Study on Emission-Reducing Method With New Lean NO{sub}x Catalyst for Diesel Engines

摘要

In recent years, emission regulations have become more stringent as a result of increased environmental awareness in each region of the world. For diesel engines, reducing NO{sub}x emissions is a difficult technical challenge. To respond to these strict regulations, an exhaust gas aftertreatment system was developed, featuring a lean NO{sub}x catalyst (LNC) that uses a new chemical reaction mechanism to reduce NO{sub}x. The feature of the new LNC is the way it reduces NO{sub}x through an NH{sub}3-selective catalytic reduction (SCR), in which NO{sub}x adsorbed in the lean mixture condition is converted to NH{sub}3 in the rich mixture condition and reduced in the following lean mixture condition. Thus, the new system allows the effective reduction of NO{sub}x. However, in order to realize cleaner emission gases, precise engine control in response to the state of the exhaust aftertreatment system is essential. This control includes maintaining the LNC activation state and reducing NO{sub}x emissions before LNC activation. In this study, effective NO{sub}x reduction technology was developed by combining controls, such as that for maintaining LNC activation temperature, with studies of engine emission improvements and techniques to supply reductant to the catalyst.