Browse Publications Technical Papers 2003-01-0841
2003-03-03

A One-Dimensional Computational Model for Studying the Filtration and Regeneration Characteristics of a Catalyzed Wall-Flow Diesel Particulate Filter 2003-01-0841

A one-dimensional, two layer computational model was developed to predict the behavior of a clean and particulate-loaded catalyzed wall-flow diesel particulate filter (CPF). The model included the mechanisms of particle deposition inside the CPF porous wall and on the CPF wall surface, the exhaust flow field and temperature field inside the CPF, as well as the particulate catalytic oxidation mechanisms accounting for the catalyst-assisted particulate oxidation by the catalytic coating in addition to the conventional particulate thermal oxidation. The paper also develops the methodology for calibrating and validating the model with experimental data.
Steady state loading experiments were performed to calibrate and validate the model. The experimental data were collected on a Corning EX-80 cordierite filter (100 cpi) with a loading of 5-g/ft3 Pt in the MEX catalyst type formulation using a 1995 Cummins M11-330E heavy-duty diesel engine with manual EGR and conventional low sulfur fuel (375 ppm sulfur). Good agreement was obtained between the model predictions for pressure drop, particulate mass filtration efficiency, particulate mass retained, and filter temperature profile.
The model was also used with experimental data to estimate the filter clean wall permeability, the packing density of the particulate deposited inside the filter wall, the particulate layer packing density, porosity, and permeability, as well as the activation energy and frequency factor of the particulate thermal and catalytic oxidation, including the maximum thickness of the particulate layer in contact with the catalyst. The particulate layer packing density, porosity, and permeability were then correlated with the exhaust gas Peclet number to provide a better understanding of particulate properties under various engine loads.
This model can be used as a tool to predict the pressure drop across the CPF, the particulate mass filtration efficiency, the downstream particulate concentration, and the particulate mass retained inside the CPF for different filter geometries and physical properties, as well as for different engine operating conditions. In conjunction with designed experiments, the model can also be utilized to characterize (by determing the model constants) catalyzed particulate filters with different catalysts and catalyst loadings.

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