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

Dynamics of a Transversely Excited Swirling, Lifted Flame: Flame Response Modeling and Comparison With Experiments

[+] Author and Article Information
Vishal Acharya, Timothy Lieuwen

Georgia Institute of Technology,
Atlanta, GA 30318

Michael Malanoski

GE Energy,
Greenville, SC 29615

Michael Aguilar

Greffen Systems,
Atlanta, GA 30309

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 16, 2013; final manuscript received September 16, 2013; published online January 2, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(5), 051503 (Jan 02, 2014) (10 pages) Paper No: GTP-13-1343; doi: 10.1115/1.4025790 History: Received September 16, 2013; Revised September 16, 2013

This paper describes measurements and modeling of the response of a swirling, lifted flame to transverse flow excitation. The problem is motivated by combustion instabilities associated with transverse acoustic modes of combustors. The developed formulation relates the unsteady flame response characteristics to both the spatially filtered disturbance field and mean flow field characteristics. Measured flow and flame features are used as model inputs in order to compare the global heat release fluctuations with those measured from the experiment, showing quite good agreement. As such, this paper shows that, given sufficient flow field information, the dynamic flame response can be reasonably predicted from first-principles calculations with no empiricism. We also show that the strongly helical disturbances present in the flow have minimal impact on the global response of axisymmetric flames, as the local heat release fluctuations that they induce cancel each other azimuthally.

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References

Figures

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Fig. 1

Velocity disturbance pathways for a transversely forced flame [23]

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Fig. 2

Snapshots from reacting large eddy simulation computations of (a) vorticity field magnitude and (b) isovorticity surfaces for a swirl number of 0.44, reproduced from Huang and Yang [40]

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Fig. 3

Solid model of transverse forcing test facility (a) and orientation of measurement planes (b) where (1) is the flame imaging window, (2) is the high speed PIV window, and (3) the two horizontal lines represent the r-θ planes going into the page. Full extent of combustor not shown.

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Fig. 4

Transverse forcing conditions at the nozzle for in-phase (a) and out-of-phase (b) forcing acoustic excitation

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Fig. 5

Representative instantaneous velocity vectors from PIV of the (a) axial (y-z) plane and (b) transverse (x-y) plane at z/D = 0.14 (circle denotes the outer edge of the nozzle)

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Fig. 6

Schematic of the lifted swirl-stabilized premixed flame

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Fig. 12

Spatial variation of the amplitude of the symmetric mode (m = 0) fluctuations along the flame for the 400 Hz IP case

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Fig. 11

Spatial variations of the symmetric mode amplitude (m/s) for the velocity components (|B∧i,0|), for 400 Hz IP case. (a) Axial velocity is obtained directly from r-z PIV, (b) radial velocity, and (c) azimuthal velocity are generated using interpolation detailed in the Appendix. Dashed gray curve shows the time-averaged flame position.

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Fig. 10

Helical mode decomposition for radial velocity fluctuations for 400 Hz forcing showing (a) IP and (b) out-of-phase (OP) at z/D = 0.14. Data reproduced from Malanoski et al. [52].

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Fig. 9

Spatial variation of mean flow input parameters along the flame surface for the 400 Hz IP case. The values of U¯z and U¯rat r/D = 0 and r/D = 1.2 correspond to those from the PIV measurement (z/D = 0.14 and z/D = 0.5).

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Fig. 8

Contour plot showing spatial variations of the time-averaged velocity components (m/s) for 400 Hz IP case. (a) Axial velocity obtained directly from r-z PIV, (b) radial velocity, and (c) azimuthal velocity, both generated using interpolation detailed in the Appendix. Dashed gray curve shows the time-averaged flame position.

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Fig. 7

Time-averaged flame edge obtained from time-averaged chemiluminescence images for the different forcing conditions in the experiment. Sample polynomial fit to the flame shape for use with the model shown as dashed black line. The rectangular box indicates the flow field analysis domain.

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Fig. 13

Ensemble averaged spectrum from the global CH* chemiluminescence for the 400 Hz IP case (black) in comparison to the unforced case (gray). The black circle indicates the response at the forcing frequency.

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Fig. 14

FTF amplitude comparison between model prediction (gray lines) and experiments (black lines) for both (a) in-phase and (b) out-of-phase forcing. The predicted values are staggered horizontally for clarity.

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Fig. 15

FTF phase (in degrees) comparison between model prediction (gray with error bars) and experiments (black with error bar) for both (a) in-phase and (b) out-of-phase forcing. The predicted values are staggered horizontally for clarity.

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