Analysis of the Injection of Urea-Water-Solution for Automotive SCR DeNOx-Systems: Modeling of Two-Phase Flow and Spray/Wall-Interaction

Abstract

<div class="htmlview paragraph">The selective catalytic reduction (SCR) based on urea-water-solution is an effective technique to reduce nitrogen oxides (NO<sub>x</sub>) emitted from diesel engines. A 3D numerical computer model of the injection of urea-water-solution and their interaction with the exhaust gas flow and exhaust tubing is developed to evaluate different configurations during the development process of such a DeNOx-system. The model accounts for all relevant processes appearing from the injection point to the entrance of the SCR-catalyst:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">momentum interaction between gas phase and droplets</div></li> <li class="list-item"><div class="htmlview paragraph">evaporation and thermolysis of droplets</div></li> <li class="list-item"><div class="htmlview paragraph">hydrolysis of isocyanic acid in gas phase</div></li> <li class="list-item"><div class="htmlview paragraph">heat transfer between wall and droplets</div></li> <li class="list-item"><div class="htmlview paragraph">spray/wall-interaction</div></li> <li class="list-item"><div class="htmlview paragraph">two-component wall film including interaction with gas phase and exhaust tube</div></li> </ul> </div> <div class="htmlview paragraph">The single modeling steps are verified with visualizations, patternator measurements, phase-doppler-anemometer results and temperature measurements. CFD simulations of a SCR DeNOx-system are compared to experimental data to determine the decomposition parameters for urea-water-solution droplets. Numerical results for an injection including all processes addressed above are discussed.</div>