| Model-Based Two-Stage SCR Urea Injection Strategy for Diesel Engine to Meet Low NOx Emission Regulation |
| Jincheng Li1, Haibo Sun1, Gang Li1, Zunqing Zheng1, Mingfa Yao1,2 |
1State Key Laboratory of Engines, Tianjin University, Tianjin, 300072, China
2School of Civil and Transportation Engineering, Qinghai Minzu University, Xining, 810007, China |
|
|
|
Received: August 26, 2024; Revised: October 1, 2024 Accepted: October 7, 2024. Published online: November 13, 2024. |
|
|
|
| ABSTRACT |
|
Diesel engine emission regulations are becoming stringent regarding nitrogen oxide (NOx) limits. The challenge is to improve the NOx conversion efficiency of the after treatment system under low temperatures. Although the two-stage selective catalytic reduction (SCR) has become a hot research topic, developing the urea injection strategy faces two challenges of accurately predicting ammonia (NH3) coverage and the complexity of two-stage SCR co-control. Therefore, first, control-oriented close-coupled SCR (ccSCR) and SCR models were established based on chemical reaction kinetic mechanism, mass conservation, and continuous stirred tank reactor law. The integrated model was established by coupling them with a control-oriented diesel oxidation catalyst model. Second, the effects of temperature, exhaust mass flow rate, oxygen concentration, NOx concentration, and nitrogen dioxide ratio on the NH3 coverage target value were investigated based on the integrated model. Third, a two-stage SCR co-control strategy was proposed. The NH3 coverage initial value and the threshold temperature for ccSCR to stop urea injection of the control strategy were optimized under the world harmonized transient cycle (WHTC). The results show that the NH3 coverage target value is most sensitive to temperature and decreases with increasing temperature. The composite tailpipe NOx under the WHTC is as low as 0.2 g/(kW·h). |
| Key Words:
Diesel engine · Nitrogen oxide emission control · Two-stage selective catalytic reduction · Ammonia coverage · Model-based control strategy |
|
Corresponding Author.
Mingfa Yao , Email. 
Preview 
Full text via DOI 
Download Citation
Print
