Steam turbine

Abstract

Steam turbine (100), comprising: a rotating shaft (O) extending along an axis; several rotor blades (30) extending in a radial direction from an outer circumferential surface of the rotating shaft (O) and arranged in a circumferential direction; a main housing body (2H) that covers the rotating shaft (O) and the rotor blade (30) from an outer circumferential side; and several stator blades (20) extending radially from a position on an upstream side of the rotor blades (30) on an inner circumferential surface of the main housing body (2H) and arranged in the circumferential direction, wherein several water-repellent microgrooves (R) extending in a steam flow direction are formed on a surface of at least one of the rotor blades (30) or at least one of the stator blades (20), and the steam turbine (100) further comprises: a water-repellent film (C) covering the microgrooves (R); and a substance delivery unit (5) configured to deliver a film-forming substance to the surface which has a water-repellent effect towards water droplets condensed on the surface, wherein the substance delivery unit (5) contains: a storage section (51) that stores the film-forming substance; a supply flow path (52) formed within the main housing body (2H) through which the film-forming substance flows, guided by the storage section (51); and a delivery unit (53) that delivers the film-forming substance to the surface, wherein the water-repellent film (C) is formed from the film-forming substance.

Description

[0001] The present disclosure relates to a steam turbine.

[0002] A steam turbine includes a shaft capable of rotating about a rotational axis, a plurality of turbine rotor blade stages arranged at intervals in a rotational axis direction on an outer peripheral surface of the shaft, a casing covering the shaft and the turbine rotor blade stage from an outer peripheral side, and a plurality of turbine stator blade stages arranged alternately with turbine rotor blade stages on an inner peripheral surface of the casing. An inlet port through which steam is sucked from the outside is formed on an upstream side of the casing, and an outlet port is formed on a downstream side thereof. After a flow direction and a velocity of high-temperature and high-pressure steam sucked from the inlet port are adjusted at the turbine stator blade stage, the steam is converted into a rotating power of the shaft at the turbine rotor blade stage.

[0003] The steam flowing through the turbine loses energy from upstream to downstream, and its temperature (and pressure) decreases. Therefore, at the turbine stator blade stage on the downstream side, a portion of the steam condenses and exists in the air stream as fine water droplets, and a portion of the water droplets adheres to the surface of the turbine stator blade. These water droplets rapidly grow on the blade surface to form a liquid film. The liquid film is constantly exposed to a high-speed steam flow around the liquid film. However, as the liquid film continues to grow and thicken, a portion of the liquid film is torn by the steam flow and scattered as coarse droplets. The scattered droplets flow downstream while gradually accelerating due to the steam flow. As the droplet size increases, its mass increases.Accordingly, it is difficult for the steam flow to accelerate to steam velocity, and mainstream steam cannot pass between the turbine rotor blades and collides with them. Since the peripheral speed of the turbine rotor blade can exceed the speed of sound, when scattered droplets collide with the turbine rotor blade, the droplets can erode the surface and cause erosion. Furthermore, the collision of droplets can hinder the rotation of the turbine rotor blade, resulting in loss of braking power.

[0004] To date, various techniques have been proposed to prevent the adhesion and growth of such droplets. For example, PTL 1 below describes a technique for removing moisture generated on a surface of a turbine nozzle (turbine stator blade) by heating the surface with an electric heater. PTL 1 also describes a technique for optimizing the amount of heating by the electric heater by measuring the thickness of a water film.

[0005] PTL 2 discloses a rotor blade for a steam turbine, which at least partially has an erosion protection device to protect against droplet impact erosion. The erosion protection device has a structured surface, with the individual structural elements of the structured surface arranged at a distance from one another such that droplets with an expected average droplet diameter impinge on at least two adjacent structural elements.

[0006] PTL 3 discloses that a turbine engine may include a fan section, a compressor section, a combustion section, and a turbine section in an axial flow arrangement. At least one of the fan section and compressor section may include an airfoil having a leading edge, and a plurality of fins may be arranged on the leading edge.

[0007] PTL 4 discloses a process for improving the efficiency of a steam power plant, the process comprising using steam or water from a steam cycle of a steam power plant and performing a steam cycle treatment on the steam cycle, thereby forming a hydrophobic coating in the steam cycle. Patent literature [PTL 1] JP S57- 3 082 B2 [PTL 2] EP 2 985 420 A1 [PTL 3] US 2018 / 0 283 180 A1 [PTL 4] WO 2019 / 103 799 A1

[0008] However, the velocity of a fluid flowing between turbine stator blades is high enough to reach, for example, 200 to 400 m / s. The thickness of a water film is approximately several hundred micrometers. Therefore, the technique described in PTL 1 may result in a large error in measuring the thickness of the water film, and as a result, moisture may not be properly removed by an electric heating unit.

[0009] The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a steam turbine and blades with further improved performance.

[0010] To solve the above problems, according to one aspect of the present disclosure, a steam turbine is provided according to independent claim 1. Advantageous modifications can be found in dependent claims 2 to 7.

[0011] According to the present disclosure, it is possible to provide a steam turbine and a blade with further improved performance. Fig. 1 is a diagram showing a configuration of a steam turbine according to an embodiment of the present disclosure. Fig. 2 is an enlarged view showing an internal configuration of the steam turbine according to an embodiment of the present disclosure. Fig. 3 is a perspective view showing a configuration of a microgroove according to an embodiment of the present disclosure. Fig. 4 is an explanatory diagram showing dimensions of the microgroove according to an embodiment of the present disclosure. Fig. 5 is a cross-sectional view showing a modification example of the microgroove according to an embodiment of the present disclosure. Fig. 6 is a cross-sectional view showing another modification example of the microgroove according to an embodiment of the present disclosure. Description of embodiments

[0012] Hereinafter, a steam turbine 100 according to an embodiment of the present disclosure will be described with reference to Fig. 1 to 4. As described in Fig. 1 and Fig. 2, the steam turbine includes a steam turbine rotor 1 extending along a direction of a rotation axis O, a steam turbine casing 2 covering the steam turbine rotor 1 from an outer peripheral side, and a substance supply unit 5.

[0013] The steam turbine rotor 1 includes a shaft 3 extending along the rotational axis O and a plurality of rotor blades 30 provided on an outer peripheral surface of the shaft 3. The plurality of rotor blades 30 are arranged at regular intervals in a circumferential direction of the shaft 3. Furthermore, a plurality of rows of rotor blades 30 (rotor blade stages) are arranged at regular intervals in the direction of the rotational axis O. As shown in Fig. As shown in FIG. 2, the rotor blade 30 includes a rotor blade main body 31 (turbine rotor blade) and a rotor blade cover 34. The rotor blade main body 31 protrudes radially outward from an outer peripheral surface of the steam turbine rotor 1. The rotor blade main body 31 has an airfoil-shaped cross section when viewed from a radial direction. The rotor blade cover 34 is provided at a tip portion (radially outer end portion) of the rotor blade main body 31. A platform 32 is integrally provided with the shaft 3 at a base end portion (radially inner end portion) of the rotor blade main body 31.

[0014] As in Fig. 1, the steam turbine casing 2 includes a substantially tubular casing main body 2H (casing main body) covering the steam turbine rotor 1 from the outer peripheral side, and a stator blade 20 provided on an inner peripheral surface of the casing main body 2H. A steam supply pipe (not shown) for introducing steam is provided on one side of the steam turbine casing 2 in the direction of the rotation axis O. A steam discharge pipe (not shown) for discharging steam is provided on the other side of the steam turbine casing 2 in the direction of the rotation axis O. Steam flows within the steam turbine casing 2 from one side to the other side in the direction of the rotation axis O. In the following description, a direction in which steam flows is simply referred to as a "flow direction."Further, a side on which the steam flows is called an upstream side in the flow direction, and a side on which the steam flows away is called a downstream side in the flow direction.

[0015] Several rows of stator blades 20 are provided on an inner peripheral surface of the steam turbine casing 2. As shown in Fig. 2, the stator blade 20 includes a stator blade main body 21 (turbine stator blade), a stator blade cover 22, and an outer peripheral ring 24. The stator blade main body 21 is a blade-shaped member connected to the inner peripheral surface of the steam turbine casing 2 via the outer peripheral ring 24. Further, the stator blade cover 22 is provided at a tip portion (radially inner end portion) of the stator blade main body 21. Similar to the rotor blade 30, a plurality of stator blades 20 are arranged on the inner peripheral surface along the circumferential direction and the direction of the rotation axis O. The rotor blades 30 are arranged to enter regions between the plurality of adjacent stator blades 20. That is, the stator blade 20 and the rotor blade 30 extend in a direction (radial direction with respect to the rotation axis O) that intersects the steam flow direction.In the following description, the stator blade 20 and the rotor blade 30 may be collectively referred to as a blade 90.

[0016] Steam is supplied to the interior of the steam turbine casing 2 via the steam supply pipe on the upstream side. As it flows through the interior of the steam turbine casing 2, steam alternately flows through the stator blades 20 and the rotor blades 30. The stator blade 20 rectifies the flow of steam S, and the rectified mass of steam pushes the rotor blade 30 to impart rotational force to the steam turbine rotor 1. The rotational force of the steam turbine rotor 1 is taken from a shaft end 11 and used to drive an external device (generator or the like). As the steam turbine rotor 1 rotates, steam is discharged to a subsequent device (condenser or the like) through a steam discharge pipe 13 on the downstream side.

[0017] Although not shown in detail, the shaft 3 is rotatably supported within the steam turbine casing 2 by a journal bearing and a thrust bearing.

[0018] Next, a configuration of the stator blade main body 21 will be described with reference to Fig. 2. The stator blade main body 21 extends in the radial direction (radial direction with respect to the rotation axis O), which is a direction intersecting the flow direction. A cross section of the stator blade main body 21 viewed from the radial direction has an airfoil shape. More specifically, a leading edge 21F, which is an end edge on the upstream side in the flow direction, has a curved surface shape. A trailing edge 21R, which is an end edge on the downstream side, has a tapered shape because a dimension in the circumferential direction is gradually reduced when viewed from the radial direction. From the leading edge 21F to the trailing edge 21R, the stator blade main body 21 is smoothly curved from one side in the circumferential direction with respect to the rotation axis O to the other side.Furthermore, the dimension of the stator blade main body 21 decreases toward an inner side in the radial direction in the direction of the rotation axis O. Of a pair of surfaces of the stator blade main body 21 facing the circumferential direction, the surface facing the upstream side is a pressure surface 21P, and the surface facing the downstream side is a negative pressure surface 21Q.

[0019] Of the pressure surface 21P and the negative pressure surface 21Q, a plurality of microgrooves R are formed at least on the pressure surface 21P. The microgroove R is recessed inward from the surface of the stator blade main body 21. The microgrooves R extend in the steam flow direction Fm and are arranged in a direction intersecting the flow direction Fm. The "flow direction Fm" referred to here refers to the curved direction in which steam flows within the steam turbine 100, and is different for each stage of the stator blade 20 and the rotor blade 30. It is preferable that such a "flow direction Fm" be measured and set based on, for example, numerical analysis or verification tests on an actual machine.

[0020] As in Fig. 3, the microgroove R in the present embodiment has a triangular cross-sectional shape. When, as shown in Fig. 4, a cross-sectional shape of the microgroove R is a right-angled isosceles triangle and a distance between vertices t of the microgrooves R is w, further, the value of w is set to satisfy 1 μm ≤ w < 35 μm. Further, it is preferable that a value of a height h from a root portion to the vertex t of the microgroove R is h = w / 2. By setting the height h to such a value, a size of a water droplet can be controlled. Further, during machining, a cutting edge of a tool easily reaches a bottom surface of the microgroove R, and thus both machining accuracy and ease of manufacturing can be achieved.

[0021] Furthermore, as in Fig. 2, it is preferable that the region where the microgroove R is formed is a region on the outer peripheral side where erosion of the rotor blade 30 is particularly problematic, that is, the radially outer end portion of the stator blade main body 21 up to 1 / 3 of the height of the stator blade. The microgroove R may be formed over the entire height of the stator blade.

[0022] It is preferable that the microgroove R, as described above, be formed by applying laser processing to the surface of a metallic material constituting the stator blade main body 21. Meanwhile, as long as a heat resistance requirement is met, it is possible to employ a configuration in which a film-like layer with the microgroove R formed in advance is attached to the stator blade main body 21. Due to the formation of such microgrooves R, the surface of the stator blade main body 21 exhibits water-repellent performance.

[0023] The outer peripheral ring 24 is fixed to a radially outer end portion of the stator blade main body 21. The outer peripheral ring 24 has an annular shape centered on the rotation axis O. Of surfaces of the outer peripheral ring 24, the upstream-side surface is an upstream ring surface 24A, the inner peripheral-side surface is a ring inner peripheral surface 24B, and the downstream-side surface is a downstream ring surface 24C. The upstream ring surface 24A and the downstream ring surface 24C extend in the radial direction with respect to the rotation axis O. A radial dimension of the upstream ring surface 24A is larger than a radial dimension of the downstream ring surface 24C.As a result, in the present embodiment, as an example, the ring inner peripheral surface 24B gradually expands outward in the radial direction toward the downstream side. The outer peripheral ring 24 forms a portion of the steam turbine casing 2. That is, the ring inner peripheral surface 24B is a portion of the inner peripheral surface of the steam turbine casing 2.

[0024] The downstream surface 24C of the ring faces the rotor blade cover 34 of the rotor blade 30 adjacent to the downstream side of the stator blade 20 with a gap S. Of the surfaces of the rotor blade cover 34, the upstream-side surface is a cover upstream surface 34A, the inner peripheral surface is a cover inner peripheral surface 34B, and the downstream-side surface is a cover downstream surface 34C. That is, the above-mentioned downstream surface 24C of the ring faces the cover upstream surface 34A with the gap S.

[0025] Next, the configuration of the substance supply unit 5 will be described with reference to Fig. 1 and Fig. 2. The substance supply unit 5 is provided to supply a film-forming substance (FFS) to cover the above-described microgroove R. A film C having a water-repellent effect is formed on the surface of the microgroove R by the film-forming substance.

[0026] As in Fig. 1, the substance supply unit 5 comprises a storage section 51, a supply flow path 52, and a discharge unit 53. The storage section 51 is a container for storing the film-forming substance. The supply flow path 52 is a flow path formed within the steam turbine casing 2, and the film-forming substance guided from the storage section 51 flows through the supply flow path 52. The supply flow path 52 extends in an annular shape centered on the rotation axis O. In the example of Fig. 1, the supply flow path 52 is formed only in the single-stage stator blade 20 (specifically, the last-stage stator blade 20). However, the supply flow path 52 may be provided correspondingly to the stator blades 20 of all stages.

[0027] As in Fig. 2, an end portion of the supply flow path 52 penetrates the outer peripheral ring 24 in the radial direction and opens to the inner surface (ring inner peripheral surface 24B) in the radial direction. The discharge unit 53 extends radially inward from this opening and thus extends to the inside of the stator blade main body 21. The discharge unit 53 is a flow path that supplies the film-forming substance to the surface of the stator blade main body 21. The discharge unit 53 extends radially from a radially outer end portion of the stator blade main body 21 to a length of 1 / 3 of a blade height. It is also possible to adopt a configuration in which the supply flow path 52 extends over the entire surface in a height direction of the blade.

[0028] The film-forming substance pumped from the storage section 51 by a pump or the like (not shown) is sprayed from an outlet E of the discharge unit 53 onto the pressure surface 21P and the negative pressure surface 21Q through the supply flow path 52. As a result, the film-forming substance forms the water-repellent film C covering at least the microgroove R. A supplied amount of the film-forming substance is preferably 2 to several hundred ppm with respect to a flow rate of a water film formed by the condensation of steam on the pressure surface 21P or on the negative pressure surface 21Q.

[0029] In particular, a volatile amine compound (coating amine) having volatile properties, a surface active effect, and anti-corrosive properties, and a volatile non-amine compound are preferably used as the film-forming substance. When forming the film C, in an embodiment not according to the invention, instead of the configuration in which the film-forming substance is normally supplied, a configuration in which a water-repellent coating is bonded to the pressure surface 21P or to the negative pressure surface 21Q may be used. In this case, it is possible to easily and inexpensively form the film C simply by applying the water-repellent coating to the blade 90. This makes it possible to reduce manufacturing costs and man-hours. (Effect)

[0030] According to the above configuration, the microgroove R is formed on the pressure surface 21P and the negative pressure surface 21Q. As a result, water droplets condensed on the surface of the blade 90 are guided along the microgroove R toward the downstream side of the steam flow direction Fm. As a result, the probability of water droplets growing on the surface of the blade 90 can be reduced.

[0031] Furthermore, since the microgroove R is covered with the film C, the water droplets do not grow in the microgroove R and flow away as fine water droplets. As a result, the generation of coarse water droplets can be suppressed, and the likelihood of erosion occurring in the other blades 90 on the downstream side can be reduced. Furthermore, since frictional resistance to the flow of steam is reduced, the efficiency of the steam turbine 100 can be improved.

[0032] Furthermore, according to the above configuration, since the microgroove R has a triangular cross-section, the contact area between the microgroove R and the water droplet is reduced, and the water droplet can be guided smoothly. Furthermore, since the microgroove R has a simple shape, the cost required for machining can be reduced.

[0033] Since the distance w between the tips t of the microgrooves R according to the above configuration is less than 35 µm, it is, as shown in Fig. 4, it is also possible to prevent a water droplet Wd flowing along the microgrooves R from growing into a coarse water droplet having a diameter of 50 µm or more. Furthermore, the inventors have confirmed that a diameter d of the water droplet Wd can be limited to the same extent as the distance w when the microgroove has a groove shape in which a tip is pointed, as shown in Fig. 5. That is, depending on the shape of the groove, an allowable value of the distance w is 50 µm. This makes it possible to further reduce the probability of erosion occurring at the blade 90 on the downstream side. Furthermore, since the distance w is 1 µm or more, it is possible to prevent the accuracy required for machining the microgroove R from becoming excessively high and ensure ease of manufacturing.

[0034] Furthermore, according to the above configuration, the film-forming substance (FFS) is directly supplied to the surface of the blade 90 through the discharge unit 53. As a result, the water-repellent film C is formed on the surface, and the adhesion probability of condensed water droplets can be reduced. Therefore, the generation of coarse water droplets caused by the growth of small water droplets is suppressed, and the erosion caused by the collision of the coarse water droplets with the rotor blade 30 on the downstream side can be avoided. Furthermore, since the film-forming substance has a turbulent friction reducing effect (Toms effect), it is possible to improve a flow field of the fluid on the surface of the blade 90. Furthermore, since the film-forming substance forms the film C on the metal surface, an anti-corrosion effect can be obtained.Moreover, since the film-forming substance can be normally supplied through the substance supply unit 5, it is possible to suppress the decrease of water repellency due to long-term use to a lesser extent compared with the configuration in which the film C is formed by, for example, coating.

[0035] The embodiment of the present disclosure has been described above. Various changes and modifications to the above configuration are possible as long as they do not deviate from the gist of the present disclosure. For example, in the above embodiment, the configuration in which the microgroove R has a cross-sectional shape of a right-angled isosceles triangle was described. However, the cross-sectional shape of the microgroove R is not limited to the above, and the Fig. 5 or Fig. 6 can be used. As shown in these figures, the cross-sectional shape of the microgroove R is not limited to the right-angled, isosceles triangle. In the example of Fig. 5, the microgroove Rb has a curved cross-sectional shape that is concave from the surface of the blade 90 and convex inward. According to this configuration, since a slope near a vertex is almost perpendicular to the surface of the blade 90, the diameter of the water droplet can be suppressed to a smaller value than in the case of a triangular groove. That is, in a case where the vicinity of the vertex, as in Fig. 5, when the pitch w of the microgroove Rb is less than 50 μm, the water droplet Wd flowing along the microgroove R can be prevented from growing into a coarse water droplet having a diameter of 50 μm or more. This makes it possible to further reduce the probability of erosion occurring at the blade 90 on the downstream side.

[0036] Furthermore, in the example of Fig. 6, a flat, flat-spreading bottom surface P is formed between the microgrooves Rc. Even with such a configuration, the same action and effect as those described above can be achieved.

[0037] Furthermore, a configuration is adopted in which the film C is formed on the surface of the rotor blade 30 in addition to the stator blade 20, and thus the film C formed on the surface of the rotor blade 30 can improve corrosion protection performance of the rotor blade 30. In this case, it is conceivable that a flow path is formed within the shaft 3 and a film-forming substance is supplied from the flow path to the surface of the rotor blade 30, or that a coating is applied to the surface of the rotor blade 30. Since the stator blade 20 and a means for supplying the film-forming substance can be used together, rust protection of the rotor blade 30 can be improved with a minimal configuration.

[0038] Further, a configuration in which the microgroove R is covered with the film-forming substance supplied from the substance supply unit 5 described in the above-described embodiment and a configuration in which the surface of the blade 90 is coated in advance as the film C may be combined.

[0039] Since the above-mentioned microgroove R itself has water-repellent effect due to its shape, it is possible to use a configuration in which the film C is not provided and only the microgroove R has water-repellent effect against water droplets.

[0040] The steam turbine 100 described in each embodiment is understood, for example, as follows. (1) According to a first aspect, there is provided a steam turbine 100 comprising: a shaft 3 extending along a rotation axis O; a plurality of rotor blades 30 extending in a radial direction from an outer peripheral surface of the shaft 3 and arranged in a circumferential direction; a casing main body (casing main body 2H) covering the shaft 3 and the rotor blade 30 from an outer peripheral side; and a plurality of stator blades 20 extending in the radial direction from a position on an upstream side of the rotor blade 30 on an inner peripheral surface of the casing main body and arranged in the circumferential direction, wherein a plurality of water-repellent microgrooves R extending in a steam flow direction Fm are formed on a surface of at least one of the rotor blade 30 and the stator blade 20.

[0041] According to the above configuration, the microgroove R is formed on the surface of at least one of the rotor blade 30 and the stator blade 20. As a result, water droplets condensed on the surface of the blade 90 flow along the microgroove R toward the downstream side in the steam flow direction Fm. As a result, the probability of water droplets growing on the surface of the blade 90 can be reduced. (2) In the steam turbine 100 according to a second aspect, the microgroove R may have a triangular cross-sectional shape recessed from the surface.

[0042] According to the above configuration, the contact area between the microgroove R and the water droplet is reduced, and the water droplet can be guided smoothly. Furthermore, since the microgroove R has a simple shape, the machining costs required can be reduced. (3) In the steam turbine 100 according to a third aspect, the microgroove Rb may have a curved cross-sectional shape that is concave from the surface and convex inward.

[0043] According to the above configuration, since the microgroove Rb has a curved cross section, the contact area between the microgroove Rb and the water droplet is further reduced, and the water droplet can be guided more smoothly. (4) In the steam turbine 100 according to a fourth aspect, when w is a distance between peaks t of the microgrooves R, 1 µm ≤ w < 35 µm can be set.

[0044] Since the distance w between the tips t of the microgrooves R is less than 35 μm according to the above configuration, it is possible to prevent water droplets Wd flowing along the microgrooves R from growing into coarse water droplets with a diameter of 50 μm or more. This makes it possible to further reduce the probability of erosion occurring at the blade 90 on the downstream side. (5) In the steam turbine 100 according to a fifth aspect, when w is a distance between peaks t of the microgrooves R, 1 µm ≤ w < 50 µm can be set.

[0045] Since the distance w between the tips t of the microgrooves R is less than 50 μm according to the above configuration, it is possible to prevent the water droplets Wd flowing along the microgrooves R from growing into coarse water droplets with a diameter of 50 μm or more. This makes it possible to further reduce the probability of erosion occurring at the blade 90 on the downstream side. (6) The steam turbine 100 according to a sixth aspect may further include a water-repellent film C covering the microgroove R.

[0046] Since the microgroove R is covered with the film C according to the above configuration, the water droplets do not grow in the microgroove R and flow away as fine water droplets. As a result, the generation of coarse water droplets can be suppressed, and the likelihood of erosion occurring in the other blades 90 on the downstream side can be reduced. Furthermore, since frictional resistance to the flow of steam is reduced, the efficiency of the steam turbine 100 can be improved. (7) The steam turbine 100 according to a seventh aspect may further include a substance supply unit 5 that supplies a film-forming substance having a water-repellent effect against water droplets condensed on the surface to the surface, wherein the substance supply unit 5 may include a storage portion 51 that stores the film-forming substance, a supply flow path 52 formed inside the casing main body and through which the film-forming substance supplied from the storage portion 51 flows, and a discharge unit 53 formed inside at least one of the rotor blade 30 and the stator blade 20 and that supplies the film-forming substance to the surface, and the film C may be formed from the film-forming substance.

[0047] According to the above configuration, the film-forming substance (FFS) is directly supplied to the surface of at least one of the rotor blade 30 and the stator blade 20 through the discharge unit 53. As a result, the water-repellent film C is formed on the surface, and the adhesion probability of condensed water droplets can be reduced. Therefore, the generation of coarse water droplets caused by the growth of small water droplets is suppressed, and the erosion caused by the collision of the coarse water droplets with the rotor blade 30 on the downstream side can be avoided. Furthermore, since the film-forming substance has a turbulent friction reducing effect (Toms effect), it is also possible to improve a flow field of fluid on the surface of at least one of the rotor blade 30 and the stator blade 20.Furthermore, since the film-forming substance forms film C on the metal surface, an anti-corrosive effect can be obtained. Furthermore, since the film-forming substance can be normally supplied through the substance supply unit 5, it is possible to prevent a decrease in water-repellent effect due to long-term use. (8) In the steam turbine 100 according to an eighth aspect, in addition to the features of the seventh aspect, a coating formed of a water-repellent material and bonded to the surface may be provided. (9) In the steam turbine 100 according to a ninth aspect, there is provided a blade 90 extending in a steam flow direction Fm and including a water-repellent microgroove R formed on a surface of the blade 90.

[0048] According to the above configuration, the microgroove R is formed on a surface of a main body of the blade 90. As a result, water droplets condensed on the surface of the blade 90 flow along the microgroove R toward the downstream side in the steam flow direction Fm. As a result, the probability of water droplets growing on the surface of the blade 90 can be reduced. (10) In the steam turbine 100, the microgroove R may have a triangular cross-sectional shape recessed from the surface.

[0049] According to the above configuration, the contact area between the microgroove R and the water droplet is reduced, and the water droplet can be guided smoothly. Furthermore, since the microgroove R has a simple shape, the machining costs required can be reduced. (11) In the steam turbine 100 according to an eleventh aspect, the microgroove Rb may have a curved cross-sectional shape that is concave from the surface and convex inward.

[0050] According to the above configuration, since the microgroove Rb has a curved cross section, the contact area between the microgroove Rb and the water droplet is further reduced, and the water droplet can be guided more smoothly. (12) In the steam turbine 100 according to a twelfth aspect, when w is a distance between peaks t of the microgrooves R, 1 µm ≤ w < 35 µm can be set.

[0051] Since the distance w between the tips t of the microgrooves R is less than 35 μm according to the above configuration, it is possible to prevent water droplets Wd flowing along the microgrooves R from growing into coarse water droplets with a diameter of 50 μm or more. This makes it possible to further reduce the probability of erosion occurring at the blade 90 on the downstream side. (13) In the steam turbine 100 according to a thirteenth aspect, when w is a distance between peaks t of the microgrooves R, 1 µm ≤ w < 50 µm can be set.

[0052] Since the distance w between the tips t of the microgrooves R is less than 50 μm according to the above configuration, it is possible to prevent the water droplets Wd flowing along the microgrooves R from growing into coarse water droplets with a diameter of 50 μm or more. This makes it possible to further reduce the probability of erosion occurring at the blade 90 on the downstream side. (14) In the steam turbine 100 of a fourteenth aspect, it may further include a water-repellent film covering the microgroove R.

[0053] Since the microgroove R is covered with the film according to the above configuration, water droplets do not grow in the microgroove R and flow away as fine water droplets. As a result, the generation of coarse water droplets can be suppressed, and the likelihood of erosion occurring in the other blades 90 on the downstream side can be reduced. Furthermore, since frictional resistance to the flow of steam is reduced, the efficiency of the steam turbine 100 can be improved.

[0054] According to the present disclosure, it is possible to provide a steam turbine with further improved performance. 100 steam turbines 1 steam turbine rotor 2 steam turbine casings 2H housing main body 3 Wave 5 Substance supply unit 20 stator blades 21 Stator blade main body 21F leading edge 21P printing area 21Q negative pressure area 21R trailing edge 22 Stator blade cover 24 Outer circumference ring 24A upstream surface of ring 24B Ring inner peripheral surface 24C downstream surface of ring 30 rotor blades 31 Rotor blade main body 32 Platform 34 Rotor blade cover 34A upstream surface of cover 34B Cover inner peripheral surface 34C downstream surface of cover 51 storage section 52 Supply flow path 53 dispensing unit 90 shovel C-Film Fm steam flow direction O axis of rotation P floor area R, Rb, Rc microgroove t tip

Claims

[1] Steam turbine (100), comprising: a rotary shaft (O) extending along an axis; a plurality of rotor blades (30) extending from an outer peripheral surface of the rotary shaft (O) in a radial direction and arranged in a circumferential direction; a casing main body (2H) covering the rotary shaft (O) and the rotor blade (30) from an outer peripheral side; and a plurality of stator blades (20) extending from a position on an upstream side of the rotor blades (30) on an inner peripheral surface of the casing main body (2H) in the radial direction and arranged in the circumferential direction, wherein a plurality of water-repellent microgrooves (R) extending in a steam flow direction are formed on a surface of at least one of the rotor blades (30) or at least one of the stator blades (20), and wherein the steam turbine (100) further comprises: a water-repellent film (C) covering the microgrooves (R); and a substance supply unit (5) configured to supply the surface with a film-forming substance having a water-repellent effect against water droplets condensed on the surface, wherein the substance supply unit (5) contains: a storage section (51) which stores the film-forming substance; a supply flow path (52) formed within the housing main body (2H) and through which the film-forming substance supplied from the storage section (51) flows; and a delivery unit (53) which delivers the film-forming substance to the surface, wherein the water-repellent film (C) is formed from the film-forming substance. [2] The steam turbine (100) of claim 1, wherein each of the microgrooves (R) has a triangular cross-sectional shape recessed from the surface. [3] Steam turbine (100) according to claim 2, wherein when w is a distance between tips of the microgrooves (R), 1 µm ≤ w < 35 µm. [4] The steam turbine (100) of claim 1, wherein each of the microgrooves (R) has a curved cross-sectional shape that is concave from the surface and convex inwardly. [5] The steam turbine (100) according to claim 1, wherein when w is a distance between tips of the microgrooves, 1 µm ≤ w < 50 µm. [6] Steam turbine (100) according to claim 1, wherein the discharge unit (53) is formed within the at least one of the rotor blades (30) or the at least one of the stator blades (20). [7] Steam turbine (100) according to claim 1, wherein the output unit (53) is formed within at least one of the rotor blade (30) and the stator blade (20).

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