Analysis of the interaction of thermoacoustic modes with a Green's function approach. (December 2018)

• Record Type: Journal Article
• Authors: Bigongiari, Alessandra; Heckl, Maria
• Is Part Of: International journal of spray and combustion dynamics. Volume 10:Number 4(2018)
• Page Start: 326
• Page End: 336
• Publication Date: 2018-12
• Subjects: Non-normality -- nonlinearity -- thermoacoustic instability -- Green's function -- heat release model -- flame describing function -- network model -- distributed time-lags -- thermoacoustic feedback; Combustion engineering -- Periodicals; Fluid dynamics -- Periodicals; Combustion -- Periodicals; Spraying -- Periodicals; Combustion; Combustion engineering; Fluid dynamics; Spraying; Periodicals; 541.361
• DOI: 10.1177/1756827718809570
• Languages: English
• ISSNs: 1756-8285

Abstract

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.