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research-article

Mixed acoustic-entropy combustion instabilities in a model aeronautical combustor: Large Eddy Simulation and Reduced Order Modeling

[+] Author and Article Information
Florent Lacombe

Safran Aircraft Engines, Rond-Point René Ravaud, 77550 Moissy Cramayel − France
florent.lacombe@safrangroup.com

Yoann Mery

Safran Aircraft Engines, Rond-Point René Ravaud, 77550 Moissy Cramayel − France
yoann.mery@safrangroup.com

1Corresponding author.

ASME doi:10.1115/1.4037960 History: Received July 13, 2017; Revised July 27, 2017

Abstract

This article focuses on Combustion Instabilities (CI) driven by entropy fluctuations which is of great importance in practical devices. A simplified geometry is introduced. It keeps the essential features of an aeronautical combustion chamber (swirler, dilution holes, outlet nozzle) while it is simplified sufficiently to ease the analysis (rectangular vane, one row of holes of the same diameter, no diffuser at the inlet of the chamber, circular nozzle at the outlet). A Large Eddy Simulation (LES) is carried out on this geometry and the limit cycle of a strong CI involving the convection of an entropy spot is obtained. The behavior of the instability is analyzed using phenomenological description and classical signal analysis. One shows that the system can be better described by considering two reacting zones: a rich mainly premixed flame is located downstream of the swirler and an overall lean diffusion flame is stabilized next to the dilution holes. In a second step, Dynamic Mode Decomposition (DMD) is used to visualize, analyze and model the complex phasing between the different processes affecting the reacting zones. Using these data, a 0D modeling of the premixed flame and of the diffusion flame is proposed. These models provides an extended understanding of the combustion process in an aeronautical combustor and could be used or adapted to address mixed acoustic-entropy CI in an acoustic code.

Copyright (c) 2017 by ASME
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