Lean limit phenomena

Technical Report · Sun Apr 01 04:00:00 EST 1984

OSTI ID:6053230

Law, C K

The concept of flammability limits in the presence of flame interaction, and the existence of negative flame speeds are discussed. Downstream interaction between two counterflow premixed flames of different stoichiometries are experimentally studied. Various flame configurations are observed and quantified these include the binary system of two lean or rich flames, the triplet system of a lean and a rich flame separated by a diffusion flame, and single diffusion flames with some degree of premixedness. Extinction limits are determined for methane/air and butane/air mixtures over the entire range of mixture concentrations. The results show that the extent of flame interaction depends on the separation distance between the flames which are functions of the mixtures concentrations, the stretch rate, and the effective Lewis numbers (Le). In particular, in a positively-stretched flow field Le 1 ( 1) mixtures tend to interact strongly (weakly), while the converse holds for flames in a negatively-stretched flow. Also established was the existence of negative flames whose propagation velocity is in the same general direction as that of the bulk convective flow, being supported by diffusion alone. Their existence demonstrates the tendency of flames to resist extinction, and further emphasizes the possibility of very lean or rich mixtures to undergo combustion.

• Research Organization: Northwestern Univ., Evanston, IL (USA)
• OSTI ID: 6053230
• Report Number(s): N-84-20552
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
AIR
ALKANES
CHEMICAL REACTIONS
COMBUSTION PROPERTIES
FLAME PROPAGATION
FLAMMABILITY
FLUIDS
FUEL-AIR RATIO
GASES
HYDROCARBONS
METHANE
ORGANIC COMPOUNDS
STOICHIOMETRY