Shaft seal structure for gas turbine

Abstract

To protect a bearing that is applied to a gas turbine.SOLUTION: A shaft seal structure includes: a rotor 11 including an impeller 12; a bearing 7 for supporting the rotor 11 so as to be rotatable; a housing 13 having a storage space 14 for storing the impeller 12 and holding the bearing 7; a drain 26 for draining oil supplied to the bearing 7 to the outside of the housing 13; an air supply passage 33 for supplying air for sealing the bearing 7 from the storage space 14 between the rotor 11 and the housing 13; and an air discharge passage 34 for discharging the air supplied from the air supply passage 33 to the outside of the housing 13.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a shaft seal structure for a gas turbine. [Background technology]

[0002] Patent Document 1 discloses a gas turbine engine equipped with a labyrinth seal interposed between a bearing that supports a shaft and a housing that holds the bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-048781 A Summary of the Invention [Problem to be solved by the invention]

[0004] At least a portion of the air supplied to the labyrinth seal may flow into the housing, and if foreign matter is present in the air, the foreign matter may reach the bearing and thus disrupt stable operation of the bearing.

[0005] An object of the present invention is to protect bearings applied to gas turbines. [Means for solving the problem]

[0006] One aspect of the present invention provides a shaft seal structure for a gas turbine comprising: a rotor having an impeller, a bearing rotatably supporting the rotor, a housing having an accommodation space for accommodating the impeller and holding the bearing, a drain for discharging oil supplied to the bearing outside the housing, an air supply passage for supplying air to the accommodation space between the rotor and the housing to seal the bearing, and an air discharge passage for discharging the air supplied from the air supply passage outside the housing.

[0007] According to the above configuration, the air discharge passage is provided separately from the drain. Therefore, air supplied between the rotor and the housing is prevented from remaining in the housing until it passes through the drain and is discharged together with the oil, and is actively discharged to the outside of the housing via the air discharge passage. Therefore, even if foreign matter is mixed in the air, the foreign matter is unlikely to reach the bearing. This makes it possible to protect the bearing from foreign matter and maintain stable operation of the rotor.

[0008] The housing may have an inner circumferential surface that surrounds the outer circumferential surface of the rotor between the bearing and the accommodating space in the axial direction, the drain may open to a lower part of the inner circumferential surface, and the air discharge passage may open to a part of the inner circumferential surface other than the lower part.

[0009] According to the above configuration, the drain opens at the bottom. The oil flow inside the housing is affected by the weight of the oil itself. As a result, the oil is smoothly discharged from the housing. Meanwhile, the air flow inside the housing is affected by the centrifugal force accompanying the rotation of the rotor, and an air flow toward the outside in the radial direction is generated inside the housing. The air rides on the air flow toward the inner circumferential surface of the housing. Even if the air discharge passage opens to the remaining part (a part other than the bottom), it is possible to smoothly guide the air to the air discharge passage and smoothly discharge it from the housing. Therefore, both oil and air can be smoothly discharged.

[0010] A plurality of the air discharge passages may be provided, each of the plurality of air discharge passages may open into the inner circumferential surface, and the openings of the plurality of air discharge passages may be arranged at intervals in the circumferential direction. This allows the openings of the air discharge passages to be distributed in the circumferential direction, allowing air to be smoothly discharged from the chamber.

[0011] The shaft seal structure may further include a fin disposed within the housing and extending radially outward from an outer circumferential surface of the rotor, the air discharge passage opening relative to the fin on the side of the accommodation space.

[0012] According to the above configuration, the fins prevent air from flowing axially toward the bearing. Even if foreign matter is mixed in the air, the foreign matter is unlikely to reach the bearing. Furthermore, the fins guide the air to flow radially outward on the opposite side of the fins from the bearing in the axial direction. Since the air discharge passage opens there, the air can be smoothly guided to the air discharge passage, and the retention time of foreign matter in the air inside the housing is shortened.

[0013] The fins may be integrally formed with a sleeve that is fitted onto the rotor, whereby the fins having the above-mentioned functions can be easily attached to the rotor by simply inserting the rotor into the sleeve.

[0014] The shaft seal structure may further include an air cleaner that cleans the air before it reaches the housing, the air cleaner having a strainer, thereby reducing the risk of foreign matter being mixed into the air and protecting the bearing from foreign matter.

[0015] The air cleaner may be disposed outside the housing, which facilitates maintenance of the air cleaner. Effect of the Invention

[0016] According to the present invention, it is possible to protect a bearing applied to a gas turbine. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a gas turbine according to an embodiment; [Diagram 2] 1 is a cross-sectional view of a compressor section of a gas turbine. [Diagram 3] Cross-sectional view of the shaft seal structure. [Figure 4] FIG. 4 is a cross-sectional view of a shaft seal structure showing air flow and oil flow within a chamber. [Diagram 5] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment will be described with reference to the drawings. Note that the same or corresponding elements are designated by the same reference numerals throughout the drawings, and detailed description thereof will be omitted.

[0019] 1, a gas turbine 1 is, by way of example only, stationary on land and used as a power source for a driven machine such as a generator (not shown). A main shaft 2 of the gas turbine 1 is connected to the driven machine such as a generator via a reduction gear mechanism (not shown). In this disclosure, unless otherwise specified, the "axial direction" refers to a direction along the axis A of the main shaft 2, the "axial orthogonal direction" or the "radial direction" refers to a direction perpendicular to the axis A of the main shaft 2, and the "circumferential direction" refers to a direction around the axis A.

[0020] The gas turbine 1 includes a compression section 3, a combustion section 4, and a turbine 5. The main shaft 2 includes a rotor 11 of the compression section 3, a turbine rotor 5a of the turbine 5, and an input shaft 6 of the reduction mechanism. The input shaft 6, the rotor 11, and the turbine rotor 5a are arranged in this order from one side to the other in the axial direction (from left to right on the page in FIG. 1), are arranged coaxially around the axis line A, are connected in sequence, and rotate integrally around the axis line A. In this disclosure, a "rotor" refers to a shaft-shaped member itself, or a member having a shaft-shaped portion, and rotates around its own central axis.

[0021] The main shaft 2 is rotatably supported by two bearings 7, 8 spaced apart from each other in the axial direction. The bearing 7 rotatably supports one end of the rotor 11. The bearing 8 may support the other end of the rotor 11 or may support the turbine rotor 5a. The type of the bearings 7, 8 is not particularly limited, and the illustrated single-row groove ball bearing is merely one example. The shaft seal structure according to this embodiment is applied to the bearing 7 of the gas turbine 1.

[0022] The compression section 3 takes in outside air and compresses it. The combustion section 4 injects fuel into the compressed air, combusts the mixture, and generates high-temperature, high-pressure combustion gas. The turbine 5 is driven by the combustion gas. When the turbine 5 operates, the main shaft 2 rotates. This drives the compression section 3, and the input shaft 6 is rotated to provide power to the driven machine. Exhaust gas is discharged from the turbine 5 to the other axial side. The input shaft 6 is disposed on one axial side of the compression section 3, and the turbine 5 is disposed on the other axial side of the compression section 3. The combustion section 4 is adjacent to the other axial side of the compression section 3, and is disposed on the radially outer periphery of the turbine 5.

[0023] The rotor 11 has an impeller 12. The rotor 11 and its impeller 12 function as a centrifugal compressor by rotating. The impeller 12 is provided integrally with the rotor 11, and its diameter increases from one side to the other side in the axial direction. The compression section 3 has a housing 13. The housing 13 forms an accommodation space 14 that accommodates the impeller 12, and also holds a bearing 7 that supports the rotor 11.

[0024] The housing 13 has an outer wall 15, an inner wall 16, and a plurality of support columns 17 for forming the accommodation space 14. The outer wall 15 extends in a direction perpendicular to the axis. The inner wall 16 is separated from the outer wall 15 in the axial direction and extends in a direction perpendicular to the axis on the other axial side of the outer wall 15. The support columns 17 bridge between the inner surface of the outer wall 15 (the side surface on the other axial side) and the inner surface of the inner wall 16 (the side surface on one axial side). The plurality of support columns 17 are arranged at intervals in the circumferential direction and extend roughly parallel to the axial direction.

[0025] The housing 13 is covered with a cover 18. The storage space 14 is surrounded by an outer wall 15, an inner wall 16, and the cover 18, and the cover 18 is provided with a duct 18a that connects the outside of the housing 13 to the storage space 14. An intake guide 19 is fixed to the inner wall 16. The intake guide 19 is cylindrical with a constriction in the axial center, extends from the inner wall 16 to one axial side, surrounds the impeller 12, and opens at one axial end side. Outside air is guided into the storage space 14 through the duct 18a. The intake air that has flowed into the storage space 14 flows into the intake guide 19 and is compressed by the action of the impeller 12 while flowing inside the intake guide 19 from one side to the other in the axial direction.

[0026] A reducer case 40 is provided on one axial side of the housing 13. The reducer case 40 forms a reducer chamber 40a that houses the reducer and its input shaft 6. The reducer case 40 is fixed to the outer wall 15. The accommodation space 14 and the reducer chamber 40a are partitioned in the axial direction by the outer wall 15.

[0027] Next, the shaft seal structure will be described.

[0028] 2, the housing 13 has a bearing case 20 and a retaining ring 21 for holding the bearing 7. The bearing case 20 is fitted into a mounting hole 15a that penetrates the center of the outer wall 15. The mounting hole 15a is cylindrical with both ends open, and has a uniform circular cross section along the axial direction.

[0029] The bearing case 20 has a cylindrical portion 20a that fits into the mounting hole 15a, and a conical portion 20b that continues from the cylindrical portion 20a to the other axial side. With the cylindrical portion 20a fitted, a ring-shaped mounting plate 22 is provided on the outer surface side of the outer wall 15. Both the bearing case 20 and the outer wall 15 are fastened to the mounting plate 22 in the axial direction, whereby the bearing case 20 is fixed to the outer wall 15 via the mounting plate 22. Note that reference symbol 20f shown in Fig. 5 denotes a screw hole into which a bolt is screwed for fastening to the mounting plate 22.

[0030] The conical portion 20b is sharpened on the other axial side and protrudes toward the other axial side with respect to the mounting hole 15a. The tip of the conical portion 20b enters the intake guide 19. The outer surface of the conical portion 20b forms a curved surface that smoothly connects with the inner surface of the outer wall 15, and guides the intake air into the inside of the intake guide 19.

[0031] 3, a shaft hole 23 is formed in the center of the bearing case 20, extending in the axial direction and open at both ends. A bearing accommodating portion 24 is formed at one axial end of the shaft hole 23. The bearing accommodating portion 24 is defined by a cylindrical surface 24a and an annular stepped surface 24b extending radially inward from the other axial end of the cylindrical surface 24a. The cylindrical surface 24a has a uniform diameter in the axial direction and defines an opening on one axial end side of the shaft hole 23. The bearing 7 is accommodated in the bearing accommodating portion 24 with the outer peripheral surface of the outer ring thereof in close contact with the cylindrical surface 24a and the end face on the other axial side thereof abutting against the stepped surface 24b in the axial direction.

[0032] The retaining ring 21 has a cylindrical portion 21a that is fitted into the bearing accommodating portion 24, and a flange portion 21b that extends radially outward from one axial end of the cylindrical portion 21a. The other axial end of the cylindrical portion 21a abuts against the outer ring of the bearing 7 in the axial direction, and the flange portion 21b abuts against a side surface of the cylindrical portion 20a of the bearing case 20 on the axial end side.

[0033] In this state, the flange portion 21b is fastened to the cylindrical portion 20a in the axial direction. As a result, the bearing case 20 and the retaining ring 21 are fixed to the outer wall 15, and the bearing 7 is held by the bearing case 20 and the retaining ring 21. Reference symbol 20g shown in Fig. 5 denotes a screw hole into which a bolt is screwed for fastening to the retaining ring 21.

[0034] One axial end of the rotor 11 is inserted into the shaft hole 23 of the bearing case 20. A journal portion 11a is provided at one end of the rotor 11. The journal portion 11a is a portion that is inserted into the bearing 7 and is rotatably supported by the bearing 7. The rotor 11 has a stepped surface 11b that extends radially outward from the other axial end of the journal portion 11a. The inner ring of the bearing 7 abuts against the stepped surface 11b in the axial direction, thereby positioning the bearing 7 in the axial direction with respect to the rotor 11.

[0035] A seal 9 is provided on the housing space 14 side of the bearing 7, i.e., on the other axial side. The seal 9 is, for example, an axial type labyrinth seal. The seal 9 is composed of an outer circumferential seal portion 9a provided on the bearing case 20 and an inner circumferential seal portion 9b provided on the rotor 11. The outer circumferential seal portion 9a is provided on the inner surface of the shaft hole 23 at a portion that penetrates the conical portion 20b. The outer circumferential seal portion 9a and the inner circumferential seal portion 9b are closely opposed to each other in the radial direction and form a plurality of expansion chambers and throttle portions that are alternately arranged in the axial direction. High-pressure seal air is supplied to the seal 9 (see FIG. 2), and the seal 9 seals the bearing housing portion 24 from the housing space 14 without contacting the bearing housing portion 24.

[0036] 4, the bearing case 20 and the rotor 11 form a chamber 10 between the bearing 7 and the seal 9. The chamber 10 is a space surrounded by the outer circumferential surface of the rotor 11 and the inner circumferential surface of the bearing case 20 (i.e., the inner surface that defines the axial hole 23). The chamber 10 has an annular cross section when viewed in the axial direction.

[0037] With regard to the portion forming the chamber 10, the inner surface of the axial hole 23 includes a first inner circumferential surface 23a extending toward the other axial side from a step surface 24b against which the outer ring of the bearing 7 abuts, a second inner circumferential surface 23b located on the other axial side of the first inner circumferential surface 23a and having a larger diameter than the first inner circumferential surface 23a, a step surface 23c radially connecting the other axial end of the first inner circumferential surface 23a and one axial end of the second inner circumferential surface 23b, and a chamber end surface 23d radially connecting the other axial end of the second inner circumferential surface 23b and the inner circumferential seal portion 9b.

[0038] As shown in Fig. 5, when the bearing case 20 is viewed in the axial direction from one axial side to the other side, the step surface 24b of the bearing accommodating portion 24 extends in an annular belt shape inside the opening on the axial one end side. The first inner circumferential surface 23a forms a circle at the radial inner circumferential edge of the step surface 24b. The chamber end surface 23d extends in an annular belt shape inside the first inner circumferential surface 23a. The outer circumferential seal portion 9a forms a circle at the radial inner circumferential edge of the chamber end surface 23d. The second inner circumferential surface 23b has a larger diameter than the first inner circumferential surface 23a and is located on the other axial side of the first inner circumferential surface 23a, and is therefore indicated by a dashed line in Fig. 5.

[0039] Returning to Figure 4, with regard to the portion forming the chamber 10, the rotor 11 has an intermediate portion 11c extending from the step surface 11b against which the inner ring of the bearing 7 abuts toward the other axial side toward the inner circumferential seal portion 9b, and a flange portion 11d protruding radially outward from the other axial end portion of the intermediate portion 11c.

[0040] A sleeve 25 is fitted onto the intermediate portion 11c. The sleeve 25 has a cylindrical portion 25a into which the intermediate portion 11c is inserted, and fins 25b protruding radially outward from the other axial end of the cylindrical portion 25a. The other axial end of the sleeve 25 (or the cylindrical portion 25a) is abutted against the flange portion 11d of the rotor 11. The fins 25b are molded integrally with the sleeve 25 (the cylindrical portion 25a), and protrude radially outward beyond the outer circumferential edge of the flange portion 11d.

[0041] One axial end of the chamber 10 is defined by the end face on the other axial side of the bearing 7. The other axial end of the chamber 10 is defined by the chamber end face 23d of the bearing case 20. The clearance between the inner ring and the outer ring of the bearing 7 communicates with the chamber 10. In addition, the seal 9 is a non-contact type labyrinth seal, and the clearance between the outer peripheral seal portion 9a and the inner peripheral seal portion 9b also communicates with the chamber 10.

[0042] The chamber 10 receives the lubricating oil (hereinafter simply referred to as oil) supplied to the bearing 7. In this regard, reference symbol 20e shown in Fig. 5 is an oil inlet port that allows the lubricating oil to flow into the bearing case 20 from outside the bearing case 20. Reference symbol 21d shown in Fig. 3 is an oil supply passage that communicates with this oil inlet port 20e (not shown in Fig. 3) and guides the lubricating oil to one end face in the axial direction of the bearing 7. The oil inlet port 20e is formed in the bearing case 20, and the oil supply passage 21d is formed in the cylindrical portion 21a of the retaining ring 21.

[0043] A drain 26 is formed in the bearing case 20 to guide oil in the chamber 10 to the outside of the chamber 10. One end of the drain 26 opens to the second inner circumferential surface 23b, i.e., the chamber 10. The other end of the drain 26 opens to one axial end and to the radial outer circumferential edge of the cylindrical portion 20a of the bearing case 20. The drain 26 extends obliquely within the bearing case 20, such that the further it moves from the chamber 10 toward one axial side, the more it moves toward the radial outer circumferential side.

[0044] Next, the flow of the seal air will be described. The seal air is supplied to the seal 9 and seals the oil supplied to the bearing 7 against the accommodation space 14.

[0045] 2, the gas turbine 1 includes an upstream flow path 31, an air cleaner 32, an air supply passage 33, and an air discharge passage 34. Seal air is taken out of the accommodation space 14 and cleaned by the air cleaner 32. The air cleaner 32 cleans the seal air before it reaches the seal 9. The air supply passage 33 supplies air between the rotor 11 and the bearing case 20. The air discharge passage 34 discharges the seal air supplied from the air supply passage 33 to the outside of the housing 13.

[0046] The air cleaner 32 has a housing 32a and a strainer 32b that divides the storage space of the housing 32a into a dirty side and a clean side. The housing 32a is provided with an inlet 32c and an outlet 32d. The inlet 32c opens to the dirty side, and the outlet 32d opens to the clean side. The storage space 14, which is the seal air source, and the seal 9, which is the supply destination of the seal air, are both provided inside the housing 13, while the air cleaner 32 is disposed outside the housing 13.

[0047] The upstream flow passage 31 guides the compressed air taken out as seal air from the accommodation space 14 to the inlet 32c of the air cleaner 32. In this regard, the gas turbine 1 includes a partition member 27 disposed on the other axial side of the inner wall 16 and extending in the axially orthogonal direction. The partition member 27 faces closely to the inner wall 16 in the axial direction. The partition member 27 and the inner wall 16 form a flow passage 28 for guiding the compressed air from inside the intake guide 19 to the combustion section 4, on the radially outer circumferential side of the other axial end of the intake guide 19. The partition member 27 has an extraction hole 27a on the radially inner circumferential side of a portion that defines the flow passage 28. The extraction hole 27a penetrates the partition member 27. The upstream end of the upstream flow passage 31 is connected to the extraction hole 27a.

[0048] The upstream flow path 31 is constituted by a pipe 31a, an axial hole 17a and a radial hole 17b formed in one of the plurality of supports 17, and a pipe 31b.

[0049] One end of the pipe 31a forms the upstream end of the upstream flow passage 31 and is connected to the extraction hole 27a. The pipe 31a extends radially inward in the space on the other axial side of the partition member 27 and is folded back toward the one axial side. The other end of the pipe 31a penetrates the radial outer peripheral edge of the partition member 27, crosses the flow passage 28 along the axial direction, and is connected to the outer peripheral edge of the inner wall 16. The axial hole 17a extends along the axial direction and communicates with the downstream end of the pipe 31a at the other axial end side. The axial hole 17a may be a non-through hole that opens only at the other axial end side, or may be a through hole that opens on both axial sides of the support 17. In the case of a through hole, a plug 29 is provided to close one axial end of the axial hole 17a in order to prevent leakage of seal air from the axial hole 17a. The radial hole 17b communicates with the axial hole 17a and opens to the outer surface of the support 17. One end of the pipe 31b is connected to the radial hole 17b, and the other end of the pipe 31b is connected to the inlet 32c.

[0050] The air supply passage 33 is composed of a piping 33a, a radial hole 15b and an outlet 15c formed in the outer wall 15, a piping 33b, an inlet 21c connected to the retaining ring 21, and a downstream portion 33c formed in the bearing case 20.

[0051] One end of the pipe 33a is connected to the outlet 32d of the air cleaner 32. The radial hole 15b is a non-through hole that extends radially inside the outer wall 15 and opens on the outer peripheral surface of the outer wall 15. The other end of the pipe 33a is connected to the opening of the radial hole 15b. The outlet 15c communicates with the radial hole 15b and opens on one axial side of the outer wall 15. The inlet 21c penetrates the flange portion 21b of the retaining ring 21. The pipe 33b is disposed on one axial side of the outer wall 15. That is, the pipe 33b is accommodated in the reducer chamber 40a. One end of the pipe 33b is connected to the radial hole 15b of the outer wall 15, and the other end of the pipe 33b is connected to the inlet 21c of the retaining ring 21.

[0052] The downstream portion 33c of the air supply passage 33 is formed inside the bearing case 20, and connects the inlet 21c to the outer circumferential seal portion 9a of the seal 9. One end of the downstream portion 33c opens into the side surface of the cylindrical portion 20a, and communicates with the inlet 21c that penetrates the retaining ring 21. The other end of the downstream portion 33c opens into the inner surface of the portion of the axial hole 23 that penetrates the conical portion 20b, i.e., the outer circumferential seal portion 9a.

[0053] As an example, the downstream section 33c is composed of a straight section 20c extending in the axial direction inside the cylindrical section 20a and an inclined section 20d extending obliquely toward the radial center side as it approaches the other axial side inside the conical section 20b. The other axial end of the straight section 20c is connected to one axial end of the inclined section 20d.

[0054] Compressed air in the accommodation space 14 flows into the upstream flow passage 31 through the outlet hole 27a. The seal air flows through the upstream flow passage 31 and flows into the dirty side of the air cleaner 32 through the inlet 32c. The seal air is filtered and purified when passing through the strainer 32b. The seal air flows out from the clean side of the air cleaner 32 through the outlet 32d. The air supply passage 33 supplies the seal air that flows out of the air cleaner 32 to the seal 9.

[0055] Since the air cleaner 32 is disposed outside the housing 13, it is easy to perform maintenance work on the air cleaner 32. In addition, since the air cleaner 32 is disposed outside the housing 13, the seal air can be air-cooled.

[0056] The controller 50 measures the differential pressure between the primary pressure of the air cleaner 32 detected by the primary pressure sensor 51 and the secondary pressure of the air cleaner 32 detected by the secondary pressure sensor 52. The controller 50 compares the measured differential pressure with a predetermined threshold value. If the measured value is equal to or greater than the threshold value, the controller 50 may determine that the strainer 32b is clogged and may activate an alarm device (not shown). This makes it possible to notify an operator that it is time to perform maintenance on the air cleaner 32.

[0057] Within the seal 9, the seal air flows to both sides in the axial direction while its pressure gradually decreases. A part of the seal air flows to the other axial side within the seal 9 and is discharged from the seal 9 into the inside of the intake guide 19, where it is mixed with the intake air. A part of the seal air flows to one side in the axial direction within the seal 9 and flows from the seal 9 into the chamber 10. The seal air within the chamber 10 can be discharged to the outside of the housing 13 together with the oil via the drain 26.

[0058] 3 and 4, the air discharge path 34 is provided independently of the drain 26. The air discharge path 34 is a flow path for guiding the seal air in the chamber 10 to the outside of the housing 13 in order to prevent the seal air from accumulating in the chamber 10.

[0059] The air discharge passage 34 is formed inside the bearing case 20. The air discharge passage 34 is configured as a through hole that is open at both ends. There are no particular limitations on the method for forming the air discharge passage 34, and drilling or casting may be used.

[0060] One end of the air discharge passage 34 opens into the chamber 10. More specifically, the air discharge passage 34 opens into the bearing case 20, which is one of the members that define the chamber 10. As described above, the bearing case 20 has the first inner circumferential surface 23a, the second inner circumferential surface 23b, the step surface 23c, and the chamber end surface 23d as portions that define the chamber 10. Of these, the first inner circumferential surface 23a and the second inner circumferential surface 23b surround the outer circumferential surface of the rotor 11 and form the outer periphery of the chamber 10 in the radial direction.

[0061] In this embodiment, the air discharge passage 34 opens into the second inner circumferential surface 23b. The second inner circumferential surface 23b has a larger diameter than the first inner circumferential surface 23a and forms the outermost periphery of the chamber 10. The second inner circumferential surface 23b also forms the other axial side of the chamber 10. The air discharge passage 34 opens at such a location of the chamber 10.

[0062] The opening 35 of the air discharge passage 34 has a width in the axial direction on the second inner circumferential surface 23b, as is clearly shown in the cross section passing through the axis A. The edge of the opening 35 on the other axial side (seal 9 side) is located closer to the other axial side (seal 9 side) than the fins 25b. In this embodiment, the edge of the opening 35 on one axial side (bearing 7 side) is located closer to the one axial side (bearing 7 side) than the fins 25b, but the entire width of the opening 35 may be located closer to the seal 9 side than the fins 25b.

[0063] The air discharge passage 34 extends obliquely within the bearing case 20 from an opening 35 at one end toward one axial side toward the radially outer periphery. The other end of the air discharge passage 34 opens into an end face on one axial side of the cylindrical portion 20a. In other words, an outlet 36 (see FIGS. 3 and 5) of the air discharge passage 34 opens into the reducer chamber 40a, which is outside the housing 13 of the compression section 3.

[0064] 5, in this embodiment, a plurality of air discharge passages 34 are provided in the gas turbine 1. Both the drain 26 and the plurality of air discharge passages 34 open to the second inner circumferential surface 23b of the bearing case 20. Here, the gas turbine 1 is installed on land with the axis A of the main shaft 2 oriented horizontally. In a plane perpendicular to the horizontal axis A, the second inner circumferential surface 23b is represented by a circle.

[0065] The drain 26 opens to a lower part of the second inner circumferential surface 23b. The multiple air discharge passages 34 open to a part other than the lower part. The opening 35 of each air discharge passage 34 is disposed on a horizontal line B passing through the axis A, or is disposed in a part above the horizontal line B. The openings 35 of the multiple air discharge passages 34 are disposed at intervals from each other in the circumferential direction.

[0066] In this embodiment, three drains 26 and five air discharge passages 34 are provided in the bearing case 20.

[0067] The three drains 26 include a bottom drain 26a and a pair of side drains 26b, 26c arranged on both circumferential sides of the bottom drain 26a. The bottom drain 26a has a wider opening width on the second inner circumferential surface 23b than the side drains 26b, 26c. The "opening width" refers to the central angle of an arc from one circumferential end to the other circumferential end of the opening of the drain 26, or the length of the arc.

[0068] A vertical line C that passes vertically through the axis A in a plane perpendicular to the axis A passes through the opening of the lower end drain 26a. The lower end drain 26a is located on the second inner circumferential surface 23b so as to be line-symmetrical with respect to the vertical line C when viewed in the axial direction. The pair of side drains 26b, 26c are spaced at the same interval in the circumferential direction from the lower end drain 26a and are arranged line-symmetrical with respect to the vertical line C. Both of the pair of side drains 26b, 26c are located below a horizontal line B that passes through the axis A. That is, all of the three drains 26 open to the lower part of the second inner circumferential surface 23b.

[0069] The openings 35 of the five air discharge passages 34 are arranged line-symmetrically with respect to the vertical line C. The five air discharge passages 34 include an upper end discharge passage 34a, a pair of side discharge passages 34b and 34c, and a pair of intermediate discharge passages 34d and 34e. The opening 35 of the upper end discharge passage 34a is arranged on the vertical line C and faces the lower end drain 26a in the diametric direction. The openings of the side discharge passages 34b and 34c are arranged on the horizontal line B and face each other in the diametric direction. The opening 35 of the intermediate discharge passage 34d is arranged between the upper end discharge passage 34a and the side discharge passage 34b in the circumferential direction, and the opening 35 of the intermediate discharge passage 34e is arranged between the upper end discharge passage 34a and the side discharge passage 34c in the circumferential direction. The pair of intermediate discharge passages 34d and 34e are arranged line-symmetrically with respect to the vertical line C.

[0070] In this way, the openings 35 of the five air discharge passages 34 are provided in the upper half of the second inner circumferential surface 23b, and are disposed so as to be dispersed within a range of approximately 180 degrees. The openings 35 of the five air discharge passages 34 do not need to be disposed at perfectly equal intervals in the circumferential direction.

[0071] The oil flows into the chamber 10 after being supplied to the bearing 7. The bearing 7 defines one axial side of the chamber 10 and faces the chamber 10. The flow of oil in the chamber 10 is affected by the oil's own weight. The oil tends to flow vertically downward in the chamber 10. A drain 26 is opened at the bottom of the chamber 10. Therefore, the oil is smoothly discharged to the outside of the housing 13 through the drain 26, and can be prevented from reaching the seal 9. In particular, in this embodiment, the rotor 11 is provided with fins 25b. The fins 25b act as baffles to prevent the oil from flowing to the other axial side in the chamber 10, and can further prevent the oil from reaching the seal 9.

[0072] The fins 25b are formed integrally with the sleeve 25 that is fitted onto the rotor 11. Therefore, by simply inserting the rotor 11 into the sleeve 25, the fins 25b that provide such an effect can be easily provided on the rotor 11.

[0073] On the other hand, the flow of the seal air that has flowed into the chamber 10 from the seal 9 is affected by the centrifugal force that accompanies the rotation of the rotor 11. Therefore, the seal air tends to flow toward the outer periphery in the radial direction within the chamber 10. Even if the seal air tries to flow toward one side in the axial direction, it is blocked by the fins 25b. Combined with the blocking and guidance by the fins 25b, the seal air flows toward the outer periphery in the axial direction.

[0074] A part of the seal air flows vertically downward or obliquely downward from near the outer circumferential surface of the rotor 11 and from the other axial side of the fins 25b. This seal air is discharged together with the oil to the outside of the housing 13 via the drain 26. The drain 26 opens to the second inner circumferential surface 23b that defines the radial outer circumferential side of the chamber 10. Therefore, the seal air that flows downward smoothly flows into the opening of the drain 26 and is quickly discharged from the chamber 10.

[0075] A portion of the seal air flows horizontally, vertically upward, or diagonally upward from near the outer circumferential surface of the rotor 11 and from the other axial side of the fins 25b, and reaches the second inner circumferential surface 23b. In a portion other than the lower part of the second inner circumferential surface 23b, openings 35 of a plurality of air discharge paths 34 are arranged in a dispersed manner. Therefore, the seal air flowing horizontally or upward smoothly flows into the openings 35 of the air discharge paths 34 and is quickly discharged from the chamber 10 to the outside of the housing 13. Since the openings 35 of the air discharge paths 34 are arranged closely together in the circumferential direction, the air can be smoothly discharged from the housing 13.

[0076] If such an air discharge passage 34 did not exist, the seal air flowing upward would be likely to remain for a long time inside the chamber 10. During this retention period, the seal air would be likely to flow to one side in the axial direction and reach the bearing. If foreign matter is mixed in the seal air, the foreign matter may enter the bearing 7 and impede stable operation of the bearing 7 and, ultimately, stable operation of the rotor 11.

[0077] In contrast, in this embodiment, the retention of such seal air can be prevented due to the presence of the air discharge passage 34. Therefore, the bearing 7 can be protected, and the rotor 11 can be operated stably.

[0078] The seal air uses compressed air generated in the compression section 3, and the compressed air is generated based on outside air. Therefore, if the gas turbine 1 is placed in an environment where dust is likely to be generated, for example, there is a high possibility that foreign matter such as dust will be mixed into the compressed air. In this embodiment, even if the gas turbine 1 is placed in such an environment, the bearings 7 can be protected from foreign matter.

[0079] An air cleaner is provided in the system that supplies compressed air as seal air to the seal 9. Therefore, even if foreign matter is mixed into the outside air or compressed air, the foreign matter can be removed by the air cleaner, and purified seal air can be supplied to the seal 9. This also helps protect the bearing 7.

[0080] Although the embodiment has been described above, the above configuration is merely an example, and additions, modifications, or omissions can be made within the scope of the present invention. [Explanation of symbols]

[0081] 1. Gas turbine 2 main shaft 3 Compression section 4 Combustion section 5. Turbine 5a Turbine rotor 6 Input shaft 7,8 Bearings 9 Seal 9a Outer seal part 9b Inner seal part 10. Chamber 11 Rotor 11a Journal Section 11b Step surface 11c middle part 11d Flange part 12 Impeller 13. Housing 14 Containment Space 15 Exterior Wall 15a Mounting hole 15b radial hole 15c Outlet 16 Inner wall 17 Posts 17a Axial hole 17b radial hole 18 Cover 18a Duct 19 Intake guide 20 Bearing case 20a Cylindrical part 20b Cone section 20c Straight section 20d slope part 20e Oil inlet port 20f,20g screw holes 21 Retaining ring 21a Cylindrical part 21b Flange part 21c Inlet 21d Oil supply path 22 Mounting plate 23 Shaft hole 23a 1st inner surface 23b Second inner peripheral surface 23c Step surface 23d Chamber end face 24 Bearing housing 24a Cylindrical surface 24b Step surface 25 Sleeve 25a Cylindrical part 25b Fins 26 Drain 26a Bottom drain 26b, 26c Side drain 27 Partition wall member 27a Ejection hole 28 Flow Path 29 Plug 31 Upstream flow path 31a, 31b Piping 32 Air cleaner 32a Case 32b Strainer 32c inlet 32d outlet 33 Air supply line 33a,33b Piping 33c downstream 34 Air exhaust passage 34a Upper end discharge passage 34b, 34c Side exhaust passage 34d,34e Intermediate discharge passage 35 Aperture 36 Outlet 40 Gearbox case 40a Reducer room 50 Controller 51 Primary pressure sensor 52 Secondary pressure sensor 53 On-off valve 54 Bypass valve 55 Check valve A axis

Claims

1. A rotor having an impeller; a bearing that rotatably supports the rotor; a housing having an accommodation space for accommodating the impeller and for holding the bearing; a drain that discharges the oil supplied to the bearing to the outside of the housing; an air supply passage between the rotor and the housing for supplying air to the accommodation space for sealing the bearing; an air discharge passage that discharges the air supplied from the air supply passage to the outside of the housing; A shaft seal structure for a gas turbine comprising:

2. the housing has an inner circumferential surface that surrounds an outer circumferential surface of the rotor between the bearing and the accommodation space in the axial direction, The drain opens to a lower portion of the inner circumferential surface, and the air discharge passage opens to a portion of the inner circumferential surface other than the lower portion. The shaft seal structure of a gas turbine according to claim 1.

3. A plurality of the air discharge paths are provided, and each of the plurality of air discharge paths opens onto the inner circumferential surface, The openings of the plurality of air discharge passages are circumferentially spaced apart from one another. The shaft seal structure of a gas turbine according to claim 2.

4. a fin disposed within the housing and extending radially outward from an outer circumferential surface of the rotor; The air discharge passage opens on the storage space side relative to the fin. The shaft seal structure of a gas turbine according to any one of claims 1 to 3.

5. The fins are integrally formed on a sleeve fitted to the rotor. The shaft seal structure of a gas turbine according to claim 4.

6. an air cleaner for cleaning the air before it reaches the housing; The air cleaner has a strainer. The shaft seal structure of a gas turbine according to claim 1.

7. The air cleaner is disposed outside the housing. A shaft seal structure for a gas turbine according to claim 6.

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