EFFECT OF BIODIESEL-ETHANOL BLENDED FUEL SPRAY CHARACTERISTICS ON THE REDUCTION OF EXHAUST EMISSIONS IN A COMMON-RAIL DIESEL ENGINE

An experiment was performed to analyze the effects of biodiesel-ethanol blended fuel spray on the combustion and exhaust emission characteristics of a single-cylinder common-rail diesel engine. To analyze the macroscopic and microscopic characteristics of biodiesel blended fuel spray, measurements of the injection rate, droplet diameter, and spray tip penetration were taken using an injection rate meter, spray visualization and a droplet measuring system. The combustion, exhaust emission characteristics and size distributions of particulate matter were determined for various engine operating conditions using biodiesel-ethanol blends, and the results were compared to those of conventional diesel fuel. In this investigation, the measured results of biodiesel-ethanol blended fuels show that the Sauter mean diameter (SMD) decreased with an increase of relative velocity between the injected fuel and ambient gas. Comparing the combustion characteristics of diesel fuel and biodiesel-ethanol blended fuels, both diesel and blended fuel showed similar trends in combustion pressure and the rate of heat release. However, the combustion of biodiesel-ethanol blends had lower combustion characteristics such as combustion pressures and heat release rates than those of diesel fuel because of their lower heating values. In the case of exhaust gas recirculation (EGR), the indicated specific NO(x) (ISNO(x)), and soot concentrations were lower than those of conventional diesel fuel.