Design and Optimization of Wave-Dispersion Screws
Final Report Abstract
In single-screw extrusion, wave-dispersion screws can achieve superior melting and mixing performance at simultaneously lower energy input compared to conventional screw concepts. Due to these benefits, wave-dispersion screws are increasingly employed in the polymer processing industry. Yet the design of these screws is solely based on experience, since the effects of screw geometry on process performance are poorly understood. Consequently, large room for process optimisation remains unused. Within this research project, two different approaches were pursued for the simulation of single-screw extruders. Using these simulation models, the goal is to capture the complex flow in wave-dispersion screws more accurately, thus allowing for a more targeted screw design. The chair of plastic processing in Paderborn (KTP) focused on CFD simulations considering solids conveying and plastication, which can predict the disperse melting in wave-dispersion screws. For a better understanding of the process, material transport was simulated in various wave-dispersion screws for two commercial polymer grades with distinct flow properties. Based on the simulations results, in total three optimum designs were obtained: one design for each polymer, and one universal design for both. The selected screw designs were experimentally investigated alongside three already existing configurations and assessed by means of a self-defined screw performance index. At the Institute of Polymer Processing and Digital Transformation (IPPD), the melt conveying performance of wave-dispersion screws was predicted using an institute-owned calculation routine. This routine models the channel and leakage flow in single-screw extruders by means of network theory and operates considerably faster compared to three-dimensional CFD simulations. The implemented models for the local pumping capability and viscous dissipation were adapted to genuinely represent the three-dimensional curved channel shape, which is important to obtain accurate predictions also along the deep-flighted sections of wave-dispersion screws. The improved prediction quality of the adapted calculation routine was successfully demonstrated on throughput tests on a high-speed extruder. The knowledge gained and the simulation models developed in this project collaboration provide the foundation for a physically based design of wave-dispersion screws for the polymer processing industry. This eventually contributes to more profitable and sustainable shaping processes.
Publications
-
Development of an Analytical Mathematical Modelling Approach for a More Precise Description of Disperse Melting in Solid Bed Breaking Screw Concepts, Conference Proceedings ANTEC 2021, Denver
Dörner, M. & Schöppner, V.
-
Vorteilhaftes Prozessverhalten von Wave-Schnecken in der Einschneckenextrusion, Fachtagung TECHNOMER, 2021, Chemnitz
Schall, C.; Dörner, M. & Schöppner, V.
-
Melt Conveying in Single-Screw Extruders: Modeling and Simulation. Polymers, 14(5), 875.
Marschik, Christian; Roland, Wolfgang & Osswald, Tim A.
-
On the Wave to Successful Mixing, Kunststoffe International 3/2022.
Frank, M.; Dörner, M.; Marschik, C.; Schall, C. & Schöppner, V.
-
Correction factors for the drag and pressure flows of power‐law fluids through rectangular ducts. Polymer Engineering & Science, 63(7), 2043-2058.
Marschik, Christian & Roland, Wolfgang
-
Extended melt‐conveying models for single‐screw extruders: Integrating domain knowledge into symbolic regression. Polymer Engineering & Science, 63(11), 3639-3656.
Marschik, Christian; Roland, Wolfgang & Kommenda, Michael
-
Predicting the pumping capability of single-screw extruders: A comparison of two- and three-dimensional modeling approaches. AIP Conference Proceedings, 2773, 020002. AIP Publishing.
Marschik, Christian & Roland, Wolfgang
-
The Wave Must Be Right, Plastics Insights 7/2023, 2023
Schall, C.; Frank, M. & Schöppner, V.
