Automated design and optimisation of dynamic mixing and shear elements for single-screw extruder

混合和剪切元件越来越多地用于单螺杆挤出机，因为在保持塑料熔体均匀性的同时需要更高的吞吐量。混合和剪切元件的任务是在塑料熔体中均匀分散和分布添加剂和填料，并使熔体热均匀化。迄今为止，混合元素的设计是基于设计师的经验。相比之下，通过三维模拟可以更详细地了解混合过程。然而，用于计算挤出机混合操作的现有方法往往有很大的局限性，并且通常仅用于单个混合元件的示例性评估。困难一方面在于选择合适的混合指标。另一方面，在混合元素的数值优化上付出的巨大努力阻碍了在设计阶段使用流动模拟。到目前为止，还没有软件可以自动优化混合元素。在此背景下，该项目的目标是开发一个优化框架，使单螺杆挤出机的混合和剪切元件的自动化模拟设计和优化成为可能。有了这个框架，就可以了解理想的混合元件几何形状与混合任务的关系。为此，将对申请人CATS现有的内部流动求解器进行修改，以便能够对挤出机熔体区的混合过程进行非等温模拟。然后将修改后的求解器集成到优化例程中。同时，IKV将通过对模拟结果和实验参考数据的比较，为复杂混合元素的真实三维模拟确定合适的边界条件。下一步，IKV将模拟比较不同的混合指标，并确定特别适合混合元件设计的指标。在优化框架中，这些混合指标被组合成一个单一的目标函数。此外，IKV将模拟分析和描述混合元件几何形状与产生的流动条件之间的因果关系。这种知识的获得将被纳入优化框架，并有助于识别将用于优化的合适混合元件部分。在其成功实施之后，优化框架将被IKV和CATS用于设计和优化混合元素序列，这适用于非常广泛的应用。开发的混合单元序列将最终被制造并用于优化框架的实际验证。

Mixing and shear elements are increasingly used in single-screw extruders due to the demand for ever higher throughputs while maintaining plastics melt homogeneity. The task of mixing and shear elements is to disperse and distribute additives and fillers evenly in the plastics melt and homogenise the melt thermally. To date, the design of mixing elements is based on the experience of the designer. By contrast, a much more detailed insight into the mixing process can be achieved via three-dimensional simulations. However, available approaches for the computation of mixing operations in extruders often have great limitations and are generally used only for exemplary evaluation of individual mixing elements. Difficulties arise on the one hand in the choice of a suitable mixing index. On the other hand, the high effort in the numerical optimisation of mixing elements is an obstacle to the use of flow simulations in the design phase. So far, there is no software for the automated optimisation of mixing elements available.Against this background, it is the goal of this project to develop an optimisation framework that enables the automated simulative design and optimisation of mixing and shear elements in single-screw extruders. With this framework knowledge about the ideal mixing element geometry in dependence of the mixing task will be acquired. For this purpose, the existing in-house flow solver of the applicant CATS will be modified in order to enable the non-isothermal simulation of the mixing processes in the melt zone of the extruder. The modified solver will then be integrated into an optimisation routine. Meanwhile, the IKV will identify suitable boundary conditions for a realistic three-dimensional simulation of complex mixing elements using a comparison of simulation results and experimental reference data. In the next step, the IKV will simulatively compare different mixing indexes and identify those indexes that are particularly well suited for the design of mixing elements. These mixing indexes are combined into a single objective function in the optimisation framework. In addition, the IKV will simulatively analyse and characterise the cause-effect relationships between the mixing element geometry and the resulting flow conditions. This gain in knowledge will be incorporated into the optimisation framework and facilitate the identification of suitable mixing element sections that will be enabled for the optimisation. Following its successful implementation, the optimisation framework will be used by IKV and CATS in order to design and optimise a mixing element sequence, which is suitable for a very wide range of applications. Thedeveloped mixing element sequence will finally be manufactured and used for the practical validation of the optimisation framework.