JPH11294102A - Steam turbine bucket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bucket having an integral shroud to restrict fluctuation of a blade lattice pitch even when torsion return force is applied to a blade part. SOLUTION: A tapered protrusion 8 of which protruded tip is enlarged in a roughly perpendicular direction to a length direction axial line of a blade cross section is provided on a blade back side shroud part 1 of a bucket, and a groove 10 is provided at a back edge part of the bucket to correspond to the protrusion 8. An adjacent bucket is integrated with it by engagement of the protrusion 8 with the groove 10, and both side surfaces of the protrusion 8 are formed as taper surfaces in such directions that their interval is enlarged in the direction from the base part toward the tip. The groove 10 is also formed in such a way that its interval is larger on the blade back side than on the front side to correspond to the taper of the protrusion 8, and in the condition where the protrusion 8 is engaged with the groove 10, an adjacent shroud is restrained from moving even when back edge parts of the bucket start to be displaced in mutually opening directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine, and more particularly, to a method for restraining torsional return caused by centrifugal force on long blades of a low pressure stage (final stage and blades located one or two stages before the last stage). The present invention relates to a steam turbine blade having a shroud integrated with the blade.

[0002]

2. Description of the Related Art Generally, a turbine blade is continuously excited in a wide frequency range by a flow of a working fluid and a turbulent component thereof. The vibration response of the wing structure to these excitation forces is related to the natural frequency and the magnitude of damping in each vibration mode. Therefore, while avoiding the resonance of the lower-order vibration mode with a large resonance response, in the higher-order vibration mode with a small resonance response, adjacent wings are connected with a shroud or the like to design a wing structure that is reliable even if it resonates. Many means have been adopted. This is because, if adjacent blades are connected, an additional effect of increasing the rigidity of the blade structure and vibration damping can be expected.

FIG. 5 shows an example of a turbine rotor blade formed by integrally molding a shroud and a blade. 5, reference numeral 1 denotes a blade back side shroud portion, 2 denotes a blade ventral shroud portion, 3 denotes a blade portion, and 4 denotes a disk outer peripheral portion of the turbine rotor. The turbine rotor blade is implanted in a groove provided in the outer peripheral portion 4 of the disk of the turbine rotor, and comes into circumferential contact with adjacent blades by shrouds 1 and 2 provided at the tip of the rotor blade.

It is well known that the centrifugal force acting on the blade at the turbine speed causes the blade to twist back (untwist) in the direction indicated by reference numeral 9 in the drawing. The contact surface 5 restrains the torsional return and enhances the wing connection action between the wings. A wing having such a structure is hereinafter referred to as an integral shroud wing.

For example, Japanese Patent Application Laid-Open No. 3-26801 discloses that a blade cover provided at the tip of a blade forms an S-shape when viewed from the outer peripheral direction, and blade covers of blades adjacent to each other have an S-shaped center. It is described that the contact is made. This structure is a typical integral shroud wing.

[0006]

The above-mentioned conventional method has the following problems.

FIG. 6 shows a detailed view of a conventional shroud portion. In the figure, 5 is a contact surface, 6 is a gap formed by the contact between the blade back side shroud portion and the blade abdomen side shroud portion, and 7 is a distance between adjacent blades (hereinafter referred to as a blade row pitch). FIG.
In the meantime, during the rotation of the turbine, the gap 6 is not constant at each blade connection portion due to the manufacturing tolerance and the assembly tolerance of the blade.

[0008] For this reason, the cascade pitch 7 of the adjacent blades in each blade connection portion is not constant. Since the cascade pitch 7 has the greatest influence on the performance of the turbine rotor blade, even if an optimum cascade pitch is found at the time of blade design, a result in which the target blade performance is not actually obtained is brought.

SUMMARY OF THE INVENTION An object of the present invention is to provide a steam turbine blade having an integral shroud which is excellent in performance and can maintain the cascade pitch constant even if the blade is twisted back, eliminating the above-mentioned disadvantages of the prior art. To provide.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a turbine blade having a tapered protrusion projecting substantially perpendicularly to a longitudinal surface of a blade section on a blade rear shroud portion. A trailing edge portion of the tip of the wing is provided with a groove extending in a direction substantially perpendicular to the longitudinal surface of the wing cross section, and having a shape matching the protruding tapered projection provided on the wing back side shroud portion, This is achieved by integrating adjacent shrouds.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described in detail with reference to FIG.

FIG. 1 is a perspective view of the tip of a blade of a steam turbine blade incorporating the present invention, and FIG. 2 is a structural view of the steam turbine blade incorporating the present invention as viewed from the outer peripheral side. FIG. 3 is a diagram showing how to assemble a steam turbine blade incorporating the present invention, and FIG. 4 is an assembly diagram in which the last one of the steam turbine blades incorporating the present invention is buried.

In FIG. 1, a tapered projection 8 is provided integrally with the shroud portion 1 on the back side shroud portion 1 of the moving blade 3, and the shroud portion near the rear edge of the tip of the moving blade 3 has a tapered shape. Are formed so as to be substantially perpendicular to the longitudinal center line of the blade section. Then, the adjacent shrouds are integrated via the projections 8 and the grooves 10. Next, FIG. 2 which is a plan view of the steam turbine blade of FIG. 1 as viewed from the outer peripheral side thereof will be described.

Adjacent rotor blades are integrated by the protrusion 8 being fitted into the groove 10, and both side surfaces 11 and 12 of the protrusion 8 are tapered surfaces in a direction in which the distance increases from the base to the tip. It has become. The shape of the groove 10 is also wider on the dorsal side than on the abdominal side of the blade in accordance with the taper of the protrusion 8, and when the protrusion is fitted in the groove, the adjacent shroud is the trailing edge of the blade. Even if the parts are to be displaced in a direction to open each other, the movement is restricted.

The thickness t of the projection 8 in the thickness direction is set to about half the thickness T of the shroud 1.

The rotor blade 3 is subjected to a torsional return as shown by an arrow 9 in FIG. 2, but the displacement in this direction is mainly caused by the force in the direction of increasing the contact force of the contact portion 5 between the shrouds 1 and 2. Therefore, the movement is restricted by the contact portion 5.

Even if a torsional force in the direction opposite to the arrow 9 acts on the moving blade 3 during the operation of the turbine, the force is restricted by the engagement between the projection 8 and the groove 10.

Therefore, no matter what direction the torsional return force acting on the rotor blade 3 is applied, the contact surface 5, the protrusion 8 and the groove 10 restrict the rotor blade 3 so that the blade pitch 7 during operation can be kept constant. it can.

FIGS. 3 and 4 show a rotor blade 3 embodying the present invention.
1 shows a work procedure for assembling into the outer peripheral portion 4 of the disk of the turbine rotor. As shown in FIG. 3, the fork portion 31 formed at the base of the rotor blade is inserted into an annular groove 41 provided on the disk outer peripheral portion 4 from the radial direction of the turbine rotor. At this time, the projection 8 of the shroud 1 is fitted into the groove 10 of the shroud of the rotor blade already mounted on the outer peripheral portion of the disk. The wing incorporated in the disk outer peripheral portion 4 is fixed by driving a fixing pin 20.

The rotor blades are sequentially incorporated into the outer peripheral portion 4 of the disk,
The shroud part of the rotor blade to be assembled last has projections 8 and 8a formed on both sides as shown in FIG. 4, and the projections 10 and 10a of the blade already assembled are formed.
By fitting into a shroud of one ring all around.

[0021]

As described above, according to the present invention, a steam turbine blade having an integral shroud excellent in performance and capable of maintaining a cascade pitch constant even if the blade is twisted back can be constituted. .

[Brief description of the drawings]

FIG. 1 is a perspective view of a moving blade embodying the present invention.

FIG. 2 is a plan view of the rotor blade of FIG. 1 viewed from an outer peripheral direction.

FIG. 3 is a perspective view showing a situation where a moving blade is incorporated into a turbine rotor.

FIG. 4 is a perspective view showing a situation in which the last one blade is incorporated into a turbine rotor.

FIG. 5 is a perspective view of a conventional moving blade.

FIG. 6 is a plan view of the moving blade of FIG. 5 viewed from the outer peripheral direction.

[Explanation of symbols]

1: Shroud part on wing back side, 2: Shroud part on wing ventral side, 3
... rotor blade, 4 ... disk outer peripheral part, 5 ... contact part, 6 ... gap,
7: Cascade pitch, 8: Projection, 9: Torsion return direction, 10
... Groove, 11, 12 ... Tapered surface, 20 ... Fixing pin, 31 ...
Blade root fork, 41 ... Disk outer peripheral groove of turbine rotor.

Continued on the front page (72) Inventor Kiyoshi Namura 7-2-1, Omika-cho, Hitachi City, Ibaraki Pref.

Claims (1)

[Claims] 1. A steam turbine, which is a twisted blade formed integrally with a blade and having adjacent shrouds connected to each other by restraining torsional return due to centrifugal force by a pair of shrouds on the back side and the abdomen side of the blade tip. In the rotor blade, a tapered projection is provided on the blade back side shroud portion of one turbine rotor blade so as to project substantially perpendicularly to the longitudinal surface of the blade section, while the blade is provided on the trailing edge of the tip of the rotor blade. A groove extending in a direction substantially perpendicular to the longitudinal surface of the cross section and having a shape matching the tapered protrusion protruding from the back side shroud portion is provided to integrate adjacent blade shroud portions. A steam turbine blade characterized by the above-mentioned.