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Research Papers

Adaptive and Efficient Ammonia Storage Distribution Control for a Two-Catalyst Selective Catalytic Reduction System

[+] Author and Article Information
Ming-Feng Hsieh

Junmin Wang

 Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210wang.1381@osu.edu

J. Dyn. Sys., Meas., Control 134(1), 011012 (Dec 05, 2011) (11 pages) doi:10.1115/1.4005372 History: Received April 15, 2010; Accepted September 14, 2011; Published December 05, 2011; Online December 05, 2011

This paper presents an adaptive urea-SCR dosing control design for a two-catalyst SCR system. A novel SCR ammonia storage distribution control (ASDC) approach aiming to simultaneously increase the SCR NOx conversion efficiency and reduce the tailpipe ammonia slip was proposed and experimentally validated. Based on the insight into SCR operational principles, a high ammonia storage level at the upstream part of the catalyst can generally yield a higher NOx reduction efficiency while a low ammonia storage level at the downstream part of the catalyst can reduce the undesired tailpipe ammonia slip. To achieve such an ammonia storage distribution control, a two-catalyst (in series) SCR system with NOx and NH3 sensors was devised. Grounded in a newly developed SCR control-oriented model, an adaptive (with respect to the SCR ammonia storage capacity) controller was designed to control the urea injection rate for achieving different ammonia storages in the two catalysts. Experimental data from a US06 test cycle conducted on a medium-duty Diesel engine system showed that, with the similar total engine-out NOx emissions and NH3 (AdBlue) consumptions, the proposed ASDC strategy simultaneously reduced the tailpipe NOx emissions by 57% and the ammonia slip by 74% in comparison to those from a conventional controller.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic presentation of ammonia storage distribution control strategy

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Figure 2

Schematic presentation of the controller architecture

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Figure 12

Ammonia coverage ratios of the two SCR catalysts in the US06 cycle test

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Figure 13

Measured NOx and NH3 concentrations before, between, and after the SCR catalysts in the US06 cycle test

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Figure 14

Measured ammonia slip between the two SCR catalysts and downstream of the SCR catalysts (tailpipe) in the US06 cycle test

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Figure 15

NOx and NH3 concentrations before, between, and after the SCR catalysts in the US06 cycle test controlled by the LSCC

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Figure 16

Ammonia slip between the two SCR catalysts and downstream of the SCR catalysts (tailpipe) in the US06 cycle test controlled by the LSCC

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Figure 17

Comparisons of ammonia coverage ratios controlled by the two different controllers in the US06 cycle tests

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Figure 18

Comparisons of NOx concentrations of the two controllers in the US06 cycle tests

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Figure 19

Comparisons of NH3 concentrations of the two controllers in the US06 cycle tests

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Figure 20

Comparison of cumulative NH3 consumption and tailpipe NOx and NH3 emissions from the 155th s

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Figure 3

Simulation results of the ammonia coverage ratios controlled by the proposed control law based on a US06 test cycle

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Figure 4

Simulation results of the NOx and ammonia concentrations before, between, and after the SCR catalysts

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Figure 5

Zoom-in of the high NOx emission regions

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Figure 6

Schematic presentation of the experimental setup

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Figure 7

Diesel engine and aftertreatment system test bench

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Figure 8

Engine operating condition and SCR catalyst temperatures in the test of Figs.  1011

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Figure 9

Engine operating condition and SCR catalyst temperatures in the US06 cycle test

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Figure 10

Ammonia coverage ratios of the upstream catalyst (theta 2) and the downstream catalyst (theta 1)

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Figure 11

NOx and NH3 concentrations upstream, between, and downstream of the SCR catalysts

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