Combustion and emission characteristics of premixed charge compression ignition engine

To improve the combustion and emission of a diesel engine, the effects of dimethyl ether (DME) pre-mixing ratio and cold exhaust gas recirculation (EGR) on combustion and emission characteristics of DME-diesel dual fuel PCCI (premixed charge compression ignition) engine were experimentally investigated on a 2105 diesel engine. DME was inducted to the intake air and diesel was injected directly into the cylinder to realize PCCI combustion mode. The results show that with increasing DME pre-mixing ratio, the heat release process is divided into three stages instead of two stages and combustion is advanced; the peak values of in-cylinder pressure increase and the corresponding phases are advanced; the decreasing level of the maximum in-cylinder pressure and the degree of phase latency corresponding to the maximum instantaneous heat release rate and the maximum pressure rise rate decline gradually with increasing DME pre-mixing ratio; the equivalent fuel consumption rate reduces and effective thermal efficiency increases with increasing pre-mixing ratio and decreasing EGR rate; NOx emission effectively decreases with increasing pre-mixing ratio and EGR rate, while HC and CO emissions increase. The optimum DME pre-mixing ratio is suggested as 30%.