The Effect of Various Petrol-Ethanol Blends on Exhaust Emissions and Fuel Consumption of an Unmodified Light-Duty SI Vehicle

Due to limited fossil fuel resources and a need to reduce anthropogenic CO₂ emissions, biofuel usage is increasing in multiple markets. Ethanol produced from the fermentation of biomass has been of interest as a potential partial replacement for petroleum for some time; for spark-ignition engines, bioethanol is the alternative fuel which is currently of greatest interest. At present, the international market for ethanol fuel consists of E85 fuel (with 85 percent ethanol content), as well as lower concentrations of ethanol in petrol for use in standard vehicles (E5, E10). The impact of different petrol-ethanol blends on exhaust emissions from unmodified vehicles remains under investigation. The potential for reduced exhaust emissions, improved security of fuel supply and more sustainable fuel production makes work on the production and usage of ethanol and its blends an increasingly important research topic. This paper evaluates the possibility of using petrol-ethanol blends in a modern Euro 4 vehicle without substantial engine modification. The influence of different quantities of ethanol in petrol blends (E5, E10, E25, E50 and E85) on the emission measurement of the gaseous pollutants carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NO_x) and carbon dioxide (CO₂) for a passenger car were analyzed over the New European Driving Cycle (NEDC) on a chassis dynamometer.

The results obtained revealed that exhaust emissions are affected by the proportion of ethanol in the blend. Engine-out emissions of HC, CO and NO_x were found to vary significantly with the blend used. Fuel injection time, engine-out and exhaust temperatures and the efficiency of the aftertreatment system were all also found to vary from blend to blend. Fuel consumption increased approximately in line with blend energetic content for all blends, apart from when running on E85.

The experimental work presented in this paper was performed as part of a test program evaluating biofuels' influence on light-duty petrol engines for passenger cars and light commercial vehicles.