CFD-DEM study of gas-solid flow regimes in a Wurster type fluidized bed with experimental validation by electrical capacitance tomography
CFD-DEM study of gas-solid flow regimes in a Wurster type fluidized bed with experimental validation by electrical capacitance tomography
复制标题
Wurster 型流化床中气固流态的 CFD-DEM 研究并通过电容断层扫描进行实验验证
DOI：
10.1016/j.cej.2020.124280
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发表时间：
2020-06
影响因子：
15.1
通讯作者：
L.J. Xu
中科院分区：
文献类型：
--
作者：
H.Q. Che;D. Liu;W.B. Tian;S. Gao;J.T. Sun;L.J. Xu
Wurster型流化床被广泛应用于许多工业部门的颗粒包覆，流化床内的气固流动状态是一个重要的问题，但很少在文献中讨论，无论是数值计算还是实验。在这项工作中，提出了一种耦合计算流体力学与离散元方法（CFD-DEM）的数值方法来研究气固流动动力学在Wurster型流化床，重点是现有的气固流动状态。两种模拟案例，即，进行冷流情况和考虑粘附力的情况。利用电容层析成像（ECT）实验数据验证了仿真结果。在冷态流动条件下，在流化床的环形区域观察到两种流化状态，包括塞状和多鼓泡。结果表明，在不同风速下，多鼓泡区可进一步分为底部流化、局部流化和整体流化，且83%以上的颗粒质量保持在环空区。随着颗粒间粘附力的增加，环空区域的流型由多鼓泡转变为单鼓泡，然后是塞流，最后是反流化。多鼓泡、单鼓泡和活塞流可以分别通过0-4、4-15和大于15的循环时间范围来区分。最后，发现颗粒循环时间在3-9 s之间，气固两相流态可以作为颗粒循环时间分布的一个指标。本研究的方法和新发现补充了Wurster型流化床包衣过程优化的现有技术和知识。
Wurster type fluidized bed is widely used for particle coating in many industrial sectors, the gas-solid flow regimes within the fluidized bed is an important issue but rarely discussed in the literature, either numerically or experimentally. In this work, a numerical method that couples computational fluid dynamics with the discrete element method (CFD-DEM) was proposed to investigate the gas-solid flow dynamics in a Wurster type fluidized bed, with a focus on the existing gas-solid flow regimes. Two types of simulation cases, i.e., cold flow cases and the cases accounting for adhesion forces, were carried out. Experimental data by electrical capacitance tomography (ECT) imaging was employed to validate the simulation results. In cold flow cases, two fluidization regimes, including plug, and multi-bubbling were observed in the annulus region of the fluidized bed. It was found that the multi-bubbling regime can further be classified into bottom, localized and global fluidization under different air velocities, and more than 83% of the total particle mass is kept within annulus region. With increase in the inter-particle adhesion force, the flow regime in the annulus region changed from multi-bubbling to single-bubbling, followed by plug flow and eventually defluidization. The multi-bubbling, single-bubbling, and plug flows can be discriminated by cycle time ranges of 0–4, 4–15 and more than 15, respectively. Finally, it was discovered that the particle circulation times was within the ranges of 3–9 s, and the gas-solid flow regimes can be used as an indicator of the circulation time distribution. The methodology and new findings in this study complement the existing techniques and knowledge for the optimization of coating process in a Wurster type fluidized bed.
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影响因子：
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作者：
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DOI：
10.1016/j.ijmultiphaseflow.2010.12.007
发表时间：
2011-06
影响因子：
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