A comprehensively validated compact mechanism for dimethyl ether oxidation: an experimental and computational study

Dimethyl ether (DME) is regarded as one of the most promising alternatives to fossil fuels used in compression ignition engines. In order to critically evaluate its overall combustion behaviour via numerical simulations, an accurate as well as compact kinetic mechanism to describe its oxidation is most essential. In the present study, a short kinetic mechanism consisting of 23 species and 89 reactions is proposed to describe the oxidation of DME. This is based on the detailed San Diego mechanism. The short mechanism accurately reproduces the available experimental data for ignition delays, laminar flame speeds, and species profiles in flow reactors as well as jet-stirred reactors. To assess the validity of this reaction mechanism in non-premixed systems, extinction strain rates of DME-air mixtures, which are not available in the literature, are measured in a counter-flow diffusion flame burner as a part of the present work. The 23 species reaction mechanism is also able to predict the experimental data for extinction within the uncertainty limits. This mechanism is further reduced by introducing quasi-steady state assumptions for six intermediate species to finally obtain a 14-step global kinetic scheme. A code is developed in MATLAB to obtain these 14 global steps and their corresponding rate expressions in terms of the individual reaction rates. The 14-step mechanism performs as good as the 23 species mechanism for all the experimental data sets tested for.