Method of producing and assembling a cooling device inside an axial-flow gas turbine blade, and axial-flow gas turbine blade produced using such a method

Abstract

A method of producing and assembling a cooling device inside an axial-flow gas turbine blade; the airfoil profile of the blade has an inner surface defining a chamber, and is connected to a supporting structure by two opposite end pins having respective openings for the passage of cooling air and which come out inside the chamber; the method provides for forming an insert having a number of holes and defined by a first and at least a second body separate from each other, and each of a size approximating but no larger than that of at least one of the openings; the bodies are inserted successively through the openings in the pins, and are positioned inside the chamber to direct a relative stream of air through each hole on to the inner surface of the airfoil profile.

1 ) A method of producing and assembling a cooling device ( 15 ) inside a blade ( 1 ) of an axial-flow gas turbine; the blade comprising an airfoil profile ( 2 ) having an inner surface ( 9 ) defining a chamber ( 8 ), and two connecting end portions ( 6   a,    6   b ) located on opposite sides of said airfoil profile ( 2 ) for connection to respective supporting structures forming part of said turbine, and having respective openings ( 7   a,    7   b ) for the passage of a cooling fluid and which come out inside said chamber ( 8 ); the method comprising the steps of forming an insert ( 16 ) having a number of holes ( 22 ); and positioning said insert ( 16 ) inside said chamber ( 8 ) so as to face said inner surface ( 9 ) and direct a relative stream of said cooling fluid through each said hole ( 22 ) on to said inner surface ( 9 ); characterized in that said insert ( 16 ) is formed by producing a first ( 17 ,  18 ,  20 ) and at least a second ( 19 ) body separate from each other and each of a size approximating but no larger than that of at least one of said openings ( 7   a,    7   b ); and in that positioning said insert ( 16 ) inside said chamber ( 8 ) comprises the step of inserting said first ( 17 ,  18 ,  20 ) and said second ( 19 ) body successively through said openings ( 7   a,    7   b ).  
     
     
         2 ) A method as claimed in  claim 1 , characterized in that positioning said insert ( 16 ) inside said chamber ( 8 ) comprises the further step of fitting said first ( 17 ,  18 ,  20 ) and said second ( 19 ) body resting against each other inside said chamber ( 8 ) in a direction (A) crosswise to an insertion axis ( 5 ) through said openings ( 7   a,    7   b ).  
     
     
         3 ) A method as claimed in  claim 2 , characterized in that the step of fitting said first ( 17 ,  18 ,  20 ) and said second ( 19 ) body resting against each other is effected by forcing said first body ( 17 ,  18 ,  20 ) in said direction (A).  
     
     
         4 ) A method as claimed in  claim 3 , characterized in that said first body ( 17 ,  18 ,  20 ) is forced by moving said second body ( 19 ) along said insertion axis ( 5 ).  
     
     
         5 ) A method as claimed in  claim 3 , characterized by comprising the further step of at least axially locking said second body ( 19 ) with respect to said airfoil profile ( 2 ) after forcing said first body ( 17 ,  18 ,  20 ).  
     
     
         6 ) A method as claimed in  claim 5 , characterized in that said second body ( 19 ) is locked by brazing to at least one of said end portions ( 6   a,    6   b ).  
     
     
         7 ) A method as claimed in  claim 5 , characterized in that said second body ( 19 ) is locked by interposing a retaining member ( 43 ) between said second body ( 19 ) and one ( 6   b ) of said end portions, and by connecting said retaining member ( 43 ) integrally to the end portion ( 6   b ).  
     
     
         8 ) A method as claimed in  claim 7 , characterized by comprising the further step of forcing said first body ( 18 ,  20 ) inside said chamber ( 8 ) in a direction parallel to said insertion axis ( 5 ).  
     
     
         9 ) A method as claimed in  claim 8 , characterized in that said first body ( 18 ,  20 ) is forced by axially interposing elastic means ( 48 ,  49 ) between said retaining member ( 43 ) and said first body ( 18 ,  20 ), and by preloading said elastic means ( 48 ,  49 ).  
     
     
         10 ) A method as claimed in  claim 9 , characterized in that said elastic means ( 48 ,  49 ) are preloaded when connecting said retaining member ( 43 ) to the relative said end portion ( 6   b ).  
     
     
         11 ) A method as claimed in  claim 1 , characterized in that said first and said second body ( 17 ,  18 ,  19 ,  20 ) are formed with respective inner cavities ( 24 ,  25 ,  28 ,  34 ) which communicate with one another after insertion of the bodies inside said chamber ( 8 ).  
     
     
         12 ) A method as claimed in  claim 1 , characterized by forming said insert ( 16 ) to obtain at least a third body ( 20 ), and positioning said second body ( 19 ) inside said chamber ( 8 ) in an intermediate position between said first ( 17 ,  18 ) and said third ( 20 ) body.  
     
     
         13 ) A blade ( 1 ) for an axial-flow gas turbine; the blade comprising an airfoil profile ( 2 ) having an inner surface ( 9 ) defining a chamber ( 8 ); two connecting end portions ( 6   a,    6   b ) located on opposite sides of said airfoil profile ( 2 ) for connection to respective structures forming part of said turbine, and having respective openings ( 7   a,    7   b ) for the passage of a cooling fluid and which come out inside said chamber ( 8 ); and a cooling device ( 15 ) comprising an insert ( 16 ) having a number of holes ( 22 ) and positioned inside said chamber ( 8 ) so as to face said inner surface ( 9 ) and direct a relative stream of said cooling fluid through each said hole ( 22 ) on to said inner surface ( 9 ); characterized in that said insert ( 16 ) comprises a first and at least a second body ( 17 ,  18 ,  19 ,  20 ) separate from each other and each of a size approximating but no larger than that of at least one of said openings ( 7   a,    7   b ), so as to be insertable through the openings ( 7   a,    7   b ).  
     
     
         14 ) A blade as claimed in  claim 13 , characterized in that said first and said second body ( 17 ,  18 ,  19 ,  20 ) are fitted resting against each other inside said chamber ( 8 ) in a direction (A) crosswise to an insertion axis ( 5 ) through said openings ( 7   a,    7   b ).  
     
     
         15 ) A blade as claimed in  claim 14 , characterized in that said cooling device ( 15 ) comprises first forcing means ( 31 ,  32 ,  33 ) for forcing said first body ( 17 ,  18 ,  20 ) in said direction (A).  
     
     
         16 ) A blade as claimed in  claim 15 , characterized in that said first forcing means ( 31 ,  32 ,  33 ) comprise a wedge connection, between said first ( 17 ,  18 ,  20 ) and said second ( 19 ) body, comprising two mating surfaces ( 31 ,  32 ,  33 ) sloping with respect to said axis ( 5 ).  
     
     
         17 ) A blade as claimed in  claim 15 , characterized by comprising locking means ( 42   a,    43 ) for at least axially locking said second body ( 19 ) with respect to said airfoil profile ( 2 ).  
     
     
         18 ) A blade as claimed in  claim 17 , characterized in that said locking means comprise a brazed joint ( 42   a ) connecting said second body ( 19 ) to at least one of said end portions ( 6   a,    6   b ).  
     
     
         19 ) A blade as claimed in  claim 17 , characterized in that said locking means comprise a retaining member ( 43 ) interposed between said second body ( 19 ) and one of said end portions ( 6   b ), and connected integrally to the end portion ( 6   b ).  
     
     
         20 ) A blade as claimed in  claim 19 , characterized in that said cooling device ( 15 ) comprises second forcing means ( 43 ,  48 ,  49 ) for forcing said first body ( 18 ,  20 ) inside said chamber ( 8 ) in a direction parallel to said axis ( 5 ).  
     
     
         21 ) A blade as claimed in  claim 20 , characterized in that said second forcing means ( 43 ,  48 ,  49 ) comprise preloaded elastic means ( 48 ,  49 ) interposed between said retaining member ( 43 ) and said first body ( 18 ,  20 ).  
     
     
         22 ) A blade as claimed in  claim 13 , characterized in that said insert ( 16 ) comprises at least a third body ( 20 ); said second body ( 19 ) being interposed between said first ( 18 ) and said third ( 20 ) body.  
     
     
         23 ) A blade as claimed in  claim 13 , characterized in that said end portions are defined by respective pins ( 6   a,    6   b ) hinged to respective supporting structures of said turbine.  
     
     
         24 ) A blade as claimed in  claim 13 , characterized in that said first and said second body ( 17 ,  18 ,  19 ,  20 ) define respective inner cavities ( 24 ,  25 ,  28 ,  34 ) communicating with each other.