The core noise components of a dual spool turbofan engine (Honeywell TECH977) were separated by the use of a coherence function. A source location technique based on adjusting the time delay between the combustor pressure sensor signal and the far-field microphone signal to maximize the coherence and remove as much variation of the phase angle with frequency as possible was used. While adjusting the time delay to maximize the coherence and minimize the cross spectrum phase angle variation with frequency, the discovery was made that for the 130 microphone a 90.027 ms time shift worked best for the frequency band from 0 to 200 Hz while a 86.975 ms time shift worked best for the frequency band from 200 to 400 Hz. Since the 0 to 200 Hz band signal took more time to travel the same distance, it is slower than the 200 to 400 Hz band signal. This suggests the 0 to 200 Hz coherent cross spectral density band is partly due to indirect combustion noise attributed to hot spots interacting with the turbine. The signal in the 200 to 400 Hz frequency band is attributed mostly to direct combustion noise.


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    Title :

    Spectral Separation of the Turbofan Engine Coherent Combustion Noise Component


    Contributors:

    Conference:

    46th AIAA Aerospace Sciences Meeting and Exhibit ; 2008 ; Reno, NV, United States


    Publication date :

    2008-05-01


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English


    Keywords :


    Spectral Separation of the Turbofan Engine Coherent Combustion Noise Component

    Miles, J. / American Institute of Aeronautics and Astronautics | British Library Conference Proceedings | 2008





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