Modeling of Urea-Water Solution Injection Spray in SCR System

Abstract:

To control the emissions from the diesel engines of modern automobiles, it requires the development of adequate and advanced exhaust gas aftertreatment devices. Selective Catalytic Reduction (SCR) is a method that can be used in mobile diesel engine aftertreatment systems to reduce harmful NOx emissions. Due to the toxicity and handling problems of ammonia, currently injection of a liquid Urea-Water Solution (UWS) into the exhaust stream approach is used. The water evaporates and the urea undergoes thermal decomposition producing ammonia that reacts with the NOx in the exhaust gas inside a SCR catalyst to produce nitrogen and water vapor. This work presents the study of UWS injection spray using commercial available CFD code, Fire v8.3. The evaporation of water from a single droplet of UWS is investigated theoretically and droplets are treated with Lagrangian particle tracking. Simulation study at different exhaust gas temperatures and injector locations is carried out and compared with experimental values. Thus, the present study results predict the local distribution and the conversion of the reducing agent.

• Periodical: Applied Mechanics and Materials (Volume 232)
• Pages: 583-587
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.232.583
• Online since: November 2012
• Authors: Nayak S. Nagaraj, N. Kapilan, Prabhu S. Sadashiva
• Keywords: Computational Fluid Dynamics (CFD), Injection, NO_x, SCR, Spray

References

[1] Manfred Koebel, Martin Elsener and M Kleemann, Urea-SCR a Promising Technique to Reduce NOx Emissions from Automotive Diesel Engines, Catalysis Today, 59: 335-345, (2000).

DOI: 10.1016/s0920-5861(00)00299-6

[2] D.S. Yim, S.J. Kim et al, Decomposition of Urea into NH3 for SCR process, Ind. Eng. Chem. Res 43(1): 4856-4863, (2004).

[3] Munnannur A, Liu Z. G, A multi-dimensional model for DEF Injection and Urea Decomposition in Mobile SCR De-NOx Systems, Proceedings of AFS 4th Biennial Conference, Ann arbor MI, (2009).

[4] J.Y. Kim, S.H. Ryu, J.S. Ha, Numerical Prediction on the Characteristics of Spray-induced Mixing and Thermal decomposition of Urea Solution in SCR system, Proc. 2004 ASME Fall Technical Conference ICE Division, California USA, (2004).

DOI: 10.1115/icef2004-0889

[5] F. Birkhold, U. Meingast, P. Wassermann, O. Deutchmann, Analysis of the injection of urea-water solution for automotive SCR De-NOx system; Modelling of two phase flow and spray/wall interaction, SAE 2006-01-0643, (2006).

DOI: 10.4271/2006-01-0643

[6] J.C. Wurzenberger, R. Wanker, Multi-Scale SCR Modeling, ID Kinetic Analysis and 3D System Simulation, SAE 2005-01-0948, (2005).

DOI: 10.4271/2005-01-0948

[7] J K Dukowicz, A Particle Fluid Numerical Model for Liquid Sprays, Journal of Computational Physics, 35: 229-253, (1980).

DOI: 10.1016/0021-9991(80)90087-x

[8] AVL FIRE -Aftertreatment Manual, v8. 3 edition, AVL List GmbH, Graz, (2004).

[9] L. Schiller and A. Z. Naumann. A drag coefficient correlation. VDI, 77: 318–320, (1933).

[10] WA Sirignano, Fuel Droplet Vapourization and Spray Combustion Theory, Prog. Energy Combustion System 9: 291-322, (1983).

DOI: 10.1016/0360-1285(83)90011-4