Influence mechanism of non-adjacent blade rows on vibration of embedded rotor blades in a multi-stage compressor

Vibration issues of embedded rotor blades frequently occur due to inter-row interference. This study presents an investigation into vibration cracks observed at the roots of the third-stage rotor blades (R3) of a 4.5-stage compressor. Preliminary studies ruled out forced response or classical flutter as the root causes of the cracks. The underlying mechanism remained elusive. To explore the key factors inducing blade vibration in the multi-stage environment, the aerodynamic damping of R3 under isolated-row, 3-row (S2-R3-S3) and 5-row (R2-S2-R3-S3-R4) models via the Fluid-Structure Interaction (FSI) method is presented. The results demonstrate that non-adjacent blade rows (R2, R4) exert a notable influence on the aeroelastic stability of R3 within the low Nodal Diameter (ND) region, particularly at ±1 ND. Specifically, the aerodynamic damping of −1 ND decreases by 117.67%, transitioning from aeroelastic stability to critical instability. Further studies confirmed that blade rows more than two rows away exert no significant impact on the aeroelastic performance of the embedded rotor. Finally, applying the theory of acoustic wave propagation, reflection and transmission, the influence mechanism of low-circumferential-wavenumber acoustic modes on aerodynamic damping was investigated. It is clarified that non-adjacent blade rows affect the reflection of pressure waves with low circumferential wavenumbers, constituting the primary driver of embedded blade vibration. This work highlights the limitations of traditional aeroelastic analysis methods in addressing inter-row interference-related vibration problems, providing a basis for blade flutter prediction and structural design optimization of multi-stage compressors.