An improved shaft seal structure for a packing bushing

Abstract

The application provides an improved shaft seal structure of a sealing bush, comprising a sealing bush, a high-pressure shaft, and a sealing track, a graphite ring, a back ring and a wave spring arranged between the sealing bush and the high-pressure shaft, wherein the sealing track comprises a first sealing track and a second sealing track, the first sealing track is fixedly installed at an end of the high-pressure shaft to axially limit the second sealing track, the back ring and the graphite ring; wherein the sealing bush comprises a bush shell, a graphite track, an end cover and a compression spring assembly, a groove is arranged on an inner surface of the bush shell, the compression spring assembly is arranged in the groove, the graphite track is assembled on the inner surface of the bush shell to cooperate with the graphite ring for sealing, and the graphite track and the compression spring assembly are interference-fitted on the inner surface of the bush shell through the end cover.

Description

Technical Field

[0001] This application belongs to the field of sealing technology, and specifically relates to an improved inter-shaft sealing structure for sealing bushings. Background Technology

[0002] As the thrust-to-weight ratio, pressure ratio, and temperature ratio of aero-engines continue to increase, the linear velocity, sealing pressure differential, and operating temperature of the main shaft seals are also constantly increasing, leading to increasingly harsh operating conditions. In advanced aero-engines, the high-pressure turbine is typically supported on top of the low-pressure turbine, limiting the space available for the bearing cavity seal and necessitating the use of compact inter-shaft sealing devices. Furthermore, the high sealing pressure differential in advanced aero-engines means that traditional non-contact grate seals would result in high bearing cavity temperatures and excessive oil consumption, causing significant performance losses for the engine.

[0003] Currently, the inter-shaft seal employs a floating film inter-shaft seal structure. This structure consists of two graphite ring floats, a sealing raceway, and a sealing bushing. During operation, the sealing raceway rotates with the high-pressure shaft, the sealing bushing rotates with the low-pressure shaft, and the graphite rings rotate at a specific speed of the high- and low-pressure rotors. The end faces of the graphite rings and the sealing raceway form the primary sealing surfaces, while the outer diameter of the graphite rings and the inner surface of the sealing bushing form the secondary sealing surfaces, thus achieving the sealing function of the inter-shaft seal. The sealing bushing is made of metal, while the sealing rings are made of graphite. Graphite is coated at the mating point between the sealing bushing and the sealing ring to reduce the coefficient of friction. The linear expansion coefficient of metal is approximately three times that of graphite. During operation, under high temperature and centrifugal force, a large gap may form between the sealing bushing and the outer diameter of the graphite ring, increasing leakage and causing failure of the secondary sealing surfaces. Summary of the Invention

[0004] The purpose of this application is to provide an improved inter-shaft sealing structure for sealing bushings to solve or mitigate at least one of the problems in the prior art.

[0005] The technical solution of this application is: an improved inter-shaft sealing structure for sealing bushings, comprising:

[0006] Sealing bushing;

[0007] High-pressure shaft; and

[0008] A sealing runway, graphite ring, back ring, and wave spring are provided between the sealing bushing and the high-pressure shaft. The sealing runway includes a first sealing runway and a second sealing runway. The first sealing runway is fixedly installed at the end of the high-pressure shaft to axially limit the second sealing runway, back ring, and graphite ring.

[0009] The sealing bushing includes a bushing housing, a graphite raceway, an end cap, and a compression spring assembly. The inner surface of the bushing housing is provided with a groove, and the compression spring assembly is disposed in the groove. The graphite raceway is assembled on the inner surface of the bushing housing to cooperate with the graphite ring for sealing. The graphite raceway and the compression spring assembly are interference-fitted on the inner surface of the bushing housing through the end cap.

[0010] In a preferred embodiment of this application, the inter-shaft sealing structure further includes an anti-rotation pin and a retaining ring. The retaining ring is installed inside the high-pressure shaft, and the anti-rotation pin passes through the retaining ring, the high-pressure shaft, and the first sealing track to circumferentially limit the three.

[0011] In a preferred embodiment of this application, a groove is provided on the high-pressure shaft at the position adapted to the second sealing track, and a rubber ring is provided in the groove. The sealing is achieved by the rubber ring cooperating with the second sealing track.

[0012] In a preferred embodiment of this application, the graphite ring includes a first graphite ring and a second graphite ring, which are disposed on both sides of the second sealed runway.

[0013] In a preferred embodiment of this application, the end cap and the bushing housing are fixed by welding.

[0014] In a preferred embodiment of this application, the end cap is provided with an axial boss, and the graphite track is provided with an axial groove adapted to the axial boss. The axial clearance between the axial boss and the axial groove prevents the circumferential rotation of the graphite track.

[0015] In a preferred embodiment of this application, the graphite ring and the graphite track are made of the same graphite material.

[0016] In a preferred embodiment of this application, the graphite material is carbon fiber reinforced graphite material.

[0017] In a preferred embodiment of this application, the compression spring assembly includes a spring and a spring retainer ring. The spring retainer ring is U-shaped, and the spring is disposed in the U-shaped groove of the spring retainer ring. Before assembly, the U-shaped opening of the spring retainer ring is a straight structure, and after assembly, the U-shaped opening of the spring retainer ring is a closed structure.

[0018] In a preferred embodiment of this application, the compression spring assembly has an open structure.

[0019] The shaft sealing structure provided in this application solves the matching problem between the graphite ring and the metal sealing bushing in the shaft sealing by improving the sealing bushing, ensuring the minimum radial clearance of the secondary seal during the operation of the shaft sealing, reducing the leakage of the shaft sealing, and ensuring the reliability and low leakage of the shaft sealing. Attached Figure Description

[0020] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0021] Figure 1 This is a schematic diagram of the inter-shaft sealing structure of this application.

[0022] Figure 2 This is a schematic diagram of the sealing bushing structure in this application.

[0023] Figure 3 For based on Figure 2 A-direction view.

[0024] Figure 4 This is an overall view of the compression spring assembly in this application.

[0025] Figure 5 For based on Figure 4 BB section view.

[0026] Figure 6 For based on Figure 5 View from C. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0028] To address the problem in existing technologies where the significant difference in the linear expansion coefficients of the sealing bushing and the sealing ring leads to a large gap during operation, resulting in increased leakage and secondary sealing surface failure, this application proposes an inter-shaft sealing structure employing a composite sealing bushing. This structure combines a ring-shaped structure made of the same material as the graphite ring with a metal reinforcement structure. This design not only minimizes contact friction during operation but also ensures that both materials have the same coefficient of thermal expansion, maintaining a minimum radial sealing gap under various operating conditions to guarantee the performance of the inter-shaft seal.

[0029] like Figure 1 As shown, the inter-shaft sealing structure of this application includes a sealing bushing 1, a high-pressure shaft 2, a sealing raceway 3, a back ring 4, a graphite ring 5, an anti-rotation pin 7, a fixing ring 8, a rubber ring 9, and a wave spring 10.

[0030] The high-pressure shaft 2 is mounted on the outer ring 6 of the bearing. The sealing raceway 3, back ring 5, and graphite ring 5 are located between the high-pressure shaft 2 and the sealing bushing 1, and are all mounted on the high-pressure shaft 2. The sealing raceway 3 includes a first sealing raceway 31 and a second sealing raceway 32. The second sealing raceway 31 is mounted on the high-pressure shaft 2, and the first sealing raceway 31 is located at the end of the high-pressure shaft 2. It is locked to the high-pressure shaft 2 by a threaded structure, thereby axially limiting the first sealing raceway 31, the back ring 4, and the graphite ring 5. The fixing ring 8 is installed inside the high-pressure shaft 2 and close to the outer ring 6 of the bearing. The anti-rotation pin 7 passes through the fixing ring 8, the high-pressure shaft 2, and the first sealing raceway 31, thereby circumferentially limiting the three. The wave spring 10 is located between the boss of the high-pressure shaft 2 and the back ring 4. The compression height of the wave spring 10 is ensured by the locking of the first sealing raceway 31 to the high-pressure shaft 2.

[0031] The sealing bushing 1 is bolted to the low-pressure shaft (not shown). During operation, the sealing bushing 1 rotates with the low-pressure shaft, while the other structural components (except for the graphite ring 5) rotate with the high-pressure shaft. The graphite ring 5 rotates at a certain speed between the high and low-pressure shafts to achieve a seal.

[0032] Specifically, a groove is provided on the high-pressure shaft 2 at the position where the second sealing track 32 is adapted, and a rubber ring 9 is provided in the groove. The sealing is achieved by the rubber ring 9 cooperating with the second sealing track 32.

[0033] In some embodiments of this application, there are two graphite rings 5, including a first graphite ring 51 and a second graphite ring 52, which are disposed on both sides of the second sealed runway 32.

[0034] like Figure 2 As shown, the sealing bushing 1 mainly consists of a bushing housing 11, a graphite raceway 12, an end cap 13, and a compression spring assembly 14. The inner end face of the bushing housing 11 has at least one circumferential groove, and the compression spring assembly 14 is disposed in the groove. The graphite raceway 12 is assembled onto the inner surface of the bushing housing 11 to cooperate and seal with the graphite ring 5, and the fit between the graphite raceway 12 and the compression spring assembly 14 is interference-fit. The end cap 13 is disposed at the end of the graphite raceway 12, and the end cap 13 is fixed to the bushing housing 11 by welding 15 after assembly. In a preferred embodiment of this application, there are two grooves on the bushing housing 11, roughly distributed at both ends of the graphite raceway 12, thereby providing stable support for the graphite raceway 12.

[0035] like Figure 3 As shown, the end cap 13 is provided with an axial boss 16, and the graphite track 12 is provided with an axial groove 17 that is adapted to the axial boss 16. During assembly, the axial boss 16 and the axial groove 17 are matched and a certain distance S is maintained, thereby preventing the circumferential rotation of the graphite track 12.

[0036] In a preferred embodiment of this application, the graphite ring 5 and the graphite track 12 are made of the same graphite material, preferably carbon fiber reinforced graphite material.

[0037] like Figures 4 to 6 As shown, the compression spring assembly 14 includes a spring 141 and a spring retaining ring 142. The spring retaining ring 142 is U-shaped, and the spring 141 is disposed in the U-shaped groove of the spring retaining ring 142. Before assembly, the U-shaped opening of the spring retaining ring 142 is a straight structure. After assembly, the retaining ring of the spring retaining ring 142 is closed by tooling.

[0038] In this application, the compression spring assembly 14 is an open structure with an opening gap h to accommodate deformation during operation.

[0039] During operation, the sealing bushing 1 rotates with the low-pressure shaft, while the graphite ring 5 rotates at a certain speed between the high and low-pressure shafts. Since the graphite ring 5 and the graphite raceway 12 are made of the same material, not only is minimal contact friction ensured during operation, but they also share the same coefficient of thermal expansion, guaranteeing a minimum radial sealing gap under various operating conditions and ensuring the performance of the shaft seal. Due to the influence of temperature and rotational speed, a gap may form between the graphite raceway 12 (with its low coefficient of thermal expansion) and the bushing housing 11. Because the graphite raceway 12 and the compression spring assembly 14 are in an interference fit, even if a gap exists between the graphite raceway 12 and the bushing housing 11, the spring force provided by the compression spring assembly 14 can apply a full-turn radial force to the graphite raceway 12, thereby achieving radial centering of the graphite raceway 12 and ensuring a small-gap fit between the graphite raceway 12 and the graphite ring 5 during operation.

[0040] The improved sealing bushing shaft sealing structure provided in this application solves the matching problem between the graphite ring and the metal sealing bushing in the shaft seal by improving the sealing bushing, ensuring the minimum radial clearance of the secondary seal during the operation of the shaft seal, reducing the leakage of the shaft seal, and ensuring the reliability and low leakage of the shaft seal.

[0041] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An improved inter-shaft sealing structure for a sealing bushing, characterized in that, include: Sealing bushing (1); High-pressure shaft (2); as well as A sealing runway (3), a graphite ring (5), a back ring (4), and a wave spring (10) are provided between the sealing bushing (1) and the high-pressure shaft (2). The sealing runway (3) includes a first sealing runway (31) and a second sealing runway (32). The first sealing runway (31) is fixedly installed at the end of the high-pressure shaft (2) to axially limit the second sealing runway (32), the back ring (4), and the graphite ring (5). The sealing bushing (1) includes a bushing housing (11), a graphite track (12), an end cap (13), and a compression spring assembly (14). The inner surface of the bushing housing (11) is provided with a first groove, and the compression spring assembly (14) is disposed in the first groove. The graphite track (12) is assembled on the inner surface of the bushing housing (11) to cooperate with the graphite ring (5) for sealing. The graphite track (12) and the compression spring assembly (14) are interference-fitted on the inner surface of the bushing housing (11) through the end cap (13).

2. The improved inter-shaft sealing structure of the sealing bushing as described in claim 1, characterized in that, It also includes an anti-rotation pin (7) and a fixing ring (8), the fixing ring (8) being installed inside the high-pressure shaft (2), and the anti-rotation pin (7) passing through the fixing ring (8), the high-pressure shaft (2) and the first sealing runway (31) to circumferentially limit the three.

3. The improved inter-shaft sealing structure of the sealing bushing as described in claim 1, characterized in that, The high-pressure shaft (2) is provided with a second groove at the position adapted to the second sealing track (32), and a rubber ring (9) is provided in the second groove. The sealing is achieved by the rubber ring (9) cooperating with the second sealing track (32).

4. The improved inter-shaft sealing structure of the sealing bushing as described in claim 1, characterized in that, The graphite ring (5) includes a first graphite ring (51) and a second graphite ring (52), which are disposed on both sides of the second sealed runway (32).

5. The improved inter-shaft sealing structure of the sealing bushing as described in claim 1, characterized in that, The end cap (13) and the bushing housing (11) are fixed by welding.

6. The improved inter-shaft sealing structure of the sealing bushing as described in claim 1, characterized in that, The end cap (13) is provided with an axial boss (16), and the graphite track (12) is provided with an axial groove (17) adapted to the axial boss (16). The axial clearance between the axial boss (16) and the axial groove (17) prevents the circumferential rotation of the graphite track (12).

7. The improved inter-shaft sealing structure of the sealing bushing as described in claim 1, characterized in that, The graphite ring (5) and the graphite track (12) are made of the same graphite material.

8. The improved inter-shaft sealing structure of the sealing bushing as described in claim 7, characterized in that, The graphite material is carbon fiber reinforced graphite material.

9. The improved inter-shaft sealing structure of the sealing bushing as described in claim 7, characterized in that, The compression spring assembly (14) includes a spring (141) and a spring retainer (142). The spring retainer (142) is U-shaped, and the spring (141) is disposed in the U-shaped groove of the spring retainer (142). Before assembly, the U-shaped opening of the spring retainer (142) is a straight structure, and after assembly, the U-shaped opening of the spring retainer (142) is a closed structure.

10. The improved inter-shaft sealing structure of the sealing bushing as described in claim 9, characterized in that, The compression spring assembly (14) has an open structure.

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