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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

On the Influence of Fuel Distribution on the Flame Structure of Bluff-Body Stabilized Flames

[+] Author and Article Information
Jeffery A. Lovett

e-mail: Jeffery.Lovett@pw.utc.com

Kareem Ahmed


Pratt & Whitney Aircraft Engines,
East Hartford, CT 06108

Ben T. Zinn

e-mail: Zinn@gatech.edu
Georgia Institute of Technology,
Atlanta, GA 30332

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received August 5, 2013; final manuscript received October 6, 2013; published online December 10, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(4), 041503 (Dec 10, 2013) (10 pages) Paper No: GTP-13-1295; doi: 10.1115/1.4025728 History: Received August 05, 2013; Revised October 06, 2013

This paper describes recent learning on the flame structure associated with bluff-body stabilized flames and the influence of the fuel distribution with nonpremixed, jet-in-crossflow fuel injection. Recent experimental and analytical results disclosing the flame structure are discussed in relation to classical combustion reaction zone regimes. Chemiluminescence and planar fluorescence imaging of OH* radicals as an indicator of the flame zone are analyzed from various tests conducted at Georgia Tech using a two-dimensional vane-type bluff-body with simple wall-orifice fuel injectors. The results described in this paper support the view that combustion occurs in separated flame zones aligned with the nonpremixed fuel distribution associated with the fuel jets that are very stable and contribute to flame stability at low fuel flow rates. The experimental data is also compared with computational reacting flow large-eddy simulations and interpreted in terms of the fundamental reaction zone regimes for premixed flames. For the conditions of the present experiment, the results indicate combustion occurs over a wide range of flame regimes including the broken reaction zone or separated flamelet regimes.

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References

Figures

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Fig. 1

Classical depiction of the flame zone

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Fig. 2

Example laminar flame characteristics (inlet Φ = 0.275, T = 1100 K, P = 117 KPa)

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Fig. 3

Possible range of flame regimes

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Fig. 4

Instantaneous images of the bluff-body flame for nearly premixed (upper) and close-coupled (lower) fueling at Φ = 0.61 [12]

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Fig. 5

Mean equivalence ratio distributions for close-coupled fueling with the 0.559 mm fuel injectors

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Fig. 6

Schematic of the OH* PLIF system

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Fig. 7

Diagram of the PLIF images captured

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Fig. 8

Example of instantaneous PLIF image and relationship to the test section

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Fig. 9

Planar images of the time-mean fluorescence at several axial positions and fuel flow rates

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Fig. 10

Planar images of the mean flame fluorescence at several axial positions for Φ = 0.47 using the 0.483 mm INJ

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Fig. 11

Planar images of the mean flame fluorescence at several axial positions for Φ = 0.77 using the 0.483 MM INJ

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Fig. 12

Planar images of the mean flame fluorescence at several axial positions for Φ = 0.45 using the 0.559 MM INJ

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Fig. 13

Depiction of the fuel equivalence ratio contours and resulting reaction zone at the edge of a flameholder

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Fig. 14

Instantaneous planar image of the bluff-body flame structure from LES-LEM CFD simulations at Φ = 0.61

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Fig. 15

Instantaneous spanwise planar images of the bluff-body flame structure from LES-LEM CFD simulations at Φ = 0.61

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Fig. 16

Map of premixed flame regimes calculated from the LES-LEM CFD simulations at Φ = 0.61

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Fig. 17

Premixed flame regimes calculated for three local positions in the flow from the LES-LEM CFD simulations at Φ = 0.61

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