Infrared Imaging, Computations, and Tomography of Bluff Body Stabilized Laminar Diffusion Flames

Comparative studies of computed and measured infrared images provide a non-intrusive approach for studying flame structure. Narrowband radiation intensity measurements of three soot producing laminar diffusion flames were acquired using an infrared camera. The data are compared with computational results to gain insights into spatial scalar distributions in the flame stabilization region and beyond. Select mixtures of ethylene/nitrogen and air/nitrogen were flowed from a centerbody burner to achieve different sooting characteristics in the flames. The radiative transfer equation was evaluated along lines-of-sight using a narrowband radiation model and computed scalar values. The size and shape of the computed and measured images are similar indicating that the computed scalar values adequately capture the bulk thermo-physics of the flows. Computed and measured intensities agree within 20% on average when normalized by the maximum intensity. Larger differences occur in the flame stabilization region. Planar temperature distributions were determined by utilizing infrared emission tomography, inverse analysis, and the computed species concentrations. Computed and tomographic temperature distributions agree within 20% on average, with the largest differences occurring in the flame stabilization region. Improvements in models and computations of the flame stabilization region are prompted by a quantitative comparison of the computed and measured infrared images.