Performance and emissions assessment of n-butanol–methanol–gasoline blends as a fuel in spark-ignition engines

The sleek of using alternatives to gasoline fuel in internal combustion engines becomes a necessity as the environmental problems of fossil fuels as well as their depleted reserves. This research presents an experimental investigation into a new blended fuel; the effects of n-butanol–methanol–gasoline fuel blends on the performance and pollutant emissions of an SI (spark-ignition) engine were examined. Four test fuels (namely 0, 3, 7 and 10 volumetric percent of n-butanol–methanol blends at equal rates, e.g., 0%, 1.5%, 3.5% and 5% for n-butanol and methanol, in gasoline) were investigated in an engine speed range of 2600–3400 r/min. In addition, the dual alcohol (methanol and n-butanol)–gasoline blends were compared with single alcohol (n-butanol)–gasoline blends (for the first time) as well as with the neat gasoline fuel in terms of performance and emissions. The experimental results showed that the addition of low content rates of n-butanol–methanol to neat gasoline adversely affects the engine performance and exhaust gas emissions as compared to the results of neat gasoline and single alcohol–gasoline blends; in particular, a reduction in engine volumetric efficiency, brake power, torque, in-cylinder pressure, exhaust gas temperature and CO 2 emissions and an increase in concentrations of CO and UHC (unburned hydrocarbons) emissions were observed for the dual alcohols. However, higher rates of n-butanol–methanol blended in gasoline were observed to improve the SI engine performance parameters and emission concentration. Oppositely the higher rates of single alcohol–gasoline blends were observed to provide adverse results, e.g., higher emissions and lower performance than those of lower rates of single alcohol. Finally, dual alcohol–gasoline blends could exceed (i.e. provide higher performance and lower emissions) single alcohol–gasoline blends and pure gasoline at higher rates (>10 vol.%) in the blend and, in turn, it is recommended to be used at high rate conditions.