Power turbine rear bearing cavity self-balancing high reliability seal structure

Abstract

The application belongs to the field of aero-engine sealing design, and relates to a self-balancing high-reliability sealing structure of a power turbine rear bearing cavity, which comprises a bearing assembly, a bearing casing, a cavity sealing ring and a power turbine shaft; the cavity sealing ring comprises a fifth sealing ring and a sixth sealing ring, an unloading cavity is arranged between the fifth sealing ring and the cavity sealing ring, a pressurizing cavity is arranged between the sixth sealing ring and the cavity sealing ring, and the unloading cavity and the pressurizing cavity are communicated with each other through a vent hole. A third vent hole is arranged at the front end of the power turbine shaft and communicated with a front sealing cavity, a fourth vent hole is arranged at the rear end of the power turbine shaft and communicated with a rear sealing cavity, the front sealing cavity and the rear sealing cavity are communicated through the third vent hole, the fourth vent hole and an axial vent cavity, and when the air pressure in the front sealing cavity and the rear sealing cavity is unbalanced, the sealing air will flow into the cavity with smaller air pressure, so that the air pressure in the front sealing cavity and the rear sealing cavity is balanced, and the reliability of the sealing flow path is improved.

Description

Technical Field

[0001] This application belongs to the field of aero-engine sealing design, and specifically relates to a self-balancing high-reliability sealing structure for the rear bearing cavity of a power turbine. Background Technology

[0002] One of the important functions of the gas turbine air system is to design a sealed flow path in the bearing cavity to prevent lubricating oil in the bearing cavity from leaking into the internal chambers of the gas turbine outside the bearing cavity, causing contamination of components such as the disc and shaft, and even posing a fire risk. Alternatively, the lubricating oil may cause changes in rotor imbalance, leading to gas turbine vibration and safety hazards.

[0003] Generally, the rear bearing cavity of a power turbine has two sealing cavities at its front and rear ends. The front sealing cavity is connected to the rear cavity of the final stage disk of the power turbine, while the rear sealing cavity is connected to the outside atmosphere. The conventional sealing scheme for the rear bearing cavity of a power turbine is as follows: a high-pressure gas from the intermediate stage of the compressor is introduced as the sealing gas. After passing through the rear casing of the power turbine bearing via a pipeline, it is divided into two branches, flowing in the front and rear directions respectively, and reaching the front and rear sealing cavities to achieve front and rear sealing of the bearing cavity and prevent lubricating oil leakage.

[0004] However, when the pressure in the cavity behind the final stage of the power turbine is high, the high-pressure gas behind the final stage of the power turbine enters the adjacent front sealing cavity through the grate seal, causing the front sealing cavity to have a high pressure. During actual testing, the high-pressure gas in the front sealing cavity blows the lubricating oil vapor in the bearing cavity through the bearing cavity sealing structure and leaks from the low-pressure side, resulting in increased lubricating oil consumption and the output shaft being contaminated by the leaked lubricating oil.

[0005] As gas turbine power increases, the pressure in the cavity behind the last-stage disk of the power turbine also rises continuously, reaching 800 kPa in some gas turbines, while the external atmospheric pressure connected to the rear sealing cavity is 100 kPa. Given the significant pressure difference between the cavities connected to the front and rear ends of the bearing cavity, designing a sealing flow path to achieve the sealing function of the bearing cavity is a major challenge in the design of the sealing flow path for the rear bearing cavity of the power turbine. Summary of the Invention

[0006] The purpose of this application is to provide a self-balancing, high-reliability sealing structure for the rear bearing cavity of a power turbine, in order to solve the problem that the existing rear sealing cavity has a large pressure difference with the outside atmosphere and is prone to oil leakage.

[0007] The technical solution of this application is: a self-balancing high-reliability sealing structure for the rear bearing cavity of a power turbine, comprising a bearing assembly, a bearing housing, a cavity sealing ring, and a power turbine shaft; the bearing assembly is located inside the cavity sealing ring, and the bearing assembly has a bearing cavity inside; the cavity sealing ring has a sealing cavity inside, and the cavity sealing ring has a turbine disk rear cavity inside; the cavity sealing ring includes a fifth sealing ring and a sixth sealing ring, and the sealing cavity includes a front sealing cavity and a rear sealing cavity; the sealing gas of the intermediate stage of the compressor flows into the front sealing cavity and the rear sealing cavity respectively after passing through the support plate of the rear housing of the power bearing; an unloading cavity is provided between the fifth sealing ring and the cavity sealing ring, and a pressurizing cavity is provided between the sixth sealing ring and the cavity sealing ring; the outside of the sixth sealing ring is the outside atmosphere; a vent is provided on the bearing housing; and the unloading cavity and the pressurizing cavity are interconnected through the vent.

[0008] Preferably, the bearing housing includes a front bearing housing and a rear bearing housing, and the front and rear bearing housings form an exhaust chamber with the bearing assembly. The front bearing housing has a first vent hole that communicates with the exhaust chamber and the unloading chamber. The rear bearing housing has a second vent hole that communicates with the exhaust chamber and the pressurization chamber. An exhaust pipe is provided inside the exhaust chamber.

[0009] Preferably, the bearing assembly includes a ball bearing, an inner ring of the ball bearing, an outer ring of the ball bearing, a roller bearing, an inner ring of the roller bearing, and an outer ring of the roller bearing; the inner ring of the ball bearing is connected to the power turbine shaft, the outer ring of the ball bearing is connected to the front housing of the bearing, the balls are connected between the inner ring of the ball bearing and the outer ring of the ball bearing, and a bearing cavity is formed between the ball bearing, the inner housing, and the power turbine shaft; the inner ring of the roller bearing is connected to the power turbine shaft, the outer ring of the roller bearing is connected to the bearing housing, and the roller bearing is located in the bearing cavity; the power turbine shaft is a hollow shaft, the hollow shaft cavity is a shaft venting cavity, the front end of the power turbine shaft has a third vent hole communicating with the front sealing cavity, the rear end of the power turbine shaft has a fourth vent hole communicating with the rear sealing cavity, the front end of the inner ring of the ball bearing has a first sealing tooth communicating with the front sealing cavity, and the rear end of the inner ring of the roller bearing has a second sealing tooth communicating with the rear sealing cavity.

[0010] Preferably, the cavity sealing ring further includes a first sealing ring, a second sealing ring, a third sealing ring, and a fourth sealing ring. The front bearing housing is bolted to the first sealing ring, the third sealing ring, and the fifth sealing ring, respectively. The rear bearing housing is bolted to the second sealing ring, the fourth sealing ring, and the sixth sealing ring, respectively, and a stop fit is formed at the connection. Furthermore, the front bearing housing and the rear bearing housing are bolted together.

[0011] Preferably, the sealing air supply pipe assembly further includes a front sealing pipe and a rear sealing pipe; a sealing air duct is provided inside the rear housing of the power bearing, the sealing air duct, the front sealing pipe, and the rear sealing pipe are connected to each other, a third sealing grate is provided between the third sealing ring and the power turbine shaft, a front cooling hole communicating with the front sealing cavity is provided inside the front housing of the bearing, the front cooling hole is connected to the front sealing pipe; a fourth sealing grate is provided between the fourth sealing ring and the power turbine shaft, a rear cooling hole communicating with the rear sealing cavity is provided inside the rear housing of the bearing, the rear cooling hole is connected to the rear sealing pipe.

[0012] Preferably, multiple sets of three-way connectors are evenly distributed circumferentially on the outer wall of the bearing front casing, and the sealing air vent pipe, the front sealing pipe and the rear sealing pipe are respectively connected to the three interfaces of the three-way connectors.

[0013] This application discloses a self-balancing, high-reliability sealing structure for the rear bearing cavity of a power turbine, comprising a bearing assembly, a bearing housing, a sealing air supply pipe assembly, sealing grates, a cavity sealing ring, an exhaust pipe, and a power turbine shaft. The bearing assembly is located inside the cavity sealing ring, and a bearing cavity is provided inside the bearing assembly. A sealing cavity is provided inside the cavity sealing ring, and a turbine disk rear cavity is provided inside the cavity sealing ring. The cavity sealing ring includes a fifth sealing ring and a sixth sealing ring. An unloading cavity is provided between the fifth sealing ring and the cavity sealing ring, and a pressurizing cavity is provided between the sixth sealing ring and the cavity sealing ring. The unloading cavity and the pressurizing cavity are interconnected through a vent hole. The power turbine shaft is a hollow shaft, and the hollow shaft cavity is a shaft ventilation cavity. The front end of the power turbine shaft has a third vent hole that communicates with the front sealing cavity, and the rear end of the power turbine shaft has a fourth vent hole that communicates with the rear sealing cavity. The front sealing cavity and the rear sealing cavity are connected through the third vent hole, the fourth vent hole, and the shaft ventilation cavity. When the air pressure in the front sealing cavity and the rear sealing cavity is unbalanced, the sealing air will flow into the cavity with lower air pressure, thereby achieving air pressure balance in the front sealing cavity and the rear sealing cavity. This avoids oil leakage caused by a large pressure difference between the front and rear sealing cavities and improves the reliability of the sealing flow path. Attached Figure Description

[0014] 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.

[0015] Figure 1 This application specifies the bleed air section for sealing the flow path of the rear bearing cavity of the power turbine.

[0016] Figure 2 This application specifies the exhaust section sealing flow path for the rear bearing cavity of the power turbine.

[0017] 1. Bearing cavity; 2. Turbine disc rear cavity; 3. Fifth sealing ring; 4. Sixth sealing ring; 5. Front sealing cavity; 6. Rear sealing cavity; 7. Unloading cavity; 8. Pressurization cavity; 9. Bearing front housing; 10. Bearing rear housing; 11. First vent; 12. Second vent; 13. Centerline; 14. Shaft vent cavity; 16. Fourth vent; 15. Third vent; 17. First sealing grate; 18. Second sealing grate; 19. Exhaust valve 20. Trachea; 21. Inner ring of roller bearing; 22. Outer ring of roller bearing; 23. First sealing ring; 24. Second sealing ring; 25. Power turbine shaft; 26. Inner ring of ball bearing; 27. Outer ring of ball bearing; 28. Third sealing ring; 29. ​​Fourth sealing ring; 30. Front sealing tube; 31. Rear sealing tube; 32. Sealing vent tube; 33. Three-way connector; 34. Exhaust chamber; 35. Third sealing grate; 36. Fourth sealing grate. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] A self-balancing, high-reliability sealing structure for the rear bearing cavity of a power turbine is proposed. The reason why existing sealing solutions for the rear bearing of power turbines have the risk of oil leakage is mainly due to the large pressure difference between the sealing cavities on the front and rear sides of the bearing cavity, which causes the lubricating oil in the bearing cavity to leak from the high-pressure side to the low-pressure side.

[0020] For this reason, this application reduces the pressure difference and prevents lubricating oil leakage by maintaining the connection between the front sealing cavity and the rear sealing cavity. The specific design is as follows:

[0021] like Figure 1-2 As shown, it includes a bearing assembly, a bearing housing, a sealing air supply pipe assembly, a cavity sealing ring, an exhaust air pipe 19, and a power turbine shaft 24; the bearing assembly is located inside the cavity sealing ring, the bearing assembly has a bearing cavity 1 inside, the cavity sealing ring has a sealing cavity inside, and the cavity sealing ring has a turbine disk rear cavity 2 inside.

[0022] The diaphragm sealing ring includes a fifth sealing ring 3 and a sixth sealing ring 4. The sealing cavity includes a front sealing cavity 5 and a rear sealing cavity 6. The sealing gas of the intermediate stage of the compressor flows into the front sealing cavity 5 and the rear sealing cavity 6 respectively after passing through the support plate of the power bearing and the casing. An unloading cavity 7 is provided between the fifth sealing ring 3 and the diaphragm sealing ring. A pressurizing cavity 8 is provided between the sixth sealing ring 4 and the diaphragm sealing ring. The outside of the sixth sealing ring 4 is the outside atmosphere. A vent is provided on the bearing casing. The unloading cavity 7 and the pressurizing cavity 8 are connected to each other through the vent.

[0023] When the sealing gas from the intermediate stage of the compressor flows into the sealing structure, it splits into two streams. One stream flows into the front sealing chamber 5 and the other stream flows into the rear sealing chamber 6. Part of the sealing gas flowing into the front sealing chamber 5 flows into the unloading chamber 7 and the other part flows into the bearing chamber 1. Part of the sealing gas flowing into the rear sealing chamber flows into the boosting chamber 8 and the other part flows into the bearing chamber 1.

[0024] Both the unloading chamber 7 and the pressurizing chamber 8 are back pressure chambers. They are connected through the first vent 11, the second vent 12, and the exhaust chamber 33, ensuring that the pressure in the back pressure chambers of the front sealing chamber 5 (unloading chamber 7) and the rear sealing chamber 6 (pressurizing chamber 8) is equal. The front sealing chamber 5 and the rear sealing chamber 6 are connected through the third vent, the fourth vent, and the axial venting chamber, ensuring that their pressures are equal. The connection between the front and rear sealing chambers of the bearing chamber 1 ensures pressure self-balancing. The connection between the back pressure chambers of the sealing chambers other than the bearing chamber 1 (i.e., unloading chamber 7 and pressurizing chamber 8) ensures pressure self-balancing of the back pressure chambers of the sealing chambers, thus preventing oil leakage caused by a large pressure difference between the front and rear sealing chambers and improving the reliability of the sealing flow path.

[0025] Preferably, the bearing assembly includes a ball bearing, a ball bearing inner ring, a ball bearing outer ring, a roller bearing, a roller bearing inner ring 20, and a roller bearing outer ring 21; the ball bearing inner ring 25 is connected to the power turbine shaft 24, the ball bearing outer ring 26 is connected to the bearing front housing 9, the balls are connected between the ball bearing inner ring 25 and the ball bearing outer ring 26, and a bearing cavity 1 is formed between the ball bearing, the inner housing, and the power turbine shaft 24; the roller bearing inner ring 20 is connected to the power turbine shaft 24, and the roller bearing outer ring 21 is connected to... The bearing is connected to the rear housing, the roller bearing is located in the bearing cavity 1, the power turbine shaft 24 is a hollow shaft, the shaft cavity is the shaft ventilation cavity 14, the front end of the power turbine shaft 24 is provided with a third ventilation hole 15 communicating with the front sealing cavity 5, the rear end of the power turbine shaft 24 is provided with a fourth ventilation hole 16 communicating with the rear sealing cavity, the front end of the inner ring 25 of the ball bearing is provided with a first sealing tooth 17 communicating with the front sealing cavity 5, and the rear end of the inner ring 20 of the roller bearing is provided with a second sealing tooth 18 communicating with the rear sealing cavity 6.

[0026] When the air pressure in the front sealing chamber 5 and the rear sealing chamber 6 is unbalanced, the air pressure in the front sealing chamber 5 is generally higher. At this time, the sealing air in the front sealing chamber 5 will enter the shaft ventilation chamber 14 through the third vent hole, cooling the power turbine shaft 24 and bearing chamber 1 along the way. Then, it will enter the rear sealing chamber 6 through the fourth vent hole and be discharged into the unloading chamber 7 or bearing chamber 1 together, realizing a dual sealing air circulation, thereby further improving the air pressure balance between the front sealing chamber 5 and the rear sealing chamber 6.

[0027] Preferably, multiple sets of T-connectors 32 are evenly distributed circumferentially on the outer wall of the inner casing, and the sealing cooling pipe 31, the front sealing pipe 29, and the rear sealing pipe 30 are respectively connected to the three interfaces of the T-connectors 32 to ensure the stability of the sealing airflow.

[0028] The exhaust pipe 19 and the sealing cooling pipe 31 are staggered in the circumferential direction of the bearing rear casing 10, and each occupies a different power turbine rear casing support plate. The bearing casing and the power turbine rear casing form an exhaust chamber. Figure 2 As shown.

[0029] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0030] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0031] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-balancing, high-reliability sealing structure for the rear bearing cavity of a power turbine, comprising a bearing assembly, a bearing housing, a sealing air supply pipe assembly, a cavity sealing ring, and a power turbine shaft (24); the bearing assembly is disposed inside the cavity sealing ring, the bearing assembly has a bearing cavity (1), the cavity sealing ring has a sealing cavity, and the cavity sealing ring has a turbine disk rear cavity (2); characterized in that: The cavity sealing ring includes a fifth sealing ring (3) and a sixth sealing ring (4). The sealing cavity includes a front sealing cavity (5) and a rear sealing cavity (6). The sealing gas of the intermediate stage of the compressor flows into the front sealing cavity (5) and the rear sealing cavity (6) respectively after passing through the support plate of the power bearing rear casing. An unloading cavity (7) is provided between the fifth sealing ring (3) and the cavity sealing ring. A pressurizing cavity (8) is provided between the sixth sealing ring (4) and the cavity sealing ring. The outside of the sixth sealing ring (4) is the outside atmosphere. A vent is provided on the bearing casing. The unloading cavity (7) and the pressurizing cavity (8) are connected to each other through the vent. The bearing housing includes a front bearing housing (9) and a rear bearing housing (10). The front bearing housing (9) and the rear bearing housing (10) form an exhaust gas chamber (33) with the bearing assembly. The front bearing housing (9) is provided with a first vent hole (11), which is connected to the exhaust gas chamber (33) and the unloading chamber (7). The rear bearing housing (10) is provided with a second vent hole (12), which is connected to the exhaust gas chamber (33) and the pressurization chamber (8). An exhaust gas pipe (19) is provided in the exhaust gas chamber (33). The bearing assembly includes a ball bearing, a ball bearing inner ring, a ball bearing outer ring, a roller bearing, a roller bearing inner ring (20), and a roller bearing outer ring (21). The ball bearing inner ring (25) is connected to the power turbine shaft (24), and the ball bearing outer ring (26) is connected to the bearing front housing (9). The balls are connected between the ball bearing inner ring (25) and the ball bearing outer ring (26). A bearing cavity (1) is formed between the ball bearing, the inner housing, and the power turbine shaft (24). The roller bearing inner ring (20) is connected to the power turbine shaft (24), and the roller bearing outer ring (21) is connected to the bearing front housing (9). The casing is connected, the roller bearing is located in the bearing cavity (1), the power turbine shaft (24) is a hollow shaft, the shaft cavity is the shaft ventilation cavity (14), the front end of the power turbine shaft (24) is provided with a third ventilation hole (15) communicating with the front sealing cavity (5), the rear end of the power turbine shaft (24) is provided with a fourth ventilation hole (16) communicating with the rear sealing cavity, the front end of the inner ring (25) of the ball bearing is provided with a first sealing tooth (17) communicating with the front sealing cavity (5), and the rear end of the inner ring (20) of the roller bearing is provided with a second sealing tooth (18) communicating with the rear sealing cavity (6); The cavity sealing ring further includes a first sealing ring (22), a second sealing ring (23), a third sealing ring (27), and a fourth sealing ring (28). The front bearing housing (9) is connected to the first sealing ring (22), the third sealing ring (27), and the fifth sealing ring (3) by bolts. The rear bearing housing (10) is connected to the second sealing ring (23), the fourth sealing ring (28), and the sixth sealing ring (4) by bolts, and a stop fit is formed at the connection. The front bearing housing and the rear bearing housing are connected by bolts.

2. The self-balancing high-reliability sealing structure for the rear bearing cavity of the power turbine as described in claim 1, characterized in that: The sealing air supply pipe assembly also includes a front sealing pipe (29) and a rear sealing pipe (30); a sealing air intake pipe (31) is provided inside the rear housing of the power bearing, and the sealing air intake pipe (31), the front sealing pipe (29) and the rear sealing pipe (30) are connected to each other. A third sealing grate (34) is provided between the third sealing ring (27) and the power turbine shaft (24). A front cooling hole communicating with the front sealing cavity (5) is opened inside the bearing front housing (9), and the front cooling hole is connected to the front sealing pipe (29). A fourth sealing grate (35) is provided between the fourth sealing ring (28) and the power turbine shaft (24). A rear cooling hole communicating with the rear sealing cavity (6) is opened inside the bearing rear housing (10), and the rear cooling hole is connected to the rear sealing pipe (30).

3. The self-balancing high-reliability sealing structure for the rear bearing cavity of the power turbine as described in claim 2, characterized in that: The outer wall of the bearing front casing is provided with multiple sets of three-way connectors (32) evenly distributed along the circumference. The sealing air vent (31), the front sealing pipe (29) and the rear sealing pipe (30) are respectively connected to the three interfaces of the three-way connectors (32).

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