Abstract

Oblique detonation waves (ODWs) in stoichiometric acetylene-oxygen mixtures, highly diluted by 81–90% argon, are studied using the reactive Euler equations with a detailed chemistry model. Numerical results show that the incident Mach number M0 changes the ODW initiation structure, giving both the smooth transition in the case of M0 = 10 and the abrupt transition in the case of M0 = 7. By comparing results of numerical simulation and theoretical analysis, the initiation processes are found to be chemical kinetics-controlled regardless of M0, different from those in hydrogen-air mixtures which are wave-controlled in the low M0 regime. The argon dilution effect on the initiation morphology is investigated, showing that the structures are determined by the dilution ratio and M0 collectively. However, the initiation length is found to be independent of the dilution ratio and only determined by M0, which is attributed to the competing effect of the high density and high temperature.