CO_(2)气泡群上升过程的CFD-PBM模拟

CFD-PBM simulation of rising process of CO_(2)bubble group

为揭示CO_(2)气泡群在方形鼓泡塔中上升过程的气液两相流行为,采用双流体模型耦合PBM(种群平衡方法)进行数值模拟,考虑气泡间的聚并和破碎现象,与部分实验结果相互对比,验证数值模型具有一定的可靠性,并分析入口气速、塔高宽比和入口分布器结构对气液流动情况、相含率和液相速度的影响,模拟结果表明:气泡群的上升过程出现了周期性的羽流震荡现象,改变气速会影响塔内气泡羽流的震荡程度;流动过程液相发生湍动,随着塔高宽比增大,液相循环模式实现了从“冷却塔”形式到“交错涡旋”的转变;不同入口结构下相含率分布有差异,大入口的震荡更早到来,但震荡持续时间较小入口结构短。研究CO_(2)气泡群的多相流动规律为鼓泡塔的设计和优化提供了理论参考。

In order to reveal the gas-liquid two-phase flow behavior of CO_(2)bubble group rising in a square bubble column,a two-fluid model was used for numerical simulation,considering the coalescence and break-up between bubbles,the PBM(population balance method)was coupled.The numerical model was verified to have a certain reliability by comparing with some experimental results.The effects of inlet gas velocity,column aspect ratio and inlet distributor structure on gas-liquid flow,phase holdup and liquid phase velocity were analyzed.The simulation results show that periodic plume oscillation occurs during the rising process of bubble group,and changing the gas velocity will affect the degree of bubble plume oscillation.The liquid phase is turbulent in the flow process,and with the increase of the column aspect ratio,the liquid phase circulation mode changes from"cooling tower"to"staggered vortex".The phase holdup distribution of different distributor structures is different.The plume oscillation of large distributor comes earlier,but the duration is shorter than small distributor structure.The study of the multiphase flow law of CO_(2)bubble group provides theoretical reference for the design and optimization of bubble column.