Abstract-Gupta The structure of flames is examined under conditions of highly preheated air using methane or propane as the fuel. Specific matters of interest include flame stability limits, flame signature, flame radiation and emission-adsorption spectra, flame temperature, and chemical species within the flame as affected by air preheat temperature, fuel, and flame equivalence ratio. The experimental facility uses a pair of regenerative burners which allow the test section to be maintained at any temperature up to 1800( K; combustion air can be preheated up to 1300( K, giving a much higher air temperature than in conventional furnaces. The test section is optically accessible permitting the use of a number of optical diagnostics. Highly-preheated air combustion offers many potential advantages but has not been deemed practical up to now. It can reduce fuel consumption up to 30%, reduce carbon dioxide emissions, reduce equipment size, and reduce pollutants by 20-30% for a given therm production. The recirculating system used in this study may be a practical way to exploit these benefits.
