当飞行器以高超声速在大气中飞行的时候，飞行器会强烈压缩周围空气，导致空气温度急剧升高，高温气体会将热量传递给飞行器，形成气动加热，会烧蚀飞行器的表面材料，严重时导致事故的发生，所以对气动热进行准确的测量是至关重要的。

激波风洞是高超声速空气动力学研究中重要的地面试验设备，JF-12复现高超声速飞行条件激波风洞能提供的有效试验时间长达 130 ms。激波风洞中的热流测量是一项重要课题，在众多热流测量设备中，同轴热电偶具有抗冲刷能力强，测量精度高，结构简单易于安装，灵敏度高等优点，因此被广泛应用于激波风洞的热流测量。同轴热电偶的热流原理是基于一维半无限体热传导理论。传统型同轴热电偶通过打磨其端面导通正负极并形成热节点，其端面受热时，由于Seebeck效应，同轴热电偶的正负极会产生感应热电势并被记录，再由固定关系可以得到端面和冷端的温度差，再由一维半无限体热传导理论公式处理端面温度数据得到表面热流。但是在实际测量过程中，由于绝缘层的存在和正负极材质的区别，同轴热电偶节点区域存在复杂的多维热传导，其中横向热传导会造成同轴热电偶表面热流测量与一维半无限体热传导理论间的差异。当壁面材质的热物性参数与同轴热电偶不同时会造成偏大或偏小的热流测量误差。同时一维半无限体热传导理论在大曲率模型中的适用性也是有待研究的内容。主要研究工作如下：

首先，研究节点过热现象以及正负极材料的差异对节点区域横向传热的影响，通过数值模拟复现了E型同轴热电偶的节点过热现象。在100ms加热时间内，研究了打磨形成的节点的深度和材质以及绝缘层的厚度对节点的表面温升和热流的影响规律。同轴热电偶的表面温度最高值会决定感应电势的大小，通过抛物线近似确定了节点各个时刻表面温度最高点的径向位置。由于负极材料的导热系数k大于正极材料，随着加热时间的增加，节点表面温度最高点的位置会从节点表面的中点逐渐向正极移动。通过增大同轴热电偶的正极外径可以减小温度最高点的径向位移量，同时可以缓解节点过热现象，从而降低节点表面的温度最高值，减小热流测量误差，并由数值模拟验证。

其次，针对安装在平整壁面模型中的同轴热电偶热流测量，本文通过数值模拟，采用控制变量的方法从导热系数和体积比热容两个方面分析了壁面材料对同轴热电偶温度造成的影响，并分析各种不同真实壁面材料对同轴热电偶热流测量的影响规律。同时研究了绝热内壁面和恒温内壁面对模型表面及同轴热电偶的温度影响规律。

更进一步，本文将尖前缘等具有大曲率特征的飞行器结构分别简化为柱壳加热模型。通过理论推导，在50ms加热时间内，从横向热流分布和热流传递空间两个方面对柱壳结构导热进行了分析，发现影响驻点温度和测量热流的因素有柱壳表面热流加载形式，凸形柱壳曲率半径、凹形柱壳曲率半径以及柱壳的热物性参数，阐述了一维半无限体热传导理论在大曲率柱壳模型表面热流测量中的不适用性。

与柱壳加热模型研究思路相似，研究了在50ms加热时间内，球壳模型表面轴对称热流加载形式、凸形球壳曲率半径、凹形球壳曲率半径和球壳模型材质对驻点热流测量的影响规律。同时分析了球头气动加热局部相似理论在Legendre多项式近似下，球壳驻点温度和热流误差随时间的变化。相比于柱壳模型，大曲率球壳加热模型的多维结构导热造成的热流测量误差更大。

When an aircraft is flying in the atmosphere at hypersonic speeds, the aircraft will strongly compress the surrounding air, causing the air temperature to rise sharply. High-temperature gas will transfer heat to the aircraft to form aerodynamic heating, which will ablate the surface material of the aircraft and cause accidents in severe cases. Therefore, accurate measurement of aerodynamic heat flux is important.

The shock wind tunnel is an important ground test equipment in the study of hypersonic aerodynamics. The JF-12 hypersonic duplicated wind tunnel can provide 130ms effective test time. Heat flux measurement in shock tunnels is an important topic. Among many heat flux measurement equipment, coaxial thermocouples have the advantages of strong anti-scour ability, high measurement accuracy, simple structure and easy installation, and high sensitivity, so they are widely used in heat flux measurement in shock wind tunnels. The principle of the coaxial thermocouple getting heat flux is based on the theory of one-dimensional semi-infinite body heat conduction. Traditional coaxial thermocouple conducts the positive and negative electrodes by grinding face to form a thermal junction. When the face of coaxial thermocouple is heated, the positive and negative electrodes of the coaxial thermocouple will generate an induced potential due to the seeback effect and be recorded, and the temperature difference between the heating face and the cold end can be obtained then by a fixed relationship. Then surface heat flux can be obtained by processing the face temperature data by the one-dimensional semi-infinite body heat conduction theoery. However, in the actual heat flux measurement, due to the existence of the insulating layer and the difference between the positive and negative materials, there is a complex multi-dimensional heat conduction in the coaxial thermocouple junction area, in which the lateral heat conduction will cause the difference between surface heat flux measurement and the one-dimensional semi-infinite body heat conduction theory, and verified by numerical simulations.

Firstly, in order to further study the junction overheating phenomenon and the effect of the difference of positive and negative materials on the lateral heat transfer in the junction region, the junction overheating phenomenon of E-type coaxial thermocouple was reproduced by numerical simulation. During the heating time of 100ms, the influence of the depth and material of junction formed by grinding and the thickness of the insulating layer on temperature rise and heat flux of junction surface were studied. The temperature maximum value of coaxial thermocouple surface will determine the magnitude of induced potential.The radial position of the temperature highest point of junction surface at any time is determined by parabolic approximation method. We found that since the thermal conductivity k of the negative electrode material is greater than that of the positive electrode material, the position of the highest temperature point of junction surface will gradually move from the midpoint of junction surface to the positive electrode with the increase of heatng time. By increasing the diameter of the positive electorde of coaxial thermocouple, the radial displacement of the highest temperature point could be reduced, and the overheating phenomenon of junction could be alleviated, which could reduce the maximum temperature of junction surface and the error of heat flux measurement.

Aiming at the heat flux measurement of coaxial thermocouple installed in the flat wall model, this paper analyzed the effect of the wall material on the temperature of the coaxial thermocouple from thermal conductivity and volumetric specific heat capacity by means of numerical simulation and control variables method. And the influence law of various real wall materials on the heat flux measurement of the coaxial thermocouple were analyzed. Then the influence of the temperature of the adiabatic inner wall and the constant temperature inner wall on the surface of model and coaxial thermocouple was studied.

Further, the aircraft structures with large curvature characteristics such as sharp leading edges were simplified as cylindrical shell heating models respectively. Through theoretical derivation, the thermal conductivity of the structure was analyzed from two aspects of lateral heat flux distribution and heat flux transfer space within 50ms heating time. It was found that the factors affecting the stagnation temperature and measured heat flux include the form of heat flux loading on the surface of cylindrical shell, radius of curvature of a convex and concave cylindrical shell, and thermophysical parameters of shell. The inapplicability of the one-dimensional semi-infinite body heat conduction theory in the measurement of surface heat flux in large curvature models was expounded.

Similar to the research idea of the cylindrical shell heating model, the effects of the axisymmetric heat flux loading form on the surface of the spherical shell model, the curvature radius of the convex spherical shell, the curvature radius of the concave spherical shell and the material of the spherical shell model on the stagnation point heat flux measurement are studied in the 50ms heating time. At the same time, the variation of stagnation point temperature and heat flux error of spherical shell with time under the Legendre polynomial approximation of the local similarity theory of aerodynamic heating of spherical head was analyzed. Compared with the cylindrical shell model, the heat flux measurement error caused by the multi-dimensional structure heat conduction of the large curvature spherical shell heating model was larger.