Characteristics of High-Pressure Spray and Exhaust Emissions in a Single- Cylinder Di Diesel Engine

Regulations on exhaust emissions from light- and heavy-duty diesel engines have generated interest in high-pressure fuel injection systems. It has been recognized that high-pressure injection systems produce fuel sprays that may be more conductive to reducing exhaust emissions in direct-injection diesel engines. However, for such a system to be effective it must be matched carefully with the engine design and its operating parameters. A common-rail type of fuel injection system was investigated in the present study. The injection system utilizes an intensifier to generate injection pressures as high as 160 MPa. The fuel spray characteristics were evaluated on a test bench in a chamber containing pressurized nitrogen gas. The injection system was then incorporated in a single-cylinder diesel engine. The injection system parameters were adjusted to match engine specifications and its operating parameters. The spray characteristics were found to depend on peak and average injection pressures during the injection period. Both of these factors were found to influence fuel consumption and emissions of smoke and oxides of nitrogen. An advantage of the high pressure, electronic fuel injection system is the ability to vary injection timing and optimize the engine performance for efficiency and exhaust emissions.