Automated Optimization of Spiral Shearing and Mixing Elements for Single-screw Extruders

During the processing of polymers in various extrusion lines, more and more single-screw extruders with a grooved feed section are being used. This is due to their constant conveying characteristics which aren’t being influenced by the extrusion die. Because of the highly specific throughputs of these high-speed extruders, mixing units are applied at the end of the screw to ensure thermal and material homogeneity of the melt. A great challenge here is the design of these mixing units under consideration of varying requirements, which are interacting with each other. Therefore, a pure experimental evaluation of mixing elements is very time-consuming and cost-intensive. Also, the experimental setup does not allow a detailed insight into the mixing processes. In that case, the mixing unit represents a black-box which responds incalculably to any changes in the process or to modifications to the processed material properties. The computational fluid dynamics simulation is an alternative to the pure experimental design of mixing units. Regrettably, the existing methods for the prediction of the mixing quality have substantial shortcomings, which make the virtual design impossible. This fact has been verified in the literature as well as in own preliminary studies. In recent years, further research has been carried out at the applicant's research institute on the current state of the art, so that new and verified simulation models are now available that allow a holistic view of the mixing process in terms of distributive and dispersive mixing capability.The objective of this research project is to provide a tool which automatically optimizes a mixing geometry in regard to the distributive and dispersive mixing performance within a profitable time frame. Beside the mixing performance, flow and thermal properties such as pressure drop, residence time and melt temperature will be influencing the optimization as well. During an extensive validation of the optimization tool within a particular experimental setup, the validity of the simulation tool will be verified under different conditions. This experimental setup additionally enables a local evaluation of the mixing quality inside the mixing unit. Finally, this new approach will be compared to conventional alternatives and its advantages and disadvantages will be worked out.

在各种延伸线的聚合物处理过程中，使用越来越多的单螺钉挤出机带有凹槽的进料部分。这是由于它们不断传达的特征不受扩展模具的影响。由于这些高速挤出机的高度特异性吞吐量，在螺钉末端使用混合单元，以确保熔体的热和材料均匀性。这里的一个巨大挑战是，这些混合单元的设计正在考虑各种要求，它们相互交互。因此，对混合元件的纯实验评估非常耗时且成本密集。同样，实验设置不允许对混合过程有详细的了解。在这种情况下，混合单元代表一个黑框，该黑盒对过程中的任何变化或修改材料属性的响应不足。计算流体动力学模拟是混合单元纯实验设计的替代方法。遗憾的是，预测混合质量的现有方法具有实质性的缺点，这使虚拟设计变得不可能。在文献以及自己的初步研究中已经验证了这一事实。近年来，在申请人的研究研究所就艺术的现状进行了进一步的研究，因此现在可以使用新的和经过验证的仿真模型，可以从分布式和分散性混合能力方面对混合过程进行整体视图。该研究项目的目标是为在分布式和分布式中的混合过程中自动提供了在杂种中的优化，可以在杂乱无章的范围内进行既定的时间范围均可进行辅助效果。在混合性能之外，流量和热特性（例如压降，停留时间和熔体温度）也将受到优化的影响。在特定实验设置中对优化工具进行广泛验证时，将在不同条件下验证仿真工具的有效性。这种实验设置还可以对混合单元内的混合质量进行本地评估。最后，将这种新方法与常规替代方案进行比较，其优势和缺点将被解决。