二维超声速空气引射器启动特性试验研究

Experimental Investigation of the Starting Performances of the 2-D Supersonic Air Ejector

超声速引射器是高空模拟试车台的重要组件,在发动机启动前利用引射器对试验舱预抽真空,可避免发动机启动初始时刻燃气漏入试验舱造成燃气在发动机中分离,对获取发动机在高空环境下的完整推力特性具有重要意义。而该工况下超声速引射器的启动过程是引射器工作过程中最为恶劣的工况,设计不合理的引射器会导致启动压力过高甚至不能实现启动。建立了缩比超声速空气引射器试验台对超声速引射器的启动特性进行研究,采用压力测量方法结合纹影技术对超声速引射器处于极限启动压比时的流场进行了描述,研究结果表明混合室收缩比越小,引射器极限启动压比越低。同时给出了定位超声速引射器不启动原因的判据:当引射器不启动是由引射总压不足引起时,盲腔压力在引射总压提高时降低,并在临界启动状态下达到最小值;而由混合室收缩比过小导致的引射器不启动在引射总压提高时盲腔压力单调上升。

Supersonic ejector is an important component of the high altitude test facility.Evacuating the test cell before engine start by the ejector can arrest the rocket exhaust leak into the cell,thereby prevent the potential exhaust separation in the rocket nozzle.Meanwhile,the start phase of the ejector is the most critical condition for ejector operation,and an ejector designed improperly will result in an unacceptable high starting pressure and inability to be started of the ejector.In order to investigate the starting performances under this condition,a test facility for small scale supersonic air ejector is constructed.By using pneumatic method and schlieren technology,the flow field is studied when the ejector on utmost starting pressure ratio.The result shows that the utmost starting pressure goes down with the mixing-room contraction ratio.The low mixing-room contraction ratio will cause the ejector unable to be started as well as insufficient ejecting pressure.It is observed that the chamber pressure will go up monotonously with the ejecting pressure when the inability of the ejector is induced by low mixing-room contraction ratio.In contrast,if the ejector unstart is induced by insufficient ejecting pressure,the chamber pressure will go down with the ejecting pressure.