A novel method for spectral and spatial characterisation of flames using a custom-developed hyperspectral imaging system

This study introduces a pioneering approach to flame diagnostics by employing a radiometrically calibrated Hyperspectral Imaging (HSI) system to visualise the radiant power of methane-air flames both spectrally and spatially, a first in combustion research literature. Traditional flame diagnostic techniques rely heavily on chemiluminescence, with limitations in accurately depicting the physical radiative heat release and energy quantification. Our methodology involved the indirect calibration of a HSI system using a radiometer after comprehensive pre-calibrations and corrections for non-uniformities attributable to optical and electronic components, enhancing the accuracy and reliability of our radiant power measurements. The calibrated radiant power was validated against conventional chemiluminescence measurements with the comparisons of the peak C2*(0,0)/CH* ratio. The calibrated HSI system enabled the detailed mapping of radiant power emitted by various radicals, notably different types of C2*and CH*, within the hydrocarbon flames. Our results revealed distinct emission distributions and corresponding concentrations, highlighting the diverse roles of these radicals in the combustion process. We presented spatially resolved maps depicting the variations in radiant power and C2*/CH* ratios, providing a direct visualisation of dominated energy-release radical distributions at different equivalence ratios. These visualisations serve as a promising tool for advancing our understanding of flame behaviours, combustion dynamics and energy conversion efficiency. The methodology developed in our work could offer valuable data for simulations and mechanism studies and contribute substantially to both academic research and practical applications in combustion technology.