Combustion process analysis in a DISI engine fuelled with n-butanol through UV-VIS emission spectroscopy

In this paper, the study on the effects of n-butanol on the combustion process in a DISI engine has been conducted.Experiments were performed on a direct injection SI engine operated on gasoline and butanol, with combined analysis of in-cylinder pressure traces, exhaust emissions and optical data. The optically accessible power unit was fitted with a commercial head and a high pressure wall guided injection system working at 100 bar. The engine speed was set at 2000 rev/min as a representative value for mid-road load automotive use. Different spark timings were tested. All trials were performed at close to stoichiometric air-fuel ratio.UV-visible natural emission spectroscopy was applied to investigate the formation and the evolution of the main compounds characterizing the spark ignition and combustion process. Pollutant measurements (HC, CO and NOx) at undiluted exhaust, for gasoline and butanol, were correlated with pressure related data and optical results.