Abstract
本研究為利用有限元素法分析兩流體自押出機 ( 或幫浦 ) 中送出，經過進料組合系統 (feed block system) 形成二層流體後再進入一模具內開展成液膜的整個過程， 而最主要之分析重點為利用最適化方法，設計一雙層共擠壓型模具， 使得出口流量分佈達到合乎要求的範圍，其次則是利用節流栓 (choker bar) 進行最適化之改良設計， 使得同一模具能適用多種流變性質的流體。在分析的方法上， 流體從押出機出來到進入模具前的這一段，採用三維有限元素法計算流場及界面位置。 流體進入模具後則是以 Hele-Shaw flow 之模式為基礎，以二維有限元素法計算整個模具的界面位置及壓力分佈，並進而求得模具出口流量分佈。 至於入口界面位置的給定則是採用三維有限元素法所計算出來的結果，入口壓力則是在合理的範圍內任意給定,再予修正。An integrated numerical approach is proposed to simulate thepolymeric liquid flows in a bicomponent coextrusion die witha feed block inlet system. The three-dimensional finiteelement method is applied to determine the fluidmotion and the interfacial position of the two polymericliquids before entering the die body, whereas the two-dimensional Hele-Shaw model is assumed to be applicable forfluid flow in the manifold and the slot section of the diebody. The optimal design procedure is incorporated intothe simulation and the dimensions of the manifold can beproperly selected so that the die can deliver the compositeliquid film with acceptable uniformity, a speciallydesigned choker bar can also be inserted to reduce theflow non-uniformities caused by production variations. Thecontraction of the composite liquid film emanating from thedie exit is also predicted under different draw ratios.