STEAM TURBINE CAPABLE OF SUPPRESSING EROSION AND EFFICIENCY DECREASE

Abstract

Steam turbine (2, 2A, 2C), comprising: a rotor (16); a housing (18) that accommodates the rotor; a plurality of impeller blades (20) arranged around the rotor (16); and a multitude of guide vanes (22) which are mounted on the housing (18), wherein the guide vane (22) comprises a blade body section (24) and an inner ring (26) which is arranged on an inner side of the blade body section (24) in the radial direction of the rotor, wherein the plurality of guide vanes comprises a first guide vane (22a) with a through hole (30) which is formed in the radial direction through the blade body section (24), wherein the rotor comprises a cavity (32) which has a concave shape and is designed such that at least a part of the inner ring (26) of the first guide vane (22a) is housed in the cavity (32), wherein the steam turbine comprises a steam passage (34), wherein the steam passage (34) has a steam outlet (36) which is arranged on an upstream surface (38) of the inner ring (26), and wherein the steam passage (34) is arranged to deliver steam taken from a space upstream of the first guide vane (22a) in the housing to the cavity (32) from the steam outlet (36) through the through hole (30) of the first guide vane.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a steam turbine. STATE OF THE ART

[0002] Near the final stage of a steam turbine, the moisture content tends to increase. For example, the moisture content in the final stage of a geothermal or nuclear high-pressure turbine is approximately 15%. In a wet steam zone with high moisture content, liquid droplets adhering to the turbine blade surfaces separate downstream and collide with downstream blades. This leads to erosion and moisture loss.

[0003] To address such problems, JP 3 617 212 B2 discloses a steam turbine which allows high-temperature steam to flow through the interior of guide vanes arranged in front of low-pressure rotor blades operating in the wet steam range to heat the guide vanes, thus preventing the formation of liquid droplets on the surfaces of the guide vanes.

[0004] The publications JP H09- 195 705 A, SU 996 735 A2 and JP S59- 39 902 A represent further state of the art. PRESENTATION OF THE INVENTION

[0005] The present invention is defined by the steam turbine according to the features of independent claim 1. The dependent claims relate to preferred embodiments. Problems to be solved

[0006] The steam turbine described in JP 3 617 212 B2 is configured such that high-temperature steam is discharged to the tips of the downstream rotor blades after passing through the interior of the guide vanes, and thus a large loss is caused by interference between the main flow passing through each stage and the high-temperature steam discharged after passing through the interior of the guide vanes, and probably causes a deterioration in the efficiency of the steam turbine.

[0007] At least one embodiment of the present invention was developed with regard to the typical problem mentioned above. An object of at least one embodiment of the present invention is to provide a steam turbine capable of suppressing erosion and efficiency degradation. Problem solving

[0008] According to at least one embodiment of the present invention, a steam turbine comprises: a rotor; a casing that houses the rotor; a plurality of rotor blades arranged around the rotor; and a plurality of guide vanes mounted on the casing. The guide vane comprises a blade body section and an inner ring arranged on an inner surface of the blade body section in the radial direction of the rotor. The plurality of guide vanes includes a first guide vane having a through-hole formed through the blade body section in the radial direction. The rotor includes a cavity having a concave shape and configured such that at least a portion of the inner ring of the first guide vane is accommodated in the cavity.The steam turbine comprises a steam passage, wherein the steam passage has a steam outlet located on an upstream surface of the inner ring, and wherein the steam outlet is configured to discharge steam taken from a space upstream of the first guide vane in the casing to the cavity from the steam outlet through the through-hole of the first guide vane.

[0009] With the steam turbine (1) described above, the temperature of the steam taken from the space upstream of the first guide vane is higher than the temperature of the first guide vane, and thus it is easily possible to heat the first guide vane by allowing the steam to flow through the through-hole of the first guide vane. Accordingly, it is possible to suppress the formation of liquid droplets on the surface of the first guide vane and thus to prevent erosion.

[0010] Furthermore, since steam flowing through the through-hole of the first guide vane is discharged from the inner ring of the first guide vane into the cavity, in contrast to the configuration of the JP 3 617 212 B2 (where steam flowing through the interior of the guide vane is discharged towards the tips of the rotor blades), it is possible to reduce the loss due to interference between the main flow flowing through the casing (steam flow in the axial direction, which alternately flows through the guide vane and the rotor blade) and the steam discharged through the through-hole, and to suppress the efficiency deterioration of the steam turbine.

[0011] Furthermore, it is possible to reduce leakage steam (leakage flow from the main flow) that flows into the cavity from the upstream side of the first guide vane, and thus it is possible to reduce the loss due to leakage steam and suppress the efficiency deterioration of the steam turbine.

[0012] (2) In some embodiments of the steam turbine (1) above, the first guide vane is arranged in a region where the moisture content is not less than 3%.

[0013] With the steam turbine (2) described above, erosion is likely to occur in an area with high moisture content. Therefore, by heating the first guide vane, which is located in an area with high moisture content, with steam intended for the through-hole, it is possible to suppress the formation of liquid droplets on the surface of the first guide vane and effectively suppress erosion.

[0014] In some embodiments of the steam turbine (2) above, the first guide vane is arranged in a region where the moisture content is not lower than 10%.

[0015] With the aforementioned steam turbine (3), erosion is likely to occur in an area with high moisture content. Therefore, by heating the first guide vane, which is located in an area with high moisture content, with steam intended for the through-hole, it is possible to suppress the formation of liquid droplets on the surface of the first guide vane and effectively suppress erosion.

[0016] (4) In some embodiments of the steam turbine according to any of the preceding (1) to (3), the casing comprises a tip section facing a space between a first-stage rotor blade of the plurality of rotor blades and a second-stage guide vane of the plurality of guide vanes, and a steam inlet of the steam passage is arranged at the tip section.

[0017] With the steam turbine (4) described above, it is possible to introduce steam with a higher temperature and pressure into the steam passage by arranging the steam inlet of the steam passage upstream in the casing. Therefore, for heating the first guide vane, it is preferable to position the steam inlet of the steam passage as far upstream as possible. However, for the purity of the steam introduced into the steam passage, it is preferable to introduce steam into the steam passage after it has passed through the guide vane of the first stage.

[0018] Thus, as described above, by arranging the steam inlet of the steam passage at the tip section facing the space between the rotor blade of the first stage and the guide vane of the second stage, it is possible to introduce steam with a relatively higher purity into the steam passage and to effectively heat the first guide vane.

[0019] Furthermore, it is likely that high-temperature outflow resulting from steam condensation accumulates in the tip section, but this outflow has not been effectively utilized. In this respect, by providing the steam inlet at the tip section, as described above, it is possible to introduce not only steam from the space but also high-temperature outflow accumulated in the tip section into the steam passage and to use the outflow to heat the first guide vane, thus enabling effective heating of the first guide vane.

[0020] (5) In some embodiments of the steam turbine according to any of the preceding (1) to (3), the guide vane comprises an outer ring which supports the blade body section. The steam passage has a steam inlet located on an upstream surface of the outer ring of the first guide vane.

[0021] With the steam turbine (5) described above, the temperature of the steam drawn from the space facing the upstream side of the outer ring of the first guide vane is higher than the temperature of the first guide vane, and thus it is easily possible to heat the first guide vane by allowing the steam to flow through the through-hole of the first guide vane. Therefore, it is possible to achieve the effect described above in (1) (suppression of erosion and suppression of efficiency decrease) with a simple configuration.

[0022] (6) In some embodiments, the steam turbine according to any of the preceding (1) to (3) comprises a sealing section arranged in a gap between the rotor and the casing to seal leakage steam flowing radially inwards from a gap between a first-stage guide vane of the plurality of guide vanes and a first-stage rotor blade of the plurality of rotor blades. The first-stage guide vane includes a through-hole extending radially. A steam inlet of the steam passage is configured to receive some of the leakage steam. The steam passage is configured to supply some of the leakage steam into the cavity via the through-hole of the first-stage guide vane and the through-hole of the first guide vane.

[0023] With the steam turbine described above (6), it is possible to effectively heat the first guide vane by introducing a portion of the high-temperature, high-pressure leakage steam, which flows radially inwards from a gap between the first-stage guide vane and the first-stage rotor blade, into the steam passage and feeding the leakage steam through the through-hole of the first guide vane into the cavity. Accordingly, it is possible to suppress the formation of liquid droplets on the surface of the first guide vane and effectively prevent erosion.

[0024] (7) In some embodiments of the steam turbine according to any of the preceding (1) to (6), the plurality of rotor blades comprises a first rotor blade which is arranged adjacent to and downstream of the first guide vane in an axial direction of the rotor, the rotor comprises a first disk section to which the first rotor blade is attached, the first disk section has a balancing hole formed through the first disk section in an axial direction, and the balancing hole is designed such that a portion of the steam which is discharged from the inner ring through the through-hole of the first guide vane into the cavity flows into the balancing hole.

[0025] With the steam turbine (7) described above, the sum of the flow rate of the leakage steam flowing through the inner ring sealing section located at the radially inner end of the inner ring, the flow rate of the leakage steam flowing into the cavity from the gap between the first guide vane and the first rotor blade, and the flow rate of the heating steam discharged into the cavity from the inner ring of the first guide vane, is equal to the flow rate of the steam flowing through the balancing hole. With this configuration, it is possible to reduce the leakage loss near the blade root section of the first rotor blade. Beneficial effects

[0026] According to at least one embodiment of the present invention, a steam turbine is provided with which it is possible to suppress erosion and efficiency deterioration. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is an overall configuration diagram of a steam turbine plant with a steam turbine device 2 according to an embodiment of the present invention. Fig. Figure 2 is a cross-sectional view of a schematic configuration of the steam turbine device 2 (2A) according to one embodiment. Fig. 3 is an enlarged partial view of the in Fig. 2 steam turbine device 2 (2A) shown. Fig. Figure 4 is an enlarged partial view of a modified example of the one described in Fig. 2 steam turbine device 2 (2A) shown. Fig. Figure 5 is a cross-sectional view of a schematic configuration of the steam turbine device 2 (2B) according to one embodiment. Fig. 6 is an enlarged partial view of the in Fig. 5 steam turbine device 2 (2B) shown. Fig. Figure 7 is a cross-sectional view of a schematic configuration of the steam turbine device 2 (2C) according to one embodiment. Fig. 8 is an enlarged partial view of the in Fig. 7 steam turbine device 2 (2C) shown. Fig. Figure 9 is a cross-sectional view showing an embodiment in which a first disk section 56 has a compensating hole 58. DETAILED DESCRIPTION

[0027] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, it is intended that the dimensions, materials, shapes, relative positions, and the like of the components described in the embodiments, unless specifically indicated, are to be interpreted only for illustrative purposes and are not intended to limit the scope of the present invention.

[0028] For example, an expression of a relative or absolute arrangement such as "in a direction", "along a direction", "parallel", "orthogonal", "centered", "concentric" and "coaxial" is not to be interpreted as indicating only the arrangement in the narrow literal sense, but also encompassing a state in which the arrangement is shifted relative by a tolerance, an angle or a distance, making it possible to achieve the same function.

[0029] For example, an expression of an identical state such as "equal", "equivalent" and "uniform" should not be interpreted as indicating only the state in which the characteristic is absolutely identical, but also includes a state in which there is a tolerance or a difference that can still achieve the same function.

[0030] Furthermore, for example, an expression of a shape, such as a rectangular shape or a cylindrical shape, is not only to be interpreted as a geometrically strict shape, but also includes a shape with irregularities or chamfered corners within the area in which the same effect can be achieved.

[0031] On the other hand, an expression such as "comprise", "include", "have", "contain" and "form" is not intended to exclude other components.

[0032] Fig. Figure 1 is an overall configuration diagram of a steam turbine plant with a steam turbine according to an embodiment of the present invention. Fig. 1 The steam turbine plant 1 comprises a steam turbine device 2, a boiler 4, a water supply pump 6, a generator 10 and a condenser 12.

[0033] In the Fig. In the steam turbine system 1 shown in Figure 1, the steam St generated in boiler 4 is supplied to the steam turbine 2 via a steam supply line 8a. After the steam turbine 2 has been driven, the steam St supplied to the steam turbine 2 is fed to the condenser 12 via a condensate supply line 8b. Furthermore, the condensate water condensed in the condenser 12 is pressurized by the water supply pump 6 and thus supplied to boiler 4 as boiler water via a boiler water supply line 8c.

[0034] Fig. Figure 2 is a cross-sectional view of a schematic configuration of the steam turbine device 2 (2A) according to one embodiment.

[0035] As in Fig. As shown in Figure 2, the steam turbine device 2 comprises a rotor 16, a casing 18 which accommodates the rotor 16, a plurality of rotor blades 20 which are arranged around the rotor 16, and a plurality of guide vanes 22 which are mounted on the casing 18.

[0036] Unless otherwise specified, the radial direction of the rotor 16 will henceforth be referred to simply as the "radial direction", the axial direction of the rotor 16 simply as the "axial direction", and the circumferential direction of the rotor 16 simply as the "circumferential direction". Furthermore, unless otherwise specified, the upstream side and the downstream side in the direction of flow of the main flow "f" (steam flow in the axial direction, which flows alternately through the guide vanes 22 and the rotor blades 20) flowing through the casing 18 will be referred to simply as "upstream" and "downstream", respectively.

[0037] Each of the guide vanes 22 comprises a blade body section 24, an inner ring 26 (dividing plate section) arranged radially inside the blade body section 24, and an outer ring 28 arranged radially on the outside of the blade body section 24. In guide vane 22f of the first stage of the plurality of guide vanes 22, the inner ring 26 and the outer ring 28 are coupled to the housing 18. In guide vanes 22 that are not guide vane 22f of the first stage of the plurality of guide vanes 22, only the outer ring 28 is connected to the housing 18. Furthermore, the plurality of guide vanes 22 comprises a first guide vane 22a with a through-hole 30 formed radially through the blade body section 24. In an illustrative embodiment of the steam turbine device 2 with five stages, the guide vane 22 of the fourth stage is the first guide vane 22a.

[0038] The rotor 16 has a cavity 32 with a concave shape, designed such that at least a part of the inner ring 26 of the first guide vane 22a is housed in the cavity 32. Furthermore, the steam turbine device 2 includes a steam passage 34, which is configured to discharge steam taken from the space S upstream of the first guide vane 22a in the casing 18 from the inner ring 26 of the first guide vane 22a through the through-hole 30 of the first guide vane 22a into the cavity 32.

[0039] With the above configuration, the temperature of the steam taken from space S upstream of the first guide vane 22a is higher than the temperature of the first guide vane 22a, and thus it is easily possible to heat the first guide vane by allowing the steam to flow through the through-hole 30 of the first guide vane 22a. Accordingly, it is possible to suppress the formation of liquid droplets on the surface of the first guide vane 22a and thus prevent erosion.

[0040] Furthermore, since steam flowing through the through-hole 30 of the first guide vane 22a is discharged from the inner ring 26 of the first guide vane 22a into the cavity 32, in contrast to the configuration of the JP 3 617 212 B2 (where steam flowing through the interior of the guide vane is discharged towards the tips of the downstream rotor blades), it is possible to reduce the loss due to interference between the main flow “f” (steam flow in axial direction, which alternately flows through the guide vane 22 and the rotor blade 20) flowing through the casing 18 and the steam discharged through the through-hole 30, and to suppress the efficiency deterioration of the steam turbine 2.

[0041] Furthermore, it is possible to reduce leakage steam (leakage flow from the main flow “f”) that flows from the upstream side of the first guide vane 22a into the cavity 32, and thus it is possible to reduce the loss due to leakage steam and suppress the efficiency deterioration of the steam turbine 2.

[0042] This point is discussed in relation to Fig. 3 described. Fig. 3 The arrow Gc indicates the leakage steam flow that flows from the upstream side of the first guide vane 22a into the cavity 32 (leakage flow from the main flow “f”), the arrow Gr indicates the leakage steam flow that flows radially outwards from the cavity 32 downstream of the first guide vane 22a and interferes with the main flow “f”, and the arrow GL indicates the steam that is released from the inner ring 26 of the first guide vane 22a into the cavity 32 (hereinafter also referred to as “heating steam”).

[0043] The flow rate of the leakage steam Gr is equal to the sum of the flow rate of the leakage steam Gc and the flow rate of the heating steam GL, and the flow rate of the leakage steam Gr does not change significantly due to the presence or absence of the heating steam GL. By introducing the heating steam GL into cavity 32, it is therefore possible to suppress the leakage steam Gc from the main flow "f". This makes it possible to reduce the loss due to the leakage steam Gc.

[0044] Furthermore, the steam outlet 36 of the steam passage 34 can be arranged on a surface 38 upstream of the inner ring 26 of the first guide vane 22a (surface upstream of the inner ring sealing section 40, which is arranged at the radially inner end of the inner ring 26) as in Fig. 3 is shown, or be arranged on the downstream surface 42 of the inner ring 26 of the first guide vane 22a (surface downstream of the inner ring sealing section 40, which is arranged at the radially inner end of the inner ring 26). In each of the configurations shown in the Fig. 3 and Fig. 4. It is possible to achieve the effect that the leakage vapor Gc described above is suppressed.

[0045] In one embodiment, the first guide vane 22a is arranged in a region where the moisture content is 3% or more (or preferably, 10% or more). Erosion is likely to occur in such a high-moisture region. Therefore, by heating the first guide vane 22a, which is located in a high-moisture region, with steam supplied to the through-hole 30, it is possible to suppress the formation of liquid droplets on the surface of the first guide vane 22a and effectively suppress erosion.

[0046] In one embodiment as in Fig. As shown in Figure 2, the housing 18 comprises a tip section 44 (of the housing 18, a section surrounding the space S1) which faces the space S1 between the rotor blade 20f of the first stage of the plurality of rotor blades 20 and the guide blade 22s of the second stage of the plurality of guide blades 22, and the steam inlet 46 of the steam passage 34 is arranged on the tip section 44.

[0047] It is possible to introduce high-pressure and high-temperature steam into the steam passage 34 by arranging the steam inlet 46 of the steam passage 34 upstream in the casing 18. Therefore, for heating the first guide vane 22a, it is preferred to position the steam inlet 46 of the steam passage 34 as far upstream as possible. However, for the purity of the steam introduced into the steam passage 34, it is preferred to introduce steam into the steam passage 34 after it has passed through the guide vane 22f of the first stage.

[0048] Thus, as described above, by arranging the steam inlet 46 of the steam passage 34 at the tip section 44, which faces the space S1 between the rotor blade 20f of the first stage and the guide vane 22s of the second stage, it is possible to introduce high-pressure and high-temperature steam, which has a relatively higher purity, into the steam passage 34 without using a pump or the like, and to effectively heat the first guide vane.

[0049] Furthermore, it is likely that high-temperature outflow, generated by steam condensation, accumulates in the area of ​​the peak section 44, but this outflow has not been effectively utilized. In this respect, by providing the steam inlet 34 at the peak section 44, it is possible to introduce not only steam from space S1, but also the high-temperature outflow accumulating in the peak section 44 into the steam passage 34 and to use the outflow to heat the first guide vane 22a, thus making it possible to effectively heat the first guide vane 22a.

[0050] Fig. Figure 5 is a cross-sectional view of a schematic configuration of the steam turbine device 2 (2B) according to one embodiment. Fig. 6 is an enlarged partial view of the in Fig. 5 Steam turbine device 2 (2B) shown. The basic configuration according to steam turbine device 2 (2B) is similar to the basic configuration according to steam turbine device 2 (2A), and the same reference numerals as above are used and the description is not repeated.

[0051] As in Fig. As shown in Figure 5, steam turbine device 2 (2B) differs from steam turbine device 2 (2A) in the specific configuration of the steam passage 34. As shown in Fig. As shown in Figure 6, the steam inlet 46 of the steam passage 34 is arranged on the upstream surface 48 of the outer ring 28 of the first guide vane 22a (surface upstream of the connecting section between the outer ring 28 and the housing 18), and the steam outlet 36 of the steam passage 34 is arranged on the downstream surface 42 of the inner ring 26 of the first guide vane 22a. In the illustrated embodiment, the inner ring sealing section 40, which has a labyrinth structure, is arranged at the radially inner end of the inner ring 26 of the first guide vane 22a, and the steam outlet 36 of the steam passage 34 is arranged on the surface 42 downstream of the inner ring sealing section 40 of the inner ring 26.

[0052] With this configuration, there is a pressure differential across the inner ring sealing section 40, and the pressure of chamber U, which faces the surface 42 upstream of the outer ring 28 of the first guide vane 22a, is higher than the pressure of chamber S(S2), which faces the downstream surface 48 in the inner ring 26 of the first guide vane 22a. Thus, even without the use of a pump or the like, steam can flow from chamber S(S2) through the through-hole 30 of the first guide vane 22a. Furthermore, the temperature of the steam taken from the space S (S2), which faces the upstream surface 42 of the outer ring 28 of the first guide vane 22a, is higher than the temperature of the first guide vane 22a, and thus it is easily possible to heat the first guide vane 22a by allowing the taken steam to flow through the through-hole 30 of the first guide vane 22a.Accordingly, it is possible to suppress the generation of liquid droplets on the surface of the first guide vane 22a and to suppress erosion through a simple configuration.

[0053] Furthermore, since steam flowing through the through-hole 30 of the first guide vane 22a is discharged from the inner ring 26 of the first guide vane 22a into the cavity 32, compared to the configuration of the JP 3 617 212 B2 (where steam flowing through the interior of the guide vane is discharged towards the tips of the rotor blades), it is possible to reduce the loss due to interference between the main flow “f” (steam flow in axial direction, which alternately flows through the guide vane 22 and the rotor blade 20) flowing through the casing 18 and the steam discharged through the through-hole 30.

[0054] Furthermore, it is possible to reduce leakage steam (leakage flow from the main flow) that flows from the upstream side of the first guide vane 22a into the cavity 32, and thus it is possible to reduce the loss due to leakage steam.

[0055] Fig. Figure 7 is a cross-sectional view of a schematic configuration of the steam turbine device 2 (2C) according to one embodiment. Fig. 8 is an enlarged partial view of the in Fig. 7 Steam turbine device 2 (2C) shown. The basic configuration according to steam turbine device 2 (2C) is similar to the basic configuration according to steam turbine device 2 (2A, 2B), and the same reference numerals as above are used and the description is not repeated.

[0056] As in the Fig. 7 and Fig. As shown in Figure 8, steam turbine device 2 (2C) differs from steam turbine device 2 (2A, 2B) in the specific configuration of the steam passage 34. As shown in Fig. As shown in Figure 8, the steam turbine device 2 comprises a sealing section 50, which is arranged in the gap “g” between the rotor 16 and the casing 18 upstream of the first-stage rotor blade 20f in the axial direction, to seal leakage steam Gf flowing radially inwards from the gap between the first-stage guide vane 22f of the plurality of guide vanes 22 and the first-stage rotor blade 20f of the plurality of rotor blades 20. The sealing section 50 has an annular structure and forms a labyrinth structure between the inner circumferential surface of the sealing section 50 and the outer circumferential surface of the rotor 16.

[0057] In the steam turbine device 2 (2C) the guide vane 22 of the first stage includes a through-hole 52 that penetrates in the radial direction, and the steam inlet 46 of the steam passage 34 is arranged on the inner circumferential surface 54 of the inner ring 26 of the guide vane 22f of the first stage to receive some of the leakage steam Gf.

[0058] As in the Fig. 7 and Fig. As shown in Figure 8, the steam passage 34 of the steam turbine device 2 (2C) is designed to supply the cavity 32 with a portion of leakage steam Gf via the through-hole 52 of the guide vane 22f of the first stage and the through-hole 30 of the first guide vane 22a.

[0059] Furthermore, in the above configuration, the temperature and pressure of the leakage steam Gf, which is drawn from the space S (S3) surrounded by the rotor 16 and the casing 18 upstream of the first-stage guide vane 20f, are higher than the temperature and pressure of the steam within the cavity 32 and higher than the temperature of the first guide vane 22a. Thus, it is possible to allow the leakage steam Gf to flow through the through-hole 30 of the first guide vane 22a without the use of a pump or similar device, gently heating the first guide vane 22a. Accordingly, it is possible to suppress the formation of liquid droplets on the surface of the first guide vane 22a and to minimize erosion through this simple configuration.

[0060] Furthermore, since steam flowing through the through-hole 30 of the first guide vane 22a is discharged from the inner ring 26 of the first guide vane 22a into the cavity 32, compared to the configuration of the JP 3 617 212 B2 (where steam flowing through the interior of the guide vane is discharged towards the tips of the rotor blades), it is possible to reduce the loss due to interference between the main flow “f” (steam flow in axial direction, which alternately flows through the guide vane 22 and the rotor blade 20) flowing through the casing 18 and the steam discharged through the through-hole 30.

[0061] Furthermore, it is possible to reduce leakage steam (leakage flow from the main flow “f”) that flows from the upstream side of the first guide vane 22a into the cavity 32, and thus it is possible to reduce the loss due to leakage steam.

[0062] For example, if, as in Fig.9 is shown in the steam turbine device 2 (2a to 2c) described above, where the first rotor blade 20a is the rotor blade 20 from the plurality of rotor blades 20 which is arranged in the axial direction next to and downstream of the first guide blade 22a, and the first disk section 56 of the rotor 16 is the disk section to which the first rotor blade 20a is attached, the first disk section 56 may have a compensating hole 58 which is formed through the first disk section 56 in the axial direction. In this case, part of the steam GL, which is introduced from the inner ring 26 of the first guide vane 22a through the through hole 30 of the first guide vane 22a into the cavity 32, flows from the upstream side in an axial direction into the equalizing hole 58. Steam that has flowed into the equalizing hole 58 is discharged to the downstream side of the first disk section 56 through the interior of the first disk section 56.

[0063] With the above configuration, the sum of the flow rate of leakage steam Gb flowing through the inner ring sealing section 40, located at the radially inner end of the inner ring 26, the flow rate of leakage steam Gr flowing into the cavity from the gap between the first guide vane 22a and the first rotor blade 20a downstream of the first guide vane 22a, and the flow rate of heating steam GL discharged from the inner ring 26 of the first guide vane 22a into the cavity 32, is equal to the flow rate of steam G flowing through the balancing hole 58. With this configuration, it is possible to reduce the leakage loss near the blade root section of the first rotor blade 20a.

[0064] Furthermore, providing the balancing hole 58 for the rotor blade 20 of the last stage in the steam turbine device 2 causes an increase in exhaust steam loss. Therefore, it is preferable to provide the balancing hole 58 for the first rotor blade 20a, which is a rotor blade downstream of the last stage. Description of the reference symbols 1 steam turbine plant 2 Steam turbine device 4 boilers 6 Water supply pump 8a Steam supply line 8b Condensate feed line 8c Boiler water supply line 10 Generator 12C capacitor 16 Rotor 18 cases 20 Running shovel 20a First guide vane 20f First stage guide vane 22 Guide vane 22a First guide vane 22f First stage guide vane 22s guide vane of the second stage 24 Blade body section 26 inner ring 28 Outer ring 30, 52 Through hole 32 cavities 34 Steam passage 36 Steam outlet 38, 42, 48 surface 40 Inner ring sealing section 44 Peak section 46 Steam inlet 50 Sealing section 54 Inner circumferential surface 56 First disc section 58 Compensation hole

Claims

[1] Steam turbine (2, 2A, 2C), comprising: a rotor (16); a housing (18) that accommodates the rotor; a plurality of impeller blades (20) arranged around the rotor (16); and a multitude of guide vanes (22) which are mounted on the housing (18), wherein the guide vane (22) comprises a blade body section (24) and an inner ring (26) which is arranged on an inner side of the blade body section (24) in the radial direction of the rotor, wherein the plurality of guide vanes comprises a first guide vane (22a) with a through hole (30) which is formed in the radial direction through the blade body section (24), wherein the rotor comprises a cavity (32) which has a concave shape and is designed such that at least a part of the inner ring (26) of the first guide vane (22a) is housed in the cavity (32), wherein the steam turbine comprises a steam passage (34), wherein the steam passage (34) has a steam outlet (36) which is arranged on an upstream surface (38) of the inner ring (26), and wherein the steam passage (34) is arranged to deliver steam taken from a space upstream of the first guide vane (22a) in the housing to the cavity (32) from the steam outlet (36) through the through hole (30) of the first guide vane. [2] Steam turbine (2, 2A, 2C) according to claim 1, wherein the first guide vane (22a) is arranged in a region where the moisture content is not less than 3%. [3] Steam turbine (2, 2A, 2C) according to claim 2, wherein the first guide vane (22a) is arranged in a region where the moisture content is not less than 10%. [4] Steam turbine (2, 2A, 2C) according to any one of claims 1 to 3, wherein the housing (18) has a tip area section (44) which faces a space (S1) between a rotor blade (20f) of the first stage of the plurality of rotor blades (20) and a guide blade (22s) of the second stage of the plurality of guide blades (22), and wherein a steam inlet (46) of the steam passage (34) is arranged at the tip section (44). [5] Steam turbine (2, 2A, 2C) according to any one of claims 1 to 3, wherein the guide vane comprises an outer ring (28) which is arranged on an outside of the blade body section (24) in the radial direction of the rotor, and wherein the steam passage has a steam inlet (46) which is arranged on an upstream surface (48) of the outer ring (28) of the first guide vane (22a). [6] Steam turbine (2, 2A, 2C) according to one of claims 1 to 3, further comprising a sealing section (50) arranged in a gap (g) between the rotor (16) and the casing (18) to seal leakage steam (Gf) flowing radially inwards from a gap between a guide vane (22f) of the first stage of the plurality of guide vanes (22) and a rotor blade of the first stage (20f) of the plurality of rotor blades (20), wherein the guide vane of the first stage includes a through hole (52) which is formed in the radial direction, wherein a steam inlet (46) of the steam passage (34) is arranged to receive some of the leakage steam, and wherein the steam passage (34) is arranged to supply part of the leakage steam into the cavity (32) via the through-hole of the first stage guide vane and the through-hole of the first guide vane. [7] Steam turbine (2, 2A, 2C) according to any one of claims 1 to 6, wherein the plurality of rotor blades comprises a first rotor blade which is arranged adjacent to and downstream of the first guide blade in an axial direction of the rotor, wherein the rotor comprises a first disk section (56) to which the first impeller blade is attached, wherein the first disk section (56) has a compensating hole (58) which is formed through the first disk section in the axial direction, and wherein the compensating hole (58) is designed such that part of the steam which is released from the inner ring (26) through the through hole of the first guide vane (22a) into the cavity flows into the compensating hole.

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