Effect of swirl on performance and emissions of CI engine in HCCI mode

A promising combustion strategy that combines the advantages of both SI and CI combustion modes is the homogeneous charge compression ignition (HCCI) combustion mode. A volumetric combustion of a lean mixture of charge is the advantage of HCCI combustion, leading to low NO x emissions and soot. In this work, HCCI combustion mode is analyzed to study the effect of swirl motion of intake charge on performance and emissions of the engine using a Three-Zone Extended Coherent Flame Combustion Model (ECFM-3Z, Compression Ignition). The present study revealed that ECFM-3Z of STAR-CD predicts well the in-cylinder pressures, temperatures, cylinder wall heat transfer losses, piston work and emissions such as CO, CO 2 and NO x of the CI engine in the HCCI mode. The ECFM-3Z model has a predicted variation in turbulent kinetic energy and velocity magnitudes inside the cylinder during combustion, facilitating better understanding of the combustion process. The simulation results show that the there is a reduction in in-cylinder peak pressures and temperatures, as the swirl increases and CO emissions increase because of reduced temperatures, and CO 2 and NO x emissions decrease because of the reduced in-cylinder temperatures. It is found that there is a trade-off between the emissions and piston work. Higher turbulent energy and velocity magnitude levels are obtained with increase in swirl, indicating efficient combustion without a demanding combustion chamber design.