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

Large Eddy Simulation of Flame Response to Transverse Acoustic Excitation in a Model Reheat Combustor

[+] Author and Article Information
Mathieu Zellhuber

e-mail: zellhuber@td.mw.tum.de

Wolfgang Polifke

Lehrstuhl für Thermodynamik,
Technische Universität München,
Garching 85747, Germany

Bruno Schuermans

Alstom,
Baden 5401, Switzerland

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received May 19, 2013; final manuscript received June 20, 2013; published online August 21, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 135(9), 091508 (Aug 21, 2013) (9 pages) Paper No: GTP-13-1136; doi: 10.1115/1.4024940 History: Received May 19, 2013; Revised June 20, 2013

The response of a perfectly premixed, turbulent jet flame at elevated inflow temperature to high frequency flow perturbations is investigated. A generic reheat burner geometry is considered, where the spatial distribution of heat release is controlled by autoignition in the jet core on the one hand, and kinematic balance between flow and flame propagation in the shear layers between the jet and the external recirculation zones on the other. To model autoignition and heat release in compressible turbulent flow, a progress variable/stochastic fields formulation adapted for the LES context is used. Flow field perturbations corresponding to transverse acoustic modes are imposed by harmonic excitation of velocity at the combustor boundaries. Simulations with single-frequency excitation are carried out in order to study the flame response to transverse fluctuations of velocity. Heat release fluctuations are observed predominantly in the shear layers, where flame propagation is important. The flow-flame coupling in these regions is analyzed in detail with a filter-based postprocessing approach, invoking a local Rayleigh index and providing insight into the interactions of flame wrinkling by vorticity and convection due to mean and fluctuating velocity.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Schematic cutview of Alstom’s GT24/GT26 gas turbine family (source: Alstom)

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Fig. 2

3D view of investigated geometry with temperature distribution in symmetry plane

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Fig. 3

Comparison of progress variable source terms in 0d reactors and premixed flames at pertinent conditions

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Fig. 4

Orientation of momentum source terms for excitation of transverse modes; instantaneous snapshots of resulting pressure contours

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Fig. 5

Impact of inlet velocity on flame position given by chemical source term in a single stochastic field

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Fig. 6

Instantaneous distribution of vorticity (filled contours) and normalized progress variable (isolines) for case without excitation

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Fig. 7

Phase lock evolution of normalized reaction progress over fluctuation period of 1T case (left: 0 deg phase, middle: 120 deg, right: 240 deg)

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Fig. 8

Distribution of average heat release in symmetry plane for unexcited case (top), 1 T and 2 T excitation cases (middle and bottom)

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Fig. 9

Rms fluctuation amplitude of heat release in symmetry plane for 1 T (top) and 2 T (bottom) excitation cases

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Fig. 10

Distribution of heat release phase lag in radians for 1 T excitation case

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Fig. 11

Rms fluctuation amplitude of normalized progress variable in symmetry plane for 1T excitation case

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Fig. 12

Schematic description of flame dynamics in shear layers: superposition and interference of wrinkling and vertical displacement

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Fig. 13

Distribution of Rayleigh index for 1T (top half) and 2T (bottom half) excitation cases

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Fig. 14

Distribution of heat release phase lag in radians for 2T excitation case

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Fig. 15

Definition of observation windows

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Fig. 16

Evolution of normalized heat release amplitudes along shear layer for 1T and 2T excitation cases

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