JP3697041B2 - Turbine impeller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a turbine impeller, and more specifically, a moving blade assembly in which a plurality of blades are erected on a platform and a shroud is provided at a free end of the blades to connect the blades. The present invention relates to the structure of a turbine impeller in which the blades are connected and fixed in the circumferential direction of the disk. In the present specification, the turbine impeller refers to an impeller including blades.
[0002]
[Prior art]
FIG. 6 shows a moving blade portion of a turbine impeller employed in a speed control stage of a conventional steam turbine. The turbine impeller shown in the figure employs a structure called a triple-pin rotor blade, and three blades 2 are erected on the platform 1 and the free ends of the blades 2 are connected by a shroud 3. A moving blade assembly 4 is formed. The blade assembly 4 has three pins 6 inserted into teeth 5 called prongs and is coupled to the disk 7 by a cold fit.
[0003]
[Problems to be solved by the invention]
By the way, the final adjustment of the natural frequency is performed by adjusting the shroud 3 or the like in the conventional speed turbine blades of the conventional steam turbine. However, when this method alone cannot sufficiently adjust the frequency. There is. Further, since the blade 2 and the shroud 3 are integrally formed by electric discharge machining, the damping effect is small, and a large resonance stress is generated when resonating with the excitation force generated by the upstream nozzle wake (wake). The blade 2 may be damaged.
[0004]
The present invention has been made in view of such a situation, and an object of the present invention is to provide a turbine capable of easily adjusting the frequency and preventing damage to the blades even when resonating. To provide an impeller.
[0005]
[Means for Solving the Problems]
In the turbine impeller of the present invention, a plurality of blades are erected on the platform, and a moving blade assembly in which a shroud is disposed at a free end of the blades and the blades are connected to each other in the circumferential direction of the disk. In the turbine impeller fixedly connected to the turbine blade , the upper surface, which is the surface away from the turbine shaft, is directed from the inside toward the external end surface on the end surface of the platform or shroud of the blade assembly that is connected in series. A groove formed in an inclined surface that is inclined upward is provided to define a space between the platforms or shrouds, and a damper piece having a circular cross-section or a trapezoidal cross-section is fitted into the space.
[0006]
According to the present invention, it is possible to change the natural frequency by trimming the damper piece, thereby preventing resonance with the external excitation force, and by interposing the damper piece between the rotor blade assemblies. Even when resonance occurs, the blade can be prevented from being damaged by the damping effect.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments.
[0008]
FIG. 1 shows a first embodiment of a moving blade assembly 10, in which three blades 12 are erected on the upper surface (outer peripheral surface) of a platform 11, and a shroud is provided at the free end of these blades 12. 13 is arranged by passing. Further, three teeth 14 called prongs are formed on the lower surface (inner peripheral surface) of the platform 11. The platform 11, the blades 12, and the shroud 13 are integrally formed by electric discharge machining or the like. Further, in the blade assembly 10, three holes 15 are formed through the three teeth 14 formed in the platform 11, and a groove 16 is formed in the end surface 11 a of the platform 11. As shown in FIG. 2, the groove 16 has a semi-pentagonal cross section, and an upper surface (a surface away from the turbine shaft) is inclined to an inclined surface 16a inclined upward from the inside toward the outer end surface. Is formed.
[0009]
The rotor blade assembly 10 is configured such that the teeth 14 of the platform 11 are fitted into the teeth 17a formed on the disk 17 of the turbine wheel, and holes (not shown) formed in the teeth 17a and the platform 11 are formed. A pin 18 is coupled to the hole 15 formed in the tooth 14 by a cold fit to fix the rotor blade assembly 10 to the disk 17 of the turbine wheel. Next, the next blade assembly 10 is arranged on the blade assembly 10 and fixed to the disk 17 of the turbine wheel in the same manner as described above. At the same time or before that, the damper piece 19 is loaded into the groove 16 formed in the end surface 11a of the platform 11 of the previously installed blade assembly 10. In this way, the rotor blade assembly 10 is sequentially fixed to the entire circumference of the disk 17 of the turbine wheel. In the turbine impeller assembled in this way, as shown in FIG. 2, the damper pieces 19 are arranged one by one in the space defined between the blade assemblies 10 by the grooves 16 of each blade assembly 10. It will be inserted. As the material of the damper piece 19, the same stainless steel as that of the wing 12 is used.
[0010]
In the turbine impeller configured as described above, when the turbine impeller is rotated, the adjacent blade assembly 10 is coupled to each other on the platform 11 by the wedge action due to the centrifugal force of the damper piece 19. The vibration characteristics change as shown in FIG.
[0011]
That is, when the number of node diameters of the blades of the entire circumference and the disk system vibration mode (disk mode) is 0, N / 2, N, 3N / 2, 2N. The frequency of the conventional moving blade and the moving blade of the embodiment of the present invention is almost the same, but the frequency of the other nodal diameter modes is different. Resonance condition formula H ± n = λN
H: Number of excitation harmonics (number of nozzles)
n: Number of node diameters of vibration mode λ: Arbitrary integer N: The natural frequency of the vibration mode satisfying the number of blade groups on the entire circumference may be adjusted, so the frictional force of the damper piece 19, that is, the weight of the damper piece 19 By appropriately selecting the angle of the groove 16 or the groove 16, the frequency can be adjusted as required without changing the shape of the blade 12 or the shroud 13. Further, even when resonance occurs, the vibration stress can be suppressed by the damping effect of the damper piece 19 and the platform 11, so that the blades can be prevented from being damaged.
[0012]
FIG. 4 shows a second embodiment of a turbine impeller according to the present invention. As in the first embodiment, the blade assembly 20 of the turbine impeller includes three blades 12 standing on the upper surface (outer peripheral surface) of the platform 11 and a shroud at the free end of the blades 12. 13 are arranged so as to be integrated, and they are integrally formed. In addition, three teeth 14 called prongs are formed on the lower surface (inner peripheral surface) of the platform 11, and three holes 15 penetrating the teeth 14 are formed in the teeth 14. ing. In the blade assembly 20, a groove 16 is formed in the end surface 13 a of the shroud 13. The shape of the groove 16 may be the same as that of the groove 16 formed on the end surface 11a of the platform 11 in the first embodiment.
[0013]
The blade assembly 20 is sequentially fixed to the disk 17 of the turbine impeller in the same manner as in the first embodiment. When the blade assembly 20 is fixed to the disk 17, the damper piece 19 is loaded into the groove 16 formed in the end surface 13 a of the shroud 13 of the blade assembly 20 previously installed. Between the rotor blade assemblies 20 attached in this manner, the damper pieces 19 are inserted one by one in the groove 16, and these damper pieces 19 are in the state of the first embodiment. Similarly to the configuration, when the turbine impeller is rotated, the adjacent rotor blade assemblies 20 are connected to each other by the shroud 13 due to the centrifugal force of the damper piece 19, so that the vibration characteristics change as shown in FIG. To do.
[0014]
In any of the above-described embodiments, the shape of the groove 16 and the shape of the damper piece 19 are not limited to the end surface of one rotor blade assembly 10 (20), as shown in FIG. A groove 16 is also formed in the end face of the other rotor blade assembly 10 (20) arranged opposite to each other, and a cross section as shown in FIG. The cross-sectional shape (such as the angle of the groove 16), the weight, etc. are appropriately changed according to the purpose (the necessary amount of adjustment of the frequency and the additional amount of damping), such as by inserting a trapezoidal damper piece 19 ′. be able to.
[0015]
Further, a combination of the first embodiment and the second embodiment, that is, grooves 16 and 16 are provided in both the shroud 13 and the platform 11, and damper pieces 19 and 19 ′ are provided in the grooves 16. If each is loaded, the frequency can be adjusted in a larger range, and the damping effect is also increased. Therefore, even if resonance occurs, the blade damage prevention effect is increased.
[0016]
The present invention can be applied not only to a speed-control stage rotor blade, but also to a rotor blade of another stage, and only to a rotor blade assembly in which the platform 11, the blade 12 and the shroud 13 are integrally formed. In addition, the present invention can also be applied to a rotor blade assembly in which they are assembled by appropriate means such as caulking or fitting.
[0017]
【The invention's effect】
As described above, the turbine impeller according to the present invention has a blade assembly in which a plurality of blades are erected on a platform and a shroud is disposed at a free end of the blades to connect the blades. The upper surface, which is the surface away from the turbine shaft, is externally connected to the end surface of the platform or shroud of the blade assembly that is connected in series in the circumferential direction of the disk. provided inclined surface formed grooves toward the end face of the inclined upwards, defining a space between those platforms or shrouds, by fitting the circular cross section or a damper piece of trapezoidal cross-section in the space because there, or choose a weight by KezuSei the damper piece, can change the natural frequency, such as by or select the cross-sectional shape of the groove including the angle of the inclined surface, very easily external exciting force Can be the resonance can be prevented, also tentatively prevents resonance can suppress the vibration stress by attenuating effect of the damper piece and bucket assembly even when that occurred Do Runode, damage to the blade.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a moving blade assembly of a turbine impeller according to a first embodiment of the present invention.
FIG. 2 is a conceptual cross-sectional view showing a main part in a state in which the moving blade assembly of the turbine impeller according to the first embodiment of the present invention is assembled.
FIG. 3 is a graph showing vibration characteristics of a moving blade of a turbine impeller according to the present invention and a moving blade of a conventional turbine impeller.
FIG. 4 is a perspective view showing a moving blade assembly of a turbine impeller according to a second embodiment of the present invention.
FIG. 5 shows another form of the damper piece and the groove of the rotor blade assembly that accommodates the damper piece in the turbine impeller according to the present invention, in which (a) is a cross-sectional view showing the groove; ) Is a perspective view of the damper piece.
FIG. 6 is a partially cutaway perspective view showing a main part of a conventional turbine impeller.
[Explanation of symbols]
10 Blade assembly 11 Platform 11a End face 12 Wing 13 Shroud 13a End face 14 Teeth (prongs)
15 hole 16 groove 17 disk 17a tooth 18 pin 19, 19 'damper piece 20 blade assembly

Claims (2)

A turbine in which a plurality of blades are erected on a platform, and a moving blade assembly in which shrouds are arranged at the free ends of the blades and the blades are connected to each other is connected and fixed in the circumferential direction of the disk. In the impeller , an upper surface, which is a surface away from the turbine shaft, is formed on an end surface of the platform of the rotor blade assembly connected to each other so as to incline upward from the inside toward the outer end surface. A turbine impeller characterized in that a groove is provided to define a space between the platforms, and a damper piece having a circular cross section or a trapezoidal cross section is fitted into the space. A turbine in which a plurality of blades are erected on a platform, and a moving blade assembly in which shrouds are arranged at the free ends of the blades and the blades are connected to each other is connected and fixed in the circumferential direction of the disk. In the impeller , an upper surface, which is a surface away from the turbine shaft, is formed on the end surface of the shroud of the blade assembly that is connected to each other so as to be inclined upward from the inside toward the outer end surface. A turbine impeller characterized in that a groove is provided , a space is defined between the shrouds, and a damper piece having a circular cross section or a trapezoidal cross section is inserted into the space.

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