Airfoil tip geometry to reduce blade wear in gas turbine engines

Abstract

An airfoil for use in a turbomachine includes a pressure sidewall and a suction sidewall coupled to the pressure sidewall. The suction sidewall and the pressure sidewall define a leading edge and an opposite trailing edge. The leading edge and the trailing edge define a chord distance. The airfoil further includes a root portion, and a tip portion. The tip portion extends between the pressure sidewall and the suction sidewall such that the tip portion is substantially perpendicular to each sidewall. The tip portion includes at least one planar section and at least one oblique section that forms a recess within the tip portion. The at least one oblique section extends from the at least one planar section towards the root portion along the chord distance. The tip portion is configured to reduce airfoil wear during contact with a surrounding casing.

What is claimed is: 
     
       1. An airfoil for use in a turbomachine, said airfoil comprising: a pressure sidewall; a suction sidewall coupled to said pressure sidewall, wherein said suction sidewall and said pressure sidewall define a leading edge and an opposite trailing edge, wherein said leading edge and said trailing edge define a chord distance; a root portion; and a tip portion extending between said pressure sidewall and said suction sidewall such that said tip portion is substantially perpendicular to each sidewall, said tip portion comprises at least one planar section and at least one oblique section that forms a recess within said tip portion, said at least one oblique section extends from said at least one planar section towards said root portion along said chord distance, said tip portion is configured to reduce airfoil wear during contact with a surrounding casing, wherein said at least one oblique section comprises a first oblique section and a second oblique section, said first oblique section extends convexly from said leading edge to said at least one planar section and said second oblique section extends concavely from said trailing edge to said at least one planar section. 
     
     
       2. The airfoil in accordance with  claim 1 , wherein said at least one oblique section extends from said leading edge within a range from approximately 5% to approximately 15% of said chord distance to said at least one planar section, wherein said leading edge has a first length that extends between said root portion and said at least one oblique section and said trailing edge has a second length that extends between said root portion and said at least one planar section such that said first length is less than said second length, and
 wherein the at least one planar section defines a radially outer surface of the airfoil. 
 
     
     
       3. The airfoil in accordance with  claim 1 , wherein said at least one oblique section extends from said leading edge within a range from approximately 15% to approximately 30% of said chord distance to said at least one planar section, wherein said leading edge has a first length that extends between said root portion and said at least one oblique section and said trailing edge has a second length that extends between said root portion and said at least one planar section such that said first length is less than said second length. 
     
     
       4. The airfoil in accordance with  claim 1 , wherein said at least one oblique section extends from said leading edge within a range from approximately 30% to approximately 50% of said chord distance to said at least one planar section, wherein said leading edge has a first length that extends between said root portion and said at least one oblique section and said trailing edge has a second length that extends between said root portion and said at least one planar section such that said first length is less than said second length. 
     
     
       5. The airfoil in accordance with  claim 1 , wherein said at least one oblique section extends from said trailing edge within a range from approximately 5% to approximately 15% of said chord distance to said at least one planar section, wherein said leading edge has a first length that extends between said root portion and said at least one planar section and said trailing edge has a second length that extends between said root portion and said at least one oblique section such that said first length is greater than said second length. 
     
     
       6. The airfoil in accordance with  claim 1 , wherein said at least one oblique section extends from said trailing edge within a range from approximately 15% to approximately 30% of said chord distance to said at least one planar section, wherein said leading edge has a first length that extends between said root portion and said at least one planar section and said trailing edge has a second length that extends between said root portion and said at least one oblique section such that said first length is greater than said second length. 
     
     
       7. The airfoil in accordance with  claim 1 , wherein said at least one oblique section extends from said trailing edge within a range from approximately 30% to approximately 50% of said chord distance to said at least one planar section, wherein said leading edge has a first length that extends between said root portion and said at least one planar section and said trailing edge has a second length that extends between said root portion and said at least one oblique section such that said first length is greater than said second length. 
     
     
       8. The airfoil in accordance with  claim 2 , wherein said at least one oblique section comprises a first oblique section and a second oblique section, said first oblique section extends from said leading edge approximately 15% of said chord distance to said at least one planar section and said second oblique section extends from said trailing edge approximately 15% of said chord distance to said at least one planar section. 
     
     
       9. The airfoil in accordance with  claim 8 , the at least one planar section comprising exactly one planar section, the exactly one planar section extending from the first oblique section to the second oblique section,
 wherein said leading edge has a first length that extends between said root portion and said first oblique section and said trailing edge has a second length that extends between said root portion and said second oblique section such that said first length is substantially equal to said second length. 
 
     
     
       10. The airfoil in accordance with  claim 1 , wherein said at least one oblique section extends from said at least one planer section towards said root portion within a range including approximately 2 mils to less than 5 mils. 
     
     
       11. The airfoil in accordance with  claim 1 , wherein said at least one planar section comprises a first planar section adjacent said leading edge and a second planar section adjacent trailing edge, said at least one oblique section extends between said first planar section and said second planar section. 
     
     
       12. The airfoil in accordance with  claim 9 , wherein said at least one oblique section is defined with a convex curve. 
     
     
       13. A turbomachine comprising: a casing; a rotor assembly, said casing at least partially extending about said rotor assembly, said rotor assembly comprising: a rotor shaft; a plurality of rotor blades coupled to said rotor shaft, each rotor blade of said plurality of rotor blades comprises an airfoil comprising a pressure sidewall and a suction sidewall coupled to said pressure sidewall, wherein said suction sidewall and said pressure sidewall define a leading edge and an opposite trailing edge, wherein said leading edge and said trailing edge define a chord distance, said airfoil further comprising a root portion and a tip portion extending between said pressure sidewall and said suction sidewall such that said tip portion is substantially perpendicular to each sidewall, said tip portion comprising at least one planar section and at least one oblique section that forms a recess within said tip portion, said at least one oblique section extends from said at least one planar section towards said root portion along said chord distance, said tip portion is configured to reduce rotor blade wear during contact with said casing, wherein said at least one oblique section comprises a first oblique section and a second oblique section, said first oblique section extends convexly from said leading edge approximately 15% of said chord distance to said at least one planar section and said second oblique section extends concavely from said trailing edge approximately 15% of said chord distance to said at least one planar section. 
     
     
       14. The turbomachine in accordance with  claim 13 , wherein said at least one oblique section extends from said leading edge to said at least one planar section, wherein a distance measured between said casing and said leading edge is greater than a distance measured between said casing and said trailing edge, and
 wherein each rotor blade of the plurality of rotor blades comprises a turbine rotor blade. 
 
     
     
       15. The turbomachine in accordance with  claim 13 , wherein said at least one oblique section extends from said trailing edge to said at least one planar section, wherein a distance measured between said casing and said trailing edge is greater than a distance measured between said casing and said leading edge. 
     
     
       16. A method for reducing blade wear during turbomachine operation, the turbomachine including a casing, a rotor shaft, and a plurality of rotor blades, each rotor blade of the plurality of rotor blades including an airfoil including a pressure sidewall and a suction sidewall coupled to the pressure sidewall, wherein the suction sidewall and the pressure sidewall define a leading edge and an opposite trailing edge, wherein the leading edge and the trailing edge define a chord distance, the airfoil further includes a root portion and a tip portion extending between the pressure sidewall and the suction sidewall such that the tip portion is substantially perpendicular to each sidewall, said method comprising: removing blade material from the tip portion comprising forming a recess from at least one oblique section adjacent at least one planar section on the tip portion, the at least one oblique section extends from the at least one planar section towards the root portion along the chord distance; and coupling the rotor blade to the rotor shaft such that during turbomachine operation when the tip portion contacts the casing, wear of the rotor blade is reduced, wherein the at least one oblique section extends from the at least one planar section to at least one of the leading edge and the trailing edge, wherein said at least one oblique section comprises a first oblique section and a second oblique section, said first oblique section extends convexly from said leading edge to said at least one planar section and said second oblique section extends concavely from said trailing edge to said at least one planar section. 
     
     
       17. The method in accordance with  claim 16 , wherein removing blade material from the tip portion further comprises removing blade material from the tip portion at the leading edge such that the leading edge has a first length that extends between the root portion and the at least one oblique section and the trailing edge has a second length that extends between the root portion and the at least one planar section such that the first length is less than the second length. 
     
     
       18. The method in accordance with  claim 16 , wherein removing blade material from the tip portion further comprises removing blade material from the tip portion at the trailing edge such that the leading edge has a first length that extends between the root portion and the at least one planar section and the trailing edge has a second length that extends between the root portion and the at least one oblique section such that the first length is greater than the second length, and wherein the recess is not centered about a mid-chord line. 
     
     
       19. The method in accordance with  claim 16 , wherein removing blade material from the tip portion further comprises:
 removing the leading edge tip portion via a grinding process to form a first oblique section; and 
 removing the trailing edge tip portion via a grinding process to form a second oblique section.