Subsequent development of collided droplets in impinging streams

doi:10.11949/j.issn.0438-1157.20171225

Abstract

Abstract:

In order to study subsequent development of collided droplets in impinging streams, a high-speed digital camera system, consisting of laser point source and high-speed digital camera, and a gas-liquid two-phase experimental platform was designed. The high-speed digital camera system was used to record droplet coalescence or secondary atomization caused by collisions in coaxially opposite gas-liquid two-phase impinging streams. Images of droplet movement were processed to analyze influence of droplet size, velocity, viscosity, and impact angle on collision outcomes. The results showed that droplets would be busted upon collision with unlimited increase in size and velocity. As surface tension was increased but viscosity and Ohnesorge number were decreased, inlet droplets were more inclined to break. Under experimental conditions, droplets upon collision were coalesced when moved coaxially in the same direction, were stretchily separated when moved in a certain angle, and were reflexively separated or busted moved coaxially in the opposite direction.

Key words: gas-liquid flow, impinging streams, multiphase flow, coalescence, droplet collision

摘要：

为了探索撞击流内液滴碰撞后续发展行为，设计搭建了由激光点光源和高速数码摄像机构成的高速数码摄像系统及气液两相撞击流实验平台。利用高速数码摄像系统记录下同轴对置气液两相撞击流中液滴碰撞导致的融合聚结或二次雾化过程，通过处理记录下的液滴运动过程图像，分析了进口液滴粒径、速度、黏度以及液滴碰撞角度等对撞击流中液滴碰撞结果的影响规律。结果表明：随着进口液滴粒径和速度的无限增大，液滴碰撞后最终发生炸裂；进口液滴黏度越小、表面张力越大、Ohnesorge数越小，液滴碰撞后越容易破碎；在本实验条件下，液滴同轴同向运动发生碰撞时，液滴碰撞后全部聚结，当液滴以一定角度发生斜碰时，碰撞后发生拉伸断裂，而当液滴同轴相向运动发生碰撞时，液滴碰撞后可能发生反射分离也可能炸裂。

关键词: 气液两相流, 撞击流, 多相流, 聚结, 液滴碰撞

CLC Number:

TK121

DU Min, HUANG Bin, LU Qicheng, GONG Jun, LUO Ming, WANG Zhuliang. Subsequent development of collided droplets in impinging streams[J]. CIESC Journal, 2018, 69(5): 2023-2031.

杜敏, 黄彬, 卢麒丞, 龚俊, 罗明, 王助良. 撞击流内液滴碰撞后续发展行为[J]. 化工学报, 2018, 69(5): 2023-2031.

References 31

[1]	WHELPDALE D M, LIST R. The coalescence process in raindrop growth[J]. Journal of Geophysical Research Atmospheres, 1971, 76(12):2836-2856.
[2]	BRADLEY S G, STOW C D. On the production of satellite droplets during collisions between water drops failing in still air[J]. Journal of the Atmospheric Sciences, 1979, 36(3):494-500.
[3]	HOUBEN R J. Equipment for printing of high viscosity liquids and molten metals[D]:Enschede:Universiteit Twente, 2012.
[4]	魏明锐, 沃傲波, 文华. 燃油喷雾初始破碎及二次雾化机理的研究[J]. 内燃机学报, 2009, 27(2):128-133. WEI M R, WO A B, WEN H. Investigation of the initial breakup and secondary atomization mechanism of fuel spray[J]. Transaction of CSICE, 2009, 27(2):128-133.
[5]	陈圆圆, 徐进良, 李季巍. 液滴碰撞亲-疏水性组合壁面的数值分析[J]. 化工学报, 2016, 67(12):5006-5014. CHEN Y Y, XU J L, LI J W. Numerical simulation of droplet impact on hybrid surfaces with different wettabilities[J]. CIESC Journal, 2016, 67(12):5006-5014.
[6]	YARIN A L. Drop impact dynamics:splashing, spreading, receding, bouncing[J]. Annual Review of Fluid Mechanics, 2006, 38(1):159-192.
[7]	JUNG J, JEONG S, KIM H. Investigation of single-droplet/wall collision heat transfer characteristics using infrared thermometry[J]. International Journal of Heat & Mass Transfer, 2016, 92:774-783.
[8]	郑志伟, 李大树, 仇性启, 等. 液滴碰撞球形凹曲面复合level set-VOF法的数值分析[J]. 化工学报, 2015, 66(5):1667-1675. ZHENG Z W, LI D S, QIU X Q, et al. Numerical analysis of coupled level set-VOF method on droplet impact on spherical concave surface[J]. CIESC Journal, 2015, 66(5):1667-1675.
[9]	QIAN K C. Regimes of coalescence and separation in droplet collision[J]. Journal of Fluid Mechanics, 1997, 331(1):59-80.
[10]	HU C, XIA C, LI C, et al. Three-dimensional numerical investigation and modeling of binary alumina droplet collisions[J]. International Journal of Heat and Mass Transfer, 2017, 113:569-588.
[11]	TANGUY S, BERLEMONT A. Application of a level set method for simulation of droplet collisions[J]. International Journal of Multiphase Flow, 2005, 31(9):1015-1035.
[12]	MASHAYEK F, ASHGRIZ N, MINKOWYCZ W J, et al. Coalescence collision of liquid drops[J]. International Journal of Heat and Mass Transfer, 2003, 46(1):77-89.
[13]	MERDASI A, EBRAHIMI S, MOOSAVI A, et al. Numerical simulation of collision between two droplets in the T-shaped microchannel with lattice Boltzmann method[J]. AIP Advances, 2016, 6(11):115307.
[14]	HIRSCHLER M, OGER G, NIEKEN U, et al. Modeling of droplet collisions using smoothed particle hydrodynamics[J]. International Journal of Multiphase Flow, 2017, 95:175-187.
[15]	ADAM J R, LINDBLAD N R, HENDRICKS C D. The collision, coalescence, and disruption of water droplets[J]. Journal of Applied Physics, 1968, 39(11):5173-5180.
[16]	BRENN G, VALKOVSKA D, DANOV K D. The formation of satellite droplets by unstable binary drop collisions[J]. Physics of Fluids, 2001, 13(9):2463-2477.
[17]	BRAZIER-SMITH P R, JENNINGS S G, LATHAM J. The interaction of falling water drops:coalescence[C]//Proceedings of the Royal Society of London A:Mathematical, Physical and Engineering Sciences. Great Britain:The Royal Society, 1972:393-408.
[18]	ASHGRIZ N, POO J Y. Coalescence and separation in binary collisions of liquid drops[J]. Journal of Fluid Mechanics, 1990, 221(221):183-204.
[19]	JIANG Y J, UMEMURA A, LAW C K. An experimental investigation on the collision behaviour of hydrocarbon droplets[J]. Journal of Fluid Mechanics, 1992, 234:171-190.
[20]	TANG C L, ZHANG P, LAW C K. Bouncing, coalescence, and separation in head-on collision of unequal-size droplets[J]. Physics of Fluids, 2012, 24(2):022101.
[21]	WILLIS K, ORME M. Binary droplet collisions in a vacuum environment:an experimental investigation of the role of viscosity[J]. Experiments in Fluids, 2003, 34(1):28-41
[22]	KUSCHEL M, SOMMERFELD M. Investigation of droplet collisions for solutions with different solids content[J]. Experiments in Fluids, 2013, 54(2):1440.
[23]	ROISMAN I V, PLANCHETTE C, LORENCEAU E, et al. Binary collisions of drops of immiscible liquids[J]. Journal of Fluid Mechanics, 2012, 690(1):512-535.
[24]	PLANCHETTE C, LORENCEAU E, BRENN G. The onset of fragmentation in binary, liquid drop collisions[J]. Journal of Fluid Mechanics, 2012, 702(702):5-25.
[25]	CHEN R H, CHEN C T. Collision between immiscible drops with large surface tension difference:diesel oil and water[J]. Experiments in Fluids, 2006, 41(3):453-461.
[26]	王凯, 易诗婷, 周倩倩, 等. 微通道内纳米颗粒对液滴聚并的影响规律[J]. 化工学报, 2016, 67(2):469-475. WANG K, YI S T, ZHOU Q Q, et al. Effect of nano-particles on droplet coalescence in microchannel device[J]. CIESC Journal, 2016, 67(2):469-475.
[27]	ELPERIN I T. Heat and mass transfer in opposing currents[J]. J. Engng. Physics, 1961, 6:62-68.
[28]	伍沅. 撞击流-原理·性质·应用[M]:北京:化学工业出版社, 2006:3-12. WU Y. Impinging Streams:Fundamental, Properties and Applications[M]. Beijing:Chemical Industry Press, 2006:3-12.
[29]	KITRON A, ELPERIN T, TAMIR A. Stochastic modelling of the effects of liquid droplet collisions in impinging streams absorbers and combustors[J]. International Journal of Multiphase Flow, 1991, 17(2):247-265.
[30]	吴鸽平, 龚俊, 杜敏, 等. 撞击流内液滴碰撞的后续发展行为[J]. 江苏大学学报(自然科学版), 2016, 37(5):525-529. WU G P, GONG J, DU M, et al. Subsequent development of droplet collision in impinging stream[J]. Journal of Jiangsu University (Natural Science Edition), 2016, 37(5):525-529.
[31]	O'ROURKE P J. Collective drop effects on vaporizing liquid sprays[D]. United States:Princeton University, 1981.ociety, 1972:393-408.
[18]	ASHGRIZ N, POO J Y. Coalescence and separation in binary collisions of liquid drops[J]. Journal of Fluid Mechanics, 1990, 221(221):183-204.
[19]	JIANG Y J, UMEMURA A, LAW C K. An experimental investigation on the collision behaviour of hydrocarbon droplets[J]. Journal of Fluid Mechanics, 1992, 234:171-190.
[20]	TANG C L, ZHANG P, LAW C K. Bouncing, coalescence, and separation in head-on collision of unequal-size droplets[J]. Physics of Fluids, 2012, 24(2):022101.
[21]	WILLIS K, ORME M. Binary droplet collisions in a vacuum environment:an experimental investigation of the role of viscosity[J]. Experiments in Fluids, 2003, 34(1):28-41
[22]	KUSCHEL M, SOMMERFELD M. Investigation of droplet collisions for solutions with different solids content[J]. Experiments in Fluids, 2013, 54(2):1440.
[23]	ROISMAN I V, PLANCHETTE C, LORENCEAU E, et al. Binary collisions of drops of immiscible liquids[J]. Journal of Fluid Mechanics, 2012, 690(1):512-535.
[24]	PLANCHETTE C, LORENCEAU E, BRENN G. The onset of fragmentation in binary, liquid drop collisions[J]. Journal of Fluid Mechanics, 2012, 702(702):5-25.
[25]	Chen R H, Chen C T. Collision between immiscible drops with large surface tension difference:diesel oil and water[J]. Experiments in Fluids, 2006, 41(3):453-461.
[26]	王凯, 易诗婷, 周倩倩, 等. 微通道内纳米颗粒对液滴聚并的影响规律[J]. 化工学报, 2016, 67(2):469-475. WANG K, YI S T, ZHOU Q Q, et al. Effect of nano-particles on droplet coalescence in microchannel device[J]. CIESC Journal, 2016, 67(2):469-475.
[27]	Elperin I T. Heat and mass transfer in opposing currents[J]. J Engng Physics, 1961, 6:62-68.
[28]	伍沅. 撞击流-原理·性质·应用[M]:北京:化学工业出版社, 2006:3-12. WU Y. Impinging streams:Fundamental, Properties and Applications[M]. Beijing:Chemical Industry Press, 2006:3-12.
[29]	KITRON A, ELPERIN T, TAMIR A. Stochastic modelling of the effects of liquid droplet collisions in impinging streams absorbers and combustors[J]. International Journal of Multiphase Flow, 1991, 17(2):247-265.
[30]	吴鸽平, 龚俊, 杜敏,等. 撞击流内液滴碰撞的后续发展行为[J]. 江苏大学学报(自然科学版), 2016, 37(5):525-529. WU G P, GONG J, DU M, et al. Subsequent development of droplet collision in impinging stream[J]. Journal of Jiangsu University (Natural Science Edition), 2016, 37(5):525-529.
[31]	O'ROURKE P J. Collective Drop Effects on Vaporizing Liquid Sprays[D]. United States:Princeton University, 1981.