The main objective of the presented work is to investigate the effect of volute design on the impeller–volute interaction. Therefore a low specific speed centrifugal pump impeller has been employed and three different volutes with circular cross-sections have been designed using the constant-velocity approach. Numerical simulations of the simplified pump model have been performed by means of ANSYS® CFX®, solving the 3D unsteady Reynolds-averaged Navier–Stokes equations. The three designs are compared in terms of hydraulic performance and also the flow patterns in the different volutes are examined in detail, including velocity, swirl and pressure distributions on different cross-sections along the volute as well as the charging of the volute. To show the impact of the volute on the impeller flow, also the pump impeller has been simulated without the volute and a thorough comparison of the time averaged results has been conducted. This has been done at the design flow rate as well as for overload and part load conditions. Also the unsteady flow inside a blade channel of the impeller during a revolution is investigated, revealing significant variations of its operating point, especially at off-design conditions. As a result of the performed studies it can be seen how the different volute designs interact with the impeller depending on the operation point and how this affects the hydraulic performance of the pump.

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