Bubble breakup mechanism in Venturi-type bubble generator

doi:10.11949/j.issn.0438-1157.20171279

Abstract

Abstract:

As efficient and safe equipment, Venturi-type bubble generators have wide application in general and chemical industry. There are few researches about process and mechanism of bubble breakup inside generators. Previous studies showed that large bubbles were rapidly decelerated after entered diverging section of a Venturi-type bubble generator, which was probably critical to bubble breakup process. In this paper, large-eddy simulation on flow in a Venturi-type bubble generator showed existence of an obvious vortex region near wall of the diverging section. A strong collision between front of the vortex region and fluid from upstream fast decelerated fluid upon entering the region and significantly increased static pressure near confluence of vortex region and mainstream. When a bubble was moving through the region, it would be greatly decelerated by a surge in pressure gradient force and mass-added force, which intensified interaction with ambient fluid. Under a high liquid velocity condition, the bubble could be severely deformed and even broken..

Key words: Venturi-type bubble generator, deceleration process, numerical analysis, vortex field, static pressure

摘要：

作为一种高效、安全的气泡发生装置，文丘里式气泡发生器在工业、化工等过程有广泛的应用，但对其内部气泡破碎过程和作用机制相关研究较少。前期研究发现，较大气泡进入文丘里管扩张段后会发生迅速减速，并对气泡碎化过程产生极大影响。基于大涡模拟方法，对文丘里式气泡发生器内的流动过程进行了数值模拟，发现在扩张段近壁面存在明显的涡流区，涡流区前端与上游来流发生强烈的碰撞，造成进入此区域的流体发生迅速减速，使得涡流区与主流交汇区附近静压急速增大；当此区域存在运动的气泡时，激增的压力梯度力以及附加质量力导致气泡运动速度迅速减小，并与周边流体形成了更强的相互作用；高流速条件下，会使气泡发生严重变形、甚至破碎。

关键词: 文丘里式气泡发生器, 减速过程, 数值分析, 涡流场, 静压

CLC Number:

TQ021.1

SHAO Ziyi, ZHANG Haiyan, SUN Licheng, MO Zhengyu, DU Min. Bubble breakup mechanism in Venturi-type bubble generator[J]. CIESC Journal, 2018, 69(6): 2439-2445.

邵梓一, 张海燕, 孙立成, 莫政宇, 杜敏. 文丘里式气泡发生器内气泡破碎机制分析[J]. 化工学报, 2018, 69(6): 2439-2445.

References 30

[1]	ROBERTSON. MSRE design and operation report I[R]. Atomic Energy Commission, 1965:205-243.
[2]	徐志强, 皇甫京华, 曾鸣, 等. 射流浮选柱气泡发生器及其充气性能的研究[J]. 中国矿业大学学报, 2003, 32(6):19-23. XU Z Q, HUANGFU J H, ZENG M, et al. Research on bubble generator of jet flotation column and its aerating performance[J]. Journal of China University of Mining & Technology, 2003, 32(6):19-23.
[3]	QUIROZ-PÉREZ E, VÁZQUEZ-ROMÁN R, LESSO-ARROYO R, et al. An approach to evaluate Venturi-device effects on gas wells production[J]. Journal of Petroleum Science and Engineering, 2014, 116:8-18.
[4]	邓超, 杨丽, 陈海军, 等. 微纳米气泡发生装置及其应用的研究进展[J]. 石油化工, 2014, 43(10):1206-1213. DENG C, YANG L, CHEN H J, et al. Progresses in research and application of micro-nano bubble generating device[J]. Petrochemical Technology, 2014, 43(10):1206-1213.
[5]	莫政宇, 杜敏, 邵梓一, 等. 文丘里式气泡发生器内气泡输运过程研究[J]. 原子能科学技术, 2016, 50(6):1034-1039. MO Z Y, DU M, SHAO Z Y, et al. Investigation of bubble transportation in Venturi-type bubble generator[J]. Atomic Energy Science and Technology, 2016, 50(6):1034-1039.
[6]	SOUBIRAN J, SHERWOOD J D. Bubble motion in a potential flow within a Venturi[J]. International Journal of Multiphase Flow, 2000, 26(11):1771-1796.
[7]	严润刚, 潘良明, 何辉, 等. 多微通道内两相流动阻力特性及气泡行为[J]. 化工学报, 2017, 68(S1):66-70. YAN R G, PAN L M, HE H, et al. Characteristics of two-phase flow resistance and bubble behavior in microchannels[J]. CIESC Journal, 2017, 68(S1):66-70.
[8]	FUJIWARA A, TAKAGI S, MATSUMOTO Y. Bubble breakup phenomena in a Venturi tube[C]//ASME/JSME 2007 Fluids Engineering Division Summer Meeting. San Diego, USA, 2007:FEDSM2007-37243.
[9]	RZEHAK R, KREPPER E. Closure models for turbulent bubbly flows:a CFD study[J]. Nuclear Engineering and Design, 2013, 265:701-711.
[10]	GASTON M J, REIZES J A, EVANS G M. Modelling of bubble dynamics in a Venturi flow with a potential flow method[J]. Chemical Engineering Science, 2001, 56:6427-6435.
[11]	顾汉洋, 郭烈锦. 垂直圆管内湍流泡状流的数值研究[J]. 化工学报, 2004, 55(4):563-568. GU H Y, GUO L J. Numerical simulation of turbulent bubble flow in vertical pipe[J]. Journal of Chemical Industry and Engineering(China), 2004, 55(4):563-568.
[12]	周吉, 朱恂, 丁玉栋, 等. 液体通流微小槽道内气泡动力学行为模拟[J]. 化工学报, 2011, 62(10):2740-2746. ZHOU J, ZHU X, DING Y D, et al. Numerical simulation of gas bubble emerging from pore into liquid flow micro-channel[J]. CIESC Journal, 2011, 62(10):2740-2746.
[13]	RODIO M G, CONGEDO P M. Robust analysis of cavitating flows in the Venturi tube[J]. European Journal of Mechanics, B/Fluids, 2014, 44:88-99.
[14]	王玲玲. 大涡模拟理论及其应用综述[J]. 河海大学学报(自然科学版), 2004, 32(3):261-265. WANG L L. Large eddy simulation theory and its application[J]. Journal of Hohai University (Natural Sciences), 2004, 32(3):261-265.
[15]	周力行. 离散型两相流动的大涡模拟[J]. 中国科学:技术科学, 2014, 44:162-171. ZHOU L X. Large-eddy simulation of dispersed two-phase flows[J]. Sci. Sin. Tech., 2014, 44:162-171.
[16]	张鹏. 竖直圆管内气泡运动的大涡模拟研究[J]. 原子能科学技术, 2012, 46:225-230. ZHANG P. Large eddy simulation of bubbly flow in vertical tube[J]. Atomic Energy Science and Technology, 2012, 46:225-230.
[17]	DHOTRE M T, NICENO B, SMITH B L. Large eddy simulation of a bubble column using dynamic sub-grid scale model[J]. Chemical Engineering Journal, 2008, 136(2):337-348.
[18]	LUCAS D, KREPPER E, PRASSER H M. Development of co-current air-water flow in a vertical pipe[J]. International Journal of Multiphase Flow, 2005, 31(12):1304-1328.
[19]	LUCAS D, KREPPER E, PRASSER H M. Use of models for lift, wall and turbulent dispersion forces acting on bubbles for poly-disperse flows[J]. Chemical Engineering Science, 2007, 62(15):4146-4157.
[20]	LUCAS D, KREPPER E, RZEHAK R, et al. CFD models for poly dispersed bubbly flows[J]. International Journal of Multiphase Flow, 2007, 29:1148-1159.
[21]	ISHⅡ M, ZUBER N. Drag coefficient and relative velocity in bubbly, droplet or particulate flows[J]. AIChE Journal, 1979, 25(5):843-855.
[22]	BASSET A B. A Treatise on Hydrodynamics[M]. Cambridge:Dover Publications Inc., 1888.
[23]	BOUSSINESQ J. On a simple mode of flow of infiltration water tables with a horizontal stream bed, with a vertical ledge all around, when a part of this ledge is taken away from the surface to the bottom[J]. Comptes Rendus Hebdomadaires Des Séances De Lacademie Des Scienses, 1903, 137(2):5-11.
[24]	MEI R. Velocity fidelity of flow tracer particles[J]. Experiments in Fluids, 1996, 22(1):1-13.
[25]	ANTON D. On the role of the history force for inertial particles in turbulence[J]. Journal of Fluid Mechanics, 2015, 782:567-593.
[26]	BIESHEUVEL A, SPOELSTRA S. The added mass coefficient of a dispersion of spherical gas bubbles in liquid[J]. International Journal of Multiphase Flow, 1989, 15(6):911-924.
[27]	潘良明, 张文志, 陈德奇, 等. 附加惯性力对气泡破裂的影响[J]. 核动力工程, 2011, 32(4):37-41. PAN L M, ZHANG W Z, CHEN D Q, et al. Effects of additional inertia force on bubble breakup[J]. Nuclear Power Engineering, 2011, 32(4):37-41.
[28]	CAI X L, WALLIS G B. Potential flow around a row of spheres in a circular tube[J]. Physics of Fluids A-Fluid Dynamics, 1992, 4(5):904-912.
[29]	CLIMENT E. Simulation d'ecoulements induits par des bulles dans un liquide initialement aurepos[J]. C. R. Acad. Sci., 1997, 324:91-98.
[30]	HUNT F. Review of the problems of modeling disperse two-phase flows[J]. Multiphase Science and Technology, 1997, 8:595-643.