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RESEARCH PAPERS: Processes Equipment and Devices

Modeling Full-Scale Monolithic Catalytic Converters: Challenges and Possible Solutions

[+] Author and Article Information
Sandip Mazumder

Department of Mechanical Engineering, The Ohio State University, Columbus, OH 43210mazumder.2@osu.edu

J. Heat Transfer 129(4), 526-535 (Jul 24, 2006) (10 pages) doi:10.1115/1.2709655 History: Received March 27, 2006; Revised July 24, 2006

Modeling full-scale monolithic catalytic converters using state-of-the-art computational fluid dynamics algorithms and techniques encounters a classical multiscale problem: the channels within the monolith have length scales that are 1–2 mm, while the converter itself has a length scale that is 5–10 cm. This necessitates very fine grids to resolve all the length scales, resulting in few million computational cells. When complex heterogeneous chemistry is included, the computational problem becomes all but intractable unless massively parallel computation is employed. Two approaches to address this difficulty are reviewed, and their effectiveness demonstrated for the computation of full-scale catalytic converters with complex chemistry. The first approach is one where only the larger scales are resolved by a grid, while the physics at the smallest scale (channel scale) are modeled using subgrid scale models whose development entails detailed flux balances at the “imaginary” fluid–solid interfaces within each computational cell. The second approach makes use of the in situ adaptive tabulation algorithm, after significant reformulation of the underlying mathematics, to accelerate computation of the surface reaction boundary conditions. Preliminary results shown here for a catalytic combustion application involving 19 species and 24 reactions indicate that both methods have the potential of improving computational efficiency by several orders of magnitude.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Monolithic core of a catalytic converter

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Figure 2

The various length scales within a monolithic catalytic converter (cross-sectional view shown in figure), their relationship, and the idea behind the subgrid scale modeling approach

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Figure 3

Procedure for determining the diffusion length scale, δ

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Figure 4

Procedure for determining the effective surface to volume ratio (S∕V)eff

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Figure 5

Geometry and boundary conditions for the full-scale catalytic converter modeled using the subgrid scale approach.

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Figure 6

Flow and temperature distributions in a full-scale catalytic converter modeled using the subgrid scale approach

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Figure 7

Mass fractions of one of the reactants (CH4) and products (CO2) and the site fraction of platinum

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