Abstract
In order to improve emissions of diesel vehicles, this research focused on the three-way conversion effects of a diesel oxidation catalyst (DOC) and a lean NOx trap catalyst (LNT) when the air-fuel ratio of combustion gas was accurately controlled at stoichiometric value. The effects were used in warming-up and high engine-load conditions to increase the NOx conversion efficiency of an aftertreatment system. The air-fuel ratio control for this concept has to have higher control accuracy and robustness than that for a gasoline engine because the oxygen-storage characteristics of the DOC and the LNT is lower than that of a three-way catalyst of the gasoline engine. Consequently, this research designed a unique adaptive air-fuel ratio control, and realized lower emissions than the levels required by LEV III SULEV30 and expected for Euro-6c.
KEYWORDS – LEV III SULEV, Euro-6c, Emission control, Diesel engine, adaptive control