为了更深入地了解宇宙，研究生命的起源，甚至星际移民，深空探测是人类必然会肩负的使命，火星是目前人类地外探索的首选目标。在火星进入中，探测器外表面会处于严酷的气动环境，火星大气含高浓度CO₂，对此类高超声速流场进行深入研究是成功进入火星的关键。在如此极端的流场中，热化学非平衡效应在激波形状与辐射加热等方面均发挥着关键性影响，因此需要更多试验探索其物理本质。本文从CO₂热力学非平衡效应出发，研究了风洞试验中CO₂的流动特性，设计了CO₂振动非平衡试验并针对试验环境开展了相关工作。本文主要研究内容概括如下：

1．开发了CO₂的一维热化学平衡与二维轴对称非平衡程序，并针对不同运行状态下的激波管与喷管分别进行了数值模拟与风洞试验。分析了激波管以CO₂为试验气体时其运行状态与空气工况的不同及各自的缝合难度，对比了不同驱动模式下CO₂的气体状态以及激波速度衰减差异。之后数值分析了喷管中CO₂的流动特点。

2．评估了不同驱动模式并设计了纯CO₂振动非平衡试验。分析了静压杆表面粘性干扰参数与压力修正系数，最终的设计满足了试验的静压测量需求。此外，面对可能存在的驱动气体污染，定性地研究了自由流中可能存在的组分及其浓度，最终选择了水分子7181.156 cm^-1与7185.597 cm^-1吸收线，进行了基于吸收光谱的H₂O浓度测量。

3．基于高温气体动力学国家重点实验室的JFX激波风洞，国际上首次在常规激波管模式下开展了纯CO₂振动非平衡试验并进行了试验环境研究。在试验与数值相结合的方法下，采用多种观测手段对喷管出口自由流进行分析。针对不同工况下的自由流皮托压力、静压，高压段污染、R35 mm半圆球激波脱体距离与热流进行测量，分别分析了膨胀流与压缩流状态下CO₂非平衡试验结果，指出了试验中的不确定性。

本文主要意义为较完整地研究了风洞试验中CO₂的流动特性，并且首次在反射型激波风洞中设计了纯CO₂振动非平衡研究并进行了初步试验，为后续深入研究奠定了基础。另外，加深了对风洞试验中污染过程的认识。

To have a better understanding of the universe, the origin of lives and even realize interstellar migration, deep space exploration is an inevitable mission and the most attractive destination of all is Mars at present. During Mars entry, the external environment of the Mars probe is extremely severe. The key factor of a successful entry is to make a profound study on the hypersonic flow field containing CO₂. In such severe flow field, thermochemical nonequilibrium plays an important role in the shock shape and radiative heating, etc. More experimental research is needed to investigate its physical nature. This thesis starts from the thermodynamic nonequilibrium effect of CO₂, and studies the flow characteristics of CO₂ in shock tunnel. Thermodynamic nonequilibrium tests in pure CO₂ are designed and relevant work on the test environment is conducted. The main contents of this thesis are summarized as follows:

1. One dimensional thermochemical equilibrium program and axisymmetric thermochemical nonequilibrium program are developed for CO₂. Numerical simulations and shock tube tests under different conditions are conducted to investigate the distinct behavior when using air or CO₂ as test gas, along with an assessment of the difficulty of achieving a tailored condition. Conditions of the reservoir and shock decelerates of CO₂ in different drive modes are also studied. Additionally, the flow characteristics in a nozzle designed based on air flow are also analyzed when using CO₂ as test gas.

2. Evaluating the freestream conditions in different drive modes to design the CO₂ thermodynamic nonequilibrium test. Subsequently, static pressure probes are numerically simulated to analyze viscous interaction parameter and pressure correction coefficient. The resulting design met the measurement’s demand. Furthermore, as the test gas can be contaminated by driver gas, we investigate the possible components and their concentrations in the freestream. Finally, absorption line 7181.156 cm^-1 and 7185.597 cm^-1 of H₂O are selected to build a TDLAS system to study the driver gas contamination.

3. Shock tunnel tests are conducted in JFX shock tunnel of the State Key laboratory of High Temperature Gas Dynamics (LHD). This is the first time to study the experimental environment of pure CO₂ flow in a reflected shock tunnel. Various observation techniques are used in this study. Freestream pitot pressure, static pressure, driver gas contamination, shock standoff distance and heat flux of a R35 mm hemisphere are analyzed in different test conditions. Thermodynamic condition of CO₂ and uncertainties in experiments during expansion and compression are both investigate.

The main significance of this thesis is to investigate the flow characteristic of CO₂ in shock tunnel. Furthermore, tests in pure CO₂ environment are conducted for the first time in reflected shock tunnel, and deepen understanding in driver gas contamination.