中文摘要：

临界压力是暂冲式高超声速风洞实验段流场破坏时真空罐中的压力值，临界压力比影响Ma10以上大型高超声速风洞真空系统的设计。在Φ0.3m高超声速低密度风洞中进行了Ma10以上喷管的实验，测量了风洞实验段静压、流场的皮托压力、扩压器内表面前后压力、真空罐压力等参数，了解了各部位流场随真空罐压力升高的变化过程，获得了现有风洞Ma10、Ma12和Ma16各自的流场维持所需临界压力比分别为0.34、0.35和0.5。采用FASTRAN软件模拟了风洞流场建立到破坏的非定常过程，计算结果与实验结果较为一致。临界压力比的获得为类似大型高超声速风洞真空系统设计提供了关键基础数据。

英文摘要：

When the pressure in the vacuum container of the intermittent type hypersonic wind tunnel rises up to a certain extent, the flow field in the test section begins to destroied, and the static pressure in the test section would be unstable. The pressure in the vacuum container at the corresponding unstable point is called the critical pressure. The critical pressure would affect the vacuum system design of large-scale hypersonic wind tunnels （Ma ≥ 10）. The experiment is carried out in the Φ0.3m hypersonic low density wind tunnel, where the Mach number is over 10. The pressures in the test section, the pitot tube, the diffuser and the vacuum container have been measured. The critical pressure ratio of Ma10, Ma12 and Ma16 is 0.34, 0.35 and 0.5 respectively. The wind tunnel flow field unsteady process from establishment to destruction is simulated by FASTRAN software. The calculation result is in agreement with experimental result. The investigation provides key data for the vacuum system design of similar larger hypersonic wind tunnels.