Cooled blade for a gas turbine

Abstract

A cooled blade for a gas turbine includes an airfoil section which extends in the radial direction of the turbine or in the longitudinal direction of the blade between a platform and a blade tip which is provided with a cap. The airfoil section is bounded transversely with respect to the longitudinal direction by a leading edge and a trailing edge and has a pressure face and a suction face. Cooling channels extend in a radial direction between the platform and the blade tip in an interior of the airfoil section. The cooling channels can be acted upon by a cooling air flow from the platform. The blade tip is cooled by first cooling holes for convection cooling provided on the pressure face of the blade, and second cooling holes for film cooling provided on the suction side of the blade, through the cap of the blade, in the blade tip from the cooling channels, and distributed over the blade width.

What is claimed is: 
     
         1 . A blade for a gas turbine, comprising:
 an airfoil section extending in a radial direction of the turbine or in a longitudinal direction of the blade between a platform and a blade tip, the blade tip being provided with a cap, the airfoil section being bounded transversely with respect to the longitudinal direction by a leading edge and a trailing edge and having a pressure face and a suction face;   cooling channels extending substantially in a radial direction between the platform and the blade tip in an interior of the airfoil section, for receiving a cooling medium flow,   first cooling holes for convection cooling provided on the pressure face of the blade; and   second cooling holes for film cooling provided on the suction face of the blade, the first and second cooling holes being arranged in an area of the blade tip and operatively connected to the cooling channels and distributed over the blade width, the cooling medium being passed to an exterior of the area of the cap and/or through the cap of the blade.   
     
     
         2 . The blade as claimed in  claim 1 , wherein the first and second cooling holes comprise:
 at least a section formed as a cylindrical bore with a predetermined first diameter.   
     
     
         3 . The blade as claimed in  claim 2 , wherein the first cooling holes are formed as long cylindrical bores which run obliquely upwards and include a first angle (α 1 ) of between 25° and 35° with an outer surface of the blade. 
     
     
         4 . The blade as claimed in  claim 2 , wherein the first cooling holes open into an environment of the blade with a fan-shaped section of the bore. 
     
     
         5 . The blade as claimed in  claim 4 , wherein first cooling holes arranged outside the trailing edge of the blade open into the environment of the blade with a 3D symmetric fan-shaped section of the bore, whereby the 3D symmetric fan-shaped section has a first aperture angle ( 2 φ 1 ) having a range of 10° to 50°, and a second aperture angle (φ 2 ) perpendicular to the first aperture angle ( 2 φ 1 ), a second aperture angle (φ 2 ) having a range of 5° to 25°. 
     
     
         6 . The blade as claimed in  claim 5 , wherein first cooling holes arranged outside the trailing edge of the blade include a second angle (α 2 ) of between 15° and 45°, with the outer surface of the blade. 
     
     
         7 . The blade as claimed in  claim 4 , wherein first cooling holes arranged at the trailing edge of the blade open into the environment of the blade with a 2D symmetric fan-shaped section of the bore, whereby the 2D symmetric fan-shaped section has a third aperture angle ( 2 φ 3 ) having a range of 10° to 40°. 
     
     
         8 . The blade as claimed in  claim 7 , wherein first cooling holes arranged at the trailing edge of the blade include a third angle (α 3 ) of between 5° and 45°, with the outer surface of the blade. 
     
     
         9 . The blade as claimed in  claim 7 , wherein first cooling holes arranged at the trailing edge of the blade have a bore of a predetermined first length, which is subdivided into the 2D symmetric fan-shaped section and a cylindrical section of a predetermined second length, whereby a ratio of the second length and the first length is in the range of 0.2 to 0.7. 
     
     
         10 . The blade as claimed in  claim 3 , wherein the first cooling holes are arranged along the pressure face in a row with a predetermined first periodicity, and a ratio between the first periodicity and the first diameter is in the range of 3 to 8. 
     
     
         11 . The blade as claimed in  claim 2 , wherein the second cooling holes pass through the cap of the blade in a radial direction. 
     
     
         12 . The blade as claimed in  claim 11 , wherein the second cooling holes are formed as long cylindrical bores which run obliquely upwards and include an angle (γ) of 0° to 45° with the longitudinal axis of the blade. 
     
     
         13 . The blade as claimed in  claim 11 , wherein the second cooling holes are arranged along the suction face in a row with a predetermined second periodicity, and a ratio between the second periodicity and the first diameter is in the range of 3 to 8. 
     
     
         14 . The blade as claimed in  claim 3 , wherein the first cooling holes exit into the environment of the blade at a predetermined height below an upper end of the blade tip, and a ratio between the height and the first diameter is in a range between 5 and 10. 
     
     
         15 . The blade as claimed in  claim 2 , comprising:
 dust holes arranged along the cap between the leading edge and trailing edge, the dust holes having a second diameter, such that a ratio between the second diameter and the first diameter is between 1.2 and 4.5.   
     
     
         16 . The blade as claimed in  claim 11 , wherein the cap of the blade is bounded at an edge on its upper face by a circumferential blade crown, and the second cooling holes open into an outside area within the blade crown. 
     
     
         17 . The blade as claimed in  claim 1 , wherein the blade has a blade crown at the blade tip, which is bounded by a circumferential rail having a predetermined thickness, whereby a width between opposing rails varies with a distance along the chord line, such that t/W is between 0.05 and 0.15 for κ/κ 0  between 0 and 0.3, that t/W is between 0.15 and 0.3 for κ/κ 0  larger than 0.3 and up to 1.0, κ 0  being the overall chord line length. 
     
     
         18 . The blade as claimed in  claim 1 , wherein the blade has a ratio D/W between 0.1 and 0.3 for κ/κ 0  between 0 and 0.3, and the ratio D/W is between 0.3 and 0.8 for κ/κ larger 0.3 and up to 1.0. 
     
     
         19 . The blade as claimed in  claim 3 , wherein the first angle (α 1 ) is substantially 30°. 
     
     
         20 . The blade as claimed in  claim 5 , wherein the first aperture angle ( 2 φ 1 ) is substantially 24° and the second aperture angle (φ 2 ), is substantially 12°. 
     
     
         21 . The blade as claimed in  claim 6 , wherein the second angle (α 2 ) is substantially 30°. 
     
     
         22 . The blade as claimed in  claim 7 , wherein the third aperture angle ( 2 φ 3 ) is substantially 20°. 
     
     
         23 . The blade as claimed in  claim 8 , wherein the third angle (α 3 ) is substantially 30°. 
     
     
         24 . The blade as claimed in  claim 9 , wherein the ratio of the second length and the first length is substantially 0.5. 
     
     
         25 . The blade as claimed in  claim 10 , wherein the ratio between the first periodicity and the first diameter is substantially 6. 
     
     
         26 . The blade as claimed in  claim 12 , wherein the angle (γ) is substantially 30°. 
     
     
         27 . The blade as claimed in  claim 13 , wherein the ratio between the second periodicity and the first diameter is substantially 6. 
     
     
         28 . The blade as claimed in  claim 14 , wherein the ratio between the height and the first diameter is substantially 6.5.