The asymptotic structure of premixed methane-air flames with slow CO oxidation

Journal Article · Mon Jun 01 04:00:00 EDT 1992 · Combustion and Flame; (United States)

DOI:https://doi.org/10.1016/0010-2180(92)90020-P· OSTI ID:7271796

Bui-Pham, M; Seshadri, K; Williams, F A ^[1]

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1. Dept. of Applied Mechanics and Engineering Sciences, Univ. of California, San Diego, La Jolla, CA (US)

The asymptotic structures of methane-air flames, for equivalence ratios from 0.5 to 1.4 and pressures from 1 to 70 arm, are analyzed on the basis of a reduced four-step chemical-kinetic mechanism that has previously predicted burning velocities with reasonable accuracy. The rates of these four steps are related to the rates of elementary reactions appearing in the C{sub 1}-chain mechanism for oxidation of methane. In the analysis, the overall flame structure is subdivided into four zones a preheat zone with thickness of order unity, an inner fuel-consumption layer with thickness of order {delta}, a H{sub 2}-oxidation layer with thickness of order {epsilon}, and a CO-oxidation layer with thickness of order {nu}. It is presumed here that {delta} {much lt} {epsilon} {much lt} {nu} {lt} 1, contrary to previous investigations which treated {delta} {much lt} {nu} {much lt} {epsilon} 1. The reason for introducing this modification is that recent estimates suggest that {epsilon} {lt} {nu}, so that this opposite limit seems worthy of exploration. The inner layer is located between the preheat zone and the oxidation layers, and in this layer finite-rate reactions related to the consumption of the fuel are introduced by appropriate analysis essentially identical to that of Seshadri and Peters. In the H{sub 2}-oxidation layer, the variations of the concentrations of CO and O{sub 2} are presumed to be negligible, leading to a new asymptotic analysis, and the H atoms are presumed to be in steady state. In the CO-oxidation layer, H{sub 2} and H are both presumed to be in steady state, again requiring a new analysis.

• OSTI ID: 7271796
• Journal Information: Combustion and Flame; (United States), Journal Name: Combustion and Flame; (United States) Vol. 89:3; ISSN CBFMA; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
ACCURACY
AIR
ALKANES
ASYMPTOTIC SOLUTIONS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CONCENTRATION RATIO
ELEMENTS
FLAMES
FLUIDS
FUEL-AIR RATIO
GASES
HYDROCARBONS
HYDROGEN
KINETICS
MEDIUM PRESSURE
METHANE
MIXING
MODIFICATIONS
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN
OXYGEN COMPOUNDS
REACTION KINETICS
VARIATIONS
VELOCITY