A Comparison of Drop-In Diesel Fuel Blends Containing Heavy Alcohols Considering Both Engine Properties and Global Warming Potentials
Journal article, 2016
Heavy alcohols can be mixed with fossil diesel to produce blended fuels that can be used in diesel engines. Alcohols can be obtained from fossil resources, but can also be produced more sustainably from renewable raw materials. The use of such biofuels can help to reduce greenhouse gas (GHG) emissions from the transport sector. This study examines four alcohol/diesel blends each containing one heavy alcohol: n-butanol, iso-butanol, 2-ethyl hexanol and n-octanol. All of the blends where prepared to function as drop-in fuels in existing engines with factory settings. To compensate for the alcohols′ low cetane numbers (CN), a third component with high CN was added to each blend, namely hydrotreated vegetable oil (HVO). The composition of each mixture was selected to give an overall CN equal to that of fossil diesel fuel. The four blends were compared in terms of sustainability, their performance in engine tests using a single-cylinder light duty engine, and their general physicochemical properties. Lifecycle analyses indicated that replacing fossil diesel with diesel-biofuel blends could reduce GHG emissions by between 22 and 58 %. The greatest reduction was predicted to occur with the isobutanol containing blend and the second greatest with the 2-ethylhexanol blend. Analysis of the blends' physical properties showed that the ones including octanol isomers resemble fossil diesel more closely than those containing butanol. Engine experiments indicated that the blends' combustion behavior and thermal efficiencies were very similar to those of conventional diesel fuel. However, on average, the blends produced approximately 50% less soot than diesel.