CFD Study for Assessment of Axial Thrust Balance in Centrifugal Multistage Pumps

Present work aims to the numerical investigation of horizontal multistage centrifugal pumps in opposite impeller configuration. Its main target is to apply a three-dimensional CFD based tool to the axial thrust prediction in a multistage industrial machine. A flexible use of CFD is presented to extend the hydraulic behaviour evaluation for the single components to the whole pump characterization. A mixing plane technique has been chosen to study the interaction between rotating and stationary parts. This procedure takes into account the effects of different incidences and inlet velocity distortions. The 3D CFD investigation on every single component of the multistage pump allows a thorough knowledge of its fluid dynamic fields, but only a correct matching and interpretation of all the components provide a reliable prediction of pump axial thrust as well as its performance curve. Despite the potential high degree of realism allowed by CFD, modelling the whole pump geometry may be quite expensive. In fact, the pump includes a great amount of components and several geometrical details (i.e. inlet and outlet volutes, inter-stage cross-over, leakages through wear rings and balancing drums) that have to be taken into account for a good prediction of the axial thrust. These issues lead to a consistent amount of numerical modelling problems which are considered and discussed