化学非平衡效应对返回舱再入气动力特性的影响

摘要

高空高马赫数条件下，化学非平衡效应将对飞行器气动特性产生影响，影响飞行器气动布局优化和飞行弹道设计。文章通过三维化学非平衡流动求解程序，针对再入返回器开展数值研究与机理分析，通过对比完全气体模型和化学非平衡气体模型获得的气动力参数，揭示化学非平衡效应对流场结构和气动力特性的影响和规律。结果表明，对Apollo的气动力计算结果验证了模型和计算方法；化学非平衡效应影响下，激波层内化学反应消耗大量能量，致使激波脱体距离减小，气体压缩性增强；典型状态高度为70 km，Ma=30条件下，化学非平衡效应导致返回器升力系数增大约6%、阻力系数增大约1.3%～3.3%、升阻比增大3%左右、俯仰力矩系数增大，从而使配平攻角减小约2.5°；通过机理分析，发现化学非平衡效应影响下表面压力系数发生变化的原因是飞行器周围激波形状及驻点压力改变，表现为气体沿流线经激波层、压缩区和膨胀区的历程变化；对于钝体形状的返回器，迎风面前体压力系数增加和后体压力系数降低，造成轴向力和法向力系数增大。%Chemical non-equilibrium effect has a strong impact on aerodynamic characteristics of vehi-cles flying at high altitude and highMa number, which will affect aerodynamic shape optimization and flight trajectory design. The numerical investigation and mechanism analysis are carried out on reentry vehicles using a three dimensional chemical non-equilibrium flow solver, to understand the impact and regularity of chemical non-equilibrium effect on the flow field structures and aerodynamic forces, in comparison with a perfect gas model. The good agreement between current result and reference data for AS-202 flight test validates the model and numerical methods. The stand-off distance of the forebody shockwave is reduced, and the compressibility of the gas is enhanced, because of large energy consumption of the chemical reactions; In typical status, at alti-tude 70 km,Ma=30, chemical non-equilibrium causes the lift coefficient increased by 6%, the drag coefficient grown up by 1.3%~3.3%, the ratio of lift to drag raised by 3% and the trim angle decreased by 2.5 degrees for the pitching moment coefficient rises up in chosen typical flight conditions; through the mechanism analysis, it has been found that the reason why the surface pressure contribution changes under the influence of chemical non-equilibrium effect is that the shape of the shock around the vehicle varies and the stagnation pressure in-creases; in that case the journey of the gas flowing past the shock, the compression and the expansion zone would be different; for blunt reentry vehicles, because the pressure coefficient in windward increases on fore-body and decrease on afterbody, the axial and normal force coefficients get bigger.