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Products in methane combustion near surfaces
Author(s) -
Vlachos D. G.,
Schmidt L. D.,
Aris R.
Publication year - 1994
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690400612
Subject(s) - methane , combustion , stoichiometry , selectivity , formaldehyde , chemistry , carbon dioxide , carbon monoxide , hydrogen , equivalence ratio , carbon fibers , thermodynamics , analytical chemistry (journal) , materials science , organic chemistry , combustor , catalysis , composite material , physics , composite number
Emission of carbon monoxide (CO), formaldehyde (CH 2 O), and unburned methane (CH 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 4 , molecular hydrogen (H 2 ), CO, and CH 2 O dominate, whereas on the ignited branch carbon dioxide (CO 2 ) predominates near the surface. Cold walls can promote the selectivity to CO and CH 2 O near extinction, and high flow rates can increase considerably the formation of CO, CH 2 O, and unburned CH 4 . For example, an ignited stoichiometric methane/air mixture (9.5% CH 4 in air) impinging on a surface of 1,000 K is calculated to produce 2% CO, 150 ppm CH 2 O, and 3% unburned CH 4 for a strain rate of 500 s −1 . Maximum efficiency of CH 4 and minimum selectivity to CH 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.