High-Frequency Thermoacoustic Modulation Mechanisms in Swirl-Stabilized Gas Turbine Combustors—Part I: Experimental Investigation of Local Flame Response

Berger, Frederik; Hummel, Tobias; Hertweck, Michael; Kaufmann, Jan; Schuermans, Bruno; Sattelmayer, Thomas

doi:10.1115/1.4035591

Cited by 31 publications

(7 citation statements)

References 20 publications

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“…Besides, it can be noted that, in the work of Berger et al. (2017) and of Hummel et al. (2017), the response of a non-compact swirled flame to transverse acoustic excitation was investigated for the case of high frequency thermoacoustic instabilities.…”

Section: Thermoacoustic Wave Equationmentioning

confidence: 99%

Spontaneous and explicit symmetry breaking of thermoacoustic eigenmodes in imperfect annular geometries

et al. 2022

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This article deals with the symmetry breaking of azimuthal thermoacoustic modes in annular combustors. Using a nominally symmetric annular combustor, we present experimental evidence of a predicted spontaneous reflectional symmetry breaking, and also an unexpected explicit rotational symmetry breaking in the neighbourhood of the Hopf bifurcation which separates linearly stable azimuthal thermoacoustic modes from self-oscillating modes. We derive and solve a multidimensional Fokker–Planck equation to unravel a unified picture of the phase space topology. We demonstrate that symmetric probability density functions of the thermoacoustic state vector are elusive, because the effect of asymmetries, even imperceptible ones, is magnified close to the bifurcation. This conclusion implies that the thermoacoustic oscillations of azimuthal modes in real combustors will systematically exhibit a statistically dominant orientation of the mode in the vicinity of the Hopf bifurcation.

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Section: Thermoacoustic Wave Equationmentioning

confidence: 99%

Spontaneous and explicit symmetry breaking of thermoacoustic eigenmodes in imperfect annular geometries

et al. 2022

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“…However, it should be noted that the total thermoacoustic driving of this mode is not solely due to shear layer modulation, and is instead the result of superposition of several mechanisms. Flame displacement by the acoustic velocity field, as observed in studies of swirl-stabilised combustors, 20,21 is expected to contribute to driving in reheat combustors, as is compression and expansion of the flame due to deformation induced by the displacement. Furthermore, modulation of the auto-ignition delay time by the acoustic pressure likely also represents a source of thermoacoustic driving.…”

Section: Resultsmentioning

confidence: 95%

Observation of reactive shear layer modulation associated with high-frequency transverse thermoacoustic oscillations in a gas turbine reheat combustor experiment

McClure

Berger

Bertsch

et al. 2022

International Journal of Spray and Combustion Dynamics

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This paper presents the investigation of high-frequency thermoacoustic oscillations and associated flame dynamics in an experimental gas turbine reheat combustor at atmospheric pressure. Examination of dynamic pressure measurements reveals bursts of high-frequency periodic oscillations which appear randomly amidst stochastic fluctuations in the reheat combustor. Analysis of the flame dynamics during these bursts of periodic behaviour reveals that increased heat release in the reactive shear layers of the reheat flame is associated with greater thermoacoustic driving potential. This redistribution of heat release is likely due to the stochastic nature of auto-ignition kernel formation. To determine the underlying flame-acoustic coupling mechanism behind the driving potential, phase-resolved flame dynamics over the acoustic cycle are investigated which reveal the presence of an oscillatory heat release pattern associated with the first transverse eigenmode. An in-phase interaction between the acoustic field and these heat release oscillations in the shear layer regions indicates that this phenomenon likely constitutes a thermoacoustic driving mechanism. This is an important step towards the development of models for high-frequency thermoacoustic driving mechanisms relevant to reheat combustion systems, which will allow accurate prediction and mitigation of thermoacoustic instabilities in future designs.

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“…During the review, the subject of this work was continued and extended in Berger et al, 18 and Hummel et al 19,20 …”

Section: Discussionmentioning

confidence: 99%

Impact of the heat release distribution on high-frequency transverse thermoacoustic driving in premixed swirl flames

Hertweck

Berger

Hummel

et al. 2016

International Journal of Spray and Combustion Dynamics

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Self-excited, high-frequency first transversal thermoacoustic instabilities in a cylindrical combustion chamber equipped with a premixed swirl-stabilized flame are investigated. Phase-locked image analysis of the phenomena shows the displacement of the flame and a higher burning rate in the region of elevated pressure. The impact of diffuser angle and fuel composition on the stability limits and the flame position is investigated. The Rayleigh-Index is computed for a threedimensional domain based on analytical flame transfer functions for experimentally obtained data of OH*-chemiluminescence as measure for the spatial heat release. Two models from different sources are applied, which describe the interaction between flame and acoustic locally. The axial dependence of the amplitude of the transversal mode is computed by a numerical model, which takes the temperature distribution inside the combustion chamber into account. The comparison of the Rayleigh-Index of different operation points shows a correlation with the stability limits for some, but not for all investigated configurations.

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High-Frequency Thermoacoustic Modulation Mechanisms in Swirl-Stabilized Gas Turbine Combustors—Part I: Experimental Investigation of Local Flame Response

Cited by 31 publications

References 20 publications

Spontaneous and explicit symmetry breaking of thermoacoustic eigenmodes in imperfect annular geometries

Spontaneous and explicit symmetry breaking of thermoacoustic eigenmodes in imperfect annular geometries

Observation of reactive shear layer modulation associated with high-frequency transverse thermoacoustic oscillations in a gas turbine reheat combustor experiment

Impact of the heat release distribution on high-frequency transverse thermoacoustic driving in premixed swirl flames

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