Abstract:
A brush seal in which an increase in steady-state wear is prevented and the influence of turbulence is eliminated is provided. The invention includes a brush seal including brush seal bristles formed of a plurality of wires and mounted to a seal box in such a manner that one end thereof is in contact with a downstream cylindrical portion; and a downstream support plate mounted next to the brush seal bristles in a direction in which combustion gas flows, for restricting the motion of the brush seal bristles. The brush seal seals the combustion gas flowing between the seal box and the downstream cylindrical portion. The brush seal includes restraint bristles mounted opposite to the downstream support plate and next to the brush seal bristles in the direction in which the combustion gas flows. The restraint bristles have a degree of elasticity such that the downstream cylindrical portion is not damaged even if coming into contact with the downstream cylindrical portion and such that the contact deformation of the brush seal bristles is not hindered.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a brush seal and a turbine using the same. 
         [0003]    This application is based on Japanese Patent Application, Publication No. 2008-121512, the content of which is incorporated herein by reference. 
         [0004]    2. Description of Related Art 
         [0005]    Gas turbines and steam turbines have, for example, a sealing mechanism, around their rotation shafts, for preventing gas from leaking from a high pressure side to a low pressure side. 
         [0006]    One common example of this sealing mechanism is a labyrinth seal, which is a non-contact seal. 
         [0007]    The labyrinth seal has a limitation in reducing the amount of leakage, that is, in improving sealing performance, because it is a non-contact seal. Therefore, brush seals are starting to be used to improve the sealing performance. 
         [0008]    Brush seals have a plurality of bristles formed in a ring shape (brush seal bristles) to achieve sealing in such a manner that the ends of the brush seal bristles are in contact with a rotating part. 
         [0009]    The rotating part, for example, the rotor of a gas turbine is deformed by a centrifugal force and heat caused by the operation thereof, while on the other hand, a stator housing is also expanded by the heat, causing a change in the distance between the brush seal and the rotor. 
         [0010]    Although this change is absorbed by the deflection of the bristles, a deflection towards the downstream side may deteriorate its sealing performance. Therefore, a back plate is provided downstream of the brush seal bristles to prevent deflection towards the downstream side. 
         [0011]    For the deflection of the bristles, a space is provided upstream of the bristles. 
         [0012]    Since brush seals are contact seals, the ends of the bristles that are in contact with the rotating part are worn down with time. 
         [0013]    In addition to this wear over time, if the fluid passing through the brush seal bristles becomes turbulent, this will cause the bristles to flutter (which is significant, in particular, at the upstream side), thus breaking the bristles. 
         [0014]    This breakage of the bristles causes the broken portion to be out of contact with the rotor, thus deteriorating the sealing performance of the brush seal. 
         [0015]    The deterioration of the sealing performance of the brush seal is problematic because, for example, it decreases the output of the turbine. 
         [0016]    Another problem is that the frequency of replacement of the brush seal must be increased in order to prevent a decrease in output, thus increasing maintenance costs. 
         [0017]    One example of a solution to such problems is proposed in Japanese Unexamined Patent Application, Publication No. 2001-73708. 
         [0018]    It involves limiting the deflection of brush seal bristles by providing a brake plate also upstream of the brush seal bristles and reducing the occurrence of turbulence by providing a through hole in the brake plate, thereby preventing, particularly, upstream bristles from fluttering. 
         [0019]    However, the solution described in Japanese Unexamined Patent Application, Publication No. 2001-73708 strongly restricts motion of the brush seal bristles to the vicinity of the rotor by using the downstream back plate and the upstream brake plate, so that the available length for deflection of the brush seal bristles is short. 
         [0020]    This increases the rigidity of the brush seal bristles, which increases a contact pressure on the rotor, thus posing the problem of increasing the wear of the bristles and the rotor in a steady state. 
         [0021]    Therefore, this approach does not yet sufficiently maintain the sealing performance of the brush seal. 
         [0022]    Moreover, since the back plate and the brake plate are rigid, they may damage the rotor when coming into contact with the rotor. 
       BRIEF SUMMARY OF THE INVENTION 
       [0023]    In view of the above problems, an object of the present invention is to provide a brush seal in which an increase in steady-state wear is prevented and the influence of turbulence is eliminated and a turbine using the same. 
         [0024]    To solve the above problems, the present invention adopts the following solutions. 
         [0025]    A brush seal according to a first aspect of the present invention includes a bristle section formed of a plurality of bristles and mounted to a stationary section in such a manner that one end thereof is in contact with a rotating section; and a brake section mounted next to the bristle section in a direction in which fluid flows, for restricting the motion of the bristle section, the brush seal sealing the fluid flowing between the stationary section and the rotating section, wherein the brush seal includes a restraint section mounted opposite to the brake section and next to the bristle section in the direction in which the fluid flows, the restraint section having a degree of elasticity such that the rotating section is not damaged even if coming into contact with the rotating section and such that the contact deformation of the bristle section is not hindered. 
         [0026]    The brush seal according to the first aspect of the present invention is configured such that, when the distance between the stationary section and the rotating section changes, the change is absorbed by the deflection of the bristle section. The bristle section is limited in motion by the brake section mounted next thereto in the fluid flowing direction, so that it deflects toward the restraint section. 
         [0027]    Since the restraint section has a degree of elasticity such that the contact deformation of the bristle section is not hindered, the restraint section can be elastically deformed to absorb the deflection of the bristle section. 
         [0028]    When the restraint section can absorb the deflection of the bristle section, the contact frictional force of the bristle section is not increased with changes in the distance between the stationary section and the rotating section, which prevents an increase in steady-state wear. 
         [0029]    When turbulence occurs in fluid to cause parts of the bristles to flutter, the motion of the bristles is restricted by the restraint section because the force of the parts of the bristles that acts on the restraint section is much smaller than the force of the bristle section, that is, the whole of the bristles. 
         [0030]    Thus, the motion of parts of the bristles due to the turbulence is prevented, which prevents fluttering, thereby preventing breakage of the bristles caused by the fluttering. 
         [0031]    This prevents deterioration of the sealing performance of the brush seal, thereby preventing, for example, a decrease in the output of the turbine and reducing the frequency of replacement of the brush seal so that maintenance costs are decreased. 
         [0032]    Moreover, since the restraint section has a degree of elasticity such that the rotating section is not damaged even if coming into contact with the rotating section, there is no possibility of damaging the rotating section even if the restraint section comes into contact with the rotating section. 
         [0033]    If the restraint section comes into contact with the rotating section, the rotating section is worn down and may be damaged. Therefore, it is preferable that the end position of the restraint section be farther away from the rotating section than the end of the bristle section. 
         [0034]    In the first aspect of the present invention, it is preferable that the restraint section be disposed upstream of the bristle section in the direction in which the fluid flows. 
         [0035]    With this structure, the brake section is disposed at the downstream side, which prevents the bristle section from deflecting toward the downstream side, thereby preventing a decrease in sealing performance. 
         [0036]    In the brush seal according to the first aspect, it is preferable that the restraint section be a bundle of bristles formed of a plurality of bristles whose end is farther away from the rotating section than the end of the bristles. 
         [0037]    In this structure, the bristle bundle is formed of a plurality of bristles. Therefore, the elasticity of the restraint section in the axial direction and the radial direction can easily be set to a specified value by appropriately adjusting the elasticity of the bristles and the space among the bristles. 
         [0038]    A turbine according to a second aspect of the present invention uses the brush seal according to the first aspect. 
         [0039]    The turbine according to the second aspect of the present invention uses a brush seal in which an increase in steady-state wear is prevented and the influence of turbulence is eliminated. This prevents the deterioration of the sealing performance of the brush seal and a decrease in the output of the turbine. 
         [0040]    This also decreases the frequency of replacement of the brush seal so that maintenance costs are reduced. 
         [0041]    In the present invention, the restraint section has a degree of elasticity such that the contact deformation of the bristle section is not hindered. This prevents an increase in contact frictional force with changes in the distance between the stationary section and the rotating section, thereby preventing an increase in steady-state wear. 
         [0042]    Moreover, the motion of the bristles due to the turbulence of fluid is restrained by the restraint section. This prevents breakage of the bristles due to the turbulence. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0043]      FIG. 1  is a longitudinal sectional view showing part of a gas turbine incorporating an embodiment of the present invention. 
           [0044]      FIG. 2  is a longitudinal sectional view of a downstream brush seal according to an embodiment of the present invention. 
           [0045]      FIG. 3  is a front view of the downstream brush seal according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0046]    Referring to  FIGS. 1 to 3 , an embodiment of the present invention will be described. 
         [0047]      FIG. 1  is a fragmentary longitudinal sectional view showing the schematic structure of an inlet of a gas turbine  1  equipped with a brush seal according to this embodiment. 
         [0048]    The gas turbine  1  has, in its interior, a plurality of moving blades  3  mounted to a rotor (not shown) and a plurality of stationary blades  5  provided at the stator side around the rotor, which are arranged alternately along the axis of the rotor (in the lateral direction in  FIG. 1 ), to form a combustion gas passage  7  therethrough. Individual adjacent stationary blades  5  and moving blades  3  form a plurality of stages, which are arranged along the axis of the rotor (in the lateral direction in  FIG. 1 ) 
         [0049]    A multistage structure is formed of continuous stages, that is, first, second, third, and fourth stages, and so on, counting from the upstream side where combustion gas flows in. 
         [0050]      FIG. 1  shows blades from a first-row moving blade  3   a  to a second-row moving blade  3   b.    
         [0051]    In  FIG. 1 , suffixes “a” and “b” added to the reference numerals are used for distinguishing between the first row and the second row; a indicates a part or a component of the first row and b indicates a part or a component of the second row. In the following specification, when the first and second rows are to be distinguished, a and b are added, whereas when no particular distinction is needed, parts or components are denoted only by reference numerals without adding a or b. 
         [0052]    The combustion gas supplied into the gas turbine  1  rotates the moving blades  3  when flowing in the combustion gas passage  7  in a flowing direction  9  to apply a rotating force to the rotor. This rotating force rotates, for example, a generator (not shown) connected to the rotor, to generate power. 
         [0053]    The plurality of moving blades  3  are arranged radially and are firmly mounted to the outer circumference of a disk (a rotating section)  11  which protrudes from the periphery of the rotor (not shown) in a cylindrical shape. 
         [0054]    A large number of the stationary blades  5  are arranged radially and are retained by a ring-shaped outer partition ring  15  and a ring-shaped inner partition ring (a stationary section)  17  which are firmly fixed to a turbine blade ring  13 . 
         [0055]    A sealing structure  19  for preventing leakage of combustion gas is provided between the inner partition ring  17  and the disk  11 . 
         [0056]    The end of the inner partition ring  17  adjacent to the rotor has a seal box  21  that constitutes the sealing structure  19 . 
         [0057]    The end of a disk  11   a  downstream in the flowing direction  9  has a double cylindrical portion that gradually decreases in diameter in the downstream direction, that is, an upstream cylindrical portion  23  and a downstream cylindrical portion  25 . 
         [0058]    The surface of the seal box  21  opposite the upstream cylindrical portion  23  has an upstream brush seal (a brush seal)  27 , and the surface opposite the downstream cylindrical portion  25  has a downstream brush seal (a brush seal)  29 . 
         [0059]    The upstream end of a disk  11   b  of the second row has a cylindrical portion  31  which has substantially the same diameter as the downstream cylindrical portion  25 . 
         [0060]    A labyrinth seal  33  is disposed between the cylindrical portion  31  and the seal box  21 . 
         [0061]    A seal  35  is mounted between the downstream cylindrical portion  25  and the cylindrical portion  31 . 
         [0062]    The upstream brush seal  27  and the downstream brush seal  29  have substantially the same structure, but different sizes. Accordingly, a description of the downstream brush seal  29  will be given and a duplicated description of the upstream brush seal  27  will be omitted hereinafter. Like or corresponding parts are given the same names, and the upstream brush seal  27  and the downstream brush seal  29  are not distinguished from each other in the following description. 
         [0063]      FIG. 2  is an enlarged longitudinal sectional view of the downstream brush seal  29  in  FIG. 1 .  FIG. 3  is a front view of the downstream brush seal  29 . 
         [0064]    The downstream brush seal  29  is mounted in a ring-shaped installation space  22  provided under the lower surface of the seal box  21 . 
         [0065]    The downstream brush seal  29  is a ring-shaped component, which is circumferentially divided into a plurality (for example, six) of brush seal segments  37 , as shown in  FIG. 3 . 
         [0066]    The brush seal segments  37  include brush seal bristles (a bristle section)  39 , restraint bristles (a restraint section, a bundle of bristles)  41 , an upstream support plate  43 , and a downstream support plate  45  (a brake section). 
         [0067]    The brush seal bristles  39  are formed of wires (bristles)  47  with a diameter of 0.1 to 0.2 mm (in this embodiment, for example, 0.13 mm) and a length of 30 to 40 mm, and are bundled together with a wire density of about 60 to 100 per 3 mm 2  (in a cross-sectional view parallel to the rotor axis). 
         [0068]    The wires  47  are disposed at a predetermined angle relative to the radius of the downstream brush seal  29 , that is, inclined in the rotating direction  10  of the downstream cylindrical portion  25  (see  FIG. 3 ). 
         [0069]    The wires  47  are made of a cobalt-based heat-resisting alloy, for example, HAYNES alloy (a trademark of Haynes International, Inc.) No. 25. 
         [0070]    The outer circumferential ends of the brush seal bristles  39  are clamped by an upstream retainer  49  and a downstream retainer  51  which are rectangular cross-section arc-shaped components. The outer circumferential end faces of the brush seal bristles  39  are fixed across the upstream retainer  49  and the downstream retainer  51  by a weld  53 . 
         [0071]    The restraint bristles  41  are formed of wires (bristles)  55  with a diameter of 0.1 to 0.2 mm (in this embodiment, for example, 0.13 mm) and a length of 15 to 18 mm, and are bundled together with a wire density of about 60 to 100 per 3 mm 2  (in a cross-sectional view parallel to the rotor axis). 
         [0072]    The wires  55  are made of a cobalt-based heat-resisting alloy, for example, HAYNES alloy (a trademark of Haynes International, Inc.) No. 25. 
         [0073]    The wires  55  have low elasticity in themselves but can provide higher elasticity when bundled. The elasticity of the restraint bristles  41  can be adjusted to a predetermined value by adjusting the density of the wires  55 . 
         [0074]    The wires  55  are disposed at a predetermined angle relative to the radius of the downstream brush seal  29 , that is, inclined in the rotating direction  10  of the downstream cylindrical portion  25  (see  FIG. 3 ). 
         [0075]    The outer circumferential end faces of the restraint bristles  41  are fixed to a restraint-bristle retainer  57  which is a rectangular cross-section arc-shaped component by a weld  59 . 
         [0076]    The upstream support plate  43  is a substantially rectangular cross-section arc-shaped component. 
         [0077]    The upstream support plate  43  has, substantially at the center of the upstream surface in the radial direction, a recessed portion  61  in which a ring-shaped protruding portion  63  provided at the lower part of the installation space  22  in the seal box  21  is to be fitted. 
         [0078]    The upstream support plate  43  has, in the vicinity of the outer circumference in the downstream surface in the radial direction, an upstream retaining groove  65  for accommodating the upstream retainer  49 . 
         [0079]    The width, that is, the radial length, of the upstream retaining groove  65  is set a little larger than the total length of the upstream retainer  49  and the weld  53 . 
         [0080]    The downstream surface of the upstream support plate  43  has, from the inner circumferential end to the vicinity of the upstream retaining groove  65 , a restraint-bristle retaining recessed portion  67  for accommodating the restraint bristles  41 . 
         [0081]    The restraint-bristle retaining recessed portion  67  has a restraint-bristle retaining groove  69  for accommodating the restraint-bristle retainer  57  substantially at the center in the radial direction. 
         [0082]    The width, that is, the radial length, of the restraint-bristle retaining groove  69  is set a little larger than the total length of the restraint-bristle retainer  57  and the weld  59 . 
         [0083]    The upstream surface of the upstream support plate  43  has, substantially in the radially outer circumference, a rotation stop groove  71  extending in the radial direction. 
         [0084]    The downstream support plate  45  is a substantially rectangular cross-section arc-shaped component. 
         [0085]    The downstream support plate  45  has, substantially in the center of the downstream surface in the radial direction, a recessed portion  75  in which a ring-shaped protruding portion  73  provided at the lower part of the installation space  22  in the seal box  21  is to be fitted. 
         [0086]    The downstream support plate  45  has, in the vicinity of the outer circumference in the upstream surface in the radial direction, a downstream retaining groove  77  for accommodating the downstream retainer  51 . 
         [0087]    The width, that is, the radial length, of the downstream retaining groove  77  is set a little larger than the total length of the downstream retainer  51  and the weld  53 . 
         [0088]    The upstream surface of the downstream support plate  45  is cut off from the downstream retaining groove  77  to the inner circumferential end by a depth corresponding to the axial length of the brush seal bristles  39  so as to accommodate the brush seal bristles  39 . 
         [0089]    The upstream support plate  43  and the downstream support plate  45  are butted against each other, with the upstream retainer  49  accommodated in the upstream retaining groove  65  and the downstream retainer  51  accommodated in the downstream retaining groove  77 , and with the restraint-bristle retainer  57  accommodated in the restraint-bristle retaining groove  69 , and then the outer circumferences are joined to form the brush seal segment  37 . 
         [0090]    The brush seal segments  37  are combined in sequence so that the recessed portions  61  and  75  are fitted on the protruding portions  63  and  73  of the installation space  22  in the seal box  21 , respectively. 
         [0091]    At that time, a rotation stop bolt  79  fixed to the seal box  21  and to be engaged with the rotation stop groove  71  is mounted to define the circumferential positions of the individual brush seal segments  37  and to limit the circumferential movements of the individual brush seal segments  37 . 
         [0092]    The operation of the upstream brush seal  27  and the downstream brush seal  29  of this embodiment, having the above structure, will be described. 
         [0093]    When the gas turbine  1  is started, combustion gas is supplied from a combustion apparatus (not shown) into the combustion gas passage  7 . 
         [0094]    The supplied combustion gas is expanded by the stationary blades  5  when flowing through the combustion gas passage  7  in the flowing direction  9  to generate velocity energy, so that it changes in flowing direction to produce kinetic energy in the axial rotating direction. 
         [0095]    The combustion gas energy converted to the velocity energy is absorbed by the moving blades  3  to rotate them. The rotor rotates by this rotation of the moving blades  3 . This rotating force rotates, for example, a generator (not shown) connected to the rotor to generate power. 
         [0096]    Since the energy is thus absorbed by the individual moving blades  3  in sequence, the combustion gas is higher in temperature and pressure at the upstream side. 
         [0097]    The larger the amount of combustion gas that passes through the combustion gas passage  7 , the higher the energy efficiency is. 
         [0098]    Therefore, the upstream brush seal  27 , the downstream brush seal  29 , and the labyrinth seal  33  seal combustion gas that moves from the first-row moving blade  3   a  to the second-row moving blade  3   b  without passing through the combustion gas passage  7 . 
         [0099]    When the gas turbine  1  is driven, the moving blades  3  are off-centered outwardly because a centrifugal force acts on the moving blades  3 . The rotor and the stationary blades  5  are expanded because they are heated by the combustion gas. 
         [0100]    This changes the distance between the seal box  21  at the stator side and the disk  11  at the rotor side, which generally brings them closer together. 
         [0101]    When the seal box  21  and the disk  11  come close to each other in this way, the brush seal bristles  39  are pushed by the downstream cylindrical portion  25  to move to the outer circumference. 
         [0102]    When the outer circumferential ends of the brush seal bristles  39  come into contact with the outer circumferential surface of the downstream retaining groove  77 , the brush seal bristles  39  cannot move to the outer circumference any more, so that the brush seal bristles  39  are deflected. 
         [0103]    At that time, the movement of the downstream ends of the brush seal bristles  39  is firmly limited by the downstream support plate  45 , so that the brush seal bristles  39  are deflected upstream, that is, entirely moved upstream. That is, the entireties of the brush seal bristles  39  are moved, thus remarkably increasing pressure. 
         [0104]    Thus, this prevents the brush seal bristles  39  from deflecting downstream, thereby preventing a decrease in sealing performance. 
         [0105]    The brush seal bristles  39  are deflected toward the restraint bristles  41  mounted next thereto at the upstream side to apply high pressure thereto, whereas the restraint bristles  41  have a specific elasticity which is the total of the elasticity of the gaps among the wires  55  and the elasticity of the wires  55  themselves in the flowing direction  9 , so that the restraint bristles  41  can absorb the movement of the brush seal bristles  39 , that is, prevent the brush seal bristles  39  from moving by the elasticity. 
         [0106]    Thus, the restraint bristles  41  absorb the contact pressure that acts between the brush seal bristles  39  and the downstream cylindrical portion  25 , so that the contact frictional force therebetween is hardly increased. 
         [0107]    Since the contact frictional force is not increased, an increase in steady-state wear can be prevented. 
         [0108]    If turbulence occurs in the combustion gas flowing between the brush seal bristles  39  and the downstream cylindrical portion  25  to cause parts of the wires  47  to flutter, the force generated by the parts of the wires  47  is much smaller than that when the whole of the brush seal bristles  39  deflect. 
         [0109]    Thus, this force is not large enough to overcome the elastic force of the restraint bristles  41  to deform them, so that this force does not deform the restraint bristles  41 . In other words, the restraint bristles  41  can restrain the movement of parts of the wires  47 . 
         [0110]    This prevents the movement of parts of the wires  47  due to turbulence and prevents fluttering, thereby preventing breakage of the wires  47  caused by the fluttering. 
         [0111]    This prevents the deterioration of the sealing performance of the downstream brush seal  29  and the upstream brush seal  27 , thereby preventing, for example, a decrease in the output of the turbine and reducing the frequency of replacement of the brush seal, thus decreasing maintenance costs. 
         [0112]    Since the end position of the restraint bristles  41  is separated from the surface of the downstream cylindrical portion  25  more than the end position of the brush seal bristles  39 , there is little possibility that the restraint bristles  41  come into contact with the downstream cylindrical portion  25  even if the distance between the seal box  21  and the disk  11  at the rotor side is decreased. 
         [0113]    Moreover, even if the restraint bristles  41  come into contact with the downstream cylindrical portion  25 , there is little possibility that the surface of the downstream cylindrical portion  25  is worn down or damaged because the restraint bristles  41  are formed of the thin, weak wires  55 . 
         [0114]    The upstream brush seal  27  also operates in the same way as the downstream brush seal  29  described above. 
         [0115]    The upstream brush seal  27  and the downstream brush seal  29  of this embodiment, described above, are not limited to the above description and may be modified variously without departing from the spirit of the present invention. 
         [0116]    For example, while this embodiment uses the restraint bristles  41  which is a bundle of the wires  55  as a restraint section, the restraint section needs only enough elasticity to limit the movement of the wires  47  while absorbing the deflection of the brush seal bristles  39 ; for example, a thin sheet-like restraint section or a layer thereof may be used. 
         [0117]    Although this embodiment is applied to the sealing structure between the stationary blades and the moving blades, the present invention is not limited to that and may be applied to other components. 
         [0118]    Furthermore, the present invention is not necessarily applied to gas turbines but may be applied to other rotary machines, for example, a steam turbine.