Investigation of Ethanol-Gasoline Dual Fuel Combustion on the Performance and Exhaust Emissions of a Small SI Engine

The growing concerns over the pollutant emissions as well as the depletion of fossil fuel led to the research of advanced combustion mode and alternative fuels for the reduction both of fuel consumption and exhaust emissions. The dual-fuel injection system can be used to improve the engine performance and reduce the fossil fuel consumption performing simultaneously a direct-injection (DI) and a port-fuel-injection (PFI) of different fuels. Ethanol is one of the most promising alternative fuels for SI engines. It offers high anti-knock quality because of the high octane number; moreover, being an oxygenated fuel is very effective in particle emissions reduction. On the other hand, it is characterized by lower energy density mainly because of the low lower heating value (LHV).

The aim of the paper is the investigation of the ethanol-gasoline dual fuel combustion on engine performance and emissions. The experimental activity was carried out in a single cylinder engine for two wheel vehicles with a displacement of 250 cc. It was equipped with a prototype gasoline direct injection (GDI) head and with an injector in the intake manifold. This makes it possible to run in dual fuel mode performing a direct injection of ethanol and a port fuel injection of gasoline. This configuration was chosen in order to reduce the particle emissions typical of GDI engines. The tests were carried out at engine operating points representative of the typical urban driving conditions: 2000 rpm, 4000 rpm and 5000 rpm full load. The in-cylinder pressure was measured by means of a quartz pressure transducer flush-mounted in the region between intake and exhaust valves. The gaseous emissions and particle concentration were measured at the exhaust by means of a gas analyzer and a smoke meter. Particle size distribution function was measured in the range from 5.6 nm to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS).