Patent Publication Number: US-11391159-B2

Title: Blade and rotary machine having the same

Description:
TECHNICAL FIELD 
     The present disclosure relates to a blade and a rotary machine having the same. 
     BACKGROUND ART 
     With regard to a blade to be applied to a machine such as a rotary machine, separation of a flow may occur in the vicinity of the blade surface of the blade, depending on the operation conditions or the like. When separation of a flow occurs, work on the blade surface decreases, which may lead to deterioration of the performance or operation efficiency of the machine. Thus, it is necessary to design the airfoil so as to reduce the loss generated by separation of the flow or the like. 
     For instance, Patent Document 1 discloses a blade used for a turbine engine. A flow passage (channel) is disposed inside the airfoil portion of the blade. A gas extraction inlet disposed on the suction surface and the tip end of the airfoil portion is in communication via the flow passage. Furthermore, as a part of the air flow that flows along the airfoil portion is sucked into the flow passage inside the airfoil portion via the gas extraction inlet, separation of the air flow from the blade surface is reduced. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Document 1: JP2017-190776A 
       
    
     SUMMARY 
     As described in Patent Document 1, by taking a part of the flow near the blade surface into the internal passage of the airfoil, it could be possible to reduce separation of the flow from the blade surface. Furthermore, in order to suppress such separation more effectively, it is desirable to suitably set the position or the like of the intake port (in Patent Document 1, the gas extraction inlet) on the bade surface more suitably. 
     In view of the above, an object of at least one embodiment of the present invention is to provide a blade and a rotary machine having the same, whereby it is possible to suppress separation that may occur in the vicinity of the blade surface effectively. 
     (1) According to at least one embodiment of the present invention, a blade includes: an airfoil portion having a pressure surface and a suction surface each of which extends between a base end and a tip end along a blade height direction between a leading edge and a trailing edge; and an internal passage passing through an inside of the airfoil portion, the internal passage having a first opening end opening to one of the pressure surface or the suction surface and a second opening end being positioned closer to the tip end than the first opening end in the blade height direction and opening to a surface of the airfoil portion. When L is a length from the base end to the tip end in the blade height direction, a distance from the base end to the first opening end in the blade height direction is not less than zero and not greater than 0.3 L. 
     In some cases, separation of the flow in the vicinity of the blade surface in a rotary machine tends to occur relatively in a region at the side of the base end of the airfoil portion (e.g. the region within 30% from the base end in the blade height direction). 
     In this regard, with the above configuration (1), the internal passage passing through the inside of the airfoil portion includes a first opening end which opens to the blade surface (pressure surface or suction surface) at a position where the distance from the base end in the blade height direction is not greater than 0.3 L, and a second opening end which is positioned closer to the tip end than the first opening end in the blade height direction and which opens to the surface of the airfoil portion. Thus, when the blade rotates about the rotor center axis, in the above described internal passage, a pressure increase is caused by a centrifugal force (pumping pressure increase) due to the radius difference between the first opening end at the radially inner side (at the side of the base end) and the second opening end at the radially outer side (at the side of the tip end). Accordingly, in the internal passage, a flow that flows from the first opening end at the radially inner side to the second opening end at the radially outer side is generated. Thus, it is possible to take the flow in the vicinity of the blade surface where the first opening end is provided (that is, the region near a position whose distance from the base end is not greater than 0.3 L, where separation is likely to occur) into the internal passage from the first opening end, and thereby it is possible to suppress separation that may occur in the vicinity of the blade surface effectively. Therefore, with the above configuration (1), it is possible to reduce the separation region on the blade surface, and suppress deterioration of the efficiency of the rotary machine. 
     (2) In some embodiments, in the above configuration (1), the first opening end opens to the suction surface. 
     With regard to a blade of a rotary machine, in some cases, separation of the flow is likely to occur at the suction surface side, depending on the operation conditions and load on the blade rows. In this regard, with the above configuration (2), the first opening end of the internal passage is disposed at the suction surface side, and thus it is possible to take in the flow in the vicinity of the suction surface from the first opening end by utilizing the above described pumping effect, and thereby suppress separation of the flow that may occur in the vicinity of the suction surface of the blade effectively. 
     (3) In some embodiments, in the above configuration (1) or (2), the internal passage includes: a radial-directional passage portion extending along the blade height direction; and an intake portion extending between a base-end side end of the radial-directional passage portion and the first opening end. When seen from the blade height direction, an extension direction of the intake portion forms an angle of not greater than 45 angular degrees with a portion of a tangent to the one of the pressure surface or the suction surface at the first opening end, the portion being disposed at a trailing edge side with respect to the first opening end. 
     With the above configuration (3), the internal passage includes the radial-directional passage portion extending in the blade height direction, and thereby the fluid flowing into the internal passage is likely to be pressurized effectively by the above described pumping effect. Thus, it is possible to take in the flow in the vicinity of the blade surface effectively via the first opening end, and suppress separation that may occur in the vicinity of the blade surface effectively. 
     Furthermore, with the above configuration (3), when seen from the blade height direction, the extension direction of the intake portion extending between the base-end side end of the radial-directional passage portion and the first opening end forms an angle of not greater than 45 angular degrees with the above described tangent. That is, the intake portion has a shape along the blade surface (suction surface or pressure surface) at the position of the first opening end, and thus it is possible to take the fluid flowing in the vicinity of the blade surface smoothly into the internal passage via the intake portion. 
     (4) In some embodiments, in any one of the above configurations (1) to (3), the first opening end has a plurality of holes opening to the one of the pressure surface or the suction surface. 
     With the above configuration (4), the first opening end of the internal passage has a plurality of holes that open to the blade surface (pressure surface or suction surface), and thus it is possible to take in the flow of the fluid from a broader region near the blade surface via the plurality of holes. Thus, it is possible to suppress separation of the flow that may occur in the vicinity of the blade surface more effectively. 
     (5) In some embodiments, in any one of the above configurations (1) to (4), the internal passage includes a radial-directional passage portion extending along the blade height direction, and when t max  is a maximum blade thickness of the airfoil portion at a position of the tip end in the blade height direction, the radial-directional passage portion has a blade-thickness directional length of not smaller than 0.3 t max  and not greater than 0.7 t max . 
     With the above configuration (5), with the blade-thickness directional length of the radial-directional passage portion being not greater than 0.3 t max , it is possible to ensure the flow-passage cross sectional area of the radial-directional passage portion and obtain the above described pumping effect suitably, whereby it is possible to take the flow in the vicinity of the blade surface into the internal passage via the first opening end suitably. Furthermore, with the above configuration (5), with the blade-thickness directional length of the radial-directional passage portion being not greater than 0.7 t max , it is possible to maintain a suitable strength of the airfoil portion. 
     (6) In some embodiments, in any one of the above configurations (1) to (5), the internal passage includes a radial-directional passage portion extending along the blade height direction, and when t max  is a maximum blade thickness of the airfoil portion at a position of the tip end in the blade height direction, the radial-directional passage portion has a flow-passage cross sectional area whose equivalent diameter is not smaller than 0.7 t max . 
     With the above configuration (6), since the radial-directional passage portion has a flow-passage cross sectional area whose equivalent diameter is 0.7 t max , it is possible to increase the flow-passage cross sectional area, whereby it is possible to achieve the above described pumping effect effectively from the increased flow rate of the internal passage, and take the flow in the vicinity of the blade surface into the internal passage effectively via the first opening end. 
     (7) In some embodiments, in any one of the above configurations (1) to (6), the internal passage includes a radial-directional passage portion extending along the blade height direction, and the ratio S 1 /S 3  of the flow-passage cross sectional area S 1  of the internal passage at the first opening end to the flow-passage cross sectional area S 3  of the radial-directional passage portion or the ratio S 2 /S 3  of the flow-passage cross sectional area S 2  of the internal passage at the second opening end to the flow-passage cross sectional area S 3  of the radial-directional passage portion is not smaller than 0.8 and not greater than 1.2. 
     With the above configuration (7), the above described ratio S 1 /S 3  or S 2 /S 3  is close to one. That is, there is no significant difference between the flow-passage cross sectional area S 1  at the first opening end, the flow-passage cross sectional area S 2  at the second opening end, and the flow-passage cross sectional area S 3  at the radial-directional passage portion  58 , and thus the flow-passage cross sectional area of the internal passage does not change considerably from the first opening end to the second opening end. Thus, it is possible to suppress separation of the flow that may occur in the vicinity of the blade surface effectively while reducing pressure loss in the internal passage. 
     (8) In some embodiments, in any one of the above configurations (1) to (7), a distance from the base end to the second opening end in the blade height direction is not smaller than 0.9 L and not greater than 1.0 L. 
     With the above configuration (8), the distance from the base end to the second opening end in the blade height direction is not smaller than 0.9 L and not greater than 1.0 L. That is, since the second opening end is disposed in the range of 10% from the tip end in the blade height direction, it is possible to ensure a larger distance between the first opening end and the second opening end in the blade height direction. Accordingly, in the internal passage, it is possible to increase the centrifugal difference due to the radius difference between the first opening end at the radially inner side (at the side of the base end) and the second opening end at the radially outer side (at the side of the tip end), whereby it is possible to effectively obtain the pressurizing effect from pumping. Thus, thanks to the pumping effect, it is possible to suppress separation that may occur in the vicinity of the blade surface more effectively. 
     Further, in a rotary machine, a tip leakage flow (tip clearance flow) may occur between the tip end of the rotor blade and the casing. In this regard, with the above configuration (8), the flow taken into the internal passage via the first opening end is discharged from the tip end or the second opening end disposed near the tip end in the blade height direction. Thus, it is possible to suppress the above described leakage flow by utilizing the flow discharged from the second opening end, and improve the efficiency of the rotary machine even further. 
     (9) In some embodiments, in any one of the above configurations (1) to (8), the second opening end opens to one of the pressure surface or the suction surface. 
     In a blade of a rotary machine, separation of a flow may occur in a region at the tip-end side (radially outer side) of the position where the first opening end is disposed in the blade height direction. In this regard, with the above configuration (9), the second opening end disposed closer to the tip end than the first opening end in the blade height direction opens to the blade surface (pressure surface or suction surface). Thus, as the flow taken into the internal passage via the first opening end is discharged from the second opening end, a kinetic momentum is supplied to the flow in the vicinity of the blade surface where the second opening end is provided, and thus it is possible to suppress separation of the flow that may occur in the vicinity of the blade surface. Thus, it is possible to suppress separation that may occur in the vicinity of the surface more effectively. 
     (10) In some embodiments, in the above configuration (9), the internal passage includes: a radial-directional passage portion extending along the blade height direction; and an outflow portion extending between a tip-end side end of the radial-directional passage portion and the second opening end. When seen from the blade height direction, an extension direction of the outflow portion forms an angle of not greater than 45 angular degrees with a portion of a tangent to the one of the pressure surface or the suction surface at the second opening end, the portion being disposed at a leading edge side with respect to the second opening end. 
     With the above configuration (10), when seen from the blade height direction, the extension direction of the outflow portion extending between the tip-end side end of the radial-directional passage portion and the second opening end forms an angle of not greater than 45 angular degrees with the above described tangent. That is, the outflow portion has a shape along the blade surface (pressure surface or suction surface) at the position of the second opening end, and thus it is possible to cause the flow flowing out from the second opening end via the outflow portion to flow along the blade surface. Accordingly, it is possible to reduce mixing loss of the flow flowing out from the second opening end and the fluid flowing in the vicinity of the blade surface. 
     (11) In some embodiments, in any one of the above configurations (1) to (10), the internal passage includes: a radial-directional passage portion extending along the blade height direction; and an outflow portion extending between a tip-end side end of the radial-directional passage portion and the second opening end. The outflow portion has a shape whose flow-passage cross sectional area increases gradually toward the second opening end, at a portion including the second opening end. 
     With the above configuration (11), the outflow portion has a shape whose flow-passage cross sectional area gradually increases toward the second opening end, at a portion including the second opening end, whereby it is possible to supply a fluid having a kinetic momentum to a broad region in the vicinity of the blade surface, via the outflow portion. Thus, it is possible to suppress the above described tip leakage flow effectively, and suppress separation of the flow that may occur in the vicinity of the blade surface effectively. 
     (12) In some embodiments, in any one of the above configurations (1) to (11), in a cross section at a position of the second opening end in the blade height direction, when C is a chord length of the airfoil portion, a distance between the leading edge and the second opening end in a chord direction of the airfoil portion is greater than zero and not greater than 0.5 C. 
     Separation of the flow in the vicinity of the blade surface may occur near the center position in the chord direction. In this regard, with the above configuration (12), with the second opening end being disposed relatively upstream in the chord direction, separation in the vicinity of the blade surface is likely to occur at a position downstream of the second opening end. Thus, it is possible to suppress separation of the flow that may occur in the vicinity of the blade surface more effectively. 
     (13) In some embodiments, in any one of the above configurations (1) to (12), when seen from the blade height direction, the second opening end is positioned downstream of the first opening end in a chord direction of the airfoil portion. 
     With the above configuration (13), the second opening end is positioned downstream of the first opening end, and thus it is possible to reduce loss of the flow flowing toward the downstream side from the upstream side, and suppress separation that may occur in the vicinity of the blade surface effectively while suppressing deterioration of the efficiency of the rotary machine. 
     (14) According to at least one embodiment of the present invention, a rotary machine includes the blade according to any one of the above (1) to (13). 
     With the above configuration (14), the internal passage passing through the inside of the airfoil portion includes a first opening end which opens to the blade surface (pressure surface or suction surface) at a position where the distance from the base end in the blade height direction is not greater than 0.3 L, and a second opening end which is positioned closer to the tip end than the first opening end in the blade height direction and which opens to the surface of the airfoil portion. Thus, when the blade rotates about the rotor center axis, in the above described internal passage, a centrifugal force difference (pumping) is caused by the radius difference between the first opening end at the radially inner side (at the side of the base end) and the second opening end at the radially outer side (at the side of the tip end). Accordingly, in the internal passage, a flow that flows from the first opening end at the radially inner side to the second opening end at the radially outer side is generated. Thus, it is possible to take the flow in the vicinity of the blade surface where the first opening end is provided (that is, a region near a position whose distance from the base end is not greater than 0.3 L, where separation is likely to occur) into the internal passage from the first opening end, and thereby it is possible to effectively suppress separation that may occur in the vicinity of the blade surface. Therefore, with the above configuration (14), it is possible to reduce the separation region on the blade surface, and suppress reduction of the efficiency of the rotary machine. 
     According to at least one embodiment of the present invention, it is possible to provide a blade and a rotary machine having the same, whereby it is possible to suppress separation that may occur in the vicinity of the blade surface effectively. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic configuration diagram of a gas turbine according to an embodiment. 
         FIG. 2  is a perspective view of a rotor blade according to an embodiment. 
         FIG. 3  is a perspective view of a rotor blade according to an embodiment. 
         FIG. 4  is a perspective view of a rotor blade according to an embodiment. 
         FIG. 5  is a front view of the rotor blade depicted in  FIG. 2 . 
         FIG. 6  is a schematic diagram of the tip end of a rotor blade according to an embodiment, as seen from the blade height direction. 
         FIG. 7A  is a cross-sectional view of the rotor blade depicted in  FIG. 2 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 7B  is a cross-sectional view of the rotor blade depicted in  FIG. 2 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 7C  is a cross-sectional view of the rotor blade depicted in  FIG. 2 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 8A  is a cross-sectional view of the rotor blade depicted in  FIG. 4 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 8B  is a cross-sectional view of the rotor blade depicted in  FIG. 4 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 8C  is a cross-sectional view of the rotor blade depicted in  FIG. 4 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 9A  is a partial schematic cross-sectional view of an airfoil portion of a rotor blade according to an embodiment. 
         FIG. 9B  is a partial schematic cross-sectional view of an airfoil portion of a rotor blade according to an embodiment. 
         FIG. 10  is a schematic cross-sectional view of an airfoil portion of a rotor blade according to an embodiment. 
         FIG. 11  is a schematic cross-sectional view of an airfoil portion of a rotor blade according to an embodiment. 
         FIG. 12  is a perspective view of a rotor blade according to an embodiment. 
         FIG. 13A  is a cross-sectional view of the rotor blade depicted in  FIG. 12 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 13B  is a cross-sectional view of the rotor blade depicted in  FIG. 12 , taken along a direction that is orthogonal to the blade height direction. 
         FIG. 13C  is a cross-sectional view of the rotor blade depicted in  FIG. 12 , taken along a direction that is orthogonal to the blade height direction. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will now be described in detail 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 in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present invention. 
     A rotary machine to which a blade according to the embodiment of the present invention is to be applied may be a compressor or a turbine, for instance, or a gas turbine that includes a compressor or a turbine. Firstly, with reference to  FIG. 1 , the gas turbine to which a blade according to some embodiments is to be applied will be described. 
       FIG. 1  is a schematic configuration diagram of a gas turbine according to an embodiment. As depicted in  FIG. 1 , the gas turbine  1  includes a compressor  2  for producing compressed air, a combustor  4  for producing combustion gas from the compressed air and fuel, and a turbine  6  configured to be rotary driven by combustion gas. In the case of the gas turbine  1  for power generation, a generator (not illustrated) is connected to the turbine  6 . 
     The compressor  2  includes a plurality of stator vanes  16  fixed to the side of the compressor casing  10  and a plurality of rotor blades  18  implanted on the rotor  8  so as to be arranged alternately with the stator vanes  16 . 
     The above compressor  2  is configured to be supplied with air taken in from an air intake  12 , and the air flows through the plurality of stator vanes  16  and the plurality of rotor blades  18  to be compressed, and turns into compressed air having a high temperature and a high pressure. 
     The combustor  4  is configured to be supplied with fuel and the compressed air produced in the compressor  2 , and combusts the fuel to produce combustion gas that serves as a working fluid of the turbine  6 . As depicted in  FIG. 1 , the gas turbine  1  includes a plurality of combustors  4  arranged along the circumferential direction around the rotor  8  inside the casing  20 . 
     The turbine  6  has a combustion gas passage  28  formed by a turbine casing  22 , and includes a plurality of stator vanes  24  and a plurality of rotor blades  26  disposed in the combustion gas passage  28 . The stator vanes  24  and the rotor blades  26  of the turbine  6  are disposed downstream of the combustor  4 , with respect to the flow of combustion gas. 
     The stator vanes  24  are fixed to the side of the turbine casing  22 , and a plurality of stator vanes  24  arranged along the circumferential direction of the rotor  8  form a stator vane row. Furthermore, the rotor blades  26  are implanted on the rotor  8 , and a plurality of rotor blades  26  arranged along the circumferential direction of the rotor  8  form a rotor blade row. The rotor rows and the vane rows are arranged alternately in the axial direction of the rotor  8 . 
     In the turbine  6 , the rotor  8  is rotary driven by combustion gas from the combustor  4  flowing into the combustion gas passage  28  and passing through the plurality of stator vanes  24  and the plurality of rotor blades  26 , and thereby a generator coupled to the rotor  8  is driven and electric power is generated. The combustion gas having driven the turbine  6  is discharged outside via the discharge chamber  30 . 
     Hereinafter, the blade according to some embodiments will be described. According to some embodiments, the blade is to be applied to a rotary machine, and configured to be attached to a rotor of the rotary machine and rotate with the rotor. For instance, according to some embodiments, the blade may be a rotor blade  18  of the compressor  2  or a rotor blade  26  of the turbine  6 , of the above described gas turbine  1 . Hereinafter, the rotor blade  18  of the compressor  2  will be described as a blade according to some embodiments. 
       FIGS. 2 to 4, and 12  are each a perspective view of the rotor blade  18  ( 18 A to  18 D) according to an embodiment.  FIG. 5  is a front view of the rotor blade  18 A depicted in  FIG. 2 .  FIG. 6  is a schematic diagram of the tip end  44  of the rotor blade  18  according to an embodiment, as seen from the blade height direction.  FIGS. 7A to 7C  are each a cross-sectional view of the rotor blade  18 A depicted in  FIG. 2 , taken along a direction that is orthogonal to the blade height direction.  FIGS. 8A to 8C  are each a cross-sectional view of the rotor blade  18 C depicted in  FIG. 4 , taken along a direction that is orthogonal to the blade height direction.  FIGS. 13A to 13C  are each a cross-sectional view of the rotor blade  18 D depicted in  FIG. 12 , taken along a direction that is orthogonal to the blade height direction. 
     In the present specification, the blade height direction refers to a direction connecting the base end  43  and the tip end  44  of the airfoil portion  40 , and substantially coincides with the radial direction of the rotor in a state where the rotor blade  18  is mounted to the rotor of the compressor  2 . 
     As depicted in  FIGS. 2 to 5 and 12 , the rotor blade  18  according to some embodiments includes the airfoil portion  40  extending between the base end  43  and the tip end  44 , in the blade height direction. The base end  43  of the airfoil portion  40  is connected to the blade root portion  34 . The rotor blade  18  is configured to be mountable to the rotor by embedding the blade root portion  34  into the rotor of the compressor  2 . The airfoil portion  40  includes a pressure surface  45  and a suction surface  46  that extend between the leading edge  41  and the trailing edge  42  along the blade height direction. When seen from the blade height direction, the pressure surface  45  has a concave shape that is recessed toward the inner side of the airfoil portion  40 , and the suction surface  46  has a convex shape that protrudes from the inner side toward the outer side of the airfoil portion  40 . 
     The rotor blade  18  further includes an internal passage  50  that passes through the inside of the airfoil portion  40 . The internal passage  50  includes a first opening end  52  which opens to the pressure surface  45  or the suction surface  46 , and a second opening end  54  which is positioned closer to the tip end  44  than the first opening end  52  in the blade height direction and which opens to the surface of the airfoil portion  40 . In the illustrative embodiments depicted in  FIGS. 2 and 4 , the first opening end  52  and the second opening end  54  open to the suction surface  46 . In the illustrative embodiment depicted in  FIG. 3 , the first opening end  52  opens to the suction surface  46 , and the second opening end  54  opens to the surface of the tip end  44 . In the illustrative embodiment depicted in  FIG. 12 , the first opening end  52  and the second opening end  54  open to the pressure surface  45 . In some embodiments, one of the first opening end  52  or the second opening end  54  may open to the suction surface  46 , and the other one may open to the pressure surface  45 . In some embodiments, the first opening end  52  may open to the pressure surface  45 , and the second opening end  54  may open to the surface of the tip end  44 . 
     In the rotor blade  18 , when L is the length from the base end  43  to the tip end  44  in the blade height direction (see  FIG. 5 ), the distance L 1  (see  FIG. 5 ) from the base end  43  to the first opening end  52  in the blade height direction is not smaller than zero and not greater than 0.3 L. 
     In the above described embodiment, the internal passage  50  passing through the inside of the airfoil portion  40  includes a first opening end  52  which opens to the suction surface  46  at a position where the distance from the base end  43  in the blade height direction is not greater than 0.3 L, and a second opening end  54  which is positioned closer to the tip end  44  than the first opening end  52  in the blade height direction and which opens to the surface of the airfoil portion  40  (the suction surface  46  or the surface of the tip end  44 ). Thus, when the rotor blade  18  rotates about the rotor center axis, in the above described internal passage  50 , a centrifugal force difference (pump) is caused by the radius difference between the first opening end  52  at the radially inner side (at the side of the base end  43 ) and the second opening end  54  at the radially outer side (at the side of the tip end  44 ). Accordingly, in the internal passage  50 , a flow that flows from the first opening end  52  at the radially inner side to the second opening end  54  at the radially outer side is generated. Thus, it is possible to take the flow in the vicinity of the suction surface  46  where the first opening end  52  is provided (that is, a region near a position whose distance from the base end  43  is not greater than 0.3 L, where separation is likely to occur) into the internal passage  50  from the first opening end  52 , and thereby it is possible to suppress separation that may occur in the vicinity of the suction surface  46  effectively. Therefore, according to the above described embodiment, it is possible to suppress reduction of the work region on the suction surface  46 , and suppress deterioration of the efficiency of the compressor  2 . 
     Furthermore, in the rotor blade  18 , when L is the length from the base end  43  to the tip end  44  in the blade height direction (see  FIG. 5 ), the distance L 2  (see  FIG. 5 ) from the base end  43  to the second opening end  54  in the blade height direction may be not smaller than 0.9 L and not greater than 1.0 L. 
     In this case, the second opening end  54  is disposed in the range of 10% from the tip end  44  in the blade height direction, and thereby it is possible to ensure a larger distance between the first opening end  52  and the second opening end  54  in the blade height direction. Accordingly, in the internal passage  50 , it is possible to increase the centrifugal difference caused by the radius difference between the first opening end  52  at the radially inner side (at the side of the base end  43 ) and the second opening end  54  at the radially outer side (at the side of the tip end), whereby it is possible to effectively obtain the pressurizing effect of pumping. Thus, thanks to the pumping effect, it is possible to suppress separation that may occur in the vicinity of the suction surface  46  more effectively. 
     Further, in the compressor  2 , a tip leakage flow (tip clearance flow) may occur between the tip end  44  of the rotor blade  18  and the casing. In this regard, according to the above described embodiment, the flow taken into the internal passage  50  via the first opening end  52  is discharged from the tip end  44  or the second opening end  54  disposed near the tip end in the blade height direction. Thus, it is possible to suppress the above described leakage flow by utilizing the flow discharged from the second opening end  54 . For instance, by discharging the flow from the second opening end  54  toward the gap between the tip end  44  of the rotor blade  18  and the casing of the compressor  2  and forming a fluid curtain in the gap, it is possible to block and suppress the leakage flow that passes through the gap. Accordingly, it is possible to further improve the efficiency of the compressor  2 . 
     As depicted in  FIGS. 2 and 4 , the second opening end  54  may open to the suction surface  46 . In this case, as the flow taken into the internal passage  50  via the first opening end  52  is discharged from the second opening end  54 , a kinetic momentum is supplied to the flow in the vicinity of the suction surface  46  where the second opening end  54  is provided, and thus it is possible to suppress separation of the flow that may occur in the vicinity of the suction surface  46  closer to the tip end  44  than the first opening end  52 . Thus, it is possible to suppress separation that may occur in the vicinity of the suction surface  46  more effectively. 
     Alternatively, as depicted in  FIG. 12 , the second opening end  54  may open to the pressure surface  45 . In this case, as the flow taken into the internal passage  50  via the first opening end  52  is discharged from the second opening end  54 , a kinetic momentum is supplied to the leakage flow near the pressure surface  45  where the second opening end  54  is provided, that is, the tip clearance, and thus it is possible to suppress separation of the flow that may occur in the tip clearance portion in the vicinity of the pressure surface  45  closer to the tip end  44  than the first opening end  52 . Thus, it is possible to suppress separation that may occur in the vicinity of the pressure surface  45  more effectively. 
     Furthermore, as depicted in  FIG. 3  for instance, the second opening end  54  may open to the surface of the tip end  44  of the airfoil portion  40 . In this case, the flow from the internal passage  50  is more easily discharged from the second opening end  54  opening to the surface of the tip end  44  toward the gap between the tip end  44  and the casing of the compressor  2 . Thus, it is possible to suppress the tip clearance flow between the tip end  44  of the rotor blade  18  and the casing effectively. 
     In some embodiments, in the cross section at the position of the second opening end  54  in the blade height direction, when C is the chord length of the airfoil portion  40  (see  FIG. 7A ), the distance C 2  between the leading edge  41  and the second opening end  54  in the chord direction of the airfoil portion  40  (see  FIG. 7A ) is greater than zero and not greater than 0.5 C. 
       FIG. 7A  is a schematic cross-sectional view of the airfoil portion  40  at the position of the second opening end  54  in the blade height direction. 
     Furthermore, the chord direction of the airfoil portion  40  is a direction connecting the leading edge  41  and the trailing edge  42  of the airfoil portion  40 , and the chord length is the distance between the leading edge  41  and the trailing edge  42 . 
     Separation of the flow in the vicinity of the blade surface (suction surface  46  or pressure surface  45 ) may occur near the center position in the chord direction (position of 0.5 C). In this regard, according to the above described embodiment, with the second opening end  54  being disposed relatively upstream in the chord direction, separation in the vicinity of the blade surface is likely to occur at a position downstream of the second opening end  54 . Thus, it is possible to suppress separation of the flow that may occur in the vicinity of the blade surface more effectively. 
     In some embodiments, when seen from the blade height direction, the second opening end  54  is positioned downstream of the first opening end  52  in the chord direction (or, at the side of the trailing edge  42  in the chord direction) of the airfoil portion  40 . 
     In this case, the second opening end  54  is positioned downstream of the first opening end  52 , and thus it is possible to reduce loss of the flow flowing toward the downstream side from the upstream side, and suppress separation that may occur in the vicinity of the blade surface effectively while suppressing deterioration of the efficiency of the compressor  2 . 
     Of  FIGS. 7A to 7C, 8A to 8C, and 13A to 13C ,  FIGS. 7A, 8A, and 13A  are schematic cross-sectional views of the airfoil portion  40  at the position of the second opening end  54  in the blade height direction (VIIIA-VIIA cross section in  FIG. 2 , VIIIA-VIIIA cross section in  FIG. 4 , and XIIIA-XIIIA cross section in  FIG. 12 ).  FIGS. 7B, 8B, and 13B  are schematic cross-sectional views of the airfoil portion  40  at the position between the first opening end  52  and the second opening end  54  in the blade height direction (VIIB-VIIB cross section in  FIG. 2 , VIIIB-VIIIB cross section in  FIG. 4 , and XIIIB-XIIIB cross section in  FIG. 12 ).  FIGS. 7C, 8C, and 13C  are schematic cross-sectional views of the airfoil portion  40  at the position of the first opening end  52  in the blade height direction (VIIC-VIIC cross section in  FIG. 2 , VIIIC-VIIIC cross section in  FIG. 4 , and XIIIC-XIIIC cross section in  FIG. 12 ). 
     In the illustrative embodiments depicted in  FIGS. 2 to 4 and 12 , the internal passage  50  includes a radial-directional passage portion  58  extending along the blade height direction (radial direction of the rotor of the compressor  2 ) inside the airfoil portion  40 . 
     As described above, with the radial-directional passage portion  58  extending in the blade height direction inside the airfoil portion  40 , the fluid flowing into the internal passage  50  is likely to be pressurized effectively by the above described pumping effect. Thus, it is possible to take in the flow in the vicinity of the blade surface effectively via the first opening end  52 , and suppress separation that may occur in the vicinity of the blade surface effectively. 
     In the illustrative embodiments depicted in  FIGS. 2 to 4 and 12 , the internal passage  50  further includes an intake portion  60  that extends between the base-end side end  58   a  of the radial-directional passage portion  58  and the first opening end  52 , inside the airfoil portion  40 . The intake portion  60  may extend along the chord direction of the airfoil portion  40 , when seen from the blade height direction (see  FIGS. 7C, 8C, and 13C , for instance). The intake portion  60  can be disposed so as to extend along the flow in the vicinity of the blade surface compared to the radial-directional passage portion  58 , and thus it is possible to incorporate the flow in the vicinity of the blade surface into the internal passage  50  smoothly via the intake portion  60 . 
     In the illustrative embodiments depicted in  FIGS. 2, 4, and 12 , the internal passage  50  further includes an outflow portion  62  that extends between the tip-end side end  58   b  of the radial-directional passage portion  58  and the second opening end  54 , inside the airfoil portion  40 . The outflow portion  62  may extend along the chord direction of the airfoil portion  40 , when seen from the blade height direction (see  FIGS. 7A, 8A, and 13A , for instance). The outflow portion  62  can be disposed so as to extend along the flow in the vicinity of the blade surface compared to the radial-directional passage portion  58 , and thus it is possible to cause the flow from the internal passage  50  to flow along the blade surface, via the outflow portion  62 . 
     The cross-sectional shape of the internal passage  50  is not particularly limited, and may be a circle, an oval, or a rectangle. 
     For instance, in the illustrative embodiments depicted in  FIGS. 2 and 7A to 7C , or  FIGS. 12 and 13A to 13C , the radial-directional passage portion  58 , the intake portion  60 , and the outflow portion  62  each have a circular cross-sectional shape. 
     Furthermore, in the illustrative embodiment depicted in  FIG. 3 , the radial-directional passage portion  58  and the intake portion  60  each have a circular cross-sectional shape. 
     Furthermore, in the illustrative embodiments depicted in  FIGS. 4 and 8A to 8C , the radial-directional passage portion  58 , the intake portion  60 , and the outflow portion  62  each have a slit-shaped rectangular cross-sectional shape. 
     In some embodiments, when t max  is the maximum blade thickness of the airfoil portion  40  at the position of the tip end  44  in the blade height direction (see  FIG. 6 ), the radial-directional passage portion  58  has a blade-thickness directional length of not smaller than 0.3 t max  and not greater than 0.7 t max . In  FIGS. 7B and 8B , the blade-thickness directional length of the radial-directional passage portion  58  is indicated as m 1  and m 2 , respectively. 
     In the present specification, the blade thickness refers to the thickness of the airfoil portion  40  in the chord orthogonal direction, and the blade thickness direction refers to the chord orthogonal direction. 
     As described above, with the blade-thickness directional length of the radial-directional passage portion  58  being not greater than 0.3 t max , it is possible to ensure the flow-passage cross sectional area of the radial-directional passage portion  58  and obtain the above described pumping effect suitably, whereby it is possible to take the flow in the vicinity of the blade surface into the internal passage  50  via the first opening end  52 . Furthermore, as described above, with the blade-thickness directional length of the radial-directional passage portion  58  being not greater than 0.7 t max , it is possible to maintain a suitable strength of the airfoil portion  40 . 
     In some embodiments, the radial-directional passage portion  58  has a flow-passage cross sectional area whose equivalent diameter is not smaller than 0.7 t max . 
     In a case where the radial-directional passage portion  58  has a circular cross-sectional shape, when the diameter of the cross section of the radial-directional passage portion  58  is d 1  (see  FIG. 7B ), the equivalent diameter De of the flow-passage cross sectional area is d 1 . 
     Furthermore, in a case where the radial-directional passage portion  58  has a rectangular cross-sectional shape, when the lengths of the two pairs of opposite sides are m 2  and m 3  (see  FIG. 8B ), the equivalent diameter De of the flow-passage cross sectional area is represented by an expression De=4×m 2 ×m 3 /{2×(m 2 +m 3 )}. In general, an equivalent diameter De is represented by an expression De=4Af/Wp. Herein, Af is the flow-passage cross sectional area, and Wp is the perimeter of the cross section. 
     According to the above embodiment, with the radial-directional passage portion  58  having a flow-passage cross sectional area whose equivalent diameter is not smaller than 0.7 t max , It is possible to increase the flow-passage cross sectional area, whereby it is possible to achieve the above described pumping effect effectively, and take the flow in the vicinity of the blade surface into the internal passage effectively via the first opening end  52 . 
     In some embodiments, the ratio S 1 /S 3  of the flow-passage cross sectional area S 1  of the internal passage  50  at the first opening end  52  to the flow-passage cross sectional area S 3  of the radial-directional passage portion  58  is not smaller than 0.8 and not greater than 1.2. Alternatively, the ratio S 2 /S 3  of the flow-passage cross sectional area S 2  of the internal passage  50  at the second opening end  54  to the flow-passage cross sectional area S 3  of the radial-directional passage portion  58  is not smaller than 0.8 and not greater than 1.2. 
     Herein, the flow-passage cross sectional areas S 1  to S 3  are the respective areas of the cross sections taken in a direction orthogonal to the flow direction of the fluid at the respective positions of the internal passage  50  (that is, at the positions of the first opening end  52 , the radial-directional passage portion  58 , or the second opening end  54 ). 
     In the above described case, the ratio S 1 /S 3  or S 2 /S 3  is not smaller than 0.8 and not greater than 1.2, which is a numeral range close to 1.0. In other words, there is no significant difference between the flow-passage cross sectional area S 1  at the first opening end  52  and the flow-passage cross sectional area S 3  at the radial-directional passage portion  58 , or between the flow-passage cross sectional area S 2  at the second opening end  54  and the radial-directional passage portion  58 . Thus, the flow-passage cross sectional area of the internal passage  50  does not change considerably from the first opening end  52  to the radial-directional passage portion  58 , or from the radial-directional passage portion  58  to the second opening end  54 . Thus, according to the above embodiment, it is possible to suppress separation of the flow that may occur in the vicinity of the blade surface effectively while reducing pressure loss in the internal passage  50 . 
     In some embodiments, as depicted in  FIGS. 7C, 8C, and 13C  for instance, when seen from the blade height direction, the extension direction of the intake portion  60  (in the drawings, the direction of line L 11 ) forms angle θ 1  of not greater than 45 angular degrees with a portion of a tangent L 12  to the pressure surface  45  or the suction surface  46  (suction surface  46  in  FIGS. 7C and 8C , and pressure surface  45  in  FIG. 13C ) at the first opening end  52 , the portion being disposed at the side of the trailing edge  42  with respect to the first opening end  52 . 
     In this case, the intake portion  60  has a shape along the blade surface (suction surface  46  in  FIGS. 7C and 8C , and pressure surface  45  in  FIG. 13C ) at the position of the first opening end  52 , and thus it is possible to take in the fluid flowing in the vicinity of the blade surface smoothly into the internal passage  50  via the intake portion  60 . 
     In some embodiments, as depicted in  FIGS. 7A, 8A, and 13C  for instance, when seen from the blade height direction, the extension direction of the outflow portion  62  (in the drawings, the direction of line L 13 ) forms angle θ 2  of not greater than 45 angular degrees with a portion of a tangent L 14  to the pressure surface  45  or the suction surface  46  (suction surface  46  in  FIGS. 7C and 8C , and pressure surface  45  in  FIG. 13C ) at the second opening end  54 , the portion being disposed at the side of the leading edge  41  with respect to the second opening end  54 . 
     In this case, the outflow portion  62  has a shape along the blade surface (suction surface  46  in  FIGS. 7C and 8C , and pressure surface  45  in  FIG. 13C ) at the position of the second opening end  54 , and thus it is possible to cause the flow flowing out from the second opening end  54  via the outflow portion  62  to flow along the blade. Accordingly, it is possible to reduce mixing loss of the flow flowing out from the second opening end  54  and the fluid flowing in the vicinity of the blade surface. 
       FIGS. 9A and 9B  are partial schematic diagrams of the airfoil portion  40  of the rotor blade  18  according to an embodiment, taken along a direction orthogonal to the blade height direction at the position of the first opening end  52 . 
     In some embodiments, as depicted in  FIG. 9A  for instance, the first opening end  52  may include a plurality of holes  53  that open to the pressure surface  45  or the suction surface  46  (in  FIG. 9A , the suction surface  46 ). Further, in some embodiments, as depicted in  FIG. 9B , a perforated plate  55  may be disposed on the first opening end  52 . In a case where the first opening end  52  includes a plurality of holes as in the above embodiments, as depicted in  FIGS. 9A and 9B , the intake portion  60  may have a tapered portion whose flow-passage cross sectional area gradually increases toward the first opening end  52 . As described above, by using both of the first opening end  52  including a plurality of holes and the intake portion  60  having a flow-passage cross sectional area that gradually increases toward the first opening end  52 , it is possible to take in the flow of the fluid from a broader region in the vicinity of the blade surface without increasing the opening area excessively. Thus, it is possible to reduce influence on the flow in the vicinity of the blade surface, and suppress deterioration of the efficiency of the compressor. 
       FIGS. 10 and 11  are schematic diagrams of the airfoil portion  40  of the rotor blade  18  according to an embodiment, taken along a direction orthogonal to the blade height direction at the position of the second opening end  54 . 
     In some embodiments, as depicted in  FIG. 10  for instance, the outflow portion  62  includes a diameter-enlarged portion  64  whose flow-passage cross sectional area gradually increases toward the second opening end  54 , at a portion including the second opening end  54 . As described above, by providing the diameter-enlarged portion  64  whose flow-passage cross sectional area gradually increases toward the second opening end  54 , at a portion including the second opening end  54 , it is possible to supply a fluid having a kinetic momentum to a broad region in the vicinity of the blade surface, via the outflow portion  62 . Thus, it is possible to suppress the above described tip clearance flow effectively, and suppress separation of the flow that may occur in the vicinity of the blade surface effectively. 
     In some embodiments, as depicted in  FIG. 11  for instance, the outflow portion  62  may have a curved shape along the blade surface (in  FIG. 11 , the suction surface  46 ). In this case, it is possible to let the flow flowing out from the second opening end  54  via the outflow portion  62  flow along the blade surface. Accordingly, it is possible to reduce mixing loss of the flow flowing out from the second opening end  54  and the fluid flowing in the vicinity of the blade surface. 
     Embodiments of the present invention were described in detail above, but the present invention is not limited thereto, and various amendments and modifications may be implemented. 
     Further, in the present specification, 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 cylindrical 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, an expression such as “comprise”, “include” and “have” are not intended to be exclusive of other components.