高焓化学非平衡流条件下C/SiC复合材料的催化性能

碳化硅陶瓷基复合材料（C/SiC）成为最有希望满足临近空间高超声速飞行器热防护要求的耐高温关键材料之一，其在高焓化学非平衡流条件下的催化性能是评估新一代高超声速飞行器表面气动热载荷，热防护系统精细化设计的关键参数。基于1 MW高频等离子体风洞，采用已建立起的防热材料催化特性试验测试方法开展了C/SiC材料在驻点压力分别为1.0、1.8、3.3和6.0 kPa，焓值为19.3~35.9 MJ/kg范围内的高焓离解空气环境下，在表面温度为1 453~2 003 K范围内的表面催化反应复合效率随表面温度和表面原子压力的变化关系研究。试验结果表明：C/SiC材料在高温条件下的表面催化复合效率应该同时被定义为表面温度、驻点压力和原子分压的函数。根据试验所得到的催化数据，计算了采用C/SiC作为钝头体材料的美国某典型飞行器（飞行高度H=73 km，飞行速度U=6.478 km/s，钝头体半径R_n=410 mm）的气动热环境参数，获得了考虑完全催化和有限催化条件下飞行器表面温度变化历程，结果进一步验证了飞行器热防护系统所承受的气动热载荷以及表面温度响应在很大程度上受到防热材料表面催化特性的影响。

Catalytic performance of C/SiC composites in high enthalpy chemical non-equilibrium flow

Ultrahigh temperature ceramic matrix composite (C/SiC) is one of the key materials for the Thermal Protection System (TPS) of near space vehicles. The catalytic performance of the C/SiC material in the high enthalpy chemical non-equilibrium flow is the key parameter of the design, optimization and accurate evaluation of the thermal protection system of the hypersonic flight vehicle. Using the high frequency plasma wind tunnel, the surface catalytic recombination coefficients of C/SiC were determined at the surface temperature range of 1453-2003 K, in the high disassociated air with the enthalpies of 19.3-35.9 MJ/kg, and with the stagnation pressures of 1.0,1.8,3.30 and 6.0 kPa. It shows that the catalytic recombination coefficient of C/SiC under high surface temperature condition depends not only on the surface temperature but also on stagnation point pressure and the partial pressure. According to the catalytic results, the aerothermal parameters for the typical America reentry flight (H=73 km,U=6.478 km/s, R_n=410 mm) with blunt body using C/SiC and its surface temperature history with test catalytic data and full-catalytic have been carried out. The results have strengthened that accurate estimation of the aerodynamic heating and temperature response to thermal protection system are greatly affected by catalytic performance of thermal protection material.