NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Collections About News Help Login
Back to Results
Noise reduction for model counterrotation propeller at cruise by reducing aft-propeller diameterThe forward propeller of a model counterrotation propeller was tested with its original aft propeller and with a reduced diameter aft propeller. Noise reductions with the reduced diameter aft propeller were measured at simulated cruise conditions. Reductions were as large as 7.5 dB for the aft-propeller passing tone and 15 dB in the harmonics at specific angles. The interaction tones, mostly the first, were reduced probably because the reduced-diameter aft-propeller blades no longer interacted with the forward propeller tip vortex. The total noise (sum of primary and interaction noise) at each harmonic was significantly reduced. The chief noise reduction at each harmonic came from reduced aft-propeller-alone noise, with the interaction tones contributing little to the totals at cruise. Total cruise noise reductions were as much as 3 dB at given angles for the blade passing tone and 10 dB for some of the harmonics. These reductions would measurably improve the fuselage interior noise levels and represent a definite cruise noise benefit from using a reduced diameter aft propeller.
Document ID
19870009624
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Dittmar, James H. (NASA Lewis Research Center Cleveland, OH, United States)
Stang, David B. (Sverdrup Technology, Inc. Cleveland, Ohio, United States)
Date Acquired
September 5, 2013
Publication Date
January 1, 1987
Subject Category
Acoustics
Report/Patent Number
E-3378
NAS 1.15:88936
NASA-TM-88936
Accession Number
87N19057
Funding Number(s)
PROJECT: RTOP 535-03-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

There are no records associated with this record.
No Preview Available