Performance prediction of centrifugal pumps with CFD-tools

Abstract

Some of the authors of this publication are also working on these related projects: Project1: Models for laminar-turbulent transition in turbomachinery boundary layer flows. View project Project2: Algorithms for unsteady flow of compressible fluids with largely varying Mach number. View project Abstract: The CFD-code FLUENT, version 5.4, has been used for the flow analysis of two test pumps of end-suction volute type: one of low specific speed and one of medium specific speed. For both, head as function of flow rate for constant rotational speed is known from experiments. FLUENT provides three calculation methods for analysis of turbomachinery flows: the Multiple Reference Frame method (MRF), the Mixing Plane method (MP) and the Sliding Mesh method (SM). In all three methods, the flow in the rotor is calculated in a rotating reference frame, while the flow in the stator is calculated in an absolute reference frame. In the MRF and MP methods steady flow equations are solved, while in the SM method, unsteady flow equations are solved. The SM method does not introduce physical approximations. The steady methods approximate the unsteady interaction between rotor and stator. The cost of the unsteady method is, however, typically 30 to 50 times higher than the cost of the steady methods. It is found that the MRF and MP methods lead to completely erroneous flow field predictions for flows far away from the best efficiency point. This makes the steady methods useless for general performance prediction.