turbine stator blades, and steam turbines

Abstract

The turbine stator has a stator body extending in a diameter direction intersecting the steam flow direction, a recovery section formed on the surface of the stator body and recovering a liquid film flowing along the surface, and a central region formed on the surface of the stator body and having a plurality of first microgrooves formed extending from the upstream side of the flow direction toward the recovery section, and as it extends from the upstream side toward the recovery section, the spacing between adjacent first microgrooves becomes narrower.

Description

Technology Field

[0001] The present disclosure relates to turbine stator blades and steam turbines.

[0002] The present application claims priority to patent application No. 2021-106944 filed in Japan on June 28, 2021, and incorporates the contents thereof herein by reference. Background Technology

[0003] A steam turbine comprises a rotating shaft rotatable around an axis, a plurality of turbine blade rows arranged spaced apart in the axial direction on the outer surface of the rotating shaft, a casing covering the rotating shaft and the turbine blade rows from the outer side, and a plurality of turbine static blade rows supported in the radial direction by an inner ring and an outer ring on the inner side of the casing. Each turbine blade row has a plurality of blades arranged in the circumferential direction of the rotating shaft, and each turbine static blade row has a plurality of static blades arranged in the circumferential direction of the rotating shaft. The turbine blade rows are arranged adjacent to the turbine static blade rows in the axial direction downstream to form a single section. An intake port connected to an inlet pipe for introducing 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 control valve and its flow rate regulated by a turbine inlet valve before flowing into the turbine. The high-temperature, high-pressure steam introduced from the inlet piping has its flow direction and speed adjusted in the turbine static blades, after which it is converted into rotational force for the rotating shaft in the turbine dynamic blades.

[0004] Steam passing through a turbine loses energy as it moves from the upstream side to the downstream side, causing its temperature (and pressure) to decrease. In particular, steam turbines for thermal power generation are generally composed of a high-pressure turbine, a medium-pressure turbine, and a low-pressure turbine. In the two short circuits (pairs of turbine stator blades and turbine moving blades) counting from the downstream side of the low-pressure turbine, a gas-liquid two-phase flow environment exists. Therefore, in the short circuit on the downstream side, a portion of the steam liquefies and exists in the airflow as fine droplets, and some 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 as they aggregate on the blade surface, they grow to form a liquid film. This liquid film is always exposed to a high-speed steam flow. As the liquid film grows and its thickness increases, a portion of it is dispersed by the steam flow and flies downstream as coarse droplets. Since larger droplets possess greater inertial force, they cannot travel between the turbine blades with the steam flow and instead collide with the blades. Given that the circumferential velocity of the turbine blades increases toward the leading edge and can sometimes exceed the speed of sound, the impact of these flies can cause erosion on the blade surfaces. Furthermore, the collision of these droplets can impede the rotation of the turbine blades, potentially resulting in braking losses.

[0005] In order to prevent the occurrence of such 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 blade. It is said that by guiding the liquid drop along this guide groove, it is possible to prevent the liquid drop from flowing toward the leading edge of the turbine blade, which has a high circumferential speed. Prior art literature

[0006] Japanese Patent Publication No. 2016-166569 The problem to be solved

[0007] However, merely regulating the flow of droplets on the turbine blades as described above does not constitute a fundamental solution to the problem. Therefore, there has been a growing demand for technology capable of suppressing or recovering droplets from the turbine stator blades.

[0008] The present disclosure is made to solve the above problem and aims to provide a turbine stator and a steam turbine capable of more efficiently suppressing or recovering droplets. means of solving the problem

[0009] To solve the above problem, the turbine stator according to the present disclosure comprises a stator body extending in a diameter direction intersecting the direction of steam flow, a recovery portion formed on the surface of the stator body and recovering a liquid film flowing along the surface, and a central region formed on the surface of the stator body and having a plurality of first microgrooves formed extending from the upstream side of the flow direction toward the recovery portion, wherein the spacing between adjacent first microgrooves is narrowed as it extends from the upstream side toward the recovery portion. Effects of the invention

[0010] According to the present disclosure, a turbine stator and a steam turbine capable of more efficiently suppressing or recovering droplets can be provided. Brief explanation of the drawing

[0011] FIG. 1 is a cross-sectional view showing the configuration of a steam turbine according to an embodiment of the present disclosure. FIG. 2 is an enlarged cross-sectional view of a key part of a steam turbine according to an embodiment of the present disclosure. FIG. 3 is a cross-sectional view showing the shape of a microgroove according to an embodiment of the present disclosure. FIG. 4 is a figure showing a first modified example of a turbine stator blade according to an embodiment of the present disclosure. FIG. 5 is a figure showing a second modified example of a turbine stator blade according to an embodiment of the present disclosure. FIG. 6 is a cross-sectional view showing a first modified example of a microgroove according to an embodiment of the present disclosure. FIG. 7 is a cross-sectional view showing a second modified example of a microgroove according to an embodiment of the present disclosure. FIG. 8 is a cross-sectional view showing a third modified example of a microgroove according to an embodiment of the present disclosure. FIG. 9 is a cross-sectional view showing a fourth modified example of a microgroove according to an embodiment of the present disclosure. Specific details for implementing the invention

[0012] (Composition of a steam turbine)

[0013] Hereinafter, a steam turbine (1) and a stator (10) (turbine stator) according to an embodiment of the present disclosure will be described with reference to FIG. 1 and FIG. 2. As shown in FIG. 1, the steam turbine (1) has a rotor (2) and a casing (3).

[0014] The rotor (2) has a rotation axis (6) with a circular cross section extending along the axis (O), and a plurality of rotor blade rows (7) provided on the outer surface of the rotation axis (6). The rotation axis (6) is rotatable around the axis (O). The plurality of rotor blade rows (7) are arranged spaced apart in the direction of the axis (O). Each rotor blade row (7) has a plurality of rotor blades (8) arranged in the direction of the axis (O). The rotor blades (8) extend outward in the radial direction from the outer surface of the rotation axis (6). The detailed configuration of the rotor blades (8) will be described later.

[0015] The casing (3) has a casing body (3H) that covers the rotor (2) from the outer side, and a plurality of static blade rows (9) that are supported from the outer side and the inner side by an outer ring (21) (described later) and an inner ring (23) (described later) provided on the inner side of the casing body (3H). The casing body (3H) has a tubular shape centered on the axis (O). The plurality of static blade rows (9) are arranged at intervals in the direction of the axis (O). The steam turbine (1) is equipped with the same number of moving blade rows (7) as the static blade rows (9), and one moving blade row (7) is located between a pair of static blade rows (9) adjacent in the direction of the axis (O). That is, the moving blade rows (7) and the static blade rows (9) are arranged alternately in the direction of the axis (O). One fixed wing row (9) and one moving wing row (7) form a single "segment." Each fixed wing row (9) has multiple fixed wings (10) arranged in a circumferential direction along the axis (O). The fixed wings (10) extend in a diameter direction along the axis (O).

[0016] On one side of the axial direction (O) in the casing body (3H), a steam passage (11) is formed to introduce high-temperature, high-pressure steam induced from an inlet pipe into the short circuit of the casing body (3H). On the other side of the axial direction (O) in the casing body (3H), an exhaust chamber (12) responsible for recovering the steam pressure is provided.

[0017] Steam flowing into the steam passage (11) passes through the short circuit within the casing body (3H), then passes through the exhaust chamber (12) and is sent to a condenser (not shown). In the following description, the side where the steam passage (11) is located, viewed from the exhaust chamber (12), is referred to as the upstream side in the direction of steam flow. The side where the exhaust chamber (12) is located, viewed from the steam passage (11), is referred to as the downstream side.

[0018] (Composition of Dong-ik)

[0019] As shown in FIG. 2, the wing (8) has a platform (81), a wing body (82), and a shroud (83). The platform (81) is installed on the outer surface of the rotation axis (6) (outer surface of the rotation axis (6A)). On the outer side of the platform (81), the wing body (82) is provided. The wing body (82) extends in the diameter direction and has a wing-shaped cross-sectional shape when viewed in the diameter direction. The wing body (82) is formed such that, for example, the dimensions in the axis (O) direction gradually decrease as it moves from the inner side in the diameter direction to the outer side. A shroud (83) is provided at the outer end of the wing body (82) in the diameter direction. The shroud (83) has a roughly rectangular cross-sectional shape with the axis (O) direction as the length direction. The outer surface of the shroud (83) is spaced apart in the diameter direction from the inner surface (inner surface of the casing (3A)) of the casing body (3H).

[0020] (Composition of Jeongik)

[0021] The stator (10) has an outer ring (21), a stator body (22) (wing body), and an inner ring (23). Additionally, the stator body (22) has a central region (41), an outer region (42), an inner region (43), and a slit (13) (recovery part (14)). The outer ring (21) forms an annular shape centered on an axis (O). The outer ring (21) is supported by a support member (not shown) interposed with the casing body (3H). The stator body (22) is fixed between the outer ring (21) and the inner ring (23). The stator body (22) extends inward in the radial direction from the inner circumferential surface (21A) of the outer ring and has an airfoil cross-sectional shape when viewed in the radial direction. That is, the stator body (22) extends in a direction that intersects the direction of steam flow. As an example, the dimensions of the stator body (22) in the axial direction (O) gradually decrease as it moves from the outer side in the radial direction to the inner side. An inner ring (23) is provided at the inner end in the radial direction of the stator body (22). The inner ring (23) has a roughly rectangular cross-sectional shape with the axial direction (O) as the length direction. The inner surface of the inner ring (23) faces the outer surface (6A) of the rotation axis at a distance in the radial direction.

[0022] On the surface of the stator body (22) (more specifically, the side facing upstream among the two sides in the thickness direction of the stator body (22): the ventral side), a central region (41), an outer region (42), an inner region (43), and a slit (13) are formed. In these central region (41), outer region (42), and inner region (43), a plurality of micro-grooves (5) are formed that are concavely recessed from the surface of the stator body (22) toward the inside. The micro-grooves (5) are provided to transport liquid droplets generated on the surface of the stator body (22) to the downstream side along the steam flow. The micro-grooves (5) are arranged at intervals in the diameter direction.

[0023] The micro-grooves (5) (first micro-grooves (51)) formed in the central region (41) are spaced further apart from adjacent first micro-grooves (51) as they extend from the leading edge (22a) side of the wing body (22) toward the trailing edge (22b) side. That is, the central region (41) gradually decreases in diameter as it extends from the leading edge (22a) side toward the trailing edge (22b) side. The downstream end of these first micro-grooves (51) is connected to the slit (13) described later.

[0024] The outer region (42) is formed on the outer side in the radial direction of the central region (41). The micro-groove (5) (second micro-groove (52)) formed in the outer region (42) is curved outward in the radial direction as it extends from the leading edge (22a) side toward the downstream side. The downstream end of the second micro-groove (52) is connected to the inner circumference of the outer ring (21).

[0025] The inner region (43) is formed in the radial inner direction of the central region (41). The micro-groove (5) (third micro-groove (53)) formed in the inner region (43) is curved in the radial inner direction as it extends from the leading edge (22a) toward the downstream side. The downstream end of the third micro-groove (53) extends to the radial inner region (near the inner ring (23)) at the trailing edge (22b).

[0026] On the leading edge (22a) side, the central area (41) (first microgroove (51)) occupies the largest proportion, and the outer area (42) and inner area (43) occupy a smaller area than the central area (41).

[0027] In the central region (41) above, on the rear edge (22b) side, a slit (13) is formed as a recovery section (14) for recovering the liquid film that has flowed through the first micro-groove (51). The slit (13) extends along the rear edge (22b). The slit (13) is one or more long holes that communicate with the interior of the main body (22). That is, the main body (22) is hollow. It is preferable that the internal space of the main body (22) be in a negative pressure state by a device not shown.

[0028] Next, the dimensions of the micro-groove (5) will be described with reference to FIG. 3. As shown in the same figure, in this embodiment, the micro-groove (5) has a rectangular cross-sectional shape. When the spacing (pitch) between adjacent micro-grooves (5) is p, the depth of the micro-groove (5) is h, the width of the opening is w, and the width of the bottom surface is b, the value of w is preferably 0.3 to 2.0 mm. Also, the value of b / w is preferably 0 to 2.0 (details will be described later, but the case where this value is 0 corresponds to the case where the micro-groove (5) has a triangular cross-section). Also, the value of h / w is preferably 0.5 to 2.0. The value of p / w is preferably 0.5 to 3.0.

[0029] (Effective effects)

[0030] Next, the operation of the steam turbine (1) and the behavior of droplets on the stator blades (10) according to the present embodiment will be explained. When operating the steam turbine (1), high-temperature, high-pressure steam is first introduced into the interior of the casing body (3H) through the steam flow path (11). As the steam flows through the interior of the casing body (3H) toward the downstream side, it alternately passes through the stator blade row (9) and the moving blade row (7) described above. The stator blade row (9) rectifies the flow of steam and flows into the moving blade row (7) adjacent to the downstream side. As the steam acts on the moving blade row (7), torque is applied to the rotating shaft (6) through said moving blade row (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 for driving a generator (not shown), etc.

[0031] Here, as steam passes through the short circuits within the main flow path of the turbine, energy is converted into rotational energy and the temperature (and pressure) decreases each time it passes through a short circuit as it moves from the upstream side to the downstream side. Therefore, at the stator blade row (9) at the far downstream side, some of the steam is liquefied and exists in the airflow as fine droplets, and some of these droplets are attached to the surface of the stator blade (10) (stator blade body (22)). These droplets grow to form a liquid film. Furthermore, as the droplets continue to increase and the thickness of the liquid film increases as it flows downstream, some of it is scattered by the steam flow, or the liquid film attached to the stator blade row is scattered as a coarse droplet from the trailing edge of the stator blade. The scattered droplets flow downstream while being gradually accelerated by the steam flow. If the coarse droplets collide with the moving blade (8) on the downstream side, it may cause erosion on the surface of the moving blade (8). In addition, there are cases where the rotation of the rotor (2) is hindered by the collision of droplets, resulting in braking loss.

[0032] Accordingly, in this embodiment, as described above, a plurality of micro-grooves (5) are formed on the surface of the main body (22) of the stator. Droplets captured in the micro-grooves (5) flow downstream along the steam flow. In the central region (41), the droplets flow along the first micro-grooves (51) toward the slit (13). The droplets are recovered by the negative pressure of the slit (13). Also, in the outer region (42), the droplets flow outward in the radial direction along the second micro-grooves (52) and are guided to the inner surface of the outer ring (21). That is, the droplets do not reach the moving blade (8) on the downstream side. Likewise, in the inner region (43), the droplets flow inward in the radial direction along the third micro-grooves (53). As a result, the droplets do not reach the tip of the moving blade (8), which has a high circumferential speed.

[0033] In particular, according to the above configuration, as one moves toward the recovery section (14) (slit (13)) from the upstream side, the spacing between the first micro-grooves (51) is narrowed. This allows the liquid film or droplet to be guided toward the recovery section (14) from a wider range on the upstream side. Additionally, this allows the size of the recovery section (14) itself to be kept small. As a result, compared to the case where the recovery section (14) is made large, the possibility of affecting the main stream of steam can be reduced.

[0034] Additionally, according to the above configuration, the liquid film generated on the outer side in the radial direction of the central region (41) can be further guided toward the outer side in the radial direction (e.g., the inner surface of the outer ring (21)) by the second micro-groove (52). This further reduces the possibility of liquid droplets scattering downstream of the stator body (22).

[0035] In addition, according to the above configuration, the liquid film generated in the inner diameter direction of the central region (41) can be further guided toward the inner diameter direction by the third micro-groove (53). This further reduces the possibility of liquid droplets scattering downstream of the main body (22).

[0036] (Other embodiments)

[0037] The embodiments of the present disclosure have been described above. Furthermore, various changes or improvements can be made to the above configurations without departing from the gist of the present disclosure.

[0038] For example, it is possible to adopt the configuration shown in FIG. 4 as a first variant of the stator (10). In this first variant, the first microgroove (51b) is curved outward in the diameter direction as it moves from the leading edge (22a) side toward the slit (13) side. Additionally, as it moves toward the slit (13), the angle of forward movement, which is the angle formed by the direction of extension of the first microgroove (51b) relative to the steam flow direction (F), gradually decreases. That is, in the portion of the first microgroove (51b) toward the slit (13) side, the radius of curvature is larger compared to the portion toward the leading edge (22a) side. In other words, as it moves from the leading edge (22a) side toward the slit (13) side, the rate of increase of the above angle of forward movement gradually decreases. Additionally, it is possible to make the portion toward the slit (13) side a clothoid curve.

[0039] According to the above configuration, as it approaches the slit (13), the direction of extension of the first micro-groove (51b) changes to follow the direction of steam flow. As a result, as it approaches the slit (13), the flow velocity of the liquid film increases, and it becomes possible to recover the liquid film more efficiently.

[0040] In addition, it is also possible to adopt the configuration shown in FIG. 5 as a second variant of the fin (10). In this second variant, a main groove (51c) and a sub-groove (51d) are formed as fine grooves (5) in the central region (41). The main groove (51c) extends from the leading edge (22a) toward the slit (13), and the spacing between adjacent main grooves (51c) is narrowed. The sub-groove (51d) starts at the leading edge (22a) and joins one of the main grooves (51c) at the end point. With this configuration, it is possible to recover the liquid film over a wider range on the leading edge (22a) side.

[0041] In addition, in the above embodiment, an example in which the micro-groove (5) has a rectangular cross-sectional shape was described. However, as long as the conditions of the dimensions described above are satisfied, the shape of the micro-groove (5) can be varied. For example, as shown in FIG. 6, it is possible to make the width b of the bottom portion larger than the width w of the opening (b > w). As shown in FIG. 7, it is also possible to make the width b of the bottom portion smaller than the width w of the opening (b < w). As shown in FIG. 8, it is also possible to make the cross-sectional shape of the micro-groove (5) triangular (b = 0). Furthermore, as shown in FIG. 9, it is also possible to make the bottom portion arc-shaped.

[0042] <Appendix>

[0043] The device X described in each embodiment is understood, for example, as follows.

[0044] (1) A turbine stator (stator (10)) according to the first embodiment has a stator body (22) extending in a diameter direction intersecting the direction of steam flow, a recovery section (14) formed on the surface of the stator body (22) and recovering a liquid film flowing along the surface, and a central region (41) formed on the surface of the stator body (22) and having a plurality of first micro-grooves (51) extending from the upstream side of the flow direction toward the recovery section (14), and as it extends from the upstream side toward the recovery section (14), the spacing between the first micro-grooves (51) that are adjacent to each other is narrowed.

[0045] According to the above configuration, as it moves from the upstream side toward the recovery section (14), the spacing between the first micro-grooves (51) is narrowed. This allows the liquid film to be guided toward the recovery section (14) from a wider range on the upstream side. Additionally, the size of the recovery section (14) itself can be kept small. This reduces the possibility of affecting the main stream of steam.

[0046] (2) In the turbine stator (stator (10)) of the second embodiment, the angle of forward movement, which is the angle formed by the direction of extension of the first micro-groove (51b) with respect to the flow direction, may gradually decrease as it faces the recovery section (14).

[0047] According to the above configuration, as it approaches the recovery section (14), the direction of the first micro-groove (51b) changes to follow the direction of steam flow. As a result, as it approaches the recovery section (14), the flow velocity of the liquid film increases, and it becomes possible to recover the liquid film more efficiently.

[0048] (3) In the turbine stator (stator (10)) of the third embodiment, the rate of increase of the forward angle, which is the angle formed by the extending direction of the first micro-groove (51b) with respect to the flow direction, may gradually decrease as it faces the recovery section (14).

[0049] According to the above configuration, as it approaches the recovery section (14), the rate of increase of the forward angle of the first micro-groove (51b) gradually decreases. As a result, as it approaches the recovery section (14), the flow velocity of the liquid film increases, making it possible to recover the liquid film more efficiently.

[0050] (4) The turbine stator (stator (10)) according to the fourth embodiment may further have an outer region (42) formed on the outer side in the radial direction of the central region (41) on the surface of the stator body (22), and having a plurality of second micro-grooves (52) formed extending outward in the radial direction from the upstream side to the downstream side.

[0051] According to the above configuration, the liquid film generated on the outer side in the radial direction of the central region (41) can be further guided toward the outer side in the radial direction (e.g., the inner surface of the outer ring (21)) by the second micro-groove (52). This further reduces the possibility of liquid droplets scattering downstream of the stator body (22).

[0052] (5) The turbine stator (stator (10)) according to the fifth embodiment may further have an inner region (43) formed in the inner diameter direction of the central region (41) on the surface of the stator body (22), and having a plurality of third fine grooves (53) formed in the inner diameter direction extending from the upstream side to the downstream side.

[0053] According to the above configuration, the liquid film generated in the diametrically inner side of the central region (41) can be further guided toward the diametrically inner side by the third micro-groove (53). This further reduces the possibility of liquid droplets scattering downstream of the vane body (22).

[0054] (6) A steam turbine (1) according to the sixth embodiment has a rotating shaft (6) extending along an axis (O), a plurality of turbine blades (blades (8)) arranged in a circumferential direction extending outward in a radial direction from the outer surface of the rotating shaft (6), a casing (3) covering the rotating shaft (6) and the plurality of turbine blades from the outside, and a plurality of turbine stator blades (blades (10)) according to any one embodiment arranged in a circumferential direction extending inward in a radial direction from the inner surface of the casing (3).

[0055] According to the above configuration, a steam turbine (1) can be provided in which the occurrence of erosion caused by droplets scattering downstream is suppressed.

[0056] Industrial applicability

[0057] According to the present disclosure, a turbine stator and a steam turbine capable of more efficiently suppressing or recovering droplets can be provided. Explanation of the symbols

[0058] 1 Steam turbine 2 rotors 3 casings If you give the 3A casing 3H Casing Body 5 micro-grooves 6 rotation axes 6A outer surface of the rotation axis 7 Dongik Ikryeol 8 rotor blades (turbine rotor blades) 9 Jeongik Ikryeol 10 Stabilizer (Turbine Stabilizer) 11 Steam Euro 12 exhaust chambers 13 slits 14 Recovery Unit 21 outer ring 21A outer ring inner surface 22 Main body of the wing (wing body) 22a Entire line 22b trailing edge 23 inner ring 41 Central area 42 outer area 43 Medial area 51, 51b First microgroove 51c Main Home 51d Part Home 52 Second micro-groove 53 Third microgroove 81 Platform 82 Dongik Main Body 83 Shroud O axis

Claims

Claim 1 A turbine stator having a stator body extending in a diameter direction intersecting the direction of steam flow, a recovery section formed on the surface of the stator body and recovering a liquid film flowing along the surface, and a central region formed on the surface of the stator body and having a plurality of first micro-grooves formed extending from the upstream side of the flow direction toward the recovery section, wherein as it extends from the upstream side toward the recovery section, the spacing between adjacent first micro-grooves becomes narrower, the spacing between the centers in the width direction of adjacent first micro-grooves becomes narrower, and the diameter dimension of the central region becomes smaller. Claim 2 A turbine stator having a stator body extending in a diameter direction intersecting the direction of steam flow, a recovery section formed on the surface of the stator body and recovering a liquid film flowing along the surface, and a central region formed on the surface of the stator body and having a plurality of first micro-grooves extending from the upstream side of the flow direction toward the recovery section, wherein as one moves toward the recovery section from the upstream side, the spacing between adjacent first micro-grooves narrows, and as one moves toward the recovery section, the angle of deflection, which is the angle formed by the direction of extension of the first micro-grooves relative to the flow direction, gradually decreases so that the direction of extension of the first micro-grooves follows the flow direction. Claim 3 A turbine stator according to claim 1, wherein the rate of increase of the forward angle, which is the angle formed by the extending direction of the first microgroove with respect to the flow direction, gradually decreases as it faces the recovery portion. Claim 4 A turbine stator according to any one of claims 1 to 3, further comprising an outer region formed on the radially outer side of the central region on the surface of the stator body, and having a plurality of second microgrooves formed extending radially outward from the upstream side to the downstream side. Claim 5 A turbine stator according to any one of claims 1 to 3, further comprising an inner region formed in the radial inner side of the central region on the surface of the stator body, and having a plurality of third microgrooves formed therein extending inward in the radial direction from the upstream side to the downstream side. Claim 6 A steam turbine comprising a rotating shaft extending along an axis, a plurality of turbine blades arranged circumferentially while extending outwardly in the radial direction from the outer surface of the rotating shaft, a casing covering the rotating shaft and the plurality of turbine blades from the outside, and a plurality of turbine stator blades described in any one of claims 1 to 3 arranged circumferentially while extending inwardly in the radial direction from the inner surface of the casing.

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