Investigation of acoustic characteristics of foreign object damage in compressor blades based on acoustic mode decomposition

Local blade damage such as corner loss and edge curling may occur in compressor rotors of aero-engines during service, which can significantly affect the acoustic characteristics of the ducted flow. An experimental investigation was conducted on the acoustic characteristics of a compressor with local blade damage based on duct circumferential mode analysis. A 3.5-stage axial compressor was taken as the research object. A circumferentially arranged ring microphone array was employed to measure the in-duct flow-induced acoustic signals under different rotational speed conditions, and the measured data were decomposed into circumferential acoustic modes. Combined with duct acoustic propagation theory, the influence mechanism of local blade damage on the order, amplitude, and energy distribution of acoustic modes was analyzed from the perspective of circumferential non-uniform disturbances. The results show that local blade damage introduces a finite-scale non-uniform disturbance in the circumferential direction of the rotor, which tends to excite low-order circumferential acoustic modes, leading to a significant enhancement of low-order mode energy that is relatively weak under normal conditions. In the circumferential mode spectra, this feature appears as oblique ridge-like structures associated with the rotational frequency. These results reveal the variation characteristics of circumferential acoustic mode structures under local blade damage conditions and provide experimental evidence for the understanding and analysis of the acoustic characteristics of local blade damage.