Fundamental investigation of particle-layer rearrangement events in ceramic wall flow filters by resolved particle simulations

• Applicant: Privatdozent Dr. Mathias Joachim Krause
• Subject Area: Mechanical Process Engineering
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 422374351

Cross or wall-flow filters are used in the exhaust gas aftertreatment of internal combustion engines. Soot is deposited in the filter and removed from it by regeneration through oxidation. Over long-term operation, an inert fraction remains in the filter and is deposited in the filter in form of different deposition patterns. The type pattern type influences the pressure drop and separation behavior of the filter. To date, it is not understood in detail how those patterns are created and which influencing factors are relevant for this process and to what extent. The aim of the overall project is to predict the deposition patterns that occur during the filtration process as a function of influencing factors relevant in an engineering context and to derive operating strategies with which wall-flow filters can be operated in accordance with the desired target quantities in such a way that maximum service life can be achieved by specifically minimizing the pressure loss. For this purpose, surface-resolved particle simulations were carried out in the first project phase using the Lattice Boltzmann method based on a model developed for this purpose. This model was used to investigate layer breakup, resuspension and transport of individual particle agglomerates for lower operating limits. In a second project phase, the model was then extended and applied for the systematic and isolated linking of relevant input parameters and resulting target variables. Furthermore, an intensive examination of the results of an experimental partner project took place. It turns out that the stability of the simulations with the existing model cannot be guaranteed over the entire range of relevant gas velocities. Furthermore, a global consideration of the oxidation reaction leads to an artificial acceleration of the rearrangement processes. Comparisons with literature data could only be implemented to a limited extent due to different scales between documented integral measurement quantities and local effects. The goal of the third project phase is therefore to extend the model to take into account higher Reynolds numbers as well as local oxidation reactions on several scales. Further parameter studies over the full application-relevant operating range are planned in order to achieve greater accordance with real-world applications. This results in new knowledge about reproducible possibilities of influencing the filtration process in wall-flow filters. Thus, the overall project contributes to ensuring efficient filtration behavior with a long filter service life while optimizing sustainability and environmental impact.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Achim Dittler