Abstract

This current study analyses a low specific speed centrifugal pump for flow instability under part-load conditions by experimental and numerical analysis. Three-dimensional steady-state flow analysis is conducted over the actual impeller model having an outlet width of 44 mm. Numerical solutions are solved by Reynolds-averaged Navier-Stokes (RANS) equations using the shear-stress transport (SST) k-ω turbulence model. Numerical solutions at different operating flow rates are compared with an experimental performance test. The numerical and experimental results agree well. Some methods have been developed to improve the stability of hydraulic performance. One of the methods, alternate impeller vane cutback was adopted and tested successfully. In the investigated flow simulation it was observed that reverse flow between vane-to-vane passages caused pressure fluctuations under part load conditions. Impeller flow channels were blocked by the vortices forming in the vane passages. The reversed flow and the vortices in the impeller flow passages generates instability in the flow inside the impeller and will affect the hydraulic performance of the pump.

Keywords

Specific speed, Centrifugal Pump, Drooping zone, Flow instability, Hydraulic performance.