This application claims priority under 35 U.S.C. ยง119 to Russian Federation application no. 2010148728, 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 in particular to axial flow gas turbines.
2. Brief Description of the Related Art
The invention relates to an axial flow gas turbine, an example of which is shown in
The gas turbine 10 according to
A section of a typical cooled gas turbine stage TS of a gas turbine 10 is shown in FIG. 1. Within a turbine stage TS of the gas turbine 10, a row of vanes 13 is mounted on a vane carrier 11. Downstream of the vanes 13 a row of rotating blades 16 is provided, each of which has an outer platform 17 at its tip. Opposite to the tips of the blades 16, stator heat shields 18 are mounted on the vane carrier 11. Each of the vanes 13 has an outer platform 14. The vanes 13 and blades 16 with their respective outer platforms 14 and 17 border a hot gas path 12, through which the hot gases from the combustion chamber flow.
To ensure operation of such a high temperature gas turbine 10 with long-term life span, all parts forming its flow path 12 should be cooled effectively. Therefore, cooling air 23 is directed through respective cooling bores 21 and 22 from a plenum 20 to the stator heat shields 18 and vanes 13 and hot outer platforms 17 of the blades 16. However, the known turbine design of
One of numerous aspects of the present invention includes a gas turbine with a turbine stage cooling scheme, which can avoid drawbacks of the known cooling configuration and substantially reduce the consumption of cooling air within the turbine stage.
Another aspect includes an axial flow gas turbine that comprises a rotor with alternating rows of air-cooled blades and air-cooled rotor heat shields, and a stator with alternating rows of air-cooled vanes and air-cooled stator heat shields mounted on a vane carrier, whereby the stator coaxially surrounds the rotor to define a hot gas path in between, such that the rows of blades and stator heat shields, and the rows of vanes and rotor heat shields are correlated with each other, respectively, and a row of vanes and the next row of blades in the downstream direction define a turbine stage. Within a turbine stage, means are provided to reuse the cooling air that has already been used to cool, especially the airfoils of, the vanes of the turbine stage, for cooling the stator heat shields of that turbine stage downstream of the vanes.
According to an embodiment, the means for reusing comprises first means for collecting the used cooling air when exiting the vanes, and second means for directing the collected used cooling air onto the stator heat shields of said turbine stage downstream of the vanes, for cooling.
Preferably, the means for reusing further comprises third means for directing the collected used cooling air onto outer platforms of the blades of said turbine stage downstream of the vanes, for cooling.
According to another embodiment, the vanes of the turbine stage each comprise an outer platform, and the means for reusing are integrated into the vanes just above the outer platforms.
According to another embodiment, the collecting means comprises a first cavity for each of the vanes located at the exit of the vane cooling air on the upper side of the outer platform, the directing means comprises a second cavity extending in the circumferential direction and being connected to said first cavity, whereby a plurality of first, axially oriented holes, which are equally distributed along the circumferential direction, direct used cooling air from the second cavity onto the outside of the adjacent stator heat shields of the turbine stage, for cooling.
According to another embodiment, a plurality of second axially oriented holes, which are equally distributed along the circumferential direction, direct used cooling air from the second cavity onto the outside of the outer platforms of the adjacent blades of the turbine stage, for cooling.
Preferably, the outer platforms of the blades of the turbine stage each comprise a circumferentially oriented forward tooth, the vanes of the turbine stage overlap said forward tooth with a circumferentially extending downstream projection at the rear wall of their outer platform, and each downstream projection is provided with a honeycomb just opposite to the forward tooth.
According to another embodiment, the first cavity is established by a rib in the form of a frame on the upper side of the outer platform, which frame is covered by a sealing screen.
According to another embodiment, the second cavity is established by a recess in the rear wall of the outer platform, which recess is covered by a sealing screen.
The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings.
Air used up in the vane 33 passes from the vane airfoil through the outer platform 34 into a small cavity 39 partitioned off from the basic (outer) platform 34 with a rib 40 (see
The efficient utilization of used-up air described above makes it possible to avoid an additional supply of fresh cooling air to the stator heat shields 38 and blade shrouds or outer platforms 37.
Another innovation of the design according to
When the proposed shape of the outer vane platform 34 according to
Used-up air passes also into a cavity 52 between the vane carrier 31 and stator heat shields 38 through gaps in part joints. Used-up air passing through the second holes 43 serves to protect the forward teeth 50 of the outer blade platforms 37.
With the foregoing, the following advantages can be achieved:
1. Air used up in a vane is then utilized to cool other parts.
2. There is no need to introduce additional air for cooling the stator heat shields.
3. The proposed shape of the outer vane platform with an additional projection 47 on its rear wall makes it possible to avoid additional cooling air leakages through the slit marked by zone A in
4. Utilized air fills the cavity 52 (see
Thus, a combination of the vane with projection 47 at its outer platform 34 and a separate collector (cavity 39) for utilized air, as well as a combination of a non-cooled stator heat shield 38 and a three-pronged outer blade platform 37 with the cavity 46 formed in between, enables a modern high-performance turbine to be created.
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.
Number | Date | Country | Kind |
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2010148728 | Nov 2010 | RU | national |