Turbine stator blades and steam turbines

Abstract

The turbine stator blade comprises: a stator blade body extending in a radial direction intersecting with the flow direction of the steam; a recovery portion formed on the surface of the stator blade body, recovering the liquid film flowing along the surface; and a central area formed on the surface of the stator blade body, having a plurality of first fine grooves extending from the upstream side of the flow direction toward the recovery portion, wherein the intervals between adjacent first fine grooves become narrower as the distance from the upstream side approaches the recovery portion.

Description

Technical Field

[0001] The present invention relates to a turbine stator blade and a steam turbine.

[0002] This application claims priority to Japanese Patent Application No. 2021-106944 filed in Japan on June 28, 2021, and incorporates the contents herein. Background Art

[0003] A steam turbine comprises a rotating shaft rotatable about its axis; a plurality of turbine blade rows arranged axially and spaced apart on the outer circumference of the shaft; a casing covering the shaft and turbine blade rows from the outer circumference; and a plurality of turbine stator blade rows radially supported by inner and outer rings on the inner circumference of the casing. Each turbine blade row has a plurality of rotor blades arranged circumferentially of the shaft, and each turbine stator row has a plurality of stator blades arranged circumferentially of the shaft. Turbine blade rows are arranged adjacent to each other axially downstream of the turbine stator rows to form a stage. An intake port connected to an inlet pipe for drawing in steam from the outside is formed on the upstream side of the casing, and an exhaust chamber is formed on the downstream side. Steam generated in the boiler has its pressure and temperature regulated by a regulating valve, and its flow rate regulated by a turbine inlet valve before flowing into the turbine. The high-temperature, high-pressure steam drawn in from the inlet pipe has its flow direction and velocity regulated in the turbine stator rows, where it is converted into rotational force for the rotating shaft.

[0004] The steam passing through the turbine loses energy as it moves from the upstream side to the downstream side, and its temperature (and pressure) decreases. In particular, steam turbines for thermal power generation are generally composed of a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine. In the two stages (a pair of turbine stator blades and a turbine rotor blade cascade) counting from the most downstream side of the low-pressure turbine, a gas-liquid two-phase flow environment is formed. As a result, in the most downstream stage, part of the steam liquefies and exists in the airflow as tiny droplets (water droplets), and part of these droplets adhere to the surface of the turbine stator blades. These droplets exist on the surface of the turbine stator blades from the upstream side to the downstream side, and these droplets grow by gathering on the blade surface and form a liquid film. The liquid film is always exposed to the high-speed steam flow. If the liquid film grows further and its thickness increases, part of it is torn apart by the steam flow and scattered to the downstream side as coarse droplets. The larger the droplets, the greater the inertia force, so they cannot pass between the turbine rotor blades along the steam flow, but collide with the turbine rotor blades. The circumferential speed of the turbine blades increases toward the front end, sometimes exceeding the speed of sound. Therefore, when scattered liquid droplets collide with the turbine blades, erosion may occur on the blade surfaces. Furthermore, the collision of the liquid droplets may hinder the rotation of the turbine blades, resulting in braking loss.

[0005] To prevent this type of erosion, various technologies have been proposed. For example, in the steam turbine described in Patent Document 1 below, a guide groove is formed on the surface of the turbine blades. By directing liquid droplets along these guide grooves, it is possible to prevent the droplets from flowing toward the tip of the turbine blades, where the circumferential speed is high.

[0006] Previous technical literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Publication No. 2016-166569 Summary of the Invention

[0009] Technical issues to be solved by the invention

[0010] However, as mentioned above, simply restricting the flow of liquid droplets on turbine blades cannot be a fundamental solution to erosion. Therefore, there is an increasing demand for technology that can suppress or recover liquid droplets on turbine blades.

[0011] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a turbine stator blade and a steam turbine that can more effectively suppress or recover liquid droplets.

[0012] Means for solving technical problems

[0013] In order to solve the above-mentioned problems, the turbine stator blade involved in the present invention comprises: a stator blade body, extending in a radial direction intersecting with the flow direction of steam; a recovery portion, formed on the surface of the stator blade body, recovering the liquid film flowing along the surface; and a central area, formed on the surface of the stator blade body, having a plurality of first fine grooves extending from the upstream side of the flow direction toward the recovery portion, and the intervals between adjacent first fine grooves become narrower as they approach the recovery portion from the upstream side.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to provide a turbine stator blade and a steam turbine capable of more effectively suppressing or recovering liquid droplets. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a cross-sectional view showing the structure of a steam turbine according to an embodiment of the present invention.

[0017] Figure 2 This is an enlarged cross-sectional view showing a main portion of a steam turbine according to an embodiment of the present invention.

[0018] Figure 3 It is a cross-sectional view showing the shape of a fine groove according to an embodiment of the present invention.

[0019] Figure 4 It is a diagram showing a first modified example of the turbine stator blade according to the embodiment of the present invention.

[0020] Figure 5 It is a diagram showing a second modified example of the turbine vane according to the embodiment of the present invention.

[0021] Figure 6 It is a cross-sectional view showing a first modified example of the fine groove according to the embodiment of the present invention.

[0022] Figure 7 It is a cross-sectional view showing a second modified example of the fine groove according to the embodiment of the present invention.

[0023] Figure 8 It is a cross-sectional view showing a third modified example of the fine groove according to the embodiment of the present invention.

[0024] Figure 9 It is a cross-sectional view showing a fourth modified example of the fine groove according to the embodiment of the present invention. DETAILED DESCRIPTION

[0025] (Structure of a steam turbine)

[0026] Below, reference Figure 1 and Figure 2 The steam turbine 1 and the stator blade 10 (turbine stator blade) according to the embodiment of the present invention will be described. Figure 1 As shown, the steam turbine 1 includes a rotor 2 and a casing 3 .

[0027] The rotor 2 includes a rotating shaft 6 having a circular cross-section extending along an axis O, and a plurality of moving blade cascades 7 disposed on the outer circumference of the rotating shaft 6. The rotating shaft 6 is rotatable about the axis O. The plurality of moving blade cascades 7 are arranged at intervals along the axis O. Each moving blade cascade 7 includes a plurality of moving blades 8 arranged circumferentially about the axis O. The moving blades 8 extend radially outward from the outer circumference of the rotating shaft 6. The detailed structure of the moving blades 8 will be described later.

[0028] The casing 3 includes a casing body 3H that covers the rotor 2 from the outer circumference, and a plurality of stationary blade cascades 9 supported from the outer circumference and inner circumference by an outer ring 21 (described later) and an inner ring 23 (described later) provided on the inner circumference of the casing body 3H. The casing body 3H is cylindrical with the axis O as the center. The plurality of stationary blade cascades 9 are arranged at intervals in the direction of the axis O. The steam turbine 1 includes the same number of moving blade cascades 7 as the stationary blade cascades 9, with one moving blade cascade 7 being located between a pair of adjacent stationary blade cascades 9 in the direction of the axis O. That is, the moving blade cascades 7 and the stationary blade cascades 9 are arranged alternately in the direction of the axis O. One stationary blade cascade 9 and one moving blade cascade 7 form one "stage". Each stationary blade cascade 9 includes a plurality of stationary blades 10 arranged in the circumferential direction of the axis O. The stationary blades 10 extend in the radial direction relative to the axis O.

[0029] A steam flow path 11 is formed on one side of the housing body 3H in the direction of the axis O. This steam flow path 11 is used to draw high-temperature, high-pressure steam introduced from the inlet pipe into the stages of the housing body 3H. An exhaust chamber 12 is provided on the other side of the housing body 3H in the direction of the axis O to perform pressure recovery of the steam.

[0030] The steam flowing into the steam flow path 11 flows through the stages within the housing body 3H, then passes through the exhaust chamber 12 and is delivered to the condenser (not shown). In the following description, the side where the steam flow path 11 is located, as viewed from the exhaust chamber 12, is referred to as the upstream side in the steam flow direction. The side where the exhaust chamber 12 is located, as viewed from the steam flow path 11, is referred to as the downstream side.

[0031] (Structure of the moving blade)

[0032] like Figure 2 As shown, the moving blade 8 has a platform 81, a moving blade body 82 and a shroud 83. The platform 81 is provided on the outer peripheral surface of the rotating shaft 6 (the rotating shaft outer peripheral surface 6A). The moving blade body 82 is provided on the outer peripheral side of the platform 81. The moving blade body 82 extends in the radial direction and has a blade-shaped cross-sectional shape when viewed from the radial direction. As an example, the moving blade body 82 is formed so that the dimension in the direction of the axis O gradually decreases as it goes from the radial inside to the outside. A shroud 83 is provided at the radially outer end of the moving blade body 82. The shroud 83 has a substantially rectangular cross-sectional shape with the axis O direction as the longitudinal direction. The outer peripheral surface of the shroud 83 is radially opposed to the inner peripheral surface of the casing body 3H (the casing inner peripheral surface 3A).

[0033] (Structure of stationary blades)

[0034] The stator blade 10 includes an outer ring 21, a stator blade body 22 (blade body), and an inner ring 23. The stator blade body 22 includes a central region 41, an outer region 42, an inner region 43, and a slit 13 (recovery portion 14). The outer ring 21 is annular centered on the axis O. The outer ring 21 is supported by the casing body 3H via a support member (not shown). The stator blade body 22 is fixedly mounted between the outer ring 21 and the inner ring 23. The stator blade body 22 extends radially inward from the outer ring inner circumferential surface 21A and has a blade-like cross-sectional shape when viewed radially. That is, the stator blade body 22 extends in a direction intersecting the direction of steam flow. For example, the dimension of the stator blade body 22 in the direction of the axis O gradually decreases as it moves radially inward. The inner ring 23 is provided at the radially inner end of the stator blade body 22. The inner ring 23 has a generally rectangular cross-sectional shape, with the axis O direction as its longitudinal direction. The inner peripheral surface of the inner ring 23 faces the rotating shaft outer peripheral surface 6A with a gap therebetween in the radial direction.

[0035] A central region 41, an outer region 42, an inner region 43, and slits 13 are formed on the surface of the vane body 22 (more specifically, the upstream-facing surface (ventral surface) of both surfaces in the thickness direction of the vane body 22). A plurality of fine grooves 5, recessed inward from the surface of the vane body 22, are formed in these central region 41, outer region 42, and inner region 43. The fine grooves 5 are provided to transfer droplets generated on the surface of the vane body 22 downstream along the steam flow. The fine grooves 5 are arranged at intervals in the radial direction.

[0036] The fine grooves 5 (first fine grooves 51) formed in the central region 41 have the spacing between adjacent first fine grooves 51 narrow as they move from the leading edge 22a of the vane body 22 toward the trailing edge 22b. In other words, the radial dimension of the central region 41 gradually decreases as it moves from the leading edge 22a toward the trailing edge 22b. The downstream ends of these first fine grooves 51 communicate with the slits 13, described below.

[0037] The outer region 42 is formed radially outward of the central region 41. The fine groove 5 (second fine groove 52) formed in the outer region 42 curves radially outward as it moves from the leading edge 22a toward the downstream side. The downstream end of the second fine groove 52 is connected to the inner circumferential surface of the outer ring 21.

[0038] The inner region 43 is formed radially inward of the central region 41. The fine groove 5 (third fine groove 53) formed in the inner region 43 curves radially inward as it moves from the leading edge 22a side toward the downstream side. The downstream end of the third fine groove 53 extends to the radially inner region of the trailing edge 22b (near the inner ring 23).

[0039] On the front edge 22 a side, the central region 41 (first fine groove 51 ) occupies the largest ratio, and the areas occupied by the outer region 42 and the inner region 43 are smaller than the area occupied by the central region 41 .

[0040] On the trailing edge 22b side of the central region 41, a slit 13 is formed as a recovery portion 14 for recovering the liquid film flowing through the first fine groove 51. The slit 13 extends along the trailing edge 22b. The slit 13 is one or more elongated holes communicating with the interior of the stator blade body 22. In other words, the stator blade body 22 is hollow. The interior of the stator blade body 22 is preferably maintained at a negative pressure by a device (not shown).

[0041] Next, refer to Figure 3 , the size of the fine groove 5 is described. Figure 3 As shown, in this embodiment, the fine groove 5 has a rectangular cross-sectional shape. When the spacing (pitch) between adjacent fine grooves 5 is denoted by p, the depth of the fine groove 5 is denoted by h, the width of the opening is denoted by w, and the width of the bottom portion is denoted by b, the desired w value is 0.3 to 2.0 mm. Furthermore, the desired b / w value is 0 to 2.0 (as will be described in detail later; a value of 0 corresponds to a case where the fine groove 5 has a triangular cross-sectional shape). Furthermore, the desired h / w ​​value is 0.5 to 2.0. The desired p / w value is 0.5 to 3.0.

[0042] (Effect)

[0043] Next, the operation of the steam turbine 1 involved in this embodiment and the operation of the droplets in the stationary blades 10 are described. When the steam turbine 1 is operated, first, high-temperature and high-pressure steam is introduced into the interior of the casing body 3H through the steam flow path 11. The steam alternately passes through the above-mentioned stationary blade cascade 9 and the moving blade cascade 7 while flowing toward the downstream side inside the casing body 3H. The stationary blade cascade 9 straightens the steam flow so that it flows into the moving blade cascade 7 adjacent to the downstream side. Since the steam acts on the moving blade cascade 7, torque is applied to the rotating shaft 6 through the moving blade cascade 7. Due to this torque, the rotor 2 rotates around the axis O. The rotational energy of the rotor 2 is extracted from the shaft end and used to drive the generator (not shown) and the like.

[0044] Here, the steam passing through the stages in the main flow path of the turbine converts energy into rotational energy each time it passes through the stages from the upstream side to the downstream side, and the temperature (and pressure) decreases. As a result, in the stator blade cascade 9 on the most downstream side, part of the steam liquefies and exists in the airflow as tiny droplets, and part of the droplets adheres to the surface of the stator blade 10 (stator blade body 22). The droplets grow and become a liquid film. In addition, as the droplets continue to increase, if the thickness of the liquid film increases as it flows downstream, part of it is torn apart by the steam flow, or the liquid film attached to the stator blade cascade is scattered from the trailing edge of the stator blade as coarse droplets. The scattered droplets flow toward the downstream side while being gradually accelerated by the steam flow. If the coarse droplets collide with the moving blade 8 on the downstream side, erosion may occur on the surface of the moving blade 8. In addition, the collision of the droplets may also hinder the rotation of the moving blade 8 (rotor 2) and cause braking loss.

[0045] Therefore, in this embodiment, as described above, a plurality of fine grooves 5 are formed on the surface of the stationary blade body 22. The droplets captured in the fine grooves 5 flow toward the downstream side along the steam flow. In the central area 41, the droplets flow along the first fine grooves 51 toward the slits 13. The droplets are recovered by the negative pressure of the slits 13. Furthermore, in the outer area 42, the droplets flow radially outward along the second fine grooves 52 and are guided to the inner circumferential surface of the outer ring 21. In other words, the droplets do not reach the moving blades 8 on the downstream side. Similarly, in the inner area 43, the droplets flow radially inward along the third fine grooves 53. As a result, the droplets do not reach the leading end of the moving blades 8, which have a high circumferential speed.

[0046] In particular, according to the above structure, the spacing between the first fine grooves 51 narrows as the distance from the upstream side approaches the recovery section 14 (slit 13). As a result, the liquid film or droplets can be guided toward the recovery section 14 from a wider range than the upstream side. Furthermore, the size of the recovery section 14 itself can be suppressed to a smaller size. As a result, the possibility of affecting the main flow of the steam can be reduced compared to a case where the recovery section 14 is ensured to be larger.

[0047] Furthermore, the above configuration allows the second fine grooves 52 to guide the liquid film generated radially outside the central region 41 further radially outward (e.g., toward the inner circumferential surface of the outer ring 21). This further reduces the possibility of liquid droplets scattering downstream of the vane body 22.

[0048] Furthermore, according to the above configuration, the liquid film generated radially inwardly of the central region 41 can be guided further radially inwardly by the third fine grooves 53. This further reduces the possibility of liquid droplets scattering downstream of the stationary blade body 22.

[0049] (Other embodiments)

[0050] The embodiments of the present invention have been described above. However, various changes or improvements can be made to the above configuration without departing from the spirit of the present invention.

[0051] For example, as a first modification of the stationary blade 10, Figure 4 The structure shown. In this first modified example, the first fine groove 51b is curved in a radially outward manner as it moves from the leading edge 22a side to the slit 13 side. In addition, as it moves toward the slit 13, the angle formed by the direction in which the first fine groove 51b extends relative to the flow direction F of the steam, that is, the steering angle, gradually becomes smaller. That is, in the portion on the slit 13 side of the first fine groove 51b, the radius of curvature becomes larger than that of the portion on the leading edge 22a side. In other words, the rate of increase of the steering angle gradually becomes smaller as it moves from the leading edge 22a side to the slit 13 side. Alternatively, the portion on the slit 13 side may be set as a clothoid curve.

[0052] According to the above structure, the direction in which the first fine grooves 51b extend changes along the flow direction of the vapor as it approaches the slit 13. As a result, the flow velocity of the liquid film increases as it approaches the slit 13, allowing for more efficient recovery of the liquid film.

[0053] In addition, as a second modification of the stationary blade 10, it is also possible to adopt Figure 5 The structure shown in FIG. In this second modified example, a main groove 51c and a sub-groove 51d are formed in the central region 41 as the fine grooves 5. The main grooves 51c extend from the leading edge 22a toward the slit 13, and the intervals between adjacent main grooves 51c narrow. The sub-groove 51d originates from the leading edge 22a and merges with one of the main grooves 51c at its end point. This structure allows the liquid film to be recovered over a wider area than the leading edge 22a.

[0054] Furthermore, in the above embodiment, the example in which the fine groove 5 has a rectangular cross-sectional shape is described. However, as long as the above-mentioned dimensional conditions are met, the shape of the fine groove 5 can be changed in various ways. For example, Figure 6 As shown in FIG, the width b of the bottom portion can also be made larger than the width w of the opening portion (b>w). Figure 7 As shown in FIG, the width b of the bottom portion can also be made smaller than the width w of the opening portion (b<w). Figure 8 As shown in FIG, the cross-sectional shape of the fine groove 5 can also be set to a triangle (b=0). Figure 9 As shown, the bottom portion may also be arc-shaped.

[0055] <Note>

[0056] The device X described in each embodiment can be understood, for example, as follows.

[0057] (1) The turbine stator blade (stator blade 10) involved in the first embodiment comprises: a stator blade body 22 extending in a radial direction intersecting the flow direction of steam; a recovery portion 14 formed on the surface of the stator blade body 22, which recovers the liquid film flowing along the surface; and a central area 41 formed on the surface of the stator blade body 22, in which a plurality of first fine grooves 51 extending from the upstream side of the flow direction toward the recovery portion 14 are formed, and the intervals between adjacent first fine grooves 51 become narrower as they approach the recovery portion 14 from the upstream side.

[0058] According to the above structure, the spacing between the first fine grooves 51 narrows as the liquid film approaches the recovery section 14 from the upstream side. This allows the liquid film to be guided toward the recovery section 14 from a wider range than the upstream side. Furthermore, the size of the recovery section 14 itself can be kept small, thereby reducing the possibility of affecting the main flow of the vapor.

[0059] (2) In the turbine vane (vane 10 ) according to the second embodiment, the angle formed by the direction in which the first fine groove 51 b extends relative to the flow direction, that is, the turning angle, may gradually decrease as the direction approaches the recovery portion 14 .

[0060] According to the above configuration, the direction in which the first fine grooves 51b extend changes along the flow direction of the vapor as it approaches the recovery unit 14. Thus, the flow velocity of the liquid film increases as it approaches the recovery unit 14, allowing for more efficient recovery of the liquid film.

[0061] (3) In the turbine vane (vane 10) according to the third embodiment, the rate of increase of the turning angle, which is the angle formed by the extending direction of the first fine groove 51b with respect to the flow direction, may gradually decrease as the vane approaches the recovery portion 14.

[0062] According to the above configuration, the rate of increase of the turning angle of the first fine groove 51b gradually decreases as it approaches the recovery portion 14. Thus, the flow velocity of the liquid film increases as it approaches the recovery portion 14, allowing the liquid film to be recovered more efficiently.

[0063] (4) The turbine stator blade (stator blade 10) involved in the fourth embodiment can also have an outer region 42, which is formed radially outside the central region 41 in the surface of the stator blade body 22 and has a plurality of second fine grooves 52 extending radially outward as it goes from the upstream side to the downstream side.

[0064] With this configuration, the liquid film generated radially outside the central region 41 can be guided further radially outward (e.g., to the inner circumferential surface of the outer ring 21) by the second fine grooves 52. This further reduces the possibility of liquid droplets scattering downstream of the vane body 22.

[0065] (5) The turbine stator blade (stator blade 10) involved in the fifth embodiment can also have an inner area 43, which is formed radially inside the central area 41 in the surface of the stator blade body 22 and has a plurality of third fine grooves 53 extending radially inside as it goes from the upstream side to the downstream side.

[0066] According to the above configuration, the liquid film generated radially inwardly of the central region 41 can be guided further radially inwardly by the third fine grooves 53. This further reduces the possibility of liquid droplets scattering downstream of the stationary blade body 22.

[0067] (6) The steam turbine 1 involved in the sixth embodiment comprises: a rotating shaft 6 extending along the axis O; a plurality of turbine blades (blades 8) extending radially outward from the outer peripheral surface of the rotating shaft 6 and arranged circumferentially; a casing 3 covering the rotating shaft 6 and the plurality of turbine blades from the outside; and turbine stator blades (stator blades 10) involved in any of the above embodiments, extending radially inward from the inner peripheral surface of the casing 3 and arranged circumferentially in plurality.

[0068] According to the above configuration, it is possible to provide the steam turbine 1 in which erosion caused by droplets scattering toward the downstream side is suppressed.

[0069] Industrial applicability

[0070] According to the present invention, it is possible to provide a turbine stator blade and a steam turbine capable of more effectively suppressing or recovering liquid droplets.

[0071] Explanation of symbols

[0072] 1-steam turbine, 2-rotor, 3-casing, 3A-casing inner circumference, 3H-casing body, 5-fine groove, 6-rotating shaft, 6A-rotating shaft outer circumference, 7-moving blade cascade, 8-moving blade (turbine moving blade), 9-stationary blade cascade, 10-stationary blade (turbine stationary blade), 11-steam flow path, 12-exhaust chamber, 13-slit, 14-recovery part, 21-outer ring, 21A-outer ring inner circumference, 22-stationary blade body (blade body), 22a-leading edge, 22b-trailing edge, 23-inner ring, 41-center area, 42-outer area, 43-inner area, 51, 51b-first fine groove, 51c-main groove, 51d-secondary groove, 52-second fine groove, 53-third fine groove, 81-platform, 82-moving blade body, 83-shroud, O-axis line.

Claims

1. A turbine stator blade comprising: a stationary blade body extending in a radial direction intersecting the flow direction of the steam and having a leading edge on the upstream side and a trailing edge on the downstream side in the flow direction; a recovery portion formed on a surface of the stationary blade body, extending in a radial direction along the trailing edge and recovering a liquid film flowing along the surface of the stationary blade body; and A central region is formed on the surface of the stationary blade body and has a plurality of first fine grooves extending from the upstream side in the flow direction toward the recovery portion. The size of the leading edge of the central area in the radial direction is larger than the size of the recovery portion in the radial direction. The intervals between adjacent first fine grooves become narrower as they go from the upstream side toward the recovery portion.

2. The turbine stator blade according to claim 1, wherein: As the flow moves toward the recovery portion, the angle formed by the direction in which the first fine groove extends relative to the flow direction, ie, the turning angle, gradually decreases.

3. The turbine stator blade according to claim 1, wherein: As the angle of the direction in which the first fine groove extends relative to the flow direction, that is, the rate of increase of the turning angle gradually decreases toward the recovery portion.

4. A turbine stator blade comprising: The stationary blade body extends in a radial direction intersecting the flow direction of the steam; a recovery portion formed on a surface of the stationary blade body for recovering a liquid film flowing along the surface; and A central region is formed on the surface of the stationary blade body and has a plurality of first fine grooves extending from the upstream side in the flow direction toward the recovery portion. As the distance from the upstream side to the recovery portion increases, the intervals between the adjacent first fine grooves decrease. As the flow moves toward the recovery portion, the angle formed by the direction in which the first fine groove extends relative to the flow direction, ie, the turning angle, gradually decreases.

5. A turbine stator blade comprising: The stationary blade body extends in a radial direction intersecting the flow direction of the steam; a recovery portion formed on a surface of the stationary blade body for recovering a liquid film flowing along the surface; and A central region is formed on the surface of the stationary blade body and has a plurality of first fine grooves extending from the upstream side in the flow direction toward the recovery portion. As the distance from the upstream side to the recovery portion increases, the intervals between the adjacent first fine grooves decrease. As the angle of the direction in which the first fine groove extends relative to the flow direction, that is, the rate of increase of the turning angle gradually decreases toward the recovery portion.

6. The turbine stator blade according to any one of claims 1 to 5, further comprising an outer region, wherein the outer region is formed radially outward of the central region in the surface of the stator blade body and has a plurality of second fine grooves extending radially outward from the upstream side to the downstream side.

7. The turbine stator blade according to any one of claims 1 to 5, further comprising an inner region, wherein the inner region is formed radially inward of the central region in the surface of the stator blade body and has a plurality of third fine grooves extending radially inward from the upstream side toward the downstream side.

8. A steam turbine comprising: Axis of rotation, extending along the axis; a plurality of turbine blades extending radially outward from the outer peripheral surface of the rotating shaft and arranged circumferentially; a housing covering the rotating shaft and the plurality of turbine blades from outside; and The turbine stator blade according to any one of claims 1 to 7 extends radially inward from the inner peripheral surface of the casing and is arranged in plurality in the circumferential direction.

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