A labyrinth seal structure comprising a brush wire bushing

Abstract

The application discloses a brush wire bushing-containing labyrinth sealing structure, and belongs to the field of aero-engine sealing. The sealing structure comprises a plurality of labyrinths on a rotor rotating shaft and a brush wire assembly on an inner circumferential surface of a stator bushing. The plurality of labyrinths are arranged along the axial direction of the rotor rotating shaft, and form a plurality of annular non-closed cavity structures around the circumferential direction of the rotor rotating shaft, i.e. a plurality of tooth cavities, for reducing the speed of an upstream high-pressure airflow. The brush wire assembly comprises an annular front baffle on the inner circumferential surface of the bushing, a rear baffle and a brush wire bundle between the front baffle and the rear baffle. The inner end of the brush wire bundle is coupled with the labyrinth at the axial end of the rotating shaft, so as to realize end sealing. The sealing structure improves the sealing effect and reduces the gas leakage amount.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine sealing, specifically relating to a comb-tooth sealing structure containing a brush bushing and its design method. Background Technology

[0002] With the continuous development of turbine machinery such as aero engines, high-performance sealing devices have a significant impact on maintaining stable and reliable operation and improving overall performance. Employing advanced sealing devices can not only reduce the overall failure rate of aero engines but also increase thrust by reducing airflow losses in the aero engine's air system, thereby improving engine performance. Currently, common sealing structures in aero engines include: toothed seals, brush seals, and graphite seals. Among these, toothed seals have advantages such as simple structure, reliable performance, and relatively low manufacturing difficulty, and are widely used.

[0003] As a non-contact dynamic seal, the principle of a toothed seal is to increase flow resistance by suddenly expanding and contracting the channel to reduce gas leakage. However, its inherent gaps can significantly affect its sealing performance. If the operating gap is too small, it can easily lead to collisions and wear between the teeth and the wall surface, making it difficult for typical toothed seals to meet the increasingly stringent sealing requirements of aero-engines. Therefore, further improving the sealing performance and operational stability of toothed seals and reducing tooth collisions and wear has become an urgent problem to be solved.

[0004] Compared to grate seals, brush seals offer superior sealing performance. However, under high-speed conditions, the intense friction between the brush bristles and the wall surface can lead to bristle breakage and reduced service life. Currently, some sealing structures combine brush bristles with grate teeth, mostly arranging the bristles on the rotor or grate teeth. While this structure can improve sealing performance to some extent, it still cannot alleviate the problem of grate teeth rubbing against the stator during radial displacement. Furthermore, the brush bristles are prone to breakage and increased leakage due to intense friction with the wall surface.

[0005] Therefore, in view of the above situation, the present invention combines the key advantages of brush sealing and toothed sealing to provide a toothed sealing structure that includes brush bristles installed on the stator, i.e., a brush bristle bushing. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To overcome the shortcomings of existing technologies, this invention provides a toothed sealing structure with a bristle bushing. By cooperating with the bristle bushing and the teeth on the rotating shaft, a larger radial installation clearance is allowed for the teeth while maintaining good sealing performance, thereby reducing tooth wear. Therefore, the sealing structure of this invention improves the sealing effect and reduces gas leakage.

[0008] The technical solution of this invention is: a design method for a bristle sealing structure containing a bristle bushing, the specific steps of which are as follows:

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

[0010] The position and number of tooth cavities are determined based on the axial length of the gap; the tooth cavity is an annular, non-closed cavity structure composed of adjacent grating teeth arranged on the circumferential surface of the rotating shaft.

[0011] The height of the tooth cavity is determined by the radial distance of the gap, thus obtaining the radial height of the tooth;

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

[0013] A further technical solution of the present invention is: the number of tooth cavities is 4, the axial spacing of the first 4 stages of the tooth cavities is consistent, all being 6-7mm, and the first 4 stages of the tooth cavities form a 75° angle with the circumferential surface of the rotating shaft in the direction of the incoming flow.

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

[0015] A toothed sealing structure with a bristle bushing includes multiple teeth on a rotor shaft and a bristle assembly on the inner circumferential surface of a stator bushing.

[0016] Multiple grating teeth are arranged along the axial direction of the rotor shaft to form multiple annular non-closed cavity structures around the rotor shaft, i.e. multiple tooth cavities, which reduce the speed of the upstream high-pressure airflow.

[0017] The bristle assembly includes an annular front baffle, a rear baffle, and a bristle bundle located on the inner circumferential surface of the bushing. The inner end of the bristle bundle is coupled to the grating 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 grating teeth are arranged axially on the circumferential surface of the rotor shaft, the radial height of the first four levels of grating teeth along the incoming flow direction is equal, and the radial height of the fifth level of grating teeth is less than the radial height of the first four levels of grating teeth.

[0019] A further technical solution of the present invention is: the first four stages of the grating teeth form a 75° angle with the circumferential surface of the rotating shaft in the direction of the incoming flow, the axial distance between adjacent grating teeth is 6-7 mm, and the radial gap between the end of the first four stages of the grating teeth and the inner circumferential surface of the stator bushing is 0.8-1.2 mm during installation.

[0020] A further technical solution of the present invention is: the fifth-level sieve tooth is the sieve tooth at the axial end of the rotating shaft, which forms an angle of 90 degrees with the circumferential surface of the rotating shaft and is perpendicular to the circumferential surface of the rotating shaft, and together with the first four levels of sieve teeth, forms four sieve tooth cavities.

[0021] A further technical solution of the present invention is that the radial height of the fifth-level sieve tooth is 1 / 2 to 2 / 3 of the radial height of the first four-level sieve teeth.

[0022] A further technical solution of the present invention is as follows: the radial height of the front baffle and the rear baffle is greater than the radial gap between the end of the first four-stage grate teeth and the inner circumferential surface of the stator bushing; the radial length of the brush filaments at 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, complementing the radial height of the fifth-stage grate teeth, and 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 brush filaments on the outer side near the front and rear baffles is 0.1 to 0.2 mm greater than the height of the front and rear baffles.

[0023] A further technical solution of the present invention is: the brush filaments of the brush bundle are inclined at 45° in the circumferential direction, and the brush filaments of adjacent rows are arranged in an axially staggered manner.

[0024] Beneficial effects

[0025] The beneficial effects of this invention are as follows: The sealing bushing with a bristle assembly can further reduce the leakage gap of the final-stage grate teeth, increase flow resistance, and significantly reduce airflow leakage. The bristle assembly, installed above the final-stage grate teeth, allows the upstream high-pressure airflow to form vortices in the first four tooth cavities, enhancing turbulent dissipation and thus reducing the axial velocity of the airflow, thereby minimizing the impact of the airflow on the bristles.

[0026] Compared to a structure using straight-through grates throughout, the first to fourth stages of grates are designed as helical teeth with a 75° angle to the rotor wall. This allows for sufficient energy dissipation of the airflow within the first four stages, resulting in a lower axial velocity of the airflow in the fourth stage and reduced overall leakage. Using five stages of grates with an axial spacing of 6–7 mm avoids excessive axial length of the sealing structure, and allows the vortices formed by the airflow within the grates to develop fully, leading to more complete energy dissipation. The fifth stage grates are designed as straight-through grates to prevent rubbing between the grates and the baffle during axial displacement.

[0027] Unlike sealing structures where brush filaments and grating teeth are simultaneously mounted on the rotor, mounting the brush filaments on the stator in conjunction with the grating teeth converts the friction between the grating teeth and the stator wall during radial displacement into contact friction between the grating tooth tips and the flexible brush filaments, significantly reducing grating tooth wear. The brush filaments, installed at a 45° circumferential angle, can bend and contact the grating teeth when they undergo certain radial and axial displacement, ensuring that the sealing performance is not significantly affected.

[0028] Meanwhile, because the bristle assembly and the fifth-stage grate teeth work together to achieve a good sealing effect, the first four stages of helical teeth can have a large gap between them, thus avoiding wear. Compared to the wear caused by contact between the grate teeth and the bushing when using non-metallic bushings such as honeycomb bushings, this invention uses flexible bristles that can recover their original shape after interference between the grate teeth and the bristles, enhancing the stability of the sealing structure and extending its service life. Attached Figure Description

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

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

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

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

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

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

[0035] Explanation of reference numerals in the attached diagram: 1-Sealing bushing, 2-Front baffle, 3-Rear baffle, 4-Brush bristle bundle, 5-Spindle, 6-First-stage grate teeth, 7-Second-stage grate teeth, 8-Third-stage grate teeth, 9-Fourth-stage grate teeth, 10-Fifth-stage grate teeth. Detailed Implementation

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

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] Existing grate seals typically suffer from poor sealing performance and are prone to rubbing against the inner circumferential surface of the stator bushing during high-speed operation. To improve the sealing effect of grate seals, the gap between the grate tips and the stator wall needs to be further reduced; however, reducing the gap exacerbates rubbing, and vice versa. Brush seals, as a type of contact seal, can adapt to rotor movement and maintain a good sealing effect when their precisely staggered flexible bristles are installed at an angle. However, under high-speed conditions, the intense friction between the free ends of the bristles and the rotor contact surface can easily cause the bristles to melt and break, leading to increased leakage and reduced lifespan. Therefore, combining the key advantages of brush seals with grate seals is one direction for solving these problems. However, some existing sealing structures combining grate and bristles cannot effectively solve the problem of severe rubbing or even breakage between the grate and the inner circumferential surface of the stator bushing when the grate undergoes large radial displacement.

[0039] To address the aforementioned problems, this invention provides a grate sealing structure with a bristle bushing, comprising multiple grates on a rotor shaft and a bristle assembly on the inner circumferential surface of a stator bushing; the multiple grates are arranged axially along the rotor shaft to form multiple annular non-closed cavity structures, i.e., multiple tooth cavities, around the rotor shaft to reduce the speed of the upstream high-pressure airflow; the bristle assembly includes an annular front baffle, a rear baffle, and a bristle bundle located on the inner circumferential surface of the bushing, the inner end of the bristle bundle being coupled to the grates at the axial end of the rotor shaft to achieve end sealing.

[0040] Specifically, the rotor shaft has 5 levels of grating teeth arranged axially on its circumferential surface. The radial height of the first 4 levels of grating teeth along the incoming flow direction is equal, while the radial height of the 5th level of grating teeth is less than that of the first 4 levels.

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

[0042] Specifically, the fifth-level grating tooth is the grating tooth at the axial end of the rotating shaft, which forms a 90-degree angle with the circumferential surface of the rotating shaft and is perpendicular to the circumferential surface of the rotating shaft. Together with the first four levels of grating teeth, they form four grating tooth cavities.

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

[0044] Specifically, the radial height of the front baffle and the rear baffle is greater than the radial gap between the ends of the first four stages of the grate teeth and the inner circumferential surface of the stator bushing; the radial length of the brush filaments at the axial middle position of the bristle bundle is 0.1 to 0.2 mm shorter than the radial height of the front and rear baffles, complementing the radial height of the fifth stage of the grate teeth, and located in 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 near the front and rear baffles is 0.1 to 0.2 mm greater than the height of the front and rear baffles.

[0045] Specifically, the bristles of the bristle bundle are inclined at 45° circumferentially, and the bristles of adjacent rows are arranged in an axially staggered manner.

[0046] This invention discloses a grate sealing structure with a brush bushing. The sealing bushing, incorporating flexible brush filaments, engages with the grate teeth, maintaining a good sealing effect while reducing wear on the teeth during radial and axial displacement. In practical operation, the high-pressure airflow passes through the widening and contracting structures of the first four stages of the grate teeth, forming vortices within the tooth cavity, thus dissipating some of the gas kinetic energy. Subsequently, the gas flows through the brush structure and the final stage of the grate teeth, interacting with the brush filaments to further improve the sealing effect and reduce gas leakage. Compared to traditional grate seals and brush seals, this structure solves the problems of poor sealing effect and the tendency for the teeth to rub against the stator at high speeds, leading to tooth tip wear or breakage. Unlike brush seals that typically use transition or interference fit installation methods, the sealing bushing proposed in this invention has a certain gap between the brush filament bundle and the grate tooth tips during installation. This avoids severe friction between the free ends of the brush filaments and the grate teeth under high-speed conditions, which could lead to brush filament melting and increased airflow leakage. Compared to existing sealing structures where brush filaments and grate teeth are installed on the rotor simultaneously, installing the brush filament structure on the stator to cooperate with the grate teeth converts the friction between the grate teeth and the stator wall during radial displacement into contact friction between the grate tooth tips and the flexible brush filaments, significantly reducing the wear of the fifth-stage grate teeth. Simultaneously, the first four stages of helical teeth, due to the good sealing effect provided by the brush filament bushing and the fifth-stage grate teeth, can have a larger grate tooth gap to avoid rubbing against the stator wall. This sealing structure can be applied to components in aero engines or gas turbines where pressure differentials and relative rotation require gas sealing to reduce the location of gas leakage.

[0047] The above technical solution will be further explained below with reference to the accompanying drawings:

[0048] Reference Figure 1 , Figure 2As shown, this embodiment discloses a bristle sealing structure with a bristle bushing, comprising a sealing bushing 1 and a rotating shaft 5. The rotating shaft 5 has five levels of bristles along its axial direction: a first-level bristle 6, a second-level bristle 7, a third-level bristle 8, a fourth-level bristle 9, and a fifth-level bristle 10. These five levels of bristles form four bristle cavities. A bristle assembly is provided on the inner circumferential surface of the sealing bushing 1, including a front baffle 2, a rear baffle 3, and a bristle bundle 4. The bristle assembly is installed in a position corresponding to the fifth-level bristle 10, with the shorter bristles at their center radial length aligned with the tip of the bristle 10.

[0049] Reference Figure 3 , Figure 4 As shown, the five-stage grating structure axially arranged on the rotating shaft is characterized by the first to fourth stages of grating forming a 75° angle with the rotor wall, allowing for a radial clearance of 0.8–1.2 mm between the grating and the stator wall during installation. The radial height of the fifth-stage grating 10 is less than that of the first-stage grating 6, second-stage grating 7, third-stage grating 8, and fourth-stage grating 9, and is 1 / 2 to 2 / 3 the height of the first four stages. The grating spacing is 0.6–0.7 mm. In actual operation, the upstream high-pressure airflow passes through the tooth cavities of the first to fourth stages of grating, forming vortices within the cavities. This reduces the axial velocity of the airflow, decreases leakage, and reduces the impact of the airflow on the brush filament bundle 4.

[0050] Reference Figure 5 As shown, the bristle bundle 4 is installed at a 45° circumferential angle, with a bristle diameter of 0.07–0.09 mm. The radial length of the middle bristle is the smallest, gradually increasing towards both sides. The middle bristle is 0.1–0.2 mm shorter than the height of the front and rear baffles, while the radial length of the outer bristles is 0.1–0.2 mm greater than the height of the front and rear baffles. There is a certain gap between the bristle bundle 4 and the comb teeth 10.

[0051] Reference Figure 6 As shown, this design converts the friction between the grate teeth and the stator wall into contact friction between the tooth tips and the flexible bristles when the grate teeth undergo a certain axial or radial displacement, greatly reducing the wear of the fifth-stage grate teeth 10. Simultaneously, the larger gaps between the first four stages of the grate teeth prevent them from rubbing against the stator wall. The interference between the bristle bundle 4 and the fifth-stage grate teeth 10 maintains the sealing performance and recovers after interference, improving 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 and fourth-stage grates can be appropriately increased; the number of grates can be reduced to four or three stages when the sealing requirements are met; the radial height of the first four stages of grates can also be appropriately reduced to avoid severe rubbing; and the tooth profile of the grates can also be changed and adjusted.

[0053] This embodiment presents a design method for a comb-like sealing structure containing a brush bristle bushing, the specific steps of which are as follows:

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

[0055] Step 2: Determine the position and number of tooth cavities based on the axial length of the gap; the tooth cavity is an annular, non-closed cavity structure composed of adjacent grating teeth set on the circumferential surface of the rotating shaft;

[0056] Step 3: Determine the height of the tooth cavity based on the radial distance of the gap, thus obtaining the radial height of the tooth;

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

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A labyrinth seal having a brush wire bushing, characterized by: The brush wire assembly comprises a plurality of gill teeth on the rotor shaft and an inner circumferential surface of the stator bushing; The plurality of gill teeth are arranged along the axial direction of the rotor shaft to form a plurality of annular non-closed cavity structures around the circumferential direction of the rotor shaft, i.e., a plurality of tooth cavities, to slow down the upstream high-pressure airflow; the rotor shaft is provided with five stages of gill teeth along the axial direction on the circumferential surface thereof, the radial heights of the first four stages of gill teeth in the incoming airflow direction are equal, and the radial height of the fifth stage of gill teeth is smaller than that of the first four stages of gill teeth; the first four stages of gill teeth form an angle of 75° with the circumferential surface of the rotor shaft in the incoming airflow direction, the axial spacing between adjacent gill teeth is 6-7 mm, and the radial gap between the end of the first four stages of gill teeth and the inner circumferential surface of the stator bushing is 0.8-1.2 mm when installed; the fifth stage of gill teeth is the gill tooth at the axial end of the rotor shaft, which forms an angle of 90° with the circumferential surface of the rotor shaft and is perpendicular to the circumferential surface of the rotor shaft, and the first four stages of gill teeth together form four gill tooth cavities; The brush wire assembly comprises an annular front baffle on the inner circumferential surface of the bushing, a rear baffle and a brush wire bundle between the front and rear baffles, the inner end of the brush wire bundle is coupled with the gill tooth at the axial end of the rotor shaft to achieve end sealing; The radial height of the fifth stage of gill teeth is 1 / 2-2 / 3 of the radial height of the first four stages of gill teeth; The radial height of the front and rear baffles is greater than the radial gap between the end of the first four stages of gill teeth and the inner circumferential surface of the stator bushing; the radial length of the brush wire at the middle axial position of the brush wire bundle is 0.1-0.2 mm shorter than the radial height of the front and rear baffles, which is complementary to the radial height of the fifth stage of gill teeth and is located at the same axial position; the radial length of the brush wire gradually increases on both sides of the middle part, and the radial length of the brush wire near the outer side of the front and rear baffles is 0.1-0.2 mm greater than the height of the front and rear baffles; The brush wires of the brush wire bundle are inclined by 45° in the circumferential direction, and the brush wires of adjacent rows are arranged in an axial staggered manner.

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