Effect of Exhaust Gas Recirculation on the Combustion and Emissions of Dimethyl Ether in a Passenger Vehicle Diesel Engine

The purpose of this work was to investigate the effect of the combustion and emission characteristics of dimethyl ether (DME), diesel fuel, and a DME-biodiesel blend on a passenger vehicle diesel engine. In this study, DME properties, atomization characteristics, and effects of the exhaust gas recirculation (EGR) rate on the combustion performance and emission characteristics of a diesel engine were investigated under single and split injection. The results show that DME atomization is better than that of conventional diesel fuel, and that increasing the EGR rate decreases the combustion pressure and heat release rate of the DME-biodiesel blend. Upon comparison, the maximum pressures of the pilot injections were significantly lower than those of the single injection for the DME-biodiesel. In addition, the maximum pressure decreased with the increasing EGR rate. However, the decrease was small compared with that of the pilot injection strategy. Exhaust emissions from the engine showed that increasing the EGR rate decreased combustion pressure and nitrogen oxide emissions, and increased hydrocarbon and carbon monoxide emissions. The soot was almost zero for the DME-biodiesel fuel and for the EGR rate variations.