JP2567044B2 - Turbine rotor blade coupling device - Google Patents

Description

The present invention relates to a turbine rotor blade coupling device, and more particularly to a turbine rotor blade that can effectively suppress vibration of the turbine rotor blade during operation. Regarding the coupling device.

(Prior Art) Generally, with the increase in the base load operation of nuclear power generation, the so-called frequent start-stop of the thermal power turbine is called.
Many DSS operations are performed. Therefore, in the thermal power turbine, in addition to the reliability for the rated speed or the low load operation, sufficient reliability is required for the operating condition at the time of starting and stopping.

By the way, the turbine rotor blades in operation are twisted back (hereinafter referred to as untwist) by the centrifugal force of rotation. Conventionally, there is known a coupling device that couples turbine blades to each other while suppressing the vibration of the turbine blades by utilizing the action of the untwist. FIG. 6 shows a conventional coupling device of this kind. 1a and 2a indicate the tips of adjacent turbine blades, and 1b and
Reference numeral 2b denotes a leading edge snubber integrally formed with the blade on the leading edge side of the blade, and 1c and 2c denote trailing edge snubbers integrally formed with the blade on the trailing edge side of the blade.

When the centrifugal force that acts on the blades increases as the rotation speed of the turbine rotor increases, untwist acts on the blades, and the contact surfaces 1f and 2f of the snubbers 1c and 2b contact each other. D is a clearance set when the turbine rotor blade is assembled. This gap D
Is set in consideration of the snubber contact start member rotation when the rotation is increased and the snubber reaction force at the rated rotation. If this gap D is too large, the contact surfaces 1f, 2f will not contact even if the untwist acts during operation, and if it is too small, excessive stress will be applied to the joint between the blade and the snubber when the untwist acts. Occurs.

FIG. 7 shows a state where the snubbers 1c and 2b are in contact with each other during operation. The relative positional relationship between the snubbers 1c and 2b during contact is determined by the initial clearance.Therefore, after contact at a certain rotational speed, the positional relationship does not change as the rotational speed increases, and only the reaction force increases. Go. Therefore, the contact start rotation speed of the snubber must be set in consideration of the stress generated at the rated rotation, especially the stress at the boundary between the snubber and the blade. Setting the contact start rotation speed is, in other words, setting the initial clearance between the snubbers. If this initial clearance is increased, the contact start rotation speed is increased and the stress of the blade at the time of rating is reduced, while the contact area is reduced due to the relative position change of the adjacent snubbers, and the surface pressure may be excessive. The clearance between the snubbers depends on the contact surface pressure and the blade stress.
It will be mainly determined from the three limits.

(Problems to be solved by the invention) By the way, when the turbine is frequently started and stopped, not only the static strength and vibration characteristics at the time of rated rotation and at overspeed are examined, but also when the rotation speed is increased. It is also necessary to thoroughly study the vibration characteristics when descending. A particular problem with the vibration characteristics when the rotational speed increases and decreases is when the low-order mode frequency of the blade resonates in agreement with the low-order component of the rotational multiple. This depends on the shape of the passenger compartment, etc., but the excitation force acting on the blade tends to increase as the rotational order decreases, and the vibration response of the blade increases significantly in the lower mode than in the higher mode. There is a tendency.

FIG. 8 is an example of a Campbell diagram and shows the relationship between the turbine rotor rotation speed and the natural frequency change, and the rotation multiple excitation component. T indicates the natural frequency of the lower-order mode of the blade, and indicates that it resonates with the excitation component twice the rotation speed at the rotation speed Rr. The resonance speed Rr is determined by the natural frequency of the blade. Rc is the rotation speed at which the snubber starts contact. With this rotational speed Rc as a boundary, the blade vibration characteristics shift from the single-blade mode (vibration mode with a single blade) to the all-round one-group mode. The rotation speed Rc is determined by the assembly clearance between the snubbers. Further, in the all-round first-group mode vibration, the lowest-order vibration, that is, the tangential primary vibration is a noise level vibration. The example in the figure shows that the lowest-order tangential primary vibration of the single-blade mode vibration that the snubber does not contact resonates with the double excitation component of the rotation speed and Fr.

FIG. 9 shows the relationship between the assembly clearance between the snubbers and the contact start rotational speed. If the assembly clearance is d1, the snubber comes into contact at the rotation speed R1, and at the time when the rotation speed further rises to the rated rotation speed, the reaction force F1 is generated because the deformation is restricted. Further, if the assembly clearance is d2, the snubber comes into contact at the rotation speed R2, and when the rotation speed further rises to the rated rotation speed, the deformation is restrained, so that the reaction force F2 is generated. If the assembly clearance is increased and the snubber contact start speed is set higher in this way, the reaction force between snubbers at rated speed or at overspeed is reduced, but when the resonance speed Rr is passed, it passes in the single blade state. Will be done. The single blade state is a free standing state in which adjacent blades are not in contact with each other. In the single blade state, there is no snubber contact, so vibration damping effect cannot be expected, and structural damping as a blade can only be expected in the blade implant portion. However, since the blade-implanted portion has a complicated shape, stress due to centrifugal force tends to concentrate, and when vibration is applied to the blade-implanted portion, the blade-implanted portion itself becomes in a dangerous state. Also,
The structural damping effect of the blade-implanted portion is comparatively small, and if a large vibration stress is applied at every start / stop, the structural reliability of the blade-implanted portion is significantly reduced.

If the assembly clearance between the snubbers is small, the snubbers come into contact with each other before the low-order mode vibration of the blade resonates with the low-order component of the rotation multiple, so that the blade rotates while 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, since the reaction force between the snubbers increases at the rated rotation or overspeed, excessive stress acts on the blade. If this stress is unacceptable by design, the clearance between the snubbers must be increased. Further, even if the stress can be allowed, the stress caused by restraining the snubber from the low speed rotation is added to the centrifugal stress and remains, so that the reliability against vibration of the blade is lowered.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology, to prevent excessive stress from being generated at the time of rated rotation or overspeed, and to expect a vibration damping drop for resonance at the time of rotation increase or rotation decrease. Another object of the present invention is to provide a coupling device for turbine blades.

(Means for Solving the Problems) In order to achieve the above object, the present invention forms a leading edge snubber projecting to the leading edge side and a trailing edge snubber projecting to the trailing edge side at the blade tip of a turbine rotor blade, A flat contact surface is formed on one side surface of one of the leading edge snubber and the trailing edge snubber, and a flat contact surface is formed on one side surface of the other snubber of the adjacent turbine rotor blade when rotating or falling. And a contact surface capable of contacting at the time of rated rotation.

(Operation) According to the present invention, the contact surfaces of the leading edge snubber and the trailing edge snubber, which may be in contact at that time when the turbine is rotating up or down, may be in contact at the time of the rated rotation of the turbine. Since the contact surfaces of the leading edge snubber and the trailing edge snubber come into contact with each other, the contact surfaces come into contact with each other in two steps, so that not only the reaction force due to the untwisted constraint decreases, but also the rotation during rising The vibration stress at the time of resonance can also be suppressed.

(Embodiment) An embodiment of a 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 those in FIG. 6 are designated by the same reference numerals.

In Fig. 1, 1a and 2a indicate the tips of adjacent turbine rotor blades, and the leading edge of the blade 1a has a leading edge snubber.
1b is integrally formed, and the trailing edge snubber is provided at the trailing edge of the wing 1a.
1c is integrally formed. A leading edge snubber 2b is integrally formed at the front edge portion of the blade 2a, and a trailing edge snubber 2c is integrally formed at the trailing edge portion of the blade 2a. On one side surface of the trailing edge snubber 1c of the blade 1a, that is, on one side facing the leading edge snubber 2b of the blade 2a, stepped contact surfaces 1f and 1g having two steps and a step d are formed. A substantially flat contact surface is formed on one side surface of the leading edge snubber 2b of the blade 2a facing the surfaces 1f and 1g.
2h is formed. That is, similarly to any of the blades, a flat contact surface is formed on one side surface of the leading edge snubbers 1b and 2b, and a step shape having two steps and a step d on one side surface of the trailing edge snubbers 1c and 2c. 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 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 1f and 2h are in contact with each other during the rated rotation and the reaction force at that time does not become excessive. Also, the clearance between the contact surface 1g and the contact surface 2h is such that the contact surfaces 1g and 2h contact each other at a low rotational speed before the lowest-order mode natural vibration of the blade resonates with the rotation multiple component when the rotation is increased. Is set to a small value.

 Next, the operation of this embodiment will be described.

2 and 3 each show a state where untwist acts on the turbine rotor blade. FIG. 2 shows a state during low speed rotation during rotation increase, and FIG. 3 shows a state during rated rotation.

First, when the rotation of the turbine is increased, the contact surfaces 1g and 2h come into contact with each other as shown in FIG. In this state, even if the lowest-order vibration of the blade resonates with the low-order component of the rotation multiple during rotation, the vibration is damped by the friction acting on both contact surfaces 1g, 2h. At this time, a slight clearance may be left in advance between the contact surfaces 1g, 2h, and the snubbers may collide with each other when the blades resonate to dampen the vibration.

Next, when the low-order mode vibration of the blade passes through the resonance state with the rotation multiple component, and the rotation speed further rises from this, and the rotation of the turbine reaches the rated rotation, the action of the untwist increases, As shown in FIG. 3, the contact surfaces 2f and 2h contact each other. In this state, it is possible to expect a vibration damping effect due to friction with respect to excitation of steam force or the like. Moreover, during the sliding movement of the contact portion (from FIG. 2 to FIG. 3), the end surface 2j of the snubber 2b is attached to the contact surface step portion 1i of the snubber 1c.
Since the collision occurs, the vibration damping effect due to the collision can be expected at the same time.

In addition, the stress generated in the blade due to the untwist constraint is
It can be adjusted by setting the assembling clearance between the contact surface 1f and the contact surface 2h to a predetermined amount. Further, the number of contact start boundary points between the contact surface 1g and the contact surface 2h can be freely adjusted by setting the initial clearance at the time of assembly to a predetermined amount.

According to the present embodiment, the snubbers do not contact with each other at the time of low speed rotation, but are not untwisted, and the contact changes in two steps. The reaction force between snubbers can be adjusted so that high stress is not generated in the blade during rotation. Further, not only the reaction force due to the untwisted constraint can be reduced, but also the contact state of the snubber is created at the time of resonance during the rotation increase, so that the vibration stress can be reduced.

 FIG. 4 shows another embodiment.

A contact surface 1k is formed on one side surface of the trailing edge snubber 1c of the blade 1a, and a protrusion 1m is formed at substantially the center of the contact surface 1k. In addition, the leading edge snubber of the blade 2a facing the contact surface 1k
A flat contact surface 2n is formed on one side surface of 2b. According to this, at low speed rotation, the contact surface 1k-shaped protrusion 1m and the contact surface
2n contact or collide with each other, and the contact surface 1k and the contact surface 2n contact or collide with each other at the rated rotation. Therefore, according to this embodiment as well, not only the reaction force due to the untwist restraint is reduced, but also the contact state of the snubber is created at the time of resonance during the rotation increase, so that the vibration stress can be reduced.

 FIG. 2 shows another embodiment.

A flat contact surface 1p is formed on one side surface of the trailing edge snubber 1c of the blade 1a, and the leading edge snubber of the blade 2a facing the contact surface 1p.
Step-shaped contact surfaces 2q and 2r having two steps are formed on one side surface of 2b. According to this, the contact surface 1p and the contact surface 2r contact or collide with each other at the low speed rotation, and the contact surface 1p at the rated rotation.
And the contact surface 2q contact or collide. Therefore, according to this embodiment as well, not only the reaction force due to the untwist restraint is reduced, but also the contact state of the snubber is created even at the time of resonance during the rotation increase, so that the vibration stress can be reduced.

〔The invention's effect〕

As is clear from the above description, according to the present invention, when the turbine is rotated up or down, the contact surfaces of the leading edge snubber and the trailing edge snubber, which may be in contact at that time, contact each other, and at the time of rated rotation of the turbine, Since the contact surfaces of the leading edge snubber and the trailing edge snubber that can contact at that time are configured to come into contact with each other, the contact surfaces come into contact with each other in two stages during operation of the turbine. Not only can the reaction force due to the restraint be reduced, but also the vibration stress at the time of resonance during rising of rotation can be suppressed. Further, this not only increases the reliability at the time of rated rotation, but also has the effect of making it sufficiently durable under severe operating conditions such as DSS operation.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a turbine blade coupling device according to the present invention, FIGS. 2 and 3 are explanatory views for explaining the same operation, and FIGS. 4 and 5 are turbine blades according to the present invention. FIG. 6 is a plan view showing another embodiment of the coupling device, FIG. 6 is a plan view showing a conventional coupling device for turbine moving blades, FIG. 7 is an explanatory view for explaining the same operation, and FIG. 8 is a snubber all-round single group blade. Fig. 9 is a diagram showing an example of a Campbell diagram of Fig. 9, and Fig. 9 is a diagram showing the relationship between the assembly clearance, the contact start rotational speed, and the reaction force between snubbers. 1a, 2a …… Wing tip, 1b, 2b …… Leading edge snubber, 1c, 2c…
… Trailing edge snubber, 1f, 1g, 1k, 1m …… Contact surface, 2h, 2n ……
Contact surface, 1i …… step, 2j …… snubber end surface.

Claims (1)

(57) [Claims] 1. A leading edge snubber projecting to a leading edge side and a trailing edge snubber projecting to a trailing edge side are formed at a blade tip portion of a turbine rotor blade, and one of the leading edge snubber and the trailing edge snubber is snubber. Form a flat contact surface on one side,
A turbine moving blade coupling device, wherein a contact surface capable of contacting during rotation ascent or rotation and a contact surface capable of contacting during rated rotation are formed on one side surface of the other snubber of the adjacent turbine blades.