激波-膨胀风洞超高速热化学非平衡流动的光学诊断研究

Hypervelocity flows occur when a space vehicle penetrates the atmosphere at ultra-high speeds. The high-temperature flow features strong thermo-chemically non-equilibrium phenomena including vibration excitation, dissociation, ionization, etc. Such features dominate the aerothermodynamics of the vehicle and should be taken into full account during the design phase. However, it is a great challenge to generate test flows at such high velocities in a ground-based test facility, as well as model testing and measurement. In the present proposal, the detonation-driven shock-expansion tunnel (JF-16E) which has been upgraded to simulate 6~10 km/s test flows will be employed to study non-equilibrium flows over typical hypervelocity models. Schlieren, self-illumination and direct measurements of electron number density, spectrum emission and temperature will be obtained especially within key flow regions with large gradients over the test models. The effects of composition, total enthalpy and Mach number of the test flow, as well as the configuration and scale of the test models will be thoroughly evaluated. Direct measurement and visualization obtained in the present proposal will provide computation validation and get further understanding on the mechanism of the interaction between thermo-chemical non-equilibrium and the aerothermodynamics environment of the hypervelocity models.

超高速流动是航天飞行器穿越大气层时的典型流动，在头部强激波后将发生气体分子的振动激发、离解、电离等复杂高温热化学非平衡过程，该非平衡过程是飞行器气动力/热环境的重要影响因素，是其控制和热防护设计必须考虑的环节。然而，在风洞中产生超高速试验气流以及开展试验测量都极具挑战。本项目拟利用最新改建的爆轰驱动激波-膨胀风洞JF-16E（气流速度5~10 km/s），开展典型模型的超高速流动试验。主要应用纹影、自发光成像、电子密度测量和辐射光谱等电、光学测量手段，重点关注模型流场大梯度区域的非平衡粒子构成、电子密度、温度等关键参数的直接测量数据。详细考察试验气流成分、总焓和马赫数、模型结构与尺度对流场非平衡特性的影响。通过本项目研究获取的直接测量数据，结合数值辅助诊断方面的前期研究成果，为相关数值模拟提供验证数据，并阐释超高速流动的热化学非平衡特性及其对模型气动力/热环境的影响机理。

超高速流动是航天飞行器穿越大气层时的典型流动，在头部强激波后将发生气体分子的振动激发、离解、电离等复杂高温热化学非平衡过程，该非平衡过程是飞行器气动力/热环境的重要影响因素，是飞行器控制和热防护设计必须考虑的环节。本项目拟利用爆轰驱动激波-膨胀风洞JF-16E（气流速度5~10 km/s），开展典型模型的超高速流动试验。主要应用光学纹影显示、自发光成像、电子密度测量和光谱成像诊断等试验手段结合热化学非平衡流动数值分析方法，详细考察试验气流成分、总焓和马赫数、模型结构与尺度对流场非平衡特性的影响。研究成果如下：高超声速俯仰异常的机理是分子振动激发在头部强解区引起压力提升而在下游弱解区引起压力降低。辐射光谱由几个原子线和分子带系统组成，试验获得详细数据包括辐射光谱、激波形状、激波脱体距离和辐射强度随空间和波长的变化。数值辅助流场诊断表明，激波强度与波后气体化学反应进程耦合，可以表征为氮分子分解进程。在JF-16超高速激波-膨胀风洞的典型超高速来流条件(总焓35 MJ/kg)下，Cu作为壁面催化材料时的驻点热流分布曲线要明显高于Al2O3镀膜。镀膜Al2O3的驻点热流约为14.0 MW/m2，而镀膜Cu则约为21.5 MW/m2，高出前者53.6%。不同催化材料导致壁面催化效应有显著差异，表明壁面催化反应复合放热的超高速流动极端热载荷机理。