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This paper describes an analytical and a numerical study of wall-flow filters with equilateral triangular channels. The flow fields of these filters are modeled analytically using a one-dimensional approach, and also simulated numerically using a three-dimensional approach. The flow distributions and pressure drops are presented and discussed in this paper. The results are also compared with experimental data. Among some interesting findings, re-circulation regions are observed in the areas near the filter entrance behind each front plug of outlet channels, and near the filter exit in front of and also behind each rear plug of inlet channels. Uneven distribution of wall flow velocity across the porous media is also observed. Pressure drop as a function of the Reynolds number, media permeability and inertial resistance coefficient, channel width, and channel length is discussed in this study.

A ceramic composite filter has been developed which uses depth filtration for particle capture. The advantages of composite fiber-based filtration are presented as part of an overview of filtration mechanisms. Next, base media and material issues are discussed along with materials development. Once a stable base media formulation was determined, robust design and statistical tolerancing methods were applied as part of a design for six sigma (DFSS) methodology to determine the optimal filter cell geometry. These methods were also used to assess the impact various component tolerances had on overall filter pressure drop and their potential impact to manufacturing. Next, the composite filter initial performance was compared to commercially available filters as part of a benchmarking study. Filter performance with respect to soot capacity, filtration efficiency, pressure drop, weight, catalyzation, and durability was evaluated.

Much attention has been paid to the effect different catalyst formulations have on conversion efficiency. However, the role of the catalyst support structure has not been investigated. The purpose of this study is to investigate the effect that the catalyst support structure has on gas phase conversion efficiency. Understanding this effect is important in the assessment of the practicality of 4-way diesel exhaust emission control based on current, commercially available, technologies. This investigation begins with an analysis of the mass transfer properties of flow-through and wall-flow style honeycomb materials. Next, chemical reaction kinetics are discussed and theoretical models are developed for both structures. Results of the analysis presented in this paper conclude that flow-through type structures have better conversion efficiency than wall-flow style supports due to increased reaction residence time.

The monolithic, large frontal area (LFA), extruded ceramic substrates for diesel flow-through catalysts offer unique advantages of design versatility, longterm durability, ease of packaging and low Cost [1, 2]*. This paper examines the effect of cell density and cell size on catalyst light-off performance, back pressure, mechanical and thermal durability, and the steady-state catalytic activity. The factors which affect these performance characteristics are discussed. Certain trade-offs in performance parameters, which are necessary for optimum systems design, are also discussed. Following a brief discussion of design methodology, substrate selection, substrate/washcoat interaction and packaging specifications, the durability data for ceramic flow-through catalysts are summarized. A total of over 18 million vehicle miles have been successfully demonstrated by ceramic LFA catalysts using the systems design approach.