Development of NSR and DiAir System to Achieve Clean Emissions under Transient Cycle

In this paper, a control strategy to switch NSR (NOx storage and reduction) function from standard DeNOx by rich combustion to DiAir (Diesel NOx After-treatment by Adsorbed Intermediate Reductants) and additional advantages to use HCI (Hydrocarbon Injector) during desulfation were introduced. Investigations under a transient cycle suggest that NOx conversion with DiAir is strongly affected by preliminary NOx storage condition in the NSR catalyst. To avoid NOx breakthrough just after starting HC dosing for DiAir, a rich operation to reduce stored NOx was shown to be important and high NOx conversion could be maintained using this control strategy under a transient cycle. Furthermore, by combining HCI and in-cylinder post injection, usage of rich condition for NSR DeSOx can be expand to wider engine speed and load area. Thanks to a high NOx conversion efficiency in high temperature, including DPF(diesel particulate filter) regeneration, with DiAir, a NOx storage function in low load driving and the advantage of HCI during DeSOx, promising potential to reduce NOx emission in real driving condition was shown.