Combustion of transverse hydrogen injection under interaction with shock wave in a supersonic airstream

Experimental and numerical studies of the interaction between a shock wave and combustion of a hydrogen jet in supersonic air flow were performed. The Mach number of the free-stream conditions was 1.5, the total pressure was 0.25 MPa, and the total temperature was 520 K to 840 K. A preburner was installed upstream of the hydrogen injection since self-ignition of hydrogen was difficult under these conditions. The injected gases contained a large amount of unburned hydrogen at high temperature since the equivalence ratio of the gases in the pre-burner was higher than 2.0 and the temperature in the pre-burner was lower than the adiabatic flame temperature of H₂/air premixed flames of the mixture. Without the incident shock wave, flameholding under such conditions could not be attained. When the incident point of the shock wave was upstream of the hydrogen injection slit, the flameholding was successful. In comparison with the case without the incident shock wave, the separation point of the boundary layer due to the incident shock wave moved further upstream and the separation region of the boundary layer extended further. It is presumed that the residence time of reactants increased in the separation region so that the flame-holding limit was extended.