Mid-Infrared Imaging of Supersonic Combustion Exhaust

Abstract

This paper presents a study on the application of mid-wave infrared (MW-IR) imaging for diagnostics in supersonic combustion exhaust flows, with the objective of enhancing optical access and measurement accuracy. The MW-IR camera was positioned to view the exhaust of the combustor to provide an unobstructed view of the flow, addressing limitations in past studies where windowed setups restricted long-wavelength emissions from CO and CO2. By calibrating the MW-IR imaging system and implementing a shock detection algorithm, the study accurately captured radiance data across multiple spectral filters, providing a direct measure of combustion species concentrations and temperature distributions within the exhaust flow. Utilizing a combination of radiance-to-temperature conversion methods, including Radcal 2.0, EES Gas Emittance, and Gray Gas Emissivities, the temperature profiles were derived for quasi-steady combustion conditions for varied fuel flow rates. The results demonstrate the MW-IR imaging approach as a viable and precise method for obtaining spatially resolved temperature and species data in high-speed combustion exhausts, offering significant insights for future developments in high-speed air-breathing propulsion diagnostics.