柴油机尿素 SCR 反应特性的试验研究

利用可独立控制尿素喷射量的SCR系统，通过柴油机台架试验，研究了钒基催化剂温度和空速对SCR催化还原反应NOx 转化效率和反应速率的影响，以及尿素喷嘴安装位置对转化效率的影响。结果表明：NOx 转化率随着氨氮比（NH3与NOx 物质的量之比）的升高而逐渐升高，由于尿素水解和热解不完全等因素，氨氮比上升到2时NOx 转化率才可达到最大；NOx 转化率随着催化剂温度升高而升高，到400℃时基本趋于稳定，NOx 转化率随空速升高略有下降；SCR反应速率随温度的升高而升高，随空速的变化不明显；相同氨氮比时，尿素喷嘴与催化剂的距离增加，有利于NOx 转化率的升高。

Experimental Study on Reaction Characteristics of Urea-SCR System for Diesel Engine

The influences of vanadium‐based catalyst temperature and space velocity on NOx conversion efficiency and reaction rate and the influences of nozzle position on NOx conversion efficiency were investigated on engine test bench through the SCR system which could control the urea injection quantity independently .The results show that NOx conversion efficiency increases with the increase of NH3/NOx ratio and reaches the peak when the ratio increases to 2 due to urea incomplete hydrolysis and pyrolysis .NOx conversion efficiency increases with the increase of catalyst temperature and reaches the peak at 400 ℃ ,but de‐creases slightly with the increase of space velocity .The SCR reaction rate increases with the increase of temperature ,but dose not change obviously with the increase of space velocity .For the same NH3/NOx ratio ,the larger distance between urea nozzle and catalyst is beneficial to improve NOx conversion efficiency .