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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Modifying the Classical One-Dimensional Catalyst Model to Include Axial Conduction and Diffusion

[+] Author and Article Information
Sudarshan Loya

University of Kansas,
Lawrence, KS 66045
e-mail: skloya31@ku.edu

Christopher Depcik

University of Kansas,
3144C Learned Hall,
1530 W. 15th Street,
Lawrence, KS 66045
e-mail: depcik@ku.edu

Contributed by the Combustion and Fuels Committee of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received April 23, 2013; final manuscript received May 2, 2013; published online August 19, 2013. Editor: Davis Wisler.

J. Eng. Gas Turbines Power 135(9), 091506 (Aug 19, 2013) (8 pages) Paper No: GTP-13-1108; doi: 10.1115/1.4024421 History: Received April 23, 2013; Revised May 02, 2013

Abstract

Lean NOx trap (LNT) catalytic aftertreatment devices are one potential option for the reduction of oxides of nitrogen (NOx) in the exhaust of compression ignition engines. They work through a controlled modulation between a storage phase that captures NOx over an alkali earth metal and a regeneration phase that reduces the stored nitrates on the surface using a rich pulse of injected fuel or via stoichiometric engine operation. This rich phase has an associated fuel penalty while being relatively difficult to control through temperature and chemical species. In order to improve system efficiency, a number of researchers have proposed dual leg LNT systems using two LNTs, one of which is always storing while the other is undergoing regeneration. The majority of the exhaust flows through the storage LNT while only a small fraction (low space velocity) advects across the regeneration LNT. This increases the regeneration residence time, improving effectiveness and decreasing the amount of fuel used. From an LNT simulation standpoint, most researchers utilize the classical one-dimensional (1D) aftertreatment model constructed from the Euler equations of motion that neglect axial conduction and diffusion. This paper explores the applicability of this model under low flow situations prevalent in a dual leg LNT system through a carbon monoxide light-off experiment. The authors chose this type of experiment in order to focus purely on fluid mechanics and not the choice of LNT reaction mechanism. The results suggest that a Navier–Stokes (N–S) version of the 1D aftertreatment model is preferred for the regeneration leg of a dual LNT system. Moreover, the authors provide the solution of such a model within this paper.

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Figures

Fig. 1

Dual path system for parallel LNT storage and regeneration [7]

Fig. 2

Classical 1D catalyst model description [18,20]

Fig. 3

Comparison of the classical and modified 1D model conversion curves for CO oxidation

Fig. 4

Simulation of the 0.1% CO conversion at various velocities

Fig. 5

Simulation of the 0.01% CO conversion at various velocities

Fig. 6

Computational time for both of the models for different nodes in 0.01% CO oxidation simulation

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