Validation and improvement of dimethyl ether kinetic models: Insights from ȮH laser-absorption measurements across a wide pressure range

Abstract

Aiming to provide stronger constraints on the detailed kinetic models of dimethyl ether (DME) over a wide range of temperatures, pressures, and equivalence ratios, reflected shock waves combined with UV laser absorption were used to quantitatively measure microsecond-resolved ȮH time-histories in the oxidation of highly Ar-diluted DME mixtures with varying equivalence ratios of 0.5, 1.0, and 2.0 over the temperature range of 1188–1823 K. Diagnostic wavelengths near 306.687 nm (1.5 atm) and 306.689 nm (15.5 atm) were selected at the peak of the R₁(5) transition of the ȮH A-X (0,0) rovibronic band. Details on the temperature- and pressure-dependence of the ȮH profiles were revealed by a series of meticulously designed measurements. The first ȮH time-history measurements under high pressures and more fuel-lean conditions provided additional validation targets for the modern reaction models. Comparative evaluation of five recent reaction kinetic models of DME against the new data revealed that none of them perfectly align with all the ȮH time-histories measured in this study. Nevertheless, NUIG Mech1.1 and the Hashemi model demonstrated superior overall predictive performance. Taking into account the predictive performance on the global parameter of ignition delays, NUIG Mech1.1 was chosen to identify key reactions governing the ȮH evolution behavior. A modified NUIG Mech1.1 was proposed by incorporating the recent experimental and literature theoretical work. These new quantitative measurements of ȮH time-histories of DME particularly at 15.5 atm provide a critical contribution to the database needed for further model development at micro-level and combustion organization.