Products in methane combustion near surfaces
- Univ. of Minnesota, Minneapolis, MN (United States)
Emission of carbon monoxide (CO), formaldehyde (CH[sub 2]O), and unburned methane (CH[sub 4]) are calculated for premixed methane/air mixtures impinging on a flat surface as functions of surface temperature, equivalence ratio, and strain rate with detailed chemistry involving 46 reversible reactions and 16 species using numerical bifurcation theory. Multiple solutions with different selectivities to stable products are found. On the extinguished branch unburned CH[sub 4], molecular hydrogen (H[sub 2]), CO, and CH[sub 2]O dominate, whereas on the ignited branch carbon dioxide (CO[sub 2]) predominates near the surface. Cold walls can promote the selectivity to CO and CH[sub 2]O near extinction, and high flow rates can increase considerably the formation of CO, CH[sub 2]O, and unburned CH[sub 4]. For example, an ignited stoichiometric methane/air mixture (9.5% CH[sub 4] in air) impinging on a surface of 1,000 K is calculated to produce 2% CO, 150 ppm CH[sub 2]O, and 3% unburned CH[sub 4] for a strain rate of 500 s[sup [minus]1]. Maximum efficiency of CH[sub 4] and minimum selectivity to CH[sub 2]O occur near the stoichiometric ratio, whereas minimum selectivity to CO occurs for fuel lean mixtures. Comparison of combustion near surfaces with freely propagating flames is also shown.
- DOE Contract Number:
- FG02-88ER13878
- OSTI ID:
- 7259550
- Journal Information:
- AIChE Journal (American Institute of Chemical Engineers); (United States), Journal Name: AIChE Journal (American Institute of Chemical Engineers); (United States) Vol. 40:6; ISSN 0001-1541; ISSN AICEAC
- Country of Publication:
- United States
- Language:
- English
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