关键词: 湍流模型, 气液搅拌槽, 气泡尺寸分布, 局部气含率, 计算流体力学, 群体平衡模型

Abstract: This paper investigated the simulation of liquid velocity, local gas holdup and bubble size in a stirred tank with dual turbine impellers using computational fluid dynamics(CFD). The results from three different turbulence models (Standard k-ε，RNG k-ε，Realizable k-ε) were compared. The Euler-Euler multiphase flow model and multiple frames of reference(MFR) method were used in the simulations. A population balance model(PBM) was implemented in order to account for the combined effect of bubble break-up and coalescence in the tank. The results showed that the flow patterns of liquid phase and the total gas holdups predicted by the three models had no significant difference, and the total gas holdups agreed well with the experimental data. The standard k-ε and RNG k-ε models over predicted the local gas holdup values at the impeller regions, and in the upper part of the vessel near the liquid-free surface where the local gas holdups predicted all were lower than the measurements. The realizable k-ε model gave the best result compared with the experimental data. The simulated results and experimental data agreed well at most of the points in the tank except for the part near the liquid-free face for the bubble sizes. The bubble size distribution was consistent with the turbulence length distribution.

Key words: turbulent models, gas-liquid stirred tank, bubble size distribution, local gas holdup, computational fluid dynamics(CFD), population balance model