Bennett G. J., Mahon J., Fitzpatrick J. A., Non-linear Identification Applied to Broadband Turbomachinery Noise, 12th CEAS-ASC Workshop on Turbomachinery Broadband Noise, Bilbao, Spain, 23-24 October, 2008, Emilio Campos and Ana Villate, 2008, 12 - 15
Coherence based source analysis techniques can be used to identify the contribution of
broadband noise sources in the exhaust of a gas turbine and hence enable the design of noise
reduction devices. However, when the broadband noise source propagates in a non-linear
fashion the identified contribution using ordinary coherence methods will be inaccurate.
In this paper, an analysis technique to enable the contribution of linear and non-linear
mechanisms to the propagated sound to be identified is reported. An experimental rig
to study the propagation of noise through a rotor/stator set-up using a vane-axial fan
mounted in a duct so that non-linear interactions between a sound source and the fan
could be investigated is described. The technique which is used to identify non-linear noise
contributions generated by the interaction of the rotor and propagated narrowband noise
is reported. The analysis techniques enabled non-linear interactions to be identified and
linear and contributions to be determined.
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