Effects of mixture enleanment in combustion and emission parameters using a flex-fuel engine with ethanol and gasoline

The growing global energy demand, the fossil fuel depletion and increasing CO2 and pollutant emissions in arising from human activities are increasingly impacting the economy and government measures. For this reason, the automotive industry is constantly in search for new and environment friendly technologies and strategies, such as the use of biofuels and the variation in air-fuel ratio. These strategies have already been vastly studied, but few studies were conducted with ethanol. Thereby, this paper aims to analyze and compare the effects of ethanol and gasoline mixture enleanment in a flex-fuel engine in terms of performance, emissions and combustion. For this, it was evaluated how indicated specific fuel consumption (ISFC), emissions and combustion patterns are affected when using both Brazilian commercial gasoline (E27) and hydrous ethanol (E96) in lean conditions. The results show similar combustion parameter behavior for both fuels, pointing to ISFC reduction when operating in lean combustion modes of more than 5% and 12% for ethanol and gasoline, respectively. Despite the lower thermal and fuel conversion efficiencies resulting from the smaller Lower Heating Value (LHV), the advantage of the biofuel appears in the emission analysis. For both fuels, lean combustion results in virtual elimination of carbon monoxide (CO) emission, decreasing of 89% in nitrogen oxides (NOx) for ethanol and 74% for gasoline. Added to this, ethanol's combustion results in lower HC emission, highlighting the potential of this biofuel.