Characteristics of self-excited spinning azimuthal modes in an annular combustor with turbulent premixed bluff-body flames
| Autor: | James R. Dawson, Håkon Tormodsen Nygård, Nicholas A. Worth, Marek Mazur |
|---|---|
| Přispěvatelé: | Norwegian University of Science and Technology [Trondheim] (NTNU), Norwegian University of Science and Technology (NTNU) |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
020209 energy
General Chemical Engineering media_common.quotation_subject 02 engineering and technology Azimuthal modes 01 natural sciences Asymmetry Instability 010305 fluids & plasmas Physics::Fluid Dynamics [SPI]Engineering Sciences [physics] 0103 physical sciences 0202 electrical engineering electronic engineering information engineering Annular combustor Physical and Theoretical Chemistry Spinning media_common Physics [SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph] Turbulence Advection Modal dynamics Mechanical Engineering [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment Mechanics Flame dynamics Amplitude Combustor Combustion instability Intensity (heat transfer) |
| Zdroj: | Symposium, International, on combustion Proceedings of the Combustion Institute Proceedings of the Combustion Institute, Elsevier, 2019, 37 (4), pp.5129-5136. ⟨10.1016/j.proci.2018.07.080⟩ |
| ISSN: | 1540-7489 |
| Popis: | In this paper we investigate self-excited azimuthal modes in an annular combustor with turbulent premixed bluff-body stabilised flames. Previous studies have shown that both swirl and equivalence ratio influence modal dynamics, i.e. the time-varying nature of the modes. However, self-excited azimuthal modes have not yet been investigated in turbulent flames without bulk swirl, which do not generate any preferential flow in either azimuthal direction, and may therefore lead to different behaviour. Joint probability density functions of the instability amplitudes at various flowrates and equivalence ratios showed a strong bi-modal response favouring both ACW and CW spinning states not previously observed. Operating conditions leading to a bi-modal response provide a unique opportunity to investigate whether the structure of the global fluctuating heat release rate of self-excited spinning modes in both directions exhibit similar dynamics and structure. This was investigated using high-speed OH* chemiluminescence images of the annular combustor and a new rotational averaging method was applied which decomposes the spinning components of the global fluctuating heat release rate. The new rotational averaging, which differs from standard phase-averaging, produces spatial averages in a frame of reference moving with the spinning wave. The results show that the structure of the fluctuating heat release rate for spinning modes is highly asymmetric as characterised by large, crescent shaped regions of high OH* intensity, located on the far side of each flame, relative to the direction of the azimuthally propagating pressure wave. In comparison with interacting swirling flames, these results indicate that the previously observed radial asymmetry of OH* fluctuations may be introduced through advection by local swirl. © 2018 The Author(s). Published by Elsevier Inc. on behalf of The Combustion Institute. This is an open access article under the CC BY license. (http://creativecommons.org/licenses/by/4.0/) |
| Databáze: | OpenAIRE |
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