Abstract
The performance of absorbers dissipating acoustic energy in rocket combustion chambers is investigated experimentally in cold ow tests. Applying procedures already used in a former investigation on the damping of eigenmodes in a combustor equipped with one absorber, the investigation is extended to absorber rings composed of multiple absorbers. It is shown by experiments and numerical modal analysis that due to the coupling of the additional resonance volumes of the absorbers and the cylindrical combustor the eigenfrequencies of the system are shifted to lower values. For typical lengths of absorbers tuned to the 1T-mode peaks are found in the resonance spectrum that do not correspond to the frequencies of cylinder modes. A general systematics of an absorber ring with N absorbers tuned to the 1T-resonance is presented. Measurements of the damping rate of the modes as a function of the absorber length have been done and are compared with admittance data derived from numerical modal analysis.
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