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Selective Catalytic Reduction (SCR) is a most promising technique for reduction of nitrogen oxides (NOx) emitted from the exhaust of diesel engines. Urea Water Solution (UWS) is injected to hot exhaust gas stream to generate reducing agent ammonia. The droplet evaporation of Urea Water Solution (UWS) is investigated for single droplet in heated environment ranging temperatures 373K-873K theoretically. The theoretical methods which are implemented into CFD code Fire 8.3 from AVL Corp. involve Rapid Mixing model and Diffusion Limit model which consider stationary droplet and variable properties of the UWS. The UWS droplet revealed different evaporation characteristics depending on its ambient temperatures which are numerically predicted by simulated results. The simulated results are validated with experimental values of Wang et al. [9] which are helpful in predicting the evaporation and UWS dosing strategy at different exhaust gas temperatures in real SCR system.

The Selective Catalytic Reduction (SCR) based on Urea-Water-Solution (UWS) injection is an effective technique to reduce the nitrogen oxides (NOx) emitted from the exhaust gases of diesel engines. The evaporation characteristics obtained for single Urea-Water-Solution (UWS) droplet using CFD code AVL FIRE is compared with experimental values. 3D numerical model of the injection of UWS and its interaction with the exhaust gas flow and exhaust tubing is developed. The model accounts for all relevant processes appearing from the injection point to the entrance of the SCR catalyst, especially during evaporation and thermolysis of droplets, hydrolysis of isocyanic acid in gas phase, heat transfer between wall and droplets and spray/wall-interaction. The spray wall deposition is found to be varying with temperature and residence time.