Time-frequency characterization of the unsteady phenomena in a centrifugal pump

The paper presents an experimental investigation of the flow field instability in a centrifugal pump. Pressure fluctuations were measured with transducers placed flush with the inlet duct, and at the impeller discharge. Two impeller rotation speeds were utilized in the study, as well as several angular and radial transducer positions at design, and at off-design flow rates. A spectral analysis was carried out on the pressure signals in frequency and in time-frequency domains. The results highlighted the existence of an asymmetrical rotating pressure structure at the impeller discharge, having a fluid-dynamical origin and propagating both in the radial and circumferential direction, inside and downstream of the impeller.