Stepped labyrinth sealing structure combining smooth bushing and straight-through tooth abrasion groove bushing

Abstract

The invention relates to a stepped labyrinth sealing structure with combination of a smooth bushing and a straight-through tooth wear groove bushing, and belongs to the field of aero-engine sealing, the labyrinth sealing structure comprises a rotor and a stator, the periphery of the rotor is axially provided with multi-stage stepped integral-ring-shaped labyrinth, the radial heights of two adjacent labyrinth are different, and the radial heights of the labyrinth are different. The axial distance between every two adjacent comb teeth is the same, and a comb tooth cavity is formed between every two adjacent comb teeth. The inner circumference of the stator is provided with step-shaped step bushes matched with the multiple stages of step labyrinth teeth in a one-to-one correspondence mode, gaps between each axial step face of the step bushes and the corresponding labyrinth teeth are the same, and an annular groove with a rectangular section is formed in the position, right opposite to the corresponding labyrinth teeth, of each axial step face. The smooth bush is combined with the straight-through tooth abrasion groove bush, an improved stepped tooth groove bush structure is obtained, the performance of the labyrinth sealing structure is improved by combining the improvement of the labyrinth structure, and the leakage amount is further reduced.

Description

Technical Field

[0001] The present invention relates to the field of aero-engine seals, and particularly to a stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing. Background Art

[0002] Since the birth of aero-gas turbine engines, the sealing of gases and liquids has become one of the main problems. The sealing effect has a significant impact on the performance, reliability, life, and maintainability of the engine. To further improve the overall performance of the engine, two aspects of labyrinth sealing can be considered: on the one hand, it is necessary to improve the sealing material, select materials with high temperature resistance, wear resistance, high chemical stability, and small thermal deformation, to avoid the degradation of the performance of the labyrinth teeth during long-term operation; on the other hand, it is also necessary to improve the original labyrinth seal structure to enhance the ability to reduce leakage while maintaining the original advantages. With the continuous increase in the rotational speed of aero-engines, the design temperature at the combustion chamber outlet is also constantly rising, and the over-temperature problem of hot-end components is becoming more and more serious. Therefore, the improvement of sealing technology is urgent.

[0003] Typical labyrinth seal structures commonly used in existing aero-engines include straight-through type and stepped type. The straight-through labyrinth seal structure is relatively simple, consisting of straight-through teeth provided on the outer periphery of the rotor and wear groove bushings provided on the inner periphery of the stator. It has a strong ventilation effect but poor sealing performance, and is only used in low-speed and low-pressure difference working conditions, and is commonly found in some auxiliary systems or low-speed rotating machinery with low requirements for sealing performance. In high-pressure difference or high-flow velocity working conditions, the leakage of the straight-through tooth-wear groove bushing structure will increase significantly. The sealing performance of the stepped tooth labyrinth seal structure is much improved compared with that of the straight-through teeth. It consists of stepped teeth provided on the outer periphery of the rotor and smooth bushings provided on the inner periphery of the stator. This structure can be used for the sealing of low- and medium-pressure difference flow paths, but there is a large problem of tooth tip wear; moreover, the pressure difference adaptability of the stepped tooth labyrinth seal structure is limited. For example, in high-pressure difference or high-flow velocity working conditions, the sealing effect of the stepped teeth may decrease and the leakage will increase; in addition, the stepped tooth-smooth bushing structure is sensitive to the clearance, and too large a clearance will significantly reduce the sealing effect.

[0004] It can be seen that the stepped tooth-smooth bushing is suitable for medium-pressure difference and flow velocity working conditions, with good sealing performance, but is sensitive to clearance and thermal deformation. The straight-through tooth-wear groove bushing is suitable for low-pressure difference and low-flow velocity working conditions, with wear compensation ability, but poor sealing performance, and is not suitable for high-pressure difference or high-flow velocity occasions.

[0005] By improving the internal flow channel structure of the labyrinth seal, the fluid leakage can be effectively reduced, but most of the existing research focuses on the labyrinth tooth profile, and less research has been done on the bushing structure.

[0006] Therefore, it is necessary to provide a stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing to solve the above problems. Summary of the Invention

[0007] Technical problems to be solved: In order to avoid the deficiencies of the prior art, the present invention provides a stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing. By improving the stepped labyrinth teeth on the outer periphery of the rotor, a certain front inclination angle is formed relative to the stepped surface of the bushing formed by the inner periphery of the stator. By improving the bushing formed by the inner periphery of the stator, grooves corresponding to the labyrinth teeth are provided on the stepped surface of the bushing to solve the existing problems.

[0008] The technical solution of the present invention is: A stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing, comprising: A rotor, on the outer periphery of which multi-stage stepped integral ring-shaped labyrinth teeth are provided along the axial direction. The radial heights of two adjacent labyrinth teeth are different, the axial distances between two adjacent labyrinth teeth are the same, and a labyrinth tooth cavity is formed between two adjacent labyrinth teeth; And a stator, on the inner periphery of which a stepped stepped bushing corresponding to the multi-stage stepped labyrinth teeth is arranged. The gaps between each axial stepped surface of the stepped bushing and the corresponding labyrinth teeth are the same, and an annular groove with a rectangular cross-section is provided at the position opposite to the corresponding labyrinth teeth on each axial stepped surface; Each radial stepped surface of the stepped bushing is located at the axial middle position of the corresponding labyrinth tooth cavity.

[0009] A further technical solution of the present invention is: The structure of each stage of labyrinth teeth is the same. The height of the labyrinth teeth is 4.4 - 4.5 mm, the width of the teeth is 0.3 - 0.4 mm, and the stepped steps at the bottoms of two adjacent labyrinth teeth are radially offset by 1 mm, so that the radial heights of the tips of two adjacent labyrinth teeth differ by 1 mm.

[0010] A further technical solution of the present invention is: The front inclination angle of the labyrinth teeth is 120°, and the rear inclination angle of the teeth is 75°.

[0011] A further technical solution of the present invention is: The multi-stage stepped labyrinth teeth are provided with at least four stages, and the axial distance between adjacent labyrinth teeth is 6.1 - 6.2 mm.

[0012] A further technical solution of the present invention is: The radius of the rotor is 165 - 166 mm.

[0013] A further technical solution of the present invention is: The depth of the annular groove is determined according to the height of the labyrinth teeth and the size of the labyrinth tooth cavity. The axial center position of the annular groove is aligned with the axial midpoint of the tip of the labyrinth tooth, and the width of the groove of the annular groove is determined according to the axial width of the tip of the labyrinth tooth.

[0014] A design method for a stepped comb tooth sealing structure combining a smooth bushing and a straight-through tooth wear groove bushing, the method comprising: Step 1: Based on the structural characteristics of the non-contact dynamic seal, obtain the theoretical gap size between the rotor grate teeth and the stator bushing; Step 2: Determine the position of the comb tooth cavity and the number of comb teeth according to the axial length of the rotor and the stator; Step 3: Determine the height of the comb tooth cavity according to the radial distance between the rotor and the stator, obtain the radial height of the comb teeth, and determine the radial height difference between two adjacent comb teeth; Step 4: Determine the size of the stator step bushing according to the gap size, the position of the comb tooth cavity, the number of comb teeth, the radial height of the comb teeth and the radial height difference between two adjacent comb teeth, and determine the position of the annular groove according to the position of the corresponding comb teeth; determine the width of the annular groove according to the axial width of the comb tooth tip, and determine the depth of the annular groove according to the radial height of the comb teeth and the size of the comb tooth cavity; This completes the design.

[0015] The beneficial effects of the present invention are as follows: the step-type comb tooth sealing structure combining a smooth bushing and a straight-through tooth wear groove bushing of the present invention integrates the advantages of the straight-through comb tooth sealing structure and the step-tooth comb tooth sealing structure. The present invention arranges a series of groove structures on the axial step surface of the step-type smooth bushing to transform it into a step-type tooth groove bushing structure, so as to increase the kinetic energy dissipation of the airflow along the comb teeth, reduce the flow velocity, and thus achieve the purpose of reducing the leakage.

[0016] The present invention improves the angle of the comb teeth, sets the tooth forward inclination angle to 120°, the tooth backward inclination angle to 75°, and the tooth tip of each comb tooth faces the rectangular annular groove on the step bushing of the stator, thereby forming a reasonable airflow channel. The 120° tooth forward inclination angle can guide the airflow to flow along the front surface of the tooth more smoothly when the airflow enters the comb teeth, avoiding the airflow directly hitting the tooth surface to generate large energy loss and turbulence. At the same time, the 75° tooth backward inclination angle allows the airflow to flow out at a suitable angle after passing through the gap between the teeth, so that the airflow forms a relatively stable flow channel between the teeth, reduces the backflow of the airflow, and thus improves the sealing effect. In addition, such an angle combination helps to form a reasonable pressure distribution between the teeth of the comb teeth. The 120° tooth forward inclination angle can form a relatively high pressure in the front area of the teeth through a certain compression and deceleration effect when the airflow enters between the teeth, thereby preventing further leakage of the gas. The tooth back inclination angle of 75° can gradually reduce the pressure of the airflow when it flows out of the teeth, avoiding the formation of a large pressure difference behind the teeth and reducing gas leakage caused by the pressure difference. The annular groove in the present invention not only reduces the airflow velocity but also forms a wear groove on the tooth tip of the comb teeth, which can well prevent wear caused by the elongation of the tooth tip and increase the wear margin.

[0017] The labyrinth seal structure of the present invention can reduce the fuel consumption rate of the engine, improve the turbine efficiency, enhance the engine safety, and extend the service life of the high-temperature components of the engine. This structure integrates the advantages of the straight-through labyrinth seal structure and the stepped tooth labyrinth seal structure, resulting in an improved stepped tooth groove bushing structure, achieving the optimization of the labyrinth seal structure, enhancing the performance of the labyrinth seal structure, and further reducing the leakage amount. Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a cross-sectional schematic view of a stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing of the present invention; Figure 2 It is the total pressure diagram of the labyrinth seal structure of the present invention.

[0020] In the figure: 1. Rotor, 1-1. First-stage labyrinth teeth, 1-2. Second-stage labyrinth teeth, 1-3. Third-stage labyrinth teeth, 1-4. Fourth-stage labyrinth teeth, 1-5. Labyrinth tooth tips, 2. Stator, 2-1. Axial stepped surface, 2-2. Radial stepped surface, 2-3. Annular groove. Detailed Embodiments

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0022] The existing brush seal structure and finger seal structure are both contact zero-clearance seals. The brush filaments or finger seal segments maintain contact with the rotor component by bending and deforming, thereby keeping the leakage rate at a relatively low level. However, during operation, the brush filaments have problems such as wear, hysteresis, shedding, and hardening. Similarly, the finger seal also has relatively serious wear and hysteresis problems and still needs improvement at present. In comparison, the non-contact labyrinth seal will still be a main sealing method in aeroengines. The typical labyrinth seal structures commonly used in aeroengines include straight-through type and stepped type. But as described in the background art, the existing straight-through labyrinth seal structure and stepped labyrinth seal structure each have their own advantages and disadvantages. How to combine the advantages of both and design a new type of stepped labyrinth seal structure to effectively reduce the fluid leakage rate is what this invention aims to study.

[0023] Embodiment 1: This embodiment provides a stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing, as Figure 1 shown, which includes a rotor 1 and a stator 2.

[0024] The rotor 1 is a columnar structure with a radius of 165 - 166 mm. In this embodiment, the radius of the rotor 1 is 166 mm. Four levels of stepped integral ring-shaped labyrinth teeth are provided along the axial direction on the outer periphery of the rotor 1, namely the first-level labyrinth teeth 1-1, the second-level labyrinth teeth 1-2, the third-level labyrinth teeth 1-3, and the fourth-level labyrinth teeth 1-4. The radial heights of adjacent two labyrinth teeth are different, the axial distances between adjacent two labyrinth teeth are the same, and an annular unclosed labyrinth tooth cavity is formed between adjacent two labyrinth teeth. The rotor 1 and the four levels of labyrinth teeth provided on its outer periphery are an integral structure.

[0025] Specifically, the structure of each level of labyrinth teeth is the same. The height of the labyrinth teeth is 4.4 - 4.5 mm, the width of the teeth is 0.3 - 0.4 mm, and the bottom steps of adjacent two labyrinth teeth are radially staggered by 1 mm, so that the radial heights of the tips 1-5 of adjacent two labyrinth teeth differ by 1 mm. The front rake angle of each labyrinth tooth is 120°, and the rear rake angle is 75°, so as to form a relatively high pressure in the front area of the teeth to prevent further gas leakage, and make the pressure gradually decrease when the air flow flows out between the teeth, avoiding a large pressure difference formed behind the teeth and reducing the gas leakage caused by the pressure difference. The axial distance between adjacent labyrinth teeth of the four levels of labyrinth teeth is 6.1 - 6.2 mm. In this embodiment, the axial distance between adjacent labyrinth teeth is taken as 6.2 mm. The fluid flow direction is from the fourth-level labyrinth teeth 1-4 to the first-level labyrinth teeth 1-1.

[0026] The stator 2 is sleeved outside the rotor 1. A stepped step bushing corresponding to the four-stage stepped labyrinth teeth is arranged on the circumferential inner wall of the stator 2. The step bushing and the stator 2 are of an integral structure, and the step bushing forms the inner diameter wall of the stator 2. The clearance between each axial step surface 2-1 of the step bushing and the corresponding labyrinth tooth is the same. An annular groove 2-3 with a rectangular cross-section is arranged at the position opposite to the corresponding labyrinth tooth on each axial step surface 2-1. The annular groove 2-3 not only reduces the air flow velocity but also forms a wear groove for the tip of the labyrinth tooth 1-5, which can effectively prevent wear caused by the elongation of the tooth tip. Each radial step surface 2-2 of the step bushing is located at the axial middle position of the corresponding labyrinth tooth cavity.

[0027] The groove depth of the annular groove 2-3 is determined according to the tooth height of the labyrinth tooth and the size of the labyrinth tooth cavity. The axial center position of the annular groove 2-3 is aligned with the axial midpoint of the labyrinth tooth tip. The groove width of the annular groove 2-3 is determined according to the axial width of the labyrinth tooth tip 1-5.

[0028] In the present invention, the rotor 1 and the stator 2 are also provided with a stepped labyrinth seal structure. By arranging corresponding annular grooves 2-3 on the inner wall of the stator 2 and the radial stepped labyrinth teeth, the labyrinth tooth cavity can be divided along the radial direction of the rotor to form a continuous radial cavity area. By utilizing the cavity throttling effect between the corresponding radial inclined labyrinth teeth (with a certain inclination angle) and the step surface and the eddy current inside the labyrinth tooth cavity, the axially flowing air flow can be formed into a fluctuating flow, increasing the axial flow resistance of the fluid and reducing the fluid leakage amount.

[0029] In the structure of the present invention, the stepped bushing on the inner circumference of the stator 2 cooperates with the four-stage labyrinth teeth of the stepped structure, which can achieve multi-stage throttling, greatly increase the gas flow resistance, and significantly reduce the leakage. Under complex working conditions such as high temperature, high pressure and high speed, it always maintains stable and reliable, and is suitable for various harsh working environments. With the annular groove 2-3 arranged on the axial step surface 2-1 of the stator 2, traditional hidden dangers such as wear and rubbing of the labyrinth teeth are effectively reduced. Refer to Figure 2 , from Figure 2 it can be seen the pressure distribution condition of each labyrinth tooth cavity. The smaller the total pressure drop, the better the sealing effect. Through simulation experiments, the actual sealing effect of the structure of the present invention is verified, and the feasibility of the structure of the present invention is confirmed. At the same time, the present invention explores three groove types of the annular groove 2-3 with rectangular, triangular and semi-circular cross-sections, and demonstrates that the annular groove 2-3 with a rectangular cross-section is the best structural groove type under the condition of the same groove depth. The structure of the present invention is a stepped groove bushing labyrinth seal structure, which is superior to the linear combination of the traditional stepped tooth-smooth bushing and the straight-through tooth-wear bushing in terms of performance. The eddy current and boundary layer formed by the structure of the present invention dissipate the kinetic energy of the air flow far better than the simple superposition of the performance of the existing two structures.

[0030] The labyrinth seal structure achieves the purpose of pressure reduction and throttling by allowing high-pressure fluid to flow through the four-stage labyrinth teeth and the labyrinth tooth cavities. Its sealing principle is a series of throttling gaps and expansion cavities formed between the sealing labyrinth teeth and the stator bushing. When the leakage fluid flows through the throttling gaps, part of its pressure energy is converted into velocity energy. On the one hand, this velocity energy drives part of the jet flow to enter the next throttling gap at a certain speed until it flows out as leakage loss; on the other hand, a large part of the diffused jet flow accumulates near the windward side of the next sealing tooth and is redirected into the cavity. Part of the energy in the cavity is dissipated as heat energy due to turbulent vortices, while the other part of the energy drives the second eddy current in the cavity, thus causing throttling and thermodynamic effects on the passing fluid, and the pressure of the leakage fluid gradually decreases to achieve the sealing effect. The present invention improves the stepped labyrinth seal structure with stepped teeth, changing its smooth bushing structure to a wear groove bushing structure, that is, a ring-shaped groove 2-3 is provided on the axial step 2-1 surface, which is equivalent to adding a small tooth cavity at the tip 1-5 of the labyrinth tooth. In the ring-shaped groove 2-3 at the tooth tip, an eddy current similar to the labyrinth tooth cavity will be formed, strengthening the dissipation of energy, and thus achieving the purpose of reducing the leakage amount.

[0031] Embodiment 2: This embodiment provides a design method for a stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing. The method includes: Step 1: Based on the structural characteristics of non-contact dynamic seals, the theoretical clearance size between the labyrinth teeth of the rotor and the bushing of the stator is obtained to be approximately 0.2 mm.

[0032] Step 2: According to the axial lengths of the rotor and the stator, the position of the labyrinth tooth cavity and the number of labyrinth teeth are determined to be 4. The labyrinth tooth cavity is an annular non-closed cavity structure formed by adjacent labyrinth teeth provided on the circumferential wall surface of the rotor 1.

[0033] Step 3: According to the radial distance between the rotor and the stator, the height of the labyrinth tooth cavity is determined, and the radial height of the labyrinth teeth is obtained to be 4.4 - 4.5 mm, and the radial height difference between two adjacent labyrinth teeth is determined to be 0.1 mm.

[0034] Step 4: According to the clearance size, the position of the labyrinth tooth cavity, the number of labyrinth teeth, the radial height of the labyrinth teeth, and the radial height difference between two adjacent labyrinth teeth, the size of the stepped bushing of the stator is determined, and the position of the ring-shaped groove is determined according to the position of the corresponding labyrinth teeth. According to the axial width of the tip of the labyrinth tooth, the width of the ring-shaped groove is determined so that the two widths are basically the same. In this embodiment, the width of the ring-shaped groove is approximately 0.36 mm. And according to the radial height of the labyrinth teeth and the size of the labyrinth tooth cavity, the depth of the ring-shaped groove is determined. In this embodiment, the depth of the ring-shaped groove is approximately 0.1 mm.

[0035] The design of the stepped labyrinth seal structure is completed according to the above steps.

[0036] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing, characterized in that Comprising: A rotor, on the outer peripheral circle of which there are multi-stage stepped integral annular labyrinth teeth arranged axially. The radial heights of adjacent two labyrinth teeth are different, the axial spacings between adjacent two labyrinth teeth are the same, and labyrinth tooth cavities are formed between adjacent two labyrinth teeth; And a stator, on the inner peripheral circle of which there are stepped stepped bushings arranged in one-to-one correspondence with the multi-stage stepped labyrinth teeth. The gaps between each axial step surface of the stepped bushing and the corresponding labyrinth tooth are the same, and annular grooves with a rectangular cross-section are provided at the positions opposite to the corresponding labyrinth teeth on each axial step surface; Each radial step surface of the stepped bushing is located at the axial middle position of the corresponding labyrinth tooth cavity.

2. The stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing according to claim 1, characterized in that, The structure of each stage of labyrinth teeth is the same. The height of the labyrinth teeth is 4.4 - 4.5 mm, the width of the teeth is 0.3 - 0.4 mm, and the stepped steps at the bottoms of adjacent two labyrinth teeth are radially staggered by 1 mm, so that the radial heights of the tips of adjacent two labyrinth teeth differ by 1 mm.

3. The stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing according to claim 2, characterized in that, The front inclination angle of the labyrinth teeth is 120°, and the rear inclination angle of the teeth is 75°.

4. The stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing according to claim 1, characterized in that, The multi-stage stepped labyrinth teeth are provided with at least four stages, and the axial spacing between adjacent labyrinth teeth is 6.1 - 6.2 mm.

5. The stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing according to claim 1, characterized in that, The radius of the rotor is 165 - 166 mm.

6. The stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing according to claim 1, characterized in that, The depth of the annular groove is determined according to the height of the labyrinth teeth and the size of the labyrinth tooth cavity. The axial center position of the annular groove is aligned with the axial midpoint of the tip of the labyrinth tooth, and the width of the annular groove is determined according to the axial width of the tip of the labyrinth tooth.

7. A design method for a stepped labyrinth seal structure combining a smooth bushing and a straight-through tooth wear groove bushing according to any one of claims 1-6, characterized in that, The method comprises: Step 1: Based on the structural characteristics of non-contact dynamic sealing, obtain the theoretical clearance size between the labyrinth teeth of the rotor and the bushing of the stator; Step 2: Determine the positions of the labyrinth tooth cavities and the number of labyrinth teeth according to the axial lengths of the rotor and the stator; Step 3: Determine the height of the labyrinth tooth cavity according to the radial distance between the rotor and the stator, obtain the radial height of the labyrinth teeth, and determine the radial height difference between adjacent two labyrinth teeth; Step 4: Determine the size of the stepped bushing of the stator according to the theoretical clearance size, the positions of the labyrinth tooth cavities, the number of labyrinth teeth, the radial height of the labyrinth teeth and the radial height difference between adjacent two labyrinth teeth, and determine the position of the annular groove according to the position of the corresponding labyrinth tooth; Determine the width of the annular groove according to the axial width of the tip of the labyrinth tooth, and determine the depth of the annular groove according to the radial height of the labyrinth teeth and the size of the labyrinth tooth cavity; Thus, the design is completed.

Images