Shocked and unshocked thermoacoustic oscillations in a looped tube

Six burner/furnace systems which operated successfully without vibration are evaluated for resistance to thermoacoustic oscillations. The evaluation is based on the Rijke and Sondhauss models representing the combined burner/furnace (cold/hot) thermoacoustic systems. Frequency differences between the lowest vulnerable furnace acoustic frequencies in the burner axial direction and those of the systems’ Rijke and Sondhauss frequencies are evaluated to check for resonances. Most importantly, the stability of the Rijke and Sondhauss models is checked against the published design stability diagram of Eisinger [1] and Eisinger and Sullivan [2]. It is shown that the resistance to thermoacoustic oscillations is adequately defined by the published design stability diagram to which the evaluated cases generally adhere. Once the system falls into the stable range, the frequency differences or resonances appear to play only a secondary role. It is concluded, however, that in conjunction with stability, the primary criterion, sufficient frequency separations shall also be maintained in the design process to preclude resonances. The paper provides sufficient details to aid the design engineers.

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Excitation of Thermoacoustic Oscillations by Premixing Domestic Gas Burners

Combustion Science and Technology ◽

10.1080/00102200701739222 ◽

2007 ◽

Vol 180 (2) ◽

pp. 314-342 ◽

Cited By ~ 3

Author(s):

C. M. Coats ◽

Z. Chang ◽

P. D. Williams

Keyword(s):

Thermoacoustic Oscillations

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Thermoacoustic oscillations in cryogenics. Part 1: basic theory and experimental verification

Cryogenics ◽

10.1016/0011-2275(92)90277-h ◽

1992 ◽

Vol 32 (8) ◽

pp. 690-697 ◽

Cited By ~ 17

Author(s):

H. Luck ◽

Ch. Trepp

Keyword(s):

Experimental Verification ◽

Basic Theory ◽

Thermoacoustic Oscillations

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Thermoacoustics of Can-Annular Combustors

Volume 4A: Combustion, Fuels, and Emissions ◽

10.1115/gt2018-75799 ◽

2018 ◽

Cited By ~ 1

Author(s):

G. Ghirardo ◽

C. Di Giovine ◽

J. P. Moeck ◽

M. R. Bothien

Keyword(s):

Experimental Work ◽

Rotational Symmetry ◽

Acoustic Response ◽

Open Area ◽

Mode Localization ◽

Downstream Side ◽

Upstream Side ◽

Turbine Inlet ◽

Adjacent Transition ◽

Thermoacoustic Oscillations

Can-annular combustors consist of a set of independent cans, connected on the upstream side to the combustor plenum, and on the downstream side to the turbine inlet, where a transition duct links the round geometry of each can with the annular segment of the turbine inlet. Each transition duct is open on the sides towards the adjacent transition ducts, so that neighbouring cans are acoustically connected through a so called cross-talk open area. This theoretical, numerical and experimental work discusses the effect that this communication has on the thermoacoustic frequencies of the combustor. We show how this communication gives rise to axial and azimuthal modes, and that these correspond to particularly synchronised states of axial thermoacoustic oscillations in each individual can. We show that these combustors typically show clusters of thermoacoustic modes with very close frequencies and that a slight loss of rotational symmetry, e.g. a different acoustic response of certain cans, can lead to mode localization. We corroborate the predictions of azimuthal modes, clusters of eigenmodes and mode localization with experimental evidence.

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Experiments on Self-excited Thermoacoustic Oscillations in an Air-filled Looped Tube with a Pair of Stacks

Journal of the Physical Society of Japan ◽

10.7566/jpsj.87.104401 ◽

2018 ◽

Vol 87 (10) ◽

pp. 104401 ◽

Cited By ~ 2

Author(s):

Nobumasa Sugimoto ◽

Keisuke Minamigawa

Keyword(s):

Thermoacoustic Oscillations

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Effects of Nozzle Helmholtz Number on Indirect Combustion Noise by Compositional Perturbations

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4037914 ◽

2017 ◽

Vol 140 (3) ◽

Cited By ~ 3

Author(s):

Luca Magri ◽

Jeffrey O'Brien ◽

Matthias Ihme

Keyword(s):

Velocity Profile ◽

Combustion Chamber ◽

Transfer Functions ◽

Mixture Fraction ◽

Supersonic Nozzle ◽

Noise Pollution ◽

Combustion Noise ◽

Dipole Source ◽

Multicomponent Gas ◽

Thermoacoustic Oscillations

By modeling a multicomponent gas, a new source of indirect combustion noise is identified, which is named compositional indirect noise. The advection of mixture inhomogeneities exiting the gas-turbine combustion chamber through subsonic and supersonic nozzles is shown to be an acoustic dipole source of sound. The level of mixture inhomogeneity is described by a difference in composition with the mixture fraction. An n-dodecane mixture, which is a kerosene fuel relevant to aeronautics, is used to evaluate the level of compositional noise. By relaxing the compact-nozzle assumption, the indirect noise is numerically calculated for Helmholtz numbers up to 2 in nozzles with linear velocity profile. The compact-nozzle limit is discussed. Only in this limit, it is possible to derive analytical transfer functions for (i) the noise emitted by the nozzle and (ii) the acoustics traveling back to the combustion chamber generated by accelerated compositional inhomogeneities. The former contributes to noise pollution, whereas the latter has the potential to induce thermoacoustic oscillations. It is shown that the compositional indirect noise can be at least as large as the direct noise and entropy noise in choked nozzles and lean mixtures. As the frequency with which the compositional inhomogeneities enter the nozzle increases, or as the nozzle spatial length increases, the level of compositional noise decreases, with a similar, but not equal, trend to the entropy noise. The noisiest configuration is found to be a compact supersonic nozzle.

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