The Effect of Tip Leakage Flow on Part Load Performance of a Mixed Flow Pump Impeller", ASME 91-GT-84

Introduction Mixed-flow pumps often show an abrupt decrease in pressure head and positively sloped head-flow characteristic when the flow rate is reduced below a critical value. In the present paper, this condition when the slope becomes positive will be referred to as "stall onset." Since the occurrence of a positively sloped characteristic is more likely to cause instabilities in a pumping system, it is usually a contractual requirement to guarantee a substantial margin between operating and stall points or to achieve a head-flow curve with a monotonously negative slope. Despite a lot of experimental investigations (see review by The performance difference between shrouded impellers (most commonly used for multistage configurations) and unshrouded impellers at various tip clearances is a matter of great interest, because they often show quite different characteristics, especially at partial flow rates. With regard to centrifugal impellers