气 体 引 射 效 应 对 壁 面 热 流 和 摩 擦 阻 力 的 影 响

The ablative thermal protection material will be pyrolyzed under high thermal load. The produced pyrolysis gas is injected into the boundary layer, reducing heat flux and skin-friction drastically. Firstly, the boundary condition of wall mass injection is established, and the accuracy of this boundary is verified. After that, for the hypersonic blunt wedge model, the mechanisms of the influence of different angles of attack and different gases on the wall heat flux and skin-friction are studied. The numerical results show that due to the existence of wall mass injection, the distance of the windward detached shock from the wall increases, and the high-temperature region is pushed away from the wall, reducing the wall heat flux and skin-friction. Compared with air injection, the distance of the detached shock due to pyrolysis gas at the same mass flow rate is farther from the wall, and the temperature gradient, viscosity coefficient, and velocity gradient also decrease obviously in the boundary layer. Therefore, the reduction of heat flux and skin-friction by pyrolysis gas injection is more significant, and the efficiency of heat flux and skin-friction reduction increases with the decrease of the attack angle. Comparison of the results at different mass flow rates finds that the increase in air injection mass flow rate improves the efficiency of heat flux and skin-friction reduction, and the efficiencies of both is nearly equal when the air injection mass flow rate is twice that of the pyrolysis gas.