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AssigneeMcDonnell Douglas Helicopter Company
InventorsAhmed A. Hassan, Friedrich K. Straub, David B. Domzalski, Dennis K. Kennedy
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A pressurized porous surface near the leading edge of a rotorcraft blade, is designed to be used as an active control device which alleviates the aerodynamics of blade vortex interactions (BVI) and thus the impulsive BVI noise levels and signature. The pressurized porous surface can be actuated on an azimuth-dependent deployment schedule or actuated continuously. The pressurized porous surface is supplied with either positively pressurized air, negatively pressurized air, or a combination of both, when actuated. The pressurized porous surface targets the local blade aerodynamics, rather than the vortex strength or blade/vortex separation distance. This targeting can be achieved through use of negatively pressurized air (suction) blowing in a direction normal to the blade surface to reduce the rotor blade's effective thickness resulting in a smaller leading edge radius as perceived by the vortex wake, and positively pressurized air (blowing) to increase the effective thickness resulting in an increase in the leading edge radius of the blade.
An active control device for reducing blade-vortex-interaction (BVI) noise generated by a rotorcraft having a rotor blade including an interior, a tip end, a root end, a leading edge, a trailing edge, an upper surface, a lower surface, a radius, and a chord, the rotor blade being attached at the root end to a rotor hub on the rotorcraft and extending radially outwardly therefrom such that when the rotor hub is rotatably driven the rotor blade rotates about the hub through a 360 degree azimuth, the active control device comprising:
An active control device, comprising:
A method of reducing blade-vortex-interaction (BVI) noise generated by a rotor blade having an upper surface and a lower surface, the rotor blade further having a leading edge vicinity, an interior volume, and a porous vent area disposed on both the upper surface and the lower surface near the leading edge vicinity, the porous vent area fluidly connecting the interior volume to an ambient atmosphere, the method comprising the following steps:
Dependencies are inferred from the claim text.