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The main objectives of this research are to establish the practical use of DME (Dimethyl ether) diesel engine with high performance and clear the emission regulation in urban area by securing a stable DME supply system and the engine durability and reliability. In this research, the fuel injection system including a fuel supply system that provides a long-term stable engine operation was developed. The effect of thermal efficiency improvement using larger EGR (Exhaust gas recirculation) was not found by changing injection parameter. The decrease of suction temperature by cooling the EGR was the most effective in thermal efficiency improvement at the target NOx (Oxides of nitrogen) of 100 ppm (13%O2 conversion). With DME, the amount of PM (Particulate matter) with EGR was extremely low compared with diesel fuel. The endurance test was conducted for a continuous operation of 5000hrs and the engine and fuel system durability were achieved.

Time resolved changes in unburned hydrocarbon emissions and their components were investigated in a DI diesel engine with a specially developed gas sampling system and gas chromatography. The tested transient operations include starting and increasing loads. At start-up with high equivalence ratios the total hydrocarbon (THC) at first increased, and after a maximum gradually decreased to reach a steady state value. Reducing the equivalence ratio of the high fueling at start-up and shortening the high fueling duration are effective to reduce THC emissions as long as sufficient startability is maintained. Lower hydrocarbons, mainly C1-C8, were the dominant components of the THC and mainly determined the THC behavior in the transient operations while the proportion of hydrocarbon (HC) components did not significantly change. The unregulated toxic substances, 1,3 butadiene and benzene were detected in small quantities.