Airfoil trailing edge apparatus for noise reduction

Abstract

A ridge ( 28 ) mounted or defined along a trailing edge ( 22 ) of an airfoil ( 20 ) for noise reduction. Sides ( 32, 34 ) of the ridge converge from respective suction and pressure sides ( 46, 48 ) of the trailing edge to a peak ( 30 ) of the ridge pointing aft. The sides of the ridge may be concave. The ridge may be hollow ( 42 ) or have a core ( 43 ) of a sound-absorbing material. The sides of the ridge may be perforated ( 44 A, 44 B) for pressure equalization across the ridge. The ridge may be covered with bristles ( 56 ) or be defined by the tips ( 58 ) of bristles ( 56 A, 56 B) of varying length. The peak of the ridge and/or at least one corner ( 64, 66 ) of the ridge and/or of the trailing edge ( 46, 48 ) may be serrated.

The invention claimed is: 
     
         1 . An airfoil trailing edge apparatus for noise reduction, comprising:
 a ridge along a trailing edge of an airfoil;   wherein the ridge comprises first and second sides converging from a respective suction side and pressure side of the trailing edge to an aft-pointing peak of the ridge.   
     
     
         2 . The airfoil trailing edge apparatus of  claim 1  wherein the first side of the ridge spans between the peak and a suction side corner of the trailing edge, and the second side of the ridge spans between the peak and a pressure side corner of the trailing edge. 
     
     
         3 . The airfoil trailing edge apparatus of  claim 1  wherein the sides of the ridge are concave. 
     
     
         4 . The airfoil trailing edge apparatus of  claim 3  wherein the peak of the ridge is serrated. 
     
     
         5 . The airfoil trailing edge apparatus of  claim 1  wherein the ridge is hollow. 
     
     
         6 . The airfoil trailing edge apparatus of  claim 5  wherein at least one side of the ridge is perforated. 
     
     
         7 . The airfoil trailing edge apparatus of  claim 1  wherein the ridge is perforated with a plurality of holes of at least two different diameters. 
     
     
         8 . The airfoil trailing edge apparatus of  claim 1  wherein the ridge comprises a core of a sound absorbing material. 
     
     
         9 . The airfoil trailing edge apparatus of  claim 1  wherein the ridge comprises a core of a breathable sound absorbing material, and both sides of the ridge are perforated with holes that provide pressure equalization between the two sides of the ridge through the breathable core. 
     
     
         10 . The airfoil trailing edge apparatus of  claim 1  wherein at least one of the sides of the ridge comprises a spoiler in the form of a secondary ridge. 
     
     
         11 . The airfoil trailing edge apparatus of  claim 10  wherein spoilers on the first and second sides of the ridge each comprise an outer surface aligned with a nearer one of a pressure side or suction side of the airfoil or aligned with a mean camber line or a chord line of the airfoil. 
     
     
         12 . The airfoil trailing edge apparatus of  claim 1 , further comprising a plurality of bristles attached to at least one side of the ridge. 
     
     
         13 . The airfoil trailing edge apparatus of  claim 1 , further comprising first and second pluralities of bristles of varying length that provide bristle tips arranged to define respectively the first and second sides of the ridge. 
     
     
         14 . The airfoil trailing edge apparatus of  claim 13 , further comprising a splitter plate between the first and second pluralities of bristles, wherein the splitter plate is aligned with a mean camber line or a chord line of the airfoil, and a distal end of the splitter plate defines the peak of the ridge. 
     
     
         15 . The airfoil trailing edge apparatus of  claim 1 , wherein the trailing edge further comprises a suction side corner, a pressure side corner, and a plurality of serrations along at least one of the corners of the trailing edge, the serrations crossing a respective attached corner of the ridge. 
     
     
         16 . The airfoil trailing edge apparatus of  claim 1 , wherein the ridge comprises a suction side corner and a pressure side corner, and a plurality of serrations along at least one of the corners of the ridge. 
     
     
         17 . An airfoil trailing edge noise reduction apparatus, comprising:
 a ridge along a trailing edge of an airfoil;   wherein the ridge comprises first and second sides converging from a respective suction side and pressure side of the trailing edge at respective inward angles of at least 20 degrees relative to respective extensions of the pressure side or suction side of the airfoil, wherein the sides converge to an aft pointing peak.   
     
     
         18 . The airfoil trailing edge of  claim 17 , wherein the ridge is separately formed and is attached to the airfoil at the trailing edge. 
     
     
         19 . The airfoil trailing edge of  claim 18 , wherein the ridge is formed integral to the airfoil. 
     
     
         20 . An airfoil trailing edge shaped for noise reduction, comprising:
 a suction side corner and a pressure side corner of the trailing edge; and   a plurality of serrations along at least one of the corners of the trailing edge.