Evaporative Emissions from Gasolines and Alcohol-Containing Gasolines with Closely Matched Volatilities 861556
Alcohol-gasoline blends have attracted considerable attention for a variety of reasons, including their higher evaporative emissions compared with gasolines. To better understand the reasons for higher evaporative emissions with blends and to determine if blends with similar volatility (closely matched Reid vapor pressure and distillation temperatures) to gasoline would have equivalent evaporative emissions, experimental and modelling studies were undertaken.
Evaporative emissions with alcohol-gasoline blends were nearly equal to or slightly lower than corresponding emissions with gasolines of similar volatility characteristics. By measuring vapor generation in the SHED test, it was determined that the alcohol-gasoline blends generated less mass of vapors than the corresponding gasolines. The mathematical model developed to predict the evaporative vapor losses from the fuel tanks showed that the lower vapor generation by the oxygenated fuels was due to their lower vapor pressures at the test temperatures and the lower molecular weights of the vapors generated by these fuels.