Numerical simulation of bubble breakup and coalescence in centrifugal impeller based on PBM

In addressing the issue of larger and unevenly distributed bubble sizes within the impeller during the preparation of microbubbles using a centrifugal pump, this study investigates the impact of different inlet gas volume fraction (IGVF) and rotational speeds on the diameter and distribution of bubbles within the impeller. The Euler-Euler non-uniform two-fluid model is coupled with the population balance model (PBM) to solve the rotating two-phase flow field within the impeller of the centrifugal pump. Additionally, vortex identification methods and the Luo fragmentation and coalescence model are employed to analyze the distribution patterns of bubbles within the impeller. The results indicate the following: ① Vortices near the leading edge and the suction side of the blades cause gas accumulation, causing the local gas content in the flow channel to increase, where the bubble merger effect dominates. ② When the flow rate and rotational speed are constant, as the IGVF increases, the turbulence intensity in the flow channel increases, and the vortex moves backward, causing the gas phase accumulation area to also extend backward. The region of high local gas content on the suction surface significantly surpasses that on the pressure surface. Consequently, the bubble merging behavior on the suction surface becomes more pronounced, resulting in larger bubble diameters. ③ When the IGVF and flow rate are constant, increasing the rotation speed in a small range can enhance the bubble crushing effect and obtain smaller diameter bubbles. © 2024 Materials China. All rights reserved.