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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.

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.