Effect of the Volute on Performance of a Centrifugal Pump Impeller

Abstract

An experimental study of volute influence on radial flow impeller performance was conducted by operating a single impeller with three different sets of volute vanes. In each case, over-all performance was measured and internal flow study within the volute was made. The results show that at their respective design flow rates the influence of the volutes is least and the deviation of performance from the free impeller operation is small. At off-design flow rates there are major changes in the impeller performance due to the presence of the volutes. Large real fluid effects, coupled with a quite nonuniform velocity pattern at the impeller exit, result in a flow through the volute that does not resemble a potential flow. Even so, the fluid losses through the volute are comparatively small. It is also shown that at off-design conditions, the flow cannot be irrotational and therefore potential flow theories cannot be used in describing the flow or predicting performance.