A labyrinth steam seal structure at the top of a steam turbine rotor blade

Abstract

The utility model discloses a labyrinth steam seal structure at the top of a steam turbine blade, comprising an annular chamber, steam seal teeth and a baffle plate, wherein the number of the steam seal teeth is more than two, the steam seal teeth are evenly arranged in the annular chamber, at least one baffle plate is circumferentially mounted on the steam seal teeth, the baffle plate axially penetrates the entire steam seal channel from the first steam seal tooth, the baffle plate is provided with a plurality of through holes, and the baffle plate divides the annular chamber into more than two small chambers along the circumferential direction. The utility model can reduce the leakage airflow entering the gap at the top of the moving blade on the one hand, and is conducive to reducing the mixing loss at the outlet of the moving blade on the other hand, thereby achieving the best sealing effect and improving the working efficiency of the steam turbine moving blade.

Description

Technical Field

[0001] The utility model relates to the technical field of steam seal structures for steam turbine rotor blades, in particular to a labyrinth steam seal structure for the top of a steam turbine rotor blade. Background Art

[0002] In order to avoid friction between the static and dynamic parts of the turbine flow stage, there is usually a certain gap between the top of the moving blade and the static part of the cylinder. Due to the pressure difference between the inlet and outlet of the moving blade, part of the mainstream steam will flow from the high-pressure end to the low-pressure end through the gap at the top of the moving blade to form a leakage flow. The leakage flow at the top of the moving blade does not do work and mixes with the mainstream at the outlet of the moving blade, so the leakage flow reduces the efficiency of the moving blade. The role of the steam seal is to ensure that there is an appropriate gap between the moving and static parts and prevent excessive steam leakage between the moving and static parts.

[0003] By reducing the steam seal gap, modifying the steam seal structure and methods, the leakage can be reduced and the efficiency of each level of the steam turbine can be significantly improved. With the change of actual operating conditions, the size of the gap at the top of the moving blade changes, especially for long twisted blades, the radial displacement of the top of the blade is large when rotating at high speed. In order to avoid friction and collision between static and dynamic parts during operation, the initial design of the top steam seal gap cannot be too small. Therefore, the key to reducing leakage lies in the steam seal structure and method.

[0004] The leakage of a simple straight-through labyrinth steam seal is 50% higher than that of a honeycomb steam seal, but it is still widely used as the steam seal on the top of turbine moving blades due to its simple structure, mature technology, safety and reliability. In view of the large leakage of a simple straight-through labyrinth steam seal, this application proposes an improved steam seal structure, which reduces the circumferential velocity of the leakage flow to reduce the leakage steam, and proposes a sealing method to enhance the sealing effect by adjusting the steam seal structure, so as to achieve the best sealing effect without affecting the stable operation of the moving blades, while increasing the swirl of the leakage steam to increase the pressure in the cavity; reducing the axial velocity and circumferential velocity of the leakage steam outlet to reduce the mixing loss between the leakage steam and the mainstream, and improve the efficiency of the moving blades. Utility Model Content

[0005] The utility model aims to provide a labyrinth steam seal structure at the top of a steam turbine rotor blade, which can achieve a better sealing effect of the labyrinth seal, effectively reduce the leakage amount, and simultaneously reduce the mixing of the leakage flow with the mainstream steam.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A labyrinth steam seal structure at the top of a steam turbine moving blade comprises an annular chamber formed by a stationary component of the steam turbine and a shroud of the top of the moving blade, steam seal teeth and a baffle plate, wherein the number of the steam seal teeth is more than two, the steam seal teeth are mounted on the stationary component above the top of the steam turbine moving blade and are evenly arranged in the annular chamber, at least one baffle plate is mounted on the steam seal teeth along the circumferential direction (direction of rotation of the moving blade), the baffle plate runs through the entire steam seal channel along the axial direction (direction of rotation of the moving blade) from the first steam seal tooth, the baffle plate is provided with a plurality of through holes, and the baffle plate divides the annular chamber into more than two small chambers along the circumferential direction.

[0008] Preferably, the number of through holes is an integer multiple of the number of steam seal teeth, a through hole is provided on the right side of each steam seal tooth, at least one through hole is provided between two adjacent steam seal teeth, and each through hole has a regular shape and is evenly distributed on the baffle plate.

[0009] Preferably, the number of through holes is the same as the number of steam seal teeth, the center of each through hole is arranged on the center line of the width of the flow-blocking orifice plate, the axial length of the center of each through hole from the left steam seal tooth is the same, and is 1 / 2 of the length between adjacent steam seal teeth.

[0010] The through hole is a regular geometric polygonal structure, preferably at least one of a circle, an ellipse, a triangle, a rectangle, and a trapezoid.

[0011] Preferably, the axial distance between the first steam seal tooth and the last steam seal tooth is L, the length of the baffle plate is a, and a≥L.

[0012] Preferably, the width of the baffle plate is b, and the width of the baffle plate is the same as the height of the lowest steam seal tooth among the steam seal teeth.

[0013] Preferably, the thickness of the baffle plate is c, and c≥1 mm.

[0014] Preferably, the installation angle of the blade tip profile of the moving blade is α, and the size of the installation angle β of the baffle plate satisfies α-5°≤β≤α+5°.

[0015] Preferably, the linear speed of rotation of the blade tip of the moving blade is Vt, the width of the baffle plate is b, the through hole radius of the baffle plate is R, when Vt≤228m / s, R=b / 4, when Vt>228m / s, R=b / 3.

[0016] Preferably, the linear speed of rotation of the blade tip of the moving blade is Vt, the number of the baffle plates is N, N is directly proportional to Vt, when 50m / s≤Vt<63m / s, N=2, when 63m / s≤Vt<94m / s, N=3, when 94m / s≤Vt<125m / s, N=4, and so on, and N increases by one for every 31m / s increase in the Vt interval.

[0017] Based on the application of the above technical solution, the utility model has the following beneficial effects:

[0018] 1. The simple straight-through labyrinth steam seal in the prior art has a large leakage. The utility model divides the annular chamber into multiple small chambers along the circumferential direction through the baffle plate. The leakage airflow is hindered by the baffle plate, the circumferential speed of the leakage airflow is reduced, and the pressure in the labyrinth seal chamber is increased, thereby effectively reducing the leakage. The vortex flow of the leakage airflow is denser and the dissipation is more sufficient, thereby improving the sealing performance of the labyrinth steam seal.

[0019] 2. The utility model suppresses the axial velocity of the leakage airflow at the outlet through the circumferential flow-blocking orifice plate, reduces the mixing loss between the leakage airflow and the mainstream, and can effectively improve the efficiency of the turbine rotor blades.

[0020] 3. Overall, the labyrinth steam seal structure at the top of the turbine moving blade provided by the utility model can, on the one hand, reduce the leakage airflow entering the gap at the top of the moving blade, and on the other hand, is conducive to reducing the mixing loss at the outlet of the moving blade, thereby achieving a better sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a front view of the labyrinth steam seal structure at the top of the steam turbine blade of the utility model;

[0022] Figure 2 This is an AA cross-sectional view of the labyrinth steam seal structure at the top of the steam turbine rotor blade of the utility model;

[0023] Figure 3 This is a view in the direction of A of the labyrinth steam seal structure at the top of the steam turbine rotor blade of the utility model;

[0024] Among them: 1-steam seal teeth, 2-baffle plate, 3-through hole, 4-moving blades, 5-blade tip line, 6-shroud. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0026] In the description of the present invention, it should be noted that the terms "circumferential", "axial", "center", "left" and "right" etc. indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0027] Example 1

[0028] A labyrinth steam seal structure at the top of a steam turbine rotor blade, such as Figure 1 As shown, it includes an annular chamber, steam seal teeth and a baffle plate. The steam seal teeth are installed in the annular chamber and are located above the shroud 6. A plurality of baffle plates 2 are arranged on the steam seal teeth 1 of the labyrinth steam seal along the circumferential direction of the moving blades 4 (the direction of rotation of the moving blades). The baffle plate 2 runs through the entire steam seal channel in the axial direction of the moving blades 4 (the direction of rotation of the moving blades). A plurality of through holes 3 are arranged on the baffle plate 2. The centers of the through holes 3 are arranged in sequence on the width center line of the baffle plate 2 to ensure that there is a through hole 3 on the right side of each steam seal tooth 1. The baffle plate divides the annular chamber into two or more small chambers along the circumferential direction (the direction of rotation of the moving blades).

[0029] The straight-through labyrinth steam seal is still widely used as the steam seal on the top of steam turbine moving blades due to its simple structure, mature technology, safety and reliability. There must be a certain gap between the top of the moving blade and the steam seal teeth to ensure that the moving blades avoid collision with moving and static parts under any operating conditions. Especially for long twisted blades, when rotating at high speed, the radial displacement of the top of the blade is large. The initially designed top steam seal gap needs to be large enough, resulting in large leakage at the top of the moving blade. The leakage flow does not do work and mixes with the mainstream at the moving blade outlet, reducing the efficiency of the moving blade. The leakage can be reduced by reducing the steam seal gap and modifying the steam seal structure and method. However, the steam seal gap is subject to structural and operational limitations. Therefore, the key to reducing leakage losses lies in improving the steam seal structure and method. In view of the current problems of large leakage and large mixing losses of the leakage flow in the straight-through labyrinth steam seal, the sealing results of the utility model are as follows: Figure 1-2 As shown, a plurality of baffle plates 2 are arranged on the steam seal teeth 1 of the labyrinth steam seal along the circumference of the moving blades 4. The baffle plates 2 penetrate the entire steam seal channel in the axial direction of the moving blades 4. A plurality of through holes 3 are arranged on the baffle plates 2. The centers of the through holes 3 are arranged in sequence on the width center line of the baffle plates 2 to ensure that there is a through hole 3 on the right side of each steam seal tooth 1.

[0030] In this embodiment, the baffle plate 2 divides the labyrinth seal chamber into a plurality of small chambers along the circumferential direction. The leakage airflow is blocked by the baffle plate 3. The leakage airflow passes through the through hole 3, and the circumferential velocity is reduced. The pressure in the labyrinth seal chamber is increased, thereby effectively reducing the leakage amount. The vortex flow of the leakage airflow is denser and the dissipation is more sufficient, thereby improving the sealing performance of the labyrinth steam seal and the efficiency of the moving blades. At the same time, the circumferential baffle plate 2 suppresses the axial velocity of the leakage airflow at the outlet, reduces the mixing loss of the leakage airflow and the mainstream, and improves the efficiency of the moving blades.

[0031] It can be understood that although the through hole 3 in this embodiment is designed to be circular, the through hole can be other regular geometric polygonal structures such as ellipse, triangle, rectangle, trapezoid, etc., which also has the effect of reducing leakage, enhancing sealing, and improving the working efficiency of the moving blades.

[0032] Example 2

[0033] Based on the above embodiment 1, Figure 1 As shown, there are three steam seal teeth on the steam seal tooth 1 of the labyrinth steam seal, and four flow blocking orifice plates 2 are evenly distributed along the circumference of the moving blade 4. The flow blocking orifice plates 2 penetrate the entire steam seal channel in the axial direction of the moving blade 4. Three through holes 3 are arranged on the flow blocking orifice plates 2. The centers of the through holes 3 are arranged in sequence on the center line of the width of the flow blocking orifice 2 plate. There is a through hole 3 on the right side of each steam seal tooth 1. According to practical applications, more than two through holes 3 can also be arranged on the right side of each steam seal tooth 1. The steam seal structure of the utility model improves the efficiency of the moving blade in two aspects. On the one hand, due to the blocking effect of the flow blocking orifice plates 2, the leakage airflow passes through the through hole 3, the circumferential velocity is reduced, the vortex flow of the leakage airflow increases, the dissipation is more sufficient, and the pressure in the labyrinth seal chamber increases, thereby effectively reducing the leakage amount and improving the sealing performance of the labyrinth steam seal; on the other hand, the flow blocking orifice plates 2 suppress the axial velocity of the leakage airflow at the outlet, reducing the mixing loss of the leakage airflow and the mainstream.

[0034] Example 3

[0035] Based on the above embodiment 2, Figure 1 As shown, the number of seal teeth of the labyrinth seal is Z, and the entire seal channel is axially penetrated from the first seal tooth, the length of the baffle plate 2 is a, a=(1+1 / (Z-1))L; the width of the baffle plate 2 is b, which is the same as the height of the lowest seal tooth among the seal teeth 1; the thickness of the baffle plate c is 1mm; the number of through holes 3 is Z; the through holes 3 are distributed on the right side of each seal tooth, and the axial length of the center of the circle from the left seal tooth is the same, both of which are 0.5L / (Z-1); the center of the through hole 3 is located on the center line of the width of the baffle plate. In this embodiment, a baffle plate 2 of a reasonable size and a through hole 3 of a reasonable size and position are set, so that the baffle plate 2 with the smallest area can block the circumferential movement of the leakage airflow without affecting the stable operation of the moving blades, increase the vortex flow, and increase the pressure in the sealing chamber to achieve a better sealing effect.

[0036] Example 4

[0037] Based on the above-mentioned embodiments 1-3, the sealing method of the labyrinth steam seal structure at the top of the steam turbine rotor blade adopted in this embodiment includes the following steps:

[0038] Step 1: a plurality of steam seal teeth are evenly installed on the stationary component above the top of the steam turbine rotor blade, and each steam seal tooth and the top shroud of the steam turbine rotor blade form a labyrinth structure;

[0039] Step 2: Install a baffle plate on the steam seal tooth along the circumferential direction (rotation direction of the moving blade). The baffle plate runs through the entire steam seal channel along the axial direction (rotation direction of the moving blade) from the first steam seal tooth. The baffle plate is provided with a plurality of through holes. Each steam seal tooth is provided with a through hole on the right side. The plurality of baffle plates divide the annular chamber into a plurality of small chambers along the circumferential direction. The leakage airflow enters the small chamber after throttling through the through holes, so that its circumferential velocity is reduced and the vortex flow is increased, thereby increasing the pressure in the small chamber;

[0040] Step 3: Adjust the labyrinth steam seal structure to achieve the best sealing effect and reduce the mixing loss between the leaking steam and the mainstream.

[0041] like Figure 1 As shown, a plurality of baffle plates 2 divide the annular chamber into a plurality of small chambers along the circumferential direction. The leakage airflow enters the small chamber after throttling from the through hole 3, so that its circumferential velocity is reduced and the vortex flow is increased, thereby increasing the pressure in the small chamber. According to the rotational linear velocity of the blade tip, the labyrinth steam seal structure at the top of the turbine moving blade is adjusted, such as the number, size and installation angle of the baffle plates, or the number, position, radius and shape of the through holes, to achieve the best sealing effect, and at the same time suppress the axial velocity of the leakage airflow at the outlet, reduce the mixing loss between the leakage airflow and the mainstream, and improve the efficiency of the turbine moving blade.

[0042] Example 5

[0043] Based on the above embodiment 4, Figure 2 As shown, the installation angle of the blade tip profile 5 of the moving blade is α; the installation angle of the baffle plate 2 is β, α-5°≤β≤α+5°; in this embodiment, setting a reasonable baffle plate installation angle can maximize the effect of the baffle plate in blocking the circumferential movement of the leakage airflow, so that the sealing effect is the best.

[0044] Example 6

[0045] Based on the above embodiment 5, Figure 3 As shown, the rotating linear velocity of the blade tip is Vt, the width of the baffle plate is b, the radius of the through hole 3 of the baffle plate is R, when Vt≤228m / s, R=b / 4; when Vt>228m / s, R=b / 3. In this embodiment, a reasonable through hole radius of the baffle plate is set to ensure that the baffle plate does not affect the stable operation of the blade and has the effect of reducing the circumferential velocity of the leakage airflow.

[0046] Example 7

[0047] Based on the above embodiment 6, Figure 3As shown, the tip rotation linear speed of the moving blade 4 is Vt, the number of the baffle plates 2 is N, N is proportional to Vt, when 50m / s≤Vt<63m / s, N=2, when 63m / s≤Vt<94m / s, N=3; when 94m / s≤Vt<125m / s, N=4; and so on, N increases by one for every 31m / s increase in the Vt interval.

[0048] In this embodiment, according to the different rotation speeds of the moving blades, the best sealing effect can be achieved by providing a minimum number of baffle plates.

[0049] The above is only a preferred specific implementation of the utility model, but the protection scope of the utility model is not limited to this. Any changes or replacements that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the utility model should be included in the protection scope of the utility model. The utility model extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A labyrinth steam seal structure at the top of a steam turbine rotor blade, characterized in that: The invention comprises an annular chamber formed by a stationary component of a steam turbine and a shroud on the top of a moving blade, a steam seal tooth (1) and a baffle plate (2), wherein the number of the steam seal teeth (1) is more than two, the steam seal teeth (1) are mounted on a stationary component above the top of the moving blade of the steam turbine and are evenly arranged in the annular chamber, at least one baffle plate (2) is mounted on the steam seal tooth (1) along the circumferential direction, the baffle plate (2) axially penetrates the entire steam seal channel from the first steam seal tooth (1), the baffle plate (2) is provided with a plurality of through holes (3), and the baffle plate (2) divides the annular chamber into more than two small chambers along the circumferential direction.

2. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The number of the through holes (3) is an integral multiple of the number of the steam seal teeth (1); a through hole (3) is provided on the right side of each steam seal tooth (1); at least one through hole (3) is provided between two adjacent steam seal teeth (1); and each through hole (3) has a regular shape and is evenly distributed on the baffle plate (2).

3. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The number of the through holes (3) is the same as the number of the steam seal teeth (1), the center of each through hole (3) is arranged on the center line of the width of the baffle plate (2), and the axial length from the center of each through hole (3) to the left steam seal tooth (1) is the same, and is 1 / 2 of the length between adjacent steam seal teeth (1).

4. A labyrinth seal structure at the top of a steam turbine rotor blade according to any one of claims 1 to 3, characterized in that: The through hole (3) is at least one of a circular shape, an elliptical shape, a triangular shape, a rectangular shape, and a trapezoidal shape.

5. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The axial distance between the first steam seal tooth (1) and the last steam seal tooth (1) is L, the length of the baffle plate (2) is a, and a≥L.

6. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The width of the baffle plate (2) is b, and the width of the baffle plate (2) is the same as the height of the lowest steam seal tooth (1) among the steam seal teeth (1).

7. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The thickness of the flow-blocking orifice plate (2) is c, and c≥1 mm.

8. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The installation angle of the blade tip profile (5) of the moving blade is α, and the size of the installation angle β of the baffle plate (2) satisfies α-5°≤β≤α+5°.

9. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The tip rotation linear speed of the moving blade is Vt, the width of the baffle plate (2) is b, the through hole radius of the baffle plate (2) is R, when Vt ≤228 m / s, R=b / 4, when Vt>228 m / s, R=b / 3.

10. The labyrinth seal structure at the top of a steam turbine rotor blade according to claim 1, characterized in that: The tip rotation linear speed of the moving blade is Vt, the number of the baffle plates (2) is N, and N is proportional to Vt. When 50m / s≤Vt<63m / s, N=2, when 63m / s≤Vt<94m / s, N=3, when 94m / s≤Vt<125m / s, N=4, and so on. When the Vt interval increases by 31m / s, N increases by one.

Images