湍流对双组分颗粒流化床气体径向扩散的影响

doi:10.11949/0438-1157.20241497

摘要/Abstract

摘要：

针对模拟研究双组分流化床内气体扩散过程中出现的计算偏差，提出通过优化标准k-ε湍流模型常数提高计算精度，从而消除计算偏差。研究结果表明：采用Launder湍流模型常数时，计算获得流化床内流场湍流强度偏大，导致模拟结果与实验数据相差较大；通过调整湍流模型常数可以明显提高计算精度，模拟结果与实验数据更为一致。在气速较低时，湍流对气体径向扩散影响不大；但在气速较高时，采用新模型常数模拟结果与实验数据的吻合度明显提高。随着重组分颗粒的增加，流化床中心区示踪气体浓度呈现先降低后升高的变化趋势。第二组分颗粒的添加对流化床内湍流强度影响较为复杂。

关键词: 流化床, 湍流模型常数, 气体扩散, 两相流, 计算流体力学

Abstract:

In this work, the constants of the standard k-ε turbulence model were optimized to reduce numerical diffusion during simulations of gas diffusion in a binary fluidized bed. The research results show that when the Launder turbulence model constants are used, the turbulence intensity of the flow field in the fluidized bed is too large, resulting in a large difference between the simulation results and the experimental data. By adjusting the turbulence model constants, the calculation accuracy can be significantly improved, and the simulation results are more consistent with the experimental data. When the gas velocity is low, turbulence has little effect on the radial diffusion of gas. But when the gas velocity is high, the consistency between the simulation results and the experimental data using the new model constants is significantly improved. As the concentration of heavy particles in the fluidized bed increased, the tracer concentration in the central region initially decreased, and then increased. The introduction of the second component affected the turbulence intensity in the fluidized bed in a more complex manner.

Key words: fluidized bed, turbulent model constants, gas diffusion, two phase flow, CFD

中图分类号:

TQ 021.1

张亿韵, 陈恒志, 李洋, 慕长安, 王泉海. 湍流对双组分颗粒流化床气体径向扩散的影响[J]. 化工学报, 2025, 76(6): 2559-2568.

Yiyun ZHANG, Hengzhi CHEN, Yang LI, Chang'an MU, Quanhai WANG. Effects of turbulence on radial gas diffusion in binary particle fluidized bed[J]. CIESC Journal, 2025, 76(6): 2559-2568.

图/表 15

图1 实验装置示意图

Fig.1 Schematic diagram of experimental setup

表1 实验所用颗粒物性参数

Table 1 Physical properties of particles used in this work

硅胶

玻璃珠

750

2500

425~880

652

0.22

0.41

表2 鼓泡流化床模拟参数

Table 2 Modeling parameters in bubbling fluidized bed

Flow field	Unsteady
Pressure-velocity coupling	Phase Couple SIMPLE
Discretization	Second-order upwind
Solid pressure	Lun et al
Radial distribution	Lun et al
Granular temperature	Algebraic
Granular viscosity	Gidaspow
Granular bulk visosity	Lun et al
Frictional viscosity	Schaeffer
Frictional pressure	Based-KTGF
Angle of internal friction	30.0°
Time step size	5×10^-4 s
Mesh size	2 mm×5 mm

图2 Cμ 对流化床内湍流强度的影响(C1=1.64,C2=1.62)

Fig.2 Effect of Cμ on turbulence intensity in fluidized bed

表3 标准k-ε湍流模型常数

Table 3 Constants of standard k-ε turbulence model

Case	C_μ	C₁	C₂
1	0.03	1.84	1.42
2	0.05	1.64	1.62
3	0.09	1.44	1.92
4	0.12	1.2	2.2

图3 比较4组模型参数计算获得的流化床内湍流强度(Ug= 0.66 m/s, XJ= 37.5%)

Fig.3 Comparison of turbulence intensity in fluidized bed predicted with four groups of model constants

图4 不同模型参数计算的示踪气体浓度与实验数据的比较

Fig.4 Comparison of tracer gas concentration calculated by different model constants with experimental data (Ug= 0.995 m/s, XJ= 37.5%)

图5 不同模型参数计算得到的气体横向速度

Fig.5 Comparison of lateral gas velocity calculated with different model constants(Ug= 0.995 m/s, XJ= 37.5%)

图6 CO2摩尔分数分布云图

Fig.6 Contour of distribution of molar ratio of CO2(Ug= 0.66 m/s, XJ= 37.5%)

图7 流化床内湍流强度云图

Fig.7 Contour of the distribution of turbulence intensity(Ug= 0.66 m/s, XJ= 37.5%) in fluidized bed

图8 不同气速下由不同模型计算的示踪气体浓度与实验数据的比较

Fig.8 Comparison of tracer gas concentration calculated by different model constants with experimental data at various gas velocities(XJ= 37.5%, H= 0.15 m)

图9 气速对气体径向扩散的影响

Fig.9 Effect of gas velocity on radial gas diffusion(XJ= 37.5%)

图10 不同颗粒组成下示踪气体浓度计算值与实验数据的比较

Fig.10 Comparison of predicted tracer concentration with experimental data at different particle composition(Ug= 0.995 m/s, H=0.15 m)

图11 重组分含量对气体径向扩散的影响

Fig.11 Effect of ratio of heavy component on radial gas diffusion(Ug= 0.995 m/s)

图12 重组分含量对湍流强度的影响

Fig.12 Effect of ratio of heavy component on turbulence intensity(Ug= 0.995 m/s)

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