Investigations on the Deposit Formation and Decomposition from Urea in SCR Systems
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AUTHORS
Dipl.-Ing. Uladzimir Budziankou is Project Assistant in the area of SCR Modeling at the Institute for Powertrains and Automotive Technology (IFA) of the Vienna University of Technology (TUW) (Austria).
Investigations on the Deposit Formation and Decomposition from Urea in SCR Systems Long-term reliability and high conversion rates are major criteria for engine exhaust aftertreatment with selective catalytic reduction by a Urea-water Solution. Unfavorable operating conditions may lead to the formation of solid deposits which degrade the system efficiency. Within the framework of the FVV project no. 1262, at the Karlsruhe Institute of Technology (KIT) and the Vienna University of Technology (TUW), fundamental experimental and numerical investigations on deposit formation and decomposition were carried out.
Christian Kuntz, M. Sc. is Research Associate in the group “Multiphase Processes and Reactors” at the Institute of Chemical Technology and Polymer Chemistry (ITCP) of the Karlsruhe Institute of Technology (KIT) (Germany).
Dr. Marion Börnhorst is Head of the group “Multiphase Processes and Reactors” at the Institute of Chemical Technology and Polymer Chemistry (ITCP) of the Karlsruhe Institute of Technology (KIT) (Germany).
Prof. Dr. Thomas Lauer is Associate Professor at the Institute of Powertrains and Automotive Technology (IFA) of the Vienna University of Technology (TUW) (Austria).
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the formation of solid by-products like biuret, cyanuric acid or ammelide [1, 2]. Solid deposits affect the system efficiency in a negative way, as they increase back pressure and decrease the formation of ammonia and its uniformity over the catalyst cross-section. Therefore, a numerical approach is desirable in order to predict deposit formation and thus contribute to a costeffective development of SCR systems. The necessary research was carried out in the framework of this FVV project at the Institute of Chemical Technology and Polymer Chemistry (ITCP) of the Karlsruhe Institute of Technology (KIT) and at the Institute for Powertrains and Automotive Technology (IFA) of the Vienna University of Technology (TUW).
1 MOTIVATION 2 E XPERIMENTAL SE TUP S 3 MODELING APPROACH 4 MODEL VALIDATION WITH E XPERIMENTS 5 SUMMARY
2 EXPERIMENTAL SETUPS
Detailed experimental observations are necessary to understand the underlying processes of deposit formation and to develop and validate the numerical models. The test bench setup at the Vienna University of Technology, FIGURE 1, is designed to produce solid deposits under conditions, which are similar to those within a mixing section of a mobile SCR system [3]. To measure the propagation of the liquid film due to shear forces and gravity, an optically accessible box was integrated in which the UWS injection is carried out on a 2 mm thick impingement plate. The spray deflection, film propagation, deposit formation and cooling of the impingement plate were documented with laser diffraction, video and infrared imaging. Exhaust-typical
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