Steam-cooled gas turbine

Abstract: In recovery type steam-cooled gas turbine, steam passage leading to moving blade is provided on central side of rotor for reducing leakage of steam. Cooling steam 70 of low temperature and high pressure is led into moving blade 1, 2 through supply side steam passage 12, 13 and steam passage 15, 16 and, after used for cooling, flows into cavity 22 through steam passage 16, 17 to be recovered as recovery steam 71 of high temperature and low pressure at rotor end 20 through recovery side steam passage 19, 21. The cooling steam 70 of low temperature and high pressure is led passing on inner side of the recovery steam 71 in rotor, hence there are less places from where the high pressure steam leaks outside as compared with prior art in which the high pressure steam is supplied from outer side in the rotor, and leakage amount of steam is reduced.

Description: BACKGROUND OF THE INVENTION: Field of the Invention: The present invention relates to a recovery type steam-cooled gas turbine in which supply steam for cooling is prevented from leaking outside. Description of the Prior Art: Fig. 2 is a cross sectional view of a gas turbine which employs a representative steam-cooled system in the prior art. In Fig. 2, numeral 50 designates a compressor and numeral 51 designates a gas turbine. In the gas turbine 51, there are provided moving blades 21, 22, 23 on a periphery of a rotor 30 and a high temperature combustion gas is led into a combustion gas passage 52 to flow therethrough to rotate the moving blades 21, 22, 23 between stationary blades 43, 44, 45 on a stationary side and to thereby rotate the rotor 30. In a rotor disc 31, there are provided steam passages 33, 32, which connect to each other and pass-through the rotor disc 31 in an axial direction thereof. The steam passages 33, 32 are provided in plural pieces along a circumferential direction of the rotor 30. Cooling steam 80 is led into a steam passage 33 via a steam inlet 35 of a shaft 34 to flow through a steam passage 32 and to enter a cavity 36 and then the moving blade 22 of second stage via a supply side passage 37 for cooling of the blade and, after having cooled the blade, the steam flows into a cavity 39 via a recovery side passage 38. On the other hand, the steam flowing in the steam passage 32 enters a supply side passage 41 via a cavity 40 to flow therefrom into the moving blade 21 of first stage for cooling of the blade and, after having cooled the blade, the steam flows into the cavity 39 via a recovery side passage 42 to be joined with the recovery steam which has come out of the moving blade 22 of second stage. The steam, so joined, flows out into a cavity 60 to flow through a central portion of the rotor 30 and to be recovered in the shaft 34 portion. Also, a portion of the steam in the steam passage 32 flows through a cavity 61 to be supplied into the compressor 50 portion for cooling thereof. While many combined cycle power plants are now being constructed accompanying with needs for a high temperature and high efficiency in recent power plants, the gas turbine using such a steam-cooled system as mentioned above is being eagerly studied to be employed, in place of the air-cooled system, as a leading cooling system of gas turbine. Especially in the combined cycle power plant, a portion of steam generated at a steam turbine is extracted to be led into the gas turbine for cooling thereof and the steam, used for the cooling and temperature-elevated, is recovered to be further returned to the steam turbine side, hence an effective use of heat is carried out so as to contribute to a higher efficiency of the power plant and a high attention is being paid thereon recently. In the gas turbine using the representative steam-cooled system in the prior art as mentioned above, the steam extracted from the steam turbine side is led into the moving blade for cooling thereof via the plurality of the steam passages provided in the periphery of the rotor and via the disc, and the steam which has been used for the cooling and temperature-elevated is led into the central portion of the rotor via the cavity to be recovered through the rotor central portion, and then the steam is returned to the steam turbine side to be made use of effectively. In the mentioned prior art steam-cooled system, however, because a low temperature high pressure steam is supplied through the rotor periphery, there are many places from where the steam, while being supplied, leaks to the outside low pressure side through joint portions etc., hence it is necessary to provide a lot of seal portions. Thus, it has been a large problem in the steam-cooled system how the supply steam on the high pressure side is .prevented from leaking to the low pressure side. CA-A-2 209 850 discloses a recovery type steam-cooled gas turbine where the supply side steam passage passes through the rotor disc central portions essentially throughout the rotor axial length and the recovery side steam passage extends through passages bored through the rotor discs and cavities provided between adjacent rotor discs in alternating fashion. JP-A-09 195702 discloses a recovery type steam-cooled gas turbine in which the cooling steam supply passage, too, passes through the rotor disc central portion essentially throughout the axial length of the rotor. The recovery side steam passage is formed of various cavity parts between members constituting the rotor. EP-A-0 735 238 discloses a further rotor cooling circuit for cooling turbine rotor components. SUMMARY OF THE INVENTION It is an object of the present invention to provide a recovery type steam-cooled gas turbine which is improved with respect to the cooling steam passages in order to improve the cooling efficiency. According to the present invention there is provided a recovery type steam-cooled gas turbine with the features set out in the claim. In the invention the cooling steam of low temperature and high pressure is supplied from the rotor end into the supply side steam passage in the rotor to be led into the moving blades for cooling thereof and the steam used. for the cooling and temperature-elevated passes through the recovery side steam passage to be recovered at the rotor end' and further to be returned to the steam turbine side for effective use thereof. The supply side steam passage, into which the supply steam of high pressure is supplied, passes on the inner side of the recovery side steam passage, hence there are less places from where the steam leaks outside as compared with the prior art in which the high pressure steam is supplied in the outer side, and leakage amount of steam is reduced by that degree and reliability of the recovery type steam-cooled gas turbine is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 is a cross sectional view of a recovery type steam-cooled gas turbine of an embodiment according to the present invention. Fig. 2 is a cross sectional view of a prior art recovery type steam-cooled gas turbine. DESCRIPTION OF THE PREFERRED EMBODIMENTS: Herebelow description will be made concretely on an embodiment according to the present invention with reference to the figure. Fig. 1 is a cross sectional view of a recovery type steam-cooled gas turbine of an embodiment according to the present invention. In Fig. 1, numerals 1 to 4 designate moving blades, which are provided on a periphery of a rotor 10. Numerals 5 to 8 designate stationary blades on a stationary side, which are provided alternately with the moving blades 1 to 4. Numeral 11 designates a rotor disc, in which a supply side steam passage 13 is provided in an axial direction of the rotor 10. The supply side steam passage 13 is provided in plural pieces along a circumferential direction of the rotor 10, although not' shown in the figure, for passing of the steam therethrough. Numerals 14, 15 designate steam passages, which connect respectively to the supply side steam passage 13 so that the steam is supplied into the moving blades, 1, 2 therethrough. Numerals 16, 17 also designate steam passages, through which the steam used for the cooling of the moving blades 1, 2 flows out to be led into a cavity 22. Numeral 19 designates a recovery side steam passage, which passes through on an outer side of the supply side steam passage 13 in the axial direction of the rotor 10 and is provided in plural pieces (not shown). The recovery side steam passage 19 connects to the cavity 22 and the steam used for the cooling flows through this recovery side steam passage 19 to be recovered. Numeral 20 designates a rotor end, in which a recovery side steam passage 21, elongated from the recovery side steam passage 19 on the rotor disc 11 side, is provided passing through in the axial direction of the rotor 10. Also, a supply side steam passage 12, elongated from the supply side steam passage 13 on the rotor disc 11 side, is provided on a central side of the rotor end 20. In the gas turbine constructed as mentioned above, cooling steam 70, which has been extracted from a steam turbine side (not shown), is led to be supplied into the supply side steam passage 12 on the central side of the rotor end 20. The steam 70 so supplied enters the supply side steam passage 13 from the rotor end 20 to be supplied to a supply port of the moving blade 2 of second stage via the steam passage 15, and while passing through the moving blade 2 and cooling it, the steam is heated to a high temperature and then flows out into the cavity 22 via a recovery port of the moving blade 2 and the steam passage 17. On the other hand, the steam from the supply side steam passage 13 passes through the steam passage 14 to enter the moving blade 1 of first stage via a supply port thereof and, while cooling the moving blade 1, is heated to a high temperature and then flows out into the cavity 22 via a recovery port of the moving blade 1 and the steam passage 16. In the cavity 22, the steam which has cooled the moving blade 1, on one hand, and the moving blade 2, on the other hand, and has been heated to a high temperature joins together and, flowing through the recovery side steam passages 19, 21, is recovered at the rotor end 20 as a recovery steam 71 of high temperature, which is returned to the steam turbine side for effective use thereof. In the mentioned steam-cooled system, the steam flows in the moving blade for cooling thereof, the steam used for the cooling is recovered and this recovered steam is returned to the steam turbine side for effective use thereof. Especially, while the moving blades 1, 2 of first and second stages have a large thermal capacity in which a steam-cooled effect is large, the moving blades 3, 4 of later stages have less thermal capacity, hence in the present embodiment, the moving blades 1, 2 of first and second stages only are cooled but it is a matter of course that all the moving blades 1 to 4 may be cooled also. According to the recovery type steam-cooled gas turbine of the embodiment, the cooling steam 70 of low temperature and high pressure passes through the central portion of the rotor end 20 and the supply side steam passage 13 on the rotor disc 11 side to be supplied into the moving blades 1, 2 for cooling thereof, and the recovery steam which has become a high temperature low pressure steam is recovered through the recovery side steam passages 19, 21 provided on the outer side of the supply side steam passages 12, 13. Thus, the high pressure steam flows on the inner side in the rotor 10 and through the central portion of the rotor end 20, hence there are less places from where the steam leaks outside as compared with the prior art where the high pressure steam has been supplied from the outer side and leakage amount of the steam is reduced.

Claims: A recovery type steam-cooled gas turbine, comprising: a rotor (10) comprising a plurality of rotor discs (11); moving blades (1,2,3,4) provided on the periphery of said rotor discs (11); a first supply side steam passage (12) which passes through the rotor interior in a rotor axial direction from a rotor end (20); a second supply side steam passage (13) which is provided on the rotor disc (11) side in plural pieces along a circumferential direction of the rotor so as to pass through the rotor discs (11) along the rotor axial direction and communicate on the one hand with said first supply side steam passage (12) on the rotor end (20) side and on the other hand with the moving blade interior for leading cooling steam (70) into the moving blade interior; a second recovery side steam passage (19) which is provided on the rotor disc (11) side in plural pieces so as to communicate with the moving blade interior and so as to pass through the rotor discs (11) in the rotor axial direction for recovering cooling steam after use for cooling from the moving blade interior; a first recovery side steam passage (21) elongated from said second recovery side steam passage (19) on the rotor disc (11) side to said rotor end (20); wherein, at each location along the rotor axis on the rotor end (20) side and on the rotor disc (11) side, said first and second supply side steam passages (12,13) are provided radially inwards of said first and second recovery side steam passages (19,21), respectively.

Inventors: UEMATSU KAZUO, UEMATSU, KAZUO, Uematsu, Kazuo, Takasago M. Works of Mitsubishi
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 1998
Main classification: F01D5
IPC codes: F01D5, F02C7