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An investigation on performance and combustion characteristics of pure n-butanol and a blend of n-butanol/ethanol as fuels in a spark ignition engine

Fagundez, J.L.S., Golke, D., Martins, M.E.S., Salau, N.P.G.
Energy 2019 v.176 pp. 521-530
butanol, combustion, ethanol, gasoline, physicochemical properties, spark ignition engines
The n-butanol, an alcohol with chemical characteristics similar to gasoline, was evaluated experimentally in a spark ignition (SI) engine and through two-zone computer modelling. To do so, n-butanol was burned as a pure fuel and compared to hydrous ethanol, and a blend of n-butanol/ethanol was compared to a blend of gasoline/ethanol in order to evaluate combustion characteristics and engine performance. Experimental results have shown that n-butanol performed worse than hydrous ethanol, especially due to its lower octane number, which at 13.5:1 compression ratio and 7 bar BMEP tested gave advantage to the second alcohol fuel properties due to knock limitation. At the same test conditions, n-butanol blend showed similar engine efficiency parameters, such as indicated power, when compared to the gasoline blend, indicating that n-butanol is a potential surrogate for gasoline when blended with ethanol. In order to evaluate auto-ignition occurrence, an ignition sweep was done at a 9.5:1 compression ratio and 6 bar BMEP, showing that pure n-butanol had its performance rather limited by knocking combustion and cyclic variability, while its blend with ethanol was able to avoid sporadic knock, achieving a desired performance with stable combustion.