液-液两相流的共直线液滴运动聚结特性
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摘要
当前液-液两相流理论研究多集中于液滴群在反应器内的宏观动力学行为,对于微观下液滴与液滴相互作用机理的研究尚不彻底。为了研究油水两相流共直线上升的双液滴(油滴)之间的相互作用,基于液-液两相流理论,运用COMSOL仿真软件Cahn-Hilliard方程的相场方法建立了油滴运动模型,模拟了油滴间距离、油滴粒径、两相物性等参数对双油滴间相互作用的影响规律,进而分析油滴之间的尾流对油滴聚结的影响。结果表明:先行油滴的尾流影响跟随油滴的上浮速度,从而促使两油滴发生聚结,随着油滴间距离的增大,影响减弱,且油滴粒径越大、黏度越小,聚结时间越短。研究结果为更复杂的液-液两相流体系研究提供了参考。
At present, the theoretical study of liquid-liquid two-phase flow mostly focuses on the macro-kinetics behaviors of liquid drop swarms in the reactors while the microscopic mechanisms of drop-drop interaction are not researched thoroughly. In order to investigate, the interaction between two collinear rising liquid drops(oil drops) of oil-water twophase flow, based on the theory of liquid-liquid two-phase flow, the oil-drop motion model was established by using the phase field method of Cahn-Hilliard equation in the simulation software COMSOL. By virtue of this model, the influences of drop-drop distance, drop size and two-phase physical parameters on the drop-drop interaction were simulated and the effects of the wake between drops on the drop coalescence were analyzed. It is indicated that leading drop's wake affects the floating velocity of its following drop, promoting the coalescence of two drops. And the larger the drop-drop distance is, the weaker the effect is. And the larger the drop size is and the lower the viscosity is, the shorter the coalescence time is. The research results provide the reference for the further study of more complex liquid-liquid two-phase flow systems.
At present, the theoretical study of liquid-liquid two-phase flow mostly focuses on the macro-kinetics behaviors of liquid drop swarms in the reactors while the microscopic mechanisms of drop-drop interaction are not researched thoroughly. In order to investigate, the interaction between two collinear rising liquid drops(oil drops) of oil-water twophase flow, based on the theory of liquid-liquid two-phase flow, the oil-drop motion model was established by using the phase field method of Cahn-Hilliard equation in the simulation software COMSOL. By virtue of this model, the influences of drop-drop distance, drop size and two-phase physical parameters on the drop-drop interaction were simulated and the effects of the wake between drops on the drop coalescence were analyzed. It is indicated that leading drop's wake affects the floating velocity of its following drop, promoting the coalescence of two drops. And the larger the drop-drop distance is, the weaker the effect is. And the larger the drop size is and the lower the viscosity is, the shorter the coalescence time is. The research results provide the reference for the further study of more complex liquid-liquid two-phase flow systems.
引文
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[2]B?UMLER K,WEGENER M,PASCHEDAG A R,et al.Drop rise velocities and fluid dynamic behavior in standard test systems for liquid/liquid extraction-experimental and numerical investigation[J].Chemical Engineering Science,2011,66(3):426-439.
[3]姜雪梅,董守平,张红光,等.牛顿型液-液两相流中分散相液滴碰撞模型及实验研究[J].流体机械,2007,35(9):5-8.JIANG X M,DONG S P,ZHANG H G,et al.Collision frequencies model and experiment of dispersed droplets in Newtonian liquid-liquid flow[J].Fluid Machinery,2007,35(9):5-8.
[4]李广军,郭烈锦,高晖,等.螺旋管内油-水液液两相流流型[J].化工学报,2000,51(2):239-242.LI G J,GUO L J,GAO H,et al.Flow patterns of oil-water liquid-liquid two-phase flow in hellcally coiled tubes[J].Journal of Chemical Industry and Engineering(China),2000,51(2):239-242.
[5]陆耀军,王金昌.油水重力分离技术及其进展[J].油气田地面工程,1999,18(4):6-8,79.LU Y J,WANG J C.The technology of gravity oil water separation and its progress[J].Oil-Gasfield Surface Engineering,1999,18(4):6-8,79.
[6]MYINT W,HOSOKAWA S,TOMIYAMA A.Shapes of single drops rising through stagnant liquids[J].Journal of Fluid Science and Technology,2007,2(2):184-195.
[7]DONG H,WANG X,LIU L,et al.The rise and deformation of a single bubble in ionic liquids[J].Chemical Engineering Science,2010,65(10):3240-3248.
[8]ZAISHA M,CHAO Y.Challenges in study of single particles and particle swarms[J].Chinese Journal of Chemical Engineering,2009,17(4):535-545.
[9]LIU L L,TANG H,QUAN S P.Shapes and terminal velocities of a drop rising in stagnant liquids[J].Computers&Fluids,2013,81(9):17-25.
[10]唐海.液滴降落过程的数值研究[D].成都:四川大学,2007:57.TANG H.Numerical studies of falling droplet[D].Chengdu:Sichuan University,2007:57.
[11]李彦鹏,关卫省.应用Level Set方法模拟三维气泡与液滴的运动[J].地球科学与环境学报,2007,29(2):217-220.LI Y P,GUAN W S.Simulation of bubble motion and droplet with Level Set method[J].Journal of Earth Sciences and Environment,2007,29(2):217-220.
[12]高一娟.微通道内两相流界面追踪的数值模拟[D].天津:天津大学,2009:59.GAO Y J.Tracking the interface of two-phase flow in microchannels[D].Tianjin:Tianjin University,2009:59.
[13]刘向东,陈永平,张程宾,等.双乳液液滴形变及破碎特性[J].工程热物理学报,2012,33(3):457-459.LIU X D,CHEN Y P,ZHANG C B,et al.Deformation and breakup characteristics of double emulsion drop[J].Journal of Engineering Thermophysics,2012,33(3):457-459.
[14]骆政园,和龙,白博峰.具有复杂界面的三维弹性液滴动力学模拟[J].工程热物理学报,2014,35(6):1132-1135.LUO Z Y,HE L,BAI B F.Three-dimensional numerical simulation of dynamics of elastic capsules[J].Journal of Engineering Thermophysics,2014,35(6):1132-1135.
[15]柳安军,陈杰,杨超,等.含有可变形界面的两相流和传递数值模拟[J].中国科学:物理学力学天文学,2017,47(7):101-116.LIU A J,CHEN J,YANG C,et al.Simulation of two-phase flow and mass transfer with deformable interface[J].Scientia Sinica(Physica,Mechanica&Astronomica),2017,47(7):101-116.
[16]JACQMIN D.Calculation of two-phase Navier-Stokes flows using phase-field modeling[J].Journal of Computational Physics,1999,155(1):96-127.
[17]STOKES G.On the effect of the internal friction of fluids on the motion of pendulum[M].Cambridge:Transactions of the Cambridge Philosophical Society,1851:8.
[18]CLIFTR,GRACE J,WEBER M.Bubbles,drops and particles[M].New York:Academic Press New York,1978:16-28.
[19]NAVARRO S K,LAHEY R T,DREW D A.Analysis of the bubbly/slug flow regime transition[J].Nuclear Engineering and Design,1994,151(1):15-39.
[20]NARAYANAN S,GOOSSENS L H J,KOSSEN N W F.Coalescence of two bubbles rising in line at low Reynolds numbers[J].Chemical Engineering Science,1974,29(10):2071-2082.