Numerical Simulation of Transient flow through Single Blade Centrifugal Pump Impellers with Tipgap Leakage

Abstract:- This paper is concerned with the application of Computational Fluid Dynamics (CFD) to a low specific speed (Ns=60) single blade impeller. Single blade centrifugal pump impellers are the extreme example of impeller design, with gross deviation from conventional design practice. A time accurate three-dimensional viscous flow simulation is performed, using the multiple frames of reference sliding mesh technique, at different flow rates (q = Q/Qdesign = 0.5 to 1.5) and varying tip gap clearances. Time marching is controlled through the use of an implicit Second Order Backward Euler scheme with a physical timestep, corresponding to 6 ° impeller rotation. A hybrid prism / tetrahedral mesh is used in order to provide adequate grid resolution in the turbulent boundary layer while scalable wall functions are used to model the near wall region. The results obtained show quantitative agreement with physical test results in terms of global performance characteristics such as head developed and power consumption. One particular phenomenon highlighted in the results is the periodic pressure fluctuation due to interaction between impeller and volute. This is significantly exaggerated by the single blade impeller. The steady state, symmetric flow assumptions upon which Euler’s pump and turbine equation are based are clearly violated for single blade impellers