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Development and Demonstration of Active Noise Control ConceptsThis report details design methods for and feasibility of an Active Noise Control (ANC) system using flush-wall-mounted sensors and actuators to reduce turbofan engine rotor-stator interaction noise. ANC concepts capable of suppressing discrete-tone spinning modes containing several cut-on radial mode were identified, developed analytically, and evaluated. Separate ANC systems that suppressed at least three radial modes in a cylindrical inlet duct and three radial modes in an exhaust annulus were developed. These designs resulted in inlet duct and exhaust duct tests that were performed at NASA on the 4-ft ANC Fan in the NASA Glenn AAPL facility. Effective suppression of 2-BPF spinning mode m = 2 tone noise was achieved over a range of fan speeds 1800 to 2450 rpm, where up to 4 radials were present. In the inlet duct, up to 12 dB reduction was obtained for 3 radial modes, and up to 4 dB was obtained with 4 radial modes. In the exhaust duct, up to 15 dB PWL reduction was obtained with either two or three radial modes present. Thus, the ability to suppress multiple radial modes for tones in both the inlet and exhaust ducts has been successfully demonstrated. Implications of ANC system design requirements on installation and system integration issues for ANC systems capable of suppressing higher order radial mode content when applied to a 767 using twin CF6 engines were evaluated analytically. The analytical results indicated an ANC system must be part of an integrated design to be effective.
Document ID
20000112947
Acquisition Source
Glenn Research Center
Document Type
Contractor Report (CR)
Authors
Kraft, R. (General Electric Co. Cincinnati, OH United States)
Hu, Z. (General Electric Co. Schenectady, NY United States)
Sommerfeldt, S. (Brigham Young Univ. Provo, UT United States)
Walker, B. (Hersh Acoustical Engineering, Inc. Westlake Village, CA United States)
Hersh, A. (Hersh Acoustical Engineering, Inc. Westlake Village, CA United States)
Luo, H. (General Electric Co. Schenectady, NY United States)
Spencer, M. (Signal Processing Solutions Redondo Beach, CA United States)
Hallman, D. (General Electric Co. Schenectady, NY United States)
Mitchell, C. (Colorado State Univ. Fort Collins, CO United States)
Sutliff, D. (AYT Corp. Brook Park, OH United States)
Date Acquired
September 7, 2013
Publication Date
September 1, 2000
Subject Category
Acoustics
Report/Patent Number
NAS 1.26:210037
NASA/CR-2000-210037
E-12235
Funding Number(s)
CONTRACT_GRANT: NAS3-27720
PROJECT: RTOP 522-81-11
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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