Browse > Article

Numerical Study on the Injector Shape and Location of Urea-SCR System of Heavy-duty Diesel Engine for Preventing $NH_3$ Slip  

Jeong Soo-Jin (Department of Automotive Engineering, Hanzhong University)
Lee Sang Jin (Department of Mechanical Engineering, Graduate School of Hanyang University)
Kim Woo-Seung (Department of Mechanical Engineering, Hanyang University)
Lee Chun Beom (Korea Automotive Technology Institute)
Publication Information
Transactions of the Korean Society of Automotive Engineers / v.14, no.1, 2006 , pp. 68-78 More about this Journal
Abstract
In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia$(NH_3)$ in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis cannot be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea. Hence the key factor to implementation of SCR technology on automobile is fast thermolysis, good mixing of Ammonia and gas, and reducing Ammonia slip. In this context, this study performs three-dimensional numerical simulation of urea injection of heavy-duty diesel engine under various injection pressure, injector locations and number of injector hole. This study employs Eulerian-Lagrangian approach to consider break-up, evaporation and heat and mass-transfer between droplet and exhaust gas with considering thermolysis and the turbulence dispersion effect of droplet. The SCR-monolith brick has been treated as porous medium. The effect of location and number of hole of urea injector on the uniformity of Ammonia concentration distribution and the amount of water at the entrance of SCR-monolith has been examined in detail under various injection pressures. The present results show useful guidelines for the optimum design of urea injector for reducing Ammonia slip and improving DeNOx performance.
Keywords
Urea; SCR; Injector; Heavy-duty diesel engine;
Citations & Related Records
연도 인용수 순위
  • Reference
1 STAR-CD Ver.3.15 Manual, Computational Fluid Dynamics Ltd., 2001
2 M. Pilch and C. Erdman, 'Use of Breakup Time Data Velocity History Data to Predict the Maximum Size of Stable Fragments for Acceleration-induced Breakup of a Liquid Drop,' Int. J. Multiphase Flow, Vol.13, No.6, pp.741-757, 1987   DOI   ScienceOn
3 M. Nagaoka, H. Kawazoe and N. Nomura, 'Modeling Fuel Spray Impingement on a Hot Wall for Gasoline Engines,' SAE 940525, 1994
4 C. Winkler, P. Florchinger and M. D. Patil, J. Gieshoff, P. Spurk and M. Pfeifer, 'Modeling of SCR DeNOx Catalyst-Looking at the Impact of Substrate Attributes,' SAE 2003-01-0845, 2003
5 H. Weltens, H. Bressler, F. Terres, H. Neumaier and D. Rammoser, 'Optimization of Catalytic Converter Gas Flow Distribution by CFD Distribution,' SAE 930780, 1993
6 C. Bai and A. D. Gosman, 'Development of Methodology for Spray Impingement Simulation,' SAE 950283, 1995
7 A. P. Watkins, 'Three-dimensional Modellmg of Gas Flow and Sprays in Diesel Engines,' ed. Markatos, N.C., Computer Simulation for Fluid Flow, Heat and Mass Transfer, and Combustion in Reciprocating Engines, pp.193-237, 1989
8 J. Walker and B. K. Speronello, 'Development of an ammonoia/SCR NOx Reduction System for a Heavy Duty Natural Gas Engine,' SAE 921673, 1992
9 S. Saito, R. Shinozaki, A. Suzuki, H. Jyoutaki and Y. Takeda, 'Development of Urea- SCR System for Commercial Vehicle-Basic Characteristics and Improvement of NOx convers ion at Low Load Operation,' SAE 2003-01-3248, 2003
10 S.-J. Jeong and W. S. Kim, 'A Numerical Approach to Investigate Transient Thermal and Conversion Characteristics of Automotive Catalytic Converter,' SAE 980881, 1998
11 B. R. Rich, 'An Investigation of Heat Transfer from an Inclined Flat Plate in Free Convection,' Trans. ASME, Vol.75, pp.489-499, 1953
12 J. N. Mattavi and C. A. Amann, 'Combustion Modeling in Reciprocating Engines,' Plenum Press, pp.369-401, 1980