Aeroacoustic Nonlinear turbomachinery noise source identification frequency scattering Aerospace engineering
Gareth J. Bennett, Ian Davis, Ulf Tapken, John Mahon, Nonlinear Frequency Scattering of Broadband Noise in Turbomachinery, 16th AIAA/CEAS Aeroacoustics Conference, Stockholm, Sweden, 7-9 June, 2010
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 bench-test 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 and validated using this rig. The techniques are subsequently applied to data
generated from within an FP7 Collaborative European Aeroacoustics Project: TEENI.
The analysis techniques enabled non-linear interactions to be identified and linear and
non-linear contributions to be determined.
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