Ethanol is the most promising alternative fuel for spark ignition (SI) engines, that is blended with gasoline, typically. Moreover, in the last years great attention is paid to the dual fueling, ethanol and gasoline are injected simultaneously. This paper aims to analyze the better methods, blending or dual fueling in order to best exploit the potential of ethanol in improving engine performance and reducing pollutant emissions.
The experimental activity was carried out in a small displacement single cylinder engine, representative of 2-3 wheel vehicle engines or of 3-4 cylinder small displacement automotive engines. It was equipped with a prototype gasoline direct injection (GDI) head. The tests were carried out at 3000, 4000, and 5000 rpm full load. The investigated engine operating conditions are representative of the European homologation urban driving cycle. Engine performance and gaseous and particle emissions 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 to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS). The gaseous and particle measurements were performed upstream and downstream of a three way catalyst (TWC), respectively. The results show that the dual fuel configuration allows an improvement of the engine performance and a reduction of exhaust emissions.