气泡泵提升管内气泡群运动特性分析

Analysis on the Characteristics of Bubble Group Motion Inside Bubble Pump Riser

为探索溴化锂溶液气泡泵的工作机理,在Inamuro大密度比两相流的格子Boltzmann自由能模型的基础上,以时间邻点替代空间邻点,将参数控制的差分项引入相变的分布函数f_i中,利用二阶迎风差分求解一阶偏导数,利用十四点中心差分格式求解二阶偏导数,将改进模型可模拟的两相流密度比从1000提高到3000,扩展并增强采用格子Boltzmann方法模拟大密度比多相流问题的适应性。通过模拟实际工况下气液密度比为2778的气泡泵垂直管中溴化锂溶液内并排多气泡的上升过程和聚并行为,获得不同初始条件下多气泡的密度场、速度矢量分布图,并对多气泡的运动规律进行分析和总结。研究结果表明,气泡在上升过程中的相互吸引作用和相互排斥作用与气泡群内的气泡大小及其初始位置有关,且气泡间聚并临界距离随着气泡直径的增大或气泡数量的增加而减小。

In order to study the working mechanism of lithium bromide bubble pump, two-phase flow lattice Boltzmann free energy model with Inamuro＇s large density ratio is taken as the basis where the space neighboring points are replaced by time neighboring points, and the parametrically controlled difference terms are introduced into the phase transitional distribution function f_i. The second order upwind difference scheme is used to solve the first order partial terms and the fourteen points central difference scheme is to solve the second order partial terms. Then the simulated two-phase flow density ratio of the enhanced model is increased from 1000 to 3000 for the first time, expanding and improving the adaptability of the lattice Boltzmann method to simulate the large density ratio multi-flow problems. Through simulating the parallel bubbles rising and coalescing in the lithium bromide inside the vertical pipe of the bubble pump with a gas-liquid density ratio of 2778, the bubbles＇ density field and velocity vector distribution diagram under different initial conditions are obtained, and the motion patterns of the bubbles are analyzed and summarized. The result shows that the mutual attraction and repelling interactions in between the bubbles are related to the size and initial position of the bubbles in the bubble group. The critical distance of the coalesced bubbles decreases when the diameter or quantity of bubbles increases.