JP2024009621A - Method for balancing rotating body - Google Patents

Abstract

To improve the correction effect while suppressing an increase in cost in a method for balancing a rotating body.SOLUTION: A method for balancing a rotating body including at least two bearings, a rotor, and a heavy object attached to the rotor, includes: a first step of performing balance processing on a rotor in a single state in a high rotation speed range until a mode is generated having a translational mode component, a conical mode component, a first bending mode component, and a second bending mode component; and performing low-speed balancing processing on the rotor in a rotational speed range lower than the rotational speed in the first step in an assembled state in which a heavy object is attached to the rotor.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for balancing a rotating body, and in particular to a method for balancing a rotor that is applicable to an elastic or quasi-elastic rotor such as a steam turbine.

Generally, the rotor of a steam turbine includes a plurality of disks on the rotor shaft, each of which has a row of turbine rotor blades incorporated therein. Since the specifications of the blade cascade are determined by performance aspects, the specifications of the disks are also determined almost uniformly. At this time, an increase in the number of blade rows, an increase in the rotor axis length, and a decrease in the disk diameter are factors that reduce the rigidity of the rotor, and a critical speed including a bending component exists below the rated rotation speed. Such a rotor is called an elastic rotor. Here, the critical speed refers to the rotational speed of the rotating body that corresponds to the resonance frequency determined by the mass of the rotating body and the bearing system and the rigidity of the material. Even if the critical speed including the bending component of the rotor is higher than the actual operating speed, if the critical speed is close to the actual operating speed, the vibration displacement at the actual operating speed will increase and the reliability of the rotor will be affected. It may reduce the Therefore, in the rotor as described above, there are two types of balance: low-speed balance, which is performed in a low rotational speed range that is sufficiently lower than the actual operating rotational speed, and high-speed balance, which is performed in a high rotational speed range that is equivalent to the actual operating rotational speed. By performing balance, vibration displacement is reduced.

A method for balancing a rotating body is proposed in Patent Documents 1 and 2. That is, in the balance method described in Patent Document 1, based on the information on the balance weight conveniently discovered at the shaft end, a balance weight that can achieve (N+2) plane balance in the impeller part other than the end of the rotor is determined. The unbalance is improved by equivalently converting it to , and cutting the impeller. In the balancing method described in Patent Document 2, vibration displacement in a mode that includes many bending components is reduced by performing balancing work only in a low rotation speed range. There are a total of three balance weight mounting and correction surfaces: the end portions of both shafts of the rotor and the center portion, and past actual measurements and calculation results are reflected in the measurement results in the low rotation speed range.

Japanese Patent Application Publication No. 6-273254 Japanese Patent Application Publication No. 2007-327369

Turbomachinery Association Vol. 47 No. 7 pp. 393-403 W.Kellenberger, “Should a Flexible Rotor Be Balanced in N or (N+2) Planes?”, Trans.ASME, J of Eng. For Ind., Vol.94, No.2, pp548-559(1972)

However, in the technique described in Patent Document 1, while vibration displacement can be effectively reduced by (N+2) plane balance, in a turbine or the like, blade rows or disks are not ground for balance. Even in the case of grinding, the working time increases and redoing after grinding becomes difficult, which may actually increase costs. Furthermore, if a balance weight cannot be attached near the center of the rotor, which is an effective position for modes that include many bending components, there is a possibility that no correction effect can be obtained.

Furthermore, in the technique described in Patent Document 2, the amount of unbalance that a rotating machine has and its position differ depending on the rotating body, and furthermore, a mode that includes many bending components does not occur in a low rotational speed range. Therefore, compared to a balance method that actually generates a mode that includes many bending components, the possibility of obtaining a balance effect is lower, and the problem remains that a sufficient correction effect cannot be obtained. Furthermore, since there are three balance weight attachment and correction surfaces, there remains the problem that vibration displacement in secondary and subsequent bending modes cannot be reduced.

The present invention has been made in view of the above, and an object thereof is to provide a method for balancing a rotating body that can improve the correction effect while suppressing an increase in cost when balancing a rotating body. It's about doing.

In order to solve the above problems and achieve the objects, a method for balancing a rotating body according to a first aspect of the present invention includes at least two bearings, a rotor, and a heavy object attached to the rotor. A method of balancing a rotating body comprising: a first step of performing a balance process on the rotor, and performing a low-speed balance process on the rotor in a rotation speed range lower than the rotation speed in the first step in an assembled state in which the heavy object is attached to the rotor; a second step.

In the method for balancing a rotating body according to a second aspect of the present invention, in the first aspect, the rotation speed range of the second step is a rotation speed range having the translational mode component and the conical mode component. be.

A third aspect of the present invention provides a method for balancing a rotating body according to the first or second aspect, in which the rotating body is provided with a structure in which the rigidity of the bearing portion is reduced so that the critical speed is reduced. It has a built-in structure.

A method for balancing a rotating body according to a fourth aspect of the present invention is a mode having the translational mode component, the conical mode component, the first-order bending mode component, and the second-order bending mode component in the above-mentioned third aspect. occurs below the actual operating speed.

In the method for balancing a rotating body according to a fifth aspect of the present invention, in the third or fourth aspect described above, the bearing portion is provided with an elastic body.

In the method for balancing a rotating body according to a sixth aspect of the present invention, in any one of the first to fifth aspects described above, the rigidity of the elastic body attached in series to the bearing part is 50% or less of the rigidity of

A method for balancing a rotating body according to a seventh aspect of the present invention is a method for balancing a rotating body according to any one of the first to sixth aspects described above, in which the translational mode component, the conical mode component, and the bending primary mode component are and (N+2) correction surfaces corresponding to the bending secondary mode components.

A rotating body balancing method according to an eighth aspect of the present invention is, in any one of the first to seventh aspects described above, in the second step, the mounting of the heavy object and the low-speed balancing process are performed. Execute multiple times.

A method for balancing a rotating body according to a ninth aspect of the present invention is a method for balancing a rotating body according to any one of the first to eighth aspects described above, in which, in the first step, at least a part of the heavy object is attached. Then, the balance processing in the high rotational speed range is executed.

According to the method for balancing a rotating body according to the present invention, it is possible to improve the correction effect while suppressing an increase in cost.

FIG. 1 is a diagram schematically showing a turbine rotor to which a rotating body balancing method according to a first embodiment of the present invention is applied. FIG. 2 is a flowchart for explaining a method for balancing a rotating body according to the first embodiment of the present invention. FIG. 3A is a diagram for explaining a method for balancing a rotating body according to the first embodiment of the present invention. FIG. 3B is a diagram for explaining a method for balancing a rotating body according to the first embodiment of the present invention. FIG. 3C is a diagram for explaining a method for balancing a rotating body according to the first embodiment of the present invention. FIG. 4 is a flowchart for explaining a method for balancing a rotating body according to a second embodiment of the present invention. FIG. 5 is a flowchart for explaining a method for balancing a rotating body according to a third embodiment of the present invention. FIG. 6 is a diagram for explaining a critical map of a turbine rotor according to an embodiment of the present invention. FIG. 7 is a diagram schematically showing a turbine rotor to which a rotating body balancing method according to a fourth embodiment of the present invention is applied. FIG. 8 is a diagram illustrating an example of turbine rotor imbalance according to a specific example of the embodiment of the present invention. FIG. 9A is a graph showing the calculation results of the vibration displacement at the first measurement point before and after the low-speed balance correction of the single rotor in an example of unbalance of the turbine rotor according to the embodiment of the present invention. FIG. 9B is a graph showing the vibration displacement at the second measurement point before and after low-speed balance correction of the single rotor in an example of unbalance of the turbine rotor according to the embodiment of the present invention. FIG. 10A shows the vibration displacement at the first measurement point after high-speed balance correction of a single rotor, after attachment of a heavy object, and after removal of a spring in an example of unbalance of a turbine rotor according to an embodiment of the present invention. This is a graph showing. FIG. 10B shows the vibration displacement at the second measurement point after high-speed balance correction of a single rotor, after attachment of a heavy object, and after removal of a spring in an example of unbalance of a turbine rotor according to an embodiment of the present invention. This is a graph showing. FIG. 11A is a graph illustrating modal components during vibrational displacement before low speed balancing in an example of turbine rotor imbalance according to an embodiment of the invention. FIG. 11B is a graph illustrating the modal components in vibrational displacement after low speed balancing in an example of turbine rotor imbalance according to an embodiment of the present invention. FIG. 11C is a graph illustrating modal components during vibrational displacement before high speed balancing in an example of turbine rotor imbalance according to an embodiment of the invention. FIG. 11D is a graph illustrating the modal components during vibrational displacement after a low-speed balancing process after installing a heavy object in an example of turbine rotor imbalance according to an embodiment of the present invention. FIG. 11E is a graph illustrating the modal components in the vibrational displacement after performing a low speed balancing process in an example of turbine rotor imbalance according to the prior art. FIG. 12 is a flowchart for explaining a conventional method for balancing a rotating body.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In addition, in all the figures of the following embodiment, the same code|symbol is attached to the same or corresponding part. Furthermore, the present invention is not limited to the embodiments described below.

First, in order to facilitate understanding of the present invention, problems with the prior art and intensive studies conducted by the present inventor regarding the problems with the prior art will be described. FIG. 12 is a flowchart for explaining a conventional method for balancing a rotating body. As shown in FIG. 12, in the conventional method for balancing a rotating body, in step ST101, a heavy object is attached to a rotor as a rotating body. Next, the process moves to step ST102 and low-speed balance processing is executed. Subsequently, the process moves to step ST103 and high-speed balance processing is executed. The conventional method for balancing a rotating body includes only step ST100, in which a heavy object is attached to the rotor and then balancing is performed in the assembled state.

In the prior art method for balancing a rotating body, as in step ST100, the balancing process is performed in an assembled state after a heavy object such as a turbine rotor blade is attached to the rotor. Therefore, the size of the chamber in which the rotary machine is stored during rotation needs to be sized in consideration of the diameter of the heavy object.

Here, in the low-speed balance process in step ST102, the rotational speed of the rotor is usually lower than the actual operating rotational speed, for example, about several hundred times per minute. Therefore, processing devices such as a drive motor and a chamber used for low-speed balance processing can be cheaper and simpler in structure than processing devices such as a drive motor and a chamber used for high-speed balance processing. Depending on the conditions when executing the low-speed balance process, it may not be necessary to evacuate the chamber, and furthermore, the chamber itself may not be necessary.

In the low-speed balance process, two balance weight mounting correction surfaces provided near both ends of the rotor are used. Here, the vibration modes that can be suppressed in the low rotation speed range are two modes: a translation mode (parallel mode) and a tilt mode (conical mode). Since both of the modes are modes in which both ends of the rotor swing, low-speed balance processing can be performed by using the two balance weight attachment correction surfaces provided near both ends of the rotor.

On the other hand, in the high-speed balance process in step ST103, the rotational speed of the rotor is usually increased to about the actual operating rotational speed or to a level equivalent to the actual operating rotational speed. Therefore, when performing high-speed balance processing, it is necessary to store the rotating machine in a chamber and evacuate the inside of the chamber. Furthermore, in order to drive the rotor to a high rotational speed range, a motor that is more expensive than the drive motor used for low-speed balance processing is required as a drive motor.

In high-speed balance, modes (N) including many bending components are added to vibration suppression targets. Therefore, the (N+2) plane is used as the balance weight attachment correction plane. The N-plane balance weight mounting correction surface added for high-speed balance is the part that becomes the antinode of the vibration mode.For example, if it is in the primary bending mode, it is easier to obtain a balance effect if it is installed in the center of the rotor. Become.

Furthermore, high-speed balance processing is also executed with a heavy object attached to the rotor. Therefore, attachment of the N side of the balance weight attachment correction surface added in the high-speed balance process is more difficult than the two sides used in the low-speed balance process. For example, if the spacing between the blade rows is narrow, the balance weight cannot be attached because it is obstructed by the already attached blade rows, so the area near the center of the rotor may not be able to be used as a correction surface.

Furthermore, high-speed balance processing requires operation in a high rotational speed range equivalent to the actual operating rotational speed. In an assembled state where a heavy object such as a turbine rotor blade is attached, the outermost diameter of the rotating machine is often determined by the diameter of the tip of the final stage of the turbine blade row. Therefore, the assembled rotor requires a larger chamber than a single rotor. When maintaining balance in an assembled state with turbine rotor blades attached, the rotational load due to the turbine rotor blades becomes large even when rotating in the atmosphere. Therefore, in order to drive the assembled rotor, it is necessary to increase the size of the processing device including the drive motor etc. in proportion to the size of the assembled rotor.

In this way, an assembled rotor is closer to the final stage than a single rotor, and is almost similar to the actual product, so it is thought that it is easier to achieve a balance effect, but on the other hand, the burden of handling increases and the processing equipment also becomes larger. There's a problem. Furthermore, when a heavy object such as a turbine rotor blade is attached to the rotor, a problem arises in that the positions where vibration displacement can be measured and the positions where the balance weight can be attached are limited.

Therefore, the present inventor conducted various experiments and studies regarding a method for balancing a rotating body that includes at least two bearings, a rotor, and a heavy object attached to the rotor. The present inventor then developed a method for rotating a rotor in a single state with no heavy object attached to it until a mode having a translational mode component, a conical mode component, a bending first mode component, and a bending second order mode component occurs. A first step in which a balance process is performed depending on the speed, and a second step in which a low-speed balance process is performed on the rotor in a rotation speed range lower than the rotation speed in the first step in an assembled state with a heavy object attached to the rotor. We devised a balance method that includes . According to the inventor's study, by including the first step and the second step, the unbalance between the rigid body component and the bending component of the single rotor is reduced in the first step, and the unbalance in the first step is reduced. In the second step, it is possible to reduce the unbalance of the rigid body component caused by the attached heavy object in the assembled state. The embodiment described below was devised based on the above study by the present inventor.

FIG. 1 is a schematic diagram showing a turbine rotor to which a rotating body balancing method according to a first embodiment of the present invention is applied. In the embodiments described below, a turbine rotor will be described as a rotating body, but the rotating body is not limited to a turbine rotor, and any rotating machine to which the present invention is applicable can be used as a rotating body. It is. Further, in the following figures, the longitudinal direction of the rotor is defined as the axial direction, and the direction perpendicular to the axial direction is defined as the radial direction.

As shown in FIG. 1, a rotor 11, which is a rotor axis of a turbine rotor 1, is provided with at least one, preferably a plurality of disks 12 along the axial direction, for attaching a heavy object such as a turbine rotor blade. ing. A bearing 13 and a frame 14 for fixing the bearing 13 are provided near both shaft ends of the rotor 11, respectively. The pedestal 14 supports the rotor 11 in the radial direction. A balance weight mounting groove 15 is selectively formed in the disk 12 of the rotor 11. In the example shown in FIG. 1, balance weight mounting grooves 15 are formed in the disk 12 at three locations in total.

In this embodiment, the minimum number of correction surfaces used for attaching the balance weight is two in the low-speed balance process and three in the high-speed balance process. The balance weight attachment groove 15 is provided in a portion where attachment work is possible. In this case, in conventional balance processing, heavy objects such as attached turbine rotor blades may become a constraint on the work. Further, if the distance between the correction surfaces of the disk 12 in the axial direction is short, it may be difficult to obtain a sufficient balance correction effect on each surface. On the other hand, increasing the distance between the disks 12 for balance processing results in an increase in cost. In this embodiment, in consideration of the above points, a total of two surfaces of the disk 12 at or near the outermost end of the rotor 11 and near the central portion of the rotor 11 along the axial direction, It is preferable to select one surface having a space in the axial direction as the balance surface.

FIG. 2 is a flowchart for explaining a method for balancing a rotating body according to the first embodiment of the present invention. 3A, 3B, and 3C are diagrams each schematically showing a turbine rotor for explaining the method for balancing a rotating body according to the first embodiment.

As shown in FIG. 2, in the first embodiment, first, in step ST1, a balance process is performed with the rotor 11 in a single state. Thereafter, in step ST2, a balance process is performed in the assembled state after the heavy object is attached to the rotor 11.

Step ST1 as the first step includes a step ST11 in which low-speed balance processing is performed on the single rotor 11 as shown in FIG. 3A, and a step in which high-speed balance processing is performed following step ST11 as shown in FIG. 3B. ST12. In addition, in the low-speed balance process in step ST11, as shown in FIG. 3A, it is possible to use a column 17 for low-speed balance process instead of the bearing 13.

As shown in FIG. 2, step ST2 as the second step includes step ST21 of attaching the heavy object 18 to the rotor 11, and step ST22 of performing low-speed balance processing. In addition, in the low-speed balance process, it is possible to use the support column 17 for low-speed balance process in place of the bearing 13, similarly to step ST11.

As shown in FIG. 2, the method for balancing the turbine rotor 1 according to the first embodiment starts with a step ST1 in which a balancing process is performed with the rotor 11 in a single unit state. First, the balance process in step ST1 can suppress the rigid body mode component during vibration displacement by performing low-speed balance process on the single rotor 11 in step ST11. Second, by performing high-speed balance processing in step ST12, bending mode components during vibration displacement can be suppressed.

In the execution stage of step ST1, the unbalance of the rigid body mode of the rotor 11 as a single unit can be made almost 0, and the unbalance of the elastic mode can be made almost 0. That is, an actual machine equipped with an actual turbine rotor 1 is in a highly balanced state (hereinafter referred to as a highly balanced state) over the entire range of actual rotational speeds. In this way, the feature of the balancing method according to the first embodiment is that the altitude balance state of the rotor 11 in a single unit state is achieved before the work of attaching a heavy object.

In the next step ST2, a heavy object attachment operation is performed in which various heavy objects are attached to the rotor 11. In step ST2, it is confirmed that the unbalance of the additional object is approximately 0 by executing a low-speed balance process for each attachment of the heavy object. This maintains the above-mentioned altitude balance state after assembly. That is, after the balance process is performed on the rotor 11 in step ST1, the process moves to step ST2. By step ST2, the rigid body mode component during vibration displacement can be suppressed.

The method for balancing the turbine rotor 1 according to the first embodiment is particularly effective when the single rotor 11 contains a large amount of unbalance that is a pure bending component of vibration displacement. In this case, if the bending mode component during vibration displacement can be suppressed in step ST1, there is no need to suppress the bending mode component in the next step ST2, and therefore balance processing in the high rotational speed range becomes unnecessary.

(Second embodiment)
Next, a method for balancing a rotating body according to a second embodiment of the present invention will be described. FIG. 4 is a flowchart for explaining a method for balancing a rotating body according to the second embodiment.

The flowchart shown in FIG. 4 is a flowchart specifying in more detail the low-speed balance process and the high-speed balance process in the rotating body balance method according to the first embodiment described above. In the method for balancing a rotating body according to the second embodiment, similarly to the first embodiment, there are steps ST1 in which a balance process is performed using the rotor 11 in a single state, and a balance process is performed after a heavy object is attached to the rotor 11. It consists of step ST2.

In step ST1, after executing the low-speed balance process in step ST11, the high-speed balance process in step ST12 is executed. Furthermore, step ST11 in which the low-speed balance process is executed in step ST1 is comprised of step ST111 in which vibration is measured in a low rotation speed range, and step ST112 in which a balance weight is attached after step ST111. Further, the high-speed balance processing in step ST12 includes step ST121 in which vibration is measured in a high rotation speed range, and step ST122 in which a balance weight is attached after step ST121.

In the balance method according to the second embodiment, similarly to the first embodiment, the process moves to step ST2 after execution of step ST1. In step ST2, similarly to the first embodiment, first, in step ST21, a task of attaching a heavy object to the rotor 11 is performed. Next, the process moves to step ST22. In step ST22, low-speed balance processing is executed, and specifically includes step ST221 in which vibration is measured in a low rotation speed range, and step ST222 in which a balance weight is attached after step ST221.

Note that if the vibration displacement measured in the low-speed balance process and the high-speed balance process described above is sufficiently small, that is, if the rotor 11 is in the high balance state, the process of attaching the balance weights (steps ST122 and ST222) may be omitted. can. Note that the same applies to the following explanation, but the explanation each time will be omitted.

Even in the second embodiment described above, after sequentially executing the low-speed balance process and the high-speed balance process, a heavy object is attached to the rotor 11 and the low-speed balance process is executed, which makes it different from the first embodiment. A similar effect can be obtained.

(Third embodiment)
Next, a method for balancing a rotating body according to a third embodiment of the present invention will be described. FIG. 5 is a flowchart for explaining a method for balancing a rotating body according to the third embodiment.

As shown in FIG. 5, the method for balancing a rotating body according to the third embodiment includes a step ST1 in which a balancing process is performed using the rotor 11 as a single unit, and a step ST3 in which balancing is performed after a heavy object is attached to the rotor 11. It consists of Note that step ST1 is the same as in the first or second embodiment.

In the method for balancing the turbine rotor 1 according to the third embodiment, after performing the balancing process in step ST1, the process moves to step ST3. Step ST3 consists of step ST31 of attaching a heavy object to rotor 11, step ST32 of performing low-speed balance processing, and step ST33 of judgment processing for repeating steps ST31 and ST32 a predetermined number of times (X times). . That is, steps ST31 and ST32 in step ST3 are configured to repeat the heavy object attachment process and the low-speed balance process X times. Note that X times is preferably 2 times or more and less than half of the total number of heavy objects (2≦X≦total number of heavy objects/2).

Thereby, with respect to the possibility of occurrence of unbalance due to attaching a heavy object to the rotor 11, the unbalance caused by the heavy object can be suppressed more carefully in step ST3. In particular, if X times is set to half the total number of heavy objects (X=total number of heavy objects/2), the bending mode component during vibration displacement can be theoretically reduced to approximately 0. Therefore, compared to step ST2 according to the first and second embodiments, the vibration displacement after performing step ST3 not only reduces the rigid body mode component but also suppresses an increase in the bending mode component.

FIG. 6 is a diagram for explaining an example of the critical map of the turbine rotor shown in FIG. In FIG. 6, the horizontal axis is the spring constant [kN/mm], and the vertical axis is the rotation speed [rpm] or frequency [Hz]. The critical map shown in FIG. 6 shows the natural frequencies of the first-order mode M1, the second-order mode M2, and the third-order mode M3. The values of the natural frequencies of these primary mode M1, secondary mode M2, and tertiary mode M3 all change depending on the spring constant. In the example shown in FIG. 6, the secondary mode M2 in particular changes greatly depending on the spring constant. Such characteristics vary depending on the product specifications of the turbine rotor 1. For example, in the critical map of the drive turbine rotor described in Non-Patent Document 1, the secondary mode M2 changes greatly depending on the spring constant.

As shown in FIG. 7, when the spring constant during actual machine operation is B1, the natural frequency R11 of the primary mode M1 and the natural frequency R12 of the secondary mode can be derived. In the example of FIG. 6, assuming the rated rotational speed FR, it can be seen that the natural frequency R11 of the primary mode M1 is sufficiently low, and the natural frequency R12 of the secondary mode M2 is somewhat high. Note that the vibration displacement component of the first-order mode M1 has only a translational mode component when the spring constant is 0 kN/mm, and only has a first-order bending mode component when the spring constant is infinite. When the spring constant is outside these ranges (0<spring constant: finite value), the proportion of the first-order bending mode component during vibration displacement increases as the spring constant increases. Similarly, the vibration displacement component of the secondary mode M2 has only the tilt mode component when the spring constant is 0 kN/mm, and has only the bending secondary mode component when the spring constant is infinite. Become. When the spring constant is outside these ranges (0<spring constant: finite value), the proportion of the second-order bending mode component during vibration displacement increases as the spring constant increases.

From these facts, in the case of a turbine rotor with a critical map as shown in Fig. 6, if the rigid body mode components (translational mode, tilt mode) and bending mode components (first-order bending mode, second-order bending mode) are suppressed, Vibration displacement can be suppressed in the high rotation speed range equivalent to the rated rotation speed without depending on the spring constant. In this case, if N+2 (=2+2=) four surfaces are used as the number of correction surfaces (N+2), vibration displacement can be effectively suppressed (see Non-Patent Document 2).

Here, when the natural frequency R12 of the secondary mode M2 is close to the rated rotational speed FR, vibrations due to the secondary mode M2 occur in the turbine rotor 1 at the rated rotational speed. In this case, if the engine cannot be operated at the peak rotational speed of the natural frequency R12 of the secondary mode M2 or at a rotational speed near the peak rotational speed, there is a possibility that vibrations caused by the secondary mode M2 cannot be suppressed. Therefore, the inventors of the present invention have conducted extensive studies on this problem and have devised a method to solve the problem as follows. This balancing method will be explained in the fourth embodiment below.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. FIG. 7 is a diagram schematically showing a turbine rotor to which a rotating body balancing method according to a fourth embodiment of the present invention is applied. As shown in FIG. 7, in a turbine rotor 1A according to the fourth embodiment, a bearing 13 is connected to a pedestal 14 via a spring 16. A spring 16 is attached to the bearing 13 in series. Here, the rigidity of the spring 16 is preferably 50% or less of the rigidity of the bearing 13. At this time, in the critical map shown in FIG. 6, the spring constant decreases. Specifically, for example, when the spring constant shown in FIG. 6 decreases to spring constant B2, the critical speed (rotation speed) of the primary mode M1 decreases to the natural frequency R21, and the critical speed of the secondary mode M2 decreases to the natural frequency R21. It drops to R22. In this manner, by appropriately selecting the spring 16, it is possible to balance the primary mode M1 and the secondary mode M2 at a rotation speed lower than the actual operating rotation speed.

Here, in order to properly balance the turbine rotor 1A, it is desirable to create a quantitative critical map in advance based on calculations and actual measurements of similar machines. Although the spring 16 is an elastic body used for balance in a high rotation speed range, it is also possible to use the spring 16 in a low rotation speed range. For example, in a facility that performs a balancing method, low-speed balance processing for the single rotor 11, high-speed balance processing for the single rotor 11, and low-speed balance processing after attaching a heavy object are performed in the same equipment. Now, it is also possible to perform these balancing processes using the spring 16.

Further, in the turbine rotor 1A shown in FIG. 7, balance weight mounting grooves 15 are formed on four sides. These four planes are necessary for (N+2) plane balance. Specifically, for example, in low-speed balance processing, the two surfaces of the outermost disk 12 along the axial direction of the rotor 11 are , the central portion, specifically the two surfaces of the disks 12 on both sides of the central disk 12, are used. In the fourth embodiment, the (N+2) plane balance is performed on the single rotor 11 before attaching heavy objects such as turbine rotor blades. The options for correction will be larger. The same applies to measurement, and there is no need to limit measurement to shaft ends, bearings, and their vicinity, as in the prior art.

(Example)
Next, an example of unbalance of a turbine rotor according to a specific example for explaining the effects of the embodiment of the present invention described above will be described. FIG. 8 is a diagram illustrating an example of turbine rotor imbalance according to an example of an embodiment of the present invention. Furthermore, an example of regulations regarding shaft vibration is JIS B 8101 general specifications for steam turbines.

As shown in FIG. 8, a total of four unbalances P ₁ , P ₂ , P ₃ , and P ₄ are arranged in the axial direction. The amount of imbalance is shown in Table 1 below.

Regarding this example, the effects of the embodiment will be explained through calculations. In this embodiment, the spring constant of the bearing 13 is constant regardless of the rotational speed and is isotropic. The balance correction positions are two planes (correction planes 25 and 26) in the low-speed balance process, and four planes (the correction planes 21, 22, 23, and 24) in the high-speed balance process. The vibration displacement meter side points are measured at the first measurement point 31 and the second measurement point 32. The peak rotational speed (critical speed) of each mode in the turbine rotor 1B according to this embodiment is approximately 50% of the rated rotational speed in the primary mode M1, and approximately 130% of the rated rotational speed in the secondary mode M2. It exists nearby.

9A and 9B show, respectively, before and after execution of the low-speed balancing process (step ST11) of the rotor 11 in a single state at the first measurement point 31 and the second measurement point 32 of an example of unbalance caused by the turbine rotor 1B according to the embodiment. This is the result of vibrational displacement. In FIGS. 9A and 9B, the rotation speed on the horizontal axis is normalized by the rated rotation speed, and the vibration displacement on the vertical axis is normalized by the maximum vibration displacement before low-speed balance processing. In this embodiment, a spring is used as the spring 16, which is set so that the peak rotational speeds of the primary mode M1 and the secondary mode M2 are sufficiently lower than the rated rotational speed. It can be seen from FIGS. 9A and 9B that by executing the low-speed balance process, the vibration displacement is reduced to about 1/20 or more and 1/6 or less.

FIGS. 10A and 10B show the state after execution of the high-speed balancing process (step ST12) of the single rotor 11 at the first measurement point 31 and the second measurement point 32 in an example of unbalance caused by the turbine rotor 1B according to the embodiment, respectively. This is the result of vibration displacement during the low-speed balance process (step ST22) after the heavy object 18 is attached, which is the final state.

It can be seen from FIGS. 10A and 10B that the vibration displacement is reduced to nearly 1/100 by the high-speed balance process. After that, when the heavy object 18 is attached to the disk 12 of the rotor 11, the peak rotation speeds in the primary mode M1 and the secondary mode M2 increase, and only the peak of the primary mode M1 is within the calculation range. In this case, the peak of the primary mode M1 becomes even smaller, and it can be seen that the effect of achieving balance in the single rotor 11 is maintained. In addition, in the high rotational speed range, it seems that the vibration displacement tends to increase due to the influence of the secondary mode M2, but it was confirmed that the vibration displacement is sufficiently small even in this case.

11A, FIG. 11B, FIG. 11C, and FIG. 11D show changes in mode components during vibrational displacement in an example of unbalance of the turbine rotor 1 according to the present embodiment. FIGS. 11A and 11B are before and after execution of the low-speed balance process in step ST11, respectively. FIG. 11C shows the state before execution of the high-speed balance process in step ST12. FIG. 11D shows the state after execution of the low-speed balance process in step ST22. FIG. 11E shows changes in mode components during vibrational displacement after execution of step ST102 in an example of unbalanced turbine rotor according to the prior art. In FIGS. 11A to 11E, the horizontal axis represents the components of translation mode δp, conical mode δΘ, first-order bending mode Φ1, second-order bending mode Φ2, and third-order bending mode Φ3, and the dimensionless amplitude on the vertical axis is shown in FIG. 11A. This is the amplitude normalized by setting the value of the first-order bending mode Φ1 shown in 1 to 1.

From FIG. 11A, it can be seen that the vibration displacement in the rotor 11 before the balance processing (before step ST11 is executed) includes components of all modes other than the tertiary bending mode Φ3. After that, when the low-speed balance process is executed (after execution of step ST11), it can be seen from FIG. 11B that the translational mode δp and conical mode δΘ, which are unbalanced rigid body components, are almost suppressed. When the high-speed balance process is subsequently executed (after execution of step ST12), it can be seen from FIG. 11C that the components of the unbalanced first-order bending mode Φ1 and second-order bending mode Φ2 are also suppressed. Furthermore, even if the heavy object 18 is attached to the rotor 11 in this state, it can be seen from FIG. 11D that the values of each mode component do not change significantly.

On the other hand, it can be seen from FIG. 11E that after execution of the low-speed balance process according to the prior art (after execution of step ST102), the mode components are almost the same as those in FIG. 11B. From these facts, it can be seen that in order to reduce the bending mode component, the balancing work should be performed at a rotation speed at which a mode having a bending mode occurs.

According to the embodiment described above, in the first step, the rotor alone is operated in a high rotation speed range, but since heavy objects such as turbine rotor blades are not attached, the operating equipment is operated at normal high speeds. This can be done with something smaller and cheaper than a balance, which prevents an increase in costs. In addition, since there is a high degree of freedom in selecting positions for the balance weight mounting correction surface and vibration displacement measurement points, higher balance effects can be expected in terms of accuracy.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the technical idea of the present invention. For example, the numerical values given in the above-described embodiments are merely examples, and different numerical values may be used as necessary.

That is, the present invention can be applied to all rotating bodies and rotating machines that can obtain the effects intended by the present invention, as long as they have the configuration intended by the present invention. For example, the shape of the turbine rotor is not limited to the disk shape shown in FIG. 1, but may also have a structure in which the turbine rotor blades are attached by machining concave grooves in the rotor. Further, a plurality of heavy objects may be attached in advance in high-speed balance processing in a high rotation range performed on a single rotor on the condition that the balance processing is not affected by equipment, measurement, etc. For example, the present invention can be similarly applied to a turbine front stage where the blade length is short and a large load is not applied during rotation without affecting the installation of the balance weight.

The present invention also includes configurations in which the constituent elements of each embodiment and each modification example described above are combined as appropriate. Moreover, further effects and modifications can be easily derived by those skilled in the art. The broader aspects of the invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various changes may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

1, 1A, 1B Turbine rotor 11 Rotor 12 Disk 13 Bearing 14 Frame 15 Balance weight mounting groove 16 Spring 17 Support column 18 Heavy object 21, 22, 23, 24, 25, 26 Correction surface 31 First measurement point 32 Second measurement point

Claims (9)

A method for balancing a rotating body comprising at least two bearings, a rotor, and a heavy object attached to the rotor, the method comprising:
A first step of performing a balancing process on the single rotor in a high rotational speed range until a mode having a translational mode component, a conical mode component, a first-order bending mode component, and a second-order bending mode component is generated;
a second step of performing low-speed balance processing on the rotor in a rotational speed range lower than the rotational speed of the first step in an assembled state in which the heavy object is attached to the rotor; Balancing a rotating body; Method. The method for balancing a rotating body according to claim 1, wherein the rotational speed range in the second step is a rotational speed range having the translational mode component and the conical mode component. The method for balancing a rotating body according to claim 1, wherein the rotating body has a structure in which a structure in which the rigidity of the bearing portion is reduced and a critical speed is reduced. 4. The method for balancing a rotating body according to claim 3, wherein a mode having the translational mode component, the conical mode component, the first-order bending mode component, and the second-order bending mode component is generated at an actual operating rotation speed or lower. The method for balancing a rotating body according to claim 3, wherein the bearing portion is provided with an elastic body. The method for balancing a rotating body according to claim 5, wherein the elastic body attached in series to the bearing section has a rigidity of 50% or less of the rigidity of the bearing section. The method for balancing a rotating body according to claim 1, wherein (N+2) correction surfaces are used, each corresponding to the translational mode component, the conical mode component, the first-order bending mode component, and the second-order bending mode component. The method for balancing a rotating body according to claim 1, wherein in the second step, the attachment of the heavy object and the low-speed balancing process are executed multiple times. The method for balancing a rotating body according to claim 1, wherein in the first step, the balancing process in the high rotational speed range is executed with at least a part of the heavy object attached.

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