Simulation of the effects of dilution gas for the formation of CJ plane during the oblique detonation

This study aims to properly simulate transition patterns (the initiation structure between oblique shock wave and oblique detonation wave) to better understand the performance of oblique detonation wave engines under practical operating conditions. The former two cases are observed in a stoichiometric hydrogen-air mixture, the oblique detonation originates from the impact shock region where the pre-combustion hot gas near the wall interacts with the oblique shocks. In the second case, different proportions of dilution gas are tested. It is noted that a thermal choking condition due to strong compression waves during a sufficient duration results in the turning transverse waves and the inhomogeneous Chapman-Jouguet (CJ) plane. Therefore, the deformed CJ plane, the nonuniform combustion structures, and the overheated oblique detonation wave (ODW) with the excessive pressure rise are shown. Finally, it is concluded that the chemical equilibrium shift and the stability of ODW in the combustor are significantly affected by the expanding flow of dilution gases.