The performance curve of a high specific speed mixed-flow pump with and without impeller guide vanes (IGV) is experimentally investigated. The three-dimensional flow field near a closed impeller and around IGV's with different leading angles is measured by a hot wire probe and an angular trigger. The experimental results revealed that the entry flow of the impeller strongly influences the pump performance curve. The stationary guide vanes fixed in the pump suction pipe are normally used to suppress the part load swirl. A newly developed IGV with special leading angles has the advantages e.g. to improve the flow field near the impeller and the efficiency and stability of a pump at all operating points. With optimal guide vanes for example secondary flows, leakage flow and back flow are effectively suppressed and the impeller inlet flow is increased.
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