New Urea-SCR Control System for Super Clean Diesel
Hisao Haga, Eiji Hashimoto, Koichi Nakajima, Hideki Matsunaga, and Yuji Yasui
Honda R&D Co., Ltd.
4630 Shimotakanezawa, Haga-machi, Haga-gun, Tochigi 321-3393, Japan
Diesel engines effectively reduce automotive CO2 emissions. Technologies for reducing NOx emissions are also essential, however, for diesel engine use. The research discussed in this paper focuses on urea-SCR as after-treatment system for converting NOx, and proposes the urea-SCR control based on NH3 sensor output. The NH3 sensor effectively reduces both NOx, and NH3 slip. The control adjusts the amount of urea dosed to the catalyst based on changes in NH3 slip timing and NH3 concentration in order to compensate for part-to-part variations in the SCR catalyst and catalyst aging. The proposed urea-SCR system using the NH3 sensor and applied to a test vehicle increased NOx conversion performance and improved emission robustness over that of conventional control using a NOx sensor.
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