Coupled dynamics of lift-off and precessing vortex core formation in swirl flames

An, Qiang; Kwong, Wing Yin; Geraedts, Benjamin D.; Steinberg, Adam M.

doi:10.1016/j.combustflame.2016.03.011

Cited by 76 publications

(24 citation statements)

References 36 publications

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“…As a results, the PIV-z data contains more detail about the future state of the combustor. This agrees with prior analyses in that the PIV-z data was actually found to be at the root of flame transitions [1,30]. The flame lift-off, for example, is aided by high-strain rates in the inner recirculation zone, which causes flame extinction and formation of a PVC.…”

Section: Horizon Time Comparisonssupporting

confidence: 89%

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Experimental data-based reduced-order model for analysis and prediction of flame transition in gas turbine combustors

Barwey

Hassanaly

et al. 2019

Combustion Theory and Modelling

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In lean premixed combustors, flame stabilization is an important operational concern that can affect efficiency, robustness and pollutant formation. The focus of this paper is on flame lift-off and re-attachment to the nozzle of a swirl combustor. Using time-resolved experimental measurements, a data-driven approach known as cluster-based reduced order modeling (CROM) is employed to 1) isolate key flow patterns and their sequence during the flame transitions, and 2) formulate a forecasting model to predict the flame instability. The flow patterns isolated by the CROM methodology confirm some of the experimental conclusions about the flame transition mechanism. In particular, CROM highlights the key role of the precessing vortex core (PVC) in the flame detachment process in an unsupervised manner. For the attachment process, strong flow recirculation far from the nozzle appears to drive the flame upstream, thus initiating re-attachment. Different data-types (velocity field, OH concentration) were processed by the modeling tool, and the predictive capabilities of these different models are also compared. It was found that the swirling velocity possesses the best predictive properties, which gives a supplemental argument for the role of the PVC in causing the flame transition. The model is tested against unseen data and successfully predicts the probability of flame transition (both detachment and attachment) when trained with swirling velocity with minimal user input. The model trained with OH-PLIF data was only successful at predicting the flame attachment, which implies that different physical mechanisms are present for different types of flame transition. Overall, these aspects show the great potential of data-driven methods, particularly probabilistic forecasting techniques, in analyzing and predicting large-scale features in complex turbulent combustion problems.

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Section: Horizon Time Comparisonssupporting

confidence: 89%

“…The issue of flame stabilization is critical for lean premixed flames with the perspective of controlling pollutant formation and ensuring robustness at various operating loads [1]. In swirl-stabilized combustors, the interaction of multiple recirculation zones with flame propagation impacts the stabilization process.…”

Section: Introductionmentioning

confidence: 99%

Experimental data-based reduced-order model for analysis and prediction of flame transition in gas turbine combustors

Barwey

Hassanaly

et al. 2019

Combustion Theory and Modelling

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“…Such considerations may also be needed for understanding and predicting unsteady phenomenons such as periodic fluctuations and transient behaviors in certain combustion systems. This work concentrates on such a phenomenon that is encountered in swirl stabilized flames, namely the intermittent transitions between attached (V-shape) and lifted (M-shaped) flames at socalled bi-stable operating conditions [4,5]. The transition from V-to M-flame occurs as a sequence of local extinction near the flame root, formation of a helical precessing vortex core (PVC) [6] and an eventual total lift-off.…”

Section: Introductionmentioning

confidence: 99%

Responses of combustor surface temperature to flame shape transitions in a turbulent bi-stable swirl flame

Yin

Nau

Meier

2017

Experimental Thermal and Fluid Science

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“…[11][12][13][14] It was shown that a PVC arises as soon as a V-shaped flame detaches from the burner outlet and transitions to a detached M-flame. [3][4][5]11,12 Moreover, it was further shown that the strong velocity fluctuations near the burner outlet induced by the PVC enhance the mixing of fuel and air. [15][16][17] The interaction of the PVC with thermoacoustic instability is an open question and subject to several studies.…”

Section: Introductionmentioning

confidence: 99%

Excitation of the precessing vortex core by active flow control to suppress thermoacoustic instabilities in swirl flames

Lückoff

Oberleithner

2019

International Journal of Spray and Combustion Dynamics

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In this study, we apply periodic flow excitation of the precessing vortex core at the centerbody of a swirl-stabilized combustor to investigate the impact of the precessing vortex core on flame shape, flame dynamics, and especially thermoacoustic instabilities. The current control scheme is based on results from linear stability theory that determine the precessing vortex core as a global hydrodynamic instability with its maximum receptivity to open-loop actuation located near the center of the combustor inlet. The control concept is first validated at isothermal conditions. This is of utmost importance for the proceeding studies that focus on the exclusive impact of the precessing vortex core on the combustion dynamics. Subsequently, the control is applied to reacting conditions considering lean premixed turbulent swirl flames. Considering thermoacoustically stable flames first, it is shown that the actuation locks onto the precessing vortex core when it is naturally present in the flame, which allows the precessing vortex core frequency to be controlled. Moreover, the control allows the precessing vortex core to be excited in conditions where it is naturally suppressed by the flame, which yields a very effective possibility to control the precessing vortex core amplitude. The control is then applied to thermoacoustically unstable conditions. Considering perfectly premixed flames first, it is shown that the precessing vortex core actuation has only a minor effect on the thermoacoustic oscillation amplitude. However, we observe a continuous increase of the thermoacoustic frequency with increasing precessing vortex core amplitude due to an upstream displacement of the mean flame and resulting reduction of the convective time delay. Considering partially premixed flames, the precessing vortex core actuation shows a dramatic reduction of the thermoacoustic oscillation amplitude. In consideration of the perfectly premixed cases, we suspect that this is caused by the precessing vortex core-enhanced mixing of equivalence ratio fluctuations at the flame root and due to a reduction of time delays due to mean flame displacement.

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Coupled dynamics of lift-off and precessing vortex core formation in swirl flames

Cited by 76 publications

References 36 publications

Experimental data-based reduced-order model for analysis and prediction of flame transition in gas turbine combustors

Experimental data-based reduced-order model for analysis and prediction of flame transition in gas turbine combustors

Responses of combustor surface temperature to flame shape transitions in a turbulent bi-stable swirl flame

Excitation of the precessing vortex core by active flow control to suppress thermoacoustic instabilities in swirl flames

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