Unsteady Flow Analysis for a Diffuser Pump in Off-design Operation by Vortex Method.

Abstract

The vortex method was applied to the unsteady flow in a diffuser pump with 6 impeller blades and II diffuser vanes at various off-design operating points. The calculated unsteady total pressure rise showed a good agreement with the experimental data and the CFD calculated ones. The numerical results of unsteady flow at a partial discharge range (approximately 83 percent of the rated flow-rate) showed that the asymmetrical separation bubble appears near the pressure surface side of the impeller blade. It was concluded that the intermittence of the separation bubble is one of the main factors to cause the unstable characteristics of the test diffuser pump. The calculated unsteady flow at lower partial discharge range (50 percent of the rated flow-rate) presented the rotating stall in impeller passage as well as in diffuser passage.