Design and Optimization of Wave-Dispersion Screws

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Content:Single-screw extruders are indisputably the most important machines in the polymer processing industry. During plasticating extrusion, polymer is fed to the extruder in the solid-state and the material is melted as it is conveyed by the rotating extruder screw from the feed port to the die. Based on the economic framework, the primary objective of machine manufacturers is to increase the output capacity while guaranteeing high melt quality. Meeting these demands requires proper screw design and thus a thorough understanding of the transport phenomena governing the extrusion process. Focusing on solid bed breaking screw concepts, this lead-agency research project will investigate wave-dispersion screws in detail. To increase the understanding for the complex processes in wave-dispersion screws, new process models will be developed with the help of 3D-CFD-Simulations and validated by experimental studies carried out on smooth-barrel (KTP) as well as grooved-barrel (IPEC) single screw extruders, covering a wide range on possible extrusion processes. This will increase the modeling accuracy of wave-dispersion screws in comparison to existing simplified models of the process behavior and thus give potential for screw optimization of wave-dispersion screws so that they can exploit their full potential.Hypothesis and methods:3D-CFD-Simulations will be carried out in two different ways. On the one hand, a data driven pressure/throughput model is generated by means of many melt-dominated curved screw channel simulations. On the other hand, a non-isothermal 3D-CFD simulation model, which also considers the melting of the solid material, is introduced and used for the analysis of the different wave-dispersion screws. Furthermore, design guidelines for common material types processed on wave-dispersion screws are developed. This will help to meet the high demands in terms of output capacity and melt quality in the field of single-screw extrusion. Additionally, experimental studies will be carried out on various 45mm single-screw extruders to validate these models.Innovation and novelty:The few scientific papers dealing with the above-mentioned topic still leave many questions unanswered and show that the contents of this proposal are highly relevant. It has been shown, that wave-dispersion screws can lead to higher throughput and better melt homogeneity, but the analytical calculation models for designing a screw have a lack of precision. Since the investigated screw concept must be meticulously designed in order to unfold its full advantages, the aim is to merge the expertise in the field of modeling and simulation of the KTP, Paderborn and the IPEC, Linz to produce new modeling approaches that considerably increase the accuracy of the predictions. As a result, a successful and trustful design and use of the wave-dispersion screws will be possible.