Compressor rotor blade undercut

Abstract

A rotor blade for an axial compressor that may include an airfoil, which includes a leading edge, and a root, which includes a platform, the platform being the outer radial face of the root from which the airfoil extends, and a dovetail, the dovetail including a dovetail leading-face, which is the face of the dovetail that generally points up-stream once the rotor blade is installed in the axial compressor. The rotor blade may include an undercut groove that is formed on the dovetail leading-face that undercuts at least partially the intersection of the leading edge of the airfoil and the platform.

1 . A rotor blade for an axial compressor that comprises an airfoil, which includes a leading edge, and a root, which includes a platform, the platform being the outer radial face of the root from which the airfoil extends, and a dovetail, the dovetail including a dovetail leading-face, which is the face of the dovetail that generally points up-stream once the rotor blade is installed in the axial compressor, the rotor blade comprising:
 an undercut groove that is formed on the dovetail leading-face that undercuts at least partially the intersection of the leading edge of the airfoil and the platform.   
     
     
         2 . The rotor blade according to  claim 1 , wherein:
 the airfoil further includes an airfoil suction-side and an airfoil pressure-side;   the leading edge of the airfoil is the edge defined between the airfoil suction-side and the airfoil pressure-side that generally points up-stream once the rotor blade is installed in the axial compressor;   the dovetail is used, at least in part, to connect the rotor blade to a rotor wheel; and   the dovetail further includes a dovetail suction-side and a dovetail pressure-side, each of which, respectively, correspond to the same side of the rotor blade as the airfoil suction-side and the airfoil pressure-side.   
     
     
         3 . The rotor blade according to  claim 1 , wherein the undercut groove substantially undercuts the intersection of the leading edge of the airfoil and the platform. 
     
     
         4 . The rotor blade according to  claim 1 , wherein the undercut groove completely undercuts the intersection of the leading edge of the airfoil and the platform. 
     
     
         5 . The rotor blade according to  claim 1 , wherein the phrase “undercuts at least partially the intersection of a leading edge of the airfoil and the platform” is defined to mean that the undercut groove extends to a depth in the dovetail such that a portion of the undercut groove is axially aligned with at least a portion of the intersection of the leading edge of the airfoil and the platform. 
     
     
         6 . The rotor blade according to  claim 1 , wherein the undercut groove is positioned such that it is in close proximity to and radially inward of the radial height of the platform. 
     
     
         7 . The rotor blade according to  claim 6 , wherein the distance between the outward most radial height of the undercut groove and the radial height of the platform is between approximately 0.1 to 1.0 inches. 
     
     
         8 . The rotor blade according to  claim 6 , wherein the undercut groove begins in the approximate center of the dovetail leading-face and extends toward an edge of the dovetail that separates the dovetail leading-face and the dovetail pressure side. 
     
     
         9 . The rotor blade according to  claim 8 , wherein the undercut groove extends through the dovetail pressure-side such that the undercut groove is open through the dovetail pressure-side. 
     
     
         10 . The rotor blade according to  claim 9 , wherein the undercut groove tapers such that the width of the undercut groove is narrower at the dovetail leading-face and wider as the undercut groove extends into the dovetail. 
     
     
         11 . The rotor blade according to  claim 8 , wherein the undercut groove is substantially parallel to the platform. 
     
     
         12 . The rotor blade according to  claim 1 , wherein the undercut groove comprises a substantially rectangular profile on the dovetail leading-face and on the dovetail pressure-side. 
     
     
         13 . The rotor blade according to  claim 1 , wherein the undercut groove comprises a substantially “U” shape profile on the dovetail leading-face and on the dovetail pressure-side. 
     
     
         14 . The rotor blade according to  claim 1 , wherein the angle of the cut into the dovetail leading-face that is made to form the undercut groove is approximately 90 degrees with respect to a mean camber line of the airfoil at the platform. 
     
     
         15 . The rotor blade according to  claim 1 , wherein the depth of the undercut groove is such to that the undercut groove enters the stress line of the rotor blade at a base of the leading edge that is caused by blade load during operation of the axial compressor. 
     
     
         16 . The rotor blade according to  claim 1 , wherein the rotor blade is configured to function in a first stage of the axial compressor. 
     
     
         17 . A rotor blade for an axial compressor that includes an airfoil and a root, the airfoil including an airfoil suction-side, an airfoil pressure-side, and a leading edge, which is the edge defined between the airfoil suction-side and the airfoil pressure-side that generally points up-stream once the rotor blade is installed in the axial compressor, the root including a platform, which is the outer radial face of the root from which the airfoil extends, and a dovetail that is used to connect the rotor blade to a rotor wheel, the dovetail including a dovetail leading-face, which is the face of the dovetail that generally points up-stream once the rotor blade is installed in the axial compressor, a dovetail suction-side and a dovetail pressure-side, the rotor blade comprising:
 an undercut groove that is formed on the dovetail leading-face that substantially undercuts the intersection of the leading edge of the airfoil and the platform;   wherein the undercut groove begins in the approximate center of the dovetail leading-face and extends toward an edge of the dovetail that separates the dovetail leading-face and the dovetail pressure side.   
     
     
         18 . The rotor blade according to  claim 17 , wherein the undercut groove extends through the through the dovetail pressure-side such that the undercut groove is open through the dovetail pressure-side. 
     
     
         19 . The rotor blade according to  claim 18 , wherein:
 the distance between the outward most radial height of the undercut groove and the radial height of the platform is approximately 0.1 to 1.0 inches; and   the undercut groove is substantially parallel to the platform.   
     
     
         20 . The rotor blade according to  claim 17 , wherein the angle of the cut into the dovetail leading-face is approximately 90 degrees with respect to a mean camber line of the airfoil at the platform.