Influence of suction vortex and submergence depth on pressure pulsation and vibration of a centrifugal pump

During pump station operation， suction vortices inevitably form under low submergence depth， causing severe hydraulic vibrations that threaten the operational safety of the station. This study investigated the characteristics of vortex-induced pressure fluctuation and vibrations in a vertical centrifugal pump under different submergence depths. High-speed photography was used to capture the morphological evolution of vortex across 11 submergence depths， while synchronous pressure pulsation and vibration signals were acquired. Key findings reveal that when the submergence depth falls below a critical level， vortices transition from stable structures to air-entraining and fragmenting states， exhibiting enlarged vortex cores and reduced stability. Pressure pulsation analysis demonstrates that under low submergence， vortex-induced low-frequency pressure fluctuations replace blade-passing frequency as the dominant frequency component， with peak-to-peak amplitudes increasing by 62% and maximum kurtosis reaching 5.2， indicating intensified flow impacts. Vibration analysis shows a 90% growth in axial vibration amplitude and heightened radial vibration asymmetry with decreasing submergence depth. Transfer entropy analysis identifies low-frequency pressure pulsations as the primary excitation source for amplified vibrations. By adopting the innovative method of capturing vortex morphology by high-speed photography synchronized with pressure pulsation and vibration signal acquisition， this study systematically reveals the coupling mechanism between the suction vortex evolution cycle and low-frequency hydraulic excitation， providing a direct theoretical basis for vibration early warning and safe operation control of pumping stations.