JP5357338B6 - Wing arrangement method - Google Patents

Description

  The present invention relates to a method for arranging blades when planting blades in a turbine rotor.

  In turbomachines such as jet engines, gas turbines, and steam turbines, a large number of blades are attached to the outer periphery of a disk-shaped turbine rotor at equal intervals and used at high speed. Each blade is manufactured within a predetermined design tolerance, and it is inevitable that characteristics such as mass and natural frequency vary from blade to blade within the tolerance.

  Furthermore, when a single crystal material or a unidirectional solidified material is used for the blade, the crystal orientation also varies from blade to blade. If the crystal orientation varies, the physical property values such as the longitudinal elastic modulus also vary, which causes the natural frequency to change from blade to blade.

  A wing system with variations among the wings is called a mistuned system, and a wing system with no variability among the wings is called a uniform system. As described above, since the actual wing system varies within the tolerance range, it is also understood as a mistune system.

  During operation of the turbomachine, the blade is excited by the mainstream gas flowing around the moving blade, and vibration stress is generated. High vibration stress can cause blade damage, reducing the reliability of the turbomachine.

  In addition, as a prior art regarding the arrangement | sequence method of a wing | blade, there exists a thing of patent document 1, 2, for example.

Japanese Patent Laid-Open No. 10-47007 JP-A-6-248902

  Assuming an ideal homogeneous system with no variation from blade to blade, the vibration stress generated in the blades is the same for all blades. In this case, higher vibration stress is generated than when the blade system is assumed to be a homogeneous system, so the reliability is lower than that of the homogeneous system.

  The present invention has been made in view of the above problems, and the object of the present invention is to suppress the vibration level generated in the attachment of a plurality of blades manufactured within a predetermined design tolerance to the outer periphery of the rotor. The object is to provide a method for arranging wings.

  In order to achieve the above object, the blade arrangement method of the present invention is a blade arrangement method in which a plurality of blades that are attached to the outer periphery of the turbine rotor to form an annular blade row are provided. Dividing into a low frequency group and a high frequency group, arranging the blades of the low natural frequency group in a half region of the turbine rotor, and arranging the high frequency group of blades in the half region of the turbine rotor It arrange | positions in the area | region on the opposite side to.

  According to the blade arrangement method according to the present invention, when the turbine rotor is viewed from the front, blades having a low natural frequency are disposed in one region, and blades having a high natural frequency are disposed in the opposite region. For this reason, the node radii are not equally spaced in the circumferential direction and are not synchronized with the node radii of the excitation source, so that the vibration stress of the turbine blade is reduced.

Arrangement of wings by the arrangement method of the first embodiment A perspective view showing two of the wings 1 The top view which looked at the wing | blade in FIG. 2 from the shroud side Vibration mode analysis result of blade system arranged by conventional method Front view of FIG. 4 viewed from the axial direction Vibration mode analysis results of blades arranged according to this example Arrangement of wings by arrangement method of second embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of the present invention, which shows an arrangement of blades for one stage assembled on a wheel. 1 is a blade, 2 is a shroud integrally formed at the blade tip, and 3 is a turbine rotor in which the blade 1 is planted. The number of wings 1 is n. That is, n blades 1 are planted in the turbine rotor 3. The n blades are sequentially attached in the circumferential direction of the turbine rotor 3 to form an annular blade row. Moreover, the area | region of the circumferential direction of the turbine rotor 3 is divided into the half, and is set as A area | region and B area | region.

  The root portion of the blade 1 is planted in the turbine rotor and fixedly held by the turbine rotor. Further, by bringing the shroud 2 at the tip of the blade 1 into contact with the shroud of the adjacent blade, the blades of the entire circumference are connected together. In a state where all n blades 1 are attached in the circumferential direction of the turbine rotor 3, the shroud 2 has a ring shape as a whole.

  FIG. 2 is a perspective view showing two of the wings 1. The wing 1 includes a shroud 6, a wing portion 7, and a root portion 8. Further, the shroud 6 is in contact with the shroud of the adjacent wing at the contact surface 9. FIG. 3 is a plan view of the blade 1 in FIG. 2 as viewed from the shroud side (radially outer side), and shows a state in which the shroud 6 is in contact with the two blades at the contact surface 9.

  During operation, the blade 1 undergoes torsional deformation in the direction of the rotation direction 10 in FIG. 3 due to centrifugal force, and the contact surface 9 comes into contact with the adjacent blade. By the same phenomenon, all the shrouds of the wing 1 come into contact with the shrouds of the adjacent wings, and the shroud portion has a ring-like structure as a whole during operation.

  The blade 1 is manufactured within a predetermined design tolerance, and it is inevitable that characteristics such as mass and natural frequency vary from blade to blade within the tolerance. Further, when a single crystal material or a unidirectional solidified material is used for the blade 1, the crystal orientation varies from blade to blade. If the crystal orientation varies, the physical property values such as the longitudinal elastic modulus also vary, which causes the natural frequency to change from blade to blade.

  A wing system with variations among the wings is called a mistuned system, and a wing system with no variability among the wings is called a uniform system. As described above, since the actual wing system has variations within the tolerance range, it can be strictly interpreted as a mistune system.

  During operation of the turbomachine, the blade 1 is excited by the mainstream gas flowing around the rotor blade, and vibration stress is generated. If the vibration stress is high, the blade 1 may be damaged, and the reliability of the turbomachine is lowered.

  Assuming an ideal homogeneous system with no variation from blade to blade, the vibration stress generated in the blades is the same in all blades. When the blade system is assumed to be uniform, higher vibrational stress is generated on the blades and may cause damage. As a result, the reliability of the blade system which is a mistune system is lower than that of the uniform system.

  In order to solve such a problem, the present embodiment provides a blade arrangement method capable of sufficiently suppressing the vibration level generated in a blade of a blade system that is a mistuned blade.

  As a conventional blade arrangement method, a method of keeping the blade weight non-uniformity vector within a tolerance so as to reduce the rotor unbalance is common. However, since the natural frequency of the blade is not taken into consideration in this method, it is highly possible that the natural frequency of the blade is randomly arranged as a whole.

  FIG. 4 shows a perspective view of a vibration mode analysis result of blade systems arranged by a conventional method. Reference numeral 11 denotes a node radius, which indicates a straight line drawn from a location where the amplitude becomes a node toward the rotor center when focusing on the axial vibration mode of the shroud portion of the turbine rotor blade. The node of the amplitude of the shroud portion equivalent to the node radius 11 is 12.

  FIG. 5 is a front view of FIG. 4 viewed in the axial direction. As can be seen from FIG. 4, the nodal radii appear at approximately equal intervals in the circumferential direction. Here, since the excitation mode of the fluid that excites the blade is also equally spaced in the circumferential direction, the vibration mode of the blade matches the excitation mode, and the blade system is supplied with energy greater than the excitation force of the fluid, resulting in a large vibration stress. Will occur.

  Below, the arrangement | sequence method of the wing | blade in Example 1 shown in FIG. 1 is shown.

  (1) All the natural frequencies of the blade 1 are measured and divided into a group of blades having a low natural frequency and a group of blades having a high natural frequency.

  (2) A group of blades having a low natural frequency is arranged in the A region (half of the turbine rotor), and a group of blades having a high natural frequency is arranged in the B region (region opposite to the A region).

  According to the first embodiment, blades having a low natural frequency are arranged in the A region, and blades having a high natural frequency are arranged in the B region. In this example, all of the wings having a low natural frequency are arranged in the A region and all of the wings having a high natural frequency are arranged in the B region. However, several wings deviate from the above rule. The blades originally arranged in the A region may be arranged in the B region. The intention of this embodiment is that the blade natural frequency distribution in the half region is generally low and the blade natural frequency in the other half region is generally high so that the blade natural frequency distribution is asymmetric as a whole. It is to be.

  In addition, after forming the annular blade row by the above-described process, the unbalance generated in the turbine rotor may be removed by balancing.

  FIG. 6 shows the vibration mode analysis results of the blades subjected to the arrangement method according to this embodiment. As can be seen from FIG. 6, the nodal radii have different intervals in the circumferential direction. Since the excitation modes of the fluid that excites the blades are equally spaced in the circumferential direction, the blade vibration mode does not match the excitation mode, and the blade system is not supplied with energy greater than the fluid excitation force. For this reason, the vibration stress which generate | occur | produces in a wing | blade can be reduced.

  FIG. 7 shows a second embodiment of the present invention. The arrangement method is shown below.

  (1) Measure all the natural frequencies of the blade 1, and number them as # 1, # 2, # 3,.

  (2) Arrange the blade (# 1) having the lowest natural frequency at an arbitrary location of the turbine rotor.

  (3) Two blades (# 2, # 3) having the next lowest natural frequency are arranged next to both sides of # 1.

  (4) Two blades (# 4, # 5) having the lowest natural frequency next to # 2, # 3 are arranged next to # 2, # 3.

  (5) Two wings (# i + 1, # i + 2) having the next lowest natural frequency after # i-1 and #i are arranged next to # i-1 and #i.

  (6) Repeat (5) until all wings are arranged.

  According to this embodiment, wings having a low natural frequency are arranged in the A region, and wings having a high natural frequency are arranged in the B region. In FIG. 7, # 2 is arranged on the right side of # 1, but it may be on the left side. (In this case, # 3 is arranged to the right of # 1.) That is, the positions of # 2 and # 3 may be reversed. Similarly, the positions of # i + 1 and # i + 2 may be reversed. In this embodiment, only the blades having a low natural frequency are arranged in the half region, and only the blades having a high natural frequency are arranged in the other half region, so that the natural frequency distribution of the blade is made asymmetric as a whole. It is the intention of

  According to the second embodiment, the blades having a particularly low natural frequency are concentrated in the vicinity of the center of the A region, and the blades having a particularly high natural frequency are concentrated in the vicinity of the center of the B region. Asymmetry of the natural frequency distribution increases, and the difference in the nodal radius spacing between the A region and the B region increases. As a result, the discrepancy between the vibration mode and the excitation mode of the blade increases, and a greater vibration stress reduction effect than in the first embodiment can be expected.

  It can be applied to turbine blades of gas turbines and steam turbines.

1 blade 2 shroud 3 rotor 6 shroud 7 blade 8 root 9 contact surface 11 node radius 12 node of vibration mode

Claims (4)

In the blade arrangement method of forming a plurality of annular blade rows attached to the outer periphery of the turbine rotor,
Dividing the plurality of blades forming the annular cascade into a group having a low natural frequency and a group having a high natural frequency,
Arranging the blades of the low natural frequency group in a half region of the turbine rotor;
The blade arrangement method, wherein the blades of the group having a high natural frequency are arranged in a region opposite to the half region of the turbine rotor. In the blade arrangement method of forming a plurality of annular blade rows attached to the outer periphery of the turbine rotor,
Among the plurality of blades forming the annular blade row, the blade having the lowest natural frequency is disposed at an arbitrary position of the turbine rotor,
Two wings with the next lowest natural frequency are arranged next to both sides of the wing with the lowest natural frequency,
The method for arranging blades is characterized in that the annular blade row is formed by repeating two blades having the next lowest natural frequency next to the two blades. The method for arranging wings according to claim 2,
A blade having the second lowest natural frequency is arranged next to one of the blades having the lowest natural frequency, a blade having the third lowest natural frequency is arranged next to the other, and the blade having the second lowest natural frequency is arranged. The fourth blade having the lowest natural frequency is arranged next to the blade having the fourth lowest natural frequency, and the blade having the fifth lowest natural frequency is arranged next to the third blade having the lowest natural frequency. A method of arranging blades, characterized in that the annular blade row is formed by sequentially repeating up to the second blade. The method for arranging wings according to claim 1 or 2,
After forming the annular blade row, an unbalance generated in the turbine rotor is removed by balancing, thereby arranging the blades.

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