Abstract: In order to increase the effective working time of vacuum ball exhaust system for supersonic wind tunnel with Ma=4 and Ma=7, secondary-throat is utilized as a part of diffuser between test section and vacuum ball. To optimize the performance of vacuum ball exhaust system, two related aspects are numerically investigated with computational fluid dynamics software in this paper. The first is about the effects of blockage ratio (engine model vs. main nozzle) on cross area of secondary-throat to start the supersonic wind tunnel while the other is about the effects of secondary-throat cross area on critical pressure (maximum working pressure) of vacuum ball. It is concluded that the area of secondary-throat nonlinearly increases with engine/main nozzle blockage ratio, and the critical pressure is decreasing rapidly as well.The secondary-throat area should be optimized according to different engine/main nozzle blockage ratio and different testing Mach number.

Key words: Supersonic wind tunnel; Vacuum ball; Secondary throat; Blockage ratio

摘要： 为了延长采用真空球排气系统的超声速风洞的工作时间,拟采用二次喉道提高真空球临界工作压强。本文针对Ma=4和Ma=7超声速风洞,采用计算流体软件系统地研究了不同发动机堵塞比对二次喉道起动能力的影响以及不同尺度的二次喉道对真空球临界工作压强的影响。研究结果表明,随着发动机堵塞比的增大,二次喉道的临界起动直径相应增大,呈非线性变化,同时,真空球的临界工作压强下降。因此,二次喉道直径应针对不同的模拟状态和发动机堵塞比范围综合优化选取。 

关键词: 超声速风洞;真空球;二次喉道;堵塞比