Experimental and computational imaging of mid-infrared radiation from a turbulent ethylene flame

Quantitative Imaging of Radiation Intensity (QIRI) was utilized to study time dependent radiation intensity from major product species in an ethylene-air turbulent non-premixed luminous flame. The flame was stabilized on a jet burner (8 mm inner diameter) identical to that used for the DLR-A flame of the TNF workshop. The fuel flow rate was selected to yield a Reynolds number of 15, 200, which is identical to that of the DLR-A flame. A high speed infrared camera with four band-pass filters was used to acquire images of radiation intensity emitted by: carbon dioxide, water vapor, combined carbon dioxide and water vapor, and soot. A Large Eddy Simulation (LES) of the soot containing flame was carried out. Resolved scale temperature, CO₂ and H₂O mole fractions, and soot volume fraction distributions from the simulations were extracted and used in conjunction with the radiation transfer equation and a narrow band model to compute the quantitative spectral radiation intensity images. The computed images and statistics were compared with the measurements and showed encouraging agreement for the 4.3 μm CO₂ band but required adjustments in the soot volume fractioins for the 2.58 μm H₂O band and the continuum soot radiation. QIRI is demonstrated to be useful tool for identifying potential shortcomings in the soot model.