JPS5918208A - Labyrinth packing - Google Patents

Abstract

PURPOSE:To reduce the leakage of turbine working fluid by a method wherein a packing fin for composing a narrow part and an enlarged part on a leakage passage of the turbine working fluid is formed by a shape memory alloy which displaces the packing fin toward the direction narrowing the leakage passage under high temperature environment. CONSTITUTION:Plural circumferential grooves 2 are provided on a surface of a turbine rotor 1, and a packing ring 4 is fixed on a casing 3 by an expansion and contraction member 5. Plural packing fins 6 are provided on a surface opposing to the rotor 1 of the packing ring 4, a narrow part of the leakage passage is formed by a clearance between the top ends of the fins 6 and the surface of the rotor 1, also an enlarged part is formed by respectively adjacent each fin 6. In this case, said fins 6 are formed by a shape memory alloy which stores the configuration to displace said fins 6 toward the direction narrowing the clearance between the top ends of the fins 6 and the surface of the rotor 1. Thereby, the narrow part of the leakage passage can be adequately maintained at all time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a labyrinth packing used in steam turbines and the like.

[Technical background of the invention and its problems]

Generally, various gaskets are used to prevent leakage of turbine working fluid, such as steam, of a turbine. For example, a labyrinth packing is used to prevent leakage of steam from a leakage passage along the rotor axis that occurs in a gap between a turbine rotor and a casing of a steam turbine. This labyrinth seal has many circumferential grooves on the surface of the turbine rotor that are coaxial with the axis of the turbine rotor, and one end of the labyrinth fin is fixed to the casing.The other end of the labyrinth fin is a free end. is located close to.

A plurality of these packing fins are provided in the axial direction of the turbine rotor, and are installed in narrow parts in the gap between the turbine rotor and the casing.
A large number of enlarged portions are formed.

When the labyrinth packing is provided in this manner, leaking steam is repeatedly constricted in the narrow portion and its velocity is reduced in the enlarged portion, thereby preventing steam leakage.

However, for steam turbine operation, e.g.
Since kumquats contain high-temperature, high-pressure steam of approximately 46 hlct&, as the temperature rises during operation of the steam turbine, leakage passages such as the gap between the casing and the turbine rotor expand due to thermal expansion, causing an increase in the amount of leakage steam. There was a problem with it being put away. There is also the problem that such an increase in leakage steam causes pressure loss and reduces the efficiency of the steam turbine. Steam leakage due to thermal expansion is
This problem has become more prominent as steam becomes hotter and more pressurized in order to achieve higher efficiency.

In order to prevent the above-mentioned leakage, methods such as reducing the distance between the packing fins and the rotor and increasing the number of packing fins can be considered, but the former causes the operational trouble of rubbing, and the latter reduces the span. Since this leads to problems such as the turbine rotor becoming longer, there is a natural limit, and reducing the amount of leaked steam has been a very difficult problem.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a labyrinth packing that reduces leakage of turbine working fluid and improves turbine efficiency.

[Summary of the Invention] The labyrinth packing of the present invention is designed to prevent leakage of turbine working fluid from narrow or enlarged areas such as the gap between the turbine rotor and the casing, the gap between the turbine rotor and the inner ring of the nozzle diaphragm, or the gap between the casing and the rotor blades. A packing fin made of a shape memory alloy is provided to form a part.
This packing fin made of a shape memory alloy is configured to be displaced in a direction that narrows this leakage passage in a high-temperature environment during turbine operation.

As the turbine working fluid uses high-temperature, high-pressure fluid such as steam or high-temperature combustion gas, the gaps in the leakage passages described above widen due to the thermal expansion of the casing, turbine rotor, etc. as the temperature rises during turbine operation. According to the invention, the packing fin is displaced to narrow the leakage passage due to the shape memory effect, so it is possible to prevent an increase in the leakage amount of the turbine working fluid due to the expansion of the leakage passage due to thermal expansion.

[Embodiments of the invention]

An embodiment in which the present invention is used to prevent steam leakage from a gap between a turbine rotor and a casing of a steam turbine will be shown. Fig. 1 shows a complete partial cross-sectional view of the steam turbine, and Fig. 2 shows a partial cross-sectional view of the steam turbine.
An enlarged view of main part a in the figure is shown.

On the surface of the turbine rotor (1), there is a surface of the turbine rotor (1).
) A plurality of circumferential grooves (2) coaxial with the rotating shaft are provided in the axial direction. In addition, the casing (3) has an arc-shaped packing ring (4) attached to an expandable and contractible fixing member such as a spring (
A plurality of such packing rings (3) are combined to form an annular shape. A packing fin (6) is provided on the surface of the packing ring (3) facing the turbine rotor (1).
) A plurality of packing fins (6) are provided along the axial direction, one end of which is fixed to the packing ring (4), and the other end is a free end that is connected to the circumferential groove (2) of the turbine rotor (1). It is provided in close proximity to the surface on which it is provided. Therefore, the gap between the free end of the packing fin (6) and the surface of the turbine rotor (1) constitutes a narrow part of the leakage passage, and the space between adjacent packing fins (6) becomes an enlarged part. Repeating this will prevent steam leakage.

This packing fin (6) connects the tip of the packing fin (6) and the turbine rotor (1) in a high-temperature environment during turbine operation.
It is made of a shape memory alloy, such as a nickel/ψ tan alloy, which has a shape memorized such that it is displaced in a direction in which the distance from the surface becomes narrower. For example, as shown in Fig. 1 and Fig. 2, the packing fin (6) can be made into a curved plate shape, and the shape can be memorized so that the degree of curvature becomes smaller or the shape becomes closer to a flat plate in a high-temperature environment. It is possible to perform operations like this.

In the steam turbine configured as described above, both the turbine rotor (1) and the casing (3) undergo thermal expansion due to the high temperature steam, and the gap between the turbine rotor (1) and the casing (3) widens. As a result of this effect, the packing fin (6) is displaced in the direction of narrowing this gap, so that the gap can be prevented from widening, and the distance between the free end of the packing fin (6) and the surface of the turbine rotor (11) is reduced. It never spreads.

Therefore, it is possible to prevent an increase in the amount of leaked steam due to the widening of this interval, thereby improving steam turbine efficiency. Further, the displacement due to the shape memory effect is determined by the differential pressure between the memorized shape and the designed shape, and since this amount of displacement can be quite large, it is possible to significantly suppress the amount of steam leakage. Furthermore, by using a shape memory alloy, leakage can be prevented without changing the number of parts, which is very effective. By using the shape memory effect, the gap after displacement can be set relatively easily with good dimensional accuracy, which is very effective in terms of design.

In recent years, there has been a trend to increase the temperature and pressure of steam in order to improve thermal efficiency, but as the temperature increases, the gap widens more significantly due to this thermal expansion, so the effect of the present invention in preventing gap widening is extremely effective. , leading to improved turbine efficiency. In addition, as temperatures and pressures increase, the use of iron-based austenitic steel instead of conventional iron-based ferritic steel is being considered for materials such as turbine rotors and casings, but the former has a thermal expansion coefficient of 12.5 Compared to 10'/1:, the latter is approximately 18.5×lO7°C, which is 1.5 times larger. Therefore, the gap widens significantly due to thermal expansion, so the effects of the present invention are particularly effective.

In addition, the packing ring (4) is an expandable fixing member (5).
If the packing fin (6) comes into contact with the turbine rotor for some reason, this fixing member (51) will contract and the packing fin (6), !: will reduce contact with the turbine rotor (1). This can prevent damage to the turbine rotor (1) due to this contact.Furthermore, the curved packing fin (6) itself has a spring effect, so if such a contact occurs, it can be quickly removed. The packing fin (6) is retracted and damage to the turbine rotor (1) can be prevented.

Moreover, if a soft material that is easily worn is provided at the tip of the packing fin (6), this damage can be further prevented.

The packing fin (6) may be fixed to the packing ring (4) by a general fixing method such as implantation, bolting, welding, pinning, or caulking. In addition, Patsukinfin (
If the concave surface of 6) is placed so that the high pressure side A1 and the convex surface are located on the low pressure side B, the packing fin (6) will be pushed by the high pressure steam, and the packing fin (6) will be displaced in the direction of narrowing the steam leakage passage. Therefore, the amount of steam leakage can be further reduced.

In addition, the material, shape, plate thickness, etc. of the shape memory alloy that constitutes the packing fin should be selected appropriately depending on the size of the turbine, the materials used, etc., and designed to the extent that the packing fin does not come into contact with the turbine rotor and cause rubbing. is necessary.

Further, it is preferable to use a material that is softer than the material of the turbine rotor so that it wears out quickly in case of rubbing. Furthermore, the material can be changed depending on the temperature conditions at the location where the labyrinth packing is provided; for example, a material such as brass may be used in a relatively low temperature location.

In addition to the shape of the packing fin shown in this example,
It goes without saying that the effects of the present invention can be obtained by using a packing fin made of bimetal that is displaced in a direction to narrow the steam leakage passage in a high-temperature environment. For example, a shape memory alloy bent into a dogleg shape may be used, or a shape memory alloy having a partially curved portion may be used. Alternatively, the shape may include a plurality of curved portions. In either case, it is sufficient to memorize a shape in which the length of the packing fin increases in the direction of the turbine rotor. By providing a plurality of curved portions in this manner, the amount of displacement of the packing fin can also be increased. Further, even if the fin is not curved, a similar effect can be obtained by using a patch fin that is implanted diagonally. In this case, the shape may be memorized so that it curves toward the turbine rotor (1).

Further, the thickness of the plate material constituting the packing fin does not need to be uniform; for example, the thickness may become thinner as it approaches the tip. With this configuration, when the packing fin comes into contact with the turbine rotor, it is likely to wear out, so damage to the turbine rotor can be prevented. Also, if you limit it to one plate and join it so that one end is not aligned but offset from each other, the width of the steam leakage passage can be increased and the number of packing fins has been increased, and the labyrinth packing. The effect can be made even more effective.

Another embodiment of the present invention in which the packing fin (6) is constructed using two plates (6') and (6'') is schematically shown in FIG. 3. The plate (6') made of a shape memory alloy is ), (One end of the six fully connected packing fins (6) is fixed to the packing ring (4), and the other end is set as a free end to the turbine rotor (
1) Provided close to the surface. At the free end of this packing fin (6) each plate (6'),
(6') are joined without aligning their tips, and the two narrow parts C2σ are formed by one packing fin (6). Patsukin fin (6) curved in a dogleg shape1. The shape is memorized so that the degree of curvature is reduced in the high temperature environment during turbine operation. The other configurations are the same as the embodiment shown in FIG. 17. In the embodiment shown in FIG. In addition to obtaining the effect of preventing damage to the turbine rotor (1) due to the spring effect of
Since two narrow portions 'f can be provided with one packing fin (6), the same effect as increasing the number of packing fins to prevent leakage can be obtained.

Furthermore, in the embodiment shown in FIG. 3, the turbine rotor (1
) nearer the board (6') '! An abrasive material may be used instead of i=shape memory alloy. With this configuration, even if the packing fin (6) is the turbine rotor (1)
Even if the gasket fin (6) comes into contact with the turbine rotor (1), the gasket fin (6) will quickly wear out, so there is no risk of damaging the turbine rotor (1).

In the above embodiments, the case where the packing fin is joined to the packing ring is explained, but the packing fin may be provided directly to the casing. Even if the packing fin is provided directly on the casing in this way, the spring sound effect can be created on the packing fin itself as described above, so it is possible to obtain the same effect as fixing the packing ring with an expandable fixing member. Can be done. Furthermore, since the present invention can prevent the leakage passage from widening, it is possible to reduce or eliminate the depth of the circumferential groove on the surface of the turbine rotor, which is provided to reduce steam leakage.

This circumferential groove tends to cause concentration of thermal stress and steam tightness, which contributes to environmental damage to the turbine rotor such as stress corrosion cracking and corrosion fatigue. A cause of environmental damage to the rotor can be eliminated, and the reliability of the turbine can be improved.

In this example, the labyrinth packing was used to prevent steam leakage from the gap between the turbine rotor and the casing, but the labyrinth packing was also used to prevent steam leakage from the gap between the casing and the rotor blades, the gap between the nozzle diaphragm and the turbine rotor, etc. It may also be used to prevent steam leakage from a steam leakage passage in the rotor axial direction.

FIG. 4 schematically shows another embodiment of the present invention in which a labyrinth packing is used to prevent leakage of turbine working fluid from the gap between the rotor blade (9) and the casing (3). The packing fin (6) is formed by joining a plate material (8) made of a shape memory alloy and an abrasive material so that it is convex and pointed in the direction from the plate material (7) to the plate material (8). It is curved.Furthermore, a plate material made of this shape memory alloy (
The force is stored in a shape that is displaced in a high temperature environment during turbine operation such that the degree of this curvature decreases and the substantial length of the packing fin (6) increases. In addition, one end of the packing fin (6) is identified with the casing (3), and the tip is set close to the rotor blade (9), but in this case, the part located near the rotor blade (9) is abrasive. Let it be a plate material (8) made of material.

In the labyrinth patchkin configured in this way,
The shape memory effect of the packing fins (6) can cancel out the widening of the gap 9 due to thermal expansion accompanying the temperature rise during turbine operation, so the amount of leakage of the turbine working fluid can be reduced. Also, since the Patsukin fin (6) has a spring effect, for some reason the Patsukin fin (6)
) comes into contact with the rotor blade (9), this contact can be completely relieved and damage to the rotor blade (9) can be prevented. Furthermore, by providing an abrasive material, the packing fins (6) will quickly wear out when they come into contact, and this is effective in preventing damage to the fins (9) caused by this contact.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent an increase in the leakage of the working fluid due to the expansion of the leakage passage of the turbine working fluid due to thermal expansion, and thus it is possible to improve the turbine efficiency. Therefore, there are also advantages such as significant fuel cost savings, which is very effective.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a steam plane for explaining the present invention in detail. 6...Patsukinfin (7317) Agent: Patent Attorney Noriyuki Chika (
1 other person) Figure 1 Figure 2? Figure 8

Claims (1)

[Claims] A labyrinth packing including a packing fin provided to form a narrow part and an enlarged part in a leakage passage of turbine working fluid, wherein the packing fin is shaped to be displaced in a direction to narrow the leakage passage in a high temperature environment during turbine operation. The labyrinth patchkin is made of a shape memory alloy that has a memorized memory.