Title of the invention: Method for manufacturing a diaphragm of a steam turbine
Technical field
[0001]
　The present invention relates to a method for manufacturing a diaphragm of a steam turbine.
Background technology
[0002]
　In a steam turbine, a structure in which a seal fin that seals a gap between the outer ring of the diaphragm and the tip of the rotor blade is implanted in the outer ring of the diaphragm may be adopted (see Patent Document 1 and the like).
Prior art literature
Patent documents
[0003]
Patent Document 1: Japanese Unexamined Patent Publication No. 2016-194306
Outline of the invention
Problems to be solved by the invention
[0004]
　In a steam turbine, a diaphragm has a heat drop, and steam is condensed especially on the downstream side of the steam turbine to generate a large amount of drainage. If the generated drain collides with the moving blade on the downstream side of the diaphragm, erosion may occur on the moving blade. Since the drain is carried along the side surface of the outer ring of the diaphragm and the circumferential direction, a collector ring is installed for the purpose of collecting the drain without hitting the tip of the moving blade. However, a part of the drain carried along the streamline collides with the moving blade and adheres to it, and the drain attached to the moving blade scatters radially outward due to centrifugal force. There is concern about the occurrence of erosion on the inner surface of the collector ring near the fins.
[0005]
　During operation, in the wet paragraph of the steam turbine, the drain adhering to the surface of the rotor blades scatters radially outward due to centrifugal force, so erosion may occur in the outer ring of the diaphragm, especially near the seal fin facing the rotor blades. is there. Therefore, the portion that holds the seal fin may be made into a separate member as a collector ring, and this may be connected to the outer ring of the diaphragm with a bolt. In the case of this configuration, if the erosion of the opposite portion of the moving blade progresses, it is not necessary to replace the entire diaphragm with a new product, but only the collector ring with advanced erosion needs to be replaced.
[0006]
　Here, some existing steam turbines having a conventional structure have seal fins implanted from the inner diameter side of the collector ring and crimped, but the crimped portion where the collector ring and the seal fin engage is scattered from the rotor blades. You will be directly exposed to the incoming drain. One of the improvements in the reliability of the engagement portion between the seal fin and the collector ring is the radial spill strip (RSS) structure of the seal fin.
[0007]
　However, the RSS-structured seal fin has a larger root that is inserted into the collector ring than the implantable seal fin of the same class. When the seal fin is RSS-structured, it is necessary to increase the pitch circle diameter (PCD) of the bolt connecting the collector ring and the outer ring of the diaphragm in order to avoid interference with the root of the enlarged seal fin. is there. However, on the outer diameter of the existing diaphragm outer ring, the bolt P. C. The wall thickness sufficient to allow the expansion of D may not be secured, or it may interfere with the slit. In this case, the enlarged bolt P.I. C. D. It is necessary to make a new diaphragm outer ring that allows for the above, but the diaphragm outer ring is a part of the integrally configured diaphragm. Therefore, in order to expand the outer diameter of the outer ring of the diaphragm, the actual situation is that the entire diaphragm including the wing and the inner ring of the diaphragm is newly manufactured by spending a long construction period.
[0008]
　An object of the present invention is to provide a method for manufacturing a steam turbine and a diaphragm having a structure in which the reliability of a fixed structure of a seal fin can be improved and the construction period can be significantly shortened.
Means to solve problems
[0009]
　In order to achieve the above object, the present invention has a collector ring arranged on the downstream side of the diaphragm outer ring in a diaphragm for a steam turbine in which a diaphragm inner ring, a diaphragm outer ring, and a blade portion are integrally formed. A seal fin having a radial spill strip structure fitted into the diaphragm, and an adapter ring interposed between the diaphragm outer ring and the collector ring are further provided, and the diaphragm outer ring and the adapter ring are vertically inserted from the downstream side. The outer ring of the diaphragm and the facing surface of the adapter ring are in close contact with each other and sealed with the first bolt of the above, and the collector ring and the adapter ring have a larger outer diameter than the outer ring of the diaphragm and are more than the seal fin. Is also connected by a plurality of second bolts inserted in the axial direction from the downstream side at the position on the outer peripheral side.
Effect of the invention
[0010]
　According to the present invention, the reliability of the fixed structure of the seal fin can be improved and the construction period can be expected to be significantly shortened.
A brief description of the drawing
[0011]
FIG. 1 is a schematic view of a steam turbine facility according to an
embodiment of the present invention [Fig. 2] A cross-sectional view of a steam turbine according to an embodiment of the present invention
[Fig. 3] An enlarged view of part III in FIG. FIG
. 4 is a diagram showing a main structure of a diaphragm according to an embodiment of the present invention [Fig. 4] A flowchart showing a procedure for determining application of a method for manufacturing a diaphragm of the present invention
[Fig. 5] A diagram showing an explanatory diagram of a manufacturing method and showing a diaphragm before modification
[Fig. 6] A diagram showing a structure of a diaphragm manufactured by modifying the diaphragm of FIG. 3 according to the manufacturing method according to a comparative example.
Mode for carrying out the invention
[0012]
　An embodiment of the present invention will be described below with reference to the drawings.
[0013]
　-Steam Turbine Power Generation Equipment-
　Fig. 1 is a schematic diagram of the steam turbine equipment according to the embodiment of the present invention. The steam turbine power generation facility 100 shown in the figure includes a steam generation source 1, a high-pressure turbine 3, a medium-pressure turbine 6, a low-pressure turbine 9, a condenser 11, and a load device 13. Hereinafter, the flow direction of steam, which is a working fluid, is used as a reference in each turbine. In the case of the low-pressure turbine 9 (FIG. 2), the mainstream flow direction of the steam S flowing through the working fluid flow path F is the reference.
[0014]
　The steam generation source 1 is a boiler, which heats the water supplied from the condenser 11 to generate high-temperature and high-pressure steam. The steam generated in the steam generation source 1 is guided to the high-pressure turbine 3 via the main steam pipe 2 to drive the high-pressure turbine 3. The steam that has been decompressed by driving the high-pressure turbine 3 is guided to the steam generation source 1 via the high-pressure turbine exhaust pipe 4 and is heated again to become reheated steam.
[0015]
　The reheated steam generated by the steam generation source 1 is guided to the medium-pressure turbine 6 via the reheated steam pipe 5 to drive the medium-pressure turbine 6. The steam that has been decompressed by driving the medium-pressure turbine 6 is guided to the low-pressure turbine 9 via the medium-pressure turbine exhaust pipe 7 to drive the low-pressure turbine 9. The steam that drives the low-pressure turbine 9 and is decompressed is guided to the condenser 11 via the diffuser. The condenser 11 is provided with a cooling water pipe (not shown), and heat exchanges heat between the steam guided to the condenser 11 and the cooling water flowing in the cooling water pipe to condense the steam. The water condensed by the condenser 11 is sent to the steam source 1 again by the water supply pump P.
[0016]
　The turbine rotors 12 of the high-pressure turbine 3, the medium-pressure turbine 6, and the low-pressure turbine 9 are coaxially connected. The load device (typically a generator) 13 is connected to the turbine rotor 12 and is driven by the rotational outputs of the high-pressure turbine 3, the medium-pressure turbine 6, and the low-pressure turbine 9.
[0017]
　A pump may be used in the load device 13 instead of the generator. Further, although the configuration including the high-pressure turbine 3, the medium-pressure turbine 6 and the low-pressure turbine 9 is illustrated, for example, the configuration in which the medium-pressure turbine 6 is omitted may be omitted. The configuration in which the same load equipment 13 is driven by the high-pressure turbine 3, the medium-pressure turbine 6, and the low-pressure turbine 9 is illustrated, but the configuration is such that the high-pressure turbine 3, the medium-pressure turbine 6, and the low-pressure turbine 9 drive different load equipment. You may. The high-pressure turbine 3, the medium-pressure turbine 6, and the low-pressure turbine 9 may be divided into two groups (that is, two turbines and one turbine), and one load device may be driven for each group. Further, although the configuration including the boiler as the steam generation source 1 has been illustrated, a configuration in which a waste heat recovery steam generator (HRSG) utilizing the exhaust heat of the gas turbine is adopted as the steam generation source 1 may be adopted. In other words, it is a combined cycle power generation facility. A nuclear reactor is also an example of a steam source 1.
[0018]
　-Steam Turbine-
　FIG. 2 is a cross-sectional view of the low pressure turbine 9. As shown in the figure, the low-pressure turbine 9 includes the turbine rotor 12 and a stationary body 15 covering the turbine rotor 12. A diffuser is arranged at the outlet of the stationary body 15. In the specification of the present application, the rotation direction of the turbine rotor 12 is defined as "circumferential direction", the extension direction of the rotation center line C of the turbine rotor 12 is defined as "axial direction", and the radial direction of the turbine rotor 12 is defined as "diameter direction". ..
[0019]
　The turbine rotor 12 includes a rotor disk 13a-13d and a moving blade 14a-14d. The rotor disks 13a-13d are disk-shaped members arranged so as to be stacked in the axial direction. The rotor disks 13a-13d may be superposed alternately with spacers (not shown). A plurality of moving blades 14a-14d are provided at equal intervals in the circumferential direction of the outer peripheral surface of the rotor disk 13a-13d, respectively. The rotor blades 14a-14d extend radially outward from the outer peripheral surface of the rotor disk 13a-13d and face the annular working fluid flow path F. The fluid energy of the steam S flowing through the working fluid flow path F is converted into rotational energy by the moving blades 14a-14d, and the turbine rotor 12 integrally rotates around the rotation center line C.
[0020]
　The stationary body 15 includes a casing 16 and diaphragms 17a-17d. The casing 16 is a tubular member that forms the outer peripheral wall of the low-pressure turbine 9. A diaphragm 17a-17d is attached to the inner peripheral portion of the casing 16. The diaphragms 17a-17d are segments, each of which is integrally formed including a diaphragm outer ring 18, a diaphragm inner ring 19, and a plurality of wing portions 20. A plurality of diaphragms 17a to 17d are arranged in the circumferential direction to form an annular shape.
[0021]
　The diaphragm outer ring 18 is a member that defines the outer periphery of the working fluid flow path F on its inner peripheral surface, and is supported by the inner peripheral surface of the casing 16. The diaphragm outer ring 18 forms an annular shape. In the present embodiment, the inner peripheral surface of the diaphragm outer ring 18 is inclined outward in the radial direction toward the downstream side (right side in FIG. 2). The diaphragm inner ring 19 is a member that defines the inner circumference of the working fluid flow path F on its outer peripheral surface, and is arranged radially inward with respect to the diaphragm outer ring 18. The inner ring 19 of the diaphragm has an annular shape (cylindrical shape in this example). A plurality of wing portions 20 are arranged side by side in the circumferential direction, and extend in the radial direction to connect the diaphragm inner ring 19 and the diaphragm outer ring 18.
[0022]
　In addition, one paragraph is composed of a diaphragm and a moving blade adjacent to the downstream side thereof. In the present embodiment, the diaphragm 17a and the moving blade 14a are in the first paragraph (first stage), the diaphragm 17b and the moving blade 14b are in the second paragraph, the diaphragm 17c and the moving blade 14c are in the third paragraph, and the diaphragm 17d and the moving blade 14d are in the fourth paragraph. It is a paragraph (final row).
[0023]
　-Diaphragm outer ring-
　FIG. 3 is an enlarged view of part III in FIG. 2 and is a cross-sectional view showing a main part structure of the diaphragm according to an embodiment of the present invention. The structure described below is applied to the diaphragm 17d of at least one paragraph (eg, a wet paragraph in which drain tends to adhere to the surface of the rotor blade, typically the final stage of the low pressure turbine 9). In the low-pressure turbine 9, the applicability of paragraphs other than the fourth paragraph to the diaphragm is higher in the downstream paragraph, that is, the applicability is higher in the order of the diaphragms 17c, 17b, 17a. The case where the diaphragm 17d in the fourth paragraph of the low-pressure turbine 9 is applied will be described as an example with reference to FIG. 3, but the same structure is used when the diaphragm 17d in the fourth paragraph is applied to the diaphragms in other paragraphs. If necessary, it can also be applied to the diaphragm of the high-pressure turbine 3 and the medium-pressure turbine 6.
[0024]
　As shown in FIG. 3, the diaphragm 17d includes a collector ring 21, a seal fin 22, and an adapter ring 23 in addition to the diaphragm outer ring 18, the diaphragm inner ring 19 (FIG. 2), and the wing portion 20.
[0025]
　The collector ring 21 is an annular member arranged on the downstream side of the diaphragm outer ring 18 and holding the seal fins 22, and is divided into a plurality of parts in the circumferential direction (for example, divided into two or 4 in the upper half and the lower half). -Divided into 6 pieces). The outer diameter R1 of the collector ring 21 is larger than the outer diameter R0 of the downstream end of the diaphragm outer ring 18. The inner diameter of the collector ring 21 is about the same as the inner diameter of the downstream end of the diaphragm outer ring 18. The upstream end surface 21a and the downstream end surface 21b of the collector ring 21 are flat surfaces parallel to the plane orthogonal to the rotation center line C (FIG. 2) of the turbine rotor 12.
[0026]
　A slit 24 extending in the circumferential direction is provided on the inner peripheral surface of the collector ring 21. The slit 24 has a T-shaped cross section formed by a radial groove 24a extending in the radial direction and an axial groove 24b extending in the axial direction. The radial groove 24a has a role of restraining the movement of the seal fin 22 in the axial direction. The axial groove 24b has a role of restraining the radial movement of the seal fin 22. The axial groove 24b is located radially outside the inner peripheral surface of the collector ring 21, is separated from the working fluid flow path F by the structural material of the collector ring 21, and does not face the working fluid flow path F. ..
[0027]
　The collector ring 21 is provided with through holes 25 penetrating in the axial direction at intervals in the circumferential direction. The through hole 25 is provided with a counterbore 25a on the downstream end surface side of the collector ring 21. All of the through holes 25 including the counterbore 25a are located radially outside the slit 24 so as not to interfere with the slit 24 or to have a insufficient wall thickness. Further, at least a part of the through hole 25 is located outside the outer diameter of the downstream end portion of the diaphragm outer ring 18. The pitch circle diameter (PCD) D1 of the through hole 25 centered on the rotation center line C (FIG. 2) is set to be larger than the pitch circle diameter D2 of the through hole 26 described later (through hole). The pitch circle of 25 is located radially outside the pitch circle of the through hole 26).
[0028]
　The seal fin 22 projects radially inward from the inner peripheral surface of the collector ring 21 and seals the gap between the tip surface of the rotor blade 14d and the inner peripheral surface of the collector ring 21. The seal fin 22 is an annular member, but is divided into a plurality of parts in the circumferential direction (for example, the seal fin 22 is divided into two or 4-6 pieces in the upper half and the lower half). The seal fin 22 is provided with a root portion 22a of a radial spill strip (RSS) structure having a T-shaped cross section formed in accordance with the slit 24 of the collector ring 21. The seal fin 22 is fixed to the inner peripheral portion of the collector ring 21 by fitting the root portion 22a into the slit 24 from the circumferential direction.
[0029]
　Note that FIG. 3 shows the state when the operation is stopped, and the seal fin 22 is located on the downstream side of the moving blade 14d. The axial position with the moving blade 14d overlaps. Further, although FIG. 3 illustrates a seal fin 22 having one row of fins, when a plurality of rows of fins are installed in the axial direction, the structure of the seal fins 22 is changed to a structure having a plurality of rows of fins in the axial direction. It can be dealt with by replacing it.
[0030]
　The adapter ring 23 is a ring that is interposed between the diaphragm outer ring 18 and the collector ring 21 to attach the collector ring 21 to the diaphragm outer ring 18 having a diameter smaller than that of the collector ring 21. It is desirable that the adapter ring 23 is a seamless and integrated ring, but like the collector ring 21, the adapter ring 23 is divided into a plurality of rings in the circumferential direction (for example, the upper half and the lower half are divided into two or 4-6 pieces. (Structure divided into) may be used. The adapter ring 23 has an outer diameter similar to that of the collector ring 21, and has a larger outer diameter than the downstream end of the diaphragm outer ring 18. The inner diameter of the adapter ring 23 is about the same as the inner diameter of the downstream end of the diaphragm outer ring 18. The upstream end surface 23a and the downstream end surface 23b of the adapter ring 23 are flat surfaces parallel to the plane orthogonal to the rotation center line C (FIG. 2) of the turbine rotor 12.
[0031]
　Bolt holes (screw holes) 27 are provided on the downstream end surface 23b of the adapter ring 23 at intervals in the circumferential direction corresponding to the through holes 25 of the collector ring 21. Further, the adapter ring 23 is provided with through holes 26 penetrating in the axial direction at intervals in the circumferential direction. The positions of these through holes 26 correspond to bolt holes (screw holes) 28 provided at intervals in the circumferential direction on the downstream end surface 18a of the diaphragm outer ring 18. The downstream end surface 18a of the diaphragm outer ring 18 is also a flat surface parallel to the plane orthogonal to the rotation center line C. Each through hole 26 is provided with a counterbore 26a on the downstream end surface side of the adapter ring 23. As described above, the pitch circle diameter D2 of the through hole 26 centered on the rotation center line C (FIG. 2) is smaller than the pitch circle diameter D1 of the through hole 25 of the collector ring 21 (that is, the pitch circle diameter of the bolt hole 27). In the present embodiment, the through hole 26 or counterbore 26a of the adapter ring 23 is at least partially overlapped with the root portion 22a of the seal fin 22 in the radial direction. That is, at least a part of the through hole 26 or the counterbore 26a of the adapter ring 23 overlaps the root portion 22a of the seal fin 22 when viewed from the axial direction.
[0032]
　The diaphragm outer ring 18 and the adapter ring 23 are connected by a plurality of first bolts 31 inserted in the axial direction from the downstream side. The first bolt 31 is, for example, a hexagon socket head cap screw, and is screwed into the bolt hole 28 of the diaphragm outer ring 18 via the through hole 26 of the adapter ring 23. The head of the first bolt 31 is housed in the counterbore 26a of the adapter ring 23 so as not to protrude from the downstream end surface 23b of the adapter ring 23 toward the collector ring 21. By tightening each of the first bolts 31, the facing surfaces of the diaphragm outer ring 18 and the adapter ring 23 (that is, the downstream end surface 18a and the upstream end surface 23a) are in close contact with each other to form a continuous sealing surface in the circumferential direction. .. The first bolt 31 is orthogonal to the sealing surface of the diaphragm outer ring 18 and the adapter ring 23, and the tightening force of the first bolt 31 is efficiently converted into the contact pressure of the sealing surface.
[0033]
　The adapter ring 23 and the collector ring 21 are connected by a plurality of second bolts 32 inserted in the axial direction from the downstream side at a position on the outer peripheral side of the root portion 22a of the seal fin 22. The second bolt 32 is, for example, a hexagon socket head cap screw, and is screwed into the bolt hole 27 of the adapter ring 23 via the through hole 25 of the collector ring 21. In the present embodiment, the second bolt 32 is located on the outer peripheral side of the first bolt 31. The head of the second bolt 32 is accommodated in the counterbore 25a of the collector ring 21 so as not to protrude from the downstream end surface 21b of the collector ring 21. By tightening each of the second bolts 32, the adapter ring 23 and the collector ring 21 are fastened at the facing surfaces (that is, the downstream end surface 23b and the upstream end surface 21a). The second bolt 32 is orthogonal to the facing surfaces of the adapter ring 23 and the collector ring 21.
[0034]
　As described above, the collector ring 21 for holding the seal fin 22 is mounted on the downstream side of the diaphragm outer ring 18 via the adapter ring 23. By mounting the seal fin 22, the leakage of steam S through the gap flow path on the outer peripheral side of the moving blade 14d is suppressed, and the decrease in turbine efficiency is suppressed. Further, the sealing surface of the adapter ring 23 seamlessly surrounds the working fluid flow path F, and leakage of vapor S via the facing surface between the diaphragm outer ring 18 and the adapter ring 23 is also suppressed.
[0035]
　- - Manufacturing process
　represents 4 is a flow chart showing a procedure determining the application of the manufacturing method of the diaphragm of the present invention, FIG 5 is a front retrofit an explanatory view of a manufacturing method of the diaphragm according to an embodiment of the present invention the diaphragm It is a figure. The diaphragm shown in FIG. 5 is used in an existing steam turbine facility, and an example in which a seal fin is RSS-structured based on the diaphragm shown in the figure will be described.
[0036]
　The diaphragm shown in FIG. 5 is for a steam turbine, and a diaphragm inner ring (not shown), a diaphragm outer ring a, and a blade portion f are integrally formed. A collector ring b is connected to the downstream side of the diaphragm outer ring a by a bolt c. The bolt c is inserted in the axial direction from the collector ring b side and screwed into the diaphragm outer ring a. Seal fins d are implanted on the inner peripheral surface of the collector ring b. The seal fin d is fixed to the collector ring b by caulking. In manufacturing a new diaphragm provided with an RSS-structured seal fin based on such an existing diaphragm, whether or not the present invention is applied will first be examined by the procedure of FIG.
[0037]
　Step S1
　First, it is determined whether the diaphragm of FIG. 5 belongs to the wet paragraph, that is, whether the seal fin d requires RSS structuring. In the first place, if the RSS structure has already been applied to the seal fin d, it is not necessary to apply the invention, and the procedure is moved to step S5 to end the study without applying the invention.
[0038]
　Step S2 When
　the seal fin d of the diaphragm of FIG. 5 is RSS-structured, the procedure is moved to step S2, and the RSS-structured seal fin (seal fin 22 of FIG. 3) and a new collector ring with a slit for holding the seal fin d are held. (Collecting 21 in FIG. 3) is designed.
[0039]
　Step S3
　Next, it is determined whether the slit of the new collector ring (slit 24 in FIG. 3) interferes with the fastening hole e of the diaphragm outer ring a, that is, whether the slit and the fastening hole e overlap when viewed from the axial direction. .. If the slit does not overlap the fastening hole e, a new collector ring can be mounted using the fastening hole e, so that it is not necessary to separately prepare an adapter ring (adapter ring 23 in FIG. 3). In this case, the procedure is moved to step S5 to end the study.
[0040]
　If
　a new collector ring slit interferes with or the wall thickness is insufficient in the fastening hole e of the diaphragm outer ring a in step S4 , the pitch circle diameter is expanded and a new bolt hole is machined on the downstream end surface of the diaphragm outer ring a. Determine if it is possible. If there is a margin in the outer diameter (that is, the wall thickness) of the diaphragm outer ring a and a new bolt hole can be machined, it is not necessary to prepare an adapter ring separately in this case as well. A new bolt hole can be machined into the diaphragm outer ring a, a through hole corresponding to the bolt hole can be provided in the new collector ring, and the new collector ring can be directly attached to the diaphragm outer ring a. In this case as well, the procedure is moved to step S5 to end the examination.
[0041]
　If
　a new bolt hole cannot be provided on the downstream end surface of the outer ring a of the diaphragm in step S6, the examination is terminated by shifting the procedure to step S6 and applying the invention.
[0042]
　When the invention is applied, the procedure for modifying the diaphragm of FIG. 5 to manufacture the diaphragm 17d of FIG. 3 largely includes a process of processing the outer ring of the diaphragm, a process of manufacturing parts, and a process of assembling.
[0043]
　In the process of processing the outer ring of the diaphragm, the downstream end of the outer ring a of the diaphragm is removed so that the seal fin 22 comes to a desired position when the collector ring 21 is attached via the adapter ring 23, and the outer ring of the diaphragm of FIG. 3 is formed. 18 is formed. In this example, the portion on the right side is removed from the alternate long and short dash line of the diaphragm outer ring a in FIG. However, the amount of removal of the downstream end portion of the diaphragm outer ring a can be arbitrarily set as long as it does not interfere with the blade portion f. When removing the downstream end of the diaphragm outer ring a, for example, a method of cutting the downstream end of the diaphragm outer ring a by machining to finish the downstream end surface 18a can be adopted. It is possible to roughly finish the downstream end surface 18a by machining after gas cutting the downstream end of the diaphragm outer ring a, but by finishing only by machining, thermal deformation of the diaphragm outer ring 18 due to heat input can be suppressed. Further, a bolt hole 28 is machined in the downstream end surface 18a of the diaphragm outer ring 18.
[0044]
　In the parts manufacturing process, the collector ring 21, the seal fin 22, and the adapter ring 23 shown in FIG. 3 are manufactured. The manufacturing process of this part may be performed before or after the processing process of the diaphragm outer ring, or may be performed in parallel. The order of manufacturing the collector ring 21, the seal fin 22, and the adapter ring 23 is also random, and the collector ring 21, the seal fin 22, and the adapter ring 23 may be manufactured in any order, and of course, a plurality of them may be manufactured at the same time.
[0045]
　In the assembly process, the seal fin 22 having an RSS structure is fitted into the slit 24 of the collector ring 21 from the circumferential direction. Further, the adapter ring 23 is arranged on the downstream side of the diaphragm outer ring 18, and a plurality of first bolts 31 are inserted in the axial direction from the downstream side to connect the adapter ring 23 to the diaphragm outer ring 18. Then, the collector ring 21 is arranged on the downstream side of the adapter ring 23, and a plurality of second bolts 32 are inserted in the axial direction from the downstream side to connect the collector ring 21 to the adapter ring 23.
[0046]
　- Comparative Example -
　FIG. 6 is a diagram illustrating the structure of a diaphragm fabricated by modifying the diaphragm of FIG. 3 by the manufacturing method according to a comparative example. For comparison, the collector ring b'in FIG. 6 has the same size and shape as the collector ring 21 in FIG.
[0047]
　In FIG. 4, when the seal fin of the existing diaphragm is RSS-structured, the pitch circle diameter of the fastening hole e of the diaphragm outer ring a cannot be expanded, and the structure is modified to the structure of FIG. 3 by applying the invention. However, conventionally, when the outer diameter of the diaphragm outer ring a is insufficient and a new collector ring b'that holds the seal fin of the RSS structure cannot be attached as shown in FIG. 6, the design of the diaphragm outer ring has a large outer diameter. It was changed to. In FIG. 6, the diaphragm outer ring a excluding the hatched portion is an existing one, and the diaphragm outer ring a'with a larger diameter including the hatched portion is the one after the design change. In this case, the collector ring b'can be attached without any problem, but since the diaphragm outer ring is a part of the integrally configured diaphragm, the entire diaphragm including the wing and the diaphragm inner ring is newly manufactured due to the design change of the diaphragm outer ring. There must be. It takes a long time to manufacture a diaphragm with revised specifications. It is also conceivable to build-up weld the outer peripheral portion of the existing diaphragm outer ring a, but this is not desirable because the heat input is large and there is a concern about thermal deformation.
[0048]
　-Effect-
　(1) In the present embodiment, by making the seal fin 22 an RSS structure, the root portion inserted into the collector ring 21 becomes large, and the reliability of the fixed structure of the seal fin 22 with respect to erosion can be improved. Further, since the downstream end of the outer ring of the diaphragm can be removed and most of the existing diaphragm can be used, it is expected that the construction period of the RSS structure of the seal fin in the diaphragm can be significantly shortened.
[0049]
　Further, since the diaphragm outer ring 18, the adapter ring 23, and the collector ring 21 are fastened with bolts, thermal deformation is suppressed unlike the case of welding, and the shape of the diaphragm can be finished with high accuracy.
[0050]
　(2) At least a part of the first bolt 31 overlaps the seal fin 22 when viewed from the axial direction, and the head is housed in the counterbore 26a provided on the adapter ring 23. By sharing the radial space between the first bolt 31 and the seal fin 22 in this way, it is possible to secure a margin of space for providing the bolt hole 27 for mounting the collector ring 21 on the adapter ring 23. Further, by providing the counterbore 26a on the adapter ring 23 to accommodate the head of the first bolt 31, it is possible to avoid interference of the head of the first bolt 31 with respect to the facing surface between the adapter ring 23 and the collector ring 21. Further, the counterbore 26a is closed by the collector ring 21 and the first bolt 31 is completely confined. Since the first bolt 31 is restrained by the collector ring 21, loosening of the first bolt 31 can be suppressed.
[0051]
　(3) Since the sealing surfaces of the diaphragm outer ring 18 and the adapter ring 23 are flat surfaces orthogonal to the first bolt 31, the tightening force of the first bolt 31 is wasted on the contact pressure of the sealing surfaces of the diaphragm outer ring 18 and the adapter ring 23. Can be converted without. As a result, good sealing performance can be ensured on the sealing surfaces of the diaphragm outer ring 18 and the adapter ring 23.
Code description
[0052]
17a-17d ... Diaphragm, 18 ... Diaphragm outer ring, 18a ... Downstream end face (diaphragm outer ring and adapter ring facing surface, seal surface), 19 ... Diaphragm inner ring, 20 ... Wing, 21 ... Collector ring, 21a ... Upstream end face (Opposite surface of adapter ring and collector ring), 22 ... Seal fin, 23 ... Adapter ring, 23a ... Upstream end surface (diaphragm outer ring and adapter ring facing surface, seal surface), 23b ... Downstream end surface (adapter ring and collector) Ring facing surface), 26a ... Counterbore, 31 ... 1st bolt, 32 ... 2nd bolt, R1 ... Collector ring outer diameter, R2 ... Diaphragm outer ring outer diameter
The scope of the claims
[Claim 1]
　In a diaphragm for a steam turbine in which an inner diaphragm ring, an outer diaphragm ring, and a wing portion are integrally formed,
　a collector ring arranged on the downstream side of the outer ring of the diaphragm, and
　a seal fin having a radial spill strip structure fitted in the collector ring. and
　further comprising a diaphragm outer ring and the adapter ring interposed between the collector ring,
　the diaphragm outer ring and the adapter ring is connected by a plurality of first bolt that is inserted from the downstream side in the axial direction, the diaphragm outer ring and The facing surfaces of the adapter ring are in close contact with each other and sealed, and the
　collector ring and the adapter ring have a larger outer diameter than the diaphragm outer ring, and are axially downstream from the downstream side at a position on the outer peripheral side of the seal fin. A diaphragm connected by a plurality of inserted second bolts.
[Claim 2]
　In the diaphragm of claim 1, at least a part of the first bolt overlaps the seal fin when viewed from the axial direction, and the adapter ring is provided with a counterbore for accommodating the head of the first bolt. Diaphragm.
[Claim 3]
　The diaphragm according to claim 1, wherein the sealing surfaces of the outer ring of the diaphragm and the adapter ring are flat surfaces orthogonal to the first bolt.
[Claim 4]
　A steam turbine to which the diaphragm of claim 1 is applied to at least one paragraph.
[Claim 5]
　Diaphragm inner ring, a diaphragm outer ring, and the diaphragm manufacturing method of the blade portion to produce a new diaphragm having a sealing fin of the radial spill strip structure is based on the diaphragm for a steam turbine which is integrally formed,
　said diaphragm A collector ring and an adapter ring having an outer diameter larger than that of the outer ring are manufactured, the
　seal fin is fitted into the collector ring,
　the downstream end of the diaphragm outer ring is removed, and the
　adapter ring is arranged on the downstream side of the diaphragm outer ring. Then, a plurality of first bolts are inserted in the axial direction from the downstream side to connect the adapter ring to the diaphragm outer ring, the
　collector ring is arranged on the downstream side of the adapter ring, and the outer circumference is outer than the seal fin. A method for manufacturing a diaphragm in which a plurality of second bolts are inserted axially from the downstream side at a position on the side to connect the collector ring to the adapter ring.