Analysis of the interaction of thermoacoustic modes with a Green’s function approach

In this paper, we will present a fast prediction tool based on a one-dimensional Green's function approach that can be used to bypass numerically expensive computational fluid dynamics simulations. The Green’s function approach has the advantage of providing a clear picture of the physics behin...

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Bibliographic Details
Published in:International journal of spray and combustion dynamics 2018-12, Vol.10 (4), p.326-336
Main Authors: Bigongiari, Alessandra, Heckl, Maria
Format: Article
Language:English
Subjects:
Combustion stability
Computational fluid dynamics
Computer simulation
Evolution
Green's functions
Limit cycle oscillations
Modal analysis
Normality
Perturbation
Transfer functions
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Summary:In this paper, we will present a fast prediction tool based on a one-dimensional Green's function approach that can be used to bypass numerically expensive computational fluid dynamics simulations. The Green’s function approach has the advantage of providing a clear picture of the physics behind the generation and evolution of combustion instabilities. In addition, the method allows us to perform a modal analysis; single acoustic modes can be treated in isolation or in combination with other modes. In this article, we will investigate the role of higher-order modes in determining the stability of the system. We will initially produce the stability maps for the first and second mode separately. Then the time history of the perturbation will be computed, where both the modes are present. The flame will be modelled by a generic Flame Describing Function, i.e. by an amplitude-dependent Flame Transfer Function. The time-history calculations show the evolution of the two modes resulting from an initial perturbation; both transient and limit-cycle oscillations are revealed. Our study represents a first step towards the modelling of nonlinearity and non-normality in combustion processes.
ISSN:1756-8277
1756-8285
DOI:10.1177/1756827718809570