Abstract

This work studies gas and soot radiation in axisymmetric ethylene coflow flames using calibrated four-band infrared imaging combined with a forward, line-by-line (LBL) radiative-transfer model tailored to a Telops multispectral infrared camera. Two cases, low-sooting (Yale 32) and highly-sooting (Yale 80), are simulated with CoFlame to provide temperature, CO2, H2O, and soot volume fraction fields, serving as input for a forward radiative code producing synthetic band images. These images reproduce measured shapes and regions of maximum radiance across channels, although they present discrepancies in absolute values. The multi-band agreement is interpreted as forward consistent when compared to experimental measurements obtained with the multispectral camera. Fields of species contributions and LBL spectra clarify band roles (gas-dominant, mixed, and soot-prominent), while a sensitivity study quantifies the impact of each species. Temperature is the main driver in all bands, and soot gains importance at shorter wavelengths and higher soot loading. These trends suggest a staged inversion process for retrieving flame temperature and radiating species concentrations from multispectral IR measurements. First, temperature and soot volume fraction should be estimated, followed by the refinement of gas mole fractions. Data acquisition is simple (fixed bands, standard blackbody calibration), and the main effort lies in instrument-aware post-processing and forward radiative modeling.