A numerical model including urea water solution(UWS) spray atomization

urea droplets evaporation and decomposition

spray-wall interaction and NOx catalytic reaction in urea-based selective catalytic reduction（SCR）systems was established by using computational fluid dynamics(CFD）code. The influence of the different layout schemes of static mixer on the atomization

evaporation

and decomposition of urea solution and the distribution uniformity of NH3 at the entrance of SCR catalytic converter was investigated. The numerical results show that the static mixer can improve the atomization performance of urea spray

the evaporation and decomposition efficiency of urea droplets and the distribution uniformity of NH3. The SCR system achieves the optimum atomization performance and the maximum decomposition efficiency of urea droplets when the static mixer is placed 1D（equal to the diameter of the exhaust pip） away from the injector. While the SCR system has the best distribution uniformity of NH3 when the static mixer is placed 3D away from the injector. The results of the bench test and numerical calculation reveal that the SCR system can achieve a better NOx conversion efficiency when the static mixer is placed 1D away from the injector.