Investigation of Acoustical Mode in Instable Combustor

Premixed combustion is widely used for simulation of combustion chambers of gas turbines، utilized for low NOx emission applications. However، this category of gas turbines is susceptible to combustion instability. Combustion instability has already been studied for industrial burners، ram jets، and pulse jets. But، in regard to modern gas turbines، there are limited works، which are performed recently. Therefore، the maim aim of this investigation is focused on Thermo-acoustic instability modes in gas turbine combustion chambers. Both analytical and experimental methods are applied for this study. For this purpose، an experimental combustion chamber is design and fabricated and various experiments are planned and performed in order to achieve the behavior of combustion chamber during stable and unstable conditions. Moreover، analytical method is applied، and a computer code is written and elaborated for this purpose. Instability frequencies are derived experimentally and analytically and the results are compared with each other. Accordingly، good agreements are observed between the results. In addition histograms، spectral diagrams and wave forms of thermo-acoustic code instability is achieved experimentally.