鼓泡塔中离子液体-空气两相流的CFD-PBM耦合模拟

CFD-PBM coupled simulation of ionic liquid-air two-phase flow in bubble column

针对咪唑类离子液体介质,采用Eule-rEuler双流体模型与群平衡模型(PBM)耦合的方法,引入由实验结果拟合获得的适用于该介质的气液相间曳力系数模型,对内径0.203 m、高2 m的鼓泡塔中离子液体-空气两相流进行计算流体力学模拟,研究了不同表观气速下塔内气液两相速度场分布、气含率和气泡尺寸分布等流体动力学性质。与现有的相间曳力系数模型Schille-rNaumann模型模拟结果对比,采用本文模型得到的气含率与实验值吻合更好,气泡尺寸分布与实验结果一致。

Abstract： Ionic liquids have been regarded as a new and effective solvent and absorbent, however, the fluid dynamics of ionic liquids have not been thoroughly investigated. Computational fluid dynamics （CFD） is an increasingly important method to understand the fluid dynamics of multiphase fluid. In this work, the gas holdup, bubble size distribution and flow velocities of ionic liquid-air two-phase flow in bubble column were investigated by using Euler-Euler method and population balance model （PBM） coupled numerical model. Considering the special properties of ionic liquids, ionic liquid drag coefficient and Schiller-Naumann model were both used as interphase drag coefficient. The numerical simulation results showed that the general gas holdup and the uniformity of gas distribution both increased with increasing superficial gas velocity. The predicted general gas holdup with ionic liquid drag coefficient agreed with the experimental data better than that of Schiller-Naumann model. Ionic liquid drag coefficient overestimated the general gas holdup and the average error of simulation result with drag coefficient was 8.1~//00. Schiller-Naumann underestimated general gas holdup and the average error of simulation result with Schiller-Naumann model was 22.8~/6o. The bubble size distribution was studied by using PBM model, discrete method was used to solve the population balance equations, and the bubbles in the column were divided into 10 groups ranging from 1 mm to 9.85 mm. The simulated bubble size distributions agreed with experimental results. The bubbles of low superficial gas velocity were larger than those of high superficial gas velocity, and the bubblesize range o{ low gas velocity was wider than that of high gas velocity. This was caused by different bubble coalescence and breakup rates of different superficial gas velocities The study of bubble and liquid velocity distribution showed that the uniformity of liquid velocity in the column increased with increasing gas velocity.