Air supply system of gas turbine bearing sealing cavity

Abstract

The invention provides an air supply system of a gas turbine bearing sealing cavity. Comprising a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine, a power turbine, a low-pressure compressor front bearing cavity, a transition section bearing cavity, a high-pressure compressor rear bearing cavity, a low-pressure turbine supporting ring bearing cavity and a power turbine supporting ring bearing cavity. Sealing air cooled by the three gas-liquid air coolers flows through the four bearing cavity runners, the two cold air surrounding cavities and the inner hole of the output shaft and then flows into a bearing sealing cavity, heat generated in the bearing cavity of the gas turbine can be reduced, and due to the adoption of a reasonable air supply system, the heat generated in the bearing cavity of the gas turbine can be reduced. Therefore, heat convection between high-temperature air outside the bearing cavity and the wall surface of the cavity can be effectively isolated, and the temperature of the wall surface of the bearing cavity is effectively cooled, so that heat convection between the wall surface of the bearing cavity and lubricating oil and oil gas in the cavity is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of gas turbines, and in particular relates to an air supply system for a bearing sealing cavity of a gas turbine. Background Art

[0002] The gas turbine device is a high-speed rotating power machine that uses a continuously flowing gas as a working fluid to drive the impeller to rotate at high speed, converting the energy of the fuel into useful work. The gas turbine rotor is mostly supported by rolling bearings. As the temperature, speed and heat load before the gas turbine turbine continue to increase, in order to ensure the normal operation of the rolling bearings, the lubricating oil system and the main bearing cavity sealing technology are particularly important.

[0003] The existing three-shaft gas turbine device has five bearing cavities, namely the front bearing cavity of the low-pressure compressor, the bearing cavity of the transition section, the rear bearing cavity of the high-pressure compressor, the bearing cavity of the low-pressure turbine support ring, and the bearing cavity of the power turbine support ring. Since the cavity sizes of the rear bearing cavity of the high-pressure compressor, the bearing cavity of the low-pressure turbine support ring, and the bearing cavity of the power turbine support ring are relatively small and are located in the high-temperature area of ​​the gas turbine, the oil inlet, the sealing air, and the ambient temperature are relatively high. In order to prevent the leakage of the lubricating oil in the bearing cavity, it is necessary to introduce compressed air from the transition section to the sealing cavity of the bearing cavity. Due to the air pressure The temperature after shrinkage is relatively high, and the high-temperature sealing air enters the bearing cavity through the sealing device to mix with the oil and gas, causing the lubricating oil in the cavity to heat up and evaporate to form an oil-gas mixture with a certain temperature and pressure. Due to the high temperature of the sealing air, when the high-temperature air flows through the bearing cavity flow channel, the cavity flow channel is wrapped by the hot air of the high-temperature air, and then this part of the air enters the bearing cavity from the sealing device, thereby bringing a certain amount of heat to the lubricating oil in the bearing cavity, causing the temperature of the lubricating oil and oil and gas in the bearing cavity to rise, and the wind resistance of the bearing rotation to increase, while also increasing the adverse effects of heat generation at the sealing device. Summary of the invention

[0004] The present invention aims to provide an air supply system for a gas turbine bearing sealing cavity, aiming to solve the problems that the sealing air system does not have the advantages of simple system, good cooling effect, simple cavity structure, low lubricating oil return temperature and extended lubricating oil service life.

[0005] The present invention is implemented as follows: an air supply system for a gas turbine bearing sealing cavity includes a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine, a power turbine, a low-pressure compressor front bearing cavity, a transition section bearing cavity, a high-pressure compressor rear bearing cavity, a low-pressure turbine support ring bearing cavity and a power turbine support ring bearing cavity, wherein the high-pressure compressor includes a transition section and a load-bearing casing, the low-pressure turbine includes a low-pressure turbine support ring, and the power turbine includes a power turbine support ring and an output shaft, and sealing air is extracted from the transition section. For the high-pressure compressor rear bearing cavity, the sealing air flows into the gas-liquid air cooling through an external air pipe After cooling, it flows to the interface on the load-bearing casing, and is introduced into the bearing cavity of the high-pressure compressor rear casing through the intermediate air supply pipe; for the bearing cavity of the low-pressure turbine support ring, the sealed air flows into the gas-liquid air cooler through the external air pipe, and flows to the interface on the low-pressure turbine support ring after cooling, and is introduced into the bearing cavity of the low-pressure turbine support ring through the intermediate air flow channel; for the bearing cavity of the power turbine support ring, the sealed air flows into the gas-liquid air cooler through the external air pipe, and flows to the pipe mouth on the power turbine support ring after cooling, and flows to the power turbine support ring bearing cavity through the intermediate air supply pipe, and the cooling medium flows into the inlet of the gas-liquid air cooler and flows out from the outlet.

[0006] Furthermore, the sealed air is drawn in from the air pipe openings, and is supplied to the gas-liquid air cooler 1, the gas-liquid air cooler 2 and the gas-liquid air cooler 3 respectively through the external air pipe 1, the external air pipe 2 and the external air pipe 3.

[0007] Furthermore, after the sealed air is cooled by gas-liquid air cooler 1, gas-liquid air cooler 2 and gas-liquid air cooler 3, it flows to the air pipe openings on the load-bearing casing, the low-pressure turbine support ring and the power turbine support ring through external air pipe 1, external air pipe 2 and external air pipe 3 respectively for air supply.

[0008] Furthermore, the air pipe port on the load-bearing casing flows into the bearing cavity through the intermediate air supply pipe, and the flow channel flowing into the bearing cavity is divided into two paths, respectively passing through the cold air surround cavity and entering the sealing cavity. Under the action of the pressure difference between the sealing cavity and and the bearing cavity, the lubricating oil is prevented from leaking outward from the sealing device and, and the comb tooth sealing device and plays a role in preventing external high-temperature air from entering the sealing cavity and. Since the temperature of the cooled sealing air is relatively low, it can play a role in cooling the bearing cavity. Therefore, thermal insulation coating layer 1, thermal insulation coating layer 2 and thermal insulation coating layer 3 may not be set.

[0009] Furthermore, the air pipe opening on the low-pressure turbine support ring flows into the bearing cavity through the intermediate air supply pipe, and flows into the sealing cavity through the bearing cavity flow channel. Under the action of the pressure difference between the sealing cavity and the bearing cavity, the lubricating oil is prevented from leaking outward from the sealing device. The comb tooth sealing device prevents external high-temperature air from entering the sealing cavity. Since the temperature of the cooled sealing air is relatively low, it can cool the bearing cavity. Therefore, a thermal insulation coating layer may not be provided.

[0010] Furthermore, the air from the air pipe port on the power turbine support ring flows into the bearing cavity through the intermediate air supply pipe, flows into the sealing cavity through the bearing cavity flow channel, and the sealing air flows into the sealing cavity along the output shaft inner hole flow channel. Under the pressure difference between the sealing cavity 4, the sealing cavity 5 and the bearing cavity, the lubricating oil is prevented from leaking out of the sealing device. The comb tooth sealing device plays a role in preventing the sealing air from leaking out. A part of the sealing air flows into the power turbine flow along the bearing cavity flow channel. Since the temperature of the cooled sealing air is relatively low, the heat insulation coating layer in the bearing cavity flow channel may not be provided.

[0011] Furthermore, the transition section bearing cavity contains a low-pressure compressor rear bearing and a high-pressure compressor front bearing.

[0012] The beneficial effects of the present invention are:

[0013] By adopting cooling technology, the sealed air cooled by three gas-liquid air coolers flows through four bearing cavity flow channels, two cold air surround cavities, and the inner hole of the output shaft and then flows into the bearing sealing cavity, which can reduce the heat generation in the gas turbine bearing cavity. Due to the adoption of a reasonable air supply system, it can not only effectively isolate the convective heat exchange between the high-temperature air outside the bearing cavity and the cavity wall, but also effectively cool the bearing cavity wall temperature, thereby reducing the convective heat exchange between the bearing cavity wall and the lubricating oil and oil and gas in the cavity. At the same time, the cooled sealed air enters the bearing cavity and exchanges heat with the high-temperature lubricating oil and oil and gas in the cavity, which can reduce the lubricating oil temperature and oil and gas temperature in the bearing cavity, and can also reduce the wind resistance of the main bearing rolling element, which can meet the requirements of the gas turbine air supply system for less lubricating oil leakage, good cooling effect, low lubricating oil return temperature, extended lubricating oil service life, and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of a three-shaft gas turbine of the present invention;

[0015] Figure 2 It is a schematic diagram of the air bleed pipe distribution structure of the AA section of the transition section after the low-pressure compressor of the present invention;

[0016] Figure 3It is a schematic diagram of the air intake pipe distribution structure of the load-bearing casing BB section, the low-pressure turbine support ring CC section, and the power turbine support ring DD section of the present invention;

[0017] Figure 4 is an enlarged view of the rear bearing cavity of the high-pressure compressor of the present invention;

[0018] Figure 5 It is an enlarged view II of the bearing cavity of the low-pressure turbine support ring of the present invention;

[0019] Figure 6 It is an enlarged view III of the bearing cavity of the power turbine support ring of the present invention.

[0020] In the figure: 1, low-pressure compressor; 2, high-pressure compressor; 3, combustion chamber; 4, high-pressure turbine; 5, low-pressure turbine; 6, power turbine; 7, low-pressure compressor front bearing cavity; 8, transition section bearing cavity; 9, high-pressure compressor rear bearing cavity; 10, high-pressure compressor rear bearing cavity; 11, power turbine support ring bearing cavity; 12, transition section; 13, load-bearing casing; 14, low-pressure turbine support ring; 15, low-pressure turbine support ring; 16, external air pipe 1; 17, external air pipe 2; 18, external air pipe 3; 19, output shaft; 20, gas-liquid air cooler 1; 21, gas-liquid air cooler 2; 22, gas-liquid air cooler 3; 23, intermediate air supply pipe 1; 24, intermediate air supply pipe 2; 25, cold air surround cavity 1; 26, cold air surround cavity 2; 27, thermal insulation coating layer 1; 28, Insulation coating layer 2; 29, sealing chamber 1; 30, sealing chamber 2; 31, sealing device 1; 32, sealing device 2; 33, bearing chamber 1; 34, comb seal device 1; 35, comb seal device 2; 36, intermediate air supply pipe 3; 37, sealing chamber 3; 38, bearing chamber 2; 39, sealing device 3; 40, comb seal device 3; 41, insulation coating layer 3; 42, bearing chamber flow channel 1 ; 43. Sealing chamber four; 44. Sealing chamber five; 45. Sealing device four; 46. Sealing device five; 47. Bearing chamber three; 48. Comb tooth sealing device four; 49. Comb tooth sealing device five; 50. Thermal insulation coating layer four; 51. Thermal insulation coating layer five; 52. Bearing cavity flow channel two; 53. Bearing cavity flow channel three; 54. Bearing cavity flow channel four; 55. Thermal insulation coating layer six; 56. Inlet; 57. Outlet. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings.

[0022] The embodiment of the present invention provides a sealed air system, such as Figure 1-6As shown, it includes a low-pressure compressor 1, a high-pressure compressor 2, a combustion chamber 3, a high-pressure turbine 4, a low-pressure turbine 5, a power turbine 6, a low-pressure compressor front bearing cavity 7, a transition section bearing cavity 8, a high-pressure compressor rear bearing cavity 9, a low-pressure turbine support ring bearing cavity 10 and a power turbine support ring bearing cavity 11. The high-pressure compressor 2 includes a transition section 12 and a load-bearing casing 13, the low-pressure turbine 5 includes a low-pressure turbine support ring 14, and the power turbine 6 includes a power turbine support ring 15 and an output shaft 19. Sealed air is extracted from the transition section 12. For the high-pressure compressor rear bearing cavity 9, the sealed air flows into the gas-liquid air cooler 20 through the external air pipe 16, and flows to the interface on the load-bearing casing 13 after cooling. , introduced into the high-pressure compressor rear casing bearing cavity 9 through the intermediate air supply pipe 24; for the low-pressure turbine support ring bearing cavity 10, the sealed air flows into the gas-liquid air cooler 21 through the external air pipe 17, flows to the interface on the low-pressure turbine support ring 14 after cooling, and is introduced into the low-pressure turbine support ring bearing cavity 10 through the intermediate air flow channel; for the power turbine support ring bearing cavity 11, the sealed air flows into the gas-liquid air cooler 22 through the external air pipe 18, flows to the pipe opening on the power turbine support ring 15 after cooling, flows to the power turbine support ring bearing cavity 11 through the intermediate air supply pipe, and the cooling medium flows in from the inlet 56 of the gas-liquid air coolers 20, 21 and 22, and flows out from the outlet 57.

[0023] It should be noted that, since the existing three-shaft gas turbine device has a total of five bearing cavities, namely the front bearing cavity of the low-pressure compressor, the bearing cavity of the transition section, the rear bearing cavity of the high-pressure compressor, the bearing cavity of the low-pressure turbine support ring, and the bearing cavity of the power turbine support ring, etc., since the cavity sizes of the rear bearing cavity of the high-pressure compressor, the bearing cavity of the low-pressure turbine support ring, and the bearing cavity of the power turbine support ring are relatively small and are located in the high-temperature area of ​​the gas turbine, the oil inlet, sealing air, and ambient temperatures are relatively high. In order to prevent the leakage of lubricating oil in the bearing cavity, it is necessary to lead compressed air from the transition section to the sealing cavity of the bearing cavity. In the bearing cavity, due to the high temperature of the compressed air, the high-temperature sealed air enters the bearing cavity through the sealing device to mix with the oil and gas, causing the lubricating oil in the cavity to heat up and volatilize to form an oil-gas mixture with a certain temperature and pressure. Since the sealed air has a high temperature, when the high-temperature air flows through the bearing cavity flow channel, the cavity flow channel is wrapped by the hot air of the high-temperature air, and then this part of the air enters the bearing cavity from the sealing device, thereby bringing a certain amount of heat to the lubricating oil in the bearing cavity, causing the temperature of the lubricating oil and oil and gas in the bearing cavity to rise, and the wind resistance of the bearing rotation to increase, while also increasing the sealing device. Therefore, in order to solve the problem that the existing sealing air system does not have the advantages of simple system, good cooling effect, simple cavity structure, low lubricating oil return temperature and extended lubricating oil service life, this scheme adopts cooling technology. The sealing air cooled by the three gas-liquid air coolers flows through the four bearing cavity flow channels, two cold air surround cavities, and the inner hole of the output shaft 19 before flowing into the bearing sealing cavity, which can reduce the heat generation in the gas turbine bearing cavity. Due to the use of a reasonable air supply system, it can not only effectively isolate the outside of the bearing cavity The convective heat exchange between the high-temperature air and the cavity wall also effectively cools the bearing cavity wall temperature, thereby reducing the convective heat exchange between the bearing cavity wall and the lubricating oil and oil gas in the cavity. At the same time, the cooled sealed air enters the bearing cavity and exchanges heat with the high-temperature lubricating oil and oil gas in the cavity, which can reduce the lubricating oil temperature and oil gas temperature in the bearing cavity, and can also reduce the wind resistance of the main bearing rolling element, which can meet the requirements of the gas turbine air supply system for less lubricating oil leakage, good cooling effect, low lubricating oil return temperature, extended lubricating oil service life, and high reliability.

[0024] Specifically, in this embodiment, this scheme mainly includes sealing air and drawing air from the air pipe openings respectively, and supplying air to the gas-liquid air cooler 1 20, the gas-liquid air cooler 2 21 and the gas-liquid air cooler 3 22 respectively through the external air pipe 1 16, the external air pipe 2 17 and the external air pipe 3 18.

[0025] In a further preferred embodiment of the present invention, Figure 1-5As shown, after the sealed air is cooled by the gas-liquid air cooler 1 20, the gas-liquid air cooler 21 and the gas-liquid air cooler 3 22, it flows to the air pipe openings on the load-bearing casing 13, the low-pressure turbine support ring 14 and the power turbine support ring 15 through the external air pipe 1 16, the external air pipe 2 17 and the external air pipe 3 18 respectively for air supply.

[0026] In this embodiment, when the gas turbine is operating under all working conditions, the main bearings supporting the high-pressure rotor, the low-pressure rotor and the power turbine rotor can operate normally at high speed. This is mainly because the working pressure in the bearing cavity is in a certain equilibrium state under the joint action of the oil supply system, the oil return system, the ventilation system and the air supply system. The air supply system draws sealing air from the transition section, and passes it into the bearing sealing cavity after passing through the gas-liquid air cooler 1 20, the gas-liquid air cooler 21 and the gas-liquid air cooler 3 22, ensuring that the positive pressure difference between the sealing cavity and the bearing cavity is within the normal working range, thereby preventing the lubricating oil in the bearing cavity from leaking out from the sealing device. The cold air surround cavity is a flow channel arranged on the outer wall of the bearing cavity, and its interior is filled with cooled air, forming a cold air package, which can achieve the effect of cooling the bearing cavity. The output shaft inner hole flow channel is a flow channel, and when the sealing air flows through the bearing cavity flow channel, it can play a certain cooling role.

[0027] In a further preferred embodiment of the present invention, Figure 1-5 As shown, the air flows from the air pipe opening on the load-bearing casing 13 into the bearing cavity 9 through the intermediate air supply pipe 24, and then flows into the bearing cavity flow channel 52 and is divided into two paths, respectively entering the sealing cavities 29 and 30 through the cold air surround cavities 25 and 26. Under the action of the pressure difference between the sealing cavities 29 and 30 and the bearing cavity 33, the lubricating oil is prevented from leaking outward from the sealing devices 31 and 32. The comb tooth sealing devices 34 and 35 prevent external high-temperature air from entering the sealing cavities 29 and 30. Since the temperature of the cooled sealing air is relatively low, it can cool the bearing cavity 9. Therefore, it is not necessary to set the thermal insulation coating layer 1 27, the thermal insulation coating layer 28 and the thermal insulation coating layer 3 55.

[0028] In this embodiment, the lubricating oil can be prevented from leaking outward under the action of pressure difference, and the external high-temperature air can be prevented from entering the sealing cavity. Since the temperature of the sealed air after cooling is relatively low, it can cool the bearing cavity 9.

[0029] In a further preferred embodiment of the present invention, Figure 1-5As shown, the air from the air pipe opening on the low-pressure turbine support ring 14 flows into the bearing cavity 10 through the intermediate air supply pipe 36, and flows into the sealing cavity 37 through the bearing cavity flow channel 53. Under the action of the pressure difference between the sealing cavity 37 and the bearing cavity 38, the lubricating oil is prevented from leaking outward from the sealing device 39. The comb tooth sealing device 40 prevents external high-temperature air from entering the sealing cavity 37. Since the temperature of the cooled sealing air is relatively low, it can cool the bearing cavity 10. Therefore, a thermal insulation coating layer 41 may not be provided.

[0030] In this embodiment, the lubricating oil can be prevented from leaking outward under the action of the pressure difference, thereby preventing the external high-temperature air from entering the sealing cavity 37.

[0031] In a further preferred embodiment of the present invention, Figure 1-5 As shown, the air flows from the air pipe opening on the power turbine support ring 15 through the intermediate air supply pipe 23 into the bearing cavity 11, and flows into the sealing cavity four 43 through the bearing cavity flow channel 42. The sealed air flows along the inner hole flow channel of the output shaft 19 into the sealing cavity five 44. Under the action of the pressure difference between the sealing cavity four 43, the sealing cavity five 44 and the bearing cavity 47, the lubricating oil is prevented from leaking outward from the sealing devices 45 and 46. The comb tooth sealing device 48 prevents the sealing air from leaking outward. A part of the sealing air flows along the bearing cavity flow channel 54 into the power turbine flow. Since the temperature of the sealing air after cooling is relatively low, the thermal insulation coating layers 51 and 50 in the bearing cavity flow channel 54 may not be provided.

[0032] In this embodiment, it plays a role in preventing the sealed air from leaking outward.

[0033] In a further preferred embodiment of the present invention, Figure 1 As shown, the transition section bearing cavity 8 contains the low-pressure compressor rear bearing and the high-pressure compressor front bearing.

[0034] In this embodiment, it is possible to carry out activities after positioning.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An air supply system for a gas turbine bearing sealing cavity, characterized in that: The invention comprises a low-pressure compressor (1), a high-pressure compressor (2), a combustion chamber (3), a high-pressure turbine (4), a low-pressure turbine (5), a power turbine (6), a low-pressure compressor front bearing cavity (7), a transition section bearing cavity (8), a high-pressure compressor rear bearing cavity (9), a low-pressure turbine support ring bearing cavity (10) and a power turbine support ring bearing cavity (11), wherein the high-pressure compressor (2) comprises a transition section (12) and a bearing casing (13), the low-pressure turbine (5) comprises a low-pressure turbine support ring (14), and the power turbine (6) comprises a power turbine support ring (15) and an output shaft (19), and sealed air is extracted from the transition section (12), and at the high-pressure compressor rear bearing cavity (9), the sealed air flows into a gas-liquid air cooler (20) through an external air pipe (16), and flows to the bearing casing after being cooled. The air is introduced into the high pressure compressor rear casing bearing cavity (9) through the interface on the low pressure turbine support ring (13) through the intermediate air supply pipe (24); for the low pressure turbine support ring bearing cavity (10), the sealed air flows into the gas-liquid air cooler (21) through the external air pipe (17), flows to the interface on the low pressure turbine support ring (14) after cooling, and is introduced into the low pressure turbine support ring bearing cavity (10) through the intermediate air flow channel; for the power turbine support ring bearing cavity (11), the sealed air flows into the gas-liquid air cooler (22) through the external air pipe (18), flows to the pipe opening on the power turbine support ring (15) after cooling, flows to the power turbine support ring bearing cavity (11) through the intermediate air supply pipe, and the cooling medium flows in from the inlet (56) of the gas-liquid air cooler (20), (21) and (22), and flows out from the outlet (57).

2. The air supply system for the gas turbine bearing sealing cavity according to claim 1, characterized in that: The sealed air is drawn from the air pipe ports and supplied to the gas-liquid air cooler 1 (20), the gas-liquid air cooler 2 (21) and the gas-liquid air cooler 3 (22) respectively through the external air pipe 1 (16), the external air pipe 2 (17) and the external air pipe 3 (18).

3. The air supply system for the gas turbine bearing sealing cavity according to claim 1, characterized in that: After being cooled by the gas-liquid air cooler 1 (20), the gas-liquid air cooler 2 (21) and the gas-liquid air cooler 3 (22), the sealed air flows through the external air pipe 1 (16), the external air pipe 2 (17) and the external air pipe 3 (18) to the air pipe openings on the load-bearing casing (13), the low-pressure turbine support ring (14) and the power turbine support ring (15) for air supply.

4. The air supply system for the gas turbine bearing sealing cavity according to claim 1, characterized in that: The air from the air pipe opening on the load-bearing casing (13) flows into the bearing cavity (9) through the intermediate air supply pipe (24), and then flows into the bearing cavity flow channel (52) and is divided into two paths, respectively entering the sealing cavity (29) and (30) through the cold air surround cavity (25) and (26). Under the action of the pressure difference between the sealing cavity (29) and (30) and the bearing cavity (33), the lubricating oil is prevented from leaking outward from the sealing device (31) and (32). The comb tooth sealing device (34) and (35) play a role in preventing external high-temperature air from entering the sealing cavity (29) and (30). Since the temperature of the cooled sealing air is relatively low, it can play a role in cooling the bearing cavity (9). Therefore, it is not necessary to set the thermal insulation coating layer 1 (27), the thermal insulation coating layer 2 (28) and the thermal insulation coating layer 3 (55).

5. The air supply system for the gas turbine bearing sealing cavity according to claim 1, characterized in that: The air from the air pipe opening on the low-pressure turbine support ring (14) flows into the bearing cavity (10) through the intermediate air supply pipe (36), and flows into the sealing cavity (37) through the bearing cavity flow channel (53). Under the action of the pressure difference between the sealing cavity (37) and the bearing cavity (38), the lubricating oil is prevented from leaking outward from the sealing device (39). The comb seal device (40) plays a role in preventing external high-temperature air from entering the sealing cavity (37). Since the temperature of the cooled sealing air is relatively low, it can play a role in cooling the bearing cavity (10). Therefore, a heat insulating coating layer (41) may not be provided.

6. The air supply system for the gas turbine bearing sealing cavity according to claim 1, characterized in that: The air from the air pipe port on the power turbine support ring (15) flows into the bearing cavity (11) through the intermediate air supply pipe (23), and flows into the sealing cavity (43) through the bearing cavity flow channel (42). The sealing air flows into the sealing cavity (44) along the inner hole flow channel of the output shaft (19). Under the pressure difference between the sealing cavity (43) four, the sealing cavity (44) five and the bearing cavity (47), the lubricating oil is prevented from leaking outward from the sealing device (45) and (46). The comb tooth sealing device (48) plays a role in preventing the sealing air from leaking outward. A part of the sealing air flows into the power turbine throughflow along the bearing cavity flow channel (54). Since the temperature of the cooling sealing air is relatively low, the heat insulation coating layers (51) and (50) in the bearing cavity flow channel (54) may not be provided.

7. The air supply system for the gas turbine bearing sealing cavity according to claim 1, characterized in that: The transition section bearing cavity (8) contains a low-pressure compressor rear bearing and a high-pressure compressor front bearing.

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