Quantitative infrared imaging of impinging turbulent buoyant diffusion flames

A buoyant fire impinging on a horizontal ceiling at a certain distance from the fuel source occurs in many practical fire scenarios. Motivated by this application, infrared radiation from buoyant diffusion flames with and without impingement on a flat plate is studied using a quantitative comparison of measured and simulated images. The measured quantitative images of the radiation intensity are acquired using a calibrated high speed camera. Simulated radiation intensities are rendered in the form of images and compared quantitatively with the measured images. The simulated radiation intensities are obtained using the radiative transfer equation with local absorption coefficients evaluated using a narrowband radiation model. The instantaneous local species concentrations, soot volume fractions, and temperatures necessary for these simulations are calculated using the Fire Dynamics Simulator (FDS) version 6. The measured images reveal that the characteristic necking and bulging (7Hz±1Hz) of the free buoyant flame is suppressed to a large extent by impingement on the plate. The roll-up vortices in the impinging flame are much smaller than those in the free flame. The stagnation point boundary layer inferred from the computed images is thicker at some instances than that inferred from the measurements. Qualitative and quantitative comparisons between the measured and computed infrared images for both the free and the impinging fires reveal many similarities as well as differences useful for model evaluation.