Comparaisons between numerical calculations and measurements in the vaned diffusor of SHF impeller

Abstract

The paper presents analysis of the performance and the internal flow behaviour in the vaned diffusor of a radial flow pump using PIV technique and pressure probe traverses. PIV measurements have been performed at mid height inside one diffusor channel passage for a given speed of rotation and various mass flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. For each angular position, instantaneous velocities charts have been obtained on two simultaneous views, which allows, firstly ,to cover the space between the leading edge and the diffusor throat and secondly, to get a rather good evaluation of phase averaged velocity charts and “fluctuating rates “. Probe traverses have been performed using a 3 holes pressure probe from hub to shroud diffusor width at different radial locations in between the two diffusor geometrical throats. The numerical simulations were realized with the commercial codes: i-Star CCM+ 7.02.011, ii-CFX. Frozen rotor and fully unsteady calculations of the whole pump were performed. Comparisons between numerical and experimental results are presented and discussed for one mass flow rate. In this respect, the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model are analysed and discussed.