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Application of Transpiration Cooling in Heat Shields of Hypersonic Vehicles to Mitigate Material Oxidation

蒸发冷却在高超声速飞行器隔热罩中的应用以减轻材料氧化

基本信息

批准号：
2102704
负责人：
金额：
--
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-2102704
关键词：
Application Transpiration Cooling Heat Shields

项目摘要

Transpiration cooling is a promising active thermal protection system (TPS), in which a coolant gas is fed through a porous material. The gas cools the material through internal convection and forms a protective film upon exiting the porous medium. The film reduces aerothermal heating and can also act as a barrier against mass diffusion. This project will investigate whether transpiration cooling can prevent material oxidation on the heat shields of hypersonic vehicles. One of the limiting factors for the cooling performance of heat shields is oxidation, which leads to ablation and surface recession and is detrimental for the heat shield performance. For many Ultra-High-Temperature-Ceramics (UHTCs), the oxidation temperature is the limiting boundary of the material. This reduces the passive cooling performance due to radiation and confines the flight envelope. The mitigation of oxidation would hence make a significant and substantial contribution to the heat shield design of hypersonic vehicles. A test campaign in the PWK 1 plasma wind tunnel at the IRS in Stuttgart in September 2018 marks the first milestone of this investigation. A 42\% porous $ZrB_2$ disk will be exposed to stagnation point heat fluxes of 3 $MW/m^2$ and 3.5 $MW/m^2$. A numerical simulation coupled with a theoretical model for $ZrB_2$ oxidation predicts that the uncooled sample will start oxidising at these heat fluxes. Surface temperatures of 1800 $\degree$C and 2100 $\degree$C are to be expected. The coolant mass flux will be increased until the Echelle spectrometer detects a reduction in the intensity of the characteristic spectral lines of the oxidation products. The results will provide an initial experimental assessment of the oxidation reduction due to transpiration cooling. The second milestone will be an investigation of whether oxidation can be further reduced if a fraction of Ammonia ($NH_3$) is added to the coolant. $NH_3$ reacts with oxygen and could potentially capture the oxygen molecules and atoms in the boundary layer before they undergo surface catalysis. This could reduce the surface heat flux and prevent surface damage. The third milestone will be an experiment in the High Density Tunnel, which can replicate the real-flight aerodynamic re-entry conditions such as Reynolds and Mach number. Pressure sensitive paint will be employed on the porous surface to mark the changes in oxygen diffusion.This projects relates to the Engineering theme of EPSRC. It aligns with the EPSRC strategy, since it focuses on a technology in which the UK is set to become world-leading, thanks to the Transpiration Cooling Research Programme. The collaborators involved include Imperial College London, who are supplying the UHTCs and the University of Manchester, who will share their expertise on Pressure Sensitive Paint for the last experiment.

发汗冷却是一种很有前途的主动热防护系统（TPS），其中冷却剂气体通过多孔材料供给。气体通过内部对流冷却材料，并在离开多孔介质时形成保护膜。该膜减少了空气加热，并且还可以作为防止质量扩散的屏障。本项目将研究发汗冷却是否可以防止高超音速飞行器隔热屏上的材料氧化。隔热屏冷却性能的限制因素之一是氧化，其导致烧蚀和表面凹陷，并且对隔热屏性能有害。对于许多超高温陶瓷（UHTC），氧化温度是材料的极限边界。这降低了被动冷却性能，由于辐射和限制飞行包线。因此，减少氧化将对高超音速飞行器的隔热罩设计作出重大的贡献。2018年9月在斯图加特IRS的PWK 1等离子体风洞中进行的测试活动标志着这项研究的第一个里程碑。42%多孔ZrB 2圆盘将暴露于3 $MW/m2 $和3.5 $MW/m2 $的驻点热流。结合ZrB_2氧化理论模型的数值模拟预测，未冷却的样品将在这些热通量下开始氧化。预计表面温度为1800 $\degree$C和2100 $\degree$C。冷却剂质量通量将增加，直到中阶梯光谱仪检测到氧化产物的特征光谱线的强度降低。结果将提供一个初步的实验评估的氧化还原由于发汗冷却。第二个里程碑将是研究如果向冷却剂中添加一小部分氨（$NH_3$）是否可以进一步减少氧化。NH_3与氧反应，并可能在边界层中捕获氧分子和原子，然后进行表面催化。这可以减少表面热通量并防止表面损坏。第三个里程碑将是在高密度风洞中进行的实验，该实验可以复制真实飞行的气动再入条件，如雷诺数和马赫数。压力敏感涂料将被用于多孔表面，以标记氧气扩散的变化。该项目涉及EPSRC的工程主题。它符合EPSRC的战略，因为它专注于英国将成为世界领先的技术，这要归功于蒸腾冷却研究计划。参与的合作者包括为UHTCs提供支持的伦敦帝国理工学院（Imperial College伦敦）和曼彻斯特大学（University of Manchester），后者将在最后一次实验中分享他们在压敏涂料方面的专业知识。