Simulation and modelling of the pressure drop in industrial polymer melt filters depending on different process conditions and their contamination

挤出是聚合物加工中最常用的方法之一。聚合物加工的主要要求之一是最终产品的稳定质量。这种质量直接取决于挤出过程中的熔体质量。在加工过程中，有多种可能性将污染物带入挤出生产线。这些污染物会对熔体质量产生负面影响。由于当今对挤出产品的高要求，熔体过滤被广泛应用于纤维和薄膜挤出领域。聚合物熔体过滤器的技术设计，对所产生的压降和过滤元件的污染行为的了解是优化加工和高质量挤出产品的基础。在实践中，过滤系统通常是基于长期经验设计的。压力损失的计算通常是基于多孔介质的一般计算，本研究的主要目的是借助CFD模拟小尺度的聚合物熔体过滤器在挤出过程中的流动情况。这个小规模然后应该外推到相关的大小。在这种情况下，中心目标值是过滤介质的最终压力损失。聚合物的剪切稀化行为也应考虑在内。对于这项调查，不同过滤介质的几何数据应创建CAD格式。然后将这些数据移交给CFD模拟，以计算通过过滤介质的压降。这些模拟将在实验研究的基础上进行验证和优化，以获得通过过滤介质的压降的真实计算。第二步，应使用固体颗粒分析过滤器的污染。为此，应通过使用DEM模拟来计算颗粒在过滤介质中的沉积行为。过滤器区域的所得新流动横截面应返回到CFD压降模拟。这样，污染行为和由此产生的过滤器上的压力增加就可以通过模拟来表示。在研究项目结束时，应该分析是否可以模拟软污垢颗粒（所谓的凝胶）对过滤器的污染。为此，应研究凝胶颗粒的行为是否可以用DEM模拟来模拟。然后，在所要求的研究项目的可能扩展期间，可以对凝胶颗粒污染过滤器的模拟和实验研究进行调查。

Extrusion is one of the most common methods in polymer processing. One of the main requests of polymer processing is a steady quality of the final product. This quality directly depends on the melt quality in the extrusion process. During processing there are multiple possibilities of bringing in a contamination into the extrusion line. These contaminations can negatively affect the melt quality. Because of todays high requirements to extrusion products, melt filtration is widely used especially in the field of fiber- and filmextrusion.The technical design of polymer melt filters, the knowledge of the resulting pressure drop and the soiling behavior of filter elements are basics for optimal processing and high quality extrusion products. In practice, filter systems are often designed based on long time experience. The calculations of pressure loss are usually based on general calculations of porous media.The primary objective of this research project is to map the flow situation of a polymer melt filters during the extrusion process with the help of CFD simulations an a small scale. This small scale should then be extrapolated to relevant sizes. The central target value in this case is the resulting pressure loss of the filter medium. The shear thinning behavior of polymers should also be taken into account.For this investigation geometric data of different filter mediums shall be created in CAD format. This data should then be handed over to CFD simulations for calculating the pressure drop of through the filter medium. These simulations will be validated and optimized based on experimental studies in order to obtain a realistic calculation of the pressure drop through a filter medium.In the second step, the contamination of a filter should be analyzed by using solid particles. For this purpose, the deposition behavior of the particles in the filter medium should be calculated by using a DEM simulation. The resulting new flow cross section of the filter area should be passed back to the CFD pressure drop simulation. By this, the soiling behavior and the resulting increase in pressure on the filter can be represented by the simulation.At the end of the research project it should be analyzed if it is possible to simulate a filter contamination with soft dirt particles, so called gels. For this it should be investigated whether the behavior of gel particles can be simulated with a DEM simulation. The simulation and experimental study of soiling a filter with gel particles can then be investigated during a possible extension of the requested research project.