双流体模型的细网格模拟  

Fine-grid simulation of fluidized beds using two-fluid model

作　　者：石战胜[1] 洪坤[1] 王维[1] 

机构地区：[1]中国科学院过程工程研究所,多相复杂系统国家重点实验室,北京100190

出　　处：《计算机与应用化学》2013年第9期959-962,共4页Computers and Applied Chemistry

基　　金：国家重点基础研究发展计划项目(2012CB215003)

摘　　要：对于A类颗粒,鼓泡流化床中,随着网格尺寸的减小,膨胀高度降低,细网格模拟达到网格无关的值接近于实验数据即网格细化可以预测鼓泡流化床的膨胀高度,但是,当前的计算能力无法达到工业规模反应器的计算要求;流化气速越高,达到网格无关时的网格尺寸越大。与传统的基于平均方法的曳力系数相比,耦合了EMMS厂bubbling曳力系数的双流体(TFM)模型允许使用更粗网格,且准确性大大改善,将为工业化大型反应器模拟提供很好的方法,其中,EMMS/bubbling曳力模型如以前的论文(Shi et a1.,2011)。This work analyzed the applicability of using fine-grid simulation of two-fluid model （TFM） for Geldart A particles. First of all, the effect about aspect ratio of mesh was investigated, if grid size was constant and its axial height was varied, the simulation result of aspect ratio 1：2 was in well agreement with one of 1：1, but lower than one of 1：4, which showed the aspect ratio 1：2 and 1：1 are reliable. If mesh area keeps constant, the expansion height was the same but the solids concentration in the center of reactor was varied. Secondly, the grid size was investigated, when the grid size was larger, there were the higher expanding height and more homogeneous solids concentration, where no clear bubbles; when the grid size became smaller, the heterogeneous structure gradually occurs. With the decrease of grid size, the expansion height keeps invariable at the grid size of 0.3mm which is equal to 4.6 particles diameter. Besides, with increasing gas velocity, the expansion height increased and the values of grid size needed for convergence became larger and larger but the deviation between simulation and experiments also grows. At last, the validated results show that, with the decrease of grid size, the expansion height of the fluidized bed lowers and the simulation agrees well with experimental data when converging to its asymptotic solution. But current computation capability hardly meets the requirements for large scale simulations. By comparison, the coarse-grid TFM simulation with EMMS/bubbling drag coefficient which was proposed by Shi et al. （2011） allows using coarser grid than with homogeneous drag coefficient, and its predictions agree reasonably with experimental data. The TFM simulation coupled with bubble-based EMMS （energy-minimization multi-scale） drag model will be a promising method for industrial reactor simulations.

关 键 词：双流体 细网格 曳力 动力学 鼓泡流化床 

分 类 号：TQ021.1[化学工程]