Spray strategy and mixer optimization in Urea-SCR system based on frozen flow modeling

Abstract

An integrated after-treatment device model was established by Converge and the experiments were conducted on rapid urea deposits platform under low and medium load conditions. The model was validated by back pressure of catalysts, mixer wall temperature and distribution of urea deposits. In order to reduce the computational costs, the urea injection strategy and mixer structure was optimized based on the frozen flow method. The effects of frozen flow method on the simulation errors and computational costs were evaluated by film mass, film distribution and cycle numbers. The results show that the simulation errors after frozen flow were larger under low load condition but lower under medium load condition. However, the frozen flow method could effectively reduce the cycle numbers under both low and medium load conditions, which was reduced by 9.05% and 17.77%. Furthermore, the cycle numbers were reduced by 31.23% in 5 times injection simulation. With the optimal scheme under low and medium load conditions, the urea deposition rate was reduced by 43.51% and 23.16%. The mass of NH3 was increased by 23.99% under medium load condition. The NH3 uniformity coefficient increased by 5.04% and 2.69%, and the mixer back pressure declined by 24.40% and 27.44%.