In twin-screw extrusion, the geometry of a mixing element mainly determines the basic flow pattern, which eventually affects the mixing ability as well as the dispersive ability of the mixing element. The effects of geometrical modification, with both forward and backward pitched tips, of a conventional forward kneading disks element (FKD) in the pitched-tip kneading disks element on the flow pattern and mixing characteristics are discussed. Numerical simulations of fully filled, nonisothermal polymer melt flow in the melt-mixing zone were performed, and the flow pattern structure and the tracer trajectories were investigated. The pitched tips largely affect the inter-disk fluid transport, which is mainly responsible for mixing. These changes in the local flow pattern are analyzed by the distribution of the strain-rate state. The distribution of the finite-time Lyapunov exponent reveals a large inhomogeneity of the mixing in FKD is suppressed both by the forward and backward tips. By the forward tips on FKD, the mixing ability is relatively suppressed compared to FKD, whereas for the backward tips on FKD, the mixing ability is enhanced while maintaining the same level of dispersion efficiency as FKD. From these results, the pitched tips on the conventional KD turn out to be effective at reducing the inhomogeneity of the mixing and tuning the overall mixing performance. © 2017 American Institute of Chemical Engineers AIChE J, 2017

中文翻译：

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在双螺杆挤出机的捏合元件中使用倾斜尖端改善混合特性

在双螺杆挤出中，混合元件的几何形状主要决定基本流动模式，这最终会影响混合元件的混合能力和分散能力。讨论了前倾捏合盘元件中常规前向捏合盘元件（FKD）的几何变形（具有向前和向后的倾斜尖端）对流型和混合特性的影响。对熔体混合区中完全填充的非等温聚合物熔体流动进行了数值模拟，并研究了流型结构和示踪剂轨迹。倾斜的尖端极大地影响了盘间流体的输送，这主要是造成混合的原因。通过应变率状态的分布分析了局部流动模式中的这些变化。有限时间李雅普诺夫指数的分布表明，前向和后向尖端都抑制了FKD中混合的较大不均匀性。与FKD相比，通过FKD的前向尖端可相对抑制混合能力，而对于FKD的后向尖端，可增强混合能力，同时保持与FKD相同的分散效率。从这些结果可以看出，传统KD上的倾斜尖端可有效减少混合的不均匀性并调节整体混合性能。©2017美国化学工程师学会 而对于FKD的后向技巧，则在保持与FKD相同水平的分散效率的同时，增强了混合能力。从这些结果可以看出，传统KD上的倾斜尖端可有效减少混合的不均匀性并调节整体混合性能。©2017美国化学工程师学会 而对于FKD的后向技巧，则在保持与FKD相同水平的分散效率的同时，增强了混合能力。从这些结果可以看出，传统KD上的倾斜尖端可有效减少混合的不均匀性并调节整体混合性能。©2017美国化学工程师学会AIChE的Ĵ，2017年