Ignition of methane flames in oxygen near inert surfaces: Effects of composition, pressure, preheat, and residence time
- Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science
- Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering
- Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemical Engineering
Ignition behavior of premixed methane-oxygen mixtures in stagnation flow near a heated inert surface was examined using the GRI reaction mechanism. The effects of pressure (1--100 atm), preheat (298--773 K), and residence time (3--250 ms) on ignition temperature were investigated for the full range of fuel-to-oxygen ratios. A minimum in ignition temperature with composition occurred at about a 15% methane in oxygen feed ({phi} = 0.3) and was not affected strongly by pressure, preheat, or residence time. At atmospheric pressure, thermal feedback from the heat of reaction was a prerequisite for ignition at all fuel-to-oxygen ratios. However, at 50 atm, thermal feedback was only necessary for ignitions of mixtures leaner than 15% methane. For mixtures richer than 15% methane at 50 atm, ignitions due to chain branching preceded thermal ignitions. These chain-branching ignitions were unaffected when the thermal feedback was computationally turned off. Moreover, the fuel-rich ignitability limit increased from 55% methane at atmospheric pressure to 66% methane at 50 atm, while the fuel lean ignitability limit at 7% methane was not affected significantly by pressure. Reaction path analysis before ignition showed that for high-temperature ignitions, methane consumption for fuel-lean mixtures was by OH and O radicals, while for fuel-rich mixtures, it was by H and OH radicals. The main source of OH radicals for these ignitions was by the reaction of H and O{sub 2}. For low-temperature ignitions, methane was predominantly consumed by OH radicals before ignition regardless of feed composition, and the main source of OH radicals was by reactions involving HO{sub 2} and H{sub 2}O{sub 2}.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-88ER13878
- OSTI ID:
- 543441
- Journal Information:
- Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 3 Vol. 110; ISSN CBFMAO; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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