Linear instability of a premixed slot flame: Flame transfer function and resolvent analysis

Wang, Chuhan; Kaiser, Thomas Ludwig; Meindl, Max; Oberleithner, Kilian; Polifke, Wolfgang; Lesshafft, Lutz

doi:10.1016/j.combustflame.2022.112016

Cited by 11 publications

(3 citation statements)

References 62 publications

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“…Secondly, it is known that regions of receptivity for hydrodynamic modes are localized inside nozzles and close to burner lips where shear layers separate (Wang et al. 2022). Determining time-averaged flow fields in these regions for the present nozzle using PIV is challenging.…”

Section: Discussionmentioning

confidence: 99%

“…Firstly, the highly turbulent and density stratified nature of the present flow field would introduce large quantitative uncertainties in a hydrodynamic stability analysis of the current flow since unambiguous quantitatively accurate density fields are not directly measured. Secondly, it is known that regions of receptivity for hydrodynamic modes are localized inside nozzles and close to burner lips where shear layers separate (Wang et al 2022). Determining time-averaged flow fields in these regions for the present nozzle using PIV is challenging.…”

Section: Complex Network Analysismentioning

confidence: 99%

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Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

et al. 2022

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Global instabilities in swirling flows can significantly alter the flame and flow dynamics of swirl-stabilized flames, such as those in modern gas turbine engines. In this study, we characterize the interaction between the precessing vortex core (PVC), which is the consequence of a global hydrodynamic instability, and thermoacoustic instabilities, which are the result of a coupling between combustor acoustics and the unsteady heat release rate. This study is performed using experimental data obtained from a model gas turbine combustor employing two concentric swirling nozzles of air, separated by a ring of fuel injectors, operating at five bar pressure. The flow split between the two streams is systematically varied to observe the impact of flow structure variation on the system dynamics at both non-reacting and reacting conditions. High-speed stereoscopic particle image velocimetry, OH planar laser-induced fluorescence and acetone planar laser-induced fluorescence are used to obtain information about the velocity fields, flame and fuel flow behaviour, respectively. Spectral proper orthogonal decomposition and a complex network analysis are used to identify and characterize the dominant oscillation mechanisms driving the system. In the non-reacting data, a PVC is present in most cases and the amplitude of the oscillation increases with increasing flow through the centre nozzle. In the reacting data, three dominant modes are seen: two thermoacoustic modes and the PVC. Our results show that in the cases where the frequency of the PVC overlaps with either of the thermoacoustic modes, the thermoacoustic modes are suppressed. The complex network analysis coupled with a weakly nonlinear theoretical analysis suggests the mechanisms by which this coupling and suppression of the thermoacoustic mode occur.

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Section: Discussionmentioning

confidence: 99%

Section: Complex Network Analysismentioning

confidence: 99%

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

et al. 2022

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“…Their studies were extended to M-shaped swirling flames by Skene & Schmid (2019). In a recent study, we used resolvent analysis to identify the optimal forcing structures in a slot flame, leading to maximal heat release (Wang et al 2022). For linear analysis of diffusion jet flames, one may refer to Nichols & Schmid (2008), Qadri, Chandler & Juniper (2015), Moreno-Boza et al (2016), Qadri et al (2021) and Sayadi & Schmid (2021).…”

Section: Introductionmentioning

confidence: 99%

Global linear stability analysis of a flame anchored to a cylinder

2022

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This study investigates the linear stability of a laminar premixed flame, anchored on a square cylinder and confined inside a channel. Many modern linear analysis concepts have been developed and validated around non-reacting bluff-body wake flows, and the objective of this paper is to explore whether those tools can be applied with the same success to the study of reacting flows in similar configurations. It is found that linear instability analysis of steady reacting flow states accurately predicts critical flow parameters for the onset of limit-cycle oscillations, when compared to direct numerical simulation performed with a simple one-step reaction scheme in the low Mach number limit. Furthermore, the linear analysis predicts a strong stabilising effect of flame ignition, consistent with documented experiments and numerical simulations. Instability in ignited wake flows is, however, found to set in at sufficiently high Reynolds number, and a linear wavemaker analysis characterises this instability as being driven by hydrodynamic mechanisms of a similar nature as in non-reacting wake flows. The frequency of nonlinear limit-cycle flame oscillations in this unstable regime is retrieved accurately by linear eigenmode analysis performed on the time-averaged mean flow, under the condition that the full set of the reacting flow equations is linearised. If, on the contrary, unsteadiness in the density and in the reaction rate are excluded from the linear model, then the congruence between linear and nonlinear dynamics is lost.

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Prediction of flame transfer function and combustion instability on a partially premixed swirling combustor by the system identification and CFD methods

Ke,

Ji,

Wang

et al. 2024

Aerospace Science and Technology

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Linear instability of a premixed slot flame: Flame transfer function and resolvent analysis

Cited by 11 publications

References 62 publications

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

Impact of precessing vortex core dynamics on the thermoacoustic instabilities in a swirl-stabilized combustor

Global linear stability analysis of a flame anchored to a cylinder

Prediction of flame transfer function and combustion instability on a partially premixed swirling combustor by the system identification and CFD methods

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