Is closed-loop SCR control required to meet future emission targets?

F.P.T. Willems, R.P.M. Cloudt, E.A.C. Eijnden, van den, M.H.P. Genderen, van, R. Verbeek, A.G. Jager, de, W. Boomsma, I.T.M. van den Heuvel

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To meet 2010 emission targets, optimal SCR systemperformance is required. In addition, attention has to bepaid to in-use compliance requirements. Closed-loopcontrol seems an attractive option to meet the formulatedgoals. This study deals with the potential and limitationsof closed-loop SCR control.High NOx conversion in combination with acceptable NH3slip can be realized with an open-loop control strategy.However, closed-loop control is needed to make theSCR system robust for urea dosage inaccuracy, catalystageing and NOx engine-out variations. Then, the systemmeets conformity of production and in-use compliancenorms.To demonstrate the potential of closed-loop SCR control,a NOx sensor based control strategy with cross-sensitivity compensation is compared with an adaptivesurface coverage/NH3 slip control strategy and an open-loop strategy. The adaptive surface coverage/NH3 slipcontrol strategy shows best performance over simulatedESC and ETC cycles.SCR catalyst dynamics, time delay in the urea injectionand maximum NH3 slip targets limit the performance ofclosed-loop SCR control. If new reagent dosage systemsand future catalyst technology are able to relieve theselimitations, closed-loop control has the potential toreduce the calibration effort and to improve the transientcontrol performance.
Original languageEnglish
Title of host publicationProceedings of the SAE World Congress & Exhibition 2007, Detroit, Michigan, USA
Publication statusPublished - 2007
EventSAE 2007 World Congress and Exhibition - Cobo Center, Detroit, United States
Duration: 16 Apr 200719 Apr 2007


ConferenceSAE 2007 World Congress and Exhibition
Country/TerritoryUnited States


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