Simulation of Particle Structure Rearrangement and Reaction in Wall-Flow Filters at High Flow Velocities with Lattice Boltzmann Methods

Abstract

Abstract

Wall-flow filters are used in exhaust gas after treatment systems to reduce particulate matter emissions from internal combustion engines. The particles accumulate on the filter surface during operation, forming a layer that progressively increases the flow resistance and thus the pressure drop. This layer consists mostly of combustible materials but also contains inert ash parts. The pressure drop increase leads to the necessity of regenerating the filter. Filter regeneration may cause particle structure fragments to rearrange within single-filter channels, leading to specific ash deposition patterns that modify the filter’s pressure drop, loading behavior, and separation efficiency. This work advances previous investigations toward application-relevant temperature and inflow-velocity conditions by extending the existing resolved-particle methodology with turbulence and reaction models, enabling temperature-dependent effects on particle-structure fragments to be considered. The rearrangement process is studied in detail. It can be shown that at high velocity, most gas crosses into the outlet channel at the end of the inflow channel, leading to a pressure spike. A fragment-local reaction model was introduced and shows qualitative agreement with the experimental results. These simulations also showed a temperature difference of about 15 K between particles at the beginning and end of the inlet channel, leading to faster oxidation close to the inlet. The presented modeling approach helps to assess the formation of deposition patterns and their influence on filter behavior, engine efficiency, fuel consumption, and long-term filter durability.