T型微通道反应器内气液两相流动机制及影响因素
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摘要
基于液滴或气泡的多相微流控是近年来微流控技术中快速发展的重要分支之一.本文利用高速显微摄影技术和数字图像处理技术对T型微通道反应器内气液两相流动机制及影响因素进行实验研究.实验采用添加表面活性剂的海藻酸钠水溶液作为液相,空气作为气相.研究T型微通道反应器内气液两相流型的转变过程,并根据微通道内气泡的生成频率和生成气泡的长径比对气泡流进行分类.研究发现当前的进料方式下,可以观测到气泡流和分层流2种流型,且依据气泡生成频率和微通道内气泡的长径比可将气泡流划分为分散气泡流、短弹状气泡流和长弹状气泡流3种类型,并基于受力分析确定3种气泡流的形成机制分别为剪切机制、剪切–挤压机制和挤压机制.考察不同液相黏度和表面张力系数对不同类型气泡流范围的影响规律.结果表明:液相黏度相较于表面张力系数而言,对气泡流生成范围影响更大.给出不同类型气泡流流型转变条件的无量纲关系式,实现微通道生成微气泡过程的可控操作.
Multiphase microfluidics based on droplets or bubbles is one of the important branches in the microfluidic technology with rapid development in recent years. In this study, an experimental study of gas-liquid two-phase flow regimes and impact factors was conducted in a T-junction microchannel based on high-speed microscope photography and digital image processing technology. Surfactant-added sodium alginate aqueous solutions were selected as the liquid phase, and air was the gas phase. The transition process of the gas-liquid two-phase flow in the T-junction microchannel was studied, and then the bubble flow was classified according to the frequency of bubble generation and the aspect ratio of the generated gas slug in the microchannel. Under the current feeding mode, bubble flow and stratified flow were observed, and the bubble flow could be divided into dispersed bubble flow, short-slug bubble flow and long-slug bubble flow according to the frequency of bubble generation and the aspect ratio of the generated gas slug. Based on the force analysis, the formation mechanisms of the three types of bubble flow were observed as shearing, shearingto-squeezing and squeezing. The effects of liquid viscosity and surface tension coefficient on the operating range of different types of bubble flows were investigated. It is indicated that liquid viscosity has a greater influence on the operating ranges of bubble flow than that of the surface tension coefficient. The dimensionless correlations of the bubble flow regime transition boundaries were proposed to achieve the controllable operation of the microbubble generation process.
Multiphase microfluidics based on droplets or bubbles is one of the important branches in the microfluidic technology with rapid development in recent years. In this study, an experimental study of gas-liquid two-phase flow regimes and impact factors was conducted in a T-junction microchannel based on high-speed microscope photography and digital image processing technology. Surfactant-added sodium alginate aqueous solutions were selected as the liquid phase, and air was the gas phase. The transition process of the gas-liquid two-phase flow in the T-junction microchannel was studied, and then the bubble flow was classified according to the frequency of bubble generation and the aspect ratio of the generated gas slug in the microchannel. Under the current feeding mode, bubble flow and stratified flow were observed, and the bubble flow could be divided into dispersed bubble flow, short-slug bubble flow and long-slug bubble flow according to the frequency of bubble generation and the aspect ratio of the generated gas slug. Based on the force analysis, the formation mechanisms of the three types of bubble flow were observed as shearing, shearingto-squeezing and squeezing. The effects of liquid viscosity and surface tension coefficient on the operating range of different types of bubble flows were investigated. It is indicated that liquid viscosity has a greater influence on the operating ranges of bubble flow than that of the surface tension coefficient. The dimensionless correlations of the bubble flow regime transition boundaries were proposed to achieve the controllable operation of the microbubble generation process.
引文
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25 Burns JR,Ramshaw C.The intensification of rapid reactions in multiphase systems using slug flow in capillaries.Lab Chip,2001,1:10-15
26 Zhao Y,Chen G,Yuan Q.Liquid-liquid two-phase flow patterns in a rectangular microchannel.A.I.Ch.E.Journal,2006,52:4052-4060
27 De Menech M,Garstecki P,Jousse F,et al.Transition from squeezing to dripping in a microfluidic T-shaped junction.Journal of Fluid Mechanics,2008,595:141-161
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29 Fu T,Ma YG,Funfschilling D,et al.Squeezing-to-dripping transition for bubble formation in a microfluidic T-junction.Chemical Engineering Science,2010,65:3739-3748
30 Fu T,Ma YG.Bubble formation and breakup dynamics in a microfluidic device:A review.Chemical Engineering Science,2015,135:343-372
31 Rodriguez-Rodriguez J,Sevilla A,Mart′?nez-Baz′an C,et al.Generation of microbubbles with applications to industry and medicine.Annual Review of Fluid Mechanics,2015,47(1):405-429
2 Rong N,Zhou H,Liu R,et al.Ultrasound and microbubble mediated plasmid DNA uptake:A fast,global and multi-mechanisms involved process.Journal of Controlled Release,2018,273:40-50
3王兆伟,武晓刚,陈魁俊等.一种力-电协同驱动的细胞微流控培养腔理论模型.力学学报,2018,50(1):124-137(Wang Zhaowei,Wu Xiaogang,Chen Kuijun,et al.A theoretical microfluidic flow model for the cell culture chamber under the pressure gradient and electric field driven loads.Chinese Journal of Theoretical and Applied Mechanics,2018,50(1):124-137(in Chinese))
4 Jahnisch K,Hessel V,Lowe H,et al.Chemistry in microstructured reactors.Angewandte Chemie International Edition,2004,43:406-446
5 Goran TV,Ekanem EE,Zilin Z,et al.Long-term stability of droplet production by microchannel(step)emulsification in microfuidic silicon chips with large number of terraced microchannels.Chemical Engineering Journal,2018,333:380-391
6 Evangelio A,Campo-Cortes F,Gordillo JM.Pressure gradient induced generation of microbubbles.Fluid Mechanics,2015,778(1):653-668
7刘赵淼,杨洋.几何构型对流动聚焦生成微液滴的影响.力学学报,2016,48(4):867-876(Liu Zhaomiao,Yang Yang.Influence of geometric configuration on the formation of microdroplets by flowfocusing device.Chinese Journal of Theoretical and Applied Mechanics,2016,48(4):867-876(in Chinese))
8 Dhanaliwala AH,Chen JL,Wang S,et al.Liquid flooded flowfocusing microfluidic device for in situ generation of monodisperse microbubbles.Microfluidics and Nanofluidics,2013,14(3-4):457-467
9 Li YK,Wang K,Xu JH,et al.A capillary-assembled micro-device for monodispersed small bubble and droplet generation.Chemical Engineering Journal,2016,293:182-188
10 Parhizkar M,Strideab E,Edirisinghe M.The effect of surfactant type and concentration on the size and stability of microbubbles produced in a capillary embedded T-junction device.Lab Chip,2014,14(14):2437-2446
11 Wang K,Xie L,Lu Y,et al.Generating microbubbles in a coflowing microfluidic device.Chemical Engineering Science,2013,100:486-495
12 Parhizkar M,Edirisinghe M,Stride E.Effect of operating conditions and liquid physical properties on the size of monodisperse microbubbles produced in a capillary embedded T-junction device.Microfluidics and Nanofluidics,2013,14(5):797-808
13 Yue J,Luo L,Gonthier Y,et al.An experimental investigation of gas-liquid two-phase flow in single microchannel contactors.Chemical Engineering Science,2008,63(16):4189-4202
14 Gupta R,Fletcher D,Haynes BS,et al.Taylor flow in microchannels:A review of experimental and computational work.Journal of Computational Multiphase Flows,2010,2(1):1-31
15 Waelchli S,Rudolf Von Rohr P.Two-phase flow characteristics in gas-liquid microreactors.International Journal of Multiphase Flow,2006,32(7):791-806
16刘赵淼,刘丽昆,申峰.Y型微通道两相流内部流动特性.力学学报,2014,46(2):209-216(Liu Zhaomiao,Liu Likun,Shen Feng.Two-phase flow characteristics in Y-junction microchannel.Chinese Journal of Theoretical and Applied Mechanics,2014,46(2):209-216(in Chinese))
17 Fu T,Ma Y,Funfschilling D,et al.Bubble formation in nonNewtonian fluids in a microfluidic T-junction.Chemical Engineering and Processing:Process Intensification,2011,50(4):438-442
18陈晓东,胡国庆.微流控器件中的多相流动.力学进展,2015,45(1):55-110(Chen Xiaodong,Hu Guoqing.Multiphase flow in microfluidic devices.Advances in Mechanics,2015,45(1):55-110(in Chinese))
19 Damianides CA,Westwater JW.Two-phase flow patterns in a compact heat exchanger and in small tubes.Proceedings of the Second UK National Conference on Heat Transfer,1988,11:1257-1268
20 Galbiati L,Andreini P.Flow pattern transition for horizontal airwater flow in capillary tubes.A microgravity“equivalent system”simulation.Heat Mass Transfer,1994,21(4):461-468
21 Fourar M,Bories S.Experimental study of air-water two-phase flow through a fracture(narrow channel).International Journal of Multiphase Flow,1995,21(4):621-637
22 Mandhane JM,Gregory GA,Aziz K.A flow pattern map for gasliquid flow in horizontal pipes.International Journal of Multiphase Flow,1974,1(4):537-553
23 Ahmed B,Barrow D,Wirth T.Enhancement of reaction rates by segmented fluid flow in capillary scale reactors.Advanced Synthesis and Catalysis,2006,348:1043-1048
24 Burns JR,Ramshaw C.Development of a microreactor for chemical production.Transactions of the Institution of Chemical Engineers,1999,77:206-211
25 Burns JR,Ramshaw C.The intensification of rapid reactions in multiphase systems using slug flow in capillaries.Lab Chip,2001,1:10-15
26 Zhao Y,Chen G,Yuan Q.Liquid-liquid two-phase flow patterns in a rectangular microchannel.A.I.Ch.E.Journal,2006,52:4052-4060
27 De Menech M,Garstecki P,Jousse F,et al.Transition from squeezing to dripping in a microfluidic T-shaped junction.Journal of Fluid Mechanics,2008,595:141-161
28 Xu JH,Li SW,Tan J,et al.Correlation of droplet formation in T-junction microfluidic devices:From squeezing to dripping.Microfluidics and Nanofluidics,2008,5:711-717
29 Fu T,Ma YG,Funfschilling D,et al.Squeezing-to-dripping transition for bubble formation in a microfluidic T-junction.Chemical Engineering Science,2010,65:3739-3748
30 Fu T,Ma YG.Bubble formation and breakup dynamics in a microfluidic device:A review.Chemical Engineering Science,2015,135:343-372
31 Rodriguez-Rodriguez J,Sevilla A,Mart′?nez-Baz′an C,et al.Generation of microbubbles with applications to industry and medicine.Annual Review of Fluid Mechanics,2015,47(1):405-429