Patent Publication Number: US-2022228510-A1

Title: Steam turbine stator vane, steam turbine, and production method for steam turbine stator vane

Description:
TECHNICAL FIELD 
     The present disclosure relates to a steam turbine stator vane, a steam turbine including the steam turbine stator vane, and a production method for the steam turbine stator vane. 
     BACKGROUND 
     In the vicinity of a last stage of a steam turbine, the wetness of a steam flow is not less than 8%. Water droplets generated from the wet steam flow cause a moisture loss, decreasing turbine efficiency. Further, the water droplets generated from the wet steam flow adhere to the surface of the stator vane, forming a water film. The above-described water film becomes a water film flow on the surface of the stator vane, flows to a trailing edge side of the stator vane, and is scattered at the trailing edge of the stator vane, forming coarse water droplets. Collision of the above-described coarse water droplets against a rotor blade rotating at high speed is one of major causes of triggering erosion of the rotor blade. 
     In order to prevent the erosion and the moisture loss of the steam turbine, removing a liquid (water droplets) adhering to the surface of the stator vane is effective. Conventionally, in order to remove a liquid adhering to the surface of a stator vane, a groove and a slit are formed in the surface of the stator vane (see Patent Documents 1, 2). The liquid adhering to the surface of the stator vane is sent in the groove and the slit, and is discharged from the groove and the slit to the outside of a system. Patent Document 1 discloses forming one or a plurality of grooves in the surface of the stator vane. The groove described in Patent Document 1 extends toward the radial direction of a steam turbine over one end portion to another end portion of the stator vane in the longitudinal direction. Patent Document 2 discloses forming, in the surface of a hollow stator vane internally including a cavity, one or a plurality of slits communicating with the cavity. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Document 1: U.S. Pat. No. 6,474,942B 
         Patent Document 2: JPH3-26802A 
       
    
     SUMMARY 
     Technical Problem 
     In order to improve removal efficiency of the liquid adhering to the surface of the stator vane, it is considered that two of the grooves described in Patent Document 1 are disposed in parallel in the surface of the stator vane along the height direction. However, due to low removal efficiency of the above-described grooves themselves, a removal amount of the liquid is small even if the above-described two grooves are disposed in parallel, which may be unable to improve removal efficiency of the liquid. 
     Further, in order to improve removal efficiency of the above-described liquid, it is considered that two of the slits described in Patent Document 2 are disposed in parallel in the surface of the stator vane along the height direction. In this case, due to a pressure difference between the first slit disposed upstream in the above-described axial direction and the second slit disposed downstream in the above-described axial direction, the liquid sucked from the first slit to the cavity may spout (flow back) from the second slit having a lower pressure than the first slit. Thus, it is impossible to increase the removal amount of the liquid, which may be unable to improve removal efficiency of the liquid. In order to prevent the backflow of the liquid, if the width of the slit is increased to improve a suction pressure of the slit, the amount of drive steam leaking to the cavity through the slit increases, which may decrease performance of the steam turbine. 
     In view of the above issues, an object of at least one embodiment of the present invention is to provide a steam turbine stator vane capable of preventing the decrease in performance of the steam turbine as well as improving removal efficiency of the liquid adhering to the surface of the stator vane, and a steam turbine including the steam turbine stator vane. 
     Solution to Problem 
     (1) A steam turbine stator vane according to at least one embodiment of the present invention includes a vane body portion which has a vane surface including a pressure surface and a suction surface, a moisture removal channel disposed in the above-described vane body portion, at least one slit opening to the above-described vane surface to communicate with the above-described moisture removal channel, and extending along a height direction from a base end portion toward a tip end portion of the above-described vane body portion, and at least one groove portion disposed in the above-described vane surface and extending from the above-described base end portion along the above-described height direction, at least a part of the at least one groove portion overlapping the above-described at least one slit along the above-described height direction. 
     With the above configuration (1), the steam turbine stator vane includes the slit and the groove portion disposed in the vane surface which is the surface of the stator vane, and the slit and the groove portion overlap at least partially along the height direction. Thus, it is possible to remove a liquid collected in the vane surface by a section (upstream drainage section) of the slit and the groove portion disposed upstream of the vane surface. Further, it is possible to remove a liquid collected downstream of the upstream drainage section in the vane surface, by a section (downstream drainage section) of the slit and the groove portion disposed downstream of the vane surface. That is, the above-described steam turbine stator vane can remove the liquid adhering to the vane surface, by the groove portion and the slit having higher removal efficiency of the liquid than the groove portion. Thus, it is possible to improve the removal efficiency of the liquid adhering to the vane surface. 
     Further, since one of the upstream drainage section or the downstream drainage section is the groove portion that does not communicate with the moisture removal channel, the above-described steam turbine stator vane can reduce the amount of drive steam leaking to the moisture removal channel through the slit, as compared with a configuration, where two slits overlapping each other along the height direction are disposed in the vane surface, as in a steam turbine stator vane according to a comparative example. Further, unlike the configuration, where the two slits overlapping each other along the height direction are disposed in the vane surface, as in the steam turbine stator vane according to the comparative example, the above-described steam turbine stator vane is free from the risk that the liquid flows back from the moisture removal channel via the slit, and thus a slit width need not be increased to improve a suction pressure of the slit. By suppressing the suction pressure of the slit, it is possible to further reduce the amount of the drive steam leaking to the moisture removal channel through the slit. Thus, the above-described steam turbine stator vane can reduce the amount of the drive steam leaking to the moisture removal channel through the slit, making it possible to prevent a decrease in performance of the steam turbine. 
     (2) In some embodiments, in the steam turbine stator vane according to the above configuration (1), the above-described at least one groove portion is configured to be inclined to a side of a trailing edge from the above-described tip end portion toward the above-described base end portion. 
     With the above configuration (2), since the at least one groove portion is configured to be inclined to the side of the trailing edge from the tip end portion toward the base end portion, the liquid stored in the groove portion is pushed by the flow of the steam flowing through in the steam turbine and flows toward the base end portion which is a discharge side of the liquid. Thus, the above-described groove portion can improve removal efficiency of the liquid stored in the groove portion. 
     (3) In some embodiments, in the steam turbine stator vane according to the above configuration (1) or (2), the above-described at least one slit includes a plurality of slits disposed separately from each other in the above-described height direction. 
     With the above configuration (3), since the plurality of slits are disposed separately from each other in the height direction, as compared with a case where the single slit extends along the height direction, it is possible to improve strength of the steam turbine stator vane in the vicinity of the slit. Improving the strength of the steam turbine stator vane in the vicinity of the slit, it is possible to reduce the thickness of the steam turbine stator vane, and thus to reduce a production cost of the steam turbine stator vane. 
     (4) In some embodiments, the steam turbine stator vane according to the above configuration (3) further includes a recess which is disposed in the above-described vane surface and to which the above-described plurality of slits open. 
     With the above configuration (4), since the plurality of slits disposed separately from each other open to the recess disposed in the vane surface, the liquid adhering to the vane surface is stored in the recess. Thus, the steam turbine stator vane including the above-described recess can prevent the liquid adhering to the vane surface from flowing downstream of the slits in the vane surface through the slits. Thus, the steam turbine stator vane including the above-described recess can improve removal efficiency of the liquid adhering to the vane surface. 
     (5) In some embodiments, in the steam turbine stator vane according to anyone of the above configurations (1) to (4), the above-described at least one slit is disposed between the above-described at least one groove portion and a leading edge. 
     With the above configuration (5), it is possible to remove the liquid that cannot be removed from the vane surface by the slit or the liquid adhering between the slit and the trailing edge on the vane surface, by the groove portion disposed between the slit and the trailing edge on the vane surface. 
     (6) In some embodiments, in the steam turbine stator vane according to anyone of the above configurations (1) to (4), the above-described at least one slit is disposed between the above-described at least one groove portion and a trailing edge. 
     With the above configuration (6), it is possible to remove the liquid that cannot be removed from the vane surface by the groove portion or the liquid adhering between the groove portion and the trailing edge on the vane surface, by the slit disposed between the groove portion and the trailing edge on the vane surface. The groove portion can reduce the amount of the liquid reaching the slit, and the slit has higher removal efficiency of the liquid adhering to the vane surface than the groove portion, making it possible to remove the liquid reaching the slit. Thus, with the above configuration, by disposing the slit between the groove portion and the trailing edge, it is possible to effectively remove the liquid adhering to the vane surface. 
     (7) In some embodiments, in the steam turbine stator vane according to any one of the above configurations (1) to (6), the above-described vane body portion includes a curved plate encompassing the above-described moisture removal channel and configured such that a difference between a maximum value and a minimum value of a thickness of the above-described curved plate falls within 40% of an average value of the above-described thickness. 
     With the above configuration (7), by equalizing the thickness of the curved plate, it is possible to reduce a material cost of the curved plate by cutting wasteful consumption of a material forming the curved plate, and thus to reduce the production cost of the stator vane. 
     (8) In some embodiments, in the steam turbine stator vane according to the above configuration (7), the above-described curved plate includes a pressure surface-side curved plate which has a surface including at least a part of the above-described pressure surface, and a suction surface-side curved plate which has a surface including at least a part of the above-described suction surface, and one of the above-described at least one slit or the above-described at least one groove portion is configured to include a joint where one end portion of the above-described pressure surface-side curved plate and one end portion of the above-described suction surface-side curved plate are joined by welding. 
     With the above configuration (8), one of the slit or the groove portion includes the joint where the one end portion of the pressure surface-side curved plate and the one end portion of the suction surface-side curved plate are joined by welding. That is, the shape of one of the slit or the groove portion is formed, when the curved plate is formed by welding the one end portion of the pressure surface-side curved plate and the one end portion of the suction surface-side curved plate. With the above configuration, since additional processing such as cutting is not needed to form one of the slit or the groove portion, it is possible to reduce a processing cost, and thus to reduce the production cost of the stator vane. Further, with the above configuration, since one of the slit or the groove portion can be formed without processing such as cutting, it is possible to prevent a decrease in strength in the vicinity of one of the slit or the groove portion. 
     (9) In some embodiments, in the steam turbine stator vane according to the above configuration (8), the above-described vane body portion further includes a trailing edge portion disposed between the above-described joint and a trailing edge, the trailing edge portion having a trailing edge-side pressure surface connected to the above-described trailing edge and a trailing edge-side wall surface extending from a front end portion on the above-described trailing edge-side pressure surface along a direction intersecting with the above-described trailing edge-side pressure surface, and the above-described at least one groove portion includes the above-described joint, and a part of the above-described at least one groove portion is defined by the above-described trailing edge-side wall surface. 
     With the above configuration (9), the at least one groove portion includes the joint, and a part of the at least one groove portion is defined by the trailing edge-side wall surface. That is, the shape of the groove portion is formed as a part of the trailing edge-side wall surface of the trailing edge portion, when the curved plate is formed by welding. Since a part of the above-described groove portion is defined by the trailing edge-side wall surface extending along the direction intersecting with the trailing edge-side pressure surface, it is possible to effectively prevent the liquid adhering to the vane surface from flowing toward the trailing edge-side pressure surface from the trailing edge-side wall surface. 
     (10) In some embodiments, in the steam turbine stator vane according to the above configuration (8), the above-described vane body portion further includes a trailing edge portion disposed between the above-described joint and a trailing edge, the trailing edge portion having a trailing edge-side pressure surface connected to the above-described trailing edge and a trailing edge-side wall surface extending from a front end portion on the above-described trailing edge-side pressure surface along a direction intersecting with the above-described trailing edge-side pressure surface, and the above-described at least one slit includes the above-described joint, and a part of the above-described at least one slit is defined by the above-described trailing edge-side wall surface. 
     With the above configuration (10), the at least one slit includes the joint, and apart of the slit is defined by the trailing edge-side wall surface. That is, the shape of the slit is formed as a part of the trailing edge-side wall surface of the trailing edge portion, when the curved plate is formed by welding. Since a part of the above-described slit is defined by the trailing edge-side wall surface extending along the direction intersecting with the trailing edge-side pressure surface, the liquid adhering to the vane surface is removed from the vane surface by the slit in the trailing edge-side wall surface. Thus, with the above configuration, it is possible to effectively prevent the liquid adhering to the vane surface from flowing toward the trailing edge-side pressure surface from the trailing edge-side wall surface. 
     (11) In some embodiments, in the steam turbine stator vane according to the above configuration (8), the above-described suction surface-side curved plate includes an extension portion extending from a trailing edge toward a leading edge, the extension portion having a surface including at least a part of the above-described pressure surface, the above-described one end portion of the above-described suction surface-side curved plate includes a front end portion of the above-described extension portion located on a side of the leading edge, and the above-described at least one groove portion includes the above-described joint, and a part of the above-described at least one groove portion is defined by an end surface at the above-described front end portion of the above-described extension portion. 
     With the above configuration (11), the at least one groove portion includes the joint, and a part of the at least one groove portion is defined by the end surface at the front end portion of the extension portion. That is, the shape of the groove portion is formed as a part of the end surface at the front end portion of the extension portion, when the curved plate is formed by welding the one end portion of the pressure surface-side curved plate and the above-described front end portion. Since a part of the above-described groove portion is defined by the end surface at the front end portion of the extension portion located on the side of the leading edge, it is possible to effectively prevent the liquid adhering to the end surface from flowing toward the pressure surface of the extension portion. 
     (12) A steam turbine according to at least one embodiment of the present invention includes the steam turbine stator vane according to any one of the above configurations (1) to (11), an annular member for supporting the above-described steam turbine stator vane, and a cavity disposed in the above-described annular member and configured to receive a liquid from each of the above-described moisture removal channel and the above-described at least one groove portion in the above-described vane body portion. 
     With the above configuration (12), since the steam turbine includes the cavity disposed in the annular member and configured to receive the liquid from each of the moisture removal channel and the at least one groove portion in the vane body portion, it is possible to store, in the cavity, the liquid removed from the vane surface by the slit and the groove portion. Storing, in the cavity, the liquid removed from the vane surface by the slit and the groove portion, it is possible to prevent that the liquid accumulates in the slit and the moisture removal channel in the vane body portion, and removal efficiency of the liquid adhering to the vane surface by the slit and the groove portion is decreased. Thus, the above-described steam turbine can effectively remove the liquid adhering to the vane surface by the slit and the groove portion. 
     (13) A production method for a steam turbine stator vane according to at least one embodiment of the present invention includes a slit forming step of forming at least one slit that opens to a vane surface of a vane body portion, which has the above-described vane surface including a pressure surface and a suction surface, to communicate with a moisture removal channel disposed in the above-described vane body portion, and extends along a height direction from a base end portion toward a tip end portion of the above-described vane body portion, and a groove portion forming step of forming at least one groove portion extending from the above-described base end portion in the above-described vane surface along the above-described height direction, at least a part of the at least one groove portion overlapping the above-described at least one slit along the above-described height direction. 
     With the above method (13), the production method for the steam turbine stator vane includes the slit forming step of forming the at least one slit, and the groove portion forming step of forming the at least one groove portion. The steam turbine stator vane produced by the production method for the steam turbine stator vane includes the slit and the groove portion disposed in the vane surface which is the surface of the stator vane, and the slit and the groove portion overlap at least partially along the height direction. Thus, the steam turbine stator vane produced by the production method for the steam turbine stator vane can improve removal efficiency of the liquid adhering to the vane surface and can prevent the decrease in performance of the steam turbine. 
     Advantageous Effects 
     According to at least one embodiment of the present invention, provided are a steam turbine stator vane capable of preventing a decrease in performance of a steam turbine as well as improving removal efficiency of a liquid adhering to the surface of a stator vane, and a steam turbine including the steam turbine stator vane. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a steam turbine including a steam turbine stator vane according to an embodiment of the present invention, taken along the axial direction. 
         FIG. 2  is a schematic partially enlarged cross-sectional view of the steam turbine including the steam turbine stator vane according to an embodiment of the present invention, taken along the axial direction. 
         FIG. 3  is a schematic cross-sectional view of the steam turbine stator vane according to an embodiment of the present invention, taken along a direction orthogonal to the height direction. 
         FIG. 4  is a schematic view of the steam turbine stator vane according to a comparative example, taken along the axial direction. 
         FIG. 5  is a schematic cross-sectional view of the steam turbine stator vane according to a comparative example, taken along the direction orthogonal to the height direction. 
         FIG. 6  is a graph for describing a relationship between a slit width and a steam suction amount of each of the steam turbine stator vane according to an embodiment of the present invention and the steam turbine stator vane according to the comparative example. 
         FIG. 7  is a schematic view of the steam turbine stator vane according to a first modified example, taken along the axial direction. 
         FIG. 8  is a schematic view of the steam turbine stator vane according to a second modified example, taken along the axial direction. 
         FIG. 9  is a schematic cross-sectional view of the steam turbine stator vane according to the second modified example, taken along the direction orthogonal to the height direction. 
         FIG. 10  is a schematic view of the steam turbine stator vane according to a third modified example, taken along the axial direction. 
         FIG. 11  is a schematic cross-sectional view of the steam turbine stator vane according to the third modified example, taken along the direction orthogonal to the height direction. 
         FIG. 12  is a schematic cross-sectional view of the steam turbine stator vane according to a fourth modified example, taken along the direction orthogonal to the height direction. 
         FIG. 13  is a schematic cross-sectional view of the steam turbine stator vane according to a fifth modified example, taken along the direction orthogonal to the height direction. 
         FIG. 14  is a schematic cross-sectional view of the steam turbine stator vane according to a sixth modified example, taken along the direction orthogonal to the height direction. 
         FIG. 15  is a flowchart showing an example of a production method for the steam turbine stator vane according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Some embodiments of the present invention will be described below with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions and the like of components described or shown in the drawings as the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present invention. 
     For instance, an expression of relative or absolute arrangement such as“in a direction”, “along a direction”, “parallel”, “orthogonal”, “centered”, “concentric” and “coaxial” shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function. 
     For instance, an expression of an equal state such as “same”, “equal”, and “uniform” shall not be construed as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or a difference that can still achieve the same function. 
     Further, for instance, an expression of a shape such as a rectangular shape or a tubular shape shall not be construed as only the geometrically strict shape, but also includes a shape with unevenness or chamfered corners within the range in which the same effect can be achieved. 
     On the other hand, the expressions “comprising”, “including” or “having” one constitutional element is not an exclusive expression that excludes the presence of other constitutional elements. 
     The same configurations are indicated by the same reference characters and may not be described again in detail. 
       FIG. 1  is a schematic cross-sectional view of a steam turbine including a steam turbine stator vane according to an embodiment of the present invention, taken along the axial direction. Each arrow FS shown in  FIG. 1 , and  FIGS. 2 to 5 and 7 to 14  to be described later schematically illustrates a steam flow direction. Hereinafter, the steam turbine stator vane may simply be referred to as a stator vane, and a steam turbine rotor blade may simply be referred to as a rotor blade. 
     As shown in  FIG. 1 , a steam turbine  1  includes a rotor  11  configured to be rotatable about an axis LA, at least one rotor blade  12  mechanically coupled to the rotor  11 , an annular member  13  for rotatably housing the rotor  11  and the rotor blade  12 , and at least one stator vane  3  disposed opposite to the rotor blade  12  across a gap as well as mechanically coupled to the annular member  13 . The rotor  11  is rotatably supported by a bearing  14 . 
     The annular member  13  defines an inner space  15  with the rotor  11 . The annular member  13  and the stator vane  3  remain still without being linked to rotations of the rotor  11  and the rotor blade  12 . The stator vane  3  extends along the radial direction (a direction orthogonal to the axis LA of the steam turbine  1 ) so as to traverse the inner space  15  from the annular member  13  toward the rotor  11 . The rotor blade  12  extends along the radial direction so as to traverse the inner space  15  from the rotor  11  toward the annular member  13 . 
     As shown in  FIG. 1 , the steam turbine  1  further includes a casing  16  for supporting the annular member  13  as well as housing the annular member  13 . The casing  16  internally defines an exhaust hood  17 . Further, in the casing  16 , a steam inlet  18  for introducing steam to the inner space  15 , and a steam outlet  19  for discharging steam to the outside of the steam turbine  1  are formed. 
     In the illustrated embodiment, as shown in  FIG. 1 , the steam inlet  18  is configured to allow inflow of steam, which is discharged from a steam generation device  21  for generating steam, via a steam introduction line  20 . As the steam generation device  21 , a boiler can be given as an example. As the steam introduction line  20 , a steam supply pipe for connecting the steam inlet  18  and the steam generation device  21  can be given as an example. The steam discharged from the steam generation device  21  and passing through the steam inlet  18  flows into the inner space  15 . 
     The steam introduced to the inner space  15  mainly flows along the axial direction (a direction in which the axis LA of the steam turbine  1  extends). Hereinafter, upstream of the steam flow direction may simply be referred to as “upstream”, and downstream of the steam flow direction may simply be referred to as “downstream”. 
     With the steam flowing through the inner space  15  along the axial direction being a working fluid, the steam turbine  1  is configured to convert energy of the working fluid into rotational energy of the rotor  11 . In the illustrated embodiment, provided that the combination of a vane row of the stator vanes  3  and a blade row of the rotor blades  12  is one stage, the steam turbine  1  includes a plurality of stages. The stator vanes  3  of each stage are disposed at predetermined intervals along the circumferential direction. The rotor blades  12  of each stage are disposed at predetermined intervals along the circumferential direction of the rotor  11 . The stator vanes  3  of each stage rectify steam when the steam passes between the stator vanes  3  of each stage, and upon reception of the steam rectified by the stator vanes  3 , the rotor blades  12  of each stage convert a force received from the steam into a rotational force to rotate the rotor  11 . By the rotation of the rotor  11 , a generator (not shown) mechanically connected to the rotor  11  is driven. 
     As shown in  FIG. 1 , the exhaust hood  17  is disposed downstream of the inner space  15 . The steam having passed through the stator vanes  3  and the rotor blades  12  in the inner space  15  flows into the exhaust hood  17  from an exhaust hood inlet  22  located downstream of a last-stage rotor blade  12 A which is a rotor blade located most downstream in the steam flow direction. The inflow steam passes through the exhaust hood  17 , and is then discharged from the above-described steam outlet  19  to the outside of the steam turbine  1 . 
       FIG. 2  is a schematic partially enlarged cross-sectional view of the steam turbine including the steam turbine stator vane according to an embodiment of the present invention, taken along the axial direction.  FIG. 3  is a schematic cross-sectional view of the steam turbine stator vane according to an embodiment of the present invention, taken along a direction orthogonal to the height direction. 
     As shown in  FIG. 2 , the stator vane  3  includes a vane body portion  4  extending along the height direction (the vertical direction in  FIG. 2 ). In the illustrated embodiment, the vane body portion  4  includes a base end portion  41  disposed at one end in the height direction, and a tip end portion  42  disposed at another end in the height direction. The base end portion  41  is connected to the above-described annular member  13 , and the tip end portion  42  is connected to an annular diaphragm  23  having a smaller diameter than the annular member  13 . 
     As shown in  FIG. 3 , the vane body portion  4  has a vane surface  47  that includes a pressure surface  45  which is one surface extending between a leading edge  43  and a trailing edge  44 , and a suction surface  46  which is another surface extending between the leading edge  43  and the trailing edge  44 . The pressure surface  45  includes a surface curved into a concave shape, and the suction surface  46  includes a surface curved into a convex shape. 
     The stator vane  3  is disposed in a region  15 A of the inner space  15  where a wet steam flow flows. In a certain embodiment, the region  15 A is a region that satisfies a condition where the wetness of the steam flow is not less than 5% during the operation of the steam turbine  1 . The vane body portion  4  is disposed such that the leading edge  43  is located upstream and the trailing edge  44  is located downstream in the steam flow direction. The pressure surface  45  is disposed to intersect with the steam flow direction so as to receive steam. Moisture in the wet steam flow adheres to the vane surface  47  (the pressure surface  45  and the suction surface  46 ) as water droplets (liquid). 
     As shown in  FIG. 3 , the vane body portion  4  internally forms a moisture removal channel  5 . In the illustrated embodiment, the vane body portion  4  includes a curved plate  6  encompassing the moisture removal channel  5 . The moisture removal channel  5  is defined by an inner surface  61  which is located opposite to the vane surface  47  of the curved plate  6  having the vane surface  47 . In some other embodiments, the moisture removal channel  5  may be formed in the hollow vane body portion  4 . 
     As shown in  FIG. 2 , the moisture removal channel  5  extends toward the tip end portion  42  from a base end-side opening portion  51  opening to the base end portion  41  along the height direction. In the illustrated embodiment, the moisture removal channel  5  extends from the base end-side opening portion  51  to a tip end-side opening portion  52  opening to the tip end portion  42 . 
     As shown in  FIG. 3 , the stator vane  3  includes at least one slit  7  opening to the vane surface  47  and communicating with the moisture removal channel  5 , and at least one groove portion  8  disposed in the vane surface  47 . The at least one groove portion  8  is configured not to communicate with the moisture removal channel  5 . As shown in  FIG. 2 , the at least one slit  7  extends along a height direction from the base end portion  41  toward the tip end portion  42  of the vane body portion  4 . Further, the at least one groove portion  8  extends from the base end portion  41  of the vane body portion  4  along the height direction, at least a part of the groove portion  8  overlapping the at least one slit along the height direction. 
     As shown in  FIG. 2 , inside the annular member  13 , a cavity  24  capable of storing a liquid is disposed. The cavity  24  is configured to receive a liquid W from each of the moisture removal channel  5  and the at least one groove portion  8  in the vane body portion  4 . In the illustrated embodiment, the annular member  13  internally forms a first communication hole  131  for causing the moisture removal channel  5  and the cavity  24  to communicate with each other, a second communication hole  132  for causing the groove portion  8  and the cavity  24  to communicate with each other, and a third communication hole  133  for causing the cavity  24  and the exhaust hood  17  to communicate with each other. During the operation of the steam turbine  1 , the exhaust hood  17  is lower in pressure than the cavity  24 , and the cavity  24  is lower in pressure than the moisture removal channel  5 . Then, the moisture removal channel  5  is lower in pressure than a section  15 B of the region  15 A facing the vane surface  47 . 
     The liquid W adhering between the leading edge  43  and the slit  7  in the vane surface  47  is sucked to the moisture removal channel  5  via the slit  7  by a differential pressure between the moisture removal channel  5  and the section  15 B of the region  15 A facing the vane surface  47 . The liquid W sucked to the moisture removal channel  5  is sucked to the cavity  24  via the first communication hole  131  by a differential pressure between the moisture removal channel  5  and the cavity  24 . 
     The liquid W adhering between the leading edge  43  and the groove portion  8  in the vane surface  47  is pushed by the flow of the steam flowing through the region  15 A and enters the groove portion  8 . The liquid W entering the groove portion  8  is sucked to the cavity  24  via the second communication hole  132  by a differential pressure between the groove portion  8  and the cavity  24 . 
     The liquid W stored in the cavity  24  is discharged to the exhaust hood  17  via the third communication hole  133  by a differential pressure between the cavity  24  and the exhaust hood  17 . In some other embodiments, the liquid W may be discharged to the outside of the steam turbine  1 , or it may be configured such that the liquid W is sucked by a suction device (not shown) such as a suction pump. 
     In the embodiment shown in  FIG. 2 , each of the slit  7  and the groove portion  8  is disposed between the center and the base end portion  41  in the height direction. In some other embodiments, each of the slit  7  and the groove portion  8  may extend between the center and the tip end portion  42  in the height direction, or may extend over the entire length in the height direction. 
     In the embodiment shown in  FIG. 3 , each of the slit  7  and the groove portion  8  is disposed between the trailing edge  44  and the center of the pressure surface  45 . The slit  7  includes an inlet opening  71  opening to the pressure surface  45 , and an outlet opening  72  opening to the inner surface  61  of the curved plate  6  and communicating with a trailing edge-side end portion  53  of the moisture removal channel  5 . The groove portion  8  is disposed between the slit  7  and the leading edge  43 . 
     In some other embodiments, each of the slit  7  and the groove portion  8  may be disposed between the leading edge  43  and the center of the pressure surface  45  or in the suction surface  46 . However, since liquid (water film flow) is collected on the side of the trailing edge  44  in the pressure surface  45 , each of the slit  7  and the groove portion  8  is preferably disposed in the pressure surface  45  relative to the suction surface  46  and is preferably disposed near the trailing edge  44  in the pressure surface  45 . Further, the groove portion  8  may be disposed between the slit  7  and the trailing edge  44 . 
       FIG. 4  is a schematic view of the steam turbine stator vane according to a comparative example, taken along the axial direction.  FIG. 5  is a schematic cross-sectional view of the steam turbine stator vane according to a comparative example, taken along the direction orthogonal to the height direction. 
     As shown in  FIG. 4, 5 , the stator vane  30  according to the comparative example is different from the stator vane  3  as shown in  FIG. 2, 3  in that instead of the groove portion  8 , a second slit  70  is disposed in the pressure surface  45  (vane surface  47 ). As shown in  FIG. 5 , as with the slit  7 , the second slit  70  communicates with the moisture removal channel  5 . The slit  7  is disposed between the second slit  70  and the trailing edge  44 , and is lower in pressure than the second slit  70 . In this case, the liquid W adhering to the vane surface  47  is sucked to the moisture removal channel  5  by the second slit  70 , and the liquid W sucked to the moisture removal channel  5  may spout (flow back) from the slit  7  due to a differential pressure between the slit  7  and the second slit  70 . 
       FIG. 6  is a graph for describing a relationship between a slit width and a steam suction amount of each of the steam turbine stator vane according to an embodiment of the present invention and the steam turbine stator vane according to the comparative example. In  FIG. 6 , the abscissa indicates the slit width of the slit  7  or the second slit  70 , and the ordinate indicates the suction amount of the steam sucked from the outside of the stator vane  3  to the moisture removal channel  5  via the slit  7  or the second slit  70 . As shown in  FIG. 6 , if the slit width is increased, the suction amount of the steam sucked to the moisture removal channel  5  is increased. Further, the stator vane  3  where the one slit  7  communicates with the moisture removal channel  5  has a smaller steam suction amount corresponding to any slit width than a stator vane  30  where two slits (the slit  7  and the second slit  70 ) communicate with the moisture removal channel  5 . That is, as compared with the stator vane  30 , the stator vane  3  can reduce the suction amount of the steam sucked to the moisture removal channel  5 . By reducing the suction amount of the steam sucked to the moisture removal channel  5 , it is possible to prevent a decrease in amount of the drive steam for rotating the rotor blade  12 , making it possible to prevent a decrease in performance of the steam turbine  1 . 
     As described above, for example, as shown in  FIG. 2, 3 , the stator vane  3  according to some embodiments includes the above-described vane body portion  4 , the above-described moisture removal channel  5 , the above-described at least one slit  7 , and the above-described at least one groove portion  8  at least a part of which overlaps the at least one slit  7  along the height direction. 
     In the illustrated embodiment, as shown in  FIG. 2 , the at least one slit  7  includes a single slit  7 A extending along the height direction. The at least one groove portion  8  has a cross-sectional shape formed into a U-shape, and includes an opening end portion  81  opening to the base end portion  41 . 
     With the above configuration, the stator vane  3  includes the slit  7  and the groove portion  8  disposed in the vane surface  47  which is the surface of the stator vane  3 , and the slit  7  and the groove portion  8  overlap at least partially along the height direction. Thus, it is possible to remove the liquid W collected in the vane surface  47  by a section (upstream drainage section) of the slit  7  and the groove portion  8  disposed upstream (the side of the leading edge  43 ) of the vane surface  47 . Further, it is possible to remove the liquid W collected downstream of the above-described upstream drainage section in the vane surface  47 , by a section (downstream drainage section) of the slit  7  and the groove portion  8  disposed downstream (the side of the trailing edge  44 ) of the vane surface  47 . That is, the stator vane  3  can remove the liquid W adhering to the vane surface  47 , by the groove portion  8  and the slit  7  having higher removal efficiency of the liquid W than the groove portion  8 . Thus, it is possible to improve the removal efficiency of the liquid W adhering to the vane surface  47 . 
     Further, since one of the above-described upstream drainage section or the above-described downstream drainage section is the groove portion  8  that does not communicate with the moisture removal channel  5 , the stator vane  3  can reduce the amount of the drive steam leaking to the moisture removal channel  5  through the slit, as compared with the configuration, where the two slits (the slit  7 , the second slit  70 ) overlapping each other along the height direction are disposed in the vane surface  47 , as in the stator vane  30  according to the comparative example. Further, unlike the configuration, where the two slits overlapping each other along the height direction are disposed in the vane surface  47 , as in the stator vane  30  according to the comparative example, the stator vane  3  is free from the risk that the liquid W flows back from the moisture removal channel  5  via the slit  7 , and thus the slit width need not be increased to improve a suction pressure of the slit  7 . By suppressing the suction pressure of the slit  7 , it is possible to further reduce the amount of the drive steam leaking to the moisture removal channel  5  through the slit  7 . Thus, the stator vane  3  can reduce the amount of the drive steam leaking to the moisture removal channel  5  through the slit  7 , making it possible to prevent the decrease in performance of the steam turbine  1 . 
     In some embodiments, for example, as shown in  FIG. 2 , the above-described at least one groove portion  8  is configured to be inclined to the side of the trailing edge  44  from the tip end portion  42  toward the base end portion  41 . In this case, since the at least one groove portion  8  is configured to be inclined to the side of the trailing edge  44  from the tip end portion  42  toward the base end portion  41 , the liquid W stored in the groove portion  8  is pushed by the flow of the steam flowing through the region  15 A (in the steam turbine  1 ) where the steam flow flows, and flows toward the side of the base end portion  41  which is a discharge side of the liquid W. Thus, the above-described groove portion  8  can improve removal efficiency of the liquid stored in the groove portion  8 . 
       FIG. 7  is a schematic view of the steam turbine stator vane according to a first modified example, taken along the axial direction.  FIG. 8  is a schematic view of the steam turbine stator vane according to a second modified example, taken along the axial direction.  FIG. 9  is a schematic cross-sectional view of the steam turbine stator vane according to the second modified example, taken along the direction orthogonal to the height direction. 
     In some embodiments, for example, as shown in  FIG. 7, 8 , the at least one slit  7  includes a plurality of slits  7 B disposed separately from each other in the height direction. In the illustrated embodiments, the plurality of slits  7 B are arranged in series along the height direction and extend along the height direction. 
     With the above configuration, since the plurality of slits  7 B are disposed separately from each other in the height direction, as compared with a case where the single slit  7 A extends along the height direction, it is possible to improve strength of the stator vane  3  in the vicinity of the slit  7 . Improving the strength of the stator vane  3  in the vicinity of the slit  7 , it is possible to reduce the thickness of the stator vane  3 , and thus to reduce a production cost of the stator vane  3 . 
     In some embodiments, for example, as shown in  FIG. 8, 9 , the above-described stator vane  3  includes a recess  9  which is disposed in the vane surface  47  and to which the plurality of slits  7 B open. In the illustrated embodiment, the recess  9  extends from the base end portion  41  of the vane body portion  4  along the height direction, and at least a part of the recess  9  overlaps the at least one groove portion  8  along the height direction. The recess  9  has a cross-sectional shape formed into a U-shape, and includes an opening end portion  91  opening to the base end portion  41 . In each of the plurality of slits  7 B, the inlet opening  71  opens to the bottom of the recess  9 . 
     In the embodiment shown in  FIG. 8 , the recess  9  is disposed between the center and the base end portion  41  in the height direction. In some other embodiments, the recess  9  may extend between the center and the tip end portion  42  in the height direction, or may extend over the entire length in the height direction. 
     With the above configuration, since the plurality of slits  7 B disposed separately from each other open to the recess  9  disposed in the vane surface  47 , the liquid W adhering to the vane surface  47  is pushed by the flow of the steam flowing through the region  15 A, enters the recess  9 , and is stored in the recess  9 . Thus, the stator vane  3  including the recess  9  can prevent the liquid W adhering to the vane surface  47  from flowing downstream of the slits  7 B in the vane surface  47  through the slits  7 B. Thus, the stator vane  3  including the recess  9  can improve removal efficiency of the liquid W adhering to the vane surface  47 . 
     In some embodiments, as shown in  FIG. 8 , the above-described recess  9  is configured to be inclined to the side of the trailing edge  44  from the tip end portion  42  toward the base end portion  41 . In this case, since the recess  9  is configured to be inclined to the side of the trailing edge  44  from the tip end portion  42  toward the base end portion  41 , the liquid W stored in the recess  9  is pushed by the flow of the steam flowing through the region  15 A (in the steam turbine  1 ) where the steam flow flows, and flows toward the side of the base end portion  41  which is the discharge side of the liquid W. The liquid W flowing toward the side of the base end portion  41  passes through the slit  7 B located on the side of the base end portion  41  or is discharged from the opening end portion  91  opening to the base end portion  41  to be sent to the cavity  24 . Thus, the above-described recess  9  can improve removal efficiency of the liquid W stored in the recess  9 . 
       FIG. 10  is a schematic view of the steam turbine stator vane according to a third modified example, taken along the axial direction.  FIG. 11  is a schematic cross-sectional view of the steam turbine stator vane according to the third modified example, taken along the direction orthogonal to the height direction.  FIG. 12  is a schematic cross-sectional view of the steam turbine stator vane according to the fourth modified example, taken along the direction orthogonal to the height direction.  FIG. 13  is a schematic cross-sectional view of the steam turbine stator vane according to the fifth modified example, taken along the direction orthogonal to the height direction.  FIG. 14  is a schematic cross-sectional view of the steam turbine stator vane according to the sixth modified example, taken along the direction orthogonal to the height direction. 
     In some embodiments, as shown in  FIGS. 10 to 13 , the above-described slit  7  is disposed between the above-described groove portion  8  and the leading edge  43 . In this case, it is possible to remove the liquid W that cannot be removed from the vane surface  47  by the slit  7  or the liquid W adhering between the slit  7  and the trailing edge  44  on the vane surface  47 , by the groove portion  8  disposed between the slit  7  and the trailing edge  44  on the vane surface  47 . 
     In some embodiments, as shown in  FIGS. 2, 3, 7 to 9, and 14 , the above-described slit  7  is disposed between the above-described groove portion  8  and the trailing edge  44 . In this case, it is possible to remove the liquid W that cannot be removed from the vane surface  47  by the groove portion  8  or the liquid W adhering between the groove portion  8  and the trailing edge  44  on the vane surface  47 , by the slit  7  disposed between the groove portion  8  and the trailing edge  44  on the vane surface  47 . The groove portion  8  can reduce the amount of the liquid W reaching the slit  7 , and the slit  7  has higher removal efficiency of the liquid W adhering to the vane surface  47  than the groove portion  8 , making it possible to remove the liquid W reaching the slit  7 . Thus, with the above configuration, by disposing the slit  7  between the groove portion  8  and the trailing edge  44 , it is possible to effectively remove the liquid W adhering to the vane surface  47 . 
     In some embodiments, as shown in  FIGS. 3, 9, and 11 to 14 , the above-described vane body portion  4  includes the above-described curved plate  6  encompassing the moisture removal channel  5  and configured such that a difference between a maximum value and a minimum value of a thickness T of the curved plate  6  falls within 40% of an average value of the thickness T. In this case, by equalizing the thickness T of the curved plate  6 , it is possible to reduce a material cost of the curved plate  6  by cutting wasteful consumption of a material forming the curved plate  6 , and thus to reduce the production cost of the stator vane  3 . 
     In some embodiments, the vane body portion  4  including the curved plate  6  described above is a sheet-metal part where the shape of the vane body portion  4  is formed by performing sheet-metal processing on at least one sheet metal. In this case, it is possible to form the vane body portion  4  including the curved plate  6  by performing sheet-metal processing (such as cutting, bending, and welding) on one or a plurality of sheet metals (such as metal plate materials each formed into a thin flat shape by rolling or the like). Thus, it is possible to reduce the material cost and a processing cost of the vane body portion  4 . Thus, with the above configuration, since it is possible to reduce the material cost and the processing cost of the vane body portion  4 , it is possible to reduce the production cost of the stator vane  3 . 
     In some embodiments, as shown in  FIGS. 10 to 14 , the above-described curved plate  6  includes a pressure surface-side curved plate  62  which has a surface  621  including at least a part of the above-described pressure surface  45 , and a suction surface-side curved plate  63  which has a surface  631  including at least a part of the above-described suction surface  46 . One of the above-described at least one slit  7  or the above-described at least one groove portion  8  is configured to include a joint WP where one end portion  622  of the pressure surface-side curved plate  62  and one end portion  632  of the suction surface-side curved plate  63  are joined by welding. 
     In the illustrated embodiment, as shown in  FIGS. 10 to 14 , the pressure surface-side curved plate  62  and the suction surface-side curved plate  63  each have a shape which is formed by folding one sheet metal into a V-shape such that the leading edge  43  is formed. Subsequently, joining the one end portion  622  (rear end portion) of the pressure surface-side curved plate  62  and the one end portion  632  (rear end portion) of the suction surface-side curved plate  63  by welding, the above-described curved plate  6  and one of the slit  7  or the groove portion  8  are formed. In some other embodiments, the shape of the curved plate  6  may be formed by joining the plurality of sheet metals by welding. 
     With the above configuration, one of the slit  7  or the groove portion  8  includes the joint WP where the one end portion  622  of the pressure surface-side curved plate  62  and the one end portion  632  of the suction surface-side curved plate  63  are joined by welding. That is, the shape of one of the slit  7  or the groove portion  8  is formed, when the curved plate  6  is formed by welding the one end portion  622  of the pressure surface-side curved plate  62  and the one end portion  632  of the suction surface-side curved plate  63 . With the above configuration, since additional processing such as cutting is not needed to form one of the slit  7  or the groove portion  8 , it is possible to reduce the processing cost, and thus to reduce the production cost of the stator vane  3 . Further, with the above configuration, since one of the slit  7  or the groove portion  8  can be formed without processing such as cutting, it is possible to prevent a decrease in strength in the vicinity of one of the slit  7  or the groove portion  8 . 
     In some embodiments, as shown in  FIGS. 10 to 12 , the above-described vane body portion  4  includes the above-described curved plate  6  including the pressure surface-side curved plate  62  and the suction surface-side curved plate  63 , and a trailing edge portion  64  disposed between the above-described joint WP and the trailing edge  44 . The trailing edge portion  64  has a trailing edge-side pressure surface  642  connected to the trailing edge  44 , and a trailing edge-side wall surface  644  extending from a front end portion  643  on the trailing edge-side pressure surface  642  along a direction intersecting with the trailing edge-side pressure surface  642 . The above-described at least one groove portion  8  includes the above-described joint WP, and a part of the groove portion  8  is defined by the trailing edge-side wall surface  644 . 
     In the embodiment shown in  FIG. 10, 11 , the trailing edge portion  64  is disposed integrally with the one end portion  632  of the suction surface-side curved plate  63 , and the trailing edge-side suction surface  641  of the trailing edge portion  64  is loosely connected to the surface  631  of the suction surface-side curved plate  63 . The trailing edge portion  64  is formed by the sheet metal forming the suction surface-side curved plate  63 , and the shape of the trailing edge portion  64  is formed by sheet-metal processing. The groove portion  8  has a U-shaped cross-sectional shape which is defined by an end surface  623  at the one end portion  622  of the pressure surface-side curved plate  62 , the trailing edge-side wall surface  644 , and a bottom surface  645  connecting end portions of the end surface  623  and the trailing edge-side wall surface  644  on the side of the suction surface  46 . The above-described joint WP joins a section between the end surface  623  and the bottom surface  645 . The slit  7  (such as  7 B) is disposed in the pressure surface-side curved plate  62  located between the groove portion  8  and the leading edge  43 . 
     In the embodiment shown in  FIG. 10, 11 , in a section of the vane body portion  4  where the groove portion  8  does not extend in the height direction, a protruding end surface  624  protruding between the above-described end surface  623  and the trailing edge  44 , and a trailing edge-side wall surface  644  are joined by welding. 
     In the embodiment shown in  FIG. 12 , the trailing edge portion  64  is disposed integrally with the one end portion  632  of the suction surface-side curved plate  63 , and the trailing edge-side suction surface  641  of the trailing edge portion  64  is loosely connected to the surface  631  of the suction surface-side curved plate  63 . The trailing edge portion  64  is formed by the sheet metal forming the suction surface-side curved plate  63 , and the shape of the trailing edge portion  64  is formed by sheet-metal processing. In the one end portion  622  of the pressure surface-side curved plate  62 , an inclined surface  625 , with an edge portion on the side of the pressure surface  45  being inclined between the trailing edge  44  and an edge portion on the side of the suction surface  46 , is formed. The above-described inclined surface  625  is joined by welding in contact with the inner surface  633  at the one end portion  632  of the suction surface-side curved plate  63 . The groove portion  8  is defined by the trailing edge-side wall surface  644 , the bottom surface  645  extending from the suction surface-side end portion  646  of the trailing edge-side wall surface  644  along the direction intersecting with the trailing edge-side wall surface  644 , and a surface  621 A of the surface  621  of the pressure surface-side curved plate  62  in the vicinity of the one end portion  622 . The above-described surface  621 A is loosely connected to the bottom surface  645 . The above-described joint WP joins a section between the surface  621 A and the bottom surface  645 . The slit  7  is disposed in the pressure surface-side curved plate  62  located between the groove portion  8  and the leading edge  43 . 
     In the embodiment shown in  FIG. 12 , the trailing edge-side pressure surface  642  is disposed to protrude between the surface  621  of the pressure surface-side curved plate  62  and the suction surface  46  of the stator vane  3  adjacent in the circumferential direction, and a gap between the trailing edge-side pressure surface  642  and the above-described suction surface  46  is narrow. A section between the trailing edge  44  of the stator vane  3  and the suction surface  46  of the stator vane  3  adjacent in the circumferential direction is a throat section TH. In the above-described throat section TH, it is configured such that the gap between the stator vanes  3  is minimum. The flow velocity of steam is low upstream of the throat section TH, and thus a pressure loss is small. Thus, the above-described trailing edge-side pressure surface  642  does not impair the steam flow. 
     With the above configuration, the at least one groove portion  8  includes the joint WP, and a part of the groove portion  8  is defined by the trailing edge-side wall surface  644 . That is, the shape of the groove portion  8  is formed as a part of the trailing edge-side wall surface  644  of the trailing edge portion  64 , when the curved plate  6  is formed by welding. Since a part of the above-described groove portion  8  is defined by the trailing edge-side wall surface  644  extending along the direction intersecting with the trailing edge-side pressure surface  642 , it is possible to effectively prevent the liquid W adhering to the vane surface  47  from flowing toward the trailing edge-side pressure surface  642  from the trailing edge-side wall surface  644 . 
     In some embodiments, as shown in  FIG. 13 , the above-described vane body portion  4  includes the above-described curved plate  6  including the pressure surface-side curved plate  62  and the suction surface-side curved plate  63 , and the trailing edge portion  64  disposed between the above-described joint WP and the trailing edge  44 . The trailing edge portion  64  has the trailing edge-side pressure surface  642  connected to the trailing edge  44 , and the trailing edge-side wall surface  644  extending from the front end portion  643  on the trailing edge-side pressure surface  642  along the direction intersecting with the trailing edge-side pressure surface  642 . The above-described at least one slit  7  includes the above-described joint WP and a part of the slit  7  is defined by the trailing edge-side wall surface  644 . 
     In the embodiment shown in  FIG. 13 , the trailing edge portion  64  is disposed integrally with the one end portion  632  of the suction surface-side curved plate  63 . The trailing edge-side suction surface  641  of the trailing edge portion  64  is loosely connected to the surface  631  of the suction surface-side curved plate  63 . Further, the trailing edge-side wall surface  644  is connected to the inner surface  61 . The trailing edge portion  64  is formed by the sheet metal forming the suction surface-side curved plate  63 , and the shape of the trailing edge portion  64  is formed by sheet-metal processing. The above-described one end portion  632  may include the trailing edge portion  64 . The trailing edge portion  64  includes a thick portion  64 A configured such that a thickness gradually increases toward the side of the leading edge  43 . 
     The shape of the slit  7  is defined by the end surface  623  at the one end portion  622  of the pressure surface-side curved plate  62 , the trailing edge-side wall surface  644 , and the joint WP joining a section between the end surface  623  and the trailing edge-side wall surface  644 . The groove portion  8  is disposed in the trailing edge-side pressure surface  642  of the thick portion  64 A (trailing edge portion  64 ) located between the slit  7  and the trailing edge  44 , and has a U-shaped cross-sectional shape. By thus disposing the groove portion  8  in the trailing edge portion  64  located between the slit  7  and the trailing edge  44 , as compared with a case where the groove portion  8  is disposed in the pressure surface-side curved plate  62  located between the slit  7  and the leading edge  43 , it is possible to improve removal efficiency of the liquid adhering to the vane surface  47 . Further, the process of forming the groove portion  8  in the trailing edge portion  64  can be performed more easily than the process of forming the groove portion  8  in the pressure surface-side curved plate  62 . Furthermore, with the configuration where the groove portion  8  is not disposed in the pressure surface-side curved plate  62 , it is possible to reduce the thickness of the pressure surface-side curved plate  62  (curved plate  6 ). 
     Moreover, setting the joint WP on the trailing edge-side wall surface  644  to a section  644 A spaced apart from the front end portion  643  toward the side of the suction surface  46 , it is possible to form the above-described recess  9  by a section  644 B of the trailing edge-side wall surface  644  between the above-described section  644 A and the front end portion  643 , and the surface  621  of the pressure surface-side curved plate  62 . That is, the shape of the recess  9  is formed as a part of the trailing edge-side wall surface  644  of the trailing edge portion  64 , when the curved plate  6  is formed by welding. 
     With the above configuration, the at least one slit  7  includes the joint WP, and a part of the slit  7  is defined by the trailing edge-side wall surface  644 . That is, the shape of the slit  7  is formed as a part of the trailing edge-side wall surface  644  of the trailing edge portion  64 , when the curved plate  6  is formed by welding. Since a part of the above-described slit  7  is defined by the trailing edge-side wall surface  644  extending along the direction intersecting with the trailing edge-side pressure surface  642 , the liquid W adhering to the vane surface  47  is removed from the vane surface  47  by the slit  7  in the trailing edge-side wall surface  644 . Thus, with the above configuration, it is possible to effectively prevent the liquid W adhering to the vane surface  47  from flowing toward the trailing edge-side pressure surface  642  from the trailing edge-side wall surface  644 . 
     In some embodiments, as shown in  FIG. 14 , the above-described vane body portion  4  includes the above-described curved plate  6  including the pressure surface-side curved plate  62  and the suction surface-side curved plate  63 . The above-described suction surface-side curved plate  63  includes an extension portion  65  which extends from the trailing edge  44  toward the leading edge  43  and has a surface  651  including at least a part of the pressure surface  45 . The one end portion  632  of the suction surface-side curved plate  63  includes a front end portion  652  of the extension portion  65  located on the side of the leading edge  43 . The above-described at least one groove portion  8  includes the above-described joint WP, and a part of the groove portion  8  is defined by an end surface  653  at the front end portion  652  of the extension portion  65 . 
     In the embodiment shown in  FIG. 14 , the suction surface-side curved plate  63  and the extension portion  65  each have a shape which is formed by folding one sheet metal into a V-shape such that the trailing edge  44  is formed. The end surface  653  at the front end portion  652  extends along the direction intersecting with the surface  651  and the surface  621  of the pressure surface-side curved plate  62 , and is a stepped surface connecting the surface  621  and the surface  651 . The groove portion  8  is defined by the end surface  653  and the surface  621 A of the surface  621  of the pressure surface-side curved plate  62  in the vicinity of the one end portion  622 . The above-described joint WP joins a section between the end surface  653  and the surface  621 A. The slit  7  is disposed in the extension portion  65  located between the groove portion  8  and the trailing edge  44 , and the inlet opening  71  opens to the surface  651 . 
     With the above configuration, the at least one groove portion  8  includes the joint WP and a part of the groove portion  8  is defined by the end surface  653  at the front end portion  652  of the extension portion  65 . That is, the shape of the groove portion  8  is formed as a part of the end surface  653  at the front end portion  652  of the extension portion  65 , when the curved plate  6  is formed by welding the one end portion  622  of the pressure surface-side curved plate  62  and the front end portion  652 . Since a part of the above-described groove portion  8  is defined by the end surface  653  at the front end portion  652  of the extension portion  65  located on the side of the leading edge  43 , it is possible to effectively prevent the liquid W adhering to the end surface  653  from flowing toward the surface  651  (pressure surface) of the extension portion  65 . 
     As shown in  FIG. 2 , the steam turbine  1  according to some embodiments includes the above-described stator vane  3 , the above-described annular member  13  for supporting the stator vane  3 , and the above-described cavity  24  disposed in the annular member  13  and configured to receive the liquid W from each of the moisture removal channel  5  and the at least one groove portion  8  in the vane body portion  4 . 
     With the above configuration, since the steam turbine  1  includes the cavity  24  disposed in the annular member  13  and configured to receive the liquid from each of the moisture removal channel  5  and the at least one groove portion  8  in the vane body portion  4 , it is possible to store, in the cavity  24 , the liquid W removed from the vane surface  47  by the slit  7  and the groove portion  8 . Storing, in the cavity  24 , the liquid W removed from the vane surface  47  by the slit  7  and the groove portion  8 , it is possible to prevent that the liquid W accumulates in the slit  7  and the moisture removal channel  5  in the vane body portion  4 , and removal efficiency of the liquid W adhering to the vane surface  47  by the slit  7  and the groove portion  8  is decreased. Thus, the above-described steam turbine  1  can effectively remove the liquid W adhering to the vane surface  47  by the slit  7  and the groove portion  8 . 
       FIG. 15  is a flowchart showing an example of a production method for the steam turbine stator vane according to an embodiment of the present invention. 
     As shown in  FIG. 15 , a production method  100  for the steam turbine stator vane according to some embodiments includes a slit forming step S 102  of forming the above-described at least one slit  7 , and a groove portion forming step S 103  of forming the above-described at least one groove portion  8 . In the illustrated embodiment, as shown in  FIG. 15 , the production method  100  for the steam turbine stator vane further includes a curved plate forming step S 101  of forming the above-described curved plate  6 . The curved plate forming step S 101  includes forming the above-described curved plate  6  from one or a plurality of sheet metals by sheet-metal processing. 
     The slit forming step S 102  includes forming the at least one slit  7  ( 7 A,  7 B) that opens to the vane surface  47  of the vane body portion  4 , which has the vane surface  47  including the pressure surface  45  and the suction surface  46 , to communicate with the moisture removal channel  5  disposed in the vane body portion  4 , and extends along the height direction from the base end portion  41  toward the tip end portion  42  of the vane body portion  4 . 
     The groove portion forming step S 103  includes forming the at least one groove portion  8  which extends from the base end portion  41  along the height direction in the vane surface  47  and at least a part of which overlaps the at least one slit  7  along the height direction. 
     Each of the slit  7  and the groove portion  8  may be formed by cutting, or the shape of each of the slit  7  and the groove portion  8  may be formed when the curved plate  6  is formed as described above. 
     With the above method, the production method  100  for the steam turbine stator vane includes the slit forming step S 102  of forming the at least one slit  7 , and the groove portion forming step S 103  of forming the at least one groove portion  8 . The stator vane  3  produced by the production method  100  for the steam turbine stator vane includes the slit  7  and the groove portion  8  disposed in the vane surface  47  which is the surface of the stator vane  3 , and the slit  7  and the groove portion  8  overlap at least partially along the height direction. Thus, the stator vane  3  produced by the production method  100  for the steam turbine stator vane can improve removal efficiency of the liquid W adhering to the vane surface  47  and can prevent the decrease in performance of the steam turbine  1 . 
     The present invention is not limited to the above-described embodiments, and also includes an embodiment obtained by modifying the above-described embodiments and an embodiment obtained by combining these embodiments as appropriate. 
     REFERENCE SIGNS LIST 
     
         
           1  Steam turbine 
           3  Stator vane 
           30  Stator vane according to comparative example 
           4  Vane body portion 
           41  Base end portion 
           42  Tip end portion 
           43  Leading edge 
           44  Trailing edge 
           45  Pressure surface 
           46  Suction surface 
           47  Vane surface 
           5  Moisture removal channel 
           51  Base end-side opening portion 
           52  Tip end-side opening portion 
           53  Trailing edge-side end portion 
           6  Curved plate 
           61  Inner surface 
           62  Pressure surface-side curved plate 
           63  Suction surface-side curved plate 
           64  Trailing edge portion 
           64 A Thick portion 
           65  Extension portion 
           7 ,  7 A,  7 B Slit 
           70  Second slit 
           71  Inlet opening 
           72  Outlet opening 
           8  Groove portion 
           81  Opening end portion 
           9  Recess 
           91  Opening end portion 
           11  Rotor 
           12  Rotor blade 
           12 A Last-stage rotor blade 
           13  Annular member 
           131  First communication hole 
           132  Second communication hole 
           133  Third communication hole 
           14  Bearing 
           15  Inner space 
           15 A Region 
           15 B Section 
           16  Casing 
           17  Exhaust hood 
           18  Steam inlet 
           19  Steam outlet 
           20  Steam introduction line 
           21  Steam generation device 
           22  Exhaust hood inlet 
           23  Diaphragm 
           24  Cavity 
           100  Production method for stator vane 
         LA Axis 
         S 101  Curved plate forming step 
         S 102  Slit forming step 
         S 103  Groove portion forming step 
         T Thickness 
         TH Throat section 
         W Liquid 
         WP Joint