Experimental investigation of formation mechanisms and rearrangement phenomena of reactive-inert particle layers in cross-flow filters in gas cleaning applications

横流或壁流过滤器是当今废气后处理的标准组件，通过去除灰尘和烟尘颗粒来减少内燃机的颗粒排放。在达到由于层形成而产生的临界压降后，过滤器被再生。烟尘颗粒通过连续(C-NO2)或不连续(O2)反应被氧化。这会导致层分解。颗粒结构可以沿着过滤通道分离和输送。在此过程中，均质层的沉积图案可导致沟道填充。颗粒层的破碎行为是一个决定性的过程，取决于颗粒层的组成和烟尘的反应性。整个项目的目标是对活性颗粒和惰性颗粒的颗粒层之间的关系、O2-期间颗粒结构的重排过程(层破裂-再悬浮-传输)以及模型过滤通道中基于NO2的再生进行结构化研究。在第一个项目阶段，开发了一个实验装置，可以在模型过滤通道中研究基于O2的再生过程中再悬浮颗粒结构的重排过程。用高速摄像机在整个流道长度上观测了团聚体层的破碎、再悬浮和输送过程，并从再悬浮位置、团聚体大小和速度等方面进行了分析。制定的方法和关于再悬浮过程的现有知识是在第二个供资期间确定的目标的基础。因此，第二个项目阶段的目标是从根本上调查烟尘反应性(高活性与低活性)和烟尘分散性以及氧化气体(NO2与O2)对壁流过滤器中重排过程的影响。所得结果随后被用来解释文献中的不一致之处，即在壁流过滤器中产生的沉积图案取决于所使用的氧化气体(连续再生(NO2)均质层；不连续再生(O2)通道填充)。提出的假设是，决定重排行为的不是氧化气体，而是基本的粒子技术过程。通过明确调整工艺参数(例如流速、温度)和生成已知组成的颗粒层(反应惰性比)，所获得的知识还可以扩展到其他应用领域，例如新开发的燃料，其烟尘反应性和废气中的烟尘浓度发生了变化。这提供了对灰尘和烟尘颗粒过滤过程的基本理解。

Cross-flow or wall-flow filters are nowadays a standard component in exhaust gas aftertreatment and reduce particulate emissions from internal combustion engines by removing ash and soot particles. After reaching a critical pressure drop due to the layer formation, the filter is regenerated. The soot particles are oxidized by a continuous (C-NO2) or discontinuous (O2) reaction. This results in a layer break-up. Particulate structures can be detached and transported along the filter channel. In this process, the deposition pattern of the homogenous layer can result in a channel filling. The break-up behavior of the particle layer is a decisive process that depends on the layer composition and the soot reactivity. The aim of the overall project consists of the structured investigation of the relationship be-tween the particle layer of reactive and inert particles and the rearrangement processes (layer break-up – resuspension - transport) of particulate structures during O2- as well as NO2-based regeneration in a model filter channel. In the first project phase, an experimental setup was developed in which the rearrangement processes of resuspended particulate structures during O2-based regeneration can be investigated in a model filter channel. The layer break-up, resuspension and transport of agglomerates is observed over the entire channel length with a high-speed camera and analyzed in terms of resuspension location, agglomerate size and velocity. The developed methods and existing knowledge on the resuspension processes serve as a basis for the objectives de-fined in the second funding period. The goal of the second project phase is therefore to fundamentally investigate the influence of soot reactivity (high reactive vs. low reactive) and soot dispersity as well as the oxidation gas (NO2 vs. O2) on the rearrangement processes in a wall-flow filter. The resulting findings are subsequently used to elucidate the inconsistency from the literature that the resulting deposition patterns in a wall-flow filter are dependent on the oxidation gas used (continuous regeneration (NO2) homogenous layer; discontinuous regeneration (O2) channel filling). The hypothesis is pursued that it is not the oxidation gas but the fundamental particle-technological processes that determine the rearrangement behavior. Through the defined adjustment of process parameters (e.g. flow velocity, temperature) and the generation of particle layers with known composition (reactive inert ratio), the knowledge obtained can also be extended to other fields of application, e.g. newly developed fuels with altered soot reactivities and soot concentrations in the exhaust gas. This provides a fundamental understanding of the processes occurring during the filtration of ash and soot particles.