Tailor-Made Fuels from Biomass: Potentials of 2-butanone and 2-methylfuran in direct injection spark ignition engines

Two possible future biofuels, 2-butanone also referred to as methyl ethyl ketone (MEK) and 2-methylfuran, identified within the Cluster of Excellence “Tailor-Made Fuels from Biomass” (TMFB), have been evaluated as pure fuels in the present study. Investigations of the autoignition tendency were carried out on a rapid compression machine (RCM), whereas thermodynamic investigations were conducted on a direct injection spark ignition single cylinder research engine. 2-Methylfuran and 2-butanone were compared against the present benchmark biofuel for spark ignition engines ethanol and conventional RON95 gasoline. A similar autoignition tendency compared to ethanol was found for 2-methylfuran. In case of 2-butanone very high ignition delay times were measured, even higher than for ethanol and 2-methylfuran. For 2-butanone and 2-methylfuran, the lower heat of vaporization in combination with higher vapor pressure and better primary breakup compared to ethanol are beneficial for mixture formation. During the engine testing for both fuels, superior characteristics compared to conventional gasoline and ethanol were identified. In case of 2-methylfuran, an increased combustion stability, especially at low engine load and cold boundary conditions, could be found at a higher knock resistance than conventional gasoline. In combination with increased compression ratio this enables an efficiency increase of up to 19%, whereas for ethanol an even further increase of up to 21% is possible. 2-Butanone shows increased combustion stability at low engine load and cold boundary conditions compared to ethanol and also conventional gasoline as well as highest knock resistance equal to ethanol. However, for both 2-butanone and 2-methylfuran increased emissions of nitrogen oxides were found when compared to ethanol. For both possible future biofuels and also ethanol, a significant reduction of particle emissions compared to conventional gasoline was found.