A combined oscillation cycle involving self-excited thermo-acoustic and hydrodynamic instability mechanisms
File(s)POF21-AR-02310.pdf (9.29 MB)
Accepted version
Author(s)
Fredrich, D
Jones, W
Marquis, A
Type
Journal Article
Abstract
The paper examines the combined effects of several interacting thermo-acoustic and hydrodynamic instability mechanisms that are known to influence self-excited combustion instabilities often encountered in the late design stages of modern low-emission gas turbine combustors. A compressible large eddy simulation approach is presented, comprising the flame burning regime independent, modeled probability density function evolution equation/stochastic fields solution method. The approach is subsequently applied to the PRECCINSTA (PREDiction and Control of Combustion INSTAbilities) model combustor and successfully captures a fully self-excited limit-cycle oscillation without external forcing. The predicted frequency and amplitude of the dominant thermo-acoustic mode and its first harmonic are shown to be in excellent agreement with available experimental data. Analysis of the phase-resolved and phase- averaged fields leads to a detailed description of the superimposed mass flow rate and equivalence ratio fluctuations underlying the governing feedback loop. The prevailing thermo-acoustic cycle features regular flame liftoff and flashback events in combination with a flame angle oscillation, as well as multiple hydrodynamic phenomena, i.e., toroidal vortex shedding and a precessing vortex core. The periodic excitation and suppression of these hydrodynamic phenomena is confirmed via spectral proper orthogonal decomposition and found to be controlled by an oscillation of the instantaneous swirl number. Their local impact on the heat release rate, which is predominantly modulated by flame-vortex roll- up and enhanced mixing of fuel and oxidizer, is further described and investigated. Finally, the temporal relationship between the flame “surface area,” flame-averaged mixture fraction, and global heat release rate is shown to be directly correlated.
Date Issued
2021-08-17
Date Acceptance
2021-08-01
ISSN
1070-6631
Publisher
American Institute of Physics
Start Page
1
End Page
22
Journal / Book Title
Physics of Fluids
Volume
33
Issue
8
Copyright Statement
© 2021 The Author(s)
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (E
Siemens Industrial Turbomachinery Ltd
Siemens Industrial Turbomachinery Ltd
Identifier
https://aip.scitation.org/doi/10.1063/5.0057521
Grant Number
EP/K026801/1
BH172740 (EP/R029369/1)
9000001563
See further info
Subjects
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
Fluids & Plasmas
Publication Status
Published
Date Publish Online
2021-08-17