Prediction of pump–circuit interactions by computational fluid dynamics calculations coupled with a one-dimensional acoustic model

Abstract

Centrifugal pumps generate perturbations due to the intermittent interaction between the blades and the volute that represent a dynamic load which limit the pump’s performance. Their magnitude depends on the acoustic coupling between pump and piping, and so there is interest in reducing the blade-passing frequency excitation by modification of the acoustic impedance of the piping. The objective of this work is to investigate the pressure pulsations predicted in a three-dimensional numerical model of a commercial pump under different coupling conditions. For this purpose, an expression for the acoustic impedance in a basic arrangement is deduced first. This impedance is imposed at the exit boundary of the model by means of an external user-defined function to characterize the impulse pipeline. Simulations are carried out from part flow to overflow and a range of impedances. The predictions for a specific flow rate are compared with experimental measurements of the blade-passing frequency amplitude at the exit of the pump. It is observed that the largest amplitudes among the coupling conditions tested reach relative values of about 11%.