基于PBM的离心式叶轮内气泡破碎合并数值模拟

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

针对利用离心泵制备微气泡时叶轮内气泡尺寸较大且分布不均问题探究不同入口含气率(IGVF)和转速对离心泵叶轮内气泡直径和分布的影响,采用欧拉-欧拉非均匀双流体模型与群体平衡模型进行耦合,求解离心泵叶轮内气液两相旋转流场,并且结合涡识别方法、Luo破碎合并模型对离心泵叶轮内气泡分布规律进行分析。结果表明:①叶片前缘以及吸力面附近存在的涡旋导致气体聚集,引起流道内局部含气率增大,此处气泡合并效应占主导;②流量和转速一定时,随IGVF的增加,流道内湍流强度增加,旋涡后移导致气相聚集区域同样向后延伸,吸力面的高局部含气率区域增大面积显著高于压力面,因此吸力面气泡合并行为更为显著,气泡直径更大;③IGVF和流量一定时,小范围内提升转速可以使气泡破碎效应增强,获得更小直径的气泡。

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:①Vortices 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.②When 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.③When 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.