A Reduced Kinetic Reaction Mechanism for the Autoignition of Dimethyl Ether

A reduced kinetic reaction mechanism for the autoignition of dimethyl ether is presented in this paper. Dimethyl ether has proven to be one of the most attractive alternatives to traditional fossil fuels for compression ignition engines. It can either be produced from biomass or from fossil oil. For dimethyl ether, Fischer et al. (Int. J.Chem. Kinet. 32 ( 12 ) (2000) 713-740) proposed a detailed reaction mechanism consisting of 79 species and 351 elementary reactions. In the present work, this detailed mechanism is systematically reduced to 31 species and 49 reactions. The reduced mechanism is discussed in detail with special emphasis on the high temperature thermal decomposition of dimethyl ether and on the fuel specific depleting reactions, which produce the methoxymethyl radical. In addition, a reaction pathway analysis for low temperature combustion is applied, where hydroperoxy-methylformate is found to be the dominating parameter for the low temperature regime. A validation of the reduced mechanism is performed by calculating the ignition delay times in a pressure range from 1 bar to 40 bar, as well as at different equivalence ratios varying from 0.5 to 2.0 and temperatures from 625 K to 1650 K. These results are compared with experimental findings and values obtained using the detailed mechanism. Overall, very good agreement is achieved.