This application claims priority to EP Application No. 15160092.1, filed Mar. 20, 2015, the contents of which is hereby incorporated herein by reference.
1. Field of the Invention
The invention relates to a cooling system for a gas turbine.
2. Background of the Invention
A cooling system for a gas turbine is disclosed in the U.S. Pat. No. 7,163,376 B2. The cooling system comprises adjacent turbine blade platforms in the form of bucket platforms having opposed slash faces and a generally cylindrical-shaped pin having a plurality of channels formed about peripheral portions of the pin at spaced axial locations there along for communicating a cooling medium through the channels and cooling at least one of the slash faces of the adjacent turbine blade platforms. The channels extend along opposite sides of said pin.
In view of this, it is in particular the object of the invention to propose a cooling system for a gas turbine, which enables turbine blades with very high thermal and mechanical load capacities. This object is satisfied in accordance with the invention by a cooling system for a gas turbine described herein.
The cooling system for a gas turbine according the invention comprises an annular array of turbine blades. Each turbine blade has a blade platform having a blade trailing edge side, a blade convex side, a blade concave side and a blade leading edge side. The turbine blades further comprise a blade profile portion connected to the blade platform and a blade root portion connected to the blade platform arranged on the other side of the blade platform in relation to the blade profile portion. Additionally the turbine blades comprise an undercut formed in the blade platform. The undercut is formed as a groove, which in particular runs from the blade concave side to the blade trailing edge side of the blade platform. It is also possible that the undercut is formed as a groove, which runs from the blade concave side to the blade convex side of the blade platform. The undercut results in a reduced mechanical and thermal stress condition in a root trailing edge of the blade profile portion and a higher stressed condition in the undercut. This is possible because the groove is located in a region of cooler metal temperature having greater material fatigue strength.
The turbine blades are arranged so that the blade convex side of the blade platform of a first turbine blade faces towards a blade concave side of the blade platform of a second turbine blade. Each blade convex side and each blade concave side include an elongated in particular at least in part arcuate groove and an in particular substantially cylindrical damper pin disposed along adjacent pairs of such grooves. The damper pin is used to dampen vibrations especially during startup and shutdown of the gas turbine and at operational speed of the gas turbine. The damper pin comprises a cut-out which is constructed and arranged so that at least a portion of a gas flow which generally flows from the blade root portion to the blade profile portion is directed to the undercut. Since the gas flow has a lower temperature than the blade platform and especially the undercut, a cooling of the undercut is performed by the gas flow. The gas flow is caused by a higher pressure of the gas in the area of the blade root portion in comparison to the pressure of the gas in the blade profile portion. So the cooling system, according the invention, enables particularly low temperatures of the undercut, so the mentioned technical effect of the undercut is very high which results in turbine blades with very high thermal and mechanical load capacities. Since the manufacturing of the damper pin including the cut-out is very easy and cheap, an easy and cost effective realization of the cooling system is possible.
In an aspect of the invention, the damper pin comprises only one cut-out. This configuration results in a very strong gas flow through this only one cut-out and thus a very effective cooling of the undercut and a very low temperature of the undercut.
In an advantageous embodiment of the invention, the cut-out runs over the whole circumference of the damper pin.
In an advantageous embodiment of the invention, the cut-out is in axial direction spirally executed. This results in an additional gas flow in the axial direction of the damper pin. This additional gas flow cools the environment of the damper pin and so indirectly the undercut. So a direct and an indirect cooling of the undercut is performed. This results in an especially effective cooling of the undercut.
The cut-out of the damper pin has especially a width in axial dimension between 5 and 12 mm and a depth in radial direction between 1 and 4 mm.
Further advantages, features and details of the invention result with reference to the following description of embodiments and with reference to the drawings in which elements which are the same or have the same function are provided with identical reference numerals.
The invention will be explained in more detail hereinafter with reference to the drawings.
In accordance with
A groove 20 for receiving a damper pin (see
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The undercut 17 comprises an inner part with a round cross-section and an outer part with a rectangular cross section (not shown). It's also possible that the inner part of the cross section of the second portion of the groove has an elliptical cross section.
A couple of turbine blades 10 according
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In
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Number | Date | Country | Kind |
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15160092.1 | Mar 2015 | EP | regional |