Thermo-acoustic coupling in can-annular combustors: A numerical investigation

Thermo-acoustic instabilities in modern, high power density gas turbines need to be predicted and understood in order to avoid unexpected damage and engine failure. While the annular combustor design is expected to suffer from the occurrence of transverse waves and burner-to-burner acoustic interaction, the can-annular combustor design should be less vulnerable to transverse waves and acoustic burner-to-burner interaction, as the burners are acoustically coupled only by means of the turbine stator stage. Measurements in such machines, however, indicate that the pressure modes in neighboring cans synchronize and oscillate in or out of phase. This fact implies the existence of non-negligible cross-talk between neighboring cans. The objective of this work is to investigate the acoustic interaction between the cans, focusing on the turbine inlet section where the cans connect. The can-can transfer function of a realistic combustor system is computed. To reduce CPU time, simplified 2D equivalent systems are investigated. The simulations are carried out with compressible CFD solvers based on the OpenFOAM framework. Realistic boundary conditions for the flow and the acoustics are applied.