人类在探索宇宙的过程，发射了越来越多的空间探测器，这些探测器在返回地球的过程中会以高超声速经过大气层。为保证飞行器能够成功返回地面，需要设计轻便又可靠的防热系统，避免飞行器被再入过程中的气动热烧毁。设计良好的防热系统，需要能够精准的预测热载荷的大小。由于飞行速度极快，飞行器周围流场具有很高的温度，流场的辐射加热作用已不可忽略。

高超声速再入流场的辐射特性计算的难点在于流场处于热化学非平衡状态。化学非平衡效应影响了各组分浓度的分布，而热力学非平衡影响了各组分能态的分布，二者皆会影响流场的光学辐射性质。非平衡状态的出现，使得流场和辐射场的数值计算复杂度大为增加。

本文采用理论建模与实验测量相结合的手段，建立了一套适用于简单轴对称外形的高超声速流场及辐射场的数值计算模型分别计算其在紫外和红外波段的辐射光谱和亮度，并通过有限的地面模拟实验验证数值计算的精度、优化了理论模型。论文的主要研究内容如下：

（1）将CR模型全面耦合入高超声速流场辐射特性的数值计算当中。通过该数值计算方法分析了一维正激波、二维高超声速球体绕流场中各个位置分子电子能级偏离当地电子温度下Boltzmann分布的程度，并得到了能级分布情况对辐射光谱的影响。

建立了一套考虑非平衡效应的流场辐射计算模型，得到了典型高超声速飞行条件下流场各种辐射机制的光谱贡献，仿真了各个组分的辐射跃迁谱线在整个辐射光谱的作用。

（2）针对高超声速流场开展了红外波段的辐射特性测量。基于弹道靶初步探索了烧蚀产物对整个高超声速流场辐射特性的影响，发现碳基烧蚀材料可以产生大量的C元素分子进入流场，引起红外辐射量级的增加。

基于高焓风洞，测量了4个细分中波红外波段的高超声速流场辐射亮度分布。发现头激波的红外辐射小于尾迹的红外辐射，并且空气高超声速流场的中波红外辐射主要来自CO₂。流场中波红外辐射亮度的分布主要受密度主导。

（3）针对激波管正激波后平衡区与非平衡区的辐射光谱，对比分析了数值计算与实验测量的辐射光谱，研究了N₂分子相关的碰撞激发跃迁速率对辐射光谱的影响，并最终甄选了一套合适的N元素分子碰撞激发跃迁速率参数集，使的数值计算的结果与实验测量结果更匹配。

In the process of exploring the universe, more and more space detectors are launched, which will pass through the atmosphere at hypersonic speed during their return to Earth. In order to ensure the successful return of the aircraft to the ground, it is necessary to design a portable and reliable thermal protection system to avoid the aircraft being burned by aerodynamic heat during reentry. A well-designed thermal protection system needs to be able to accurately predict the size of the thermal load. Because of the high flying speed and the high temperature of the flow field around the aircraft, the radiation heating effect of the flow field can not be ignored.

The difficulty in calculating the radiation characteristics of hypersonic reentry flow field is that the flow field is in a thermochemical nonequilibrium state. Chemical nonequilibrium affects the concentration distribution of each component, while thermodynamic nonequilibrium effect affects the energy distribution of each component, both of which affect the optical radiation properties of the flow field. The emergence of nonequilibrium state greatly increases the computational complexity of the flow field and radiation field.

In this paper, a set of numerical computational models for hypersonic flow and radiation fields with simple axisymmetric shapes are established by combining theoretical modeling with experimental measurements to calculate their radiation in the ultraviolet and infrared bands respectively, and the accuracy of numerical calculation is verified by limited ground simulation experiments. The main contents of this paper are as follows:

(1)The CR model is fully coupled into the numerical calculation of radiation characteristics of hypersonic flow field. By using this numerical method, the degree of the deviation of the Boltzmann distribution of molecular electronic energy levels from the local electron temperature in the flow field around a one-dimensional positive shock wave and a two-dimensional hypersonic sphere is analyzed, and the influence of the energy level distribution on the radiation spectrum is obtained.

A set of radiation calculation model considering non-equilibrium effect is established. The spectral contributions of various radiation mechanisms in the flow field under typical hypersonic flight conditions are obtained. The effect of radiation transition lines of each component on the whole radiation spectrum is simulated.

(2)The infrared radiation characteristics of hypersonic flow field were measured. Based on the ballistic target, the effects of ablation products on the radiation characteristics of the whole hypersonic flow field were preliminarily explored. It was found that carbon-based ablative materials can generate a large number of C elements into the flow field, which can increase the infrared radiation level.

Based on the high enthalpy wind tunnel, the radiance distribution of hypersonic flow field in four subdivided mid-wave infrared bands was measured. It is found that the infrared radiation of head shock wave is less than that of wake, and the medium wave infrared radiation of hypersonic air flow mainly comes from CO₂. The distribution of mid-wave infrared radiation brightness in flow field is mainly dominated by density.

(3)Aiming at the radiation spectra of the equilibrium and non-equilibrium regions after the positive shock wave in shock tube, the radiation spectra measured by numerical calculation and experiment are compared and analyzed. The influence of N₂-related collision excitation transition rate on the radiation spectra is studied. Finally, a suitable set of parameters of N-element molecular collision excitation transition rate is selected, which makes the numerical calculation results more consistent with the experimental measurement results.