FOIL STRUCTURES WITH REDUCED SOUND GENERATION

• US 3,853,428 A
• Filed: 09/21/1973
• Issued: 12/10/1974
• Est. Priority Date: 01/27/1972
• Status: Expired due to Term

• Current Assignee: Richard Earle Hayden, Robert Charles Chanaud
• Original Assignee: Richard Earle Hayden, Robert Charles Chanaud
• Inventors: Hayden, Richard Earle, Chanaud, Robert Charles
• Primary Examiner(s): Powell, Jr., Everette A.
• Application Number:
  US05/399,453
• Time in Patent Office: 445 Days
• Field of Search: 416/231,224,228 415/119
• US Class Current: 416/231.00R
• CPC Class Codes: B64C 21/10 using other surface properties, e.g. roughness
• CPC Class Codes: B64C 2230/20 by passively inducing fluid flow, e.g. by means of a pressure difference between both ends of a slot or duct
• CPC Class Codes: B64C 2230/22 by using a surface having multiple apertures of relatively small openings other than slots
• CPC Class Codes: B64C 2230/28 at propeller or rotor blades
• CPC Class Codes: F01D 5/14 Form or construction selecting particular materials, measures against erosion or corrosion F01D5/28
• CPC Class Codes: F01D 5/282 Selecting composite materials, e.g. blades with reinforcing filaments
• CPC Class Codes: F04D 29/388 characterised by construction
• CPC Class Codes: F04D 29/668 damping or preventing mechanical vibrations
• CPC Class Codes: G10K 11/161 in systems with fluid flow G10K11/162 takes precedence; gas flow silencers or exhaust apparatus for machines or engines in general or for internal combustion engine F01N, noise absorbers in pipes or pipe systems F16L55/02; noise absorption in air conditioning and ventilation F24F13/24; silencing exhaust or propulsion jets in aircraft B64D33/06
• CPC Class Codes: Y02T 50/10 Drag reduction
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

This disclosure deals with preventing or at least reducing sound generation that normally results from fluid flow in various rotor and stator systems about the foil or blade surfaces from the developed fluid forces, by rendering at least portions of the blade of reduced flow impedance, as by rendering the same porous in various degrees.

Claims

1. For use as rotors, stators, flaps and the like in a fluidflow medium, a foil structure having means for reducing the flow impedance of at least one of leading and trailing edge portions of the foil surfaces to a value substantially closer to the characteristic impedance of the medium and at which the flow impedance and the characteristic impedance are substantially matched.

2. A foil structure as claimed in claim 1 and in which said means comprises pores provided in at least one of said surfaces.

3. A foil structure as claimed in claim 2 and in which different portions of said foil have different porosity.

4. A foil structure as claimed in claim 2 and in which a portion of the foil is solid.

5. A foil structure as claimed in claim 4 and in which the solid portion is an intermediate portion of the foil.

6. A foil structure as claimed in claim 1 and in which the ratio of the reduced flow impedance to the characteristic impedance of the medium is within the range of substantially 1 to substantially 10.

7. A foil structure as claimed in claim 1 and in which said means comprises a comb-like structure protruding from the trailing edge of the foil.