In-Cylinder Flow Analysis of a Spark Ignition Engine using Different Piston Head Geometries
Keywords:
Tumble flow, CFD, Piston head geometry, Fuel injection characteristics, Contours of mole fraction, Velocity magnitude.Abstract
The present study deals with the study of the in-cylinder tumble flow structures in a single-cylinder, two-valve, SI engine with three different piston crown shapes under motoring conditions at an engine speed of 2,000 revs/min., at various crank angle degrees (CADs) using Computational Fluid Dynamics (CFD). In this study we simulated the intake, compression, expansion, and exhaust processes in an SI engine cylinder, without considering fuel combustion, using Fluent. The port injection is modeled and evaporation of fuel droplets is included. The interaction of the fuel spray with the intake valve is modeled through the wall film modeling features available in Fluent. The geometry was modified twice by changing the shape of the piston head using GAMBIT. The geometries used were with the flat-crown piston, slightly concave-crown piston and dome piston. The whole simulation procedure was then carried out using modified geometries. The variations of the above-mentioned parameters with the piston head geometry were analyzed. The following parameters were plotted for the three geometries: fuel injection characteristics, contours of mole fraction, and contours of velocity magnitude. The optimum piston geometry was found out and it is suggested that the flat piston is a better choice in order to have good performance as well as low emission for modern SI engines.
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