Shock wave enhanced turbulent mixing in a wide-speed-range strut-based scramjet combustor

Abstract The efficient mixing of fuel and oxidizer in a scramjet combustor is a critical issue for achieving future wide-speed-range flight. A numerical study is conducted using Reynolds-averaged Navier–Stokes equations coupled with shear stress transport k - ω turbulence model to investigate the mixing characteristics of hydrogen and air in a wide-speed-range supersonic combustor. Validation case using the numerical simulations shows remarkable consistency with experimental observations, confirming the reliability and accuracy of the computational approach. The results indicate that during a wide-speed-range flight, the enhancement effect of shock waves on the growth of the mixing region thickness within the combustor persists. This is attributed to the baroclinic torque and volumetric expansion effects caused by the interaction of shock waves and the turbulent shear layer, which enhance vorticity. When the combustor entrance Mach number is relatively low, this enhancement effect is more pronounced. As the combustor entrance Mach number increases, the enhancement effect gradually decreases. The area of the fuel–air mixing region decreases significantly as the combustor entrance Mach number increases, with this reduction being more pronounced at a low equivalence ratio compared to a higher one. The mixing efficiency of the fuel–air decreases with increasing combustor entrance Mach number. At a low equivalence ratio, a higher combustor entrance Mach number delays the location of full mixing. At a higher equivalence ratio, increasing the combustor entrance Mach number may result in the fuel and air remaining incompletely mixed by the time they reach the combustor exit.