Combining analytical models and LES data to determine the transfer function from swirled premixed flames

Dupuy, Fabien; Gatti, Marco; Mirat, Clément; Gicquel, Laurent; Nicoud, Franck; Schuller, Thierry

doi:10.1016/j.combustflame.2020.03.026

Cited by 23 publications

(11 citation statements)

References 62 publications

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“…The frequency at which these destructive interferences take place depends on the bulk flow velocity and the distance l s between the swirler and the burner outlet [14]. The frequency f m of the first valley corresponds to a situation where axial and azimuthal velocity disturbances are out of phase by ∆ϕ u z −u θ = π at the burner outlet [42][43][44]. When this condition is met, oscillations of the flame angle at the flame anchoring region are the largest due to large oscillations of the swirl level.…”

Section: Effects Of Swirlmentioning

confidence: 99%

Influence of hydrogen content and injection scheme on the describing function of swirled flames

Schuller

Marragou

Öztarlık

et al. 2022

Combustion and Flame

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Section: Effects Of Swirlmentioning

confidence: 99%

Influence of hydrogen content and injection scheme on the describing function of swirled flames

Schuller

Marragou

Öztarlık

et al. 2022

Combustion and Flame

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“…It has been observed that this response is a function of the non-dimensionalized pulsation ω *, the flame angle α, the phasing ϕ between axial and azimuthal velocity perturbations and the coefficients ζ and χ, specifics to swirling flames. The determination of these two coefficients, as of today, has been undertaken experimentally 17 or numerically 24 without theoretical attempt such as proposed in the present paper. In addition, the effect of swirling flame angle has been studied and documented in a few studies only.…”

Section: Introduction: Context and State Of The Artmentioning

confidence: 99%

The flame displacement speed: A key quantity for turbulent combustion and combustion instability

Palies¹

2022

International Journal of Spray and Combustion Dynamics

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Future combustion power and propulsion systems may operate in premixed regime enabling reduced fuel burn and reduced pollutant emissions. The turbulent premixed regime in those future combustion systems is likely to be in the corrugated regime where modeling the flame as a thin interface propagating into the fresh gas is made possible. The flame displacement speed is thus a key quantity for turbulent combustion in this regime. This quantity is also important for combustion instabilities. Indeed, the flame displacement speed [Formula: see text] combined to the flow speed [Formula: see text] determines the flame surface location by determining the flame surface speed [Formula: see text]. The flame surface location has shown to play a major role on combustion instabilities. Research work have also demonstrated the role of the flame displacement speed on the flame response which is used for subsequent combustion instability prediction. In this context, the derivation of flame speed models and flame transfer function models based on this quantity are required. This paper presents the theoretical derivation of flame transfer function coefficients for swirling premixed flames in this context. The derivation is based on the definition of the flame speed for turbulent flame, its perturbed form for oscillating flow, and the kinematic flame-flow speed budget. The obtained results are compared to previous literature data and discussed. The effect of the flame angle, id est the effect of the swirl number on the flame response is also investigated. This works motivates detailed local measurements and simulations to evaluate flow-flame speed budget terms.

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“…In this approach, the flame models are derived from flame transfer/ describing functions [15,16]. The transfer functions are obtained either computationally [17,18] or experimentally [19,20]. While performing linear stability analysis with such approaches, the oscillations tended to zero or "fixed-points" during stable condition, even though there might be unsteadiness in the flame/ flow, which do not excite acoustic oscillations .…”

Section: Introductionmentioning

confidence: 99%

Understanding dynamical states observed in a thermo-acoustic system from perspective of frequency-phase relationship derived from a probabilistic oscillator model

Ramanan

Ramankutty

Sreed

et al. 2022

Preprint

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We perform lab scale experiments in a swirl combustor by reducing the equivalence ratio for two cases involving slightly different inlet air flow rates. Reduction in equivalence ratio at a constant air flow results in the combustor transiting from stable to unstable combustion. The transition passes through stable, type-2 intermittency and beat oscillations. The beat oscillations are seen to fluctuate at a single frequency, and hence suggestive of a process involving spatio-temporal variations in the phase of the driver (i.e., heat release rate fluctuations). This is understood in the manner of a reduced order model, where the driver is considered to an ensemble of phase oscillators with time delays and a probabilistic distribution of natural frequencies, similar to Kuramoto oscillator. The acoustic field is modeled as a Van-der-pol Duffing system, with natural frequency equal to the duct acoustic mode. The coupling between the oscillators is varied based on the physical premise of Rayleigh criterion. The coupled system is seen to qualitatively and quantitatively match the pressure data obtained from experiments. Insights into various conditions illustrate the role of mean and fluctuating instantaneous frequency amongst the phase oscillators in determining the modeled pressure oscillations. By quantifying the extent of fluctuating frequency coupling among the phase oscillators, it is observed that beat oscillations have high correlation with lower deviation compared to intermittency and stable oscillations.

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Combining analytical models and LES data to determine the transfer function from swirled premixed flames

Abstract: Combining analytical models and LES data to determine the transfer function from swirled premixed flames. (2020) Combustion and Flame, 217. 222-236.

Cited by 23 publications

References 62 publications

Influence of hydrogen content and injection scheme on the describing function of swirled flames

Influence of hydrogen content and injection scheme on the describing function of swirled flames

The flame displacement speed: A key quantity for turbulent combustion and combustion instability

Understanding dynamical states observed in a thermo-acoustic system from perspective of frequency-phase relationship derived from a probabilistic oscillator model

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