随着高超声速飞行器的飞行速度更快、飞行时间更长以及飞行空域更加广泛，飞行器机体面临着日益严重的气动加热问题。可重复使用、轻质化是高超声速飞行器重要的研究方向，而主动热防护可以有效降低飞行器结构质量与体积、保持机体外形不变，因此有望应用于可重复使用高超声速飞行器的机体防热领域。以机载燃料为冷却剂的再生冷却是超燃冲压发动机最有效的热防护手段之一，其相关的基础科学与应用研究已经比较充分。然而将燃料再生冷却应用于大面积的飞行器机体热防护的研究很少，相关的热防护特性尚不清楚。因此，本文将高超声速飞行器大曲率半径的机体结构分割、简化为带冷却通道的平板结构，并结合被动热防护技术，开展了带再生冷却通道的平板型结构件的流/固耦合传热与热防护特性研究。

本文搭建了石英灯辐射加热台用于模拟飞行器机体表面的气动热载荷，并且推导了辐射台与平板型结构件上表面之间的辐射传热计算公式，最大计算误差不超过12%。基于辐射加热台和燃料流动与传热测试平台，选用航空煤油为冷却剂，开展了单个冷却通道的平板型结构件的主动热防护特性实验研究，分析了冷却通道管间距（结构件宽度）为100 mm和200 mm的铝合金和管间距为100 mm的不锈钢结构件在热平衡状态时的温度特性、总体传热系数、导热热阻和流阻等参数随辐射热流密度、冷却剂质量流量的变化规律。实验结果表明，主动热防护只需付出冷却剂小温升和低流阻的代价就可以大幅度遏制结构件温度的升高。总辐射加热功率为6.72 kW时，采用约30 g/s的煤油至少可以降低铝合金板面温度75 K，煤油温升在4.5 K以内、流阻不超过2.0 kPa。管间距为100 mm的铝合金主动热防护结构件的导热热阻占总热阻的36.4%-55.4%，相同几何尺寸的不锈钢结构件的导热热阻占总热阻的78.4% ~ 87.7%。因此，降低对流热阻和降低导热热阻对提高铝合金结构件的热防护性能均有着重要的意义。而且，主动热防护结构件的导热热阻受材料热物性和管间距的影响较大，受冷却剂质量流量和加热功率的影响很小。此外，在平板型结构件上表面喷涂并高温固化了纳米复合陶瓷涂层，开展了主/被动复合热防护特性实验研究，分析了涂层的隔热和防热性能。定义复合热防护系数为被动涂层的导热热阻与主动冷却基体的导热热阻之比，可以为主/被动复合热防护设计提供参考。

采用三维数值仿真方法较系统地研究了平板型结构件的主动热防护特性和主/被动复合热防护特性。数值结果表明平板型结构件的最大温度随着热流密度的增大而近似线性增大，随着管间距的增大而高阶非线性增大。基于数值仿真结果拟合得到了铝合金和不锈钢主动热防护结构件的导热热阻计算公式，与实验结果相比，误差在11%以内。此外，采用热/结构耦合分析方法研究了不同冷却条件下平板结构件的最大热应力变化规律。研究结果表明，主动冷却可以降低结构件的热膨胀量，因此有利于降低结构件的最大热应力。由于不锈钢结构件的温度较高，且弹性模量较大，因此不锈钢结构件的最大热应力远大于相同冷却与构型条件下铝合金结构件的最大热应力。

基于能量守恒原理，采用微元法和分段积分法建立了平板型结构件的温度预测模型，该模型可以快速确定主动热防护结构件和主/被动复合热防护结构件的最大温度和温度分布，计算时间约为三维数值仿真的千分之一。温度预测模型主要考虑了材料的热物性、结构件几何参数以及热边界条件的影响效应。与三维数值仿真结果较为吻合，最大温度误差在4.0%以内。此外，基于三维热弹性理论和温度预测模型，建立了平板型主动热防护结构件的最大热应力预测模型，模型考虑了结构件的温度分布、材料热物性和形变率等参数，与三维热/结构耦合分析结果相比，最大热应力的误差在20%以内。温度预测模型和最大热应力预测模型为深入了解主动冷却、被动隔热对结构温度与应力的影响提供了理论参考，同时为工程实际问题的快速评估提供了有效工具。

With the faster flight speed, longer flight time and wider flight altitude of hypersonic vehicle, the vehicle body is facing an increasingly serious problem of aerodynamic heating. Reusable and lightweight are important research directions for hypersonic vehicles. Active thermal protection can effectively reduce the mass and volume of the vehicle and keep the shape of the airframe unchanged, therefore, it is expected to be applied in the reusable hypersonic vehicles. Regenerative cooling is one of the most effective thermal protection technologies for scramjet engine, and the basic science and application studies related to it have been relatively well studied. However, there are few studies on the application of regenerative cooling to large-area airframes, and the thermal protection characteristics are not yet clear. Therefore, in this paper, the large curvature radius of hypersonic airframe is divided and simplified into multiple plate structure with a cooling channel. Combined with passive thermal protection technology, the studies on fluid/solid coupling heat transfer and thermal protection characteristics of plate structures with a regenerative cooling channel were conducted.

In this paper, a quartz lamp radiation heating platform was built to simulate the aerodynamic heat load on the surface of the airframe. The radiation heat transfer equations between the quartz lamps and the top surface of the plate structure are derived. The maximum calculation error is within 12% compared with the experimental results. Based on the radiation heating platform and the fuel flow and heat transfer test platform, the experimental studies of the active thermal protection characteristics of plate structure with a single cooling channel were investigated using aviation kerosene as the coolant. The temperature characteristics, overall heat transfer coefficient, thermal conductivity, thermal resistance and flow resistance of aluminum alloy structure with 100 mm and 200 mm channel spacing (width of structure) and stainless steel structure with 100 mm channel spacing were analyzed in the thermal equilibrium state with the variation of radiation heat flux and coolant mass flow rate. The experimental results show that active thermal protection can significantly curb the temperature rise of plate structure by paying the price of small temperature rise and low flow resistance of coolant. When the total radiation heating power is 6.72 kW, kerosene with about 30 g / s can reduce the surface temperature of aluminum alloy by at least 75 K, the temperature rise of kerosene is less than 4.5 K, and the flow resistance is less than 2.0 kPa. The thermal conductive resistance of aluminum alloy structure with a channel spacing of 100 mm accounts for 36.4% ~ 55.4% of the total thermal resistance, while that of stainless steel structures of the same geometric size accounts for 78.4% ~ 87.7% of the total thermal resistance. Therefore, reducing the convective thermal resistance and the conductive thermal resistance are of great significance to improve the thermal protection performance of aluminum alloy structure. Moreover, the conductive thermal resistance is strongly influenced by the material and the channel spacing, and is minimally influenced by the coolant mass flow rate and heat flux. In addition, a nanocomposite ceramic coating was sprayed on the surface of a plate structure and solidified at high temperature. The experimental studies of the active and passive composite thermal protection characteristics were carried out. The thermal insulation and thermal prevention properties of the coatings were analyzed. The composite thermal protection coefficient was defined as the ratio of the conductive thermal resistance of the passive coating to the conductive thermal resistance of the actively cooled substrate, which can provide quantitative analysis for the design of active and passive composite thermal protection structure.

The active thermal protection characteristics and the active-passive composite thermal protection characteristics of the plate structures are studied more systematically using three-dimensional numerical simulation methods. The numerical results show that the maximum temperature of the plate structure increases approximately linearly with increasing heat flux and increases non-linearly in higher order with increasing channel spacing. The conductive thermal resistance equations for aluminum alloy and stainless steel structures were obtained based on the fitting of numerical simulation results. Compared with the experimental results, the error of the equations is within 11%. In addition, the variation of the maximum thermal stress of the plate structure under different boundary conditions was investigated using the thermal-structural coupling analysis method. The results show that active cooling can reduce the thermal expansion, therefore contributing to the reduction of the maximum thermal stress of the plate structure. Due to the higher temperature and higher elastic modulus of stainless steel structure, the maximum thermal stress of stainless steel structure is significantly higher than that of aluminum alloy structure with the same boundary and geometric conditions.

Based on the principle of energy conservation, the temperature prediction model of plate structure is established using the micro-element method and segmental integration method. It can quickly evaluate the maximum temperature and temperature distribution of active thermal protection structure and active-passive composite thermal protection structure. The calculation time is about one thousandth of the three-dimensional numerical simulation. The main input parameters of the temperature prediction model are the thermal properties of the material, the geometric parameters of the structure, and the thermal boundary conditions. The prediction results are relatively consistent with the three-dimensional numerical simulation, and the maximum temperature error is within 4.0%. In addition, based on the thermoelasticity theory and temperature prediction model, the maximum thermal stress prediction model for the plate type active thermal protection structure was established. The main input parameters of the maximum thermal stress model are the temperature distribution, material properties and deformation rate of the structure. Compared with the 3D thermal-structural coupling analysis, the error of the maximum thermal stress model is within 20%. The temperature prediction model and the maximum thermal stress prediction model provide theoretical references for an in-depth understanding of the effects of active cooling and passive thermal insulation on structural temperature and thermal stress, as well as effective tools for the rapid assessment of practical engineering problems.