JPH01193004A - Steam turbine power generator - Google Patents

Abstract

PURPOSE:To eliminate twist exciting force and prevent any breakage of turbine blades by constituting the rotary shaft of a steam turbine power generator in such a way that the linked twist rotational frequency formed with those of the rotary shaft and a turbine long blade is not shifted from a frequency twice as much as the operation system frequency of a steam turbine power generator. CONSTITUTION:A coupling part 12 is provided on a journal part 11 located on the turbine shaft side of the rotary shaft 10 in a steam turbine power generator. A weight 13 for adjustment as an added weight, is fixed on a side surface opposite to a turbine shaft side of this coupling part 12. The weight of this weight 13 is set to such a weight as the node 16a of a twist oscillation mode 16 is located on the central part, in longitudinal direction, of a shaft part 14 with the coil of the power generator wound thereon. On the other hand, a journal part 15 is provided on the side opposite to the turbine shaft side on the rotary shaft 10, so that the diameter D1 is set larger than the diameter D2 of the journal part 11. Thereby, it is possible to hold the balance of the rigidity in an axial direction and mass with respect to the coupling part 12 provided on the journal part 11.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a steam turbine generator, and in particular, to a rotary shaft system for coupled torsional rotation motion between a rotary ring and a long turbine blade. This invention relates to a steam turbine generator with a structure that is difficult to damage.

(Prior Art) A rotating shaft system of a steam turbine generator is configured by alternately connecting a heavy rotor portion with a large diameter and a long shaft portion with a thin diameter. In the rotating shaft system of this steam turbine generator, excessive torque is generated in the rotating wheel system due to transient vibrations excited by power transmission system failures and subsequent high-speed reclosing circuits, and the repetition of this excessive torque causes the rotating shaft to Torsional fatigue may accumulate in the system. Such torsional imaging problems are treated as low-cycle fatigue of the journal section, coupling section, etc. due to the low-order shaft torsional vibration mode that occurs in the rotating shaft system, and a monitoring device has been developed to monitor the accumulation of such fatigue. has been used.

The above torsional vibration also causes the problem of coupling between the steam turbine generator shaft and the blades of the turbine represented by the final stage, and the fast-forming torsional vibration between the blades and shaft causes the generator reverse sequence current. The fluctuating torque at a frequency twice the system frequency generated by this causes torsional motion in the shaft system.

When torsional vibration occurs in the shaft system, the shaft and the shaft connected to this shaft work together while influencing each other, and when the fast-growing torsional natural frequency of the joint and shaft matches the double frequency loss of the system, a resonance phenomenon occurs. This may cause vibrations and damage the inside. The above system frequency is 501-1z in eastern Japan, so the double frequency that causes fluctuating torque is 100H2
On the other hand, in western Japan, the frequency is 60H2, so the double frequency that produces the fluctuating torque is 120Hz.

The above shaft torsional vibration mode is shown in FIG. Although it is shown in terms of torsion angular displacement, the high-pressure steam turbine (+-I P
> rotary shaft 1 and low pressure steam turbines (LP-A, LP
-B, LP-C) (7) Rotating shaft 2, 3°4 and generator (G
EN) are connected in a twisted mode in each direction, and the four 6 coupled to these rotating shafts also vibrate in a coupled manner, indicating that they vibrate in the torsional direction. Torsional vibration of only the shaft does not affect the blade, and only the torsional vibration of the shaft is shown on the mode diagram.

There are 211 types of vibration modes of 116 as shown in Figs. 6 and 7. One is the in-phase mode (Fig. 6) that generates torsional vibration in the same direction as the torsional direction of the shaft 4, and the other is the in-phase mode (Fig. This is an anti-phase mode (FIG. 7) in which FJ6 causes torsional vibration in a direction opposite to the torsional direction of No. 4. In other words, the natural frequency in the torsional direction as vibration 6 is in principle one, but when the blade 6 and shaft 4 are coupled, it is expressed as two vibrations, an in-phase mode and an anti-phase mode, and the natural frequency is Two numbers will appear as moving numbers.

Since this vibration occurs in proportion to the number of long blades 6 that move in conjunction with the shaft 4, the number of vibrations that should be considered in design is small, 111
443! Due to the structure of the steam turbine generator, the torsional vibration frequency is likely to be approximately twice the system frequency.

Further, as shown in FIG. 8(a), the node 7a of the vibration mode 7 on the rotating shaft 5 of the steam turbine generator is as shown in FIG. 8(b).
As shown in the figure, if the rotating shaft 5 is located away from the center in the longitudinal direction of the shaft around which the coil is wound, the vibration mode that cancels the excitation force in the longitudinal direction when the rotating shaft 5 is torsionally excited becomes symmetrical. As a result, a resonance phenomenon occurs and the rotating shaft 5
Large torsional vibrations occur. As a result, the vibration response stress 8 within the turbine increases as shown in FIG. 9, leading to fatigue damage to the turbine blades.

On the other hand, the negative sequence current of the generator generates an unbalanced electric torque, which causes the generator shaft to twist and vibrate. This negative-sequence current flows even during normal operation, and its value as unbalanced torque is about 2 to 3% of the rated transmission torque, but since this is a problem dealing with a resonance phenomenon, and the damping is small, the blade shaft speed formation torsion If the frequency resonates at twice the system frequency, there is a risk of damage to other components.

(FF, the problem that Akira is trying to solve) As mentioned above, the basic design is to prevent the blade shaft coupled torsional frequency from resonating with twice the system frequency, and the design of the shaft of the steam turbine generator is In addition to the design of engineering 1 and the long turbine blades, it is necessary to consider the vibration design after coupling, making the design extremely complicated.

Also, depending on the model, due to problems with vibration analysis accuracy, a design with at least ±3 Hz VI degree detuning is required for analysis, so it is not possible to design with a large detuning, and it is necessary to design with resonance in mind. Furthermore, the design becomes more complicated.

The present invention has been made in view of the above points, and the nodes of the torsional vibration mode in the generator shaft section are set to pass through approximately the center in the longitudinal direction of the generator shaft, and the torsional excitation force is transmitted by the torsional 16 lh mode. Ki 1! An object of the present invention is to provide a steam turbine generator in which damage to turbine blades is eliminated.

[Structure of the invention]

(Means for Solving the Problems) The steam turbine generator of the present invention has a rotating shaft of the steam turbine generator whose coupled torsional rotational frequency between the rotating shaft and the turbine long blade is equal to the operating system frequency of the steam turbine generator. In addition to maintaining a configuration that does not deviate from the double frequency, the journal diameter on the turbine side of the generator shaft is set so that the vibration node in the torsional vibration mode of the generator shaft is located at the longitudinal center of the shaft around which the generator coil is wound. The diameter of the journal is smaller than that of the opposite journal.

(Function) In the steam turbine generator of the present invention, even if the coupled torsional natural frequency of the rotating shaft and the long turbine blade resonates with a frequency twice the system frequency, the vibration node in the torsional vibration mode of the generator shaft is designed to be positioned δ at the longitudinal center of the shaft around which the generator coil is wound, so the rotating shaft of the steam turbine generator torsionally vibrates in the opposite phase to the excitation direction of the resonance phenomenon. It becomes possible to suppress the resonance phenomenon dynamically, and the vibration response stress of the turbine blades is also reduced. Therefore, fatigue damage to the turbine blades can be effectively prevented.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 10 is a rotating shaft of a steam turbine generator, and a coupling portion 12 is provided on a journal portion 11 located on the turbine shaft side of this rotating shaft 10. As shown in FIG. An adjustment weight 13 as additional weight is fixed to the side surface of the coupling portion 12 on the side opposite to the turbine shaft side.

The weight of this adjustment weight 13 is set so that the node 16a of the torsional vibration mode 16 is located at the longitudinal center of the shaft portion 14 around which the coil of the generator is wound, as shown in FIG. ing. Further, as shown in FIG. 1, a journal portion 15 is provided on the opposite side of the rotating shaft 10 from the turbine shaft side.

The diameter D1 of the journal portion 15 is larger than the diameter D2 of the journal portion 11. The reason why the diameter D1 of the journal part 15 is made larger than the diameter D2 of the journal part 11 is to balance the axial rigidity and quality m with respect to the coupling part 12 provided in the journal part 11. .

On the other hand, the distance L1 from the end face of the journal part 11 of the rotating ring 10 to the longitudinal center of the shaft part 14 is smaller than the distance L2 from the end face of the journal part 15 of the rotating shaft 10 to the longitudinal center of the shaft part 14. It is set to be the value.

This is to match the longitudinal rigidity of the shaft portion 14 for obtaining electrical output to the vibration mode.

As shown in FIG. 2(b), the photographing mode 16 of the rotating shaft 10 is set so that the node 16a is located at the center in the longitudinal direction of the shaft portion 14 around which the coil of the generator is wound.

Even if a torsional excitation force acts on the rotating shaft 10, the rotating shaft 10 torsionally moves in an opposite phase to the excitation direction, which mechanically suppresses the resonance phenomenon. 1
0 means no vibration, and the vibration response stress 17 of the turbine blade has a value close to zero even at the resonance point, as shown in FIG.

Therefore, even if the coupled torsion natural frequency of the rotating shaft 10 and the long turbine blade (not shown) resonates with a frequency twice the system frequency, the turbine blade may suffer fatigue damage depending on the torsional vibration mode of the rotating shaft 10. I never receive it.

That is, by adopting the structure according to this embodiment, the separation W between the blade axis coupled torsional vibration frequency and the frequency twice the system frequency can be reduced without modifying the structure of the conventional turbine blade.
A highly reliable steam turbine generator can be obtained without carrying out strict design.

FIG. 4 shows another embodiment of the present invention, in which J3
In this case, a shrink-fit ring 18 is attached to the coupling part 12 provided on the journal part 11 of the rotating shaft 10 as an additional weight, and by changing the rigidity and texture of the coupling part 12 at the same time, the vibration mode can be changed. Is the node wrapped around the generator coil 1? It is located at the center in the longitudinal direction of the foot 81114.

In this embodiment as well, even if a torsional excitation force acts on the rotating shaft 10, the rotating shaft 10 torsionally vibrates in an opposite phase to the excitation direction, so resonance development is suppressed, and the rotating shaft 10 fatigue damage can be prevented in the same manner as in the previous embodiment.

Further, by appropriately adjusting the shape or mass of the shrink fit ring 18, the position of the vibration mode node of the steam turbine 5Q electric machine can be easily adjusted from the outside.

〔Effect of the invention〕

As described above, according to the present invention, the shaft system can be adjusted without changing the structure of the turbine blade and without sufficiently separating the blade-shaft coupled shear natural frequency and the frequency twice the system frequency. 1. I can design. The design can be simplified and the reliability of the steam turbine generator can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the rotating shaft of the steam turbine generator according to the present invention, and FIGS. 2(a) and 2(b) show the rotating shaft, the position of the rotating shaft, and the vibration mode, respectively. 3 is a diagram showing the relationship between the torsional vibration mode and the vibration response stress of the turbine blade. FIG. 4 is a diagram showing another embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the torsional vibration mode and the vibration response stress of the turbine blade. Figure 6 shows an example of the torsional vibration mode along with the position of the steam turbine generator. Figure 6 is a diagram showing the blade-shaft coupled torsional vibration mode in which the inner parts are in the same phase. Figure 7
The figure shows the blade-axis coupled torsional vibration mode when the blades are in opposite phase, and Figures 8(a) and 8(b) respectively show the rotation axis and
FIG. 9 is a diagram showing the relationship between the position of the rotating shaft and the vibration mode, and FIG. 9 is a diagram showing the relationship between the torsional vibration mode and the i-force response stress of the turbine blade. 1.2.3.4.5...rotation axis, 6...four, 7...
・Vibration mode, 7a... Node, 8... Vibration response stress,
10... Rotating shaft, 11... Journal part, 12...
・Coupling part, 13...Adjustment weight, 14・
...Shaft part, 15...Journal part, 16...
Torsional vibration mode, 16a... Node, 17... Vibration response stress, Dl. D2...Journal diameter. Applicant's agent Hisashi Hatano 1st (Bu) 16 Leather 2 Fig. shoulder straps ft5z> Brown 3 Fig. 4 Figure 9

Claims (1)

[Claims] The rotating shaft of the steam turbine generator is configured such that the coupled torsional rotation frequency between the rotating shaft and the long turbine blades does not deviate from twice the operating system frequency of the steam turbine generator, and the turbine side of the generator shaft A steam turbine power generation device characterized in that the journal diameter is made smaller than the journal diameter on the opposite side so that the vibration node in the torsional vibration mode of the generator shaft is located in the longitudinal center of the shaft around which the generator coil is wound. Machine.