Study on Ignition Delay Times of DME and n-Butane Blends

Ignition delay times of stoichiometric dimethyl ether (DME) and n-butane blends were measured in a shock tube at varied DME blending ratios, temperatures and pressures. Simulation work extended the pressure to 20 atm by using Chemkin and NUI C4_47 mechanism. The experimental ignition delay times of DME/n-butane were obtained at different DME blending ratios. Measured ignition delay times were compared to simulations based on NUI C4_47 mechanisms by Curran et al. The mechanism predicts the magnitude of ignition delay times well and a slightly higher activation energy. The ignition delay times increase linearly with the increase of 1000/T and the overall activation energy keeps almost the same value at the conditions in this study. Increasing pressure decreases exponentially the ignition delay time. Ignition delay time decreases linearly with the increase of DME blending ratio. The peak mole fractions of H radicals increase, and the timing at peak value of H radicals advances as DME increases. Sensitivity analysis shows that the dominant reactions affecting ignition delay time are mainly the small molecule elementary reactions.