EFFECT OF BUTANOL BLEND ON IN-CYLINDER COMBUSTION PROCESS. PART 1: SPARK IGNITION ENGINE

The addition of alcohol to conventional hydrocarbon fuels for a spark-ignition engine can increase the fuel octane rating and the power for a given engine displacement and compression ratio. In this work, the influence of butanol addition to gasoline in a port fuel-injection, spark ignition engine was investigated. The experiments were realized in a single cylinder ported fuel injection SI engine with an external boosting device. The optical accessible engine was equipped with the head of commercial SI turbocharged engine with the same geometrical specifications (bore, stroke, compression ratio) as the research engine. The effect on the spark ignition combustion process of 40% n-butanol blended in volume with gasoline was investigated by cycle resolved visualization. The engine worked at low speed, medium boosting and wide open throttle. Changes in spark timing and fuel injection phasing were considered in order to investigate normal and abnormal combustion. Comparisons between the parameters related to the flame luminosity and to the pressure signals were performed. The duration of injection for butanol blend was increased to obtain stoichiometric mixture. In open valve injection condition, the fuel deposits on intake manifold and piston surfaces decreased, allowing a reduction in fuel consumption. Butanol blend granted the performance levels of gasoline and in open valve injection allowed to minimize the abnormal combustion effects and the formation of ultrafine carbonaceous particles.