Oscillation Modes and Characteristics of Shock Waves in Supersonic Cascade With Different Throttling Ratios

The study was based on the SAV21 supersonic cascade designed by the German Aerospace Centre. The shock wave structure and oscillation characteristics under different conditions of throttling ratios was experimentally studied. The results show that the expansion waves generated on the curved configuration of cascade can effectively suppress the oscillation of shock train. Under the condition of large throttling ratio, four oscillation modes appear. In the oscillation mode 1, the shock wave moves back and forth upstream of the pressure surface tip. In the oscillation mode 2, small-amplitude oscillations around the tip of suction surface and the large-amplitude oscillations appear alternately. In the oscillation mode 3, only the large-amplitude oscillations exist. In the oscillation mode 4, the shock wave propagates into the upstream passage. The irregular fluctuation of downstream pressure leads to the random occurrence of the oscillation mode 4.