Study On Screw Configurations Of S Element In Intermeshing Co-Rotating Twin-Screw Extrusion

S element is new screw element used in the intermeshing co-rotating twin-screwextruder. The special geometrical design endows it with excellent melting and mixingability and the adaptability to high screw speed production. This study is a further studyof the characteristics of S element. For the full-filled melt conveying zone consisting ofS element, three dimensional non-Newtonian flow field simulations have been carriedout by using ANSYS FEM software. Pressure profile, velocity profile and viscosityprofile are obtained first, later the flow rate, back flow rate, back flow coefficient, shearrate, shear stress and viscous dissipative energy are calculated with post-processingprograms to illustrate the output and mixing ability and temperature rise. The comparisons of S element and conventional screw element under the highscrew speeds show, the average field parameters increase linearly or semi-linearly withthe increase of screw speed, so the performances of both high speed and low speedabide by the same tendency. While the conventional screw element has too muchtemperature rise and the melting ability decrease. The examination of S element andkneading blocks shows that the two elements have similar dispersive mixing ability; Selement has better distributive mixing ability than kneading blocks; S element has theadvantage of avoiding high temperature rise over the kneading blocks. The study on thecharacteristics of different configurations of S element shows the ratio of positive andnegative pumping components has little to do with the dispersive mixing ability and theV-shaped high pressure zone where the positive and negative parts meet is significant tothe circumferential distributive mixing ability. Therefore, the configuration with thelargest V-shaped high pressure zone has the best circumferential distributive mixingability. Some experiments, such as RTD testing and on-line sampling experiments arecarried out to verify the results derived from the flow field simulations. So we can cometo the conclusion that the model is right, FEM are practical and the results are reliable.