Images of the quenching of a flame by a vortex--To quantify regimes of turbulent combustion

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Combustion and Flame; (United States)

DOI:https://doi.org/10.1016/0010-2180(93)90019-Y· OSTI ID:6041292

Roberts, W L; Driscoll, J F ^[1]; Drake, M C ^[2]; Goss, L P ^[3]

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1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Aerospace Engineering
2. General Motors Research Labs., Warren, MI (United States)
3. Systems Research Labs., Dayton, OH (United States)

A laminar toroidal vortex is interacted with a laminar premixed flame in order to isolate and to visualize some of the fundamental physics of turbulent combustion. Localized quenching of the flame was observed using planar laser-induced fluorescence imaging of superequilibrium OH molecules in the counterflow flamefront region near the vortex leading edge. A quenching limit curve was measured as a function of vortex size and strength. In the second part of the study, the measurements are combined with concepts proposed by Poinsot. Veynante, and Candel in order to infer the thin flame limit, namely, the onset of distributed reactions, on a classical premixed turbulent combustion regime diagram. The measured thin flame limit indicates when laminar flamelet theories become invalid, since quenching allows hot products and reactants to coexist. Results are compared with the Klimov-Williams criterion. Vortex core diameters were as small as the flame thickness in some cases. The main conclusion is that small vortices are less effective at quenching a flame than was previously believed; therefore the inferred regime within which thin flame theories are valid extends to a turbulence intensity that is more than an order of magnitude larger than that which was previously predicted. Results also indicate that micromixing models, which assume that the smallest eddies exert the largest strain on a flame, are not realistic. The measured vortex Karlovitz number that is required to quench a flame is not constant but decreases by a factor of four as a vortex size increases from one to five flame thicknesses. Thin-film pyrometry was used to quantify the radiative heat losses; quenching occurs when the products cool to approximately 1,300 K. The quenching Karlovitz number for propane-air flames differs from that of methane-air flames, indicating the importance of detailed chemistry and transport properties.

• OSTI ID: 6041292
• Journal Information: Combustion and Flame; (United States), Journal Name: Combustion and Flame; (United States) Vol. 94:1-2; ISSN CBFMAO; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
034000 -- Natural Gas-- Combustion
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
AIR
ALKANES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMBUSTION
COMBUSTION KINETICS
DIMENSIONS
EMISSION SPECTROSCOPY
ENERGY LOSSES
ENERGY TRANSFER
FLAMES
FLUID FLOW
FLUIDS
FLUORESCENCE SPECTROSCOPY
GASES
HEAT LOSSES
HEAT TRANSFER
HYDROCARBONS
HYDROXYL RADICALS
KINETICS
LAMINAR FLOW
LASERS
LOSSES
MASS TRANSFER
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
METHANE
ORGANIC COMPOUNDS
OXIDATION
PROPANE
PYROMETERS
QUENCHING
RADIANT HEAT TRANSFER
RADICALS
REACTION KINETICS
SPECTROSCOPY
TEMPERATURE RANGE
TEMPERATURE RANGE 1000-4000 K
THERMOCHEMICAL PROCESSES
THICKNESS
TURBULENT FLOW
VORTEX FLOW
VORTICES