同向雙螺桿擠出纖維排向預測

Abstract

本研究以數值方式模擬六組雙螺桿(Type1、Type2、Type3、Type4、Type5、Type6)在轉速300 RPM、流量10kg/hr以及工作溫度200℃條件下的纖維混練流場。首先根據雙螺桿組態生成旋轉周期內各角度的流場網格，並在等溫流場與不可壓縮流的假設下，求解三維暫態連續方程式、動量方程式，以獲得雙螺桿流場特性。接著根據流場的模擬結果，以四階Runge-Kutta方法預測虛擬粒子在套筒內部的移動路徑，並計算出暫留時間與混合效率，分析雙螺桿混練的分散與分佈特性。最後使用纖維排向張量方程組，預測纖維於流場流動的排向行為，並分析纖維於不同纖維交互作用係數下對於纖維排向之影響。本研究以上述方法模擬六組螺桿組態之混練製程。計算結果顯示，Type2、Type5、Type6有較高的平均暫留時間，具有較好的分配性; Type5與Type6有較高的平均剪應力，具有較佳的分散性; Type2、Type3、Type6有較高的平均剪切率型態因子，具有較好的分配性; Type1、Type5、Type6有較高的平均Manas-Zloczower混合因子，表示流場更接近於拉伸流動。綜合上述結果，Type6螺桿組態為最佳之組態設計。此外，纖維交互作用係數越小對於纖維於螺桿出口的排向率越佳，纖維的排向角亦更趨近垂直於套筒表面。計算結果顯示當纖維交互作用係數為0.001時，6組螺桿的排向率皆接近95%。

In this thesis, a numerical approach is employed to study the fiber-compounding process of a twin-screw extruder under the working conditions of 300 RPM, 10 kg/hr, and 200℃. Based on the screw element configuration, the numerical grid for each specified angle within a rotational period is generated. An unsteady three-dimensional model is applied to solve the continuity and momentum equations under the assumption of isothermal and incompressible flow. The particle movement in the barrel is then predicted via a fourth-order Runge-Kutta method according to the calculated flow field and the mixing efficiency is forecasted to evaluate the dispersion and distribution characteristics. Finally, the behavior of fiber orientation in the compounding process is predicted using the equation of orientation tensor, while the influence of the fiber interaction coefficient on fiber orientation is also investigated. Six different twin-screw configurations (Type1-6) are employed in modeling the extrusion process for fiber compounding. Numerical predictions indicate that screw configuration Types 2, 5, and 6 have a high average residence time and exhibit better distributive mixing. The high average shear stress of Types 5 and 6 indicates better dispersion in mixing. Types 2, 3, and 6 with a high mean strain-rate-type identifier deliver better distributive mixing, while the Manas-Zloczower mixing index of Types 1, 5, and 6 indicates improved mixing behavior. Based on these results, twin-screw configuration Type6 is identified as the optimal design. In addition, the smaller the fiber interaction coefficient, the higher the degree of fiber orientation in the outlet plane, accompanied by the fiber orientation angle more perpendicular to the barrel surface. The calculation results show that the degree of fiber orientation reaches approximately 95% when the fiber-interaction coefficient is 0.001.