562 / 2019-01-18 08:59:38

Effects of butanol isomers on the combustion and emission characteristics of a direct-injection CI engine

Compression ignition (CI) engine; Butanol isomers; Combustion; Exhaust emission

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Advanced combustion techniques including diesel fuel reformulation and the use of renewable fuels are promising ways to reduce pollutant emissions and improve thermal efficiency. Oxygenated hydrocarbons, particularly alcohol compounds, are being studied extensively as alternatives and additives to conventional fuels due to their propensity of decreasing soot formation. Butanol is of particular interest as a renewable biofuel for advanced compression ignition (CI) engines due to its preferable properties compared to that of lower alcohols. Previous studies have shown large differences in the combustion chemistry of linear and branched alcohols, but how about their performances when applied on the engine? In this study, an experimental study was conducted on a four cylinders light duty diesel engine under constant engine speed and various engine load conditions. Three butanol isomers (e.g.,1-, 2-, iso-butanol) was tested and compared. The in-cylinder pressure was measured and the combustion process was analyzed based on a zero-zone heat release model. Regulated gaseous emission as well as the particle size distributions (PSDs) were also examined. The results showed that despite the significant differences in the reaction pathways of the butanol isomers, their combustion and emission performances on the engine did not show much differences. The ignition delay (ID) periods for three isomers under various loads were：iso-butanol>2-butanol>1-butanol. Most of the particles emitted by the butanol isomers were ultra-fine particles. The particle number emission for linear butanol isomers (1-butanol) was higher than that of branched butanol isomers (2-butanol, iso-butanol).