The use of Helmholtz resonators in a practical combustor

The drive to reduce emissions has led to the development of lean premixed combustors. However lean premixed combustion is often associated with combustion oscillations which can be so severe that they can cause structural damage to the engine. Since the associated frequencies are typically of the order of hundreds of Hertz, there is a need for a compact device to absorb the noise which drives the oscillation. Helmholtz resonators are commonly used as absorbers of incident acoustic power. In addition they are relatively compact. However, their use in combustors creates practical issues, such as placement within the chamber, neck length and cooling, which need to be addressed. In this paper we consider these practical problems and describe how to overcome them in a real combustor.