Multiscale Modeling and Analysis of Pressure Drop Contributions in Catalytic Filters

Abstract

Catalytic monolith filters with a honeycomb structure represent a key component of modern automotive exhaust gas aftertreatment systems. In this paper, we present and validate a multiscale modeling methodology for the prediction of filter pressure loss depending on the monolith channel geometry as well as the microscopic structure of the wall including catalytic coating. The approach is based on the combination of a 3D pore-scale model of flow through the wall reconstructed from X-ray tomography and a 1D+1D model of the filter channels. Several cordierite and SiC filter samples with varying substrate pore sizes and catalyst distributions are examined. A series of experiments are performed at different gas flow rates and filter lengths in order to validate the model predictions and to distinguish individual pressure drop contributions (inlet and outlet, channel, and wall). The predicted pressure drop shows a strong impact of the coating location and agrees well with the experiments.

Modeling the Catalytic Performance of Coated Gasoline Particulate Filters under Various Operating Conditions

“…where the local resistance coefficient ζ j is set to 1.25 according to Leskovjan et al 63 The heat transfer coefficient h is derived via the Nusselt correlation of Bissett et al 61 The porous medium is assumed as homogeneous, and the ideal gas law is used. All material properties, for example, viscosity, heat capacity, or diffusion coefficients, are calculated with correlations from the VDI Heat Atlas.…”

“…The permeability k w is fitted to pressure drop measurements. The additional pressure loss due to expansion and contraction at the filter’s inlet and outlet is determined with eq . where the local resistance coefficient ζ j is set to 1.25 according to Leskovjan et al . The heat transfer coefficient h is derived via the Nusselt correlation of Bissett et al The porous medium is assumed as homogeneous, and the ideal gas law is used.…”

Developing a Coupled CFD Solver for Mass, Momentum and Heat Transport in Catalytic Filters

“…Replacing the catalytic converters and PM filters with a single device is cheaper, decreases the system heat losses and facilitates the CF regeneration in the presence of the catalyst. On the other hand, the overall CF performance strongly depends on the catalytic material distribution that has to be carefully optimized [3]. The catalytic material distribution can vary (i) on the pore scalethe deposition of the catalyst on or in the wall, c.f.…”

“…Such a multi-scale CFD framework has been recently developed in our laboratory [1,2,3]. Up to now, we assumed the system to be isothermal on all the scales of interest.…”

Applying 3D X-ray Microscopy to Model Coated Gasoline Particulate Filters under Practical Driving Conditions

“…This opens up the possibility to simulate the fluid flow, chemical reaction kinetics, or even filtration behavior by means of three-dimensional (3D) computational fluid dynamics (CFD) approaches. For flow behavior with focus on pressure drop and permeability, XRM scans can be analyzed by 3D CFD. − Kočí et al . and Greiner et al introduced such a methodology for a pore-scale simulation of flow, diffusion, and reaction in a coated catalytic filter.…”