Intrinsic thermoacoustic instabilities

Silva, Camilo F.

doi:10.1016/j.pecs.2022.101065

Cited by 20 publications

(5 citation statements)

References 67 publications

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“…It might be believed that such an anechoic system is unconditionally stable. However, this is a consequence of neglecting the internal acoustic loop , usually known as the intrinsic thermoacoustic (ITA) feedback loop 30–33 (shown in green in Figure 1). The previously described unsteady volumetric gas expansion of the flame (I), produced by the unsteady heat release rate Q ˙ ′, causes an acoustic wave g normalu to travel in the upstream direction, which in turn modulates the acoustic velocity at the reference position u normalref ′ (II).…”

Section: Modeling Approachesmentioning

confidence: 99%

Incompressible versus compressible large eddy simulation for the identification of premixed flame dynamics

Eder

Silva

Haeringer

et al. 2023

International Journal of Spray and Combustion Dynamics

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The present work compares the respective advantages and disadvantages of compressible and incompressible computational fluid dynamics (CFD) formulations when used for the estimation of the acoustic flame response. The flame transfer function of a turbulent premixed swirl-stabilized burner is determined by applying system identification (SI) to time series data extracted from large eddy simulation (LES). By analyzing the quality of the results, the present study shows that incompressible simulations exhibit several advantages over their compressible counterpart with equal prediction of the flame dynamics. On the one hand, the forcing signals can be designed in such a way that desired statistical properties can be enhanced, while maintaining optimal values in the amplitude. On the other hand, computational costs are reduced and the implementation is fundamentally simpler due to the absence of acoustic wave propagation and corresponding resonances in the flame response or even self-excited acoustic oscillations. Such an increase in efficiency makes the incompressible CFD/SI modeling approach very appealing for the study of a wide variety of systems that rely on premixed combustion. In conclusion, the present study reveals that both methodologies predict the same flame dynamics, which confirms that incompressible simulation can be used for thermoacoustic analyses of acoustically compact velocity-sensitive flames.

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Section: Modeling Approachesmentioning

confidence: 99%

Incompressible versus compressible large eddy simulation for the identification of premixed flame dynamics

Eder

Silva

Haeringer

et al. 2023

International Journal of Spray and Combustion Dynamics

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“…Combustion instability has a significant meaning in land-based gas turbine installations due to the widespread method of burning lean, preliminarily blended mixtures. This approach allows for significantly reducing the most harmful nitrous oxides (NOx) while sacrificing combustion stability [1].…”

Section: Introductionmentioning

confidence: 99%

“…The self-excited fluctuations are produced by the rightphase correlation between combustion and reflected sound waves. In his explanation of the thermodynamic cycle, which increases the internal energy of sound waves, he also neglected the mean flow effect, so he gets, as a result, the Putnam interpretation of Rayleigh's criterion Equation (1). In the following chapters of his work, the author studied moving systems in which the produced work can be compared with Equation (1):…”

Section: Introductionmentioning

confidence: 99%

Exergy as Lyapunov Function for Studying the Dynamic Stability of a Flow, Reacting to Self-Oscillation Excitation

Skiba,

Zubrilin,

Yakushkin

2024

Applied Sciences

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This article introduces a new, physically-based Lyapunov function definition that can be used as acoustic energy for finite-amplitude pressure oscillations in reacting systems, especially in combustion chambers. Reacting flow is seen as an open, non-equilibrium (parameters are distributed unevenly locally) thermodynamic system. This Lyapunov function is defined as the maximum mechanical work that could be extracted by a heat engine from the studied system if this system were disconnected from the inlet and outlet and from any other surrounding environment and the engine could transfer to the surrounding environment only mechanical work.

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“…Energy conversion from heat to sound is desired in thermoacoustic engines [1][2][3], because there are no or fewer moving parts and non-exotic materials involved. When this occurs in most modern combustion equipment with high energy densities (such as in liquid/solid rocket engines [4][5][6], aero-engines [7][8][9], or land-based gas turbines [10][11][12]), intense thermoacoustic oscillations may occur, which pose a significant risk due to destructive damage [13][14][15]. This may include, structural vibration fatigue, overloaded heating to the combustor walls, and even explosion.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Stochastically Forced Rijke-Type Supercritical Thermoacoustic Systems

Zhang¹,

WANG²,

Li³

et al. 2023

Preprint

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Intense thermoacoustic oscillations may lead to severe deterioration due to the induced intolerable damage to combustors. A better understanding of unstable behaviors is important to prevent or suppress these oscillations. Active thermoacoustic coupling in practical combustors is caused primarily by two approaches: inherent turbulent fluctuations and the flame response to acoustic waves. Turbulent fluctuations are generally characterized by random noise. This paper experimentally expands on previous analytic studies regarding the influence of colored disturbances on the thermoacoustic response near the supercritical bifurcation point. Therein, a laboratory-scale Rijke-type thermoacoustic system is established, and both supercritical and subcritical bifurcations are observed. Then, Ornstein–Uhlenbeck (OU)-type external colored noise is introduced near the supercritical bifurcation point, and the effects of the corresponding correlation time τc and noise intensity D are studied. The experimental results show that these variables of the colored noise significantly influence the dynamics of thermoacoustic oscillations in terms of the most probable amplitude, autocorrelation, and correlation time. A resonance-like behavior is observed as the noise intensity or the autocorrelation time of the colored noise is continuously varied, which means that the coherent resonance occurs in the thermoacoustic system. Finally, when the system is configured closer to the stability boundary, the extent of the coherence motion is intensified in the stochastic system response. Meanwhile, the Signal to Noise Ratios (SNRs) of the colored-noise-induced response are found to become more distinguished, the optimal colored noise intensity decreases, and the optimal autocorrelation time increases. This provides valuable guidance to predict the onset of thermoacoustic instabilities.

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Intrinsic thermoacoustic instabilities

Cited by 20 publications

References 67 publications

Incompressible versus compressible large eddy simulation for the identification of premixed flame dynamics

Incompressible versus compressible large eddy simulation for the identification of premixed flame dynamics

Exergy as Lyapunov Function for Studying the Dynamic Stability of a Flow, Reacting to Self-Oscillation Excitation

Experimental Investigation on the Stochastically Forced Rijke-Type Supercritical Thermoacoustic Systems

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