Combustion Instability Analysis of a Model Gas Turbine by Application of Dynamic Mode Decomposition

Dynamic mode decomposition (DMD) technique is applied to analyze combustion instabilities in a model gas turbine combustor. The flame transfer function (FTF) obtained by the DMD method agrees with the experimental results qualitatively. However, FTF results show that the perturbation frequency with the largest gain is 100Hz, which contradicts the 1000Hz with the largest amplitude in the fast Fourier transform (FFT) results. In order to figure out this, gains and damping coefficients of all resonance frequencies are calculated by DMD technique. Results show the possibility that the model combustor has high-frequency instabilities as a results of coupling between flame and chamber responses. Another finding is that to obtain a pure FTF, the combustor must be removed to exclude coupling of chamber response with flame response.