JPH0598907A - Turbine disk and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a turbine disk having high reliability in which vibration mode of planning design for avoiding resonance, and an excitation degree range which is in resonant condition in relation to the mode can be clearly restricted. CONSTITUTION:At least two kinds of circumferencial direction connecting structures made of tie wire 3 and shroud 2, etc., are provided in positions different from each other in radial direction of a rotor blade 1 installed on a rotor disk 4, and a total circumference one ring blade structure and a group blade structure are provided on one turbine disk. The number of one circumference direction dividing group of the connecting structure of the top end part of the turbine rotor blade 1 by the shroud 2 or the connecting structure of the intermediate part of the turbine rotor blade 1 by the tie wire 3, is set to 12 to 30 pieces. Since an excitation degree range which is in resonant condition is restricted by difference between vibration mode by total circumference one ring blade structure and a vibration mode by group blade structure, it is possible to make design for avoiding resonance easily, and also suppress breakage of rotor blade certainly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine of a steam turbine or a gas turbine, and more particularly to a structure of a turbine rotor suitable for a rotor having a large rotor length such as a low pressure side, and a turbine rotor of such turbine rotor. It relates to a manufacturing method.

[0002]

2. Description of the Related Art A moving blade such as a steam turbine or a gas turbine is continuously excited in a wide frequency range due to a flow of a working fluid such as steam and stress caused by its turbulent component.
For this reason, the rotor blades generate vibrations with a large number of natural frequencies, which greatly affects the reliability and durability of the rotor blades.

However, in this case, not all the vibrations appearing on the moving blades become a problem, but vibrations at the same natural frequency as the frequency of a large exciting force which may cause damage to the moving blades. This is a problem, and therefore, the natural vibration of the blade having a small excitation force and the same frequency component that does not cause damage to the moving blade is often not taken into consideration in the resonance avoidance design.

By the way, the vibration response of the rotor blade to these various exciting forces is related to the natural frequency and the magnitude of damping in each vibration mode. Therefore, in order to design a wing structure that avoids resonance in a low-order vibration mode with a large resonance response, but can resonate in a high-order vibration mode with a small resonance response, the adjacent blades should be A method of connecting with a tie wire or a band-shaped shroud has been widely adopted from the past. This is because if the adjacent moving blades are connected, the effect of increasing the rigidity of the blade structure and damping the vibration can be expected.

Here, as described above, the blade structure for connecting the moving blades to each other has a predetermined number of blades connected as a unit group among the moving blades of the entire circumference of the turbine wheel. A so-called group wing structure that has multiple unit groups,
Alternatively, there is known a so-called all-round one-ring blade structure, in which the outer circumferences of all the moving blades forming the turbine impeller are collectively connected in the circumferential direction.

Of these, the full-circumference 1-ring blade structure will be described in detail. In this structure, as shown in FIG. 8, a vibration mode unique to the vibration mode of the disc, that is, a vibration mode of the disc is similar to that. It has one wavelength, two wavelengths, etc. all around the circumference, and has a natural vibration mode of a series of node diameter modes in which nodes exist at several diameter positions.

As is well known, the advantage of this all-round one-ring blade structure is that, in these node diameter vibration modes, the excitation force of the frequency component of an integral multiple of the rotational speed (harmonics) is generated during turbine operation. When it acts, it resonates only when certain conditions, for example, the harmonic diameter orders of the node diameter number and the rotation number match, so that the number of resonant vibration modes of the wing structure to be finally avoided is greatly reduced. ,For this reason,
It is to facilitate the design of avoiding resonance of the wing.

Incidentally, as a device related to this kind of device, for example, JP-A-57-99213 and JP-B-58 are known.
-57603 or the respective disclosures of JP-A-3-30902 can be mentioned.

[0009]

The prior art has the following problems. Usually, as the exciting force acting on the turbine rotor blade, there is a fluid exciting force generated because the flow of the working fluid is not uniformly distributed in the circumferential direction of the impeller. This fluid excitation force has a frequency component of an integral multiple of the rotation speed (hereinafter, this is referred to as an excitation order) for a blade rotating in a non-uniform distribution of flow in the impeller circumferential direction. It acts as an exciting force to have. It is generally known that these excitation forces are stronger as the excitation order is smaller and weaker as the excitation order is larger.

By the way, conventionally, as a result of experience, in a portion having a long blade structure such as a low pressure side of a steam turbine, if the excitation order is 15 or more, the moving blade may be damaged even if it resonates. It is known to be small. In other words, conversely, when expressed by the excitation order that should avoid resonance, it is less than the 15th order. Even in the region where the excitation order is less than 15th order, depending on the design of the blade, there is a case where the risk of breakage does not occur even if it resonates, but when it becomes 6th order or less, it is always said that resonance occurs. However, since the damage will occur as much as possible, it is necessary to absolutely prevent resonance from occurring in any region of the sixth order and below.

Therefore, in the prior art, a full-circle 1-ring blade structure having a resonance condition is adopted only when the harmonics order of the node diameter number and the rotational speed match, and the node diameter number is 6 or less, and in some cases 15 or less. The natural frequency in the vibration mode of
It was designed so as not to match the frequency of the excitation force with the same excitation order as each node diameter number.

Here, FIG. 4 is a graph schematically showing the change in the value of the natural frequency corresponding to the node diameter number of each node diameter vibration mode in the all-circle one-ring blade structure. Is
As shown in FIG. 4, the value of the natural frequency corresponding to the node diameter number in each node diameter vibration mode tends to monotonically increase as the node diameter number increases. And, as described above, the conditions under which these nodal diameter modes resonate are when the nodal diameter number and the excitation order match, and the range of nodal diameter numbers that should be empirically studied for avoiding resonance is as described above. 6th or lower, or 15
All areas below.

However, even if the order in which resonance is to be avoided is limited to a specific order range, the actual change in natural frequency of each node diameter mode is as shown in FIG. Since the number is small for each number, there is little difference in the natural frequency between the orders before and after the specific order as a boundary.Therefore, in the node diameter mode above the specific order, there is a risk of damage even when resonating. I cannot always say that there is no
Therefore, the conventional technique has a problem in providing sufficient reliability.

Further, as described above, it has been conventionally empirically argued that the order of excitation for avoiding resonance is from 6th to 15th or less. Since the rigidity of the blade decreases and the vibration amplitude of the blade tip increases, even in a vibration mode with a large number of nodes diameter, which was not predicted by conventional experience, there are cases of accidents where the blade breaks due to resonance. Therefore, the conventional technique has a problem that it is difficult to provide sufficient reliability in this respect as well.

Furthermore, in the blade structure design, the natural frequency of the vibration mode and the excitation order frequency component of the excitation force at which the blade structure should avoid resonance do not match, and it is sufficiently safe by vibration analysis and experiments. Although the structure is designed so as to be ensured, in actual turbine blades, it often happens that harmful resonance cannot be completely eliminated from the turbine operating speed range. Therefore, it is necessary to improve the connecting structure of the blades.For that reason, in the prior art, in order to change the strength and rigidity of the connecting member, the connecting structure is changed to a new connecting structure, or the connecting portion between the blade and the connecting member is changed. There is a problem in that it is necessary to change the coupling conditions so that the damping effect of No. 1 changes, and the manufacturing process becomes complicated and it is difficult to reduce costs.

An object of the present invention is to provide a turbine wheel having sufficient reliability, which can limit the vibration mode to be designed to avoid resonance and the excitation order range related thereto.

Another object of the present invention is that there is no risk of blade damage even if the rotor blade resonates in a vibration mode of a higher order exceeding the excitation order range for which resonance avoidance design is to be performed, and there is sufficient reliability. The object is to provide a turbine impeller having properties.

Still another object of the present invention is to provide a method for manufacturing a turbine wheel, which can change the vibration characteristics of the turbine rotor blade in a simple working process and can sufficiently reduce the cost.

[0019]

DISCLOSURE OF THE INVENTION The present invention relates to an all-round 1-ring blade structure in which the outer circumferences of all moving blades constituting a turbine impeller are gathered together in the circumferential direction and the entire circumference is seamlessly connected, and a turbine impeller. By combining a predetermined number of blades as a unit group among the rotor blades of the entire circumference that make up a group blade structure having a plurality of unit groups as a whole, The natural frequency for each vibration mode can be changed stepwise and drastically depending on the node diameter, and the shroud connection structure at the blade tip suppresses the vibration amplitude at the blade tip to achieve a relatively high frequency. The present invention is based on the idea that the resonance response of the next vibration mode can be reduced. Therefore, in order to achieve the above object, the present invention adopts the following means.

(1) The turbine rotor blade is provided with at least two kinds of independent circumferential connection structures separated from each other in the radial direction of the turbine rotor blade, and at least one of the plurality of circumferential connection structures is provided.
The seed is a group wing structure, and the number of groups divided in the circumferential direction by this is in the range of 12 to 30.

(2) The turbine rotor blades are provided with at least two kinds of independent circumferential connection structures separated from each other in the radial direction of the turbine impeller, and all of the plurality of circumferential connection structures are provided for each circumferential connection structure. The number of groups of blades in the unit group is different, and the number of groups divided by any of the groups is 12 to 30 among the number of groups divided in the circumferential direction. It is a thing.

(3) At least two different radial positions in the radial direction of the turbine impeller, when connecting turbine blades by connecting members extending in the circumferential direction, the number of blades on the blade tip side and the blade intermediate portion. The number of wing splicing is the same, and the number of groups divided in the circumferential direction is 12 to 30.
After the connection is made within the range of the individual pieces, the connecting structure of the blade intermediate portion is connected all at once with no break by means such as a sleeve.

(4) When connecting adjacent turbine moving blades by connecting members extending in the circumferential direction at at least two different radial positions in the radial direction of the turbine impeller,
The number of groups that are divided in the circumferential direction after the connection structure of the blade tip side and the connection structure of the blade middle part are connected together all at once around the whole circumference, and then the connection structure of the blade middle part or the blade tip part is cut. Is in the range of 12 to 30.

[0024]

In the turbine impeller of the present invention, for example, a group wing structure divided into several groups by the connecting structure of the blade tips and a grouping structure of the middle part of the blade are gathered together seamlessly in the circumferential direction of the entire circumference. All around 1 connected to
Since two types of connection structures of ring blade structures are mixed in one turbine impeller, the vibration characteristics of this blade structure have intermediate vibration characteristics between the group blade structure and the all-round one ring blade structure.

By the way, the vibration mode of the group wing structure is shown in FIG.
As shown in, there are as many vibration modes as there are splicing blades of the connecting members forming the group blade. The difference in the natural frequency between the vibration modes is significantly larger than the difference in the natural frequency between the node diameter modes in the case of the all-circle 1-ring blade structure.

In view of the fact that each group of the group blade structure existing over the entire circumference of the blade structure according to the present invention has a vibration mode as shown in FIG. 7, the blade tips forming the group blade structure are considered. The natural frequency changes greatly depending on whether or not the connecting structure of the parts has a node of vibration swinging in the axial direction.

Therefore, in the turbine wheel according to the present invention,
Due to the difference in vibration mode depending on whether the connecting member of the group wing structure has a node of vibration oscillating in the axial direction, there is a difference in the difference in natural frequency for each vibration mode, and there is a natural difference at a certain node diameter. Since the frequency changes drastically, the range of the excitation order related to resonance can be limited.

Here, if the connecting structure on the blade tip side in the present invention is performed by a shroud connecting structure for connecting the blade tip portions, compared to a structure in which only the middle portion of the blade is connected by a tie wire or the like, the blade tip side. Twisting and bending in the circumferential direction are restrained. Therefore, in relatively high-order vibration modes, the tip of the blade almost becomes the node, so the vibration amplitude of the blade is suppressed to a small level compared to the case where only the middle portion of the blade is connected. It is possible to suppress the resonance response to the excitation order such as the extremely small value.

Further, according to the method for manufacturing a turbine impeller according to the present invention, in order to interconnect the turbine rotor blades,
Using a connecting member such as a sleeve that can be easily separated and re-joined, once the whole-circle 1-ring blade structure or the group blade structure is formed, and then the blade tip connecting structure or the connecting structure of the blade middle portion is changed to the all-round 1-ring blade structure Can be made into a group wing structure divided into 12 to 30 groups in the circumferential direction, or a group wing structure can be made into a full-circle 1-ring wing structure.
Since two types of connection structures, which are the all-round 1-ring blade structure and the group blade structure, can be mixed in one impeller, a turbine impeller with excellent vibration characteristics can be easily manufactured by a simple working process. ..

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A turbine impeller and a method for manufacturing a turbine impeller according to the present invention will be described in detail below with reference to the illustrated embodiments. 1 and 2 show an embodiment of a turbine wheel according to the present invention. In these drawings, 1 is a moving blade, 2 is a shroud, 3 is a tie wire, and 4 is a rotor disk.
The rotor blade 1 has its root portion implanted in and fixed to the rotor disk 4, so that it is provided over the entire circumference of the rotor disk 4. Further, each rotor blade 1 is formed so that a connecting portion by the shroud 2 at the tip portion in the radial direction and a connecting portion by the tie wire 3 at the middle portion in the radial direction are present.

At this time, the structure of the connecting portion of the moving blades 1 by the shroud 2 is made so as to form a group blade structure, and the number of splicing of the moving blades 1 by the shroud 2 at this time is the total number of the moving blades 1. The number is divided into 12 groups in the circumferential direction. On the other hand, the structure of the connecting portion of the moving blades 1 by the tie wire 3 is an all-round 1-ring blade structure in which all the moving blades 1 are connected together in a seamless manner in the circumferential direction. ing.

That is, referring to some moving blades 1a and 1b in FIGS. 1 and 2, these have a shroud 2 at the tip end thereof. The spaces are not connected by the shroud 2 but are connected by the tie wire 3, and a plurality of (three in this embodiment) moving blades 1 connected by the shroud 2 are grouped together. As a unit, the blades 1a and 1b are formed so that the blade-connecting portions periodically exist in the circumferential direction.

Therefore, in this embodiment, as is clear from FIG. 1 and FIG. 2, the all-round 1-ring blade structure formed by the tie wire 3 and the group blade structure formed by the shroud 2 are formed in one impeller. You can see that you will also have it. As a result, the turbine impeller according to this embodiment has a node diameter vibration mode in which the blades of the entire circumference have several nodes in the circumferential direction, like the vibration mode of the all-circle 1-ring blade structure shown in FIG. , And locally, the portions belonging to any one of the vibration modes shown in FIG. 7 are mixed.

Therefore, in the turbine impeller according to the embodiment of FIG. 1, when an exciting force of a frequency component of an integral multiple of the rotation speed (harmonics) acts on the turbine impeller, as in the case of the all-circle one-ring impeller structure, The condition is that resonance occurs when the diameter number and the excitation order match.

On the other hand, in addition to this, in the turbine impeller according to the embodiment of FIG. 1, the vibration mode of the shroud 2 forming the group blade structure is the vibration mode of the number of blades connected by the shroud as shown in FIG. Since it belongs to any one of them, the difference in natural frequency in each vibration mode depends on whether or not the shroud portion, which is the connecting member of the group blade structure, has a node of vibration oscillating in the axial direction. It also has the property of becoming significantly larger than the difference in natural frequency for each node diameter mode.

Then, considering the vibration modes of the group blade structure constituted by the shroud 2 in the blade structure shown in the embodiment of FIG. 1, first, in FIG. It is assumed that each group of adjacent group wing structures in the direction oscillates in opposite axial directions. Then, in this embodiment, the number of groups in the entire circumference divided by the shroud in the entire circumference is 12, so that the number of node diameters in the entire circumference is 6, which is half the number of groups, as shown in FIG. ..

Further, in this case, in the shroud portion,
Considering the vibration mode with one node,
It can be inferred that the number of node diameters becomes 6 as shown by 0.
That is, in the blade structure shown in the embodiment of FIG. 1, there are two kinds of vibration modes having a node diameter number of 6, and among these vibration modes, the shroud portion which is the connecting member of the group blade structure swings in the axial direction. It can be seen that the natural frequency changes significantly depending on whether or not it has a vibration node. FIG. 3 is a graph qualitatively showing the relationship between the series of knot diameter numbers k and natural frequencies.

By the way, in the case of the wing structure according to the embodiment of FIG. 1, although the natural frequency varies greatly with the node diameter number 6, the connecting member of the group wing structure has nodes, and the natural frequency is stepwise. A general relationship between the number N of node diameters and the number M of groups will be described in the case where the number k of node diameters significantly changes to N and the number of groups constituting the group wing structure is represented by M.

In each of the vibration mode in which the connecting member of the group wing structure has no node and the vibration mode in which there is one node of vibration oscillating in the axial direction, the vibration mode in which the number of node diameters of the wing structure on the entire circumference is the same. Shows the vibration waveform for one cycle in the circumferential direction in the two groups that make up the group wing structure, so it is half the number of groups that make up the group wing structure (that is, the number of all groups divided by 2). And the natural frequency becomes the same numerical value as the node diameter number at which the natural frequency changes stepwise, and therefore the relation of M = 2N is established.

Therefore, if this relationship is utilized, the range of the excitation order of the low-order vibration mode which should avoid resonance in the blade design is N.
Then, if a wing structure having a group wing structure with twice the number of groups N and a 1-ring wing structure all around the circumference is adopted,
With the node diameter number k = N, the vibration characteristic in which the natural frequency changes stepwise as shown in FIG. 3 is obtained, and the node diameter at which the resonance should be avoided with the vibration mode of the node diameter number k = N as the boundary. It is possible to limit the range of several ranges and higher-order vibration modes.

By the way, when the number of groups of the group wing structure in the circumferential direction must be an odd number such as 13, 15 in designing the wing structure, (M-1) / 2
The natural frequency changes significantly between the number of nodes represented by and the number of nodes represented by (M + 1) / 2. The reason for this is
When the number of nodal diameters is (M-1) / 2 or less, the shroud part, which is the connecting member of the group wing structure, is a vibration mode without nodes, and when the number of nodal diameters is (M + 1) / 2 or more, the group wing is This is because the shroud portion, which is the connecting member of the structure, has a vibration node that shakes in the axial direction.

Therefore, in the case where the range of the number of node diameters and the range of higher-order vibration modes in which resonance is to be avoided are limited on the basis of the vibration mode of the number N of node diameters, the shroud having the number of groups twice N is used. A 2N + 1 shroud group wing structure may be used instead of the group wing structure, and the effects of the present invention can be obtained by the embodiment as described above.

On the other hand, generally, the vibration characteristics of the turbine rotor blade are such that the root of the blade is in a fixed condition, and therefore the tip end side of the blade has the largest amplitude and is apt to swing.
In the embodiment, since the tip portion of the moving blade 1 is connected by the shroud 2, the twisting moment and the bending moment in the circumferential direction appearing at the blade tip portion are further increased as compared with the case where a connecting means such as a tie wire is adopted. It can be restrained greatly and vibration can be suppressed sufficiently.

In the higher-order vibration mode in which the number of node diameters increases, the position of the connecting member becomes a node of the vibration mode in the radial direction. In the embodiment of FIG. 1, however, the tip of the blade 1 is connected by the shroud 2 and the connecting means by the tie wire 3 is further provided in the middle portion. Therefore, in the higher order vibration mode, the tip of the blade is The part that has the connecting structure of the middle part and the middle part becomes a node, and as a result, compared with the blade structure that connects only the middle part of the moving blade, vibration with a large amplitude is sufficiently suppressed, There is an advantage that the structure can sufficiently withstand the excitation force related to resonance.

Next, another embodiment of the present invention will be described. In the above-mentioned embodiments, the case where the whole-circumference 1-ring blade structure is described as the connecting structure of the intermediate portions of the moving blades by the tie wire or the like has been described.
Even if about / 4 is connected, a vibration characteristic similar to a full-circumference 1-ring blade structure can be obtained. Therefore, the object of the present invention can be achieved by this embodiment as well. An embodiment of the present invention thus configured will be described below.

As described above, FIG. 3 is a diagram qualitatively showing the relationship between the node diameter k and the natural frequency for each blade structure. In FIG. Considering a kind of group wing structure in which four blades are connected, the value of N in this case is N = 2 because the number of groups in the entire circumference by the group wing structure is four. That is, on the graph of FIG. 3, the value of the natural frequency is scattered in the vibration mode every time the node diameter number k increases by 2.

Considering a wing structure having a group wing structure in which the number of groups along the entire circumference is 12 and a group wing structure in which one-fourth of the number of blades in the entire circumference are connected, is included in one impeller. , Its vibration characteristics are expected to have a natural frequency distributed in the shaded area of the graph of FIG. 5, and it depends on whether or not the group wing structure has a vibration node that swings in the axial direction. Based on the knowledge that the frequency changes greatly, it can be predicted that the natural frequency will change significantly when the node diameter is 6.

Therefore, the connecting structure of the middle portion of the turbine rotor blade is not a one-ring blade structure all around, but a group blade structure at the tip of the blade as long as it is divided into four groups in the circumferential direction. Even if it is different from the number of spells that make up the
It can be said that this is an embodiment of the present invention, and the effects of the present invention can be expected.

Also in this embodiment, since the blade tips are connected by the shroud, the tips of the blades become nodes in high-order vibration modes and do not vibrate with a very large amplitude. It has the advantage that it can sufficiently withstand the exciting force involved and reliably obtain high reliability.

Next, as an embodiment of the present invention, as long as there is no problem in the design of the blade structure, contrary to the embodiment of FIG. A wing structure may be used, and the intermediate connecting portion of the wing made of tie wire or the like may have a group wing structure. The reason is that one impeller has at least a double or more connecting structure in the radial direction, and if any part of the connecting structure has a group blade structure with a group number of 12 to 30, This is because the purpose can be achieved.

By the way, in the above description, the material of the connecting members such as the shroud or the tie wire is not particularly mentioned, but as one embodiment of the present invention, these connecting members are made of titanium. Good. Titanium material has a smaller specific gravity than steel material and has a high strength for that reason, so the centrifugal force that acts on the rotor blade can be reduced, and as a result, it is possible to achieve weight reduction and good corrosion resistance. Not only the erosion resistance effect of the steam turbine is increased, but also the vibration characteristics of the blade structure can be easily and finely adjusted due to the difference in the physical property values from steel materials, etc. Therefore, an example using titanium as this connecting member According to the above, when it is necessary to change the vibration characteristics in the resonance avoidance design, the position of connecting the moving blades with the connecting member or the shape of the connecting member is changed, or the connection condition or contact condition between the blade and the connecting member is changed. Even if such means as described above are not adopted, there is an effect that it is possible to easily and easily cope with the structure, form, etc. of the blade as it is, without impairing the flow conditions flowing between the blades.

Next, an embodiment of the method for manufacturing a turbine wheel according to the present invention will be described. FIG. 6-1 is a flow chart in one embodiment of the method for manufacturing a turbine impeller according to the present invention. First, by vibration analysis, experiments, etc., vibrations that should avoid resonance when the turbine moving blade operates A group blade structure is predicted that the natural frequency of the mode does not substantially match the excitation order frequency component of the excitation force, and at least two or more radial positions of the turbine rotor blade are arranged so that this group blade structure is obtained. A connecting member extending in the circumferential direction is provided to connect adjacent moving blades (611). At this time, the number of groups divided in the circumferential direction of the rotor blade is 12
-30 so that a group wing structure is obtained.

Next, an actual steam excitation experiment was conducted using this turbine impeller to investigate whether the natural frequency of the vibration mode in which resonance should be avoided does not match the excitation order frequency component of the excitation force at all. (612), then confirm this
(613). When it is unavoidable that the vibration characteristics of the moving blade have to be changed in the resonance avoidance design of the blade structure, a connecting means such as a sleeve is connected to the connecting structure at either the blade middle portion or the blade tip portion. Is applied so that the entire circumference is seamlessly connected (614).

Then, again, using this blade structure, a steam excitation experiment is actually conducted to investigate whether or not the natural frequency of the vibration mode in which resonance should be avoided does not coincide with the excitation order frequency component of the excitation force. Yes (615).

FIG. 6-2 is a flow chart of another embodiment of the method for manufacturing a turbine impeller according to the present invention. First, when the turbine rotor blade is operated by vibration analysis and experiments in advance. In order to avoid this resonance, the natural frequency of the vibration mode should be determined so that it does not substantially match the excitation order frequency component of the excitation force. At least two or more radial positions of the turbine rotor blade are provided with connecting members extending in the circumferential direction, respectively, to connect adjacent rotor blades (621).

Next, an actual steam excitation test or the like is carried out using this turbine impeller to investigate whether the natural frequency of the vibration mode in which resonance should be avoided does not match the excitation order frequency component of the excitation force at all. (622), then confirm this
(623). In the design to avoid the resonance of the blade structure, if it is unavoidable that the vibration characteristics of the moving blade must be changed, disconnect the connecting member to the connecting structure at either the blade middle portion or the blade tip portion. Then, the number of groups divided in the circumferential direction of the blade connecting structure is set to 12 to 30 to form a group blade structure (624). Then, again, using this blade structure, an actual steam excitation test is conducted to investigate whether the natural frequency of the vibration mode in which resonance should be avoided does not match the excitation order frequency component of the excitation force (625). ).

In the prior art, due to the resonance avoidance design of the wing structure,
When it is unavoidable to change the vibration characteristics of the blade structure, one or both of the connecting condition or the connecting condition between the moving blade and the connecting member is changed. Explaining with a concrete example, the designed blade structure that was initially set uses tie wires for the connecting members, drills holes at the connecting members of the connecting members of the moving blades, inserts the tie wires there, and welds with silver brazing etc. In such a structure, the vibration characteristics of the blade connecting structure were changed by removing the welding using silver brazing or the like so that the moving blade and the tie wire were connected in a loose state. That is, if the coupling condition between the moving blade and the connecting member is changed in this way, the vibration damping ratio between the blade and the connecting member changes, and the vibration characteristic can be changed.

However, in this conventional technique, it is necessary to change a number of coupling conditions between the moving blades and the connecting members, such as removing welding of all the moving blades and the connecting members over the entire circumference.
For this reason, there are many work processes, and as a result, it is difficult to predict how much the vibration damping ratio between the moving blade and the connecting member will change, and how effectively the result will affect the change in the vibration characteristics of the moving blade. It is a sort of fumbling work, and there is no guarantee that the necessary vibration characteristics will be obtained immediately.

However, according to the embodiments shown in FIGS. 6A and 6B, the number of working steps can be reduced as compared with the work conventionally performed in improving the vibration characteristics of the moving blade, and the
In addition, there is an advantage that the expected vibration characteristic can be surely obtained.

[0060]

According to the present invention, it is possible to clearly limit the vibration mode for which the resonance of the turbine rotor blade is to be avoided and the excitation order range related thereto, and it is possible to surely avoid the resonance while suppressing extra resonance avoidance measures. There is an effect that high reliability can be easily obtained.

Further, according to the present invention, even if resonance occurs in a moving blade in a high-order vibration mode exceeding the excitation order range for which resonance avoidance design is to be performed, it is possible to prevent the blade from being damaged, so that sufficient reliability is ensured. It is possible to easily obtain a turbine turbine wheel having good properties.

Further, according to the present invention, since the vibration characteristic of the turbine blade structure can be changed by a simple working process, it is possible to easily manufacture a turbine impeller capable of sufficiently avoiding resonance.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a turbine wheel according to the present invention.

FIG. 2 is a partially enlarged perspective view showing details of an embodiment of the present invention.

FIG. 3 is a characteristic diagram qualitatively showing vibration characteristics of a turbine wheel according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram qualitatively showing vibration characteristics of a turbine rotor blade according to a conventional technique.

FIG. 5 is a characteristic diagram qualitatively showing vibration characteristics of a turbine rotor blade according to another embodiment of the present invention.

FIG. 6 is a flow chart showing an embodiment of a method for manufacturing a turbine wheel according to the present invention.

FIG. 7 is an explanatory diagram showing an example of vibration modes exhibited by a turbine rotor blade having a group blade structure.

FIG. 8 is an explanatory diagram showing an example of vibration modes exhibited by a turbine rotor blade having a full-circle one-ring blade structure.

FIG. 9 is an explanatory diagram showing an example of a vibration mode exhibited by a turbine rotor blade according to an embodiment of the present invention.

FIG. 10 is an explanatory diagram showing an example of vibration modes exhibited by the turbine rotor blade according to the embodiment of the present invention.

[Explanation of symbols]

 1 Turbine rotor blade 1a Turbine rotor blade 1b Turbine rotor blade 2 Shroud 3 Tie wire 4 Rotor disk

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshio Kano Yoshio Kano 502 Jinritsucho, Tsuchiura-shi, Ibaraki Machinery Research Institute, Hiritsu Manufacturing Co., Ltd. (72) Inventor Kazuo Ikeuchi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Stock Hitachi Works Hitachi Factory

Claims (7)

[Claims] 1. A turbine impeller having independent circumferential connection structures at different positions in the radial direction of a turbine rotor blade, wherein at least one of the circumferential connection structures has a full-circle 1-ring vane structure, and the rest. A turbine impeller, characterized in that a group blade structure is formed by at least one of the above. 2. The turbine impeller according to claim 1, wherein the number of groups formed by dividing the group of blades in the circumferential direction is 12 to 30. 3. The turbine wheel according to claim 1, wherein one of the circumferential connection structures is a shroud connecting the turbine rotor blade tips. 4. The invention according to claim 1, wherein the all-round 1-ring blade structure is a connecting structure for connecting a turbine rotor blade intermediate portion, and the group blade structure is a connecting structure for a turbine blade tip side. Characteristic turbine impeller. 5. The turbine wheel according to claim 1, wherein at least one of the circumferential connection structures is made of a titanium material. 6. At least two in the radial direction of the turbine wheel.
In a method for manufacturing a turbine impeller in which adjacent turbine blades are connected by connecting members extending in the circumferential direction at different positions, the number of blades on the tip side of the turbine blade and the number of blades on the middle portion of the turbine blades In the same number, and connecting the turbine moving blades so that the number of groups divided in the circumferential direction is 12 to 30, and the connecting structure of the intermediate portion of the turbine moving blades is provided by a sleeve or the like. And a step of connecting the entire circumference in one piece without interruption by a means. 7. At least two in the radial direction of the turbine wheel.
In a method for manufacturing a turbine impeller in which adjacent turbine moving blades are connected by connecting members extending in the circumferential direction at different positions, a connecting structure at a turbine moving blade tip side and a connecting structure at a turbine moving blade intermediate portion are respectively formed. At least one of a step of forming a structure in which the entire circumference is seamlessly connected together, and a structure of connecting the turbine rotor blade intermediate portion and the turbine blade tip end portion so that the number of groups divided in the circumferential direction is 12 to 30. A method of manufacturing a turbine impeller, comprising: