Experimental investigation of the morphology and stability of diffusion and edge flames in an opposed jet burner

Journal Article · Wed Aug 15 00:00:00 EDT 2007 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2007.04.006· OSTI ID:20919417

Ciani, A; Kreutner, W; Hubschmid, W ^[1]; Frouzakis, C E; Boulouchos, K ^[2]

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1. Combustion Research Laboratory, Paul Scherrer Institut (Switzerland)
2. Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology (ETH), Zurich (Switzerland)

The stability of methane/air and hydrogen/air flames in an axisymmetric counterflow burner was investigated experimentally for different burner geometries, degrees of fuel dilution, and combinations of flow velocities. Both planar diffusion flames and edge flames were observed, and the transitions between these flame types were studied. The experimental results confirmed previously published numerical predictions on diluted hydrogen/air flames: the existence of two distinct stable flame types; the possibility of switching between the two flame types by perturbing the flames, e.g., by suitably changing a flow velocity; and the strong hysteresis for the transition from one flame type to the other. Flame stability diagrams were compiled which delineate the range of fuel and air flow velocities for which the planar diffusion flame and the toroidal edge flame are stable. The lower boundary curve for the edge flame stability exhibits a characteristic minimum at a well-defined value of the fuel velocity. For fuel velocities lower than this value, the transition between the edge and the diffusion structure is reversible, and the flames exhibit bistable behavior. For higher fuel velocities, the decrease of air velocity leads to the extinction of the edge flame. An investigation of both the cold and the reactive flow field identified bistable behavior for the flow field as well. Except for very low flow rates, the stagnation plane stabilizes in two positions, close to either of the two nozzles. Detailed numerical simulations of hydrogen flames capture the essentials of this behavior. The observed flame extinction results from the interaction of the flame dynamics with the dynamics of the flow field. (author)

• OSTI ID: 20919417
• Journal Information: Combustion and Flame, Vol. 150, Issue 3; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AIR
FLAMES
HYDROGEN
VELOCITY
DIFFUSION
FUELS
STABILITY
BURNERS
METHANE
AIR FLOW
DIAGRAMS
JETS
AXIAL SYMMETRY
CONFIGURATION
MORPHOLOGY
SIMULATION
STAGNATION
FLAME EXTINCTION
FLOW RATE
DILUTION
FORECASTING
HYSTERESIS
NOZZLES
COMBUSTION KINETICS
COUNTERFLOW SYSTEMS