Abstract:
Provided are turbine blades and a gas turbine capable of damping the vibrations caused by an excitation force and facilitating mounting/disassembly. Included are a shroud portion disposed at an end portion of an airfoil portion; a holder casing that can slide relative to the shroud portion, that can also be attached thereto/detached therefrom, and that forms a space with the shroud portion therebetween; and an elastic portion that is disposed in the space, that biases the shroud portion in a direction that separates it from the holder casing, and is disposed in a movable manner relative to the shroud portion; and a pressing portion that is disposed between the elastic portion and the holder casing and that can be moved toward and away from the shroud portion.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to turbine blades and gas turbines. 
       BACKGROUND ART 
       [0002]    Cantilever stator blades in which shrouds are provided as separate pieces, shrouded stator blades in which shrouds are integrally provided, and so on, are typically employed as stator blades of gas turbine compressors. 
         [0003]    With the shrouded stator blades, leakage of air, etc. is less likely to occur at tips of airfoil portions thereof as compared with the cantilever stator blades and, in addition, a rotor seal structure that suppresses leakage of air, etc. between the stator blades and the rotor can be provided at the inner circumferences of the shrouds. This allows the shrouded stator blades to reduce the air leakage level to an appropriate amount; therefore, they are considered advantageous in terms of performance. 
         [0004]    In the above-described shrouded stator blades, circumferential base portions referred to as shroud portions are provided at outer and inner end portions of the airfoil portions (profile portions). 
         [0005]    Examples of methods for securing the airfoil portions to the shroud portions include the tenon-type securing method, in which insertion portions protruding from the airfoil portions are inserted into insertion openings provided in the shroud portions, and the pork-chop-type securing method, in which insertion-flange portions formed in a widening shape from the airfoil portions are inserted into the above-described insertion openings. 
         [0006]    With the tenon-type securing method or the pork-chop-type securing method, the insertion portions or the insertion-flange portions may be secured by mechanically inserting them into the insertion openings, or they may be secured by brazing or welding. The shroud portions of the stator blades are assembled into a ring shape in this way. 
         [0007]    In addition, in some cases, the airfoil portions and the shroud portions are molded or machined as an integral structure. 
         [0008]    In order to absorb thermal expansion in the circumferential directions in a ring-shaped assembled state, to enhance the ease of machining and assembly of the shroud portions, and to achieve enhanced ease of maintenance for the shroud portions, etc., the shroud portions are typically divided into a plurality of portions in the circumferential direction. For example, in the case of the shrouded stator blades, the shroud portions are divided in correspondence with each stator blade. 
         [0009]    Furthermore, a seal structure, such as a labyrinth seal, a honeycomb seal or the like, is provided between the shroud portions and a rotating rotor shaft (for example, see Patent Literature 1). 
         [0010]    In consideration of the ease of machining or the ease of repairing, the configuration of the seal structure may be such that the seal structure is formed as a separate structure from the airfoil portions or the shroud portions, wherein the seal structure is combined with the airfoil portions or the shroud portions after being formed. 
         [0011]    In addition to the structure disclosed in Patent Literature 1, examples of configurations in which the shroud portions are combined with the seal structure include a configuration in which a seal structure is fitted to groove structures provided in shroud portions. 
         [0012]    On the other hand, in a flow field of air or gas inside a compressor of a gas turbine, it is known that when stator blades receive an excitation force having a frequency matching the natural frequency of the stator blades or a frequency that is an integral multiple of the rotation speed, the airfoil portions and the shroud portions of the stator blades exhibit large vibrations (exhibit a vibration response). 
         [0013]    Examples of the above-described excitation force include the excitation force of a wake flow (wake) of rotating rotor blades, the excitation force of an interference flow (potential), and so forth. 
         [0014]    When the stress that acts on the stator blades caused by the above-described vibration response increases, exceeding the fatigue resistance of materials that constitute the stator blades, fatigue cracks may form in the stator blades, and the stator blades may be broken due to the fatigue cracks. 
         [0015]    Because of this, it is necessary to design the airfoil portions and the shroud portions so as to have physical-frame strength that prevents fatigue crack formation even if the vibration response occurs, and the natural frequency of the stator blades also needs to be shifted, in other words, detuned, from the excitation frequency that is expected to act on the stator blades. 
         [0016]    On the other hand, along with increases in output power, enhancement of performance, and reduction of costs in gas turbines in recent years, the size of profile portions is being increased, including enlargement of the blade profile width (blade chord), enlargement of the blade length (span), and so forth in the profile portions. 
         [0017]    When the profile portions are increased in size in this way, the aerodynamic force or force of gas that acts on the airfoil portions increases, and the load or moment that acts on base portions of the airfoil portions, in other words, connection portions between the airfoil portions and the shroud portions, increases. In order to endure such increases in load or moment, sufficient strength needs to be ensured by increasing the radial size of the radius of curvature R of fillets formed at the base portions of the airfoil portions. 
         [0018]    With regard to this, in contrast to ensuring sufficient strength at the base portions of the airfoil portions, there is a demand from an aerodynamic standpoint, that it is preferred to reduce the radial size of the radius of curvature R of the fillets formed at the base portions of the airfoil portions. 
         [0019]    The profile portions compress gas-containing air, etc. by being rotationally driven, and, on the other hand, receive air (containing gas) resistance in the flow field. Therefore, in order to decrease this air resistance, the profile shape is optimized, the leading-edge diameter and trailing-edge diameter in the profile portions are decreased in the radial sizes thereof, and the airfoil thickness itself is reduced. 
         [0020]    However, the above-described reduction of the radial size or thickness is a factor that decreases the strength of the stator blades, in particular the strength against a resonant response. Accordingly, with regard to designs of the profile portions, there are restrictions on the above-described reduction of the radial size or thickness in order to ensure the strength of the profile portions. 
         [0021]    In addition, in order to prevent the stator blades from breaking through resonating with the excitation force, the natural frequency of a stator-blade ring as a whole, in which a plurality of stator blades are combined, is shifted from the frequency of the excitation source; that is, detuning design is conducted so that the frequencies do not match. 
         [0022]    However, because the above-described natural frequency depends on the shape of the profile portions, the shape of the shroud portions, and so forth, when detuning between the natural frequency and the frequency of the excitation source is given priority, the stator blades in many cases are inevitably designed at the expense of the aerodynamic characteristics of the stator blades. 
         [0023]    Patent Literature 1 proposes a technique of pressing the stator blades with wave-shaped plate springs in order to restrict the relative movement of the stator blades. 
         [0024]    Furthermore, in order to reduce the vibration response in the stator blades, there is also a known technique for damping vibrations due to the vibration response in the stator blades by vibration damping (damping) which uses a frictional force using springs. 
         [0025]    More specifically, a known structure damps vibrations in the stator blades with a structure in which doughnut-ring shaped springs are inserted between a shroud ring that is disposed on an inner circumferential side and a seal holder that holds a seal, pressing the springs against the shroud rings. 
         [0026]    By doing so, when the shroud portions articulated with the profile portions vibrationally deform due to resonance, the shroud portions and the springs slide, and a frictional force acts between the shroud portions and the springs. Consequently, vibrational energy is converted into frictional energy (thermal energy) at the sliding surfaces between the shroud portions and the springs, thus damping the vibrations of the stator blades. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         {PTL 1} Japanese Unexamined Patent Application, Publication No. 2002-276304. 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0028]    However, when physical frames of blades such as stator blades increase in size, the vibrational energy associated with vibrations also relatively increases; therefore, it is also necessary to increase the damping force in a mechanism for damping the vibrations in the stator blades. For example, in the case of the above-described structure in which the springs are pressed against the shroud rings, it is necessary to increase the spring force in order to obtain sufficient damping force due to friction. 
         [0029]    When the seal holder ring and the shroud ring are assembled with a runner guided structure under such circumstances, there is a problem in that assembly or disassembly of the seal holder ring and the shroud rings becomes difficult. 
         [0030]    That is, the expanding force of the above-described spring acts between the seal holder ring and the shroud rings, and a frictional force also acts between the springs and the seal holder ring or between the springs and the shroud rings; therefore, there is a problem of increasing force required when the seal holder ring and the shroud rings slide, making assembly or disassembly thereof difficult. 
         [0031]    In addition, with the configuration disclosed in Patent Literature 1, because the structure does not consider the above-described spring replacement, there is a problem in that, when the springs become deteriorated due to wear from long-term use, it is difficult to replace the springs whose spring force is increased as described. 
         [0032]    The present invention is for solving the above-described problems and provides a turbine blade and a gas turbine that are capable of damping vibrations caused by an excitation force and that are capable of facilitating mounting or disassembly of a seal holder ring and a shroud ring and replacement of an elastic member, such as a spring. 
       Solution to Problem 
       [0033]    In order to achieve the above-described object, the present invention provides the following solutions. 
         [0034]    Turbine blades according to a first aspect of the present invention include a shroud portion disposed at an end portion of an airfoil portion; a holder casing that can slide relative to the shroud portion, that can also be attached thereto/detached therefrom, and that forms a space with the shroud portion therebetween; and an elastic portion that is disposed in the space, biases the shroud portion in a direction that separates it from the holder casing, and is disposed in a movable manner relative to the shroud portion. 
         [0035]    With the turbine blades according to the first aspect of the present invention, when the airfoil portions and the shroud portions vibrate and slide relative to the holder casing, the elastic portions, which have been pressing the shroud portions in the direction away from the holder casing, and the shroud portions relatively move; that is, the elastic portions and shroud portions slide. Accordingly, energy associated with vibrations in the airfoil portions and the shroud portions is converted into thermal energy (frictional energy) due to sliding, thereby damping the vibrations in the airfoil portions and the shroud portions. In addition, the elastic portions are moved by sliding together with the holder casing to be attached to/detached from the shroud portions, and thereby, the elastic portions can easily be replaced. 
         [0036]    With the above-described turbine blades according to the first aspect, it is desirable that the configuration thereof be such that the shroud portion is independently disposed for each of a plurality of the airfoil portions, and, for a plurality of the shroud portions, a single holder casing is configured in an attachable/detachable manner. 
         [0037]    With this configuration, because the shroud portions are independently disposed for each of the plurality of the airfoil portions, the individual airfoil portions and the shroud portions readily move relative to the elastic portions, as compared with the case in which the plurality of the shroud portions are integrally formed. In other words, the sliding distance between the shroud portions and the elastic portions is extended. 
         [0038]    Accordingly, a greater amount of energy associated with the vibrations in the airfoil portions and the shroud portions is converted into thermal energy (frictional energy) due to sliding, and therefore, the vibrations in the airfoil portions and the shroud portions are more readily damped. 
         [0039]    With the above-described turbine blades according to the first aspect, the configuration thereof may be such that the elastic portion extends parallel to the direction in which the plurality of the shroud portions form a row and is a plate spring formed in substantially a wave shape, and peak portions of the plate spring are in contact with the shroud portion or the holder casing. 
         [0040]    With this configuration, by employing the plate springs formed into a wave-like shape as the elastic portions, a larger pressing force can be exerted on the shroud portions as compared with the case in which other types of springs are employed. 
         [0041]    In addition, by making each of the peak portions of the plate springs individually contact the shroud portions, the plurality of the shroud portions can be moved, by sliding them, with respect to a single plate spring. 
         [0042]    With the turbine blades according to the first aspect, the configuration thereof may further include a pressing portion that is disposed between the elastic portion and the holder casing and that can be moved toward and away from the shroud portion. 
         [0043]    With this configuration, because the compression level of the elastic portions is adjusted by moving the pressing portion closer to the shroud portions, the force with which the elastic portions press the shroud portions is adjusted. In other words, because the frictional force between the elastic portions and the shroud portions is adjusted, the level of damping of vibrations in the airfoil portions and the shroud portions is adjusted. 
         [0044]    In addition, by moving the pressing portion closer to the shroud portions, the biasing force of the elastic portions is received by the shroud portions and the pressing portion. In other words, the biasing force of the elastic portions does not act on the holder casing. Accordingly, when moving the holder casing by sliding it relative to the shroud portions or when attaching/detaching the holder casing, the frictional force that acts at contact surfaces between the shroud portions and the holder casing is reduced, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
         [0045]    With the above-described turbine blades according to the first aspect, the configuration thereof may be such that a single pressing portion is disposed in the space formed by the plurality of the shroud portions and the single holder casing. 
         [0046]    With this configuration, because a single holder casing is provided for the plurality of the airfoil portions and the shroud portions, the sealing level between the upstream side and the downstream side of the turbine blades is increased, as compared with the case in which the holder casings are disposed for each of the plurality of the airfoil portions and the shroud portions. 
         [0047]    With the above-described turbine blades according to the first aspect, the configuration thereof may be such that the elastic portion extends parallel to the direction in which the plurality of the shroud portions form a row and is a plate-like spring formed in substantially a wave shape, and peak portions of the spring are in contact with the shroud portions or the pressing casing. 
         [0048]    With this configuration, by employing plate-like springs formed into a wave-like shape as the elastic portions, a larger pressing force can be exerted on the shroud portions as compared with the case in which other types of springs are employed. 
         [0049]    In addition, by making each of the peak portions of the springs individually contact the shroud portions, the plurality of the shroud portions can be moved, by sliding, with respect to a single spring. 
         [0050]    With the above-described turbine blades according to the first aspect, the configuration thereof may be such that a plurality of the springs are disposed in substantially parallel rows and, relative to peak portions of the first spring, peak portions of the other spring are disposed shifted therefrom. 
         [0051]    With this configuration, it is possible to make the springs contact all of the shroud portions, even when arrangement intervals of the peak portions in the first spring are wider than arrangement intervals of the shroud portions. That is, the shroud portions with which the peak portions of the first spring are not in contact are in contact with the peak portions of the other spring, thereby making it possible to have all of the shroud portions in contact with the springs. 
         [0052]    With the above-described turbine blades according to the first aspect, the configuration thereof may be such that the pressing portion is provided with a compressing portion that compresses the elastic portion by moving the pressing portion closer to the shroud portion. 
         [0053]    With this configuration, the pressing portion can be moved closer to the shroud portions using the compressing portions. Accordingly, the compression level of the elastic portions is adjusted, thereby adjusting the force with which the elastic portions press the shroud portions. In other words, because the frictional force between the elastic portions and the shroud portions is adjusted, it is possible to adjust the level of damping of vibrations in the airfoil portions and the shroud portions. 
         [0054]    In addition, by moving the pressing portion closer to the shroud portions, the biasing force of the elastic portions is received by the shroud portions and the pressing portion. Accordingly, when moving the holder casing by sliding it relative to the shroud portions or when attaching/detaching the holder casing, the frictional force that acts at contact surfaces between the shroud portions and the holder casing is reduced, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
         [0055]    Turbine blades according to a second aspect of the present invention include a shroud portion disposed at an end portion of an airfoil portion; a holder casing that can be moved by sliding relative to the shroud portion, that can also be attached thereto/detached therefrom, and that forms a space with the shroud portions therebetween; an elastic portion that is disposed in the space and that biases the shroud portion in a direction that separates it from the holder casing; and a friction portion that is disposed between the elastic portion and the shroud portion, that can be moved closer to/away from the shroud portion, and that is disposed in a movable manner relative to the shroud portion. 
         [0056]    With the turbine blades according to the second aspect, when the airfoil portions and the shroud portions vibrate and slide relative to the holder casing, the friction portions, which have been pressed against the shroud portions by the elastic portions, and the shroud portions relatively move; that is, the friction portions and shroud portions slide. Accordingly, energy associated with vibrations of the airfoil portions and the shroud portions is converted into thermal energy (frictional energy) due to sliding, thereby damping the vibrations in the airfoil portions and the shroud portions. 
         [0057]    On the other hand, by moving the friction portions closer to the holder casing, the biasing force of the elastic portions is received by the friction portions and the holder casing. In other words, the biasing force of the elastic portions does not act on the shroud portions. Accordingly, when moving the holder casing by sliding it relative to the shroud portions or when attaching/detaching the holder casing, the frictional force that acts at contact surfaces between the shroud portions and the holder casing is reduced, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
         [0058]    With the above-described turbine blades according to the second aspect, it is desirable that the configuration thereof be such that the shroud portion is independently disposed for each of a plurality of the airfoil portions; for a plurality of the shroud portions, a single holder casing be configured in a attachable/detachable manner; and, in the space formed by the plurality of the shroud portions and the single holder casing, a single friction portion be disposed for a single shroud portion. 
         [0059]    With this configuration, because the shroud portions are independently disposed for each of the plurality of the airfoil portions, the individual airfoil portions and the shroud portions readily move relative to the friction portions, as compared with the case in which the plurality of the shroud portions are integrally formed. In other words, the sliding distance between the shroud portions and the friction portions is extended. 
         [0060]    Accordingly, a greater amount of energy associated with the vibrations in the airfoil portions and the shroud portions is converted into thermal energy (frictional energy) due to sliding, and therefore, the vibrations in the airfoil portions and the shroud portions are more readily damped. 
         [0061]    On the other hand, because a single holder casing is provided for the plurality of the airfoil portions and the shroud portions, the sealing level between the upstream side and the downstream side of the turbine blades is increased as compared with the case in which the holder casings are disposed for each of the plurality of the airfoil portions and the shroud portions. 
         [0062]    With the above-described turbine blades according to the second aspect, it is desirable that the configuration thereof be such that the elastic portion extends parallel to the direction in which the plurality of the shroud portions form a row and is a plate-like spring formed in substantially a wave shape, and peak portions of the spring are in contact with the friction portion or the pressing portion. 
         [0063]    With this configuration, by employing springs formed into a wave-like shape as the elastic portions, a larger pressing force can be exerted on the shroud portions as compared with the case in which other types of springs are employed. 
         [0064]    On the other hand, by making each of the peak portions of the springs individually contact the shroud portions, the plurality of the friction portions are pressed against the shroud portions by a single spring. 
         [0065]    With the above-described turbine blades according to the second aspect, it is desirable that the configuration thereof be such that the friction portion is provided with a compressing portion that extends from the friction portion toward the holder casing, protrudes so as to penetrate the holder casing, and compresses the elastic portion by moving the friction portion closer to the holder casing. 
         [0066]    With this configuration, because the compressing portions protrude from the friction portions penetrating the holder casing, the compressing portions and the friction portions are movable in directions toward and away from the holder casing, while being restricted in movement in the direction that intersects with the direction of movement toward and away from the holder casing. Accordingly, it is ensured that sliding occurs between the shroud portions and the friction portions. 
         [0067]    With the above-described turbine blades according to the second aspect, it is desirable that the configuration thereof be such that a relief groove that extends in a direction that intersects with the direction into which the holder casing slides is provided at a surface where the friction portion comes in contact with the shroud portion. 
         [0068]    With this configuration, by providing the relief grooves, the surfaces of the friction portions that come into contact with the shroud portions are divided into two with the relief grooves therebetween, and each surface comes into contact with the shroud portions. Accordingly, even if the shroud portions and the friction portions slide, the shroud portions and the friction portions come into stable contact at the above-described two surfaces, thereby preventing the occurrence of problems such as partial contact or the like. 
         [0069]    A gas turbine according to the present invention includes any of the above-described turbine blades. 
         [0070]    With the gas turbine according to the present invention, because the turbine blades of this embodiment are provided, energy associated with the vibrations of the airfoil portions and the shroud portions of the turbine blades is converted into thermal energy (frictional energy) due to sliding, thereby damping the vibrations in the airfoil portions and the shroud portions. 
         [0071]    With a gas turbine provided with the turbine blades according to the above-described first aspect, when moving the holder casing by sliding it relative to the shroud portions or when attaching/detaching the holder casing, the frictional force that acts at contact surfaces between the shroud portions and the holder casing is reduced by moving the pressing portion closer to the shroud portions, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
         [0072]    With a gas turbine provided with the turbine blades according to the above-described second aspect, when moving the holder casing by sliding it relative to the shroud portions or when attaching/detaching the holder casing, the frictional force that acts at contact surfaces between the shroud portions and the holder casing is reduced by moving the friction portions closer to the holder casing, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
       Advantageous Effects of Invention 
       [0073]    With the turbine blades and the gas turbine according to the first aspect of the present invention, because the elastic portions, which have been pressing the shroud portions in the direction away from the holder casing and the shroud portions relatively move, that is, the elastic portions and shroud portions slide, energy associated with vibrations in the airfoil portions and the shroud portions is converted into thermal energy (frictional energy) due to sliding. As a result, an advantage is afforded in that the vibrations in the airfoil portions and the shroud portions can be damped. 
         [0074]    In addition, an advantage is afforded in that, by moving the pressing portion closer to the shroud portions, the biasing force of the elastic portions is received by the shroud portions and the pressing portion; therefore, the frictional force exerted on contact surfaces between the shroud portions and the holder casing is reduced when moving the holder casing by sliding it relative to the shroud portions or when attaching/detaching the holder casing, and thus, mounting and disassembling can be facilitated. 
         [0075]    In addition, an advantage is afforded in that the elastic portions can be easily replaced by attaching them to or detaching them from the shroud portions through moving the elastic portions by sliding them together with the holder casing. 
         [0076]    With the turbine blades and the gas turbine according to the second aspect of the present invention, an advantage is afforded in that, because the friction portions and the shroud portions slide, the energy associated with the vibrations in the airfoil portions and the shroud portions is converted into thermal energy (frictional energy) due to sliding, thereby damping the vibrations in the airfoil portions and the shroud portions. 
         [0077]    In addition, an advantage is afforded in that, by moving the friction portions closer to the holder casing, the biasing force of the elastic portions is received by the friction portions and the holder casing; therefore, the frictional force exerted at contact surfaces between the shroud portions and the holder casing is reduced when moving the holder casing by sliding relative to the shroud portions or when attaching/detaching the holder casing, and thus, it is possible to facilitate the sliding movement or attaching/detaching. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0078]      FIG. 1  is a schematic diagram for explaining the configuration of gas turbines according to first to third embodiments of the present invention. 
           [0079]      FIG. 2  is a schematic diagram for explaining the configuration of a rotor disc and stator blades in a compressor of a gas turbine according to the first embodiment of the present invention. 
           [0080]      FIG. 3  is a cross-sectional view for explaining the configuration near a seal holder in the stator blades in  FIG. 2 . 
           [0081]      FIG. 4  is a schematic diagram for explaining another arrangement example of springs in  FIG. 3 . 
           [0082]      FIG. 5  is a schematic diagram for explaining attaching and detaching of the seal holder in the stator blades in  FIG. 3 . 
           [0083]      FIG. 6  is a schematic diagram for explaining the state after the seal holder is attached to the stator blades in  FIG. 3 . 
           [0084]      FIG. 7  is a schematic diagram for explaining yet another arrangement example of the springs in  FIG. 3 . 
           [0085]      FIG. 8  is a schematic diagram for explaining the configuration of a rotor disc and stator blades in a compressor of a gas turbine according to the second embodiment of the present invention. 
           [0086]      FIG. 9  is a cross-sectional view for explaining the configuration near a seal holder in the stator blades in  FIG. 8 . 
           [0087]      FIG. 10  is a schematic diagram for explaining another arrangement example of springs in  FIG. 9 . 
           [0088]      FIG. 11  is a schematic diagram for explaining the configuration of damping plates in  FIG. 9 . 
           [0089]      FIG. 12  is a schematic diagram for explaining attaching and detaching of the seal holder to and from the stator blades in  FIG. 9 . 
           [0090]      FIG. 13  is a schematic diagram for explaining the state after the seal holder is attached to the stator blades in  FIG. 9 . 
           [0091]      FIG. 14  is a schematic diagram for explaining yet another arrangement example of the springs in  FIG. 3 . 
           [0092]      FIG. 15  is a schematic diagram for explaining another configuration of the seal holder in  FIG. 9 . 
           [0093]      FIG. 16  is a schematic diagram for explaining the configuration of a rotor disc and stator blades in a compressor of a gas turbine according to the third embodiment of the present invention. 
           [0094]      FIG. 17  is a cross-sectional view for explaining the configuration near a seal holder in the stator blades in  FIG. 16 . 
           [0095]      FIG. 18  is a schematic diagram for explaining another arrangement example of springs in  FIG. 17 . 
           [0096]      FIG. 19  is a schematic diagram for explaining yet another arrangement example of the springs in  FIG. 17 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0097]      FIG. 1  is a schematic diagram for explaining the configuration of gas turbines according to first to third embodiments of the present invention described below. 
         [0098]    As shown in  FIG. 1 , a gas turbine  1  is provided with a compressor  2 , a combustor  3 , a turbine unit  4 , and a rotational shaft  5 . 
         [0099]    As shown in  FIG. 1 , the compressor  2  sucks in air to compress it and supplies the compressed air to the combustor  3 . A rotational driving force is transmitted from the turbine unit  4  to the compressor  2  via the rotational shaft  5 , and, upon being rotationally driven, the compressor  2  sucks in air and compresses it. 
         [0100]    Note that any known configurations can be employed for the compressor  2 ; it is not particularly limited. 
         [0101]    As shown in  FIG. 1 , the combustor  3  mixes externally supplied fuel and the supplied compressed air, generates high-temperature gas by combusting the mixed air, and supplies the generated high-temperature gas to the turbine unit  4 . 
         [0102]    Note that any known combustors can be employed as the combustor  3 ; it is not particularly limited. 
         [0103]    As shown in  FIG. 1 , the turbine unit  4  extracts rotational driving force from the supplied high-temperature gas to rotationally drive the rotational shaft  5 . 
         [0104]    Note that any known configurations can be employed for the turbine unit  4 ; it is not particularly limited. 
       First Embodiment 
       [0105]    A gas turbine according to a first embodiment of the present invention will now be described with reference to  FIGS. 1 to 7 . Note that, in this embodiment, turbine blades of the invention of the present application will be described as applied to stator blades of sixth to ninth stages in the compressor  2  of the gas turbine  1 . 
         [0106]      FIG. 2  is a schematic diagram for explaining the configuration of a rotor disc and stator blades in a compressor of a gas turbine according to this embodiment. 
         [0107]    As shown in  FIGS. 1 and 2 , the compressor  2  is provided with stator blades (turbine blades)  10  that are attached to a casing  6  of the gas turbine  1  and rotor blades that are disposed at a circumferential surface of a circular plate-shaped rotor disc (not shown) which is rotationally driven by the rotational shaft  5 . 
         [0108]    The stator blades  10  and the rotor blades are disposed in rows in the circumferential direction of the rotational shaft  5  at regular intervals and are disposed in alternating rows in the axial direction of the rotational shaft  5 . 
         [0109]    Next, the stator blades  10 , which are the feature of this embodiment, will be described. 
         [0110]      FIG. 3  is a cross-sectional view for explaining the configuration near a seal holder in the stator blade in  FIG. 2 . 
         [0111]    As shown in  FIGS. 2 and 3 , the stator blades  10  are provided with an outer shroud portion  11 , airfoil portions  12 , inner shroud portions (shroud portions)  13 , a seal holder (holder casing)  14 , springs (elastic portions)  15 , a spacer (pressing portion)  16 , and a honeycomb seal  17 . 
         [0112]    As shown in  FIG. 2 , the outer shroud portion  11  is a member that forms part of wall surfaces of a flow channel in which fluid flows in the compressor  2 . Furthermore, the outer shroud portion  11  is a curved plate-like member disposed at end portions of the airfoil portions  12  on the radially outer side thereof, and a single outer shroud portion  11  is disposed for a plurality of the airfoil portions  12 . In other words, the outer shroud portion  11  is formed of a cylindrical member that has been divided into a plurality of portions, and the plurality of the airfoil portions  12  are connected to an inner circumferential surface thereof. 
         [0113]    With regard to the shape of the outer shroud portion  11  and the connection method with the airfoil portions  12 , any known shapes and methods can be employed; they are not particularly limited. 
         [0114]    As shown in  FIG. 2 , the airfoil portions  12  are members whose cross-sections extending in the radial direction of the rotational shaft  5  are formed in airfoil shapes and that, together with the rotor blades rotationally driven by the rotational shaft  5 , compress a fluid, such as air, and send it toward the combustor  3 . 
         [0115]    The airfoil portions  12  are provided with leading edges LE, which are upstream-end portions relative to a flow of surrounding fluid, trailing edges TE, which are downstream-end portions, negative pressure surfaces, which are surfaces curved in convex shapes, and positive pressure surfaces, which are curved in concave shapes. 
         [0116]    As shown in  FIGS. 2 and 3 , the inner shroud portions  13 , as well as the outer shroud portion  11 , form part of the flow channel in which the fluid flows inside the compressor  2 . Furthermore, the inner shroud portions  13  are curved plate-like members disposed at end portions of the airfoil portions  12  on the radially inner side thereof, and a single inner shroud portion  13  is disposed for a single airfoil portion  12 . In other words, the inner shroud portions  13  are formed of a cylindrical member that has been divided into a plurality of portions, and the airfoil portions  12  are connected to outer circumferential surfaces thereof. 
         [0117]    Fitting grooves  13 A that fit with the seal holder  14 , extending in the circumferential direction (direction perpendicular to the plane of the drawing in  FIG. 3 ), are provided at end portions on the leading edge LE side and trailing edge TE side of the inner shroud portions  13 . 
         [0118]    As shown in  FIG. 3 , the seal holder  14  is a member that is attached to the inner shroud portions  13  on the inner circumferential side thereof (bottom side in  FIG. 3 ), that, together with the inner shroud portions  13 , forms a space for accommodating the springs  15  and the spacer  16  inside thereof, and that supports the honeycomb seal  17 . 
         [0119]    As with the outer shroud portion  11 , a single seal holder  14  is disposed for the plurality of the airfoil portions  12  and the inner shroud portions  13 . 
         [0120]    The seal holder  14  is provided with a pair of side wall portions  14 S that extend in radial directions at the leading edge LE side and the trailing edge TE side and a bottom plate portion  14 B which connects end portions of the pair of side wall portions  14 S at the radially inner side thereof. 
         [0121]    In other words, a groove portion is formed in the seal holder  14 , opening outward in the circumferential direction (top side in  FIG. 3 ). 
         [0122]    The radially outer-side end portions of the side wall portions  14 S are provided with protrusions  14 A which protrude inward in the seal holder  14 , extending in the circumferential direction thereof, and fit with the fitting grooves  13 A of the inner shroud portions  13 . 
         [0123]    The bottom plate portion  14 B is provided with through-holes  14 H into which compressing bolts (compressing portions)  18  that press the spacer  16  together with the springs  15  are inserted. The through-holes  14 H are provided in the bottom plate portion  14 B at an equidistant position from each of the pair of side wall portions  14 S, and a plurality thereof are provided in the circumferential direction (direction perpendicular to the plane of the drawing in  FIG. 3 ) at predetermined intervals. 
         [0124]    As shown in  FIGS. 2 and 3 , the springs  15  are elastic members that bias the inner shroud portions  13  in directions that separate them from the spacer  16  and the seal holder  14 . Furthermore, by sliding on the inner shroud portions  13 , the springs  15  damp the vibrations in the stator blades  10 , i.e., the airfoil portions  12  and the inner shroud portions  13 . 
         [0125]    In this way, by having the springs  15  bias the inner shroud portions  13  in the directions that separate them from the seal holder  14 , the fitting grooves  13 A and the protrusions  14 A are pressed together, coming into close contact with each other, thereby making it possible to ensure the sealing level between the inner shroud portions  13  and the seal holder  14 . 
         [0126]    The springs  15  are substantially rectangularly formed plate springs that are formed into substantially a wave shape, and the spring force of the springs  15  is adjusted by adjusting the plate thickness of the plate springs. With regard to the material forming the springs  15 , the material is desirably capable of maintaining the required spring properties while the gas turbine  1  is in operation, that is, even if the springs  15  are heated to high temperature. 
         [0127]    The springs  15  are disposed in a space formed between the inner shroud portions  13  and the seal holder  14 , more specifically, between the inner shroud portions  13  and the spacer  16 . Furthermore, a total of two springs  15 , one on the leading edge LE side and another on the trailing edge TE side, are disposed in a parallel arrangement. 
         [0128]    In this embodiment, descriptions will be given as applied to an example in which these two springs  15  are disposed at the same phase, in other words, an example in which peak portions of the two springs  15  come in contact with the inner shroud portions  13  or the spacer  16  at the same positions. 
         [0129]      FIG. 4  is a schematic diagram for explaining another arrangement example of the springs. 
         [0130]    Note that, the two springs  15  may be disposed at the same phase, as described above, or they may be disposed at different phases, as shown in  FIG. 4 ; it is not particularly limited. 
         [0131]    With the arrangement of the springs  15  shown in  FIG. 4 , at locations where the peak portions of the first spring  15  are in contact with the inner shroud portions  13 , the peak portions of the other spring  15  are in contact with the spacer  16 . 
         [0132]    By doing so, it is possible to make the springs  15  contact all of the inner shroud portions  13 , even when arrangement intervals of the peak portions in the first spring  15  are wider than arrangement intervals of the inner shroud portions  13 . That is, the inner shroud portions  13  with which the peak portions of the first spring  15  are not in contact are in contact with the peak portions of the other spring  15 , thereby making it possible to have all of the inner shroud portions  13  in contact with the springs  15 . 
         [0133]    The shapes of the springs  15  are determined such that the amplitude of the wave shape (peak-to-peak distance in the radial direction) is longer than the distance from the inner circumferential surfaces of the inner shroud portions  13  to the outer circumferential surface of the spacer  16  and so that the peak portions of the springs  15  are in contact with the inner circumferential surfaces of individual inner shroud portions  13 . 
         [0134]    More specifically, the amplitude of the wave shape in the springs  15  is determined on the basis of the frictional force for damping the vibrations of the stator blades  10 , that is, the compression level of the springs  15  required for generating the spring force. The wavelength (peak-to-peak distance in the circumferential direction) in the wave shape of the springs  15  is determined on the basis of the arrangement intervals of the inner shroud portions  13 , that is, the pitch thereof. 
         [0135]    As shown in  FIG. 3 , the spacer  16 , together with the compressing bolts  18 , presses the springs  15  toward the inner shroud portions  13  and is disposed between the bottom plate portion  14 B of the seal holder  14  and the springs  15 . 
         [0136]    As with the seal holder  14 , a single spacer  16  is disposed for the plurality of the airfoil portions  12  and the inner shroud portions  13 . In other words, the spacer  16  is formed of a cylindrical member that has been divided into a plurality of portions, and the springs  15  come in contact with the inner circumferential surface thereof. 
         [0137]    The spacer  16  is provided with through-holes  16 H into which the compressing bolts  18  are inserted. 
         [0138]    As shown in  FIG. 3 , the honeycomb seal  17 , together with seal fins  22  provided in a rotor  21 , suppresses leakage of the fluid that flows between the stator blades  10  and the rotor  21 . 
         [0139]    Any known honeycomb seal may be used as the honeycomb seal  17 ; it is not particularly limited. 
         [0140]    Next, an assembly method of the stator blades  10  having the above-described configuration will be described. 
         [0141]      FIG. 5  is a schematic diagram for explaining attaching and detaching of the seal holder in the stator blades in  FIG. 3 . 
         [0142]    First, the springs  15  and the spacer  16  are disposed on the inner circumferential surface side in the inner shroud portions  13 , and the compressing bolts  18  are screwed onto the inner shroud portions  13  via the through-holes  16 H of the spacer  16 . Then, by screwing the compressing bolts  18  further into the inner shroud portions  13 , the spacer  16  is brought closer to the inner shroud portions  13  to compress the springs  15 . 
         [0143]    At this time, the distance from the inner circumferential surfaces of the inner shroud portions  13  to the outer circumferential surface of the spacer  16  is made shorter than the distance from the inner circumferential surfaces of the inner shroud portions  13  to the outer circumferential surface of the bottom plate portion  14 B of the seal holder  14 . 
         [0144]    Subsequently, the seal holder  14  is fitted to the inner shroud portions  13 . More specifically, the protrusions  14 A of the seal holder  14  are fitted to the fitting grooves  13 A in the inner shroud portions  13 . At this time, the seal holder  14  is fitted while sliding it in the circumferential direction relative to the inner shroud portions  13 . 
         [0145]      FIG. 6  is a schematic diagram for explaining the state after the seal holder is attached to the stator blades in  FIG. 3 . 
         [0146]    Then, as shown in  FIG. 6 , the compressing bolts  18  are removed from the inner shroud portions  13  via the through-holes  14 H of the seal holder  14 , and thus, attaching of the seal holder  14  is completed. 
         [0147]    The seal holder  14  is removed by carrying out the above-described steps sequentially in reverse order. 
         [0148]    Note that, the compressing bolts  18  may be completely removed from the stator blades  10  as described above, or they may remain on the stator blades  10  in a state in which a predetermined level of compression is exerted on the springs  15 ; it is not particularly limited. 
         [0149]    Next, a method of damping vibrations in the stator blades  10  having the above-described configuration will be described. 
         [0150]    When the gas turbine  1  is operated, vibrations are generated in the stator blades  10  due to the influence of the fluid or the like flowing in the compressor  2 . More specifically, vibrations are generated by which the airfoil portions  12  and the inner shroud portions  13  of the stator blades  10  vibrate in the circumferential direction. 
         [0151]    When the inner shroud portions  13  vibrate as described above, sliding occurs between the peak portions of the springs  15 , which are pressed against the inner shroud portions  13 , and the inner circumferential surfaces of the inner shroud portions  13 . The pressing force of the springs  15  and the frictional force in accordance with the friction coefficient between the inner shroud portions  13  and the springs  15  act between the inner shroud portions  13  and the springs  15 . 
         [0152]    The above-described sliding converts vibrational energy of the airfoil portions  12  and the inner shroud portions  13  into frictional energy, such as thermal energy and so forth, thereby damping the vibrations in the stator blades  10 . 
         [0153]    With the above-described configuration, when the airfoil portions  12  and the inner shroud portions  13  vibrate and slide relative to the seal holder  14 , the springs  15 , which have been pressing the inner shroud portions  13  in the direction away from the seal holder  14 , and the inner shroud portions  13  relatively move; that is, the springs  15  and the inner shroud portions  13  slide. Accordingly, energy associated with the vibrations in the airfoil portions  12  and the inner shroud portions  13  is converted into thermal energy (frictional energy) due to sliding, thereby making it possible to damp the vibrations in the airfoil portions  12  and the inner shroud portions  13 . 
         [0154]    Furthermore, because the compression level of the springs  15  is adjusted by moving the spacer  16  closer to the inner shroud portions  13 , the force with which the springs  15  press the inner shroud portions  13  is adjusted. In other words, because the frictional force between the springs  15  and the inner shroud portions  13  is adjusted, it is possible to adjust the level of damping of vibrations in the airfoil portions  12  and the inner shroud portions  13 . 
         [0155]    On the other hand, the springs  15  can be easily replaced by attaching/detaching the springs  15 , together with the seal holder  14 , to/from the inner shroud portions  13  by sliding them. Accordingly, even if the springs  15  become deteriorated due to wear from long-term use, the springs  15  can easily be replaced. 
         [0156]    In addition, the springs  15  are disposed inside the space surrounded by the seal holder  14  and the inner shroud portions  13 ; therefore, even if the springs  15  break, it is possible to prevent them from leaping out of the space to damage the airfoil portions  12 . 
         [0157]    Furthermore, by moving the spacer  16  closer to the inner shroud portions  13 , the biasing force of the springs  15  is received by the inner shroud portions  13  and the spacer  16 . In other words, the biasing force of the springs  15  does not act on the seal holder  14 . Accordingly, when moving the seal holder  14  by sliding it relative to the inner shroud portions  13  or when attaching/detaching the seal holder  14 , the frictional force that acts at contact surfaces between the inner shroud portions  13  and the seal holder  14  is reduced, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
         [0158]    Because the inner shroud portions  13  are independently disposed for each of the plurality of the airfoil portions  12 , the individual airfoil portions  12  and the inner shroud portions  13  readily move relative to the springs  15 , as compared with the case in which the plurality of the inner shroud portions  13  are integrally formed. In other words, the sliding distance between the inner shroud portions  13  and the springs  15  is extended. 
         [0159]    Accordingly, a greater amount of energy associated with the vibrations in the airfoil portions  12  and the inner shroud portions  13  is converted into thermal energy (frictional energy) due to sliding, and therefore, the vibrations in the airfoil portions  12  and the inner shroud portions  13  are more readily damped. 
         [0160]    On the other hand, because a single seal holder  14  is provided for the plurality of the airfoil portions  12  and the inner shroud portions  13 , the sealing level between the upstream side and the downstream side of the stator blades  10  can be increased as compared with the case in which the seal holders  14  are disposed for each of the plurality of the airfoil portions  12  and the inner shroud portions  13 . 
         [0161]    By employing plate-like springs formed into a wave-like shape as the springs  15 , a larger pressing force can be exerted on the inner shroud portions  13  as compared with the case in which other types of springs are employed. 
         [0162]    On the other hand, by making each of the peak portions of the springs  15  individually contact the inner shroud portions  13 , the plurality of the inner shroud portions  13  can be moved, by sliding them, with respect to a single spring  15 . 
         [0163]    The spacer  16  can be moved closer to the inner shroud portions  13  using the compressing bolts  18 . Accordingly, the compression level of the springs  15  is adjusted, thereby adjusting the force with which the springs  15  press the inner shroud portions  13 . In other words, because the frictional force between the springs  15  and the inner shroud portions  13  is adjusted, it is possible to adjust the level of damping of vibrations in the airfoil portions  12  and the inner shroud portions  13 . 
         [0164]    On the other hand, by moving the spacer  16  closer to the inner shroud portions  13 , the biasing force of the springs  15  is received by the inner shroud portions  13  and the spacer  16 . Accordingly, when moving the seal holder  14  by sliding it relative to the inner shroud portions  13  or when attaching/detaching the seal holder  14 , the frictional force that acts at contact surfaces between the inner shroud portions  13  and the seal holder  14  is reduced, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
         [0165]      FIG. 7  is a schematic diagram for explaining yet another arrangement example of the springs in  FIG. 3 . 
         [0166]    Note that, two springs  15  may be disposed between the inner shroud portions  13  and the spacer  16 , as in the embodiment described above, or, as shown in  FIG. 7 , four springs  15  may be disposed between the inner shroud portions  13  and the spacer  16 ; the number of the springs  15  is not particularly limited. 
         [0167]    Furthermore, the spacer  16  may be pressed toward the inner shroud portions  13  by screwing the compressing bolts  18  onto the inner shroud portions  13  as in the above-described embodiment, or the spacer  16  may be pressed toward the inner shroud portions  13  by screwing the pressing springs  15  onto the seal holder  14  to thereby press the tip of the pressing springs  15  against the spacer  16 ; it is not particularly limited. 
         [0168]    As in the embodiment described above, the gas turbine  1  may be operated in a state in which the spacer  16  remains between the seal holder  14  and the inner shroud portions  13 , or the gas turbine  1  may be operated with the spacer  16  removed from between the seal holder  14  and the inner shroud portions  13 ; it is not particularly limited. 
         [0169]    As in the embodiment described above, the spring force of the springs  15  may be adjusted by adjusting the compression level of the springs  15  using the compressing bolts  18  or, even in a state in which the compressing bolts  18  are removed, the spring force of the springs  15  may be adjusted by adjusting only the plate thickness of the spacer  16 ; it is not particularly limited. 
       Second Embodiment 
       [0170]    A gas turbine according to a second embodiment of the present invention will be described with reference to  FIGS. 8 to 15 . Note that, in this embodiment, turbine blades of the invention of the present application will be described as applied to stator blades of first to fourth stages in the compressor  2  of the gas turbine  1 . 
         [0171]      FIG. 8  is a schematic diagram for explaining the configuration of a rotor disc and stator blades in a compressor of a gas turbine according to this embodiment. 
         [0172]    As shown in  FIGS. 1 and 8 , the compressor  2  is provided with stator blades (turbine blades)  110  that are attached to a casing  6  of the gas turbine  1  and rotor blades that are disposed at a circumferential surface of a circular plate-shaped rotor disc (not shown) which is rotationally driven by the rotational shaft  5 . 
         [0173]    The stator blades  110  and the rotor blades are disposed in rows in the circumferential direction of the rotational shaft  5  at regular intervals and are disposed in alternating rows in the axial direction of the rotational shaft  5 . 
         [0174]    Next, the stator blades  110 , which are the feature of this embodiment, will be described. 
         [0175]      FIG. 9  is a cross-sectional view for explaining the configuration near a seal holder in the stator blade in  FIG. 8 . 
         [0176]    As shown in  FIGS. 8 and 9 , the stator blades  110  are provided with an outer shroud portion  111 , airfoil portions  112 , inner shroud portions (shroud portions)  113 , a seal holder (holder casing)  114 , springs (elastic portions)  115 , damping plates (friction portions)  116 , and a honeycomb seal  117 . 
         [0177]    As shown in  FIG. 8 , the outer shroud portion  111  is a member that forms part of wall surfaces of a flow channel in which fluid flows in the compressor  2 . Furthermore, the outer shroud portion  111  is a curved plate-like member disposed at end portions of the airfoil portions  112  on the radially outer side thereof, and a single outer shroud portion  111  is disposed for a plurality of the airfoil portions  112 . In other words, the outer shroud portion  111  is formed of a cylindrical member that has been divided into a plurality of portions, and the plurality of the airfoil portions  112  are connected to an inner circumferential surface thereof. 
         [0178]    With regard to the shape of the outer shroud portion  111  and the connection method with the airfoil portions  112 , any known shapes and methods can be employed; they are not particularly limited. 
         [0179]    As shown in  FIG. 8 , the airfoil portions  112  are members whose cross-sections extending in the radial direction of the rotational shaft  5  are formed in airfoil shapes and that, together with the rotor blades rotationally driven by the rotational shaft  5 , compress a fluid, such as air, and send it toward the combustor  3 . 
         [0180]    The airfoil portions  112  are provided with leading edges LE, which are upstream-end portions relative to a flow of surrounding fluid, trailing edges TE, which are downstream-end portions, negative pressure surfaces, which are surfaces curved in convex shapes, and positive pressure surfaces, which are curved in concave shapes. 
         [0181]    As shown in  FIGS. 8 and 9 , the inner shroud portions  113 , as well as the outer shroud portion  111 , form part of the flow channel in which the fluid flows inside the compressor  2 . Furthermore, the inner shroud portions  113  are curved plate-like members disposed at end portions of the airfoil portions  112  on radially inner side thereof, and a single inner shroud portion  113  is disposed for a single airfoil portion  112 . In other words, the inner shroud portions  113  are formed of a cylindrical member that has been divided into a plurality of portions, and the airfoil portions  112  are connected to outer circumferential surfaces thereof. 
         [0182]    Fitting grooves  113 A that fit with the seal holder  144 , extending in the circumferential direction (direction perpendicular to the plane of the drawing in  FIG. 9 ), are provided at end portions on the leading edge LE side and trailing edge TE side of the inner shroud portions  113 . 
         [0183]    As shown in  FIG. 9 , the seal holder  114  is a member that is attached to the inner shroud portions  113  on the inner circumferential side thereof (bottom side in  FIG. 9 ), that, together with the inner shroud portions  113 , forms a space for accommodating the springs  115  and the damping plates  116  inside thereof, and that supports the honeycomb seal  117 . 
         [0184]    As with the outer shroud portion  114 , a single seal holder  114  is disposed for the plurality of the airfoil portions  112  and the inner shroud portions  113 . 
         [0185]    The seal holder  114  is provided with a pair of side wall portions  114 S that extend in radial directions at the leading edge LE side and the trailing edge TE side and a bottom plate portion  114 B which connects end portions of the pair of side wall portions  114 S at the radially inner side thereof. 
         [0186]    In other words, a groove portion is formed in the seal holder  114 , opening outward in the circumferential direction (top side in  FIG. 9 ). 
         [0187]    The radially outer-side end portions of the side wall portions  114 S are provided with protrusions  114 A which protrude inward in the seal holder  114 , extending in the circumferential direction thereof, and fit with the fitting grooves  113 A of the inner shroud portions  113 . 
         [0188]    The bottom plate portion  114 B is provided with through-holes  114 H into which compressing bolts (compressing portions)  118  that press the damping plates  116  together with the springs  115  are inserted. The through-holes  114 H are provided in the bottom plate portion  114 B at an equidistant position from each of the pair of side wall portions  114 S and a plurality thereof are provided in the circumferential direction (direction perpendicular to the plane of the drawing in  FIG. 9 ) at predetermined intervals. 
         [0189]    As shown in  FIGS. 8 and 9 , the springs  115  are elastic members that bias the inner shroud portions  113  and the damping plates  116  in directions that separate them from the seal holder  114 . Furthermore, the springs  115 , together with the damping plates  116 , damp the vibrations in the stator blades  110 , i.e., the airfoil portions  112 , and the inner shroud portions  113 . 
         [0190]    In this way, by having the springs  115  bias the inner shroud portions  113  in the directions that separate them from the seal holder  114 , the fitting grooves  113 A and the protrusions  114 A are pressed together, coming into close contact with each other, thereby making it possible to ensure the sealing level between the inner shroud portions  113  and the seal holder  114 . 
         [0191]    The springs  115  are substantially rectangularly formed plate springs that are formed into substantially a wave shape, and the spring force of the springs  115  is adjusted by adjusting the plate thickness of the plate springs. With regard to the material forming the springs  115 , the material is desirably capable of maintaining the required spring properties while the gas turbine  1  is in operation, that is, even if the springs  115  are heated to high temperature. 
         [0192]    The springs  115  are disposed in the space formed between the inner shroud portions  113  and the seal holder  114 , more specifically, between the seal holder  114  and the damping plates  116 . Furthermore, a total of two springs  115 , one on the leading edge LE side and another on the trailing edge TE side, are disposed in a parallel arrangement. 
         [0193]    In this embodiment, descriptions will be given as applied to an example in which these two springs  115  are disposed at the same phase, in other words, an example in which peak portions of the two springs  115  come in contact with the damping plates  16  or the seal holder  114  at the same positions. 
         [0194]      FIG. 10  is a schematic diagram for explaining another arrangement example of the springs in  FIG. 9 . 
         [0195]    Note that, the two springs  115  may be disposed at the same phase, as described above, or they may be disposed at different phases, as shown in  FIG. 10 ; it is not particularly limited. 
         [0196]    With the arrangement of the springs  115  shown in  FIG. 10 , at locations where the peak portions of the first spring  115  are in contact with the damping plates  116 , the peak portions of the other spring  115  are in contact with the seal holder  114 . 
         [0197]    By doing so, it is possible to make the springs  115  contact all of the damping plates  116 , even when arrangement intervals of the peak portions in the first spring  115  are wider than arrangement intervals of the inner shroud portions  113  and the damping plates  116 . That is, the damping plates  116  with which the peak portions of the first spring  115  are not in contact are in contact with the peak portions of the other spring  115 , thereby making it possible to have all of the damping plates  116  in contact with the springs  115 . 
         [0198]    The shapes of the springs  115  are determined such that the amplitude of the wave shape (peak-to-peak distance in the radial direction) is longer than the distance from the outer circumferential surfaces of the damping plates  116  to the inner circumferential surface of the seal holder  114  and so that the peak portions of the springs  115  are in contact with the inner circumferential surfaces of individual damping plates  116 . 
         [0199]    More specifically, the amplitude of the wave shape in the springs  115  is determined on the basis of the frictional force for damping the vibrations of the stator blades  110 , that is, the compression level of the springs  115  required for generating the spring force. The wavelength (peak-to-peak distance in the circumferential direction) in the wave shape of the springs  115  is determined on the basis of the arrangement intervals of the inner shroud portions  113  and damping plates  116 , that is, the pitch thereof. 
         [0200]    As shown in  FIG. 9 , the damping plates  116  are pressed against the inner circumferential surfaces of the inner shroud portions  113  by the springs  15  and are disposed between the inner shroud portions  113  and the springs  115 . 
         [0201]    As with the inner shroud portions  113 , one damping plate  116  is disposed for each of the plurality of the airfoil portions  112  and the inner shroud portions  113 . 
         [0202]      FIG. 11  is a schematic diagram for explaining the configuration of the damping plates in  FIG. 9 . 
         [0203]    The damping plates  116  are provided with bolt holes  116 H into which the compressing bolts  118  are screwed and relief grooves  116 G formed on surfaces facing the inner shroud portions  113 . 
         [0204]    The bolt holes  116 H are female screw holes formed substantially at the center of the damping plates  116  and the compressing bolts  118  are screwed thereinto. 
         [0205]    First end portions of the compressing bolts  118  are screwed into the bolt holes  116 H of the damping plates  116 . Second end portions of the compressing bolts  118  are inserted into the through-holes  114 H of the seal holder  114 . The nuts (compressing portions)  119 , which compress the springs  115  together with the compressing bolts  118 , are threaded onto the second end portions of the compressing bolts  118 . 
         [0206]    As shown in  FIGS. 9 and 11 , the relief grooves  116 G are grooves formed on the surfaces (top-side surfaces in  FIGS. 9 and 11 ) of the damping plates  116  facing the inner shroud portions  113 . In addition, the relief grooves  116 G are grooves extending in the direction parallel to the direction in which the rotational shaft  5  extends (direction perpendicular to the plane of the drawing in  FIG. 9 ), in other words, grooves extending in a direction that intersect with, more preferably a direction perpendicular to, the direction in which the damping plates  116  and the inner shroud portions  113  slide. 
         [0207]    By providing the relief grooves  116 G in this way, the surfaces of the damping plates  116  that come into contact with the inner shroud portions  113  are divided into two with the relief grooves  116 G therebetween, and each surface comes into contact with the inner shroud portions  113 . Accordingly, even if the inner shroud portions  113  and the damping plates  116  slide, the inner shroud portions  113  and the damping plates  116  come into stable contact at the above-described two surfaces, thereby preventing the occurrence of problems such as partial contact or the like. 
         [0208]    As shown in  FIG. 9 , the honeycomb seal  117 , together with seal fins  122  provided in a rotor  21 , suppresses leakage of a fluid that flows between the stator blades  110  and the rotor  21 . 
         [0209]    Any known honeycomb seal may be used as the honeycomb seal  117 ; it is not particularly limited. 
         [0210]    Next, an assembly method of the stator blades  110  having the above-described configuration will be described. 
         [0211]      FIG. 12  is a schematic diagram for explaining attaching and detaching of the seal holder in the stator blades in  FIG. 9 . 
         [0212]    First, the springs  115  and the damping plates  116  are disposed inside the seal holder  114 , and the second end portions of the compressing bolts  118  are inserted into the through-holes  114 H of the seal holder  114 . Then, by threading the nuts  119  on the second end portions of the compressing bolts  118 , the damping plates  116  are brought closer to the bottom plate portion  114 B of the seal holder  114 , thereby compressing the springs  115 . 
         [0213]    At this time, the distance from the outer circumferential surface of the bottom plate portion  114 B to the outer circumferential surfaces of the damping plates  116  is made shorter than the distance from the outer circumferential surface of the bottom plate portion  114 B to the inner circumferential surfaces of the inner shroud portions  113 . 
         [0214]    Subsequently, the seal holder  114  is fitted to the inner shroud portions  113 . More specifically, the protrusions  114 A of the seal holder  114  are fitted to the fitting grooves  113 A in the inner shroud portions  113 . At this time, the seal holder  114  is fitted while sliding it in the circumferential direction relative to the inner shroud portions  113 . 
         [0215]      FIG. 13  is a schematic diagram for explaining the state after the seal holder is attached to the stator blade in  FIG. 9 . 
         [0216]    Then, as shown in  FIG. 13 , the nuts  119  are removed from the compressing bolts  118 , and the damping plates  116  are brought into contact with the inner shroud portions  113 , thereby completing the attaching of the seal holder  114 . 
         [0217]    The seal holder  114  is removed by carrying out the above-described steps sequentially in reverse order. 
         [0218]    Note that, the compressing bolts  118  may be left attached to the damping plates  116 , as described above, or they may be removed from the damping plates  116 ; it is not particularly limited. 
         [0219]    Next, a method of damping vibrations in the stator blades  110  having the above-described configuration will be described. 
         [0220]    When the gas turbine  1  is operated, vibrations are generated in the stator blades  110  due to the influence of the fluid or the like flowing in the compressor  2 . More specifically, vibrations are generated by which the airfoil portions  112  and the inner shroud portions  113  of the stator blades  110  vibrate in the circumferential direction. 
         [0221]    When the inner shroud portions  113  vibrate as described above, sliding occurs between the damping plates  116 , which are pressed against the inner shroud portions  113 , and the inner circumferential surfaces of the inner shroud portions  113 . The pressing force of the springs  115  and the frictional force in accordance with the friction coefficient between the inner shroud portions  113  and the damping plates  116  act between the inner shroud portions  113  and the damping plates  116 . 
         [0222]    The above-described sliding converts vibrational energy of the airfoil portions  112  and the inner shroud portions  113  into frictional energy, such as thermal energy and so forth, thereby damping the vibrations in the stator blades  110 . 
         [0223]    With the above-described configuration, when the airfoil portions  112  and the inner shroud portions  113  vibrate and slide relative to the seal holder  114 , the damping plates  116 , which have been pressed against the inner shroud portions  113 , and the inner shroud portions  113  relatively move; that is, the damping plates  116  and the inner shroud portions  113  slide. Accordingly, energy associated with the vibrations in the airfoil portions  112  and the inner shroud portions  113  is converted into thermal energy (frictional energy) due to the sliding, thereby making it possible to damp the vibrations in the airfoil portions  112  and the inner shroud portions  113 . 
         [0224]    On the other hand, by moving the damping plates  116  closer to the seal holder  114 , the biasing force of the springs  115  is received by the damping plates  116  and the seal holder  114 . In other words, the biasing force of the springs  115  does not act on the inner shroud portions  113 . Accordingly, when moving the seal holder  114  by sliding it relative to the inner shroud portions  113  or when attaching/detaching the seal holder  114 , the frictional force that acts at contact surfaces between the inner shroud portions  113  and the seal holder  114  is reduced, thereby making it possible to facilitate the sliding movement or attaching/detaching. 
         [0225]    Furthermore, the springs  115  can be easily replaced by attaching/detaching the springs  115 , together with the seal holder  114 , to/from the inner shroud portions  113  by sliding them. Accordingly, even if the springs  115  become deteriorated due to wear from long-term use, the springs  115  can easily be replaced. 
         [0226]    In addition, the springs  115  are disposed inside the space surrounded by the seal holder  114  and the inner shroud portions  113 ; therefore, even if the springs  115  break, it is possible to prevent them from leaping out of the space to damage the airfoil portions  112 . 
         [0227]    Because the inner shroud portions  113  are independently disposed for each of the plurality of the airfoil portions  112 , the individual airfoil portions  112  and the inner shroud portions  113  readily move relative to the damping plates  116 , as compared with the case in which the plurality of the inner shroud portions  113  are integrally formed. In other words, the sliding distance between the inner shroud portions  113  and the damping plates  116  is extended. 
         [0228]    Accordingly, a greater amount of energy associated with the vibrations in the airfoil portions  112  and the inner shroud portions  113  is converted into thermal energy (frictional energy) due to sliding, and therefore, the vibrations in the airfoil portions  112  and the inner shroud portions  113  are more readily damped. 
         [0229]    On the other hand, because a single seal holder  114  is provided for the plurality of the airfoil portions  112  and the inner shroud portions  113 , the sealing level between the upstream side and the downstream side of the stator blades  110  can be increased as compared with the case in which the seal holders  114  are disposed for each of the plurality of the airfoil portions  112  and the inner shroud portions  113 . 
         [0230]    By employing springs formed into a wave-like shape as the springs  115 , a larger pressing force can be exerted on the inner shroud portions  113  as compared with the case in which other types of springs are employed. 
         [0231]    On the other hand, by making each of the peak portions of the springs  115  individually contact the damping plates  116 , the plurality of the damping plates  116  are pressed against the inner shroud portions  113  by a single spring. 
         [0232]    Because the compressing bolts  118  protrude from the damping plates  116  penetrating the seal holder  114 , the compressing bolts  118  and the damping plates  116  are movable in directions toward and away from the seal holder  114 , while being restricted in movement in the direction that intersects with the direction of movement toward/away from the seal holder  114 ; that is, movement in the circumferential direction of the rotational shaft  5  is restricted. Accordingly, it is ensured that sliding occurs between the inner shroud portions  113  and the damping plates  116 . 
         [0233]      FIG. 14  is a schematic diagram for explaining yet another arrangement example of the springs in  FIG. 3 . 
         [0234]    Note that, two springs  115  may be disposed between the damping plates  116  and the seal holder  114 , as in the embodiment described above, or, as shown in  FIG. 14 , four springs  115  may be disposed between the damping plates  116  and the seal holder  114 ; the number of the springs  115  is not particularly limited. 
         [0235]      FIG. 15  is a schematic diagram for explaining another configuration of the seal holder in  FIG. 9 . 
         [0236]    Note that, as in the above-described embodiment, the honeycomb seal  117  may be disposed in the seal holder  114 , and the seal fins  122  may be disposed at the rotor  21  or, as shown in  FIG. 15 , seal fins  122  may be disposed in the seal holder  114 , configuring them as a labyrinth seal in which steps are provided at positions that face the seal fins  122  of the rotor  21 ; it is not particularly limited. 
         [0237]    As in the embodiment described above, the spring force of the springs  115  may be adjusted by adjusting the compression level of the springs  115  using compressing bolts  118  and the nuts  119  or, even in a state in which the nuts  119  are removed, the spring force of the springs  115  may be adjusted by adjusting only the plate thickness of the damping plates  116 ; it is not particularly limited. 
       Third Embodiment 
       [0238]    A gas turbine according to a third embodiment of this invention will now be described with reference to  FIG. 1  and  FIGS. 16 to 19 . Note that, in this embodiment, turbine blades of the invention of the present application will be described as applied to stator blades of first to third, fifth to seventeenth, or tenth to fourteenth stages in the compressor  2  of the gas turbine  1 . 
         [0239]      FIG. 16  is a schematic diagram for explaining the configuration of a rotor disc and stator blades in a compressor of a gas turbine according to this embodiment. 
         [0240]    As shown in  FIGS. 1 and 16 , the compressor  2  is provided with stator blades (turbine blades)  210  that are attached to a casing  6  of the gas turbine  1  and rotor blades that are disposed at a circumferential surface of a circular plate-like rotor disc (not shown) which is rotationally driven by the rotational shaft  5 . 
         [0241]    The stator blades  210  and the rotor blades are disposed in rows in the circumferential direction of the rotational shaft  5  at regular intervals and are disposed in alternating rows in the axial direction of the rotational shaft  5 . 
         [0242]    Next, the stator blades  210 , which are the feature of this embodiment, will be described. 
         [0243]      FIG. 17  is a cross-sectional view for explaining the configuration near a seal holder in the stator blades in  FIG. 16 . 
         [0244]    In this embodiment, the stator blades  210  will be described as applied to stator blades with fixed pitch, in other words, stator blades with fixed angles of attack with respect to the flow of the fluid flowing inside the compressor  2 . 
         [0245]    As shown in  FIGS. 16 and 17 , the stator blades  210  are provided with an outer shroud portion  211 , airfoil portions  212 , inner shroud portions (shroud portions)  213 , a seal holder (holder casing)  214 , springs (elastic portions)  215 , and a honeycomb seal  217 . 
         [0246]    As shown in  FIG. 16 , the outer shroud portion  211  is a member that forms part of wall surfaces of a flow channel in which fluid flows in the compressor  2 . Furthermore, the outer shroud portion  211  is a curved plate-like member disposed at end portions of the airfoil portions  212  on the radially outer side thereof, and a single outer shroud portion  211  is disposed for a plurality of the airfoil portions  212 . In other words, the outer shroud portion  211  is formed of a cylindrical member that has been divided into a plurality of portions, and the plurality of the airfoil portions  212  are connected to an inner circumferential surface thereof. 
         [0247]    With regard to the shape of the outer shroud portion  211  and the connection method with the airfoil portions  212 , any known shapes and methods can be employed; they are not particularly limited. 
         [0248]    As shown in  FIG. 16 , the airfoil portions  212  are members whose cross-sections extending in the radial direction of the rotational shaft  5  are formed in airfoil shapes and that, together with the rotor blades rotationally driven by the rotational shaft  5 , compress a fluid such as air and send it toward the combustor  3 . 
         [0249]    The airfoil portions  212  are provided with leading edges LE, which are upstream-end portions relative to a flow of surrounding fluid, trailing edges TE, which are downstream-end portions, negative pressure surfaces, which are surfaces curved in convex shapes, and positive pressure surfaces, which are curved in concave shapes. 
         [0250]    As shown in  FIGS. 16 and 17 , the inner shroud portions  213 , as well as the outer shroud portion  211 , form part of the flow channel in which the fluid flows inside the compressor  2 . Furthermore, the inner shroud portions  213  are curved plate-like members disposed at end portions of the airfoil portions  212  on radially inner side thereof, and a single inner shroud portion  213  is disposed for a single airfoil portion  212 . In other words, the inner shroud portions  213  are formed of a cylindrical member that has been divided into a plurality of portions, and the airfoil portions  212  are connected to outer circumferential surfaces thereof. 
         [0251]    Fitting grooves  213 A that fit with the seal holder  214 , extending in the circumferential direction (direction perpendicular to the plane of the drawing in  FIG. 17 ), are provided at end portions on the leading edge LE side and trailing edge TE side of the inner shroud portions  213 . 
         [0252]    As shown in  FIG. 17 , the seal holder  214  is a member that is attached to the inner shroud portions  213  on the inner circumferential side thereof (bottom side in  FIG. 17 ), that, together with the inner shroud portions  213 , forms a space for accommodating the springs  215  inside thereof, and that supports the honeycomb seal  217 . 
         [0253]    As with the outer shroud portion  211 , a single seal holder  214  is disposed for the plurality of the airfoil portions  212  and the inner shroud portions  213 . 
         [0254]    The seal holder  214  is provided with a pair of side wall portions  214 S that extend in radial directions at the leading edge LE side and the trailing edge TE side and a bottom plate portion  214 B which connects end portions of the pair of side wall portions  214 S at radially inner side thereof. 
         [0255]    In other words, a groove portion is formed in the seal holder  214 , opening outward in the circumferential direction (top side in  FIG. 17 ). 
         [0256]    The radially outer-side end portions of the side wall portions  214 S are provided with protrusions  214 A which protrude inward in the seal holder  214 , extending in the circumferential direction thereof, and fit with the fitting grooves  213 A of the inner shroud portions  213 . 
         [0257]    As shown in  FIGS. 16 and 17 , the springs  215  are elastic members that bias the inner shroud portions  213  in directions that separate them from the seal holder  214 . Furthermore, by sliding on the inner shroud portions  213 , the springs  215  damp the vibrations in the stator blades  210 , i.e., the airfoil portions  212 , and the inner should portions  213 . 
         [0258]    In this way, by having the springs  215  bias the inner shroud portions  213  in the directions that separate them from the seal holder  214 , the fitting grooves  213 A and the protrusions  214 A are pressed together, coming into close contact with each other, thereby making it possible to ensure the sealing level between the inner shroud portions  213  and the seal holder  214 . 
         [0259]    The springs  215  are substantially rectangularly formed plate springs that are formed into substantially a wave shape, and the spring force of the springs  215  is adjusted by adjusting the plate thickness of the plate springs. With regard to the material forming the springs  215 , the material is desirably capable of maintaining the required spring properties while the gas turbine  1  is in operation, that is, even if the springs  215  are heated to high temperature. 
         [0260]    The springs  215  are disposed in a space formed between the inner shroud portions  213  and the seal holder  214 , more specifically, between the inner shroud portions  213  and the seal holder  214 . Furthermore, a total of two springs  215 , one on the leading edge LE side and another on the trailing edge TE side, are disposed in a parallel arrangement. 
         [0261]    In this embodiment, descriptions will be given as applied to an example in which these two springs  215  are disposed at the same phase, in other words, an example in which peak portions of the two springs  215  come in contact with the inner shroud portions  213  or the seal holder  214  at the same positions. 
         [0262]      FIG. 18  is a schematic diagram for explaining another arrangement example of springs in  FIG. 17 . 
         [0263]    Note that, the two springs  215  may be disposed at the same phase, as described above, or they may be disposed at different phases, as shown in  FIG. 18 ; it is not particularly limited. 
         [0264]    With the arrangement of the springs  215  shown in  FIG. 18 , at locations where the peak portions of the first spring  215  are in contact with the inner shroud portions  213 , the peak portions of the other spring  215  are in contact with the seal holder  214 . 
         [0265]    By doing so, it is possible to make the springs  215  contact all of the inner shroud portions  213 , even when arrangement intervals of the peak portions in the first spring  215  are wider than arrangement intervals of the inner shroud portions  213 . That is, the inner shroud portions  213  with which the peak portions of the first spring  215  are not in contact are in contact with the peak portions of the other spring  215 , thereby making it possible to have all of the inner shroud portions  213  in contact with the springs  215 . 
         [0266]    The shapes of the springs  215  are determined such that the amplitude of the wave shape (peak-to-peak distance in the radial direction) is longer than the distance from the inner circumferential surfaces of the inner shroud portions  213  to the outer circumferential surface of the seal holder  214  and so that the peak portions of the springs  215  are in contact with the inner circumferential surfaces of individual inner shroud portions  213 . 
         [0267]    More specifically, the amplitude of the wave shape in the springs  215  is determined on the basis of the frictional force for damping the vibrations of the stator blades  210 , that is, the compression level of the springs  215  required for generating the spring force. The wavelength (peak-to-peak distance in the circumferential direction) in the wave shape of the springs  215  is determined on the basis of the arrangement intervals of the inner shroud portions  213 , that is, the pitch, thereof. 
         [0268]    As shown in  FIG. 17 , the honeycomb seal  217 , together with seal fins  222  provided in the rotor  21 , suppresses leakage of a fluid that flows between the stator blades  210  and the rotor  21 . 
         [0269]    Any known honeycomb seal may be used as the honeycomb seal  217 ; it is not particularly limited. 
         [0270]    Next, a method of damping vibrations in the stator blades  210  having the above-described configuration will be described. 
         [0271]    When the gas turbine  1  is operated, vibrations are generated in the stator blades  210  due to the influence of the fluid or the like flowing in the compressor  2 . More specifically, vibrations are energized by which the airfoil portions  212  and the inner shroud portions  213  of the stator blades  210  vibrate in the circumferential direction. 
         [0272]    When the inner shroud portions  213  vibrate as described above, sliding occurs between the peak portions of the springs  215 , which are pressed against the inner shroud portions  213 , and the inner circumferential surfaces of the inner shroud portions  213 . The pressing force of the springs  215  and the frictional force in accordance with the friction coefficient between the inner shroud portions  213  and the springs  215  act between the inner shroud portions  213  and the springs  215 . 
         [0273]    The above-described sliding converts vibrational energy of the airfoil portions  212  and the inner shroud portions  213  into thermal energy, such as frictional energy and so forth, thereby damping the vibrations in the stator blades  210 . 
         [0274]    With the above-described configuration, when the airfoil portions  212  and the inner shroud portions  213  vibrate and slide relative to the seal holder  214 , the springs  215  and the inner shroud portions  213  relatively move; that is, the springs  215  and the inner shroud portions  213  slide. Accordingly, energy associated with the vibrations in the airfoil portions  212  and the inner shroud portions  213  is converted into thermal energy (frictional energy) due to the sliding, thereby making it possible to damp the vibrations in the airfoil portions  212  and the inner shroud portions  213 . 
         [0275]    On the other hand, the springs  215  can be easily replaced by attaching/detaching the springs  215 , together with the seal holder  214 , to/from the inner shroud portions  213  by sliding them. Accordingly, even if the springs  215  become deteriorated due to wear from long-term use, the springs  215  can easily be replaced. 
         [0276]    In addition, the springs  215  are disposed inside the space surrounded by the seal holder  214  and the inner shroud portions  213 ; therefore, even if the springs  215  break, it is possible to prevent them from leaping out of the space to damage the airfoil portions  212 . 
         [0277]    Because the inner shroud portions  213  are independently disposed for each of the plurality of the airfoil portions  212 , the individual airfoil portions  212  and the inner shroud portions  213  readily move relative to the springs  215 , as compared with the case in which the plurality of the inner shroud portions  213  are integrally formed. In other words, the sliding distance between the inner shroud portions  213  and the springs  215  is extended. 
         [0278]    Accordingly, a greater amount of energy associated with the vibrations in the airfoil portions  212  and the inner shroud portions  213  is converted into thermal energy (frictional energy) due to sliding, and therefore, greater damping of the vibrations in the airfoil portions  212  and the inner shroud portions  213  is possible. 
         [0279]      FIG. 19  is a schematic diagram for explaining yet another arrangement example of the springs in  FIG. 17 . 
         [0280]    Note that, two springs  215  may be disposed between the inner shroud portions  213  and the seal holder  214 , as in the embodiment described above, or, as shown in  FIG. 19 , four springs  215  may be disposed between the inner shroud portions  213  and the seal holder  214 ; the number of the springs  215  is not particularly limited. 
         [0281]    Note that, the technical scope of the present invention is not limited to the embodiments described above, and various alterations are permissible within a range that does not depart from the gist of the present invention. 
         [0282]    For example, in the above-described embodiments, turbine blades of this invention have been described as applied to stator blades of a gas turbine compressor; however, application to stator blades of a turbine unit of a gas turbine is also possible. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  gas turbine 
           10 ,  110 ,  210  stator blade (turbine blade) 
           12 ,  112 ,  212  airfoil portion 
           13 ,  113 ,  213  inner shroud portion (shroud portion) 
           14 ,  114 ,  214  seal holder (holder casing) 
           15 ,  115 ,  215  spring (elastic portion) 
           16  spacer (pressing portion) 
           18  compressing bolt (compressing portion) 
           116  damping plate (friction portion) 
           116 G relief groove 
           118  compressing bolt (compressing portion) 
           119  nut (compressing portion)