The control strategy of reducer injection for selective catalytic reduction (SCR) technology is proposed, in which the injection rate of reducer is calculated according to N0x emission concentration map, exhaust temperature and air velocity map of original engine. The effects of NH3/NOX ratio, exhaust temperature and air velocity on N0x conversion rate and NH3 slip concentration as well as the NH3 absorption and desorption characteristics of SCR catalyst are studied by respective tests. Based on the results the control schemes for the injection rate of urea solution for steady-state and transient conditions are determined respectively, and the test results indicate that the control objectives for ESC steady cycle and ETC transient cycle are both fulfilled. In addition, the results of cold start test show a high NOX concentration due to lower operating temperature, therefore, measures should be taken to reduce NO, emission in low temperature conditions.%为选择性催化还原技术提出了还原剂喷射的控制策略.它根据原机NOx排放浓度脉谱、排气温度和空速脉谱等计算还原剂的喷射速率.分别通过试验研究了NH3/NOx比值、排气温度和空速对NOx转化率和氨泄漏浓度的影响以及SCR催化剂的氨吸附和脱附特性,并根据研究结果,分别确定稳态和瞬态工况下尿素溶液喷射的控制方案,因而实现了ESC稳态循环和ETC瞬态循环下的控制目标.此外,冷机起动试验表明,该阶段的排气温度低,NOx排放浓度较高,故应采取措施减少低温工况下NOx的排放.
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