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-, Chen k- and RNG k- 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. For analyzing and comparison of the results, turbulent kinetic energy (TKE), tumble ratio (TR) and, axial and radial velocities at known locations inside the engine cylinder were considered. From the analysis of results, it is found that RNG k- turbulence model best predicts the in-cylinder flow fields in a two-stroke engine. Copyright © 2013 SAE International.

J. M. Mallikarjuna

Department of Mechanical Engineering

Addepalli S. Krishna

Computational fluid dynamics

Diesel engines

Flow fields

Kinetic energy

Kinetics

Turbulence models

Turbulent flow

Velocity measurement

IN-CYLINDER FLOW ANALYSIS

IN-CYLINDER FLOWS

Particle image velocimetries

RADIAL VELOCITY

SINGLE CYLINDERS

Turbulent kinetic energy

TWO-STROKE ENGINE

Velocity vectors

Engine cylinders

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

In-Cylinder Flow Analysis in a Two-Stroke Engine - A Comparison of Different Turbulence Models Using CFD

SAE Technical Papers

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. The entire CFD simulations are performed at the engine speed of 2000 rev/min., and the overall equivalence ratio (ER) of 0.75. Finally, it is observed that the PA of 140 produced a rise of about 10.5% in indicated thermal efficiency (ITE) and 3% rise in peak heat release rate (HRR) with a compromise of 10.7% higher NOx emissions than that of the base case. © 2019 SAE International. All Rights Reserved.

Effects of Cylinder Head Geometry on Mixture Stratification, Combustion and Emissions in a GDI Engine - A CFD Analysis

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. The analysis is carried out at four overall equivalence ratios at an engine speed of 2000 rpm., and a fuel injection pressure of 100 bar using a six-hole injector. From the results, it is found that better mixture stratification, higher indicated mean effective pressure (IMEP), and lower emissions are obtained for a GDI engine with the conventional intake ports at overall equivalence ratios (ER) of 0.5 and 0.6, whereas they are better in the engine with swirl intake ports at the overall ERs of 0.7 and 0.8. © 2019 SAE International. All Rights Reserved.

Comparison of Conventional Intake Port and Swirl Intake Port on Mixture Formation in a GDI Engine - A CFD Analysis

The present study focuses on the evaluation of the effect of engine parameters on the characteristics of a GDI engine by CFD analysis. The analysis was carried out at three engine speeds (2000, 3000, and 4000 rev/min), at three compression ratios (10, 11, and 12) and at three fuel injection pressures (200, 300, and 400 bar). The overall equivalence ratio of the in-cylinder mixture was maintained at 0.75 in all the above cases. Finally, it is observed that, the turbulent kinetic energy and tumble ratio were more sensitive to the engine speed than to other parameters. The fuel injection pressure was found to play a vital role in obtaining combustible mixture near the spark plug at the time of spark. In addition, a low heat release rate occurred at the engine speed of 4000 rev/min compression ratio of 10 and fuel injection pressure of 200 bar. © 2016 Faculty of Engineering, Alexandria University

Fulltext

Alexandria Engineering Journal

Parametric analysis of a 4-stroke GDI engine using CFD

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. The CFD analysis is carried out using CONVERGE software. The boundary conditions required for the analysis are obtained from the available literature. In order to predict in-cylinder flows: mass, momentum and energy equations are solved by the finite volume scheme. The turbulence, combustion and fuel spray break up are analyzed by using RNG k-?, SAGE detailed chemical kinetics, kh-rt model respectively. The pressure and the velocity coupling are carried out by using the PISO algorithm. The post processing has been bone by using ENSIGHT software. Here, a single-cylinder, four-valve, pentroof head engine, at an engine speed of 1000 rev/min., is considered. The analysis is done for a range of fuel injection pressures, spark timings, number of injector holes and multi-stage injection strategy. From the results, we found that, for various fuel injection pressures, the soot emissions decrease by about 77.8 and 88.5% respectively for 150 and 200 bar fuel injection pressures, compared to that of 110 bar. When the spark timing is advanced, the soot emissions increase by about 3.3 and 4.5 times the order of magnitude respectively, at the spark timings of 15 and 20 CAD before TDC, compared to that of the 7.5 CAD before TDC. When 8 and 10 numbers of fuel injector holes are used, the soot emissions decrease by about 0.5 and 87.7% respectively, compared to that of the 6-hole injector. With two types of multi-stage fuel injection strategies considered, the soot emissions decrease by about 72.8 and 76.1% respectively, compared to that of single-stage fuel injection. Finally, we conclude that the fuel injection pressure, number of injector holes, spark timing and multi-stage fuel injection strategy play an important role in the mixture preparation and on soot emissions of a GDI engine. © 2017 SAE International.

Parametric Study on a Gasoline Direct Injection Engine - A CFD Analysis

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. The CFD models used are validated with the available experimental results in the literature to the extent possible. The mixture stratification is quantitatively estimated by a new method developed by the authors. From the results, it is found that, the mixture stratification is better at low engine speeds and low inlet air pressure. Also, it is found that higher stratification index (SI) resulted in low heat release rate. Copyright © 2017 SAE International.

SAE International Journal of Commercial Vehicles

Effect of Engine Parameters on Mixture Stratification in a Wall-Guided GDI Engine - A Quantitative CFD Analysis

International Journal of Heat and Fluid Flow

Computational and experimental study of annular photo-reactor hydrodynamics

SAE Technical Paper Series

A Review of Turbulent Combustion Modeling for Multidimensional In-Cylinder CFD

Journal of Fluids and Structures

Topological flow evolutions in cylinder of a motored engine during intake and compression strokes

The Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines

Effect of Injection Rate Control in a HSDI Diesel Engine(Diesel Engines, Combustion Modeling II)

International Journal of Engine Research

Large eddy simulations of in-cylinder turbulence for internal combustion engines: A review

In-cylinder flow analysis in a two-stroke engine - A comparison of different turbulence models using CFD

Journal	SAE Technical Papers
Publisher	SAE International
ISSN	01487191
Open Access	No