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Analysis and modelling of entropy modes in a realistic aeronautical gas turbine

Motheau, Emmanuel and Mery, Yoann and Nicoud, Franck and Poinsot, Thierry Analysis and modelling of entropy modes in a realistic aeronautical gas turbine. (2013) Journal Of Engineering For Gas Turbines And Power, 135 (9). 1-13. ISSN 0742-4795

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Official URL: http://dx.doi.org/10.1115/1.4024953

Abstract

A combustion instability in a combustor typical of aero-engines is analyzed and modeled thanks to a low order Helmholtz solver. A Dynamic Mode Decomposition (DMD) is first applied to the Large Eddy Simulation (LES) database. The mode with the highest amplitude shares the same frequency of oscillation as the experiment (approx. 350 Hz) and it shows the presence of large entropy spots generated within the combustion chamber and convected down to the exit nozzle. The lowest purely acoustic mode being in the range 650-700 Hz, it is postulated that the instability observed around 350 Hz stems from a mixed entropy/acoustic mode where the acoustic generation associated with the entropy spots being convected throughout the choked nozzle plays a key role. A Delayed Entropy Coupled Boundary Condition is then derived in order to account for this interaction in the framework of a Helmholtz solver where the baseline flow is assumed at rest. When fed with appropriate transfer functions to model the entropy generation and convection from the flame to the exit, the Helmholtz solver proves able to predict the presence of an unstable mode around 350 Hz, in agreement with both the LES and the experiments. This finding supports the idea that the instability observed in the combustor is indeed driven by the entropy/acoustic coupling.

Item Type:Article
Additional Information:Thanks to ASME editor. The original PDF can be found at Journal Of Engineering For Gas Turbines And Power website: http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=1731900
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National d'Études Spatiales - CNES (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > EDF (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
French research institutions > Office National d'Etudes et Recherches Aérospatiales - ONERA (FRANCE)
Other partners > Total (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Other partners > Université de Montpellier 2 (FRANCE)
Other partners > European Aeronautic Defence and Space company - EADS (FRANCE)
Other partners > Météo France (FRANCE)
Other partners > SAFRAN (FRANCE)
Laboratory name:
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Deposited By: Thierry POINSOT
Deposited On:10 Oct 2013 06:08

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