Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Patent
1995-08-18
1998-08-04
Kashnikow, Andres
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
244200, B64C 2306
Patent
active
057881910
ABSTRACT:
In one embodiment for a helicopter main rotor assembly, a half-plow vortex generator is mounted in combination with the upper aerodynamic surface of each main rotor blade and is operative to generate a primary corotating vortex of sufficient strength to interact with and accelerate the dissipation of the tip vortex generated by the same main rotor blade, thereby reducing blade-vortex interaction noise radiating from the helicopter main rotor assembly. The half-plow vortex generator has a right triangular planform configuration defined by a length, a width, and an apex angle. The three-dimensional configuration of the vortex generator is further defined by an apex height. The apex height is the primary determinant of the strength of the generated primary corotating vortex and is defined in terms of the thickness of the main rotor blade at the local chord where the vortex generator is mounted. The apex height may be approximately equal to the local thickness, but preferably has a magnitude within the range of about one-eighth to about three-quarters of the local thickness. The length, width, and apex angle are secondary determinants of the strength of the primary corotating vortex generated by the half-plow vortex generator. The length and width of the vortex generator are defined in terms of the tip chord length of the main rotor blade, the length preferably having a magnitude within the range of about one-fourth to one-half of the tip chord length and the width preferably having a value of about one-third of the length of the vortex generator. The apex angle preferably has a value within the range of about twenty to about thirty degrees. The mounting site for the half-plow vortex generator is defined in terms of the length of the local and tip chords, respectively. The vortex generator is mounted inboardly from the tip of the main rotor or blade a spanwise distance having a magnitude preferably within the range of about one-half of to about equal to the tip chord length in substantial alignment with the local chord. The apex of the vortex generator is mounted inwardly from the leading edge of the main rotor blade by a chordal distance having a magnitude of about one-quarter the local chord length.
REFERENCES:
patent: 2800291 (1957-07-01), Stephens
patent: 4354648 (1982-10-01), Schenk et al.
patent: 5058837 (1991-10-01), Wheeler
"Force Mixing in Boundary Layers" by G.B. Schubauer and W.G. Spangenberg National Bureau of Standard Report Aug. 8, 1958.
"The Use of Vortex Generators to Delay Boundary Layer Separation" by D.G. Gould. National Aero Establishment Report LR-183 Dec. 19, 1956.
Egolf T. Alan
Landgrebe Anton J.
Lorber Peter F.
Wake Brian E.
Dinh Tien
Kashnikow Andres
Radke Terrance J.
Sikorsky Aircraft Corporation
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