Patent Publication Number: US-2017350264-A1

Title: Nozzle structure and rotary machine

Description:
TECHNICAL FIELD 
     The present invention relates to a nozzle structure and a rotary machine including the same. 
     BACKGROUND ART 
     Generally, in rotary machines such as steam turbines, blade trains provided on outer peripheral surfaces of rotors and vane trains provided on inner peripheral surfaces of casings are alternately arranged in axes of turbines. Thus, steam flow paths are formed inside casings. Here, in order to improve steam turbine efficiency, it is important to reduce steam leakage from a space between an inner peripheral side end of a vane and a rotor surface. 
     A device disclosed in Patent Literature 1 is known as an example of such technology. A steam turbine disclosed in Patent Literature 1 includes a diaphragm inner ring provided on an inner peripheral side of a vane train via an inner peripheral side constitution section, and a labyrinth packing fixedly supported by the diaphragm inner ring at the inner peripheral side. The labyrinth packing covers an outer peripheral surface of a rotor at an interval. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     Japanese Unexamined Patent Application, First Publication No. 2013-122221 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the device disclosed in Patent Literature 1, a gap occurs between the diaphragm inner ring and the inner peripheral side constitution section. Steam is likely to leak from the gap. 
     In addition, in the device disclosed in Patent Literature 1, when an axial runout occurs in the rotor, the rotor comes into contact with the labyrinth packing and the rotor and the labyrinth packing are likely to be damaged. 
     The present invention was made in view of the above-described circumstances, and an objective of the present invention is to provide a nozzle structure having sufficient sealing performance and durability, and a steam turbine including the same. 
     Solution to Problem 
     The present invention adopts the following means to accomplish the above-described objective. 
     A nozzle structure according to an aspect of the present invention is a nozzle structure provided in a gap between a rotor configured to rotate about an axis and a casing configured to surround the rotor from an outer peripheral side thereof, the nozzle structure including: an outer ring fixed to an inner peripheral surface of the casing and formed in an annular shape about the axis; an annular nozzle fixed to an inner radial side of the outer ring and having a blade section configured to guide a fluid in an axial direction; a labyrinth seal supported by the inner radial side of the nozzle to face an outer peripheral surface of the rotor and configured to seal a space between an inner peripheral surface of the nozzle and the outer peripheral surface of the rotor; and an elastic member provided between the nozzle and the labyrinth seal and configured to bias the labyrinth seal inward in a radial direction. 
     According to such a constitution, even when the rotor comes into contact with the labyrinth seal due to vibration thereof, the elastic member is elastically deformed outward in the radial direction so that a possibility of damage to the rotor or the labyrinth seal can be reduced. 
     Also, the nozzle structure according to an aspect of the present invention includes: a strength reinforcing section provided between the casing and the outer ring and configured to reinforce strength of the nozzle in the radial direction, wherein the outer ring may be fixed to the casing via the strength reinforcing section. 
     According to such a constitution, for example, even when a radial length of the nozzle structure is decreased when reducing a size of a device, the outer ring is attached to the casing via the strength reinforcing section to sufficiently secure the strength of the nozzle. 
     In the nozzle structure according to an aspect of the present invention, the outer ring may be fixed to the inner peripheral surface of the casing via the strength reinforcing section, and the strength reinforcing section may be an inner casing formed in an annular shape about the axis. 
     According to such a constitution, since most of a pressure component applied to the nozzle structure along the axis inside the case is received by the inner casing, the stress acting on the nozzle structure in the axial direction can be reduced. 
     In the nozzle structure according to an aspect of the present invention, the nozzle may include: a plurality of nozzle segment bodies arranged in a circumferential direction; and a welding bead configured to connect a pair of adjacent nozzle segment bodies in the circumferential direction. 
     According to such a constitution, since the nozzle is divided into the plurality of nozzle segment bodies, the nozzle structure can be more easily attached to the casing. In addition, the nozzle segment bodies are connected to each other using welding (the welding bead) in the circumferential direction. Thus, the nozzle segment bodies can be firmly fixed to each other. 
     In the nozzle structure according to an aspect of the present invention, both end surfaces of the labyrinth seal in the axial direction may be perpendicular to the axis. 
     According to such a constitution, for example, even when the radial length of the nozzle structure in the radial direction is decreased when reducing a size of a device, since both end surfaces of the labyrinth seal in the axial direction are perpendicular to the axis, a possibility of impairing sealing performance of the labyrinth seal can be reduced. 
     A rotary machine according to another aspect of the present invention includes the nozzle structure according to any one of the above-described aspects. 
     According to such a constitution, a steam turbine having sufficient sealing performance and durability can be provided. 
     Advantageous Effects of Invention 
     According to a nozzle structure and a rotary machine of the present invention, a nozzle structure with sufficient sealing performance and durability and a steam turbine including the same can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram showing a steam turbine serving as a rotary machine according to an embodiment. 
         FIG. 2  is a diagram showing a nozzle structure according to the embodiment. 
         FIG. 3  is an enlarged diagram of a main portion in the nozzle structure according to the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a constitution of a nozzle structure  3  and a rotary machine  100  according to an embodiment of the present invention will be described on the basis of the drawings. 
     As shown in  FIG. 1 , a steam turbine  100  (the rotary machine  100 ) in the embodiment is an external combustion engine configured to take steam energy as rotational power and is used for electric power generators and the like in power plants. 
     To be specific, the steam turbine  100  includes a casing  1 , a rotor  2  extending along an axis O to pass through the casing  1  and rotating about the axis O, a nozzle structure  3  (a vane) provided inside the casing  1 , a blade train  4  provided in the rotor  2 , and a bearing section  5  configured to support the rotor  2  to be rotatable about the axis. 
     A plurality of blade trains  4  are arranged on an outer peripheral surface of the rotor  2  in a direction of the axis O. Radial lengths of blades in the blade trains  4  located at an upstream side among the plurality of blade trains  4  are small. In other words, radial lengths of blades in the blade trains  4  located at a downstream side are large. 
     Also, a region in which the blade trains  4  in the rotor  2  are provided is covered from an outer peripheral side by the casing  1 . Nozzle structures  3  are provided inside the casing  1  in a region corresponding to the blade trains  4  on the rotor  2  as will be described in detail below. 
     Constant gaps are formed between the nozzle structures  3  and the blade trains  4  so that the gaps are set to be a steam flow path  6 . An external steam supply source (not shown) is connected to the steam flow path  6  via a steam inlet  7  provided at an upstream side of the casing  1 . High temperature and high pressure steam flowing from the steam inlet  7  collides with the blade trains  4  while being flowing through the steam flow path  6  to rotate the rotor  2 , and then is exhausted from an outlet  8  provided at the downstream side toward the outside. 
     Through holes are formed in both ends of the casing  1  in the direction along the axis O. Both ends of the rotor  2  protrude outside the casing  1  through the through holes. Both of the ends of the rotor  2  protruding from the casing  1  to the outside are rotatably supported by the bearing section  5 . The bearing section  5  includes journal bearings  5 A provided on both of the ends of the rotor  2  and a thrust bearing  5 B provided on one end side of the rotor  2 . 
     The nozzle structures  3  and the above-described blade trains  4  are alternately arranged inside the casing  1  in the direction of the axis O. To be specific, as shown in  FIG. 2 , each of the nozzle structures  3  includes an inner casing  10  provided on an inner peripheral surface of the casing  1  and a plurality of (two) nozzle units  30  arranged on an inner peripheral surface of the inner casing  10  in the direction of the axis O. 
     The inner casing  10  is an annular member extending along the inner peripheral surface of the casing  1 . The nozzle units  30 , which will be described below, are disposed at an inner radial side of the inner casing  10 . In other words, the nozzle units  30  are supported by the inner casing  10 , which serves as a strength reinforcing section S, from the outside in a radial direction so that strength thereof is reinforced. 
     An outer radial surface of the inner casing  10  is formed to protrude outward in the radial direction so that an attaching section  11  is formed. The attaching section  11  is fitted in an annular concave groove  12  provided in the inner peripheral surface of the casing  1  in a circumferential direction. 
     The concave groove  12  includes a concave groove bottom surface  12 A forming an outer radial surface thereof and a pair of concave groove side surfaces  12 B extending from the concave groove bottom surface  12 A inward in the radial direction. A separation length between the pair of concave groove side surfaces  12 B is substantially the same as a length of the above-described attaching section  11  in the direction of the axis O. In addition, in the embodiment, a gap is formed between the concave groove bottom surface  12 A and an outer radial end surface of the attaching section  11 . 
     In this way, the attaching section  11  is fitted in the concave groove  12  so that movement of the inner casing  10  in the direction of the axis O is restricted. 
     Two outer ring support grooves  12 C arranged in the direction of the axis O are proved on the inner peripheral surface of the inner casing  10 . The outer ring support grooves  12 C are annular-shaped angular grooves provided to recede outward in the radial direction from the inner peripheral surface of the inner casing  10 . The outer ring support grooves  12 C apart from each other in the direction of the axis O. Two outer rings  20 , which will be described below, are provided in the two outer ring support grooves  12 C, respectively. 
     A surface facing an upstream side of the steam flow path  6  among both surfaces of the inner casing  10  in the direction of the axis O is set as an upstream side end surface  10 A, and a surface facing a downstream side thereof is set as a downstream side end surface  10 B. Both of the upstream side end surface  10 A and the downstream side end surface  10 B extend in a direction which is substantially perpendicular to the direction of the axis O. 
     Each of the nozzle units  30  includes the outer ring  20 , a nozzle  31  provided inside the outer ring  20  in the radial direction, and a labyrinth seal  50  provided inside the nozzle  31  in the radial direction. Two nozzle units  30  arranged in the direction of the axis O merely have the different length in a part thereof and have the same shape as each other. Therefore, one of the nozzle units  30  will be representatively described in the following description. 
     The outer rings  20  are annular members supported by the outer ring support grooves  12 C inside the casing  1 . To be specific, as shown in  FIG. 2 , each of the outer rings  20  includes an outer ring main body  21  configured to support the nozzle  31 , which will be described below, and a blade sealing ring  22  fixed to the outer ring main body  21  in the direction of the axis O. 
     The outer ring main body  21  has a radial length smaller than that of the above-described inner casing  10 . Both surfaces of the outer ring main body  21  in the direction of the axis O extend in the direction which is substantially perpendicular to the direction of the axis O. In addition, a nozzle support groove  21 A is formed in an inner radial surface of the outer ring main body  21 . The nozzle support groove  21 A is an annular-shaped angular groove formed to recede outward in the radial direction from an inner peripheral surface of the outer ring main body  21 . Part of the nozzle  31 , which will be described below, is fitted in the nozzle support groove  21 A. 
     The blade sealing ring  22  is fixed to a downstream side surface of the above-described outer ring main body  21 . An inner radial side of the blade sealing ring  22  at the downstream side is formed to protrude toward the downstream side so that a protruding section  33  is formed. 
     Also, a plurality of flow guides  24  arranged at intervals in the direction of the axis O are provided on an inner peripheral surface of the blade sealing ring  22 . The flow guides  24  are members configured to face outer radial ends of the blades to guide flowing steam. Each of the flow guides  24  is formed of a thin plate extending inward in the radial direction from the inner peripheral surface of the blade sealing ring  22 . The flow guides  24  are fixed to the inner peripheral surface of the blade sealing ring  22  using pins  25 . 
     The outer ring main body  21  and the blade sealing ring  22  constituted as described above may be fixed to each other by performing, for example, welding or the like on end surfaces facing in the direction of the axis O. The sum of the lengths of the outer ring main body  21  and the blade sealing ring  22  in the direction of the axis O in a state in which the outer ring main body  21  and the blade sealing ring  22  are fixed to each other is substantially the same as the lengths of the above-described outer ring support grooves  12 C in the direction of the axis O. Thus, the outer rings  20  are fitted in the outer ring support grooves  12 C to be supported inside the casing  1 . 
     The nozzle  31  includes an annular nozzle ring section  32  provided on an inner peripheral surface of the outer ring  20 , a blade section  34  provided on an inner peripheral surface of the nozzle ring section  32 , and an inner ring  35  provided on an inner peripheral surface of the blade section  34 . 
     A nozzle attaching section  23  is provided on the outer peripheral surface of the nozzle ring section  32 . The nozzle attaching section  23  is formed to protrude outward in the radial direction from the outer peripheral surface of the nozzle ring section  32 . A length of the nozzle attaching section  23  in the direction of the axis O is substantially the same as a length of the above-described nozzle support groove  21 A in the direction of the axis O. Thus, the nozzle attaching section  23  is fitted in the nozzle support groove  21 A to support the nozzle  31 . In addition, the nozzle ring section  32  and the outer ring  20  are joined to each other in a state in which the nozzle attaching section  23  is fitted in the nozzle support groove  21 A using welding. To be specific, as shown in  FIG. 3 , the nozzle ring section  32  is joined to the outer ring  20  by performing buildup welding (at a buildup welding section M) on an inner radial portion of the outer ring  20  on both sides thereof in the direction of the axis O. 
     The blade section  34  is a member extending inward in the radial direction from the inner peripheral surface of the nozzle ring section  32  and having a blade profile cross section (not shown) when viewed in the radial direction. A plurality of blade sections  34  are arranged on the inner peripheral surfaces of the nozzle ring sections  32  at intervals in the circumferential direction. The blade sections  34  and the above-described blades (the blade trains  4 ) are disposed to overlap each other when viewed in the radial direction. 
     Steam serving as a working fluid of the steam turbine  100  is guided through such blade sections  34 , collides with the blade trains  4 , and rotates the rotor  2  about the axis O. 
     The inner ring  35  is provided on an inner radial edge of the blade section  34 . The inner radial edge of the plurality of blade section  34  is supported by the inner ring  35 . 
     The inner ring  35  is formed to have a substantially C-shaped cross section when viewed in the circumferential direction. The above-described blade section  34  is fixed to an outer peripheral surface of the inner ring  35 . On the other hand, a sealing support groove  36  configured to support the labyrinth seal  50  is formed in the inner peripheral surface of the inner ring  35 . The sealing support groove  36  is a grooves formed to recede outward in the radial direction from the inner peripheral surface of the inner ring  35 . In other words, the sealing support groove  36  is open inward in the radial direction. Locking sections  37  protruding to approach each other in the direction of the axis O are formed at inner radial regions at both edges of the opening in the direction of the axis O. 
     A leaf spring accommodating groove  38  configured to accommodate a leaf spring  40  (which will be described below) serving as an elastic members  40  is formed in outer radial surfaces of the sealing support grooves  36 . A length of the leaf spring accommodating groove  38  in the direction of the axis O is smaller than a length of the sealing support grooves  36  in the direction of the axis O. 
     The labyrinth seal  50  is a seal member formed of, for example, an alloy or the like including copper. The labyrinth seal  50  according to the embodiment includes a plate-like seal base  51  extending in the direction of the axis O and a plurality of thin-plate-like fins  52  extending inward in the radial direction from the seal base  51 . Both edges of the seal base  51  in the direction of the axis O are engaged with the above-described locking sections  37  of the sealing support groove  36 . 
     The fins  52  are formed such that lengths thereof in the direction of the axis O gradually decrease from outsides thereof toward insides thereof in the radial direction. In addition, two fins  52  located at both sides thereof in the direction of the axis O are an upstream fin  52 A located at the uppermost stream side and a downstream fine  52 B located at the lowermost stream side. Shapes of the upstream fin  52 A and the downstream fine  52 B are different from shapes of the other fins  52 . In other words, an end surface  521  of the upstream fin  52 A facing the upstream side is formed to be perpendicular to the direction of the axis O. Similarly, an end surface  522  of the downstream fine  52 B facing the downstream side is formed to be perpendicular to the direction of the axis O. Note that the end surface  521  and the end surface  522  need not be completely perpendicular to the direction of the axis O and may intersect to be substantially perpendicular to the direction of the axis O. 
     The labyrinth seal  50  is accommodated in the sealing support groove  36  of the inner ring  35 . On the other hand, the leaf spring  40  serving as the elastic member  40  is accommodated in the leaf spring accommodating groove  38 . The leaf spring  40  is biased to press an outer radial surface of the seal base  51  in the labyrinth seal  50  toward an inner radial side thereof 
     An elastic force toward the inner radial side is applied to the labyrinth seal  50  by the leaf spring  40 , and the labyrinth seal  50  is supported at the inner radial side by the locking sections  37  in the inner ring  35 . In this state, the plurality of fins  52  are supported inside the sealing support groove  36  by forming a slight gap in the radial direction from the outer peripheral surface of the rotor  2 . 
     The nozzle  31  constituted as described above is constituted of a plurality of nozzle segment bodies  31 D divided in the circumferential direction. The nozzle  31  is divided in accordance with the number of blade sections  34 . In other words, the nozzle  31  having n blade sections  34  is divided into n nozzle segment bodies  31 D. 
     adjacent to each other in the circumferential direction are joined to each other using welding. To be specific, as shown in  FIG. 3 , a joining section is formed by bringing both end surfaces of the inner ring  35  in the direction of the axis O and an downstream end surface of the nozzle ring section  32  in the nozzle segment bodie  31 D into contact with them in another of the nozzle segment bodie  31 D. A welding bead W is formed on the joining sections by performing welding on the joining section. 
     In the steam turbine  100  constituted as described above, steam supplied from the outside flows through the steam flow path  6  to rotate the rotor  2 . Here, while the steam turbine  100  operates, vibrations occur in the rotor  2  in some cases. When such vibrations occur, the rotor  2  is slightly moved in the radial direction. The rotor  2  is moved in the radial direction and the rotor  2  comes into contact with the labyrinth seal  50 . Here, since high stress is applied to the labyrinth seal  50  and the rotor  2  when the labyrinth seal  50  is fixed to the inner ring  35 , the labyrinth seal  50  and the rotor  2  are likely to be damaged. 
     However, in the nozzle structure  3  and the steam turbine  100  according to the embodiment, the labyrinth seal  50  is supported by the leaf spring  40  serving as the elastic member  40 . Thus, even when the rotor  2  comes into contact with the labyrinth seal  50 , the labyrinth seal  50  is moved outward in the radial direction so that stress occurring between the rotor  2  and the labyrinth seal  50  can be decreased. 
     Also, when the rotor  2  operates at a normal position, a gap between the labyrinth seal  50  and the rotor  2  is maintained to be constant by the elastic restoring force of the leaf spring  40 . Thus, sufficient sealing performance can be obtained. 
     According to the above-described constitution, since the inner ring  35  in the nozzle structure  3  is formed as a single body, it is advantageous in reducing a size of the steam turbine  100 . 
     Particularly, when other members are additionally provided on the inner ring  35 , a space in which the elastic member  40  is provided is likely to disappear due to a limitation on radial lengths of the nozzle structure  3 . However, according to the above-described constitution, since the inner ring  35  is formed as a single body, the space in which the elastic member  40  is provided (the leaf spring accommodating groove  38 ) can be provided without impairing strength of the inner ring  35 . 
     According to the above-described constitution, since most of a pressure component applied to the nozzle structure  3  in the direction of the axis O inside the casing  1  is received by the upstream side end surface  10 A in the inner casing  10 , a ratio of stresses acting on the nozzle structure  3  in the direction of the axis O can be reduced. Thus, durability of the nozzle structure  3  and the steam turbine  100  can be improved. 
     According to the above-described constitution, for example, even when a length of the nozzle structure  3  in the radial direction is decreased when reducing a size of a device, the outer ring  20  is attached to the casing  1  via the strength reinforcing section S so that strength of the nozzle  31  in the radial direction can be sufficiently secured. 
     According to the above-described constitution, since the nozzle  31  is divided into the plurality of nozzle segment bodies  31 D, the nozzle structure  3  can be more easily attached to the casing  1 . In addition, the nozzle segment bodies  31 D can be firmly fixed using the welding bead W. 
     According to the above-described constitution, for example, even when the length of the nozzle structure  3  in the radial direction is decreased when reducing a size of a device, since both end surfaces of the labyrinth seal  50  in the direction of the axis O are perpendicular to the axis O, the labyrinth seal  50  can be easily attached to the seal accommodation groove. Thus, the possibility of impairing sealing performance of the labyrinth seal  50  can be reduced. 
     Although the embodiment of the present invention has been described in detail above with reference to the drawings, specific constitutions are not limited to such an embodiment and design changes and the like are also included without departing from the gist of the present invention. 
     INDUSTRIAL APPLICABILITY 
     A nozzle structure  3  according to the present invention can be applied to a rotary machine such as a steam turbine  100 . 
     REFERENCE SIGNS LIST 
     
         
           100  Rotary machine (steam turbine) 
           1  Casing 
           2  Rotor 
           3  Nozzle structure 
           4  Blade train 
           5  Bearing section 
           6  Steam flow path 
           7  Steam inlet 
           8  Outlet 
           10  Inner casing 
           10 A Upstream side end surface 
           10 B Downstream side end surface 
           11  Attaching section 
           12  Concave groove 
           12 A Concave groove bottom surface 
           12 B Concave groove side surface 
           12 C Outer ring support groove 
           20  Outer ring 
           21  Outer ring main body 
           21 A Nozzle support groove 
           22  Blade sealing ring 
           23  Nozzle attaching section 
           24  Flow guide 
           25  Pin 
           30  Nozzle unit 
           31  Nozzle 
           31 D Nozzle segment body 
           32  Nozzle ring section 
           33  Protruding section 
           34  Blade section 
           35  Inner ring 
           36  Sealing support groove 
           37  Locking section 
           38  Leaf spring accommodating groove 
           40  Elastic member 
           40  Leaf spring 
           50  Labyrinth seal 
           51  Seal base 
           5 A Journal bearings 
           5 B Thrust bearing 
           52  Fin 
           52 A Upstream fin 
           52 B Downstream fin 
         M Buildup welding section 
         S Strength reinforcing section 
         W Welding bead