Inlet reverse flows for centrifugal impellers. Effects of blade tip clearance and blade number.

In the previous report, it was pointed out that leakage flow through the comparatively large blade tip clearance of an open impeller considerably affects the flow just before the capacity at which an inlet reverse flow occurs. Then, in this paper, unsteady flows at the impeller entrance were measured for a small blade tip clearance impeller and a closed impeller. For the former, especially, static pressure distribution measurements on the casing surface outside of impeller blades and the flow visualization in the impeller were performed. The effect of blade number was also studied. As a result, the effects of the impeller blade tip clearance and the blade number on the inlet reverse flow starting point were clarified.