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Air motion inside the engine cylinder plays a predominant role on combustion and emission processes. An attempt has been made in this investigation to simulate the in-cylinder air motion in a DI diesel engine with four different piston configurations such as dome piston, bowl on dome and pentroof piston and pentroof offset bowl piston. For computational analysis, the commercial general purpose code STAR-CD Es-ice has been used, which works on the method of finite volume. To validate the simulation, qualitative and quantitative comparisons have been done with the PIV results available in the literature. From this study, the best possible piston configuration has been arrived at.

Today, GDI engines are becoming very popular because of better fuel economy and low exhaust emissions. The gain in fuel economy in these engines is realized only in the stratified mode of operation. In wall-guided GDI engines, the mixture stratification is realized by properly shaping the combustion chamber. However, the level of mixture stratification varies significantly with engine operating conditions. In this study, an attempt has been made to understand the effect of engine operating parameters viz., compression ratio, engine speed and inlet air pressure on the level of mixture stratification in a four-stroke wall-guided GDI engine using CFD analysis. Three compression ratios of 10.5, 11.5 and 12.5, three engine speeds of 2000, 3000 and 4000 rev/min., and three inlet air pressures of 1, 1.2 and 1.4 bar are considered for the analysis. The CONVERGE software is used to perform the CFD analysis. Simulation is done for one full cycle of the engine.

Today, gasoline direct injection (GDI) engine is one of the best strategies to meet the requirement of low pollutant emissions and fuel consumption. Generally, the GDI engine operates in stratified mixture mode at part-load conditions and homogeneous mixture mode at full-load conditions. But, at part-loads, soot emissions are found to be high because of improper air-fuel mixing. To overcome the above issue, a homogenous-stratified mixture (a combination of the overall homogeneous lean mixture with a combustible mixture at the location of the spark plug) is found to be better to reduce soot emissions compared to a stratified mixture mode. It will also help reduce fuel consumption. In this study, the analysis has been done to evaluate the effect of homogeneous-stratified mixture combustion on the performance and emission characteristics of a spray-guided GDI engine under various conditions using computational fluid dynamics (CFD).

The mixture formation in gasoline direct injection (GDI) engines operating at stratified condition plays an important role in deciding the combustion, performance and emission characteristics of the engine. In a wall-guided GDI engine, piston profile is such that the injected fuel is directed towards the spark plug to form a combustible mixture at the time of ignition. In these engines, fuel injection pressure and timing play an important role in creating a combustible mixture near the spark plug. Therefore, in this study, an attempt has been made to understand the effect of fuel injection pressure with single and split injection strategy on the mixture formation in a four-stroke, wall-guided GDI engine operating under stratified conditions by using computational fluid dynamics (CFD) analysis. Four fuel injection pressures viz., 90, 120, 150 and 180 bar are considered for the analysis.

Future stringent emission norms are impelling researchers to look for new emission control techniques. Today, gasoline direct injection (GDI) engines are becoming more popular because of high potential to reduce exhaust emissions over a wide operating load range, unlike conventional port fuel injection (PFI) engines. Also, turbocharged GDI engines allow engine downsizing with a certain restriction on compression ratio (CR) due to knocking tendency, thereby limiting the fuel economy. However, use of exhaust gas recirculation (EGR) delays combustion and lowers the knocking tendency which will aid in improving the fuel economy. Therefore, this study is aimed to evaluate the effect of EGR rate on the performance and emission characteristics of a two-liter turbocharged four-stroke GDI engine by computational fluid dynamics (CFD) analysis. For the analysis, the CR of 9.3 and the engine speed of 1000 rev/min., are selected.

Mixture distribution in the combustion chamber of gasoline direct injection (GDI) engines significantly affects combustion, performance and emission characteristics. The mixture distribution in the engine cylinder, in turn, depends on many parameters viz., fuel injector hole diameter and orientation, fuel injection pressure, the start of fuel injection, in-cylinder fluid dynamics etc. In these engines, the mixture distribution is broadly classified as homogeneous and stratified. However, with currently available engine parameters, it is difficult to objectively classify the type of mixture distribution. In this study, an attempt is made to objectively classify the mixture distribution in GDI engines using a parameter called the “stratification index”. The analysis is carried out on a four-stroke wall-guided GDI engine using computational fluid dynamics (CFD).

Gasoline direct injection (GDI) engines have gained popularity in the recent times because of lower fuel consumption and exhaust emissions compared to that of the conventional port fuel injection (PFI) engine. But, in these engines, the mixture formation plays an important role which affects combustion, performance and emission characteristics of the engine. The mixture formation, in turn, depends on many factors of which fuel injector location and orientation are most important parameters. Therefore, in this study, an attempt has been made to understand the effect of fuel injector location and nozzle-hole orientation on the mixture formation, performance and emission characteristics of a GDI engine. The mixture stratification inside the combustion chamber is characterized by a parameter called “stratification index” which is based on average equivalence ratio at different zones in the combustion chamber.

In modern direct injection gasoline engines, air-fuel mixing has a strong influence on combustion and emission characteristics, which in turn largely depends on in-cylinder fluid motion. However, in-cylinder fluid motion dependent on many engine parameters viz., piston shape, engine speed, intake manifold orientation, compression ratio, fuel injection timing, duration, etc. Among them, piston shape has significant influence on the in-cylinder fluid motion. Therefore, this study aims on evaluating the effect of piston shape on in-cylinder flows in a direct injection engine using CFD. In this study, a single-cylinder, two-valve, four-stroke direct injection engine designed for two-wheeler application in India is considered for the analysis. ‘STAR-CD’ and és-ice’ are used for CFD analysis. Pressure boundary values obtained from measurements in the actual engine are employed. Two piston-shapes viz., flat and bowl types at wide-open-throttle under non-firing conditions are considered.

Direct injection diesel engines are used in both light duty and heavy duty vehicles because of higher thermal efficiency compared to SI engines. However, due to only short time available for fuel-air mixing, combustion process depends on proper mixing. As a result, DI Diesel engine emits more NOx and soot into the atmosphere. Therefore, to achieve better combustion with less emission and also to accelerate the fuel-air mixing to improve the combustion, appropriate design of combustion chamber is crucial. Hence, in this work a study has been carried out using CFD to evaluate the effect of combustion chamber configuration on Diesel combustion with two different piston bowls. The two different piston configurations considered in this study are centre bowl on flat piston and pentroof offset bowl piston.

Gasoline compression ignition using a single gasoline-type fuel has been shown as a method to achieve low-temperature combustion with low engine-out NOx and soot emissions and high indicated thermal efficiency. However, key technical barriers to achieving low temperature combustion on multi-cylinder engines include the air handling system (limited amount of exhaust gas recirculation) as well as mechanical engine limitations (e.g. peak pressure rise rate). In light of these limitations, high temperature combustion with reduced amounts of exhaust gas recirculation appears more practical. Furthermore, for high temperature Gasoline compression ignition, an effective aftertreatment system allows high thermal efficiency with low tailpipe-out emissions. In this work, experimental testing was conducted on a 12.4 L multi-cylinder heavy-duty diesel engine operating with high temperature gasoline compression ignition combustion using EEE gasoline.

Nowadays, due to the stringent engine emission norms, an efficient technique is required to reduce oxides of nitrogen (NOx) from automobiles especially from the lean burn engines. Selective Catalytic Reduction (SCR) is found to be an efficient after treatment method used to reduce oxides of nitrogen (NOx) from the exhaust. However, for light duty vehicles, because of the limited size of the catalysts, ammonia slip nullifies its advantages. Lack of uniformity of ammonia at the SCR monolith entrance causes ammonia slip. This study addresses the effect of injection parameters, location of injector and shape of injector upon the flow parameters, exhaust gas temperature and flow rate. The results obtained from this study provide useful guidelines for optimizing the injection parameters to avoid the ammonia slip. The evaporation of Urea Water Solution (UWS) is also investigated.

In the present work, experiments were conducted on a single cylinder, three-wheeler, spark ignition engine operating with hydrogen as a fuel. In this work, hydrogen was inducted through the intake manifold to the engine. The engine was always operated with wide-open throttle (WOT). To vary the output, the equivalence ratio was varied. For all outputs, the spark timing was set for MBT (minimum advance for best torque). For each output, performance, emission and combustion parameters were recorded and analyzed. For comparison of results, with the same engine, the experiments were also conducted with gasoline as a fuel using a conventional carburetor. It was observed that the hydrogen engine produces less maximum power than its gasoline counterpart. From the analysis of the results, it was found that the efficiency of hydrogen engine was quite higher than gasoline engine at optimized conditions at all the operating points.

In order to achieve good fuel spray characteristics, proper placing of the fuel injector in the intake manifold in port fuel injected (PFI) gasoline engines is very crucial. In automotive PFI engines, vehicle layout may be a constraint to mount the fuel injector in best possible location and inclination. In general, PFI engines use straight spray fuel injection. However, if there is a vehicle layout constraint, then inclined fuel spray may be suitable which is not very common. Hence, it is important to understand the effect of fuel spray inclination on fuel spray characteristics. In this study, a CFD analysis has been carried out for the four inclinations of fuel spray and the results are compared. The geometrical modeling of the fuel injector is done using ProE software. It is meshed with polyhedral cells and mesh refinement is done wherever required. Inlet air velocity and exit pressure of intake pipe at wide-open-throttle conditions are used as boundary conditions.

Diesel engines are one of the most popular combustion systems used in different types of heavy-duty applications because of higher efficiencies compared to the spark ignition engines. Combustion phasing and the rate of heat release in diesel engines are controlled by the rate at which the fuel is injected into the combustion chamber near top dead center. In this work, computational fluid dynamics (CFD) was employed to simulate the combustion behavior of a heavy-duty diesel engine equipped with a 16-hole injector, in which the nozzles were arranged in two individual rows. The two rows of nozzles have differential flow rate due to the geometrical construction of the injector. Combustion and performance characteristics of the engine were compared with and without considering the differential flow rate of the nozzle rows at a range of injection timing values.

This paper deals mainly with the computer simulation and experimental investigations on a single cylinder, four stroke, spark ignited, extended expansion engine. The simulation procedure involves thermodynamic and global modeling techniques. Submodels for predicting gas exchange processes, heat transfer and friction are used. Two-zone model is adopted for combustion process. The combustion model predicts mass burning rate, ignition delay and combustion duration. It uses sub-models for calculating flame-front area, flame-speed and chemical equilibrium composition of ten product species. Experimentally measured valve-lift data along with suitable coefficient of discharge is used in the analysis of gas exchange process. Unburned hydrocarbons, carbon monoxide and nitric oxide emissions have also been predicted. Experiments have been conducted on a single cylinder, air cooled, four stroke, spark ignition engine. A production engine was modified to run as extended expansion engine.

Water injection in diesel engines is a successful way to reduce NOx emissions and enhance brake power output. The advantages of water injection are because of its high enthalpy of vaporization and high specific heat capacity by which it absorbs heat from the in-cylinder mixture. The benefits of water injection depend on the rate of water vaporization and its spatial distribution in the combustion chamber. However, detailed effects of these parameters are very rarely studied in the past. Therefore, in the present study, an attempt has been made to assess the effect of water injector configuration on performance of a GDI engine by CFD analysis. Here, the analysis is done mainly to study and enhance the evaporation and spatial distribution characteristics of the water injection inside the combustion chamber. Water is directly injected into the cylinder of a naturally aspirated, four-stroke GDI engine.

Gasoline direct injection (GDI) engines have picked up prominence in the current circumstances in light of lower fuel consumption and exhaust emissions. Mixture formation in these engines plays a critical role which affects the combustion, performance and emission characteristics. To get better mixture formation, various factors ought to be considered, of which intake port design is one of the factors of considerable importance. Therefore, in this study, a comparison of mixture formation, performance and emission characteristics has been analyzed in a GDI engine with conventional intake port and swirl intake port. The analysis is carried out on a four-stroke wall-guided GDI engine using the computational fluid dynamics (CFD) with the help of the CONVERGE. The validation of spray breakup model is carried out to the extent possible using the experimental results available in the literature.

Gasoline compression ignition is a promising strategy to achieve high thermal efficiency and low emissions with limited modifications to the conventional diesel engine hardware. It is a partially premixed concept which derives its superiority from higher volatility and longer ignition delay of gasoline-like fuels combined with higher compression ratio typical of diesel engines. The present study investigates the combustion process in a gasoline compression ignition engine using computational fluid dynamics. Simulations are carried out on a single cylinder of a multi cylinder heavy-duty compression ignition engine which operates at a compression ratio of 17:1 and an engine speed of 1038 rev/min. In this study, a late fuel injection strategy is used because it is less sensitive to combustion kinetics compared to early injection strategies, which in turn is a better choice to assess the performance of the spray model.

Direct-injection spark-ignition engines are becoming popular nowadays in automobiles because of their low fuel economy and exhaust emissions. They operate with a lean stratified mixture in most load conditions. However, their entire performance and emissions are dependent on stratification at different load conditions. In fact, stratification in these engines depends upon in-cylinder flows and air-fuel interactions, which in turn dependent on combustion chamber shape, compression ratio and engine speed etc. Among them, combustion chamber shape plays an important role and hence understanding its effect is very much essential to optimize its configuration in these engines. Therefore, in this study, a CFD analysis using a commercial software has been carried out with different combustion chamber shapes formed by using different piston top profiles in a two-valve four-stroke engine.

In gasoline direct injection (GDI) engines, air-fuel mixture homogeneity plays a major role on engine performance, especially in combustion and emission characteristics. The performance of the engine largely depends on various engine operating parameters viz., start of injection, duration of injection and spark timing. In order to achieve faster results CFD is becoming a handy tool to optimize and understand the effect of these parameters. Therefore, this study aims on evaluating the two injection parameters viz., single and split injection to evaluate different flame characteristics. Novelty in this study is to define five different parameters which are called α, β, γ, δ and η the details of which are explained in the paper. In order to understand the flame characteristics, these five parameters are found to be very useful. In the present study, a single-cylinder, two-valve, four- stroke engine which is used in two-wheelers in India is considered for carrying out the CFD analysis.