Smart Filter Media in Gas-Particle-Filtration: Fundamental investigations with stretchable filters

深度过滤通常用于去除空调和洁净室技术等各种应用领域的颗粒物。表征深度过滤器运行性能的主要因素是分离效率、压降和负荷能力。在典型的深度过滤器中，过滤系统的压降随着过滤器中沉积颗粒质量的增加而增加。这种效果尤其是在“堵点”之后发生的。随着压降的增加，能耗也随之增加。为了延缓陡峭的过滤，需要更多的空隙，特别是在过滤器的上游部分。为新颗粒腾出空间的一种可能性是释放过滤器中堵塞的气孔。实现这一点的一种方法是拉伸整个过滤器结构或单独的纤维。通过使用这种对结构的适应，可以清理一些空白空间。整个项目的目的是研究可伸缩收集器的重新排列和分离过程，该收集器暴露在工作速度下的流动中。在该项目的第一阶段，设计和制造了一种新的光纤安装设备，以检查单纤维(微观水平)的研究。初步测试了纤维的伸长速度和气流速度(表观速度)的影响。此外，还可以确定几个拉伸循环对剥离行为和颗粒结构尺寸的影响。基于观察到的颗粒结构在纤维上的重新排列和脱离，发展了加载高度、碎片长度和应力状态之间的理论依赖的基本方法和新的DEM模型。第二个项目阶段的重点是将这些关于重排和分离过程的研究从微观层面(单纤维)转移到细观层面(纤维阵列)。因此，第二阶段开始于原子力显微镜测量颗粒与纤维之间的粘附力(S)，以及不同材料的颗粒与颗粒之间的粘附力。将研究不同拉伸状态下颗粒与纤维之间粘附力的变化(S)。实测值被整合到DEM模型中。为了观察和量化光纤阵列处的过程，将进行用于多角度观察堵塞结构内的空隙形成的设备的组装。随后，研究了纤维阵列中颗粒结构的堵塞点和演化过程。然后，在纤维阵列上改变表面流速、纤维伸长速度、纤维间距和流入方向等工艺参数。最后，对单光纤和光纤阵列的实验结果进行了总结，并对未来的自适应整体滤波器值的传递进行了展望。

Depth filtration is commonly used for particulate matter removal in various fields of applications such as air-conditioning and cleanroom technology. The primary factors to characterize the operational behavior of depth filters are separation efficiency, pressure drop and loading capacity. In typical depth filters the pressure drop across the filter system rises with increasing deposited particulate mass in the filter. This effect occurs especially after the "clogging point". The increase in pressure drop is followed by an increase of energy consumption. In order to delay the steep, more void space especially at the upstream part of in the filter is needed. A possibility to clear up space for new particles would be to release blocked pores in the filter. One way to achieve this would be to stretch the entire filter structure or the individual fibers. By using this adaption for the structure some void space could be cleared. The aim of the overall project is to investigate the re-arrangement and detachment processes from a stretchable collector, which is exposed to a flow at operational velocity.In the first phase of the project, measurement equipment a new fiber-mounting device was designed and built to examine investigations on a single fiber (micro level). Initial tests were performed on the influence of the elongation velocity of the fiber and the airflow velocity (superficial velocity). Furthermore, the influence of several stretching cycles on the detachment behavior and the size of particle structures could be determined. Based on the observed re-arrangement and detachment of particle structures on/from the fiber, basic approaches of a theoretical dependence and a newly DEM-model between loading height, fragment length and stress state were developed. The focus of the second project phase is to transfer these investigations about the re-arrangement and detachment process from the micro level (single fiber) to the meso (fiber array). Thus, the second phase starts with AFM measurements of adhesion forces between particles and fiber(s), as well as particles and particles of different materials. The change of the adhesion force between particle and fiber(s) in different stretching states will be investigated. The measured values are integrated in the DEM model. In order to observe and quantify the processes at the fiber array, a build-up of the equipment for a multi-perspective observation of the formation of voids within the clogged structures will be executed. In the following, the clogging point and evolution of particle structure at the fiber array is investigated. Afterwards, process parameters such as superficial flow velocity, fiber elongation velocity, fiber spacing and inflow direction are varied at the fiber array. Finally, a summary of the results of the single fiber and fiber array is given, as well as a transfer of values for a future adaptive overall filter.