Modeling Study on the Combusti and Emissions Characteristics of a Light-Duty DI Diesel Engine Fueled with Dimethyl Ether (DME) Using a Detailed Chemical Kinetics Mechanism 2004-01-1839

Dimethyl ether (DME) has been recognized as a prospective alternative fuel for diesel engines because of its good characteristics of excellent auto-ignition quality, low flame temperature combustion and low emissions. In the present study, the combustion and emissions characteristics of a light-duty direct injection (DI) diesel engine fueled with DME have been simulated using the CFD model based on the KIVA-3V code and a detailed chemical kinetics mechanism of DME for the ignition and combustion processes. This detailed chemical kinetics mechanism of DME consists of 291 reactions for 31 species. The results of ignition delay, engine cylinder pressure, heat release and species concentrations have also been compared with our previous experimental work and a good agreement has been demonstrated. It shows that the ignition delay of the DME is much shorter than the diesel fuel and it leads to a much lower peak pressure and nitrogen oxides (NO_x) emission due to less premixed combustion. The diffusive combustion of DME engine operation is faster than the diesel engine and it leads to the reduction of smoke, particulate matter (PM), unburned hydrocarbons and carbon monoxide emissions. Furthermore, the low temperature oxidation and high temperature pyrolysis processes for DME including the two-stage ignition phenomena of DME combustion and negative temperature coefficient region have also been analyzed in this study. The present numerical study of DME provides insight to in-cylinder engine combustion and emissions formation process.