NAFEMS Americas and Digital Engineering (DE) teamed up (once again) to present CAASE, the (now Virtual) Conference on Advancing Analysis & Simulation in Engineering, on June 16-18, 2020!

CAASE20 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, unlike any other, to share experiences, discuss relevant trends, discover common themes, and explore future issues, including:
-What is the future for engineering analysis and simulation?
-Where will it lead us in the next decade?
-How can designers and engineers realize its full potential?
What are the business, technological, and human enablers that will take past successful developments to new levels in the next ten years?

Resource Abstract

Selective catalytic reduction (SCR) has been widely employed in diesel exhaust systems to reduce NOx emissions. In this process, an aqueous solution of urea is injected into the exhaust flow which produces NH3 gas upon going through the process of thermolysis and hydrolysis. NH3 gas further goes through a reduction reaction in presence of the SCR catalyst to reduce NOx content into pure N2. Since a calibrated amount of aqueous urea solution is injected for certain content of NOx, it is essential that all urea solution is vaporized and converted to NH3. It is also important that the NH3 gas is thoroughly mixed with the exhaust gases. An uneven mixing of NH3 gas and exhaust flow might cause the vehicle to not meet the emission standards by letting the NOx escape where local NH3 concentration is insufficient for the reduction process of NOx. It also leads to slippage of NH3 into the atmosphere where local concentration of NH3 is underutilized.

Due to increasingly tighter emission requirement for NOx, a higher amount urea is dosed for increased NOx conversion. A lack of uniform mixing in this scenario creates higher localized concentration of NH3 which may lead to NH3 slippage and cause miss the emission requirement for NH3. In the current CFD study, different mixer designs have been created and evaluated to attain higher mixing. Uniformity Index at the catalyst interface is used as a metric to quantify the amount of mixing. Cold solid skin temperature often creates film on the surface which has a significant effect on the uniformity. The CFD study uses conjugate heat transfer approach to model the heat loss from the solid casing to the ambience and predict the skin temperature. It also models film formation on the walls and subsequent film stripping. The time scales of the solid and the fluid are very different. For this reason, a super-cycling approach is used to model the solid skin temperature where the solid temperature attains quasi-steady temperature quickly. The software used for this study is CONVERGE.