Structure and extinction of methane-air flamelet with radiation and detailed chemical kinetic mechanism
- Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Mechanical Engineering
The methane-air flamelet was studied with the effect of thermal radiation considered in this paper. The chemical reaction mechanism used is the latest detailed mechanism of GRI-Mech 2.11 which contains 49 species and 279 elementary reactions including C{sub 2} chemistry of methane oxidation and chemistry of thermal NO and prompt NO. The numerical results show that flame radiation can induce another extinction limit at a low scalar dissipation rate (0.029 s{sup {minus}1}), which is in addition to the well-known extinction limit caused by the overstretching of flame at a high scalar dissipation rate (18.4 s{sup {minus}1}). The influence of thermal radiation on flamelet temperature and NO{sub x} concentration is found to be significant enough in the small to moderate range of the scalar dissipation rate to change the trend of the temperature and species mass fraction profiles in the direction opposite to that when the thermal radiation is ignored. NO{sub x} production is shown to be strongly dependent upon the flamelet temperature. In the methane-air flamelet structure, it is found that the major species, H{sub 2}O, can be well predicted by the equilibrium state relationship for the scalar dissipation rates between the two extinction limits, but not CO{sub 2} or CO since they are affected not only by the mixture fraction, but also by the scalar dissipation rate. Also shown is that preheating the air side has a more profound effect on flamelet temperature than preheating the fuel side, and that raising either air or fuel temperature increases NO{sub x} and CO production. Finally, the effect of nonunity Lewis numbers of hydrogen (H{sub 2} and H) on the flamelet structure is examined and shown to increase CO{sub 2}, but decrease the flamelet temperature and mass fractions of H{sub 2}O, CO, and NO{sub x}.
- OSTI ID:
- 619584
- Journal Information:
- Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 3 Vol. 112; ISSN CBFMAO; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
Similar Records
On transient flamelets and their relationship to turbulent methane-air jet flames
Laminar flamelet structure at low and vanishing scalar dissipation rate