Shock Tube Measurements and Kinetic Study on Ignition Delay Times of Lean DME/n-Butane Blends at Elevated Pressures

In this study, the ignition delay times of lean DME/n-C4H10 fuel blends diluted with argon were measured behind reflect shock waves over a wide range of conditions: pressures from 0.2 to 2.0 MPa, temperatures from 1100 to 1600 K, and DME blending ratios from 0 to 100%. The results show that for all of the mixtures, an increase in pressure significantly promotes the ignition of the fuel blends. An empirical Arrhenius correlation with high fidelity was proposed and was used to calculate the ignition delay times of DME/n-C4H10. Under fuel-lean conditions, both neat DME and neat n-C4H10 present almost uniform global activation energies. For a given temperature and/or pressure, the ignition delay time is considerably insensitive to changes in the DME blending ratio. Comparisons of the predictions by five available kinetic mechanisms with the measured ignition delay times were made, and NUIG Aramco Mech 1.3 was found to give excellent predictions for all of the tested mixtures. Hence, NUIG Aramco Mech 1.3 was used to make the kinetic analysis, including fuel flux analysis, sensitivity analysis, and mole fraction analysis of key radicals, and to interpret the effect of DME addition on the ignition chemistry of n-C4H10.