Experimental study of the beating behavior of thermoacoustic self-excited instabilities in dual swirl combustors

Kim, Jaehyeon; Jang, Mun-Seok; Lee, Kee-Man; Masri, Assaad R.

doi:10.1016/j.expthermflusci.2019.03.007

Cited by 22 publications

(7 citation statements)

References 43 publications

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“…It is found that only Case P f M c exhibits stable combustion while the other four cases show large amplitude oscillations. A dual-frequency distribution is found in the pressure spectrum of Case P f M f as beating oscillations [15,22]. Detailed results and discussion of these three flame modes will be presented hereafter.…”

Section: Resultsmentioning

confidence: 87%

“…Recently, Kim et at. [15] reported interesting beating oscillations in a stratified swirl burner without lip structures, with a slight difference in oscillating frequencies between the pilot and the main flames. This beating phenomenon may shed light on how flame interactions between the pilot and the main stages could affect combustion instabilities in centrally-staged combustors.…”

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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Section: Resultsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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

Han

Laera

Yang

et al. 2020

Combustion and Flame

View full text Add to dashboard Cite

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“…Intensive experimental studies have been conducted to investigate the interaction between swirling flow and flames to better understand, predict and control thermoacoustic instability. Kim et al [15] performed an experimental study to evaluate the effect of thermal power operating conditions and combustor length on the amplitude and frequency of pressure. Han et al [16] developed a novel double-swirled combustion system to investigate the correlation between flame macrostructures and thermoacoustic combustion instabilities.…”

Section: Introductionmentioning

confidence: 99%

Generation and Mitigation Mechanism Studies of Nonlinear Thermoacoustic Instability in a Modelled Swirling Combustor with a Heat Exchanger

2021

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In the present work, 3D Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are performed to investigate the generation and mitigation mechanism of combustion-sustained thermoacoustic instabilities in a modelled swirl combustor. The effects of (1) swirling number SN, (2) inlet air flow rate Va and (3) inlet temperature Ti on the amplitudes and frequencies of swirling combustion-excited limit cycle oscillations are examined. It is found that the amplitude of acoustic fluctuations is increased with increasing SN and Va and decreased with the increase of Ti. The dominant frequency of oscillations is also found to increases with the increase of SN and Va. However, increasing Ti leads to the dominant frequency being decreased first and then increased. An alternative passive control method of installing an adjustable temperature heat exchanger on the combustion chamber wall is then proposed. Numerical results show that thermoacoustic oscillations could be excited and mitigated by setting the heat exchanger temperature to TH. Global and local Rayleigh indexes are applied to further reveal the excitation and attenuation effects on mechanisms. The present study is conducive to developing a simulation platform for thermoacoustic instabilities in swirling combustors. It also provides an alternative method to amplify or mitigate thermoacoustic oscillations.

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“…Extensive experimental, theoretical and numerical research on premixed and non-premixed flames under the acoustic excitation have been carried out in order to better understand and solve thermoacoustic instability problems [14][15][16]. Lieuwen [17,18] provided an excellent review on premixed flame-acoustic wave interactions via the investigation of acoustic wave interactions with turbulent, premixed flames.…”

Section: Introductionmentioning

confidence: 99%

Entropy and flame transfer function analysis of a hydrogen-fueled diffusion flame in a longitudinal combustor

Sun

Zhao

et al. 2020

Energy

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In this work, entropy generation and flame transfer function investigations are conducted on a hydrogenburnt diffusion flame in a longitudinal combustor with acoustic waves present. For this, a time-domain 2D numerical model of a jet diffusion flame is developed to gain insights on its dynamic response to acoustic disturbances at either resonant or non-resonant frequencies. The model is validated first by comparing the numerical results such as turbulence intensities, pressure and velocity mode shape and flame shapes with the experimental data available in the literature. The model is then applied to evaluate the effects of the frequencies and amplitudes of the forcing acoustic waves, and the flame-holder/nozzle axial positions on entropy generation of both hydrogen-and propane-fueled flames. It is found that the entropy generation rate is sensitive to acoustic forcing frequencies, amplitudes and the nozzle axial positons. Furthermore, entropy produced from the heat conduction and the chemical reaction processes is shown to be dominant and secondary respectively. However, the mass diffusion is found to play a negligible role on entropy generation. As the acoustic forcing frequency is set to 385 Hz near resonance, the total entropy generation rates are minimized, and the mass diffusion contribution is maximized with the flame being placed at velocity node locations in comparison with other flame-holding locations. Finally, flame transfer function (FTF) analysis is performed by using two different methods. It is shown that the flame responds strongly to low-frequency acoustic disturbances, acting like a band-pass filter. Increasing the acoustic intensity leads to the flame being more sensitive to the acoustic disturbances over more frequency bands.

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Experimental study of the beating behavior of thermoacoustic self-excited instabilities in dual swirl combustors

Cited by 22 publications

References 43 publications

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

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

Generation and Mitigation Mechanism Studies of Nonlinear Thermoacoustic Instability in a Modelled Swirling Combustor with a Heat Exchanger

Entropy and flame transfer function analysis of a hydrogen-fueled diffusion flame in a longitudinal combustor

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