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Weakly nonlinear analysis of thermoacoustic instabilities in annular combustors

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Ghirardo, G 
Juniper, MP 
Moeck, JP 

Abstract

jats:pRotationally symmetric annular combustors are of practical importance because they generically resemble combustion chambers in gas turbines, in which thermoacoustically driven oscillations are a major concern. We focus on azimuthal thermoacoustic oscillations and model the fluctuating heat release rate as being dependent only on the local pressure in the combustion chamber. We study the dynamics of the annular combustor with a finite number of compact flames equispaced around the annulus, and characterize the flames’ response with a describing function. We discuss the existence, amplitude and the stability of standing and spinning waves, as a function of: (i) the number of the burners; (ii) the acoustic damping in the chamber; (iii) the flame response. We present the implications for industrial applications and the future direction of investigations. We then present as an example the first theoretical study of thermoacoustic triggering in annular combustors, which shows that rotationally symmetric annular chambers that are thermoacoustically unstable do not experience only stable spinning solutions, but can also experience stable standing solutions. We finally test the theory on one experiment with good agreement.</jats:p>

Description

Keywords

acoustics, low-dimensional models, nonlinear dynamical systems

Journal Title

Journal of Fluid Mechanics

Conference Name

Journal ISSN

0022-1120
1469-7645

Volume Title

805

Publisher

Cambridge University Press (CUP)
Sponsorship
European Research Council (Project ALORS)