Modelling transient processes in high-performance single-screw extruders

• Applicant: Professor Dr.-Ing. Volker Schöppner
• Subject Area: Plastics Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549080467

Single-screw extrusion is one of the core competencies in plastics processing. To produce economically and sustainably, not merely an increase in throughput is crucial, but also pulsation-free material delivery as well as avoiding downtimes and rejects. This requires a targeted screw design, especially when using high-performance screws such as barrier and wave-dispersion screws. The aim of the research project is to provide simulation models that can already be used in screw design. This should make it possible to predict transient effects in particular. Examples of this are pressure, temperature and output fluctuations as a result of fluctuating material properties, which can occur in particular with recycled material. It should also be possible to simulate flushing times during material changes, so that these can already be taken into account in the screw design and thus waste can be reduced. In the targeted research project, simulation models for the transient calculation of single-screw extruders (smooth barrel and grooved barrel) are to be developed in order to be able to simulate process instabilities such as unsteady solids and melt conveying as well as process fluctuations due to inconstant material properties. The first of two approaches is the description of the entire extrusion process by means of a simulation model in which, in addition to melt conveying, solids conveying and plasticization are also solved numerically. For this purpose, the solids friction in particular must be described in a targeted manner so that the solids transport and thus the pressure-throughput behavior of the entire extrusion process can be accurately described. The advantage of combining solids and melt transport within one model is the calculation of the entire extrusion process within one simulation, but this requires high computing capacities and calculation times. The second approach uses the melt-dominated calculation of the single-screw extruder by means of network theory. For this purpose, the flow channel of the extruder is divided into many helical channel sections and the pressure-throughput behavior and the dissipation performance in the sections are calculated using regression equations already derived from numerical simulations. Within the scope of the research project, the model is additionally supplemented by models for the residence time distribution, so that the model can also be used for transient simulations. The two approaches for simulating single-screw extruders will be validated experimentally and compared with each other in order to be able to make recommendations for various problems (plugging, pressure fluctuations, flushing times), which up to now have only been insufficiently describable and predictable. Furthermore, a coupling of the models is aimed at, so that the advantages of both methods can be combined.

• DFG Programme: Research Grants
• International Connection: Austria
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partner: Professor Dr. Gerald Berger-Weber