新型高超热防护材料高温高压界面接触热阻多尺度模拟及实验研究

Thermal contact resistance has complicated formation mechanism which is affected by the interaction of geometric, thermal and mechanical factors. The thermal contact resistance between the new thermal protection materials used in hypersonic aircrafts is the biggest uncertainty factor affecting the reliability of the thermal protection system. Therefore, the accurate prediction of thermal contact resistance is a key problem to be solved urgently. In this study, multi-scale simulation and experimental study on the contact heat transfer characteristics and thermal contact resistance of three contact pairs formed by four new thermal protection materials are investigated. The three contact pairs include UHTC(ultra-high temperature ceramic)-C/SiC(braided composite), C/SiC-aerogel(nano porous composite) and aerogel-phase change composite. This study is aimed at putting forward the multi-scale characterization principle and method based on 3D actual rough surface morphology, developing thermal contact resistance prediction model and numerical simulation method based on the tested isotropic and anisotropic thermal conductivity. The thermal-mechanical coupling heat transfer characteristics is ascertained considering thermal expansion under high temperature and pressure. The influence law of overall surface roughness, temperature, loading pressure and gap pressure on the contact thermal resistance is experimentally studied and revealed with the existing test system which will be upgraded to higher temperature. This study is a fundamental research on the precise thermal management of thermal protection system on hypersonic aircrafts which has important theoretical, academic and practical application significance.

接触热阻产生机理复杂，受几何、热、机械（力）等多因素耦合作用影响，高超声速飞行器新型热防护材料界面接触热阻是影响热防护系统可靠性的最重要不确定因素，其准确预测是亟待解决的重点难点问题。本研究拟基于多尺度模拟和实验方法对四种新型热防护材料组成的三组接触对包括超高温陶瓷-C/SiC编织材料、C/SiC编织材料-纳米多孔气凝胶复合材料及纳米多孔气凝胶复合材料-相变复合材料的界面接触传热特性及接触热阻进行研究，提出三维真实粗糙表面形貌多尺度表征原则及方法，依据各向同、异性材料导热系数的测试结果，建立接触热阻预测模型及数值模拟方法，查清考虑材料热膨胀性能的高温高压接触界面热力耦合传热特性。同时升级高温高压接触热阻测试系统，研究表面整体综合粗糙度、温度、预紧力及间隙压力对接触热阻的影响并揭示其变化规律。本研究是高超声速飞行器热防护系统精确热管理的基础性研究工作，具有重要的理论、学术意义及实际应用价值。

接触热阻产生机理复杂，受几何、热、机械（力）等多因素耦合作用影响，高超声速飞行器新型热防护材料界面接触热阻是影响热防护系统可靠性的最重要不确定因素，其准确预测是亟待解决的重点难点问题。本文建立了接触热阻预测模型及数值模拟方法，查清了考虑材料热膨胀性能的高温高压接触界面热力耦合传热特性，获取接触热阻随表面整体综合粗糙度、温度、预紧力及间隙压力的变化规律。数值模拟研究了三维针刺预制体C/C-SiC复合材料接触对和八枚缎纹C/C-SiC复合材料接触对。前一接触对研究结果表明，粗糙面的离散接触导致了接触面的应力不均匀分布，且不同区域应力相差很大；即使压力达到5.52 MPa，实际接触面积仅为名义接触面积的1.76%； 后一接触对研究结果表明，考虑界面热辐射时，预测的接触热阻减小，随界面温度的提高，热辐射对接触热阻的影响增大。在给定的研究工况（界面温度为170 ℃-510 ℃，压力为1.03-2.37 MPa）下，通过实际固体接触区域的热流量与通过整个界面热流量之比最大不足17%，且该比值随温度的升高而减小，随压力增大而增大。实验测量了针刺预制体C/SiC复合材料的热扩散系数、比热以及导热系数，并利用接触热阻三元测试系统研究了该种复合材料接触对（接触对B）以及该种复合材料与超高温陶瓷所组成接触对（接触对D）之间的接触热阻。实验结果表明，接触对B的接触热阻随着温度的升高而减小，而接触对D的接触热阻随温度的升高而增大，两个接触对的接触热阻均随压力的增大而减小。