Experimental study and transient CFD/DEM simulation in a fluidized bed based on different drag models
Experimental study and transient CFD/DEM simulation in a fluidized bed based on different drag models
复制标题
DOI：
10.1039/c6ra28615a
复制
发表时间：
2017-02
期刊：
影响因子：
3.9
通讯作者：
Lingjiu Zhou;Lingjie Zhang;L. Bai;W. Shi;Wei Li;Chuan Wang;R. Agarwal
中科院分区：
文献类型：
--
作者：
Lingjiu Zhou;Lingjie Zhang;L. Bai;W. Shi;Wei Li;Chuan Wang;R. Agarwal
气固两相流动是化学链燃烧(CLC)沸腾床系统中的主要现象。相间相对运动产生的阻力是阻碍载氧颗粒运动的主要作用力。评估和了解不同阻力模型的局限性和有效范围是很重要的。本文采用离散元方法(DEM)和计算流体力学(CFD)相结合的方法，对实验室规模的喷动床进行了阻力模型的数值模拟。从床层高度、气泡直径和压力波动的角度对这三种模型的数值结果进行了比较和分析。建立了喷动流态化实验台，进行了高速成像实验，验证了数值计算结果。三种阻力模型基本上都能描述气泡形状的瞬变行为。在整个流态化过程的第一阶段，Syamal-O‘Brien阻力模型能较好地预测气泡直径和气泡形状的变化，与实验结果吻合较好，但对气泡崩塌状态的预测不是很好；Wen-Yu阻力模型低估了气泡直径的变化，过早地预测了下一个流态化阶段的发生；虽然Gidaspow阻力模型仍然略微低估了气泡直径的变化，但从气泡形状和压力波动的角度来看，该模型的结果与实验结果吻合较好。在CFD/DEM体系下，Gidaspow阻力模型对稠密气固床内的流动有较好的预测效果。研究结果为进一步应用CFD/DEM方法改进设计提供了参考。
Gas–solid two-phase flow is the main phenomena in the chemical-looping combustion (CLC) fluidized bed system. Drag force generated from relative movement between phases is the main force that hinders the movement of the oxygen carrier particles. It is important to evaluate and understand the limitations and validity range of different drag models. In this paper, based on Discrete Elements Methods (DEM) coupled with Computational Fluid Dynamics (CFD), three kinds of drag models, Wen-Yu, Syamal-O'Brien, and Gidaspow, are used for the simulation of a laboratory-scale spouted fluidized bed. The numerical results based on these three models are compared and analyzed from the views of the bed height, bubble diameter, and pressure fluctuations. A spouted fluidized bed experiment rig was established to carry out the high-speed imaging experiment and validate the numerical results. All three drag models could basically describe the transient behavior of the bubble shape. In the first stage of whole fluidization process, Syamal-O'Brien drag model could predict well both the change of the bubble diameter and the bubble shape in good agreement with experiment results, but the model for the bubble collapse status is not a good prediction; Wen-Yu drag model underestimates the variations in bubble diameter and predicts the occurrence of the next fluidization stage prematurely; although, the Gidaspow drag model still slightly underestimates the change of bubble diameter, but the results of this drag model are in good agreement with the experiment results in terms of the bubble shape, and pressure fluctuations. Under the architecture of CFD/DEM, the Gidaspow drag model gives the better prediction of the inner flow in the dense gas–solid fluidized bed. The results provide reference for the further improved design of the fluidized bed by employing the CFD/DEM method.