Abstract
Effects of the suction casing shape on the pump performance at partial flow rates are investigated using double suction pumps. The shut-off head ratio of the pumps with the volute type suction casing is higher than that of pumps with the normal type of casing. By visualization and measurement of the flow pattern, it is made clear that such the phenomenon is caused by the inflow to the impeller near the hub, which rotates in opposite direction to the pump rotation. Moreover, the reverse flow on suction side of the impeller occurs the vortex in the suction casing and its strength increases with decreasing flow rate.
