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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).

For more than a decade there is a progressive demand for fuel efficient and high specific power output engines. Optimization of engine cooling and thermal management is one of the important activities in engine design and development. In the present paper an effort has been made to simulate the heat transfer modes of cylinder block and head for a present 4-stroke air-cooled motorcycle engine. Two and three-dimensional decoupled and conjugate heat transfer analysis has been done with commercially available computational fluid dynamics (CFD) codes. Experimental results are also presented. A complete simulation model has been developed and CFD techniques have been applied to design and optimize air cooling surfaces of cylinder head and block, for an air cooled motorcycle engine. The two dimensional analysis is an easy and fast method to predict fin surface temperature, heat transfer co-efficient and flow velocity.

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).

This paper deals with a numerical investigation on swirl generation by a helical intake port and its effects on in-cylinder flow characteristics with axisymmetric piston bowls in a small four-valve direct injection diesel engine. The novelty of this study is in determining the appropriate design and orientation of the helical port to generate high swirl. A commercial CFD software STAR-CD is used to perform the detailed three dimensional simulations. Preliminary studies were carried out at steady state conditions with the helical port which demonstrated a good swirl potential and the CFD predictions were found to have reasonably good agreement with the experimental data taken from literature. For transient cold flow simulations, the STAR-CD code was validated with Laser Doppler Velocimetry (LDV) experimental velocity components’ measurements available in literature.

In this study, an attempt has been made to estimate trapping efficiency of a two-stroke engine by CFD analysis under cold flow conditions. A single-cylinder, loop-scavenged, spark-ignition, two-stroke engine extensively used for two-wheeler application in India is being considered for the analysis. Engine geometry is modeled using commercial PRO-E software. Simulation is carried out using commercial CFD code STAR-CD. The CFD predictions are validated by available experimental data. In the present study, the trapping efficiency is estimated at various engine speeds with change in configurations of ports. From the analysis of results, it is found that, increasing exhaust port area relative to total transfer port area and engine speeds increase the trapping efficiency significantly. In general, it is possible to increase the trapping efficiency by about 4% at the engine speeds considered.

Nowadays, Direct Injection Spark Ignition (DISI) engines are very popular because of their lower fuel consumption and exhaust emissions due to lean stratified mixture operation at most of load conditions. In these engines, achieving mixture stratification plays an important role on performance and emission characteristics of the engine. Also, mixture stratification is mainly dependent on in-cylinder flows and air-fuel interaction, which in turn largely dependent on valve configurations. Therefore, understanding them is very much essential in order to improve the engine performance. In this study, a CFD analysis has been carried out on two- and four-valve four-stroke engines to analyze in-cylinder flows and air-fuel interaction at different conditions. The engines specifications considered here are taken from the literature for which experimental data is available. ‘STAR-CD’ software has been used for the CFD analysis. For meshing, polyhedral trimmed cells have been adopted.

This paper deals with in-cylinder flow field analysis in a motored two-stroke engine by CFD technique using STAR-CD. The main aim of this study is to find out the best turbulence model which predicts the fluid flow field inside the cylinder of a two-stroke engine. In this study, a single-cylinder, two-stroke engine which is very commonly used for two-wheeler application in India is considered. Entire analysis is done at an engine speed of 1500 rev/min. under motoring conditions. Here, three commonly used turbulence models viz. standard k-ε, Chen k-ε and RNG k-ε are considered. In addition, experiments were also conducted on the above engine at the motoring conditions to measure velocity vectors of in-cylinder flow fields using particle image velocimetry (PIV). The results of PIV were also used for validating the CFD predictions.

Premixed Charge Compression Ignition (PCCI) is a promising LTC strategy to reduce NOx and soot emissions without relying on after-treatment devices. One major drawback of PCCI is high HC and CO emissions resulting from fuel-wall impingement due to early injection of diesel. Narrow-angle direct injection (NADI) helps reduce the wall wetting of fuel. But it is effective only at lower loads. At mid and higher loads, it increases soot and CO emissions in small-bore engines due to the formation of fuel-rich pockets in the piston bowl region. This problem is addressed using a split injection strategy in the present work. A 3-D CFD model is developed and validated with experimental data at two load conditions. Simulations are performed using CONVERGE CFD software. Split injection strategies are explored using wide (148 deg) and narrow (88 deg) spray included angles.

Gasoline direct injection (GDI) engines are well known for their ability to operate at the stratified fuel-air mixture, and thereby they are highly efficient than port fuel injection (PFI) engines. However, the stratification of the in-cylinder mixture leads to higher nitrogen oxides (NOx) and soot emissions with lower hydrocarbon (HC) emissions. The PFI works under a homogeneous mixture, which leads to lower NOx and soot emissions with compensation of HC emissions. By combining the advantages of GDI and PFI modes, it is possible to achieve higher fuel efficiency with lower emissions. Therefore, in the present study, four different injection strategies, namely, pure GDI, gasoline-direct multiple-injection (GDMI), combined GDI with PFI (GDI-PFI), and pure PFI are investigated under various load conditions using computational fluid dynamics (CFD) analysis. The effect of these strategies on mixture formation, indicated mean effective pressure (IMEP), and emissions are evaluated.

Preparation of air-fuel mixture and its stratification, plays the key role to determine the combustion and emission characteristics in a gasoline direct injection (GDI) engine working in stratified conditions. The mixture stratification is mainly influenced by the in-cylinder flow structure, which mainly relies upon engine geometry i.e. cylinder head, intake port configuration, piston profile etc. Hence in the present analysis, authors have attempted to comprehend the effect of cylinder head geometry on the mixture stratification, combustion and emission characteristics of a GDI engine. The computational fluid dynamics (CFD) analysis is carried out on a single-cylinder, naturally-aspirated four-stroke GDI engine having a pentroof shaped cylinder head. The analysis is carried out at four pentroof angles (PA) viz., 80 (base case), 140, 200 and 250 with the axis of the cylinder.

In the present work, it is aimed at developing an integrated approach for combustor modeling involving rapid prototyping and water tunnel testing to assess the cold flow numerical simulations; the physical model will be subjected to cold flow visualization and parametric studies and CFD analysis to demonstrate its capability for undergoing rigorous cold flow testing. A straight through annular combustors is chosen for the present study because of it has low pressure drop, less weight and used widely in modern day aviation engines. Numerical Analysis has been performed using ANSYS-FLUENT. Three dimensional RANS equations are solved using k-ɛ model for the Reynolds numbers ranging from 0.64 x 105-1.5 x 105 based on the annulus diameter. Post processing the results is done in terms of jet penetration, formation of recirculation zone, effective mixing, flow split and pressure drop for different cases.

Gasoline direct injection (GDI) engines are now trending in automobile field because of good fuel economy and low exhaust emissions over their port fuel injection (PFI) counter parts. They operate with a lean stratified mixture in most of conditions. However, their performance is dependent on mixture stratification which in-turn depends on fuel injection pressure, timing and strategy. But, the main challenge to GDI engines is soot and particulate matter (PM) emissions. However, they can be reduced by employing multi-stage fuel injection strategy. Therefore, in the present work, an effort has been made to study the effect of fuel injection parameters on soot emissions of a GDI engine using the CFD analysis. In addition, the study is also extended to evaluate the performance, combustion and other emission characteristics of the engine. First the engine is modelled using the PRO-E software. The geometrical details of the engine are obtained from the literature.