JP2013050044A - Seal structure and steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal structure which enables easy attachment/detachment, and a steam turbine having the same.SOLUTION: This seal structure includes: a nozzle diaphragm inner ring 6 which is provided in a turbine casing that houses a turbine rotor shaft and divided into two parts at a horizontal surface passing through the center of the turbine rotor shaft, as a division surface 6c; and a packing ring 7 disposed between the inner peripheral surface of the nozzle diaphragm inner ring 6 and the outer peripheral surface of the turbine rotor shaft. The nozzle diaphragm inner ring 6 has a recess formed at a predetermined height from the division surface 6c. The packing ring 7 is divided into two parts at the division surface 7a, and has a recess 7b formed at a predetermined height from the division surface 7a. A support plate 20 is inserted into the recess 6b and the recess 7b. The support plate 20 is fixed to the nozzle diaphragm inner ring 6 vertically to the division surface 6c, using mounting bolts 21.

Description

  Embodiments described herein relate generally to a seal structure and a steam turbine including the seal structure.

  In a geothermal turbine, steam heated by a heating source such as an underground magma is directly introduced into the turbine to be used as a working fluid to obtain rotational power. Geothermal steam contains corrosive components such as hydrogen sulfide and salt, scale components such as silica and calcium, and solid particles such as sand, mud and iron oxide due to the nature of groundwater generated by geothermal heat such as magma. .

  The geothermal turbine includes a seal structure in a gap formed by a turbine rotor shaft and a nozzle diaphragm inner ring. The seal structure has a packing ring that is fixed while forming a gap with respect to the inner ring of the nozzle diaphragm.

JP 2003-214113 A

  The scale component described above enters the gap formed by the seal structure and adheres as a fixed substance. When the geothermal turbine is operated for a long period of time, sticking matters accumulate in the gap, and the nozzle diaphragm and the packing ring, other members constituting the seal structure, or members constituting the seal structure are stuck to each other.

  During regular inspection, the fins of the packing ring are replanted or the packing ring is replaced. When the packing ring is removed from the nozzle diaphragm, both of them are fixed by a fixed object, and it is difficult to easily remove the packing ring. For this reason, when removing the packing ring, a removal work such as smashing with a hammer occurs.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a seal structure that facilitates attachment / detachment work and a steam turbine including the same.

  In order to solve the above-described problems, an embodiment of a seal structure according to the present invention is provided in a turbine casing that houses a turbine rotor shaft, and is divided into two parts with a horizontal plane passing through the center of the turbine rotor shaft as a split surface. A blade inner ring, and a seal member disposed between an inner peripheral surface of the stationary blade inner ring and an outer peripheral surface of the turbine rotor shaft. The stator blade inner ring has a stator blade inner ring side recess provided at a predetermined height from the split surface. The sealing member is divided into two parts by the dividing surface, and has a sealing member side recess provided at a predetermined height from the dividing surface. A support plate is inserted across the stationary blade inner ring side recess and the seal member side recess. The support plate is fixed to the stationary blade inner ring by a fixing member in a direction perpendicular to the dividing surface.

Sectional drawing which shows a part of seal structure and steam turbine in 1st Embodiment. Sectional drawing which shows the whole seal structure in 1st Embodiment from an axial direction. The enlarged view of the area | region III of FIG. The enlarged view of the area | region IV of FIG. The block diagram which shows a seal structure from the arrow V direction of FIG. Sectional drawing which shows especially the seal structure as a comparative example of 1st Embodiment. Sectional drawing which shows a part of seal structure as a comparative example of 1st Embodiment from an axial direction. The block diagram of the seal structure in 2nd Embodiment. The block diagram which shows the seal structure of 2nd Embodiment from an axial direction. The block diagram which shows the 1st modification of the seal structure of 2nd Embodiment. The block diagram which shows the 2nd modification of the seal structure of 2nd Embodiment.

[First Embodiment]
A first embodiment of a seal structure according to the present invention and a steam turbine including the same will be described with reference to the accompanying drawings. In each embodiment, the seal structure and the steam turbine work favorably when applied to a geothermal turbine.

  FIG. 1 is a cross-sectional view showing a part of the seal structure 10 and the steam turbine 1 in the first embodiment.

  The steam turbine 1 has turbine stages in a multi-stage structure and concentric in a turbine casing 2. The turbine stage is composed of a combination of a nozzle 3 (static blade) and a moving blade 4. The nozzle 3 is provided between a nozzle diaphragm outer ring 5 and a nozzle diaphragm inner ring 6 (stationary blade inner ring) located on the radially inner side of the nozzle diaphragm outer ring 5. The moving blades 4 are arranged opposite to the downstream side of the nozzle 3 and form blade rows in the circumferential direction of the turbine rotor shaft 9.

  A seal structure 10 is provided on the inner peripheral side of the nozzle diaphragm inner ring 6. The seal structure 10 has a packing ring 7 and seal fins 8. The packing ring 7 is disposed between the inner peripheral surface of the nozzle diaphragm inner ring 6 and the outer peripheral surface of the turbine rotor shaft 9. The packing ring 7 is supported on the nozzle diaphragm inner ring 6 by a support member 12. A plurality of seal fins 8 are provided on the seal surface of the packing ring 7 and have a comb-like cross section.

  The turbine rotor shaft 9 provided in the turbine casing 2 has an uneven groove 9 a on the outer surface facing the seal fin 8. The concave and convex grooves 9a and the seal fins 8 form a minute gap and constitute a steam seal portion having a labyrinth structure. The steam turbine 1 obtains a steam leakage prevention structure of the turbine rotor shaft 9 that prevents steam leakage by the steam seal portion.

  FIG. 2 is a cross-sectional view showing the entire seal structure 10 in the first embodiment from the axial direction. FIG. 2 shows the nozzle diaphragm inner ring 6 and the packing ring 7 in cross section to facilitate the description of the seal structure 10.

  FIG. 3 is an enlarged view of region III in FIG. FIG. 3 is an enlarged view of region III when viewed from the direction opposite to that in FIG. 1 (from the back to the front of the drawing).

  FIG. 4 is an enlarged view of region IV in FIG.

  FIG. 5 is a block diagram showing the seal structure 10 from the direction of arrow V in FIG.

  As shown in FIG. 2, the packing ring 7 (seal member) is divided into two parts in the vertical direction with a horizontal plane passing through the center of the turbine rotor shaft 9 (packing ring 7) as a dividing surface 7a, and two upper packing rings 7A and And a lower packing ring 7B. Further, as shown in FIG. 3, the packing ring 7 has a T-shaped radial cross section, and does not have irregularities having a fitting relationship in the axial direction of the rotor shaft 9 with the nozzle diaphragm inner ring 6.

  As shown in FIG. 2, the nozzle diaphragm inner ring 6 is also divided into an upper nozzle diaphragm inner ring 6 </ b> A and a lower nozzle diaphragm inner ring 6 </ b> B, similarly to the packing ring 7. When the divided pieces of the packing ring 7 and the nozzle diaphragm inner ring 6 are not particularly distinguished, they are simply referred to as the packing ring 7 and the nozzle diaphragm inner ring 6.

  As shown in FIGS. 2 and 3, the upper packing ring 7 </ b> A and the lower packing ring 7 </ b> B are coupled by a reamer bolt 13. The reamer bolt 13 is provided to make the gap between the upper and lower packing rings 7A and 7B and the rotor shaft 9 uniform over the entire circumference. That is, the reamer bolt 13 keeps the packing ring 7 in a regular circle. This is because when the gap between the packing ring 7 and the rotor shaft 9 is different over the entire circumference, pressure imbalance occurs and causes vibration.

  As shown in FIGS. 2 to 5, the upper and lower packing rings 7 </ b> A and 7 </ b> B are fixed by a lifting prevention pin 14. The anti-lifting pin 14 prevents the packing ring 7 from rotating due to the turning force of steam.

  As shown in FIGS. 2 and 3, the packing ring 7 has a plurality of gap management pins 15 projecting in the axial direction of the rotor shaft 9 on the surfaces facing the nozzle diaphragm inner ring 6 and the rotor shaft 9 in the axial direction. The gap management pin 15 may be formed by overlaying by welding, or another member may be attached to the packing ring 7. The clearance management pin 15 is provided in the clearance 17 between the dovetail 6 a of the nozzle diaphragm inner ring 6 and the packing ring 7, thereby narrowing the clearance 17. The gap 17 is a place where a fixed matter due to a scale or the like is easily generated. The seal structure 10 prevents sticking by narrowing a part of the gaps 17 provided with the gap management pins 15 without making the gaps 17 around the entire circumference narrow.

  As shown in FIGS. 2 and 3, the seal structure 10 has support members 12 for fixing the upper and lower packing rings 7A and 7B and the nozzle diaphragm inner ring 6 respectively. The support member 12 includes a support plate 20 and support plate mounting bolts 21. As shown in FIGS. 4 and 5, the packing ring 7 and the nozzle diaphragm inner ring 6 have recesses 7 b and 6 b as support members 12, respectively.

  Here, as shown in FIGS. 3 to 5, the support plate 20 is a metal plate, for example, and is disposed across the recesses 6 b and 7 b, and supports the nozzle diaphragm inner ring 6 and the packing ring 7 on the horizontal surface 20 a. The support plate mounting bolt (mounting bolt) 21 (fixing member) is mounted in a direction perpendicular to the dividing surface 6c (horizontal plane 20a) in order to fix the support plate 20 to the nozzle diaphragm inner ring 6.

  As shown in FIGS. 4 and 5, the recess 7 b (seal member side recess) of the packing ring 7 is formed at a predetermined height from the dividing surface 7 a. The upper and lower packing rings 7 </ b> A and 7 </ b> B have a fixed surface 7 c that faces the horizontal surface 20 a of the support plate 20, and a wall portion 7 d that stops the support plate 20 from entering.

  As shown in FIG. 4, the concave portion 6 b (the stationary blade inner ring side concave portion) of the nozzle diaphragm inner ring 6 is formed at a predetermined height from the dividing surface 6 c of the nozzle diaphragm inner ring 6. The nozzle diaphragm inner ring 6 has a fixed surface 6d facing the horizontal surface 20a of the support plate 20, and a bolt hole 6e perpendicular to the fixed surface 6d.

  Next, a procedure for removing the packing ring 7 from the nozzle diaphragm inner ring 6 will be described.

  As shown in FIGS. 3 and 4, the packing ring 7 is fixed to the nozzle diaphragm inner ring 6 via a support plate 20 and a mounting bolt 21. At this time, the packing ring 7 is horizontally fixed to the nozzle diaphragm inner ring 6 by a support plate 20 extending in a radial direction (a direction orthogonal to the axial direction). Further, the upper packing ring 7A is fixed to the upper nozzle diaphragm inner ring 6A via the instruction plate 20, so that the upper packing ring 7A is prevented from dropping.

  When the upper nozzle diaphragm inner ring 6A is lifted during removal, the upper packing ring 7A is lifted together with the upper nozzle diaphragm inner ring 6A via the support plate 20 and the mounting bolts 21 that are in contact with each other on the fixed surface 7c. The upper nozzle diaphragm inner ring 6 </ b> A and the upper packing ring 7 </ b> A are taken out from the steam turbine 1. At this time, the upper packing ring 7 </ b> A and the lower packing ring 7 </ b> B are released from the connection by the reamer bolt 13 and the lifting prevention pin 14. The reamer bolt 13 and the lifting prevention pin 14 are removed from the lower packing ring 7B.

  Next, as shown in FIGS. 4 and 5, when the mounting bolt 21 is removed from the bolt hole 6e, the support plate 20 is released from contact with the fixing surface 6d (fixing of the support plate 20 and the nozzle diaphragm inner ring 6). Is released). The support plate 20 is removed by sliding horizontally from the recesses 6b and 7b. The support plate 20 is removed from the recesses 6b and 7b in the front direction from the back of FIG. 4 and from the right direction to the left direction in FIG.

  By removing the support plate 20, the coupling between the packing ring 7 and the nozzle diaphragm inner ring 6 is released, and the packing ring 7 is slid with respect to the nozzle diaphragm inner ring 6 and easily removed.

  Here, a seal structure as a comparative example of the seal structure 10 in the first embodiment will be described.

  FIG. 6 is a cross-sectional view specifically showing a seal structure 50 as a comparative example of the first embodiment.

  FIG. 7 is a cross-sectional view showing a part of a seal structure 50 as a comparative example of the first embodiment from the axial direction.

  The packing ring 57 is divided into four or more even numbers in the circumferential direction. In FIG. 7, two pieces are shown among the divided packing rings 57. Each packing ring 57 has a recess 57a along the circumferential direction. Further, as shown in FIG. 6, each packing ring 57 is supported by the hook surface 56 b of the dovetail 56 a of the nozzle diaphragm inner ring 56 and fixed to the nozzle diaphragm inner ring 56 by the recess 57 a.

  The packing ring 57 is pressed and fixed in the direction of the rotor shaft 59 against the hook surface 56b via a plate spring 60 provided in the fixing groove 57b. In a state where the steam turbine is operating, a pressure difference due to steam further occurs, and the pressing force of the packing ring 57 against the hook surface 56b increases.

  At this time, as shown in FIGS. 6 and 7, the scale component contained in the vapor component enters the dovetail 56a and the butt clearance 61 formed on the dividing surface, and the gap between the packing ring 57 and the dovetail 56a, It adheres to the fixing groove 57b of the leaf spring 60 and becomes a fixed object.

  When the steam turbine is operated for a long period of time, sticking matter accumulates in the gap, and the nozzle diaphragm inner ring 56 and the packing ring 57, the nozzle diaphragm inner ring 56 or the packing ring 57, the leaf spring 60, and the packing ring 57 are fixed to each other. .

  Further, the packing ring 57 is pressed against the hook surface 56b by the leaf spring 60, and the gap disappears. However, in reality, a narrow gap is formed, and the scale enters the narrow gap and a fixed matter is generated.

  Here, as shown in FIG. 6, when such sticking occurs when the seal fins 58 of the packing ring 57 are replanted or replaced when the regular inspection is performed, the packing ring 57 is attached to the nozzle diaphragm. It is difficult to remove from the inner ring 56 easily. The seal structure 50 as a comparative example needs to be removed by tapping with a tool such as a hammer when removing the packing ring 57.

Thereby, when removing the packing ring 57, the fin of the rotor shaft 59 may be damaged or lost. Further, when removing the divided pieces of the packing ring 57 on the lower half side, it is necessary to extract the rotor shaft 59, and the time for the regular inspection work cannot be shortened.

  On the other hand, as shown in FIG. 3, the seal structure 10 in the first embodiment does not provide a hook surface on the dovetail 6a of the inner ring 6 of the nozzle diaphragm, and does not provide a recess corresponding to the dovetail 6a in the packing ring 7. . Further, a member such as a leaf spring 60 for adjusting the gap between the nozzle diaphragm inner ring 6 and the packing ring 7 is not provided.

  In other words, the seal structure 10 is not provided with an uneven structure for fixing the packing ring 7 to the nozzle diaphragm inner ring 6 on the packing ring 7 and the nozzle diaphragm inner ring 6 so that unnecessary gaps are not formed.

  Since the seal structure 10 does not deposit scale or the like in the gap between the packing ring 7 and the nozzle diaphragm inner ring 6, it is possible to reduce the adhesion between them. Thereby, the seal structure 10 can easily attach and detach the packing ring 7 and the nozzle diaphragm inner ring 6, and can reduce work processes and labor during maintenance.

[Second Embodiment]
2nd Embodiment of the seal structure which concerns on this invention, and a steam turbine provided with the same is described based on an accompanying drawing.

  FIG. 8 is a configuration diagram of a seal structure 70 provided in the steam turbine in the second embodiment.

  FIG. 9 is a configuration diagram showing the seal structure 70 of the second embodiment from the axial direction.

  The seal structure 70 in the second embodiment is different from the first embodiment in that the shape of the support plate 81 is L-shaped. Components and parts corresponding to those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 8, the seal structure 70 includes support members 80 for fixing an upper and lower packing ring (hereinafter simply referred to as packing ring) 77 and a nozzle diaphragm inner ring 76. The support member 80 includes a support plate 81 and a support plate mounting bolt (mounting bolt) 82. Further, as shown in FIG. 9, the packing ring 77 and the nozzle diaphragm inner ring 76 have recesses 77 b and 76 b as the support members 80, respectively.

  Here, as shown in FIGS. 8 and 9, the support plate 81 includes a fixing portion 81 a (the same function as the support plate 20 in the first embodiment) for fixing the packing ring 77 to the nozzle diaphragm inner ring 76, and a nozzle A sealing portion 81b having a sealing function on the split surface 76c of the diaphragm inner ring 76. The fixing portion 81a is inserted across the recess 76b and the recess 77b. The seal portion 81b seals the divided surface 76c along the divided surface 76c of the nozzle diaphragm inner ring 76 divided into two. The support plate 81 is used in common for the upper and lower nozzle diaphragm inner rings 76 and the upper and lower packing rings 77.

  As shown in FIG. 9, the recess 77 b of the packing ring 77 is formed from the split surface 77 a of the packing ring 77 to a predetermined height. The concave portion 76b of the nozzle diaphragm inner ring 76 is formed to a predetermined height in the same manner as the concave portion 77b. The recess 76 b is formed in an L shape that matches the shape of the L-shaped support plate 81.

  As shown in FIGS. 8 and 9, the nozzle diaphragm inner ring 76 has a fixing surface 76d facing the fixing portion 81a of the support plate 81, and a bolt hole 76e perpendicular to the fixing surface 76d.

  Since the support plate 81 is used in common for the upper and lower packing rings 77 and the nozzle diaphragm inner ring 76, the recesses 76b and 77b provided in the upper and lower packing rings 77 and the nozzle diaphragm inner ring 76 are connected at the dividing surfaces 77a and 76c. ing.

  The support plate 81 is attached to and detached from the nozzle diaphragm inner ring 76 and the packing ring 77 in the vertical direction (vertical direction in FIG. 8). The support plate 81 is fixed to the nozzle diaphragm inner ring 76 by the mounting bolts 82 when attached to the recesses 76b and 77b.

  At the time of removal, the mounting bolt 82 is removed and the support plate 81 is pulled out, so that the packing ring 77 is easily removed from the diaphragm inner ring 76.

  In the seal structure 70 and the steam turbine according to the second embodiment, in addition to the effects exhibited by the seal structure according to the first embodiment, the seal portion 81b of the support plate 81 seals the dividing surface 76c of the nozzle diaphragm inner ring 76 that is divided vertically. Therefore, the sealing function of the steam turbine can be enhanced.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, since the seal structure in each embodiment prevents the occurrence of a fixed object and the packing ring can be easily attached and detached, the following structure can be easily adopted for the seal structure of a geothermal turbine (steam turbine). .

  FIG. 10 is a configuration diagram illustrating a first modification of the seal structure of the second embodiment.

  FIG. 11 is a configuration diagram showing a second modification of the seal structure of the second embodiment.

  In the seal structure 70, seal fins 9 a may be provided on the outer peripheral surface of the turbine rotor shaft 9 facing the packing ring 77.

  Further, an abradable coating 78 may be applied to the sealing surface of the packing ring 77 facing the seal fin 9a.

1 Steam turbine 6, 76 Nozzle diaphragm inner ring 6A Upper nozzle diaphragm inner ring 6B Lower nozzle diaphragm inner ring 6a Dovetail 6b, 76b Recess 6c, 76c Split surface 6e, 76e Bolt hole 7, 77 Packing ring 7A Upper packing ring 7B Lower packing ring 7a, 77a Dividing surface 7b, 77b Recess 10, 70 Seal structure 12, 80 Support member 13 Reamer bolt 14 Lifting prevention pin 15 Gap management pins 20, 81 Support plate 21, 82 Support plate mounting bolt 81a Fixing part 81b Sealing part

Claims (8)

A static blade having a stationary blade inner ring side recess provided in a turbine casing that houses a turbine rotor shaft, divided into two with a horizontal plane passing through the center of the turbine rotor shaft as a split surface, and provided at a predetermined height from the split surface. The wing inner ring,
The seal member-side recess is disposed between the inner peripheral surface of the stationary blade inner ring and the outer peripheral surface of the turbine rotor shaft, divided into two by the dividing surface, and provided at a predetermined height from the dividing surface. A sealing member;
A support plate inserted across the stationary blade inner ring side recess and the seal member side recess,
A sealing structure comprising: a fixing member that fixes the support plate to the stator blade inner ring in a direction perpendicular to the dividing surface. The seal structure according to claim 1, wherein the seal member has a T-shaped radial cross section. The said support plate has a fixing | fixed part inserted over the said stator blade inner ring | wheel side recessed part and the said sealing member side recessed part, and the seal part in alignment with the division | segmentation surface of the said stator blade inner ring divided | segmented into two. 2. The seal structure according to 2. The seal structure according to any one of claims 1 to 3, wherein the seal member has a convex portion on a surface facing the stationary blade inner ring in the axial direction. The seal structure according to any one of claims 1 to 4, further comprising a coupling member that couples the two-divided seal members at a division surface. The seal structure according to claim 1, wherein the turbine rotor shaft has a seal fin on an outer peripheral surface facing the seal member. The seal structure according to claim 6, wherein the seal member has an abradable coating on a surface facing the seal fin. A turbine casing that houses a turbine rotor shaft;
A turbine stage having a stationary blade provided in the turbine casing, and a moving blade provided in a blade row in an edge circumferential direction of the turbine rotor shaft disposed opposite to the downstream side of the stationary blade;
A stator blade inner ring that is divided into two with a horizontal plane passing through the turbine rotor shaft center as a split surface, and has a stator blade inner ring side recess provided at a predetermined height from the split surface;
The seal member-side recess is disposed between the inner peripheral surface of the stationary blade inner ring and the outer peripheral surface of the turbine rotor shaft, divided into two by the dividing surface, and provided at a predetermined height from the dividing surface. A sealing member;
A support plate inserted across the stationary blade inner ring side recess and the seal member side recess,
A steam turbine, comprising: a fixing member that fixes the support plate to the stationary blade inner ring in a direction perpendicular to the dividing surface.

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