补充风对水平管高压密相气力输送影响的模拟研究

doi:10.11949/0438-1157.20191275

摘要/Abstract

摘要：

针对水平管高压密相气力输送数理模型的缺陷与不足，引入Savage径向分布函数修正的颗粒动理学理论、基于Berzi摩擦压应力模型构建的摩擦应力模型以及修正的三段式曳力模型，在欧拉-欧拉方法的基础上建立了一个能同时兼顾水平管高压密相气力输送中稀相流、过渡流以及密相流输送特性的三维非稳态数理模型。并采用该数理模型考察了补充风对水平管高压密相气力输送的影响，模拟结果精准地预测了水平管压降及其随补充风的变化规律，而且其预测的水平管固相体积浓度分布与ECT图也是相吻合的，从而验证了数理模型的可靠性。模拟结果表明：随着补充风的增加，气固两相速度和湍动能以及颗粒拟温度增大，固相体积浓度减小。

关键词: 气力输送, 两相流, 密相, 介尺度, 补充风, 数值模拟

Abstract:

In view of the defects and deficiencies of the existing mathematical model, a new three-dimensional (3D) unsteady mathematical model for dense-phase pneumatic conveying in horizontal pipe under high pressure was established based on the Euler-Euler model. This mathematical model introduced the modified kinetic theory of granular flows by Savage’s radial distribution function, the frictional stress model established on Berzi’s frictional pressure stress and the modified three-zone drag model to expound the conveying characteristics of all of three flow regimes: dilute regime, intermediate regime and dense regime. Meanwhile, this mathematical model was applied to explore the effects of supplementary gas on dense-phase pneumatic conveying in horizontal pipe under high pressure. The simulation results show that the pressure drop of horizontal pipe and its variation with the supplementary gas flow rates are predicted accurately, and the predicted solids volume fraction distribution at the cross section of horizontal pipe also basically agrees with the electrical capacitance tomography (ECT) diagram, which confirm the reliability and applicability of this mathematical model. The simulation results show that as the supplementary wind increases, the gas-solid two-phase velocity and turbulent kinetic energy and particle pseudo-temperature increase, and the solid phase volume concentration decreases.

Key words: pneumatic conveying, two-phase flow, dense-phase, mesoscale, supplementary gas, numerical simulation

中图分类号:

TQ 022

周海军, 熊源泉. 补充风对水平管高压密相气力输送影响的模拟研究[J]. 化工学报, 2020, 71(2): 602-613.

Haijun ZHOU, Yuanquan XIONG. Simulation study on influence of supplementary gas on dense-phase pneumatic conveying in horizontal pipe under high pressure[J]. CIESC Journal, 2020, 71(2): 602-613.

图/表 17

图1 高压密相气力输送试验装置1—高压气瓶；2—缓冲罐；3—流化风流量计；4—充压风流量计；5—补充风流量计；6—储料罐；7—输送管道；8—差压变送器；9—压力传感器；10—可视段；11—温度传感器；12—在线取样器；13—荷重传感器；14—电动调节阀；15—控制柜

Fig.1 Experimental facility schematic diagram of dense-phase pneumatic conveying under high pressure

表1 输送试验工况参数

Table 1 Conveying experiment parameters

No.	补充风流量，Q_s/(m³/h)	表观气速，U_g/(m/s)	固相质量流量，M_s/(kg/s)	进口固相体积浓度,α_s,in	进口固相平均速度,u_s,inlet/(m/s)	出口气相压力,P_out/MPa
1	0.40	4.71	0.213	0.318	4.43	2.91
2	0.60	5.62	0.206	0.286	5.30	2.91
3	0.80	6.43	0.194	0.245	6.09	2.92
4	1.00	7.24	0.181	0.199	6.79	2.93
5	1.20	8.10	0.168	0.184	7.72	2.93

表2 内蒙褐煤煤粉的主要物性参数

Table 2 Main physical properties of pulverized lignite

自然堆积固相体积浓度，α_s,b

全水分，

M_c

图2 水平管纵截面固相体积浓度分布

Fig.2 Solids volume fraction distribution at longitudinal section of horizontal pipe

表3 数理模型参数

Table 3 Mathematical model parameters

α_s,max	e_ss	?_i	e_sw	?	μ_w	a
0.60	0.8	32.0°	0.5	1.0×10^-5	0.5	1.8×10^-6

图3 水平管的网格划分

Fig.3 Meshes generation of horizontal pipe

表4 不同网格尺寸下模拟预测的水平管压降

Table 4 Predicted pressure drop of horizontal pipe with different grid scale

网格划分规格	端面格数	轴向网格尺寸/mm	总网格数/万	水平管模拟压降/kPa	水平管试验压降/kPa
Mesh A	180	2	21.60	3.84	4.14
Mesh B	288	1.5	46.08	3.91
Mesh C	420	1.25	80.64	4.07
Mesh D	576	1	138.24	4.08

图4 不同网格尺寸下模拟预测的气相速度沿高度方向的分布

Fig.4 Predicted gas velocities vs dimensionless height with different grid scale

图5 不同补充风下模拟预测的水平管压降与其试验值的对比

Fig.5 Comparison of predicted pressure drop of horizontal pipe with its experimental data at different supplementary gas flow rates

图6 水平管中不同横截面气固两相速度沿高度方向的分布

Fig.6 Velocities of gas and solids phase vs dimensionless height at different cross sections of horizontal pipe

图7 水平管横截面固相体积浓度分布云图

Fig.7 Solids volume fraction distribution at cross section of horizontal pipe

图8 内蒙褐煤煤粉颗粒粒径分布

Fig.8 Particle size distribution of pulverized lignite

图9 不同补充风下模拟预测的固相体积浓度分布云图与ECT图的对比

Fig.9 Comparison of predicted solids volume fraction distribution with ECT image at different supplementary gas flow rates

图10 不同补充风下模拟预测的水平高压密相气力输送特性参数沿高度方向的分布

Fig.10 Predicted conveying parameters of horizontal pipe vs dimensionless height at different supplementary gas flow rates

图11 不同补充风下模拟获得的曳力Fsg

Fig.11 Predicted drag forces at cross section of horizontal pipe at different supplementary gas flow rates

图12 不同补充风下模拟获得的固相摩擦切应力分布云图

Fig.12 Predicted solids frictional shear stress at cross section of horizontal pipe at different supplementary gas flow rates

图13 不同补充风下模拟获得的气固两相与壁面间的切应力分布云图

Fig.13 Predicted frictional shear stresses between gas, solids and wall at different supplementary gas flow rates

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