Application of CFD-PBM coupling model for analysis of gas-liquid distribution characteristics in centrifugal pump

Abstract

The gas and liquid distributions in the pump are significant for understanding the pump performance under bubble flow inlet. An accurate numerical simulation method will contribute to obtain the gas and liquid distribution characteristics in the pump. In this study, the simulation method based on the CFD-PBM (CFD-Population Balance Model) coupling model was developed and validated by experiments. The simulation results predicted by the new numerical method agreed better with the experimental results than calculations based on Eulerian-Eulerian model. The coalescence and breakup of bubbles in the centrifugal pump should be considered, which is well handled by the CFD-PBM coupling model. The influences of inlet gas volume fraction and liquid phase flow rate on the void fraction and bubble size distribution in the centrifugal pump were investigated. The results show that more bubbles accumulated in the impeller than in the volute as inlet gas volume fraction increased to a certain value. Small gas pockets accumulated in the impeller and formed large gas masses around the impeller inlet leading to “Surging” of the pump. The percentages of bubbles with large diameter increased with the inlet gas volume fraction increasing, rather, the bubbles with small diameter decreased. In addition, the bubbles were more likely to break up into smaller bubbles and difficult to aggregate into bigger bubbles when the liquid flow rate increased. Several void fraction and bubble size prediction models were also compared for the present cases. This study provides an effective method to simulate the pump characteristics under gas and liquid conditions, which is helpful to investigate the gas-liquid performance of the pump.