In-cylinder spectroscopic measurements of combustion process in a SI engine fuelled with butanol-gasoline blend

In-cylinder optical diagnostic was applied to study butanolgasoline blend combustion in a SI engine. Spark timing and fuel injection mode were changed to work in normal and knocking conditions. The experiments were realized in a single cylinder ported fuel injection SI engine with an external boosting device. The engine worked likestoichiometric mixture at 2000 rpm, medium boosting and wide open throttle. UV-visible natural emission spectroscopy allowed to follow the formation and the evolution of the main compounds and radical species that characterize the combustion process from the spark ignition until the exhaust. Particular interest was devoted to OH and CO2 * evolution, and to the spectral evidence of soot precursors due to fuel deposits burning. OH resulted the best marker for combustion both in normal and abnormal conditions.