Gareth J. Bennett, Ciarán O'Reilly, Ulf Tapken, John Fitzpatrick, Noise Source Location in Turbomachinery Using Coherence Based Modal Decomposition, 15th AIAA /CEAS Aeroacoustics Conference, Miami, Florida, 11-13 May 2009, 2009
Coherence based source analysis techniques can be used to identify the contribution of
turbomachinery core noise sources to pressure measurements in the far-field. The usual
approach is to locate a measurement sensor within the engine and to calculate the ordinary
coherence function between this and the far-field pressure measurement. If the internal
measurement is close to a dominant noise source, the technique will identify this sources’
contribution to the overall far-field energy. Modal decomposition is an advanced technique
which can provide detailed information as to the modal content of sound propagating in
ducts. When applied to aero-engines, the technique can be used as a diagnostic to determine
which of the many rotor-stator stages contribute most to the overall radiated sound power.
The method developed in this paper discusses how the two techniques can be combined to
locate the plane at which a mode is generated within an aeroengine. A proof of concept of
the technique is successfully demonstrated with the use of simulated data.
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