Combustion characteristics of oxygenated fuels Ethanol -and Butanol-gasoline fuel blends, and their impact on performance, emissions and Soot Index
Abstract
Oxygenated fuels are studied in spark combustion engines because of their potentially positive impact on greenhouse emissions, and as part of alternative renewable fuels. Furthermore, engine test results position them as a promising lever to reduce engine-out emissions, and most notably, particles. This study focuses on oxygenated fuel Butanol, which is a potential output of recent developments on Algae and Cyanobacteria harvest process. Its blending into gasoline and application into spark ignition engines is investigated. Blending levels of n-Butanol and iso-Butanol have been proposed based on standard gasoline's octane number, RON, at two ethanol concentration levels, 10 and 25%. Fuel blend impact on combustion, and on regulated and non-regulated emissions is analysed. Fuel knock resistance properties, RON and MON, determine the knocking tendencies for ethanol and butanol at 2000 rpm. However, test results highlight different knocking sensibility behaviour at higher engine speed. Emission results also illustrate a strong advantage of Butanol on particle mass emissions. Soot indices, that are conventionally used to quantify the impact of a fuel over particle emissions, are studied and confronted to results obtained on ethanol blends. The deviation in Particle Matter Indices obtained for butanol blends is analysed, on the basis of specific operating points. It highlights different particle emissions responses to the increase of oxygenates ethanol and butanol, not uniquely correlated to oxygen and aromatic concentration.
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