Fan having blades with sound reducing material attached

Details Fan having blades with sound reducing material attached Fan having blades with sound reducing material attached

1995-08-31

1997-02-11

Lopez, F. Daniel

Fluid reaction surfaces (i.e., impellers)

Specific blade structure

Coating, specific composition or characteristic

416241R, 415119, F04D 2938

Patent

active

056014104

ABSTRACT:
An air moving device such as an axial cooling fan comprises a rotatable shaft assembly and a plurality of fan blades coupled to the rotatable shaft assembly, each of the fan blades having a trailing edge when the rotatable shaft assembly is rotated in a given direction. In accordance with one illustrative embodiment of the invention, at least one of the fan blades has a sound reducing material attached thereto alongside the trailing edge thereof. The sound reducing material reduces aeroacoustic noise by reducing the aerodynamic effect that occurs when turbulence produced by the pressure differential between the two sides of one blade comes into contact either with the trailing edge of the given blade which created it, or, more significantly, with the following blade, at or near that blade's trailing edge. In various embodiments the sound reducing material may comprise felt, loops from a hook-and-loop-type fastener such as that sold under the VELCRO trademark, or a small piece of fiberglass, cotton or wool batting. In one illustrative embodiment, the sound reducing material is advantageously attached to the fan blade on the high pressure side thereof.

REFERENCES:
patent: 3275082 (1966-09-01), Stark
W. K. Blake, "Mechanics of Flow-Induced Sound And Vibration," Complex Flow-Structure Interactions Academic Press, Inc., vol. II, 1986, pp. 782-806.
T. F. Brooks et al., "Trailing Edge Noise Prediction From Measure Surface Pressures," Journal of Sound and Vibration, 1981, 78(1), pp. 69-117.
D-I.F. Kameler et al, "Experimental Investigation Of Tip Clearance Noise In axial Flow Machines," Proc. DGLR/ACAA-Aeroacoustics Conf., pp. 92-02-40, 250-259.
J. E. Ffowcs Williams et al, "Aerodynamic Sound Generation By Turbulent Flow In The Vicinity Of A Scattering half Plane," J. Fluid Mech., 1970, vol. 10, part 4, pp. 657-670.
R. K. Amiet, "Noise Due To Turbulent Flow Past A Trailing Edge," Journal of Sound and Vibration, 1976, 47(3), pp. 387-393.
R. E. Longhouse, "Control Of Tip-Vortex Noise Of Axial Flow Fans By Rotating Shrouds," Journal of Sound and Vibration, 1978, 58(2), pp. 201-214.

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