Experiment and Modeling of Urea Spray Impingement and Deposit for Diesel SCR
The formation of urea deposit in the SCR system leads the reduction of NOx conversion efficiency and catalyst lifetime. In order to investigate the formation of urea deposit at exhaust inner pipe, the weight of urea deposit and NH3 which is decomposition product of urea were measured and analyzed under different conditions. According to the experiment results, it was found that the mass of deposit is more and concentration of NH3 is less when the temperature is lower, and it’s no significant growth of urea deposit when the duration time gets longer. The mass of deposit increases with the increase of gas flow velocity, but it will decrease when the velocity continually increase. The mass of deposit reduced with the increase of the concentration of urea water solution. CFD model of urea spray impingement which is coupled spray injection, droplet atomization, evaporation and gas flow was established for airless injection system. And the model was validated by experiments. Based on the established model, the mass rate of urea water solution at exhaust inner wall (Qwall) was investigated with the variation of flow velocity, temperature, pipe diameter and spray angle for two typical injection positions which are at the elbow and pipe wall of exhaust pipes. It is found that Qwall increased with the increase of gas flow velocity, but Qwall is almost constant with continue increasing of velocity. Qwall is lower for spray injection position at pipe wall than elbow. The experimental and numerical results and conclusions are significant for reduction of urea deposit, increase of NOx conversation efficiency and extension of catalyst lifetime.
Lun Hua Tao Tang Yanguang Zhao Shijin Shuai
Tsinghua University,China
国际会议
上海
英文
1-12
2013-05-13（万方平台首次上网日期，不代表论文的发表时间）