Numerical investigation of wallfilm formation for SCR applications

Baleta, Jakov and Pachler, Klaus and Vujanović, Milan and Duić, Neven (2013) Numerical investigation of wallfilm formation for SCR applications. = Numerical investigation of wallfilm formation for SCR applications. In: 8th Conference on Sustainable Development of Energy, Water and Environment Systems – SDEWES Conference, 22-27.09.2013., Dubrovnik, Hrvatska.

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The urea-water-solution (UWS) based selective catalytic reduction (SCR) is currently most promising method to fulfil stringent requirements of upcoming Euro 6 norm on NOx emissions from diesel engines. Once UWS spray is injected into hot exhaust gas stream before SCR catalyst, water content evaporates from UWS. Afterwards, ammonia is generated through thermal decomposition of urea and hydrolysis of isocyanic acid. Generated ammonia takes part in various deNOx reactions as a reductant. The resulting spatial distribution of the reducing agent before the catalyst is a crucial factor for the conversion of NOx. The uniform distribution and the degree of processing of the reducing agent upstream of the SCR catalyst can be, besides the evaporation and decomposition, also influenced by the spray/wall interaction. The focus of this paper is therefore the investigation of the spray interaction with both the hot air stream and wall by means of numerical simulation and the validation of mathematical models integrated in commercial CFD code FIRE. To predict the generation and distribution of the reducing agent a detailed three-dimensional numerical simulation was performed. UWS droplets were treated with Lagrangian particle tracking, which solves the equation of motion, mass and enthalpy for parcels of droplets with identical properties. Deposition of droplets leads to the formation of a wall film which is modelled with a 2D finite volume method in the FIRE wall film module. To evaluate the influence of varying parameters, well-known spray parameters as an initial condition are essential for a CFD simulation. As modelling of primary breakup is still insufficiently understood, the first step is spray calibration. The single calibration steps of spray were verified with digital CCD (charge- coupled device) camera images, patternator measurements and laser light scattering measurements. After spray calibration the spray/wall-interaction and wall film formation were investigated in a rectangular flow channel geometry and the obtained simulation results were compared to experimental data.

Item Type: Conference or Workshop Item (Lecture)
Keywords (Croatian): gas aftertreatment, selective catalytic reduction, wallfilm, urea water solution, NOx reduction, computational fluid dynamics
Subjects: TECHNICAL SCIENCE > Mechanical Engineering
Divisions: 500 Department of Energy, Power Engineering and Environment > 510 Power Engineering and Energy Management Chair
Indexed in Web of Science: No
Indexed in Current Contents: No
Date Deposited: 06 Apr 2016 10:48
Last Modified: 06 Sep 2017 11:13

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