Reduced Chemical Kinetic Model of DME for HCCI Combustion

Homogeneous Charge Compression Ignition combustion engines could have a thermal efficiency as high as that of conventional compression-ignition engines and the production of low emissions of ultra-low oxides of NOx and PM. HCCI engines can operate on most alternative fuels, especially, dimethyl ether which has been tested as possible diesel fuel for its simultaneously reduced NOx and PM emissions. However, to adjust HCCI combustion to practical engines, the main problem about the HCCI engine must be solved; control of its ignition timing and burn rate over a range of engine speeds and loads. Detailed chemical kinetic modeling has been used to predict the combustion characteristics. But it is difficult to apply detailed chemical kinetic mechanism to simulate practical engines because of its high complexity coupled with multidimensional fluid dynamic models. Thus, reduced chemical kinetic modeling is desirable. A new reduced chemical kinetic mechanism has been derived, which contains 45 reactions and 28 species. Given the initial fuel-air mixture concentration, temperature, and pressure, the present model was used to predict the temperature, pressure, and species concentrations as a function of time. The calculated results were compared with the measured data and the detailed mechanism. The simulation results agreed well with the measured data in varying initial pressure and with the detailed mechanism in peak temperature. This reduced chemical kinetic model may serve as a basis for engine cycle simulation in predicting the DME oxidation in the HCCI combustion process.