A Numerical Analysis of a Mixed Flow Pump

The rotating passages of turbomachinery contain some very interesting and complex fluid flow phenomena. This paper presents the three-dimensional turbulent flow through the impeller passages and surroundings of a mixed-flow pump. The model has five impeller blades mounted on a conical hub and nine stator blades in a diffuser which brings the diagonally outward flow back to the axial direction. This pump was tested with air, giving a nominal flow-rate of 1.01 m³/s and 250 Pa at 1200 rpm. Temporal discretization has second order accuracy and this is in line with the discretization of convection which is also second order. For turbulence closure the standard k-e model has been applied with conventional wall functions employed at solid surfaces. For this transient, three-dimensional computation, the numerical grid has been decomposed into five separate regions in order to process these in a parallel cluster of five individual PC’s. The results show entirely reasonable correlations with published experimental data as detailed in the flow rate-head comparisons and the numerical / experimental flow fields. These outcomes allow us to confirm that such a complex transient phenomenon may be reasonably captured by employing a commercial CFD code.