Grate tooth sealing structure with brush wire bushing

Abstract

The invention discloses a labyrinth sealing structure with a brush wire bush, and belongs to the field of aero-engine sealing. The sealing structure comprises a plurality of comb teeth on the rotor rotating shaft and a brush wire assembly on the inner circumferential surface of the stator bushing; the multiple labyrinth teeth are arranged in the axial direction of the rotor rotating shaft to form multiple annular non-closed cavity structures in the circumferential direction of the rotor rotating shaft, namely multiple tooth cavities, and speed reduction is conducted on upstream high-pressure airflow. The brush wire assembly comprises an annular front baffle located on the inner circumferential face of the lining, a rear baffle and a brush wire bundle located between the front baffle and the rear baffle, and the inner end of the brush wire bundle is coupled with the comb teeth at the axial tail end of the rotating shaft so as to achieve tail end sealing. According to the sealing structure, the sealing effect is improved, and the gas leakage rate is reduced.

Description

Technical Field

[0001] The invention belongs to the field of aviation engine sealing, and in particular relates to a comb tooth sealing structure containing a brush bushing and a design method thereof. Background Art

[0002] With the continuous development of turbine machinery such as aircraft engines, high-performance sealing devices have an important impact on maintaining stable and reliable operation and improving overall performance. The use of advanced sealing devices can not only reduce the overall failure rate of aircraft engines, but also increase thrust by reducing the flow loss of the aircraft engine air system, thereby improving engine performance. At present, common sealing structures in aircraft engines include: comb seals, brush seals, graphite seals, etc. Among them, comb seals have the advantages of simple structure, reliable performance, and relatively low manufacturing difficulty, and are widely used.

[0003] As a non-contact dynamic seal, the principle of the grate seal is to increase the flow resistance by the sudden expansion and contraction of the channel to reduce gas leakage. However, the inherent gap will have a significant impact on the sealing performance. If the running gap is too small, it is easy to cause collision and wear between the grate teeth and the wall surface, which makes it difficult for typical grate seals to meet the increasingly stringent sealing requirements of aircraft engines. Therefore, further improving the sealing performance and working stability of the grate seal and reducing the collision and wear of the grate teeth has become a problem that needs to be solved urgently.

[0004] Compared with comb seals, brush seals have better sealing performance, but under high speed conditions, the intense friction between the brush wire and the wall surface can easily lead to problems such as brush wire melting and reduced service life. At present, there are some sealing structures that combine brush wires with comb teeth. Most of them arrange the brush wires on the rotor or comb teeth. Although this sealing structure can improve the sealing performance to a certain extent, it still cannot reduce the problem of friction between the comb teeth and the stator when radial displacement occurs. In addition, the brush wires are prone to intense friction with the wall surface, which can cause problems such as brush wire breakage and increased leakage.

[0005] Therefore, in view of the above situation, the present invention combines the key advantages of brush seal and comb seal to provide a comb seal structure in which brushes are installed on a stator, namely, a brush bushing is included. Summary of the invention

[0006] Technical issues to be solved:

[0007] In order to avoid the shortcomings of the prior art, the present invention provides a comb teeth sealing structure including a brush bushing, which cooperates with the comb teeth on the rotating shaft, and allows the comb teeth to have a larger radial installation gap while maintaining good sealing performance, thereby reducing the wear of the comb teeth. Therefore, the sealing structure of the present invention improves the sealing effect and reduces the gas leakage.

[0008] The technical solution of the present invention is: a design method of a comb tooth sealing structure containing a brush bushing, and the specific steps are as follows:

[0009] Based on the structural characteristics of the non-contact dynamic seal, the gap size between the rotor shaft and the stator bushing is obtained; the gap size includes the axial length and radial distance of the gap;

[0010] The position and number of the tooth chambers are determined according to the axial length of the gap; the tooth chamber is an annular non-closed cavity structure formed by adjacent comb teeth arranged on the circumferential surface of the rotating shaft;

[0011] The height of the tooth cavity is determined according to the radial distance of the gap, that is, the radial height of the comb teeth is obtained;

[0012] The comb teeth at the axial end of the shaft are coupled with the brush wire assembly on the inner circumference of the bushing. The two are positioned opposite to each other in the axial direction and a gap is left at the opposite ends to achieve end sealing, thus completing the design of the sealing structure.

[0013] A further technical solution of the present invention is that the number of the tooth cavities is 4, the axial spacing of the first 4 stages of comb teeth constituting the four tooth cavities is consistent, both being 6 to 7 mm, and the first 4 stages of comb teeth form an angle of 75° with the circumferential surface of the rotating shaft in the incoming flow direction.

[0014] A further technical solution of the present invention is that the comb teeth at the axial end of the rotating shaft form an angle of 90 degrees with the axial direction of the rotating shaft.

[0015] A comb tooth sealing structure with a brush bushing, comprising a plurality of comb teeth on a rotor shaft and a brush assembly on the inner circumference of a stator bushing;

[0016] A plurality of comb teeth are arranged along the axial direction of the rotor shaft to form a plurality of annular non-enclosed cavity structures around the circumference of the rotor shaft, i.e., a plurality of tooth cavities, to reduce the speed of the upstream high-pressure airflow;

[0017] The brush assembly includes an annular front baffle and a rear baffle located on the inner circumference of the bushing and a brush bundle located between the front and rear baffles. The inner end of the brush bundle is coupled with the comb teeth at the axial end of the rotating shaft to achieve end sealing.

[0018] A further technical solution of the present invention is: five levels of grate teeth are axially arranged on the circumferential surface of the rotor shaft, the radial heights of the first four levels of grate teeth along the incoming flow direction are equal, and the radial height of the fifth level of grate teeth is less than the radial heights of the first four levels of grate teeth.

[0019] A further technical solution of the present invention is: the first four stages of comb teeth form an angle of 75° with the circumferential surface of the rotating shaft in the incoming flow direction, the axial spacing between adjacent comb teeth is 6 to 7 mm, and during installation, the radial clearance between the ends of the first four stages of comb teeth and the inner circumferential surface of the stator bushing is 0.8 to 1.2 mm.

[0020] A further technical solution of the present invention is: the fifth-stage comb teeth are the comb teeth at the axial end of the shaft, which form an angle of 90 degrees with the circumferential surface of the shaft, are perpendicular to the circumferential surface of the shaft, and together with the first four stages of comb teeth, form four comb tooth cavities.

[0021] A further technical solution of the present invention is that the radial height of the fifth stage of comb teeth is 1 / 2 to 2 / 3 of the radial height of the first four stages of comb teeth.

[0022] A further technical solution of the present invention is: the radial height of the front baffle and the rear baffle is greater than the radial clearance between the ends of the first four stages of comb teeth and the inner circumference of the stator bushing; the radial length of the brush filaments in the axial middle position of the brush filament bundle is 0.1 to 0.2 mm shorter than the radial height of the front and rear baffles, and is complementary to the radial height of the fifth stage of comb teeth, and is located at the same axial position; the radial length of the brush filaments on both sides of the middle gradually increases, and the radial length of the outer brush filaments close to the front baffle and the rear baffle is 0.1 to 0.2 mm larger than the height of the front and rear baffles.

[0023] A further technical solution of the present invention is that the brush filaments of the brush filament bundle are inclined 45 degrees in the circumferential direction, and the brush filaments in adjacent rows are staggered in the axial direction.

[0024] Beneficial Effects

[0025] The beneficial effect of the present invention is that the present invention can further reduce the leakage gap of the final comb teeth by using a sealing bushing with a brush wire assembly, increase the flow resistance, and greatly reduce the leakage of the airflow. The brush wire assembly is installed above the final comb teeth to form a vortex in the upstream high-pressure airflow in the first four tooth cavities to enhance turbulent dissipation and thus reduce the axial velocity of the airflow, thereby reducing the impact of the airflow on the brush wire.

[0026] Compared with the straight-through grate structure, the first to fourth-stage grate is set as a helical tooth with an angle of 75° with the rotor wall, which can fully dissipate the energy of the airflow in the first four tooth cavities, and the axial velocity of the airflow in the fourth tooth cavity is lower, and the overall leakage is reduced. The use of five-stage grate and the axial spacing is controlled at 6-7mm to avoid the axial length of the sealing structure being too long, and the vortex formed by the airflow in the tooth cavity can be fully developed and dissipated more fully. The fifth-stage grate is designed as a straight-through grate to prevent the grate from rubbing against the baffle when axial displacement occurs.

[0027] Different from the sealing structure where the brush wire and the comb teeth are installed on the rotor at the same time, installing the brush wire on the stator in conjunction with the comb teeth can convert the friction between the comb teeth and the stator wall when radial displacement occurs into the contact friction between the comb tooth tip and the flexible brush wire, greatly reducing the wear of the comb teeth. The brush wire installed at a 45° circumferential inclination can bend and contact the comb teeth when the comb teeth undergo a certain radial and axial displacement, ensuring that the sealing performance is not greatly affected.

[0028] At the same time, since the brush wire assembly cooperates with the fifth-stage comb teeth to achieve a better sealing effect, the first four-stage bevel teeth can leave a larger comb tooth gap to avoid collision and wear. Compared with the use of non-metallic bushings such as honeycomb bushings, the contact between the comb teeth and the bushing will cause bushing wear. The flexible brush wire used in the present invention can restore the original state after the interference between the comb teeth and the brush wire, thereby enhancing the stability of the sealing structure and extending the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 : A cross-sectional view of a comb tooth sealing structure containing a brush bushing in an embodiment of the present invention;

[0030] Figure 2 : A front view of a comb tooth sealing structure containing a brush bushing according to an embodiment of the present invention;

[0031] Figure 3 : A cross-sectional view of a sealing bushing in an embodiment of the present invention (upper half);

[0032] Figure 4 : A schematic diagram of the comb teeth structure in an embodiment of the present invention;

[0033] Figure 5 : A partial enlarged view of the brush bundle in an embodiment of the present invention;

[0034] Figure 6 : Total pressure and streamline diagram of the comb tooth sealing structure containing a brush bushing of the present invention;

[0035] Explanation of the accompanying drawings: 1-sealing bushing, 2-front baffle, 3-rear baffle, 4-brush bundle, 5-rotating shaft, 6-first-stage comb teeth, 7-second-stage comb teeth, 8-third-stage comb teeth, 9-fourth-stage comb teeth, 10-fifth-stage comb teeth. DETAILED DESCRIPTION

[0036] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] The existing comb tooth structure usually has poor sealing effect, and is prone to friction with the inner circumference of the stator bushing during high-speed operation. In order to improve the sealing effect of the comb tooth seal, the gap between the comb tooth tip and the stator wall surface needs to be further reduced, and the reduction in the gap will aggravate the friction, and vice versa. As a contact seal, the brush seal can adapt to the rotor jump and maintain a good sealing effect when its precisely staggered flexible brush wires are installed at an angle. However, under high-speed conditions, the violent friction between the free end of the brush wire and the rotor contact surface of the brush seal can easily cause the brush wire to melt, thereby causing problems such as increased leakage and reduced service life of the brush seal. Therefore, combining the key advantages of brush seals and comb tooth seals has become one of the directions for solving the above problems. However, some of the existing sealing structures combining comb teeth and brush wires cannot effectively solve the problem of severe friction or even fracture between the comb teeth and the inner circumference of the stator bushing when the comb teeth undergo large radial displacements.

[0039] Based on the above problems, the present invention provides a comb sealing structure containing a brush bushing, comprising a plurality of comb teeth on a rotor shaft and a brush assembly on the inner circumference of a stator bushing; the plurality of comb teeth are arranged along the axial direction of the rotor shaft to form a plurality of annular non-closed cavity structures around the circumference of the rotor shaft, i.e., a plurality of tooth cavities, to reduce the speed of the upstream high-pressure airflow; the brush assembly comprises an annular front baffle and a rear baffle located on the inner circumference of the bushing and a brush bundle located between the front and rear baffles, the inner end of the brush bundle is coupled with the comb teeth at the axial end of the shaft to achieve end sealing.

[0040] Specifically, five levels of grate teeth are axially arranged on the circumferential surface of the rotor shaft, the radial heights of the first four levels of grate teeth along the incoming flow direction are equal, and the radial height of the fifth level of grate teeth is less than the radial heights of the first four levels of grate teeth.

[0041] Specifically, the first four stages of comb teeth form an angle of 75° with the circumferential surface of the rotating shaft in the incoming flow direction, the axial spacing between adjacent comb teeth is 6-7 mm, and during installation, the radial clearance between the ends of the first four stages of comb teeth and the inner circumferential surface of the stator bushing is 0.8-1.2 mm.

[0042] Specifically, the fifth-stage comb teeth are the comb teeth at the axial end of the rotating shaft, which form an angle of 90 degrees with the circumferential surface of the rotating shaft, are perpendicular to the circumferential surface of the rotating shaft, and together with the first four stages of comb teeth, form four comb tooth cavities.

[0043] Specifically, the radial height of the fifth stage of comb teeth is 1 / 2 to 2 / 3 of the radial height of the first four stages of comb teeth.

[0044] Specifically, the radial height of the front baffle and the rear baffle is greater than the radial clearance between the ends of the first four stages of comb teeth and the inner circumference of the stator bushing; the radial length of the brush filaments in the axial middle position of the brush filament bundle is 0.1 to 0.2 mm shorter than the radial height of the front and rear baffles, and is complementary to the radial height of the fifth stage of comb teeth and is located at the same axial position; the radial length of the brush filaments on both sides of the middle gradually increases, and the radial length of the outer brush filaments close to the front baffle and the rear baffle is 0.1 to 0.2 mm larger than the height of the front and rear baffles.

[0045] Specifically, the brush filaments of the brush filament bundle are inclined at 45 degrees in the circumferential direction, and the brush filaments in adjacent rows are staggered in the axial direction.

[0046] The present invention discloses a comb tooth sealing structure containing a brush wire bushing, which utilizes a sealing bushing with flexible brush wires to cooperate with the comb teeth, which can not only maintain a good sealing effect, but also reduce the wear of the comb teeth when the comb teeth undergo radial and axial displacements. In actual work, the high-pressure side airflow passes through the widening and contracting structures of the first four stages of the comb teeth, forming a vortex in the tooth cavity, and the kinetic energy of the gas is dissipated to a certain extent. Subsequently, the gas flows through the brush wire structure and the final stage of the comb teeth, interacting with the brush wires, which helps to improve the sealing effect and further reduce the amount of gas leakage. Compared with traditional comb tooth seals and brush seals, this structure solves the problems of poor sealing effect of traditional comb tooth seals, easy friction between the comb teeth and the stator under high speed conditions, and thus causing wear or breakage of the comb tooth tips. Different from the transition or interference fit installation method commonly used in brush seals, the sealing bushing proposed in the present invention will leave a certain gap between the brush wire bundle and the comb tooth tip during installation, thereby avoiding severe friction between the free end of the brush wire and the comb tooth under high speed conditions, which may cause the brush wire to melt and increase the airflow leakage. Compared with the existing sealing structure in which the brush wire and the comb tooth are installed on the rotor at the same time, installing the brush wire structure on the stator and cooperating with the comb tooth can convert the friction between the comb tooth tip and the stator wall during radial displacement into the contact friction between the comb tooth tip and the flexible brush wire, greatly reducing the wear of the fifth-stage comb tooth. At the same time, the first four-stage helical teeth can leave a larger comb tooth gap to avoid friction with the stator wall due to the good sealing effect provided by the brush wire bushing and the fifth-stage comb tooth. The sealing structure can be applied to the parts in aircraft engines or gas turbines where there is a pressure difference and relative rotation and gas leakage needs to be sealed.

[0047] The above technical solution is further described below in conjunction with the accompanying drawings:

[0048] Reference Figure 1 , Figure 2As shown, a grate sealing structure with a brush bushing in this embodiment includes a sealing bushing 1 and a rotating shaft 5. The rotating shaft 5 is provided with five levels of grate teeth in the axial direction, namely, the first level grate teeth 6, the second level grate teeth 7, the third level grate teeth 8, the fourth level grate teeth 9, and the fifth level grate teeth 10. The five levels of grate teeth form four grate tooth cavities. A brush assembly is provided on the inner circumference of the sealing bushing 1, including a front baffle plate 2, a rear baffle plate 3, and a brush bundle 4. The installation position of the brush assembly corresponds to the fifth level grate teeth 10, and the brush wire with a shorter central radial length is directly opposite to the tooth tip position of the grate teeth 10.

[0049] Reference Figure 3 , Figure 4 As shown, the five-stage comb structure axially arranged on the rotating shaft is characterized in that the first to fourth stage combs are at an angle of 75° with the rotor wall, and the radial clearance with the stator wall can reach 0.8-1.2 mm during installation. The radial height of the fifth stage comb 10 is smaller than the first stage comb 6, the second stage comb 7, the third stage comb 8, and the fourth stage comb 9, and the height is 1 / 2-2 / 3 of the first four stages comb. The comb spacing is 0.6-0.7 mm. In actual work, the upstream high-pressure airflow passes through the tooth cavity of the first to fourth stage combs, and a vortex is formed in the tooth cavity, the axial velocity of the airflow is reduced, the leakage is reduced, and the airflow influence on the brush bundle 4 is reduced.

[0050] Reference Figure 5 As shown, the brush bundle 4 is installed at a 45° tilt along the circumferential direction, the brush diameter is 0.07-0.09 mm, and the radial length of the middle brush is the smallest, and the length of the brush gradually increases toward the sides. The middle brush is 0.1-0.2 mm shorter than the height of the front and rear baffles, and the radial length of the outer brush is 0.1-0.2 mm greater than the height of the front and rear baffles. There is a certain gap between the brush bundle 4 and the comb teeth 10.

[0051] Reference Figure 6 As shown in the figure, this design can convert the friction between the grate teeth and the stator wall into the contact friction between the grate tooth tip and the flexible brush wire when the grate teeth produce a certain axial or radial displacement, which greatly reduces the wear of the fifth-stage grate teeth 10. At the same time, the first four stages of the grate teeth have a large gap between the grate teeth to avoid collision with the stator wall. The interference between the brush wire bundle 4 and the fifth-stage grate teeth 10 can maintain the sealing performance and recover after the interference, which improves the stability and service life of the sealing structure.

[0052] In addition, the sealing structure can be adjusted according to actual usage requirements. For example, the axial distance between the fifth-stage comb teeth and the fourth-stage comb teeth can be appropriately increased; when the sealing requirements are met, the number of comb teeth can be reduced to four or three levels; to avoid serious collision and wear, the radial height of the first four stages of comb teeth can also be appropriately reduced; the comb tooth shape can also be changed and adjusted.

[0053] The present embodiment provides a design method for a comb tooth sealing structure including a brush bushing, and the specific steps are as follows:

[0054] Step 1: Based on the structural characteristics of the non-contact dynamic seal, the gap size between the rotor shaft and the stator bushing is obtained; the gap size includes the axial length and radial distance of the gap;

[0055] Step 2: Determine the position and number of tooth cavities according to the axial length of the gap; the tooth cavity is an annular non-closed cavity structure formed by adjacent comb teeth arranged on the circumferential surface of the rotating shaft;

[0056] Step 3: Determine the height of the tooth cavity according to the radial distance of the gap, that is, obtain the radial height of the comb teeth;

[0057] Step 4: Couple the comb teeth at the axial end of the shaft with the brush assembly on the inner circumference of the bushing. The two are positioned opposite to each other in the axial direction and a gap is left at the opposite ends to achieve end sealing, thus completing the design of the sealing structure.

[0058] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A design method for a comb tooth sealing structure containing a brush bushing, characterized in that The specific steps are as follows: Based on the structural characteristics of the non-contact dynamic seal, the gap size between the rotor shaft and the stator bushing is obtained; the gap size includes the axial length and radial distance of the gap; The position and number of the tooth chambers are determined according to the axial length of the gap; the tooth chamber is an annular non-closed cavity structure formed by adjacent comb teeth arranged on the circumferential surface of the rotating shaft; The height of the tooth cavity is determined according to the radial distance of the gap, that is, the radial height of the comb teeth is obtained; The comb teeth at the axial end of the shaft are coupled with the brush wire assembly on the inner circumference of the bushing. The two are positioned opposite to each other in the axial direction and a gap is left at the opposite ends to achieve end sealing, thus completing the design of the sealing structure.

2. A design method for a comb tooth sealing structure containing a brush bushing according to claim 1, characterized in that: The number of the tooth cavities is 4, and the axial spacing of the first four stages of comb teeth constituting the four tooth cavities is consistent, all being 6 to 7 mm, and the first four stages of comb teeth form an angle of 75° with the peripheral surface of the rotating shaft in the incoming flow direction.

3. The design method of a comb tooth sealing structure containing a brush bushing according to claim 2, characterized in that: The comb teeth at the axial end of the rotating shaft form an angle of 90 degrees with the axial direction of the rotating shaft.

4. A comb tooth sealing structure containing a brush bushing, designed based on the design method of a comb tooth sealing structure containing a brush bushing according to any one of claims 1 to 3; characterized in that: It includes a plurality of comb teeth on the rotor shaft and a brush wire assembly on the inner peripheral surface of the stator bushing; A plurality of comb teeth are arranged along the axial direction of the rotor shaft to form a plurality of annular non-enclosed cavity structures around the circumference of the rotor shaft, i.e., a plurality of tooth cavities, to reduce the speed of the upstream high-pressure airflow; The brush assembly includes an annular front baffle and a rear baffle located on the inner circumference of the bushing and a brush bundle located between the front and rear baffles. The inner end of the brush bundle is coupled with the comb teeth at the axial end of the rotating shaft to achieve end sealing.

5. A comb tooth sealing structure with a brush bushing according to claim 4, characterized in that: Five levels of grate teeth are axially arranged on the circumferential surface of the rotor shaft, the radial heights of the first four levels of grate teeth along the incoming flow direction are equal, and the radial height of the fifth level of grate teeth is less than the radial heights of the first four levels of grate teeth.

6. A comb teeth sealing structure with a brush bushing according to claim 5, characterized in that: The first four stages of comb teeth form an angle of 75° with the circumferential surface of the rotating shaft in the incoming flow direction, the axial spacing between adjacent comb teeth is 6-7 mm, and during installation, the radial clearance between the ends of the first four stages of comb teeth and the inner circumferential surface of the stator bushing is 0.8-1.2 mm.

7. A comb teeth sealing structure with a brush bushing according to claim 6, characterized in that: The fifth-stage comb teeth are the comb teeth at the axial end of the shaft, which form an angle of 90 degrees with the circumferential surface of the shaft, are perpendicular to the circumferential surface of the shaft, and together with the first four stages of comb teeth, form four comb tooth cavities.

8. A comb teeth sealing structure with a brush bushing according to claim 7, characterized in that: The radial height of the fifth stage of comb teeth is 1 / 2 to 2 / 3 of the radial height of the first four stages of comb teeth.

9. A comb tooth sealing structure with a brush bushing according to claim 8, characterized in that: The radial height of the front baffle and the rear baffle is greater than the radial clearance between the ends of the first four stages of comb teeth and the inner circumference of the stator bushing; the radial length of the brush filaments in the axial middle position of the brush filament bundle is 0.1 to 0.2 mm shorter than the radial height of the front and rear baffles, and is complementary to the radial height of the fifth stage of comb teeth and is located at the same axial position; the radial length of the brush filaments on both sides of the middle gradually increases, and the radial length of the outer brush filaments close to the front baffle and the rear baffle is 0.1 to 0.2 mm larger than the height of the front and rear baffles.

10. A comb teeth sealing structure with a brush bushing according to claim 9, characterized in that: The brush filaments of the brush filament bundle are inclined at 45 degrees in the circumferential direction, and the brush filaments in adjacent rows are staggered in the axial direction.

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