Effect of Biodiesel-Ethanol Blended Fuel Spray Characteristics on the Reduction of Exhaust Emissions in a Common-Rail Diesel Engine

摘要

An experimental investigation was performed to analyze the effects of biodiesel-ethanol blended fuel spray on the combustion, and exhaust emission characteristics in a single cylinder common-rail diesel engine. In order to analyze the macroscopic and microscopic characteristics of biodiesel blended fuel spray, parameters, such as injection rate, droplet diameter, and spray tip penetration, were measured using an injection rate meter system, spray visualization, and droplet measuring system. Also, measurements of combustion, exhaust emissions, and size distributions of particulate matter were carried out under various engine operating conditions for biodiesel-ethanol blends and the results were compared with those of conventional diesel fuel. In this investigation, the measured results of biodiesel-ethanol blended fuel show that the Sauter mean diameter decreased with the increase of relative velocity between the injected fuel and the ambient gas. Comparing the combustion characteristics of diesel fuel and biodiesel-ethanol blended fuels, both diesel and blended fuel show similar trends of combustion pressure and rate of heat release. However, the combustion of biodiesel-ethanol blends indicated lower combustion characteristics, such as combustion pressures and heat release rates, than those of diesel fuel because of its lower heating value. In the case of exhaust gas recirculation, the indicated specific NO_X (ISNO_x) and soot concentration results showed lower emissions compared with those of conventional diesel fuel.