Casing Headloss in Centrifugal Slurry Pumps

Abstract

The headlosses in slurry pump casings are caused by the energy dissipation in the flowing liquid-solid mixture, and the particle-casing wall interaction. This paper presents a quasi-three-dimensional flow analysis, in two steps: (1) the casing width-averaged parameters are obtained from the two-dimensional flow simulation in a normal plane to the pump axis, (2) the results are then used for flow computation in the casing radial cross-sections. The governing equations are averaged over the typical time interval for the periodic flow in the casing caused by the finite number of impeller blades. Finite element techniques with linear three-node and quadratic nine-node elements are used in the numerical simulation. The effect of the casing shape on the headlosses is illustrated by comparing the performances of three centrifugal slurry pumps with quasi-spiral, semi-annular and annular casings at various flowrates. The flow recirculated between the casing tongue and impeller shrouds is shown to play a major role in the overall headloss. The flow results may also be used for determining the wear in the casing and thrust on the impeller, as well as for optimizing the casing dimensions.