(1.Key Laboratory of Power Machinery and Engineering, Shanghai Jiao Tong University,Shanghai 200240,China;2.Technology Center of SAIC Motor Co.，Ltd.,Shanghai 201804,China)
The leanburn engine has the advantage of low fuel consumption and also the disadvantage of high NOx emission. The traditional SCR technology cannot be applied to light passenger vehicle due to its large size. The NOx removal of leanburn engine is mainly achieved by NSR catalyst, which cannot achieve high NOx conversion rate yet at high temperature and high space velocity. Through the experimental research, a new NSR technology for NOx removal of lean-burn engine exhaust was proposed. By injecting a hydrocarbon reductant at the front end of NSR catalyst with a certain frequency, the reductive and active intermediate species such as —CN and —NCO formed on the NSR catalyst. The intermediate species generated continuously and were consumed to reduce the NOx pollutants adsorbed on the NSR catalyst during the pulse jet of C3H6 and the NSR catalyst then regenerated. By adopting this technology, the engine could be running in a leanburn condition, which meant that it was not necessary to switch to the richburn condition. Therefore the operation was simple and the control cost was low. The experimental results show that this system can broaden the temperature window of NOx removal and maintain NOx conversion efficiency of more than 90% in the range of exhaust gas temperature between 350 ℃ and 550 ℃. In addition, the key influencing parameters of the system are also explored including the reaction temperature, the space velocity, the hydrocarbon fuel injection frequency and quantity and the air-fuel ratio.
