排气温度、排气流量和海拔高度对SCR系统NOx转化率和NH3泄漏量的影响研究

为研究不同海拔下SCR系统性能,分别在80、90、100 k Pa大气压力下对一台满足国五排放标准的高压共轨柴油机进行性能与排放试验,以研究排气温度、排气流量和海拔变化对NO_x转化率和NH₃泄漏量的影响。结果表明:在排气流量为350 kg/h情况下,NO_x转化率随排气温度升高呈现先增后减的趋势,不同温度下NO_x转化率最大差值为43.4百分点;NH₃泄漏量随着温度的升高大体上呈下降趋势,不同温度下NH₃泄漏量最大差值为328×10^-6;NO_x转化率随排气流量升高呈现先增后减的趋势,在250℃时,不同排气流量下NO_x转化效率最大相差21.5百分点;NH₃泄漏量随排气流量的增大而增加,在250℃时,不同排气流量下NH₃泄漏量最大差值为90.8×10^-6。相同工况下,海拔越高,NO_x转化率越高,NH₃泄漏量越小,大气压力为80和100 k Pa下NO_x转化率最大相差20.1百分点,NH₃泄漏量最大相差54.6×10^-6。

Study on the Effects of Exhaust Temperature,Exhaust Flow Rate and Altitude on NOx Conversion Rate and NH3 Slip of SCR System

In order to study the performance of SCR at different altitudes,the performance and emission tests on a high-pressure common-rail diesel engine meeting the national-V emission regulation are conducted under 80、90 and 100 kPa atmospheric pressures respectively to study the effects of exhaust temperature,exhaust flow rate,and altitude on NO_x conversion rate and ammonia slip.The results show that under an exhaust flow rate of 350 kg/h,with the increase of exhaust temperature,the NO_x conversion rate exhibits a tendency of rises first and then falls,with the maximum difference of NO_xconversion rate of 43.4 percentage points at different exhaust temperatures;The ammonia slip by and large reduces with the rise in exhaust temperature,and the maximum difference of ammonia slip is 328×10^-6 at different temperatures.The NO_x conversion rate show a trend of rise first and then fall as the exhaust flow rate increases,with a maximum difference of NO_x conversion rate of 21.5 percentage points at different exhaust flow rates when the exhaust temperature is 250℃;The ammonia slip increases with the increase of exhaust flow rate,and the maximum difference of ammonia slip is 90.8×10^-6 at different exhaust flow rates when the exhaust temperature is 250℃.Under the same working conditions,the higher the altitude,the greater the NO_x conversion rate and the smaller the ammonia slip,and when the atmospheric pressure lowers from 100 kPa to 80 kPa,the maximum NO_x conversion rate rises by 20.1 percentage points and the maximum ammonia slip reduces by 54.6×10^-6.