NDLI: Spectral separation of the turbofan engine coherent combustion noise component

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Spectral separation of the turbofan engine coherent combustion noise component

Content Provider	NASA Technical Reports Server (NTRS)
Author	Miles, Jeffrey Hilton
Copyright Year	2008
Description	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.
File Size	2608289
Page Count	54
File Format	PDF
Alternate Webpage(s)	http://archive.org/details/NASA_NTRS_Archive_20080023303
Archival Resource Key	ark:/13960/t3wt3np98
Language	English
Publisher Date	2008-05-01
Access Restriction	Open
Subject Keyword	Acoustics Pressure Sensors Position Location Acoustic Measurement Engine Noise Turbofan Engines Frequencies Relativistic Effects Time Lag Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science
Content Type	Text
Resource Type	Technical Report

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