Research on urea injection and NH3 distribution characteristics of scr in diesel engine under low-temperature working conditions
Based on experimental research on the installation of the DOC+CDPF+SCR aftertreatment system in diesel engines,a 3D CFD numerical simulation of SCR was constructed and conducted,studying the generation,diffusion,and hydrolysis evaporation of urea droplets during urea injection.Comparative analysis was done on the impact of NH3 distribution characteristics and uniformity on NOX conversion efficiency under different low-temperature conditions.The results indicated that under low-temperature conditions,with increasing urea injection,more urea wallfilms were formed on the surfaces inside the catalyst before and after the mixer,leading to crystallization due to continuous urea injection.The mixer and diffuser play a significant diffusive role in gas flow under low-temperature conditions.However,with increased airflow,NH3 distribution becomes concentrated in the outer areas of the carrier,resulting in higher NH3 escape on the outer side.Increasing the uniformity of NH3 distribution at the carrier inlet surface under different low-temperature conditions effectively enhances NOX conversion efficiency,reduces NH3 escape,and minimizes the possibility of urea crystallization at low temperatures.
low-temperature conditionsurea wallfilmsNH3 distribution uniformityurea crystallization
NETL
NSTL
万方数据
