The NOx Conversion Efficiency Depending on the Deviation of SCR System Components and Amount of Soot Loading in c-DPF
In this study, the parameters of SCR system which have an effect on NOx conversion efficiency have been investigated. The NOx sensor located in front of SCR catalyst and the urea injector dosing urea solutions to the SCR catalyst play important roles in N
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Abstract In this study, the parameters of SCR system which have an effect on NOx conversion efficiency have been investigated. The NOx sensor located in front of SCR catalyst and the urea injector dosing urea solutions to the SCR catalyst play important roles in NOx conversion efficiency of SCR system. First, NOx conversion efficiency has been decreased when NOx sensor reads engine out NOx emissions lower than the actual engine out NOx emissions, because it brings about the lack of urea injection quantity. Second, the NOx conversion efficiency has been also decreased when urea injector doses less amount of urea solution than the system required. Finally, Applying the aged catalyst system (DOC, c-DPF, SCR) and the soot loading amount in c-DPF also have effects on the change of NOx conversion efficiency. Keywords SCR
NOx sensor Urea dosing injector NO2/NOx ratio CRT
1 Introduction Diesel vehicle should meet the most stringent emission legislation to launch US market. SCR is the one of the promising NOx purification method, which has the benefit in fuel consumption and the stability in durability. In this reason, some of
F2012-A04-041 H. S. Kim (&) J. I. Jeon C. E. Choi W. K. Kim Hyundai-Kia Motors, Seoul, Korea e-mail: [email protected]
SAE-China and FISITA (eds.), Proceedings of the FISITA 2012 World Automotive Congress, Lecture Notes in Electrical Engineering 189, DOI: 10.1007/978-3-642-33841-0_62, Ó Springer-Verlag Berlin Heidelberg 2013
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Table 1 SCR reaction rate Reactants
Product
NO2/NOx ratio (%)
Reaction rate
Fast SCR Standard SCR Slow SCR
2N2 ? 3H2O 4N2 ? 6H2O 7N2 ? 12H2O
50 0 100
::: :: :
2NH3 ? NO ? NO2 4NO ? 4NH3 ? O2 6NO2 ? 8NH3
car makers have already developed/is developing diesel vehicles with SCR system. In this study, the result and discussion regarding the key factors which effects on tailpipe NOx will be presented. Test has done with Tier2 Bin5 vehicle application which is equipped with V6 3.0L engine and exhaust after-treatment system (DOC/ c-DPF/Urea SCR System). The test has performed with FTP-75 driving cycle. This study shows the test result and analysis of the difference of NOx conversion efficiency. The main four parameters which cause the difference of the NOx conversion efficiency are as below, 1 2 3 4
The The The The
NOx sensor which has minimum characteristic urea injector which has minimum characteristic 120 K aged catalyst system (DOC/c-DPF/SCR) soot loaded c-DPF
Topics 1 and 2 which cause the difference of NOx conversion efficiency are closely related with the urea dosing quantity. And topics 3 and 4 which cause the difference of NOx conversion efficiency are closely related with NO2/NOx ratio. The NO2 content of exhaust gas makes the difference of reaction rate when NOx emissions react with the NH3 at the SCR catalyst. The NOx (Nitrogen Oxides) emissions are composed of NO (Nitric Oxide) and NO2 (Nitrogen Dioxide). The NOx which reacted with NH3 resolves N2 and H2O as shown in Table 1 and the reaction is largely divided i
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