Technical Papers and Presentations

Modern gas turbines suffer of the phenomenon of combustion instability, also known as “humming”. The main origin of the instability is considered to be related to the interaction between acoustic waves and fluctuations of the heat released by the flame. This paper presents a novel numerical method in which the governing equations of the acoustic waves are coupled with a flame heat release model and solved in the frequency domain. The paper shows that a complex eigenvalue problem is obtained that can be solved numerically by implementing the governing equations in COMSOL Multiphysics®. This procedure allows one to identify the frequencies at which thermoacoustic instabilities are expected and the growth rate of the pressure oscillations, at the onset of instability, when the hypothesis of linear behavior of the acoustic waves can be applied.