Re-evaluation and Modeling of a Commercial Diesel Oxidation Catalyst Young-Deuk Kim *1) ·Sung-Min Shim 1) ·Deok-Kyu Choi 1) ·Woo-Seung Kim 1) ·Soo-Jin Jeong 2) · Jeong-Ho Kang 2) 1) Department of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea 2) Advanced Power & IT Research Center, Korea Automotive Technology Institute, Cheonan, Chungnam 330-912, Korea Abstract : A modeling approach to predict the performance of commercial diesel oxidation catalyst (DOC) is presented in this study. Prior to completing this prediction, the conversion behavior of DOC as previously published was re-evaluated with a verification of the present numerical model. To calibrate and validate the model adopted in this study, steady-state experiments with DOC mounted on a light duty 4-cylinder 2.0 liter turbocharged diesel engine were performed using an engine- dynamometer system. The reaction rates for CO, HC, and NO oxidations over a Pt/Al 2 O 3 catalyst were determined in conjunction with a fully transient two-phase 1D+1D monolith channel model with diesel exhaust gas temperature ranges from 150 to 450˚C and space velocity ranges from 10 5 to 5×10 5 h -1 . To determine the kinetic parameters which best fit the experimental data, a two-step optimization procedure is introduced. First, the results from the conjugated gradient method (CGM) with individual temperatures for each species are plotted in an Arrhenius plot to generate proper intermediate guesses from initial guesses for all pre-exponential factors and activation energies. Then, kinetic parameters for all species are obtained simultaneously by searching the best fits to experimental data using the CGM from the intermediate guesses for all species. The prediction accuracy of the model was improved by the optimization procedure employed in this study, and the optimized kinetic parameters were validated against experimental data obtained at both 1500 and 2000 rpm. Key words : Diesel Oxidation Catalyst, Rate Constants Estimation, Inverse Analysis, Optimization, Numerical Modeling 1. INTRODUCTION A DOC in the diesel exhaust aftertreatment system can be used as an integral component to effectively reduce engine raw emissions in combination with the aforementioned aftertreatment components. The main function of a commercial DOC is to reduce the soluble organic fraction (SOF) of the diesel particulate matter as well as the gaseous CO and HC emissions. In addition, to improve the NOX conversion over a SCR catalyst, the DOC is usually placed upstream of the SCR catalyst to enhance the fast SCR reaction (4NH 3 + 2NO + 2NO 2 4N 2 + 6H 2 O) using equimolar amounts of NO and NO 2 . Here, NO 2 fractions in excess of 50% of total NO X should be avoided because the reaction with NO 2 only (4NH 3 + 3NO 2 3.5N 2 + 6H 2 O) is slower than the standard SCR reaction (4NH 3 + 4NO + O 2 4N 2 + 6H 2 O). 1),2) The DOC is also used in conjunction with a DPF, called a continuously regenerating trap (CRT), to oxidize NO for passive particulate combustion by NO 2 and oxidize fuel for heat management with active particulate regeneration. 3),4) Thus, as the diesel aftertreatment architecture becomes more complicated with increasingly tight emission standards, more accurate mathematical modeling of aftertreatment components is required to reduce the number of required experiments and tests. Many numerical and experimental attempts 2)-7) have been conducted to analyze the chemicophysical characteristics and conversion performances of DOC and to examine the effect of DOC in the diesel exhaust aftertreatment KSAE 2008 Annual Conference Copyright @ 2008 KSAE pp.1-10 / KSAE08-A0065