The flame-holding mechanism in hypersonic propulsion technology is the most important factor in prolonging the duration time of hypersonic vehicles. The two-dimensional coupled implicit Reynolds-averaged Navier-Stokes equations, the shear-stress transport k- turbulence model and the finite-rate/eddy-dissipation reaction models were used to simulate the combustion flow field of a typical strut-based scramjet combustor. We investigated the effects of the hydrogen-air reaction mechanism and fuel injection temperature and pressure on the parametric distributions in the combustor. The numerical results show qualitative agreement with the experimental data. The hydrogen-air reaction mechanism makes only a slight difference in parametric distributions along the walls of the combustor, and the expansion waves and shock waves exist in the combustor simultaneously. Furthermore, the expansion wave is formed ahead of the shock wave. A transition occurs from the shock wave to the normal shock wave when the injection pressure or temperature increases, and the reaction zone becomes broader. When the injection pressure and temperature both increase, the waves are pushed out of the combustor with subsonic flows. When the waves are generated ahead of the strut, the separation zone is formed in double near the walls of the combustor because of the interaction of the shock wave and the boundary layer. The separation zone becomes smaller and disappears with the disappearance of the shock wave. Because of the horizontal fuel injection, the vorticity is generated near the base face of the strut, and this region is the main origin for turbulent combustion. , hypersonic propulsion technology has drawn increasing attention from researchers. However, the flame-holding mechanism in the scramjet combustor cannot satisfy the requirement for cruising a long time in near-space [3] because of the short residence time of the mixture remaining in the supersonic flow, which is in the order of milliseconds [4]. This restricts improvement of the aerodynamic performance of hypersonic vehicles. To solve this problem, some fuel injection techniques have been proposed. The strut [5][6][7][8][9][10][11][12][13][14], the cavity [15][16][17][18], the cantilevered ramp [4], the backward facing step [19][20][21] and the combination [22][23][24][25], whose principle is to generate vorticity in the vicinity of the walls of the combustor. The region forming the vorticity, namely the recirculation zone, has low flow velocity. In this region the fuel mixes with the supersonic flow and the mixture can stay in the scramjet combustor for a long time. Zou et al. [6] have used a newly-proposed partiallyresolved numerical simulation procedure to investigate turbulent combustion in a two-dimensional DLR scramjet engine, and the large-scale turbulence was defined by the temporal filtering. Oevermann [7] has used a two-equation k- turbulence model combined with a stretched laminar
