基于EMMS模型的搅拌釜内气液两相流数值模拟

Numerical simulation of gas-liquid flow in stirred tanks based on EMMS model

采用欧拉-欧拉模型对搅拌釜内气液两相流进行了三维CFD模拟,重点研究了采用不同曳力模型时CFD模拟对搅拌桨附近排出流区两相流动的预测能力。模拟结果表明CFD能准确地预测排出流区的液相速度分布,但采用传统的Schiller-Naumann曳力一定程度上低估了排出流区的气液相间曳力,导致在完全扩散区CFD预测的分布器和桨叶下方区域气含率偏小,而基于气液非均匀结构和能量最小多尺度(EMMS)方法得到的DBS-Global曳力模型能更准确地描述完全扩散区气液搅拌釜内流动情况。与传统曳力模型相比,采用DBS-Global曳力模型能显著提高对气含率的预测。

3D Eulerian-Eulerian model was applied to simulate the flow in a gas-liquid stirred tank.Simulation results with different drag models were evaluated at the discharge flow region.CFD simulation could correctly predict the liquid velocity distribution around the impeller,but the traditional Schiller-Naumann drag model under-estimates the drag force,leading to the relatively lower gas holdup at the region under the impellers and gas distributor.The DBS-Global drag model derived from the gas-liquid EMMS model could obtain more reasonable gas holdup distribution at the complete dispersion regime and significantly improved the prediction accuracy of the gas holdup distribution at the discharge flow region.