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2022 | Book

Biogas Combustion Engines for Green Energy Generation

Authors: Prof. Eiji Tomita, Prof. Nobuyuki Kawahara, Assoc. Prof. Ulugbek Azimov

Publisher: Springer International Publishing

Book Series: SpringerBriefs in Applied Sciences and Technology


About this book

This book deals with the combustion and exhaust emissions of gas engines fueled with green biogas. Biogas is a mixture of gases, primarily consisting of methane and carbon dioxide. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, food waste, etc. Biogas is considered to be a renewable source of energy. Therefore, it can contribute to the prevention of global warming.
The biogas engine is used to co-generate electricity by operating engine and heat from hot exhaust gases. The energy source used very efficiently. Unlike other green energy sources such as wind and solar, biogas is readily available when needed.
This book first describes the basics of biogas and its application to internal combustion engines. Next, it describes the engine system and the combustion phenomena in the engine cylinder. Engine technology continues to advance in spark ignition and dual-fuel engines to achieve higher thermal efficiency and lower harmful emissions. Several advanced combustion technologies are introduced to achieve higher thermal efficiency while avoiding knocking.

Table of Contents

Chapter 1. Significance of Biogas, Its Production and Utilization in Gas Engines
Fighting global warming is urgent problem in the world now. This chapter describes the significance of preventing global warming. Effective utilization of biomass is one of the very important pathways for renewable energies. Among biofuels such as biochar, biodiesel, ethanol, producer gas, biogas, etc. this book focuses on biogas. Biogas is produced through anaerobic digestion (AD) process. Purified and upgraded biogas is used for producing high quality methane for injection in natural gas pipelines and engines. Biogas has been used in both, spark ignition engines and dual-fuel engines. It is important to utilize biogas engines for producing electricity and heat because biogas is suitable to local production for local consumption. Internal combustion engines are considered as important systems for conversion of chemical energy contained in biogas to power and electricity. The engine technologies have been developed and improved for a century. This book covers characteristics of combustion and exhaust emissions in spark ignition engines and dual-fuel engines fueled with biogas, as well as several new engine combustion technologies which can be applied to biogas engines.
Eiji Tomita, Nobuyuki Kawahara, Ulugbek Azimov
Chapter 2. Combustion and Exhaust Emissions of Biogas Spark Ignition Engines
Biogas is mainly composed of methane (CH4) and carbon dioxide (CO2) as presented in Chap. 1. Spark ignition reciprocating engines are often used for biogas engine because of only small modifications of fuel supply system from gasoline engine especially at small output powers. At first, spark discharge, burning velocity and flame structure are explained. Next, the effects of CO2 ratio, equivalence ratio, compression ratio, hydrogen addition, exhaust gas recirculation (EGR), fuel property and other physical parameters are shown based on the literature sources published. An example of analyzing method of combustion by using pressure history data is introduced combined with NOx (oxides of nitrogen) emission data. When CO2 ratio in the fuel increases, the burning duration becomes longer, and the burning rate becomes smaller due to smaller laminar burning velocity. Abnormal combustion of knock must be avoided in spark ignition engines. Autoignition and knock behavior in the end-gas region is visualized with a high-speed camera. Methane number as an indicator of resistance to knock is discussed. Pre-chamber with small holes, from where burned gas jets come out and make several ignition locations in a main chamber, is used in lean burn, large-sized bore engines because of shorter flame development time.
Eiji Tomita, Nobuyuki Kawahara, Ulugbek Azimov
Chapter 3. Combustion and Exhaust Emissions of Biogas Dual-Fuel Engines
Biogas can be utilized in dual-fuel engines because of higher thermal efficiency. Biogas is supplied from intake port and liquid diesel fuel is injected in the cylinder directly. The combustion starts from the autoignition of a mixture of vaporized liquid fuel, further igniting biogas and air mixture. The initial combustion occurs at multi points, leading to certain and stable ignition followed by turbulent combustion. At first, visualization of the dual-fuel combustion with micro pilot injection is presented. The effects of liquid fuel injected, biogas flow rate, load, carbon dioxide (CO2) ratio in biogas, exhaust gas recirculation (EGR), compression ratio, H2 addition, pre-heating and other parameters are reviewed based on the literatures. Next, an example of the combustion achieving higher output and thermal efficiency with micro pilot dual-fuel combustion is described, as well as exhaust emissions. After the premixed mixture is autoignited in the end-gas region in latter half of the combustion, pressure oscillation does not occur in some conditions and transition to abnormal knocking combustion is avoided. The effect of CO2 ratio on PREMIER combustion was investigated and it was found that with higher concentrations of CO2 it was easier to keep control of PREMIER combustion.
Eiji Tomita, Nobuyuki Kawahara, Ulugbek Azimov
Chapter 4. Advanced Combustion Technologies for Higher Thermal Efficiency
Recently, new technologies for higher thermal efficiency have been developed in internal combustion engines. New types of combustion processes and technologies have been proposed regardless of the type of an engine. Low temperature combustion (LTC) such as homogeneous charge compression ignition (HCCI) has been studied to achieve low NOx (oxides of nitrogen) and particulate matter (PM). This chapter discusses history and advantages of the HCCI combustion. HCCI combustion technology has been evolved into the reactivity controlled compression ignition (RCCI) and spark assisted compression ignition (SACI) types. Abnormal knocking combustion that occurs due to the flame propagation and thermochemical autoignition in the end-gas region is considered one of the barriers to achieve higher thermal efficiency. However, under controlled conditions, knocking combustion can be avoided in SACI and in the Premixed Mixture Ignition in the End-gas Region (PREMIER) combustion processes. Furthermore, new laser- and plasma-based ignition systems have been developed instead of conventional spark ignition system. Laser ignition, non-thermal plasma assisted ignition such as microwave assisted spark ignition, nanosecond pulsed discharge, corona, etc. are described. These technologies are explained in this chapter, which shows future directions of internal combustion engines toward increasing thermal efficiency and minimizing NOx and PM emissions.
Eiji Tomita, Nobuyuki Kawahara, Ulugbek Azimov
Biogas Combustion Engines for Green Energy Generation
Prof. Eiji Tomita
Prof. Nobuyuki Kawahara
Assoc. Prof. Ulugbek Azimov
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