JPH0693803A - Labyrinth packing - Google Patents

Abstract

PURPOSE:To reduce the leakage of steam so as to enhance the internal efficiency of a turbine by dividing the seal fin of a labyrinth packing into a plurality of small pieces which are supported on the casing side by a spring part. CONSTITUTION:A rotor blade 2 is connected at its front end to a ring-like shroud 9. An arcuate packing segment 10 is fixed to the outer race of a diaphragm at a position where it faces the outer peripheral part of the front end of the rotor blade 2, through a fixing member. A plurality of seal fins 11 are provided on the surface of the packing segment 10 which faces the shroud 9, along the direction of the axis of a turbine rotor. The seal fines 11 are fixed at their one end to the packing segment 10, but are made to be free at their the other end which is near the outer surface of the shroud 9. Each of the seal fins 11 is formed of a plate-like small piece joined to a rod-like spring part 14 is attached to the packing segment 10. Thus, it is possible to reduce the leakage of steam so as to enhance the internal efficiency of the turbine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial fluid machine, and more particularly to a turbine labyrinth packing suitable for preventing performance deterioration due to leakage of a working fluid from a gap between a rotating part and a stationary part of a turbine. .

[0002]

2. Description of the Related Art In general, a labyrinth packing is used as a method for improving the performance of a turbine as a method of reducing steam leaking from a gap between a stationary part and a rotating part existing in each part of the turbine. For example, as shown in FIG. 5, a labyrinth packing 5 is provided between the diaphragm inner ring 3 that fixes the stationary blade 1 and the sliding surface of the rotor 8, and a space between the tip of the moving blade 2 and the diaphragm outer ring 4. Is a method in which one or a plurality of seal fins 6 are provided, respectively, and the amount of steam leakage is reduced by the labyrinth packing 5 and the seal fins 6.

However, in the non-contact type seal device, the leakage amount decreases as the gap amount between the turbine rotor and the tip of the seal fin decreases. However, if the gap amount is too small, the seal fin will be in operation. Contact with the turbine rotor to damage the tips of the turbine rotor and seal fins, or the contact may cause the shaft vibration to increase, making it impossible to continue operation, or heat generated by the contact may cause the turbine rotor to bend. There was such a problem.

Such contact is due to a change in the gap amount depending on the operating state of the turbine. This change is caused by uneven thermal deformation of the casing, deformation due to pressure, or thermal expansion between the rotating body and the stationary portion. It is caused by various factors such as time difference. On the other hand, during steady operation, the amount of deformation or change is extremely small, so there is a problem that the amount of leakage increases due to the large gap during steady operation for a long time.

Therefore, in order to solve this problem, even if the fins and the turbine rotor are always in contact with each other with no gap,
As a mechanism for almost completely eliminating the damage to the fins and the turbine rotor, there has been a conventional method, for example, the literature name AIAA Paper No.
0-2140 (1990). (Paper title Evalation Of
As described in (Brush Seals For Limited-Life Engines), a brush seal is proposed in which the seal fin segment is configured in the shape of a brush with a large number of fine wires, and the brush is in contact with the turbine rotor in a flexed state. There is.

[0006]

In the above-mentioned prior art, it is difficult to manufacture the seal fin segment because the brush is formed by a huge amount of fine wire, and it is not suitable for a large steam turbine or the like.

The object of the present invention is to reduce the clearance of the turbine to a small clearance corresponding to the steady displacement difference between the stationary portion and the rotating portion,
The purpose of the present invention is to provide a labyrinth packing that reduces the leakage of turbine working fluid and improves turbine efficiency.

[0008]

[Means for Solving the Problems] The labyrinth packing is
Seal fins are provided to form a narrow portion and an enlarged portion in the leakage passage of the turbine working fluid such as a clearance between the turbine rotor and the casing, a clearance between the turbine rotor and the inner ring of the nozzle diaphragm, and a clearance between the casing and the moving blade. There is. The seal fin is divided into a plurality of small pieces, and the divided small piece of the seal fin is held on the casing side by a spring member so that the seal fin is easily displaced radially outward.

[0009]

In the transient operation of the turbine, when the gap amount is larger than the steady displacement difference between the stationary portion and the rotating portion set at the stationary time, the turbine rotor surface and the seal fin come into contact with each other. In this case, the seal fin divided into small pieces and held on the casing side by the spring member is deformed in the outer peripheral direction without increasing the contact surface pressure with the turbine rotor surface.

Therefore, even if the seal fins contact the surface of the turbine rotor for a short time during the transient operation of the turbine, the tips of the turbine rotor and the seal fins may be damaged, or the shaft vibrations may increase due to the contact and the operation cannot be continued. Or the turbine rotor is not bent due to heat generated by contact.

According to the present invention, since the gap between the stationary portion and the rotating portion can be narrowed during steady operation, the amount of leakage of the turbine working fluid can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is used for preventing steam leakage from a gap between a blade tip of a steam turbine and a casing will be described with reference to FIGS.

As shown in FIGS. 1 and 2, a plurality of rotor blades 2 each rotating in the circumferential direction are connected at their tips to a ring-shaped shroud 9. Further, an arcuate packing segment 10 is fixed to the outer diaphragm 4 at a position facing the tip outer peripheral portion of the moving blade 2, for example, by a stretchable fixing member 13 such as a spring, and a plurality of such packing segments 10 are provided. Combined, they are configured in an annular shape. A plurality of seal fins 6 are provided on the surface of the packing segment 10 facing the shroud 9 along the axial direction of the turbine rotor, one end of the seal fin 11 is fixed to the packing segment 10, and the inner surface of the packing segment 10 is further fixed. It is provided so as to be in contact with the arc-shaped projection 12 of and the other end is a free end so as to be close to the surface of the shroud 9. Therefore, the gap between the free end of the seal fin 11 and the surface of the shroud 9 forms a narrow portion of the leak passage, and the space between the adjacent seal fins 11 becomes an enlarged portion. By repeating this narrow portion and the enlarged portion, leakage of steam occurs. Will be prevented.

As shown in FIG. 3, the seal fin 11 comprises a plate-shaped small piece joined to a bar-shaped spring portion 14,
As shown in FIG. 2, the rod-shaped spring portion 14 is attached to the packing segment 10 so as to be inclined in the R direction which is the turbine rotation direction. In addition, the seal fins 11 are configured such that a plurality of seal fins 11 overlap each other in the axial direction.

In the packing segment 10 thus constructed, when the packing fin 11 comes into contact with the shroud 9 for some reason, the bar-shaped spring portion 14 bends and the contact between the seal fin 11 and the shroud 9 can be alleviated. It is possible to prevent the shroud 9 from being damaged by this contact. Further, if the tip of the seal fin 11 is provided with a material that easily wears, this damage can be further prevented.

The rod-shaped spring 14 may be fixed to the packing ring 10 by a general fixing method such as implantation, screwing, welding or caulking.

Further, the material, shape, thickness, etc. of the plate material of the seal fin 11 are appropriately selected according to the size of the turbine, the material used on the rotor side such as the shroud 9, and it is preferable to use a material softer than the material on the rotor side.

Other than the shape of the seal fin shown in this embodiment, the effect of the present invention can be obtained. For example, as shown in FIG. 4, it may be manufactured by twisting a thin plate.
It is also possible to use a seal fin made by integrally or joining the seal fin 11 and the seal fin 11. According to the present invention, the amount of steam leaked from the gap during turbine operation can be reduced with a relatively simple labyrinth packing structure as compared with the conventional example.

In the above embodiments, the case where the seal fin is joined to the packing ring 10 has been described, but the seal fin may be directly provided on the outer ring of the diaphragm.

In addition to preventing steam from leaking from the gap between the casing and the moving blades, the steam leaks from the steam leak passages in the axial direction of the turbine rotor such as the gap between the turbine rotor and the casing and the gap between the nozzle day diaphragm and the turbine rotor. It may be used to prevent steam leakage.

[0021]

According to the present invention, since the gap of the seal portion of the turbine can be set to a narrow gap corresponding to the steady displacement difference between the stationary portion and the rotating portion, the steam leakage is reduced and the internal efficiency of the turbine is improved. Therefore, the heat consumption rate can be improved.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a steam turbine for explaining an embodiment of the present invention.

FIG. 2 is a partial arrow view of AA of FIG.

FIG. 3 is a perspective view of a seal fin of the present invention.

FIG. 4 is a perspective view of a seal fin of another embodiment.

FIG. 5 is a vertical cross-sectional view showing a paragraph of a conventional turbine.

[Explanation of symbols]

2 ... moving blade, 9 ... shroud, 10 ... packing ring, 1
1 ... Seal fin, 14 ... Spring part.

Claims (2)

[Claims] 1. A labyrinth packing having seal fins arranged to face a rotating part of a turbine, wherein the seal fins are divided into a plurality of small pieces and are supported by spring parts which are displaced radially outward. Labyrinth packing characterized by that. 2. The labyrinth packing according to claim 1, wherein the seal fin is made of a thin plate, and a plurality of the seal fins are overlapped with each other to form a narrow portion in a leakage passage of a turbine working fluid.