Combined effect of external mixture formation and cooled exhaust gas recirculation on engine performance and emissions characteristics of partially pre-mixed charged compression ignition engine

摘要

The present experimental study was aimed to investigate the combined effect of external mixture formation and cooled exhaust gas recirculation (EGR) on performance and emissions characteristics of partially homogeneous charge compression ignition (PCCI) engine. A conventional single-cylinder four-stroke compression ignition engine was modified to operate on PCCI mode with the supply of diesel fuel vapor via intake manifold during suction stroke. A Homogenous air-fuel charge was produced by using a retrofit system to provide fuel vapor. The engine was operated in two modes, direct injection (DI)-EGR and PCCI (DI-fuel vapor-EGR) mode, and then results were compared with DI (conventional) mode. Constant 10% EGR was maintained during DI-EGR and PCCI modes. Compared to conventional mode, in PCCI mode at full engine load, NO_X and smoke opacity were decreased by 2.39 g kW~(-1) hr~(-1) and 27% respectively, and the marginal penalty in HC and CO emissions by 0.4 and 0.1 g kW~(-1) hr~(-1) was observed. Brake thermal efficiency was slightly reduced by 2.5% compared to DI mode.