sustainability Series Editor Avinash Kumar Agarwal, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, India

AIMS AND SCOPE This books series publishes cutting edge monographs and professional books focused on all aspects of energy and environmental sustainability, especially as it relates to energy concerns. The Series is published in partnership with the International Society for Energy, Environment, and Sustainability. The books in these series are edited or authored by top researchers and professional across the globe. The series aims at publishing state-of-the-art research and development in areas including, but not limited to: • • • • • • • • • •

Renewable Energy Alternative Fuels Engines and Locomotives Combustion and Propulsion Fossil Fuels Carbon Capture Control and Automation for Energy Environmental Pollution Waste Management Transportation Sustainability

Review Process The proposal for each volume is reviewed by the main editor and/or the advisory board. The chapters in each volume are individually reviewed single blind by expert reviewers (at least four reviews per chapter) and the main editor. Ethics Statement for this series can be found in the Springer standard guidelines here https://www.springer.com/us/authors-editors/journal-author/journal-author-hel pdesk/before-you-start/before-you-start/1330#c14214

More information about this series at http://www.springer.com/series/15901

Avinash Kumar Agarwal · Hardikk Valera · ˇ Martin Pexa · Jakub Cedík Editors

Methanol A Sustainable Transport Fuel for CI Engines

Editors Avinash Kumar Agarwal Department of Mechanical Engineering Indian Institute of Technology Kanpur Kanpur, India

Hardikk Valera Department of Mechanical Engineering Indian Institute of Technology Kanpur Kanpur, India

Martin Pexa Department for Quality and Dependability of Machines Czech University of Life Sciences Prague Suchdol, Czech Republic

ˇ Jakub Cedík Department for Quality and Dependability of Machines Czech University of Life Sciences Prague Suchdol, Czech Republic

ISSN 2522-8366 ISSN 2522-8374 (electronic) Energy, Environment, and Sustainability ISBN 978-981-16-1279-4 ISBN 978-981-16-1280-0 (eBook) https://doi.org/10.1007/978-981-16-1280-0 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

Due to the increasing human population on Earth, the energy demands of the transportation sector are raising. The increased intensity of transportation causes higher levels of environmental stress. This opens a challenge for researchers in order to decrease the environmental effects and to ensure sufficient renewable energy sources. The quality of human life depends to a large extent on the availability of transportation of both people and goods. Also, the increasing amount of transportation poses a severe risk to human health mainly due to pollutant formation during the combustion of fossil fuels. The International Society for Energy, Environment and Sustainability (ISEES) was founded at Indian Institute of Technology Kanpur (IIT Kanpur), India, in January 2014 with an aim to spread knowledge/awareness and catalyze research activities in the fields of Energy, Environment, Sustainability, and Combustion. The Society’s goal is to contribute to the development of clean, affordable, secure energy resources and a sustainable environment for the society; spread knowledge in the above-mentioned areas; and create awareness about the environmental challenges, which the world is facing today. The unique way adopted by the society was to break the conventional silos of specializations (engineering, science, environment, agriculture, biotechnology, materials, fuels, etc.) to tackle the problems related to energy, environment, and sustainability in a holistic manner. This is quite evident by the participation of experts from all fields to resolve these issues. The ISEES is involved in various activities such as conducting workshops, seminars, and conferences in the domains of its interests. The society also recognizes the outstanding works done by young scientists and engineers for their contributions in these fields by conferring them awards under various categories. The Fourth International Conference on “Sustainable Energy and Environmental Challenges” (IV-SEEC) was organized under the auspices of ISEES from November 27 to November 29, 2019, at NEERI, Nagpur. This conference provided a platform for discussions between eminent scientists and engineers from various countries including India, USA, China, Italy, Mexico, South Korea, Japan, Sweden, Greece, Czech Republic, Germany, the Netherlands, and Canada. At this conference, eminent speakers from all over the world presented their views related to different aspects of energy, combustion, emissions, and alternative energy resources v

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for sustainable development and a cleaner environment. The conference presented one high-voltage plenary talk by Mrs. Rashmi Urdhwareshe, Director, Automotive Research Association of India (ARAI), Pune. The conference included 28 technical sessions on topics related to energy and environmental sustainability, including 1 plenary talk, 25 keynote talks, and 54 invited talks from prominent scientists, in addition to 70+ contributed talks and 80+ poster presentations by students and researchers. The technical sessions in the conference included Fuels, Engine Technology and Emissions, Coal and Biomass Combustion/Gasification, Atomization and Sprays, Combustion and Modelling, Alternative Energy Resources, Water and Water and Wastewater Treatment, Automobile and other Environmental Applications, Environmental Challenges and Sustainability, Nuclear Energy and Other Environmental Challenges, Clean Fuels and Other Environmental Challenges, Water Pollution and Control, Biomass and Biotechnology, Waste to Wealth, Microbiology, Biotechnological and Other Environmental Applications, Waste and Wastewater Management, Cleaner Technology and Environment, Sustainable Materials and Processes, Energy, Environment and Sustainability, Technologies and Approaches for Clean Sensors and Materials for Environmental, and Biological Processes and Environmental Sustainability. One of the highlights of the conference was the Rapid Fire Poster Sessions in (i) Engine/Fuels/Emissions, (ii) Environment, and (iii) Biotechnology, where 50+ students participated with great enthusiasm and won many prizes in a fiercely competitive environment. 300+ participants and speakers attended this 3-day conference, where 12 ISEES books published by Springer, Singapore, under a special dedicated series “Energy, Environment and Sustainability” were released. This was the third time in a row that such a significant and high-quality outcome has been achieved by any society in India. The conference concluded with a panel discussion on “Balancing Energy Security, Environmental Impacts and Economic Considerations: Indian Perspective”, where the panelists were Dr. Anjan Ray, CSIR-IIP Dehradun; Dr. R. R. Sonde, Thermax Ltd.; Prof. Avinash Kumar Agarwal, IIT Kanpur; Dr. R. Srikanth, National Institute of Advanced Studies, Bengaluru; and Dr. Rakesh Kumar, NEERI Nagpur. The panel discussion was moderated by Prof. Ashok Pandey, Chairman, ISEES. This conference laid out the roadmap for technology development, opportunities, and challenges in the Energy, Environment, and Sustainability domain. All these topics are very relevant to the country and the world in the present context. We acknowledge the support received from various funding agencies and organizations for the successful conduct of the Fourth ISEES Conference (IV-SEEC), where these books germinated. We would therefore like to acknowledge SERB, Government of India (special thanks to Dr. Sandeep Verma, Secretary); NEERI Nagpur (special thanks to Dr. Rakesh Kumar, SDirector); CSIR; and our publishing partner Springer (special thanks to Swati Mehershi). The editors would like to express their sincere gratitude to a large number of authors from all over the world for submitting their high-quality work in a timely manner and revising it appropriately at a short notice. We would like to express our special thanks to Dr. Martin Pechout, Assoc. Prof. Jozef Žarnovský, Dr. Peter Kuchar, Dr. Risto Ilves, Dr. Martin Kotek, Dr. Michal Vojtisek-Lom, Dr. Suhan Park, Prof.

Preface

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Xituwa, Dr. Vikram, and Dr. Anirudh Gautam who reviewed various chapters of this monograph and provided their valuable suggestions to improve the manuscripts. This book is focused on methanol usage for the transportation sector, specifically for compression ignition (CI) engines. The book includes chapters, presenting examples of the utilization of methanol as a fuel for CI engines in different modes of transportation, such as railroads, personal vehicles, and heavy-duty road transportation. A few chapters of this book are focused on the effect of methanol on the combustion and performance characteristics of the engine. A few chapters of this book are dedicated to the effect of methanol on exhaust emission, production, prediction, and control. Several chapters, presenting fueling strategies with the use of methanol are also included. The chapters include recent results and are more focused on current trends of methanol utilization in compression ignition engines. This book provides information about the current methanol utilization, its potential, and its effect on the engine in terms of efficiency, combustion, performance, pollutant formation, and prediction. Different aspects of methanol use, such as the utilization techniques or fueling strategy, are also presented. The physical and chemical properties of methanol, affecting its use in internal combustion engines, are also discussed in this book. Parts of the chapters of this book are based on a review of state of the art, while other chapters are dedicated to original research. We hope that the book would be of great interest to the professionals, post-graduate students involved in alternative fuels, compression ignition engines, and environmental research. Kanpur, India Kanpur, India Prague, Czech Republic Prague, Czech Republic

Avinash Kumar Agarwal Hardikk Valera ˇ Jakub Cedík Martin Pexa

Contents

Part I 1

Introduction of Methanol: A Sustainable Transport Fuel for CI Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ˇ Avinash Kumar Agarwal, Hardikk Valera, Martin Pexa, and Jakub Cedík

Part II 2

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General 3

Methanol as a Fuel

Technology Options for Methanol Utilization in Large Bore Diesel Engines of Railroad Sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dhananjay Kumar, Hardikk Valera, and Avinash Kumar Agarwal

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Application of Methanol as Clean and Efficient Alternative Fuel to Engines with Compression Ignition . . . . . . . . . . . . . . . . . . . . . . Chunde Yao, Anren Yao, Bin Wang, and Taoyang Wu

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Methanol: A Gateway to Biofuel Revolution in Global Heavy-Duty ICE-Based Transportation . . . . . . . . . . . . . . . . . . . . . . . . . Subhanker Dev

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Safety Aspects of Methanol as Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Omkar Yadav, Hardikk Valera, Deepak Dulani, Unni Krishnan, and Avinash Kumar Agarwal

Part III Application Aspects 6

Combustion and Emission Analyses of a Diesel Engine Running on Blends with Methanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 György Szabados, Justas Žaglinskis, Kristóf Lukács, and Ákos Bereczky

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Combustion Characteristics of Methanol Fuelled Compression Ignition Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 ˇ Jakub Cedík, Hardikk Valera, Martin Pexa, and Avinash Kumar Agarwal

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Heavy Duty Diesel Engines Operating on 100% Methanol for Lower Cost and Cleaner Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . 191 Julie Blumreiter and Bernard Johnson

Part IV Emission Control 9

Combustion, Performance and Emission Analysis of Diesel-Methanol Fuel Blend in CI Engine . . . . . . . . . . . . . . . . . . . . . 229 Chandan Kumar, Kunj Bihari Rana, and Brajesh Tripathi

10 Impact of Methanol on Engine Performance and Emissions . . . . . . . 247 Akshay Garg, Gaurav Dwivedi, Siddharth Jain, and Arun K. Behura 11 Potential Assessment of Methanol to Reduce the Emission in LTC Mode Diesel Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 Prem Kumar, Sarbjot Singh Sandhu, Mandeep Singh, and Akash Deep 12 Methodology to Predict Emissions and Performance Parameters of a Methanol Fueled Diesel Engine . . . . . . . . . . . . . . . . . . 293 G. K. Prashant, D. B. Lata, and M. Ravi Shankar

Editors and Contributors

About the Editors Prof. Avinash Kumar Agarwal joined the Indian Institute of Technology (IIT) Kanpur, India in 2001 after working as a post-doctoral fellow at the Engine Research Center, University of Wisconsin at Madison, USA. His interests are IC engines, combustion, alternate and conventional fuels, lubricating oil tribology, optical diagnostics, laser ignition, HCCI, emissions and particulate control, and large bore engines. Prof. Agarwal has published 290+ peer reviewed international journal and conference papers, 42 edited books, 78 books chapters and has 10,000+ Scopus and 15,300+ Google scholar citations. He is a Fellow of SAE (2012), Fellow of ASME (2013), Fellow of ISEES (2015), Fellow of INAE (2015), Fellow of NASI (2018), Fellow of Royal Society of Chemistry (2018), and a Fellow of American Association of Advancement in Science (2020). He is recipient of several prestigious awards such as Clarivate Analytics India Citation Award-2017 in Engineering and Technology; NASI-Reliance Industries Platinum Jubilee Award-2012; INAE Silver Jubilee Young Engineer Award-2012; Dr. C. V. Raman Young Teachers Award-2011; SAE Ralph R. Teetor Educational Award2008; INSA Young Scientist Award-2007; UICT Young Scientist Award-2007; INAE Young Engineer Award2005. Prof. Agarwal received Prestigious Shanti Swarup Bhatnagar Award-2016 in Engineering Sciences. For his outstanding contributions, Prof. Agarwal is conferred

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upon Sir J. C. Bose National Fellowship (2019) by SERB. Hardikk Valera is currently pursuing his Ph.D. from Engine Research Laboratory (ERL), Department of Mechanical Engineering, Indian Institute of Technology (IIT) Kanpur, India. He completed his M.Tech and B.Tech. from National Institute of Technology Jalandhar and Ganpat University, respectively. His research interests include methanol fueled SI engines, methanol fuelled CI engines, optical diagnostics, fuel spray characterization and emission control from engines. Prof. Martin Pexa is an associate professor in the field of energetics at the Czech University of Life Sciences Prague, Department for Quality and Dependability of Machines. His research work is focused on the issue of diagnosis and maintenance of machines, especially in the field energy and diagnosis of motor vehicles. As part of his activities, he regularly reviews the contributions into databases Web of Science and Scopus. He also publishes contributions in international scientific journals and conferences.

ˇ Dr. Jakub Cedík is assistant professor at the Czech University of Life Sciences Prague, Department for Quality and Dependability of Machines, where he teaches course on Operability of Machines, Quality, Dependability and Logistics of Machines, Technology of Maintenance and Repairs of Machines. He is also a researcher at Research Institute of Agriculture Engineering, Prague, Czech Republic. His research interests include biofuels, exhaust emissions, energy demands and operation of internal combustion engines of vehicles and agriculture machinery, issues of agricultural machinery and motor vehicles. He is author or co-author of more than 40 peer-reviewed scientific publications.

Editors and Contributors

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Contributors Avinash Kumar Agarwal Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, India Arun K. Behura School of Mechanical Engineering, VIT, Vellore, Tamil Nadu, India Ákos Bereczky Department of Energy Engineering, Budapest University of Technology and Economics, Budapest, Hungary Julie Blumreiter ClearFlame Engines, Inc., Geneva, IL, USA ˇ Jakub Cedík Department for Quality and Dependability of Machines, Czech University of Life Sciences, Prague, Czech Republic Akash Deep School of Mechanical Engineering, Lovely Professional University, Punjab, India Subhanker Dev The Automotive Research Association of India (ARAI), Pune, India Deepak Dulani Hero Moto Corp Ltd. Dharuhera, Gurugram, Haryana, India Gaurav Dwivedi Energy Center, Maulana Azad National Institute of Technology, Bhopal, India Akshay Garg Department of Mechanical Engineering, College of Engineering Roorkee, Roorkee, India Siddharth Jain Department of Mechanical Engineering, College of Engineering Roorkee, Roorkee, India Bernard Johnson ClearFlame Engines, Inc., Geneva, IL, USA Unni Krishnan Hero Moto Corp Ltd. Dharuhera, Gurugram, Haryana, India Chandan Kumar Mechanical Engineering Department, Rajasthan Technical University, Kota, India; I.C. Engine Laboratory, Swami Keshvanand Institute of Technology, Management & Gramothan, Jaipur, India Dhananjay Kumar Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, India Prem Kumar Department of Mechanical Engineering, Dr. B R Ambedkar National Institute of Technology, Jalandhar, Punjab, India D. B. Lata Central University of Jharkhand, Ranchi, India Kristóf Lukács Department of Energy Engineering, Budapest University of Technology and Economics, Budapest, Hungary

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Martin Pexa Department for Quality and Dependability of Machines, Czech University of Life Sciences, Prague, Czech Republic G. K. Prashant Vellore Institute of Technology, Bhopal, India Kunj Bihari Rana Mechanical Engineering Department, Rajasthan Technical University, Kota, India M. Ravi Shankar Space Engineer, Kozmoz Solutions, Dubai, UAE Sarbjot Singh Sandhu Department of Mechanical Engineering, Dr. B R Ambedkar National Institute of Technology, Jalandhar, Punjab, India Mandeep Singh Department of Mechanical Engineering, Dr. B R Ambedkar National Institute of Technology, Jalandhar, Punjab, India György Szabados Department of Internal Combustion Engines and Propulsion Technology, Széchenyi István University, Gy˝or, Hungary Brajesh Tripathi Mechanical Engineering Department, Rajasthan Technical University, Kota, India Hardikk Valera Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, India Bin Wang State Key Laboratory of Engines (SKLE), Tianjin University, Tianjin, China Taoyang Wu State Key Laboratory of Engines (SKLE), Tianjin University, Tianjin, China Omkar Yadav Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, India Anren Yao School of Environmental Science and Technology, Tianjin University, Tianjin, China Chunde Yao State Key Laboratory of Engines (SKLE), Tianjin University, Tianjin, China Justas Žaglinskis Waterborne Transport and Air Pollution Laboratory, Marine Research Institute, Klaipeda University, Klaipeda, Lithuania

Part I

General

Chapter 1

Introduction of Methanol: A Sustainable Transport Fuel for CI Engines ˇ Avinash Kumar Agarwal, Hardikk Valera, Martin Pexa, and Jakub Cedík

Abstract The rising energy demand of transportation sector worldwide causes the depletion of oil reserves. Also, the harmful exhaust emissions from transportation sector possess a risk to human health. This book presents a different aspects of methanol utilization in compression ignition (CI) engines for transportation sector. The first section of this book includes the introduction chapter, where the content of all the book chapters is summarized. The second section presents a methanol as a fuel for CI engines, introduces a different approach for methanol combustion in CI engine and presents the examples of methanol utilization as a fuel in transportation sector. This section also discusses the safety aspects of methanol utilization in transportation. The third section of the book focuses on application aspects, such as performance and combustion characteristics and integrating methanol as a fuel into a diesel engine architecture. The fourth and the last section of this book is dedicated to emissions. The effect of methanol on harmful emissions such as carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and particulate matter (PM) is evaluated. Further, the effect of partially premixed combustion strategy of methanol on emission production and the response surface models for prediction of emissions and engine performance of dual fuel engine are presented. Keywords CI engine · Methanol · Biofuel · Transportation The energy consumption in transportation sector is globally increasing, especially in fast growing countries (Chai et al. 2016). Currently, the main part of this energy has its origin in fossil oil. However, this causes depletion of the global oil reserves and have negative effect on the environment. There is a need for a clean and sufficient source of energy, which can be used as an alternative to the fossil fuels. Concerning A. K. Agarwal (B) · H. Valera Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India e-mail: [email protected] ˇ M. Pexa · J. Cedík Department for Quality and Dependability of Machines, Czech University of Life Sciences, Prague, Czech Republic © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 A. K. Agarwal et al. (eds.), Methanol, Energy, Environment, and Sustainability, https://doi.org/10.1007/978-981-16-1280-0_1

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a liquid biofuel, the methanol is showing a promising results due to its effectiveness and reasonable price. Moreover, this fuel can be utilized in both spark ignition (SI) and CI engines (Verhelst et al. 2019; Valera and Agarwal 2019; Valera et al. 2020). This book presents three important aspects of utilization of methanol in transportation sector as a fuel for CI engines. The first section of this book includes the introduction chapter, which introduces all sections of the book and presents the important aspects. The second section of this book is focused on utilization of methanol as a fuel for transportation. The different techniques of methanol combustion in CI engine are introduced and the examples of methanol utilization in different modes of transport are presented. Methanol vehicle industries are developing fast, especially in India and China, and methanol poses a sustainable source of energy suitable for transportation. The first chapter of this section is dedicated to railroad sector. Railway is mostly using diesel as a fuel for locomotive engines. Hence, emission from the locomotive engines cannot be snubbed since it causes various concerns for the environment, such as global warming and health issues. There is a need for alternative fuels for diesel locomotives, which can meet the energy demands, with reduced emissions. India possesses a large amount of high ash coal. Therefore, methanol production through coal gasification route can be a good alternative that fulfils the fuel demand of diesel locomotives. However, utilization of methanol with existing locomotive engines faces various design challenges. This chapter reviews the different techniques of methanol utilization in diesel locomotive and involves technological challenges in their usage. The chapter also suggests the potential technique for methanol adaptations in diesel locomotives. The second chapter introduces the diesel methanol compound combustion (DMCC), the fuel strategy for port injection of methanol for dual fuel diesel engines, applied to various power units such as heavy duty trucks, constructive machine, marine propeller and locomotive engines. Using DMCC the engine starts up with neat diesel fuel and switches to the mode of diesel methanol dual fuel after the engine fully warms up. The strategy of DMCC will substitute methanol to diesel fuel up to 40% for new engine and 30% for retrofitting engine when it is applied to heavy duty vehicle and constructive machine as well as marine power unit. The characteristics of diesel–methanol dual fuel combustion mode, emission control strategy and system related to catalyst, retrofitting, and modifying engine from neat diesel to running DMCC mode are also introduced. The third chapter of the second section of this book illustrates advanced combustion concepts, like partially premixed combustion, reactivity controlled compression ignition that is well suited to work with biofuels like methanol. However, each of these advanced combustion concepts has their challenges, which further paved the way for mixed mode combustion concepts where the aim is to utilize such advanced combustion concepts for their ability to deliver excellent engine efficiencies in duty cycle part of engine operating zone and switch to classical diesel combustion or SI combustion in rest of engine working map. Worldwide, there are number of research laboratories and universities which have already shown close to 50% brake thermal efficiencies. However, there are some challenges like high pressure rise rates and low load combustion stability. The last chapter presents the safety aspects of methanol production and utilization as a fuel in transportation sector.

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The third section of the book is based on the application aspects of methanol in CI engines. The first chapter of the third section provides a comprehensive overview about the methanol’s effect on the combustion and emission properties of a diesel engine. The diesel – biodiesel and diesel – biodiesel – methanol blends are investigated. The chapter contains calculations regarding theoretical combustion (oxidation process) of the different hydrogen-carbons. A rarely investigated parameter, O2 consumption or demand is also in focus besides CO2 emission and intensity throughout the calculations. For the experimental test series diesel fuel was the base fuel along with mentioned blends. Methanol’s theoretical contribution to the diesel – biodiesel blend’s O2 consumption and CO2 emission is almost negligible. Engine’s external parameters have not changed significantly if it is running on blend with methanol. The second chapter of this section is focused on combustion characteristics of CI engines fuelled with diesel – methanol, biodiesel – methanol and biodiesel – diesel – methanol blends. The effects of the different utilization techniques and fuel blends on the cylinder pressure, heat release rate and exhaust gas temperature are summarized from the literature sources and analysed. A special attention is paid to the two most used techniques of methanol utilization in diesel engine: blending and port injection. The blending is very simple technique; however, it is very sensitive to phase separation and low cetane number of the methanol. Hence, the amount of the diesel substitution is limited. Using the port injection technique, it is possible to substitute higher proportions of diesel by methanol. On the other hand, there are other challenges connected with this technique, such as cooling effect of methanol. The last chapter of this section focuses on a method of integrating methanol as a fuel into a diesel engine architecture for heavy duty applications. The result is an engine that can operate on 100% methanol (or other alcohol fuels) that has lower emissions and lower costs, while the demanding torque and efficiency required for heavy industrial applications continue to be met. The benefits of combining this promising fuel with the robust diesel engine design illustrate how heavy industry can not only successfully make the transition to a methanol economy but greatly benefit from such a transition. The last section of this book is dedicated to emission control from methanol fuelled engines. The section includes five chapters: the first chapter reviews the impact of different methanol – diesel blends on CI engine combustion, performance and emission characteristics. The combustion characteristics of the engine are evaluated by the heat release curve measured inside the cylinder pressure data under various engine operating conditions. Performance characteristics are also discussed for different methanol – diesel blends at various CI engine parameters. Smoke, CO, HC, NOx and PM emissions of CI engine have been discussed with different engine parameters using methanol – diesel blends. The role of injection timing on engine emissions has been also discussed. The second chapter in the last section describes different aspects of using methanol as a fuel for CI engines. The chapter focuses on the advantages and disadvantages of using methanol as a fuel, physical and chemical fuel properties of methanol and its comparison with other fuels, and engine performance and emissions characteristics of engines fuelled with methanol and its various blends. The third chapter studies the effect of methanol on diesel engine working in partially

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premixed combustion (PPC). PPC strategy is efficient low temperature combustion (LTC) modes having lower Soot/NOX exhaust emissions and higher efficiency. The PPC is a fuel strategy that allows the utilization of higher research octane number (RON) fuel in a modern CI engine. Unlike traditional compression ignition engines, the PPC strategy allows sufficient time for fuel/air mixing before self ignition. In PPC strategy, advanced fuel injection timing with higher octane number fuel can be used to achieve effective ignition timing, and consequently, improve combustion stability. The chapter states that high O2 concentration in methanol appears to be favourable in PPC strategy to reduce the soot emissions. Additionally, methanol has higher latent heat of vaporization, which increases the charge cooling effect that reduces NOX emissions. Thus, the combined use of PPC strategy along with methanol could be a promising upcoming solution to fulfil the strict exhaust emission norms. The fourth chapter in the section presents a response surface methodology of the experimental investigations for varying substitution of diesel fuel by methanol and load conditions performed on a four cylinder dual fuel diesel engine. Break thermal efficiency, oxides of nitrogen, unburnt hydrocarbon and carbon monoxide were considered with the response surface model. The response surface models developed were used to relate the parameters of liquid fuel substitution and varying loads with the output parameters. Comparisons of modelled and experimental results have been discussed elaborately. This monograph presents a different aspect of utilization of methanol in transportation sector to power CI engines. Specific topics covered in the monograph include: • Introduction of Methanol: A Sustainable Transport Fuel for CI Engines • Technology Options for Methanol Utilization in Large Bore Diesel Engines of Railroad Sector • Application of Methanol as Clean and Efficient Alternative Fuel to Engines with Compression Ignition • Methanol: A Gateway to Biofuel Revolution in Global Heavy-Duty ICE-Based Transportation • Safety Aspects of Methanol as Fuel • Combustion and Emission Analyses of a Diesel Engine Running on Blends with Methanol • Combustion Characteristics of Methanol Fuelled Compression Ignition Engines • Heavy Duty Diesel Engines Operating on 100% Methanol for Lower Cost and Cleaner Emissions • Combustion, Performance and Emission Analysis of Diesel–Methanol Fuel Blend in CI Engine • Impact of Methanol on Engine Performance and Emissions • Potential Assessment of Methanol to Reduce the Emission in LTC Mode Diesel Engine • Methodology to Predict Emissions and Performance Parameters of a Methanol Fueled Diesel Engine

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The topics are organized in four different sections: (i) General, (ii) Methanol as a Fuel, (iii) Application Aspects and (iv) Emission Control.

References Chai J, Lu QY, Wang SY, Lai KK (2016) Analysis of road transportation energy consumption demand in China. Transp Res Part D Transp Environ 48:112–124. https://doi.org/10.1016/j.trd. 2016.08.009 Valera H, Agarwal AK (2019) Methanol as an alternative fuel for diesel engines. In: Agarwal A, Gautam A, Sharma N, Singh A (eds) Methanol and the alternate fuel economy. Energy, environment, and sustainability. Springer, Singapore Valera H, Singh AP, Agarwal AK (2020) Prospects of methanol-fuelled carburetted two wheelers in developing countries. In: Advanced combustion techniques and engine technologies for the automotive sector. Energy, environment, and sustainability. Springer, Singapore Verhelst S, Turner JW, Sileghem L, Vancoillie J (2019) Methanol as a fuel for internal combustion engines. Prog Energy Combust Sci 70:43–88. https://doi.org/10.1016/j.pecs.2018.10.001

Part II

Methanol as a Fuel

Chapter 2

Technology Options for Methanol Utilization in Large Bore Diesel Engines of Railroad Sector Dhananjay Kumar, Hardikk Valera, and Avinash Kumar Agarwal

Abstract Railroad offers one of the most convenient and reliable ways of transport for goods and humans. It is also an economically viable mode of transport, which would continue to grow in coming decades. Railroad is mostly using large bore diesel locomotive engines. Emissions from these locomotive engines cannot be ignored since it causes adverse impact on the environments and human beings, such as global warming, health issues, etc. There is a need for alternative fuels for diesel locomotives, which can meet the energy demands while reducing emissions. Methanol has shown great potential to replace mineral diesel. Methanol can be produced from various feedstocks such as biomass, high ash coal, carbon capture, etc. India has vast resources of high ash coal. Therefore, methanol production through coal gasification could be a viable alternative that fulfils the fuel demand for diesel locomotives as well as other sectors. Utilization of methanol in existing locomotive engines faces various challenges. This chapter reviews different techniques of methanol utilization in an existing compression ignition (CI) engines and brings out the technical challenges with appropriate solutions. This chapter also throws some lights on potential techniques for methanol adaptation in diesel locomotives. Keywords Railroad sector · Large bore engines · Locomotive engines · Methanol utilization techniques

Abbreviations SI CI ICEs CO HC

Spark ignition Compression ignition Internal combustion engines Carbon monoxide Hydrocarbon

D. Kumar · H. Valera · A. K. Agarwal (B) Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 A. K. Agarwal et al. (eds.), Methanol, Energy, Environment, and Sustainability, https://doi.org/10.1007/978-981-16-1280-0_2

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NOx PM CO2 CPCB IEA UIC NRMM DME NITI CN HPDI BMEP RCCI LTC RMD CAD bTDC aTDC CVCC OEM ECU IMEP

D. Kumar et al.

Nitrogen oxide Particulate matter Carbon dioxide Central pollution control board International energy agency International union of railways Non-road mobile machinery Dimethyl ether National institution for transforming India Cetane number High pressure direct injection Brake mean effective pressure Reactivity controlled compression ignition Low temperature combustion Methanol to diesel ratio Crank angle degree Before top dead centre After top dead centre Constant volume combustion chamber Original equipment manufacturer Electronic control unit Indicated mean effective pressure

2.1 Introduction Since last few decades, human civilization has progressed rapidly in every aspect. Progress of human lifestyle is primarily because of advancements in technology and means of transport. Initially, humans used to travel on foot before gradually starting to use animals, such as camels and horses. With further advancements, humans explored all modes of transport, viz., air, sea, and land. Generally, these modes include automobiles, aero planes, trains, and ships for transport, and all these used a specific propulsion system, which could be steam engines, internal combustion engines (ICEs), gas turbines, etc. Land based transportation played a significant role in human progress in 20th –21st centuries, and it was mainly powered by ICEs. Locomotive engines are large bore engines used for railroad transportation. It is the most reliable and cheapest mode of transportation for passengers and goods. Locomotive engines fueled with diesel give high power output. However, they emit harmful pollutants due to the burning of fossil diesel. The primary pollutants are carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM). Stricter emission norms have been implemented by regulatory bodies to control these emissions worldwide for a variety of applications. Diesel locomotive

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Fig. 2.1 Schematic of 16 cylinders diesel locomotive engine

generally has 16 cylinders and use mechanical fuel injectors for direct injection of diesel. A general layout of diesel locomotive is given in Fig. 2.1. India has world’s third largest railway network. Total length of Indian railways network is ~67,415 km. In 2013, Indian railroads contributed 24.7 million tonnes of carbon dioxide (CO2 ) emission, which was ~9.7% of total CO2 emissions from India (https://164.100.107.13/Draft_Interim_Rly_Diesel_Emission_Stds_01. 05.2017.pdf), according to the report submitted by Central Pollution Control Board (CPCB). India has implemented Bharat stage (BS) emission norms for controlling emissions from small bore engines. However, there is no emission norm for diesel locomotives as of now. Few countries like Europe and USA have implemented stringent regulatory norms for large bore engines. From a small bore engine point of view, Indian automotive sector is experiencing a challenging situation to meet BS VI emission norms. It is quite challenging to meet stricter emission norms and optimal performance with carbonaceous fuels like diesel and petrol. At the same time, it is necessary to meet the customer expectation of engine performance with good mileage of the vehicle. Nowadays, diesel and petrol prices are also a matter of concern for customers since they are rising every day. The two primary reasons responsible for higher fuel prices are: (i) global geopolitics and (ii) limited domestic petroleum reserves. Therefore, the Indian government is considering adopting an innovative solution. The goal is to achieve reduction in overall emissions from diesel locomotive engines and utilization of indigenous fuel produced at an economical price. Many researchers are exploring alternative fuels, which can fulfil market demand and comply with stringent emission norms simultaneously. Various alternative fuels (Verhelst et al. 2019; Khan et al. 2015; Park and Lee 2014; Dimitriou and Tsujimura 2017) are being explored, and their feasibility studies are being carried out using various advanced engine technologies (Reitz and Duraisamy 2015; Agarwal et al.

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2017; Li et al. 2020; Lif et al. 1997; Shim et al. 2020; Kumar and Agarwal 2020). However, alternative fuels for locomotive engines should be selected such that it meets at least existing emission standards, implemented by other countries. This requires a brief analysis of existing emission standards and potential alternative fuels. Therefore, the essence of emission standards and suitable alternative fuels for large bore engines are discussed in subsequent sections.

2.1.1 Emissions Standards for Locomotive Engines Locomotive engines contribute significantly to CO2 emissions. Figure 2.2 shows the share of CO2 emissions by different sectors of economy globally. It reveals that ~25% of total CO2 emission is contributed by the transport sector, and out of that, ~4.2% is originating from railroad sector (Railroad Handbook 2017). These emissions cannot be ignored because they cause an adverse impact on the environment and on humans, such as global warming and adverse health impact. Previous studies suggested that railroad is a more sustainable transport compared to road and air, both in terms of energy required and carbon emissions per passenger-kilometer or tonne-kilometer. It is foreseen to continue to do so over next few decades. A report jointly prepared by International Energy Agency (IEA) and International Union of Railroads (UIC) also confirmed that railroad sector offers the most efficient land based mode of

Fig. 2.2 Share of global CO2 emissions from fuel combustion sector wise (2015) (Railroad Handbook 2017)

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Table 2.1 Stage III A/B Emission Standards for Rail Traction Engines (https://www.transportpol icy.net/standard/eu-locomotives-emissions-2/) Category

CO

HC

HC + NOx

NOx

PM

2006

3.5

–

4.0

–

0.2

130 ≤ P ≤ 560

2007

3.5

–

4.0

–

0.2

560 < P

2009

3.5

0.5a

–

6.0a

0.2

130 < P

2012

3.5

0.19

–

2.0

0.025

130 < P

2012

3.5

–

4.0

–

0.025

Net power

Year

Kw

g/kWh

130 < P

RL A RH A RC B RB

Stage IIIA RC A

Stage IIIB

a HC

= 0.4 g/kWh and NOx = 7.4 g/kWh for engines of P > 2000 kW and D > 5 L/cylinder

transport per passenger-kilometer and tonne-kilometer compared to any other modes of transport (Railroad Handbook 2016). To control the emissions, many developed countries have adopted emission regulations for the railroad locomotives. Europe and USA are the leading countries to have promulgated emission standards for diesel locomotives. In Europe, first emission standard was implemented in the year 1997 for non-road mobile machinery (NRMM) in two stages (Stages I and II). However, these stages did not include emission compliance for railway locomotives and covered diesel engines of medium ranges (37–560 kW) only. Stages IIIA and IIIB were applicable for different categories of railcars (RC) and railroad locomotive of different groups (RC-A, RL-A, RH-A). Table 2.1 shows the various stages and species wise reduction applicable for Stage III A/B emission standards. In United States, railroad operations are generally categories as line haul and switching. As the name suggests, line haul locomotives cover the long distances, whereas switching locomotives are used for assembling and dissembling of trains at various locations. Also, these locomotives differ in their duty cycles. Duty cycle is based on different weighting factors for different notches. Their emission limits are also different for both alternatives. The emission regulations adopted by regulatory bodies have become more stringent subsequently over the years. Currently, USA is following Tier 4 emission standards for locomotive engines. It was implemented in the year 2015 for newly manufactured and remanufactured locomotive engines. It limits the NOx emission to 1.3 g/bhp·hour, which was 8 g/bhp·hour in the Tier 0. Similar reduction in HC, CO, and PM emissions was adopted. Table 2.2 shows the different emission norms applicable to line haul and switch locomotives in the USA.

2.1.2 Alternative Fuels for Diesel Locomotives Diesel locomotives offer flexibility with ease of operation; however, they have significant challenges. These challenges include consumption of imported fuels, emissions

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Table 2.2 Tier 0–2 locomotive emission standards, g/bhp·hour (https://dieselnet.com/standards/ us/loco.php) HCa

CO

Line-haul

1.0

Switch

2.1

Line-haul

0.55

Switch

1.2

Line-haul Switch

Duty cycle

NOx

PM

5.0

9.5

0.60

8.0

14.0

0.72

2.2

7.4

0.45

2.5

11.0

0.54

0.3

1.5

5.5

0.20

0.6

2.4

8.1

0.24

Line-haul

0.5

1.5

13.5

0.34

Switch

1.1

2.4

19.8

0.41

Tier-0 (1973–2001)

Tier-1 (2002–2004)

Tier-2 (2005 and later)

Non-regulated locomotives (1997 estimated)

a Standards

is in the form of THC for diesel engines

of harmful pollutants, and negative impact on the environment. Therefore, alternative fuels are required, which can satisfy the energy demand with relatively lower emissions. To identify alternative fuels, there are few criteria to evaluate suitability of new fuels. These include availability of raw feedstock materials, technology acceptance among OEMs, customer satisfaction, favorable economics, emission compliance, and national security. Natural gas, biodiesel, and alcohol based fuels, such as methanol, ethanol, dimethyl ether (DME), are the primary alternative fuel options for locomotives. Natural gas is a clean alternative fuel as it emits lower PM, HC, and NOx emissions. However, natural gas storage is quite challenging, and fuel requirement in case of locomotive engines is very high. This problem can be solved by utilization of natural gas in liquid phase, by compressing it to very high pressure. Ethanol could be an alternative to petroleum fuels for India. Being an agrarian country, India produces a large amount of biowastes, which can be converted to biogas or biodiesel by fermentation. India is also one of the major producers of sugarcane and agricultural waste. It can be utilized as a raw material for ethanol production. Moreover, India possesses an enormous amount of high ash coal, which can be converted to methanol using suitable coal gasification process. Further, it can be converted to DME. Hence, there are various alternative fuels available for diesel locomotives, which can satisfy energy demand with relatively low emissions. Among all possible alternative fuels, methanol has emerged as a good substitute for diesel in locomotives due to vast resource availability for production, lower emissions, adaptability of existing fueling infrastructure for methanol production/supply at low price (Valera and Agarwal 2020). Also, it could reduce the burden of crude oil import and thereby reduce exhaust particulate emissions to the environment.

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2.2 Methanol: Opportunities and Challenges for Railroad Transport Several potential alternative fuels for railroad transportation are discussed in the previous section. Among discussed alternative fuels, methanol is a very strong contender for replacement of conventional fuels due to its several advantages as mentioned below: • Methanol is a single carbon fuel. Its combustion emits lower carbon based pollutants (CO and CO2 ) compared to conventional diesel. • Methanol can be produced from renewable and non-renewable sources such as biomass/municipal solid waste (MSW), natural gas, coal, catalytic hydrogenation of CO2 , etc. • Methanol does not contain sulfur in its molecular structure; thus, it does not emit any sulfur based pollutants (SO2 and SO3 ). • High octane rating of methanol makes it more suitable fuel for SI engines. Various techniques are being explored for its usage in CI engines as well. • Methanol has a relatively higher latent heat of vaporization, which reduces the overall peak combustion temperature, which leads to a reduction in NOx emissions. • Fuel bound oxygen in methanol improves the combustion, leading to higher combustion efficiency with reduced HC and CO emissions. Methanol can fully replace conventional fuels due to its superior physico-chemical properties, as mentioned in Table 2.3. Table 2.3 Comparative properties of methanol and diesel (Liu et al. 2011; Valera and Agarwal 2019)

Property

Methanol Diesel

Formula

CH3 OH

C12 H26 –C14 H30

Molecular weight (kg/kmol)

32

170–198

Lower heating value (MJ/kg)

20.1

42.7

Boiling point, °C

65

180–360

Autoignition temperature, °C

392

315

Stoichiometric air/fuel ratio

6.5

14.6

Cetane number

3–5

40–55

Density, kg/m3

796

840

Octane number

108

30

Kinetic viscosity at 20 °C, mPa s 0.7

3.4

Flash point, °C

11

78

Fraction of oxygen, wt%

50

0

Ignition temperature (°C)

470

235

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D. Kumar et al.

2.2.1 Methanol Production Process and Opportunities Methanol can be produced from biomass/ municipal solid waste, coal, and natural gas. Current production process of methanol has been summarized by Bazzano and Manenti (2016), primarily in three typical steps. First step is the preparation of synthesis gas, also known as syngas. Syngas mainly comprises of CO and H2 . The most common syngas is formed from many sources, as depicted in Fig. 2.3. The second step involves methanol production from syngas obtained in the first step. As methanol is miscible with water, it may absorb some moisture from the atmosphere. It is observed that most of methanol production processes produce crude methanol, which contains a significant amount of moisture and residual gases. Hence, the third and final step is very important for production of high grade methanol, which involves distillation process. Methanol can be produced using alternate power sources like solar, wind, etc. for suitable electrochemical reduction from CO2 (Malik et al. 2017). Also, it can be produced from natural gas either through partial reduction or synthesis using steam reforming process. Moreover, it can be produced directly by partial oxidation of methane and catalytic hydrogenation of CO2 . Technology for methanol production from methane is still immature because of selective stable catalysts. Primary problem with this reaction is oxidation of products such as CH3 OH, HCHO, and HCOOH. These products are more reactive than reactants (here, methane), which leads to formation of CO2 and H2 O. Methanol

Fig. 2.3 Methanol production from various resources

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production from various resources is illustrated in Fig. 2.3. China is one of the largest methanol producers and utilizer worldwide, especially in the transport sector. China accounted for ~55% of global methanol production as per the database shared by the methanol institute, in the year 2015 (Saraswat and Bansal 2017). From total production, ~70% of methanol production comes from coal (Saraswat and Bansal 2017). The Ministry of Industry and Information Technology (MIIT), China has announced a pilot plan via open notice on launch of methanol vehicle pilot project in January 2012, as shown in Table 2.4 (https://www.methanol.org/wp-content/ uploads/2019/03/A-Brief-Review-of-Chinas-Methanol-Vehicle-Pilot-and-Policy20-March-2019.pdf). Initially, Shannxi, Shanghai, and Shanxi were considered as piloting area with the permission of using M85 (85% methanol in conventional fuel on v/v basis) and M100 (pure methanol) fueled vehicles. Later on, two more areas Gansu and Guizhou were declared as piloting area in 2014. During the pilot review, no concentrated technical failures and negative impact on human health were observed. All pilot vehicles were operated smoothly with similar kind of corresponding maintenance as that of conventional gasoline. Emission results in passenger cars revealed that all regulated pollutants were within the limits. Besides, formaldehyde emission was also within the limit because it is a significant concern for researchers and policymakers for large scale methanol utilization. Typical observations of unregulated emission species are explained in Ref. (https://www.methanol.org/wp-content/uploads/2019/03/A-BriefReview-of-Chinas-Methanol-Vehicle-Pilot-and-Policy-20-March-2019.pdf). Apart Table 2.4 China’s pilot plan for methanol usage in transport sector (https://www.methanol.org/ wp-content/uploads/2019/03/A-Brief-Review-of-Chinas-Methanol-Vehicle-Pilot-and-Policy-20March-2019.pdf) S. no

Company

Fuel

Vehicle

Number of vehicles

1

Geely

M100

Taxis

904

2

Zhengzhou Yutong Bus

M100

Buses

100

3

Shaanxi Heavy Auto Enterprise

Methanol/diesel duel fuel

Trucks

5

4

Shaanxi Tongjia Automobile Co., Ltd.

M100

Multifunction automobiles

15

Total

1024

Parameter

Observations

Average running time

2–3 years

Methanol consumption

24,000 metric tons

No. of models operated

32

20

D. Kumar et al.

from this, China is also leading dimethyl ether (DME) production globally. Several countries, like USA, Iran, and South America, are mainly using natural gas for methanol production because of its abundant availability at low prices. Indian policymakers clearly understand the positive impact of methanol production and its utilization on the Chinese economy. Therefore, National Institution for Transforming India (NITI Ayog) has developed methanol economy vision for India. It will result in a minimum 15% fuel bill reduction annually by 2030 (https://niti.gov.in/methanol-eco nomy). In addition, it will also create ~5 million jobs via methanol production and its further applications including distribution services. India has huge reserves of high ash coal, which is underutilized and can be converted to methanol at economically viable rates. Thus, India has vast potential to produce a huge amount of methanol from high ash coal, which can then be used for various applications, including transport sector. However, India does not have any commercial methanol plant for production via coal gasification as of now. Under Indian methanol economy vision, six methanol plants are planned to be setup; out of which five are based on coal gasification and remaining on natural gas conversion in a joint venture with Israel. Methanol can be used for powering ICEs in the transport sector of India. It can be used in SI engines by blending and in CI engines through other advanced fuel induction techniques. Methanol production opens up huge opportunities for India and the world, which are summarized below: • India’s fuel dependence will be resolved through an indigenous methanol production and its utilization in the transport sector. • India can utilize abundant resources of high ash coal for methanol production and become a net exporter of energy. This will boost the economy. • Methanol utilization provides the opportunity to all countries to share their contribution to the global economy. This may end the crucial global politics due to crude oil. • Methanol production plant will create jobs for engineers, operators, and for other professionals. • If solid waste is collected from homes to produce methanol, then people will be able to use this service and earn money from domestic waste. • CO2 capture will create additional jobs for chemists/catalyst manufacturers.

2.2.2 Technological Challenges and Solutions As discussed in the previous section, methanol offers various advantages and could be a potential candidate for replacing fossil fuels. However, implementation of methanol on existing and new engines has several challenges that need to be addressed carefully. This section has discussed about technical challenges associated with methanol applications and their possible solutions. • Methanol has very low viscosity and lubricity, which may lead to leakage from fuel pump gaskets, gland seals, and other packings. This can be resolved using

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polymers like fluoroethylene propylene-perfluoro alkoxy as a chemical resistance to prevent the leakage. • Energy density of the methanol is ~20 MJ/kg, which is approximately half of conventional diesel. Hence, it becomes necessary to have a modified fuel injector and fuel line, which can ensure the required fuel flow rate to deliver optimal power like diesel. • Methanol is corrosive and can corrode fuel injection systems. This problem can be resolved by using anti-corrosive materials and additives. • Methanol has negative impacts on the rubber materials such as on O-rings, leading to swelling and sticks to metallic parts. This can be resolved using value added rubber for the O-rings. Advantages and technological challenges associated with utilization of methanol in locomotives engines have been summarized in Table 2.5. Table 2.5 Summary of technical difficulties and benefits of methanol utilization Parameter

Advantages

Challenges

Miscibility with conventional diesel

Good miscibility up to 10% (v/v) methanol

Poor miscibility with more than 10% (v/v) diesel–methanol blends. It requires an emulsifier agent

Methanol production

Abundant raw material is available such as biomass, coal, natural gas, etc.

Lack of methanol production infrastructure in India

Hazardous level

It is bio-degradable and hence it does not cause negative health impact during degradation

It is poisonous. Its ingestion can cause severe nervous problems and even death upon severe exposure. Lower energy density requires more fuel quantity to be injected for same performance as diesel and gasoline

Injector compatibility

It can be adapted easily to get similar power to diesel fueled engines via upsizing the injector hole diameter

Low lubricity requires development of new injector made of compatible materials

Safety

Higher flammability limit makes it a safer fuel

It is less safe compared to conventional diesel from storage perspective as it has a relatively lower flash point

Handling

Exist in a liquid state at Its skin contact causes atmospheric conditions, which irritation, hence requires safety makes it easy to handle protocols at methanol supply outlets

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D. Kumar et al.

2.3 Methanol Induction in Locomotive Engine As explained earlier, methanol has high octane number (~108), which makes it suitable for SI engines. SI engines are primarily used for light duty applications such as two wheelers, passenger cars, etc., whereas CI engines are used for medium and heavy duty applications. Researchers and automotive industries have keen interest to find an expeditious way to introduce methanol in CI engines due to its wide applicability. Methanol fueled engines emit less soot due to absence of carbon–carbon bond in its molecular structure. Also, it can tackle the soot/NOx trade-off because it has relatively higher latent heat of vaporization, which leads to reduction in NOx emissions. This attribute attracted researcher’s attention to explore different techniques to utilize methanol in CI engines. High octane rating of methanol implies that it has a low cetane number (CN). However, CN of methanol and methanol with 10% water was found as three and two, respectively (Hagen 1977). This CN was calculated using extrapolation during accumulation of some additives in methanol. CN also defines fuel’s auto-ignitability. Thus, lower CN of methanol restricts its direct use in CI engines. Hence, methanol needs some additional fuel or elements, which can be used in conjunction with it. Methanol utilized in conjunction with diesel has the advantage of high ignitibility of diesel. Introduction of methanol in CI engines can be achieved through several techniques such as: (i) blending, (ii) emulsion with diesel, (iii) port injection of methanol and direct injection of pilot diesel, (iv) high pressure direct injection (HPDI) of methanol, (v) glow plug concept, and (vi) use of ignition improvers. HPDI technique can be used in two ways; injection of diesel and methanol by separate injectors, or injection of both fuels using a special co-axial injector. These techniques alter the impact of methanol on overall performance of the CI engines, which are discussed below in detail.

2.3.1 Use of Methanol via Blending Blending is a simple technique to utilize methanol in locomotive engines. In this method, both diesel and methanol are mixed well prior to injection. However, this technique limits the proportion of methanol in blend due to phase separation problem. Illustration to observe phase separation in methanol diesel blend can be done, as shown in Fig. 2.4. Diesel and methanol are immiscible, and immiscibility exists due to mass density difference between them and polarity/non-polarity of both fuels. This technique can only displace diesel by 10% methanol on volume basis. This technique can be used, where methanol availability is limited. A higher percentage of methanol addition with diesel for direct injection can be tested using a computational approach. Since simulation allows experimentations of physical models without performing the experiments on expensive test cells (Valera et al. 2020), where it provides the flexibility to use methanol with maximum proportion in diesel–methanol blends. However, for testing of higher methanol blends with diesel, practical feasibility

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Fig. 2.4 Illustration of phase separation for higher methanol–diesel blends

should also be kept in mind. Additionally, a higher fraction of methanol decreases the energy content of diesel–methanol blend volumetrically. Thus, it may be difficult to maintain rated power output of the engine using existing injectors. Several studies have shown that methanol blended with diesel reduces CO and HC emissions. At the same time, NOx emission increases with increment in methanol percentage, irrespective of engine operating conditions (Huang et al. 2004; Agarwal et al. 2016; Žaglinskis et al. 2016).

2.3.2 Use of Methanol via Emulsions with Diesel Since methanol does not mix well with diesel due to poor miscibility, it can be emulsified with diesel in stabilized form using some external emulsifiers. When two immiscible liquids are blended with the help of some external agent, it is generally referred to as emulsifier/emulsifying agent. The process is called emulsification process and the mixture is called emulsion. The degree of stabilization of diesel– methanol emulsions depends on the quantity of emulsifiers used w.r.t. methanol concentration. Emulsifying agents possess both polar and non-polar candidates in compound chain; thus, creating an envelope around methanol molecules and prepare for a stable diesel–methanol emulsion. This emulsification process can be illustrated for diesel– methanol, as shown in Fig. 2.5. A mixture of oleic acid and isomers of butanol (isobutanol and n-butanol) and dodecanol are used to prepare the stable diesel–methanol emulsion (Huang et al. 2004; Agarwal et al. 2019; Valera 2017). However, addition

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D. Kumar et al.

Fig. 2.5 Diesel–methanol emulsion process

of more emulsifier affects the chemical composition of the emulsion and hence the in-cylinder combustion process (Huang et al. 2004). This technique can reduce emissions of regulated pollutants such as CO, HC, and NOx. However, engine operating conditions and pollutant formation mechanisms may affect the overall emissions. These reductions are attributed to relatively higher H/C ratios, high oxygen content, and higher latent heat of vaporization of methanol. Inherent oxygen constituent enhances the combustion quality, and higher latent heat of vaporization provides cooling effect in the engine cylinder. Methanol can replace precise quantity of diesel, with the help of emulsifying agents.

2.3.3 Port Injection of Methanol with Direct Injection of Diesel In this technique, methanol is injected in the intake port and diesel is inducted directly into the engine combustion chamber. This technique enables preparation of a homogeneous methanol–air mixture during the intake stroke, followed by pilot diesel injection. Pilot diesel injection near the TDC acts as multitude of sparks for the homogeneous mixture. This approach is sometimes also referred to as fumigation concept. In this concept, in-cylinder gas temperature gets reduced due to higher latent heat of vaporization, which leads to longer ignition delay. At low engine load, a combination of low in-cylinder fuel charge temperature, and longer ignition delay results in lower peak in-cylinder pressure. This approach can be a feasible way for methanol induction in large bore locomotive engines, where load level is defined in terms of different notches. Typically, diesel locomotives are equipped with a turbocharged engine having 16 cylinders. Two injectors are required for fuel injection, where diesel

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is injected directly into the combustion chamber at high pressure, and methanol is injected into the port at relatively lower pressure, as shown in Fig. 2.6. In this technique, methanol is known as low reactivity fuel due to lower cetane number, and diesel is known as high reactivity fuel because of higher cetane number. Therefore, combustion phasing can be controlled using different reactivity gradients; therefore, this concept is normally termed as reactivity controlled compression ignition (RCCI) (Li et al. 2013, 2014), which is also referred to as low temperature combustion (LTC). Small amount of pilot diesel injection in premixed combustion mode leads to lower NOx and soot emissions from CI engines (Blasio et al. 2017; Papagiannakis et al. 2010). Introduction of methanol as low reactivity fuel can reduce the NOx and soot emissions because it has inherent oxygen and relatively higher latent heat of vaporization (Li et al. 2016; Wei et al. 2017; Liu et al. 2015). Methanol with low reactivity is injected into the port. Various parameters, such as the start of diesel injection, premixed quantity of methanol, injection duration, and in-cylinder temperature, play vital role in determining the performance and emissions of the engine. Wei et al. (2016) studied the effect of diesel pilot injection and methanol todiesel ratio (RMD ) on different engine parameters. They retarded the injection timing of diesel to 5.5 CAD bTDC and tested different methanol to diesel ratios. From Fig. 2.7, it can be observed that the peak in-cylinder pressure decreased with increasing methanol fraction in the port. It may be possible due to high latent heat of vaporization of methanol, which results in lower in-cylinder temperature and hence, lower in-cylinder pressure. Figure 2.8 shows the effect of varying injection timing of diesel on the engine combustion at constant RMD . The variation was done in the range of 5.5° CA bTDC to 3° CA aTDC. With an increment in ignition timings, mixture becomes more homogeneous, and resulting heat release rate rises to a peak, then progressively goes to lower peak due to increased in-cylinder volume.

Fig. 2.6 Schematic of port injection of methanol with diesel pilot in a locomotive engine

26

D. Kumar et al.

Fig. 2.7 Effect of methanol to diesel ratio (RMD ) on heat release rate and in-cylinder pressure, with port injection of methanol (Liu et al. 2015)

Fig. 2.8 Effect of diesel injection timing on heat release rate and in-cylinder pressure, when methanol is injected in the intake port (Liu et al. 2015)

2.3.4 High Pressure Direct Injection (HPDI) of Methanol with Pilot Diesel Contrary to previously described technique, methanol can be injected directly into the combustion chamber. The advantages include utilization of methanol operated diesel engines, which can be suitable for heavy and medium duty applications. Previous

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27

techniques are premixed way for methanol utilization, but this technique is more like non-premixed mixture. Here, it is necessary to ensure injection of high cetane fuel like diesel near TDC. Pilot diesel will act as an expeditious spark to ignite the non-premixed methanol–air mixture. This can be achieved in two different ways as explained in the next sub-section.

2.3.4.1

HPDI Using Two Separate Injectors

In this technique, direct injection is achieved using two separate injectors. One is for injection of main fuel; methanol, while the other is for pilot injection of diesel. Typical schematic of HPDI operated methanol fueled engine using two separate injectors is shown in Fig. 2.9. It will be best suited with the use of electronic fuel injection system; however, most of the older diesel locomotives were equipped with a mechanical injector. Presently, electronic fuel injection system is used for large bore engines due to its ability to optimize different injection parameters at different engine loads and speeds. Optimization of parameters is required to meet stricter emission norms. Major challenge associated with this technique is that it uses two fuel injectors, which demand additional space on the cylinder head. It adds extra cost as well. However, this technique also gives flexibility to change the injection direction and timing, which ensures superior mixing of methanol with pilot diesel, hence superior combustion chemistry. Constant volume combustion chamber (CVCC) study performed by Wang et al. (2019) provided some experimental and theoretical insights on methanol and diesel spray interactions. They suggested that direct injection of methanol with pilot diesel injection has potential to achieve diesel like combustion efficiencies along with low emission. The advantages include variations in fuel quantity and timing, as per requirements.

Fig. 2.9 Schematic of HPDI technique using two separate injectors for locomotive engine

28

2.3.4.2

D. Kumar et al.

HPDI Using a Special Co-axial Injector

The major problem in the previous technique was additional space requirement on the compact cylinder head for adaptation of two injectors and additional costs. This problem can be overcome by using a new type of injector called “co-axial injector”. The co-axial injector gives the flexibility to use two different fuels using a single injector housing. It overcomes the problem of additional space requirement in the cylinder head. It uses two fuel lines, which carry different fuel at a time and allow some overlap period in the two fuel injections, if required. The nozzles are arranged at the periphery of the tip. This innovative concept of methanol utilization needs further development for implementation in locomotive engine. This kind of system has already been developed and demonstrated by Wartsila (https://www.classnk.or.jp/classnk-rd/assets/pdf/V_Wartsila_Gas_Engine_Dev elopment_Methanol_Adaptation.pdf). For ensuring diesel like power output, the diameter of nozzles for methanol injection should be larger. Methanol volumetric heat content is lower; hence it requires more methanol quantity injection compared to a diesel powered engine. The co-axial injector concept makes use of various alternative fuels in heavy duty engines. Typical schematic of methanol fueled locomotive engine equipped with co-axial injector is shown in Fig. 2.10.

Fig. 2.10 Schematic of HPDI technique using co-axial injector for locomotive engine (https:// www.classnk.or.jp/classnk-rd/assets/pdf/V_Wartsila_Gas_Engine_Development_Methanol_Ada ptation.pdf)

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2.3.5 Ignition Improvers and Glow Plug Concept Another technique that can be envisaged for methanol adaptation in locomotive engines is the utilization of ignition improvers. They are used to improve the cetane number of methanol. Ignition improvers are also referred to as cetane improvers. They consist of additives, which lower the ignitibility and their exothermic decomposition reduces the ignition delay and autoignition temperature of the mixture. Thus, ignition improvers allow methanol utilization in CI engines with minor hardware modifications. One recent study investigated the use of 95% ethanol in Scania ED95 engine with a 5% ignition improver (Landälv 2017). Ethanol has a cetane number in the range of 5–15, which is slightly more than methanol (https://dieselnet.com/tech/ fuel_ediesel.php). The engine was modified to increase the compression ratio to 28:1. Hence, temperature at the end of compression increases, which helps in ignition of low cetane fuels. Similar modifications may be required for methanol utilization in CI engines. Some examples of additives are dimethyl ether, alkyl nitrate, etc. Akzo Nobel suggested the use of a methanol soluble alkylene oxide adducts of glycerol additive as an ignition improver. It can be the most appropriate additive for methanol utilization in CI engines (Lif 2015). They also used some amount of lubricants, such as ester, fatty acid, etc. Many other compounds have been anticipated as cetane improvers for methanol and other primary alcohols. Therefore, ignition improvers provide an abundance of flexibility in injecting methanol in CI engines, similar to diesel. Glow plug concept is mainly derived to address methanol vulnerability toward ignition during cold weather conditions. Methanol suffers from poor ignition characteristics and slower flame speeds due to low atmospheric temperatures. Glow plug comprises a heating element that helps the mixture to start combustion. Enhanced engine performance has been observed with the use of glow plug concept. Overall, this section discussed various injection techniques that could be used for methanol adaptation in diesel locomotive engines. The advantages and shortcomings of all these techniques are discussed as well. It can be concluded from the above mentioned literature that in order to obtain diesel like performance for large bore engines, direct injection of methanol with pilot injection of diesel, and HPDI techniques would be preferred. Hence, we would further look at few other aspects of these two techniques with relevant case studies in the next section.

2.4 Case Studies on Methanol Utilization in Engines 2.4.1 Port Injection of Methanol with Pilot Injection of Diesel Cheng et al. (2008) carried out exhaustive experiments to assess the capabilities of port injection of methanol with pilot injection of diesel on naturally aspirated, four cylinder, water-cooled, 4.3 L diesel engine. This CI engine was modified for port injection of methanol using electronically controlled fuel injectors. In this study,

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three different methanol–diesel combinations were used: (i) Methanol injected such that it takes up 10% engine load, whereas diesel takes up 90% engine load; (ii) Methanol takes up 20% engine load, whereas diesel takes up 80% engine load; and (iii) Methanol takes up 30% engine load, whereas diesel takes up 70% engine load. Methanol was injected in the port at 0.3 MPa fuel injection pressure. Analysis of emissions data from this study was important as it revealed the important capabilities of this technique. Data were measured at five steady state engine load conditions (26, 65, 130, 195, and 230 Nm) at a constant engine speed of 1800 rpm. At the engine tailpipe, mass concentrations of emission were measured for 5 min each. Measurement of pollutant species such as CO2 , CO, NOx , and HC emissions are shown in Fig. 2.11. Experimental results presented in Fig. 2.11 (a) revealed that diesel–methanol combination emitted higher CO2 emissions at low load conditions, whereas similar or even slightly lower emissions at higher load compared to mineral diesel. Emission trends varied w.r.t. engine load because it is affected by fuel mass Fig. 2.11 Comparison of various emission species for diesel and diesel–methanol fueled engine (Cheng et al. 2008)

(a) CO emissions variation with loading conditions correspond to BMEP

(b) NOx emissions variation with loading conditions correspond to BMEP

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Fig. 2.11 (continued)

(c) HC emissions variation with loading conditions corresponds to BMEP

(d) CO emission variation with loading conditions corresponds to BMEP

consumption of diesel and methanol. At high load, improved combustion reduced the fuel consumption. Hence, lower CO2 emissions were observed. Figure 2.11 (b) showed that CI engine emitted high NOx emissions w.r.t. load, regardless of the fuel used. In comparison with diesel, diesel–methanol combination emitted 6%, 9%, and 11% lower NOx, respectively, for 10%, 20%, and 30% loading conditions took up by the methanol. There are mainly three mechanisms, which affect NOx emissions during methanol utilization in CI engine: (i) Inherent oxygen content in methanol expedites the combustion and increases the NOx emissions, (ii) higher latent heat of vaporization of methanol helps in reduction of NOx emissions since it absorbs the heat from the combustion chamber and reduces the in-cylinder temperature, which is the main driving factor for NOx emissions, and (iii) it reduces overall ignition delay, which increases the amount of fuel burned in premixed mode, thus increasing the peak combustion temperature and hence NOx emissions. These three factors compete with each other and increased or decreased the overall NOx emissions. In

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this study, it is clear that the first two factors dominated and resulted in overall NOx reduction. Figure 2.11 (c) shows HC emissions, which increase as methanol amount was increased to sustain additional engine load. HC was given in ppm and calibrated with propane. HC concentration was higher and lower at low load and high load conditions, respectively. The highest and lowest HC concentrations were ~7 and 3 times, when methanol was injected such that it took up 30% engine load and diesel took up 70% engine load vis-à-vis baseline diesel. Higher HC emissions may be due to three factors: (i) Trapping of methanol in crevices, (ii) unburnt methanol due to low combustion temperature, and (iii) incomplete combustion of lean homogeneous methanol–air mixtures. Figure 2.11 (d) shows CO emission measured at the tailpipe for all test fuels. Higher concentration of CO was observed for all diesel–methanol combinations compared to mineral diesel. The possible reason may be incomplete combustion at insufficient combustion temperature and locally rich combustion. In this technique, methanol burns as a homogeneous mixture. The extra cooling effect of methanol due to relatively higher latent heat of vaporization leads to emission of more CO from the engine.

2.4.2 High Pressure Direct Injection of Methanol Wartsila developed a special co-axial injector and used it for conversion of a sea going ferry “Stena Germanica” (https://www.classnk.or.jp/classnk-rd/ass ets/pdf/V_Wartsila_Gas_Engine_Development_Methanol_Adaptation.pdf). In this strategy, methanol was injected close to TDC and was ignited by pilot injection of small amount of diesel. In this diesel–methanol concept, injection pressure plays a vital role. Methanol and diesel injection pressure were kept at 600 bar and 1300 bar, respectively. Some important observations from co-axial injector study were: • • • • • •

No knocking No power reduction or engine derating Cost effective adaptation Low THC, CO, and formaldehyde emissions High NOx emissions, where NOx depends on pilot fuel quantity Good backup fuel performance

It is obvious that co-axial injector concept is useful for CO and THC reduction. There are three important factors responsible for the observed results: 1.

2.

Injected diesel quantity was small, and methanol quantity was quite high. It means the fuel injected in the combustion chamber has lesser hydrocarbons compared to conventional diesel fueled engine. Burning of less hydrocarbons in the combustion chamber lead to reduced emission of CO and HC. Methanol quantity was high, and it had inherent oxygen in its molecular structure. This extra oxygen led to complete combustion and reduced CO emission by converting CO to CO2 (Valera and Agarwal 2019).

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Fig. 2.12 Complicated cylinder head design for assessment of HPDI technique using two separate injectors (Dong et al. 2020)

3.

High latent heat of vaporization provided additional cooling effect and reduced the peak combustion temperature. This reduction in combustion temperature results in lower NOx emissions. In this study, methanol was injected at 600 bar in the hot in-cylinder environment. However, improved combustion efficiency might have increased the in-cylinder temperature, which resulted in high NOx emissions.

Dong et al. (2020) investigated the feasibility of HPDI technique using two separate injectors. They used specially designed cylinder head to incorporate two separate injectors, as shown in Fig. 2.12. Engine experiments were conducted for various indicated mean effective pressure (IMEP) conditions of 4.2–13.8 bar at engine speed of 1500 rpm. In this investigation, methanol substitution ratio was kept between 45– 95%. It emerged that combustion with HPDI technique has three heat release phases: (i) Ignition of pilot injected diesel and its combustion, (ii) diffusion flame development of pilot injected diesel, which merged with ignition and early stage methanol combustion, (iii) diffusion flame development of methanol, which has low intensity and high intensity heat release stages. This technique is preferred for medium load conditions due to lower HC emissions and stable combustion. Also, NOx emission decreased and mildly increased with increasing IMEP. HPDI technique uses a co-axial injector over two separate injectors due to reasons as mentioned below: 1.

2.

In order to use two separate injectors, the design of existing cylinder head has to be changed for adaptation of the two injectors. This modification is complicated and required extensive research for transport applications. Two separate injectors can be controlled using two separate ECUs or a single ECU. However, it is quite difficult to manage the response time of the two

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separate injectors as per rapidly changing on road conditions. Hence, this technique can be relatively easy tested in the laboratories but difficult for vehicular applications. Utilization of two injectors for this technique is certainly not an economical option. Utilization of two injectors is also not economical because their fitment in compact cylinder head requires highly skilled labors. This may lead to expensive post sales service and maintenance compared to a co-axial injector. Two injectors usage can significantly affect emissions and performance of the engine. In this condition, atomization of diesel and methanol by controlling fuel injection pressures is quite difficult for an on road operation.

HPDI technique using two separate injectors are under development. Many researchers and OEMs are working for adaptation of methanol using this technique. Based on this discussion, Table 2.6 compares the diesel and methanol for its suitability for locomotive engines. Table 2.6 Summary of different techniques for methanol adaption in locomotive engines Methanol induction techniques

Status

Using methanol via blending

Using methanol via emulsion with diesel

Ignition improvers and glow plug concept

Port injection of methanol with direct injection of diesel

HPDI technique using two separate injectors

HPDI technique using co-axial injector

Status Excellent

Good

Poor

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2.5 Concluding Remarks This chapter primarily discusses different potential alternative fuels for diesel locomotive engines. Among available alternative fuels, methanol and DME are having excellent potential. Different production aspects of methanol are also reviewed in this chapter. Potential feedstock raw material for methanol production available in India are discussed. Global status of methanol utilization has been emphasized. China is leading the world in methanol production and its utilization in different sectors of economy, including transport sector. Methanol adaption in transport engines needs few hardware modifications; however, a small replacement of conventional fuels by methanol is possible in SI engines. Furthermore, potential routes for methanol application in compression ignition engines has been reviewed comprehensively. Methanol is corrosive in nature and it is challenging to design hardware, especially in terms of material compatibility. Other technical challenges and their probable solutions are also discussed comprehensively. Injection of methanol in compression ignition engines in conjunction with diesel by preparing emulsion with the help of an emulsifying agent, port fuel injection with pilot diesel, high pressure direct injection of methanol and pilot diesel injection using two separate injectors as well as one co-axial injector have been discussed comprehensively. These techniques have been reviewed in detail in this chapter. It is finally concluded that for locomotive engines, two injections of methanol and diesel were found to be most appropriate technology. These two injection techniques include (i) port fuel injection of methanol with pilot injection of diesel and (ii) high pressure direct injection of diesel and methanol using two separate injectors or one co-axial injector. In both the techniques, pilot injected diesel is used as an ignition source. High pressure direct injection technique using two separate fuel injectors offers design and space challenges. Instead, use of a coaxial injector could be the best technology route for introduction of methanol in diesel locomotives.

References A brief review of China’s methanol vehicle pilot and policy. https://www.methanol.org/wp-content/ uploads/2019/03/A-Brief-Review-of-Chinas-Methanol-Vehicle-Pilot-and-Policy-20-March2019.pdf Agarwal AK, Shukla PC, Patel C, Gupta JG, Sharma N, Prasad RK, Agarwal RA (2016) Unregulated emissions and health risk potential from biodiesel (KB5, KB20) and methanol blend (M5) fuelled transportation diesel engines. Renew Energy 98:283–291 Agarwal AK, Singh AP, Maurya RK (2017) Evolution, challenges and path forward for low temperature combustion engines. Prog Energy Combust Sci 61:1–56 Agarwal AK, Sharma N, Singh AP, Kumar V, Satsangi DP, Patel C (2019) Adaptation of methanol–dodecanol–diesel blend in Diesel Genset engine. ASME J Energy Resour Technol 141(10):102203. https://doi.org/10.1115/1.4043390 Bozzano G, Manenti F (2016) Efficient methanol synthesis: perspectives, technologies and optimization strategies. Prog Energy Combust Sci 56:71–105

36

D. Kumar et al.

Cheng CH, Cheung CS, Chan TL, Lee SC, Yao CD (2008) Experimental investigation on the performance, gaseous and particulate emissions of a methanol fumigated diesel engine. Sci Total Environ 389(1):115–124 Di Blasio G, Belgiorno G, Beatrice C (2017) Effects on performances, emissions and particle size distributions of a dual fuel (methane-diesel) light-duty engine varying the compression ratio. Appl Energy 204:726–740 Diesel Net. https://dieselnet.com/tech/fuel_ediesel.php Dimitriou P, Tsujimura T (2017) A review of hydrogen as a compression ignition engine fuel. Int J Hydrogen Energy 42(38):24470–24486 Dong Y, Kaario O, Hassan G, Ranta O, Larmi M, Johansson B (2020) High-pressure direct injection of methanol and pilot diesel: a non-premixed dual-fuel engine concept. Fuel 277:117932 Emission Standards. https://dieselnet.com/standards/us/loco.php EU: Locomotive Emission Standards. https://www.transportpolicy.net/standard/eu-locomotivesemissions-2/ Hagen DL (1977) Methanol as a fuel: a review with bibliography. SAE paper no. 770792 Huang ZH, Lu HB, Jiang DM, Zeng K, Liu B, Zhang JQ, Wang XB (2004) Engine performance and emissions of a compression ignition engine operating on the diesel-methanol blends. Proc Inst Mech Eng Part D: J Autom Eng 218(4):435–447 Interim Report-Exhaust Emission Benchmarks for Diesel Locomotives on Indian Railroads. https:// 164.100.107.13/Draft_Interim_Rly_Diesel_Emission_Stds_01.05.2017.pdf Khan MI, Yasmin T, Shakoor A (2015) Technical overview of compressed natural gas (CNG) as a transportation fuel. Renew Sustain Energy Rev 51:785–797 Kumar D, Agarwal AK (2020) Laser ignition technology for gaseous fuelled automotive engines. Simulations and optical diagnostics for internal combustion engines. Springer, Singapore, pp 143–163 Landälv I (2017) Methanol as a renewable fuel–a knowledge synthesis. The Swedish Knowledge Centre for Renewable Transportation Fuels, Sweden Li Y, Jia M, Liu Y, Xie M (2013) Numerical study on the combustion and emission characteristics of a methanol/diesel reactivity controlled compression ignition (RCCI) engine. Appl Energy 106:184–197 Li Y, Jia M, Chang Y, Liu Y, Xie M, Wang T, Zhou L (2014) Parametric study and optimization of a RCCI (reactivity controlled compression ignition) engine fueled with methanol and diesel. Energy 65:319–332 Li G, Zhang C, Li Y (2016) Effects of diesel injection parameters on the rapid combustion and emissions of an HD common-rail diesel engine fueled with diesel-methanol dual-fuel. Appl Therm Eng 108:1214–1225 Li M, Wu H, Zhang T, Shen B, Zhang Q, Li Z (2020) A comprehensive review of pilot ignited high pressure direct injection natural gas engines: factors affecting combustion, emissions and performance. Renew Sustain Energy Rev 119:109653 Lif A (2015) A methanol-based diesel fuel and the use of an ignition improver, pp 2–4 Lif A, Svennberg S, Akzo Nobel NV (1997) Ethanol fuel and the use of an ignition improver. United States Patent US 5(628):805 Liu Y, Jiao W, Qi G (2011) Preparation and properties of methanol–diesel oil emulsified fuel under high-gravity environment. Renew Energy 36(5):1463–1468 Liu J, Yao A, Yao C (2015) Effects of diesel injection pressure on the performance and emissions of a HD common-rail diesel engine fueled with diesel/methanol dual fuel. Fuel 140:192–200 Malik K, Singh S, Basu S, Verma A (2017) Electrochemical reduction of CO2 for synthesis of green fuel. Wiley Interdiscip Rev Energy Environ 6(4):e244 Methanol Economy. https://niti.gov.in/methanol-economy Papagiannakis RG, Rakopoulos CD, Hountalas DT, Rakopoulos DC (2010) Emission characteristics of high speed, dual fuel, compression ignition engine operating in a wide range of natural gas/diesel fuel proportions. Fuel 89(7):1397–1406

2 Technology Options for Methanol Utilization in Large Bore ...

37

Park SH, Lee CS (2014) Applicability of dimethyl ether (DME) in a compression ignition engine as an alternative fuel. Energy Convers Manage 86:848–863 Railroad Handbook (2016). https://uic.org/IMG/pdf/iea-uic_Railroad_handbook_2016.pdf Railroad Handbook (2017). https://www.iea.org/reports/Railroad-handbook-2017 Reitz RD, Duraisamy G (2015) Review of high efficiency and clean reactivity controlled compression ignition (RCCI) combustion in internal combustion engines. Prog Energy Combust Sci 46:12–71 Saraswat VK, Bansal R (2017) India’s leapfrog to methanol economy Shim E, Park H, Bae C (2020) Comparisons of advanced combustion technologies (HCCI, PCCI, and dual-fuel PCCI) on engine performance and emission characteristics in a heavy-duty diesel engine. Fuel 262:116436 Valera H (2017) An experimental study on the physio-chemical properties, performance parameter in a CI engine fuelled with methanol blended diesel (MBD). M.Tech Thesis Valera H, Agarwal AK (2019) Methanol as an alternative fuel for diesel engines. In: Methanol and the alternate fuel economy. Springer, Singapore, pp 9–33 Valera H, Agarwal AK (2020) Future automotive powertrains for india: methanol versus electric vehicles. Alternative fuels and their utilization strategies in internal combustion engines. Springer, Singapore, pp 89–123 Valera H, Kumar D, Singh AP, Agarwal AK (2020) Modelling aspects for adaptation of alternative fuels in IC engines. In: Simulations and optical diagnostics for internal combustion engines. Springer, Singapore, pp 9–26 Verhelst S, Turner JW, Sileghem L, Vancoillie J (2019) Methanol as a fuel for internal combustion engines. Prog Energy Combust Sci 70:43–88 Wang Y, Wang H, Meng X, Tian J, Wang Y, Long W, Li S (2019) Combustion characteristics of high pressure direct-injected methanol ignited by diesel in a constant volume combustion chamber. Fuel 254:115598 Wartsila Gas Engine Development & Methanol Adaptation, Classnk Seminar, Singapore 3.11.2015. https://www.classnk.or.jp/classnk-rd/assets/pdf/V_Wartsila_Gas_Engine_Dev elopment_Methanol_Adaptation.pdf Wei L, Yao C, Han G, Pan W (2016) Effects of methanol to diesel ratio and diesel injection timing on combustion, performance and emissions of a methanol port premixed diesel engine. Energy 95:223–232 Wei H, Yao C, Pan W, Han G, Dou Z, Wu T, Liu M, Wang B, Gao J, Chen C, Shi J (2017) Experimental investigations of the effects of pilot injection on combustion and gaseous emission characteristics of diesel/methanol dual fuel engine. Fuel 188:427–441 Žaglinskis J, Lukács K, Bereczky Á (2016) Comparison of properties of a compression ignition engine operating on diesel–biodiesel blend with methanol additive. Fuel 170:245–253

Chapter 3

Application of Methanol as Clean and Efficient Alternative Fuel to Engines with Compression Ignition Chunde Yao, Anren Yao, Bin Wang, and Taoyang Wu

Abstract Methanol is difficult to be ignited by compression due to its low cetane number. The strategy of diesel–methanol compound combustion (DMCC) was proposed, which starts up with pure diesel fuel and switches to the mode of diesel– methanol dual fuel after the engine fully warms up. The strategy of DMCC will substitute methanol to diesel fuel up to 40% for new engine and 30% for retrofitting engine when it is applied to heavy-duty vehicle and constructive machine as well as marine power unit. The engines equipped with DMCC system are able to reduce NOx without assistance of selective catalyst reduction (SCR) urea system, as well as PM emission at the same time, which can meet the requirements of China V emission legislation and have the potential to meet the demand of China VI in future. The chapter introduces the strategy of DMCC, the main components dealing with methanol while applied to those engines mentioned above, and real examples on different power units. Additionally, the characteristics of diesel–methanol dual fuel (DMDF) combustion mode, emission control strategy, and system related to catalyst, retrofitting, and modifying engine from pure diesel to running DMCC mode are also illustrated. Again, it provides with the research results about the characteristics of DMDF combustion mode to assist the readers to understand the dual fuel combustion in depth as well as the examples applied to various power units, such as heavy-duty trucks, constructive machine, marine propeller, and locomotive engines.

3.1 Introduction The use of methanol as an alternative fuel for internal combustion engines has an important role in alleviating the energy and environmental crisis because of the wide production sources and clean combustion of methanol. At present, methanol has been C. Yao (B) · B. Wang · T. Wu State Key Laboratory of Engines (SKLE), Tianjin University, Tianjin, China e-mail: [email protected] A. Yao School of Environmental Science and Technology, Tianjin University, Tianjin, China © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 A. K. Agarwal et al. (eds.), Methanol, Energy, Environment, and Sustainability, https://doi.org/10.1007/978-981-16-1280-0_3

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widely used on ignition engines by blending with gasoline, thanks to the good mutual solubility characteristics with gasoline. However, there are some difficulties in the direct application of methanol in diesel engines because of its low cetane number. The main application methods of methanol in compression ignition engines are as follows: (1) Direct blending of methanol and diesel (Huang 2005); (2) emulsification of methanol (Bayraktar 2008); (3) heating with glow plugs (Suresh et al. 2010); and (4) fumigation (Cheng et al. 2008b). Due to the very low solubility of methanol in diesel fuel, the proportion of methanol in the direct blending method is very low (generally no more than 10%) (Yao 2017). The methanol proportion of the emulsification method can be increased to 10–30% (Zhen 2015). Nevertheless, the above two methods still cannot meet the requirements of large-scale application of methanol on diesel engines. The glow plug heating route is helpful to solve the cold start problem of the methanol engine. However, it still has the defects of difficult combustion control and complicated structure. Yao et al. from Tianjin University in China developed a methanol fumigation method called diesel–methanol compound combustion (DMCC) (Yao et al. 2008). The DMCC strategy composes the two combustion stages: one is that the engine uses pure diesel fuel to start up at cold, and another one is to run diesel–methanol dual fuel (DMDF) after it fully warms up. Methanol under low pressure is injected into manifold and mixed with intake air to form mixture into cylinder; thereafter, it burns with diesel fuel together when the DMDF mode runs. The DMCC strategy solves the problem of methanol difficult to be ignited by compression, especially at cold start, and can flexibly adjust the proportion of methanol in fuel according to the operating conditions. It just needs minor modification to the diesel engine, hence the DMCC strategy is one of the most feasible routes for methanol to be used for compression ignition (CI) engines. Currently, the DMCC system has been applied to heavy trucks as well as many power units, even including fishing boat and locomotives in China. The working principle, combustion characteristics, emission performances, and emission control system of DMCC will be introduced in detail in this chapter.

3.2 DMCC Strategy 3.2.1 Conventional Method of Methanol Applied to Compression Ignition Engine The CI engine has the highest thermal efficiency of any practical internal or external combustion engine due to its high expansion ratio and inherent lean burn. But the combustion of compression engine also brings along a row of well-known disadvantages. They have the higher emissions of nitrogen oxide (NOx) and soot pollutants, both of them been identified as significant health hazard. Methanol does not produce

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smoke, soot, and particulates during combustion process. The fact that methanol produces very low emissions of NOx because it burns at lower temperatures makes methanol attractive as a substitute for diesel fuel (Reed and Lerner 1973). However, methanol’s cetane rating is only about 3, while diesel fuel has a cetane ratings that range from 40 to 55. To overcome the low cetane rating of methanol, diesel motors must be adapted, such as higher compression ratio or ignition through spark plugs (Çelik et al. 2011). Additives can be included to increase the cetane rating of methanol to levels close to diesel fuels (Schaefer and Hardenberg 1981). With methanol and diesel fuels being substantially immiscible, the possibility of using any blends of methanol and diesel fuel in diesel vehicles is difficult. Thus, it is difficult to apply methanol to compression engine. Conventional methods of methanol applied to compression ignition engine include blending, direct injection, and fumigation. Blending method requires emulsifier to achieve fully miscible of diesel and methanol fuel. At present, it is difficult prevent diesel and methanol from stratifying for a long time. For direct injection method, methanol is hard to be fully ignited, which is due to lacking sufficient heat and time to fully atomization. Currently, fumigation method is widely used in dual fuel combustion mode. This method combined with combustion control could achieve high efficient and clean combustion of methanol on compression ignition engines, and this method is easier to implement. DMCC technology is a kind of fumigation method.

3.2.2 DMCC-Diesel Methanol Compound Combustion Mode 3.2.2.1

DMCC Strategy

DMCC strategy is first proposed by Chunde Yao, who is a Professor of Tianjin University, China (Cheng et al. 2008a). This strategy solves many problems of methanol used in compression ignition engines. These problems are difficult to start, difficult to ignite, difficult to evaporate, and the corrosiveness of methanol. Using DMCC, methanol under low pressure will be injected into the intake port of each cylinder to form a homogeneous mixture with air for combustion, while the original diesel fuel injection system will be retained but slightly modified to limit the diesel fuel injection. At engine start and low speed, the engine will operate on diesel alone to ensure cold starting capability and to avoid aldehydes production under these conditions. At medium to high loads, the engine will operate on a homogeneous air/methanol mixture ignited by pilot diesel, i.e., diesel/methanol dual fuel (DMDF) mode, to reduce particulate and NOx emissions. The system thus developed can also be retrofitted on the diesel engines in-use. The working principle of DMCC technology is shown in Fig. 3.1.

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Fig. 3.1 Working principle of DMCC technology

3.2.2.2

DMCC Application Status

The DMDF truck is widely used in China, and a lot of Chinese manufacturing companies have launched the DMDF truck products, such as Sinotruk, Shacman (Liu et al. 2015a). The Chinese government has promoted methanol fuels since fuel was higher than 30%, while the rate of methanol to replace diesel fuel in volume was much less than that of the value in terms of calorific value (2.26). The exhaust emissions from these trucks could meet the demand of China National V legislation (equivalent to Euro V) with urea-free, and formaldehyde emissions meet the MIIT requirement of 25 mg/kWh (Wei et al. 2017a). Recently, after more than three years of operation in Yulin, MIIT began the acceptance review of that project. The review included an on-site inspection and a panel review in Beijing which gave other government ministries such as the Ministry of Transportation (MOT), Ministry of Science and Technology (MOST), and National Development and Reform Commission (NDRC) the opportunity to weigh in on the findings. On March 2019, MIIT and other relevant ministries and commissions issued documents to promote methanol fuel applied to most provinces of China. On September 2019, MIIT decided to modify “Double Integral Management Method”, and methanol vehicles will be included in the category of “Double Integral Management Method”. These documents provide a guarantee for the industrialization of methanol vehicles and will promote the rapid development of methanol vehicles.

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3.2.3 Emissions from DMCC Engine Regular Emissions Figure 3.2a shows the effect of the ratio of methanol substituted for diesel (MSP) on nitrogen oxide (NOx) and soot emissions of diesel and DMDF mode at high load conditions. Under the DMDF mode, the trade-off relationship between NOx and soot emissions was broken. NOx and soot emissions were reduced with MSP increasing. It was found that as the MSP increased from 0 to 72%, NOx emissions were decreased from 3.02 to 1.98 g/kWh, and soot emissions were decreased from 0.08 to 0.004 g/kWh. Soot emission at MSP72 case was lower than the limit of Euro VI regulation. The DMDF mode could simultaneously reduce NOx and soot emissions, and the reason is as follows: the high gasification latent heat of methanol could reduce cylinder temperature during intake and compression strokes, thereby the cylinder temperature during combustion process was reduced. At high MSP conditions, the proportion of diesel diffusion combustion is reduced, which is conducive to reducing 3.2

0.10 NOx emission

2.8

0.08

Soot emission

0.06 2.4 0.04 2.0

0.02 0.00

1.6 MSP0

MSP20

MSP40

MSP60

MSP72

(a) NOx and Soot emissions 6 2090r/min 440N.m

10

4

5

2

0

0 MSP0

MSP20

MSP40

MSP60

(b) CO and THC emission

MSP72

THC emission(g/kW.h)

CO emission THC emission

Soot emission (g/kW.h)

NOx emission (g/kW.h)

2090r/min 440N.m

CO emission (g/kW.h)

Fig. 3.2 Comparison of regular emissions between diesel and DMDF mode at high load condition. a NOx and Soot emissions. b CO and THC emission

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NOx emissions. For soot emissions, the high oxygen content of methanol could reduce oxygen consumption during the combustion process, so the overall equivalent ratio in the cylinder is reduced, which could reduce soot emissions. On the other hand, low temperature heat release of diesel was suppressed by methanol, which will prolong the ignition delay of diesel fuel. This will reduce the proportion of diesel diffusion combustion, thereby reducing soot emissions (Wang et al. 2018). Figure 3.2b shows the effect of MSP on the total unburned hydrocarbon (THC) and carbon monoxide (CO) emissions of diesel and DMDF mode at high load conditions. It was found that with the increase of MSP, THC and CO emissions were greatly increased. There are several reasons that cause the THC and CO emissions of DMDF mode to be much higher than that of pure diesel mode. First, the cooling effect of methanol and the lean homogenous methanol–air mixture might cause poor combustion quality, tending to form more unburned THC and CO emissions. Secondly, due to the scavenging process, some of the methanol–air premixed mixture escapes from cylinder without burning during the valve overlap. Thirdly, during the combustion process, flame quenching at the chamber wall and crevice effect lead to the increase of THC and CO emissions (Liu et al. 2015b). Figure 3.3 shows the effect of EGR ratios and MSP on NOx and soot emissions at mid-load conditions. As shown in Fig. 3.3, the effect of EGR ratios on NOx and soot emissions for this result is very similar to most of diesel engine research results. EGR is one of the most effective ways to reduce NOx emissions toward a common view. However, there is a clear trade-off relationship between NOx and soot emission. For diesel mode, the NOx emission decreases by 78.59%, but soot increased by 26.43 times, when the EGR ratio increases from 0 to 22%. Normally, high specific heat capacity of EGR gas and the decrease of oxygen will reduce combustion temperature, which can reduce NOx emissions. Meanwhile, the decrease of oxygen will increase soot emission. However, the increase of soot emission for our result is higher than the result of the other studies that conducted the experiments on common rail engines. 12 1660r/min 220N·m -4 °CA ATDC

NOx emission (g/kW·h)

Fig. 3.3 Effect of EGR ratios and MSP on NOx and soot emissions at mid-load conditions

0% EGR 10% EGR 16% EGR 22% EGR

10 8 6

MSP increased

4 2

MSP 65

0.01

MSP 60

MSP 40

0.1

soot emission (g/kW·h)

MSP 20

MSP 0

0.5

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45

Because the injection pressure of unit pump engine is obviously lower than common rail engines, the concentration of local mixed gases here is a rich mixture. Thus, the sensitivity to oxygen concentration change here is more sensitive than lean mixture, and soot emissions increase in a larger scale. The problem of soot emission significantly increasing with high EGR ratio can be solved by high MSP under DMDF mode. Compared to MSP0 case, the soot emission of MSP65 decreases by 95.29%, which is 0.018 g/kWh. The result is like the soot emission of MSP0 is 0.014 g/kWh under 0% EGR ratio case. These results are lower than the limitation of Euro V. Meanwhile, NOx emissions also decrease with the increase of MSP, which is decreased from 2.33 to 1.607 g/kWh. Therefore, DMDF combustion mode can properly solve the problem of high soot emission of diesel engine under high EGR ratio condition. On the other hand, high MSP can reduce NOx emissions so as to achieve simultaneous reduction of NOx and soot emissions (Wang et al. 2019a). Figure 3.4 shows the effect of MSP on NOx and soot emissions at low load conditions. At low load conditions, NOx emissions were decreased with the increasing of MSP. However, soot emissions were increased first and then decreased as MSP increasing. Soot emissions were determined by production and oxidation process. When the MSP was low, methanol substitution will reduce cylinder temperature, and soot oxidation process was suppressed, thereby soot emissions were increased. With MSP increasing, the resulting of soot produce reduction exceeds the soot oxidation reduction, which results in a reduction in soot emissions. Unregulated Emissions For DMDF engine, unregulated emissions mainly include methanol, formaldehyde, formic acid, 1,3-butadiene, which is higher than diesel mode. Unregulated emissions of low load conditions are higher than that of high load. The harm of these unregulated emissions to the environment and human cannot be ignored. 12.0

0.025 1660r/min 110N·m NOx emissions soot emissions

11.0

0.020

10.5 10.0 9.5

0.015

9.0 8.5 8.0 MSP0

MSP10

MSP20

MSP30

MSP40

Fig. 3.4 Effect of MSP on NOx and soot emissions at low load conditions

0.010

soot emissions (g/kW.h)

NOx emissions (g/kW.h)

11.5

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Figure 3.5 illustrates the methanol emissions before and after DPOC from DMCC Euro V engine under ESC test procedure. The methanol emission of idle condition is 0.57 g/kWh. Under 50% of full engine load at the speed of C (mode 13), the methanol emission could even reach to 15.83 g/kWh, which is the highest among all ESC 13 operating conditions. The methanol emissions under full load condition at every engine speed (modes 2, 8, and 10) are all lower than 3 g/kWh, and it is the high in-cylinder temperature that facilitates the combustion of methanol. Under the whole ESC test procedure, the brake specific emission of methanol from DMCC Euro V engine is 7.49 g/kWh, and it is far higher than that of conventional diesel engine (Wei et al. 2017a, b). The high methanol emission from DMCC engine is because in methanol fumigation method, methanol is injected to intake manifold and then forms homogeneous mixture with fresh air. Due to the scavenging effect during valve overlap period, some fresh methanol–air mixture is swept out of the cylinder without oxidation. Meanwhile, the effect of flame quenching and crevice trapping of methanol–air mixture leads to a portion of methanol fuel could not be oxidized during power stroke where in-cylinder temperature reduces significantly, thus resulting in the emission of unburned methanol (Chao et al. 2000). As it is shown in Fig. 3.6, the efficiency of DPOC in the conversion of methanol is quite high, and for the whole operation conditions under ESC test procedure, the DPOC’s efficiency is all higher than 99%. After the catalytic oxidation of DPOC, the brake specific emission of methanol under ESC test procedure is only 0.009 g/kWh. The research done by Zhang et al. found that the catalytic converter DOC could eliminate almost all methanol emissions from DMCC engine under medium and high load conditions (Pan et al. 2015). Therefore, the methanol emission from DMCC engine is easier to eliminate by oxidation catalyst converter than formaldehyde emission. 18

Before DPOC After DPOC

CH3 OH emissions (g/kWh)

15 12 9 6 3 0.04 0.02 0.00 1

2

3

4

5

6

7

8

9

10

11

12

13 ESC

Mode number

Fig. 3.5 Methanol emissions before and after DPOC from DMCC Euro V engine under ESC test procedure

3 Application of Methanol as Clean and Efficient Alternative Fuel to Engines …

HCHO emissions (g/kWh)

0.6 0.5

Pure diesel DMCC, Before DPOC DMCC, After DPOC

47 18 12

0.4

6

0.3

0

0.2

-6 -12

0.1

-18

0.0 Idle A100 B50 B75 A50 A75 A25 B100 B25 C100 C25 C75 C50 ESC

Operation condition

Fig. 3.6 Formaldehyde emissions before and after DPOC from DMCC Euro V engine under ESC test procedure

From Fig. 3.5 we could find that DPOC is less sufficient on methanol conversion at the engine speed of C (modes 10, 11, 12, and 13) than the other two speeds. It is because the relatively high exhaust flow shortens the dwell time for methanol to be catalytically oxidized in DPOC, leading to higher methanol emissions at the engine speed of C. Figure 3.6 illustrates the formaldehyde emissions under ESC from baseline Euro IV diesel engine and DMCC Euro V engine with and without DPOC. The “ESC” on horizontal axis denotes the unregulated emission under ESC which is achieved by the weighting factors from Table 3.5. For baseline diesel engine, the formaldehyde emission at idle condition is slightly higher, which could reach to 0.22 g/kWh, but the emissions of formaldehyde are less than 0.05 g/kWh under the rest of the operating conditions. The emission tendency of formaldehyde of Euro IV diesel engine is always decreased when engine load increases. The weighted emission of formaldehyde from Euro IV diesel engine under ESC is just 0.0178 g/kWh. The red line in Fig. 3.6 represents the formaldehyde emissions without DPOC from DMCC Euro V engine. Without the catalysis of DPOC, the formaldehyde emissions of DMCC Euro V engine are remarkably increased, and the weighted emission of formaldehyde under ESC could reach to 3 g/kWh. There are several factors contributing to the increasing formaldehyde emissions of DMCC engine. First, the lower combustion temperature leads to the increase in incomplete combustion degree because of greater effect of crevice trapping and flame quenching. Furthermore, methanol fuel is injected to intake manifold on DMDF mode, thus a large amount of methanol fuel is swept out to exhaust pipe during valve overlap period and is partially oxidized to formaldehyde in exhaust pipe. When the engine load decreases, the formaldehyde emissions from DMCC engine without DPOC are significantly increased, and the formaldehyde emission under C25 condition could

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reach to 17 g/kWh. As we can see from Table 3.5, the MSRs of DMCC Euro V engine at low load conditions are higher than high load conditions. Moreover, the in-cylinder average temperature at low load conditions is relatively low. These two reasons finally cause higher formaldehyde emissions under low load conditions. With the catalysis of DPOC, the formaldehyde emissions of DMCC Euro V engine remarkably decrease. Previous studies indicated that the emissions of formaldehyde in exhaust pipe could be catalytically oxidized for more than 98% with DPOC (Wei et al. 2015a). In the present research, the weighted emission of formaldehyde under ESC is just 0.029 g/kWh, and the overall catalytic efficiency of DPOC in formaldehyde could reach to 99%. For DMCC Euro V engine, the formaldehyde emissions with DPOC are just a little higher than that of baseline Euro IV diesel engine. The experiment conducted by Sakamoto et al. Sakamoto et al. 1996) also demonstrated that the formaldehyde emissions of engine could be eliminated by after treatment device effectively, and it could catalytically oxidize even 99% of formaldehyde when the temperature of exhaust gas was high enough. Therefore, the emissions of formaldehyde from DMCC engine do increase significantly, but with the catalysis of DPOC, the formaldehyde emissions between DMCC Euro V engine and baseline Euro IV engine are not much different.

3.3 Characteristics of DMDF Mode 3.3.1 Ignition and Combustion Characteristics of DMDF Figure 3.7 shows conceptual schematic of DMDF combustion mode. Compared with conventional diesel combustion mode, there are two kinds of fuels involved in combustion for DMDF mode, including diesel and methanol. Methanol was injected in intake manifold, and formed homogenous charge with fresh air so that there are premixed methanol charge, liquid diesel, and premixed diesel before ignition. Thus, combustion processes include diesel premixed combustion, diesel diffusion combustion, methanol auto-ignition, and methanol flame propagation combustion. These combustion modes may occur at the same time in the cylinder, or only certain modes may occur (Yao et al. 2016).

3.3.2 Typical Ignition Mode of DMDF It is clearly seen in Fig. 3.8d that there are four kinds of typical combustion modes of DMDF, and the combustion modes are classified by the analysis of HRR shapes. The HRR shape of DMDF mode 1 is unimodal, which looks like a “bell-shape”. The HRR shape of DMDF mode 2 is bimodal, which looks like an “m-shape”. The HRR shape of DMDF mode 3 is bimodal, but it looks like an “M-shape”. And the

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Fig. 3.7 Conceptual schematic of DMDF combustion mode

HRR shape of DMDF mode 4 is unimodal, which is similar with that of conventional diesel combustion (Zhang et al. 2010a). In the DMDF mode 1, the HRR shape shows that the combustion event consisted solely of a premixed combustion with no visible diffusion combustion (Zhang et al. 2010b), and diesel and premixed methanol are compression ignited simultaneously. DMDF mode 1 often appears at high load conditions with EGR and high MSP. The essential combustion boundary conditions of methanol homogeneous charge compression ignition are satisfied at high load conditions. At the same time, EGR and high MSP can prolong the ignition delay of direct injection diesel, which is helpful to achieve diesel premixed combustion. Methanol combustion process will be accelerated by more premixed diesel fuel because the reactivity of premixed methanol will be increased (Wei et al. 2017c). However, the cylinder pressure and HRR curve are quite smooth, and the maximum HRR is obviously higher than other combustion modes, which indicates that controllable methanol rapid compression ignition is realized. It is verified by short combustion duration at late combustion phase, where the combustion duration of CA50–CA90 was merely 9.5°. The combustion process of DMDF mode 1 is similar with RCCI combustion mode (Wang 2016). DMDF mode 2 often appears in medium load conditions with EGR and medium MSP. In the DMDF mode 2, diesel fuel will experience a short period of atomization

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Pressure (MPa)

10 8

DMDF mode1

1660r/min 440N.m

300

(a)

200

6 4

100

SOI

2

Heat release rate (J/°CA)

Fig. 3.8 Cylinder pressure and HRR of typical ignition mode of DMDF

0

0 -20

0

20

40

60

Crank (deg)

(a) DMDF mode1 12 2520r/min 380N.m

200

(b)

8 6

100

SOI

4

Heat release rate (J/°CA)

Pressure (MPa)

10

DMDF mode2

0

2 -20

0

20

40

60

Crank (deg)

(b) DMDF mode2

(c)

DMDF mode3

150

6

4

100

Diesel injection time

2

50

0

0 -20

-10

0

10

20

Crank Angle (°CA)

(c) DMDF mode3

30

40

Heat release rate (J/°CA)

8

Cylinder Pressure (MPa)

200

1660r/min 220N.m

3 Application of Methanol as Clean and Efficient Alternative Fuel to Engines … Fig. 3.8 (continued)

8

51 150

1660r/min 110N.m MSP30

(d)

6

DMDF mode4

100

5 4 50

3 2

Heat release rate (J/°CA)

Cylinder Pressure (MPa)

7

0

1 0 -20

-10

0

10

20

30

40

Crank (deg)

(d) DMDF mode4

and evaporation process after diesel injection. Then, part of diesel and surrounding methanol and air mixture will form the mixture that the equivalent ratios are close to 1. When the cylinder mean temperature is higher than the auto-ignition temperature of diesel, these gases will be ignited first. Meanwhile, the premixed methanol around the diesel sprays will be ignited, and the first peak in the HRR shape will be generated. After the combustion of these gases, the HRR in-cylinder gradually decreases. However, the second peak is generated in a short period. The main reason is that the cumulative heat released by the premixed diesel combustion is not enough to make the premixed methanol auto-ignited in the same way as the HCCI. But after part of methanol is ignited by premixed diesel, the cumulative heat released is increased, and most of methanol auto-ignites simultaneously, resulting in the second HRR peak. DMDF mode 3 often appears in full load conditions with late diesel injection timing and low MSP. At full load, the essential combustion boundary conditions of methanol homogeneous compression ignition are satisfied before TDC, so methanol will auto-ignite before diesel injection. At such cases, MSP should not be high. If methanol ignites before diesel ignition, the cylinder temperature will be increased, and the ignition delay of diesel will be shorten, which also promotes soot formation (Reitz 2013). Meanwhile, if MSP is high, engine knock may occur, which could be able to damage the combustion chamber (Lee et al. 2017). In the DMDF mode 3, the initial peak is mainly caused by the combustion of the premixed methanol, and the combustion duration of methanol was short. This is because the combustion mode of methanol auto-ignition is similar with HCCI combustion mode. The second peak is mainly caused by the diesel diffusion combustion. DMDF mode 4 often appears in low load conditions with low MSP. The in-cylinder combustion temperature and diesel equivalence ratio are relatively low at low loads. This leads to a prolonged ignition delay, and consequently, more premixed diesel mixture is formed during the ignition delay period (Wei et al. 2017c). Therefore, the HRR peak of DMDF mode 4 is mainly caused by the combustion of the premixed

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Table 3.1 Engine test conditions, BTE, NOx, and soot emissions of four typical combustion modes Combustion mode

Speed (rpm)

Torque (N m)

MSP (%)

BTE (%)

NOx emissions (g/kWh)

Soot emissions (g/kWh)

DMDF mode 1660 1

440

80

44.5

1.47

0.01

DMDF mode 2090 2

440

68

39

2.44

0.01

DMDF mode 1660 3

220

30

39

3.12

0.11

DMDF mode 1660 4

110

30

31

11.04

0.017

diesel, together with part of methanol mixture around the diesel sprays. However, it can be observed that there was the long asymptotic tail at HRR curve, and the second-stage combustion becomes very slow. It is very likely that the second stage combustion is mainly dominated by the combustion of methanol premixed charge, which is far lower than the first one. It also results in poor engine efficiency at low load due to incomplete combustion. Table 3.1 shows engine test conditions, brake thermal efficiency (BTE), NOx, and soot emissions of four typical combustion modes. It could be found that DMDF mode 1 could achieve high efficient and clean combustion, BTE is 44.5%, NOx emissions are 1.47 g/kWh, and soot emissions are 0.01 g/kWh. For DMDF combustion mode, DMDF mode 1 is an ideal mode, which is the methods of obtaining diesel premixedonly combustion and methanol homogeneous compression ignition. However, for most of operation conditions, it is difficult to realize DMDF mode 1. In the light of those, DMDF mode 2 should be an alternative mode, which could be achieved at most of operation conditions. DMDF mode 3 is a kind of off-normal combustion mode, and this mode should be avoided. DMDF mode 4 is a kind of low-efficient combustion mode, so optimization measures should be taken to improve the efficiency of this mode.

3.3.3 Summary Compared with conventional diesel combustion mode, there are two kinds of fuels involved in combustion for DMDF mode, including diesel and methanol. DMDF combustion processes include diesel premixed combustion, diesel diffusion combustion, methanol auto-ignition, and methanol flame propagation combustion. These combustion modes may occur at the same time in the cylinder, or only certain modes may occur. There are four kinds of typical combustion modes of DMDF, and combustion modes are classified by the analysis of HRR shapes. The HRR shape of DMDF

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mode 1 is unimodal, which looks like a “bell-shape”. The HRR shape of DMDF mode 2 is bimodal, which looks like an “m-shape”. The HRR shape of DMDF mode 3 is bimodal, but it looks like an “M-shape”. And the HRR shape of DMDF mode 4 is unimodal, which is similar with that of conventional diesel combustion. DMDF mode 1 could achieve high efficiency and clean combustion. For DMDF combustion mode, DMDF mode 1 is an ideal mode, which is the methods of obtaining diesel premixedonly combustion and methanol homogeneous compression ignition. However, for most of operation conditions, it is difficult to realize DMDF mode 1. In the light of those, DMDF mode 2 should be an alternative mode, which could be achieved at most of operation conditions. DMDF mode 3 and mode 4 should be avoided. DMCC engine has obvious operating range. The operating range was restricted by four bounds: partial burning, misfire, roar combustion, and knock. The lower bound of the operating range was the partial burn bound, which occurred under very low load conditions with high MSP. As the load increased to medium load, MSP reached its maximum value of about 76%, and the onset of misfire provided the right bound for normal operation. At medium to high load, maximum MSP began to decrease. DMDF combustion with excessive MSP was extremely loud with high pressure rise rate, which defined the roar combustion bound. As it increased to nearly full load, measured pressure traces in-cylinder showed strong acoustic oscillations. The appearance of knock provided the upper bound of the operating range.

3.4 Main Components of DMCC CI engine has high thermal efficiency, and the fuel economy is better than that of spark ignition (SI) engine. A large number of tests show that the CO combustion of methanol fuel in the CI engine can greatly reduce the carbon smoke in the exhaust, and the NOx emission can also be reduced. According to the statistics of the United States, the SI engine is the main type of small bus and light vehicle in the United States. Only about 3% of the vehicles on the road use CI engine. But in 1997, more than 25% of the total NOx emission came from CI engine. The soot particles emitted by CI engine are 100–200 times of that of spark ignition engine, accounting for 45% of the soot particles. Therefore, the use of clean and efficient alcohol fuel in high thermal efficiency CI engine can not only reduce the consumption of diesel oil, relieve the shortage of oil supply, reduce CO2 emissions, but also improve the emissions of CI engine and give full play to the advantages of alcohol clean fuel. However, compared with diesel fuel, alcohol fuel has lower cetane number (less than one-sixteenth of diesel fuel), higher auto-ignition temperature, higher latent heat of vaporization, lower viscosity, poor lubricity, and is difficult to be dissolved in diesel fuel. It is not easy to use the existing oil supply equipment to directly burn or use pure alcohol fuel on the CI engine. It is more difficult to use alcohol blended fuel or pure alcohol fuel directly in CI engine than in SI engine, and the technology is also relatively complex. Therefore, although methanol has been widely used as fuel in SI engine, there is no commercial report in CI engine.

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DMCC engine uses methanol under pressure injected into the intake port to form a homogeneous mixture there, which is ignited by diesel fuel injected directly into the cylinder and burns together, thus meeting the characteristics of partially homogeneous charge compression ignition (PCCI). The high latent heat of vaporization of methanol absorbs a lot of heat in the process of atomization, vaporization, and mixing, which reduces the combustion temperature and satisfies the characteristics of low temperature combustion. Different from HCCI, the combined combustion is still diesel mode. In some conditions, methanol combustion belongs to multi-point ignition of diesel flame, and even has flame propagation (Klingbeil et al. 2003). Therefore, the diesel/methanol compression ignition engine is quasi homogeneous compression ignition, which inherits the advantages of high efficiency and cleanness of homogeneous compression ignition, and also has the characteristics of traditional compression ignition engine and ignition engine. The combustion process of the engine directly affects the fuel economy and emissions. Therefore, it is very important to understand the combustion process of the diesel/methanol compression ignition engine and control the combustion path of the diesel/methanol compression ignition engine effectively (Li et al. 2016). The typical diesel engine combustion is divided into two stages: premixed combustion and diffusion combustion, which are controlled by the chemical reaction rate and mixing rate of fuel, respectively. The diesel/methanol combined combustion is a new combustion mode that methanol is injected into the cylinder from the intake port or intake manifold, through the atomization and evaporation process and air to form a homogeneous mixture into the cylinder, and the combustion is coordinated with the direct injection diesel in the cylinder. Diesel/methanol compression ignition engine involves a variety of different combustion modes of two kinds of fuel, including premixed combustion of methanol and diesel, diffusion combustion of diesel, flame propagation of alcohol and self-ignition of methanol, etc., and the combustion process is more complex.

3.4.1 Methanol Property Methanol is liquid under normal temperature and pressure, which is convenient for transportation, storage, and filling as fuel. This is the natural advantage of methanol compared with natural gas and dimethyl ether. In addition, methanol is sulfur-free, easy to burn, and has the characteristics of single chemical component, good explosion resistance, and high oxygen content. See Table 3.2 for the comparison of the properties of methanol and gasoline and diesel oil (Dempsey et al. 2014; Chintala and Subramanian 2017). It can be seen from Table 3.2 that the differences and characteristics between methanol and gasoline and diesel oil as fuel are mainly shown in the following aspects: The oxygen content of methanol is as high as 50%, and there is only one C atom, without C–C bond, which makes the combustion calorific value of methanol lower than that of gasoline and diesel. At the same time, the amount of air required for

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Table 3.2 Comparison of properties of methanol and gasoline and diesel (Dempsey et al. 2014; Chintala and Subramanian 2017) Properties/units

Methanol

Gasoline

Diesel

Chemical formula

CH3 OH

C4–C14 Hydrocarbons

C16–C23 Hydrocarbons

Relative molecular mass 32.04

95–120

180–200

Carbon content /%

37.5

85–88

86–88

Hydrogen content /%

12.5

12–15

12–13.5

Oxygen content /%

50

0

0–0.4

C/H Atomic weight ratio 3.0

5.6–7.4

6.4–7.2

Density (20ºC)/(kg/L)

0.792

0.72–0.78

0.82–0.86

Freezing point /°C

−96

−57

−1 to −4

Boiling point /°C

64.7

27–225

180–370

Flashing point /°C

12

45

75

Spontaneous combustion 500 temperature /°C

350–468

270–350

Specific heat capacity (20 °C)/(kJ/kg)

2.55

2.3

1.9

Dynamic viscosity (20 °C)/(mPa s)

0.60

0.65–0.85

3.0–8.0

Latent heat of vaporization /(kJ/kg)

1167

310

270

Vapor pressure (38 °C)/mmHg

239

362–775

–

Conductivity (20 °C)/(S/m)

4.4 × 10–5

–

1 × 10–13

Solubility in water /(mg/L)

Mutually dissolvable

Immiscibility

Immiscibility

Ignition limit (volume fraction) /%

6.7–36.5

1.4–6.7

1.5–8.2

Low calorific value /(kJ/kg)

19,930

43,030

42,500

RON

114.4

89–98

–

Cetane Number

3

0–10

45–55

Theoretical air fuel ratio /(kg air/kg fuel)

6.5

14.8

14.6

Theoretical mixture calorific value /(kJ/kg)

2650

2780

2790

laminar burning velocity 0.523 /(m/s)

0.377

–

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complete combustion of methanol is also reduced, and the theoretical air/fuel ratio is lower than that of gasoline and diesel. It is worth noting that the calorific value of the theoretical mixture of methanol and air per unit mass is basically the same as that of gasoline and diesel. Therefore, when the engine uses methanol fuel, as long as the fuel supply is adjusted, the power output of the engine will not be affected. The conductivity of methanol is much higher than that of diesel, and the corrosion phenomenon of metal materials contacting methanol is more obvious due to electrochemistry. The density of methanol is higher than that of gasoline, but lower than that of diesel. When the mixture is stratified with gasoline, the upper part is gasoline and the lower part is methanol. When the mixture is stratified with diesel, it is just the opposite. The freezing point of methanol is lower than that of gasoline and diesel. Even if it is used in the cold zone with very low temperature, there is no possibility of solidification, but diesel is not. 0 × diesel can only be used when the temperature is higher than −5 °C. In the case of lower temperature, it is necessary to use −10 × 10 and −20 × brand diesel oil. The viscosity of methanol is much smaller than that of diesel. If the original diesel fuel injection pump and nozzle are used to inject methanol fuel into the cylinder, the influence of low viscosity and poor lubricity must be considered. However, the viscosity of methanol is equivalent to that of gasoline, which has little effect on the service life of gasoline injector. The latent heat of vaporization of methanol is 3–4 times of that of gasoline and diesel. The high latent heat of vaporization, low vapor pressure, and low boiling point will make it difficult to form the mixture and start the engine, but it can reduce the intake air temperature and improve the charging efficiency. At the same time, due to the high latent heat of vaporization of methanol, it can improve the internal cooling of the engine after combustion, improve the power performance of the engine, and reduce the exhaust temperature. The octane number of methanol is significantly higher than that of gasoline, and the motor octane number (Mon) of methanol is 94.6, while the Ron of research method can reach 114.4. Therefore, methanol can be used as a good alternative fuel for gasoline and an excellent additive to improve the octane number of gasoline. The cetane number of methanol is only 3, which is much lower than that of diesel. The auto-ignition temperature of methanol is also close to 500 °C, while that of diesel is only 270–350 °C. Therefore, compared with diesel, it is difficult to directly burn methanol in a compression ignition engine because of the poor self-ignition ability of methanol. In order to improve the spontaneous ignition performance of methanol and reduce the self-ignition temperature, other additives must be added to methanol. The cetane number of methanol was increased by adding additives to achieve the purpose of direct compression ignition. The maximum laminar combustion rate of methanol is higher than that of ether, gasoline, and aviation fuel, which is next to hydrogen and acetylene. Diesel engine is compression ignition, which belongs to multi-point spontaneous combustion in cylinder. It is difficult to describe combustion speed with the concept of flame propagation speed. Therefore, methanol combustion has better timeliness and time limit, which can be used in high-speed engines. When methanol is added into gasoline, its combustion speed can be increased.

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The ignition limit of methanol is 6.7–36.5%, which is much wider than that of diesel and gasoline. Therefore, methanol can work in a wide range of mixture concentration, with good lean burn performance, which is suitable for lean burn, and has a large degree of freedom when operating conditions are selected. In a positive ignition engine, although the flash point of methanol fuel is low, it is easy to cause early ignition, but it will not cause fire due to the imprecise control of air/fuel ratio, so as to ensure the stable operation of the engine in a wider range of mixture concentration, and it can make the fuel burn fully, which is beneficial to the purification of exhaust gas and the reduction of fuel consumption.

3.4.2 Methanol Delivery System The function of the methanol fuel supply system is to supply the methanol needed for the dual fuel mode combustion to the engine. It is mainly composed of primary methanol filter, electric methanol pump, methanol filter, methanol pressure regulator, methanol injector, methanol pipeline, liquid level gauge and pressure gauge, etc. See Fig. 3.9 for schematic diagram. Methanol is pressurized by methanol pump after being filtered out of impurities by methanol filter and maintained at a constant pressure through pressure limiting valve. In order to ensure the stable operation of methanol system on board, the system adopts two-way alcohol supply mode, which can not only ensure the supply of large flow methanol but also ensure the stability and reliability of methanol system. The two-way methanol can be switched in real time through ECU, with methanol pressure gauge and methanol level gauge, respectively. Monitor the methanol pressure and

Methanol pump Methanol filter Methanol regulator Methanol level

Methanol injector Methanol ECU

Methanol tank Engine speed Fig. 3.9 Methanol delivery system diagram

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Fig. 3.10 DC methanol pump

liquid level in real time, and transmit the signal to ECU to ensure the reliable operation of methanol system. The injection time of methanol is controlled by ECU, and ECU has control output to output the real-time alarm of system fault. In the methanol delivery system, methanol pump is a very important device, which provides power for the methanol supply system, and together with the pressure limiting valve establishes pressure for the next methanol rail. Considering the working environment of the engineering vehicle, in order to ensure the effective installation and reliability of the methanol pump, DC carbon brush pump has been used as the methanol pump, as shown in Fig. 3.10. In the application, it is found that the service life of the once through pump supplying methanol is far lower than that of other fuels such as gasoline. In the actual road test process, a large number of methanol pumps are damaged, which also affects the reliability of the whole system. Therefore, we have carried out an in-depth analysis on the failure causes of methanol pumps and proposed the improvement scheme accordingly. Methanol will contain a small amount of water due to its water absorption and will also produce a small amount of organic acids due to air oxidation or bacterial fermentation. Therefore, methanol in the pipeline can be regarded as an electrolyte solution; the main component of gasoline is hydrocarbon, which belongs to non-electrolyte solution, which is the main difference between the two. For the convenience of analysis, the working principle of DC motor is simplified as shown in Fig. 3.11. Figure 3.11a is the circuit diagram of DC motor without power on. Since the standard electrode potential of Cu is positive (+0.342 v), and the existing research shows that the tendency of oxygen absorption corrosion of Cu in methanol solution is greater, it can be considered that there is a small amount of OH− in the solution. The positive and negative pole lines are contacted by commutator and rotor coil. However, due to the same material of the positive and negative pole lines, the positive and negative poles do not form the primary battery, so the corrosion of the positive and negative poles should be the same. Figure 3.11b is the working principle diagram of the DC motor after power on. It can be seen from the figure that the current starts from the positive pole of the power supply and returns to the negative pole of the power supply after power on. If you only look at the external circuit (the circuit not

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Fig. 3.11 Working principle of DC motor

immersed in the liquid) and regard the power supply as a wire, the current can be seen as flowing from the negative pole to the positive pole, while the movement direction of the electron is opposite. In this case, the free electrons in the positive metal (Cu and Fe) are transferred to the negative electrode through the external circuit under the action of potential difference, and the positive electrode will undergo oxidation reaction, and the Cu2+ and Fe2+ generated will enter the solution so that the positive electrode will be corroded; the negative electrode will obtain electrons, and the electrons will react with the O2 in the solution to generate OH− , and the negative electrode will be protected. After the methanol pump works, the positive line is corroded and the negative line is protected, which is very similar to the “cathodic protection” in the metal electrochemical protection, that is, the metal to be protected is connected to the negative pole of the external DC power supply (the cathode of the primary battery), and the auxiliary anode is connected to the positive pole of the DC power supply so that the protected metal is always in the state of electronic excess. In fact, the positive circuit is sacrificed to protect the negative circuit in the methanol pump. According to the results of theoretical analysis, the research team has proposed an improved brushless DC pump technology scheme, whose external structure is shown in Fig. 3.12. The improved methanol pump insulates the circuit and liquid circuit by welding and packaging, eliminating the influence of electrochemical corrosion. Its continuous operation life is not less than 1000 h, and its service life is greatly improved. The filter is another important part of the methanol supply system. The methanol from the methanol tank must pass through the methanol filter before entering the methanol pump, the pressure limiting valve, and finally the methanol nozzle. Filter

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(a) Bruashless pump

(b) Appearance of pump Fig. 3.12 Schematic diagram of brushless alcohol-resistant pump

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Fig. 3.13 Three generations of methanol filters

efficiency is the key factor to determine the service life of methanol pump and nozzle. High-quality filter should not only effectively filter out the possible impurities in methanol but also have strong alcohol resistance and service life. With the support of 863 project, three generations of methanol special filters have been selected and developed, which greatly improves the service life of alcohol supply system and methanol filtering effect, particularly the shell of filter changed from aluminum to steel, as shown in Fig. 3.13.

3.4.3 DMCC Control System The function of the electronic control system is to detect the working condition of the engine and precisely control the injection quantity and time of methanol. It is mainly composed of various sensors, actuators, and controllers (also known as electronic control unit ECU). Figure 3.14 shows the electronic control system of methanol system in dual fuel engine. ECU is the core of the electronic control system. It can not only realize the bench calibration of the dual fuel engine but also inject methanol according to the sensor to judge the working condition of the engine during the actual operation of the transport vehicle. The sensors of methanol system mainly include engine speed sensor, throttle position sensor, coolant temperature sensor, methanol liquid level sensor, and methanol pressure sensor. These sensors are arranged on the transportation vehicle to judge the working condition of the engine to determine the methanol injection. The above sensors need to be installed on the mechanical pump engine, and the electronic control engine is shared with the original vehicle sensors. The function of the actuator is to fulfill its task requirements according to the instructions of methanol ECU. The actuators of methanol system mainly include: electric methanol pump, methanol nozzle, methanol system working panel, fault lamp, and methanol pipeline valve.

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Methanol injector

Throttle position

Methanolpump

Temperature sen or Working panel Methanollevel

MethanolECU

Engine speed

Alarm lamp

Vehicle speed

Methanolpipeline vavle

Fig. 3.14 Electronic control system

For DMCC system, the injection time and amount of methanol must be strictly controlled according to the combustion and emission characteristics of combined combustion and the needs of engine operation. Compared with the generator, ship and other power devices, the vehicle engine is the most complex, which is usually described by a two-dimensional plane composed of speed and load. Therefore, the control of diesel/methanol combined combustion must be timely, appropriate, accurate, and fast. For many years, although the advantages of methanol and diesel combined combustion are also recognized by everyone, it has not been widely used so far, and the difficulty of combustion control may be one of the important reasons. Fortunately, the electronic control technology that emerged in the middle of the twentieth century has been greatly developed in the new century. The mature control theory and the mass production of control elements provide strong support for the complex combustion mode of diesel/methanol compound combustion. The basic components of the electronic control management system of DMCC system include: electronic control unit (ECU), ignition key switch, throttle position sensor, speed sensor, cooling water temperature sensor, methanol level gauge, six methanol injection solenoid valves, electric methanol pump and indicator light, etc. Its arrangement on the engine is shown in Fig. 3.15. The combination of control theory and internal combustion engine technology is an important sign of the development of internal combustion engine, which greatly improves the performance of internal combustion engine in all aspects. To realize the

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Methanol tank Methanol pump

Methanol inlet Signal output

Methanol rail

DMDF ECU

Intercooler

Throttle position

Coolant-Temp

Pressure regulating valve

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Engine speed

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Signal input 6-cylinder common-rail diesel engine Fresh air

Electric dynamometer Pressure transducer

Exhaust

Turbocharger

Engine control system

Exhaust Smokemeter

Gas analyzer

Fig. 3.15 DMCC control system

efficient and stable operation of the electronic control system of the internal combustion engine, the control strategy of the internal combustion engine must be studied first, and then all kinds of ideas can be applied to the electronic control system of the internal combustion engine. As a new technology application of internal combustion engine, the DMCC system is the most important one to control it accurately and reliably. The purpose of applying the control theory is to find the optimal control mode. The research object of classical control theory is mostly the problem of linear constant system and single input and single output. The research method mainly adopts the frequency domain analysis method based on the transfer function, frequency characteristic, and root locus. Its control idea first aims to adjust the machine and make it run more stably; secondly, it uses the feedback method to make a dynamic system accurate according to the requirements of human beings, work accurately, and finally realize the control of the system according to the specified objectives. Modern control theory introduces the concept of state space to describe the changeable dynamic process and obtains the ideal control theory system by strict mathematical reasoning. Its main branches include optimal control, adaptive control, robust control, and predictive control. Classical control theory and modern control theory are based on mathematical model. They need accurate mathematical model and rigorous design reasoning thinking, which also limits its wider application. In order to solve the high dimensionality of many practical systems and the fuzziness, uncertainty, contingency, and incompleteness of system information, the control theory further develops a new generation of control theory based on the structure, function, thinking, reasoning, and decision-making of human brain, such as the large-scale system control theory, which adopts the mathematical model of state equation and algebraic equation, and uses the design of combination of decomposition and coordination. The principle simplifies the solution of complex control problems, realizes the control system combining

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centralization and decentralization, and greatly reduces the information processed by each controller, thus simplifying the structure of processor; the intelligent control theory combines control theory with artificial intelligence, and improves the intelligence level of control system in self-optimization, self-adaptation, self-learning, selforganization, etc. Its main branches include fuzzy control, neural network control, and artificial intelligence control. Early internal combustion engine control is an open-loop control using mechanical components, which controls the working state of internal combustion engine by changing the output of internal combustion engine system. The accuracy of this control method depends on the accuracy and stability of the control system. Because the control system is composed of many mechanical components, the accuracy and stability of any relevant component will have a certain effect on the control. Moreover, due to the slow response speed of mechanical components, the accuracy and stability are not good. Therefore, the control accuracy is not high, which greatly limits the performance of the internal combustion engine. The rapid development of electronic technology has greatly promoted the electronic control of internal combustion engine, making the control theory play a good role in internal combustion engine. By using the electronic control system composed of sensors, controllers, and actuators, the internal combustion engine can be controlled with high precision and full working condition optimization so that the performance of the internal combustion engine can be further improved (Wang et al. 2015; Hamosfakidis and Reitz 2003; Semenoff 1935). As a new application technology of internal combustion engine, diesel/methanol compound combustion system has also widely applied the latest control theory technology. The control theory is applied to diesel/methanol compression ignition engine, including open-loop control, closed-loop control, neural network, adaptive control, self-learning control, and fuzzy control, which greatly improves the control effect and optimizes the control process. The principle of the DMCC system is as follows: Methanol is injected into the intake manifold through the methanol injection solenoid valve installed on the intake manifold, and evaporated with the help of the high temperature of the intake valve to form a homogeneous mixture with air, which is sucked into the cylinder during the intake stroke and further evaporated during the intake and compression stroke. At the end of compression stroke, methanol homogeneous mixture was ignited by diesel. Methanol has the characteristics of oxygen and high latent heat of vaporization. Because of its high latent heat of vaporization, it will greatly reduce the intake air temperature and the maximum combustion temperature in the cylinder and reduce the opportunity of fuel cracking and NOx generation. At the same time, because methanol contains oxygen and is volatile, the homogeneous mixture formed will not generate carbon smoke when burning. In the DMCC system, the methanol nozzle injects the conical atomized methanol into the intake manifold or intake manifold and forms a homogeneous mixture with the fresh charge of the intake air into the cylinder. When the valve of the diesel engine is opened, the intake cylinder is ignited by the direct injection diesel in the cylinder so as to realize the clean combustion at low temperature with large proportion of premixed.

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In the DMCC system, the injection time of each nozzle has a great influence on the performance of the diesel engine. The diesel/methanol combined combustion system can be divided into multi-point manifold injection system and multi-point manifold injection system according to the installation position of the alcohol injector. According to the injection mode, it can be divided into simultaneous injection, group injection, sequential injection, etc. This has a high demand for the control of methanol nozzle opening time. Multi-point manifold injection is to install the alcohol injector on the intake manifold and spray alcohol to the intake manifold to form a combustible mixture, which is ignited by diesel directly injected into the cylinder. This method has the advantages of convenient installation, good running stability, and simple maintenance, but the uniformity of each cylinder is not good enough and the response is slow. Multi-point manifold injection is to install methanol nozzles on the intake manifold and spray the methanol spray into the intake manifold directly. The ECU controls separate cylinder injection or group injection to form a homogeneous mixture with the intake volume. The software module of electronic management system (EMS) is mainly divided into: actuator drive module (methanol nozzle and methanol pump drive, etc.), signal input module (analog signal and digital signal processing), interactive software module (communication module), operation algorithm module (working condition identification, interpolation algorithm, analog acquisition filtering algorithm, etc.), and fault diagnosis module. According to the specific combustion mode of the DMCC system, it is necessary to distinguish the working conditions of the engine in detail, and carry out different control modes for different operating conditions of the engine so as to achieve better fuel economy, emission, and power performance. The software has the function of OBD system (on-board diagnosis technology), which can detect the working conditions of each component of the engine electronic control unit of the diesel/methanol combined combustion system in real time during the operation of the engine. In case of any abnormality, judge the fault according to the specific algorithm of the software, and remind the user of the occurrence of the fault. The software adopts the idea of modular design, a top-down and gradually detailed structured software design method. The main body of control software is divided into eight sub-modules. In the process of engine running, the main program calls different sub-modules according to a certain priority. The main program module is shown in Fig. 3.16. Bench calibration of control map is a very important process. The accuracy of data directly affects the control accuracy, but this process is very labor-intensive, materialconsuming, and time-consuming. Therefore, in the process of bench calibration, the speed calibration interval is 200 rpm, and the opening interval of throttle control handle is 10%. The limited points are selected for calibration to form the initial map. However, such control map data interval is large, if it is written directly to ECU, and the accuracy of control variables calculated by interpolation algorithm may be affected. Therefore, after the initial control map is calibrated, the neural network method is used to optimize the control map, and the tighter and smoother control

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Fig. 3.16 Main program module

map data is obtained. The optimized data is written into the ECU data storage area as the control map for the actual operation of the engine (Liu et al. 2002; Li 2002).

3.5 Emission Control System of DMCC Studies have shown that NOx and PM emissions of DMCC engines are significantly lower than that of pure diesel mode, but CO and THC emissions are quite higher (Wei et al. 2015b, 2016). It is an inevitable requirement to be equipped with appropriate after-treatment devices for DMCC engines to meet increasingly stringent emission regulations. This section will introduce several after-treatment devices commonly used in DMCC engines.

3.5.1 DOC-Diesel Oxidation Catalyst The installation of diesel oxidation catalyst (DOC) is an effective measure to control the emissions of CO, THC, methanol, and formaldehyde in DMCC engines. The conversion efficiency of DOC to DMCC engine pollutants will be introduced in this section. The DOC used in this study adopts a cordierite ceramic carrier, the precious metal components are platinum and palladium, the ratio is 2:1, the precious metal content is 40 g/ft3 , and the pore density is 400 cpsi. The light off temperature of the DOC provided by the catalyst manual is 240–250 °C. Below light off temperature, the catalytic efficiency was low. At low engine speed and load, the exhaust gas

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temperature was low and becomes lower with high methanol proportion. Therefore, the methanol proportion should be controlled to relatively low level at low engine speed and load. The emissions of THC, CO, and formaldehyde before and after DOC are investigated by Wei et al. (2016). Previous studies illustrated that the catalytic efficiency of DOC for both THC and CO reaches over 99%. Both THC and CO emissions from DMDF combustion after DOC can be reduced to levels far below those of conventional diesel engines. Therefore, DOC can effectively eliminate the additional THC and CO emissions generated by DMDF combustion and achieve near zero emissions. Also they found that DOC has little effect on NOx emissions in general. However, it can be observed that DOC will cause a small increase in NOx emissions (maximum increase 100 times more energy available than energy carrier like battery in EV. Just to mention from reference (Smil 2006), “…Edison believed that engines will never really make it and that the future belongs to electric cars—and he spent almost the entire first decade of twentieth century in a stubborn quest to develop a battery whose energy density would rival that of gasoline. A century later we still do not have an electricity storage device that could even approach such a density—but the promise of electric cars is still with us as forecasts that promise how these vehicles will capture significant share of automobile market within a decade are being rescheduled for another decade once the original forecast fizzles.” Talking about a heavy-duty electric truck above 12 tonnes, the range presently available is typically ~400 km which is almost ~70–80% lower than conventional ICE truck. This limited range will require extensive charging network on highway system to reduce the idle time of trucks. The cost of battery (which is analogous to engine in ICE vehicle) is exorbitantly high and stands at 180–190 USD per kWh. The battery cost itself may be ~70–80% of vehicle cost in case of truck. This will increase the initial and subsequent cost of transport which will impact the payback period in case of EV vehicles impacting the economy in larger sense. Though EV along with it will bring up new opportunities but it will also pose a severe blow to existing supplier eco-system and there may be a potential threat to the employment situation. The environmental aspects are already discussed above. In such a scenario,

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where battery technology is at a nascent stage, certainly for heavy-duty trucks, longhaul tractors, trailers, marine and off-road, ICE will remain as the prime movers for freight transportation. However, in order to address the global warming and air quality prevailing in India, there is an immense need to investigate and adopt a more sustainable approach. In Sect. 4.3 we have discussed how the second-generation biofuels can be a sustainable approach for India. In a study by Argonne National Laboratory (Wang et al. 2012) six pathways were compared for well-to-wheel analysis with gasoline. And it was mentioned that how relative to petroleum gasoline, ethanol from corn, sugarcane, corn stover, switchgrass and miscanthus can reduce life-cycle GHG emissions by 19–48%, 40–62%, 90–103%, 77–97% and 101–115%, respectively. Biofuels like methanol, ethanol, synthetic fuels and even widely available natural gas should be adopted as transportation fuel for a conscious effort to reduce the global GHG emissions in phase manner thereby acting as a bridge between the present and the future scenario when majority of the electricity production will be renewable-based and transport electrification in true sense will be reducing and the mitigating the transport-related CO2 emissions. In this regard the Indian government has announced for commissioning a centre of excellence on methanol for ARAI. Also recently, Praj Industries has signed an MoU with ARAI under which they will jointly drive application development of advanced biofuels for use in industry and transportation.

4.2 Future Engines Till now diesel engines used in commercial vehicles, off-road, marine, power generation were known for their remarkable efficiency, reliability and durability. Since decades diesel engines have gone through tremendous advancements in its combustion system to reduce the pollutants at its source. Technologies like turbocharging, cooled exhaust gas recirculation, advanced common rail injection systems with higher capabilities of injection pressures, multiple injections, advanced bowl geometry, variable valve train, downsizing, two-stage turbocharging and control, advanced control systems and after-treatment systems have enabled heavy-duty diesel engines to meet the stringent emission norms and GHG targets. Moreover, engine and vehicle testing and type approval procedures have also taken newer heights with the introduction of OBD-2, in-service conformity factors in real driving conditions. These tests will only ensure that future engines are now cleaner in wider range of engine operating maps under real driving conditions. Further upcoming emissions norms like Euro-VII and California NOx ~ 0.027 g/kWh will put challenges on the present engine technologies and after-treatment to meet them. Under such situation there is a need to research on both engine and fuel together which complement each other in meeting the emissions and GHG targets and maintaining excellent engine efficiencies.

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4.3 Fuels: Why There is a Need to Look for a Future Fuel From statista (https://www.statista.com/statistics) there was a projection on global energy consumption from 1990 to 2040, which showed that there is an increasing trend in world energy consumption. It is estimated that there is almost 25% rise in energy consumption in 2040 from present level. Hence energy demand will continue to rise for all countries. And consequently, from another statista report (https://www.theguardian.com/ environment/2018/oct/08/global-warming-must-not-exceed-15c-warns-landmarkun-report), the projected carbon dioxide emissions worldwide would also rise approximately 22% from 2020 to 2050, i.e., 35.34 Gtons to 43.08 Gtons in 2050. Presently as already discussed, transport contributes to 20% of the total global CO2 emissions. And road transport contribution is around 75%, out of which HDVs are responsible for contributing closely to 50% of the CO2 emissions. As per the report (https://www.statista.com/statistics) says that in transportation sector HDV would be contributing to 38% of the total transport-related CO2 emissions in 2050. And most of the fuel used for transportation is petroleum-based, including gasoline and diesel. Such projections clearly suggest that rise in world energy consumption is inevitable and without any breakthrough in the way the energy will be generated, there will be a surge in atmospheric CO2 emissions and their heightened implications on the world climate change. There was a report from UN (https://www.theguardian.com/environment/2018/ oct/08/global-warming-must-not-exceed-15c-warns-landmark-un-report), which states that “we have only 12 years to limit climate change catastrophe”. This is a grave scenario and hence there is a conscious need to look for sustainable solutions at present that can give our future generations a better world to live in. Oil, natural gas and coal have been serving our demand for energy since long time and now they are on edge of depletion, and furthermore extending their use will only get us closer to crisis and worsen the climate conditions. A number of other alternative and renewable energy sources has to be considered and used. Some of the renewable energy sources are biomass, hydro, wind, solar etc. Utilizing one of these energy sources we can produce fuel like hydrogen, and it is widely discussed about “hydrogen economy”. According to Olah et al. (2009), producing hydrogen in long term by water electrolysis using any available energy source can give us a clean fuel in the framework of “hydrogen economy” but due to its volatile and extremely explosive nature many difficulties needed to be resolved before it becomes practical. A more viable approach would be “methanol economy” where methanol can be produced from number of ways like: • Coal • Natural gas • Biomass yielding synthetic gas.

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Most importantly, methanol can also be produced by reductive hydrogenative recycling of CO2 from atmosphere itself. A Canadian-based company, Carbon Engineering has developed facility for converting the atmospheric CO2 to synthetic fuel. And it is estimated that each such facility is capable of capturing 1 million tonnes of atmospheric CO2 per year, which is equivalent to planting 4 crore trees. Hence as mentioned by Olah et al. (2009), “methanol economy” has number of advantages and possibilities like convenient energy storage medium, readily transportable and dispensable for vehicles and as a feedstock for synthetic hydrocarbon and their products. As per the IPCC report (2019) on limiting global warming to 1.5 °C implies reaching net zero CO2 emissions globally by 2050. And the mitigation pathways are characterized by energy demand reduction, de-carbonization of electricity and other fuels etc. It was also mentioned that deep emission reduction in transport sector would be achieved by several means. And that the reduction of CO2 from transport sector would require a portfolio of options and there will be no silver bullet. This indicates that electrification and biofuels-based transportation has to work in tandem to achieve such ambitious targets. As per one of the ambitious pathways (IPCC 2019), it was predicted that among various measures for CO2 reduction in 2050, the contributions can be as 29% from efficiency improvement, 36% from biofuels, 15% from electrification and 20% avoid/shifts. Also, it is predicted that out of total amount of biofuels consumed in transport sector, HDV would stand at a higher portion of 35%, i.e., more biofuels are allocated to difficult-to-de-carbonize modes. India, which is already in the third position as one among the largest consumers of energy fuels, also needs to put tremendous effort to be in harmony with the rest of the world by 2050. As per an ICCT report (2017), it is found that there is a shift in the total diesel consumption since 2005, and the total annual diesel consumption as on 2015 in India is at approximately 8700 crore litres. And around 70% of this total diesel consumption is from transport sector, with LCV and HCV consuming ~30%, i.e., 2610 crore litres of diesel. Further, vehicles above 12 tonnes consume 2272 crore litres of diesel every year. We will now discuss two important biofuels, namely methanol and ethanol, and their potential to meet the transport-related energy demands. Both the fuels can be produced from fermentation of agricultural products, however, methanol is extensively produced presently from synthetic processes. And as mentioned by Olah et al. (2009), the agricultural production of ethanol is highly energy demanding and currently most of the energy comes from fossil fuels. However, methanol does not rely on agricultural resources but can be readily produced from varied feedstock including atmospheric CO2 . In India the situation of biofuel presently is not very encouraging, be it methanol or ethanol. Mentioning about methanol, according to report (Saraswat and Bansal 2017), the total domestic methanol production in the year 2015–2016 was only ~21 crore litres. In India methanol is largely produced from imported natural gas because of which it becomes a better economical option for India to meet around 90% of its requirement by importing methanol from Iran and Saudi Arabia in major as natural gas is much cheaper and abundantly available.

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However, India too has large reserves of coal which can be used to produce methanol. For India it is not only limited to coal, but we can also tap the biomass/municipal waste to produce methanol domestically. It is encouraging to know that using Indian high ash coal, stranded gas and biomass can produce ~2560 crore litres of methanol annually by 2025 (https:// vikaspedia.in/energy/energy-basics/methanol-economy-in-india#:~:text=India% 20has%20an%20installed%20Methanol,of%20methanol%20annually%20by% 202025). Mentioning about ethanol, they can be produced from two type of resources; first is starch and sugar from plant and plant waste, especially sugarcane molasses, corn, beet or cassava. And secondly, algae and cellulose obtained from the waste from paper and wood processing industries or non-edible plants. As per report (Purohit and Dhar 2015), though India is world’s second largest sugarcane producer and a major manufacturer of molasses-derived ethanol, it was further mentioned that even if the entire sugarcane crop is used for sugar production, the estimated ethanol yield would be 360 crore litres. If India is to achieve 20% blending, the country needs to produce 670 crore litres of ethanol by 2020 and ~910 crore litres by 2030. India needs to increase its production by three times. This situation again becomes challenging as there is little scope to increase land available from stable food production to sugarcane production. Also, from ground water consumption point of view, sugarcane consumes approximately 20,000–30,000 m3 of water per hectare per crop. Hence this would not be a sustainable approach. Referring to second-generation biofuels, here using different mechanism we break the lignocelluloses materials to either sugar or synthetic gas. Later we can use this sugar for conversion to ethanol or use the synthetic gas for conversion to liquid or gaseous fuels. The author mentioned the potentials of such secondgeneration biofuels. It was mentioned that these second-generation biofuels are derived from agricultural residue, by-products, organic/municipal wastes, material from energy plantations etc., and can also promote rural development, thereby improving economic conditions in emerging and developing regions. It was estimated that gross agricultural residue availability in India could be 877 Mt for 2030–2031. With this net availability of agricultural residue, the net ethanol availability could be 3730 crore litres in 2020–2021. Second-generation biofuels give value addition to the agricultural residue, which would otherwise be burnt by farmers encouraging emissions of CO2 , CO, SOx , NOx and particulates which is presently been seen affecting cities like Delhi in India. There are even estimation on employment creation through second-generation biofuels industry. Though second-generation biofuels offer tremendous advantages over first generation, making it more sustainable like less dependence on land availability, no fuel-food conflict, and higher yield, but author mentioned that there are hurdles like cost-effective technologies for biomass to fuel conversion and lack of proper mechanism for collection, transportation and handling of feedstock.

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Apart from the India’s potential to produce biofuels like methanol and ethanol and their direct benefits on India’s economic situation, rural development and environmental impact, it is also worth to mention that like fuel they are also quite competitive from combustion perspective. Some of the properties are as follows: • Higher hydrogen to carbon ratio—lower tendency to form soot • Higher oxygen content and lower stoichiometric air/fuel ratio—lower air requirement • Higher flame speed (methanol)—more isochoric combustion • Lower adiabatic flame temperature—lower NOx emissions • Higher enthalpy of vaporization—increased charge density • Due to lack of sulphur in ethanol compared to diesel, TBN loss for engine oil is lower which can actually offset the frequent oil change interval with alcohol fuels (Hardenberg and Schaefer 1981) • Engines running on ethanol has also been known to have thermodynamic advantage due to lower temperatures over diesel, which leads to higher polytropic exponent for expansion (Hardenberg and Schaefer 1981). In brief, • By 2040, there will be rise in global energy consumption by 25%. Consequently, that would mean a 25% rise in global CO2 emissions by 2040, and in transportation HDV would be contributing to 38% of total transport-related CO2 emissions. • As per IPCC report to limit global warming to 1.5 °C by 2050, there is no silver bullet and electrification and biofuels have to work in tandem to meet the target of net zero CO2 emissions by 2050. Among various measures to address this target, 29% would be required from fuel efficiency improvement and 36% from use of biofuels. And for HDV it would require 35% of the biofuel share in transport. • India can use high ash coal, stranded gas and biomass reserves to produce 2560 crore litres of methanol by 2025. • Though India being the second largest sugarcane producer and among top producer of ethanol based on molasses, it would not be sustainable approach to use ethanol based on first generation due to number of reasons described above. Under such situation, second-generation-based alcohols could be a sustainable approach. As an estimate with present agricultural residue worth of 150 million tonnes in India, it can yield to 3700 crore litres of ethanol. Considering the lower heating value of ethanol compared to diesel, this estimation of ethanol would suffice nearly 90% of the energy requirement for HDV above 12 tonnes, which is quite impressive. • Second-generation biofuels will also in long way enhance the rural India development by generating employment in biofuel manufacturing industry, supply chain and bio-refineries. Agricultural residue which under normal scenario is burnt will be having worth. • National economic benefit by reduction of import is another crucial aspect where we will be able to save thousand billions of currency.

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4.4 Advanced Combustion Concepts Combustion is a key process in any internal combustion engine. The timing and completeness of the combustion decides how effectively the fuel chemical energy is released. The result of combustion being the high temperature and high pressure burned gases which ultimately expands within the cylinder, thereby transferring the fuel chemical energy into useful work on the piston. Conventionally, there are two major ways for the combustion to take place in ICE vehicle, i.e., either through spark ignition (SI) combustion (SI engine or gasoline engine) or through compression ignition (CI) combustion (CI engine or diesel engine). Diesel engines are used in wide range of application ranging from on-road, off-road, marine, power generation and locomotives. Diesel engines are preferred in such application because they are highly efficient, more reliable and durable. Diesel engines are highly efficient than SI engine because they burn much leaner than SI engines, they can use higher compression ratio, high level of turbocharging, can burn more fuel, can use cylinders of bigger diameter for generating more power and high torque at low speed (better drivability) as they are not knock limited and still can produce lower CO and HC emissions because they have higher air/fuel ratio. And because diesel engines handle higher working pressures, yield higher torque and power, they are designed and built tough achieving higher durability and reliability. However, they suffer from the problem of higher NOx and PM emissions and are victim of NOx –PM trade-off. The classical diesel combustion process which has direct injection of fuel close to TDC to have control over combustion using injection, the ignition delay is shorter limiting the fuel and air mixing process before start of combustion, thus making the diesel combustion to be mostly mixing controlled. According to (Khair 2006), the ϕ (equivalence ratio) versus local temperature (T) plot can be effectively used to describe the progress of typical diesel combustion. It is known that how the diesel combustion passes through the island of soot formation and NOx formation in their progress towards completion. With present stringent emission regulations and diesel engine inherent NOx –PM trade-off any attempt to reduce the PM formation by increasing the in-cylinder temperatures will increase the NOx and vice versa, thereby making costly and complex after-treatment systems mandatory for meeting present future more stringent up-coming norms. It is now the prime time that some of the advanced combustion concepts are to be considered for future engine development. And in section ahead, we will see how such advanced combustion concepts have yielded excellent engine thermodynamic efficiencies while still maintaining extremely lower engine-out emissions. Alternate combustion techniques like homogenous charge compression ignition (HCCI) which can simultaneously reduce both the pollutants and can also achieve diesel like higher efficiencies are not new but were proposed in research articles by Onishi et al. (1979), Najt and Foster (1983). And further research on HCCI over decades led to more practical combustion modes such as premixed combustion compression ignition (PCCI) and low temperature combustion (LTC) which are better to control and can be extended to higher loads. Such combustion modes were together called as

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advanced combustion concepts. In a research paper by Yang et al. (2015), injection timing has been used to classify various advanced combustion concepts. HCCI corresponds to very early injection timings and can be even earlier in the case of port injection. In HCCI we are able to achieve homogenous charge as there is enough time for fuel and air to mix. Compared to HCCI, PCCI has injection timings relatively late but still much earlier. Though both HCCI and PCCI have been said to be reporting lower NOx and soot emissions, but they are high on CO and HC emissions and also are limited in operating loads. Compared to both HCCI and PCCI, we have LTC category which includes both early-LTC and late-LTC having injection timings close to end of compression stroke. The early-LTC has sufficient premixing of charge to achieve soot formation and enough in-homogeneity to exercise better control of combustion. The late-LTC is another LTC approach inspired by modulated kinetic (MK) (Kimura et al. 1999) where injection and combustion occurs after TDC during expansion stroke. With such concept we are able to extend the load limit with compromise on engine thermodynamic efficiency.

4.4.1 Partially Premixed Combustion Partially premixed combustion (PPC) has been researched in depth at Lund University, and have illustrated many worth mentioning findings. Such findings have only helped in further understanding the potential of PPC and its suitability with high octane fuels, like gasoline and alcohols. As mentioned in one of the researched article (Johansson et al. 2009), PPC is a combustion strategy in the region between diffusion combustion (CI) and homogenous combustion (HCCI), meaning that fuel and air mixes better than classical diesel combustion but it is not homogenous. This enables us to achieve both lower emissions and better control over combustion phasing. As shown by Johansson et al. (2006), the distinguished area of operation of conventional diesel combustion, partially premixed combustion and HCCI combustion over the map of local equivalence ratio and combustion temperature. It is clearly demonstrated that HCCI operates with most leaner equivalence ratio and lower combustion temperature and PPC operates relatively leaner than conventional diesel combustion and also at lower combustion temperatures which consequently enable PPC to escape both soot formation and NOx formation regions. It is interesting to note that PPC using quality dilution enables to achieve more premixing to avoid rich mixture pockets and maintain lower combustion temperatures. In case of diesel combustion, where injection commences just before the start of combustion, control over combustion is much easier; however, the ignition delay is much shorter. This shorter ignition delay results in much lesser mixing of fuel and air charge prior to start of combustion and majority of combustion is mixing-controlled, which happens in thin diffusion flame where fuel and air mixes and then burns almost in stoichiometric equivalence levels. As mentioned by Heywood (2018) that under typical diesel engine operating condition, 70–95% of the injected fuel is in vapour phase at the start of combustion. And when evaporation is almost 90% complete

4 Methanol: A Gateway to Biofuel Revolution …

99

within ~1 ms, only 10–35% of the vaporized fuel has been mixed to within flammability limit in a medium-sized diesel engine. Thus, combustion is largely mixingrelated rather than evaporation-limited, except at cold condition where evaporation becomes a constraint. There are evidences which support the fact that under typical diesel engine operating conditions mixing rates and burning rates are comparable in magnitude. The lack of enough premixing causes the formation of rich fuel and air mixture leading to formation of soot and high temperature regions near the diffusion flame leading to formation of high NOx emissions. Hence both NOx and soot are simultaneously formed during the progress of diesel combustion and any attempt towards reduction of one leads to increasing the other, giving rise to the challenging situation of NOx –PM trade-off. Though one of the advantages with conventional combustion is because we have injection starting commencing just before start of combustion, we can control the combustion phasing by altering the injection process. In other words, we can say that combustion phasing is closely coupled to injection process. Regarding the engine design and operating parameters, it is also worth noting that the heat release rate of mixing-controlled phase is significantly impacted by fuel injection rate or fuel injection pressure. The injection rate achieved by higher injection pressure, higher swirl level, optimized bowl geometry and multiple injection can increase the heat release rate during mixing-controlled phase. However, other engine parameters like intake air temperatures can increase the pressure and temperature at the end of compression impacting largely the ignition delay and hence the premixed combustion may also impact the diffusion peak flame temperatures and mixing rates, but it is known to have minor impact on mixing-controlled combustion. Increasing boost and timing advance can impact the premixed combustion but known to have less impact on mixing-controlled combustion. In other words, we can say that because in case of conventional diesel combustion, combustion phasing is well controlled and is dependent on injection timing, we can proportionately change the combustion phasing either retard or advance with change in injection timing (retard or advance). On the other hand, HCCI combustion where fuel and air are fully premixed is very sensitive to temperature conditions. Here the start of combustion is dependent on auto-ignition chemical kinetics. Here unlike diesel combustion, the combustion phasing control means controlling the auto-ignition which are in turn depends on the charge temperature and pressure history and charge composition. Hence intake temperature variation is a common means of controlling the combustion phasing. But under practical engine operating high load condition, where already gas temperatures and wall and surrounding temperatures are high, we need to maintain much lower intake air temperatures to achieve optimum combustion phasing in case of HCCI, which becomes quite challenging. Further because of the homogeneity of the prevailing charge inside the cylinder, the combustion is quite spontaneous and abrupt, thus leading to severe rise in cylinder pressure and pressure rise rates, which can be even higher at high load operating conditions. With advanced combustion techniques like PPC as mentioned by Johansson et al. (2009), we can adequately achieve premixing by extending the ignition delay without losing much of combustion control. There are different ways to extend the ignition delay:

100

• • • •

S. Dev

injecting fuel very early using lower cetane fuel using lower compression ratio using high level of dilution.

Due to extended ignition delay, the mixing is sufficient to avoid local-rich pockets, thereby reducing soot formation and the high dilution used lower the peak cylinder temperatures which significantly reduces the NOx emission. With PPC we can also exercise better control over combustion phasing. PPC being a regime of combustion between conventional diesel combustion and HCCI, here the combustion phasing will respond to both intake temperature and injection strategy and due to prevailing charge stratification or induced in-homogeneity better control of combustion is possible. Further the combustion is quite fast in case of PPC, making it suitable for achieving very high engine efficiency, very low emissions and better control of combustion phasing. Low cetane fuels are the topic of interest in this chapter. Fossil fuels like gasoline and alternate fuels like alcohols (ethanol and methanol) are high in octane numbers, i.e., due to high ignition resistance of such fuels it makes them a suitable fuel for PPC type of advanced combustion regimes. Their high octane characteristics enable them to achieve higher ignition delay causing high premixing of fuel and charge before combustion. Though gasoline can also be good candidate for PPC but due to inherent fuel characteristics they are higher on soot as compared to alcohol fuels. In a study, by Johansson et al. (2010a), different fuels like ethanol and fuels in the range of boiling point of gasoline were investigated in PPC. An advanced injection strategy was adopted as with high octane fuels in compression ignition (CI) engine can result in high pressure oscillations immediately succeeding the combustion event. Under this strategy, the first injection is placed very early in compression stroke and was meant for creating the premixed charge, while the second is injected close to TDC to trigger the combustion event. The fuel amount in first is independent on load and is function of compression ratio, fuel reactivity and EGR levels. The second injection was used to control load and combustion phasing. Table 4.1 shows the engine operating conditions and Table 4.2 shows the performance and emissions achieved on heavy-duty single-cylinder compression ignition engine. Typically for heavy-duty engines we prefer wider bowl with lower compression ratio which complement each other. Though for conventional combustion higher compression ratio is leveraged to gain in engine efficiency, for such advanced combustion engine with dilution and boosting already high, lower compression ratio enables pressure rise rates to acceptable levels at high load operation and wider bowl with their lower surface area have Table 4.1 Engine operating conditions (Johansson et al. 2010a)

Engine speed

1300 rpm

Engine IMEPg

~18 bar

CR

14.3

Dilution

45% EGR and Lambda ~1.6

4 Methanol: A Gateway to Biofuel Revolution … Table 4.2 Performance and emissions (Johansson et al. 2010a)

101

Combustion efficiency

~99.6%

Thermodynamic efficiency

~55%

Gas exchange efficiency

~92%

Mechanical efficiency

~96%

Brake thermal efficiency

~48.5%

NOx

~0.25 g/ikWh

Smoke

~0.06 FSN

CO

~1.2 g/ikWh

HC

~0.5 g/ikWh

Heat transfer

~19%

Combustion duration, CA90-CA10

~16.5 deg CA

PRR

~20 bar/deg CA

lower heat transfer losses which helps in achieving high thermodynamic efficiency. Hence to limit the peak pressures rise rates at high load operation, compression ratio was reduced to 14.3. With regard to swirl levels we generally avoid using very high swirl levels or charge motion with such advanced combustion concepts. In case of heavy-duty vehicles, particularly at high load, the mixture formation is mostly dominated by injection process and free jet unlike small or medium size engines were swirling motion is also important in mixture formation. Moreover, longer ignition delay also supports the mixing process. Moreover, very high swirl would result in higher flow losses and higher heat transfer losses. However, swirl, spray cone angle and bowl should be well matched as it impacts largely the precombustion mixing and late cycle oxidation. High quality dilution plays an important role in such advanced combustion techniques. As per one of the lecture (Johansson et al. 2018) on advanced IC engine technologies by Prof. Bengt, there are three temperature levels to be worried; first being the attainment of 1000 K to start the burning, maintaining higher than 1500 K for enough CO oxidation and temperatures lower than 2000 K for avoiding the thermal NOx formation. And maintaining EGR of 50% and Lambda ~1.5 the maximum temperature is always within 1500–2000 K and this seems to be applicable for all load and speed points. Further with such quality dilution offers number of useful benefits; first we have leaner mixture which increases the isentropic exponent, which in turn increases the useful work output; secondly, the peak gas temperature reduces the heat transfer losses; and thirdly, with reduced oxygen content and reduced in-cylinder temperatures, NOx emissions are greatly reduced. The test results obtained were very encouraging. The engine experimentation with PPC achieved very high thermodynamic efficiency of 55% (Johansson et al. 2010a). The thermodynamic efficiency measures the efficiency of conversion of heat released during the fuel combustion because of fuel’s chemical energy to useful work available at the piston face. The heat transfers were achieved between 20 and 25%. In this test point and for fuel ethanol heat transfer is at 19%. The two basic

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factors as mentioned by author for such low heat transfer are for such high octane fuels the mixing period is relatively short for loads higher than 7 bar IMEPg, which means most of the combustion is confined in bowl and spray-wall interactions are avoided. Secondly, the combustion duration is between 10 and 25° CAD, which is an indication of faster combustion. In this case the combustion duration is quite fast and impressive at ~16.5° CA. To maximize thermodynamic efficiency we need to optimize the combustion phasing which witnesses a trade-off between the high heat transfer and effective expansion work. Advancing combustion phasing too much can raise the heat losses, whereas retarding too much can be harmful on effective expansion work. Gas exchange process is actually a challenging area as achieving very high values of gas exchange efficiency when using high dilution is largely demanding on turbocharger efficiency. With higher EGR% we require higher lambda to maintain the dilution; higher lambda requirement though known to be improving thermodynamic efficiency can be detrimental on gas exchange process as turbine inlet temperatures fall and also the flow losses are high which can impair the gas exchange efficiency. In other words, situation can be like though with higher dilution we could achieve higher thermodynamic efficiency but ultimately we may land up in lesser optimized brake thermal efficiency. There is a practical limit on delta P (exhaust-intake manifold pressure) which drives the EGR. With higher and higher EGR% requirement, there is an increase in turbocharger overall efficiency. The turbocharger overall efficiency is defined as below by Eq. 4.1: ηTC = ηc × ηm × ηT

(4.1)

ηTC = overall turbocharger efficiency, % ηc = compressor isentropic efficiency, % ηm = mechanical efficiency of turbocharger, % ηT = turbine isentropic efficiency, % These efficiency terms actually are the ratio of actual work to isentropic compression work or isentropic expansion work in compressor and turbine, respectively. Hence, we substitute the turbine and compression efficiency terms as mentioned below by Eq. 4.2:   1 − (Pamb /PExh )(γT − 1/γT ) = (m C × C PC × Tamb )/(m T × C P T × TExh ) × (1/ηT C )   × (PI n /Pamb )(γC − 1/γC ) − 1 where Pamb = ambient pressure, bar PExh = desired exhaust manifold pressure, bar γ = ratio of specific heat T, C = turbine and compressor

(4.2)

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103

m = mass flow rate, kg/h T amb = ambient temperature, K T Exh = exhaust manifold temperature, K ηTC = over all turbocharger efficiency, % PIn = desired intake manifold pressure, bar. The above equation is actually representing the turbocharger energy balance. The turbocharger work balance is the work required by the turbine to operate the compressor to meet desired fresh air and EGR. The turbocharger design and resulting efficiency help define the work balance and thus relative placement of turbine inlet pressure and compressor output pressure selected to drive sufficient EGR. Further incylinder pressure is again dependent on turbocharger work balance, losses in intake manifold and exhaust manifold across valves, which are again captured in engine volumetric efficiency (Stanton 2013). If we see the above equation, we find that with higher value of overall turbocharger efficiency and higher exhaust manifold temperatures we can reduce the required engine back pressure for given intake manifold pressure, and if we are able to reduce back pressure we can reduce the engine pumping work, which will directly impact the gas exchange efficiency. Improving gas exchange efficiency calls for improvement in many areas, and some are mentioned here: • Optimizing the exhaust temperatures such that they are not fallen to very low levels and we can maintain reasonable engine back pressures without affecting the engine pumping work. • Variable geometry turbochargers can be very effective in creating the engine delta P for EGR flow and also maintaining the engine pumping work at lower levels by providing sufficient boost. • Minimizing the flow losses through EGR piping, turbocharger lines, intercooler, EGR cooler, manifold, port and valves, i.e., maintaining higher volumetric efficiency can also help maintain the intake manifold and in-cylinder pressure at adequate level and will put less demanding requirement on engine back pressure for achieving the required intake manifold pressure. • Effective cooling of charge in intercooler after compressor is another way through which we can reduce the intake manifold temperature and maintain the desired intake manifold pressure. It is really challenging that now with regulation being applied to wider area of engine operating zone, getting good and wider turbocharger matching so that high efficiency zone of such devices coincides with most of the mass flow parameters and pressures requirements of the engine calls for significant optimization in compressor and turbine design parameters. The author (Johansson et al. 2010a) was able to achieve highly encouraging values of brake thermal efficiency along with extremely low emissions with alcohol fuels. It was shown that with the use of ethanol brake thermal efficiency of 48.5% with extremely low emissions is possible at such high load operating conditions. It is

104

S. Dev

estimated that a heavy-duty truck running with such efficiency levels can reduce the GHG emissions by ~20% from conventional diesel truck. The test results showed NOx emission in the range of 0.25 g/ikWh and smoke emissions in the range of 0.06 FSN. The extremely low values of NOx emissions are possible due to high dilution which has reduced the in-cylinder temperatures to low values. One of the advantages of using alcohol fuels are higher oxygen content which tremendously helps to reduce the soot emissions compared to other fuels under such high load operating conditions with high dilution. Also, wide difference in engine-out smoke emissions is observed when comparing oxygenated fuels with other gasoline range fuels at even high load operations. However, the pressure rises rates (PRR) were on higher sides. Pressure rise rates of the order 20 bar/deg CA were witnessed at higher loads. As mentioned by the author, this is one of the hurdles for attaining PPC at high load conditions towards achieving higher thermodynamic efficiency. It was also concluded that for loads higher than 12 bar IMEPg, fuels with RON higher than 95 shows value of PRR ~20 bar/deg CA, decreasing the RON to 90 as it drops to 15 bar/deg CA with octane rating as 70. It is close to 12.5 bar/deg CA. In case of ethanol the PRR values could be reduced, however, that would require retarding the combustion phasing which will penalize the engine thermodynamic efficiency levels. In brief, • Brake thermal efficiency as high as 48.5%, thermodynamic efficiency as high as 55% with extremely low emissions of NOx 0.25 g/kWh and smoke at 0.06 FSN with ethanol as fuel shows the overwhelming potentials of PPC for meeting the goal of 50–55% engine efficiency. Also, future emissions norms where NOx particularly would see another 93% reduction from present levels, using alcohol fuels like ethanol/methanol can prove to be really promising for PPC like combustion systems. • Lean combustion is the only option suitable for making future engines with highest possible engine efficiencies; however, high turbocharger efficiencies are one of the key requirements. • With regard to GHG emissions such advanced combustion approach can be pathways for meeting future GHG emissions target of net zero CO2 emissions by 2050. • However, some concerns like low load combustion in-stability with high octane fuels, high pressure rise rates at high loads needs to be researched further for making them little more suitable. • Such advanced combustion concepts with high octane biofuels greatly complement each other in realizing very high engine efficiency, low engine-out emissions and can lead to net zero CO2 emissions in future.

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4.4.2 Reactivity-Controlled Compression Ignition Reactivity-controlled compression ignition (RCCI) is another advanced combustion concept which too has shown very encouraging results on both performance and emission sides. RCCI refers to in-cylinder blended premixed combustion. It involves port injection of low reactivity fuel (ethanol, methanol, gasoline and natural gas) and direct injection (diesel, DME) of high reactivity fuel. Till now we have been discussing about charge stratification, and from now onward RCCI will include both reactivity (PRF number) and charge stratification (equivalence ratio) to achieve high engine efficiency and very low emissions along with acceptable pressure rise rates. Higher the reactivity gradient between the fuels, the greater is the aid in extending the combustion duration and reducing the PRR at high load conditions. The load control is achieved by altering the reactivity. Here we use multiple injection, and the last injection acts as the ignition source for local concentration of high reactivity fuel. We will discuss one of the interesting results obtained by Reitz et al. (2011) for E85-diesel and gasoline-diesel. One of the issues with premixed combustion is the high heat release rates and high pressure rise rates at high load conditions. In case of RCCI because of spatial stratification in fuel reactivity this can be controlled to great extent. In RCCI the PRF (auto-ignition characteristic of charge) is calculated as below by Eq. 4.3: RON = 100xiso−octane + 107xethanol

  xiso−octane + xnheptane + xethanol

(4.3)

Here in this work (Reitz et al. 2011), when the cut-section of the combustion chamber was analysed for mass distribution of RON for both the gasoline-diesel blend and E5-diesel blend, an interesting observation was noticed that gasolinediesel has more mass at lower RON and E85-diesel fuel blends have a larger range of RON distributed. That is E85-diesel has larger degree of fuel reactivity stratification. And this behaviour along with the ethanol inhibitor effect on diesel low temperature reactions contributed to the extended high temperature heat release duration for E85-diesel blend as compared to gasoline-diesel blend. Tables 4.3 and 4.4 show the engine operating condition, performance and emission results obtained. We will now discuss some excellent results obtained with E85-diesel blend. Table 4.3 shows some interesting observation like high percentage of diesel substitution as the main fuel here is ethanol. The port fuel percentage is 83%. The injection pressure requirements are quite low in case of direct injection of diesel fuel. The CA50 is very well optimized at ~10° atdc at such high load with high gross indicated efficiency of ~52% and acceptable pressure rise rates of ~6 bar /deg CA. The high gross indicated efficiency is due to lower heat transfer losses and faster combustion with combustion duration ~18 deg CA. The engine out NOx and PM are at extremely low levels of ~0.05 g/kWh and ~0.007 g/kWh, respectively. With such low levels of NOx and PM emissions, the dependency on costly after-treatment is tremendously reduced.

106 Table 4.3 Engine operating conditions (Reitz et al. 2011)

Table 4.4 Performance and Emissions (Reitz et al. 2011)

S. Dev Engine speed

1300 rpm

Engine IMEPg

~16.5 bar

CR

15.0

Dilution

47% EGR and Lambda ~1.1 (charge based)

1st direct injection—diesel timing

55° btdc

1st direct injection—diesel percentage

~60%

2nd direct injection—diesel timing

36° btdc

2nd direct injection—diesel percentage

~40%

Port injection timing

−360°

Port fuel mass percentage

83%

Direct injection pressure

800 bar

Port injection pressure

4.14 bar

CA50

~10° atdc

Combustion duration, CA90-CA05

~18° CA

Gross indicated efficiency

~52%

NOx

~0.05 g/kWh

PM

~0.007 g/kWh

CO

~7.0 g/kWh

HC

~2.0 g/kWh

PRR

~6 bar/deg CA

The high CO and HC emissions at this load conditions is due to operation close to stoichiometric and changing to slightly leaner operation can solve this problem. In another low temperature advanced combustion approach, Verhelst et al. (2019) have shown impressive results for a medium speed and full load operating condition of a heavy-duty engine. Table 4.5 shows the engine operating conditions. The simulation results obtained are shown in Table 4.6. The benefit on engine brake efficiency could be attributed to reduction in incylinder exhaust loss. Also due to higher octane number of methanol all fuels could be injected into cylinder before start of combustion. Though here soot emissions are not shown but it is believed and mentioned that with fuel like methanol soot will never be an issue and there are already discussed studies which has shown that soot with methanol are several magnitude lower than gasoline.

4 Methanol: A Gateway to Biofuel Revolution … Table 4.5 Engine operating conditions (Verhelst et al. 2019)

Table 4.6 Performance and emissions (Verhelst et al. 2019)

Table 4.7 Engine operating conditions (Reitz et al. 2012)

107

Engine speed

1400 rpm

Engine load

100%

CR

17.3

EGR%

15.6

Lambda

1.45

Engine brake efficiency

44.5%

NOx

0.30 g/kWh

Combustion duration

23.8 deg CA

Engine speed

1550 rpm

Engine IMEPg

16.0 bar

CR

16.0

EGR%

32% EGR

1st direct injection—diesel timing

81° btdc

1st direct injection—diesel percentage

49%

2nd direct injection—diesel timing

39.7° btdc

2nd direct injection—diesel percentage

51%

Port fuel mass percentage

87%

Direct injection pressure

594 bar

CA50

~14° atdc

Next, we would like to consider another interesting research by Reitz et al. (2012), where RCCI was performed using natural gas as low reactivity fuel and diesel as high reactivity fuel. Tables 4.7 and 4.8 shows the engine operating condition, performance and emission results for the study. It is quite worth mentioning here that though results not shown, but up to 13.5 IMEPg there was no dilution requirement and still high efficiency and extremely low emissions were achieved. This might be attributed to larger reactivity stratification obtained in case of diesel and natural gas blend. The centroid of combustion is slightly Table 4.8 Performance and emissions (Reitz et al. 2012)

Gross indicated efficiency

~49.2%

NOx

~0.15 g/kWh

PM

~0.003 g/kWh

CO

~0.5 g/ikWh

UHC

~1.5 g/ikWh

PRR

~5.7 bar/deg CA

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retarded here in case of natural gas-diesel RCCI operation. Also, the gross indicated efficiency is slightly lower at 49.2%. Also as mentioned by author the higher adiabatic flame temperatures in case of natural gas could also increase the heat transfer and result in slightly lower indicated efficiency. With methane due to its ultralow reactivity, at high load like 23 bar IMEPg, as mentioned by author combustion efficiency becomes an issue and this increases both CO and UHC emissions similar to low load case. With late second injection of diesel can alleviate this situation by creating a local concentration of high reactive fuel. In brief, • RCCI advanced combustion approach are more premixed approach. • With greater range of reactivity stratification inside cylinder, it is possible to achieve extremely low emissions, high engine efficiencies with lower EGR requirement and acceptable pressure rise rates. • If improved for low load combustion stability, such advanced combustion technologies when utilized with biofuels like ethanol, methanol and natural gas can be undoubtedly the another future sustainable engine technologies for meeting the next upcoming harder NOx emissions norms of 0.027 g/kWh levels and it is worth mentioning that such upcoming emission levels can be met with lower conversion efficiency and lower complexity requirements for selective catalytic converter (SCR). Presently, the industry practice maintains typically engine out NOx to be at 4–5 g/kWh and requires SCR conversion efficiency of ~90–92%. This is because maintaining engine-out NOx at such levels gives typically optimum fluid consumption (diesel + urea) on field. However, this requirement on SCR conversion efficiency has to be increased largely to ~99% for meeting upcoming NOx emission norms. It is worthy to mention that RCCI holds a tremendous potential in maintaining engine out NOx levels at very low levels together with high benefits on engine brake efficiency and that too with acceptable noise levels.

4.4.3 Stoichiometric Combustion Stoichiometric combustion involving spark ignition of premixed charge is another widely accepted engine combustion technology due to its simplicity with aftertreatment system and ease with which they can achieve reasonable engine efficiency and extremely low emissions. Around the world there is immense effort to increase the engine efficiencies for making it at par with its diesel engine counterpart while maintaining very low emissions with simplified after-treatment. In a study by Naganuma et al. (2012), they have achieved engine brake efficiency of 42% with very low NOx emissions with fuel as methanol. Tables 4.9 and 4.10 show the engine operating conditions, performance and emissions obtained. Unlike conventional SI engine where throttle is used to control the engine load and which accounts for major part of engine efficiency losses at part load, here WOT

4 Methanol: A Gateway to Biofuel Revolution … Table 4.9 Engine operating conditions (Naganuma et al. 2012)

Table 4.10 Performance and emissions (Naganuma et al. 2012)

109

Engine speed

Wide range

Engine BMEP

11.6 bar

CR

19.5

EGR%

30% EGR, Lambda 1.0–1.5

CA50

~4.5° atdc

Brake efficiency

~42%

NOx

~0.0 g/kWh

+ EGR is used as load control strategy. Load was controlled by varying the amount of EGR and keeping the throttle position mostly at wide open position. Also, with the use of EGR the heat transfer losses were reduced which also enhanced the engine efficiency. The author demonstrated high engine brake efficiency levels close to 40– 42%. Such brake efficiency levels are quite a big achievement from a stoichiometric engine and is almost comparable to present diesel engines at many instances. NOx emissions were also at extremely low levels close to zero for low-medium load regions. The benefits of engine brake efficiency were possible due to switching to WOT + EGR as strategy to control load which led to reduction in losses and also enabled the wide application of EGR which reduced the NOx emissions to such low levels. Stoichiometric engines working on natural gas have also been a popular choice for many OEMs. For fuels like natural gas, stoichiometric engines have already shown encouraging results. However, in case of natural gas, one of the challenging pollutants to control is methane itself, which is very hard to oxidize. Hence, in case of stoichiometric combustion with methane, any attempt to maximize the engine efficiency would need the combustion to be made leaner and this would drastically deteriorate the oxidation of methane in three-way catalyst further. According to (https://dieselnet.com/tech/engine_natural-gas_heavy-duty.php#si), there are stoichiometric heavy-duty engines working on natural gas with throttle body injection and three-way after-treatment achieving 39% BTE (brake thermal efficiency) and NOx emission (FTP) as 0.15 g/bhp-hour and PM as 0.003 g/bhp-hour with methane emissions as 1.06 g/bhp-hour. Another prime issue when trying to improve the BTE by increasing the compression ratio is knock limitation, which is a widely known inherent issue with stoichiometric engines. However, there is considerable thrust in improving the engine brake efficiency in such stoichiometric engines. Most of such advanced research aim to either decrease the combustion duration so that the flame travels the end of combustion chamber before occurrence of knock or try to reduce the end gas temperatures and pressures so that prior spontaneous ignition do not occur. There is a work by company Hyundai (Lee et al. 2017), where advanced spark ignition system, cooled EGR and late intake valve closing (LIVC) were used to

110

S. Dev

achieve an impressive BTE of 44% on stoichiometric engine. They have used cooled EGR for both low and high load for getting improvement in BTE. In brief, • The only attraction of stoichiometric combustion is the ease with which they can achieve extremely low engine out emissions under most of the time. The threeway catalyst, most of the time, operates with highest conversion efficiency and is simpler and cost-effective than other market available emission control strategies. • Engine efficiencies are also at reasonable levels and there is immense thrust to further enhance the engine BTE with technologies like advanced ignition system enabling use of higher compression ratios, higher dilution levels to limit knock tendencies or use of delayed intake valve closing for reducing the end gas temperatures and pressures. Prechambers though not discussed here are also one great possible alternate for improving the combustion duration and enhancing the engine efficiencies. • Methane emissions are always a concern though it is less with stoichiometric combustion and more serious concern with lean combustion approaches. Advanced catalyst performance to reduce methane are latest research trends.

4.4.4 Multiple Combustion Mode With a single advanced combustion approach mapped to the entire engine operating range, there can be certain limitations. High octane fuels with ON greater than 90 have difficulty in combustion and may lead to combustion stability issues at low load, and at high load under PPC-like condition can result in high pressure rise rates. And at full load due to prevailing in-cylinder high temperatures and pressures, there could be significant overlapping of injection and combustion process. In another research by Johansson et al. (2019), it has been observed that engine becomes fuel flexible at high or full load. And under such full load situation premixed combustion would be much lower and the combustion would transition to diffusion combustion representing the typical diesel combustion. There would be no clear distinction between the cylinder pressure and heat release rate. Moreover, all the investigated fuels with wide-ranging PRF from 0 to 100 combusted in a broader sense almost similarly at high loads conditions. Though for the highest PRF of 100 which showed some premixed combustion but are still minute to the large diffusion dominant combustion. Hence at full load all fuels, at least irrespective of their auto-ignition quality, burn like standard diesel combustion. Under such conditions emissions could go high, except for fuels like oxygenated ones which due to their molecular structure could still exhibit lower emissions. On the other hand, to address the low load we can use stoichiometric combustion which could reduce the combustion in-stability issues with high octane fuels. From medium to high load we can switch to advanced combustion regimes. Figure 4.2 shows one such multiple combustion mode strategy when working with alcohol fuels. Spark-assisted compression ignition (SACI) is another intermediate combustion mode between regular flame propagation as in a

4 Methanol: A Gateway to Biofuel Revolution …

111

Fig. 4.2 Multiple mode combustion strategy for alcohol fuels

spark ignition and auto-ignition in HCCI (Johansson et al. 2010b), and it can be utilized in case if the ignition delay is becoming too longer with high octane fuels in mid to high load region. This is, however, a representation as the actual boundary of different combustion regimes would extend or shrink depending on characteristics like engine speed and load range, efficiency of air-handling system available, fuel property etc. Such multiple mode combustion strategy can yield slightly higher emissions at full load when used with gasoline fuels because when using gasoline EGR may be restricted to limit soot formation. Because with gasoline soot formation will be slightly higher than in case of alcohol fuels which could be due to high tolerance of EGR with alcohol fuels because of their lower stoichiometric air requirements and high oxygen content. And then this could be demanding on after-treatment conversion efficiencies. There is another research work (Nieman et al. 2019) which has already achieved very high engine BTE and reasonably lower engine out emissions with multiple mode combustion strategy. In this work they have mapped the following combustion regimes over the engine operating range. • Load below 5 bar bmep: Conventional diesel combustion • Load up to 15 bar bmep: RCCI combustion • Load above 15 bar bmep: Pilot dual fuel combustion It is interesting to note that unlike the previously discussed strategy they have used diesel combustion here for low load because in this multiple combustion mode they have two fuels on-board, one with low reactivity (natural gas) and another with high reactivity (diesel) and hence at low load they switch to diesel combustion mode leveraging the high ignitability characteristics of diesel fuel. Tables 4.11 and 4.12 show the engine operating characteristics, performance and emissions. In brief,

112 Table 4.11 Engine operating conditions (Nieman et al. 2019)

Table 4.12 Performance and emissions (Nieman et al. 2019)

S. Dev Engine speed

1000 rpm

Engine BMEP

20 bar

CR

18.0

EGR%

20% EGR, Lambda ~2.2

Brake efficiency

47.5%

NOx

5–6 g/kWh

Smoke

52 °C, respectively. According to UN, any liquid fuel having flash point below 23 °C is extremely flammable. Hence methanol is classified as extremely flammable liquid. Flammability limit is the concentration range within which the vapor can burn in air. Flammability range for methanol is 6 – 36% v/v, which is much wider than that of gasoline and diesel [1.4–7.6% v/v/ and 1–6% v/v]. Gasoline and methanol possess nearly neutral buoyancy and their accumulation in low, and the confined spaces are prone to explosion hazard. However, autoignition temperature of methanol (463 °C) is much higher than gasoline (280 °C) and diesel (210 °C), which makes it relatively safe fuel. Fire prevention of methanol mainly includes vapor prevention and removal of ignition sources. Both measures are discussed in detail in the following sub-sections: Vapor Control: Internal floating roof tanks are used to reduce the air, which can mix with methanol vapors. A special type of non-aluminum alloy flame arrester can be used to control the fumes that are emitted from vents. Inert gas padding can also be done. This padding provides protection against ignition within the tank vapor space, which also helps in maintaining methanol purity. Moreover, pressure relief valves along with flare headers can be used to measure the internal pressure of the tank. Use of over flow valves should be avoided since accumulation of liquid methanol also creates a fire hazard. Methanol vapor detection systems should be used to give warning to prevent the risk of methanol accumulation. Removal of Ignition Sources: Potential fire and explosion causing sources should be kept away from the methanol storage area. Fuel storage area and region where methanol vapors could be present should be designated as hazardous locations with appropriate sign boards as shown in Fig. 5.4. Also, specific rules must be followed in such areas as mentioned below: • • • •

Smoking should be prohibited. Vehicle entry should be restricted. The use of electronic gadgets, which can cause a spark, should be prohibited. Ignition sources should not be present within at least 7 m radius of small volume containers of methanol, 17 m around storage and logistics area, and minimum 70 m around large containers of methanol (https://www.methanol.org/wp-content/upl oads/2017/03/Safe-Handling-Manual.pdf).

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Fig. 5.4 Methanol storage restricted area signage

5.5.2 Fire Detection and Control Generally, soot formation results in formation of smoke and yellow flames, which make fire detection easy for most fires/flames. However, methanol burns cleanly without any soot formation, hence smoke detection technique is not useful in methanol fire detection. Therefore, utilization of newer ways for fire detection is required. Contamination of air can be detected against leakage via monitoring the concentration of oxygen and carbon dioxide. Also, thermal imaging cameras can be used for fire detection and surveillance. Flame detectors can be used mainly in the infrared range for methanol flames. Methanol has low flash point, inherent oxygen, lack of radiations, and good miscibility in water. These properties demand different fire control techniques, which are discussed below: Fixed Fire Extinguishment: An automated local or total compartment fixed extinguishment is required for methanol storage space. Other than this, an automated foam application with high alcohol resistance, e.g., water mist/water spray can be used. Also, dry powder or carbon dioxide fire extinguishing systems can be used. Water based systems are useful because they allow quick activation, continuation in operations without harming the environment, and no contamination. A permanent drainage system should be provided to control the potential spill or leakage during operation. It should neutralize the spill with the use of water and foam. Some standard fire extinguishing systems and their effectiveness against methanol fires are discussed below. Gas Fire Extinguishment: Methanol is a liquid fuel, whose flames can be extinguished using gas fire extinguishment. Existing capacity of a fixed gas fire extinguishing systems is based on the minimum extinguishing concentration (MEC) of the agent to extinguish the flames of the targeted fuel. Methanol requires the highest

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concentration of the agent for fire extinguishment. MEC values for some common agents extinguishing methanol fire are CO2 (27.2%), N2 (88.7%), IG-55 (45.4%), and IG-541 (44.2%). Water Fire Extinguishment: Methanol fire extinguishment with water is difficult because methanol has very low flash point, low radiations, inherent oxygen, and wide flammability range. In this method, fire is controlled by flame cooling, dispersion of oxygen, fuel vapors, and minimization of generated radiant heat. During flame cooling, rate of fuel vapor supply to combustion zone is reduced via minimization of heat transfer from flames to the fuel. It ceases the combustion reactions of fuel/air mixture, thus extinguishing the flames. Methanol burns cleanly without soot formation, which leads to less radiative heat losses. Therefore, flame cooling is not sufficient for fire suppression. Oxygen dispersion is one of the best mechanisms of a water mist system functioned through the expansion of steam. However, this method is not as much valid for methanol as it is for other fuels. Foam Fire Extinguishment: The spray of fire extinguishing foams during fire creates a thin film, which reduces the release of fuel vapors from the surface and stops the combustion. Methanol fire requires alcohol resistant foam for extinguishment because conventional fire extinguishing foam decomposes instantly. Alcohol resistant foam mixing as an additive in water spraying or water mist systems can significantly improve their effectiveness against methanol fire.

5.5.3 Fire Safety with Methanol–Gasoline Blends Methanol is miscible in both gasoline and water, but its affinity toward water is higher compared to gasoline. Solution of methanol and water are not miscible in gasoline and it forms separate phases in the tank. If methanol–gasoline blends catch fire and it is suppressed with water, then a separate phase is formed and concentrates at the bottom of the blended fuel tank. Moreover, the situation becomes much complicated when a metal tank is subjected to heat flux from outside fire. Since the heat capacities of gasoline and methanol–water solution are significantly different, the rate of temperature rise in respective layers will also be different. The temperature of the gasoline layer rises at a faster rate than the methanol–water layer. In the case of a transportation accident, there is a high chance of “boiling liquid expanding vapor explosion” (BLEVE). In this case, over pressure and heat flux from the fireball depends on the amount of fuel remaining in the tank at the time of BLEVE. Fire control of methanol-gasoline blends is quite difficult, but it can be controlled. Gasoline burns with a visible flame, hence the gasoline portion of fire can be easily recognized. However, methanol–water flames burn with invisible, non-luminous flames. Therefore, two to three times more foam quantity must be used to ensure that it will suppress methanol–gasoline blend fire. However, the size of the spill, spread of the fire, and extinguishment strategy is to be decided based on the composition of fuel in the blend. Based on this, the type of foam and the required inventory of extinguishment can be selected.

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5.5.4 Methanol Fire Incidents In this section, various methanol fire incidents and their causes, including possible safeguards, have been discussed in detail. Figure 5.5 shows the statistics of methanol incidents notified by users in United States, Canada, Brazil, France, Italy, Germany, Sweden, China, India, Malaysia, South Africa, and Australia between 1998 and 2011 (https://www.methanol.org/wp-content/uploads/2017/03/Safe-Han dling-Manual.pdf). Industrial sector and biodiesel production units together reported ~56% methanol related fire incidents, whereas transportation sector reported ~27% accidents of all cases reported. Among all sectors, transportation, industrial, biodiesel production were the major sectors, where high number of methanol fire accidents occurred. It is clear that high number of cases were reported in the transport sector, out of which 50% fire incidents occurred during methanol road transport and 36% fire incidents occurred during methanol transport by railway. In all these incidents, a total of 26 fatalities and 49 injuries were reported. Out of which, transport related accidents accounted for the highest number of causalities, including 54% of all deaths and 18% of all injuries. Therefore, safeguards are required at methanol using sectors, especially in industrial and transportation sectors, to prevent the occurrence of methanol fire accidents. In this section, required safeguards such as process safety management, corrosion prevention, fire prevention along with responses, and employee training are discussed in detail.

Fig. 5.5 Statistics of methanol accidents between 1998 and 2011 (https://www.methanol.org/wpcontent/uploads/2017/03/Safe-Handling-Manual.pdf)

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Process safety management: Process safety management is a regulation enforced by Occupational Safety and Health Administration (OSHA). It focuses on technology, which ensures safe handling of hazardous materials during the processes involved in the system (https://www.osha.gov/Publications/osha3132.html). Generally, it covers all methods, including handling, storage, moving, or manufacturing highly hazardous chemicals. It mainly focuses on three primary objectives: (i) prevention of hazardous materials release for accident/ injury reduction, (ii) maintenance of processing equipment for ensuring safe operating conditions, and (iii) promotion of safety culture. Prevention of release of hazardous materials is required in order to minimize injuries, illnesses, and negative impacts on the environment. The following measures are therefore required in the workplaces, involving methanol: • Identify chemicals and process hazard in the workplace and take special precautions during methanol handling and processing. • Develop a system to respond workplace hazard such that it addresses mitigation, prevention, and emergency responses. • At regular interval of time, review the workplace and take necessary actions. • Implement the chemical process procedures, operating limitations, safety, and health considerations. • Prepare safety manuals and operating information for employees. • Conduct employee training on safety measures to prevent hazards. • Contractors and their employees must have appropriate knowledge about the chemicals and required safety precautions. • Provide education to employees and contractors for an emergency response to the accidents. Corrosion Prevention: Liquid methanol is electrically conductive, which makes it more susceptible to corrosion compared to other fuels. Conductivity increases the corrosion of alloys, such as aluminum, titanium and zinc alloys, which are commonly used for fuel handling. Methanol is an excellent solvent, therefore only selected plastics and rubber containers can be used for methanol storage. In addition, corrosion and solvent resistant materials should be used for methanol handling. Fire Prevention and response: Effective action plan in the fire response involves early detection, immediate response, and appropriate action. A brief about fire prevention and response has been discussed already. Employee Training: Employers must develop a written plan of actions to implement employee participation in hazard analyses and development of preventive measures against the same. Employers must inform all employees regarding hazards and risks associated with methanol and how to effectively control these risks. Operators need to be trained to follow the standard operating procedures, safety, and emergency responses. The training must include classroom training, on job training, and events such as mock-drills. Training should be given at the time of appointment and also periodically.

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5.6 Summary Methanol is a renewable fuel, produced from both petroleum based and nonpetroleum based feedstocks. It is environment friendly and cheaper than conventional fuels. Minor modifications are required for utilizing methanol blends in the existing ICEs . Further, being a liquid fuel, it can be efficiently stored and distributed. However, certain potential risks are associated with the use of methanol as alternative fuel due to its flammability and toxicity. Hence, effective control strategies, safety precautions, and certain modifications in the infrastructure are required during methanol handling. Effective control strategies include exposure control, ventilation, fire prevention, and use of personal protective equipment. In this chapter, various exposure control measures during methanol storage, transport, and refueling stations are discussed. Also, sources and routes of methanol exposures and their negative impact on the human body are discussed. Overview of various first aid measures against methanol exposure before seeking medical attention are briefly discussed. Methanol has flammable nature, hence it should be stored in dedicated well ventilated areas, where fire extinguishing equipment are available. Methanol fire detection is not easy because methanol burns cleanly without any smoke or visible flames. Hence, special precautions are required. Vapor control and removal of ignition sources are essential for fire prevention. In this chapter, various fire detection and control techniques are discussed. Foam fire extinguishers are found to be more suitable against methanol fires. Mixing a small concentration of alcohol resistant foam as an additive in a water spraying or water mist systems can significantly improve their effectiveness against methanol fires. Methanol possesses different miscibility levels with water and gasoline. In addition, heat capacities of methanol and gasoline are quite different. Hence, depending on the size of the spill, and the spread of fire, extinguishment strategy needs to be customized. In the past, most methanol accidents have occurred in the transportation and industrial sectors. The required safeguards in the industrial and transportation sectors to prevent the occurrence of methanol accidents are discussed in this chapter. Along with process safety management, periodical employee training and awareness are also essential. By ensuring these safeguards, risks associated with methanol handling can be considerably reduced. With reduced risks and its unsurmountable advantages from a sustainability point of view, methanol is fast emerging as the best alternative fuel option for the transport sector.

References A brief review of China’s methanol vehicle pilot and policy. https://www.methanol.org/wp-content/ uploads/2019/03/A-Brief-Review-of-Chinas-Methanol-Vehicle-Pilot-and-Policy-20-March2019.pdf Agarwal AK, Shukla PC, Patel C, Gupta JG, Sharma N, Prasad RK, Agarwal RA (2016) Unregulated emissions and health risk potential from biodiesel (KB5, KB20) and methanol blend (M5) fuelled

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transportation diesel engines. Renew Energy 98:283–291. https://doi.org/10.1016/j.renene.2016. 03.058 Blumberg T, Morosuk T, Tsatsaronis G (2018) Methanol production from natural gas–a comparative exergoeconomic evaluation of commercially applied synthesis routes. In: 5th international exergy, life cycle assessment, and sustainability workshop Gong C, Peng L, Chen Y, Liu J, Liu F, Han Y (2018) Computational study of intake temperature effects on mixture formation, combustion and unregulated emissions of a DISI methanol engine during cold start. Fuel 234:1269–1277. https://doi.org/10.1016/j.fuel.2018.08.018 Jia Z, Denbratt I (2018) Experimental investigation into the combustion characteristics of a methanol-Diesel heavy duty engine operated in RCCI mode. Fuel 226:745–753. https://doi.org/ 10.1016/j.fuel.2018.03.088 Kumar S, Cho JH, Park J, Moon I (2013) Advances in diesel–alcohol blends and their effects on the performance and emissions of diesel engines. Renew Sustain Energy Rev 22:46–72. https:// doi.org/10.1016/j.rser.2013.01.017 Li G, Zhang C, Li Y (2016) Effects of diesel injection parameters on the rapid combustion and emissions of an HD common-rail diesel engine fueled with diesel-methanol dual-fuel. Appl Therm Eng 108:1214–1225. https://doi.org/10.1016/j.applthermaleng.2016.08.029 Marlin DS, Sarron E, Sigurbjörnsson Ó (2018) Process advantages of direct CO2 to methanol synthesis. Front Chem 6:446. https://doi.org/10.3389/fchem.2018.00446 Maurya RK, Agarwal AK (2014) Experimental investigations of performance, combustion and emission characteristics of ethanol and methanol fueled HCCI engine. Fuel Process Technol 126:30–48. https://doi.org/10.1016/j.fuproc.2014.03.031 Methanol Production. https://methanolfuels.org/public-policy/asia-pacific-middle-east/ Methanol safe handling manual. https://www.methanol.org/wp-content/uploads/2017/03/Safe-Han dling-Manual.pdf MMSA global methanol supply and demand. https://www.methanol.org/methanol-price-supplydemand/ Ning L, Duan Q, Chen Z, Kou H, Liu B, Yang B, Zeng K (2020) A comparative study on the combustion and emis-sions of a non-road common rail diesel engine fueled with primary alcohol fuels (methanol, ethanol, and n-butanol)/diesel dual fuel. Fuel 266:117034. https://doi.org/10. 1016/j.fuel.2020.117034 Process safety management OSHA. https://www.osha.gov/Publications/osha3132.html Production of bio-methanol. https://iea-etsap.org/E-TechDS/PDF/I09IR_Bio-methanol_MB_Jan 2013_final_GSOK.pdf Statistical Review. https://www.bp.com/content/dam/bp/business-sites/en/global/corporate/pdfs/ energy-economics/statistical-review/bp-stats-review-2019-full-report.pdf Subramanian KA (2019) Experimental investigation on effects of oxygen enriched air on performance, combustion and emission characteristics of a methanol fuelled spark ignition engine. Appl Therm Eng 147:501–508. https://doi.org/10.1016/j.applthermaleng.2018.10.066 The Global Climate in 2015–2019. https://library.wmo.int/doc_num.php?explnum_id=9936 Tian Z, Zhen X, Wang Y, Liu D, Li X (2020) Comparative study on combustion and emission characteristics of methanol, ethanol and butanol fuel in TISI engine. Fuel 259:116199. https:// doi.org/10.1016/j.fuel.2019.116199 Valera H, Agarwal AK (2019) Methanol as an alternative fuel for diesel engines. In: Methanol and the alternate fuel economy. Springer, Singapore, pp 9–33. https://doi.org/10.1007/978-981-133287-6_2 Valera H, Agarwal AK (2020) Future automotive powertrains for india: methanol versus electric vehicles. In: Alternative fuels and their utilization strategies in internal combustion engines. Springer, Singapore, pp 89–123. https://doi.org/10.1007/978-981-15-0418-1_7 Valera H, Singh AP, Agarwal AK (2020) Prospects of methanol-fuelled carburetted two wheelers in developing countries. In: Advanced combustion techniques and engine technologies for the automotive sector. Springer, Singapore, pp 53–73. https://doi.org/10.1007/978-981-15-0368-9_4

138

O. Yadav et al.

Verhelst S, Turner JW, Sileghem L, Vancoillie J (2019) Methanol as a fuel for internal combustion engines. Progress in Energy and Com-Bustion Science 70:43–88. https://doi.org/10.1016/j.pecs. 2018.10.001 Why methanol is viable alternative fuel for India. https://energy.economictimes.indiatimes.com/ energy-speak/why-methanol-is-a-viable-alternative-fuel-for-india/2533 Yao D, Ling X, Wu F (2016) Experimental investigation on the emissions of a port fuel injection spark ignition engine fueled with methanol–gasoline blends. Energy Fuels 30(9):7428–7434. https://doi.org/10.1021/acs.energyfuels.6b01586 Yao C, Pan W, Yao A (2017) Methanol fumigation in compression-ignition engines: a critical review of recent academic and technological developments. Fuel 209:713–732. https://doi.org/10.1016/ j.fuel.2017.08.038 Zhang ZH, Cheung CS, Yao CD (2013) Influence of fumigation methanol on the combustion and particulate emissions of a diesel engine. Fuel 111:442–448. https://doi.org/10.1016/j.fuel.2013. 05.014 Zincir B, Deniz C, Tunér M (2019) Investigation of envi-ronmental, operational and economic performance of methanol par-tially premixed combustion at slow speed operation of a marine en-gine. J Clean Prod 235:1006–1019. https://doi.org/10.1016/j.jclepro.2019.07.044

Part III

Application Aspects

Chapter 6

Combustion and Emission Analyses of a Diesel Engine Running on Blends with Methanol György Szabados , Justas Žaglinskis , Kristóf Lukács , and Ákos Bereczky Abstract The ambient air around us is continuously and increasingly loaded and polluted through emission that comes from different sectors, especially from the transportation sector. This fact is due to the growing energy consumption in the transport sector which is forecasted worldwide in the nearer and far future. Bio-based energy may be consumed in an increasing way in the sector until 2050. Methanol, and if it is produced on bio-basis, called bio-methanol, is the simplest alcohol. Methanol costs less than other automotive alternative alcohols, for example, ethanol or butanol, so it may be among the cheapest technical alcohols. As for methanol’s structure, it contains 30% more inherent oxygen on a molecular base than fossil diesel. The aim of this research is to give comprehensive overview about the methanol’s effect on the combustion and emission properties of a diesel engine. During the analyses of combustion and emission characteristics the most relevant parameters have been included. The study also contains calculations regarding theoretical combustion (oxidation process) of the different hydrogen-carbons. A rarely investigated parameter, O2 consumption or demand is also in focus, besides CO2 emission and intensity throughout the calculations. For our experimental test series, diesel fuel was the base fuel and it has been mixed with biodiesel first, and this mixture has been further blended with methanol. Methanol’s theoretical contribution to the diesel–biodiesel blend’s O2 consumption and CO2 emission is a small amount. Engine’s external parameters have not changed significantly if it is running on blend with methanol. Methanol has rather affected the combustion and emission properties of the engine more significantly. G. Szabados (B) Department of Internal Combustion Engines and Propulsion Technology, Széchenyi István University, Egyetem tér 1, 9026 Gy˝or, Hungary e-mail: [email protected] J. Žaglinskis Waterborne Transport and Air Pollution Laboratory, Marine Research Institute, Klaipeda University, Universiteto ave. 17, 92294 Klaipeda, Lithuania K. Lukács · Á. Bereczky Department of Energy Engineering, Budapest University of Technology and Economics, M˝uegyetem rkp. 3, 1111 Budapest, Hungary © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 A. K. Agarwal et al. (eds.), Methanol, Energy, Environment, and Sustainability, https://doi.org/10.1007/978-981-16-1280-0_6

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Keywords Methanol · Diesel engine · Combustion · Emission · Stoichiometry

Abbreviations ASTM B BTE CA CEN CLD CN D, D2 ECU EG EGR FAME FID GHG HRR ICE ISO M NDIR PM RME TDC TDI WWFC

American Society for Testing and Material Biodiesel Brake Thermal Efficiency Crankshaft Angle European Standardization Organization Chemiluminescence Detector Cetane Number Diesel fuel Electronic Control Unit Exhaust Gases Exhaust Gas Recirculation Fatty Acid Methyl Ester Flame Ionization Detector Green House Gas Heat Release Rate Internal Combustion Engine International Organization for Standardization Methanol Non-Dispersive Infrared Particulate Matter Rapeseed Methyl Ester Top Dead Centre Turbo Direct Injection Worldwide Fuel Charter

Nomenclature B30 C16 H34 C19 H34 O2 CH3 OH Cn Hm CO CO2 Cx Hy Oz dp/dϕmax

A fuel blend, in which biodiesel is blended in 30% on a volumetric basis Chemical formula of cetane (hexadecane) Chemical formula of methyl oleate (biodiesel) Chemical formula of methanol General chemical formula of a molecule built up of hydrogen-carbon Chemical formula of carbon-monoxide Chemical formula of carbon-dioxide General chemical formula of a molecule built up of hydrogen-carbon– oxygen Maximum value of pressure over a unit of crankshaft angle

6 Combustion and Emission Analyses of a Diesel Engine …

dQ/dϕmax H2 O M10 mair mO2 NOx O2 Q THC  ρb ρd ρm

143

Maximum value of heat released over a unit of crankshaft angle Chemical formula of water A fuel blend, in which methanol is blended in 10% on a volumetric basis Mass of air Mass of oxygen molecule Chemical formula of oxides of nitrogen Chemical formula of oxygen molecule Quantity of heat Total hydrogen-carbon Marking of accuracy Density of diesel Density of biodiesel Density of methanol

6.1 Introduction The air environment around us seems to be increasingly loaded and polluted through emission from many sectors. Among different sectors, the transportation sector is the most relevant to us. This fact is due to the growing energy consumption in the transport sector which is forecasted worldwide in the nearer and far future (Economics 2018; Exxon Mobil 2018; Shell 2017; Shell International 2016). According to (Fischer and Schrattenholzer 2001) and other author (Zöldy 2009), energy from bio-sources is predicted running in an increasing tendency in this sector till 2050. In (Shell International 2016) it has been suggested that the share of biofuels in transportation will be quite high (ca. 30%). In (Ricardo 2018) the author calculates with a bit lower rate (on average ~25%) in Europe in the long term, while in other’s opinion the share of renewable energy in the transportation sector will be somewhat below 5% worldwide by 2050 (Exxon Mobil 2018). Lots of renewable and alternative energy sources can be found in the sector, which can be looked as a complementary or a substitute to the conventional sources. The aim of biofuel’s usage is primarily the diversification of fuel resources, preservation of fossil stocks decreasing the GHG emissions and keeping energy security (Hancsók et al. 2006a, b). Esters produced from different feedstock have been widely used and researched as propellant for diesel engines. They originate from biological sources and because of that their chemical composition is similar to diesel, thus they are used to decrease the consumption of fossil-derived diesel, environmental pollution coming from compression ignition engines and to improve the energy efficiency in the field of transportation (Iqbal et al. 2015; Makareviˇcien˙e et al. 2014; Shahir et al. 2015). Requirements regarding utilization rate of the renewable energy in the sector in the European Union are set out in a related regulation, which is compulsory for every member state of the Union (European Parliament and Council 2009). This utilization rate differs from country

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to country. For example, in Poland this value is not so high, approximately 12%, while the share of renewable energy compared to the total energy consumption of Brazil reaches the 42%, making this country a world leader from this point of view (M˛aczy´nska et al. 2019), but much of it comes from wood burning heating. Biofuels are not clearly judged as good or bad, advantageous or disadvantageous. Their use is questionable if they are viewed from a broader perspective, for example as far as their usage is concerned. Their physicochemical properties relevant to using them in internal combustion engine are diverse from those of standardized fossil-derived fuels (Zöldy 2019). After that, their effect on emission of an internal combustion engine is always playing a key role and it creates a mixed situation. As for components carbon-monoxide and hydrocarbon biofuels have advantages, these components decrease in almost every case while using biofuel (Shahir et al. 2015; Rajasekar and Selvi 2014). That is also the case if CO2 is in focus (Torok and Zoldy 2010). As for other emission-components like particulate mass, it can be increased using biofuel as a blending component in the investigated fuel (Shahir et al. 2015; Rajasekar and Selvi 2014). Fuels are used in the transportation sector, and therefore, it is relevant for biofuels as well. They have to be related with long-term storage which could have an effect on the fuel itself, namely the change of relevant properties due to biodiesel oxidation. Synthetic antioxidants (i.e. butylhydroxytoluene, butylhydroxyanisole, propylgallate, etc.) are commonly used against fuel’s oxidation. However, the oxidation reaction takes place in biodiesel which is stored for a long time (Lebedevas et al. 2013), and that affects the change of the physicochemical properties of biodiesel. Throughout oxidation viscosity grows and this factor, among others, has a negative effect on fuel’s atomization and mixing quality. As a consequence, it reduces the combustion efficiency (Ayhan 2008). In parallel with viscosity, increased density affects higher consumption of fuel, while the sediment can cause a coking and damage the injector nozzle (Ayhan 2008; Mollenhauer and Tschoke 2010). This is especially relevant for today’s high-pressure common rail electronic-controlled fuel systems, which are highly sensitive to fuel composition and quality (Rimkus et al. 2015). In order to eliminate or reduce the negative effects of undesirable values of density and viscosity, the addition of alcohol to the blend or to the neat biodiesel can be a solution. Methanol is a good aspirant among technical alcohols. Methanol costs less than other automotive alternative alcohols like ethanol or butanol, so it may be among the cheapest alcohols (Ayhan 2008; Guo et al. 2011). Methanol is an alcohol that contains 30% more oxygen (O2 ) on a molecular base than fossil diesel (Yasin et al. 2014). A higher amount of oxygen which takes place in a combustion process can decrease the emission of all the combustion products. Based on different researches (Yasin et al. 2014; Yilmaz 2012), the emission of carbon-monoxide and hydrocarbons, furthermore the engine cold start, as well as cold exploitation and engine efficiency could be improved with methanol, if it is an additive for diesel (D) and biodiesel (B) blends. Methanol is a similar fuel to gasoline, thus using methanol in a diesel engine can have harmful consequences. For example, higher level of fuel consumption and higher emission rates of nitrogen-oxides have resulted in scientific researches (Yasin et al. 2014; Qi et al. 2010). Other negative consequence on blending

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methanol with diesel is limited by separation. One of the solutions can be the use of fuels on acidic base, i.e., vegetable oil or esters of vegetable oil that would be proper in blends of methanol and diesel. The ICE and combustion relevant physical and chemical properties of diesel (D), biodiesel (FAME) and methanol (M) blend have been widely researched (Anand et al. 2011; Sayin et al. 2009; Zhen and Wang 2015). The levels of nitrogen-oxides (NOx ), carbon-monoxide (CO), hydrocarbons (HC) emitted, fuel consumption, engine’s efficiency and particulate relevant emission as well are researched, i.e., by (Cheung et al. 2009; Li et al. 2014). However, many scientific studies observed controversial results. In (Cheung et al. 2009) the use of biodiesel and methanol (in 15 V/V %) blend improved the emission values, including the NOx concentration, as well as the BTE compared to those of diesel. Scientists, such as the authors of (Iqbal et al. 2015; Shahir et al. 2015), have achieved opposite results, in case of using methanol in a lower blending rate (5–20 V/V %) in the investigated fuel blend across the tested engine’s load range. Exactly the NOx values in the exhaust gas increased in comparison to the results while running on fossil diesel. There are many scientific studies that deal with analysis of ecological and energy parameter characteristics, while diesel engine is fed with fuel blends containing methyl-alcohol. Some relevant works provide results regarding in-cylinder pressure and heat release rates in a wide engine load and speed ranges. Methanol has a low cetane number, which is less than 5 (Yilmaz 2012; Cheng et al. 2008; Kumar et al. 2013; Yu et al. 2011; Zhu et al. 2010) and prolongs the ignition delay of air–fuel mixture (Wei et al. 2015; Yusaf et al. 2013); at the same time, increases the peak values of cylinder pressure, pressure rise rate and heat release rate. A comprehensive review (Valera and Agarwal 2019) is done about production of methanol, use of methanol in diesel engine, combustion characteristic of methanol and safety requirements of methanol for diesel engines. It summarizes that methanol has a quite high-level opportunity regarding its usage in diesel engines. The aim of this research is to give comprehensive overview about how methanol influences the combustion and emission quality of a diesel engine. In analyses of combustion and emission characteristics, the most relevant parameters have been included. The study contains calculations regarding theoretical combustion (oxidation process) of the different hydrogen-carbons investigated within the framework of this study. A rarely investigated parameter, O2 consumption or demand is also in focus, besides CO2 emission and intensity throughout the calculations.

6.1.1 Methanol as an Alternative Methanol is built up of carbon, hydrogen and oxygen. Its chemical formula is CH3 OH. It is an alcohol and belongs to the group of simple alcohols based on its molecular weight. If it is produced on a bio-basis, then it is called bio-methanol (Ayhan 2008). There is an international standard regarding methanol for industrial use (International Organization for Standardization 1982). Based on the properties listed in Table 6.1, methanol seems to be a similar one to gasoline. Its density, kinematic viscosity,

146 Table 6.1 Physical and chemical properties of methanol (International Energy Agency 2020; Žaglinskis et al. 2016)

G. Szabados et al. Properties

Methanol

Formula

CH3 OH

Molecular weight [g/mol]

32

Carbon/Hydrogen/Oxygen [m/m %]

37.5/12.5/49.9

Density at 15 °C [kg/dm3 ]

0.796

Kinematic viscosity [m2 /s]

7.37 × 10–7

Boiling point [°C]

64.6

Freezing point [°C]

−97.6

Flash point (closed vessel) [°C]

11 (12)

Research Octane Number

107–109

Vapor pressure at 37.8 °C [kPa]

32

Lower Heating Value [MJ/kg] ([MJ/l])

20 (15.9)

Heat of vaporization [kJ/kg]

1160–1174

Heat capacity (at 25 °C, 101.3 kPa) [J/(mol × K)] Liquid/vapor

81.08/44.06

Auto-ignition temperature

464–470

Ignition limits (fuel in air) (V/V %)

7–36

Stoichiometric air to fuel ratio

6.4

Solubility in water

Fully miscible

Surface tension at 25 °C m [J/m2 ]

22.07

Laminar flame speed (1 bar, 300 K, λ = 1) [m/s]

0.5

research octane number, lower heating value, self-ignition temperature etc. show the similarity to gasoline. It is therefore used with higher blending rate or neat as well for spark ignition engines. Methanol is more prevalent in the USA and Japan, where higher mixing ratios are used. In the USA, there are two standards for regulation of the fuel properties. One of them is for the fuel with higher (70– 85 V/V %) methanol mixing ratios (American Society for Testing and Material 2007), and the other one regulates the fuel used in a neat form (American Society for Testing and Material 1997,2012). In a lower (M15–M25) and in a higher (M85– M100) blending rate is widespread in China, where there are different standards for methanol for each province (Zhao 2019). In Europe methanol is not so accepted. According to the relevant European standard for gasoline (European Committee for Standardization 2008a), the upper limit of methanol’s mixing ratio to gasoline is 3 V/V %. To analyze a bit deeper the properties of methanol and to compare them with those of gasoline arises that there are differences as well. Higher density, lower LHV, higher octane number, higher heat of vaporization, higher self-ignition temperature, lower stoichiometric air/fuel ratio etc. show that these differences can be advantageous and at the same time disadvantageous compared to gasoline, but it is still closer to gasoline’s quality than to those of diesel.

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6.1.2 Comparison of methanol’s Properties In the previous section it has been shown that ICE and combustion-relevant physicochemical properties of methanol is closer to gasoline than to diesel. Therefore, investigation of methanol as a blending component to diesel is a researched area nowadays. Table 6.2 shows some combustion-relevant properties of diesel, biodiesel and methanol. The cetane number is one of the most striking differences. Methanol with cetane number 3 shows that its flammability (ability to ignition under circumstances of a diesel engine) is far from those of diesel and biodiesel. Cetane number of a fuel is the most important parameter about a fuel regarding its usability in diesel engine. Its oxygen content is much higher compared to others. That can be advantageous, but rather in higher mixing ratios. If oxygen consumption of an engine can be a relevant parameter with attention to our environment then methanol’s air to fuel ratio is more favorable. Thus, stoichiometric calculations have been made in the first section of the manuscript. Here is the question of the blending ratio as well. Heating value of a fuel determines greatly the cycle’s work. In this regard methanol has disadvantage in comparison to the two other fuel D and B. As for density of the fuels compared, it can be said that there is no high difference. Flash point is a Table 6.2 ICE relevant properties of tested fuels (Chen et al. 2013)

Parameters

Diesel

Biodiesel

Methanol

Molecular formula

C12 –C25 (basis)

C12 –C24 (basis)

CH3 OH

Octane number

–

–

111

Cetane number

40–55

47–52

3

Oxygen content [m/m %]

–

10

50.0

Theoretic air/fuel ratio [kg/kg]

14.3

12.5

6.49

LHV [MJ/kg] 42.5

38.81

19.9

Density at 0.820 20 °C [g/cm3 ]

0.87

0.796

Viscosity at 40 °C [mm2 /s]

1.9–4.0

4.0

0.59

Flash point [°C]

65–88

166

12

Auto-ignition temperature [°C]

246

363

470

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G. Szabados et al.

property which is important rather in transportation and logistics of fuel. Methanol’s high auto-ignition temperature is also a disadvantage compared to those of diesels.

6.2 Theoretical investigations 6.2.1 Stoichiometric Calculations Liquid phase transportation fuels used in the transportation sector basically consist of hydrocarbons (Mollenhauer and Tschoke 2010). The basic equation regarding the oxidation process of hydrocarbons can be described as follows (Hartmann and Braun 1973):  m m O2 → nCO2 + H2 O + Q Cn Hm + n + 4 2

(6.1)

which means that a certain amount of oxygen is needed to burn a hydrocarbon perfectly that contains a given amount of carbon and hydrogen. The process above generates a certain amount of carbon-dioxide, water, and heat. The oxidation process runs in another way if the hydrogen-carbon contains additional oxygen. Equation 6.2 shows this reaction (Herbinet et al. 2010; Westbrook et al. 2011):  y z y O2 → xCO2 + H2 O + Q Cx Hy Oz + x + − 4 2 2

(6.2)

Based on the equation, it can be concluded that in case of a molecule which is built up of hydrogen-carbon–oxygen and it is intended to combust, it requires lower amount of oxygen theoretically compared to Eq. 6.1, and the quantity of produced carbon-dioxide depends only on the quantity of carbon in the hydrocarbon molecule in both cases. Theoretical combustion process of diesel. According to (Mollenhauer and Tschoke 2010), diesel fuel consists of more times higher types of different hydrocarbons than gasoline which consists of 200–300 different types. However, for the calculation, this should be simplified. In the following, the diesel is replaced by cetane (hexadecane) (Heywood 1988). The theoretical oxidation process of hexadecane can be shown with the help of Eq. (6.3): C16 H34 + 24.5O2 → 16CO2 + 17H2 O

(6.3)

This equation is based on amount of substance (mol, kmol). In order to be manageable and understandable, it needs to be converted onto a base of mass. Therefore, the molar mass values of the different chemical elements (Hartmann and Braun 1973) are useful. The following equation arises:

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kg kg kg (C) + 34 kmol × 1 (H) + 24, 5 kmol × 32 (O2 ) kmol kmol kmol     kg kg kg kg + 32 + 16 → 16 kmol × 12 (CO2 ) + 17 kmol × 2 (H2 O) kmol kmol kmol kmol

16 kmol × 12

(6.4) By performing the multiplications in Eq. (6.4), the next equation is the following: 192 kg(C16 ) + 34 kg(H34 ) + 784 kg(O2 ) → 704 kg(CO2 ) + 306 kg(H2 O) (6.5) Carbon and hydrogen should be combined, resulting in the following equation: 226 kg(C16 H34 ) + 784 kg(O2 ) → 704 kg(CO2 ) + 306 kg(H2 O)

(6.6)

The specific factors related to per unit mass of fuel can be defined: Oxygen consumption of the fuel’s combustion would be the first parameter. On the left-hand side of Eq. (6.6), it can be seen that how the theoretical oxygen demand develops on a mass basis. To combust cetane (C16 H34 ) perfectly per unit of mass: 784 kg (O2 ) kg (O2 ) = 3.47 226 kg (C16 H34 ) kg (C16 H34 )

(6.7)

3.47 kg of oxygen molecule would be required. Air consumption can be determined with the help of the oxygen demand if the mass-based ratio of air to oxygen content in the air is known (Hartmann and Braun 1973). It is shown in Eq. (6.8): m air 1 → m air = 4.31 × m O2 = m O2 0.232

(6.8)

If (6.7) and (6.8) have been taken into consideration, the theoretical specific air demand develops as follows: 3.47

kg (air) kg (O2 ) × 4.31 = 14.95 kg (C16 H34 ) kg (C16 H34 )

(6.9)

This is the fuel’s theoretical or stoichiometric air demand. Expressed in words, the theoretical oxidation of 1 kg of hexadecane (C16 H34 ) requires 14.95 kg of air. To determine the CO2 emissions Eq. (6.6) is used as well. The result in terms of per unit mass of fuel is the following: 704 kg (CO2 ) kg (CO2 ) = 3.12 226 kg (C16 H34 ) kg (C16 H34 )

(6.10)

Two parameters are specified regarding CO2 . One is called CO2 emission and related to a unit mass of fuel. If it is related to energy content (lower heating value)

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of the fuel, then in this case CO2 emission is called CO2 intensity throughout this study. Using the lower heating value of diesel (hexadecane) (Chen et al. 2013), CO2 intensity of hexadecane arises: 704 kg (CO2 ) 226 kg (C16 H34 ) 42.5 kg (CMJ 16 H34 )

= 0.073

kg (CO2 ) MJ (C16 H34 )

(6.11)

Theoretical combustion process of biodiesel. Biodiesels are produced on oil or fat basis with the help of alcohols. Their typical chain length is C14 –C22 (Bart et al. 2010). Biodiesels or bio-derived diesels have been intensively studied as an alternative fuel for diesel engines. Methyl-oleate with chemical formula of C19 H34 O2 is commonly in focus in researches dealing with detailed chemical kinetics (Herbinet et al. 2010; Westbrook et al. 2011) of renewable liquid diesel-similar fuel. In our case, methyl-oleate is intended to calculate with in the following calculation series. Equation (6.2) can be further written as: C19 H34 O2 + 26.5O2 → 19CO2 + 17H2 O

(6.12)

It seems to be on a mass basis as follows: 294 kg(C19 H34 O2 ) + 848 kg(O2 ) → 836 kg(CO2 ) + 306 kg(H2 O)

(6.13)

Based on Eq. (6.13) the two important parameters can be calculated: first, consumption of O2 : to oxidize perfectly a unit mass of C19 H34 O2 : 848 kg (O2 ) kg (O2 ) = 2.88 294 kg (C19 H34 O2 ) kg (C19 H34 O2 )

(6.14)

2.88 kg of O2 should be used. In line with oxygen consumption the specific air demand can be determined as follows: 2.88

kg (air) kg (O2 ) × 4.31 = 12.41 kg (C19 H34 O2 ) kg (C19 H34 O2 )

(6.15)

which means that for combusting theoretically of a unit mass of methyl-oleate 12.41 kg of air would be needed. The CO2 emissions are based on Eq. (6.13) as well, in terms of per unit mass of fuel: kg (CO2 ) 836 kg (CO2 ) = 2.84 294 kg (C19 H34 O2 ) kg (C19 H34 O2 )

(6.16)

Energy content (lower heating value)-based CO2 intensity of biodiesel can be determined according to Eq. (6.17):

6 Combustion and Emission Analyses of a Diesel Engine … 836 kg (CO2 ) 294 kg (C19 H34 O2 ) 38.81 kg (C MJH34 O2 ) 19

= 0.073

kg (CO2 ) MJ (C19 H34 O2 )

151

(6.17)

Theoretical combustion process of methanol. Methanol is built up of carbon, hydrogen and oxygen as well. Its chemical formula is CH3 OH. It is an alcohol and belongs to the group of simple alcohols. If it is produced on a bio-basis, then it is called bio-methanol (Zhen and Wang 2015). With the help of Eq. (6.2), the oxidation process of methyl-alcohol can be described: CH4 O + 1.5O2 → CO2 + 2H2 O

(6.18)

It is transformed on a mass basis, and can be obtained as follows: 32 kg(CH4 O) + 48 kg 32 kg(CH4 O) + 48 kg(O2 ) → 44 kg(CO2 ) (6.19) + 36 kg(H2 O)(O2 ) → 44 kg(CO2 ) + 36 kg(H2 O) Based on Eq. (6.19) our main parameters could be calculated as follows: in the first case, the O2 consumption: to combust a unit mass of CH4 O theoretically: kg (O2 ) 48 kg (O2 ) = 1.5 32 kg (CH4 O) kg (CH4 O)

(6.20)

1.5 kg of O2 would be needed. From the Eq. (6.20) the specific air demand develops: 1.5

kg (air) kg (O2 ) × 4.31 = 6.46 kg (CH4 O) kg (CH4 O)

(6.21)

Expressed in words, for theoretical combustion of a unit mass of methanol 6.46 kg of air would be necessary. As for the CO2 emissions, they are also described on the basis of Eq. (6.19) per unit mass of fuel in the following: 44 kg (CO2 ) kg (CO2 ) = 1.37 32 kg (CH4 O) kg (CH4 O)

(6.22)

On energy content (lower heating value) bases, methanol’s CO2 intensity develops in the next formula: 44 kg (CO2 ) 32 kg (CH4 O) MJ 19.9 kg (CH 4 O)

= 0.069

kg (CO2 ) MJ (CH4 O)

(6.23)

Theoretical O2 consumption and CO2 emission and intensity of blends with methanol. Fuel standards determine the composition and physical and chemical

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properties of fuels that can be placed on the market in the European Union. In our study, diesel (European Committee for Standardization 2005) and biodiesel (European Committee for Standardization 2008b) are in service for focusing on methanol. An ISO standard has been also set for methanol (International Organization for Standardization 1982). Biodiesel is blended at 7 V/V % (European Committee for Standardization 2005) with their fossil counterpart. In the following calculations the O2 consumption and CO2 emission and intensity will be determined while taking into consideration the blending rates, which have been created for the experimental test series. O2 and CO2 results of blends have been calculated from the same parameters of the blending components on a mass basis. These are B30 and B30 + M10. Equations (6.24)–(6.35) show the calculations, whose results are also summarized in Table 6.6. O2 consumption It can be determined in case of blend B30 as follows: O2 consumptionB30 = 70 V/V % × ρd × theoretical O2 consumption of diesel + 30 V/V% × ρb × theoretical O2 consumption of biodiesel (6.24) After substitution, the equation can be written as: O2 consumption B30

  kg(O2 ) kg = 0.70 m × 0.85 3 × 3.47 m kg(diesel)    3 kg(O2 ) kg + 0.30 m × 0.88 3 × 2.88 m kg(biodiesel)  kg(O2 ) (6.25) = 2.06 + 0.76 = 2.82 kg(fuel blend) 

3



It can be determined in case of blend B30 + M10 as follows: O2 consumptionB30+M10 = 60 V/V % × ρd × theoretical O2 consumption of diesel + 30 V/V % × ρb × theoretical O2 consumption of biodiesel + 10 V/V % × ρm × theoretical O2 consumption of methanol

(6.26)

After substitution the equation can be written as:     kg (O2 ) kg O2 consumption B30+M10 = 0.60 m3 × 0.85 3 × 3.47 m kg (diesel)    3 kg (O2 ) kg + 0.30 m × 0.88 3 × 2.88 m kg (biodiesel)    3 kg kg (O2 ) + 0.10 m × 0.796 3 × 1.5 m kg (methanol)

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153

 = 1.77 + 0.76 + 0.12 = 2.65

kg (O2 ) kg (fuel blend)

(6.27)

CO2 emission It can be determined in case of blend B30 as follows: CO2 emissionB30 = 70 V/V % × ρd × theoretical CO2 emission of diesel + 30 V/V % × ρb × theoretical CO2 emission of biodiesel (6.28) After substitution the equation can be written as:     kg (CO2 ) kg CO2 emission B30 = 0.70 m3 × 0.85 3 × 3.12 m kg (diesel)    3 kg (CO2 ) kg + 0.30 m × 0.88 3 × 2.84 m kg (biodiesel)  kg (CO2 ) (6.29) = 1.86 + 0.75 = 2.61 kg (fuel blend) It can be determined in case of blend B30 + M10 as follows: CO2 emissionB30+M10 = 60 V/V % × ρd × theoretical CO2 emission of diesel + 30 V/V % × ρb × theoretical CO2 emission of biodiesel + 10 V/V % × ρm × theoretical CO2 emission of methanol

(6.30)

After substitution the equation can be written as: CO2 emission B30+M10

  kg (CO2 ) kg = 0.60 m × 0.85 3 × 3.12 m kg (diesel)    3 kg (CO2 ) kg + 0.30 m × 0.88 3 × 2.84 m kg (biodiesel)    3 kg (CO2 ) kg + 0.10 m × 0.796 3 × 1.37 m kg (methanol)  kg (CO2 ) (6.31) = 1.59 + 0.75 + 0.11 = 2.45 kg (fuel blend) 

3



CO2 intensity It can be determined in case of blend B30 as follows: CO2 intensityB30 = 70 V/V % × ρd × theoretical CO2 intensity of diesel + 30 V/V % × ρb × theoretical CO2 intensity of biodiesel (6.32)

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After substitution the equation can be written as:  

 kg (CO2 ) kg CO2 intensity B30 = 0.70 m3 × 0.85 3 × 0.073 MJ (diesel) m  

 kg kg (CO2 ) 3 + 0.30 m × 0.88 3 × 0.073 MJ (biodiesel) m  kg (CO2 ) = 0.043 + 0.019 = 0.062 MJ (fuel blend)

(6.33)

It can be determined in case of blend B30 + M10 as follows: CO2 intensityB30+M10 = 60 V/V % × ρd × theoretical CO2 intensity of diesel + 30 V/V % × ρb × theoretical CO2 intensity of biodiesel + 10 V/V % × ρm × theoretical CO2 intensity of methanol (6.34) After substitution the equation can be written as:  

 kg kg (CO2 ) CO2 intensity B30+M10 = 0.60 m3 × 0.85 3 × 0.073 MJ (diesel) m  

 kg (CO2 ) kg + 0.30 m3 × 0.88 3 × 0.073 MJ (biodiesel) m  

 kg (CO2 ) kg + 0.10 m3 × 0.796 3 × 0.069 MJ (methanol) m  kg (CO2 ) = 0.037 + 0.020 + 0.005 = 0.062 MJ (fuel blend)

(6.35)

where ρd is average value of diesel’s density [kg/dm3 ] (European Committee for Standardization 2005), ρb is average value of biodiesel’s density [kg/dm3 ] (European Committee for Standardization 2008b), ρm is density of methanol [kg/dm3 ] (International Organization for Standardization 1982).

6.3 Materials and Methods 6.3.1 Investigated Fuels For our test series, to investigate the fuel blend’s effect on the combustion and emission properties of an engine, diesel (European Committee for Standardization 2005) was the base fuel. It has been blended first with biodiesel (European Committee for

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155

Standardization 2008b) and after that the diesel–biodiesel mixture is further blended with methanol (International Organization for Standardization 1982). Blending ratios have been applied on a volumetric basis. This has been done because diesel and methanol together do not form a usable mixture, therefore biodiesel has to be used as a solvent (Yasin et al. 2014; Yilmaz 2012; Wei et al. 2015). In this form the triple blend gives a homogeneous and stable blend. The ICE relevant, from combustion and emission point of view, main fuel properties have been discussed above. The used blending scale was 30 V/V % for biodiesel to diesel. The high scale in differences among the combustion relevant properties of methanol compared to the other investigated fuels is the reason in our case for the low mixing level of methanol, which is 10 V/V %. So, during the test series D2, B30 and B30 + M10 have been investigated.

6.3.2 Test engine, experimental setup The test engine used for the test series is a classic car engine and a make of Volkswagen. This is a four-cylinder, turbocharged, direct injection engine. It has also a charge air cooler. Its compression ratio is an average one, among those of diesel engines. It has EGR as well, but the EGR system was switched off during the test series. The main parameters regarding the test engine are shown in Table 6.3. The measurement system can be divided into three main parts. These are the indication system-part, the emission measurement system-part and the part that contains Table 6.3 Basic engine parameters

Bore [mm]

79.5

Stroke [mm]

95.5

Displacement [dm3 ]

1.896

Number of cylinders

4

Compression ratio

19.5

Rated power [kW] at speed [rpm]

66 at 4000 rpm

Rated torque [Nm] at speed [rpm]

180 at 2000 – 2500 rpm

Injection system

BOSCH VE

Number of nozzles on the injector

5

Diameter of nozzle [mm]

0.184

Injection in cylinder

Direct

Combustion chamber

M chamber

Turbo charger

Yes

Charge air cooler

Yes

Exhaust gas recirculation

Yes

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G. Szabados et al.

Fig. 6.1 Experimental setup

the dyno, dyno control and the fuel consumption measurement to be able to determine the engine’s brake thermal efficiency. Indication system-part has been used in order to be able to analyze the in-cylinder processes. It is assembled of a piezo quartz crystal, a charge amplifier, an analog-to-digital converter and a computer. The crystal has been calibrated before and after the test series. One indicator diagram which can be seen in Fig. 6.5 is an average of hundred diagrams recorded during the each of the steady state points. Emission measurement system-part has been built up in order to get information about the combustion afterwards. In connection with emission measurement system the aim was to determine most important gas phase pollutants and the particulate relevant emission of the engine as well. In order to be able to determine the brake thermal efficiency of the engine, a dyno control system and a fuel consumption measurement system were needed. Fuel temperature was controlled by the fuel consumption measurement system itself. In parallel the intake air has been temperature-controlled as well in order to be able to repeat the same mass related air to fuel in-cylinder parameters in each engine test point for each tested fuel. The whole system can be seen in Fig. 6.1 and the description and accuracy parameters of the parts are plotted in Table 6.2. All the equipment was in calibrated state during the test series. The numbering of the measurement system’s elements is the same in Fig. 6.1 and Table 6.4. The calculation of Heat Release Rate has been made based on indicated pressure with the help of an own developed program. After that it has been checked in the software AVL Boost.

6.3.3 Test method The engine has been tested in a cycle, which consists of 16 steady-state points (Fig. 6.2). To be able to create this cycle, the full load curve of the engine had to be recorded before. The steady state of the engine has been controlled by the temperature of lubrication oil and exhaust gas of the engine. The order of points can

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Table 6.4 Parts of measurement system No

Equipment

Description

Uncertainty

1

Engine

1.9 Turbo Direct Injection

–

2

Dyno

Eddy-current; Borghi and Saveri FE-350S

δM,e = ±1.23% δP,e = ±1.38%

3

Fuel consumption measurement system

AVL-7030 Fuel Balance

δb = ±0.23%

4

Computer

PC—for dyno loading controls

–

5

Smoke Meter

AVL 415

δPM = ±3.00%

6

Exhaust gas analyzer system:

HORIBA MEXA-8120 F

–

CO2 analyzer

AIA-23; NDIR

δe = ±4.63%

CO analyzer

AIA-23; NDIR

δe = ±4.42%

THC analyzer

FIA-22; H FID

δe = ±4.35%

NO/NOx analyzer

CLA-53; H CLD

δe = ±4.42%

7

Measurement computer

PC—for emission data

–

8

Piezo transducer

Kistler KIAG 6005

δpi,e = ±2.66%

9

Charge amplifier

Kistler KIAG 5001

–

10

Crankshaft angle speed encoder

HENGSTLER RI 32–0/1024.ER.14KA

Resolution: 0.35 degree

11

Computer

PC—for indication display

–

Fuel temperature controller

–

±1 °C

Intake air temperature controller

–

±2 °C

Fig. 6.2 The engine test cycle

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also be seen in the same figure. At a given speed the start point was the maximal torque value and the load went to the direction of lower and lower torque. Measurements have been carried out three times in order to comply with the measurement rules.

6.4 Results and Discussion 6.4.1 Stoichiometry-specific O2 consumption and CO2 emission in case of conventional (fossil) and alternative (bio) fuels Summarizing the results from Sect. 6.2, a list of important values, so the theoretical O2 consumption, stoichiometric air demand and theoretical CO2 emission and CO2 intensity can be seen in a listed form in Table 6.5. Due to the bounded oxygen of biofuels, their theoretical oxygen demand is lower than those of fossil diesel. The situation seems to be the same in case of the stoichiometric air demand as well. They run in parallel with each other. For theoretical oxidation, methanol requires 57 and 48% less oxygen as diesel and biodiesel require, accordingly. Biodiesel’s oxygen demand is 17% less compared to fossil diesel. The case is the same as far as specific CO2 emission and intensity are concerned among the investigated fuels. Table 6.5 Data of O2 consumption and CO2 emission during theoretical oxidation of investigated fuels Theoretical O2 consumption [kg O2 / kg fuel]

Stoichiometric air Theoretical CO2 Theoretical CO2 demand emission intensity [kg air / kg fuel] [kg CO2 / kg fuel] [kg CO2 / MJ fuel]

Oxidation of diesel (D)

3.47

14.95

3.1

0.073

Oxidation of biodiesel (B)

2.88

12.41

2.84

0.073

Oxidation of methanol (M)

1.5

6.46

1.37

0.068

Difference: −17 B versus D [%]

−17

−8.3

0

Difference: M versus D [%]

−57

−57

−56

−6.8

Difference: M versus B [%]

−48

−48

−52

−6.8

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Table 6.6 O2 consumption and CO2 emission and intensity values regarding investigated fuel blends Theoretical O2 consumption [kg O2 /kg fuel]

Theoretical CO2 emission [kg CO2 /kg fuel]

Theoretical CO2 intensity [kg CO2 /MJ fuel]

Diesel

3.47

3.1

0.073

B30

2.82

2.46

0.062

B30 + M10

2.65

2.44

0.062

Difference: B30 versus Diesel [%]

−18

−20

−0.7

Difference: B30 + M10 versus Diesel [%]

−23

−21

−6.9

Difference: B30 + M10 versus B30 [%]

−6

−0.8

−6.9

During theoretical combustion biodiesel emits 8.3% less carbon-dioxide than the fossil fuel, and methanol’s emission is ca. 50% less than the two other fuel D and B. In case of CO2 intensity, it depends on the heating value of the fuel. There is no difference between diesel and biodiesel in this regard. Methanol’s CO2 intensity is by 6.8% lower than that of diesel and biodiesel. If Table 6.6 is observed, it reveals that methanol’s contribution to the blend’s O2 consumption and CO2 emission is only 6%, if B30 and B30 + M10 are compared. B30 and B30 + M10 reduce the fuel oxygen demand 18% and 23%, respectively, in comparison with fossil diesel. Methanol’s contribution to CO2 emission is almost negligible (0.8%) when blends B30 and B30 + M10 are compared. If intensity of carbon-dioxide is in focus, blend with biodiesel and methanol (B30 + M10) has the same intensity than that of biodiesel blend (B30). At such a low mixing ratio methanol has a little effect on the above combustion-relevant, investigated theoretical parameters.

6.4.2 Rated Torque Torque results can be seen in Fig. 6.3. As for the concrete results they are the same or slightly increased with biodiesel blend, but under the influence of methanol torque values decreased at each investigated speed. The reasons for this tendency are that biodiesel has higher viscosity and thus littler gap loss in fuel injection pump can be supposed which has effect on the mass of the dose which rises and the oxygen content as well. If methanol has been mixed to the diesel–biodiesel blend, it causes lower viscosity and heating value in the dose of triple blend; therefore, the output torque of the engine is lower. Part load conditions

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Fig. 6.3 Rated torque with diesel (D2), 30 V/V % biodiesel (B30) as well as 30 V/V % biodiesel and 10 V/V % methanol (B30 + M10) at different speeds (δM = ±1.23%)

(25, 50 and 75%) have been adjusted at each speed point that are calculated from the rated values.

6.4.3 Break Thermal Efficiency As it is shown in Fig. 6.4a, b, the BTE values show a risen tendency with both kinds of blends. This is typical to all over the results with exception to the 25% load over the four speed points. Based on the results it can be established that since biodiesel has the same cetane number compared to diesel, therefore oxygen bound in biodiesel can improve the combustion performance. Blending methanol to the diesel–biodiesel double mixture decreases the viscosity and with increased ignition delay, intensity of the first phase of diesel ignition can be increased that may increase the work of the engine’s cycle. On the basis of theoretical consideration, the opposite tendency would be expected since the heat of vaporization of methanol decreases the temperature of work process, but this effect is not significant based on the results.

Fig. 6.4 a, b Break thermal efficiency (BTE) in case of diesel (D2), 30 V/V % biodiesel (B30) as well as 30 V/V % biodiesel and 10 V/V % methanol (B30 + M10), over the matrix of investigated operation points (δBTE = ±1.65%)

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Fig. 6.5 a–d Indicated pressure (pind ) and the net heat release rate (HRR) over the crankshaft angle with D2, B30 and B30 + M10 at speed 3000 rpm and different loads (δpi = ±2.66%, δHRR = ±5.49%)

6.4.4 Combustion parameters Indicated pressure (pi ) and heat release rate (HRR). Because of the permissible range of the chapter only the combustion-relevant results that belong to the speed of 3000 rpm will be introduced in this subsection. The pressure and heat release rate curves over the crankshaft angle can be followed in Fig. 6.5a–d. At the part load of 25%, a pressure peak can be found at the piston’s top dead centre. The injection starts at −2.4 CA° and the ignition delay takes 6.3 CA° in case of D2 and B30 while for B30 + M10 the ignition delay is 6.9 CA°. The maximum value of HRR in the premixed phase is at 10.3 CA° for diesel and diesel–biodiesel blend and because of the increased ignition delay of methanol it is shifted to 10.9 CA° in case of the triple blend. Pressure curve has been formed as a two-humped curved. Well observable that under HRR’s maximums of the investigated blends there are no significant difference, which are exactly 6% and 8.8% for B30 and B30 + M10, respectively. As for the maximum values of pressure there are even smaller differences namely −0.9% for B30 compared to that of diesel and in case of B30 + M10 this value is −0.9%. At a part load of 50% and 3000 rpm engine operation point the injection start is 4.2 CA° before TDC. 5 CA° the ignition delay for D2 and B30 blend as well while the delay takes 5.9 CA° in case of the triple blend of diesel–biodiesel–methanol. In the first phase of the diesel combustion which is the premixed combustion phase the maximum values of the rate of the released heat are located more or less at the same place for every investigated fuel. Regarding the max figures of HRR, a greater difference can be observed. HRR max of B30 + M10 is by 16.4% higher and in

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case of B30 by 4.2% compared to the point which belongs to diesel. The diffusion phase during the diesel combustion is clearly visible at this operation point based on the HRR curves. In case of the maximal figures of the indicated pressure the differences compared to the D2 s values take 0.7% and 1.6% for B30 and B30 + M10 accordingly, which is the effect of pressure fluctuation and measurement error. When the engine runs with 75% load it can be clearly observed that due to the increased dose the HRR maximum of the diffuse phase is greater than that of the premixed phase. For D2 and B30 the injection has been started at −5.6 CA° while this value is 6.3 CA° before TDC in case of the triple blend. Including that the ignition delay drags on with methanol in the blend the maximal values of heat release rate are placed at the same point and these are higher with D2 and B30 compared to B30 + M10. The fourth investigated point at 3000 rpm is the full load. For the three different investigated fuel the start of injection is the same, exactly −10.5 CA° while the ignition delay differs from each other and the longest is in case of the triple blend (4.9 CA°). This parameter is 4.2 CA° when the engine runs on conventional diesel and 4.5 CA° while running on B30 biodiesel blend. The HRR’s maximal value of the premixed phase is near to −1.7 CA°, −1.4 CA° and −1.0 CA° for D2, B30 and B30 + M10 accordingly. Cause for deviation of maximum’s place is that the differences between ignition delays belonging to the investigated fuels have increased slightly. Under the HRR maximal figures can be experienced with more significant differences. In comparison with the diesel’s value the increase is 4.0% for B30 blend and 15.3% for B30 + M10 triple blend. If the indicated pressure is in focus, it can be stated that the value of changes is 1.1% for B30 diesel–biodiesel blend and − 1.7% for B30 + M10 diesel–biodiesel–methanol blend compared to the pure diesel operation of the engine. This value is within the measurement error. Pressure’s maximal values increase both with the load and with the speed of the engine (Fig. 6.6). In case of the blend which contains 30% biodiesel on a volumetric basis significant difference cannot be experienced compared to the pure diesel’s results. The biggest increase is 1.1% while biggest decrease is 1.7%. Against this

Fig. 6.6 Indicated pressure maximum at different loads and speeds with D2, B30 and B30 + M10, as well as the changes with B30 and B30 + M10 compared to D2 (δpi = ±2.66%)

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it seems to be a more significant deviation when the engine is running on the triple blend. Exact values are as follows: the biggest increase is 2.5% at the operation point of 2500 rpm and 75% load. The biggest decreases are 6.4% (at 3500 rpm and 25%) and 5% (at 2000 rpm and 100%). Ignition delay and Heat Release Rate (HRR). The engine’s ECU adjusts continuously the injection advance which is shifted to earlier with speed and with load as well. The accuracy of the injection advance’s angle was the same as the measurement accuracy at low and medium loads, while at 75% load the ECU increased the pre-injection angle with increasing dose. Injection advance differs under investigated fuels with the resolution of the sensor. Results are shown in Fig. 6.7. Blending methanol into the investigated fuel has an effect to increase the ignition delay. It can be clearly read from the Fig. 6.8 that in case of biodiesel blend (B30) there is no remarkable changes compared to the results of diesel at low load (25

Fig. 6.7 Injection advance at different load and speed conditions in case of fuels like D2, B30 and B30 + M10 (δCA = ±0.72°)

Fig. 6.8 Ignition delay at different load and speed for D2, B30 and B30 + M10, as well as the changes of B30 and B30 + M10 compared to D2 (δCA = ±0.72°)

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and 50%). Higher differences can be observed when the engine runs with higher load conditions (75 and 100%) but is still under 0.6 CA°. Bars on Fig. 6.8 show more significant deviation for diesel–biodiesel–methanol triple blend in comparison with diesel’s values. Aside from the results at 75% load and 3000 rpm which is an outstanding value, the increment in increase is 18% at full load condition. Trend cannot be detected neither with load nor with speed of the engine, the average increase is 12.2%. Maximum of the calculated heat release rate (HRR) among the different investigated blends differ significantly from each other at load levels of 25% and 50% (Fig. 6.9). This is evident because the released heat during the premixed phase is greater in comparison to that during the diffuse phase of the combustion and the fuel blending has effect on the premixed combustion part. At 25% load and at speed 3000 rpm the increase is the highest when the engine is running on B30, so 6.5% and the average increasing is 2.8%. When the blend B30 + M10 is investigated the increase is significant as well. It is 22% at engine operating point 2500 rpm speed and 50% load while the average value in increasing is 13.2%. At engine load 75% and 100% the maximum rates of heat release are in the diffuse combustion phase and the effect of blending is not important, but there is one point where some decrementing is observable for B30 + M10 at 100% load. If the premixed phase’s heat release rates are in focus and what can be seen is that the results differ from each other under the investigated load and speed operation points (Figs. 6.5 and 6.10). Readable that the differences for B30 are not important, apart from the values at 75% load, at speed of 2500 rpm and at full load the deviation is 7.8% and the average of differences expose 3.5%. When the B30 + M10 blend is under investigation, about the results can be said the variation are more significant and it is the highest at full load and 2500 rpm speed of the engine, namely 27.1%. Besides the average variations number 15.1%.

Fig. 6.9 Changes in maximal values of Heat Release Rate (HRR) of B30 and B30 + M10 compared to D2 (δHRR = ±5.49%)

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Fig. 6.10 Maximal values of heat release rate in the premixed phase of combustion at variation speed and load points of the engine for D2, B30 and B30 + M10 as well as the changes of B30 and B30 + M10 compared to D2 (δHRR = ±5.49%)

6.4.5 Exhaust emission Nitrogen-oxides (NOx ). The changes in exhaust emission have been investigated with three different fuel blends in this case as well. As for the NOx -emission it can be stated that emitted NOx increments with increasing engine power since the temperature increases and air/fuel ratio decreases at the same time. NOx doesn’t change significantly when speed is always higher at load level of 25%. The situation is different at load levels 50% and 75%, because at this load points NOx values decreases until the speed reaches 3000 rpm and above this speed the NOx seems to be decreased. The reason for this tendency is that with the speed increasing air/fuel ratio, and at 3500 rpm the increased injection advances (see Fig. 6.7). Ignoring the 75% load conditions it can be established that blending of biodiesel and methanol into fossil diesel has no effect on the nitrogen-oxides emission of the engine. Averaged variation is 2.5% in case of B30 and 1.8% if B30 + M10 is investigated. Results are drawn in Fig. 6.11. It is observable that blending methanol into the investigated fuel reduced the NOx emission compared to B30 s NOx emission, but it is not remarkable. Percental averaged differences seem to be 2.5% for B30 while 1.8% in case of B30 + M10, if results come from 75% load are not considered because of the not constant value of injection advance. Total Hydrocarbon (THC). Quantity of emitted THC is the highest at load level of 25%. The tendency over the engine’s seems to be decreased slightly then it increases again at full load. Results are summarized in Fig. 6.12. THC emission shows a decreasing tendency at part load operation points when the speed is increasing. This can be traced back to two things. On one hand, the air/fuel ratio decreases slightly, and the average temperature of the cycle increases with the growing engine speed. Variations are not considerable in emission of total hydrogen carbon. With an average value of 43 ppm the emission levels are 49 ppm at 25% load and 41 ppm at

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Fig. 6.11 Emission of nitrogen-oxides at various load and speed points of the engine in case of D2, B30 and B30 + M10, as well as the changes for B30 and B30 + M10 compared to D2, further between B30 and B30 + M10 (δNOx = ±4.42%)

Fig. 6.12 Total hydrocarbon (THC) emitted by the engine at various load and speed conditions while D2, B30 and B30 + M10 have been used as well as changes for B30 and B30 + M10 in comparison with D2, further between B30 and B30 + M10 (δTHC = ±4.35%)

50% load and 40 ppm and 43 ppm if the engine runs at 75% and 100% load accordingly. Blending biodiesel into the fuel investigated an average of 37% decreasing seems to be created. The highest level in reducing THC appears at 75% of load while the lowest level at 25% engine load can be detected. If methanol is mixed into the fuel, THC emission increases where the highest differences developed between investigated blends B30 and B30 + M10. This situation is typical at low loads (Fig. 6.12). The reasons can be for that the heat removal of the evaporation of methanol and the faster evaporation. Carbon-monoxide (CO). The level of the carbon-monoxide emitted by the engine decreases with growing load up to 75%. This trend is reversed at full load, where a significant rising can be detected. Results can be followed in Fig. 6.13. If the speed of the engine is adjusted to a higher level up to 3000 rpm, the injected dose increases in parallel and therefore CO seems to increase at load points 25% and 50%. CO decreases at engine speed 3500 rpm mainly because the cycle-averaged temperature increases. At full load conditions and when the speed runs higher the emitted CO seems to decrease because of the increasing air/fuel ratio. Clarification

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Fig. 6.13 Emission of carbon-monoxide (CO) at different load and speed operation points of case of D2, B30 and B30 + M10, as well as changes for B30 and B30 + M10 in comparison with D2, further between B30 and B30 + M10 (δCO = ±4.63%)

above is valid for D2. If biodiesel is mixed into the investigated fuel the CO-emission decreases. As an effect of blending methanol, with triple blend (B30 + M10) COlevel of exhaust gas rises at low loads, mainly at 25% load. The reason for that can be the methanol’s heat removal effect of evaporation. If the engine is running at full load CO decreases may be because of the oxygen content of the blend. Effect of mixing biodiesel to the fuel is slight. The rate of decreasing in CO emission is averagely 5.8%; at 25%, 50%, 75% and 100% load levels the rates are 1.3%, 5.6%, 8% and 8.5% accordingly. Methanol blending increased this on an average of 17.3% at low load operating conditions and with 4.4% at 50% of load, while a reduction can be observed, namely 5.8% and 29% at load value of three-quarter and full. This is justified by the oxygen content of methanol. Particulate Matter (PM). Emission of particulate matter develops according to theoretical considerations, so it rises with increasing load due to the growing dose. In Fig. 6.14 the results are plotted. A clear trend cannot be observed in rate of emitted PM over rising engine speed. At load level of 25%, difference cannot be experienced

Fig. 6.14 Emission of PM at various load and speed conditions of the engine for investigated fuels of D2, B30 and B30 + M10 as well as changes for B30 and B30 + M10 in comparison with D2, further between B30 and B30 + M10 (δPM = ±3.00%)

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since the boost of this engine is in operation. It seems to rise as a function of the speed, while the load is set to 50% and 75%. The highest level of emission can be read at full load and low speed (2000 rpm), which is reducing with increasing speed, since the rate of charging is getting higher. Mixing bio component into the fuel has clearly a reducing effect on PM emission in case of both biodiesel and methanol. As an effect of using biodiesel in the tested fuel PM decreasing can be read where the average takes 16.9%. Tendencies over speed and load series cannot be observed. At load rates of 25% and 75% the average value decreasing is about 18%, while the lowest reducing (14%) in PM emission seems to be at 50% load level of the engine. Blending of methanol results a greater rate of reduce in particulate emission. Averaged results are by 40% lower than diesel’s PM results. This can be traced back to several reasons. On the one hand, rise in the volume of fuel burning during the premixed phase is observed because of the less cetane number and the blend contains more oxygen (Kumar et al. 2013) in proportion to the carbon in the fuel. On the other hand, lower density and viscosity of the blend causes better mixture formation and certain carbon chains are less disposed to format particulate matter. Highest decrease in PM with triple blend compared to the diesel occur at 50% and 100% engine load, where it is more than 46%, while this value is 33% at load of 75%. An increase due to the cooling effect of methanol evaporation is observed by some researchers (Jamrozik et al. 2018), and it was not observable here, presumably due to the high compression ratio. Overall emission comparison. Averaged changes of emission of the engine running on the blends in comparison with the diesel are given in Table 6.7. B30 has a reduction effect for almost every components of emission apart from nitrogen-oxides. If B30 + M10 is compared to diesel the results show that in case of two components like carbon-monoxide and particulate matter the reduction potential is higher than B30 s reduction potential. As for NOx B30 and B30 + M10 are resulting more or less the same emission, which is a disadvantage for methanol that the THC emission rises largely when methanol is blended to the investigated fuel. PM reduces consequently with mixing biocomponent into the tested fuel and the level of reduction seems to be higher than other gaseous components. The reason for that should be looked for in the structure of fuels probably. Fossil diesel contains aromatics, which form soot, while biofuels do not contain aromatics. When biocomponents are mixed into a blend, for example, in a blending rate of 40 V/V% (B30 + M10) that changes the fuel structure in 40% which influences the particulate relevant emission, while this mixing rate does not change the combustion relevant properties of the blend much compared to diesel which are related to the emission of gaseous components of an engine. Table 6.7 Change in the measured emission-components compared to those of diesel (δNOx = ±4.42%, δCO = ±4.63%, δTHC = ±4.35%, δPM = ±3.00%) NOx change [%]

THC change [%]

CO change [%]

PM change [%]

Blend B30

2.5

−37

−6

−17

Blend B30 + M10

2

2

−9

−41

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6.5 Conclusions As a summary of the study, the following conclusions can be declared regarding blending of biodiesel and methanol into a blend as far as the diesel engine combustion and emission properties are considered: – During theoretical oxidation process, methanol itself requires less O2 compared to diesel fuels. But methanol’s contribution to the blend’s O2 consumption is almost negligible, if B30 and B30 + M10 are compared. – As far as stoichiometric combustion is concerned, methanol itself emits less CO2 compared to the CO2 emission of diesel fuels. But methanol’s contribution to the blend’s CO2 emission is almost negligible, if B30 and B30 + M10 are compared. As for CO2 intensity, blending biodiesel to diesel does not have a significant effect on it, while plus methanol reduces the value a bit more. – The engine used for testing was a diesel engine with an average compression ratio, charging and undivided combustion chamber. Regarding the rated torque of the engine, it has not changed in case of B30 and when B30 + M10 blend has been used maximal torque of the engine dropped to 94%. Primarily, it is due to the other viscosity value of methanol compared to biodiesel. – Brake thermal efficiency has increased by a small amount, when diesel blended with biodiesel and at the same time methanol does not have significant effect on the values of BTE. – As for the ignition delay it did not seem to be changed when biodiesel has been mixed to, while blending methanol to the fuel had an ignition delay’s increasing effect averagely by 10%. – When the heat release rate is under observation, its maximal value has not changed in case of B30 and in case of plus M10 it seemed to be changed (increased) but primarily the premixed combustion phase is concerned with an average value of 10%. – If only near-constant injection advance cases are considered, nitrogen oxides emitted by the engine have not changed significantly during the test series, neither when biodiesel nor when methanol mixed to the investigated fuel. The extent of change is lower than the measurement accuracy. In case of the THC emission the picture is another one. It reduced by 40% when biodiesel blended, but at the same time it increased when methanol blended to nearly by 40% as well. So it can be declared that total hydrogen–carbon emission stayed nearly constant when the results between diesel and diesel plus two bios are compared. Emission of carbon-monoxide has varied but by a small amount. Mixing methanol had an increasing effect on CO emission at low load conditions and a reducing effect at high load conditions compared to the CO emission values in case of pure diesel used in the engine. Emission of particulate matter reduced both by the blend with biodiesel and by the triple blend as well. Reducing values are averagely 14% and 40% when B30 and B30 + M10 blend have been used, respectively.

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Acknowledgement The research reported in this paper and carried out at the Budapest University of Technology and Economics has been supported by the National Research Development and Innovation Fund (TKP2020 National Challenges Subprogram, Grant No. BME-NCS) based on the charter of bolster issued by the National Research Development and Innovation Office under the auspices of the Ministry for Innovation and Technology.

References American Society for Testing and Material (1997) ASTM D1152–97 standard specification for methanol (methyl alcohol). West Conshohocken, PA, USA American Society for Testing and Material (2007) ASTM D5797–07 standard specification for fuel methanol (M70–M85) for automotive spark-ignition engines. West Conshohocken, PA, USA American Society for Testing and Material (2012) ASTM D1152–12 standard specification for methanol (methyl alcohol). West Conshohocken, PA, USA Anand K, Sharma RP, Mehta PS (2011) Experimental investigations on combustion, performance and emissions characteristics of neat karanji biodiesel and its methanol blend in a diesel engine. Biomass Bioenerg 35(1):533–541. https://doi.org/10.1016/j.biombioe.2010.10.005 Ayhan D (2008) Biodiesel a realistic fuel alternative for diesel engines. ISBN 978-1-84628-994-1 Bart JC, Palmeri N, Cavallaro S (2010) Biodiesel science and technology: from soil to oil. Elsevier Cheng CH, Cheung CS, Chan TL, Lee SC, Yao CD, Tsang KS (2008) Comparison of emissions of a direct injection diesel engine operating on biodiesel with emulsified and fumigated methanol. Fuel 87(10–11):1870–1879. https://doi.org/10.1016/j.fuel.2008.01.002 Chen G, Shen Y, Zhang Q, Yao M, Zheng Z, Liu H (2013) Experimental study on combustion and emission characteristics of a diesel engine fueled with 2, 5-dimethylfuran–diesel, n-butanol–diesel and gasoline–diesel blends. Energy 54:333–342. https://doi.org/10.1016/j.energy.2013.02.069 Cheung CS, Zhu L, Huang Z (2009) Regulated and unregulated emissions from a diesel engine fueled with biodiesel and biodiesel blended with methanol. Atmos Environ 43(32):4865–4872. https://doi.org/10.1016/j.atmosenv.2009.07.021 European Committee for Standardization (2005) European Standard EN 590 Automotive fuels. Diesel. Requirements and test methods. CEN - European Committee for Standardization, Brussels, Belgium European Committee for Standardization (2008a) “EUROPEAN STANDARD EN 590 228 Automotive fuels—Unleaded petrol—Requirements and test methods” CEN—European Committee for Standardization. Brussels, Belgium European Committee for Standardization (2008b) “European Standard EN 14214, Automotive fuels—Fatty acid methyl esters (FAME) for diesel engines—Requirements and test methods” CEN—European Committee for Standardization. Brussels, Belgium European Parliament and Council DIRECTIVE 2009/28/EC of 23 April 2009 “Directive 2009/28/EC of the European Parliament and of the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC” Strasbourg, France Economics BE (2018) BP energy outlook 2018 edition. https://www.bp.com/content/dam/bp/ business-sites/en/global/corporate/pdfs/energy-economics/energy-outlook/bp-energy-outlook2018.pdf. Accessed May 02 2020 Exxon Mobil (2018) Outlook for energy: a view to 2040. cdn.exxonmobil.com/~/media/global/files/outlook-for-energy/2018/2018-outlook-forenergy.pdf. Accessed May 02 2020 Fischer G, Schrattenholzer L (2001) Global bioenergy potentials through 2050. Biomass Bioenerg 20(3):151–159. https://doi.org/10.1016/S0961-9534(00)00074-X

6 Combustion and Emission Analyses of a Diesel Engine …

171

Guo Z, Li T, Dong J, Chen R, Xue P, Wei X (2011) Combustion and emission characteristics of blends of diesel fuel and methanol-to-diesel. Fuel 90(3):1305–1308. https://doi.org/10.1016/j. fuel.2010.12.011 Hancsók J, Krár M, Baladincz J, Vuk T (2006a) Dízelgázolajok bioeredet˝u komponensei (Zsírsavmetilészterek) (Bio-origin components of diesel (Fatty acid methyl esters)). Magyar Kémikusok Lapja (Journal of Hungarian Chemists) 61(7): 228–235 (in Hungarian) Hancsók J, Magyar S, Szoboszlai Z (2006b) Motorbenzinek bioeredet˝u komponensei I. (Bioalkoholok) (Bio-origin components of gasoline I. (Bioalcohols)). Magyar Kémikusok Lapja (Journal of Hungarian Chemists) 61(5): 153–159 (in Hungarian) Hartmann A, Braun V (1973) Meß und Regeltechik Verbrennungstechnik. Hartmann & Braun AG Herbinet O, Pitz WJ, Westbrook CK (2010) Detailed chemical kinetic mechanism for the oxidation of biodiesel fuels blend surrogate. Combust Flame 157(5):893–908 Heywood JB (1988) Combustion engine fundamentals. 1ª Edição. Estados Unidos International Energy Agency—advanced motor fuel: fuel information „Methanol”. https://www. iea-amf.org/content/fuel_information/methanol. Accessed May 02 2020 International Organization for Standardization (1982) ISO1387:1982 methanol for industrial use— methods of test. Switzerland, Geneva Iqbal MA, Varman M, Hassan MH, Kalam MA, Hossain S, Sayeed I (2015) Tailoring fuel properties using jatropha, palm and coconut biodiesel to improve CI engine performance and emission characteristics. J Clean Prod 101:262–270. https://doi.org/10.1016/j.jclepro.2015.04.011 Jamrozik A, Tutak W, Pyrc M, Gruca M, Koˇciško M (2018) Study on co-combustion of diesel fuel with oxygenated alcohols in a compression ignition dual-fuel engine. Fuel 221:329–345. https:// doi.org/10.1016/j.fuel.2018.02.098 Kumar S, Cho JH, Park J, Moon I (2013) Advances in diesel–alcohol blends and their effects on the performance and emissions of diesel engines. Renew Sustain Energy Rev 22:46–72. https:// doi.org/10.1016/j.rser.2013.01.017 Lebedevas S, Makareviciene V, Sendzikiene E, Zaglinskis J (2013) Oxidation stability of biofuel containing Camelina sativa oil methyl esters and its impact on energy and environmental indicators of diesel engine. Energy Convers Manage 65:33–40. https://doi.org/10.1016/j.enconman.2012. 07.010 Li R, Wang Z, Ni P, Zhao Y, Li M, Li L (2014). Effects of cetane number improvers on the performance of diesel engine fuelled with methanol/ biodiesel blend. Fuel 128: 180–187. https:// doi.org/10.1016/j.fuel.2014.03.011 M˛aczy´nska J, Krzywonos M, Kupczyk A, Tucki K, Sikora M, Pi´nkowska H, B˛aczyk A, Wielewska I (2019) Production and use of biofuels for transport in Poland and Brazil—the case of bioethanol. Fuel 241: 989–996.https://doi.org/10.1016/j.fuel.2018.12.116 Makareviˇcien˙e V, Lebedevas S, Rapalis P, Gumbyte M, Skorupskaite V, Žaglinskis J (2014) Performance and emission characteristics of diesel fuel containing microalgae oil methyl esters. Fuel 120:233–239. https://doi.org/10.1016/j.fuel.2013.11.049 Mollenhauer K, Tschoke H (eds) (2010) Handbook of diesel engines (vol 1). Springer, Berlin Qi DH, Chen H, Geng LM, Bian YZ, Ren XC (2010) Performance and combustion characteristics of biodiesel–diesel–methanol blend fuelled engine. Appl Energy 87(5):1679–1686. https://doi. org/10.1016/j.apenergy.2009.10.016 Rajasekar E, Selvi S (2014) Review of combustion characteristics of CI engines fuelled with biodiesel. Renew Sustain Energy Rev 35:390–399. https://doi.org/10.1016/j.rser.2014.04.006 Ricardo (2018) Europe’s clean mobility outlook: scenarios for the EU light-duty vehicle fleet, associated energy needs and emissions, 2020–2050. https://www.epure.org/media/1751/ed51122_e pure_cmp_modelling_final-report_issue3-1.pdf. Accessed May 02 2020 Rimkus A, Žaglinskis J, Rapalis P, Skaˇckauskas P (2015) Research on the combustion, energy and emission parameters of diesel fuel and a biomass-to-liquid (BTL) fuel blend in a compressionignition engine. Energy Convers [1] Manage 106: 1109–1117. https://doi.org/10.1016/j.enc onman.2015.10.047

172

G. Szabados et al.

Sayin C, Ilhan M, Canakci M, Gumus M (2009) Effect of injection timing on the exhaust emissions of a diesel engine using diesel–methanol blends. Renew Energy 34(5): 1261–1269. https://doi. org/10.1016/j.renene.2008.10.010 Shahir VK, Jawahar CP, Suresh PR (2015) Comparative study of diesel and biodiesel on CI engine with emphasis to emissions—a review. Renew Sustain Energy Rev 45:686–697. https://doi.org/ 10.1016/j.rser.2015.02.042 Shell (2017) Shell energy transition report. https://www.shell.com/energy-and-innovation/the-ene rgy-future/shell-energy-transition-report/_jcr_content/par/toptasks.stream/1524757699226/f51 e17dbe7de5b0eddac2ce19275dc946db0e407ae60451e74acc7c4c0acdbf1/web-shell-energy-tra nsition-report.pdf. Accessed May 02 2020 Shell International BV (2016) Shell energy scenarios to 2050. https://rjohnwilliams.files.wordpr ess.com/2016/02/shell-energy-scenarios2050.pdf. Accessed May 02 2020 Torok A, Zoldy M (2010) Energetic and economical investigation of greenhouse gas emission of Hungarian road transport sector. Pollack Periodica 5(3):123–132. https://doi.org/10.1556/Pol lack.5.2010.3.10 Valera H, Agarwal AK (2019) Methanol as an alternative fuel for diesel engines. In: Methanol and the alternate fuel economy. Springer, Singapore, pp 9–33. https://doi.org/10.1007/978-981-133287-6_2 Wei L, Yao C, Wang Q, Pan W, Han G (2015) Combustion and emission characteristics of a turbocharged diesel engine using high premixed ratio of methanol and diesel fuel. Fuel 140: 156–163. https://doi.org/10.1016/j.fuel.2014.09.070 Westbrook CK, Naik CV, Herbinet O, Pitz WJ, Mehl M, Sarathy SM, Curran HJ (2011) Detailed chemical kinetic reaction mechanisms for soy and rapeseed biodiesel fuels. Combust Flame 158(4):742–755. https://doi.org/10.1016/j.combustflame.2010.10.020 Yasin MM, Yusaf T, Mamat R, Yusop AF (2014) Characterization of a diesel engine operating with a small proportion of methanol as a fuel additive in biodiesel blend. Appl Energy 114: 865–873. https://doi.org/10.1016/j.apenergy.2013.06.012 Yilmaz N (2012) Comparative analysis of biodiesel–ethanol–diesel and biodiesel–methanol–diesel blends in a diesel engine. Energy 40(1):210–213. https://doi.org/10.1016/j.energy.2012.01.079 Yusaf T, Hamawand I, Baker P, Najafi G (2013) The effect of methanol-diesel blended ratio on CI engine performance. Int J Automot Mech Eng 8(1): 1385–1395. https://doi.org/10.15282/ijame. 8.2013.26.0114 Yu W, Chen G, Zuohua H (2011) Influence of cetane number improver on performance and emissions of a common-rail diesel engine fueled with biodiesel-methanol blend. Front Energy 5(4): 412– 418. https://doi.org/10.1007/s11708-011-0163-9 Žaglinskis J, Lukács K, Bereczky Á (2016) Comparison of properties of a compression ignition engine operating on diesel–biodiesel blend with methanol additive. Fuel 170:245–253. https:// doi.org/10.1016/j.fuel.2015.12.030 Zhao K (2019) Methanol fuel blending in China. In: Presentation at Trinidad and Tobago methanol fuel blending forum. Trinidad Zhen X, Wang Y (2015) An overview of methanol as an internal combustion engine fuel. Renew Sustain Energy Rev 52:477–493. https://doi.org/10.1016/j.rser.2015.07.083 Zhu L, Cheung CS, Zhang WG, Huang Z (2010) Emissions characteristics of a diesel engine operating on biodiesel and biodiesel blended with ethanol and methanol. Sci Total Environ 408(4):914–921. https://doi.org/10.1016/j.scitotenv.2009.10.078 Zöldy M (2009) Potential future renewable fuel challenges for internal combustion engine. Járm˝uvek és Mobilgépek, II. évf, 397–403 Zöldy M (2019) Improving heavy duty vehicles fuel consumption with density and friction modifier. Int J Automot Technol 20(5):971–978. https://doi.org/10.1007/s12239-019-0091-y

Chapter 7

Combustion Characteristics of Methanol Fuelled Compression Ignition Engines ˇ Jakub Cedík, Hardikk Valera, Martin Pexa, and Avinash Kumar Agarwal

Abstract Concerned with the increasing concentration of greenhouse gases and global dependence on crude oil, researchers worldwide are making efforts to promote alternative fuels. The utilization of alternative fuels can diversify the energy sources and reduce emissions of greenhouse gases. Alcohols have evolved as a popular alternative fuel for internal combustion engines. Methanol, light alcohol, has shown great potential in alleviating the burden of the engine out emissions. A number of scientific studies presented the use of methanol in engines. For utilization in diesel engines, widely accepted methods of methanol induction include port injection and blending with diesel and/or biodiesel. The aim of this chapter is to provide an overview of these methodologies, focusing on the influence of methanol on combustion, when used with diesel like fuels. The effects of different utilization techniques and fuel blends on the cylinder pressure, heat release rate, and exhaust gas temperature are summarized from the literature and then analyzed. Thorough knowledge of the effect of methanol on engine combustion would allow its superior utilization from the viewpoint of pollutant emission reduction. Keywords Methanol · Biofuels · Diesel engines · Combustion · In-cylinder pressure · Heat release rate

7.1 Introduction With increasing population, declining environmental health, and shrinking energy resources, the utilization of renewable fuels in the transport sector is becoming important. One of the most promising alternative fuels in the transportation sector is methanol (Valera and Agarwal 2019). Methanol is the simplest alcohol and can be ˇ J. Cedík (B) · M. Pexa Department for Quality and Dependability of Machines, Czech University of Life Sciences, Prague, Czech Republic e-mail: [email protected] H. Valera · A. K. Agarwal Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 A. K. Agarwal et al. (eds.), Methanol, Energy, Environment, and Sustainability, https://doi.org/10.1007/978-981-16-1280-0_7

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produced from various resources, including bio-wastes and variety of biomass, and MSW. Fossil fuel resources such as coal or natural gas can also be used to produce methanol (Fletcher et al. 2005; Valera and Agarwal 2019, 2020; Patel et al. 2020). The process is usually based on the following basic steps, given in Fig. 7.1. Syngas (synthetic gas — a mixture of carbon dioxide, hydrogen, carbon monoxide, and hydrogen sulfide) produced from basic feedstock is converted into crude methanol under high pressure and temperature conditions. Generally, a catalyst having main active surfaces of chromium and zinc is used. The reactions involved in methanol synthesis are hydrogenation of carbon monoxide and hydrogenation of carbon dioxide (Killer 1982). Hydrogenation of carbon monoxide: CO + 2H2 → CH3 OH Hydrogenation of carbon dioxide: CO2 + 3H2 → CH3 OH + H2 O Other than the syngas route, methanol can also be produced directly from the hydrogenation of CO2 . This process can be a practical route to utilize CO2 , directly captured from the atmosphere and therefore contributes to greenhouse effect reduction (Hussin and Aroua 2020). Moreover, CO2 is a very stable, and non-toxic gas, therefore it is a very safe feedstock. Negative aspects of this process include a substantial amount of input energy in the process, and the requirement for hydrogen (Centi and Perathoner 2009; Valera and Agarwal 2019; Wang et al. 2020). Methanol, similar to other primary alcohols, is a volatile, colorless and flammable liquid. However, the fuel properties of methanol are significantly different from diesel. The basic fuel properties of methanol are listed in Table 7.1. It can be seen from the table that methanol has relatively higher autoignition temperature, latent heat of evaporation,

Fig. 7.1 Methanol production schematic

7 Combustion Characteristics of Methanol Fuelled Compression Ignition … Table 7.1 Basic fuel properties of methanol and diesel (EN 590 2013; Agarwal 2007; Valera and Agarwal 2019; Çelebi and Aydın 2019)

175

Property

Methanol

Chemical formulae

CH3 –OH

C8 –C25

Carbon content (wt %)

38

85–87

Hydrogen content (wt %)

12

13–15

Oxygen content (wt %)

50

0

Molar mass (kg/kmol)

32

183

Liquid density

(kg/m3

798

820–845

Calorific value (MJ/kg)

20.1

42.7

Boiling temperature (°C at 1 bar)

65

180–360

Kinematic viscosity

at 15 °C)

Diesel

(mm2 /s

0.59

2–4.5

Surface tension (N/m at 20 °C)

at 40 °C)

0.023

0.027

Cetane number

F” for lack of fit in the case of methanol were found to be less than 0.0440 indicating the model terms are significant.

12 Methodology to Predict Emissions and Performance …

309

Table 12.5 Post-ANOVA for quadratic model of BTE Post-ANOVA model summary statistics Source

SS

Model

2900.9

LFS Load Load x LFS

DF 5.07

2304.5

MS

F-value

P-value

Remarks

5

580.19

111.89