混炼机横截面PP熔体液滴分散过程的数值模拟研究

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。

Study on Numerical Simulation for Dispersion Process of PP Melt Droplet on Cross Section of Mixer

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.