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Novel catalytic coatings with a variety of methods based on conventional and novel synthesis routes are developed for Diesel Particulate Filters (DPFs). The developed catalytic composition exhibits significant direct soot oxidation as evaluated by reacting mixtures of diesel soot and catalyst powders in a thermogravimetric analysis apparatus (TGA). The catalyst composition was further deposited on oxide and non-oxide porous filter structures that were evaluated on an engine bench with respect to their filtration efficiency, pressure drop behavior and direct soot oxidation activity under realistic conditions. The effect of the catalyst amount on the filtration efficiency of non-oxide filters was also investigated. Evaluation of the indirect soot oxidation was conducted on non-oxide catalytic filters coated with precious metal.

A new platform of advanced ceramic composite filter materials for diesel particulate matter and exhaust gas emission control has been developed. These materials exhibit high porosity, narrow pore-size distribution, robust thermo-mechanical strength, and are extruded into high cell density honeycomb structures for wall-flow filter applications. These new high porosity filters provide a structured filtration surface area and a highly connected wall pore space which is fully accessible for multi-phase catalytic reactions. The cross-linked microstructure (CLM™) pore architecture provides a large surface area to host high washcoat/catalyst loadings, such as those required for advanced multi-functional catalysts (4-way converter applications).

In the present work we apply a computational simulation framework developed for square-cell shaped honeycomb Diesel Particulate Filters to study the filtration, pressure drop and soot oxidation characteristics of recently developed triangular-cell-shaped, high porosity wall-flow filters. Emphasis is placed on the evaluation of the applicability and adaptation of the previously developed models to the case of triangular channels. To this end Computational Fluid Dynamics, asymptotic analysis, multichannel and “unit-cell” calculations are employed to analyze filter behavior and the results are shown to compare very well to experiments available in the literature.

Despite the great effort devoted to the modeling of the operation of catalytic DPFs, even today very simple expressions are used for the soot oxidation rate. In the relevant to DPF operation case of a gas phase rich in oxygen, the structure of the soot-catalyst geometry and its evolution during oxidation determines the reaction rate. An extensive set of controlled experiments (isothermal or with linear temperature increase) using fuel borne catalysts and catalytic coatings has been performed in order to obtain corresponding soot oxidation rate-conversion curves. The shape of the resulting curves cannot be described by the typical theories for solid phase reactions posing the need for microstructural models for the micromechanics of soot catalyst interactions.

This paper describes work supporting the development of a new Diesel particulate trap system for heavy duty vehicles based on porous sintered metal materials that exhibit interesting characteristics with respect to ash tolerance. Experimental data characterizing the material (permeability, soot and ash deposit properties) are obtained in a dedicated experimental setup in the side-stream of a modern Diesel engine as well as in an accelerated ash loading rig. System level simulations coupling the new media characteristics to 3-D CFD software for the optimization of complete filter systems are then performed and comparative assessment results of example designs are given.

As use of Particulate Filters (PFs) is growing not only for diesel but also for gasoline powered vehicles, the need for better understanding of deposit structure, growth dynamics and evolution arises. In the present paper we address a number of deposit growth and restructuring phenomena within particulate filters with the aim to improve particulate filter soot load estimation. To this end we investigate the dynamic factors that quantify the amount of particles that are stored within the wall and the restructuring of soot deposits. We demonstrate that particle accumulation inside the porous wall is dynamically controlled by the dimensionless Peclet number and provide a procedure for the estimation of parameters of interest such as the loaded filter wall permeability, the wall-stored soot mass at the onset of cake filtration.

Improved understanding and compact descriptions of the pressure drop evolution of Particulate Filters (both for diesel and gasoline powered vehicles) are always in demand for intelligent implementations of exhaust emission system monitoring and control. In the present paper we revisit the loading process of a particulate filter focusing on a parametric description of the deep bed-to-cake transition in the light of recent progress in the understanding of soot deposit structure, growth dynamics and evolution. Combining experimental data, simulation models and information theoretic concepts we provide a closed-form representation of the entire evolution of pressure drop (from the initial clean state up to the evolving linear cake growth regime) parameterized in terms of the physical parameters of the system (filter and particle structure/geometry and flow properties).