Extinction of Methanol and Ethanol Flames in Premixed Flows

Alcohols like methanol (CH₃OH) and ethanol (C₂H₅OH) are well known alternative fuels. Ethanol, which replaced MTBE in California, is added to regular gasoline up to 5% without any modifications required to a normal gasoline engine. Recently E85, an ethanol-gasoline mixture of 85% ethanol and 15% gasoline derived from crude oil, got attention as an alternative fuel due to high gas prices and environmental acceptance. Therefore, it is important to understand the basics of alcohol combustion. Experimental and numerical studies are conducted on extinction of methanol and ethanol flames in premixed laminar flows. The studies are performed in a counter-flow configuration. The burner used in the experiments is made up of two opposing ducts. Two configurations are considered. In one configuration, a premixed reactant stream made up of vaporized fuel, air, and nitrogen is introduced from one duct and nitrogen from the other. In the other configuration, premixed reactant streams are introduced from both ducts. A flame is established in the laminar flow field between both ducts. The flow velocity is increased until critical conditions of extinction are reached. Temperature profiles across the distance between the two ducts and critical conditions of extinction are measured for various values of equivalence ratio and dilution factor. The temperature in the flow field is measured with a platinum/rhodium thermocouple which is coated with yt-trium/beryllium oxide to avoid catalytic effects. The temperature is corrected for radiation losses. Numerical calculations are performed using a detailed chemical kinetic mechanism at conditions corresponding to those used in the experiments. The measured and calculated values of the temperature profiles and critical conditions of extinction are compared.