Large Eddy Simulation of the Sensitivity of Vortex Breakdown and Flame Stabilisation to Axial Forcing

Iudiciani, Piero; Duwig, Christophe

doi:10.1007/s10494-011-9327-2

Cited by 44 publications

(27 citation statements)

References 52 publications

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“…Such simulations correctly retrieve velocity profiles and PVC in cold and reactive conditions of swirl stabilized flames (Roux et al 2005, Freitag & Janicka 2007. Numerical results may in turn be used to determine the swirl number and analyze PVC interactions with the flame (Iudiciani & Duwig 2011), a problem that requires advanced optical diagnostics in experiments. Palies et al (2011e) used LES to infer the coupling mechanisms between large-scale vortices and swirl number oscillations leading to heat-release rate interferences.…”

Section: Large Eddy Simulation In Swirling Flame Dynamicsmentioning

confidence: 99%

Dynamics of Swirling Flames

Candel

Durox²,

Schuller³

et al. 2014

Annu. Rev. Fluid Mech.

372

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: Large Eddy Simulation In Swirling Flame Dynamicsmentioning

confidence: 99%

Dynamics of Swirling Flames

Candel

Durox²,

Schuller³

et al. 2014

Annu. Rev. Fluid Mech.

372

157

View full text Add to dashboard Cite

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“…The reason for the frequency selection was to promote the formation of large-scale ring-like vortices beyond the nozzle rim due to strong oscillations of bulk velocity. According to Iudiciani and Duwig (2011), the frequency of the forcing can have a rather wide range of values that are smaller than the precession frequency. St ¼ 0.55 was also close to the value of 0.52, which was used for previous measurements by Alekseenko et al (2008) for a nonreacting jet with the same nozzle geometry.…”

Section: Experimental Setup and Apparatusmentioning

confidence: 99%

“…Strong perturbations were applied to the flow bulk velocity in order to force formation of ring-like vortices before the combustion domain and to investigate the effect on the combustion process. For example, based on large eddy simulation of a lean swirling flame in a model combustor, Iudiciani and Duwig (2011) have shown that application of periodic forcing with frequencies below the precession frequency of the vortex core can result in a weakening of the core precession and, consequently, shift RZ and the flame upstream of the combustor.…”

Section: Introductionmentioning

confidence: 99%

Effect of High-Amplitude Forcing on Turbulent Combustion Intensity and Vortex Core Precession in a Strongly Swirling Lifted Propane/Air Flame

Алексеенко

Дулин

Kozorezov

et al. 2012

Combustion Science and Technology

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The present work reports stereoscopic particle image velocimetry (PIV) measurements in a strongly swirling nonreacting jet and partially premixed lifted flame. The spatial distributions of the average velocity and components of turbulent kinetic energy were calculated from the measured ensembles of the instantaneous velocity fields. A pronounced bubble-type vortex breakdown was observed for the studied flows. Based on proper orthogonal decomposition (POD) of the PIV data and on estimates of velocity fluctuation spectra by a laser Doppler velocimetry (LDV) probe, it was concluded that the combustion did not fundamentally affect the type of coherent structures in the strongly swirling flow: a pair of secondary helical vortices was induced by a precessing vortex core in both cases. Because a strongly swirling jet flow is usually insensitive to weak forcing, strong perturbations were superimposed on the flow bulk velocity to force the formation of ring-like vortices in the flow and to investigate the possible outcomes on the turbulent combustion process. The forcing frequency was below that of the precession. Based on the CH Ã chemiluminescence signal, it was observed that the forcing provided an increase in the turbulent combustion rate near the flame onset, as the entrainment of ambient air to the rich mixture must have increased. Moreover, for a forcing amplitude typically above the magnitude of reverse flow inside the bubble-type recirculation zone, a dramatic suppression of the vortex core precession took place in the reacting case. This effect was accompanied by a quasi-periodical vanishing of the recirculation zone due to interaction of the forced ring-like vortices with the lifted flame.

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“…For this reason, they are often limited to the analysis of the system response to a single forcing frequency or to the simulation of the dynamics of self-sustained oscillations initiated from small or finite-level initial perturbations to a limit cycle. [21][22][23] System identification tools have also been applied to LES simulations to estimate the flame transfer function. 24,25 These techniques are based on the forcing of the flame using a small-amplitude broadband noise, assuming the flame response to be linear.…”

Section: Introductionmentioning

confidence: 99%

Response analysis of a laminar premixed M-flame to flow perturbations using a linearized compressible Navier-Stokes solver

Blanchard

Schuller

Sipp³

et al. 2015

Physics of Fluids

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International audienceThe response of a laminar premixed methane-air flame subjected to flow perturbations around a steady state is examined experimentally and using a linearized compressible Navier-Stokes solver with a one-step chemistry mechanism to describe combustion. The unperturbed flame takes an M-shape stabilized both by a central bluff body and by the external rim of a cylindrical nozzle. This base flow is computed by a nonlinear direct simulation of the steady reacting flow, and the flame topology is shown to qualitatively correspond to experiments conducted under comparable conditions. The flame is then subjected to acoustic disturbances produced at different locations in the numerical domain, and its response is examined using the linearized solver. This linear numerical model then allows the componentwise investigation of the effects of flow disturbances on unsteady combustion and the feedback from the flame on the unsteady flow field. It is shown that a wrinkled reaction layer produces hydrodynamic disturbances in the fresh reactant flow field that superimpose on the acoustic field. This phenomenon, observed in several experiments, is fully interpreted here. The additional perturbations convected by the mean flow stem from the feedback of the perturbed flame sheet dynamics onto the flow field by a mechanism similar to that of a perturbed vortex sheet. The different regimes where this mechanism prevails are investigated by examining the phase and group velocities of flow disturbances along an axis oriented along the main direction of the flow in the fresh reactant flow field. It is shown that this mechanism dominates the low-frequency response of the wrinkled shape taken by the flame and, in particular, that it fully determines the dynamics of the flame tip from where the bulk of noise is radiated

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Large Eddy Simulation of the Sensitivity of Vortex Breakdown and Flame Stabilisation to Axial Forcing

Cited by 44 publications

References 52 publications

Dynamics of Swirling Flames

Dynamics of Swirling Flames

Effect of High-Amplitude Forcing on Turbulent Combustion Intensity and Vortex Core Precession in a Strongly Swirling Lifted Propane/Air Flame

Response analysis of a laminar premixed M-flame to flow perturbations using a linearized compressible Navier-Stokes solver

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