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Optimum performance of hovering rotorsA theory for the optimum performance of a rotor hovering out of ground effect is developed. The performance problem is formulated using general momentum theory for an infinitely bladed rotor, and the effect of a finite number of blades is estimated. The analysis takes advantage of the fact that a simple relation exists between the radial distributions of static pressure and angular velocity in the ultimate wake, far downstream of the rotor, since the radial velocity vanishes there. This relation permits the establishment of an optimum performance criterion in terms of the ultimate wake velocities by introducing a small local perturbation of the rotational velocity and requiring the resulting ratio of thrust and power changes to be independent of the radial location of the perturbation. This analysis fully accounts for the changes in static pressure distribution and axial velocity distribution throughout the wake as the result of the local perturbation of the rotational velocity component.
Document ID
19720014369
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Wu, J. C. (Georgia Inst. of Tech. Atlanta, United States)
Goorjian, P. M. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 2, 2013
Publication Date
March 1, 1972
Subject Category
Aircraft
Report/Patent Number
NASA-TM-X-62138
Accession Number
72N22019
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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