基于动态双重网格下喷动床滞止区流动特性CFD-DEM数值模拟

doi:10.11949/0438-1157.20210397

摘要/Abstract

摘要：

基于Fortran语言自行开发了基于动态双重网格方法下的喷动床内气固两相流动的CFD-DEM方法，同时开展了喷动床内径向混合实验与模拟研究，又结合单网格方法对喷动床内0~2.0 s内的滞止区特性进行对比分析，验证了动态双网格方法计算结果的准确性。然后利用动态双网格方法对不同进口气速下和不同初始堆积高度下的喷动床进行数值模拟研究，对滞止区颗粒流动过程进行追踪，结果表明：径向混合实验结果与数值模拟结果有很好一致性；在喷动床内存在一定的滞止区，滞止区内的颗粒流动性较差；初始堆积高度不变，随着进口速度的增加，滞止区高度下降速率和向喷口延伸速度无明显变化；进口速度不变，随着初始堆积高度的增加，滞止区颗粒下降速度随之增加，但其向喷口延伸速度逐渐变慢。

关键词: 动态双重网格, 流化床, 两相流, CFD-DEM, 混合, 实验验证, 颗粒流, 滞止区

Abstract:

A CFD-DEM model of gas-solid two-phase flow in spouted bed was established based on the dynamic double-grid method. At the same time, the radial mixing experiment and simulation study in spouted bed were carried out. The characteristics of stagnation zone in spouted bed within 0—2.0 s were compared and analyzed with the single-grid method, which verified the reliability of the calculation results using the dynamic double-grid method. Then, the spouted bed with different inlet gas velocities and different initial stacking heights is numerically simulated, focusing on tracking the particle flow process in the stagnation area. The results show that: the experimental results of radial mixing are in good agreement with the numerical simulation results. There is a certain stagnation area in the spouted bed, and the particle mobility in the stagnation area is poor. The initial stacking height is constant, and with the increase of inlet velocity, the height decline rate of stagnation zone and the extension speed to nozzle have no obvious change. The inlet velocity remains the same. With the increase of the initial accumulation height, the falling velocity of particles in the stagnation zone also increases, but the extension velocity toward the nozzle gradually slows down.

Key words: dynamic double grid, fluidized bed, two-phase flow, CFD-DEM, mix, experimental verification, particle flow, stagnation zone

中图分类号:

TQ 028.8

王洪远, 纪律, 孟繁旭, 李斌, 杨建蒙, 陈海生. 基于动态双重网格下喷动床滞止区流动特性CFD-DEM数值模拟[J]. 化工学报, 2021, 72(11): 5563-5572.

Hongyuan WANG, Lyu JI, Fanxu MENG, Bin LI, Jianmeng YANG, Haisheng CHEN. CFD-DEM numerical simulation of flow characteristics in stagnation zone of spouted bed based on dynamic dual grid[J]. CIESC Journal, 2021, 72(11): 5563-5572.

图/表 13

图1 网格模型划分示意

Fig.1 Schematic diagram of grid model division

图2 颗粒径向混合过程实验与模拟对比

Fig.2 Comparison between experiment and simulation of radial mixing process of particles

图3 颗粒径向混合过程垂直速度云图

Fig.3 Vertical velocity nephogram of particle radial mixing process

图4 喷动床几何模型

Fig.4 Geometric model of spouted bed

表1 数值模拟计算参数

Table 1 Calculation parameter in numerical simulation

参数	数值	参数	数值
颗粒形状	球形	气体密度/(kg/m³)	1.205
颗粒直径D/m	0.004	气体黏度/(Pa·s)	1.8×10^-5
颗粒弹性系数/(N/m)	200	空气进口速度/(m/s)	27
恢复系数	0.9	床体几何尺寸/m	0.15×0.004×0.9
颗粒数目	1904	喷口参数/m	0.01×0.004
颗粒密度/(kg/m³)	2700	初始床高/m	0.18
摩擦系数	0.1	时间步长/s	1×10^-5

图5 单网格模型2 s内混合序列图

Fig.5 Mixed sequence diagram within 2 s of single grid model

图6 动态双网格模型2 s内混合序列图

Fig.6 Mixed sequence diagram within 2 s of dynamic double grid model

图7 两种网格方法下滞止区示踪颗粒平均高度

Fig.7 Average height of tracer particles in stagnation zone under two grid methods

图8 两种网格方法下示踪颗粒平均宽度

Fig.8 Average width of tracer particles under two grid methods

图9 不同速度下滞止区示踪颗粒平均高度

Fig.9 Average height of tracer particles in stagnation zone at different speeds

图10 不同速度下示踪颗粒平均宽度

Fig.10 Average width of tracer particles at different speeds

图11 不同初始高度下示踪颗粒平均高度

Fig.11 Average height of tracer particles at different heights

图12 不同初始高度下示踪颗粒平均宽度

Fig.12 Average width of tracer particles at different heights

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