Urea water solution selective catalyst reduction mixer multi-objective optimization

Mihai  Chiruta, Cummins Emission Solutions

Urea water solution selective catalyst reduction mixer multi-objective optimization

Isabel Montgomery, Lindsey Henry, Guilherme Daldegan*, Jun Li**, Gaurish Sharma***, Mihai Chiruta
Cummins Emission Solutions, Stoughton Wisconsin USA
*Cummins Power Generation Fridley Minnesota USA, ** AVL PEI, ***Esteco North America

Abstract
The purpose of this article is to present the integration of an automotive applications specialized computational fluid dynamics package (AVL FIRE) with a optimization platform (modeFRONTIER) applied to a urea water solution selective catalyst reduction mixer multi-objective optimization.
Ammonia is needed to reduce the nitrogen oxides resulted from the diesel combustion. For automotive applications, due to its toxicity, ammonia is made on demand from a non-toxic precursor: urea. The resulting ammonia must be presenting itself uniformly at the inlet of the SCR catalyst – reductant uniformity index. Urea decomposition can lead to solid deposits given the condition in the SCR mixer.
In developing an SCR mixer, we take into consideration the optimization of the following parameters: minimize the pressure drop across the mixer, maximize the exhaust flow distribution uniformity at the face of the SCR catalyst, maximize the reductant uniformity, and minimize the amount of solid deposits formed as the result of DEF spray impingement on different mixer components. This optimization is at the core of the analysis led design and validation process. Until now this was done one case at a time since the analysis is complex and typically takes days to complete.
The recent progress done in accelerating the run time in AVL FIRE without sacrificing the accuracy of the results, and the availability of the optimization platform modeFRONTIER raised the possibility of integrating FIRE with modeFRONTIER. With the accelerating procedures in place and the seamless integration among the CAD, CFD, and optimization platforms we can run about a hundred cases in the same time as it took to run a single case.
The integration of the FIRE with modeFRONTIER will be exemplified on the simple concept mixer with generic input data, pertinent to the automotive applications.

 

 

 

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