A composite air bleed structure for a gas turbine

Abstract

The present invention discloses a composite air bleed structure for a gas turbine, belonging to the technical field of gas turbines. The structure comprises a first-stage disc and a third-stage disc arranged opposite each other, a second-stage disc disposed between the first-stage disc and the third-stage disc, a cavity disposed at the joint between the first-stage disc and the second-stage disc, and a third-stage disc cavity disposed between the second-stage disc and the third-stage disc. A through hole is provided on the side of the first-stage disc, the through hole sequentially passing through the first-stage disc, the second-stage disc, and the third-stage disc. A first gear ring is fixed to the side of the first-stage disc near the second-stage disc, and a second gear ring is fixed to the side of the second-stage disc near the first-stage disc. The first gear ring meshes with the second gear ring, and the first and second gear rings divide the cavity into an upstream disc cavity and a downstream disc cavity. A plurality of nozzle holes are provided at the meshing point between the first gear ring and the second gear ring, and a plurality of vortex reducing holes are provided on the inner bottom surface of the downstream disc cavity, which connect the downstream disc cavity and the third-stage disc cavity. The present invention has the effect of reducing the pressure loss and energy loss generated when gas passes through a radial inflow gas structure.

Description

Technical Field

[0001] The present invention relates to the technical field of gas turbines, and in particular to a composite air bleed structure for a gas turbine. Background Art

[0002] From a gas turbine design perspective, the multi-stage axial-flow compressor, combustor, and multi-stage cooled turbine are key components of heavy-duty gas turbines. Key technologies for the axial-flow compressor primarily focus on blade aerodynamic design and research; key technologies for the combustor primarily focus on combustion characteristics, cooling, and sealing design; and key technologies for the multi-stage cooled turbine focus on integrated cooling technology. The secondary air system, closely coupled with the compressor and turbine, not only impacts turbine cooling but also the performance of the compressor itself. The secondary air system comprises the internal shaft air passages and external ducting within a heavy-duty gas turbine, which effectively cool the turbine blades and moving blades, respectively. The secondary air system plays a vital role in the efficient and safe operation of heavy-duty gas turbines. The internal bleed air flow path of advanced heavy-duty gas turbines bleeds air from the compressor hub, flowing radially inward and then through the shaft cavity to the turbine end, where it is used for cooling and sealing turbine components. The use of vortex reducers can reduce the vortex pressure drop of the bleed air, reducing windage losses and improving unit efficiency.

[0003] An existing gas turbine composite air bleed mechanism includes a first-stage disc 1 and a third-stage disc 12 arranged opposite to each other, a second-stage disc 11 is arranged between the first-stage disc 1 and the third-stage disc 12, and two side surfaces of the second-stage disc 11 are fixedly connected to the side surfaces of the first-stage disc 1 and the third-stage disc 12 that are close to each other. A cavity 17 is defined between the first-stage disc 1 and the second-stage disc 11, and a third-stage disc cavity 25 is defined between the second-stage disc 11 and the third-stage disc 12. A plurality of vortex-reducing holes 24 are defined on the inner circumference of the cavity 17, and the vortex-reducing holes 24 are connected to the cavity 17 and the third-stage disc cavity 25. An annular through groove 22 is defined on the outer circumference of the first-stage disc 1, and the annular through groove 22 is connected to the cavity 17.

[0004] In the above-mentioned related technologies, when the gas enters the cavity through the annular groove, the gas in the cavity flows into the three-stage disc cavity through the vortex reduction hole, so that the gas has a longer distance through the vortex reduction hole, thereby causing pressure loss and energy loss when the gas passes through the radial inlet air ducting structure. Summary of the Invention

[0005] In order to improve the problem of pressure loss and energy loss when gas passes through a radial inlet air bleed structure, the present application provides a gas turbine composite air bleed structure.

[0006] The present application provides a gas turbine composite air bleed structure that adopts the following technical solutions:

[0007] A gas turbine composite air bleed structure comprises a first-stage disc and a third-stage disc arranged opposite to each other, a second-stage disc is arranged between the first-stage disc and the third-stage disc, two side surfaces of the second-stage disc are respectively in contact with the side surfaces of the first-stage disc and the second-stage disc close to each other, a cavity is provided at the contact point between the first-stage disc and the second-stage disc, a third-stage disc cavity is provided between the second-stage disc and the third-stage disc, a through hole is opened on the side surface of the first-stage disc, the through hole passes through the first-stage disc, the second-stage disc and the third-stage disc in sequence, the third-stage disc cavity is connected to the through hole, and the first-stage disc is close to the second-stage disc. A gear ring 1 is fixed to the side near the second-stage disk, and a gear ring 2 is fixed to the side of the second-stage disk near the first-stage disk. The gear ring 1 is meshed with the gear ring 2. The gear ring 1 and the gear ring 2 divide the cavity into an upstream disk cavity and a downstream disk cavity. A driving member 1 for driving the third-stage disk to rotate is provided on the second-stage disk. A plurality of nozzle holes are provided at the meshing point of the gear ring 1 and the gear ring 2. The nozzle holes communicate with the upstream disk cavity and the downstream disk cavity. A plurality of vortex reducing holes are provided on the inner bottom surface of the downstream disk cavity. The vortex reducing holes communicate with the downstream disk cavity and the third-stage disk cavity.

[0008] By adopting the above technical solution, the gas enters the upstream disc cavity through the annular groove, and then enters the downstream disc cavity through the nozzle hole, so that the downstream disc cavity can regularize the gas. When the gas in the downstream disc cavity flows into the third-stage disc cavity through the vortex-reducing hole, the distance of the gas passing through the vortex-reducing hole is reduced, thereby reducing the pressure loss and energy loss generated when the gas passes through the radial inlet air ducting structure.

[0009] Preferably, the driving member includes a gear ring three fixed to the second stage disk close to the third stage disk, a gear ring two is fixed to the side of the third stage disk close to the second stage disk, and the gear ring two is meshed with the gear ring three.

[0010] By adopting the above technical solution, when the first-stage disk rotates, the first-stage disk drives the ring gear 1 to rotate, so that the ring gear 1 drives the ring gear 2 to rotate, and the ring gear 2 drives the second-stage disk to rotate, so that the second-stage disk drives the ring gear 3 to rotate, and the ring gear 3 drives the ring gear 4 to rotate, so that the ring gear 4 drives the third-stage disk to rotate.

[0011] Preferably, an air guide tube is inserted into the bottom end of the nozzle hole, a ball is fixed to the bottom end of the air guide tube, an air guide hole is provided on the outer circumference of the ball, the air guide hole is communicated with the air guide tube, a spherical groove is provided on the inner circumference of the air guide hole, a spherical valve is rotatably provided on the inner circumference of the spherical groove, an air outlet hole is provided on the outer circumference of the spherical valve, a clearance groove is provided on the outer circumference of the ball, an air outlet tube is inserted in the air outlet hole, the air outlet tube passes through the clearance groove, and a driving component for driving the spherical valve to rotate is provided on the first-stage disk.

[0012] By adopting the above technical solution, the ball valve is driven to rotate by the driving assembly, so that the ball valve drives the air outlet pipe to rotate, thereby facilitating the adjustment of the airflow direction from the upstream disc cavity to the downstream disc cavity through the nozzle hole.

[0013] Preferably, the driving assembly includes a gear ring five rotatably arranged on the side of the first-stage disk close to the second-stage disk, a rotating shaft is fixed to the outer peripheral surface of the spherical valve, the rotating shaft passes through the ball, the rotating shaft is rotatably connected to the ball, a gear one is provided on the rotating shaft, the gear one is engaged with the gear ring five, and a power part for driving the gear ring five to rotate is provided on the first-stage disk.

[0014] By adopting the above technical solution, the power part drives the ring gear five to rotate, so that the ring gear five drives the gear one to rotate, and the gear one drives the rotating shaft to rotate, so that the rotating shaft drives the spherical valve to rotate, thereby facilitating the adjustment of the air outlet size.

[0015] Preferably, the power component includes a motor arranged on the side of the first stage disk close to the second stage disk, and a second gear is provided on the output shaft of the motor, and the second gear is meshed with the fifth gear ring.

[0016] By adopting the above technical solution, the motor is started, and the output shaft of the motor drives the gear 2 to rotate, so that the gear 2 drives the ring gear 5 to rotate.

[0017] Preferably, a circular ring is fixed on the side of the first-stage disk close to the second-stage disk, the gear ring five is sleeved on the outer circumference of the circular ring, a plug-in ring is fixed on the inner circumference of the gear ring five, an annular groove is opened on the top surface of the circular ring, and the plug-in ring is arranged in the annular groove.

[0018] By adopting the above technical solution, when the ring gear five rotates, the ring gear five drives the splice ring to rotate in the annular groove, thereby reducing the possibility of the ring gear five being separated from the circular ring.

[0019] Preferably, the opposite inner side surfaces of the annular groove are each provided with a plurality of mounting grooves, and balls are roamingly mounted in the mounting grooves, and the balls can roll on the side surfaces of the plug-in ring.

[0020] By adopting the above technical solution, when the plug-in ring rolls in the annular groove, the balls roll on the side walls of the plug-in ring, thereby reducing the friction between the two side surfaces of the plug-in ring and the opposite inner side surfaces of the annular groove, thereby facilitating the plug-in ring to roll in the annular groove.

[0021] Preferably, a rounded corner is provided at the intersection of the third-stage disk and the through hole.

[0022] By adopting the above technical solution, a rounded corner is provided at the intersection of the third-stage disk and the through hole, thereby facilitating the outflow of gas from the through hole.

[0023] Preferably, a plurality of obliquely arranged reverse rotation holes are provided at the meshing portion of the gear ring 1 and the gear ring 2, and the reverse rotation holes are communicated with the upstream disc cavity and the downstream disc cavity.

[0024] By adopting the above technical solution, the upstream disc cavity and the downstream disc cavity are connected through the obliquely arranged reverse rotation hole, so that the gas in the upstream disc cavity enters the reverse rotation hole to do negative work.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. The gas enters the upstream disc cavity through the annular groove and then enters the downstream disc cavity through the nozzle hole, causing the downstream disc cavity to regulate the gas. When the gas in the downstream disc cavity flows into the tertiary disc cavity through the vortex-reducing holes, the gas travel through the vortex-reducing holes is shortened, thereby reducing the pressure loss and energy loss caused by the gas passing through the radial inlet bleed structure.

[0027] 2. By starting the motor, the motor's output shaft drives Gear 2 to rotate, Gear 2 drives the ring gear to rotate, the ring gear drives Gear 1 to rotate, Gear 1 drives the rotating shaft to rotate, and the rotating shaft drives the ball valve to rotate, so that the air outlet on the ball valve deviates from the air guide hole, thereby facilitating the control of the flow rate of gas flowing through the nozzle hole into the downstream disc cavity;

[0028] 3. When the plug-in ring rolls in the annular groove, the balls roll on the side walls of the plug-in ring, thereby reducing the friction between the two side surfaces of the plug-in ring and the opposite inner side surfaces of the annular groove, thereby facilitating the plug-in ring to roll in the annular groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a cross-sectional view of the composite air bleed structure of a gas turbine in the background technology of an embodiment of the present application.

[0030] Figure 2 It is a schematic diagram of the overall structure of the composite air bleed structure of the gas turbine in Example 1 of the present application.

[0031] Figure 3 This is a cross-sectional view of the first-level disk of Example 1 of the present application.

[0032] Figure 4 yes Figure 3 Enlarged schematic diagram of point A in the middle.

[0033] Figure 5 A cross-sectional view of the sphere in Example 1 of the present application.

[0034] Figure 6 It is a cross-sectional view of the first-level disk, the second-level disk and the third-level disk in Example 2 of the present application.

[0035] Figure numerals: 1. first-stage disc; 11. second-stage disc; 12. third-stage disc; 13. gear ring one; 14. gear ring two; 15. gear ring three; 16. gear ring four; 17. cavity; 18. fillet; 2. upstream disc cavity; 21. downstream disc cavity; 22. annular groove; 23. nozzle hole; 24. vortex reduction hole; 25. third-stage disc cavity; 26. through hole; 3. air guide tube; 31. ball; 32. air guide hole; 33. spherical groove; 34. spherical valve; 35. air outlet; 36. rotating shaft; 37. gear one; 38. give way groove; 39. air outlet pipe; 4. circular ring; 41. gear ring five; 42. plug-in ring; 43. annular groove; 44. mounting groove; 45. ball; 46. motor; 47. gear two; 5. anti-rotation hole. DETAILED DESCRIPTION

[0036] The following is combined with Figure 2-6 This application is described in further detail.

[0037] Example 1

[0038] Reference Figure 2 A gas turbine composite air bleed structure includes a first-stage disk 1 and a third-stage disk 12 arranged opposite to each other, a second-stage disk 11 is arranged between the first-stage disk 1 and the third-stage disk 12, and both end surfaces of the second-stage disk 11 are combined with the side surfaces of the first-stage disk 1 and the third-stage disk 12 that are close to each other.

[0039] Reference Figure 2 and Figure 3 A cavity 17 is defined between the mating sides of the first-stage disc 1 and the second-stage disc 11. A first gear ring 13 is fixed to the side of the first-stage disc 1 near the second-stage disc 11, and a second gear ring 14 is fixed to the side of the second-stage disc 11 near the first-stage disc 1. Gear rings 13 and 14 mesh with each other, dividing cavity 17 into an upstream disc cavity 2 and a downstream disc cavity 21. A third-stage disc cavity 25 is defined between the mating sides of the second-stage disc 11 and the third-stage disc 12. A third gear ring 15 is fixed to the side of the second-stage disc 11 near the third-stage disc 12, and a fourth gear ring 16 is fixed to the side of the third-stage disc 12 near the second-stage disc 11. Gear rings 15 and 16 mesh with each other. A through hole 26 is provided on the side of the first-stage disk 1 . The through hole 26 sequentially passes through the first-stage disk 1 , the second-stage disk 11 and the third-stage disk 12 . A fillet 18 is provided at the intersection of the through hole 26 and the third-stage disk 12 .

[0040] When the first-stage disk 1 rotates, the first-stage disk 1 drives the ring gear 13 to rotate, the ring gear 13 drives the ring gear 2 14 to rotate, the ring gear 2 14 drives the second-stage disk 11 to rotate, the second-stage disk 11 drives the ring gear 3 15 to rotate, the ring gear 3 15 drives the ring gear 4 16 to rotate, and the ring gear 4 16 drives the third-stage disk 12 to rotate.

[0041] Reference Figure 3 and Figure 4 The outer circumference of the first-stage disc 1 is provided with an annular through-groove 22, which is connected to the upstream disc cavity 2 and passes through the side of the first-stage disc 1 near the second-stage disc 11. A plurality of nozzle holes 23 are provided at the meshing point between the ring gear 13 and the ring gear 2 14. The plurality of nozzle holes 23 are arranged at equal intervals along the circumference of the ring gear 1 13, and the central axis of the nozzle hole 23 is perpendicular to the central axis of the first-stage disc 1. The inner circumference of the downstream disc cavity 21 is provided with a plurality of inclined vortex-reducing holes 24, which are arranged at equal intervals along the circumference of the second-stage disc 11. The vortex-reducing holes 24 pass through the second-stage disc 11 and connect the downstream disc cavity 21 and the third-stage disc cavity 25.

[0042] Reference Figure 4 and Figure 5 An air guide tube 3 is inserted into the nozzle hole 23. The outer circumference of the air guide tube 3 is fixedly connected to the ring gear 13. A ball 31 is fixed to the end of the air guide tube 3 near the central axis of the first-stage disk 1. The outer circumference of the ball 31 defines an air guide hole 32, which communicates with the air guide tube 3. The inner circumference of the air guide hole 32 defines a spherical groove 33. A ball valve 34 is rotatably mounted within the spherical groove 33. The outer circumference of the ball valve 34 fits in contact with the inner circumference of the spherical groove 33. The outer circumference of the ball valve 34 defines an air outlet hole 35, which communicates with the air guide hole 32. The outer circumference of the ball 31 defines a clearance groove 38. An air outlet tube 39 is inserted into the air outlet hole 35 and is movable within the clearance groove 38.

[0043] Reference Figure 3 、 Figure 4 and Figure 5 A rotating shaft 36 is fixed to the outer circumference of the ball valve 34. The end of the rotating shaft 36 away from the ball valve 34 passes through the outer circumference of the ball 31, and the rotating shaft 36 is rotatably connected to the ball 31. A gear 1 37 is fixed to the end of the rotating shaft 36 away from the ball valve 34. A circular ring 4 is fixed to the side of the first-stage disk 1 near the second-stage disk 11. A gear ring 5 41 is mounted on the outer circumference of the circular ring 4. The gear ring 5 41 is rotatably connected to the circular ring 4, and the gear 1 37 meshes with the gear ring 5 41. A motor 46 is fixed to the side of the first-stage disk 1 near the second-stage disk 11. A gear 2 47 is mounted on the output shaft of the motor 46. The gear 2 47 meshes with the gear ring 5 41. A plug-in ring 42 is fixed to the inner circumference of the gear ring 5 41. An annular groove 43 is formed on the outer circumference of the circular ring 4, and the plug-in ring 42 is disposed in the annular groove 43. The opposite inner sides of the annular groove 43 are provided with a plurality of mounting grooves 44 , which are arranged at equal intervals along the circumference of the ring 4 . Balls 45 are rollingly mounted in the mounting grooves 44 , and the balls 45 can roll on the side walls of the plug-in ring 42 .

[0044] Start the motor 46, and the output shaft of the motor 46 drives the gear 2 47 to rotate, the gear 2 47 drives the ring gear 5 41 to rotate, the ring gear 5 41 drives the gear 1 37 to rotate, and the gear 1 37 drives the rotating shaft 36 to rotate, so that the rotating shaft 36 drives the ball valve 34 to rotate, and the ball valve 34 drives the outlet pipe 39 to rotate, thereby facilitating the adjustment of the outlet direction of the outlet pipe 39.

[0045] The implementation principle of a gas turbine composite bleed structure according to an embodiment of the present application is as follows: When the first-stage disc 1 rotates, the first-stage disc 1 drives the ring gear 1 13 to rotate, which in turn drives the ring gear 2 14 to rotate, which in turn drives the second-stage disc 11 to rotate, which in turn drives the ring gear 3 15 to rotate, which in turn drives the ring gear 4 16 to rotate, which in turn drives the third-stage disc 12 to rotate. When the first-stage disc 1 rotates, gas flows into the upstream disc cavity 2 through the annular groove 22, causing the gas in the upstream disc cavity 2 to continuously flow into the downstream disc cavity 21 through the nozzle holes 23, causing the downstream disc cavity 21 to regulate the gas, thereby reducing the pressure loss and energy loss caused by the gas passing through the radial inlet bleed structure.

[0046] By starting the motor 46, the output shaft of the motor 46 drives the second gear 47 to rotate, so that the second gear 47 drives the ring gear to rotate, and the ring gear drives the first gear 37 to rotate. The first gear 37 drives the rotating shaft 36 to rotate, so that the rotating shaft 36 drives the ball valve 34 to rotate, and the ball valve 34 drives the outlet pipe 39 to rotate, thereby facilitating the adjustment of the direction of the airflow from the upstream disc cavity 2 to the downstream disc cavity 21 through the nozzle hole 23.

[0047] Example 2

[0048] Reference Figure 6 The difference between this embodiment and embodiment 1 is that a plurality of obliquely arranged anti-rotation holes 5 are provided at the meshing point of the gear ring 13 and the gear ring 2 14. The plurality of anti-rotation holes 5 are arranged at equal intervals along the circumference of the second-stage disk 11, and the anti-rotation holes 5 are connected to the upstream disk cavity 2 and the downstream disk cavity 21.

[0049] The implementation principle of Example 2 is: the upstream disc cavity 2 and the downstream disc cavity 21 are connected through the obliquely arranged reverse rotation hole 5, so that the gas in the upstream disc cavity 2 enters the reverse rotation hole 5 to do negative work.

[0050] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A composite air bleed structure for a gas turbine, characterized by: The invention comprises a first-stage disk (1) and a third-stage disk (12) which are arranged opposite to each other, a second-stage disk (11) is arranged between the first-stage disk (1) and the third-stage disk (12), two side surfaces of the second-stage disk (11) are respectively fitted with the side surfaces of the first-stage disk (1) and the second-stage disk (11) which are close to each other, a cavity (17) is provided at the fitting position of the first-stage disk (1) and the second-stage disk (11), a third-stage disk cavity (25) is provided between the second-stage disk (11) and the third-stage disk (12), a through hole (26) is provided on the side surface of the first-stage disk (1), and the through hole (26) passes through the first-stage disk (1), the second-stage disk (11) and the third-stage disk (12) in sequence, and the three The first-stage disc cavity (25) is connected to the through hole (26), a gear ring 1 (13) is fixed on the side of the first-stage disc (1) close to the second-stage disc (11), and a gear ring 2 (14) is fixed on the side of the second-stage disc (11) close to the first-stage disc (1), the gear ring 1 (13) is meshed with the gear ring 2 (14), and the gear ring 1 (13) and the gear ring 2 (14) divide the cavity (17) into an upstream disc cavity (2) and a downstream disc cavity (21), and a driving member 1 for driving the third-stage disc (12) to rotate is provided on the second-stage disc (11), and a plurality of nozzle holes (23) are provided at the meshing position of the gear ring 1 (13) and the gear ring 2 (14), and the nozzle holes ( 23) connects the upstream disc cavity (2) and the downstream disc cavity (21), the inner bottom surface of the downstream disc cavity (21) is provided with a plurality of vortex reduction holes (24), the vortex reduction holes (24) connect the downstream disc cavity (21) and the third-stage disc cavity (25), the driving member includes a gear ring three (15) fixed to the second-stage disc (11) close to the third-stage disc (12), the third-stage disc (12) is fixed with a gear ring two (14) on the side close to the second-stage disc (11), the gear ring two (14) is meshed with the gear ring three (15), the bottom end of the nozzle hole (23) is inserted with an air guide tube (3), the bottom end of the air guide tube (3) is fixed with a ball (31), the outer surface of the ball (31) is fixed with a ball (31), and the outer surface of the ball (31) is fixed with a ball (31). An air guide hole (32) is provided on the circumference, and the air guide hole (32) is connected to the air guide pipe (3). A spherical groove (33) is provided on the inner circumference of the air guide hole (32). A spherical valve (34) is rotatably provided on the inner circumference of the spherical groove (33). An air outlet hole (35) is provided on the outer circumference of the sphere (31). A clearance groove (38) is provided on the outer circumference of the sphere (31). An air outlet pipe (39) is inserted into the air outlet hole (35). The air outlet pipe (39) passes through the clearance groove (38). A driving component for driving the spherical valve (34) to rotate is provided on the first-stage disk (1). A fillet (18) is provided at the intersection of the third-stage disk (12) and the through hole (26).

2. The gas turbine composite air bleed structure according to claim 1, characterized in that: The driving assembly includes a gear ring five (41) rotatably arranged on the side of the first-stage disk (1) close to the second-stage disk (11); a rotating shaft (36) is fixed to the outer peripheral surface of the spherical valve (34); the rotating shaft (36) passes through the sphere (31); the rotating shaft (36) is rotatably connected to the sphere (31); a gear one (37) is arranged on the rotating shaft (36); the gear one (37) is meshed with the gear ring five (41); and a power part for driving the gear ring five (41) to rotate is arranged on the first-stage disk (1).

3. The gas turbine composite air bleed structure according to claim 2, characterized in that: The power member includes a motor (46) arranged on the side of the first-stage disk (1) close to the second-stage disk (11), and a gear 2 (47) is arranged on the output shaft of the motor (46), and the gear 2 (47) is meshed with the gear ring 5 (41).

4. The gas turbine composite air bleed structure according to claim 2, characterized in that: A circular ring (4) is fixed on the side of the first-stage disc (1) close to the second-stage disc (11); the gear ring five (41) is sleeved on the outer circumference of the circular ring (4); a plug-in ring (42) is fixed on the inner circumference of the gear ring five (41); an annular groove (43) is provided on the top surface of the circular ring (4); and the plug-in ring (42) is arranged in the annular groove (43).

5. The gas turbine composite air bleed structure according to claim 4, characterized in that: The opposite inner sides of the annular groove (43) are each provided with a plurality of mounting grooves (44), wherein balls (45) are rollingly mounted in the mounting grooves (44), and the balls (45) can roll on the side of the plug-in ring (42).

6. The gas turbine composite air bleed structure according to claim 1, characterized in that: A plurality of obliquely arranged reverse rotation holes (5) are provided at the meshing portion of the gear ring 1 (13) and the gear ring 2 (14), and the reverse rotation holes (5) are communicated with the upstream disc cavity (2) and the downstream disc cavity (21).

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