Impact of multiple injections on adBlue Spray Decomposition in a SCR-like system using Large Eddy Simulation
Amsini Sadiki  1@  , Kaushal Nishad  1, *@  , Florian Ries  1@  , Yujun Liao  2@  , Dimopoulos Panayotis  2@  
1 : Institute of Energy and Power Plant Technology, Technische Universität Darmstadt,
Otto-Berndt Strasse 3, 64287 Darmstadt, -  Germany
2 : Laboratory for Combustion Engines, Empa Swiss Federal Laboratories for Materials Science and Technology,
Überlandstrasse 129, 8600 Dübendorf, -  Switzerland
* : Corresponding author

In the present paper, numerical investigations of the adBlue injection are reported in a SCR-like system using Large Eddy Simulation (LES) based on a WALE subgrid-scale model. Thereby, the influence of multiple injections on both, the thermal decomposition of adBlue spray and the urea SCR reduction performance is especially assessed. The spray module relies on a Eulerian-Lagrangian approach and includes phenomena, like spray atomization, multi-component droplet evaporation and film deposition. The chemical reaction kinetics is described by a global mechanism of urea thermolysis and hydrolysis. Applying an uniformity index of scalar field in transient operating conditions, the impact of two different urea injection frequencies is analyzed. The results demonstrate that: (1) injection frequency affects strongly the investigated processes and quantities such as, spray evolution, mixture fraction, temperature field and NH3 conversion; (2) adBlue deposition on SCR duct wall is a critical parameter which further affects these processes. This is, in turn, regulated by injection frequency. The suggested uniformity index provides information about the phenomena related to airborne adBlue spray and wall deposited mass. It turns out, that the multi-injection with higher frequencies seems to be favorable in getting continuous conversion and uniform distribution of NH3 and in minimizing the adBlue deposition.

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