存在烧蚀的高超声速压缩拐角流动数值研究

Numerical study for the hypersonic compression corner flow with ablation

耦合求解热化学非平衡流控制方程和烧蚀壁面边界条件,进行存在石墨烧蚀的压缩拐角流场数值模拟。流场化学反应采用16组元(N_2,O_2,NO,N,O,NO^+,N_2^+,O^+,N^+,CO,CO_2,C,C_2,C_3,CN,e^-)29个反应的非平衡模型,热力非平衡的双温度模型下,不同反应采用不同控制温度。石墨材料表面反应包括碳的氧化反应、碳催化的O原子复合反应和碳的升华反应。对15°、18°、24°压缩拐角模型,在自由流Ma=10~30,总焓值6~55MJ/kg范围,分别进行无烧蚀的壁面催化与非催化条件和石墨烧蚀条件下的流场计算,分析各类条件下的流场结构、流动分离特性以及流场热化学参数分布特点,研究壁面条件对流动特性的影响。结果表明:流动分离可能性和分离区范围随着压缩拐角斜面倾角增大而增大,随来流马赫数增大而减小;相对于低壁温条件,无烧蚀的辐射平衡壁温和壁面烧蚀条件下流动分离区增大,斜面上压力、摩阻和热流峰值点也有所后移。

Hypersonic flow over a compression corner with ablation of heat shield made of graphite is numerically simulated through solving the Navier-Stokes equations of thermochemical nonequilibrium flow coupled with the ablating boundary condition,and the effects of the wall conditions on the flowfield properties are investigated.Sixteen chemical species （N2 ,O 2 ,NO,N, O,NO ＋ ,N2 ＋ ,O ＋ ,N＋ ,CO,CO 2 ,C,C2 ,C3 ,CN,e- ）are considered,the two-temperature model is taken to describe thermal nonequilibrium.The oxidation and sublimation of C,as well as the recombination of O catalyzed by C are considered at the wall surface.The hypersonic flow over 15＆#176;,18＆#176;,24＆#176;compression corners are calculated with Mach number varied from 10 to 30 and total enthalpy from 6 to 55 MJ/kg.Both ablating and non-ablating surface condition are used to investigate the effects of ablation.The flow structure,the characteristics of shock—boundary-layer interaction,the separation properties,and the distribution of the thermochemical properties are analyzed.The results show that the possibility of flow separation and the separation range become larger as the corner angle increases,while smaller as the free stream Mach number rises. Compared with the cases with low-temperature wall,the flow separation zones are lager with ablating wall or with high-temperature wall in radiation equilibrium,and this leads to the positions for peak values of pressure,skin friction and heat flux move downstream.