Novel Internal Combustion Engine Technologies for Performance Improvement and Emission Reduction

In the last two decades, efficient and clean internal combustion (IC) engines have become the main requirement of society. To fulfil this demand, a lot of research is going on throughout the world. Few researchers have already focussed on advanced engine technologies for improving engine efficiency; however, current emission standards are pushing researchers to carry out some fundamental investigations to reduce the pollutant formation inside the combustion chamber and the development of advanced after-treatment systems to cut down the emissions from tail pipe. This book is based on these two aspects. The first section of this book covers several fundamental studies related to laser induced fluorescence (LIF) for pollutant formation, particle image velocimetry (PIV) for in-cylinder air flow characteristics and fuel spray investigations. The second section of this book is based on performance improvement and emission reduction by using after-treatment technologies and other techniques such as blending of nano-additives. Overall this book is based on the current measures of engine technologies used for performance improvement and emission reduction.

Laser diagnostic techniques have evolved as a pioneering tool for understanding the combustion and fluid dynamics in internal combustion (IC) engines. These are non-intrusive techniques, which provide fundamental insights about the in-cylinder processes such as spray characteristics, fuel-air mixing, combustion, pollutant formation, etc. without affecting/altering the underlying physics. This chapter is based on one such laser diagnostic technique namely ‘laser-induced fluorescence (LIF)’, which is capable of imaging the temperature-field and in situ species concentration during combustion. This chapter discusses a brief overview of optical diagnostics techniques, fundamentals of LIF, design, and development, current status and future trends for the application of this technology in IC engine research. This chapter also includes a comprehensive literature review of the applications of LIF in combustion investigations with a special emphasis on IC engines. Several examples and case studies have also been included in this chapter for a better understanding.

To make further progress on in situ reduction of pollutant formation in engines, the understanding of combustible mixture preparation is vital. Time-dependent development of flow structures and distribution of turbulent kinetic energy (TKE) are instrumental in charge preparation for both premixed as well as mixing controlled combustion phases. Non-linear and unsteady nature of in-cylinder air motion has remained a grey area ever since the days of initial development of internal combustion (IC) engines. The optimization of in-cylinder flow structures and development of numerical models for an in-depth understanding of the in-cylinder processes has become critical in view of the need for complying with stringent emission regulations. This can be realized by in-cylinder flow visualization and continuous tuning and validation of Computational Fluid Dynamics (CFD) models. Particle Image Velocimetry (PIV) has evolved as a pioneering tool for the investigation of intake air-flow structure, flow interaction and fluid motion. However, there are several challenges for the utilization of PIV for in-cylinder flow investigations in IC engines. While the intricate geometry of engine creates hindrance for optical access, the dynamic nature of ambient conditions complicates the selection of seeds. The work presented in this chapter summarizes these critical issues along with the possible solutions. Comprehensive literature on the evolution of PIV as a diagnostics tool for engine application has been covered. A brief review on the impact of flow structures on the combustion and pollutant formation has been also discussed. This chapter is useful for thorough understanding of PIV and its applications in IC engine and provides direction for further innovations in the field.

In the current scenario, alternative fuels are being explored, which can fulfil the global energy demand and meet stringent emission norms simultaneously. Dimethyl ether (DME) is one such alternative fuel that satisfies both these requirements. It has a high cetane number, which makes it suitable for heavy-duty engine applications. However, before the implementation of these new fuels in existing engines, various parameters need to be investigated and optimised. In compression ignition (CI) engines, one of the most important parameters is fuel–air ratio, which has a tremendous effect on engine combustion, performance, and emissions. Spray characteristics have a dominating effect on fuel–air mixture preparation. It depends on various parameters such as fuel injection pressure (FIP), injector geometry, fuel properties, and ambient conditions. Selection of fuel injection strategies and injector nozzle dimensions are primarily governed by spray characteristics of the fuel, injection timings, FIP, injection angle, and injector nozzle dimensions. This chapter summarises the production and application of DME in CI engines. The focus of this chapter is to analyse spray characteristics of DME under different ambient temperature and pressure conditions. The effect of spray characteristics on the in-cylinder mixture formation and engine combustion has also been discussed.

In the present scenario, research in the area of Internal Combustion (IC) engines is mainly driven to address the alarming depletion of conventional fossil fuels and to control the tail-pipe emissions in order to comply with stringent emission norms. Combustion is one of the primary reasons for global warming; however, ~80% of total global energy production is based on combustion of conventional fuels. Hence, researchers have been trying to understand the in-cylinder combustion phenomenon to improve efficiency of energy conversion devices and new ways to utilize alternate fuels. Spray studies in engine-like environment play vital role in combustion and consequent heat loss to the cylinder walls. Fuel spray affects the air–fuel mixture formation, which is responsible for combustion and emission formation in the engine combustion chamber. To study mixing processes and spray distribution, in-cylinder conditions need to be simulated in constant volume combustion chamber (CVCC). Development of high-pressure high-temperature chambers and optical diagnostics involves lasers and high-speed cameras. These investigations enable us to understanding the insights into combustion that takes place in few milliseconds. This chapter starts with design of combustion chambers, followed by explanation of prominent optical techniques. This is followed by detailed discussions with the help of recent studies involving these chambers and techniques to understand spray atomization and combustion in different operating conditions. This chapter aims to give an understanding of different aspects of experimental spray studies and their impact in the field of IC engines.

The demand for more efficient engines is increasing gradually and will continue to rise in the coming decades. In the present era, with the continuous rise in a global energy crisis and increasing ecological awareness, waste heat recovery became a common concern in various sectors of energy. The goal of this chapter is to address the role of waste heat recovery methods such as turbocharging, turbo-compounding, organic Rankine cycle, and thermoelectric generators, to enhance the thermal efficiency of the internal combustion (IC) engine over the past few decades. The maximum efficiency achieved in turbocharging is 44.1%, which is more than the conventional engines by 9.1–14.1%. The efficiency of turbo-compounding can be brought closer to 50%. The concept of compounded Rankine cycle increases the combined engine and waste heat recovery efficiency almost by 10%. The highest increment in the efficiency of the IC engine can be achieved with the thermoelectric generators which have tremendously increased the efficiency by almost 15–20%. This chapter provides some of the important basic information on IC engines and demonstrates some of the latest advanced technologies, such as engine downsizing, advance engine controls, variable valve timing, variable geometry engine design, advanced fuel injection, advanced compression ignition engines, advanced spark-ignition engines, alternative fuels that keep IC engines competitive due to their ability to improve the fuel economy and better performance of IC engines with near-zero emissions. Furthermore, the chapter presents opportunities, challenges, and technical barriers related to the future areas of IC engines.

Engine exhaust species such as nitrogen oxides (NOx), carbon monoxide (CO) and unburnt hydrocarbons (HC) are hazardous and pose a significant threat to the environment and the human health. Catalytic converter is installed in the engine exhaust manifold of modern vehicles for emission reduction. This device plays a significant role by simultaneous catalytic oxidation and catalytic reduction reactions. Catalytic converters themselves do not take part in chemical reactions but catalyse these reactions. There is a drastic reduction in CO, HC and NOx emissions in the exhaust, and these species are converted to harmless products exiting through the tailpipe. Catalytic converters are among the most developed and matured technologies to control exhaust emissions. Emissions concentrations of different emission species can be analysed upstream and downstream of the catalytic converter to evaluate their conversion efficiencies. Also, real-time catalyst temperatures can be determined by 1-D thermal modelling of the three-way catalytic converters. This chapter gives insights into the flow behaviour along with the transient temperature field across the catalytic converter, which helps understand overall working of the catalytic converter. Also, catalyst temperature distributions are discussed based on engine operating conditions in order to understand the effect of exhaust gas temperature on the catalytic converter efficiency.

Internal combustion engines (ICEs) have wide applications in several sectors, which are responsible for boosting the economy. However, engine emissions are of major concern as they significantly contribute to global air pollution. Worsening air quality has negative impact on human beings and nature. Regulated engine emissions include carbon monoxide (CO), unburned hydrocarbon (HC), oxides of nitrogen (NO_x), and particulate matter (PM). Globally, these emissions have been put under strict regulations by various emission regulation bodies. Severe issues related to the engine emissions can be resolved using efficient and advanced after-treatment devices. Use of exhaust gas after-treatment devices is one of the effective ways for engine emission reduction to meet the stringent emissions norms effectively. These devices involve complex chemical reactions. In this chapter, simultaneous reduction of PM and NO_x is focused, as both pollutants are difficult to reduce together because of PM/NO_x trade-off. Several NO_x and PM control devices used in ICEs, such as lean NOx traps (LNT), selective catalytic reduction (SCR) catalysts, and diesel particulate filter (DPF), are discussed in detail. Each after-treatment device has its advantages and limitations. Different integrated exhaust gas systems have been developed in the last couple of decades to address these limitations and enhance emission control efficiency. Various challenges and solutions to meet the emission norms using exhaust gas after-treatment devices have been discussed in this chapter.

Particulate matter structural modifications do not only impact the oxidative/mutagenic properties of the particulates but also influence the motion and contact between the aggregates in the exhaust. Those interactions have a direct impact on the porosity, permeability, and packing density of the soot cake deposited in the diesel particulate filter (DPF). This in turn will influence the filtration efficiency and pressure drop in the DPF channels. Morphology of the PM combined with the carbon layer nanostructure also has a direct impact on the DPF regeneration capability. After recognizing the importance of the particulates’ structure on the DPF performance, it becomes a subject of interest to understand if the engine-out PM will face any modifications within the aftertreatment units, e.g., diesel oxidation catalyst, selective catalytic reduction catalyst, etc., before being trapped in the DPF. While the dependency of the PM characteristics on its fueling source and engine technology is a well-researched topic, limited work has been carried out regarding the impact of the aftertreatment system on the structure (i.e., morphology and nanostructure) and chemical characteristics of the exhaust PM. This chapter will discuss the different theories and experimental work provided in the literature regarding the impact of aftertreatment systems on the PM characteristics. Special attention will be given on the impact of alcohols and other oxygenated fuels on this mechanism compared to conventional diesel fuel.

The frequent rise in the use of diesel engines in all fields emits harmful gases such as NO_x and CO, which causes significant environmental emissions, global warming, breathing problems, etc. (Sivalingam et al. 2019). In the investigation of the performance, combustion, and emission characteristics, using diesel water emulsion is mixed with hybrid nanoparticles as additives in Direct Injection (DI) diesel engine. Reducing the emission characteristics and increasing engine performance is to introduce emulsion fuels (Parthasarathy et al. 2021). The water content of 5% is added with the diesel fuel as blends of (D94% + W5%). The surfactant used is Span 80 and Tween 80 and mixed with diesel water emulsion using a mechanical stirring process. This reports on the use of cerium oxide (CeO₂), aluminum oxide (Al₂O₃), titanium dioxide (TiO₂) nanoparticles as an additive to diesel fuel. For this study, the fuel tested was prepared by blending three nanoparticles into diesel in a mass fraction of 50 ppm, 100 ppm, 150 ppm with the assistance of an ultrasonic stirrer. The diesel water emulsion is mixed with the nanoparticle and prepared as three different fuel blends such as (D90% + W5% + S5% + HBNP 50 ppm), (D90% + W5% +S5% + HBNP 100 ppm), and (D90% + W5% +S5% + HBNP 150 ppm). Based on experimental results, BTE increased by 8.3% and BSFC is reduced by 14.42% at (D94% + W5% +S1% + HB 150 ppm) blend when compared with the diesel, due to the atomization of the fuel and oxygen content available in the fuel. The emissions of CO is reduced by 10.2%; smoke, oxides of nitrogen emissions, and HC are reduced by 27.5%, 36.58%, and 27.77%, respectively, when compared with clean diesel fuel, because of microexplosion and proper atomization taking place during the combustion process. The cylinder pressure and HRR are increased by 3.2% and 2.8%, respectively, when compared with neat diesel fuel, due to increased combustion temperature and secondary atomization of fuel take places.