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Takeoff/approach noise for a model counterrotation propeller with a forward-swept upstream rotorA scale model of a counterrotating propeller with forward-swept blades in the forward rotor and aft-swept blades in the aft rotor (designated F39/A31) has been tested in the NASA Lewis 9- by 15-Foot Anechoic Wind Tunnel. This paper presents aeroacoustic results at a takeoff/approach condition of Mach 0.20. Laser Doppler velocimeter results taken in a plane between the two rotors are also included to quantify the interaction flow field. The intention of the forward-swept design is to reduce the magnitude of the forward rotor tip vortex and/or wakes which impinge on the aft rotor, thus lowering the interaction tone levels. A reference model propeller (designated F31/A31), having aft-swept blades in both rotors, was also tested. Aeroelastic performance of the F39/A31 propeller was disappointing. The forward rotor tip region tended to untwist toward higher effective blade angles under load. The forward rotor also exhibited steady state blade flutter at speeds and loadings well below the design condition. The noise results, based on sideline acoustic data, show that the interaction tone levels were up to 8 dB higher with the forward-swept design compared to those for the reference propeller at similar operating conditions, with these tone level differences extending down to lower propeller speeds where flutter did not occur. These acoustic results are for a poorly-performing forward-swept propeller. It is quite possible that a properly-designed forward-swept propeller would exhibit substantial interaction tone level reductions.
Document ID
19930007526
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Woodward, Richard P.
(NASA Lewis Research Center Cleveland, OH, United States)
Hall, David G.
(Sverdrup Technology, Inc. Brook Park, OH., United States)
Podboy, Gary G.
(NASA Lewis Research Center Cleveland, OH, United States)
Jeracki, Robert J.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1993
Subject Category
Aircraft Propulsion And Power
Report/Patent Number
E-7479
NAS 1.15:105979
AIAA PAPER 93-0596
NASA-TM-105979
Meeting Information
Meeting: AIAA Aerospace Sciences Meeting and Exhibit
Location: Reno, NV
Country: United States
Start Date: January 11, 1993
End Date: January 14, 1993
Sponsors: AIAA
Accession Number
93N16715
Funding Number(s)
PROJECT: RTOP 535-03-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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