Flow Structures and Pressure Fluctuations in a Centrifugal Pump at Design and Off-Design Conditions

Abstract

The flow structures and the pressure fluctuations in a centrifugal pump at both design and off-design points are presented in this paper. The flow structures are numerically obtained by solving the viscous incompressible Navier-Stokes equations with a 3D unsteady flow model. A sliding mesh technique is applied to take into account the impeller-volute interaction. The pressure fluctuations are obtained by both numerical simulations and experimental measurements. The former data denote all the flow field characteristics including those in the impeller, the interface, the volute and the diffuser, while the latter ones that acquisitioned by a high-frequency pressure sensor show only one position at the outlet flange. The FFT technology is adopted to process those dynamic pressure data to reveal the frequency features. All the power spectrum results present that the dominant frequencies are the blade passing ones, while the subdominant ones are varied depending on the flow rates and the positions. At design condition, the mean velocity field in both impeller and volute show well behaved flow with no separation, while subtle separation is found along the tongue side in the diffuser. Some unknown high-frequency contents are discovered in the flow field.