Steady and Unsteady Flow Characteristics of a Multi-stage Centrifugal Pump under Design and Off-design Conditions

Abstract

This paper presents detailed analyses on the steady and unsteady internal flow characteristics of a three-stage centrifugal pump under design and off-design conditions. A numerical analysis is conducted by solving three-dimensional steady and unsteady Reynolds-averaged Navier-Stokes equations with the shear stress transport (SST) turbulence model. The results of the steady and unsteady numerical analyses throughout the flow region are analyzed and compared with experimental data. A reattachment modification is used in the SST turbulence model to better capture the characteristics of flow separation due to boundary layer reattachment under the design and off-design conditions. The unsteady numerical results are in reasonable agreement with the experimental data, whereas they differ from the steady numerical results when it comes to the internal flow fields at each component stage. In particular, the time-averaged internal flow phenomena obtained from the unsteady analysis are close to the real field conditions of this pump at low flow rates. The hydraulic performances with and without the reattachment modification are similar throughout the flow region, whereas the respective flow characteristics in each impeller component are considerably different, particularly at low flow rates.