前体涡发生器对轴对称高超声速进气道激波振荡流动的影响实验

激波振荡是高超声速进气道不起动过程中常见的流动现象,会显著降低进气道气流捕获与压缩效率、产生剧烈的非定常气动力载荷而危害飞行器安全. 从激波振荡的控制出发,实验研究了前体转捩带位置的涡发生器对轴对称高超声速进气道激波振荡流动的影响. 分别在起动和激波振荡两种进气道流态下,选择无、0.5 mm与1 mm高度涡发生器工况进行对比研究. 并采用高速纹影与壁面动态测压同步记录非定常流动特征. 结果表明,1 mm高度内的涡发生器对起动状态的进气道主流流场结构、壁面压强分布影响不显著. 但对于激波振荡流动,涡发生器会明显缩小外压缩面分离区运动范围,缩短振荡周期,提升振荡周期内壁面压强的时均值. 涡发生器的影响程度随其高度的增大而增强,其中振荡周期从无涡发生器的4 ms缩短到1 mm高度涡发生器的3.13 ms. 此外,0.5 mm高度涡发生器会使得进气道内部测点的压强振荡幅值整体下降,相比无涡发生器工况的下降幅度可达23%. 流场结构与壁面压强信号的分析表明,涡流发生器主要通过其产生的流向涡影响激波振荡流动,包含流向涡对下游边界层的扰动以及流向涡与分离区的相互干扰. 

EXPERIMENTAL INVESTIGATIONS OF EFFECTS OF FOREBODY VORTEX GENERATORS ON THE OSCILLATORY FLOW OF AN AXISYMMETRIC HYPERSONIC INLET

Shock oscillations are common flow phenomena encountered in the unstarting processes of hypersonic inlets. They can significantly reduce the airflow capturing and compression efficiency and generate severe unsteady aerodynamic loads. These are highly detrimental to the fight safety of hypersonic vehicles. Aiming at the control of shock oscillation flows, the effects of vortex generators on the oscillatory flows of an axisymmetric hypersonic inlet are studied experimentally. Both started flows and oscillatory flows are investigated with synchronized high speed schlieren imaging and transient surface pressure measurement, as no vortex generators, 0.5 mm and 1 mm thick vortex generators fixed on the inlet forebody. According to the experimental results, minor effects are exerted on the main flowfield and wall pressure of the started flows for vortex generators within 1 mm thickness. However, the vortex generators can substantially reduce the scale of external separations, shorten the oscillatory period and increase the time- averaged pressure magnitude of the oscillatory flows. The effects of vortex generators enhance with the increase of their thickness, and the oscillatory period is shortened from 4 ms for no vortex generator cases to 3.13 ms for 1 mm thick vortex generator cases. In addition, the 0.5 mm thick vortex generators can generally reduce the oscillatory amplitude of surface pressure of the inlet duct, of which decreasing percentage can reach 23%. According to the analysis of the schlieren images and the surface pressure signals, effects of the vortex generators are exerted through streamwise vortexes in the wake flows, including the disturbances of streamwise vortexes exerted on the downstream boundary layers and the interactions between streamwise vortexes and separation regions.