Initiation characteristics of wedge-induced oblique detonation waves in a stoichiometric hydrogen-air mixture

The initiation features of two-dimensional oblique detonations from a wedge in a stoichiometric H₂-air mixture were studied via numerical simulations using the reactive Euler equations with detailed chemistry. A parametric study was performed to evaluate the effect of inflow pressure and Mach number on the initiation structure and length. Two transition patterns namely an abrupt transition from a multi-wave point connecting the oblique shock and the detonation surface and a smooth transition via a curved shock depend greatly on the inflow Mach number while the inflow pressure had little effect on the oblique shock-to-detonation transition type. Also a slightly more complex structure of abrupt transition type in the case of Mach number = 7.0 consisting of various chemical and gasdynamic processes in the shocked gas mixtures was observed. The initiation length decreased with increasing Mach number primarily due to the increase of -shock temperature. Furthermore the effect of Mach number on initiation length is independent of inflow pressure. Results of theoretical analysis based on the constant volume combustion theory were close to the numerical simulations in the case of high Mach number regardless of inflow pressure suggesting that the post-oblique-shock condition.