흡장형 De-NOx 촉매 시스템을 이용한 NOx 저감 연구

NOx Reduction system was newly developed; The De-NOx system is composed up of an external fuel injection system, DFC(Diesel Fuel Cracking catalyst) and LNT(Lean NOx Trap). External fuel injector was used for the supply of diesel fuel into DFC and LNT. DFC converts the injected diesel fuel gas into more effective reductants such as H₂,CO and low chain hydrocarbon. The concentration and amount of reductant can be controlled with the control of external injection. In this paper, the NOx reduction efficiency with respect to the reductant concentration was investigated with engine bench test and vehicle test. Vehicle test was conducted against EURO 6 regulation with the NEDC mode. The conclusion is that; The De-NOx system with external injection, DFC and LNT can reduce NOx efficiently even in 7% O₂ concentration, so the NOx reduction is possible without engine calibration for the lean/rich control. There is an threshold level of reductant concentration for high NOx reduction and low THC slip. This value is proportional to the O₂ contration and gas flow rate of exhaust gas.