Smooth labyrinth seal structure capable of reducing leakage rate by reducing carrying coefficient

Abstract

The invention discloses a smooth labyrinth sealing structure capable of reducing leakage amount by reducing a carrying coefficient. The smooth labyrinth sealing structure is suitable for sealing between a rotor part and a static part in a rotary machine. The structure comprises a base body extending in the axial direction and a plurality of comb teeth arranged on the base body at intervals, and based on the relational expression between the carrying coefficient of the comb tooth sealing structure and the geometric parameters of the comb teeth, for one or some non-inlet-end comb teeth, the carrying coefficient of the comb tooth sealing structure is larger than the geometric parameters of the comb teeth. The tooth spacing p, the tooth width t and the minimum gap c between the tooth crest and the opposite wall in the geometric parameters of the comb teeth are optimized and adjusted, so that the carrying coefficient K is reduced, and the leakage rate is remarkably reduced. According to the novel labyrinth sealing structure, the key technical problems in a traditional labyrinth sealing structure, such as collision and abrasion of the labyrinth and the wall surface, increase of the vibration risk of an aero-engine, single gap design and the like, are solved, and the novel labyrinth sealing structure which effectively reduces the leakage flow carrying coefficient and improves the sealing efficiency under the condition that the axial length is kept unchanged is provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aero-engine sealing, and particularly relates to a smooth labyrinth seal structure based on reduction of a carrying coefficient. BACKGROUND

[0002] As a high-efficiency sealing mechanism, the labyrinth seal technology plays a crucial role in many industrial fields, especially in aero-engines. The labyrinth seal achieves the purpose of sudden expansion and sudden contraction through the labyrinth structure, generates throttling and turbulent dissipation effects to increase the flow resistance and limit leakage. In the labyrinth seal, when the fluid passes through the throttling gap, part of the pressure energy is converted into velocity energy, and then the velocity energy is dissipated as heat energy in the labyrinth seal cavity due to turbulent vortex, so that the pressure of the leakage flow is gradually reduced to achieve the sealing effect. Research shows that the sealing mechanism of the straight-through labyrinth seal mainly includes the flow contraction effect and throttling effect at the tooth gap, the thermodynamic effect of the tooth cavity, the friction effect of the wall surface, and the gas permeation effect, etc.

[0003] In order to further improve the performance of the labyrinth seal, the prior art develops more advanced labyrinth seal structures from the smooth straight-through labyrinth seal by using the sealing mechanism, such as the honeycomb straight-through labyrinth seal, the smooth stepped labyrinth seal, the honeycomb stepped labyrinth seal, the smooth staggered labyrinth seal, etc. These structures provide more complex flow paths and enhanced throttling effects to improve the overall sealing efficiency.

[0004] However, although the labyrinth seal technology has been widely applied and researched, the smooth straight-through labyrinth seal, as one of the basic sealing structures, is still widely used in aero-engines at present due to its advantages such as simple manufacturing and convenient maintenance. Reducing the leakage of this type of labyrinth seal is beneficial to reducing the mixing loss of the leakage flow and the downstream components and improving the efficiency of the aero-engine.

[0005] Traditionally, the leakage of the smooth straight-through labyrinth seal is usually reduced by reducing the gap to increase the degree of sudden expansion and sudden contraction, thereby increasing the energy loss of the leakage flow. Although this method can theoretically increase the flow resistance of the leakage flow and thus reduce the leakage, in practice it often leads to contact and abrasion between the labyrinth and the wall surface, which not only may damage the labyrinth structure, but also may affect the rotor dynamics characteristics, thereby increasing the vibration risk of the aero-engine. In addition, wall surface friction may also form friction grooves on the wall surface, which in turn increases the flow gap of the fluid and further increases the leakage. Moreover, in the traditional smooth straight-through labyrinth seal, a uniform gap design is usually adopted, and the leakage mainly depends on the size of the gap, and the local gap cannot be optimized according to the actual flow field distribution.

[0006] In view of these problems, the traditional design method of the smooth straight-through labyrinth seal has been difficult to meet the strict performance requirements of modern aero-engines. The current technical challenge is how to effectively reduce the leakage of the smooth straight-through labyrinth seal without significant changes to the original structure, i.e., without significantly changing the labyrinth seal structure, especially in the case of increasing the gap between the smooth straight-through seal structures to reduce the risk of impact and wear. How to suppress the kinetic energy of the leakage flow and reduce the leakage by optimizing the structure form is a technical problem that needs to be solved in the field of labyrinth seals. SUMMARY

[0007] (I) Invention purposes

[0008] In order to solve at least one of the above and other technical problems in the prior art, the present application aims to provide a smooth labyrinth seal structure for reducing leakage by reducing the entrainment coefficient. By adjusting the geometric parameters of the labyrinth gap, such as tooth spacing, fillet radius, tooth width, tooth inclination angle and tooth height, the labyrinth seal gap distribution is optimized, the entrainment coefficient of the leakage flow is reduced, the dissipation amount of the fluid in the tooth cavity is increased, thereby significantly reducing the leakage, and the key technical problems in the traditional labyrinth seal structure are solved.

[0009] (II) Technical solutions

[0010] In order to achieve the purposes of the application and solve its technical problems, the application adopts the following technical solutions:

[0011] A smooth labyrinth seal structure for reducing leakage by reducing the entrainment coefficient, used for sealing between a rotating component and a stationary component in a rotating machine, comprising an axially extending base body and a plurality of labyrinth teeth arranged at intervals on the base body, characterized in that,

[0012] The entrainment coefficient of the labyrinth seal structure and the labyrinth geometric parameters satisfy the following empirical relationship:

[0013]

[0014] In the formula, K is the entrainment coefficient, which reflects the proportion of energy carried away by the fluid when passing through the labyrinth seal due to friction and other factors; p represents the distance between two adjacent labyrinth teeth; t is the tooth width, which represents the linear width of the top of the labyrinth tooth; c is the minimum gap between the tooth top and the opposite wall, which is a key factor determining the resistance of the fluid passing through the labyrinth;

[0015] For one or some non-inlet-end labyrinths, at least by optimizing the tooth spacing p, tooth width t and the minimum gap c between the tooth top and the opposite wall in the labyrinth geometry parameters to reduce the carrying coefficient K, the labyrinth sealing leakage is reduced.

[0016] Preferably, in the labyrinth sealing structure, for one or some non-inlet-end labyrinths, based on the empirical relationship of the carrying coefficient, by reducing the tooth height h to increase the tooth top gap c, reducing the tooth width t, and increasing the tooth spacing p with the previous labyrinth, the carrying coefficient K of the labyrinth sealing structure is reduced to reduce the labyrinth sealing leakage.

[0017] Preferably, the labyrinth sealing structure includes first to Nth labyrinths, N≥4, wherein the tooth width t, tooth height h and tooth spacing p between adjacent two labyrinths of the first to N-1th labyrinths are conventional design values, the tooth width t of the Nth labyrinth is smaller than that of the first to N-1th labyrinths, the tooth height h of the Nth labyrinth is smaller than that of the first to N-1th labyrinths, and the tooth spacing p between the Nth labyrinth and the adjacent N-1th labyrinth is greater than the tooth spacing between the first to N-2th labyrinths.

[0018] In this scheme, by reducing the tooth width t of the Nth labyrinth and increasing the tooth spacing p between the Nth labyrinth and the N-1th labyrinth, based on the empirical relationship of the carrying coefficient K, the carrying coefficient K at the Nth labyrinth can be reduced, thereby reducing the overall leakage of the labyrinth sealing structure.

[0019] Specifically, after the tooth width t of the Nth labyrinth is reduced, the leakage flow only impacts the upper wall of the labyrinth sealing and does not impact the lower wall, resulting in a reverse radial velocity, so that part of the leakage is more likely to escape the gap cross-sectional range. At the same time, the reduction of the tooth height of the Nth labyrinth increases the secondary vortex, consumes more energy, and further blocks the leakage flow. In addition, when the tooth spacing p between the Nth labyrinth and the N-1th labyrinth is increased, theoretically, the diffusion angle of the leakage flow above the Nth tooth cavity does not change, the leakage amount through the gap is reduced, the gas flow dissipated in the tooth cavity is increased, the equivalent tooth spacing is increased, and the amount of gas that does not flow out of the gap is increased under the blocking of the N+1th tooth. The synergistic effect of the above various mechanisms collectively results in a reduction in the carrying coefficient K at the Nth labyrinth, thereby achieving the purpose of reducing the overall leakage.

[0020] Further, the tooth body includes first, second, third and fourth tooth bodies, the tooth width, tooth height and tooth spacing between adjacent two tooth bodies of the first to third tooth bodies are conventional sizes, the tooth height of the fourth tooth body is smaller than that of the first to third tooth bodies, the tooth spacing between the fourth tooth body and the third tooth body is greater than the tooth spacing between the first and second tooth bodies and between the second and third tooth bodies, and the tooth width of the fourth tooth body is smaller than that of the first to third tooth bodies.

[0021] (3) Technical effects

[0022] Compared with the prior art, the smooth grate seal structure of the present invention, which reduces the carrying coefficient to reduce leakage, has the following beneficial and significant technical effects:

[0023] (1) The present invention proposes a smooth grate tooth sealing structure that reduces leakage by reducing the carryover coefficient. The structure reduces the carryover coefficient of the leakage flow by optimizing the geometric parameters of the grate teeth such as tooth spacing, tooth width, tooth height, etc., thereby achieving a significant improvement on the smooth straight-through grate tooth sealing structure, thereby significantly reducing the leakage volume and providing significant technical effects in reducing the risk of friction and wear between the grate teeth and the wall surface, alleviating aircraft engine vibration, and providing more flexible gap design.

[0024] (2) The smooth grate seal structure provided by the present invention significantly reduces leakage by optimizing the flow path between the grate teeth and increasing fluid dissipation within the tooth cavity, effectively reducing the carryover coefficient. This technical effect not only directly affects the sealing performance of rotating machinery but also indirectly improves the overall efficiency and operating life of the machinery.

[0025] (3) The smooth grate seal structure provided by the present invention has an outstanding structural feature of reducing the gap while ensuring the sealing performance, while the conventional smooth straight-through grate seal generally adopts a consistent gap. At the same time, the smooth grate seal structure provided by the present invention has high reliability. Under different operating conditions of the aircraft engine, the gap of the grate seal varies. Reducing the gap is conducive to reducing the possibility of collision and wear, and reducing the probability of seal damage. In addition, the smooth grate seal structure provided by the present invention has a wide range of uses. The smooth straight-through grate seal is widely used in the compressor and turbine interstage seals of aircraft engines. The reduction of its leakage is conducive to improving the efficiency of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the traditional smooth straight-through grate seal structure and related parameters;

[0028] Figure 2(a) is a schematic diagram of the strategy based on reducing the carrying coefficient (baseline structure);

[0029] Figure 2(b) is a schematic diagram of the strategy based on reducing the carrying coefficient (increasing the tooth spacing);

[0030] Figure 2(c) is a schematic diagram of the strategy based on reducing the carrying coefficient (gap reduction);

[0031] Figure 3 This is a comparison chart of the smooth straight-through grate seal optimized for reducing the carryover coefficient and the traditional smooth straight-through grate seal;

[0032] Figure 4 Performance comparison chart of the baseline structure and the optimized structure.

[0033] Description of reference numerals:

[0034] h1-tooth height of the first tooth, h2-tooth height of the second tooth, h3-tooth height of the third tooth, h4-tooth height of the fourth tooth, h5-tooth height of the fifth tooth, h6-tooth height of the sixth tooth, p-tooth pitch, r-fillet radius, t-tooth width, θ-tooth inclination angle. DETAILED DESCRIPTION

[0035] In order to better understand the present invention, the contents of the present invention are further explained in conjunction with the embodiments below. In the accompanying drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be understood as limiting the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The structure and technical solution of the present invention are further described in detail below in conjunction with the accompanying drawings, and an embodiment of the present invention is given.

[0036] In view of the defects of existing smooth straight-through grate tooth seals, such as the grate teeth are prone to friction with the wall, damage, increased risk of aircraft engine vibration, and a single gap design when reducing the gap to improve the sealing efficiency, in order to solve at least one of the above-mentioned and other technical problems in the prior art, the present invention aims to provide a smooth grate tooth sealing structure that reduces leakage by reducing the carrying coefficient. By adjusting the geometric parameters of the grate tooth gap, such as tooth spacing, fillet radius, tooth width, tooth inclination angle and tooth height, the grate tooth sealing gap distribution is optimized, the leakage flow carrying coefficient is reduced, the dissipation of the fluid in the tooth cavity is increased, thereby significantly reducing leakage, and solving the key technical problems in the traditional grate tooth sealing structure.

[0037] As a specific example, Figure 1The figure is a schematic diagram of a traditional smooth straight-through grate tooth sealing structure and related parameters. The present invention is based on the empirical relationship between the carrying coefficient of the grate tooth sealing structure and the grate tooth geometric parameters. By adjusting the tooth spacing, fillet radius, tooth width, tooth inclination angle and tooth height of each tooth, it is ensured that the smooth straight-through grate tooth sealing gap can reduce leakage. Specifically, the smooth grate tooth sealing structure of the present invention, which reduces leakage by reducing the carrying coefficient, includes an axially extending base and a plurality of grate teeth spaced apart on the base. The carrying coefficient of the grate tooth sealing structure and the grate tooth geometric parameters satisfy the following empirical relationship:

[0038]

[0039] In the formula, K is the carryover coefficient, which reflects the proportion of energy carried away by the fluid due to factors such as friction when passing through the grate seal; p represents the distance between two adjacent grate teeth; t is the tooth width, which represents the straight-line width of the top of the grate teeth; c is the minimum gap between the tooth top and the opposite wall, which is a key factor in determining the magnitude of the resistance encountered by the fluid when passing through the grate teeth; for one or some non-inlet end grate teeth, the present invention is based on the above-mentioned empirical relationship satisfied between the carryover coefficient and the grate tooth geometric parameters, and at least optimizes the tooth spacing p, tooth width t and the minimum gap c between the tooth top and the opposite wall among its grate tooth geometric parameters to reduce the carryover coefficient K, thereby reducing the amount of grate seal leakage.

[0040] In some preferred examples, in the grate tooth sealing structure, for one or some non-inlet end grate teeth, based on the empirical relationship of the carrying coefficient, by reducing its tooth height h to increase its tooth top clearance c, reducing its tooth width t, and at the same time increasing its tooth spacing p with the previous grate tooth, the carrying coefficient K of the grate tooth sealing structure is reduced, thereby achieving a reduction in the grate tooth seal leakage.

[0041] In some preferred embodiments, the grate tooth sealing structure includes the first to Nth grate teeth, N≥4, wherein the tooth width t, tooth height h, and tooth spacing p between adjacent grate teeth of the first to N-1th grate teeth are conventional design values, the tooth width t of the Nth grate tooth is smaller than the tooth width of the first to N-1th grate teeth, and the tooth height h of the Nth grate tooth is smaller than the tooth height of the first to N-1th grate teeth, and the tooth spacing p between the Nth grate tooth and the adjacent N-1th grate tooth is larger than the tooth spacing between the first to N-2th grate teeth. In this solution, by reducing the tooth width t of the Nth grate tooth and increasing the tooth spacing p between the Nth grate tooth and the N-1th grate tooth, based on the empirical relationship of the carrying coefficient K, the carrying coefficient K at the Nth grate tooth can be reduced, thereby reducing the comprehensive leakage of the entire grate tooth sealing structure. Specifically, after the tooth width t of the Nth grate tooth is reduced, the leakage flow will only impact the upper wall of the grate seal and will not impact the lower wall, resulting in a reverse radial velocity, making it easier for some leakage to escape from the gap cross-section range. At the same time, the reduction in the tooth height of the Nth grate tooth will increase the secondary vortex, consume more energy, and further block the leakage flow. In addition, when the tooth spacing p between the Nth grate tooth and the N-1th grate tooth increases, theoretically the diffusion angle of the leakage flow above the Nth tooth cavity remains unchanged, the leakage amount through the gap is reduced, and the amount of gas dissipated in the tooth cavity increases, which is equivalent to increasing the tooth spacing. Under the obstruction of the N+1th tooth, the amount of gas that does not flow out of the gap is increased. The synergistic effect of the above-mentioned various mechanisms jointly leads to a reduction in the carrying coefficient K at the Nth grate tooth, achieving the purpose of reducing the overall leakage amount.

[0042] In a further preferred example, the tooth body includes a first tooth body, a second tooth body, a third tooth body and a fourth tooth body, the tooth width, tooth height and tooth spacing between the first to third tooth bodies and their adjacent two tooth bodies are regular sizes, the tooth height of the fourth tooth body is smaller than the tooth height of the first to third tooth bodies, and the tooth spacing between the fourth tooth body and the third tooth body is larger than the tooth spacing between the first and second tooth bodies and between the second and third tooth bodies, and the tooth width of the fourth tooth body is smaller than the tooth width of the first to third tooth bodies.

[0043] Figure 2 illustrates a strategy for reducing the carryover factor. While maintaining the same axial length, the tooth width is minimized, the tooth pitch is increased, and some tooth heights are reduced by determining appropriate tooth inclination angles and fillet radii. A smaller tooth width shortens the gap path through which the leakage flow passes. A short tooth width causes the leakage flow to impact only the upper wall of the grate seal. When the tooth width increases, the leakage flow impacts not only the upper wall but also the lower wall, resulting in increased leakage losses. On the other hand, a reduced tooth width causes the leakage flow to impact only the upper wall, resulting in a reverse radial velocity. This allows some leakage to escape the gap cross-section more easily, reducing the carryover factor. In a smooth, straight-through grate seal, the leakage flow exiting the tooth gap behaves as a semi-wall jet. When the tooth pitch increases, theoretically, the diffusion angle of the leakage flow above the tooth cavity remains unchanged, reducing the amount of leakage through the gap and increasing the amount of gas dissipated within the tooth cavity. Furthermore, a sudden gap reduction, if it does not disrupt the semi-wall jet behavior, is equivalent to increasing the tooth pitch. The third tooth blocks the leakage flow, increasing the amount of gas that does not escape the gap, thus reducing the carryover factor. At the same time, the reduction of tooth height will lead to the increase of secondary vortex, which consumes more energy, makes the leakage flow more obstructed, and reduces the leakage amount.

[0044] Figure 3 This chart compares a smooth, straight-through grate seal optimized for reduced carryover coefficient with a conventional smooth, straight-through grate seal. Compared to the conventional straight-through grate seal, the fourth tooth of this optimized structure has a reduced tooth height, a larger gap, and a wider tooth spacing. Figure 4 The following chart compares the performance of the baseline and optimized structures. Under different pressure ratios, the smooth, straight-through grate seal, which reduces the carryover coefficient, reduces leakage by a minimum of 10.53% and a maximum of 11.77%. Furthermore, the increased clearance in this structure reduces the possibility of wear, resulting in high reliability and wide adaptability. This unique, smooth, straight-through grate seal structure holds great promise for future applications.

[0045] When optimizing the geometric parameters of the grate gap, the combined effects of fluid dynamics and thermodynamics were taken into account to ensure that the optimized grate sealing structure can maintain good sealing performance under different working conditions. In particular, high-precision processing technology is used to adjust the minimum gap c between the top of the grate and the wall to ensure the uniformity and accuracy of the gap, further improving the sealing efficiency. In addition, the design of the grate sealing structure of the present invention takes into account material selection and surface treatment technology to enhance the wear resistance of the grate and reduce the friction coefficient between the fluid and the contact surface of the grate, thereby reducing energy loss and extending the service life of the grate seal. The embodiments of the present invention demonstrate the significant advantages of the smooth grate sealing structure in improving the sealing efficiency of rotating machinery, reducing energy loss, and improving the overall performance of the equipment, providing a new solution for the sealing design of high-performance rotating machinery.

[0046] Furthermore, the smooth grate seal structure was optimized using a combination of simulation and experimentation. Predictive analysis using fluid dynamics simulation software identified key factors influencing leakage, and the accuracy of the simulation results was verified experimentally. This approach ensures the efficiency and reliability of the design, providing a scientific basis for optimizing the sealing structure. Furthermore, the present invention also considers the stability and reliability of the grate seal structure under extreme operating conditions. Through the special selection and processing of materials, and through optimized structural design to withstand extreme conditions such as high temperature, high pressure, and high speed, it is ensured that the grate seal maintains good performance in a variety of harsh environments.

[0047] Ultimately, this invention not only theoretically proposes a smooth grate seal structure that reduces leakage by reducing the carryover coefficient, but also demonstrates its effectiveness and superiority in practical applications through specific design examples and experimental verification. The implementation of this invention provides valuable insights for the advancement of rotary mechanical seal technology and is of great significance for promoting technological development in related fields.

[0048] Through the above-mentioned embodiments, the present invention fully presents the smooth grate seal structure that optimizes the geometric parameters of the grate gap to reduce the carryover coefficient and significantly reduce the leakage, and fully and effectively achieves the purpose of the present invention. Those skilled in the art will understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Although the present invention has been described with respect to the embodiments currently considered to be the most practical and preferred, it should be understood that the present invention is not limited to the disclosed embodiments, and any modifications that do not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A smooth grate seal structure for reducing leakage by reducing the carrying coefficient, comprising a base extending in the axial direction and a plurality of grate teeth spaced apart on the base, characterized in that: The carrying coefficient of the grate tooth sealing structure and the grate tooth geometric parameters satisfy the following empirical relationship: Where K is the carryover coefficient, which reflects the proportion of energy carried away by the fluid due to friction and other factors when passing through the grate seal; p is the distance between two adjacent grate teeth; t is the tooth width, which represents the straight width of the top of the grate teeth; c is the minimum gap between the tooth top and the opposite wall, which is the key factor determining the resistance of the fluid when passing through the grate teeth. For one or some non-inlet end grate teeth, the tooth spacing p, tooth width t and minimum clearance c between the tooth top and the opposite wall in the grate tooth geometric parameters are optimized to reduce the carrying coefficient K and achieve reduction in grate tooth seal leakage.

2. The smooth grate tooth sealing structure according to claim 1, characterized in that: In the grate tooth sealing structure, for one or some non-inlet end grate teeth, based on the empirical relationship of the carrying coefficient, by reducing its tooth height h to increase its tooth top clearance c, reducing its tooth width t, and at the same time increasing its tooth spacing p with the previous grate tooth, the carrying coefficient K of the grate tooth sealing structure is reduced, thereby reducing the grate tooth sealing leakage.

3. The smooth grate tooth sealing structure according to claim 1, characterized in that: The grate tooth sealing structure includes the first to Nth grate teeth, N≥4, wherein the tooth width t, tooth height h and tooth spacing p between two adjacent grate teeth of the first to N-1th grate teeth are conventional design values, the tooth width t of the Nth grate tooth is smaller than the tooth width of the first to N-1th grate teeth and the tooth height h of the Nth grate tooth is smaller than the tooth height of the first to N-1th grate teeth, and the tooth spacing p between the Nth grate tooth and the adjacent N-1th grate tooth is greater than the tooth spacing between the first to N-2th grate teeth.

4. The smooth grate teeth sealing structure according to claim 3, characterized in that: The tooth body includes a first tooth body, a second tooth body, a third tooth body and a fourth tooth body. The tooth width, tooth height and tooth spacing between the first to third tooth bodies and the adjacent two tooth bodies are of conventional sizes. The tooth height of the fourth tooth body is smaller than the tooth height of the first to third tooth bodies, and the tooth spacing between the fourth tooth body and the third tooth body is larger than the tooth spacing between the first and second tooth bodies and between the second and third tooth bodies. The tooth width of the fourth tooth body is smaller than the tooth width of the first to third tooth bodies.

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