JPH08284607A - Steam turbine stationary blade - Google Patents

Abstract

PURPOSE: To obstruct occurrence of an unconformable event such as breakdown of stationary blades by constituting a shroud out of a first shroud secured on the inner circumferential end of maximum stationary blades and a secondary shroud elastically combined with the first shroud. CONSTITUTION: In maximum stationary blades 2 used in the low pressure stage of a steam turbine, a shroud fixing the stationary blades 2 is divided into two parts, a first shroud 3 and a second shroud 4, and the stationary blades 2 are in the condition of being fixed with rubber bolts 5 by fixing the shrouds through the rubber bolts 5. Hereby, the large damping effect of rubber itself of the rubber bolts 5 is applied to the stationary blades 2, and hence even if the stationary blades 2 are excited by steam flow at the low pressure stage and intended to vibrate, the vibration is restrained by the damping effect of the rubber itself, and the vibration is prevented from being enlarged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine stationary blade in which vibration suppression of a long stationary blade installed in a low pressure stage of a steam turbine is improved.

[0002]

2. Description of the Related Art A steam turbine is generally composed of a high-pressure stage or a high-pressure stage and an intermediate-pressure stage and a low-pressure stage. The so-called volume flow rate increases rapidly. Therefore, the vanes installed in the low-pressure stage tend to be long and the rigidity of the vanes tends to decrease.

An example of such a steam turbine vane having long vanes conventionally used in the low pressure stage of the steam turbine is shown in FIGS. 3 and 4. In the figure, 1 is an outer peripheral edge fitted into a groove provided on an inner peripheral surface of a casing of a steam turbine,
A blade root ring for holding the stationary blade 2 at a predetermined position in the steam passage, 3
Reference symbol a denotes a shroud provided on the inner periphery of a sealing device held on the outer peripheral surface of a rotating rotor, and the inner peripheral surface of the blade root ring 1, the outer diameter end of the stationary blade 2, and the inner diameter end of the stationary blade 2 respectively. The outer peripheral surface of the shroud 3a is fixed by overlay welding 7.

Thus, the conventional steam turbine vane is
Since the inner peripheral side of the stationary blade 2 is composed of the shroud 3a and the outer peripheral side is composed of the blade root ring 1 and rigid-body couplings fixed by the overlay welding 7, respectively, the damping effect on vibration is very small. That is, in the steam turbine stationary blade having such a structure, the stationary blade 2 becomes a large stationary blade and its rigidity becomes low, so that the vibration of the stationary blade 2 is increased by the passing steam force, and the damping effect is small. Therefore, it is considered that a nonconformity event occurs in which the stationary blade 2 is damaged.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the conventional steam turbine stationary blade, the present invention enhances the damping effect on the vibration generated in the stationary blade by the steam force,
An object of the present invention is to provide a steam turbine stationary blade that does not cause a nonconformity event that the stationary blade is damaged.

[0006]

Therefore, the steam turbine vane of the present invention has the following means. A shroud fixed to the inner peripheral side of the stationary vane, a first shroud fixed to the inner peripheral end of the long stationary vane by welding or the like, and a second shroud coupled to the first shroud via an elastic body. It was decided to divide it into shrouds. There is a rubber bolt as one means for connecting the first shroud and the second shroud with an elastic body interposed. That is, a male screw provided on the other end side of the bolt, one end of which is fixed to one side of an elastic body such as rubber, is screwed into a female screw provided on the first shroud fixed to the stationary blade by welding, A male screw having one end fixed to the other side and provided on the other end side of another bolt can be fixed by a nut and a second shroud that is not fixed to the stationary blade by welding and can be connected. . Further, as another coupling means, a rubber shaft coupling conventionally used for connecting a driving shaft and a driven shaft,
Alternatively, a joint having a so-called elastic body interposed, such as a metal spring shaft joint, can be adopted.

[0007]

The outer peripheral edge of the first shroud, to which the second shroud is connected via the elastic body, is fixed to the inner peripheral edge of the vane by welding or the like, while the second shroud is made of the elastic body. Due to the interposition of, the rigid vanes are not completely rigidly coupled, and the elastic body acts as a damper. That is,
With this structure, the stationary blade is fixed on the elastic body, and a high damping effect of the elastic body itself can be obtained as compared with the conventional connection by only welding. Therefore, a large damping effect is obtained and vibration of the stationary blades is suppressed, as compared with the conventional case of a rigidly coupled steam turbine stationary blade having a small damping effect. As a result, even if the stationary blade vibrates in the presence of steam with a large volume flow rate, the damping effect of the elastic body will not damage even the large stationary blade with small rigidity, and reliability will be improved. It can be a steam turbine stationary blade that can be secured.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the steam turbine vane of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a cross-sectional view of a steam turbine low-pressure stage vane as an example of the steam turbine vane of the present invention. In the embodiment showing the present invention, the same members as those of the conventional steam turbine vane shown in FIGS. 3 and 4 are designated by the same reference numerals and their description is omitted.

In the figure, the inner peripheral side of the blade root ring 1 is fixed to the outer peripheral side of the stationary blade 2 by overlay welding 7.
On the other hand, the outer peripheral side of the first shroud 3 is fixed to the inner peripheral side of the stationary blade 2 by welding 7. The second shroud 4 has a groove 8 formed in the outer peripheral surface in the circumferential direction, and has a structure capable of supporting the first shroud 3 loosely fitted therein in a freely movable manner in the radial direction. The rubber bolt 5 has a central portion formed of an elastic material such as a rubber material, and two metal bolts are joined to face the rubber material.
Then, the bolt connected to one side of the rubber bolt 5 is screwed into a female screw formed in the inner circumference of the first shroud 3, and the bolt connected to the other side is the second screw.
The shroud 4 penetrates the bottom of the groove 8 and is fastened with the nut 6 to be connected to the second shroud 4.

As described above, in the long and large stationary blade used in the low pressure stage of the steam turbine, the shroud for fixing the stationary blade 2 is divided into two, that is, the first shroud 3 and the second shroud 4, which are divided into two parts. By fixing via the rubber bolts 5, the stationary blade 2 is in a state of being fixed by the rubber bolts. As a result, the large damping effect of the rubber itself of the rubber bolt 5 acts on the stationary blade 2, and even if the stationary blade 2 is excited by the flow of steam in the low pressure stage and tries to vibrate, the large damping effect of the rubber itself causes The vibration is suppressed, the vibration is prevented from becoming large, the vane 2 is not damaged by the vibration, and the reliability is improved.

Although one embodiment of the steam turbine stationary blade of the present invention has been described above, the present invention is not limited to such an embodiment, and is within the technical scope described in the claims. It includes things. That is, in the above-described embodiment, the elastic body interposed between the first shroud 3 and the second shroud 4 is the rubber bolt 5, but other elastic bodies such as a rubber shaft joint or a metal spring joint are used. It is also possible to connect the first shroud 3 and the second shroud 4 with a similar elastic joint.

[0012]

As described above, according to the steam turbine vane of the present invention, the structure shown in the claims provides
Even in a large-sized stationary vane with low rigidity used in a low-pressure stage of a steam turbine, vibration due to steam force can be reduced, and a nonconforming event of vane damage can be eliminated. Further, it is possible to prevent the occurrence of excessive stress even when another advantage due to the elastic body being interposed, for example, when the axis of the steam turbine stationary blade is deviated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a steam turbine low-pressure stage stator blade as an embodiment of a steam turbine stator blade of the present invention,

FIG. 2 is a perspective view showing details of the shroud shown in FIG.

FIG. 3 is a side view showing a conventional low pressure stage stationary blade,

FIG. 4 is a perspective view of the shroud portion shown in FIG. 3.

[Explanation of symbols]

 1 blade root ring 2 stationary blade 3 first shroud 4 second shroud 5 rubber bolt 6 nut 7 build-up welding 8 concave groove

Claims (1)

[Claims] 1. A steam turbine stationary vane having an outer peripheral end fixed to a blade root ring, an inner peripheral end fixed to a shroud, and a long stationary vane installed in a low pressure stage of a steam turbine. A steam turbine stationary blade comprising a first shroud fixed to an inner peripheral end of the stationary blade and a second shroud coupled to the first shroud via an elastic body.