Study on the vibration characteristics induced by rotating stall in a centrifugal pump based on improved variational mode decomposition

Rotating stall within the centrifugal pump has been found to induce enhanced unstable flow, which subsequently exacerbates pump vibration, posing serious risks to the safe and stable operation of the pump. To investigate the rotating stall and its induced vibration characteristics, numerical simulations have been employed to study the flow field of the rotating stall within the pump. Additionally, experimental measurements of the pump vibration signals under rotating stall conditions have been conducted, establishing the relationship between the internal rotating stall and external pump vibrations. The results have demonstrated that the reduction in flow rate promotes the development of rotating stall, with a similar distribution pattern of stall cells within the pump. The propagation speed of the stall cells within the impeller channels was approximately 20 % of the impeller rotational speed. Under deep stall conditions, the stall cells consistently moved from the suction side to the pressure side, accompanied by vortex structures of varying scales. These vortices extended to the pressure-side outlet, forming reverse vortices that blocked the impeller channels. Reconstructed external pump vibration signals, analyzed using the generalized S-transform, revealed persistent strong vibration signals in the 6 kHz-9kHz frequency range under stall conditions. Power spectral density analysis further indicated that the amplitude in the low-frequency range positively correlated with the development of rotating stall, with the primary frequency at 12 times the shaft frequency, which can be considered a characteristic frequency of stall conditions. These findings provide a scientific basis for ensuring the stable operation of centrifugal pumps.