The effect of size, location and pumping direction of pitched blade turbine impellers on flow patterns: LDA measurements and CFD predictions

A combined LDA-CFD (MRF method) study has been undertaken of the turbulent flow associated with two sizes of 6-bladed 45degrees pitch blade turbine at three clearances, either pumping up or down. Good quantitative agreement for mean velocity vectors has been obtained but that for RMS values was poor. The mean discharge angle is more vertical: (a) for the smaller impeller at all clearances; (b) for both sizes when an impeller approaches a surface towards which it is pumping.