Quantitative model-based imaging of mid-infrared radiation from a turbulent nonpremixed jet flame and plume

Current understanding of turbulent reacting flows can be improved by novel quantitative comparisons using highly scalable visualization methods based on volume rendering of time-dependent mid-infrared intensities in the form of images with multiple view angles. In this work, the effects of radiation and buoyancy in a turbulent nonpremixed flame and plume are studied by quantitatively comparing measured and computed images of the mid-infrared radiation intensity. To this end, a turbulent nonpremixed jet flame (Reynolds number 15,200 and CH4/H-2/N-2 fuel composition) is considered, representing a benchmark flame configuration of the International Workshop on Measurement and Computation of Turbulent Nonpremixed Flames (TNF Workshop). Quantitative images of the radiation intensity from the flame are acquired using a calibrated high-speed mid-infrared camera and band-pass filters. The camera and filters enable time-dependent measurements of radiation from water vapor and carbon dioxide over the entire flame length and beyond. Results of the solution to the radiative transfer equation are rendered in the form of images using scalar values from large eddy simulations (LES) and a narrowband radiation model. Planar images obtained from experiments and simulations for the radiation intensity display qualitatively comparable features, including localized regions of high and low intensity that are characteristic of turbulent flames. The quantitative comparison of the measured and computed temperature profiles and radiation intensities, particularly in the plume region downstream of the stoichiometric flame length, indicate that including radiation heat loss is important even for weakly radiating flames. The results demonstrate that quantitative experimental and model-based imaging of mid-infrared radiation intensity is useful for assessing the results of narrowband radiation and combustion models. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.