Effect of system response on partial surge initiated instability in a transonic axial flow compressor

Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region. Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system, which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge. For further verification, a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study. In the first case, an additional test point is set on the wall of the plenum to detect the system response. Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions, the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated. In the second case, a screen is mounted at the compressor outlet to prevent positive feedback from the plenum. The experimental results demonstrate that in the absence of system feedback, it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge. In addition, three flow phenomena in the second case are discussed, including the occurrence of the single pulse, the unstable process during the stall evolution and the switch of instability inception.