A turbine blade is provided having an airfoil and a platform manufactured in two separate pieces, which are joined together. The blade includes a seal, which is a mechanically decoupled seal, interposed between the airfoil and platform in a position closer to a hot gases path than a joint.
1. A turbine blade, comprising:
an airfoil;
a platform manufactured in separate pieces from the airfoil, the airfoil and the platform being directly connected together at a portion separated from a sealing portion; and
a mechanically decoupled seal is interposed between said airfoil and said platform in a position closer to a hot gases path than the portion where the airfoil and the platform are connected, wherein the platform has an inner surface portion, the inner portion being directly connected to a corresponding outer surface portion of the airfoil.
2. The blade as claimed in claim 1 , wherein said mechanically decoupled seal transmits no forces or only marginal forces between the airfoil and the platform.
3. The blade as claimed in claim 1 , wherein said connection is a permanent joint.
4. The blade as claimed in claim 1 , wherein said connection is realized in portions of the airfoil and platform separated from the seal.
5. The blade as claimed in claim 4 , wherein said connection is placed in a zone of the airfoil and platform where deformations of the airfoil and platform are less than those in zones that come directly in contact with the hot gases.
6. The blade as claimed in claim 1 , wherein said seal is realized at the regions of the airfoil and platform facing the hot gases path.
7. The blade as claimed in claim 1 , wherein said seal is made of a metallic felt or metallic foam or a brush or leaf connected to the airfoil or platform.
8. The blade as claimed in claim 7 , wherein said airfoil and/or platform comprise cooling holes that open in a gap between the airfoil and the platform in a zone of the gap housing the seal or between the seat and the connection.
9. A turbine blade comprising an airfoil and a platform manufactured in separate pieces joined together at a joint, wherein a mechanically decoupled seal is interposed between said airfoil and said platform in a position closer to a hot gases path than the joint, wherein said seal comprises recessed seats indented in the airfoil and platform and facing one another, said seats housing a plate made of several layers connected to one another.
10. The blade as claimed in claim 1 , wherein said seal comprises at least a spring element connected to the airfoil and/or platform.
11. The blade as claimed in claim 10 , wherein said seal comprises two spring elements, one connected to the airfoil and the other connected to the platform.
12. A turbine blade comprising an airfoil and a platform manufactured in separate pieces joined together at a joint, wherein a mechanically decoupled seal is interposed between said airfoil and said platform in a position closer to a hot gases path than the joint, wherein said seal has a protruding portion from the airfoil or platform having a knife edge that presses against a softer material of a corresponding portion of the platform or airfoil.
13. The blade as claimed in claim 12 , wherein said softer material is a metal felt.
14. A turbine blade comprising an airfoil and a platform manufactured in separate pieces joined together at a joint, wherein a mechanically decoupled seal is interposed between said airfoil and said platform in a position closer to a hot gases path than the joint, wherein said seal comprises a labyrinth seal.
15. The blade as claimed in claim 1 , wherein the blade is a guide vane or a rotor blade of a gas turbine.