Spectral Radiation Properties of a Turbulent Ethylene Pool Fire

In the present work, line-of-sight spectral radiation intensities (I_λ) were measured in a 7.1 cm ethylene (C₂H₄) buoyant diffusion flame, designed to mimic pool fires. Various time series statistics were calculated using the radiation data. Both soot and gaseous species had significant radiation emissions, emphasizing the need for spectrally-resolved radiation measurements. Significant fluctuations were observed in the radiation intensities from the fire, especially at higher elevations and near the flame edges. In addition, root-mean-square (rms) and probability density functions (PDF) of I_λ indicated higher fluctuations in soot compared to gaseous species. Autocorrelations of I_λ showed periodic oscillations due to the puffing phenomenon typically seen in pool fires. The observed oscillation frequencies ranged from 7.47 to 7.86 Hz and are in excellent agreement with empirical correlations based on past data. Characteristic frequencies of these oscillations were also reflected in the power spectral densities (PSD) of I_λ. Based on the measured autocorrelations of I_λ, it was observed that the integral time scales decrease with increasing height above the burner exit, which is expected since mean velocities increase with height due to combustion-induced buoyancy in pool fires and buoyant flames.