Transonic compressor rotors with non-monotonic meanline angle distributions

Abstract

Airfoils are provided having non-monotonic meanline angle distributions and local negative camber along a length of the meanline between a point on a leading edge of the airfoil and a point on the trailing edge of the airfoil. The improved airfoil shape decreases the peak of a Mach number of a shock wave that develops in a passage between adjacent airfoils and attenuates or eliminates the shock wave at the suction surface of the airfoil within the passage. A blade constructed by this type of airfoil provides improved fluid flow in the passages between the airfoils, increased efficiency and an improved stall margin, among other benefits.

1 . A method of forming an airfoil, comprising:
 providing an airfoil meanline that includes a non-monotonic meanline angle distribution along a length of the airfoil meanline; and   adding a thickness distribution to the airfoil meanline.   
     
     
         2 . The method according to  claim 1 , wherein the non-monotonic meanline angle distribution comprises a slope of the meanline angle distribution and includes at least one sign change along the length of the airfoil meanline. 
     
     
         3 . The method according to  claim 2 , wherein the sign of the meanline angle slope varies from a negative value to a positive value to a negative value, respectively, along the length of the airfoil meanline or from a positive value to a negative value to a positive value, respectively, along the length of the airfoil meanline. 
     
     
         4 . The method according to  claim 1 , wherein the non-monotonic meanline angle distribution includes a negative camber. 
     
     
         5 . The method according to  claim 4 , wherein the negative camber is positioned downstream of a leading edge of the airfoil. 
     
     
         6 . The method according to  claim 4 , wherein the negative camber is positioned downstream of a throat of an airfoil passage. 
     
     
         7 . A rotor assembly, comprising:
 a hub;   a plurality of airfoils positioned along a perimeter of the hub and extending in a substantially radial direction, the airfoils comprising an airfoil meanline that includes a non-monotonic meanline angle distribution along a length of the airfoil meanline; and   a passage defined between adjacent airfoils that receives fluid flow therebetween, wherein the passage is defined by a suction surface of a first airfoil and a pressure surface of the adjacent airfoil.   
     
     
         8 . The rotor assembly of  claim 8 , wherein the non-monotonic meanline angle distribution comprises slope values that include at least one sign change along the length of the airfoil meanline. 
     
     
         9 . The rotor assembly of  claim 8 , wherein the sign of the meanline angle slope varies from a negative value to a positive value to a negative value, respectively, along the length of the airfoil meanline. 
     
     
         10 . The rotor assembly of  claim 8 , wherein the sign of the meanline angle slope varies from a positive value to a negative value to a positive value, respectively, along the length of the airfoil meanline. 
     
     
         11 . The rotor assembly of  claim 8 , wherein the non-monotonic meanline angle distribution includes a negative camber. 
     
     
         12 . The rotor assembly of  claim 7 , wherein the negative camber is positioned downstream of a leading edge of the first airfoil. 
     
     
         13 . The rotor assembly of  claim 7 , wherein the negative camber is positioned downstream of a throat of the airfoil passage. 
     
     
         14 . A combustion turbine, comprising:
 a compressor that includes a rotor assembly located in an adverse pressure environment, the rotor assembly comprising:
 a hub; 
 a plurality of airfoils positioned along a perimeter of the hub and extending in a substantially radial direction; and 
 a passage defined between adjacent airfoils that receives fluid flow therebetween, wherein the passage is defined by a suction surface of a first airfoil and a pressure surface of the adjacent airfoil, wherein the suction surface of the first airfoil includes a negative camber; 
   a combustor coupled to the compressor; and   a turbine coupled to the combustor.   
     
     
         15 . The combustion turbine of  claim 14 , wherein the plurality of airfoils include an airfoil meanline having a non-monotonic meanline angle distribution along a length of the airfoil meanline. 
     
     
         16 . The combustion turbine of  claim 15 , wherein the non-monotonic meanline angle distribution comprises angle values that include at least one sign change along the length of the airfoil meanline. 
     
     
         17 . The combustion turbine of  claim 16 , wherein the sign of the meanline angle slope varies from a negative value to a positive value to a negative value, respectively, along the length of the airfoil meanline or from a positive value to a negative value to a positive value, respectively, along the length of the airfoil meanline. 
     
     
         18 . The combustion turbine of  claim 15 , wherein the non-monotonic meanline angle distribution includes a negative camber. 
     
     
         19 . The combustion turbine of  claim 14 , wherein the negative camber is positioned downstream of a leading edge of the first airfoil. 
     
     
         20 . The combustion turbine of  claim 14 , wherein the negative camber is positioned downstream of a throat of an airfoil passage.