Simulation Analysis of the Effects of EGR Rate on HCCI Combustion of Free-piston Diesel Engine Generator

摘要

The effects of exhaust gas recirculation (EGR) rate on homogeneous charge compression ignition (HCCI) combustion and emission of free-piston diesel engine generator (FPDEG) was investigated by using a three-dimensional (3-D) computational fluid dynamics (CFD) model of FPDEG.In the 3-D CFD model of FPDEG, the diesel mechanism with 109 species and 543 reactions was incorporated into the combustion model, and the soot and NOx production were calculated by Hiroyasu-NSC model and 12 steps NOx model.The simulation results showed that the EGR rate had great influence on the HCCI combustion and emission performance of FPDEG.As the EGR rate was changed from 0 to 10%, the HCCI combustion phase of FPDEG slightly lagged, the peak value of heat release, the maximum in-cylinder temperature and pressure and the NOx content significantly decreased, but SOOT content increased.When the EGR rate was 20%, the HCCI combustion of FPDEG was incomplete, and the UCH, SOOT and CO content all obviously increased.