Transparent Combustion Chamber Research Articles

Acoustic resonance in a solid fuel combustion chamber

The resonance frequencies of a solid fuel comb are predicted by a model, including part of the piping system and diffuser. Visual observations of the flow in the transparent combustion chamber by a high-speed movie camera reveal that a large vortex structure periodically moves down the flow. The large-amplitude velocity oscillations eventually lead to extinction of the combustion process. The driving terms in the acoustic equations are of fluid-dynamic and thermodynamic origin. This analysis is concentrated on the investigation of the role of the fluid-dynamic terms. Making use of the method devised by Howe, the strength of the source term due to the periodically generated vortex system is computed. The response of the model to this source term leads to the conclusion that its magnitude is too small to play a role of importance. As an acoustic source it yields a response in counterphase with the occurring oscillations, so in this configuration its role is a damping one.