FLAME TRANSFER FUNCTION IDENTIFICATION AND THERMOACOUSTIC ANALYSIS OF AN ANNULAR HEAVY-DUTY GAS TURBINE COMBUSTOR

In the present work a linear stability analysis of a lean premixed annular combustor equipped on a heavy duty gas turbine is carried out. The Flame Transfer Function (FTF) of the (technically)-premixed flame is studied using URANS simulations. Mass flow perturbations are introduced in the system imposing a broadband excitation as inlet boundary condition. Starting from commonly used input signals, a broadband excitation was designed and chosen to perform the simulation. The selected signal allowed the direct control of the frequency range of the excitation and signal intensity without deteriorating its quality. The heat release rate response of the flame is then correlated to the acoustic perturbation exploiting the system identification (SI) technique. The obtained results are implemented into a finite element model (FEM) of the combustor to analyse its stability. A satisfactory agreement has been obtained comparing the results against the available experimental data.