Study on ignition delay times of dimethyl ether/propane/O₂/Ar mixtures at elevated pressures

Ignition delay times of dimethyl ether (DME) and propane blends were measured in a shock tube at varied DME blending ratios (0%, 20%, 50%, 80%, 100%), equivalence ratios (0.5, 1.0, 2.0), temperatures (1100-1500 K) and pressures of 20 atm. Mechanism validations were conducted using different chemical kinetic models. A new C5 chemical model with DME sub-model was developed and it can well predict experimental ignition delay times of pure propane, DME and their blends. Experimental and numerical results show that with the decrease of temperature, the ignition delay times increase and the activation energy decreases slightly. With the increase of equivalence ratio, ignition delay times increase for propane and decrease for DME in this study. Ignition delay times decrease with the increase of DME blending ratio and the decrease rates become larger with the increase of equivalence ratio. The peak values of H and OH mole fraction increase with increasing the DME blending ratio, and they promote the ignition of DME/propane blends. Sensitivity analysis shows that the reaction rates of R1 and R353 increase with the increase of DME blending ratio and induces the decrease of the ignition delay time of DME/propane blends.