Method and device for cooling steam turbine generating facility

Abstract

A steam turbine of an opposed-current single-casing type has a high pressure turbine part and an intermediate-pressure turbine part housed in a single casing. A dummy ring partitions the high-pressure turbine part and the intermediate-pressure part, and a cooling steam supply path and a cooling steam discharge path are formed in the dummy ring in the radial direction. Extraction steam or discharge steam of the high-pressure turbine part, whose temperature is not less than that of the steam having passed through a first-stage stator blade, is supplied to the cooling steam supply path. The cooling steam is fed throughout the clearance to improve the cooling effect of the dummy ring and a turbine rotor. The cooling steam is then discharged through a cooling steam discharge path to a discharge steam pipe which supplies the steam to a subsequent steam turbine.

Claims

1. A cooling method for a steam turbine generating facility comprising an opposed-flow single casing steam turbine which is arranged on a higher pressure side of a low pressure turbine and in which a plurality of turbine parts are housed in a single casing and a dummy seal isolates the plurality of turbine parts from one another, the steam turbine generating facility cooling the dummy seal and a rotor shaft arranged on an inner side of the dummy seal, the method comprising: supplying cooling steam generated in the steam turbine generating facility to a cooling steam supply path formed in the dummy seal, the cooling steam having a temperature lower than a temperature of working steam which has been supplied to each of the plurality of turbine parts of the opposed-flow single casing steam turbine and has passed through a first-stage stator blade, the cooling steam having a pressure which is not less than a pressure of the working steam which has passed through the first-stage stator blade, and cooling the dummy seal and the rotor shaft by introducing the cooling steam to a plurality of clearances formed between the dummy seal and the rotor shaft via the cooling steam supply path and streaming the cooling steam in the clearances against the steam from an exit of the first-stage stator blade, wherein: the opposed-flow single casing steam turbine includes a first turbine part and a second turbine part which are provided symmetrically in the single casing and are driven by the same working steam; the cooling steam supply path is arranged between a steam inlet part of the first turbine part and a steam inlet part of the second turbine part; in said cooling the dummy seal and the rotor shaft, the cooling steam supplied via the cooling steam supply path is configured to branch off, the cooling steam branched off being configured to stream into each of a pair of the clearances arranged symmetrically; the steam turbine generating facility comprises a very-high-pressure turbine, a high pressure turbine which is driven by high pressure steam obtained by reheating discharge steam of the very-high-pressure turbine, an intermediate pressure turbine which is driven by intermediate pressure steam obtained by reheating discharge steam of the high pressure turbine, and the low pressure turbine which is driven by discharge steam of the intermediate pressure turbine; the high pressure turbine is formed as the opposed-flow single casing steam turbine and includes a first high pressure turbine part and a second high pressure turbine part which are provided symmetrically in the single casing; the cooling steam supply path of the high pressure turbine is arranged between a steam inlet part of the first high pressure turbine part and a steam inlet part of the second high pressure turbine part; in said supplying the cooling steam, the discharge steam of the very-high-pressure turbine is configured to be supplied to the cooling steam supply path of the high pressure turbine as the cooling steam; and in said cooling the dummy seal and the rotor shaft, the discharge steam of the very-high-pressure turbine supplied via the cooling steam supply path as the cooling steam is configured to branch off, the discharge steam of the very-high-pressure turbine branched off being configured to stream into each of the pair of the clearances of the high pressure turbine.

2. The cooling method according to claim 1, wherein the rotor shaft is formed by joining split members which are made of different materials, and wherein a joint section at which the split members are joined to form the rotor shaft is formed facing the clearances, the joint section being cooled by the cooling steam.

3. The cooling method according to claim 1, wherein: the intermediate pressure turbine is formed as the opposed-flow single casing steam turbine and includes a first intermediate pressure turbine part and a second intermediate pressure turbine part which are provided symmetrically in the single casing; the cooling steam supply path of the intermediate pressure turbine is arranged between a steam inlet part of the first intermediate pressure turbine part and a steam inlet part of the second intermediate pressure turbine part; in said supplying the cooling steam, the discharge steam of the high pressure turbine is configured to be supplied to the cooling steam supply path of the intermediate pressure turbine as the cooling steam; and in said cooling the dummy seal and the rotor shaft, the discharge steam of the high pressure turbine supplied via the cooling steam supply path as the cooling steam is configured to branch off, the discharge steam of the high pressure turbine branched off being configured to stream into each of the pair of the clearances of the intermediate pressure turbine.

4. A cooling device for a steam turbine generating facility comprising an opposed-flow single casing steam turbine which is arranged on a higher pressure side of a low pressure turbine and in which a plurality of turbine parts are housed in a single casing and a dummy seal isolates the plurality of turbine parts from one another, the steam turbine generating facility cooling the dummy seal and a rotor shaft arranged on an inner side of the dummy seal, the device comprising: a cooling steam supply path formed in the dummy seal and configured to open to a plurality of clearances between the dummy seal and the rotor shaft; and a cooling steam pipe connected to the cooling steam supply path so as to supply cooling steam generated in the steam turbine generating facility to the cooling steam supply path at a temperature lower than that of working steam which has been supplied to each of the plurality of turbine parts of the opposed-flow single casing steam turbine and has passed through a first-stage stator blade and at a pressure not less than the pressure of the working steam at an exit of the first-stage stator blade, wherein: the cooling steam is configured to stream into the clearances between the dummy seal and the rotor shaft via the cooling steam supply path to cool the dummy seal and the rotor shaft; the opposed-flow single casing steam turbine includes a first turbine part and a second turbine part which are provided symmetrically in the single casing and are driven by the same working steam; the cooling steam supply path is arranged between a steam inlet part of the first turbine part and a steam inlet part of the second turbine part; the cooling steam supplied via the cooling steam supply path branches off, the cooling steam branched off streaming into each of a pair of the clearances arranged symmetrically; the steam turbine generating facility comprises a very-high-pressure turbine, a high pressure turbine which is driven by high pressure steam obtained by reheating discharge steam of the very-high-pressure turbine, an intermediate pressure turbine which is driven by intermediate pressure steam obtained by reheating discharge steam of the high pressure turbine, and the low pressure turbine which is driven by discharge steam of the intermediate pressure turbine; the high pressure turbine is formed as the opposed-flow single casing steam turbine and includes a first high pressure turbine part and a second high pressure turbine part which are provided symmetrically in the single casing; the cooling steam supply path of the high pressure turbine is arranged between a steam inlet part of the first high pressure turbine part and a steam inlet part of the second high pressure turbine part; the discharge steam of the very-high-pressure turbine is configured to be supplied to the cooling steam supply path of the high pressure turbine as the cooling steam; and the discharge steam of the very-high-pressure turbine supplied via the cooling steam supply path as the cooling steam is configured to branch off, the discharge steam of the very-high-pressure turbine branched off being configured to stream into each of the pair of the clearances of the high pressure turbine.

5. The cooling device according to claim 4, wherein: the intermediate pressure turbine is formed as the opposed-flow single casing steam turbine and includes a first intermediate pressure turbine part and a second intermediate pressure turbine part which are provided symmetrically in the single casing; the cooling steam supply path of the intermediate pressure turbine is arranged between a steam inlet part of the first intermediate pressure turbine part and a steam inlet part of the second intermediate pressure turbine part; the discharge steam of the high pressure turbine is configured to be supplied to the cooling steam supply path of the intermediate pressure turbine as the cooling steam; and the discharge steam of the high pressure turbine supplied via the cooling steam supply path as the cooling steam is configured to branch off, the discharge steam of the high pressure turbine branched off being configured to stream each of the pair of the clearances of the intermediate pressure turbine.

6. The cooling device according to claim 4, further comprising a superheater disposed in a boiler to superheat steam, wherein steam extracted from the superheater is configured to be supplied to the cooling steam supply path as the cooling steam.

7. The cooling device according to claim 4, further comprising a reheater disposed in a boiler to reheat discharge steam from a steam turbine, wherein reheated steam extracted from the reheater is configured to be supplied to the cooling steam supply path as the cooling steam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a systematic diagram showing a first preferred embodiment of a steam turbine power plant to which the present invention is applicable.

(2) FIG. 2 is a sectional view of a structure of a working steam inlet part of a HIP turbine 3 of FIG. 1.

(3) FIG. 3A illustrates a modified example of the first preferred embodiment, which is an example of a three-stage reheater power plant.

(4) FIG. 3B illustrates another modified example of the first preferred embodiment, which is an example of a four-stage reheater power plant.

(5) FIG. 4 is a systematic diagram showing a second preferred embodiment of a steam turbine power plant to which the present invention is applicable.

(6) FIG. 5 is a sectional view of a structure of a working steam inlet part of a HP turbine 131 of FIG. 4.

(7) FIG. 6 is a systematic diagram showing a third preferred embodiment of a steam turbine power plant to which the present invention is applicable.

(8) FIG. 7 is a systematic diagram showing a fourth preferred embodiment of a steam turbine power plant to which the present invention is applicable.

(9) FIG. 8 is a systematic diagram showing a fifth preferred embodiment of a steam turbine power plant to which the present invention is applicable.

(10) FIG. 9 is a systematic diagram showing a sixth preferred embodiment of a steam turbine power plant to which the present invention is applicable.

(11) FIG. 10 is a systematic diagram showing a seventh preferred embodiment of a steam turbine power plant to which the present invention is applicable.

(12) FIG. 11 is a sectional view of a structure of a working steam inlet part of a HIP1 turbine 40 of FIG. 10.

(13) FIG. 12 is a systematic diagram showing a steam turbine power plant of related art.

(14) FIG. 13 is a sectional view of a structure of a steam inlet part of a HIP turbine 3 of FIG. 12.

DETAILED DESCRIPTION OF THE INVENTION

(15) A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, materials, shape, its relative positions and the like shall be interpreted as illustrative only and not limitative of the scope of the present invention.

First Preferred Embodiment

(16) FIG. 1 and FIG. 2 illustrate a first preferred embodiment of a steam turbine power plant to which the present invention is applicable. FIG. 1 shows a steam turbine power plant having a VHP turbine 1, a two-stage reheater boiler 2 having a superheater 21, a first-stage reheater 22 and a second-stage reheater 23, a steam turbine 3 of HIP opposed-flow single casing type and a LP turbine 4 (VHP-HIP-LP configuration). The steam turbine 3 of high intermediate pressure opposed-flow single casing type has a HP turbine part 31 and an IP turbine part 32 that are installed securely to a shaft of a turbine rotor and housed in a single casing. The steam turbine 3 of high intermediate pressure opposed-flow single casing type is referred to as the HIP turbine 3 hereinafter.

(17) VHP steam (e.g. 700° C.) generated in the superheater 21 of the boiler 2 is introduced to the VHP turbine 1 via a steam pipe 211 so as to drive the VHP turbine 1. Part of discharge steam (e.g. 500° C.) of the VHP turbine 1 is sent to the first-stage reheater 22 of the boiler 2 via a discharge steam pipe 104 so to be reheated to produce HP steam (e.g. 720° C.). The remaining part of the discharge steam of the VHP turbine 1 is supplied to the HIP turbine 3 via a steam communication pipe 100.

(18) Next, the HP steam generated in the boiler 2 is introduced to the HP turbine part 31 via a steam pipe 221 to drive the HP turbine part 31. Discharge steam of the HP turbine part 31 is sent to the second-stage reheater 23 of the boiler 2 via a discharge steam pipe 311 to produce IP steam (e.g. 720° C.). The IP steam is introduced to the IP turbine part 32 via a steam pipe 231 to drive the IP turbine part 32. Discharge steam of the IP turbine part 32 is introduced to the LP turbine via a crossover pipe 321 to drive the LP turbine 4. Discharge steam of the LP turbine 4 is condensed by a condenser 5, returned to the superheater 21 of the boiler 2 via a condensate pipe 601 by means of a boiler supply pump 6 and then superheated by the superheater 21 to produce the VHP steam again. The VHP steam is circulated to the VHP turbine 1.

(19) FIG. 2 shows a structure near the working steam inlet part of the HIP turbine 3. In the HIP turbine 3 near the inlet for the HP steam and the IP steam, a HP turbine blade cascade part 71, a HP dummy part 72, a IP dummy part 73 and an IP turbine blade cascade part 74 are formed on an outer circumferential surface of the turbine rotor 7. The HP turbine blade cascade part 71 has HP rotor blades 71a disposed at predetermined intervals. HP stator blades 8a of a HP blade ring 8 are arranged between the HP rotor blades 71a. At the most upstream part of the HP turbine blade cascade part 71, a HP first-stage stator blade 8a1 is arranged.

(20) The IP turbine blade cascade part 74 has IP rotor blades 74a disposed at predetermined intervals. IP stator blades 9a of an IP blade ring 9 are arranged between the IP rotor blades 74a. At the most upstream part of the IP turbine blade cascade part 74, an IP first-stage stator blade 9a1 is arranged. A dummy ring 10 is provided between the HP blade ring 8 and the IP blade ring 9 to seal the HP turbine part 31 and the IP turbine part 32. Also, a seal fin part 11 is provided in such places to face the blade rings 8,9, the dummy ring 10 and the turbine rotor 7 so as to suppress the leaking of the steam to those parts. The seal fin parts may be labyrinth seal.

(21) In the first preferred embodiment, a cooling steam supply path 101 is formed in the dummy ring 10 in the radial direction nearer to the HP turbine part 31. The cooling steam supply path 101 is connected to the steam communication pipe 100. The discharge steam s.sub.1 from the VHP turbine 1 is supplied to the cooling steam supply path 101 as cooling steam via the cooling steam communication pipe 100. The pressure of the discharge steam s.sub.1 is set not less than that of HP exit steam or IP exit steam. The HP exit steam is the HP steam that has passed through the first-stage stator blade 8a1 and the IP exit steam is the IP steam that has passed through the first-stage stator blade 9a1. The temperature of the discharge steam s.sub.1 is set lower than that of the HP exit steam and that of the IP exit steam.

(22) The cooling steam supply path 101 opens to the outer circumferential surface 72 of the turbine rotor and thus, the discharge steam s.sub.1 can reach the outer circumferential surface 72 of the turbine rotor 7. The discharge steam s.sub.1 branches into both axial directions of the turbine rotor to stream into clearances 720 and 721 between the dummy ring 10 and the turbine rotor 7. The discharge steam s.sub.1 streams toward the HP turbine blade cascade part 71 and the IP turbine blade cascade part 74 through the clearances 720 and 721. In this manner, the discharge steam s.sub.1 reaches the HP turbine blade cascade part 71 and the IP turbine blade cascade part 74.

(23) A cooling steam discharge path is formed in the radial direction in the dummy ring on a side nearer to the IP turbine part 32 than the cooling steam supply path 101. One end of the cooling steam discharge path 103 is connected to the cooling steam discharge pipe 311 via a discharge steam pipe 102 and other end thereof is opens to the clearance 721.

(24) In the preferred embodiment, as shown in FIG. 2, the pressure of the HP exit steam from the first-stage stator blade 8a1 of the HP turbine part 31, the pressure of the discharge steam s.sub.1 of the VHP turbine 1, the pressure of discharge steam s.sub.2 that is the HP steam having passed through the first-stage stator blade 8a1 and reached the cooling steam discharge path 103, and the pressure of the IP exit steam from the first-stage stator blade 9a1 of the IP turbine part 32 are respectively described as P.sub.0, P.sub.1, P.sub.2 and P.sub.3. And each of the pressures satisfies the relationship shown as a formula (1) below.
P.sub.1≧P.sub.0>P.sub.2>P.sub.3  (1)

(25) The discharge steam s.sub.1 has the pressure not less than the pressure of the HP discharge steam streaming into the clearance 720 and the pressure of the IP discharge steam streaming into the clearance 721. Thus, the discharge steam s.sub.1 can be spread throughout the clearances 720 and 721. In this manner, the discharge steam s.sub.1 cools the dummy ring 10 facing the clearances 720 and 721 and the HP dummy part 72 of the turbine rotor 7.

(26) Part of the discharge steam s.sub.1 is led by thrust balance to the cooling steam discharge path 103 as the discharge steam s.sub.2. The discharge steam s.sub.2 is discharged to the discharge steam pipe 311 from the discharge steam pipe connected to the cooling steam discharge path 103. The HP turbine blade cascade part 71 and the IP turbine blade cascade part 74 respectively have cooling holes 71a2 and 74a2 for streaming the discharge steam s1. Each of the cooling holes 71a2 and 74a2 is formed in a bottom part or the like of a blade groove of the first rotor blades 71a1 and 74a1. Thus, part of the discharge steam s.sub.1 can reach each cascade of the HP turbine blade cascade part 71 and the IP turbine blade cascade part 74.

(27) In the preferred embodiment, part of the discharge steam s.sub.1 (e.g. 500° C.) of the VHP turbine 1 whose temperature is much lower than that of the working steam (e.g. 720° C.) at the inlet of the IP turbine part 32, streams into the clearance 720 between the dummy part 72 of the rotor 7 and the dummy ring 10 from the cooling steam supply path 101. The part of the discharge steam s.sub.1 streams to the vicinity of the working steam inlet part of the HIP turbine 3 and thus, it is possible to cool the dummy ring 10 facing the clearance 720 and the dummy part of the turbine rotor 7 more effectively than before. This is due to the fact that the discharge steam s.sub.1 of the VHP turbine 1 is the steam having worked in the VHP turbine 1 and has a temperature much lower than the exit steam from the first stator blade 8a1 of the HP turbine part 31, which is used as cooling steam in a conventional cooling method.

(28) It is possible to improve the maintenance effect of the dummy part 72 of the turbine rotor 7 and the dummy ring 10 as well as to increase the freedom of choosing materials to be used in these parts. Particularly, it is possible to reduce the size of Ni-base alloy part of the turbine rotor 7 which is made of Ni-base alloy or the like and used in a high-temperature area, thereby making the production of the turbine rotor 7 easier.

(29) By cooling the dummy ring 10 and the HP dummy part 72 of the turbine rotor 7, it is possible to provide strength in a welding part whose strength is expected to be lower than that of a base material in the case of adopting a welding structure in a rotating part or a stationary part around the dummy ring 10 and the dummy part 72. This provides more freedom in the strength design of the welding part.

(30) Part of the discharge steam s.sub.1 streams into the clearance 721 nearer to the IP turbine part 32 than the cooling steam supply path 101, so as to cool the dummy ring facing the clearance 721 and the IP dummy part 73. Further, part of the discharge steam s.sub.1 reaches each blade cascade of the HP turbine blade cascade part 71 and the IP turbine blade cascade part through the cooling holes 71a2 and 74a2 so as to cool the HP turbine blade cascade part 71 and the IP turbine blade cascade part 74. This gives the blade cascade more freedom in terms of selection of materials, a strength design and a material design, resulting in facilitating an actual turbine design.

(31) For instance, FIG. 2 shows the case in which the turbine rotor 7 is formed by joining split members that are made of different materials at a welding part w by welding. For instance, the split member on HP turbine part 31 side is made of Ni-base alloy and the split member on the IP turbine part 21 side is made of Ni-base alloy or 12Cr steel. In that case, the cooling steam supply path 101 opens to the clearance near the welding part w and supplies the discharge steam s.sub.1 so as to sufficiently cool the welding part having lower strength than other parts. Thus, the strength of the welding part w can be maintained.

(32) In the first preferred embodiment, the example of using one VHP turbine 1 is explained. However, it is possible to apply the invention to a steam turbine power plant having a repeater system of three stages or more in which a plurality of VHP turbines are connected in series. For instance, FIG. 3A shows two VHP turbines 1a and 1b connected in series. In this exemplary case, the cooling steam is supplied from the first-stage VHP turbine 1a (VHP1) to the HIP turbine 3 via the steam communication pipe 100. Alternatively, the cooling steam may be supplied from the second-stage VHP turbine 1b (VHP2) to the HIP turbine 3 via the steam communication pipe 100.

(33) FIG. 3B shows three VHP turbines connected in series. In this exemplary case, the cooling steam is supplied to the HIP turbine 3 from the first-stage VHP turbine 1a (VHP1) and the third-stage VHP turbine 1c (VHP3) via steam communication pipes 100a and 100c respectively.

(34) Providing more than one VHP turbine allows one to arbitrarily choose which VHP turbine to take discharge steam from to be used as the cooling steam, thereby increasing the freedom of design. When there are plural stages of VHP turbines, the working steam pressure on the turbine blade cascade decreases toward the downstream side. Herein, all the VHP turbines are described as VHP turbines for convenience's sake.

Second Preferred Embodiment

(35) FIG. 4 and FIG. 5 show a second preferred embodiment of a steam turbine power plant to which the present invention is applicable. The steam turbine generating facility of the preferred embodiment includes the VHP turbine 1, a steam turbine 131 of HP opposed-flow single casing type (hereinafter referred to as HP turbine 131) having two HP turbine parts 31a0 and 31b0 in a single casing to form opposed-flows, a steam turbine 132 of IP opposed-flow single casing type (hereinafter referred to as IP turbine 132) having two IP turbine parts 32a0 and 32b0 in a single casing to form opposed-flows and two LP turbines 4a and 4b (VHP-HP-IP-LP).

(36) VHP steam generated in the superheater 21 of the boiler 2 (e.g. 700° C.) is supplied to the VHP turbine as working steam to drive the VHP turbine 1. Discharge steam of the VHP turbine 1 (e.g. 500° C.) is returned to the boiler 2 via the discharge steam pipe 104 and reheated by the first-stage reheater 22. The HP steam reheated by the first-stage reheater 22 (e.g. 720° C.) is supplied to the high-pressure turbine parts 31a0 and 31b0 of the HP turbine 131 respectively as working steam and drives the high-pressure turbine parts 31a0 and 31b0. Discharge steam of the high-pressure turbine parts 31a0 and 31b0 (e.g. 500° C.) is returned to the boiler 2 via the discharge steam pipe 311 and reheated by the second-stage reheater 23.

(37) IP steam reheated by the second-stage repeater (e.g. 720° C.) is supplied to the IP turbine parts 32a0 and 32b0 of the IP turbine 132 respectively as working steam and drives the IP turbine parts 32a0 and 32b0. Discharge steam of the IP turbine parts 32a0 and 32b0 is respectively supplied to the LP turbines 4a and 4b as working steam via the discharge steam pipe 321 to drive the LP turbines 4a and 4b.

(38) In the preferred embodiment, part of the discharge stem of the VHP turbine 1 (e.g. 500° C.) is supplied to the HP turbine 131 as cooling steam via the steam communication pipe 100 so as to cool the vicinity of the inlet part of the high-temperature steam (working steam) of the HP turbine 131. Part of the discharge steam of the HP turbine 131 is supplied to the IP turbine 132 as cooling steam via the steam communication pipe 110 so as to cool the vicinity of the working steam inlet part of the IP turbine 132.

(39) FIG. 5 shows a structure of the working steam inlet part of the HP turbine 131 of FIG. 4. As shown in FIG. 5, the HP turbine 131 has HP turbine blade cascade parts 71a0 and 71b0 arranged substantially symmetric around the turbine rotor 7. The HP turbine blade cascade parts 71a0 and 71b0 have HP rotor blades 71a and 71b disposed at equal intervals. Between the HP rotor blades 71a and 71b, HP stator blades 8a and 8b of HP blade ring 8a0 and 8b0 are arranged.

(40) At the most upstream part of the HP turbine blade cascade parts 71a0 and 71b0, HP first-stage stator blades 8a1 and 8b1 are arranged. A dummy ring is provided between the left and right HP turbine blade cascade parts 71a0 and 71b0 to seal the space between the HP steam inlet parts of the HP turbine parts 31a0 and 31b0. Also, a seal fin part 11 is provided in places near the HP blade rings 8a0 and 8b0, the dummy ring 10 being adjacent to the turbine rotor 7 so as to suppress the leaking of the steam to those parts.

(41) In the preferred embodiment, the cooling steam supply path 101 is formed in the dummy ring 10 in the radial direction between the pair of the HP inlet parts. The discharge steam s.sub.1 of the VHP turbine 1 is introduced as cooling steam to the cooling steam supply path 101. The cooling steam supply path 101 reaches the outer circumferential surface 72 of the turbine rotor 7 and is in communication with the clearances 720a and 720b disposed symmetrically between the turbine rotor 7 and the dummy ring 10. The discharge steam s.sub.1 introduced to the cooling steam supply path 101 streams in the clearances 720a and 720b toward the HP turbine blade cascade parts 71a0 and 71b0 on both sides.

(42) Cooling holes 71a2 and 71b2 for streaming the cooling steam s.sub.1 are formed in a bottom part or the like of blade grooves of the HP turbine blade cascade parts 71a0 and 71b0 and the first-stage rotor blades 71a1 and 71b1. In the preferred embodiment, the steam inlet part of the IP turbine 132 has the same structure as the HP turbine 131 of FIG. 5. Thus, the working steam inlet part of the IP turbine 132 is not further explained here.

(43) In the preferred embodiment, the discharge steam s.sub.1 of the VHP turbine 1 to be introduced to the cooling steam supply path 101 has a temperature (e.g. 500° C.) sufficiently lower than that of the HP steam at the inlet of the HP turbine 131 as well as being lower than that of the HP steam streaming into the clearances 720a and 720b through the first-stage stator blades 8a1 and 8b1. The pressure of the discharge steam s.sub.1 is set higher than that of diverted steam streaming into the clearances 720a and 720b through the first-stage stator blades 8a1 and 8b1.

(44) As shown in FIG. 5, the pressure of the discharge steam s.sub.1 of the VHP turbine 1, the pressure of the HP exit steam from the first-stage stator blade 8a1 and 8b1 (the diverted steam) are respectively described as P.sub.1 and P.sub.0. And each of the pressures satisfies the relationship shown as a formula (2) below.
P.sub.1≧P.sub.0  (2)

(45) Therefore, the discharge steam s.sub.1 can be spread all over the clearances 720a and 720b against the diverted steam. By this, it is possible to cool the dummy ring 10 and the turbine rotor inside of the dummy ring more effectively than the conventional cooling method.

(46) It is because the discharge steam s.sub.1 of the VHP turbine 1 is the steam having worked in the VHP turbine 1 and the temperature is much lower than the steam temperature of the first-stage stator blade of the HP turbine parts 31a0 and 31b0 which was used as the cooling steam in the conventional cooling method.

(47) The discharge steam s.sub.1 streams into the blade cascade parts 71a0 and 71b0 through the cooling holes 71a2 and 71b2 provided in the HP blade cascade parts 71a0 and 71b0 and thus, it is possible to cool the HP blade cascade parts 71a0 and 71b0 as well.

(48) In the preferred embodiment, the IP steam inlet part of the IP turbine 132 has the same structure as the HP steam inlet part of the HP turbine 131. The discharge steam of the HP turbine 131 (e.g. 500° C.) having a temperature much lower than that of the IP steam at the inlet of the IP turbine 132 is supplied as cooling steam to the IP steam inlet part of the IP turbine 132 via the steam communication pipe 110. Thus, it is possible to cool the vicinity of the working steam inlet part of the IP turbine 132 more effectively than the conventional cooling method.

(49) The discharge steam of the HP turbine 131 is the steam having worked in the HP turbine parts 31a0 and 31b0 and the temperature is much lower than the steam temperature of the first-stage stator blade (unshown) of the IP turbine parts 32a0 and 32b0 which was used as the cooling steam in the conventional cooling method. Thus, the cooling effect can be improved.

(50) The cooling steam that is adequate for the pressure and temperature conditions of each of the HP turbine 131 and the IP turbine 132 is used in the preferred embodiment. Thus, it is possible to effectively cool the inlet part of the high-temperature steam of each of the HP turbine 131 and the IP turbine 132 respectively.

(51) This gives the HP turbine blade cascade parts 71a0 and 71b0 and the IP turbine blade cascade parts (unshown) more freedom in terms of selection of materials, a strong design and a material design, resulting in facilitating an actual turbine design.

(52) By cooling the working steam inlet part of the HP turbine 131 and the IP turbine 132, it is possible to provide strength in a welding part whose strength is expected to be lower than that of a base material in the case of adopting a welding structure in a rotating part or a stationary part in the inlet part or its surrounding. This provides more freedom in the strength design of the welding part. On this point as well, it is advantageous for the actual turbine design.

(53) In the preferred embodiment, the structure of cooling each of the HP turbine 131 and the IP turbine 132 is explained. However it is also possible to cool one of the HP turbine 131 and the IP turbine 132 as needed.

Third Preferred Embodiment

(54) A third preferred embodiment in which the present invention is applied to a steam turbine power plant is explained in reference to FIG. 6. Instead of the discharge steam of the VHP turbine 1 in the first preferred embodiment, extraction steam extracted from an intermediate stage of the VHP turbine is supplied to the HIP turbine 3 and used as cooling steam in the third preferred embodiment as shown in FIG. 6. Specifically, the steam communication pipe 120 connects the blade cascade part of the intermediate stage of the VHP turbine 1 and the cooling steam supply path 101 of the HIP turbine. The steam communication path supplies the extraction steam of the blade cascade part of the intermediate stage of the VHP turbine 1 to the cooling steam supply path 101 of the HIP turbine 3.

(55) The rest of the structure is similar to the first preferred embodiment and thus, the structure same as the first preferred embodiment is not explained further. If the pressure of the extraction steam is P.sub.1, the pressure P.sub.1 of the extraction steam satisfies the above formula (1).

(56) The extraction steam supplied as cooling steam from the VHP turbine 1 to the HIP turbine 3 has a temperature lower than that of the steam diverted through the first-stage stator blade 8a1 of the HP turbine part 31 or the first-stage stator blade 9a1 of the IP turbine part 32 and has a pressure not less than that of the diverted steam. Thus, the extraction steam can be spread throughout the clearances 720 and 721 between the dummy ring 10 and the HP dummy part 72 of the turbine rotor 7, thereby improving the cooling effect of the dummy ring 10 and the HP dummy part 72.

(57) By arbitrarily selecting where in the blade cascade of the VHP turbine 1 to extract the steam, the cooling steam having optimum pressure and temperature for cooling the working steam inlet part of the HIP turbine 3 and thus, it is possible to cool the working steam inlet part of the HIP turbine 3 to an optimum temperature.

Fourth Preferred Embodiment

(58) FIG. 7 shows a fourth preferred embodiment in which the present invention is applied to a steam turbine power plant. In the first preferred embodiment, part of the discharge steam of the VHP turbine 1 is used as cooling steam for the HIP turbine 3. In contrast, in the third preferred embodiment, part of the steam in the process of being heated to produce VHP steam is extracted from the superheater 21 of the boiler and supplied as cooling steam to the working steam inlet part of the HIP turbine via the steam communication pipe. The rest of the structure is the same as the first preferred embodiment and thus, is not explained further.

(59) In the preferred embodiment, in the process of superheating final water supplied to the boiler 2 from the pump 6 to produce VHP steam, boiler extraction steam branched from midway of the superheater 21 is supplied to the HIP turbine 3 as cooling steam. The boiler extraction steam has sufficient superheated temperature in the superheater 21 and a temperature (e.g. 600° C.) much lower than the temperature at the inlet of the HP turbine part 31 and the IP turbine part 32 of the HIP turbine. Specifically, the extraction steam is the steam extracted from the area where the temperature is not completely raised. The extraction steam is supplied to the HIP turbine 3. Assuming that the pressure of the boiler extraction steam is P.sub.1, the pressure P.sub.1 of the extraction steam satisfies the formula (1).

(60) In the preferred embodiment, the boiler extraction steam from the superheater has a temperature much lower than the temperature of the working steam at the inlet of the HP turbine part 31. The boiler extraction steam is used as cooling gas to cool the inlet part of the high-temperature steam of the HP turbine part 31 or the IP turbine part 32 of the HIP turbine 3. Hus, it is possible to improve the cooling effect in the vicinity of the inlet part of the high-temperature steam of the HIP turbine in comparison to the conventional case. That is because the extraction steam from the superheater 21 is the steam before being completely heated to a setting temperature in the boiler 2 and has a temperature much lower than that of the steam at the exit of the first-stage stator blade 8a1 of the HP turbine part 31, which is used as cooling steam in the conventional cooing method.

(61) Instead of using the extraction steam from the superheater 21 as cooling steam in the modified example of the preferred embodiment, extraction steam of the first-stage reheater 22 or the second-stage reheater 23 of the boiler 2 may be used as cooling steam.

Fifth Preferred Embodiment

(62) FIG. 8 shows a fifth preferred embodiment in which the present invention is applied to a steam turbine power plant. FIG. 8 shows the boiler 2 having the superheater 21 and the repeater 22, a HP turbine divided into two, an IP turbine divided into two and one LP turbine 4 (HP1-IP1-HP2-IP2-LP).

(63) The HP turbine is divided into a first HP turbine part (HP1 turbine part) 31a on a high temperature and pressure side and a second HP turbine part (HP2 turbine part) 31b on a low temperature and pressure side. The IP turbine is divided into a first IP turbine part (IP1 turbine part) 32a on a high temperature and pressure side and a second IP turbine part (IP2 turbine part) 32b on a low temperature and pressure side. The HP1 turbine part 31a and the IP1 turbine part 32a are installed securely to the turbine rotor and housed in a single casing to constitute a steam turbine 40 of high and intermediate pressure opposed-flow single-casing type (hereinafter referred to as HIP1 turbine 40).

(64) The HP2 turbine part 31b and the IP2 turbine part 32b are installed securely to the turbine rotor and housed in a single casing to constitute a steam turbine 42 of high and intermediate pressure opposed-flow single-casing type (hereinafter referred to as H2P2 turbine 42). The HIP1 turbine 40, the H2P2 turbine 42 and the LP turbine 4 are coaxially connected to the turbine rotor.

(65) In the preferred embodiment, the HP steam (e.g. 650° C.) generated in the superheater 21 of the boiler 2 is introduced to the HP1 turbine part 31a via a steam pipe 212 so as to drive the HP1 turbine part 31a. The discharge steam (less than 650° C.) of the HP1 turbine part 31a is introduced to the HP2 turbine part 31b via the HP communication pipe 44 so as to drive the HP2 turbine part 31b. The discharge steam of the HP2 turbine part 31b is introduced to the reheater 22 via a discharge steam pipe 312 and reheated in the reheater 22 to generate the IP steam (e.g. 650° C.). The IP steam is then introduced to the IP1 turbine part 32a via a steam pipe 222 so as to drive the IP1 turbine part 32a.

(66) The discharge steam (less than 650° C.) of the IP1 turbine part 32a is introduced to the IP2 turbine part 32b via an IP communication pipe 46 so as to drive the IP2 turbine part 32b. Next, the discharge steam of the IP2 turbine part 32b is introduced to the LP turbine 4 via the crossover pipe 321 so as to drive the LP turbine 4. The discharge steam of the LP turbine 4 is condensed by the condenser 5, pressurized by the boiler supply pump 6 and then circulated back to the HIP1 turbine 40 as the HP steam.

(67) In the process of heating final water supplied to the from the pump 6 to produce the HP steam in the boiler 2, boiler extraction steam branched from midway of the superheater 21 is supplied to the working steam inlet part of the HIP1 turbine 40 as cooling steam. The boiler extraction steam has sufficient superheated temperature in the superheater 21 and a temperature (e.g. 600° C.) much lower than the temperature at the inlet of the HP1 turbine part 31a and the IP1 turbine part 32a. Specifically, the extraction steam is the steam extracted from the area where the temperature is not completely raised. The extraction steam is supplied to the HIP1 turbine 40. The temperature and pressure conditions of the extraction steam are the same as those of the fourth preferred embodiment.

(68) The structure near the working steam inlet part of the HIP1 turbine is the same as that of the first preferred embodiment shown in FIG. 2 and thus is not explained further.

(69) In the fifth preferred embodiment, the boiler extraction steam from the superheater 21 has a temperature much lower than the temperature of the working steam at the inlet part of the HP1 turbine part 31a and the IP1 turbine part 32a. The boiler extraction steam is used as cooling gas to cool the inlet part of the high-temperature steam of the HP1 turbine part 31a and the IP1 turbine part 32a. Thus, it is possible to improve the cooling effect in the vicinity of the inlet in comparison to the conventional case. That is because the extraction steam from the superheater 21 is the steam before being completely heated by the boiler 2 to a setting temperature and has a temperature much lower than that of the steam at the exit of the first-stage stator blade of the HP1 turbine part 31a, which is used as cooling steam in the conventional cooing method.

Sixth Preferred Embodiment

(70) FIG. 9 shows a sixth preferred embodiment in which the present invention is applied to a steam turbine power plant. In the fifth preferred embodiment, the HP turbine 31 is divided into plural turbine parts. In contrast, in the sixth preferred embodiment, the IP turbine is divided into the IP1 turbine on the high temperature and pressure side and the IP2 turbine 32b on the low temperature and pressure side. Further, the HP turbine 31 and the IP2 turbine part 32b are installed securely to the turbine rotor and housed in a single casing to constitute a steam turbine 41 (HIP turbine) of a high and intermediate pressure opposed-flow single-casing type (IP1-HP-IP2-LP). The IP1 turbine 32a, the HIP turbine 41 and the LP turbine 4 are coaxially connected to the single turbine rotor.

(71) In the sixth preferred embodiment, the HP steam (e.g. 650° C.) generated in the superheater 21 of the boiler 2 is introduced to the HP turbine part 31 of the HIP turbine 41 to drive the HP turbine part 31. The discharge steam of the HP turbine part 31 passes through the repeater 22 of the boiler to generate the IP steam (e.g. 650° C.). The IP steam is then introduced to the IP1 turbine 32a to drive the IP1 turbine 32a. The discharge steam of the IP1 turbine 32a (below 600° C.) is introduced to the IP2 turbine part 32b via the IP communication pipe 46 to drive the Ip2 turbine part 32b.

(72) Then, the discharge steam of the IP2 turbine part 32b is introduced to the LP turbine 4 through the crossover pipe 321 to drive the LP turbine 4. The discharge steam of the LP turbine 4 is condensed in the condenser 5, pressurized by the boiler supply pump 6 and then returned to the boiler 2 to generate the HP steam again. The HP steam is then circulated to the HP turbine part 31. Further, in the process of superheating final water supplied to the boiler 2 from the pump 6 to produce the HP steam in the boiler 2, boiler extraction steam branched from midway of the superheater 21 is supplied to the working steam inlet part of the HIP turbine 41 as cooling steam.

(73) The boiler extraction steam has sufficient superheated temperature in the superheater 21 and a temperature (e.g. 600° C.) lower than the steam temperature at the inlet of the HP turbine part 31 and the IP turbine 32b. Specifically, the extraction steam is the steam extracted from the area where the temperature is not completely raised. The extraction steam is supplied to the HIP turbine 41. The temperature and pressure conditions of the boiler extraction steam are the same as those of the fifth preferred embodiment.

(74) The structure of the working steam inlet part of the HIP turbine 41 is the same as that of the HIP turbine 3 in the first preferred embodiment shown in FIG. 2 except that the boiler extraction steam is supplied as the cooling steam instead of the VHP discharge steam. Thus, the working steam inlet part is not further explained in detail here.

(75) In the sixth preferred embodiment, the boiler extraction steam extracted from the superheater 21 of the boiler 2 has a temperature much lower than the temperature of the working steam at the inlet part of the HP turbine part 31 and the IP2 turbine part 32b and the boiler extraction steam is used as the cooling steam to cool the working steam inlet part of the HIP turbine 41. Thus, it is possible to improve the cooling effect of the working steam inlet part of the HIP turbine 41 in comparison to the conventional case.

Seventh Preferred Embodiment

(76) FIG. 10 shows a seventh preferred embodiment in which the present invention is applied to a steam turbine power plant. Instead of using the extraction steam from the superheater 21 as cooling steam to the HIP turbine 40 as in the case of the fifth preferred embodiment, in the seventh preferred the extraction steam extracted from between the blade cascades of the HP1 turbine part 31a is used as cooling steam. The rest of the structure is similar to that of the fifth preferred embodiment and thus not explained further.

(77) In FIG. 10, the extraction steam of the HP1 turbine part 31a is supplied to the working steam inlet part of the HIP1 turbine 40 via a steam communication pipe 724.

(78) FIG. 11 shows the structure of the working steam inlet part of the HIP1 turbine 40. The structure is generally same as the working steam inlet part of the first preferred embodiment shown in FIG. 2 except that the cooling steam is supplied to the steam inlet part and then discharged through the discharge path that is different from the first preferred embodiment. The rest of the structure that is the same as the first preferred embodiment is not explained here.

(79) In the seventh preferred embodiment, the cooling steam supply path 101 is formed in the dummy ring 10 in the radial direction on the side nearer to the IP1 turbine part 32a. The cooling steam supply path 101 opens to the clearance 721 and 723 formed between the dummy ring 10 and the HP dummy part 72 and the IP dummy part 73 of the turbine rotor 7. The blade cascade of the HP1 turbine part 31a of the HIP1 turbine 40 and the cooling steam supply path 101 are connected by the steam communication pipe 724. The extraction steam s.sub.1 extracted from between the blade cascades is introduced as cooling steam to the cooling steam supply path 101 via the steam communication pipe 724.

(80) The cooling steam discharge path 103 is formed in the dummy ring in the radial direction on the side nearer to the HP1 turbine part 31a than the cooling steam supply path 101 is. The cooling steam discharge path 103 opens to the clearance 720 and 721 formed between the dummy ring and the HP dummy part of the turbine rotor 7. The cooling steam discharge path 103 is connected to the discharge steam pipe and supplies the discharge steam of the HP1 turbine part 31a to the HP2 turbine part 31b of the HIP2 turbine 42 as the working steam via the discharge steam pipe 44.

(81) Part of the HP exit steam from the exit T of the first-stage stator blade 8a1 of the HP1 turbine part 31a, streams to the opposite side of the axial direction from the HP turbine blade cascade part 71 into the clearance 720 between the HP dummy ring 72a and the turbine rotor 7. Meanwhile, the extraction steam s.sub.1 extracted from between the blade cascades of the HP1 turbine part 31a streams into the clearance 721 on the inner side of the dummy ring 10 via the cooling steam supply path 101. Then, some of the extraction steam s.sub.1 streams through the clearance 723 to the IP turbine blade cascade part 74 while the rest of the extraction steam s.sub.1 streams through the clearance 721 to the opposite direction, i.e. to the HP1 turbine part 31a side.

(82) The extraction steam s.sub.1 branched toward the HP1 turbine part 31a and the steam that branches from the exit T of the first-stage stator blade 8a1 and passes through the clearance 720, are joined and discharged through the cooling steam discharge path 103. The discharge steam s.sub.2 passes through the cooling steam discharge path 103 and is then supplied as working steam to the HP2 turbine part 31b through the discharge steam pipe 44. The discharge steam s.sub.2 that passes through the cooling steam discharge path 103 can balance a thrust force loaded on the turbine rotor 7.

(83) All of the steam that branches from the exit T of the first-stage stator blade 8a1 of the HP1 turbine part 31a, passes through the clearance 720 and led to the discharge steam pipe 44 through the cooling steam discharge path 103 without streaming to the IP1 turbine blade cascade part 74. The extraction steam s.sub.1 of the HP1 turbine part 31a may be extracted from between the blade cascades where the pressure is equal to or higher than that of the discharge steam of the HP1 turbine part 32a.

(84) As shown in FIG. 11, the pressure of the working steam that is supplied to the inlet part of the HP1 turbine part 31a, the pressure of the HP extraction steam s.sub.1, the pressure of the discharge steam s.sub.2 that is the working steam having reached the cooling steam discharge path 103 through the first-stage stator blade 8a1, the steam pressure at the exit of the first-stage stator blade of the IP1 turbine part 32a are respectively described as P.sub.0, P.sub.1, P.sub.2 and P.sub.3. And each of the pressures satisfies the relationship shown as a formula (3) below.
P.sub.0>P.sub.1≧P.sub.2>P.sub.3  (3)

(85) If the pressure P.sub.1 of the extraction steam s.sub.1 is higher than the pressure P.sub.2 of the discharge steam s.sub.2 or the pressure P.sub.3 at the exit of the IP first-stage stator blade, the extraction steam s1 can be spread in the clearances 721 and 723 against the exit steam of the HP steam and the IP steam from the first-stage stator blades 8a1 and 9a1 respectively. The extraction steam s1 is the steam partially having worked in the HP1 turbine 32a and has a temperature much lower than that of the exit steam from the first-stage stator blade of the HP1 turbine part 31a to be used as cooling steam as in the case of the conventional cooling method. Thus, it is possible to improve the cooling effect of the dummy ring 10 and the outer circumferential surface 72 of the turbine rotor 7 arranged on the inner side of the dummy ring 10.

(86) According to the preferred embodiment, the temperature of the extraction steam s1 of the HP1 turbine part 31a is much lower than that of the working steam at the inlet part of the HP1 turbine part 31a and the inlet part of the IP1 turbine part 32a and the extractions team s1 can be introduced via the cooling steam supply path 101 throughout the clearances 721 and 723 between the outer circumferential surface 72 of the rotor 7 and the dummy ring 10. Thus, it is possible to reduce the temperature of the working steam inlet part of the HIP1 turbine 40 that is subjected to high temperature in comparison to the conventional cooling method.

(87) Particularly in the case of adopting a welding structure in a rotating part or a stationary part in and around the working steam inlet part, it is possible to provide strength in a welding part whose strength is expected to be lower than that of a base material. From this perspective, the designing of an actual turbine is made easier.

(88) Specifically, a plurality of split members of different materials are joined together by welding or the like to constitute the turbine rotor 7. In the case wherein the welding part w is on the inner side of the dummy ring 10, the welding part w is subjected to high-temperature atmosphere, which can reduce the strength of the welding part w.

(89) To take measures against this, the cooling steam s1 is introduced to the clearances 721 and 723 from the cooling steam supply path 101 so as to improve the cooling effect of the welding part w. This can prevent the strength decrease of the welding part w.

(90) In the preferred embodiment, the extraction steam s1 of the HP1 turbine part 31a is used as cooling steam. Alternatively, the discharge steam of the HP1 turbine part 31a may be used as cooling steam.

(91) As a modified example of the seventh preferred embodiment, the extraction steam s1 of the HP1 turbine part 31a may be introduced to a cooler 728 as shown in FIG. 11 and precooled before being supplied to the cooing steam supply path 101. For instance, the extraction steam s1 passes through a heat-transfer tube constituted of finned tubes, spiral tubes with increased heat-transfer area or the like. Further, a fan is used in combination, to send cold air to the heat-transfer tube, thereby air-cooling the extractions team s1.

(92) Alternatively, if the heat-transfer tube has a double tube structure, the extraction steam s1 is fed to one path and cooling water is fed to the other path so as to water-cool the extraction steam s1. The heat recovered in the process may be utilized for other devices. This can firmly reduce the temperature of the working steam inlet part of the HIP1 turbine 40 to a lower temperature.

(93) While the present invention has been described with reference to the preferred embodiments, it is obvious to those skilled in the art that various changes may be made without departing from the scope of the invention.

(94) According to the present invention, it is possible in the steam turbine generator facility to efficiently cool the vicinity of the working steam inlet part of the steam turbine of the opposed-flow single-casing type which houses in a single casing a plurality of steam turbines of different working steam pressures. Further, the present invention is applicable to all reheat turbines having a structure such as VHP-HIP-LP and VHP-HP-IP-LP.