Experimental and numerical study of spectral dependent radiation reabsorption on flame propagation

Premixed flames in CO₂ diluted CH₄-O₂-He mixtures were studied both experimentally and numerically to investigate the effects of spectral dependent radiation reabsorption on the flame propagation and flammability limit. Laminar burning velocities of CH₄-O ₂-He-CO₂ mixtures at both normal and elevated pressures up to 5 atm were measured by using a pressure-release type spherical bomb. The measured data were compared with the results from computations performed with and without spectral radiation absorption. It was found that the spectral radiation reabsorption results in higher burning velocities of CH ₄-O₂-He-CO₂ mixtures and wider flammability limits than predictions using the optically thin model. Furthermore, the enhancement becomes more significant at higher pressures. The results demonstrated that reabsorption effects must be considered to correctly predict flame speeds and extinction limits in flammability limit and burning properties of mixtures with CO₂ addition.