基于不同曳力模型的鼓泡流化床CFD-DEM数值模拟与试验研究

Numerical simulation and experimental study of CFD-DEM in bubbling fluidized bed based on different drag models

为了准确选择稠密气固两相流中的曳力模型以提高数值模拟结果的准确性,基于CFD-DEM双向耦合方法,采用现阶段气固流化床数值模拟中常用的Ergun,Wen&Yu,Syamal-O′Brien,Gidaspow,Di Felice以及Huilin&Gidaspow共6种曳力模型开展数值模拟,将其与高速摄影试验测得的床层高度、空泡形态、直径以及压力波动等运动特征进行对比.对于中等表观气速v=350 L/min的气固两相流动系统中,这6种曳力模型在描述空泡形态与床层高度的变化方面差异较大;Di Felice模型没能够预测出鼓泡破碎后出现的二级小气泡,而Ergun模型则较高估计了床层高度的变化,综合对比发现:Gidaspow模型虽然略微低估了二级小空泡直径的变化,但是在空泡形态和压力波动与试验吻合较好.在基于DEM的流化床数值模拟中,Gidaspow模型能够对稠密气固两相流动进行较为准确的预测.

In order to accurately select the drag model in dense gas-solid two-phase flow and improve the accuracy of numerical simulation results.Based on the CFD-DEM two-way coupling method,the most commonly used Ergun model Wen&Yu model,Syamal-O′Brien model,Gidaspow model,Di Felice model and Huilin&Gidaspow six drag models were used in gas-solid fluidized bed numerical simulation.This kind of drag force model was used to carry out numerical simulation,and it was compared with the bed height,cavitation shape,diameter and pressure fluctuation measured by high-speed photography experiments.For the gas-solid two-phase flow system with a medium superficial gas velocity of v=350 L/min,the six drag models were quite different in describing the changes of cavitation shapes and bed heights.The Di Felice model failed to predict the secondary small bubbles that appeared after the bubble was broken,and the Ergun model estimated the change of the bed height.After comprehensive comparison,it is found that although the Gidaspow model slightly underestimated the changes in the secondary small bubble diameters.The bubble shape and pressure fluctuations are agree well with the experiments.In the DEM-based fluidized bed numerical simulation,the Gidaspow model can accurately predict dense gas-solid two-phase flow.