Abstract

Experimental investigations have been carried out on a suddenly expanded duct in a view to determine buzz phenomenon for different Mach numbers (M), nozzle pressure ratios (NPR), and mass flow rates (MFR). The experimental facility was designed with sensitive and high-frequency pressure controls. The experiments were conducted for Mach numbers ranging from 2.0 to 3.0, with multiple NPRs of 3, 5, 7, and 9. In combination with the high-speed camera, shadowgraph mapping techniques were employed to provide optical depiction of the shock system in front of the inlet and to study the buzz features. Displacement of the shock and buzz frequency were calculated by shadowgraphs. The information gathered from the shadowgraphs was assessed against the pressure measurements and the values were in good agreement with each other. The results observed that for nominal values of MFR, the buzz frequency decreased with increasing Mach number. Furthermore, for an increasing NPR, the shock displacement further increases. The results also showed that there were significant pressure fluctuations in the expanded duct for lower Mach numbers.

摘要

对突然膨胀的管道进行了实验研究，以确定不同马赫数 (M)、喷嘴压力比 (NPR) 和质量流量 (MFR) 的嗡嗡声现象。实验设施设计有灵敏的高频压力控制。实验的马赫数范围为 2.0 到 3.0，多个 NPR 分别为 3、5、7 和 9。结合高速相机，采用阴影图映射技术提供前方冲击系统的光学描绘入口并研究嗡嗡声特征。冲击和嗡嗡声的位移由阴影图计算。从阴影图中收集的信息根据压力测量值进行评估，并且这些值彼此非常吻合。结果观察到，对于 MFR 的标称值，嗡嗡声频率随着马赫数的增加而降低。此外，对于增加的 NPR，冲击位移进一步增加。结果还表明，对于较低的马赫数，膨胀管道中存在显着的压力波动。