Numerical simulation of eddy effect in the mixing process of gas-liquid two-phase flow in stirred reactor

doi:10.16085/j.issn.1000-6613.2020-0490

Abstract

Abstract:

The straight blade and the propeller blade are taken as research objects to study the influence of the gas-liquid two-phase stirred tank blade on the flow structure and the gas-liquid mixing performance. The ICEM software was used to divide the flow field of the stirred tank with a hexahedral structure. Based on the SST-DDES turbulence model and the Euler-Euler multiphase flow model, the three-dimensional unsteady calculation of the flow field inside the stirred tank was conducted. The internal eddy structure and evolution process of the two stirred tanks were obtained, and the transient gas phase distribution and instantaneous flow field in the stirred tank were analyzed. The results showed that the eddy generated by the rotation of the blade goes through the evolution process of tearing, merging, attenuation, and dissipation. Compared with the propeller blade, the straight blade has a faster eddy dissipation speed, and its cycle from eddy generation to disappearance is shorter. Due to the differences in blade structure, the direction of motion of the main flow is different. The straight blade is distributed in the radial direction and the propeller blade is distributed along the axial direction. The former has an upper and a lower circulation zone in the tank, which is not conducive to gas phase diffusion. The latter has a large circulation zone in the tank, which accelerates the flow cycle in the tank, causing a higher gas-phase diffusion capacity than the former. A comparison shows that the T_0.95 of the propeller blade tank is smaller, approximately half that of the straight blade tank.

Key words: stirred vessel, propeller blade, gas-liquid flow, DDES, eddy structure, mixing time

摘要：

为研究气液两相搅拌釜桨叶对釜内流动结构及气液混合性能的影响，本文以直叶片和推进叶片为研究对象，采用ICEM软件对搅拌釜流场进行六面体结构网格划分，基于SST-DDES湍流模型及欧拉-欧拉多相流模型对搅拌釜内部流场进行三维非定常计算，获得两种桨叶下搅拌釜内部涡结构及其演化过程，并分析搅拌釜内瞬态气相分布和瞬时流场的分布规律。研究结果表明：由于叶片旋转而产生的涡有撕裂、合并、衰减和耗散的演化过程；直叶片相较于推进叶片，其涡耗散速度较快，涡产生到消失的周期较短；由于叶片结构不同，主流的运动方向也随之改变，直叶片沿径向分布，推进叶片沿轴向分布。前者在釜内形成上下两层循环区，不利于气相扩散。后者在釜内形成一个大循环区，加剧釜内流动循环，造成后者的气相扩散能力大于前者。比较两者T_0.95分布，推进叶片要小于直叶片，推进叶片搅拌釜T_0.95近似为直叶片搅拌釜T_0.95的50%。

关键词: 搅拌容器, 推进叶片, 气液两相流, 延迟分离涡模拟, 涡旋结构, 混合时间

CLC Number:

TQ051.7

Yibin LI, Kaiyi LIANG, Xiaohui DAI, Zhenggui LI. Numerical simulation of eddy effect in the mixing process of gas-liquid two-phase flow in stirred reactor[J]. Chemical Industry and Engineering Progress, 2021, 40(1): 99-110.

黎义斌, 梁开一, 歹晓晖, 李正贵. 搅拌反应器气液两相流混合过程的涡旋效应数值模拟[J]. 化工进展, 2021, 40(1): 99-110.

Figures/Tables 21

References 27

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断面	断面厚度/mm	断面叶宽/mm	断面与搅拌轴线夹角/(°)
S0	27.00	103.82	33.55
S1	24.75	127.95	42.33
S2	22.50	147.57	49.21
S3	20.25	162.34	54.59
S4	18.00	175.06	58.85
S5	15.75	183.56	62.27
S6	13.50	183.85	65.06
S7	11.25	174.95	67.36
S8	9.00	157.95	69.30
S9	6.75	120.76	70.94
S10	6.50	75.92	72.34

断面	断面厚度/mm	断面叶宽/mm	断面与搅拌轴线夹角/(°)
S0	27.00	103.82	33.55
S1	24.75	127.95	42.33
S2	22.50	147.57	49.21
S3	20.25	162.34	54.59
S4	18.00	175.06	58.85
S5	15.75	183.56	62.27
S6	13.50	183.85	65.06
S7	11.25	174.95	67.36
S8	9.00	157.95	69.30
S9	6.75	120.76	70.94
S10	6.50	75.92	72.34

网格类型	网格数量		y⁺
网格类型	直叶片	推进叶片	直叶片	推进叶片
粗网格	0.39×10⁶	0.40×10⁶	11.96	9.73
中等网格	1.16×10⁶	1.27×10⁶	11.82	8.77
细网格	1.75×10⁶	1.86×10⁶	9.94	8.36

网格类型	网格数量		y⁺
网格类型	直叶片	推进叶片	直叶片	推进叶片
粗网格	0.39×10⁶	0.40×10⁶	11.96	9.73
中等网格	1.16×10⁶	1.27×10⁶	11.82	8.77
细网格	1.75×10⁶	1.86×10⁶	9.94	8.36

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