Combustion and Emissions Characterization of Soy Methyl Ester Biodiesel Blends in an Automotive Turbocharged Diesel Engine

Recent increases in petroleum fuel costs, CAFE standards, and environmental concerns about CO₂ emissions from petroleum based fuels have created an increased opportunity for diesel engines and renewable alternative fuels such as biodiesel. Additionally, the Environmental Protection Agencies Tier II heavy duty and light duty emissions regulations require significant reductions in NO_x and diesel particulate matter emissions for diesel engines. As a result, the diesel engine and aftertreatment system is a highly calibrated system that is sensitive to changing fuel characteristics. This study focuses on the impact of soy methyl ester biodiesel blends on combustion performance, carbonaceous soot matter and NO_X emissions. Tests were completed with an I4 1.9L, turbocharged, high speed, direct injection diesel engine using commercially available 15 ppm ultra low sulfur diesel, a soy methyl ester B20 (20% biodiesel and 80% ultra low sulfur diesel) biodiesel blend and a pure soy methyl ester biodiesel. Results show a reduction in NO_x and carbonaceous soot matter emissions and an increase in brake specific fuel consumption with the use of biodiesel. Further, traditional methodology assumes that diesel fuels with a high cetane number have a reduced ignition delay. However, results from this study show the cetane number is not the only parameter effecting ignition delay.