Emissions, Performance, and In-Cylinder Combustion Analysis in a Light-Duty Diesel Engine Operating on a Fischer-Tropsch, Biomass-to-Liquid Fuel

SunDiesel™ is an alternative bio-fuel derived from wood chips that has certain properties that are superior to those of conventional diesel (D2). In this investigation, 100% SunDiesel was tested in a Mercedes A-Class (model year 1999), 1.7L, turbocharged, direct-injection diesel engine (EURO II) equipped with a common-rail injection system. By using an endoscope system, Argonne researchers collected in-cylinder visualization data to compare the engine combustion characteristics of the SunDiesel with those of D2. Measurements were made at one engine speed and load condition (2,500 rpm, 50% load) and four start-of-injection (SOI) points, because of a limited source of SunDiesel fuel. Significant differences in soot concentration, as measured by two-color optical pyrometry, were observed. The optical and cylinder pressure data clearly show significant differences in combustion duration and ignition delay between the two fuels. Scanning mobility particle size (SMPS) measurements showed that the SunDiesel fuel produced significantly lower amounts of engine-out soot. Concentrations of specific oxides of nitrogen (NO_x) and carbon monoxide (CO) were also reduced when the SunDiesel was used. The fuel contains significantly lower levels of aromatics and sulfur compared with D2, which likely contributes to the lower particulate matter concentrations. The reduction in specific NO_x is most likely the result of an increase in power at each test condition, due to the higher heat of combustion.