Fattahi, A., Karimi, N. and Hajialigol, N. (2020) Dynamics of entropy wave generation in a simplified model of gas turbine combustor: a theoretical investigation. Physics of Fluids, 32, 106107. (doi: 10.1063/5.0021729)
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Abstract
Entropy noise remains as a largely unexplored mechanism of combustion generated noise. Currently, little is known about the production sources of entropy waves in flames. To address this issue, the present work puts forward a theoretical investigation of the generation of entropy waves in a one-dimensional, ducted flow. A linear theory is developed for the dynamic responses of different sources of unsteady entropy generation including thermal, hydrodynamic, pressure and chemical irreversibility. For the first time in literature, dynamics of chemical sources of unsteady entropy generation are investigated extensively. It is found that the mixture fraction fluctuations are responsible for the production of almost all unsteady chemical entropy and that the effect of chemical potential is negligibly small. For the Strouhal numbers less than unity, fluctuations in pressure are the most significant source of the overall generation of unsteady entropy. However, at higher frequencies, mixture fraction fluctuations dominate the generation of entropy wave. The cut-off frequency for the generation of entropy wave is shown to depend not only on the thermal and hydrodynamic characteristics of the flame, but also on the chemical properties of the downstream gases. It is further argued that the transfer function of entropy generation for a thin flame may feature an unrealistically high amplitude. This study shows that neglecting the chemical sources of entropy wave can result in wrong predictions of the combustor acoustics and impede suppression of combustion instabilities and noise.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Karimi, Dr Nader |
| Authors: | Fattahi, A., Karimi, N., and Hajialigol, N. |
| College/School: | College of Science and Engineering > School of Engineering |
| Journal Name: | Physics of Fluids |
| Publisher: | AIP Publishing |
| ISSN: | 1070-6631 |
| ISSN (Online): | 1089-7666 |
| Copyright Holders: | Copyright © 2020 AIP Publishing |
| First Published: | First published in Physics of Fluids 32:106107 |
| Publisher Policy: | Reproduced in accordance with the publisher copyright policy |
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