Experimental and numerical investigation of the acoustic response of multi-slit Bunsen burners

Kornilov, VN Viktor; Rook, R Ronald; Boonkkamp, ten Jhm Jan Thije; Goey, de Lph Philip

doi:10.1016/j.combustflame.2009.07.017

Cited by 79 publications

(46 citation statements)

References 29 publications

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“…25 over the Strouhal number (based on the bulk velocity and the burner diameter) and exhibit typical shapes observed in previous studies [29,33,34,39]. The gain in the Attached case is highest at frequency f 1 and is of the order of one.…”

Section: Forced Flamessupporting

confidence: 74%

“…It is affected by different mechanisms acting simultaneously on the heat release rate fluctuation and therefore difficult to separate [25]: the axial velocity perturbation [26][27][28][29], the perturbation of swirl [30][31][32][33][34] and the perturbation of mixing [35][36][37][38]. The gain of FTFs for swirled flames exhibits a typical shape: it starts at 1, then increases towards a maximum, decreases to a local minimum at low frequencies, often reaches a second maximum at higher frequencies and decreases finally to low values at high frequencies.…”

Section: Introductionmentioning

confidence: 99%

“…The gain of FTFs for swirled flames exhibits a typical shape: it starts at 1, then increases towards a maximum, decreases to a local minimum at low frequencies, often reaches a second maximum at higher frequencies and decreases finally to low values at high frequencies. The FTF phase evolves in a quasi-linear way [29,33,34,39]. Both phenomena, the PVC and combustion instabilities, can be simultaneously present in swirled flames and interact with each other but the link between PVC and thermoacoustics remains a controversial issue.…”

Section: Introductionmentioning

confidence: 99%

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Bistable swirled flames and influence on flame transfer functions

Hermeth

Staffelbach

Gicquel

et al. 2014

Combustion and Flame

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Large Eddy Simulations (LES) are used to study a lean swirl-stabilized gas turbine burner where the flow exhibits two stable states. In the first one, the flame is attached to the central bluff body upstream of the central recirculation zone which contains burnt gases. In the second one the flame is detached from the central bluff body downecirculation zone which is filled by cold unburnt gases and dominated by a strong Precessing Vortex Core (PVC). The existence of these two states has an important effect on the dynamic response of the flame (FTF): both gain and phase of the FTF change significantly in the detached case compared to the attached one, suggesting that the stability of the machine to thermoacoustic oscillations will differ, depending on the flame state. Bifurcation diagrams show that the detached flame cannot be brought back to an attached position with an increased fuel flow rate, but it can be re-attached by forcing it at high amplitudes. The attached flame however, behaves inversely: it can be brought back to the detached position by both decreasing or increasing the pilot mass flow rate, but it remains attached at all forcing amplitudes. IntroductionSwirling flows are commonly used to help flame stabilization in gas turbine combustion chambers. They feature several types of vortex breakdown and can exhibit bifurcation phenomena where different states can co-exist and the flow can jump spontaneously from one to another [1,2]. Bifurcations of flames in configurations which are close to real gas turbine chambers have not been investigated so far even though engineers report that they observe these mechanisms and that there is a link between flame states and thermoacoustic instabilities: when the flame changes from one state to another, its acoustic stability characteristics also change.Two dynamic phenomena are usually observed in swirled combustion chambers: (1) a helical flow instability, the so-called precessing vortex core (PVC) and (2) thermo-acoustic instabilites.The PVC is an hydrodynamic instability in swirling flows [3].I t is a large scale structure characterized by a regular rotation of a spiral structure around the geometrical axis of the combustion chamber. It can occur at high Reynolds and swirl number flows [4][5][6][7][8][9][10] and its precession frequency is controlled by the rotation rate of the swirled flow [3]. Several studies show that combustion can suppress the PVC [6,7,11], but other cases also show PVCs which are present in reacting flows [12][13][14][15]. The interaction of PVC with flames has been analyzed for example by Stöhr et al.[16]: they found the PVC to enhance mixing and to increase the flame surface. This was associated to structures in the inner shear layer, whereas Moeck et al. [15] observed the outer shear layer to create most of the flame perturbations. Both researchers as well as Staffelbach [13] using LES evidenced a ''finger-like'' rotating structure at the flame foot around which the PVC is turning. Furthermore, asymmetric fluctuations of the he...

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Section: Forced Flamessupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Bistable swirled flames and influence on flame transfer functions

Hermeth

Staffelbach

Gicquel

et al. 2014

Combustion and Flame

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“…A similar conclusion was made by Birbaud et al [26,27] in their investigation of free jets and conical flames. Formation of travelling waves on the flames by acoustic forcing has been further confirmed by Kornilov et al [28,29]. Furthermore, it has been experimentally shown that the presence of an enclosure [30], and also flame anchoring dynamics [31] may affect the flame dynamics.…”

Section: Introductionmentioning

confidence: 76%

Response of a conical, laminar premixed flame to low amplitude acoustic forcing – A comparison between experiment and kinematic theories

Karimi

2014

Energy

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This paper presents an experimental study on the dynamics of a ducted, conical, laminar premixed flame subjected to low amplitude acoustic excitation from upstream. The heat release response of the flame to velocity disturbances is investigated through measurement of the so called 'flame transfer function' for a wide range of forcing frequencies. The results are compared with those predicted by the existing linear kinematic theories. It is observed that these theories are in general agreement with the experiment, although there exist some disparities. A detailed comparison of the experimental data with the kinematic theories shows that the phase speed of flame disturbances has an essential influence upon the level of agreement between the theory and experiment. The data set presented in this work complements that reported in an earlier study. In keeping with others, visualisation of the excited flames clearly shows that the flame response includes waves on the flame front which are formed at the base and then convect along the flame.

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“…Application of low magnitude perturbations causes the problem of signal-to-numerical noise ratio. The detailed analysis of this question can be found in [40]. The correctness of the flame TF reconstruction from the response to a stepwise perturbation is checked by varying the velocity perturbation magnitude.…”

Section: Post-processing Of Numerical Datamentioning

confidence: 99%