PTV on Volute Pump of Very Low Specific-Speed

In the very low specific speed range especially at the specific speed less than 70,efficiency of volute pump becomes remarkably low. It seems that there is a complex inner flow even at the designed point, and we must understand flow pattern to improve the pump performance. However, it had been difficult to measure the volute pump inner flow by the conventional measuring method because of a rotating impeller. In this report, we wish to show the results of measuring the inner flow of the very low specific-speed volute pump by PTV-method. Comparing the measured inner flow to the normal specific-speed one, it has been cleared that there is a large difference between them.