A Study on $NO_x$ Reduction in a Light Duty Diesel Vehicle Equipped with a SCR Catalyst

선택적환원촉매를 적용한 중소형 경유차량의 질소산화물 저감 특성 연구

  • Park, Young-Joon (Department of Automotive Engineering, Kookmin University) ;
  • Hong, Woo-Kyoung (Department of Automotive Engineering, Kookmin University) ;
  • Ka, Jae-Geum (Department of Automotive Engineering, Kookmin University) ;
  • Cho, Yong-Seok (Department of Automotive Engineering, Kookmin University) ;
  • Joo, Jae-Geon (EMS Application Team, Technical Research Center of Ssangyong Motor Company) ;
  • Kim, Hyun-Ok (EMS Application Team, Technical Research Center of Ssangyong Motor Company)
  • Received : 2011.01.24
  • Accepted : 2011.04.08
  • Published : 2011.09.01

Abstract

To reach the Euro-6 regulations of PM and $NO_x$ for light-duty diesel vehicles, it will be necessary to apply the CDPF and the de-$NO_x$ catalyst. The described system consists of a catalytic configuration, where the CDPF is placed downstream of the diesel engine and followed by a urea injection unit and a urea-SCR catalyst. One of the advantages of this system configuration is that, in this way, the SCR catalyst is protected from PM, and both white PM and deposits become reduced. In the urea-SCR system, the injection control of reductant is the most important thing in order to have good performance of $NO_x$ reduction. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency become slower, due to temperature window of SCR catalyst. And space velocity also affects to $NO_x$ conversion efficiency. In this paper, rig-tests were performed to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the urea-SCR system. And vehicle test was performed to verify control strategy of reductatnt injection. The developed control strategy of reductant injection was improved over all $NO_x$ reduction efficiency and $NH_3$ consumption in urea-SCR system. Results of this paper contribute to develop urea-SCR system for light-duty vehicles to meet Euro-5 emission regulations.

Keywords

References

  1. T. V. Johnson, "Diesel Emission Control in Review," SAE 2006-01-0030, 2006.
  2. F. Willems, R. Cloudt, E. Eijnden, M. Genderen, R. Verbeek, B. Jager, W. Boomsma and I. Heuvel, "Is Closed-loop SCR Control Required to Meet Future Emission Targets?," SAE 2007-01-1574, 2007.
  3. E. V. Hunnekes, P. V. A. M. Heijden and J. A. Patchett, "Ammonia Oxidation Catalysts for Mobile SCR Systems," SAE 2006-01-0640, 2006.
  4. J. Girard, R. Snow, G. Cavataio and Ch. Lambert, "The Influence of Ammonia to ${NO_{x}}$ Ratio on SCR Performance," SAE 2007-01-1581, 2007.
  5. S. J. Schmieg and J. H. Lee, "Evaluation of Supplier Catalyst Formulations for the Selective Catalytic Reduction of ${NO_{x}}$ with Ammonia," SAE 2005-01-3881, 2005.
  6. A. Palmqvist, E. Jobson, L. Andersson, R. Granbro, M. Wendin, L. Megas, P. Nisius, A. Wiartalla, G. Lepperhoff, P. Blakeman, T. Ilkenhans, D. Webster, G. Haeffler, P. V. Voorde, P. Schmidt-Zhang, U. Guth and M. Wallin, "LOTUS: A Co-operation for Low Temperature Urea-based Selective Catalytic Reduction of ${NO_{x}}$," SAE 2004-01-1294, 2004.