Combustion and emission characteristics of DME as an alternative fuel for compression ignition engines with a high pressure injection system

The subject of this work is the investigation of the injection characteristics of neat dimethyl ether (DME) and the effect of DME fuel on the exhaust emission characteristics and engine performance of compression ignition engines. In order to analyze the injection characteristics of DME fuel as an alternative fuel for compression ignition engines, experiments were conducted to obtain the injection rate profile. The effective nozzle diameter and its velocity, and the discharge coefficient of the nozzle were analyzed by applying a nozzle flow model that accounted for the effect of cavitation. In addition, combustion characteristics of DME and diesel fuel in terms of combustion pressure, rate of heat release, indicated mean effective pressure (IMEP), and ignition delay at various injection timings were investigated on a constant energy input basis.When a constant pulse width was applied, the results of DME injection characterization showed that the actual injection duration of DME was longer than that of diesel fuel because the injection started faster and ended with more delay. The DME fueled engine showed slightly higher IMEP and NO_x emission with drastically lower CO and HC emissions and the possible reasons for the higher IMEP of DME fuel was discussed.