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Is Closed-Loop SCR Control Required to Meet Future Emission Targets?
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 16, 2007 by SAE International in United States
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To meet 2010 emission targets, optimal SCR system performance is required. In addition, attention has to be paid to in-use compliance requirements. Closed-loop control seems an attractive option to meet the formulated goals. This study deals with the potential and limitations of closed-loop SCR control.
High NOx conversion in combination with acceptable NH3 slip can be realized with an open-loop control strategy. However, closed-loop control is needed to make the SCR system robust for urea dosage inaccuracy, catalyst ageing and NOx engine-out variations. Then, the system meets conformity of production and in-use compliance norms.
To demonstrate the potential of closed-loop SCR control, a NOx sensor based control strategy with cross-sensitivity compensation is compared with an adaptive surface coverage/NH3 slip control strategy and an open-loop strategy. The adaptive surface coverage/NH3 slip control strategy shows best performance over simulated ESC and ETC cycles.
SCR catalyst dynamics, time delay in the urea injection and maximum NH3 slip targets limit the performance of closed-loop SCR control. If new reagent dosage systems and future catalyst technology are able to relieve these limitations, closed-loop control has the potential to reduce the calibration effort and to improve the transient control performance.
- Frank Willems - TNO Automotive
- Robert Cloudt - TNO Automotive
- Edwin van den Eijnden - TNO Automotive
- Marcel van Genderen - TNO Automotive
- Ruud Verbeek - TNO Automotive
- Bram de Jager - Eindhoven University of Technology
- Wiebe Boomsma - Eindhoven University of Technology
- Ignace van den Heuvel - DAF Trucks
CitationWillems, F., Cloudt, R., van den Eijnden, E., van Genderen, M. et al., "Is Closed-Loop SCR Control Required to Meet Future Emission Targets?," SAE Technical Paper 2007-01-1574, 2007, https://doi.org/10.4271/2007-01-1574.
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