Vibration characteristic is an important factor in evaluating operation stability of centrifugal pump. The vibration of main shaft was measured using a laser vibrometer, internal flow field was simulated via the shear stress transport turbulence model, and distribution law of vibration and pressure fluctuation in the impeller were analysed to explore the induction factor of vibration and the inherent relationship with pressure fluctuation in a semi-open centrifugal pump under low flow rate condition. Results of the numerical simulation are consistent with the experimental data. In addition to rotation frequency caused by impeller rotation, vibration frequency also includes characteristic frequency with high amplitude induced by unstable flow. The complex vortex in the impeller is composed of tip leakage vortex (TLV), reverse flow vortex, passage vortex and tip separation vortex. The primary tip leakage vortex (PTLV) formed by the streamline spills from 0 to 0.2λ where λ is the dimensionless distance from leading edge to trailing edge collides with tip leakage flow, the leading edge overflow and reverse flow vortex at the frequency of 1.6fn (fn is the rotating frequency) and 2.2fn appear, respectively. The tip separation vortex formed in the tip clearance induced a frequency of 1.2fn. The frequency of unstable flow phenomenon was consistent with the vibration frequency of main shaft, which induced the vibration of centrifugal pump.
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