The Effect of Ethanol and Methanol Blends on the Performance and the Emissions of a Turbocharged GDI Engine Operating in Transient Condition

Direct injection spark ignition engines represent an effective technology to achieve the goal of carbon dioxide emission reduction. Further reduction of the carbon footprint can be achieved by using carbon-neutral fuels. Oxygenated alcohols are well consolidated fuels for spark ignition engines providing also the advantages of knock resistance and low soot tendency production. Methanol and ethanol are possible candidates as alternative fuels to gasoline due to their similar properties. In this study a blend at 25 % v/v of ethanol in gasoline (E25) and a blend with 80% gasoline, 5 % v/v ethanol and 15% v/v of methanol (GEM) were tested. These blends were considered since E25 is already available at fuel pump in some countries. The GEM blend, instead, could represent a valid alternative in the next future. Experiments were carried out on a high performance, turbocharged 1.8 L direct injection spark ignition engine over the Worldwide Harmonized Light Vehicles Test Cycle. Gaseous emissions and particles in the range 5.6 - 560 nm were measured at exhaust. Experimental results showed that gaseous emissions are affected beyond of the fuel properties also by the specific phase of the cycle. The results all over the WLTC highlighted the beneficial effect of E25 and even more of GEM blend on CO, THC and NOx emissions. With regard to the particle emissions, they are reduced for alcohol blends compared to gasoline showing a shift of size distribution versus larger particles when methanol is added to the ethanol and gasoline.