Turbine blade tip cooling construction

Abstract

A gas turbine blade ( 1 ) with a tip squealer ( 7 ) comprises cooling passages ( 12, 13 ) that provide cooling fluid for the cooling of the tip squealer ( 7 ). A first portion of the cooling passages ( 12 ) extends from an internal hollow space ( 11 ) through an end cap to a tip pocket. A second portion ( 13 ) of the cooling passage extends from the end cap in part through the rails ( 8 ) of the tip squealer ( 7 ) to the tip crown ( 9 ). The second portion ( 13 ) is partially bounded by the rail ( 8 ) and partially open to the tip pocket ( 14 ). The cooling passages according to the invention provide an improved cooling of the tip squealer and have the advantage that cooling fluid can cool the tip squealer ( 7 ) even in the event of clogging of the second portions ( 13 ) of the passages.

1 . Gas turbine blade ( 1 ) comprising a pressure sidewall ( 2 ) and suction sidewall ( 3 ) extending from a leading edge ( 4 ) to a trailing edge ( 5 ) and from a root ( 6 ) to a tip with a tip having an end cap ( 10 ) and a tip squealer ( 7 ) with rails ( 8 ) that extend radially from the end cap ( 10 ) to a tip crown ( 9 ) and along the suction sidewall ( 3 ) and pressure sidewall ( 2 ) and surrounding a tip pocket ( 14 ), and 
 furthermore comprising an internal hollow space ( 11 ) between the inner surfaces of the pressure and suction sidewall ( 2 , 3 ), through which a cooling fluid can flow and    cooling passages for directing the cooling fluid to the tip squealer ( 7 ) characterized in that 
 the cooling passages have a first portion ( 12 ) leading from the internal hollow space ( 11 ) through the end cap ( 10 ) to the tip pocket ( 14 ) and a second portion that extends in part through the rails ( 8 ) to the tip crown ( 9 ) of the tip squealer ( 7 ), where the second portion ( 13 ) is in one part bounded by a sidewall ( 15 ) in the rail and in another open to the tip pocket ( 14 ).  
   
     
     
         2 . Gas turbine blade ( 1 ) according to  claim 1  characterized in that 
 the first and second portion ( 12 ,  13 ) of the cooling passages extend radially from the internal hollow space ( 11 ) within the blade to the tip crown ( 9 ).  
 
     
     
         3 . Gas turbine blade ( 1 ) according to  claim 1  characterized in that 
 the longitudinal axis of the first and second portion ( 12 ,  13 ) of the cooling passages is oriented at an angle (θ) with respect to the radial direction either in the plane perpendicular to the blade sidewalls ( 2 , 3 ) or at an angle (φ) with respect to the radial direction in the plane of the blade sidewalls ( 2 ,  3 ) or at a compound angle with respect to the radial direction in each of these planes.  
 
     
     
         4 . Gas turbine blade ( 1 ) according to  claim 3  characterized in that 
 the angle of orientation (θ) of the longitudinal axis of the first and second portion ( 12 ,  13 ) of the cooling passages in the plane perpendicular to the blade sidewalls ( 2 , 3 ) is in the range from 0 to 45°.  
 
     
     
         5 . Gas turbine blade ( 1 ) according to  claim 3  characterized in that 
 the angle of orientation (φ) of the longitudinal axis of the first and second portion ( 12 ,  13 ) of the cooling passages in the plane of the blade sidewalls ( 2 , 3 ) is in the range from 0 to 60° 
 
     
     
         6 . Gas turbine blade ( 1 ) according to one of the foregoing claims  1  through  3  characterized in that 
 the first portion of the cooling passages ( 12 ) has a cylindrical shape leading from the internal hollow space ( 11 ) between the inner surfaces of the suction and pressure sidewall ( 2 ,  3 ) through the end cap ( 10 ) to the tip pocket ( 14 ) and the second portion of the cooling passage has the shape of a partial cylinder within the rails ( 8 ) of the tip squealer ( 7 ).  
 
     
     
         7 . Gas turbine blade ( 1 ) according to one of the foregoing claims  1  through  3  characterized in that 
 the first and second portions of the cooling passages ( 12 ,  13 ) have an elongated or oval shape in the direction along the rails ( 8 ) of the tip squealer ( 7 ).  
 
     
     
         8 . Gas turbine blade ( 1 ) according to one of the foregoing claims  1  through  3  characterized in that 
 the cooling passages have parallel extending sidewalls over a first part ( 12 ′) of the first portion ( 12 ) within the tip cap ( 10 ) and a diffused shape over a second part of its first portion ( 12 ) within the tip cap ( 10 ) and over its second portion or extension ( 13 ).  
 
     
     
         9 . Gas turbine blade ( 1 ) according to  claim 8  characterized in that 
 the diffused shape of the cooling passages is defined by angles (α,β) between the passage sidewalls and the longitudinal axis of the cooling passages that are in the range from 5 to 10°.