Turbulent 3D Flows near the Impeller of a Mixed-Flow Pump

Compared to other fluid machines, the flow patterns in a mixed-flow pump are highly complex, due to adverse pressure radial gradients, secondary flows and the flow separation effects in the impeller inlet and outlet.This paper deals with experimental investigations and their analysis. Special emphasis is laid on the three-dimensional flow fields at the inlet and the exit of a closed mixed-flow impeller to improve design and calculation methods.By means of a hot wire probe and an angular trigger blade-to-blade measurements of the flow field at the impeller inlet and outlet have been performed from the hub to the shroud within the entire operating range of the pump.Results of particular interest are the performance curve instability of a mixed-flow pump, the beginning of recirculation at the inlet and the exit of the impeller and the influence of inlet guide vanes in the pump suction side upon the pump performance.