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Research Papers

Estimation of Ammonia Storage Nonuniformity for Urea-Based Selective Catalytic Reduction Systems

[+] Author and Article Information
Qinghua Lin

Department of Mechanical Engineering,
Tennessee Technological University,
Cookeville, TN 38505

Pingen Chen

Department of Mechanical Engineering,
Tennessee Technological University,
Cookeville, TN 38505
e-mail: pchen@tntech.edu

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT,AND CONTROL. Manuscript received May 2, 2018; final manuscript received November 23, 2018; published online January 7, 2019. Assoc. Editor: Mahdi Shahbakhti.

J. Dyn. Sys., Meas., Control 141(4), 041014 (Jan 07, 2019) (10 pages) Paper No: DS-18-1214; doi: 10.1115/1.4042143 History: Received May 02, 2018; Revised November 23, 2018

Ammonia storage nonuniformity has a significant impact on the emission reduction performance of urea-based selective catalytic reduction (SCR) systems. In this paper, a unique SCR platform with two catalysts in a parallel configuration was created for investigating the impact of ammonia storage nonuniformity on the emission reduction performance in a simulation environment. The established two-cell SCR platform allows users to independently control the ammonia-to-NOx ratio (ANR) for each catalyst using two independent urea solution injectors. Simulation results over US06 cycle demonstrate that, compared to the case without ammonia storage nonuniformity, the tailpipe NOx and ammonia emissions can be increased by 6.73% and 22.0%, respectively, due to the nonuniform ammonia storage in the case of an ANR nonuniformity index (NUI) at 0.2. Furthermore, an innovative model-based method was proposed for estimating the ammonia coverage ratio nonuniformity (i.e., ammonia storage nonuniformity if storage capacity is known) by utilizing a control-oriented SCR model and the tailpipe NOx and ammonia measurements at the confluence point. Simulation results proved the effectiveness of the proposed method in estimating the ammonia coverage ratio nonuniformity.

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References

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Figures

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Fig. 1

Schematic of two-cell SCR system for simulation of ANR nonuniformity

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Fig. 2

Rich and lean ammonia storage zones in the SCR system

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Fig. 3

Exhaust temperature and flow rate over US06 cycle

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Fig. 4

O2 and NOx concentrations at SCR inlet over US06 cycle

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Fig. 5

Ammonia concentration input for cell 1, cell 2, and baseline cell over US06 cycle

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Fig. 6

Comparison of tailpipe NOx concentrations with and without ammonia storage nonuniformity over US06 cycle

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Fig. 8

Comparison of tailpipe NH3 concentrations with and without ammonia storage nonuniformity over US06 cycle

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Fig. 9

Comparison of instantaneous and cumulative tailpipe NOx concentrations with and without ammonia storage nonuniformity over US06 cycle

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Fig. 10

Comparison of instantaneous and cumulative tailpipe NH3 concentrations with and without ammonia storage nonuniformity over US06 cycle

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Fig. 11

Comparison of ammonia coverage ratio with and without ammonia storage nonuniformity over US06 cycle

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Fig. 12

Exhaust temperature and flow rate from 600th second to 1800th second in FTP cycle

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Fig. 13

O2 and NOx concentrations at SCR inlet over FTP cycle

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Fig. 14

Comparison of tailpipe NOx concentrations with and without ammonia storage nonuniformity over FTP cycle

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Fig. 15

Comparison of tailpipe NH3 concentrations with and without ammonia storage nonuniformity over FTP cycle

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Fig. 16

Comparison of instantaneous and cumulative tailpipe NOx emissions with and without ammonia storage nonuniformity over FTP cycle

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Fig. 17

Comparison of instantaneous and cumulative tailpipe NH3 emissions with and without ammonia storage nonuniformity over FTP cycle

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Fig. 18

Comparison of ammonia coverage ratio with and without ammonia storage nonuniformity over FTP cycle

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Fig. 19

NO and NH3 concentrations at SCR outlet at point D over US06 cycle

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Fig. 20

θ estimation and model results in cell 1, cell 2, and baseline over US06 cycle

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Fig. 21

Comparison of estimated and actual NUIs of ammonia coverage ratio over US06 cycle

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Fig. 22

NO and NH3 concentrations at SCR outlet at point D over FTP cycle

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Fig. 23

θ estimation and model results in cell 1, cell 2, and baseline over FTP cycle

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Fig. 24

Comparison of estimated and actual NUIs of ammonia coverage ratio over FTP cycle

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