Numerical investigation on the initiation of oblique detonation waves in stoichiometric acetylene–oxygen mixtures with high argon dilution

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.