Experimental and Kinetic Studies on Ignition Delay Times of Dimethyl Ether/n-Butane/O2/Ar Mixtures

Ignition delay times of stoichiometric dimethyl ether (DME) and n-butane blends were measured using shock tube at varied DME blending ratios (0, 30, 70, and 100%), temperatures (1200-1600 K), and pressures (1.2-5.3 atm). Simulation work was conducted using the Chemkin code with a NUI C4_47 mechanism. Correlations of ignition delay times were obtained on the basis of the measured data through multiple linear regressions. Results show that the ignition delay times increase linearly with the increase of 1000/T, and this indicates that the overall activation energy is kept unchanged at the conditions in the study. Increasing pressure decreases the ignition delay time. Ignition delay time decreases with the increase of the DME blending ratio. The peak mole fractions of H and OH radicals increase, and the timing at the peak value of H and OH radicals advances as DME increases. Analysis on the reaction pathway shows that, at high temperatures, hydrogen-abstraction reactions play a dominant role in the consumption of fuel rather than the unimolecular decomposition reactions. At high temperatures, chemical reactions of two fuel components are independent. Sensitivity analysis shows that the dominant reactions affecting ignition delay time are the reactions that mainly involve the participation of small molecules.