Potential of Cellulose-Derived Biofuels for Soot Free Diesel Combustion 2010-01-0335
Today's biofuels require large amounts of energy in the production process for the conversion from biomass into fuels with conventional properties. To reduce the amounts of energy needed, future fuels derived from biomass will have a molecular structure which is more similar to the respective feedstock.
Butyl levulinate can be gained easily from levulinic acid which is produced by acid hydrolysis of cellulose. Thus, the Institute for Combustion Engines at RWTH Aachen University carried out a fuel investigation program to explore the potential of this biofuel compound, as a candidate for future compression ignition engines to reduce engine-out emissions while maintaining engine efficiency and an acceptable noise level.
Previous investigations identified most desirable fuel properties like a reduced cetane number, an increased amount of oxygen content and a low boiling temperature for compression ignition engine conditions. Depending on the chain length, fuel compounds vary in cetane number and boiling temperature. Therefore different blends of butyl levulinate and n-tetradecane, a long-chain alkane, were investigated in this study.
To gain knowledge about the combustion process with biofuels, experiments on a single cylinder diesel research engine were performed. Engine results with blends of butyl levulinate and n-tetradcanee are compared to regular diesel fuel and rapeseed oil methyl ester (B100) with respect to all regulated emissions.
With the use of butyl levulinate the soot emissions can be significantly reduced up to 100 % depending on the load point. Furthermore, the experimental results indicate an additional potential for future diesel combustion concepts such as HCCI with respect to soot and NOx emissions in the part load range when using oxygenated fuels derived from biomass. Overall, the low particulate matter emissions provide justification for the consideration of butyl levulinate as a candidate for a fuel or fuel compound in future diesel engines. As a drawback malfunctions in various components of the fuel system like fuel hoses and fuel sealings can occur with the standard engine equipment.