Investigation on rotating instability in an axial compressor with different inlet reynolds numbers

In the near-stall condition, the axial flow compressor experiences an unstable flow phenomenon known as rotating instability (RI), which typically manifests as a broad bulge in the near-wall pressure spectrum, occurring at frequencies lower than blade passing frequency (BPF). It is considered the primary source of other instabilities such as non-synchronous vibration (NSV) and tip clearance noise (TCN), attracting considerable attention from researchers in recent years. This paper conducts a numerical simulation and experimental verification of a high-speed axial compressor to examine flow phenomenon and spectrum characteristics of RI at different inlet Reynolds numbers. The study explores the effects of inlet Reynolds numbers (Re=5.17e6 and Re=2.72e6) achieved by adjusting inlet total pressure of the compressor. Utilizing approaches such as circumferential mode decomposition to assess the frequency spectrum and mode of RI, the study elucidates the RI in association with the unstable flow structures at the blade tip. The findings indicate that: the most significant interference between the tip leakage flow and the blade occurs in the middle chord of the blade. At different Reynolds numbers, variations in the spatial distribution and number of unsteady vortexes lead to distinct peak aliasing patterns that represent RI and RI-blade interaction in the spectrum.