吸附还原催化系统降低稀燃汽油机NO_x排放试验研究

Experimental Study of NO_x Reduction in the Lean Burn Gasoline Engine by Adsorber Reduction Catalysis System

采用NOx吸附还原催化器和传统的三效催化器组合而形成的新型催化转化系统,在一台改装的产品四气门电控燃油喷射准均质稀燃汽油机上进行了催化技术降低稀燃汽油机NOx排放的试验研究。试验结果表明:当t稀∶t浓=200 s∶20 s时,仅用NOx吸附还原催化器或三效催化器位于吸附还原催化器之后的催化器布置可以使稀燃汽油机的NOx排放降低到300×10-6左右,降低62.5%,而三效催化器位于吸附还原催化器之前的催化器布置可以大幅降低稀燃汽油机的NOx排放,达到50×10-6左右,降低93%。而且随着t稀∶t浓绝对时间的减小,稀燃汽油机的NOx排放浓度降低。稀燃汽油机转速和负荷增大,NOx排放浓度增大,NOx催化转化率CNOx减小。

A new type catalyst which is the combination of NOx adsorber Catalyst and Three Way Catalyst, was tested on a modified EFI 16 valves lean burn gasoline engine. With the new type catalyst and lean burn engine, the reduction in NOx emission was studied under lean mixture condition. The results show that when tlean/trich=200 S ： 20 S, NOx emission reduces to 300×10^-6（62.5% in reduction） in the case of only NOx adsorber Catalyst or mounted the Three Way Catalyst downstream of the NOx adsorber Catalyst. When the Three Way Catalyst was installed before the NOx adsorber Catalyst, NOx emission of lean burn gasoline engine was decreased to 50×10^-6（93% in reduction）. With the decreasing of tlean/trich , NOx emission will reduce simultaneously. Increasing in engine speed and load will result in increase in NOx emission and decrease in NOT conversion rate.