Coherence-based source analysis techniques can be used to identify the contribution of combustion noise in the exhaust of a jet engine and to hence enable the design of noise-reduction devices. However, when the combustion noise propagates in a nonlinear fashion, the identified contribution using ordinary coherence methods will be inaccurate. In this paper, an analysis technique is reported that enables the contribution of linear and nonlinear mechanisms to the propagated sound to be identified. An experimental rig is described for studying the propagation of noise through a rotor/stator setup using a vane axial fan mounted in a duct so that nonlinear interactions between a sound source and the fan can be investigated. The reported technique is used to identify a nonlinear tone generated by the interaction of the rotor and a propagated tone. The identification procedures are then applied to data from fullscale turbofan engine tests instrumented with pressure transducers at the combustor can and in the hot-jet pipe with microphones in the near field. At a particular power setting, the interaction between the combustion noise and the high-pressure turbine is measured in the hot-jet pipe. The analysis techniques enable nonlinear interactions to be identified and enable linear and nonlinear coherent output powers to be determined.


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    Title :

    Noise-source identification for ducted fan systems


    Additional title:

    Lärmequellen-Identifizierung bei Bypass-Triebwerken


    Contributors:

    Published in:

    AIAA Journal ; 46 , 7 ; 1663-1674


    Publication date :

    2008


    Size :

    12 Seiten, 23 Bilder, 3 Tabellen, 20 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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