11th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
A numerical study is performed in order to evaluate the capability of the mono-dispersed multiphase model in ANSYS CFX to predict the flow of liquid-gas mixture in radial pumps. A radial research pump with annulus casing and low rotational speed is investigated for different operation points. The drag force is approximated by the Schiller Nauman model. No other interfacial forces are considered. Both, liquid and gaseous phase are treated incompressible. The inlet gas volume fraction is varied up to 7 %. The comparison of a full-geometry model and a single blade model shows that the single blade model predicts the head sufficiently accurate. A grid study is performed for single-phase flow. Head as well as blade pressure profiles are compared to experimental data. For IGVF up to 3 % the head is predicted with a good accuracy. While the experimental blade pressure profiles indicate that the accumulation of gas is located close to the blade surface, the simulation predicts their location rather in the channel center. This mislocation of large gas zones leads to an even qualitatively wrong head drop in the simulation for IGVF > 3 % and high flow rates. It can be concluded that the accuracy of the multiphase model needs to be improved, particularly by the consideration of lift force and bubble interaction, for a reliable simulation of liquid-gas flow in radial pumps, in particular at higher IGVF.