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3-D thermoacoustic instability analysis based on Green's function approach

Wang, Xiaoyu; Heckl, Maria

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Authors

Xiaoyu Wang



Abstract

A fundamental analysis is made of the thermoacoustic instability in a hard-walled box. We model the flame as an acoustically compact source with a heat release characteristic described by a directional nt-law. This has the following features: it gives the heat release rate in terms of the acoustic velocity at an earlier time t; it is linear with coupling coefficient n; the "flame surface" is a small flat patch with variable orientation.

We derive an integral equation for the acoustic field by using a Green's function tailored to a 3-D rectangular box with hard-wall boundary conditions. The integral equation is solved by two methods. Firstly, an iteration method, stepping forward in time, is used to give the time history of the acoustic velocity. By analysing this time history, we investigate the interference between two (or more) thermoacoustic modes. In the second method, we apply a Laplace transform to determine the thermoacoustic eigenfrequency and growth rate of thermoacoustic modes. This method is suitable for parameter studies, and we use it to investigate the effect of the flame orientation and flame position on the thermoacoustic instability. We show results for the 2-D case. They reveal that the stability behaviour depends strongly on the flame orientation and on the flame position in the xy-plane. We also show results for the interference between different thermoacoustic modes, especially for cases where there are two acoustic modes with similar frequencies.

Citation

Wang, X., & Heckl, M. (2022). 3-D thermoacoustic instability analysis based on Green's function approach. Journal of Sound and Vibration, 537, 1-28. https://doi.org/10.1016/j.jsv.2022.116816

Journal Article Type Article
Acceptance Date Feb 1, 2022
Online Publication Date Feb 3, 2022
Publication Date Oct 27, 2022
Publicly Available Date May 30, 2023
Journal Journal of Sound and Vibration
Print ISSN 0022-460X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 537
Article Number 116816
Pages 1-28
DOI https://doi.org/10.1016/j.jsv.2022.116816
Keywords Green's function; furnace; mode interference; thermoacoustic instability
Publisher URL https://www.sciencedirect.com/science/article/pii/S0022460X22000669?via%3Dihub

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