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Research Papers

# Coordinated Active Thermal Management and Selective Catalytic Reduction Control for Simultaneous Fuel Economy Improvement and Emissions Reduction During Low-Temperature Operations

[+] Author and Article Information
Pingen Chen

Department of Mechanical and
Aerospace Engineering,
The Ohio State University,
Columbus, OH 43210

Junmin Wang

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

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received March 6, 2015; final manuscript received July 17, 2015; published online September 2, 2015. Assoc. Editor: Zongxuan Sun.

J. Dyn. Sys., Meas., Control 137(12), 121001 (Sep 02, 2015) (11 pages) Paper No: DS-15-1092; doi: 10.1115/1.4031133 History: Received March 06, 2015; Revised July 17, 2015

## Abstract

The low-temperature operations of diesel engines and aftertreatment systems have attracted increasing attention over the past decade due to the stringent diesel emission regulations and excessive tailpipe emissions at low temperatures. The removal of NOx emissions using selective catalytic reduction (SCR) systems during low-temperature operations remains a significant challenge. One of the popular techniques for alleviating this issue is to employ active thermal management via in-cylinder postinjection to promote aftertreatment system temperatures. Meanwhile, numerous studies have focused on ammonia coverage ratio controls with the aim to maintain high NOx conversion efficiency and low tailpipe ammonia slip. However, most of the active thermal management and SCR controls in the existing literatures were separately and conservatively designed, which can lead to higher cost of SCR operation than needed including diesel fuel consumption through active thermal management and urea solution consumption. The main purpose of this study is to design and coordinate active thermal management and SCR control using nonlinear model predictive control (NMPC) approach to minimize the total cost of SCR operation while obtaining high NOx conversion efficiency and low tailpipe ammonia slip. Simulation results demonstrate that, compared to the baseline control which consists of separated active thermal management and SCR control, the coordinated control is capable of reducing the total cost of SCR operation by 25.6% while maintaining the tailpipe NOx emissions and ammonia slip at comparable levels. Such an innovative coordinated control design concept shows its promise in achieving low tailpipe emissions during low-temperature operations in a cost-effective fashion.

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## Figures

Fig. 3

Schematic diagram of integrated diesel engine and aftertreatment systems

Fig. 2

Demonstration of coordinated active thermal management and SCR control

Fig. 1

Demonstration of typical SCR control without active thermal management

Fig. 4

Coordinated active thermal management and SCR control

Fig. 6

Engine speed and torque profiles during FTP-75 cycle

Fig. 7

Exhaust flow rate and SCR temperature profiles during FTP-75 cycle

Fig. 8

O2 concentration profile in the exhaust gas during FTP-75 cycle

Fig. 19

Tailpipe ammonia slip profile with coordinated control under FTP-75 cycle

Fig. 20

Ammonia concentration input with coordinated control under FTP-75 cycle

Fig. 21

Post fuel injection rate profile with coordinated control under FTP-75 cycle

Fig. 5

Separate active thermal management and SCR controller

Fig. 16

Ammonia coverage ratio profile with coordinated control under FTP-75 cycle

Fig. 9

Upper bound and lower bound of ammonia coverage ratio without active thermal management

Fig. 17

DOC and SCR temperature profiles with coordinated control under FTP-75 cycle

Fig. 10

Ammonia coverage ratio profile with separate control during FTP-75 cycle

Fig. 11

DOC and SCR temperature profiles with separate control under FTP-75 cycle

Fig. 12

NOx concentrations before and after SCR with separate control under FTP-75 cycle

Fig. 13

Tailpipe ammonia slip with separate control during FTP-75 cycle

Fig. 14

Ammonia concentration input with separate control during FTP-75 cycle

Fig. 15

Post fuel injection rate profile with separate control under FTP-75 cycle

Fig. 18

Comparison of NOx concentrations before and after SCR with coordinated control under FTP-75 cycle

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