Bellucci V., Nowak D., Schuermans B.

In this work, the use of Helmholtz resonators for damping thermoacoustic pulsations in gas turbine combustion chambers is discussed. With respect to classical Helmholtz resonators, in combustion applications a cooling flow is usually maintained through the resonator in order to avoid overheating. Therefore, we present first a nonlinear model for predicting the resonator impedance including the effects of the cooling flow. The nonlinear resonator model is validated by means of atmospheric experiments where resonator geometry and cooling flow velocity are varied. Then, the physical mechanism responsible for the sound attenuation achieved by the use of Helmholtz dampers is discussed and a theory is presented to optimize the resonator design. The theory is validated by means of both impedance tube experiments and thermoacoustic simulations.