This paper deals with the experimental investigations of the in-cylinder tumble flows in a single-cylinder engine with five different piston crown shapes at an engine speed of 1,000 rev/min., during suction and compression strokes under motoring conditions using particle image velocimetry. Two-dimensional in-cylinder tumble flow measurements and analysis are carried out in combustion space on a vertical plane passing through cylinder axis. Ensemble average velocity vectors are used to analyze the tumble flow structure. Tumble ratio and average turbulent kinetic energy are evaluated and used to characterize the tumble flows. From results, it is found that at end of compression, pentroof-offset-bowl piston shows about 41 and 103% improvement in tumble ratio and average turbulent kinetic energy respectively, compared to that of flat piston. The present study will be useful in understanding effect of piston crown shapes on nature of the in-cylinder fluid tumble flows under real engine conditions. © 2009 Springer-Verlag.

J. M. Mallikarjuna

Department of Mechanical Engineering

Bala C. Murali Krishna

Comparative studies

COMPRESSION STROKE

CROWN SHAPE

CYLINDER AXIS

ENGINE CONDITIONS

ENGINE SPEED

ENSEMBLE AVERAGES

Experimental investigations

Particle image velocimetries

SINGLE-CYLINDER ENGINES

TUMBLE FLOW

Turbulent kinetic energy

Vertical plane

combustion

Computational fluid dynamics

Electron energy loss spectroscopy

Engine pistons

flow visualization

Kinetic energy

SWIRLING FLOW

VELOCIMETERS

Velocity measurement

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

Experiments in Fluids

In-cylinder water injection is a promising approach for reducing NOx and soot emissions from internal combustion engines. It allows one to use a higher compression ratio by reducing engine knock; hence, higher fuel economy and power output can be achieved. However, water injection can also affect engine combustion and emission characteristics if water injection and injector parameters are not properly set. Majority of the previous studies on the water injection are done through experiments. Therefore, subtle aspects of water injection such as in-cylinder interaction of water sprays, spatial distribution of water vapor, and effect on flame propagation are not clearly understood and rarely reported in literature due to experimental limitations. Thus, in the present article, a computational fluid dynamics investigation is carried out to analyze the effects of direct water injection under various injector configurations on water evaporation, combustion, performance, and emission characteristics of a gasoline direct injection engine. The emphasis is given to analyze in-cylinder water spray interactions, flame propagation, water spray droplet size distribution, and water vapor spatial distribution inside the engine cylinder. For the study, the water-to-fuel ratio is varied from 0 to 1. Various water injector configurations using nozzle hole diameters of 0.14, 0.179, and 0.205 mm, along with nozzle holes of 4, 5, 6, and 7, are considered for comparison in addition to the case of no_water. Computational fluid dynamics models used in this study are validated with the available data in literature. From the results, it is found that the emission and performance characteristics of the engine are highly dependent on water evaporation characteristics. Also, the water-to-fuel ratio of 0.6 with 6 number of nozzle holes and the nozzle diameter of 0.14 mm results in the highest indicated mean effective pressure and the lowest NOx, soot, and CO emissions compared to other cases considered. © IMechE 2019.

International Journal of Engine Research

Effects of direct water injection and injector configurations on performance and emission characteristics of a gasoline direct injection engine: A computational fluid dynamics analysis

DISI (Direct injection spark ignition engines) are very popular today because of their low fuel consumption and exhaust emissions due to their operation at lean stratified mixture. Their performance depends on the level of mixture stratification, which in turn depends on in-cylinder flows and air-fuel interaction at the time of fuel injection. However, these are very much affected by combustion chamber configuration, which in turn is mainly dependent upon the piston shape. In this study, a CFD (computational fluid dynamics) analysis is carried out to analyze in-cylinder air flows and air-fuel interaction created by different piston shapes viz., flat, flat-with-center-bowl, inclined and inclined-with-center-bowl pistons in a four-stroke engine at an engine speed of 1500rev/min. Here, a start of fuel injection is considered at end of the suction stroke with a multi-hole injector operating at an injection pressure of 500bar. Engine specifications are selected from the literature for which experimental data is available for comparison. Finally, it is found that flat-with-center-bowl piston results in about 51% higher tumble ratio and about 21% higher turbulent kinetic energy of in-cylinder flows, better mixture stratification along with 33% higher evaporation rate and 33% higher percentage of fuel evaporation as compared to those of flat piston. © 2015 Elsevier Ltd.

Energy

Effect of piston shape on in-cylinder flows and air-fuel interaction in a direct injection spark ignition engine - A CFD analysis

Air motion inside the cylinder is very important from the point of view of energy efficiency. In this direction, piston configuration plays a very crucial role. This study is concerned with the CFD analysis of in-cylinder air motion coupled with the comparison of predicted results with the experimental results available in the literature. Four configurations viz., flat, inclined, centre bowl and inclined offset bowl pistons have been studied. For numerical analysis STAR-CD CFD software has been used. Experimental results available in the literature for comparison are obtained by PIV measurements. From this study, it is concluded that a centre bowl on flat piston is found to be the best from the point of view of tumble ratio, turbulent kinetic energy, turbulent intensity and turbulent length scale which play very important role in imparting proper air motion, there by increasing the energy efficiency of the engine. © 2012 Elsevier Ltd.

Applied Energy

Energy efficient piston configuration for effective air motion - A CFD study

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. Â© 2013 SAE International.

SAE International Journal of Engines

Analysis of In-Cylinder Air Motion in a DI Diesel Engine with Four Different Piston Bowl Configuration - A CFD and PIV Comparison

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. In-cylinder flows have been predicted by solving mass, momentum and energy equations by using SIMPLE algorithm. Air-fuel interaction has been predicted by solving droplet breakup, droplet-wall interaction and atomization models. The CFD results are compared with available experimental data. From the analysis of results, it has been found that four-valve engine configuration gives better in-cylinder flows and equivalence ratio near spark plug. Also, from the analysis, it is possible to obtain best possible combustion chamber geometry for DISI engine. © 2013 SAE International.

SAE Technical Papers

Simulation of in-cylinder flow and air-fuel interaction of four and two-valve DISI engines - A comparison

Experimental Thermal and Fluid Science

In-cylinder flows of a motored four-stroke engine with flat-crown and slightly concave-crown pistons

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science

A comparative study of turbulent velocity fields in an internal combustion engine with shrouded valve and flat/bowl piston configurations

PIV analysis of in-cylinder flow structures over a range of realistic engine speeds

Journal of Physics: Conference Series

Flow and Mixture Optimization for a Fuel Stratification Engine Using PIV and PLIF Techniques

Effect of inlet port on the flow in the cylinder of an internal combustion engine

Comparative study of in-cylinder tumble flows in an internal combustion engine using different piston shapes-an insight using particle image velocimetry

Journal	Experiments in Fluids
ISSN	07234864
Open Access	No