To get a better understanding of the formation of thermoacoustic oscillations in an annular gas turbine combustor, an analysis of the acoustic eigenmodes has been conducted using the finite element method. The influence of different boundary conditions and a space-dependent velocity of sound has been investigated. The boundary conditions actually define the eigenfrequency spectrum. Hence, it is crucial to know, e.g., the burner impedance. In case of the combustion system without significant mixing air addition considered in this paper, the space-dependence of the velocity of sound is of minor importance for the eigenfrequency spectrum leading to a maximum deviation of only five percent in the eigenvalues. It is demonstrated that the efficiency of the numerical eigenvalue analysis can be improved by making use of symmetry, by splitting the problem into several steps with alternate boundary conditions, and by choosing the shift frequency in the range of frequencies one is interested in.
Detailed Analysis of the Acoustic Mode Shapes of an Annular Combustion Chamber
Contributed by the International Gas Turbine Institute (IGTI) of THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS for publication in the ASME JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Paper presented at the International Gas Turbine and Aeroengine Congress and Exhibition, Indianapolis, IN, June 7–10, 1999; ASME Paper 99-GT-113. Manuscript received by IGTI, October 1998; final revision received by the ASME Headquarters, March 1999. Associate Editor: D. Wisler.
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Walz , G., Krebs , W., Hoffmann , S., and Judith, H. (March 1, 1999). "Detailed Analysis of the Acoustic Mode Shapes of an Annular Combustion Chamber ." ASME. J. Eng. Gas Turbines Power. January 2002; 124(1): 3–9. https://doi.org/10.1115/1.1396346
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