Connector to transfer cooling fluid from a rotor disc to a turbomachine blade

Abstract: A cooling medium path of gas turbine moving blade is so constructed that a concave spherical surface C is formed on an inside surface of an end portion of a cooling medium path B on a blade side and a hollow pipe 6 in which one end thereof has a convex spherical surface D which engages the concave spherical surface C and the other end has a convex spherical surface F which engages an inside surface of a cooling medium path E on a rotor disc side is provided. The hollow pipe 6 communicates between the cooling medium path B on the blade side and said cooling medium path E on the rotor disc side. Supporting device 7, 8, 9 for holding the hollow pipe 6 is provided at the communicating position.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a cooling medium flow path structure in a gas turbine moving blade to be cooled by a cooling medium supplied thereinto from an interior of a rotor. Description of the Prior Art A conventional gas turbine moving blade structure will be described with reference to FIGs. 3 and 4. FIG. 3 shows a gas turbine using air as cooling medium, indicating an example of introducing cooling air into the gas turbine moving blade. ' Cooling air flowing through a cooling air pipe 51 as indicated by arrows passes through a hole 53 in a rotor disc 52 so that it flows into a hollow moving blade 54 so as to cool it. Meanwhile, reference numeral 55 in the Figure denotes a combustor and reference numeral 56 denotes an axial compressor. FIG. 4 shows an example of the moving blade having cooling flow path internally. . Cooling air entering from a bottom portion of a blade root 71 flows in the direction indicated by arrows so as to cool the moving blade. That is, cooling air entering from a leading edge side 72A flows in a cooling air path having a plurality of cooling fins 73 for forming turbulence promoter so as to cool the moving blade and finally goes out from a hole A on a blade top portion having a tip thinned portion 74 so that it merges with the main gas flow. On the other hand, cooling air entering from a trailing edge portion 72B flows in a cooling air path having a plurality of the cooling fins 73 in the direction indicated by arrows and finally cools a blade trailing edge through pin fins 75. Then, it flows out from a plurality of holes B provided on the blade end so that it merges with the main gas flow. Meanwhile, reference numeral 76 denotes a blade platform. As described above, the conventional blade is so constructed that cooling air transferred from the disc to the blade root is used for cooling the moving blade and finally discharged into the main gas flow. In the aforementioned conventional type, because the cooling air after cooling the moving blade is discharged into the main gas flow, it is a negative factor in terms of thermal efficiency of the turbine. Further, in the air-cooled gas turbine, by intensifying the sealing between the main gas flow and the interior of the rotor so as to block a back-flow of hot gas from a sealing portion and to minimize the amount of cooling air flowing into the main gas flow, it is possible to enhance the thermal efficiency. Thus, such a structure in which only the necessary amount of cooling air is fed to the moving blade so as to cool it while other air is fed to the sealing portion is an effective structure. In recent years, steam has been more often used as cooling medium instead of cooling air to raise the efficiency of the gas turbine. However, in such steam cooling, because extraction steam from a steam turbine composing a combined cycle, steam from a waste heat boiler or the like is used, a complete elimination of leakage of cooling steam into the gas turbine is requested for the reasons of steam cycle such as supply of demineralized water, prevention of lowering of plant thermal efficiency or the like. Thus, it has been requested that the cooling medium flow path is closed relative to outside so that only a supply port and a recovery port are provided thereby making production thereof easy. Thus, generally the cooling medium path is so designed that the cooling medium is supplied from an axial end on the discharge side of the gas turbine rotor and recovered at the axial end. In both air cooling and steam cooling, it has been demanded that the moving blade is securely cooled without allowing the cooling medium to escape. Then, although it is absolutely demanded that in either air cooling or steam cooling, the cooling medium is securely recovered, the conventional cooling medium flow path does not have an appropriate structure for recovering the cooling medium securely. Another problem of the conventional cooling medium flow path structure concerns a transfer position of the cooling medium between the disc and the blade root, that is, appropriate sealing performance there has not been secured due to internal pressure of the cooling medium, difference in thermal expansion between the disc and the blade root, centrifugal force and the like. US-A-5 318 404 discloses a cooling medium flow path structure for a gas turbine moving blade which is to be cooled by a cooling medium supplied thereinto from an interior of a rotor disc. This structure comprises at the connecting portion between the disc side cooling medium flow path and the blade side cooling medium flow path a pair of compression seals disposed in recesses formed in the bottom of a dovetail slot of the rotor disc. The seals are elastically deformable in a radial direction and are also axially movable within the recesses. At the radially outer end of each sleeve there is provided a spherical surface for sealing engagement against a seat surface formed around the inlet or outlet of the blade side cooling medium flow path. At the radial inner end the sleeves sealingly seat on flanges of the recesses. The elasticity of the compressed seals after mounting forces the sealing surfaces of the seals into sealing engagement with the seats about the inlet and outlet, respectively. SUMMARY OF THE INVENTION It is the object of the present invention to provide a cooling medium flow path structure for a gas turbine moving blade in which sealing performance is improved so as to block leakage of cooling medium thereby improving thermal efficiency of the gas turbine. To achieve this object the present invention provides the.cooling medium flow path structure as defined in claim 1. This flow path structure comprises a concave spherical surface formed on an inside surface of an end portion of a cooling medium path on a blade side and a hollow pipe in which one end thereof has a convex spherical surface which engages the concave spherical surface and the other end has a convex spherical surface which engages an inside surface of a cooling medium flow path on a rotor disc side is provided, so that the hollow pipe communicates between the cooling medium flow path on the blade side and the cooling medium flow path on the rotor disc side, while a supporting device for holding the hollow pipe is provided at a communicating position. According to this invention, because the hollow pipe communicating between the cooling medium flow path on the blade side and the cooling medium flow path on the rotor disc side is so formed that one end thereof has a convex spherical surface which engages the concave spherical surface of the inside surface of the cooling medium flow path on the blade side and the other end has a convex spherical surface which engages an inside surface of the cooling medium flow path on the rotor disc side, to perform said communication, the coupling of the spherical surface portions is further secured by centrifugal force, a difference in thermal expansion and the like in the transfer of the cooling medium, so that the sealing performance is improved thereby blocking leakage of the cooling medium. Further, because the coupling by the hollow pipe is conducted by spherical surface contacts, flexibility against relative deviation due to processing error of the rotor disc and the blade root and centrifugal force or heat during the operation is secured so as to ensure an effective sealing performance at this transfer position thereby preventing leakage sufficiently. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a gas turbine moving blade according to an embodiment of the present invention; FIG. 2 is an explanatory view showing a portion A of FIG. 1 in enlargement; FIG. 3 is an explanatory view showing a state of introduction of cooling medium in a conventional gas turbine; and FIG. 4 is an explanatory view showing a state of moving blade cooling in a conventional gas turbine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGs. 1 and 2. FIG. 1 shows a front view of a moving blade of cooling medium recovery type and FIG. 2 shows portion A of FIG. 2 in enlargement. The moving blade 1 is positioned on a blade platform 2 and a blade root 3 is located under the blade platform 2. Each of projecting portions 4 for supply side and recovery side is provided on both ends in the axial direction of a lowest portion of the blade root 3. A cooling medium flow path B is provided inside the interior of the projecting portions 4 with both ends thereof being bent, as shown by dotted lines. The cooling medium is fed as indicated by arrow to cool the interior of the hollow blade and blade root and recovered. A detail of the projecting portion 4 for transferring the cooling medium to the aforementioned cooling medium flow path B will be described with reference to FIG. 2. Mainly the supply side will be described here and a description of the recovery side is omitted, however, the structure and function of the both sides are the same. Referring to FIG. 2, the portion A comprises a plurality of parts. An inside surface of an end portion (this is not necessarily a complete end but may include a portion slightly inward) of the cooling medium flow path B provided in the blade root 3 of the moving blade 1 is processed in the form of concave spherical surface portion C. A hollow pipe 6 in which one end thereof has a convex spherical surface D and the other end has a convex spherical surface F which engages a cooling medium flow path E of a disc 5 is inserted in this concave spherical surface portion C. The hollow pipe 6 is installed such that the convex spherical surface D is inserted in the concave spherical surface C of the blade root 3 via such a supporting device as comprising a pressing metal 7, pressing metal mounting metal 8, side plate 9, etc. in this order from the side face of the end portion of the blade root 3 while the other end thereof is inserted in the cooling medium flow path E of the disc 5. With this structure, leakage of the cooling medium at this transfer position due to internal pressure is prevented thereby improving the sealing performance. Further, because the hollow pipe 6 and blade root 3 are connected by spherical surface contact between the convex spherical surface D and concave spherical surface C, flexibility against relative deviation due to processing error and centrifugal force or heat during the operation is secured so as to ensure a sealing performance at this transfer position thereby preventing leakage securely. Although the embodiment of the present invention has been described above, the present invention is not restricted to this embodiment but it is needless to say that its concrete structure may be modified in various ways within a scope of the claims. According to the present invention, a cooling medium flow path of gas turbine moving blade to be cooled by a cooling medium supplied thereinto from an interior of a rotor is so formed that a concave spherical surface is formed on an inside surface of an end portion of a cooling medium flow path on a blade side and a hollow pipe in which one end thereof has a convex spherical surface which engages the concave spherical surface and the other end has a convex spherical surface which engages an inside surface of a cooling medium flow path on a rotor disc side is provided, so that the hollow pipe communicates between the cooling medium flow path on the blade side and the cooling medium flow path on the rotor disc side, while a supporting device for holding the hollow pipe is provided at a communicating position. Thus, the sealing performance is improved by relation between the convex spherical surface provided on the hollow pipe and the concave spherical surface provided in the cooling medium flow path and the like, so that the transfer of the cooling medium is performed without any leakage. Further, the cooling medium which is used for cooling the disc and the blade and then heated is not discharged into the gas path but can be recovered outside of the gas turbine. As a result, for example, in a combined plant gas turbine, its thermal efficiency and a steam cycle efficiency of steam turbine can be improved thereby making it possible to contribute to improvement of the thermal efficiency of the entire plant. Also, according to the present invention, not only for the application to the recovery type steam-cooled gas turbine but also for the non-recovery type air-cooled gas turbine, air only in the amount necessary for cooling the moving blade can be supplied to the moving blade securely without leakage and further, a sealing air used for preventing the high temperature main gas flow from flowing into the interior of the rotor can be reduced. Thus, the amount of air flowing into the main gas flow can be reduced so that the thermal efficiency of the gas turbine can be improved.

Claims: A cooling medium flow path structure for a gas turbine moving blade which is to be cooled by a cooling medium supplied thereinto from an interior of a rotor disc, comprising: a disc side cooling medium flow path (E) , a blade side cooling medium flow path (B), and a hollow pipe (6) connecting said disc side cooling medium flow path (E) with said blade side cooling medium flow path (B); wherein a concave spherical surface (C) is formed on an inside surface of an end portion of said blade side cooling medium flow path (B); one end of said hollow pipe (6) is provided with a first convex spherical surface (D) which engages said concave spherical surface (C) of said blade side cooling medium flow path (B) , and the other end of said hollow pipe (6) is provided with a second convex spherical surface (F) which engages an inside surface of said disc side cooling medium flow path (E); and a supporting device (7,8,9) is provided at the connecting position for holding said hollow pipe (6). A cooling medium flow path structure for a gas turbine moving blade according to claim 1, wherein said supporting device (7,8,9) comprises a pressing metal (7) pressing said first convex spherical surface (D) of said hollow pipe (6) into engagement with said concave spherical surface (C) of said blade side cooling medium flow path (B) from a side face of an end portion of a blade root (3).

Inventors: CHIKAMI RINTARO, HIROKAWA KAZUHARU, MATSUO ASAHARU, CHIKAMI, RINTARO, HIROKAWA, KAZUHARU, MATSUO, ASAHARU, Chikami, Rintaro, Mitsubishi Heavy Ind. Ltd., Hirokawa, Kazuharu, Mitsubishi Heavy Ind. Ltd., Matsuo, Asaharu, Mitsub. Heavy Ind., Ltd.
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 1998
Main classification: F01D5
IPC codes: F02C7, F01D5, F01D11