火星探测器表面材料催化特性数值模拟研究

Numerical Study on Surface Catalytic Characteristics for Mars Entry Capsule

针对火星探测器高超声速进入过程中的表面材料催化作用及其对气动热环境影响这一问题,建立了变壁面温度的火星大气表面材料催化作用模型,并基于火星大气物理化学模型和求解三维热化学非平衡N-S方程的数值方法,对典型火星探测器防热大底进行了数值模拟,获得了不同催化特性下的高超声速非平衡流场和气动热数据,分析了表面材料催化特性对气动热环境影响的规律性。研究结果表明:表面催化特性对壁面附近组分分布影响很大,催化反应进程主要受O原子浓度限制;有限催化热流随催化效率增大而增大,完全催化峰值热流比催化效率为1的有限催化峰值热流高25%~64%;表面温度随催化特性的变化规律与热流变化规律类似。有限催化模型能根据表面材料的催化特性精细化预测表面热流和温度,为防热设计提供更精确合理的参考标准。

A surface catalysis model is established in which the variable temperature wall is considered,in order to investigate the surface catalytic characteristics and their effects on the aerothermal environment for a Mars entry capsule. On basis of this catalysis model,the physicochemical characteristics of the Mars atmosphere and the numerical methods by solving the nonequilibrium Navier-Stokes equations,a typical Mars entry capsule is numerically simulated to predict the hypersonic non-equilibrium flow field and aerothermal environment,and the effects of the surface catalysis are also analyzed. The numerical results show that the surface catalysis affects significantly the mass fraction distribution near the wall,and the catalytic reaction process is limited by the concentration of O atom. The partly catalytic heat flux increases with the catalysis coefficient,whereas the fully catalytic peak heat flux is about 25% ~ 64% higher than the maximal partly catalytic peak heat flux. The influence of the catalysis on the surface temperature is similar to that on the surface heat flux.More accurate aerothermal environment can be obtained by the partly catalytic model based on the catalytic characteristics of the surface material,which is suggested to be adopted in the thermal protection design.