Abstract
Total particulate number, size, and morphology were analyzed for several biofuel blends fired in a gasoline direct injection engine. The particle sampling was taken at several common operating conditions using a Scanning Mobility Particle Sizer (SMPS) unit and a thermophoretic sampling device. The fuels tested were gasoline, E10, E85, and iso-butanol-16 (iB16) and the test points were for 25%, 50%, and 75% loads at 2,000 rpm as well as idling. Exhaust gas recirculation (EGR) levels or fuel injection parameters were not changed from the manufacturer's setup. There were significant differences in the levels of particulate number produced for the fuels and for the different load/speed combinations. E85 produced significantly lower particulate levels than did any of the other fuels tested. The E10 and iB16 produced higher levels than did the gasoline fuel in the entire load rage, due to the inherent thermo-physical and chemical properties of the alcohol fuels. At a 75% engine load, the particulate size measured by the SMPS increased in the order of gasoline, E10, and iB16. This trend quite agreed with the size data measured by a transmission electron microscope. The TEM observation of particle morphology showed that particle number concentrations were extremely low at 25% and 50% loads, particularly with the biofuel blends. Further detailed analysis in morphology for the biofuels revealed the nanostructures significantly different from those for the gasoline, exhibiting a lower level of graphitic structures with some amorphous structures.
