Experimental and Numerical Investigation of Non-synchronous Blade Vibration Excitation in a Transonic Axial Compressor

The complex flow phenomenon of rotating instability (RI) and its induced non-synchronous vibration (NSV) have become a significant challenge as they continuously increase aerodynamic load. This study aims to provide an understanding of the non-synchronous blade vibration phenomenon caused by the rotating instability of a transonic axial compressor rotor. In this case, blade vibrations and non-synchronous excitation are captured by strain gauges and unsteady wall pressure transducer sensors. Unsteady numerical simulations for a full-annulus configuration are used to obtain the non-synchronous flow excitation. The results show that the first-stage rotor blade exhibits an NSV close to the first bending mode; NSV is accompanied by a sharp increase in pressure pulsation; amplitude can reach 20%, and unsteady aerodynamic frequency will lock in a structural mode frequency when the blade vibrates in a large-amplitude motion. The predicted NSV frequency aligns well with the experimental results. The dominant mode of circumferential instability flow structure is approximately 47% of the number blades, and the cell size occupies 2-3 pitches in the circumferential direction. The full-annulus unsteady simulations demonstrate that the streamwise oscillation of the shedding and reattachment vortex structure is the main cause of NSV owing to the strong interaction between the tip leakage and separation vortices near the suction surface.