Modeling of urea-water solution spray into exhaust gas flow stream in selective catalytic reduction system

In this thesis, the factors which effects the efficiency of selective catalytic reduction (SCR) system which is located at diesel engine vehicles were investigated Selective catalytic reduction system is used to reduce the nitrogen oxides emissions. Ammonia is used to reduce the nitrogen oxides and it is produced from the reactions occur after the urea-water solution is sprayed into the exhaust gas flow stream. Uniform ammonia distribution at the entrance of the catalytic area is essential for the system efficiency. Computational fluid dynamics (CFD) modeling approach was chosen. Spraying urea-water solution into the exhaust gas flow stream was modeled via ANSYS Fluent and the ammonia distribution at the outlet of the exhaust gas pipe was investigated. In order to investigate the effects of the spray conditions on the ammonia distribution, injector cone angle and injection direction were simulated at three different levels and the results were compared. Also, in order to investigate the effects of the flow conditions on the ammonia distribution, exhaust gas temperature at three different levels and the results were compared.