SYSTEM AND METHOD FOR REDUCING NOX EMISSIONS DURING TRANSIENT CONDITIONS IN A DIESEL FUELED VEHICLE

摘要

The present invention is a dual-stage fuel injection strategy for compression ignition engines in which 15-40% of the fuel is injected into the combustion chamber no later than about 20 to 30 CA ATDC and as early as IVC. The rest of the fuel is then injected in one or more fuel pulses, none of which start before about 20 to 30 CA ATDC. The fuel injected early in the compression stroke forms a lean mixture that burns with low soot and low NOx emissions. The combustion of that fuel serves to increase in-cylinder temperature such that the ignition delay of subsequent fuel injection pulses is short. This mode is utilized when it is predicted that a NOx spike is imminent. Various other alternative methods for reducing NOx spikes are also disclosed such as specialized EGR systems that can provide EGR with low manifold vacuum.