Coarse grid simulation of heterogeneous gas–solid flow in a CFB riser with EMMS drag model: Effect of inputting drag correlations
Coarse grid simulation of heterogeneous gas–solid flow in a CFB riser with EMMS drag model: Effect of inputting drag correlations
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DOI：
10.1016/j.powtec.2013.12.022
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发表时间：
2014-02
影响因子：
5.2
通讯作者：
Q. Zhou;Junwu Wang
中科院分区：
文献类型：
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作者：
Q. Zhou;Junwu Wang
双流体模型结合能量最小多尺度（EMMS）曳力模型是模拟循环流化床内非均相气固流动的有效方法。在EMMS阻力模型中，为了描述稀相、密相和相间三个子系统内的气固相互作用，必须使用由均相流化床和/或填充床得到的阻力关联式（传统的阻力关联式）。本文在EMMS阻力模型的框架下研究了不同的传统阻力关联式对气固团簇流动相间有效阻力的影响，以及它们对CFD结果的影响。结果表明，由于合理地考虑了细观结构效应，EMMS阻力模型计算结果与实验数据（包括径向和轴向固体浓度分布以及局部固体浓度的均方根值）吻合较好，且不受传统阻力关联式的影响。本文的结论与以往的研究结果有很大的不同，在以往的研究中，采用传统的阻力关联式的粗网格模拟不能预测循环流化床锅炉的流体动力学，并且对传统的阻力关联式很敏感。因此，EMMS阻力模型出现作为一个传统的阻力相关性的优势，因为它不仅是不敏感的经验输入，但也给出了更好的协议与实验。
Two-fluid model combined with Energy-Minimization Multi-Scale (EMMS) drag model has been accepted as an effective method to simulate the hydrodynamics of heterogeneous gas–solid flow in circulating fluidized beds. In the EMMS drag model, a drag correlation obtained from homogeneous fluidization and/or packed bed, denoted as traditional drag correlation, is necessary to describe the homogeneous gas–solid interactions within three (dilute-phase, dense-phase and inter-phase) sub-systems. In this article we study the effects of different traditional drag correlations on the effective inter-phase drag force of clustered gas–solid flow within the framework of EMMS drag model, and their consequent effects on CFD results. It was shown that due to the proper consideration of meso-scale structural effect, CFD results using the EMMS drag model are in a reasonable agreement with experimental data (including radial and axial solid concentration profiles and root mean square of local solid concentration), and are slightly affected by different inputting traditional drag correlations. Present conclusion is quite different from the one obtained in previous studies, where coarse grid simulation with traditional drag correlation failed to predict the hydrodynamics of CFB risers and was sensitive to the traditional drag correlation used. Therefore, the EMMS drag model appears as an advantage over traditional drag correlations, since it is not only insensitive to the empirical input, but also gives much better agreement with experiments.