混炼机横截面PP熔体液滴分散过程的数值模拟研究
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摘要
对Fluent进行二次开发,通过用户自定义函数,将黏弹性流体的动量方程和变形张量输运方程加载到Fluent中,从而实现了对聚合物黏弹性流体流动的模拟。采用VOF界面追踪方法,对聚合物熔体中的单个液滴在混炼机横截面流场作用下发生的变形、破碎行为和二次团聚过程进行了分析研究。探讨了液滴在混炼腔复杂流场中的分散过程和微观结构的形成机理,对揭示共混改性过程中分散相织态结构发展演变过程和机理具有指导意义。结果表明,PP液滴在混炼过程中经历了变形、破碎、聚并过程;PP液滴在C形区发生了不均匀变形行为,在相互作用窗混沌流场下发生了拉伸、挤压、交叉行为;PP液滴的破碎行为包括毛细不稳破碎、末端夹断以及在螺棱背风面的松弛破碎。
Through the secondary development of Fluent,the flow of polymer viscoelastic fluid was simulated by loading a user-defined function into the viscoelastic fluid momentum equation and deformation tensor transport equation in Fluent.A VOF interface-tracking method was used to analyze the deformation,breakup and coalescence process of a single droplet in the polymer melt under the cross-sectional flow field of a mixer.The dispersion process and microstructural formation mechanism of the single droplet in the complex flow field were discussed.The relevant results are instructive to explore the evolution process and mechanism of morphology development in the process of blending modification.The results indicated that the PP droplet underwent deformation,breakup and coalescence during the mixing process.The inhomogeneous deformation behavior of PP droplet happened in the C-shape zone,which resulted in the occurrence of stretching,squeezing and crossover behaviors under the chaotic flow field of interaction window.The fragmentation behavior of PP droplet included capillary instability,pinch pinching and breakup during relaxation.
Through the secondary development of Fluent,the flow of polymer viscoelastic fluid was simulated by loading a user-defined function into the viscoelastic fluid momentum equation and deformation tensor transport equation in Fluent.A VOF interface-tracking method was used to analyze the deformation,breakup and coalescence process of a single droplet in the polymer melt under the cross-sectional flow field of a mixer.The dispersion process and microstructural formation mechanism of the single droplet in the complex flow field were discussed.The relevant results are instructive to explore the evolution process and mechanism of morphology development in the process of blending modification.The results indicated that the PP droplet underwent deformation,breakup and coalescence during the mixing process.The inhomogeneous deformation behavior of PP droplet happened in the C-shape zone,which resulted in the occurrence of stretching,squeezing and crossover behaviors under the chaotic flow field of interaction window.The fragmentation behavior of PP droplet included capillary instability,pinch pinching and breakup during relaxation.
引文
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[2]GAO T,HU H.Deformation of Elastic Particles in Viscous Shear Flow[J].Journal of Computational Physics,2009,228(6):2 132-2 151.
[3]LYU S P,BATES F S,MACOSKO C W.Coalescence in Polymer Blends During Shearing[J].AIChE Journal,2000,46(2):229-238.
[4]LIN B,SUNDARARAJ U,MIGHRI F,et al.Erosion and Breakup of Polymer Drops under Simple Shear in High Viscosity Ratio Systems[J].Polymer Engineering&Science,2003,43(4):891-904.
[5]刘晓鸣,谢林生,马玉录,等.双转子连续混炼机转子混炼段流场的数值研究[J].中国塑料,2006,20(11):95-99.LIU X M,XIE L S,MA Y L,et al.Numerical Simulation of Flow Fields in the Mixing Section of the Rotor of A Two-rotor Continuous Mixer[J].China Plastics,2006,20(11):95-99.
[6]景军涛,谢林生,马玉录,等.转子结构和工艺参数对双转子连续混炼机混合性能的影响[J].中国塑料,2009,23(9):85-90.JING J T,XIE L S,MA Y L,et al.Influence of Rotor Structure and Technological Parameters on Mixing Performance of A Two-rotor Continuous Mixer[J].China Plastics,2009,23(9):85-90.
[7]张霞,谢林生,马玉录.双转子连续混炼机混炼段拉伸作用的研究[J].中国塑料,2010,24(3):108-113.ZHANG X,XIE L S,MA Y L,et al.Study on Stretching Effect in Mixing Section of Two-rotor Continuous Mixers[J].China Plastics,2010,24(3):108-113.
[8]LIU J,LI F,ZHANG L,et al.Numerical Simulation ofFlow of Rubber Compounds in Partially Filled Internal Mixer[J].Journal of Applied Polymer Science,2015,132(35):42 496.
[9]叶萍,马玉录,谢林生.单个聚合物颗粒在剪切流场中熔融模型的建立[J].塑料,2015,44(1):72-76.YE P,MA Y L,XIE L S.Establishment of Single Polymer Pellet Melting Process Model Under Shear Flow[J].Plastics,2015,44(1):72-76.
[10]景军涛,谢林生,马玉录,等.双转子连续混炼机混合过程的统计学分析[J].中国塑料,2009,23(2):93-97.JING J T,XIE L S,MA Y L,et al.Statistical Analysis on Mixing Process of A Two-rotor Continuous Mixer[J].China Plastics,2009,23(2):93-97.
[11]耿孝正.聚合物加工中固相的分散及填充改性混合设备的选用[J].中国塑料,2002,16(9):1-6.GENG X Z.Dispersion of Solid Phase in Polymer Processing and Choice of Mixing Devices for Filling Modification[J].China Plastics,2002,16(9):1-6.
[12]WANG W,MANAS-ZLOCZOWER I.Temporal Distributions:the Basis for the Development of Mixing Indexes for Scale-up of Polymer Processing Equipment[J].Polymer Engineering&Science,2001,41(6):1 068-1 077.
[13]TOMOTIKA S.On the Instability of a Cylindrical Thread of a Viscous Liquid Surrounded by Another Viscous Fluid[J].Mathematical and Physical Science,1935,150(870):322-337.
[14]KOMRAKOVA A E,SHARDT O,ESKIN D,et al.Effects of Dispersed Phase Viscosity on Drop Deformation and Breakup in Inertial Shear Flow[J].Chemical Engineering Science,2015,126:150-159.