Analysis of High-Frequency Thermoacoustic Instabilities in Lean, Premixed Gas Turbine Combustors
Modern gas turbine systems for power generation are prone develop so-called thermosacoustic instabilities in the combustion chamber. Physically, these instabilities emerge as large amplitude pressure oscillations within the combustor, which are caused by constructive feedback interactions between the flame and the combustor's natural acoustic modes. The oscillations disturb the combustion process, which may lead to prohibitively high emission levels. Hence, their avoidance/suppression represents one significant engineering challenge for design of new and retrofitting of existing systems. In this study, a full thermoacoustic characterization of high-frequency oscillations in a lab-scale gas turbine combustor was conducted using COMSOL Multiphysics® software as the analysis tool. Specifically, linear stability calculations along with dynamical system simulations were carried out. An accurate agreement between experimental and computed results was found. The analysis results can be further used to expand the physical system understanding to ultimately ensure thermoacoustically stable gas turbine operation within the high-frequency oscillation regime.