Authors: MF Hsieh J Wang
Publish Date: 2011/05/15
Volume: 12, Issue: 3, Pages: 321-
Abstract
This paper presents an observer design for SCR midcatalyst ammonia concentration estimation using tailpipe NOx and ammonia sensors UreaSCR has been popularly used by Diesel engine powered vehicles to reduce NOx emissions in recent years It utilizes ammonia converted from urea injected at upstream of the catalyst as the reductant to catalytically convert NOx emissions to nitrogen To simultaneously achieve high SCR NOx conversion efficiency and low tailpipe ammonia slip it is desirable to control the ammonia storage distribution along the SCR catalyst Such a control method however requires a midcatalyst ammonia sensor The observer developed in this paper can replace such a midcatalyst ammonia sensor and be used for SCR catalyst ammonia distribution control as well as serves for fault diagnosis purpose of the midcatalyst ammonia sensor The stability of the observer was shown based on the sliding mode approach and analyzed by simulations Experimental validation of the observer was also conducted based on a mediumduty Diesel engine twocatalyst SCR system setup with emission sensors
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