DGEN Aeropropulsion Research Turbofan (DART) Core/Combustor-Noise Infinite-Tube-Probe (ITP) Transfer Function

Boyle, Devin K

关键词: AEROACOUSTICS;    AIRCRAFT ENGINES;    COMBUSTION CHAMBERS;    DATA ACQUISITION;    MICROPHONES;    NOISE INTENSITY;    NOISE MEASUREMENT;    POSITION (LOCATION);    PRESSURE MEASUREMENT;    REMOTE SENSING;    SPECTRUM ANALYSIS;    TEMPERATURE GRADIENTS;    THERMAL ENVIRONMENTS;    TRANSDUCERS;    TRANSFER FUNCTIONS;    TURBOFAN ENGINES;   

RP-ID  :  GRC-E-DAA-TN62138

学科分类：航空航天科学

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来源: NASA Technical Reports Server

【 摘 要 】

Direct measurements of turbofan engine core unsteady pressure is complicated by the extreme thermal environment within the engine, preventing currently available transducers from operating. It is necessary to use a remote measurement configuration such as an infinite-tube-probe (ITP) configuration in which the transducer is teed into a line pneumatically coupled with the location of interest and the other end of the ITP contains an "infinite" waveguide designed to prevent any reflections. This configuration has become a standard method for experiments concerning core noise. In order to relate the spectral pressure measurements obtained remotely with the ITP, a transfer (frequency response) function needs to be calculated based on a known pressure field. This is accomplished using a normal impedance tube at Glenn Research Center, where a flush-mounted microphone is used as a reference to the ITP signal in the calculation of the ITP's transfer function.