CORRELATION BETWEEN SOOT FORMATION AND EMISSIONS IN A SMALL DISPLACEMENT SPARK IGNITION ENGINE OPERATING WITH ETHANOL MIXED AND DUAL FUELED WITH GASOLINE

This paper deals with the evaluation of the effect of different methods of ethanol fueling on in-cylinder soot formation and exhaust emissions in a small displacement spark ignition engine. The engine was fueled with gasoline and ethanol. In particular, the ethanol was both blended with gasoline (E30) and dual fueled (EDF). In this latter case, ethanol was direct injected and gasoline was injected into the intake duct. For both the injection configurations, the same percentage of ethanol was supplied: 30%v/v ethanol in gasoline. The experimental investigation was carried out in 4-stroke small single cylinder engine. The measurements were carried out at 2000 and 4000 rpm under full load condition. Optical technique based on 2D-digital imaging was used to follow the combustion process. Two-color pyrometry was applied to assess the soot formation. Particle emissions were measured at the exhaust by means of a smoke meter. Particle size distribution function was measured in the range from 5.6 to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS). For E30 the in- cylinder soot formation and emissions are larger than for EDF because of the different contribution of gasoline. In EDF the better evaporation and mixing of gasoline, typical of PFI configuration, coupled with the soot reduction tendency of ethanol lead to a low particle formation and emissions