柴油机SCR系统NOx转化率影响因素的研究

利用计算流体动力学的方法对柴油机SCR尿素水溶液喷雾分解和催化剂表面的化学反应过程进行了数值模拟,结合SCR台架试验,探究了氨氮比、温度、空速和喷嘴安装位置对NO转化率的影响。结果表明:当氨氮比在0.6~2.0时,NO转化率随氨氮比的升高呈先升后降趋势,氨氮比为1.2时的NO转化率较高;当催化剂温度在300~500℃时,NO转化率随温度的升高呈先升高后趋于稳定的变化趋势,温度达450℃时基本稳定;空速在13 000~21 000h-1时,NO转化率随空速升高逐渐降低;随着喷嘴与催化剂距离的增加,NO转化率逐渐增加,当喷嘴与催化剂距离大于450mm时,NO转化率逐渐趋于稳定。

Influencing Factors of NOx Conversion Efficiency for Diesel Enigne SCR System

The spray and decomposition process of urea solution and chemical reaction process on the surface catalyst of selective catalytic reduction(SCR) system were simulated by using computational fluid dynamics(CFD) method.Combined with SCR engine test,the influences of ammonia nitrogen ratio,temperature,space velocity and urea injector position on NO conversion efficiency were researched.The experimental results show that NO conversion efficiency first increases and then decreases when the ammonia nitrogen ratio is between 0.6 and 2 and reaches the peak when the ratio is 1.2.NO conversion efficiency increases among the range of 300-450 ℃ and becomes stable when the temperature reaches 450 ℃ till to 500 ℃.At the space velocity range of 13 000-21 000 h-1,NO conversion efficiency decreases with the increase of velocity.In addition,the increase of distance between injector and catalyst will lead to the increase of NO conversion efficiency,but has little influence on it beyond 450 mm.