This application claims priority under 35 U.S.C. 119 to Russian Federation application no. 2010148723, filed 29 Nov. 2010, the entirety of which is incorporated by reference herein.
1. Field of Endeavor
The present invention relates to gas turbines, and more specifically a blade for a gas turbine.
Especially, the invention relates to designing rotor blades of an axial-flow turbine used in a gas turbine unit. The turbine rotor includes a rotating shaft with axial fir-tree type slots where several blade rows and several rotor heat shields are installed alternately one after another.
2. Brief Description of the Related Art
The schematized section of a gas turbine stage is shown in
Inner platforms 23 of the 1st, 2nd and 3rd stage blades B1, B2 and B3, in combination with intermediate rotor heat shields R1, R2, form the inner outline of the turbine flow or hot gas path 13, which separates the cavity of rotor cooling air transit (cooling air 17) from the hot gas flow 16. To improve tightness of the cooling air flow path between adjacent blades in the circumferential direction, sealing plates 29 are installed. When cooling the rotor shaft 14, cooling air 17 in this design flows in the axial direction along a common flow path between blade roots 24 and rotor heat shields R1, R2 and enters in turn into the internal cavity (cooling channels) of the blade B1, then into that of the blade B2 and that of blade B3 (cooling air 18).
Turbine blades used in present day efficient gas turbine units are operated under high temperatures with minimum possible air supply. Striving towards cooling air saving results in complication of internal blade channel configurations. Therefore, the blade manufacturing process is very complicated. After blade casting, a problem frequently occurs in elimination (etching out) of a ceramic (casting) core from the blade internal cavity (cooling channels).
If the blade cooling scheme of the gas turbine blade in question cannot be simplified without generating significant cooling air losses, then a technological possibility for a guaranteed and complete removal of the ceramic core from the internal blade cavity should be provided.
One of numerous aspects of the present invention includes a blade for a gas turbine which can avoid the disadvantages of the known blades and allows realizing complicated cooling channel geometries and optimized cooling air distribution and supply without sacrificing the simplicity of manufacturing of the blade.
Another aspect includes a method for manufacturing such a blade.
Yet another aspect includes a gas turbine with such blades.
Another aspect includes a blade which comprises an airfoil extending along a longitudinal direction, and a blade root for mounting said blade on a rotor shaft of said gas turbine, whereby said airfoil of said blade is provided with cooling channels in the interior thereof, which cooling channels preferably extend along the longitudinal direction and can be supplied with cooling air through cooling air supply means arranged within said blade root.
The blade root is provided with a blade channel running transversely through said blade root and being connected to said cooling channels, and an insert is inserted into said blade channel for determining the final configuration and characteristics of the connections between said blade channel and said cooling channels.
A blade design with an insert and connecting means in it allows cooling air leaks to be reduced, blade reliability and life time to be increased, and turbine efficiency to be improved.
According to an embodiment, the blade channel is a cylindrical channel, and the insert is of a tubular configuration such that it fits exactly into said cylindrical channel.
Especially, the insert has at least one nozzle in its wall, through which one of said cooling channels is connected to said blade channel, and which determines the mass flow of cooling air entering said one cooling channel.
According to another embodiment, adjacent cooling channels are separated by a wall but connected via the blade channel, and the insert is configured to close the connection between the adjacent cooling channels.
According to another embodiment, cooling air is supplied to the insert at one end.
According to another embodiment, cooling air exits the insert at the other end.
Especially, the cooling air exits the insert at the other end through a nozzle.
According to another embodiment, the insert is closed at the other end, especially by means of a plug.
According to another embodiment, the insert is brazed to the blade.
Yet another aspect includes a method for manufacturing a blade embodying principles of the present invention, in a first step of which the blade is formed by a casting process, whereby a core is used to form said cooling channels within the airfoil of said blade, in a second step said blade channel is machined into the blade root of said blade, in a third step said core is removed from the interior of said blade, preferably by a wet etching process, and in a fourth step the insert is inserted into said blade channel.
According to an embodiment, in a fifth step the insert is fixed to the blade, especially by brazing.
Yet another aspect includes a gas turbine that comprises a rotor with a plurality of blades, which are mounted to a rotor shaft and are supplied with cooling air through said rotor shaft, whereby the blades are blades as described herein.
The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings.
In general terms, blades described herein include a (preferably tubular) insert in a horizontal blade channel for configuring and determining cooling air supply. An embodiment of this design is demonstrated in
According to this embodiment, a blade 30 with an airfoil 31 and a blade root 32 is provided with cooling channels 33 and 35 running along a longitudinal direction of the blade 30 through the interior of the airfoil 31. The cooling channels 33, 35 open at their lower ends into respective cavities 34 and 36, which are separated from each other by a wall 38 and from the outside by walls 37 and 39. A cylindrical blade channel 40 runs transversely through the blade root 32, thereby connecting the cavities 34 and 36 and allowing broad access to all of the cooling channels 33, 35.
As can be seen in
A basic advantage of the design stems from the tubular insert 41 with its vertical nozzle 42 (see
An advantageous feature is the cylindrical shape chosen for the insert, because in this case a minimum gap between the insert 41 and walls 37, 38 and 39 separating the cavities 34, 36 and the outside can be achieved in the simplest way due to machining matching surfaces of both blade 30 and insert 41 with high accuracy.
Another, important feature of the proposed insert 41 is the possibility for adjusting the flow-through area of the nozzle 42. The nozzle 42 is used to supply a required amount of cooling air into the blade cavity 34 and cooling channel 33, respectively. If more than one cooling channel is necessary to supply air into the blade 30, then, in accordance with
The outlet of the insert 41 can be provided with a plug 43 (see
The insert 41, 41′ or 41″ should preferably be brazed to the blade 30, 30′ or 30″ to avoid any displacement, since, if the former was cranked or displaced, air supplying nozzles 42 or 42′ could be partially closed or shut off.
Advantages of the proposed design include:
1. Cooling air overflows between internal blade channels are precluded. This improves blade cooling stability and reliability sufficiently (due to precise machining of matched part surfaces).
2. Cooling air leakages from the blade supply channel into the turbine flow path are eliminated (due to precise machining of matched part surfaces).
3. When required, nozzle flow-through area at the internal blade channel inlet (nozzle 42, 42′, 42″) can be adjusted easily by insert modification or change (see
4. When required, nozzle flow-through area at the insert inlet or outlet (nozzle 47) can be adjusted easily by insert change or nozzle change (see
5. The cooling channel configuration can be optimized independent of the process requirements with respect to removal of the casting core.
In summary, a blade with cylindrical tubular insert and vertical holes in the blade allows cooling air leaks to be reduced, blade reliability and life time to be increased, and turbine efficiency to be improved.
While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.
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English translation of Decision of Grant issued Oct. 2, 2014 by the Russian Patent Office in corresponding Russian Application No. 2010148723, and an English translation thereof. |
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20120134845 A1 | May 2012 | US |