Flame macrostructures and thermoacoustic instabilities in stratified swirling flames

Han, Xingsi; Laera, Davide; Morgans, Aimee S.; Sung, Chih-Jen; Hui, Xin; Lin, Y.

doi:10.1016/j.proci.2018.06.147

Cited by 76 publications

(29 citation statements)

References 40 publications

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“…Recently, the fact that the flame primarily responds to hydrodynamic disturbances (originally excited by the acoustics) has been exploited by using incompressible LES (Febrer et al, 2011;: the convective flow speed rather than the speed of sound then determines the time step and thus allows much larger values, making incompressible simulations significantly faster than fully compressible ones. With this approach, a complete FDF for a premixed bluff-body stabilised flame was accurately predicted , as were the nonlinear FDFs of a swirling premixed flame and a very long non-swirling flame (Xia, Li, et al, 2017;Li et al, 2017) and, recently, the linear flame response of a stratified flame (Han et al, 2018), etc.…”

Section: Introductionmentioning

confidence: 99%

Numerical prediction of the Flame Describing Function and thermoacoustic limit cycle for a pressurised gas turbine combustor

Xia

Laera

Jones

et al. 2019

Combustion Science and Technology

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The forced flame responses in a pressurised gas turbine combustor are predicted using numerical reacting flow simulations. Two incompressible 1 LES solvers are used, applying two combustion models and two reaction schemes (4-step and 15-step) at two operating pressures (3 bar and 6 bar). Although the combustor flow field is little affected by these factors, the flame length and heat release rate are found to depend on combustion model, reaction scheme and combustor pressure. The flame responses to an upstream velocity perturbation are used to construct the flame describing functions (FDFs). The FDFs exhibit smaller dependence on the combustion model and reaction chemistry than the flame shape and mean heat release rate. The FDFs are validated by predicting combustor thermoacoustic stability at 3 bar and 6 bar and, for the unstable 6 bar case, also by predicting the frequency and oscillation amplitude of the resulting limit cycle oscillation. All of these numerical predictions are in very good agreement with experimental measurements.

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Section: Introductionmentioning

confidence: 99%

Numerical prediction of the Flame Describing Function and thermoacoustic limit cycle for a pressurised gas turbine combustor

Xia

Laera

Jones

et al. 2019

Combustion Science and Technology

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“…In the present work, a novel burner (BASIS) designed at Beihang University [13,24] is used to study the aero-thermodynamic behaviour and combustion instabilities of LPP combustors. Its detailed geometry is sketched in CSL stands for the central shear layer originating from the pilot stage, while ISL and OSL stand for the inner and outer shear layer of the main stage, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…But the both combustors in Refs [6,12] feature complicated geometries and were not shown in detail. Recently, a simplified stratified burner was developed by the authors' group [13] to elucidate the role of the pilot flame in anchoring the main flame experimentally.…”

Section: Introductionmentioning

confidence: 99%

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Flame interactions in a stratified swirl burner: Flame stabilization, combustion instabilities and beating oscillations

Han

Laera

Yang

et al. 2020

Combustion and Flame

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The present article investigates the interactions between the pilot and main flames in a novel stratified swirl burner using both experimental and numerical methods. Experiments are conducted in a test rig operating at atmospheric conditions. The system is equipped with the BASIS (Beihang Axial Swirler Independently-Stratified) burner fuelled with premixed methane-air mixtures. To illustrate the interactions between the pilot and main flames, three operating modes are studied, where the burner works with (i) only the pilot flame, (ii) only the main flame, and (iii) the stratified flame (with both the pilot and main flames). We found that: (1) In the pilot flame mode, the flame changes from V-shape to M-shape when the main stage is switched from closed to supplying a pure air stream. Strong oscillations in the M-shape flame are found due to the dilution of the main air to the pilot methane flame. (2) In the main flame mode, the main flame is lifted off from the burner if the pilot stage is supplied with air. The temperature of the primary recirculation zone drops substantially and the unsteady heat release is intensified. (3) In the stratified flame mode, unique beating oscillations exhibiting dual closely-spaced frequencies in the pressure spectrum

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“…During experiments, they observed three different flame modes depending on the equivalence ratio. They demonstrated that lifted and V-type flames are more prone to flame instabilities [4].…”

Section: Introductionmentioning

confidence: 99%

Swirler geometry effects (dh/do ratio) on synthetic gas flames. Part 2: dynamic flame behaviour at external y altered acoustic conditions

Yılmaz¹,

Çam²,

Yılmaz³

2021

energetika

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In a combustion device, unsteady heat release causes acoustic energy to increase when acoustic damping (energy loss) is not that effective, and, as a result, thermo-acoustic flame instabilities occur. In this study, effects of the swirler dh/do ratio (at different swirl numbers) on dynamic flame behaviour of the premixed 20%CNG/30%H2/30%CO/20%CO2 mixture under externally altered acoustic boundary conditions and stability limits (flashback and blowout equivalence ratios) of such mixture were investigated in a laboratory-scale variable geometric swirl number combustor. Therefore, swirl generators with different dh/do ratios (0.3 and 0.5) and geometric swirl numbers (0.4, 0.6, 0.8, 1.0 1.2 and 1.4) were designed and manufactured. Acoustic boundary conditions in the combustion chamber were altered using loudspeakers, and flame response to these conditions was perceived using photodiodes and pressure sensors. Dynamic flame behaviour of respective mixture was evaluated using luminous intensity and pressure profiles. Results showed that the dh/do ratio has a minor impact on dynamic flame behaviour.

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Flame macrostructures and thermoacoustic instabilities in stratified swirling flames

Cited by 76 publications

References 40 publications

Numerical prediction of the Flame Describing Function and thermoacoustic limit cycle for a pressurised gas turbine combustor

Numerical prediction of the Flame Describing Function and thermoacoustic limit cycle for a pressurised gas turbine combustor

Flame interactions in a stratified swirl burner: Flame stabilization, combustion instabilities and beating oscillations

Swirler geometry effects (dh/do ratio) on synthetic gas flames. Part 2: dynamic flame behaviour at external y altered acoustic conditions

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