Investigation on effects of cold EGR on combustion and emission characteristics in a DME PCCI-DI engine

Part charge compression ignition and direct injection (PCCI-DI) combustion can effectively reduce NO_x emissions, however the PCCI-DI operation is liable to be effected by knocking at high load region, which would lead to engine power lowered and emissions deteriorated. In view of the fact, the experimental investigation into the effects of cold EGR on performance and emissions of DME PCCI-DI engine was carried out. Results show that for PCCI-DI engine, with EGR rate increasing the peak cylinder pressure lowers and main combustion duration delays and extends slightly, NO_x emissions reduce. However, high EGR rate may result in engine HC and CO emissions rapid rise. It is concluded, in the DME PCCI-DI engine introducing the cold EGR may improve combustion process and widen operation range to a certain extent.