Effect of Common Rail Pressure on the Relationship between Efficiency and Particulate Matter Emissions at NOx Parity 2012-01-0430

The effect of fuel injection pressure on the brake specific fuel consumption (BSFC) and brake specific particulate matter (BSPM) emissions at NOx parity (constant NOx emissions level) was investigated under different conditions of engine speed and load using a 2.5L DDC/VM-Motori common-rail, turbocharged, direct injection (DI), light-duty diesel engine. NOx parity at varying conditions of speed, load, and fuel injection pressure was achieved by changing the injection strategy and timing. The results of these analyses confirmed the well-established trends that soot emissions reduce with an increase in rail pressure at the expense of increasing NOx emissions. With an increase in engine speed (at constant load and NOx parity), it was observed that BSFC, CO, CO₂, and hydrocarbon emissions decreased, while BSPM decreased initially and increased later on. Increasing the fuel injection pressure resulted in an increase in BSFC, CO, CO₂, and hydrocarbon emissions. In contrast, with an increase in engine load (at constant speed and NOx parity), it was observed that BSFC, BSPM, CO, CO₂, and hydrocarbon emissions decreased. Increasing the fuel injection pressure resulted in a decrease in BSPM and hydrocarbon emissions while all other trends were similar to the constant load NOx parity test. This study indicates that the engine parameters can be tailored to reduce particulate matter and hydrocarbon emissions, while maintaining an optimum BSFC under the mandated NOx emissions level.