SUPERSONIC H-2-AIR COMBUSTIONS BEHIND OBLIQUE SHOCK-WAVES

In order to study the mechanisms of initiation and stabilization of H-2-Air combustions (stoechiometric mixture initially at T-0 = 293 K and p(o) = 0.5 bar) in supersonic flow conditions behind an oblique shock wave (OSW), an original technique is used where OSW is generated in this mixture by the lateral expansion of the burnt gas behind a normal CJ gaseous detonation propagating into a bounding reactive mixture. Four Mach number M of propagation of OSW are considered in the study, namely M = 7.7-6.1-4.4 and 3. Depending on the Mach number M and inclinaison angle theta of OSW different regimes of combustion may occur in the driven mixture. For high values of M (6.1 and 7.7) delayed steady overdriven oblique detonation waves (SODW) were obtained with a near CJ detonation wave as the critical regime. It was found that SODW obtained correspond quite well to prediction of the polar method. When thermal conditions behind the OSW are lower, either for high Mach number 6.1 and 7.7 for smaller angle theta than the previous case, or for lower Mach number, 4.4 and 3, the flame initiated at the apex is stabilized as a turbulent oblique flame behind the OSW. With much lower conditions, no combustion appears in the H-2-Air mixture.