利用三效催化器控制汽油机稀薄燃烧NO_x的排放

Control Strategy for NO_x Emission of Lean Burn Gasoline Engine Using Three-Way Catalyst

为降低汽油机稀薄燃烧NOx排放,研究了采用三效催化器的控制策略,分析了三效催化器在略高于当量 空燃比的稀薄燃烧条件下对NOx转化效率急剧下降的原因,从而提出了在较高空燃比的稀薄燃烧条件下利用三效 催化器控制稀薄燃烧NOx排放的策略,并进行了试验研究．在对三效催化器储氧机理分析基础上,进一步提出了一 种在空燃比浓稀变换条件下利用三效催化器控制NOx排放的策略,该策略大大降低稀薄燃烧汽油机的NOx排放; 通过试验对浓稀循环数和浓稀比例进行了优化．结果表明,稀薄燃烧时NOx转化效率可达45％,稳态NOx排放可 降至200×10-6以下．

The control strategy with three-way catalyst（TWC）was investigated to reduce NOx emission of leanburn gasoline engine. By analyzing the causes of the NOx conversion efficiency reduction of TWC under lean conditions when air fuel ratio （AFR） was a little greater than stoichiometric AFR, it is proposed that lean-burn NOx emission could be controlled with TWC under higher lean-burn AFR. Tests were carried out. On the basis of oxygen storage mechanism analysis, a new lean-burn gasoline engine emission control strategy was given using TWC. Through AFR lean/rich modulation and TWC control, the lean-burn NOx emission reduced dramatically. The number and ratio of lean/rich modulations were optimized through tests. The conversion efficiency of NOx under lean-burn conditions reached 45%. The NOx emission could be reduced to less than 200 × 10 ^-6. The strategy was proved effective in the control of lean-burn NOx emission of gasoline engines.