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Open AccessArticle

Modeling the Formation of Urea-Water Sprays from an Air-Assisted Nozzle

1
Institute for Powertrains and Automotive Technology, TU Wien, 1060 Vienna, Austria
2
Institute of Thermal Turbomachinery, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
*
Author to whom correspondence should be addressed.
Appl. Sci. 2020, 10(16), 5723; https://doi.org/10.3390/app10165723
Received: 31 July 2020 / Revised: 13 August 2020 / Accepted: 14 August 2020 / Published: 18 August 2020
(This article belongs to the Special Issue Progress in Spray Science and Technology)
Ammonia preparation from urea-water solutions is a key feature to ensure an effective reduction of nitrogen oxides in selective catalytic reduction (SCR) systems. Thereby, air-assisted nozzles provide fine sprays, which enhance ammonia homogenization. In the present study, a methodology was developed to model the spray formation by means of computational fluid dynamics (CFD) for this type of atomizer. Experimental validation data was generated in an optically accessible hot gas test bench using a shadowgraphy setup providing droplet velocities and size distributions at designated positions inside the duct. An adaption of the turbulence model was performed in order to correct the dispersion of the turbulent gas jet. The spray modeling in the near nozzle region is based on an experimentally determined droplet spectrum in combination with the WAVE breakup model. This methodology was applied due to the fact that the emerging two-phase flow will immediately disintegrate into a fine spray downstream the nozzle exit, which is also known from cavitating diesel nozzles. The suitability of this approach was validated against the radial velocity and droplet size distributions at the first measurement position downstream the nozzle. In addition, the simulation results serve as a basis for the investigation of turbulent dispersion phenomena and evaporation inside the spray. View Full-Text
Keywords: CFD; droplet kinematics; gas jet; injection processes; selective catalytic reduction; shadowgraphy; spray characteristics; turbulent dispersion CFD; droplet kinematics; gas jet; injection processes; selective catalytic reduction; shadowgraphy; spray characteristics; turbulent dispersion
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MDPI and ACS Style

Frühhaber, J.; Lieber, C.; Mattes, D.; Lauer, T.; Koch, R.; Bauer, H.-J. Modeling the Formation of Urea-Water Sprays from an Air-Assisted Nozzle. Appl. Sci. 2020, 10, 5723.

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