Effect of piston bowl geometry modification and compression ratio on the performance and emission characteristics of DI diesel engine

The present study describes the experimental investigations carried out to study the influence of modified piston bowl geometry at a constant speed of the combustion, performance and emission characteristics of a direct injection compression ignition diesel engine. The modified piston profiles, namely hemispherical combustion chamber (HCC) and toroidal combustion chamber (TCC), are manufactured with a baseline compression ratio of 17:1, and the effects of compression ratio (16:1, 17:1 and 18:1) are analyzed. Experiments are carried out with pure diesel for low load to full load conditions for better understanding. With an increasing compression ratio of the engine, TCC piston geometry has shown better improvement in brake thermal efficiency, carbon monoxide and hydrocarbon emissions than HCC. However, a slight penalty in NOx emission is observed with increasing compression ratio and TCC piston geometry. In-cylinder peak pressure, net heat release rate and rate of pressure rise are increased significantly with increasing compression ratio and the use of TCC geometry.