隔离段抽吸引起的激波迟滞现象研究

Investigation on Shock Wave Hysteresis in Isolator Caused by Wall Suction

关键词:  超燃冲压发动机  隔离段  激波反射迟滞  边界层分离迟滞

Key words:  Scramjet  Isolator  Shock wave reflection hysteresis  Boundary layer separation hysteresis

摘要:

为了研究壁面抽吸条件下隔离段流动迟滞现象，采用数值模拟和理论分析相结合的方法，模拟反压升高再降低过程，对隔离段的激波形态进行了研究。基于Zhukoski提出的中等雷诺数下(3×104<[Reδ]<1.2×106)分离区压力与马赫数的量化关系，发展了无控制措施条件下激波串首道激波的理论模型，发现来流马赫数大于2.0时激波串首道激波反射类型为规则反射，且不会出现激波反射迟滞现象。而壁面抽吸使首道激波固定在抽吸缝位置，导致激波串首道激波强度随反压升高不断增强，边界层分离角和激波角不断增大，从而进入Von Neumann准则的双解区甚至马赫反射区，在升高及降低反压的过程中隔离段出现流动迟滞现象。研究结果进一步揭示了壁面抽吸引起的流动迟滞现象不仅包含常规RR?MR激波反射迟滞，而且包含了一种新的迟滞现象——边界层分离迟滞。

Abstract:

In order to study the hysteresis in the isolator flow caused by wall suction，theoretical analysis and numerical calculation are carried out to simulate the process that the back pressure raises and subsequently drops in this paper. Based on the quantitative correlation between the free stream Mach number and the separation pressure proposed by Zhukoski，a theoretical model regarding the first shock of the shock train is developed under the condition of moderate Reynolds number (3×104<[Reδ]<1.2×106) without any control measures. It is revealed that only a regular reflection is theoretically possible for the first shock when the entrance flow Mach number is greater than 2.0 and no hysteresis phenomenon can occur. Nevertheless，the wall suction can stabilize the first shock foot by bleeding the boundary layer，resulting in an increasing of separation angle and shock wave angle with back pressure rising. As a result，the flow deflection angle is in the double solution domain of the Von Neumann criteria and a hysteresis in the RR?MR transition occurs once. The results further exhibit a new hysteresis in boundary layer separation which is induced by the back pressure.