ISSN Online: 2377-424X
ISBN Print: 1-56032-797-9
International Heat Transfer Conference 11
ANALYSES OF EXTINCTION AND FLAMMABILITY LIMIT OF STRETCHED PREMIXED FLAMES USING THE STATISTICAL NARROW-BAND MODEL
要約
Extinction and flammability limit of nonadiabatic stretched premixed methane-air flame are numerically investigated using the statistical narrow-band model. Attention is paid to the radiation induced non-linear phenomena and to the effeet of radiation reabsorption. It is found that even for a mixture at an equivalence ratio lower than the standard lean flammability limit (lean limit of one-dimensional unstrained flame), a moderate stretch can makes the mixture burn. The flammable region of this sub-limit NSF (Near Stagnation plane Flame) is bounded by the stretch extinction limit and the radiation extinction limit. For equivalence ratio larger than a critical value, it is found that the closed NSF branch opens up and yields two stable flame branches, a weak flame branch and a normal flame branch. A G-shaped curve showing the flammable regions of the weak flame and the normal flame is obtained. The effect of radiation reabsorption on flame extinction is examined by comparing the G-shaped extinction curve predicted by the narrow-band model with that calculated by optically thin model. Finally, a qualitative agreement between the experimental data and the predicted results is shown.