JPH025702A - Labyrinth seal device for steam turbine - Google Patents

Abstract

PURPOSE:To aim at improvement of sealing effect by forming a fixing piece provided with the teeth of labyrinth seal thereon from a material having heat expansion. CONSTITUTION:One end of the teeth 6 of a labyrinth divided into one-fourth circular arc arranged in an axial direction is fitted to an fixing piece 8. The fixing piece 8 is made by a material having large heat expansion and fitted to a separating plate 3 with a bolt 9. The fixing piece 8 is heat-expanded according to temperature condition during operation to keep a gap fitted for operating condition. Accordingly, sealing effect can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Object of the Invention) (Industrial Application Field) The present invention relates to a labyrinth seal device for a steam turbine.

(Prior art) Steam turbines, like general rotating machines, have a gap between the rotating part and the stationary part, which causes problems such as internal steam leaking to the outside and external gas flowing into the interior. . Therefore, a sealing device is provided between the rotating part and the stationary part to maintain airtightness inside the machine.

Among sealing devices, a labyrinth sealing device in which a large number of fin-like teeth with sharp tips are arranged in a rotating part or a stationary part is widely used.

Hereinafter, details of the labyrinth seal device will be explained with reference to one section of the steam passage section of the steam turbine.

A steam turbine is a prime mover that converts high-pressure steam into thermal energy and generates mechanical output. Steam leakage in each stage reduces the efficiency of the turbine and must be suppressed as much as possible.

Figure 5 shows a vertical cross-sectional view of the nozzle part of the steam bottle. A partition plate 2 is arranged for each stage in the car 1, and the steam flows in the direction shown by the arrow A and expands when passing through the nozzle 3 provided on the partition plate 2, creating a high-speed steam flow. The air is ejected toward the rotating blade 4 and rotates the rotating shaft 5. The partition plate 2 holds the nozzle 3 and maintains the airtightness of each stage. Labyrinth teeth 6 are provided on the inner surface facing the rotating Rh5 and the rotating blades 4 to prevent leakage of steam from each gap. hindering.

FIG. 6 shows an enlarged longitudinal sectional view of the labyrinth seal portion. A ring-shaped projection 5a is also formed on the rotating shaft 5 side at a position facing the labyrinth.

Two types of teeth, long and short, with different lengths are used as the teeth 6 of the labyrinth, and the long teeth are located at a position where there is no ring-shaped protrusion.
In addition, the short teeth are arranged alternately so as to be located outside the ring-shaped projection.

As the leaked steam flowing through the gap 7 between the teeth 6 of the labyrinth and the rotation 1N15 is repeatedly constricted and expanded by the many teeth 6 and the ring-shaped protrusion 5a, its velocity energy is reduced and the amount of leakage is kept small. This leakage suppression effect improves as the gap 7 becomes smaller.

Although the labyrinth provided between the partition plate 2 and the rotation N15 has been described above, the labyrinth 6a between the partition plate 2 and the rotating blade 4 has a similar structure.

(Problems to be Solved by the Invention) When the vehicle starts driving, the cabin 1 deforms and the rotation axis moves. When the amount of movement becomes larger than the gap 7, the rotating shaft 5 and the labyrinth m6 come into contact. rotate! F[l15
If the teeth 6 of the labyrinth come into contact with each other, the shaft will move, which is very dangerous.

Furthermore, if the degree of contact is large, the heat generated by the contact will cause permanent deformation of the rotor, causing problems such as interfering with normal turbine operation.

When setting the gap 7, it is made large in advance to prevent contact, so there is a problem that the sealing effect is reduced accordingly.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a labyrinth seal device that allows the size of the gap to be changed depending on the operating state of the turbine, enhances the sealing effect, and is highly safe.

[Structure of the invention]

(Means for Solving the Problem) A labyrinth seal device for a steam turbine having a plurality of teeth arranged in a stationary part opposite to a rotating part in order to suppress the flow rate of steam leaking from the gap between the rotating part and the stationary part. In,
The teeth are made up of a plurality of partially arc-shaped pieces arranged so as to surround the rotating part, and at least some of these pieces have one end fixed to the stationary part and are made of a material with a large coefficient of thermal expansion. It is characterized in that it is attached to a fixed piece.

(Function) When the turbine starts operating and high-temperature steam flows in, the nozzles, rotating blades, and partition plates in the steam path gradually heat up. Along with this, the material that fixes the teeth of the labyrinth attached to the partition plate has a high coefficient of linear expansion, so it gradually expands thermally. The thermal expansion causes the fixed end of the labyrinth to move, and since the narrow end of the teeth of the labyrinth are not fixed, they also move and act to change the gap.

(Example) In the following description, parts common to those in FIGS. 5 and 6 are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, one end of six teeth of a labyrinth divided into 174 circular arcs arranged in the ring direction is attached to a fixed piece 8. The method of attachment is to cut a groove in the fixed end 8, fit the teeth 6 of the labyrinth, and then apply caulking to firmly fix it.

This fixing piece 8 is made of a material with a high coefficient of linear expansion.

On the other hand, one end of the teeth 6 of the labyrinth is not fixed and left in a free state.

As described above, the fixing piece 8 fixing the labyrinth teeth 6 is attached to the partition plate 2 with bolts 9.

A groove is cut in a portion of the labyrinth on the partition plate 2 side corresponding to the teeth 6, and the teeth 6 are partially inserted into the groove, and the assembly is assembled with the tip portion protruding from the groove.

The width and depth of this groove must be set to such an extent that the movement of the teeth 6 is not restricted. FIG. 2 is a longitudinal sectional view of the assembled state.

When the turbine starts operating and high-temperature steam flows in, the nozzle 3, rotary blades 4, and partition plate 2 in the steam passage are gradually heated. Similarly, the fixed piece attached to the partition plate is also heated.

The fixed piece 8 has a larger coefficient of linear expansion than the partition plate 2 and the rotating shaft 5,
It undergoes relatively large thermal expansion.

Accordingly, the fixed ends of the teeth 6 of the labyrinth also move, and at the same time the free ends of the teeth also move in the same direction. FIG. 3 shows a cross-sectional view of an embodiment using the labyrinth seal device configured as described above in the upper half. When the operation is started, the fixed piece 8 is gradually thermally deformed, and the fixed end of the teeth 6 of the labyrinth seal moves upward, and the free end also moves upward, moving in the direction in which the upper gap 7 widens. Figure 4 shows a cross-sectional view after the gap has changed J0 The gap 7 changes due to changes in the amount of casing deformation and changes in the rotation axis movement from the time the turbine starts operating until it reaches steady operation. . When the clearance in the upper half becomes narrower due to operation, the labyrinth seal device of the present invention is used in the upper half as shown in FIG. When the clearance in the lower half is narrow, the labyrinth seal device of the present invention is used in the lower half.

According to the embodiments described above, the size of the gap can be changed appropriately depending on the operating conditions, so that it is possible to improve the sealing effect and to increase safety.

〔Effect of the invention〕

As described above, the labyrinth seal device of the present invention is configured such that one end of the teeth of the labyrinth is fixed to a fixed piece with a high coefficient of linear expansion, and the other end is attached to a partition plate so that it can move freely. The position of the labyrinth can be moved by the amount of thermal expansion of the fixed piece depending on the temperature conditions, and a gap suitable for the operating condition can be maintained, which has the advantage of improving the sealing effect and increasing safety.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of an embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view of the structure of the embodiment of the present invention, and FIG. 3 is a cross-sectional view showing the structure of the embodiment of the present invention. Fig. 4 is a cross-sectional view showing the operation of the embodiment of the present invention, Fig. 5 is a longitudinal sectional view of a steam turbine explaining a conventional labyrinth seal device, and Fig. 6 is an enlarged view showing details of the conventional labyrinth seal device. FIG. DESCRIPTION OF SYMBOLS 1... Vehicle interior, 2... Partition plate, 3... Nozzle, 4... Rotating vane, 5... Rotating shaft,
6... Labyrinth teeth, 7... Gap,
8...Fixing piece, 9...Bolt, Agent Patent attorney Nori Chika Ken Sodo Ken Daishimaru Figure 2 Figure Figure Figure Figure

Claims (1)

[Claims] In a labyrinth seal device for a steam turbine, the labyrinth seal device has a plurality of teeth arranged in a stationary part facing the rotating part in order to suppress the flow rate of steam leaking from the gap between the rotating part and the stationary part,
The teeth are composed of a plurality of partially arc-shaped pieces arranged to surround the rotating part, and at least some of these pieces have one end fixed to the stationary part and are made of a material with a large coefficient of thermal expansion. A labyrinth seal device for a steam turbine, characterized in that the labyrinth seal device is attached to a fixed piece.