Experimental and Modeling Study of the Flammability of Fuel Tank Headspace Vapors from Ethanol/Gasoline Fuels; Phase 3: Effects of Winter Gasoline Volatility and Ethanol Content on Blend Flammability; Flammability Limits of Denatured Ethanol

Abstract

Background The flammability of a fuel blend in the head space of a storage tank is controlled by the vapor pressure of the blend. Conventional gasolines are so volatile that the headspace vapors are normally too rich to sustain combustion at most ambient temperatures. Only under very cold conditions does the vapor-air mixture in the tank become flammable. Because of its different vapor pressure and stoïchiometry, pure ethanol produces vapor-air mixtures in the tank that are flammable over a wide range of ambient temperatures. Blends of ethanol and gasoline form non-ideal mixtures in which the gasoline components render the vapor-air mixture in a tank too rich for combustion at warm temperatures. Like gasoline, as temperature drops, the vapor-air mixture becomes leaner and eventually falls into the flammable region. However, the mixture becomes flammable at higher temperatures than conventional gasoline, and so presents a hazard over a greater range of conditions if a suitable ignition source is present. Objectives of the Work Reported The mission of the US Department of Energy's Clean Cities program is to advance the energy, economic, and environmental security of the United States by supporting local decisions to adopt practices that reduce the use of petroleum in the transportation sector. Part of this program includes the replacement of petroleum by alternative and renewable fuels.