基于颗粒动态恢复系数二阶矩模型的液固流化床数值模拟研究

doi:10.11949/0438-1157.20241414

摘要/Abstract

摘要：

在液固流化床中，由于液相黏附力的作用，液体附着在颗粒表面会形成一层薄膜，引起颗粒弹性恢复系数的变化，从而影响颗粒的碰撞行为。与此同时，颗粒的脉动特性也表现出各向异性。故基于双流体模型和各向异性颗粒动理学理论，考虑颗粒恢复系数的动态变化，建立了液膜作用下颗粒动态恢复系数二阶矩模型，以研究液固流化床中包裹液膜颗粒的各向异性流动行为。模拟结果表明，液膜的存在增强了颗粒碰撞时的能量耗散，并减小了颗粒速度脉动的各向异性。随着液体黏度与颗粒密度的增加，液膜厚度增大，颗粒速度脉动与各向异性减弱。另外，动态恢复系数二阶矩模型所预测的颗粒速度和孔隙率分布与Limtrakul的实验值吻合更好，可以更准确地捕捉流场的不均匀性和各向异性特征。

关键词: 计算流体力学, 流化床, 多相流, 湿颗粒动态恢复系数, 各向异性颗粒动理学

Abstract:

In liquid-solid fluidized beds, the adhesion of liquid to particle surfaces forms a thin film due to liquid phase interparticle forces, altering the particle restitution coefficient and subsequently affecting their collision behavior. Meanwhile, the particle velocity fluctuations also exhibit anisotropic characteristics. Therefore, based on the two-fluid model and the anisotropic kinetic theory of granular flow, a second-order moment model of dynamic restitution coefficient considering the effects of liquid film and the anisotropy of particle velocity fluctuations is established. The simulated results show that the presence of liquid film enhances the energy dissipation of particles during collision and reduces the anisotropy of particle velocity pulsation. With increasing liquid viscosity and particle density, the film thickness increases, both the particle fluctuations and the anisotropy decrease. Furthermore, the predicted particle velocities and porosity by the second-order moment model of dynamic restitution coefficient are in better agreement with experimental values, enabling a more accurate capture of flow field non-uniformity and anisotropic characteristics.

Key words: computational fluid dynamics, fluidized-bed, multiphase flow, dynamic restitution coefficient of wet particles, anisotropic kinetic theory of granular flow

中图分类号:

TQ 018

陈曦, 王淑彦, 邵宝力, 丁诺, 谢磊. 基于颗粒动态恢复系数二阶矩模型的液固流化床数值模拟研究[J]. 化工学报, 2025, 76(7): 3246-3258.

Xi CHEN, Shuyan WANG, Baoli SHAO, Nuo DING, Lei XIE. Numerical simulation study of liquid-solid fluidized beds based on second-order moment model of particle dynamic restitution coefficient[J]. CIESC Journal, 2025, 76(7): 3246-3258.

图/表 17

图1 液固流化床结构示意图

Fig.1 Structure scheme of liquid-solid fluidized bed

表1 液固流化床模拟参数

Table 1 Simulated parameters of liquid-solid fluidized bed

参数	实验	模拟
床高/m	1.5	1.5
床宽/m	0.14	0.14
初始床高/m	0.45	0.45
初始颗粒堆积浓度	0.598	0.598
液体黏度/(Pa·s)	0.001	0.001
液体密度/(kg/m³)	994	994
流体进口速度/(m/s)	0.07	0.07
颗粒密度/(kg/m³)	2500	2500
颗粒直径/mm	3	3
泊松比	0.25	0.25
杨氏模量/GPa	70	70

图2 不同网格尺寸下颗粒轴向速度沿径向分布

Fig.2 Distributions of particle axial velocity with different mesh sizes

图3 模拟颗粒轴向速度和孔隙率值与实验值对比

Fig.3 Comparison of simulated particle axial velocity and porosity values with experimental data

图4 瞬时颗粒浓度与速度矢量分布（从左到右依次为SOM-edynamic、SOM、KTGF-edynamic、KTGF模型）

Fig.4 Distributions of instantaneous particle concentration and velocity vector (from left to right: SOM-edynamic, SOM, KTGF-edynamic, KTGF models)

图5 壁面和中心区域瞬时颗粒浓度和轴向速度分布

Fig.5 Instantaneous axial velocity and concentration of particles in the center and near the wall

图6 颗粒碰撞频率随浓度变化

Fig.6 Collision frequency of particles as a function of particle concentration

图7 颗粒碰撞能量耗散随浓度变化

Fig.7 Collision energy dissipation of particles as a function of particle concentration

图8 颗粒二阶矩沿径向分布

Fig.8 The radial distributions of the particle second-order moments

图9 液膜厚度与恢复系数随液体黏度的变化

Fig.9 Liquid film thickness and restitution coefficient as a function of liquid viscosity

图10 液体黏度对颗粒浓度与速度分布的影响

Fig.10 Effects of liquid viscosity on axial velocity and concentration of particles

图11 液体黏度对颗粒二阶矩的影响

Fig.11 Effects of liquid viscosity on particle second-order moments

图12 液体黏度对颗粒碰撞能量耗散的影响

Fig.12 Effects of liquid viscosity on collision energy dissipation of particles

图13 液膜厚度与恢复系数随颗粒密度的变化

Fig.13 Liquid film thickness and restitution coefficient as a function of particle density

图14 颗粒密度对颗粒浓度与速度分布的影响

Fig.14 Effects of particle density on axial velocity and concentration of particles

图15 颗粒密度对颗粒二阶矩的影响

Fig.15 Effects of particle density on particle second-order moments

图16 颗粒密度对颗粒碰撞能量耗散的影响

Fig.16 Effects of particle density on collision energy dissipation of particles

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