Influence of pulsed entries on a spray generated by an air-blast injection device: An experimental analysis on combustion instability processes in aeroengines

Giuliani, Fabrice; Gajan, Pierre; Diers, Olaf; Ledoux, Michel

doi:10.1016/s1540-7489(02)80016-5

Cited by 41 publications

(28 citation statements)

References 4 publications

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“…Results have shown that the FTF is sensitive to modifications of the airflow rate, equivalence ratio, and preheat temperature (Yi & Santavica 2009), but the spray dynamics has to be considered as well. It is known (Giuliani et al 2002) that the polydisperse spray transported by large-scale structures generated by acoustic waves features a response that differs for small and large droplets, leading to a modification of the burning rate. It is also worth mentioning that large swirl number oscillations have been observed in swirling flames fed by aeronautical air-blast atomizers.…”

Section: Other Types Of Swirling Flamesmentioning

confidence: 99%

Dynamics of Swirling Flames

Candel

Durox²,

Schuller³

et al. 2014

Annu. Rev. Fluid Mech.

353

157

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In many continuous combustion processes, such as those found in aeroengines or gas turbines, the flame is stabilized by a swirling flow formed by aerodynamic swirlers. The dynamics of such swirling flames is of technical and fundamental interest. This article reviews progress in this field and begins with a discussion of the swirl number, a parameter that plays a central role in the definition of the flow structure and its response to incoming disturbances. Interaction between the swirler response and incoming acoustic perturbations generates a vorticity wave convected by the flow, which is accompanied by azimuthal velocity fluctuations. Axial and azimuthal velocities in turn define the flame response in terms of heat release rate fluctuations. The nonlinear response of swirling flames to incoming disturbances is conveniently represented with a flame describing function (FDF), in other words, with a family of transfer functions depending on frequency and incident axial velocity amplitudes. The FDF, however, does not reflect all possible nonlinear interactions in swirling flows. This aspect is illustrated with experimental data and some theoretical arguments in the last part of this article, which concerns the interaction of incident acoustic disturbances with the precessing vortex core, giving rise to nonlinear fluctuations at the frequency difference.

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Section: Other Types Of Swirling Flamesmentioning

confidence: 99%

Dynamics of Swirling Flames

Candel

Durox²,

Schuller³

et al. 2014

Annu. Rev. Fluid Mech.

353

157

View full text Add to dashboard Cite

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“…Like those operated with gaseous fuels, combustors fed by liquid fuels are prone to combustion instabilities triggered by the dynamics of the fuel [1][2][3] or air [1,4,5] supply lines. To determine the stability margins of these non-premixed systems, it is useful to characterize the flame frequency response to external flow perturbations.…”

Section: Introductionmentioning

confidence: 99%

“…In many studies of the dynamics of spray flames, the analysis is restricted to the examination of the limit cycle of a self-sustained oscillation taking place in the combustion chamber where pressure and OH * or CH * flame chemiluminescence measurements are correlated with the spray dynamics during the instability [3,5,6]. Characterizations of the response of swirl spray flames to liquid fuel flowrate modulations were realized in a few laboratory scale experiments [1,2,7]. Yi and Santavicca [2] found that the frequency response of their flame is sensitive to air mass flowrate, equivalence ratio and air preheat temperature variations, but it is invariant to fuel modulation amplitude.…”

Section: Introductionmentioning

confidence: 99%

“…For liquid fuel injectors featuring a large pressure drop, thermo-acoustic oscillations result from a resonant coupling with the air feeding line. Analysis of the response of swirl spray flames to air flowrate modulations are generally limited to a few specific forcing frequencies with a fixed amplitude [1,4,8]. It was demonstrated that the oscillation of the air flow leads to droplet clustering [1,7,9] and equivalence ratio fluctuations [6].…”

Section: Introductionmentioning

confidence: 99%

“…Analysis of the response of swirl spray flames to air flowrate modulations are generally limited to a few specific forcing frequencies with a fixed amplitude [1,4,8]. It was demonstrated that the oscillation of the air flow leads to droplet clustering [1,7,9] and equivalence ratio fluctuations [6]. The frequency response of swirl spray flames submitted to air flow rate modulations was however not characterized yet over a broad frequency range.…”

Section: Introductionmentioning

confidence: 99%

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Stability analysis of a swirl spray combustor based on flame describing function

Mirat

Durox

Schuller

2015

Proceedings of the Combustion Institute

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To cite this version:Clement Mirat, Daniel Durox, Thierry Schuller. Stability analysis of a swirl spray combustor based on flame describing function.Abstract Self-sustained combustion oscillations observed at limit cycles in a swirl combustor equipped with a series of steam assisted liquid fuel injectors are analyzed with the Flame Describing Function (FDF) framework. It is first shown that for globally fuel lean injection conditions, the spray flames investigated burn in a non-premixed mode. A nonsooty and a sooty regime are explored. Their frequency response to acoustic forcing is characterized by exploiting the OH * chemiluminescence signal and a velocity signal measured by Laser Doppler velocimetry at the air injection unit outlet. It is found that the FDF of these non-premixed swirl spray flames features a distinct response compared to lean premixed swirl flames. The gain and phase lag of these FDF are both a strong function of the perturbation amplitude. At a fixed forcing frequency, the FDF phase lag increases with the perturbation level for the non-sooty flame investigated and it decreases for the sooty flame case. The sooty flame has also a much lower cut-off frequency for the FDF gain than the non-sooty flame. It is then shown that these features are essential to reproduce the correct instability bands and oscillation frequencies observed at limit cycles in the experiments. For the sooty flame, combustion is always found stable in agreement with the low cut-off frequency found for the FDF. A linear analysis for the non-sooty flame fails to capture the low frequency instabilities observed in the experiments that have the largest oscillation levels. Only the use of the FDF enables to reproduce the correct dynamical states observed in the combustor. It is further concluded that the OH * chemiluminescence signal may safely be used to infer the frequency response of these non-premixed swirl spray flames at globally fuel lean injection conditions.

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Self‐excited Combustion Instabilities

Camporeale

Laera

Campa

2016

Handbook of Combustion

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Self‐excited combustion instabilities are dangerous phenomena that may occur in gas turbine combustors, rocket combustion systems, and industrial furnaces. In this chapter, the main mechanisms that cause instabilities are described, with attention focused on the influence of pressure waves on the fluctuations of flame heat release rates. An historical background (with reference to rocket engines) is followed by a description of the phenomenon in gas turbines, considering both cannular and annular combustion chambers. Initially, a description of mathematical models based on a lumped approach is presented; these approaches are useful for a preliminary analysis of the phenomenon. Modern, three‐dimensional codes that can be used as design and analysis tools are then described, together with instructions of how to use such tools in conjunction with experimental analyses capable of identifying linear and nonlinear flame responses to flow perturbation. A mathematical approach capable of modeling the bifurcation process that leads to steady large amplitude fluctuations known as the limit‐cycle is described, and examples are given. Analyses of combustion instabilities offered by computationally intensive simulations, making use of unsteady reactive and fluid dynamic codes, are also discussed. Finally, active and passive control techniques outlined that can be used to avoid, or at least attenuate, instabilities.

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Influence of pulsed entries on a spray generated by an air-blast injection device: An experimental analysis on combustion instability processes in aeroengines

Cited by 41 publications

References 4 publications

Dynamics of Swirling Flames

Dynamics of Swirling Flames

Stability analysis of a swirl spray combustor based on flame describing function

Self‐excited Combustion Instabilities

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