Characterization of Single-Cylinder Small-Bore 4-Stroke CIDI Engine Combustion

Direct injection diesel engines power most of the heavy-duty vehicles. Due to their superior fuel economy, high power density and low carbon dioxide emissions, turbocharged, small bore, high speed, direct injection diesel engines are being considered to power light duty vehicles. Such vehicles have to meet stringent emission standards. However, it is difficult to meet these standards by modifying the in-cylinder thermodynamic and combustion processes to reduce engine-out emissions. After-treatment devices will be needed to achieve even lower emission targets required in the production engines to account for the anticipated deterioration after long periods of operation in the field. To reduce the size, mass and cost of the after-treatment devices, there is a need to reduce engine-out emissions and optimize both the engine and the aftertreatment devices as one integrated system. For example, the trade-off between engine-out NOx and PM, suggests that one of these species can be minimized in the engine, with a penalty in the other, which can be addressed efficiently in the after-treatment devices. Controlling engine-out emissions can be achieved by optimizing many engine design and operating parameters. The design parameters include, but are not limited to, the type of injection system: (CRS) Common Rail System, (HEUI ) Hydraulically Actuated and Electronically controlled Unit Injector, or (EUI) Electronic Unit Injector; engine compression ratio, combustion chamber design (bowl design), reentrance geometry, squish area and intake and exhaust ports design. With four-valve engines, the swirl ratio depends on the design of both the tangential and helical ports and their relative locations. For any specific engine design, the operating variables need also to be optimized. These include injection pressure, injection rate, injection duration and timing (pilot, main, and post injection), EGR ratio, and swirl ratio. The goal of the program is to gain a better understanding of the spray behavior under high injection pressures in small-bore, high compression ratio, high-speed, direct-injection diesel engines equipped with advanced fuel injection system. The final results demonstrate the capability of the engine in reducing the engine-out emissions and improve the trade-off between nitrogen oxides (NOx), particulate matter, other emissions and fuel economy. This report introduces a new phenomenological model for the fuel distribution and combustion, and emissions formation in the small bore, high speed, direct injection diesel engine. This will be followed by an analysis of the effect of each of injection pressure, EGR, injection advance and retard and swirl ratio on engine-out emissions and fuel economy. A discussion will be given on the 2-D and 3-D trade of maps. Finally a discussion will be made on the low temperature combustion regimes, its major problems and proposed solutions