Study of Pilot Injection for the Improvement of Combustion and Emissions Characteristics in a Heavy-Duty Diesel Engine

Abstract

A 6-cylinder, turbocharged, common rail heavy-duty diesel engine was used in this study. The effect of pilot injection strategies on diesel fuel combustion process, heat release rate, emission and economy of diesel engine is studied. The pilot injection strategies include pilot injection timing and pilot injection mass to achieve the homogeneous compression ignition and lower temperature combustion of diesel engine. The two-color method was applied to take the flame images in the engine cylinder and obtain soot concentration distribution. The results demonstrate that with the advance of pilot injection timing, the peak in-cylinder pressure becomes lower, the ignition delay of the main combustion is shortened, the NOXand soot emissions are reduced, but the HC and CO emissions are increased. With the increase of pilot injection fuel mass, the heat release rate of the pilot injection combustion and the maximum rate of pressure rise increase, NOXand HC emissions are higher, and PM and CO emissions are reduced. The pilot combustion flame is non-luminous.