JP2017066993A - Seal structure of steam turbine and steam turbine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure that minimizes the entry of solid particulates contaminating the actuation steam into the seal portion of a turbine device in order to reduce the influence due to the entry.SOLUTION: In the present embodiment, in a seal structure of a steam turbine in which moving blade covers are formed at the tip of a plurality of moving blades rotated by the steam flowing through a steam turbine; a nozzle outer ring opposes the moving blade covers; a plurality of fins are formed by a combination of a long tooth and a short tooth on either the moving blade cover or the nozzle outer ring; a convexoconcave part is formed on the other side so as to oppose the fin; and the plurality of fins and the convexoconcave part constitute a seal portion for sealing a space between a moving blade and a nozzle outer ring, a fin located on the most upstream side of seal portions is a long tooth and a steam inlet opening part is provided on the upstream side of this long tooth to achieve the above object.SELECTED DRAWING: Figure 1

Description

Embodiments described herein relate generally to a steam turbine seal structure and a steam turbine using the same.

The present invention relates to a seal structure for a steam turbine, and relates to a structure for avoiding a seal fin provided at a tip portion of a moving blade and an opposing surface of the seal fin from erosion by solid particles.

It is well known that in a steam turbine, a passage component is eroded by solid particles from an upstream device such as a boiler. The solid particles are said to come from boilers and reheaters and their piping, and generally the degree of erosion is pronounced in the front stage of the high-pressure / medium-pressure turbine, but the particle size and Depending on the volume, the erosion may reach the downstream stage of the turbine. This erosion by solid particles is not only the phenomenon that the solid particles that flow into the first stage blade of each high-pressure / medium-pressure turbine rebound at the thick part of the leading edge of the blade and erode the thin part of the trailing edge of the front nozzle. The seal fin that seals the leaked steam that passes through the gap between the rotor blade that is the rotating portion and the nozzle outer ring that is the stationary portion may further extend to the surface facing the seal fin. Due to this erosion, the gap between the seal fin and the nozzle outer ring is increased, and when the phenomenon progresses, the seal fin may be lost. As a result, the performance of the turbine is significantly reduced, which has a serious influence on the stable supply of electric power.

A typical structure of the steam turbine passage is shown in FIG. It consists of a rotating rotor blade 1, a nozzle 2 that is a stationary part, and a nozzle outer ring 3 that is a structure that attaches the nozzle 2 to a casing. The moving blade 1 has a moving blade cover 4 formed integrally therewith, and seal fins are arranged to block steam leaking from the tip of the moving blade. The seal fin is composed of a moving blade seal fin long tooth 5 and a moving blade seal fin short tooth 6, and a combination of these constitutes a seal portion 20 that suppresses leakage steam from the blade tip. The behavior of the solid particles 7 flowing from the upstream is shown in the figure. Since the steam exiting the nozzle has a swirling component, it flows to the outer peripheral side due to its centrifugal force. Due to this steam flow, the solid particles 7 also have a swirling component, and are reflected by the centrifugal force toward the outer peripheral direction after being collided with the nozzle outer ring 3 and collide with the seal fin short teeth 6. As a result, this seal fin is worn over time, solid particles enter the next seal fin portion, and wear of the seal fin facing surface also proceeds. As a result, seal fin and seal fin facing surface 1
The gap of 2 widens, the amount of leaked steam increases, and the performance of the paragraph deteriorates. This erosion is not limited to the inlet stage of the high pressure / intermediate pressure turbine, but may extend to the downstream stage, resulting in a serious situation that the efficiency of the entire turbine is reduced.

JP 2014-31750 A

As described above, the erosion of the seal portion and the seal facing surface, which is an important factor of turbine performance, which widens the gap between the rotor blade and the nozzle outer ring, is a serious problem that greatly affects the stable supply of electric power.

A steam turbine seal structure disclosed in Japanese Patent Application Laid-Open No. 2014-31750 has been proposed to solve this problem. However, the proposed structure is not perfect and has some problems. Hereinafter, the problem of the structure will be described with reference to FIG.

The main configuration of the representative embodiment includes an inlet opening 9 provided in the nozzle outer ring 3 and a through-hole 8 that is also distributed from the steam inlet of the nozzle outer ring 3 to the steam outlet. In this structure, most of the solid particles 7 are captured by the inlet opening 9, and then pass through the through hole 8 to bypass the seal portion and escape to the rear stage.

On the other hand, the turbine shaft length increases due to the recent increase in turbine unit capacity / temperature increase, and there is a tendency that the relative thermal elongation at the time of starting and stopping increases. Although the direction and the amount of this thermal elongation vary depending on the paragraph, as shown in FIG. 7, when the moving blade 1 relatively moves due to thermal elongation, an opening 21 is generated. There is a possibility that solid particles may enter the seal portion from the opening portion 21 and erode the seal portion. During normal operation, this opening 21 does not occur and the through-hole 8 exhibits a sufficient function. However, in a plant with a large number of start / stop operations, the time during which the opening 21 is generated becomes long, and as a result, enters the seal portion. There is a problem that the amount of solid particles increases. In addition, there is also a problem that the rear fin is eroded in the process of discharging the solid particles once entering the seal portion.

In order to reduce the influence of solid particles, the present invention not only provides a structure that minimizes the penetration of the solid particles, but also refers to a technique for recovering the solid particles themselves even if they enter the seal. An object of the present invention is to provide a seal structure which is not easily eroded.

In order to solve the above-mentioned problem, the present invention provides a moving blade cover formed at the tips of a plurality of moving blades rotated by a steam flow flowing in a steam turbine, and a nozzle outer ring faces the moving blade cover, and the moving blade A plurality of fins by combining long teeth and short teeth are formed on either the cover or the nozzle outer ring, and an uneven portion is formed on the other side to face the fin, and the plurality of fins and the uneven portion In the seal structure of the steam turbine that constitutes a seal part for sealing between the moving blade and the nozzle outer ring, the fin located on the most upstream side of the seal part is a long tooth. Also, the above object is achieved by providing the steam inlet opening on the upstream side.

According to the sealing device of the present invention, it is possible to minimize the intrusion of solid particles into the seal portion, and as a result, it is possible to maintain the gap in the seal portion, thereby suppressing a decrease in turbine efficiency. be able to. In addition, damage to parts due to solid particles can be avoided, and stable power supply is possible.

(First embodiment)
A steam turbine seal structure according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is an enlarged meridional view of the vicinity of the tip of a moving blade of a steam turbine stage.

A plurality of blades 1 and nozzles 2 that are rotated by the steam flow are disposed, and a blade cover portion 12 that is formed integrally with the blade body is disposed at the tip of each blade 1. Further, seal fins arranged on the rotor blade cover 4 formed integrally with the rotor blade cover portion 12 are arranged. This seal fin alternates between the rotor blade cover seal fin long teeth 5 and the rotor blade cover seal fin short teeth 6. It is something to distribute to. Further, the seal fin facing surface 12 is provided with uneven portions corresponding to the moving blade cover seal fin long teeth 5 and the moving blade cover seal fin short teeth 6. In this way, the sealing device is constituted by the long teeth and the concave portions, and the short teeth and the convex portions. In this structure, the feature of this embodiment is a structure in which the blade cover seal fin long teeth 5 are arranged on the seal fin of the blade steam inlet.

Further, an inlet space portion 9 is provided at the inlet portion of the sealing device, and the axial dimension A of the front end thereof is larger than the gap B between the cover portion of the moving blade and the nozzle outer ring, and the outer peripheral surface of the space is the nozzle outer ring. It is provided on the outer peripheral side from the position of the facing surface 12 of the seal fin.

In addition, the transitional movement of the rotor blade 1 is illustrated as a thermal elongation direction. By arranging such seal fins, the opening 21 shown in FIG. 7 does not occur even when the moving blade 1 moves in the illustrated direction. Therefore, the solid particles 7 are generated by the nozzle outer ring 3 by the swirl speed component and the centrifugal force.
If it hits, it will flow into the steam passage part which is the main stream of steam, or it will remain in the entrance opening 9 by consumption of the kinetic energy at the time of a collision.

Moreover, since the opening part 21 does not arise, the solid particle 7 is not drawn into the seal part. Therefore, the possibility of eroding the seal portion can be reduced. Furthermore, the possibility of the solid particles 7 flowing into the seal portion can be reduced, and the risk of the solid particles 7 colliding with a plurality of seal fins can be reduced and the sealing performance can be maintained.

(Second Embodiment)
A steam turbine seal structure according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is an enlarged meridional view of the vicinity of the tip of the moving blade of the steam turbine stage.

As described in the first embodiment, when the fin arrangement of the present invention is used, an opening is not generated and most solid particles collide with the inner surface of the inlet opening 9 of the nozzle outer ring 3. However, there remains a possibility that a small part of the solid particles collide with the fin long teeth on the steam inlet side of the main component of the sealing mechanism.

In order to solve this problem, in the second embodiment, the protective projection 14 is arranged on the nozzle outer ring 3.
After the solid particles collide with the protective projection 14, the solid particles are guided to the inlet opening 9 by the centrifugal force, so that the solid particles 7 are prevented from directly colliding with the fins which are the main components of the seal and being eroded. be able to. By this action, it is possible to maintain the gap of the seal portion, and it is possible to avoid performance degradation due to an increase in the gap over time.

The defense protrusion 9 may be a simple plate shape, but may be a normal fin shape. Further, it is desirable that the material has a higher hardness than the fin material.

(Third embodiment)
A steam turbine seal structure according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is an enlarged meridional view of the vicinity of the tip of the moving blade of the steam turbine stage.

In the first embodiment or the second embodiment, the solid particles 7 are captured at the inlet opening 9 and collision and intrusion into the seal fin can be avoided. However, when the amount of the solid particles 7 is large, the inlet opening 9 alone is sufficient. Insufficient capacity. A through-hole 8 is provided in the nozzle outer ring 3 to discharge the staying solid particles 7. The through hole 8 communicates with the lower paragraph.

When the solid particles 7 enter the through-hole 8 through the inlet opening 9, due to the pressure difference before and after the rotor blade,
The through-hole 8 provided in the outer ring of the nozzle goes out to the lower paragraph because the outlet portion has a lower pressure than the inlet portion. As a result, the solid particles 7 do not enter the seal portion, and the gap can be maintained. In addition, the solid particles discharged to the lower paragraph have a particle size smaller than that at the time of inflow due to the collision with the wall surface generated in the path, and even if they flow into the seal portion of the lower paragraph, the influence is small.

(Fourth embodiment)
A seal structure for a steam turbine according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 is an enlarged meridional view of the vicinity of the tip of the moving blade of the steam turbine stage.

In the first to third embodiments, the possibility that the solid particles 7 enter the seal portion 20 is extremely low. However, it is not zero. In addition, the solid particles may be generated not only from the outside but also inside the seal structure. For example, when the rubbing occurs in which the blade cover seal fin long teeth 5 or the blade cover seal fin short teeth 6 and the seal fin facing surface 12 constituting the seal fin come into contact with each other due to transient thermal deformation or the like, the metals contact each other. There are solid particles produced by

In order to discharge the solid particles, at least one inner peripheral space 10 is provided in a recess that constitutes the opposing surface 12 of the fin. The solid particles 7 in the seal move toward the inner surface of the seal fin by centrifugal force due to the swirling component, and are captured in the internal space 10.

The internal space is not limited to one place as in the present embodiment, and may be provided in a plurality of recesses. Further, the internal space 10 may have a groove shape continuous in the circumferential direction, but may be discretely arranged.

(Fifth embodiment)
A steam turbine seal structure according to a fifth embodiment of the present invention will be described with reference to FIG. As described above, in the case of the configuration of only the internal space 10, the trapped solid particles remain in the space. However, when the amount of the solid particles is large, the capacity is insufficient in the space alone. . In order to solve this problem, a communication hole 11 is provided between the through hole 8 and the inner peripheral space 10 as shown in FIG. Since the pressure in the inner peripheral space 10 is higher than the pressure in the through-hole 8, the pressure difference is discharged backward. Since the discharge effect by the inner peripheral space 10 and the communication hole 11 depends on the pressure difference, it is more effective to dispose in the concave portion of the seal fin facing surface on the steam inlet side where the pressure is relatively high.

In addition, although it was set as the structure which provided the fin in the moving blade cover and the uneven part in the nozzle outer ring | wheel, this embodiment may be applied to the sealing device which provided the uneven part in the moving blade cover and the fin in the nozzle outer ring | wheel.

The figure which shows 1st Embodiment of the steam turbine seal structure which concerns on this invention. The figure which shows 2nd Embodiment of the steam turbine seal structure which concerns on this invention. The figure which shows 3rd Embodiment of the steam turbine seal structure which concerns on this invention. The figure which shows 4th Embodiment of the steam turbine seal structure which concerns on this invention. The figure which shows 5th Embodiment of the steam turbine seal structure which concerns on this invention. Diagram showing conventional steam turbine seal structure The figure which shows embodiment of the steam turbine seal structure of other invention

DESCRIPTION OF SYMBOLS 1 Rotating blade 2 Nozzle 3 Nozzle outer ring 4 Rotating blade cover 5 Rotating blade cover seal fin long tooth 6 Rotating blade cover seal fin short tooth 7 Solid particle 8 Through-hole 9 Inlet opening 10 Inner peripheral space 11 Communication hole 12 Opposing seal fin Surface 14 Protective projection 20 Seal portion 21 Opening portion

Claims (7)

A moving blade cover is formed at the tip of a plurality of moving blades rotated by the steam flow flowing through the steam turbine, a nozzle outer ring faces the moving blade cover, and either the moving blade cover or the nozzle outer ring is long. A plurality of fins are formed by a combination of teeth and short teeth, and an uneven portion is formed on the other side to face the fin, and the plurality of fins and the uneven portion provide a space between the moving blade and the nozzle outer ring. In a seal structure of a steam turbine that constitutes a seal part for sealing,
A steam turbine seal structure, wherein a fin located on the most upstream side of the seal portion has long teeth, and a steam inlet opening is provided on the upstream side of the long teeth. 2. The seal for a steam turbine according to claim 1, wherein a shielding object is disposed from the outer ring of the nozzle toward the moving blade cover on the steam inlet side of the fin of the steam inlet portion. 3. Construction. The axial dimension of the opening of the steam inlet opening is larger than the gap between the cover part of the rotor blade and the nozzle outer ring, and the outer peripheral surface of the space is provided on the outer peripheral side from the position of the opposing surface of the seal fin of the nozzle outer ring. The steam turbine seal structure according to claim 1, wherein the seal structure is a steam turbine. A through hole communicating with the steam inlet opening and penetrating from the moving blade inlet to the outlet side in the nozzle outer ring has a radial position on the moving blade outlet side with respect to the position on the moving blade inlet side. The steam turbine seal structure according to claim 1, wherein the steam turbine seal structure is the same or radially outward. 4. The steam turbine seal structure according to claim 1, wherein at least one inner peripheral space is provided in the nozzle outer ring constituting the opposed surface of the fin. 5. 6. The steam turbine seal structure according to claim 5, wherein the inner peripheral space communicates with the through hole. A steam turbine in which the seal structure according to claim 1 is applied to at least one paragraph.

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