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为拓展对高超声速进气道不起动机理的认识,对一截短的二元高超声速进气道的低马赫数不起动现象和再起动现象进行了风洞试验研究。试验中分别通过改变进气道攻角和在通道下游设置堵锥形成流动壅塞的方法来模拟进气道来流马赫数的改变和燃烧室内释热导致的流动壅塞。试验中采用高速纹影技术和动态压力测量技术对上述动态过程中的瞬态流动结构和壁面动态压力信号特征进行了记录。研究发现,当进气道处于低马赫数不起动时,其口部分离包诱导激波受分离包自身振荡特性的影响,在唇口附近连续的小幅振荡,进而给整个进气道通道内引入了一类无基频的小幅压力扰动。而该扰动随着马赫数的增加,进气道恢复起动后逐渐消失。此外,还捕捉到了进气道再起动过程中分离包吞入的迟滞现象,进气道从“小喘”阶段恢复至起动状态时,由于下游高压的存在使得分离包未能完全吞回,并出现了类似低马赫数不起动时的无基频小幅振荡。该振荡直至通道下游完全敞开、口部分离包被吞入才逐渐消失,至此进气道也顺利地恢复到了起动状态。
In order to expand the understanding of the non-start mechanism of the hypersonic inlet, a wind tunnel experiment was conducted on the non-start phenomenon and the restart of a low-Mach number inlet of a short binary hypersonic inlet. In the experiment, the Mach number of the inlet port and the flow blockage caused by the heat release in the combustion chamber were simulated by changing the angle of attack of the inlet port and setting the plugging cone at the downstream of the channel respectively. High-speed profiling and dynamic pressure measurement techniques were used to record the transient flow structure and dynamic pressure signal characteristics of the wall in the above dynamic process. It is found that when the inlet is at a low Mach number, the induced shock waves at the mouth of the split bag are affected by the oscillation characteristics of the separation bag and continue to oscillate slightly in the vicinity of the lip, which in turn leads to the entire intake passage A class of small pressure disturbances without fundamental frequency. However, with the increase of Mach number, the disturbance gradually disappears after the intake recovery starts. In addition, the hysteresis of the separation bag during the restart of the intake port was captured. When the intake port returned to the starting condition from the “short breath” phase, the separation bag failed to be completely swallowed due to the existence of the downstream high pressure , And there is no fundamental oscillation with small fundamental frequency when low Mach does not start. The oscillation until the channel is completely open downstream, the mouth is gradually disappear after the package is swallowed, and thus the inlet also successfully returned to the starting state.