Characteristics analysis of gas solid two-phase flow in pneumatic conveying based on CFD-DEM algorithm

doi:10.16085/j.issn.1000-6613.2023-0353

Abstract

Abstract:

Because of its light weight, ultra-light powder particles are easily disturbed by airflow in the process of transportation, and the pipeline pneumatic conveying process of material is unstable and prone to blockage. To study the gas-solid two-phase flow characteristics of ultra-light powder particles in cyclone pneumatic conveying, computational fluid dynamics and discrete element method (CFD-DEM) were used to simulate the gas-solid two-phase flow characteristics in Komax static mixer. It was found that the horizontal pipe with Komax elements can change the particles flow state, and improve the accumulation and uneven distribution of particles. From the analysis of the flow state of particle phase and fluid phase, it was concluded that the element aspect ratio A_r=3 was the preferred geometry structure. Through the range analysis of orthogonal experiments, the order of factors affecting gas-solid two-phase flow characteristics was obtained as follows: conveying gas velocity > particle mass flow rate > particle size. When the element aspect ratio A_r was 3, the collision frequency and strength of particle-particle and particle-wall were negatively correlated. Combining with the dispersion state of the particle flow at the outlet, the optimal conveying gas velocity was 3—4m/s. Considering the influence of conveying gas velocity on pressure drop in the pipeline, the empirical fitting formula of pressure drop, conveying gas velocity and axial position during pneumatic transportation of horizontal pipeline with Komax element was proposed.

Key words: static mixer, multiphase flow, dilute phase swirl pneumatic conveying, granular flow, CFD-DEM coupling method, flow characteristic

摘要：

超轻粉体颗粒由于质量较小，在运输过程中易受气流扰动而飘散，物料的管道气力输送过程不稳定，易发生堵塞。为了研究超轻粉体颗粒在旋流气力输送中气固两相流流动特性，采用计算流体力学与离散单元法（CFD-DEM），对Komax型静态混合器内气固两相流动特性进行数值模拟研究。研究发现，带有Komax型元件的水平管道可以改变颗粒的流动情况，改善了水平管道内颗粒堆积和分布不均匀的现象；分别从颗粒相和流体相的流动状态分析得到元件长径比A_r=3时为最优几何结构；通过正交实验极差分析得到影响气固两相流动特性的因素顺序: 输送气速>颗粒质量流量>颗粒粒径。当元件A_r=3时，颗粒-颗粒和颗粒-管壁的碰撞次数与碰撞强度呈现负相关，结合出口颗粒流分散状态，优选输送气速为3~4m/s；主要考虑输送气速对管内压降的影响，提出了带有Komax型元件的水平管道气力运输过程中压降与输送气速和轴向位置的经验拟合式。

关键词: 静态混合器, 多相流, 稀相旋流气力输送, 颗粒流, CFD-DEM耦合法, 流动特性

CLC Number:

TQ051.2

YU Yanfang, SHI Bowen, MENG Huibo, DING Pengcheng, YAO Yunjuan. Characteristics analysis of gas solid two-phase flow in pneumatic conveying based on CFD-DEM algorithm[J]. Chemical Industry and Engineering Progress, 2024, 43(3): 1133-1144.

禹言芳, 石博文, 孟辉波, 丁鹏程, 姚云娟. 基于CFD-DEM算法的气力输送气固两相流特性分析[J]. 化工进展, 2024, 43(3): 1133-1144.

Figures/Tables 20

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状态	参数	数值
固相	颗粒质量流量/g·s^-1	2.85
	颗粒密度/kg·m^-3	40
	颗粒直径/μm	300
	泊松比	0.206
	剪切模量/Pa	1×10⁷
	颗粒-颗粒恢复系数	0.037
	颗粒-颗粒静摩擦系数	2
	颗粒-颗粒滚动摩擦系数	0.2
	颗粒-有机玻璃恢复系数	0.047
	颗粒-有机玻璃静摩擦系数	0.894
	颗粒-有机玻璃滚动摩擦系数	0.2
	颗粒相时间步长/s	2×10^-7
	颗粒入口速度/m·s^-1	0
气相	气体密度/kg·m^-3	1.225
	气体黏度/kg·(m·s)^-1	1.7894×10^-5
	气体时间步长/s	2×10^-5

状态	参数	数值
固相	颗粒质量流量/g·s^-1	2.85
	颗粒密度/kg·m^-3	40
	颗粒直径/μm	300
	泊松比	0.206
	剪切模量/Pa	1×10⁷
	颗粒-颗粒恢复系数	0.037
	颗粒-颗粒静摩擦系数	2
	颗粒-颗粒滚动摩擦系数	0.2
	颗粒-有机玻璃恢复系数	0.047
	颗粒-有机玻璃静摩擦系数	0.894
	颗粒-有机玻璃滚动摩擦系数	0.2
	颗粒相时间步长/s	2×10^-7
	颗粒入口速度/m·s^-1	0
气相	气体密度/kg·m^-3	1.225
	气体黏度/kg·(m·s)^-1	1.7894×10^-5
	气体时间步长/s	2×10^-5

平均网格尺寸/mm	网格数量/万	压降/Pa	误差/%
1.75	5.2	15552.030	—
2.00	4.6	15651.335	0.06
2.25	3.9	15700.564	0.37
2.50	3.3	15709.938	1.01

平均网格尺寸/mm	网格数量/万	压降/Pa	误差/%
1.75	5.2	15552.030	—
2.00	4.6	15651.335	0.06
2.25	3.9	15700.564	0.37
2.50	3.3	15709.938	1.01

序号	输送气速/m·s^-1	颗粒质量流量/g·s^-1	颗粒直径/μm	压降/Pa
1	3	0.85	300	49.954
2	3	1.85	400	49.967
3	3	2.85	500	49.975
4	4	1.85	300	87.325
5	4	2.85	400	87.353
6	4	0.85	500	87.299
7	5	2.85	300	134.997
8	5	0.85	400	134.939
9	5	1.85	500	134.951
R'	84.997	0.045	0.017	—