Bifurcation dodge: avoidance of a thermoacoustic instability under transient operation

Bonciolini, Giacomo; Noiray, Nicolas

doi:10.1007/s11071-019-04815-y

“…To investigate the transition from S C to S TI via S IN , we perform experiments on a laboratory scale turbulent combustor (Komarek and Polifke 2010, Unni et al 2015, Silva et al 2017 and acquire spatiotemporal data. Our study analyses the transition between the dynamical states by continuously varying a system parameter, the air mass flow rate ( ṁair ) from low to high values (Gopalakrishnan et al 2016, Bonciolini and Noiray 2019, Pavithran and Sujith 2021. In all the experiments, we increase ṁair from 537 ± 8 SLPM to 780 ± 10 SLPM linearly with time.…”

Section: Analysis Of Fluctuations In the Global Observablesmentioning

confidence: 99%

Seeds of phase transition to thermoacoustic instability

Raghunathan

¹

,

George

²

,

Unni

³

et al. 2022

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Tackling the problem of emissions is at the forefront of scientific research today. While industrial engines designed to operate in stable regimes produce emissions, attempts to operate them at ‘greener’ conditions often fail due to a dangerous phenomenon known as thermoacoustic instability. Hazardous high amplitude periodic oscillations during thermoacoustic instability lead to the failure of these engines in power plants, aircraft, and rockets. To prevent this catastrophe in the first place, identifying the onset of thermoacoustic instability is required. However, detecting the onset is a major obstacle preventing further progress due to spatiotemporal variability in the reacting field. Here, we show how to overcome this obstacle by discovering a critical condition in certain zones of the combustor, which indicates the onset of thermoacoustic instability. In particular, we reveal the critical value of the local heat release rate that allows us to distinguish stable operating regimes from hazardous operations. We refer to these zones as seeds of the phase transition because they show the earliest manifestation of the impending instability. The increase in correlations in the heat release rate between these zones indicates the transition from a chaotic state to a periodic state. Remarkably, we found that observations at the seeds of the phase transition enable us to predict when the onset occurs, well before the emergence of dangerous large-amplitude periodic acoustic pressure oscillations. Our results contribute to the operation of combustors in more environment-friendly conditions. The presented approach is applicable to other systems exhibiting such phase transitions.

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“…Bonciolini et al [154] investigated the ratedependent transition delay along with the effect of noise in a laboratory-scale combustor system. In a quent study, Bonciolini and Noiray [155] presented a method of bifurcation dodging to avoid thermoacoustic instability by varying the parameter at fast rates. In a recent experimental study, Manikandan and Sujith [156] reported R-tipping to thermoacoustic instability via intermittency in a turbulent afterburner.…”

Section: Continuous Variation Of Control Parametersmentioning

confidence: 99%

Critical transitions and their early warning signals in thermoacoustic systems

Pavithran

¹

,

Unni

²

,

Sujith

³

2021

Eur. Phys. J. Spec. Top.

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Many complex systems undergo critical transitions. A thermoacoustic system is one such system which exhibits a catastrophic transition to a state of oscillatory instability known as thermoacoustic instability. So far, several early warning signals have been devised to detect the transition from stable operation to thermoacoustic instability in both laminar and turbulent systems. We focus on these early warning signals, and the challenges faced while detecting oscillatory instabilities in practical systems. In contrast to the transition from a fixed point to limit cycle oscillations in laminar systems, turbulent systems exhibit a transition from a chaotic state to limit cycle via a state of intermittency. In this review, we highlight the importance of the inherent fluctuations in the system in providing early warning signals for critical transitions.

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“…To investigate the transition from S C to S TI via S IN , we perform experiments on a laboratory scale turbulent combustor 39,[55][56][57][58] and acquire spatiotemporal data. Our study analyses the transition between the dynamical states by continuously varying a system parameter, the air mass flow rate (ṁ air ) from low to high values 47,[59][60][61][62] . In all the experiments, we increaseṁ air from 537 ±8 SLPM (SLPM denotes standard liters per minute) to 780 ±10 SLPM linearly with time.…”

Section: Analysis Of Fluctuations In the Global Observablesmentioning

confidence: 99%

Seeds of phase transition to thermoacoustic instability

Raghunathan¹,

George

²

,

Unni

³

et al. 2021

Preprint

View full text Add to dashboard Cite

Tackling the problem of emissions is at the forefront of scientific research today. While industrial engines designed to operate in stable regimes produce emissions, attempts to operate them at "greener" conditions often fail due to thermoacoustic instability. During thermoacoustic instability, hazardous high amplitude periodic oscillations lead to failure of these engines in power plants, aircrafts and rockets. Yet, identifying the onset of thermoacoustic instability remains elusive due to spatial variability and the continuous evolution of spatiotemporal patterns in the reacting flow field. Here, we show experimental evidence of early manifestation of the onset of thermoacoustic instability at certain zones. Our findings allow us to identify a critical threshold that enables us to distinguish stable operating regimes from hazardous operations. This opens new perspectives for predicting the onset of thermoacoustic instability and could be a step forward to "greener" operations. The developed methodology is applicable for other systems exhibiting phase transitions.

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Bifurcation dodge: avoidance of a thermoacoustic instability under transient operation

Cited by 29 publications

References 59 publications

Seeds of phase transition to thermoacoustic instability

Seeds of phase transition to thermoacoustic instability

Critical transitions and their early warning signals in thermoacoustic systems

Seeds of phase transition to thermoacoustic instability

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