Influence of Geometry Simplifications and Numerical Parameters in 3D URANS Liquid-Gas Flow Simulations of a Radial Pump with an Eulerian Mono-Dispersed Two-Phase Model

摘要

3D numerical flow simulations of liquid-gas mixtures in a radial research pump with annulus casing and low rotation speed are performed with ANSYS CFX and a mono-dispersed multi-phase and the SST turbulence model. The drag force is approximated by the Schiller Nauman model while other interfacial forces are neglected. Both, liquid and gaseous phase are treated incompressible. The inlet gas volume fraction (IGVF) is varied between 3% and 5% for two flow rates. The reduction of the full impeller geometry to a single channel computational model has a minor effect on the results. The simulations should be performed in the absolute frame of reference since the choice of a relative impeller reference frame yields spurious gas accumulations at the rotor-stator interface. The achievable solver residuum decrease and the simulation results are highly grid sensitive. Although a comparison to measurement data reveals that the gas accumulation is predicted approximately at the expected location within the blade channel, significant deviations to the data remain for the blade pressure distribution. The head drop due to the increase of IGVF can only qualitatively be predicted. It is assumed that a multi-dispersed multiphase model including bubble coalescence must be taken into account to improve the computational prediction of liquid-gas mixture flow in radial pumps.