Investigation of Closed Valve Operation Using Computational Fluid Dynamics Available to Purchase

Predicting the head of a centrifugal pump operating at closed valve remains a difficult task. The nature of the flow regime and the influence of geometric features on this flow is uncertain. In this paper both the flow regime and the influence on that regime by geometry is investigated using a commercially available CFD RANS code. A CFD methodology is presented that takes account of the difficult boundary conditions. This methodology is then used to present the flow regime in a volute pump against the background of available research. The theory of solid body rotation, as a major influence on the closed valve head, is shown by the CFD simulations to be analogous to but not representative of the actual flow regime. The nature of the flow is impulsive and unsteady with fluid interchange occurring between the pump collector and the impeller vane passages. At the inlet the pump impeller experiences a strong steady outflow from the impeller blade tip. This spiralling flow must be accommodated within the computational solution. The impeller outlet is filled with a vortex driven by the flow which cannot be accommodated within the stalled stator passageways. The annular gap between the impeller and collector is filled with a pulsating flow whose frequency is determined by the number of vanes within the impeller. Model validation was carried out by reference to experimental papers and time averaged closed valve head values obtained under standard performance testing.