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Hydrogen exhibits the notable attribute of lacking carbon dioxide emissions when used in internal combustion engines. Nevertheless, hydrogen has a very low energy density per unit volume, along with large emissions of nitrogen oxides and the potential for backfire. Thus, stratified charge combustion (SCC) is used to reduce nitrogen oxides and increase engine efficiency. Although SCC has the capacity to expand the lean limit, the stability of combustion is influenced by the mixture formation time (MFT), which determines the equivalence ratio. Therefore, quantifying the equivalence ratio under different MFT is critical since it determines combustion characteristics. This study investigates the viability of using a Laser Induced Breakdown Spectroscopy (LIBS) for measuring the jet equivalence ratio. Furthermore, study was conducted to analyze the effect of MFT and the double injection parameter, namely the dwell time and split ratio, on the equivalence ratio.

Optimizing fuel injection spray is essential to comply with stringent future emission regulations for hybrid vehicles and internal combustion engine vehicles, and the spray characteristics and geometry must be robust for various engine operating conditions. This study presents experimental and numerical assessments of spray for lateral-mounted gasoline direct injection (GDI) sprays with different plume arrangements to analyze collapse characteristics, which can significantly deteriorate the geometry and characteristics of fuel sprays. Novel spray characterization methods are applied to analyze complex spray collapse behaviors using LED-based diffusive back-illuminated extinction imaging (DBIEI) and 3D computed tomographic (CT) image reconstruction. High-fidelity computational fluid dynamics (CFD) simulations are performed to analyze the detailed spray characteristics besides experimental characterization.

Di-ethyl ether (DEE) belongs to the family of oxygenated fuels, which have been investigated as an alternative to conventional diesel. However, increasing the proportion of DEE in DEE-diesel blends changes its physicochemical properties. This work shows the non-evaporating and non-reacting spray characteristics of diesel, DEE20 (20% v/v DEE and 80% v/v diesel), and DEE40 (40% v/v DEE and 60% v/v diesel) were investigated. The effect of fuel injection pressure (FIP: 500 and 800 bar) on the spray morphology and droplet size distribution at different axial locations along the spray axis was done. FIP of 800 bar showed a reduction in Sauter mean diameter (SMD) of spray droplets with increasing axial distance due to improved spray atomisation because of the drag forces of the surrounding air on the fuel droplets. DEE20 showed a higher number of droplets having a smaller diameter than DEE40. DEE20 and DEE40 showed superior spray atomisation characteristics than diesel.

To meet the target of the CO2 regulations, it is mandatory to replace high-carbon fossil fuels with low-carbon fuels. Diesel/Natural Gas (NG) reactivity-controlled compression ignition (RCCI) can reduce CO2 emission, which stratifies two types of fuels with different reactivity. And also, RCCI produces less NOx and particulate matter emissions by reducing the in-cylinder temperature. However, RCCI must still be enhanced in terms of the thermal and combustion efficiencies at low and medium loads. In this work, a modified piston geometry was applied to improve the RCCI combustion. The piston geometry was designed to minimize heat loss and reduce flame quenching in an RCCI engine. Experiments were conducted using a single-cylinder engine with a displacement volume of 1,000 cc. Diesel was directly injected into the cylinder, and NG was fed through the intake port.

Considering the demand for sustainable transport, alternative fuels are a keen research topic for IC engine researchers. Among various alternative fuels being explored, Di-ethyl ether (DEE) is gaining popularity off-late for compression-ignition (CI) engines owing to its high cetane rating, oxygen presence in its molecular structure, and lower carbon content. This study explores the suitability of DEE blends in tractor engines. DEE blends [15% and 30% (v/v)] with diesel were compared with baseline diesel for combustion, and emission characterisation, keeping all parameters identical, including the fuel injection timings. Results were analysed for different engine loads at 1500 rpm. Delayed combustion was observed with DEE blends with diesel, possibly due to a higher cooling effect from DEE vaporisation and retarded dynamic fuel injection due to its higher compressibility. However, the DEE blend fuelled engine performance was comparable to baseline diesel.

The influence of early induction stroke direct injection on late-cycle flows was investigated for a lean-burn, high-tumble, gasoline engine. The engine features side-mounted injection and was operated at a moderate load (8.5 bar brake mean effective pressure) and engine speed (2000 revolutions per minute) condition representative of a significant portion of the duty cycle for a hybridized powertrain system. Thermodynamic engine tests were used to evaluate cam phasing, injection schedule, and ignition timing such that an optimal balance of acceptable fuel economy, combustion stability, and engine-out nitrogen oxide (NOx) emissions was achieved. A single cylinder of the 4-cylinder thermodynamic engine was outfitted with an endoscope that enabled direct imaging of the spark discharge and early flame development.

In marine or stationary engines, consistent engine performance must be guaranteed for long-haul operations. A dual-fuel combustion strategy was used to reduce the emissions of particulates and nitrogen oxides in marine engines. However, in this case, the combustion stability was highly affected by environmental factors. To ensure consistent engine performance, the in-cylinder pressure measured by piezoelectric pressure sensors is generally measured to analyze combustion characteristics. However, the vulnerability to thermal drift and breakage of sensors leads to additional maintenance costs. Therefore, an indirect measurement via a reconstruction model of the in-cylinder pressure from engine block vibrations was developed. The in-cylinder pressure variation is directly related to the block vibration; however, numerous noise sources exist (such as, valve impact, piston slap, and air flowage).

The application of dual-fuel combustion in the freight transportation sectors has received considerable attention due to the capability of achieving higher fuel efficiency and less pollutant emissions than the conventional diesel engines. In this study, high-speed flame visualization was used to investigate the phenomena of natural gas/diesel dual-fuel combustion in a single-cylinder heavy-duty engine with optical access. To implement diverse fuel blending conditions, diesel injection timing and natural gas substitution ratio were varied under constant fuel energy input. A novel flame regime separation method was implemented based on color segmentation in HSV color space to characterize the spatial distributions of premixed and non-premixed flame regimes. Flame images for larger natural gas substitution showed a significant reduction in the non-premixed flame regime accompanied by flame propagation along the vaporized diesel sprays.

The use of hydrogen as a possible fuel for internal combustion (IC) engines can help build a society with a clean transportation framework. Diluting the in-cylinder mixture can improve the efficiency of the engines. To prove the validity of lean burn in hydrogen IC engines, three different combustion modes are investigated in this study. The engine experiments are conducted in a spray-guided direct-injection (DI) spark-ignition engine with 10 MPa of hydrogen DI. When lean burn is applied to a hydrogen IC engine, the characteristics of pumping and heat transfer loss improve. The improvement in heat transfer loss is more significant than the reduction in negative pumping work for the indicated thermal efficiency. Among the three combustion modes, stratified charge combustion (SCC) develops the maximum indicated mean effective pressure. However, this mode deteriorates the combustion stability slightly. The nitrogen oxide emission is reduced when the excess air ratio is increased.

Mixture formation in GDI engine is considered crucial in determining combustion and emissions characteristics, which mainly depend on fuel spray quality. However, spray characteristics change with variations in control parameters such as fuel injection parameters, fuel injection strategy, engine operating conditions, and fuel properties. Growing research interest in the use of methanol as an additive with gasoline has motivated the need for deeper investigations of spray characteristics of these fuels. Although, it can be noted that sufficient literature is available in the area of spray characterization under several independent influencing factors, however, comparative analysis of gasohol spray behavior under different ambient conditions is hardly studied.

The rising concerns of emissions have put enormous strain on the automotive industry. Industry is, therefore looking for next-generation engines and advanced combustion technologies with ultra-low emissions and high efficiency. To achieve this, more insights into the combustion and pollutant formation processes in IC engines is required. Since conventional measures have not been insightful, in-situ measurement of combustion and pollution formation through optical diagnostics is being explored. Gaining full optical access into the diesel engine combustion chamber is a challenging task. The late-compression flow dynamics is not well understood due to limited access into the engine combustion chamber. These flow structures contribute immensely to fuel-air mixing and combustion. The objective of this study is to understand the role of combustion chamber design on vertical plane air-flow structures.

As global emission standards are becoming more stringent, it is necessary to increase thermal efficiency through the high compression ratio in spark-ignited engines. Various studies are being conducted to mitigate knocking caused by an increased compression ratio, which requires an understanding of the combustion phenomena inside the combustion chamber. In particular, the in-cylinder flow is a major factor affecting the entire combustion process from the generation to the propagation of flames. In the field of spark-ignited engine research, where interest in the concept of lean combustion and the expansion of the EGR supply is increasing, flow analysis is essential to ensure a rapid flame propagation speed and stable combustion process. In this study, the flow around the spark plug was measured by the Laser Doppler Velocimetry system, and the correlation with combustion in spark-ignited engines was analyzed.

Petroleum products are used to power internal combustion engines (ICEs). Emissions and depletion of petroleum reserves are important questions that need to be answered to ensure existence of ICEs. Indian Railways (IR) operates diesel locomotives, which emit large volume of pollutants into the environment. IR is looking for an alternative to diesel for powering the Locomotives. Methanol has emerged as a replacement for petroleum fuels because it can be produced from renewable resources as well as from non-renewable resources in large quantities on a commercially viable scale. It has similar/superior physico-chemical properties, which reduce tailpipe emissions significantly. It is therefore necessary to understand the in-cylinder phenomenon in methanol fueled engines before its implementation on a large-scale.

Alternative fuels, coupled with advanced engine technologies, are potential solutions to overcome energy crisis and environmental degradation challenges, that transport sector faces. Methanol has emerged as a potential candidate as an alternate fuel due to adequate availability of indigenous feedstocks, such as coal, biomass, and municipal solid waste (MSW). Policy makers of several countries are focusing on developing roadmap for methanol fueled vehicles, especially in developing countries like China and India. These countries have the largest two-wheeler market globally; therefore, methanol adaptability on 2-wheeler engine becomes important national priority. This study is aimed at feasibility assessment of methanol (M100) fueled two-wheeler engine using simulations. Present study was divided into four different phases.

Lean stratified combustion is a mean to dilute the fuel-air mixture leaner than stoichiometric ratio, by using stratification of fuel gradient in a spark ignition engine. Under the lean stratified combustion, differed from the stoichiometric homogeneous charge combustion, flame could propagate through extremely rich air-fuel mixture, while the global air-fuel mixture is under lean condition. The rich mixture causes considerable amount of particulate matter, but, due to large effect of efficiency improvement, the attractive point is on fuel economy compare to homogeneous charge SI combustion. The easiest way to reduce particulate matter is changing fuel to gaseous hydrocarbon, to minimize evaporating and mixing period.

Lean stratified combustion shows high potential to reduce fuel consumption because it operates without the intervention of a throttle valve. Despite its high fuel economy potential, it emits large amounts of particulate matter (PM) because the locally rich mixture is formed at the periphery of a spark plug. Furthermore, the combustion phasing angle is not realized at MBT ignition timing, which can bring high work conversion efficiency. Since PM emission and work conversion efficiency are in a trade-off relation, this research focused on reducing PM emission through achieving high work conversion efficiency. Two intake air control strategies were examined in this research; throttle operation and late intake valve closing (LIVC). The experiment was conducted in a single cylinder spray-guided direct injection spark ignition (SG-DISI) engine with liquefied petroleum gas (LPG). The injected fuel amount was fixed so as to investigate the effect of each strategy.

Most internal combustion engine makers have adopted after-treatment systems, such as selective catalytic reduction (SCR), diesel particulate filter (DPF), and diesel oxidation catalyst (DOC), to meet emission regulations. However, as the emission regulations become stricter, the size of the after-treatment systems become larger. This aggravates the price competitiveness of engine systems and causes fuel efficiency to deteriorate due to the increased exhaust pressure. Dual-fuel premixed charge compression ignition (DF-PCCI) combustion, which is one of the advanced combustion technologies, makes it possible to reduce nitrogen oxides (NOx) and particulate matter (PM) during the combustion process, while keeping the combustion phase controllability as a conventional diesel combustion (CDC). However, DF-PCCI combustion produces high amounts of hydrocarbon (HC) and carbon monoxide (CO) emissions due to the bulk quenching phenomenon under low load conditions as a huddle of commercialization.

Knocking combustion limits the downsized gasoline engines’ potential for improvement with regard to fuel economy. The high in-cylinder pressure and temperature caused by the adaptation of a turbocharger aggravates the tendency of the end-gas to autoignite. Thus, the knocking combustion does not allow for further advancing of the combustion phase. In this research, the effects of the ignition and valve timings on knocking combustion were investigated under steady-state conditions. Moreover, the optimal ignition and valve timings for the transient operations were derived with the aim of a greater fuel economy improvement, based on the steady-state analysis. A 2.0 liter turbocharged gasoline direct injection engine with continuously variable valve timing (CVVT), was utilized for this experiment. 2, 10, and 18 bar brake mean effective pressure (BMEP) load conditions were used to represent the low, medium, and high load operations, respectively.

Fuel atomization and air-fuel mixing processes play a dominant role on engine performance and emission characteristics in a direct injection compression ignition engine. Understanding of microscopic spray characteristics is essential to predict combustion phenomena. The present work investigated near nozzle flow and atomization characteristics of biodiesel fuels in a constant volume chamber. Waste cooking oil, Jatropha, and Karanja biodiesels were applied and the results were compared with those of conventional diesel fuel. The tested fuels were injected by a solenoid injector with a common-rail injection system. A high-speed camera with a long distance microscopic lens was utilized to capture the near nozzle flow. Meanwhile, Sauter mean diameter (SMD) was measured by a phase Doppler particle analyzer to compare atomization characteristics.

The maximum thermal efficiency of gasoline engine has been improving and recently the maximum of 40% has been achieved. In this study, the potential of further improvement on engine thermal efficiency over 40% was investigated. The effects of engine parameters on the engine thermal efficiency were evaluated while the optimization of parameters was implemented. Parameters tested in this study were compression ratio, tumble ratio, twin spark configuration, EGR rate, In/Ex cam shaft duration and component friction. Effects of each parameter on fuel consumption reduction were discussed with experimental results. For the engine optimization, compression ratio was found to be 14, at which the best BSFC without knock and combustion phasing retardation near sweet spot area was showed. Highly diluted combustion was applied with high EGR rate up to 35% for the knock mitigation.