Gasoline Evaporation–Ethanol and Nonethanol Blends

Abstract

Tests were performed to compare the evaporation rate of 10 volume percent (vol%) ethanol-blended gasoline (E10) with the evaporation rate of its base gasoline. Weight loss, temperature, pressure, and humidity were monitored as lab-blended E10 and base gasolines were evaporated concurrently from glass cylinders placed on balances located side by side under an exhaust hood. The averaged results of four tests at about 70°F showed that the E10 lost more total weight to evaporation than the base fuel, but less gasoline. The increased weight was due to ethanol, which was present in the E10 evaporative emissions at concentrations of about 13 weight percent (wt%). In two-hour tests at temperatures near 70°F, during which 4.5 to 5.3 wt% of initial fuel samples were evaporated, E10 fuels lost an average of about 5% less gasoline than their base fuels. A similar result was obtained for a one-hour test, during which about 2.4 to 2.5 wt% of the initial fuel samples were evaporated. Gas chromatography (GC) component analysis indicated that the compositions of the ethanol-free emissions from the two fuels were similar. Reid vapor pressure (RVP) measurements made using a Grabner CCA-VPS according to ASTM D5191-91 indicated that E10 fuels underwent an approximate 5% greater RVP reduction than their respective base fuels.