Imperial College London
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Professor Aimee S. Morgans

Faculty of Engineering, Department of Mechanical Engineering

Professor of Thermofluids
 
 
 
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Contact

 

+44 (0)20 7594 9975a.morgans

 
 
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Location

 

621City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@inproceedings{Gaudron:2020:10.1115/GT2020-16158,
author = {Gaudron, R and Yang, D and Morgans, AS},
doi = {10.1115/GT2020-16158},
title = {Acoustic energy balance during the onset, growth and saturation of thermoacoustic instabilities},
url = {http://dx.doi.org/10.1115/GT2020-16158},
year = {2020}
}
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RIS format (EndNote, RefMan)

TY  - CPAPER
AB  - Thermoacoustic instabilities can occur in a wide range of combustors and are prejudicial since they can lead to increased mechanical fatigue or even catastrophic failure. A well-established formalism to predict the onset, growth and saturation of such instabilities is based on acoustic network models. This approach has been successfully employed to predict the frequency and amplitude of limit cycle oscillations in a variety of combustors. However, it does not provide any physical insight in terms of the acoustic energy balance of the system. On the other hand, Rayleigh’s criterion may be used to quantify the losses, sources and transfers of acoustic energy within and at the boundaries of a combustor. However, this approach is cumbersome for most applications because it requires computing volume and surface integrals and averaging over an oscillation cycle. In this work, a new methodology for studying the acoustic energy balance of a combustor during the onset, growth and saturation of thermoacoustic instabilities is proposed. The two cornerstones of this new framework are the acoustic absorption coefficient  and the cycle-to-cycle acoustic energy ratio λ, both of which do not require computing integrals. Used along with a suitable acoustic network model, where the flame frequency response is described using the weakly nonlinear Flame Describing Function (FDF) formalism, these two dimensionless numbers are shown to characterize: 1) the variation of acoustic energy stored within the combustor between two consecutive cycles, 2) the acoustic energy transfers occurring at the combustor’s boundaries and 3) the sources and sinks of acoustic energy located within the combustor. The acoustic energy balance of the well-documented Palies burner is then analyzed during the onset, growth and saturation of thermoacoustic instabilities using this new methodology. It is demonstrated that this new approach allows a deeper understanding of the physical mechanisms
AU  - Gaudron,R
AU  - Yang,D
AU  - Morgans,AS
DO  - 10.1115/GT2020-16158
PY  - 2020///
TI  - Acoustic energy balance during the onset, growth and saturation of thermoacoustic instabilities
UR  - http://dx.doi.org/10.1115/GT2020-16158
ER  -
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