Effect of preheating of the reactants on the transition to thermoacoustic instability in a bluff-body stabilized dump combustor

Pawar, Samadhan A.; Raghunathan, Manikandan; Reeja, K. V.; Midhun, P. R.; Sujith, R. I.

doi:10.1016/j.proci.2020.06.370

Cited by 12 publications

(2 citation statements)

References 17 publications

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“…Based on the diameter of the bluff-body, the Reynolds number varies in the range of Re d = 3.36×10 4 to 5.67×10 4 . For the experiments reported here, the preheating temperature was maintained at T = 300 • C. Please refer to [39] for more details on the preheater setup.…”

Section: Preheated Bluff-body Stabilized Combustormentioning

confidence: 99%

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Abrupt transitions in turbulent thermoacoustic systems

Bhavi,

Pavithran,

Roy

et al. 2022

Preprint

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Abrupt transitions to the state of thermoacoustic instability (TAI) in gas turbine combustors are a significant challenge plaguing the development of next-generation lowemission aircraft and power generation engines. In this paper, we present the observation of abrupt transition in three disparate turbulent thermoacoustic systems: an annular combustor, a swirl-stabilized combustor, and a preheated bluff-body stabilized combustor. Using a low-order stochastic thermoacoustic model, we show that the reported abrupt transitions occur when an initially stable, supercritical limit cycle becomes unstable, leading to a secondary bifurcation to a large amplitude limit cycle solution. The states of combustion noise and intermittency observed in these turbulent combustors are well captured by the additive stochastic noise in the model. Through amplitude reduction, we analyze the underlying potential functions affecting the stability of the observed dynamical states. Finally, we make use of the Fokker-Planck equation, educing the effect of stochastic fluctuations on subcritical and secondary bifurcation. We conclude that a high enough intensity of stochastic fluctuations which transforms a subcritical bifurcation into an intermittency-facilitated continuous transition may have little effect on the abrupt nature of secondary bifurcation. Our findings imply the high likelihood of abrupt transitions in turbulent combustors possessing higher-order nonlinearities where turbulence intensities are disproportionate to the large amplitude limit cycle solution.

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Section: Preheated Bluff-body Stabilized Combustormentioning

confidence: 99%

“…The inner diameter of the waveguides is 4 mm. Further details on the instrumentation can be found in [16,39].…”

Section: Instrumentationmentioning

confidence: 99%