Holistic Simulation of Polymer Materials Plastification, Solid and Melt Transportation in Single-screw Extruders by means of CFDEM - Joint Examination of Feed Zone, Melting Zone and Metering Zone.

• Applicant: Professor Dr.-Ing. Christian Bonten
• Subject Area: Plastics Engineering
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324934383

In plastics processing, single-screw extruders are used to produce profiles, pipes, sheets, films and many other products. The single-screw extruder is a continuously operating production machine. Optimization often focuses on increasing throughput while maintaining high product quality. Previous studies show that the increase in throughput is limited on the one hand by the feed of the plastic into the extruder and on the other hand by the melting behavior. At high screw speeds, the screw often cannot draw in enough granules from the hopper to completely fill the screw-channels. The drawn-in plastic granules must be completely melted in the subsequent melting zone in order to ensure high product quality. In this context, simulative approaches, especially three-dimensional approaches, provide a significant contribution to the understanding of the transport processes in the feed and melting zones of the extruder. In existing simulation models, both zones are always considered separately due to the complex physical processes at the transition point. However, a cross-zone approach is absolutely necessary, since it is not expedient to increase throughput without ensuring product quality. The objective of this research project is the first cross-zone three-dimensional simulation of an entire single-screw extruder, namely the feed, melting and metering zones in a single simulation environment. The Discrete Element Method (DEM) will be used to simulate the transport of the plastic granules in the feed zone. In this process, the plastic particles are simulated individually. The following melt flow developing in the melting zone will be calculated using the Finite Volume Method (FVM) and in particular the Volume of Fluid (VoF) method for the phases melt and air in the extruder. The coupling of the fluid phases and the solid granules is carried out in the simulation environment CFDEM®coupling via a new melting model, which was developed within the framework of the predecessor project (D-A-CH cooperation project) and implemented in the simulation environment. First of all, the newly created link, which made it possible to simulate the feed zone and melting zone together for the first time, is to be validated more widely on a single-screw extruder with several operating points. Furthermore, the simulation approach will be extended and further refined on both the DEM and CFD sides, as well as the melting model itself, in order to be able to fully simulate an extruder with a three-zone screw including melting and deformation of the compacted solid bed for the first time. The simulations will be validated with experiments on an extruder. In addition to the measured pressure and temperature data of the extruder, so-called dead-stop experiments will also be used to match both the start of melting and the end of melting in the single-screw extruder.

• DFG Programme: Research Grants
• International Connection: Austria
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partner: Dr. Christoph Goniva