Relating multi-spectral infrared imaging to the direct source of combustion noise

Characterizing the sound-generating mechanisms of open flame combustion plays a fundamental role in understanding the acoustics of fire. Previous literature has utilized the correlation between the chemiluminescence of chemically reacting species and the direct source of combustion noise, the global heat release rate. The present analysis implements a multi-spectral infrared camera to identify spatial correlation regions of bandwidth-specific intermediary and product combustion species (such as hydrocarbons, carbon dioxide, and water) to estimate qualitative spatial regions of global heat release. As infrared imaging is a line-of-sight technique, acquired images are deconvolved into a 2-D projection of an assumed axisymmetric testing volume. A variety of laboratory-scale flames are analyzed, including those produced from diffusion and pre-mixed gas burners as well as aspen wood-wool combustion. The relationship between the chemical reaction components and the observed spectral footprint of each observed combustion regime is discussed. Recommendations are made to improve the coalescence of spectroscopy/thermal imaging and acoustic measurements in future testing. Data gathered was made possible through collaboration with the USDA Forest Products Laboratory.