Abstract: Transpiration cooling with phase change is an efficient active cooling technology for thermal protection on critical devices of hypersonic vehicles. With a high specific heat capacity and a high latent heat of phase change， water is effective for transpiration cooling. This paper investigated transpiration cooling with phase change on a porous plate in a supersonic wind tunnel with a Mach number of 2.2 and a total temperature of 500K. The unsteady process of coolant injection was also observed. The results show that the average cooling efficiency on the porous plate surface increases with the increase of the injection rate， and the liquid coolant flows out from the upstream surface initially and spreads downstream under supersonic mainstream condition. The cooling efficiency of the upstream region on the porous plate is higher than that of the downstream region. The uniformity of the surface temperature increases with the coolant injection rate. The injection pressure of the coolant increases first then decreases and finally increases as the injection rate increases with the water vapor generation. The cooling efficiency on the porous plate surface is above 0.6 with a small coolant injection rate of F=0.05%， which shows that transpiration cooling with phase change has the advantages of low coolant dosage and high cooling efficiency.

Key words: Transpiration cooling；Porous media；Phase change；Supersonic

摘要： 液态水具有较高的比热容和很高的相变潜热，采用水作为冷却剂的相变发汗冷却技术是解决高超声速飞行器关键部位热防护的高效主动冷却技术。利用主流马赫数2.2，总温500K的超声速风洞实验台，研究了超声速主流条件下多孔平板相变发汗冷却规律，分析了注入冷却剂时的非稳态过程。研究结果表明，在超声速主流条件下，多孔平板表面平均冷却效率随着注入率的提升而上升，且多孔平板上游冷却效率高于下游冷却效率，发现液态冷却剂优先从上游流出多孔表面并朝下游铺展。提升冷却剂的注入率可以提升多孔平板表面温度的均匀性。冷却剂的注入压力受到水蒸气影响，随着注入率的增大先增大后减小再增大。在较小冷却剂注入率时(F=0.05%)，多孔平板表面的冷却效率都保持在0.6以上，说明相变发汗冷却具有低冷却剂用量和高冷却效率的特点。

关键词: 发汗冷却；多孔介质；相变；超声速