Dynamics of Coupled Thermoacoustic Oscillators Under Asymmetric Forcing

Sahay, Ankit; Roy, Amitesh; Pawar, Samadhan A.; Sujith, R. I.

doi:10.1103/physrevapplied.15.044011

Cited by 16 publications

(28 citation statements)

References 36 publications

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“…1, we show a schematic representation of the horizontal Rijke tube used in the present study. The Rijke tube is a long duct with a rectangular cross section of 9.3 cm ×9.4 cm and a length (L duct ) of 104 cm, similar to the ones used in [29,30,33]. An electrically heated wire mesh, powered by an external DC power supply, acts as a compact heat source.…”

Section: Experimental Setup Of the Self-coupled Rijke Tubementioning

confidence: 99%

“…III C) is similar to the above description, except that we couple two identical Rijke tubes with the connecting tube. For more experimental details on mutually coupled Rijke tubes, readers may refer to [29,30].…”

Section: Experimental Setup Of the Self-coupled Rijke Tubementioning

confidence: 99%

“…Recent studies have demonstrated the occurrence of amplitude death by mutual coupling of two Rijke tubes using one or two connecting tubes [29][30][31][32]. Here, we also compare the effectiveness of suppressing limit cycle oscillations in a single Rijke tube via self-coupling against that obtained via mutual coupling of two identical Rijke tubes.…”

Section: Introductionmentioning

confidence: 95%

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Self-coupling: An Effective Method to Mitigate Thermoacoustic Instability

Srikanth¹,

Sahay²,

Pawar³

et al. 2021

Preprint

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The presence of undesirable large-amplitude self-sustained oscillations in combustors -called thermoacoustic instability -can lead to performance loss and structural damage to components of gas turbine and rocket engines. Traditional feedback controls to mitigate thermoacoustic instability possess electromechanical components, which are expensive to maintain regularly and unreliable in the harsh environments of combustors. In this study, we demonstrate the quenching of thermoacoustic instability through self-coupling -a method wherein a hollow tube is used to provide acoustic selffeedback to a thermoacoustic system. Through experiments and modeling, we identify the optimal coupling conditions for attaining amplitude death, i.e., complete suppression of thermoacoustic instabilities, in a horizontal Rijke tube. We examine the effect of both system and coupling parameters on the occurrence of amplitude death. We thereby show that the parametric regions of amplitude death occur when the coupling tube length is an odd multiple of the length of the Rijke tube. The optimal location of the coupling tube for achieving amplitude death is near the anti-node position of the acoustic standing wave in the Rijke tube. We also find that self-coupling mitigates thermoacoustic instability in a Rijke tube more effectively than mutual coupling of two identical Rijke tubes. Furthermore, our model shows that the combined application of self and mutual coupling in two identical Rijke tubes can completely suppress oscillations that are not quenched by the individual application of either self or mutual coupling. Thus, we believe that self-coupling can prove to be a simple, cost-effective solution for mitigating thermoacoustic instability in gas turbine combustors.

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Section: Experimental Setup Of the Self-coupled Rijke Tubementioning

confidence: 99%

Section: Experimental Setup Of the Self-coupled Rijke Tubementioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

Self-coupling: An Effective Method to Mitigate Thermoacoustic Instability

Srikanth¹,

Sahay²,

Pawar³

et al. 2021

Preprint

Self Cite

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“…In their follow-up study, they investigate thermoacoustic limit cycles with the same model [ 34 ]. The dynamics of two coupled thermoacoustic oscillators under asymmetric forcing is investigated in [ 35 ]. In two recent studies, the can-annular system is simplified to a network model, where the azimuthal pressure dynamics are represented by the coupling of longitudinal acoustic modes through compact apertures [ 36 , 37 ].…”

Section: Introductionmentioning

confidence: 99%

Coupling-induced instability in a ring of thermoacoustic oscillators

Pedergnana

Noiray

2022

Proc. R. Soc. A.

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Thermoacoustic instabilities in can-annular combus-tors of stationary gas turbines lead to unstable Bloch modes which appear as rotating acoustic pressure waves along the turbine annulus. The multiscale, multiphysical nature of the full problem makes a detailed analysis challenging. In this work, we derive a low-order, coupled oscillators model of an idealized can-annular combustor. The unimodal projection of the Helmholtz equation for the can acoustics is combined with the Rayleigh conductivity, which describes the aeroacoustic coupling between neighbouring cans. Using a Bloch-wave ansatz, the resulting system is reduced to a single equation for the frequency spectrum. A linear stability analysis is then performed to study the perturbation of the spectrum by the can-to-can interaction. It is observed that the acoustic coupling can suppress or amplify thermoacoustic instabilities, raising the potential for instabilities in nominally stable systems.

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“…Here, the mutual coupling between the systems is achieved by using one (or more than one) tube of a fixed length and diameter. An increase in the length of the coupling tube correspondingly increases the delay time in the coupling of the acoustic fields in the systems [10,17].…”

Section: Introductionmentioning

confidence: 99%

Mitigation of limit cycle oscillations in a turbulent thermoacoustic system via delayed acoustic self-feedback

Sahay¹,

Kushwaha²,

Pawar³

et al. 2022

Preprint

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In this paper, we report the first observation of complete mitigation of thermoacoustic instability in a bluff-body stabilized turbulent combustor through the method of self-coupling. Self-coupling is achieved by coupling the acoustic field of the combustor to itself through a coupling tube. We characterize the effects of such acoustic self-feedback on the thermoacoustic instability of the system by varying the length and diameter of the coupling tube. We observe that the amplitude and the dominant frequency of the acoustic pressure fluctuations gradually decrease as the length of the coupling tube is increased. A complete suppression of thermoacoustic instability is observed when the coupling tube length is nearly 1.5 times the combustor length. Meanwhile, as we approach the suppression of thermoacoustic instability, the dynamical behavior of acoustic pressure changes from the state of limit cycle oscillations to low amplitude aperiodic oscillations via intermittency. We also study the coupling between the acoustic field and the unsteady flame dynamics for different conditions of self-coupling in the combustor. As the combustor approaches the state of complete suppression, the temporal synchrony between the acoustic pressure and the global heat release rate signals changes from the state of synchronized periodicity to desynchronized aperiodicity through intermittent synchronization. From the spatiotemporal analysis of the combustor flow field, we find complete disruption of the coherent spatial structures of acoustic energy production observed during the state of thermoacoustic instability when the combustor is self-coupled with a tube of optimized size. Thus, we anticipate self-coupling to be a viable option to mitigate high amplitude thermoacoustic oscillations in turbulent combustion systems present in gas turbines and rocket engines.

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Dynamics of Coupled Thermoacoustic Oscillators Under Asymmetric Forcing

Cited by 16 publications

References 36 publications

Self-coupling: An Effective Method to Mitigate Thermoacoustic Instability

Self-coupling: An Effective Method to Mitigate Thermoacoustic Instability

Coupling-induced instability in a ring of thermoacoustic oscillators

Mitigation of limit cycle oscillations in a turbulent thermoacoustic system via delayed acoustic self-feedback

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