JPH08319804A - Labyrinth seal device - Google Patents

Abstract

PURPOSE: To suppress leakage of steam effectively, and also suppress unstable vibration of a rotary shaft which is generated by steam. CONSTITUTION: A plurality of seal fins 4 are arranged on a seal ring 3 which is retained on a casing 2 so as to close the circumference of a rotary shaft 1 leaxing a few clearance between the seal ring 3 and the surface of the rotary shaft 1, a plurality of passages 6 are arranged on the seal ring 3 so as to communicate chambers 5 serving as space formed between seal fins 4 with each other, and thereby, a labyrinth seal device is constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a labyrinth seal device used in a steam turbine, and more particularly, effectively suppresses unstable vibration of a rotating shaft caused by steam in the labyrinth seal to improve the stability of the steam turbine. The present invention relates to a labyrinth seal device that can be operated.

[0002]

2. Description of the Related Art Conventionally, in a steam turbine, a labyrinth seal device is arranged at an appropriate position in the axial direction of a rotary shaft in order to prevent steam from leaking from a gap in a region having a pressure difference.

The above labyrinth seal device is provided with a seal fin formed so as to close the periphery of the rotary shaft with a slight gap left between the labyrinth seal device and the surface of the rotary shaft. A plurality of sheets are arranged with an appropriate gap in the axial direction of the shaft. In this way, the labyrinth seal device prevents steam from leaking from around the rotating shaft in the axial direction as much as possible.

[0004]

In the conventional labyrinth seal device described above, steam flows into the chamber formed between the seal fins through the gap between the rotary shaft and the seal fins. Therefore, there is a problem that the rotating shaft may excite unstable vibration by the steam.

That is, when the shaft center of the rotating shaft is eccentric due to an unbalanced force existing in the steam turbine, the pressure distribution of steam in the chamber becomes uneven in the circumferential direction of the rotating shaft.
The non-uniformly distributed steam tries to move to the low pressure side chamber through the gap between the seal fin and the rotating shaft in order to return the pressure distribution to a uniform state. At that time, the steam force acts on the rotating shaft to cause the rotating shaft to vibrate.

The present invention has been made in consideration of such conventional circumstances, and an object thereof is to enable effective suppression of steam leakage and to prevent unstable vibration of a rotating shaft caused by steam. It is to provide a labyrinth seal device that can be suppressed.

[0007]

That is, the invention according to claim 1 is arranged between a rotary shaft of a steam turbine and a stationary member facing the rotary shaft, and has a high pressure region and a low pressure region. A labyrinth seal device for suppressing the leakage of steam between the seal ring, which is locked to the stationary side member and formed in an annular shape, and formed so as to extend from the seal ring to the vicinity of the rotating shaft, A plurality of seal fins arranged at intervals in the axial direction of the rotating shaft and the adjacent or separated chambers formed between the seal fins are formed in the seal ring so as to communicate with each other. And a passage that enables the movement of steam.

The invention according to claim 2 is the labyrinth seal device according to claim 1, wherein the passage is formed so as to be inclined in the circumferential direction of the rotary shaft.

According to a third aspect of the present invention, in the labyrinth seal device according to the first aspect, the passage is formed so that one opening cross-sectional area and the other opening cross-sectional area are different. Is characterized by.

[0010]

In the labyrinth seal device of the present invention having the above-described structure, a part of the vapor filled in the chamber is partially removed from the high pressure side chamber to the low pressure side chamber without passing through the gap between the rotary shaft and the seal fin. Can be moved to.

Therefore, by reducing the amount of steam passing through the gap between the rotary shaft and the seal fin, the steam force acting on the rotary shaft can be reduced, and the swirling flow of steam generated in the chamber can be reduced. Can also be suppressed by moving a part of the steam to the low-pressure side chamber through the passage.

Further, by forming the passage so as to be inclined in the circumferential direction of the rotating shaft, the vapor flow flowing out of the passage into the chamber acts so as to resist the swirling flow generated in the chamber. This makes it possible to prevent the growth of the swirling flow, which is one of the causes of causing unstable vibration on the rotating shaft. Further, by making one opening cross-sectional area of the passage and the other opening cross-sectional area different,
It is possible to control the flow state of steam.

[0013]

The details of the present invention will be described below with reference to the accompanying drawings. 1 and 2 show the configuration of an embodiment of the present invention, and FIG. 2 is a cross-sectional view of FIG. 1 as seen from the axial direction of the rotary shaft. In these drawings, 1 is a rotary shaft of a steam turbine, 2 is a casing as a stationary side member, and the labyrinth seal device is provided between the casing 2 and the rotary shaft 1 and is configured as follows. There is.

That is, a plurality of seal fins 4 are provided on the substantially annular seal ring 3 held by the casing 2 so as to close the periphery of the rotary shaft 1 with a slight gap left from the surface of the rotary shaft 1. A labyrinth seal device is configured by arranging a plurality of passages 6 in the seal ring 3 so as to communicate with the chamber 5, which is a space formed between the seal fins 4.

The chamber 5 is filled with steam that has passed through the gap between the rotary shaft 1 and the seal fin 4, and the passage 6 is constructed so that this steam can flow, as shown in FIG. , Are arranged in the circumferential direction. It should be noted that there may be a plurality of chambers 5 communicated by the passages 6 in the axial direction of the rotating shaft.

In the labyrinth seal device configured as described above, since the chamber 5 is communicated with the passage 6 capable of moving steam, the chamber 5 is connected.
A part of the steam filling the inside can be moved from the high pressure side chamber 5 to the low pressure side chamber 5 by the passage 6 without passing through the gap between the rotary shaft 1 and the seal fin 4.

That is, when the shaft center of the rotating shaft 1 is eccentric due to an unbalanced force existing in the steam turbine, the pressure distribution of the steam in the chamber 5 becomes uneven in the circumferential direction of the rotating shaft 1. The non-uniformly distributed steam tries to move to the low pressure side chamber 5 through the gap between the seal fin 4 and the rotary shaft 1 in order to return the pressure distribution to a uniform state.

At this time, the steam force acts on the rotary shaft 1 to cause vibrations on the rotary shaft. In this embodiment,
By moving a part of the steam flowing into the low-pressure side chamber 5 without passing through the gap between the seal fin 4 and the rotary shaft 1, the steam force acting on the rotary shaft 1 can be reduced. Also,
For the swirling flow of steam generated in the chamber 5, the passage 6
It can be suppressed by moving a part of the vapor through the chamber 5 to the low pressure side chamber 5.

As described above, in this embodiment, the steam force that causes the unstable vibration of the rotating shaft 1 can be suppressed. As described above, in this embodiment, since the seal ring 3 has the passage 6 capable of moving the steam, a part of the high-pressure steam is distributed between the rotary shaft 1 and the seal fin 4. Since it can be moved without a gap and the swirling driving force of steam that causes unstable vibration in the rotating shaft 1 can be reduced, the rotating shaft 1 can be stably operated.

Next, another embodiment will be described with reference to FIGS. 4 is a cross-sectional view of FIG. 3 viewed from the axial direction of the rotary shaft. As shown in FIG. 3, in the labyrinth seal device of the present embodiment, the chambers 5 that are not adjacent to each other and are separated from each other are connected by a passage 6. Further, as shown in FIG. 4, the passage 6 has at least the low pressure side chamber 5
In the vicinity of the opening of the rotary shaft 1, the rotary shaft 1 is arranged so as to be inclined with respect to the circumferential direction. This inclination direction is a direction in which the inflow direction of the steam flowing from the high pressure side into the low pressure side chamber 5 is opposite to the rotation direction of the rotating shaft 1.

The passage 6 may not have a constant cross-sectional area, and may have a different cross-sectional area from the opening side of the high-pressure side chamber 5 and the opening side of the low-pressure side chamber 5. In this way, by changing the cross-sectional area of the passage 6, the flow state of steam can be controlled.

Also in the labyrinth seal device configured as described above, it is possible to suppress the non-uniform distribution of steam that causes unstable vibration in the rotary shaft 1 as in the above-described embodiment. That is, since the chamber 5 is communicated with the passage 6 capable of moving the vapor, a part of the vapor filled in the chamber 5 is not passed through the gap between the rotary shaft 1 and the seal fin 4. Further, it is possible to move from the chamber 5 on the high pressure side to the chamber 5 on the low pressure side which is not adjacent and is separated.

Further, as described above, the passage 6 is formed obliquely so that the steam flowing from the high pressure side chamber 5 into the low pressure side chamber 5 becomes resistant to the swirling flow generated in the chamber 5. Since the gas flows obliquely, it is possible to prevent the growth of the swirling flow, which is one of the causes of causing the unstable vibration in the rotating shaft 1.

As described above, also in this embodiment, since the seal ring 3 has the passage 6 capable of moving the steam, a part of the high pressure steam is supplied to the rotary shaft 1 and the seal fins 4. It can be moved without a gap between them. Further, since the passage 6 near the opening of the chamber 5 on the low pressure side is inclined with respect to the circumferential direction of the rotary shaft 1 on the side opposite to the rotation direction of the rotary shaft 1, growth of the swirling flow in the chamber 5 is suppressed. can do. Therefore, it is possible to reduce the swirling vibration force of steam that causes unstable vibration on the rotating shaft 1.
Can be operated stably.

[0025]

As described above, according to the labyrinth seal device of the present invention, it is possible to effectively suppress the leakage of steam and to suppress the unstable vibration of the rotating shaft caused by the steam. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional configuration of a labyrinth seal device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration of the labyrinth seal device of FIG. 1 as seen from the axial direction.

FIG. 3 is a diagram showing a sectional configuration of a labyrinth seal device according to another embodiment of the present invention.

FIG. 4 is a diagram showing a cross-sectional configuration of the labyrinth seal device of FIG. 3 as seen from the axial direction.

[Explanation of symbols] 1 ... Rotating shaft 2 ... Casing 3 ... Seal ring 4 ... Seal fin 5 ... Chamber 6 ... Passage

Claims (3)

[Claims] 1. A labyrinth seal device, which is arranged between a rotary shaft of a steam turbine and a stationary member facing the rotary shaft, and which suppresses steam leakage between a high pressure region and a low pressure region. An annular seal ring that is locked to the stationary member, and a plurality of seal rings that are formed to extend from the seal ring in the vicinity of the rotary shaft and that are arranged at intervals in the axial direction of the rotary shaft. A seal fin, and a passage formed in the seal ring so as to communicate between adjacent or separated chambers formed between the seal fins and enabling passage of vapor between the chambers. Characteristic labyrinth seal device. 2. The labyrinth seal device according to claim 1, wherein the passage is formed so as to be inclined in a circumferential direction of the rotary shaft. 3. The labyrinth seal device according to claim 1, wherein the passage is formed so that a cross-sectional area of one opening and a cross-sectional area of the other opening are different from each other. .