Suppression and excitation of the precessing vortex core by acoustic velocity fluctuations: An experimental and analytical study

Steffen, Thomas; Ćosić, Bernhard; Paschereit, Christian Oliver; Oberleithner, Kilian

doi:10.1016/j.combustflame.2016.06.013

Cited by 42 publications

(26 citation statements)

References 44 publications

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“…The trace of the PVC on the flame is thus strongly impacted by the siren-induced modulations which is coherent with literature results [33][34][35][36]. This however is not enough to conclude that, in this particular setup, the siren acts directly on the PVC.…”

Section: Global Dynamics Of the Burnersupporting

confidence: 84%

“…Studies carrying out artificial flow forcing can shed light on the potential interactions between the PVC and global flow field oscillations. When the forcing frequency remains low compared to that of the PVC, several studies showed that the PVC can be damped and even completely destroyed by axial forcing [33][34][35][36]. On the other hand, Iudiciani et al showed that higher frequency forcing (at twice the PVC frequency) can reinforce the PVC [37].…”

Section: Introductionmentioning

confidence: 99%

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Experimental Study of the Precessing Vortex Core Impact on the Liquid Fuel Spray in a Gas Turbine Model Combustor

Renaud

Ducruix

Zimmer

2019

Journal of Engineering for Gas Turbines and Power

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Despite being good candidates for the reduction of pollutant emissions from gas turbines, burners operating in lean premixed prevaporized regimes often face stability issues and can be sensitive to perturbations. The swirling flow used to aerodynamically stabilize the flame can also lead to the appearance of a large-scale coherent flow structure known as the precessing vortex core (PVC). In this study, a swirl-stabilized combustor fed with liquid dodecane is studied at a globally lean operating condition with the help of high-speed diagnostics and dynamic mode decomposition (DMD) as the main postprocessing method. It is shown that the trace of a PVC originating inside the injector is still present in the fuel spray at the entrance of the chamber even though the aerodynamical structure itself is not detectable anymore. The perturbation of the fuel spray is then transmitted to the flame through local equivalence ratio fluctuations. It is observed that the PVC trace on the spray and thus on the flame can be suppressed by air flow modulations generated by a siren device. The suppression of this trace is shown to come from a decay of the aerodynamical structure itself rather than by a change in fuel mixing or vaporization. Analysis of the characteristic frequency of the PVC shows a frequency spread indicating a loss of coherence of the structure with the high-amplitude air flow rate fluctuations.

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Section: Global Dynamics Of the Burnersupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Experimental Study of the Precessing Vortex Core Impact on the Liquid Fuel Spray in a Gas Turbine Model Combustor

Renaud

Ducruix

Zimmer

2019

Journal of Engineering for Gas Turbines and Power

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“…Moreover, PVC can reappear after being suppressed under certain conditions, indicating that PVC can be suppressed under a limited range of operating conditions. However, changing the operating conditions can lead to a change in flame appearance/behaviour/dynamics [65], and this change was found responsible for suppression or excitation of PVC [66]. In other words, coherent structures have a significant influence on the flow field and flame dynamics.…”

Section: Progress and Challenges Of Ppfsmentioning

confidence: 99%

Burner geometry effect on coherent structures and acoustics of a confined swirling partially premixed methane flame

Ahmed

Birouk

2019

Experimental Thermal and Fluid Science

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The effect of burner geometry (central fuel nozzle, mixing tube length, and flame confinement) on the ensuing flowfield's coherent structures (precessing vortex core and vortex shedding) and their relationship with some combustion stability parameters, such as flashback and flame front dynamics of a swirling partially premixed methane flame, is experimentally studied. In this investigation, several measurement techniques are employed. These include particle image velocimetry (PIV), Mie scattering, laser Doppler velocimetry (LDV), Bruel & Kjaer microphone, high-speed Schlieren imaging technique, and high-speed luminescence imaging. In addition, proper orthogonal decomposition (POD) is used as a post processing technique to capture the flowfield coherent structures. In the first part of the study, the effect of central nozzle geometry on coherent structures' strength and frequency is examined inside a relatively long mixing tube.

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“…This is the framework where mean flow LSA is trustworthy as the mean-coherent interactions are the leading nonlinearities. Counter examples are subharmonic resonance in the shear layer [18], the cavity flow [19], and forced oscillator flows [20].…”

Section: Introductionmentioning

confidence: 99%

An assessment of turbulence models for linear hydrodynamic stability analysis of strongly swirling jets

Rukes

Paschereit

Oberleithner

2016

European Journal of Mechanics - B/Fluids

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Linear stability analysis has proven to be a useful tool in the analysis of dominant coherent structures, such as the von Kármán vortex street and the global spiral mode associated with the vortex breakdown of swirling jets. In recent years, linear stability analysis has been applied successfully to turbulent time-mean flows, instead of laminar base-flows, which requires turbulent models that account for the interaction of the turbulent field with the coherent structures. To retain the stability equations of laminar flows, the Boussinesq approximation with a spatially nonuniform but isotropic eddy viscosity is typically employed. In this work we assess the applicability of this concept to turbulent strongly swirling jets, a class of flows that is particularly unsuited for isotropic eddy viscosity models. Indeed we find that unsteady RANS simulations only match with experiments with a Reynolds stress model that accounts for an anisotropic eddy viscosity. However, linear stability analysis of the mean flow is shown to accurately predict the global mode growth rate and frequency if the employed isotropic eddy viscosity represents a least-squares approximation of the anisotropic eddy viscosity. Viscosities derived from the k − model did not achieve a good prediction of the mean flow nor did they allow for accurate stability calculations. We conclude from this study that linear stability analysis can be accurate for flows with strongly anisotropic turbulent viscosity and the capability of the Boussinesq approximation in terms of URANS-based mean flow prediction is not a prerequisite.

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Suppression and excitation of the precessing vortex core by acoustic velocity fluctuations: An experimental and analytical study

Cited by 42 publications

References 44 publications

Experimental Study of the Precessing Vortex Core Impact on the Liquid Fuel Spray in a Gas Turbine Model Combustor

Experimental Study of the Precessing Vortex Core Impact on the Liquid Fuel Spray in a Gas Turbine Model Combustor

Burner geometry effect on coherent structures and acoustics of a confined swirling partially premixed methane flame

An assessment of turbulence models for linear hydrodynamic stability analysis of strongly swirling jets

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