Numerical and Experimental Investigation on Combustion and Emission Characteristics of DME Fuel in a Compression Ignition Engine

The characteristics of spray behavior and combustion of DME (dimethyl ether) were investigated using experimental and numerical approaches. For experiments, injection rates and macroscopic spray characteristics were investigated at various injection parameters by using an injection rate system and a spray visualization system. The combustion and emission characteristics were also obtained from the modified engine for DME fuel and emission measurement equipment. For numerical approaches, the combustion characteristics of DME fueled engine were predicted by a 3D-CFD code, the KIVA code coupled with the CHEMKIN (KIVA-CHEMKN) and spray behavior and evaporation were calculated by considering the thermo-chemical properties of DME. In order to calculate the fuel oxidation and emission formation such as NOx, a detailed chemical kinetic mechanism which was composed of 83 species and 360 reaction paths was considered. To simulate soot emission, two-step phenomenological model was applied. Both experimental and numerical results indicate that injection delay, ignition delay, and combustion duration of DME are shorter than that of diesel because of good evaporation and mixing characteristics. The pressure history predicted by the KIVA code agrees well with the measurements from the test engine. The amount of NOx emission was predicted by the reduced NOx mechanism shows good agreements to the experiments.