TWO-WAY FLUID-STRUCTURE INTERACTION IN A GAS TURBINE COMBUSTOR IN LIMIT CYCLE OSCILLATION

In this paper the mechanical interaction between pressure oscillations induced by combustion dynamics in a laboratory scale combustor and the structural vibrations of the combustor wall (the liner) is investigated.. The combustor has operation conditions where the feedback loop between unsteady heat release and the acoustic field in the combustion chamber is unstable. This drives the amplitudes of the acoustic pressure oscillations to very high magnitudes. Under these circumstances, there is increased risk of failure due to fatigue. To investigate the two way feedback loop between the acoustic field and the structural vibrations of the liner in a gas turbine combustor, a laboratory-size combustor has been developed. The combustor has a rectangular cross section and operates under lean, partially-premixed conditions. The flame is stabilized using a triangular bluff body. To achieve a strong liner vibration feedback, the stiffness of the liner walls is made very low. In the framework of the COPAGT project, transient numerical simulations of the coupled fluid-structure interaction (FSI) system in the combustor are carried out and the results are validated by measurements. A partitioned approach is utilized, where the fluid and structural domain are calculated by different solvers. Coupling is achieved by a two-way data exchange between the fluid and structural domain. Investigated is an operating point in limit cycle oscillation with high amplitude. The numerical results show some agreement with the experimental data, but also show some aspects for improvement. The applied procedure is suitable to reproduce the coupling of the pressure with the structure, but the structural model performance needs to be improved. Neither for the measurements nor for the simulation any influence of the structural vibration is visible in the pressure spectrum, which can be seen as the major characteristic for a closed feedback loop between structural vibration and acoustic field.