This paper presents results of an experimental investigation on a flexible port dual fuel injection using different ethanol to gasoline mass fractions. A four stroke, two cylinder turbocharged SI engine was used for the experiments. The engine speed was set at 3000 rpm, tests were carried out at medium-high load and two air-fuel-ratio.
The initial reference conditions were set running the engine, fueled with full gasoline at the KLSA boundary, in accordance with the standard ECU engine map. This engine point was representative of a rich mixture (λ=0.9) in order to control the knock and the temperature at turbine inlet. The investigated fuels included different ethanol-gasoline mass fractions (E10, E20, E30 and E85), supplied by dual injection within the intake manifold. A spark timing sweep, both at stoichiometric and lean (λ=1.1) conditions, up to the most advanced one without knock was carried out. Engine performance, gaseous exhaust emissions, particle size distribution and particulate matter were measured and the results were compared to the gasoline reference case.
The main results showed that the E20 and E30 ethanol mass fractions, allowing advanced spark timings, achieved the same engine load as the gasoline case with a significant increase in thermal efficiency (≅10%), in spite of alcohol’s lower energy content. Compared to gasoline, E30 or E85 attained a significant reduction in particle number emissions as well a cut of the particulate mass (60-80%), particularly significant for the lean case (90%).