不同还原剂对稀燃NOx催化转化器转化效率的影响
Influence of Reducing Agent Types on Conversion Efficiency of Lean NOx Trap

针对稀燃NOx催化转化器(LNT)在浓燃阶段的持续时间及NOx突释溢出影响稀燃汽油机经济性及排放性的重要因素,结合LNT工作的不同阶段对吸附及脱附过程进行了建模。以试验数据为LNT入口边界条件,以灰核模型为理论依据,分别探究了3种主要还原剂H2、CO和C3H6在浓燃阶段的还原效果,进一步分析了不同还原剂在LNT连续工作时的再生能力。结果表明:H2是很好的还原剂,CO次之,C3H6还原性最差;LNT循环工作时H2与CO可以使LNT完全再生、连续工作;烯燃、浓燃切换时NOx突释是影响CO还原效果的重要因素之一,增加水蒸气与CO的比例可以减少NOx突释,进而提升LNT的整体转化效率。
The economic efficiency and emission performance of a lean combustion gasoline engine are significantly impacted by duration of rich period and NOx breakthrough in the LNT (lean NOx trap). Modeling for NOx adsorption and desorption process is conducted considering different phases of the LNT working cycle. The experimental data are set as the inlet boundary conditions, the reduction effects of three classical reduction agents, H2, CO and C3H6, and the regeneration capacity during continuous working cycles are analyzed based on the ash core model theory. The results show that H2 has the best reducing ability, followed by CO, and C3H6 the worst. The LNT is able to work continuously with H2 and CO as the reduction agents. The NOx breakthrough during the switch, which is a key factor to determine the reduction ability of CO, can be decreased by increasing the concentration of water vapor in the exhaust gas to improve the overall efficiency of LNT