JPH0216303A - Coupling device for turbine bucket - Google Patents

Abstract

PURPOSE:To improve oscillation attenuating effect against resonance at the time of rotational ascending or descending forming snappers projecting toward front/rear sides on blade ends of turbine buckets, and forming faces on sides of each snappers being in contact under different conditions according to rotational conditions of the blades. CONSTITUTION:On blade ends 1a, 2a of adjacent turbine buckets, front edge snappers 1b, 2b and 1c, 2c are integrated respectively on front edges and rear edges of each blade 1a, 2a. Stepped contact faces 1f, 1g are formed so as to extend over two steps and have a stepped part (d) on one side of the rear edge snapper 1c of the blade 1a, that is, on the opposed side of the front edge snapper 2b of the blade 2a. A substantially plane contact face 2h is formed on one side of the front edge snapper 2b of the blade 2a opposed to the contact faces 1f, 1g. At the time of normal rotation, the faces 1f, 2h are contact to each other, while at the time of rotational ascending or descending, the faces 1g, 2h are contact to each other.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a coupling device for turbine rotor blades, and particularly to a coupling device for turbine rotor blades that can effectively suppress vibrations of the turbine rotor blades during operation. Relating to a coupling device.

(Conventional technology) Generally, with the increase in base load operation of nuclear power generation, thermal power turbines are frequently started and stopped.
There is a lot of SS driving. Therefore, thermal power turbines are now required to have sufficient reliability not only under the rated rotational speed or low-load operation, but also under operating conditions during startup and shutdown.

By the way, untwisting (hereinafter referred to as untwisting) due to rotational centrifugal force acts on the turbine rotor blades during operation. Conventionally, there has been known a coupling device that utilizes this untwisting effect to couple turbine rotor blades to each other while suppressing vibrations of the turbine rotor blades. FIG. 6 shows a conventional coupling device of this type. 1a and 2a each indicate a blade tip of an adjacent turbine rotor blade, 1b and 2b each indicate a leading edge snubber formed integrally with the blade on the leading edge side of the blade, and 1c and 2c each indicate a leading edge snubber on the trailing edge side of the blade. A trailing edge snubber is shown integrally formed with the wing.

When the centrifugal force acting on the blade increases as the rotational speed of the turbine rotor increases, untwisting acts on the blade, causing the snubbers 1c, 2b, i1, f2f to contact each other. D is a gap set during assembly of the turbine rotor blade. This clearance is set in consideration of the rotational speed at which the snubber contacts start when the rotation increases, the reaction force between the snubbers at the rated rotation, and the like.

If this gap is too large, the contact surfaces if and 2f will not come into contact even if untwist is applied during operation, and on the other hand, if it is too small, excessive stress will be applied to the joint between the blade and the snubber when untwist is applied. arise.

FIG. 7 shows a state in which the snubbers lc and 2b are in contact with each other during operation. The relative positional relationship between Snappako c and 2b at the time of contact is determined by the initial clearance, therefore, after contact at a certain rotation speed, the positional relationship does not change as the rotation speed increases, and only the reaction force increases. I'll go.

Therefore, it is necessary to set the rotation speed at which the snubber starts contacting with sufficient consideration of the stress that occurs at the rated rotation, especially the stress at the boundary between the snubber and the blade. In other words, setting the contact start rotation speed is setting the initial clearance between the snubbers. If this initial clearance is increased, the rotational speed at which contact starts will increase and the stress on the blade at the time of rating will be reduced, but the contact area will decrease due to changes in the relative positions of adjacent snubbers, and there is a risk that the surface pressure will become excessive. The clearance between the snubbers is mainly determined by two limiting values: the contact surface pressure and the blade stress.

(Problem to be solved by the invention) By the way, if the turbine starts and stops frequently, it is necessary to not only consider the static strength and vibration characteristics at rated rotation and overspeed, but also to , vibration characteristics during descent, etc. will also need to be carefully considered. A particular problem with the vibration characteristics when the rotational speed increases or decreases is when the frequency of the lower-order mode of the blade resonates in agreement with the lower-order component of the rotational multiple. This varies depending on the cabin shape, etc., but the excitation force acting on the blade tends to become larger as the rotational order becomes smaller, and the response amount of the blade vibration is much larger in lower-order modes than in higher-order modes. There is a tendency.

FIG. 8 is an example of a Campbell diagram, which shows the relationship between the turbine rotor rotation speed, changes in natural frequency, and rotation multiple excitation components. T indicates the natural frequency of the lower-order moto of the blade, which indicates that it resonates with an excitation component twice the rotational speed at the rotational speed Rr. The resonance rotation speed Rr is determined by the natural frequency of the blade. Rc is the rotational speed at which the snubber starts contacting.

At this rotational speed Rc, the vibration characteristics of the blade shift from a small blade mode (vibration mode of a single blade) to a full-circle group mode. The rotation speed Rc is determined by the assembly clearance between the snubbers. In addition, in the vibration of the whole circumference group mode,
The lowest-order vibration, that is, the first-order vibration in the tangential direction, becomes noise level vibration. In the example in the same figure, the lowest order tangential direction vibration of the small blade mode vibration where the snubber does not contact is 2 of the rotation speed.
This shows that the double excitation component resonates with Fr.

FIG. 9 shows the relationship between the assembly clearance between the snubbers and the contact starting rotation speed. If the assembly clearance is dl, the snubber comes into contact at the rotational speed R1, and when the rotational speed increases further and reaches the rated rotational speed, deformation is restrained and a reaction force F1 is generated. Further, if the assembly clearance is dl, the snubber comes into contact at the rotational speed R2, and when the rotational speed increases further and reaches the rated rotational speed, the deformation is restrained and a reaction force F2 is generated. In this way, if the assembly clearance is increased and the contact start rotation speed of the snubber is set high, the reaction force between the snubbers at rated rotation or overspeed will be reduced, but when the resonance rotation speed Rr is passed, the snubber passes in a single blade state. I will do it. The single blade state refers to a free standing state where adjacent tools are not in contact with each other.

In a single blade state, since there is no contact with the snubber, no vibration damping effect can be expected, and structural damping as a blade can only be expected from the blade embedded part. However, since the blade implantation part has a complicated shape, stress due to centrifugal force tends to concentrate thereon, and if vibration is added to this, the blade implantation part itself becomes dangerous. Further, the structural damping effect of the blade implant is relatively small, and if a large vibration stress is applied every time the blade is started or stopped, the structural reliability of the blade implant will be significantly reduced.

In addition, if the assembly clearance between the snubbers is small, the snubbers will come into contact before the low-order mode vibration of the blade resonates with the low-order component of the rotation multiple, so the blade will rotate while the blade is rotating up or down. Even if it resonates with a multiple component, a large damping effect can be expected, and vibration stress can be sufficiently suppressed. However, at rated rotation or overspeed, the reaction force between the snubbers increases, causing excessive stress to act on the blade. If this stress is not allowable in the design, the assembly clearance between the snubbers must be increased. Furthermore, even if the stress can be tolerated, the stress caused by restraining the snubber from rotating at low speed remains in addition to the centrifugal stress, reducing reliability against blade vibration.

Therefore, an object of the present invention is to solve the problems of the conventional technology described above, to prevent excessive stress from occurring at rated rotation or overspeed, and to provide a vibration damping effect against resonance when rotation increases or decreases. It is an object of the present invention to provide a coupling device for turbine rotor blades that can be used.

(Means for Solving the Problems) In order to achieve the above object, the present invention forms a leading edge snubber projecting toward the leading edge side and a trailing edge snubber projecting toward the trailing edge side at the blade tip of a turbine rotor blade, A flat contact surface is formed on one side of one of the snubbers of the leading edge snubber and the trailing edge snubber, and a flat contact surface is formed on one side of the other snubber of the adjacent turbine rotor blade when the rotation increases or decreases. The present invention is characterized by forming a contact surface that can be contacted during rated rotation and a contact surface that can be contacted during rated rotation.

(Function) According to the present invention, when the rotation of the turbine increases or decreases, the contact surfaces of the leading edge snubber and the trailing edge snubber that are in contact with each other at that time contact each other, and when the turbine rotates at the rated speed,
Since the contact surfaces of the leading edge snubber and the trailing edge snubber that can come into contact at that time come into contact with each other, the contact surfaces come into contact with each other in two stages, which not only reduces the reaction force due to untwist restraint, but also It is also possible to suppress vibration stress during resonance during increasing rotation.

(Embodiment) An embodiment of the turbine rotor blade coupling device according to the present invention will be described below with reference to FIGS. 1 to 5, in which the same parts as in FIG. 6 are denoted by the same reference numerals.

In FIG. 1, 1a and 2a indicate the blade tips of adjacent turbine rotor blades, a leading edge snubber 1b is integrally formed on the leading edge of the blade 1a, and a trailing edge snubber 1b is integrally formed on the trailing edge of the blade 1a. The IC is integrally formed. A leading edge snubber 2b is integrally formed on the leading edge of Q2a, and a trailing edge snubber 2c is integrally formed on the trailing edge of g2a. One side of the trailing edge snubber IC of the wing 1a, that is, the wing 2a
A step-shaped contact surface if, Ig having two steps and a step d is formed on one side surface facing the leading edge snubber 2b, and the leading edge snubber 2b of the g2a facing the contact surface 1f, Ig is formed. A substantially flat contact surface 2h is formed on one side of the contact surface 2h. That is, in each blade, a flat contact surface is formed on one side of the leading edge snubbers 1b and 2b, and a stepped contact surface extending over two steps and having a step d is formed on one side of the trailing edge snubbers IC and 2C. A contact surface is formed. The contact surface 1g of the trailing edge snubber 1c is a contact surface during low speed rotation, and the contact surface 1f is a regular contact surface during rated rotation or overspeed.

The clearance between the snubbers during assembly is set as follows. First, the clearance between the contact surface 1f and the contact surface 2h is set so that the contact surfaces If and 2h are in contact during rated rotation and the reaction force at that time does not become excessive. In addition, the clearance between the contact surfaces 1g and 2h is such that the contact surfaces 1g and 2h come into contact at low rotational speeds before the lowest mode solid-H vibration of the blade resonates with the rotational multiple component when the rotation increases. It is set as small as .

Next, the operation of this embodiment will be explained.

FIGS. 2 and 3 each show a state in which untwist is applied to the turbine rotor blade. Figure 2 shows the state at low speed rotation while the rotation is increasing, and Figure 5 shows the state at rated rotation.

First, as the rotation of the turbine is increased, the contact surfaces 1g and 2h come into contact, as shown in FIG. In this state, even if the lowest order vibration of the blade resonates with the lower order component of the rotation multiple while the rotation is rising, the vibration is attenuated by the friction acting on both contact surfaces 1g and 2h. At this time, a slight clearance may be left in advance between the contact surfaces 1g and 2h, so that only the snubbers collide with each other when the blades resonate, thereby damping vibrations.

Next, the low-order mode vibrations of the blades pass through a resonance state with the rotation multiple component, and from there the rotation speed increases and the turbine rotation reaches the rated rotation, the untwisting effect increases and the As shown in Figure 3, the contact surfaces if and 2h are in contact. In this state, in response to excitations such as steam force,
A vibration damping effect due to friction can be expected. Moreover, since the end surface 2j of the snubber 2b collides with the contact surface stepped portion 11 of the snubber 1c during the sliding movement of the contact portion (from FIG. 2 to FIG. 3), the vibration damping effect due to this collision is also suppressed. At the same time, we can look forward to it.

Moreover, the stress generated in the blade due to the untwist constraint can be adjusted by setting the clearance between the contact surface 1f and the contact surface 2h to a predetermined amount during assembly. Also, regarding the contact start rotation speed between the contact surface 1g and the contact surface 2h,
By setting the initial clearance at the time of assembly to a predetermined amount, it can be freely adjusted.

According to this embodiment, although the snubbers once contact each other during low-speed rotation, they are not untwisted and the contact changes over two stages, so that the rated During rotation, the reaction force between the snubbers can be adjusted to prevent high stress from occurring on the blades. Also,
Not only can the reaction force due to untwist restraint be reduced, but also the contact state of the snubber is created even during resonance during rising rotation, so vibration stress can be reduced.

FIG. 4 shows another embodiment.

A contact surface 11 is formed on one side of the trailing edge snubber 1c of the blade 1a, and a protrusion 1m is formed approximately in the center of the contact surface 1.Furthermore, the blade 2a facing the contact surface 1k
A flat contact 1Iili is provided on one side of the leading edge snubber 2b of the
2n is formed. According to this, the protrusion 1m on the contact surface 1 contacts or collides with the contact surface 2n during low speed rotation, and the contact surface 1 contacts or collides with the contact surface 2n during rated rotation. Therefore, this embodiment not only reduces the reaction force due to untwist restraint, but also creates a contact state of the snubber even during resonance during rising rotation, so that vibration stress can be reduced.

FIG. 5 shows another embodiment.

A flat contact surface 1 is provided on one side of the trailing edge snubber 1c of the gla.
A two-step stepped contact surface 2q is formed on one side of the leading edge snubber 2b of g2a, which faces the contact surface 1p.
, 2r are formed.

According to this, during low speed rotation, the contact surface 1p and the contact surface 2r
contact or collide with each other, and at rated rotation, contact surface 1p and contact surface 2q contact or collide.

Therefore, this embodiment not only reduces the reaction force due to untwist restraint, but also creates a contact state of the snubber even during resonance during rising rotation, so that vibration stress can be reduced.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when the rotation of the turbine increases or decreases, the contact surfaces of the leading edge snubber and the trailing edge snubber that are in contact with each other at that time contact each other, and when the turbine rotates at the rated speed, Since the contact surfaces of the leading edge snubber and the trailing edge snubber that can come into contact at that time are configured to contact each other, the contact surfaces will come into contact with each other at two stages during turbine operation, so that untwisting Not only can the reaction force due to restraint be reduced, but also the vibration stress at resonance during rising rotation can be suppressed. Moreover, this not only increases the reliability at rated rotation but also makes it possible to sufficiently withstand severe operating conditions such as DSS operation.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a plan view showing an embodiment of the turbine rotor blade coupling device according to the present invention, Figs. 2.3 and 4.5 are respectively FIG. 6 is a plan view showing another embodiment of the turbine rotor blade coupling device according to the present invention; FIG. 6 is a plan view showing a conventional turbine rotor blade coupling device; FIG. 7 is an explanatory diagram similarly explaining the operation; The figure is a diagram showing an example of the Campbell diagram of the entire circumference of the snubber and the front wing, and FIG. 9 is a diagram showing the relationship between the assembly clearance, the rotational speed at the start of contact, and the reaction force between the snubber and the snubber. la, 2a...blade tip, lb, 2b...leading edge snubber, lc, 2c... trailing edge snubber, If, Ig. lk, 1m...contact surface, 2h, 2n...contact surface, 1
1...Step, 2j...Snatsuba end face. Applicant's agent Sato - Yukozut Oθ Sono

Claims (1)

[Claims] A leading edge snubber protruding toward the leading edge side and a trailing edge snubber protruding toward the trailing edge side are formed at the blade tip of the turbine rotor blade, and one side of the snubber of either the leading edge snubber or the trailing edge snubber is provided with a A flat contact surface is formed, and one side of the other snubber of the adjacent turbine rotor blade is formed with a contact surface that can come into contact when the rotation increases or decreases, and a contact surface that can come into contact during the rated rotation. Turbine rotor blade coupling device.