SCR催化剂动态参数的试验确定方法研究

Calculating Method Study of SCR Dynamic Parameters by Test

改进了NH_3吞吐速率计算方法,消除了现有方法因为忽视选择性催化还原(SCR)系统尿素结晶、副反应和上下游NO_x浓度偏差及波动等因素导致的计算误差。在发动机试验台架上进行了稳态工况下不同添蓝供给量的排放试验,结合对排放测试设备和数据后处理方式的特性分析,确定了这一计算方法的主要误差来源:一是下游NO_x浓度峰、谷值选择的不确定性,对储NH_3量计算结果影响最大,可能导致20%以上的误差,但通过储NH_3量和储NH_3消耗量一致的原理可以对结果进行优化,使误差控制在5%以内;二是储NH_3开始时刻和储NH_3开始消耗时刻的不确定性,可导致储NH_3量计算结果存在2.75%以上的误差,且不可避免;三是测量设备的滤波过程和响应时间的影响,主要影响储NH_3状态开始变化瞬间的NH_3吞吐速率计算值,对平均速率的影响很小。

NHx throughput rate calculating method improvement work was taken place by taken urea crystals, side reactions, NOx concentration deviation and volatility between upstream and downstream in selective catalytic reduction （SCR） system into account. Emission tests with different AdBlue supply ratio in steady operating condition were taken on engine test bench and the error of this calculating method was confirmed by the analyzing of test equipment, test conditions .and data processing methods. The uncertainty in choosing maximum and minimum value of NOx concentration downstream has the most effect of NH3 storage calculation, may lead to an error of more than 20%, but can be optimized by criterion that the amount of NHa storage is consistent with the NH3 consumption. The uncertainty of NH3 storage starting time and NHx consume starting time can lead to an error of more than 2.75% in NH3 storage calculation and it is inevitable. While the filtering process and response time of measuring equipment mainly affects the NH3 throughput rate when NHa storage state change instantly, but the influence on the average rate is quite small.