Oil return type aero-engine bearing cavity graphite sealing structure

Abstract

The invention provides an oil return type aero-engine bearing cavity graphite sealing structure. The oil return type aero-engine bearing cavity graphite sealing structure comprises a graphite ring. The graphite ring is of a single-ring multi-petal structure, the outer ring surface of the graphite ring is hooped through the circumferential extension spring, the inner ring surface of the graphite ring is a conical surface, and the conical surface is tightly attached to a rotor runway to form a circumferential sealing surface; a sealing seat is attached to one end of the graphite ring to form an end face sealing face, an unloading groove is formed in the other end of the graphite ring, and a spring seat is attached to the other end of the graphite ring. A wave spring is arranged between the sealing seat and the spring seat, and a clamping ring is arranged between the wave spring and the sealing seat. An oil collecting groove is formed in the sealing conical surface of the rotor runway, and an oil throwing rib is arranged on the side, close to the lubricating oil cavity, of the rotor runway. The radius of the air side is small, and the radius of the lubricating oil side is large, so that leaked lubricating oil flows back to the lubricating oil cavity on a rotor runway through centrifugal force, and leakage is reduced; along with the increase of the rotating speed, the lubricating oil in the oil collecting groove flows back to the lubricating oil cavity along with the centrifugal force of the runway, and lubricating oil leakage is reduced; local lubricating oil can be thrown out of a rotor runway, local pressure is increased through the centrifugal effect, and the situation that the lubricating oil leaks to a sealing face is reduced.

Description

Technical Field

[0001] The present invention relates to an oil return type aero-engine bearing cavity graphite sealing structure, belonging to the technical field of bearing cavity lubricating oil sealing in aero-engines and gas turbines, and in particular to a conical graphite circumferential sealing structure with an oil return function. Background Art

[0002] Aircraft engines operate under extreme conditions (such as high temperature, high pressure, and high speed). Lubricating oil is required within the bearing cavity to reduce friction, dissipate heat, and maintain a seal. However, oil leakage or the intrusion of external contaminants directly threatens the engine's lifespan and safety. The oil seal structure within the aircraft engine bearing cavity is a critical component for safe and efficient engine operation. Its primary function is to separate the lubricating oil in the bearing cavity from the high-pressure air in the seal cavity, preventing leakage between the two.

[0003] Bearing cavity oil seals are divided into contact and non-contact types. Contact seals are further divided into face seals, circumferential seals, and floating ring seals. Typically, the air leakage rate of a contact seal structure is 1 to 2 g / s, while the leakage rate of a non-contact seal is more than 10 times that of a contact seal.

[0004] Graphite seals are a typical contact seal structure. Graphite possesses many excellent properties, such as low density, self-lubrication, good chemical stability, high thermal conductivity, low thermal expansion coefficient, and low friction coefficient. These advantages have long made graphite seals the mainstream lubricating oil seals in aircraft engine main bearing cavities. Theoretical research and engineering experience indicate that within the engine bearing cavity, the rotation of bearings and shaft components, as well as the driving force of the rotor seal runway chamfer, can induce strong oil-gas vortices, causing localized pressure increases. This can cause a small amount of lubricating oil to rush into the sealing surface, resulting in oil leakage. Currently, reducing lubricating oil leakage from the sealing surface of graphite seals remains a technical challenge.

[0005] In the prior art, the method used is Figure 4 The conventional double-ring graphite circumferential seal structure shown in the figure features a cover ring and main ring constructed of graphite. A circumferential tension spring clamps the graphite ring against the rotor raceway, forming a circumferential sealing surface, while an axial compression spring presses the graphite ring against the seal seat, forming an end-face sealing surface. During operation, the rotation of the bearings and shaft components, as well as the driving force of the chamfered rotor seal raceway, can induce strong oil-gas vortices, causing localized pressure increases. This can cause a small amount of lubricating oil to rush into the sealing surface, leading to oil leakage. However, the circumferential sealing surface of conventional graphite circumferential seals is cylindrical, preventing oil from leaking back. Furthermore, due to the lack of an isolation device, oil from one side of the oil chamber can be sprayed heavily toward the sealing surface, exacerbating outward oil leakage and resulting in significant oil consumption, impacting flight time and safety. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an oil-returning graphite sealing structure for the bearing cavity of an aircraft engine. The oil-returning graphite sealing structure for the bearing cavity of an aircraft engine realizes the oil return function of the lubricating oil at the sealing device by opening an oil collecting tank on the sealing runway and adding an oil throwing structure, so as to achieve the purpose of reducing the lubricating oil leakage rate.

[0007] The present invention is achieved through the following technical solutions.

[0008] The present invention provides an oil-return type graphite sealing structure for a bearing cavity of an aero-engine, comprising a graphite ring; the graphite ring is a single-ring multi-petal structure or a multi-ring multi-petal structure; the outer annular surface of the graphite ring is tightened by a circumferential tensile spring; the inner annular surface of the graphite ring is a conical surface, which is tightly fitted on a rotor runway to form a conical circumferential sealing surface; one end of the graphite ring is fitted with a sealing seat to form an end face sealing surface, and the other end of the graphite ring is provided with a relief groove, which is fitted with a spring seat; a wave spring is provided between the sealing seat and the spring seat, and a retaining ring is provided between the wave spring and the sealing seat; an oil collecting groove is provided on the sealing conical surface of the rotor runway, and an oil-slinging rib is provided on the side of the rotor runway close to the lubricating oil cavity; the number of segments of each graphite ring is divided into three sections according to the sealing diameter within 120 mm; if the sealing diameter exceeds 120 mm, the arc length of each section is determined to be 120 mm to 160 mm.

[0009] One end of the clamping ring is in contact with the sealing seat, and the other end of the clamping ring is used to axially limit the wave spring.

[0010] The sealing seat is assembled on the stationary casing.

[0011] The inclination angle of the circumferential sealing surface between the graphite ring and the rotor raceway is spring seat 1° to 15°.

[0012] The wave spring may be replaced by a compression thread spring.

[0013] The clamping ring and the spring seat are fixed on the sealing seat by bolts.

[0014] The outer annular surface of the rotor runway is a conical surface.

[0015] The oil collecting trough is square, and the oil throwing ribs are straight ribs or oblique ribs.

[0016] The inner ring surface of the graphite ring is not grooved.

[0017] The graphite ring is a single ring, a double ring or a triple ring.

[0018] The beneficial effects of the present invention are as follows: the radius on the air side is small and the radius on the lubricating oil side is large, so that the leaked lubricating oil is caused to flow back to the lubricating oil cavity by centrifugal force on the rotor runway, thereby reducing leakage; as the rotation speed increases, the lubricating oil in the oil collecting tank will flow back to the lubricating oil cavity by the centrifugal force of the runway, thereby reducing lubricating oil leakage; the local lubricating oil can be thrown out of the rotor runway, and the local pressure can be increased by centrifugal action, thereby reducing the leakage of lubricating oil to the sealing surface; high-pressure gas is introduced into the sealing runway to form an air film, and the sealing pressure difference on the effective sealing surface is increased, and the inner ring surface of the graphite ring does not need to be grooved, thereby reducing the processing cost and difficulty of the graphite ring and also improving the qualified rate of graphite products. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention;

[0020] Figure 2 is a three-dimensional diagram of the rotor runway of the present invention;

[0021] Figure 3 is a three-dimensional diagram of the graphite ring of the present invention;

[0022] Figure 4 This is a schematic structural diagram of a graphite circumferential sealing structure of a bearing cavity in the prior art;

[0023] Figure 5 It is a partial structural diagram of the graphite ring of the present invention;

[0024] Figure 6 It is an enlarged view of the overlapping method of the graphite ring segments of the present invention;

[0025] In the figure: 1- sealing seat, 2- circumferential tension spring, 3- graphite ring, 4- bolt, 5- spring seat, 6- wave spring, 7- retaining ring, 8- rotor runway. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0027] Example 1

[0028] In order to reduce the amount of lubricating oil leakage, the present invention provides an oil return type aircraft engine bearing cavity graphite sealing structure, such as Figures 1 to 3As shown, it includes a graphite ring 3; the graphite ring 3 is a single-ring multi-petal structure, the outer ring surface of the graphite ring 3 is tightened by a circumferential tension spring 2, and the inner ring surface of the graphite ring 3 is a conical surface, which fits tightly on the rotor runway 8 to form a conical circumferential sealing surface; one end of the graphite ring 3 is fitted with a sealing seat 1 to form an end face sealing surface, and the other end of the graphite ring 3 is provided with a unloading groove, which is fitted with a spring seat 5. High-pressure gas flows into the inner cavity of the graphite sealing device through the unloading groove, thereby increasing the sealing pressure difference of the end face sealing surface; there is a sealing seat 1 between the sealing seat 1 and the spring seat 5. A wave spring 6, a snap ring 7 is provided between the wave spring 6 and the sealing seat 1; an oil collecting groove is provided on the sealing cone surface of the rotor runway 8, and an oil-swinging rib is provided on the side of the rotor runway 8 close to the lubricating oil cavity, which can swing the local lubricating oil out of the rotor runway 8. At the same time, the local pressure is increased through centrifugal action, reducing the leakage of lubricating oil to the sealing surface, further reducing the leakage of lubricating oil; the number of ring segments of each graphite ring 3 is divided into 3 sections according to the sealing diameter within 120mm, and the sealing diameter exceeding 120mm is determined by the arc length of each section being 120mm to 160mm.

[0029] Furthermore, the circumferential sealing surface is a conical surface with a small radius on the air side and a large radius on the oil side, so that the leaked oil flows back to the oil cavity on the rotor runway 8 due to centrifugal force, thereby reducing leakage.

[0030] One end of the clamping ring 7 is in contact with the sealing seat 1 , and the other end axially limits the wave spring 6 , so that the wave spring 6 presses the spring seat 5 , thereby making the graphite ring 3 fit tightly on the sealing seat 1 .

[0031] The sealing seat 1 is assembled on the stationary casing.

[0032] The inclination angle of the circumferential sealing surface between the graphite ring 3 and the rotor raceway 8 is 5° to 15°.

[0033] The wave spring 6 can be replaced by a compression thread spring.

[0034] The snap ring 7 and the spring seat 5 are fixed to the sealing seat 1 by means of bolts 4 , and the sealing seat 1 is assembled on the stationary casing and remains stationary.

[0035] The outer annular surface of the rotor runway 8 is a conical surface.

[0036] The oil collecting trough is square or in other shapes, and the oil throwing ribs are straight ribs or oblique ribs.

[0037] Specifically, the oil collecting tank can be used to collect leaked lubricating oil, and can also allow high-pressure gas to flow in to increase the local pressure difference of the effective sealing surface.

[0038] Specifically, the oil-slinging ribs can increase the local centrifugal force and throw the leaked lubricating oil into the lubricating oil cavity.

[0039] The inner ring surface of the graphite ring 3 is not grooved, which reduces the processing cost and difficulty of the graphite ring 3.

[0040] The graphite ring 3 is a single ring, a double ring or a triple ring.

[0041] Preferably, the elastic forces of the circumferential tension spring 2 and the wave spring 6 should meet the follow-up requirements.

[0042] Furthermore, the rotor raceway 8 is a full-ring structure with an oil collecting groove and oil-slinging ribs, the sealing surface of the rotor raceway 8 is a conical surface, and the graphite ring 3 is a multi-segment single-ring structure or a multi-ring structure uniformly distributed around the circumference.

[0043] Specifically, the circumferential tension spring 2 circumferentially clamps the multiple graphite rings 3 to form a circular ring, and the inner diameter of the circular ring is a conical surface.

[0044] During operation, when the lubricating oil in the bearing cavity enters the edge of the graphite sealing device, the oil-swinging ribs on the rotor runway 8 draw most of the lubricating oil back to the lubricating oil cavity under the action of the rotating centrifugal force, and a small part of the lubricating oil that seeps into the rotor runway 8 is gathered in the oil collecting tank. Since the rotor runway 8 is a conical surface, the lubricating oil in the oil collecting tank will be slowly drawn back to the lubricating oil cavity under the centrifugal action of the rotor runway 8, thereby greatly reducing the lubricating oil leakage rate of the bearing cavity.

[0045] Example 2

[0046] like Figure 5 and 6 As shown, the graphite ring 3 takes a single-ring six-segment structure as an example. The unloading groove of the graphite ring 3 can reduce the axial and radial gas pressure differences, and at the same time guide the high-pressure air to the end sealing surface of the graphite ring 3 and the sealing seat 1, thereby increasing the local sealing pressure difference.

[0047] Furthermore, the graphite ring segments are matched with square lap grooves and lap joints, and there is a gap of 0.2mm to 0.6mm in the circumferential direction of the ring segments to prevent the ring segments from tightening and causing the circumferential sealing surface gap to increase. The other two lap surfaces are tightly fitted to prevent lubricating oil from leaking from the gap.

[0048] Specifically, an axial anti-rotation hole is provided at the center of the ring segment, which cooperates with the anti-rotation pin to prevent the graphite ring 3 from rotating circumferentially. The anti-rotation structure cannot affect the small radial movement of the graphite ring 3, maintaining its follow-up performance.

[0049] To summarize, the circumferential sealing surface is designed to be a conical surface with a small radius on the air side and a large radius on the lubricating oil side, so that the leaked lubricating oil will flow back to the lubricating oil cavity through centrifugal force on the rotor runway, thereby reducing leakage; an oil collecting groove is designed on the rotor runway, so that the leaked lubricating oil at low speed accumulates in the oil collecting groove. As the speed increases, the lubricating oil in the oil collecting groove will flow back to the lubricating oil cavity due to the centrifugal force of the runway, thereby reducing lubricating oil leakage; oil-swinging ribs are designed on the lubricating oil side of the rotor runway, which can swing local lubricating oil out of the rotor runway, and at the same time increase local pressure through centrifugal action, thereby reducing lubricating oil leakage to the sealing surface; the oil collecting groove on the rotor runway has an unloading function, which introduces high-pressure gas into the sealing runway to form an air film, and at the same time increases the sealing pressure difference on the effective sealing surface. The inner ring surface of the graphite ring does not need to be grooved, which reduces the processing cost and difficulty of the graphite ring, and also improves the qualified rate of graphite products.

Claims

1. A graphite sealing structure for an oil-returning aircraft engine bearing cavity, comprising a graphite ring (3), characterized in that: The graphite ring (3) is a single-ring multi-petal structure or a multi-ring multi-petal structure. The outer ring surface of the graphite ring (3) is tightened by a circumferential tension spring (2). The inner ring surface of the graphite ring (3) is a conical surface. The conical surface is tightly fitted on the rotor runway (8) to form a conical circumferential sealing surface. One end of the graphite ring (3) is fitted with a sealing seat (1) to form an end face sealing surface. The other end of the graphite ring (3) is provided with a unloading groove and fitted with a spring seat (5). A wave spring (6) is provided between the sealing seat (1) and the spring seat (5), and a clamping ring (7) is provided between the wave spring (6) and the sealing seat (1). An oil collecting groove is provided on the sealing conical surface of the rotor runway (8), and an oil-splitting rib is provided on the side of the rotor runway (8) close to the lubricating oil cavity. The number of ring segments of each graphite ring (3) is divided into three sections according to the sealing diameter within 120 mm. If the sealing diameter exceeds 120 mm, the arc length of each section is determined to be 120 mm to 160 mm.

2. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: One end of the snap ring (7) is in contact with the sealing seat (1), and the other end of the snap ring (7) limits the axial position of the wave spring (6).

3. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The sealing seat (1) is assembled on the stationary casing.

4. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The inclination angle of the circumferential sealing surface between the graphite ring (3) and the rotor raceway (8) is in the range of the spring seat (5)° to 15°.

5. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The wave spring (6) can be replaced by a compression thread spring.

6. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The snap ring (7) and the spring seat (5) are fixed on the sealing seat (1) via bolts (4).

7. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The outer annular surface of the rotor runway (8) is a conical surface.

8. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The oil collecting trough is square, and the oil throwing ribs are straight ribs or oblique ribs.

9. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The inner ring surface of the graphite ring (3) is not grooved.

10. The oil return type aircraft engine bearing cavity graphite seal structure according to claim 1, characterized in that: The graphite ring (3) is a single ring, a double ring or a triple ring.

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