Helmholtz resonators are commonly used to damp thermoacoustic oscillations in aeroengine and gas turbine combustors. In practice, the Helmholtz resonator is often maintained at a cooler temperature than the combustor, but this tends to be neglected when modeling. In this work, we derive an analytical model for both the acoustic damping and the effect on the combustor thermoacoustics of Helmholtz resonators for which the volume is at a different temperature to the combustor. The energy conservation equation based on stagnation enthalpy, together with the mass and momentum conservation equations, is incorporated into a linear Helmholtz resonator sound-absorption model. These are coupled with linear wave-based models for the plane acoustic waves in the system to which the Helmholtz resonator is attached: here, a combustor. The temperature difference is found to generate an entropy wave that advects downstream of the resonator (and may generate further acoustic waves if accelerated) and to change the acoustic damping near the resonant frequency. This model for the Helmholtz resonator acoustics is then incorporated into a low-order network model for combustor thermoacoustics. The importance of capturing the effect of the Helmholtz resonator temperature difference on the overall thermoacoustic modes is clearly demonstrated.
Acoustic Models for Cooled Helmholtz Resonators
AIAA Journal ; 55 , 9 ; 3120-3127
2017-09-01
Article (Journal)
Electronic Resource
English
Acoustic Behavior of Helmholtz Resonators: Part I. Nonlinear Model
British Library Conference Proceedings | 1995
|Acoustic Behavior of Helmholtz Resonators: Part II. Grazing Flow Model
British Library Conference Proceedings | 1995
|Nonlinear behavior of Helmholtz resonators
AIAA | 1990
|