Effect of UWS injection at low exhaust gas temperature on NOx removal efficiency of diesel engine
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Urea-SCR systems have been widely used in diesel vehicles according to the strengthened NOx (Nitrogen Oxides) emission standard. The NOx removal efficiencies of the latest well optimized urea-SCR system are above 90 % at moderate exhaust gas temperature of 250 ~ 450 °C. However, a large amount of NOx is emitted from diesel vehicles at cold start or urban driving conditions, when the exhaust gas temperature is not high enough for SCR catalyst activation. Although many researchs have been stuied to improve NOx conversion efficiency at these low temperature conditions, it is still one of important technical issues. In this study, the effect of UWS injection at low exhaust gas temperature conditions is studied. This study uses a 3.4 L diesel engine equipped with a commertial urea SCR system. As a result, it is found that about 5 % of NOx removal efficiency is improved in the NRTC test when UWS injection starts at the SCR inlet temperature of 150 °C compared to 200 °C. It is also found that urea deposits can be formed on the wall of exhaust pipe, when the local wall temperature is lower than temperature of urea decomposition.
Key wordsNOx removal efficiency Urea SCR (Selective Catalytic Reduction) UWS (Urea Water Solution) NRTC (Non Road Transient Cycle)
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- Birkhold, F., Meingast, U., Wassermann, P. and Deutschmann, O. (2006). Analysis of the injection of urea water solution for automotive SCR DeNOx systems: Modeling of two phase flow and spray/wall-interaction. SAE Paper No. 2006-01-0643.Google Scholar
- Girard, J., Cavataio, G., Snow, R. and Lambert, C. (2008). Combined Fe-Cu SCR systems with optimized ammonia to NOx ratio for diesel NOx control. SAE Paper No. 2008-01-1185.Google Scholar
- Guo, G., Dobson, D., Warner, J., Ruona, W. and Lambert, C. (2012). Advanced urea SCR system study with a light duty diesel vehivle. SAE Paper No. 2012-01-0371.Google Scholar
- Li, Z., Deng, J., Li, L., Cao, L. and Wu, Z. (2011). A study on the factors affecting heated wall impinging characteristics of SCR spray. SAE Paper No. 2011-01-1311.Google Scholar
- Rudder, K. (2012). Tier 4 high efficiency SCR for agricultural applications. SAE Paper No. 2012-01-1087.Google Scholar
- Tang, T., Zhang, J., Shuai, S. and Cao, D. (2014). Urea decomposition at low temperature in SCR systems for diesel engine. SAE Paper No. 2014-01-2808.Google Scholar
- Xu, L., Watkins, W., Snow, R., Graham, G. and Cabe, R. (2007). Laboratory and engine study of urea-related deposits in diesel urea-SCR after-treatment systems. SAE Paper No. 2007-01-1582.Google Scholar
- Zheng, G., Fila, A., Kotrba, A. and Floyd, R. (2010). Investigation of urea deposits in urea SCR systems for medium and heavy trucks. SAE Paper No. 2010-01-1941.Google Scholar