JP2916336B2 - Steam turbine rotor vibration suppression device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for suppressing vibration of a rotor of a steam turbine used for power generation and industrial use.

[0002]

2. Description of the Related Art A steam turbine is a very important equipment for power generation and industrial use, and it is necessary to satisfy the technical requirements of high efficiency and high reliability. The former has recently become a strong demand not only from the perspective of saving fuel costs, but also from the standpoint of environmental protection. The most basic measure to satisfy this demand is to increase the efficiency of the steam cycle by increasing the pressure and temperature of the steam, and improvements from this point have been accumulated worldwide.
However, in a long-term operation, a rise in temperature naturally imposes severe operating conditions in terms of the strength of the material used. Therefore, in order to prevent this, a cooling technique is applied to a steam turbine.

FIG. 11 is a diagram showing a schematic configuration of a first stage section of a general steam turbine. A rotor 1 is constituted by an axle 2, a wheel 3, and a blade 4 mounted on the outer periphery of the wheel 3. Steam 6 passing through the nozzle 5
Passes through the blades 4, expands during this time, reduces the pressure and temperature, transmits torque to the rotor 1, and rotates the rotor 1.

The wheel 3 is provided at several positions in the circumferential direction with a balance hole 9 for communicating the downstream side and the upstream side of the paragraph, that is, the shell 7 and the central portion 8 of the rotor. A scoop 10 is provided on the shell 7 side, that is, on the blade outlet side.

[0005] However, a part of the steam, which has passed through the blades 4 and whose temperature has been lowered once, passes through the balance holes 9 to the shell 7.
From the side into the central part 8 of the rotor, which is upstream of the paragraph, and the central part 8 of the rotor is cooled. The steam that has cooled the central portion 8 of the rotor is supplied to the root portion 4 of the blade 4.
a and merges into the paragraph steam 6 again.

FIG. 12 is a view taken in the direction of arrows AA in FIG. 11, and all the scoops 10 are provided on the shell 7 side, that is, on the blade outlet side. FIG. 13 is a view showing the relationship between the balance holes 9 and the scoops 10 developed in the circumferential direction. The scoops 10 are mounted on the respective balance holes 9 on the rear side in the rotation direction R of the rotor. Therefore, scoop 10
Receives the dynamic pressure of steam due to the rotation of the rotor 1, generates a so-called pumping effect, and has an effect of promoting the flow of cooling steam from the shell 7 side to the center portion 8 side of the rotor.

[0007] As described above, the part of the steam on the side of the shell 7 having a low temperature is caused to flow back to the central portion 8 so that the cooling of the rotor 1 is uniformly performed over the entire circumference thereof, and the aging of the operation of the rotor at high temperatures. Embrittlement is prevented.

[0008]

On the other hand, the reliability of the latter has recently been required to be further improved from the viewpoint of stable power supply. By the way, one of the important factors influencing the reliability of a steam turbine which is a high-speed rotating machine is vibration of a rotor. There are various factors that cause this vibration, but the most typical one is imbalance. In recent years, the imbalance of the mass inside the rotor has become extremely small due to improvements in manufacturing accuracy and development of a balancing technique for eliminating imbalance. However, in a steam turbine, the internal steam temperature changes greatly due to the output generated, and the supporting conditions of the bearings that support the rotor also change. It is one.

That is, the cause of the imbalance that occurs in the rotor during operation of the steam turbine is classified into the following: imbalance remaining in the rotor at the time of manufacturing, and contact between the rotating part and the stationary part during operation. It can be broadly divided into unbalance and unbalance caused by unevenness of the physical properties of the rotor in the circumferential direction.

Incidentally, the unbalance remaining in the rotor at the time of manufacturing is caused by a processing error of the blades, a processing error of the rotor, and the like, but has become extremely small due to recent advances in manufacturing technology. Also, the removal of this imbalance can be achieved to a considerable extent, since the rotor of a steam turbine is usually finally rotated to the rated speed at the time of manufacture to correct the balance.

In addition, since steam turbines generally use high-pressure steam, in order to minimize leakage steam and to ensure a shaft seal to the outside of the steam turbine,
The radial gap between the rotating part and the stationary part is very small. Therefore, it is undeniable that the rotating part and the stationary part may cause slight contact (rubbing) during operation. In such a case, the temperature of only the contact portion becomes high, so that the temperature distribution becomes uneven inside the rotor in the circumferential direction. As a result, the entire rotor is bent by a very small amount. Increase the vibration. However, the imbalance caused by the contact between the rotating part and the stationary part can be prevented by setting an appropriate gap in consideration of even during operation.

However, even rotors manufactured using the latest steelmaking technology have completely uniform physical properties in the circumferential direction, that is, uniform thermal conductivity, specific heat, specific gravity, linear expansion coefficient, yank rate, and the like.
No rotor with Poisson's ratio, creep strength, etc. can exist. Generally, the rotor material of a steam turbine is an iron-based alloy, but Gr, Ni, and C are added in consideration of room temperature tensile strength, creep strength, toughness, elongation, drawing, and the like. In the steel making process, minute amounts of impurity elements such as Mn, S, P, and Sn also remain. Thus, segregation of these components, non-uniformity of the crystal structure, and the like result in physical properties of the rotor.

At room temperature (room temperature), such non-uniformity does not cause imbalance. However, since high-temperature steam flows into the steam turbine in the operating state, at this time, for example, the temperature distribution becomes non-uniform and the elongation increases. Non-uniformity or the like occurs, giving a small unbalance to the rotor.

FIG. 14 shows an axle 2, wheels 3 and blades 4.
FIG. 2 is a view showing the outer shape of a typical turbine rotor composed of: axles and wheels, most of which are manufactured as an integral structure due to recent advances in steelmaking technology. Since the imbalance due to the circumferential non-uniformity of the physical properties of the rotor occurs in the axle 2, a simple model of this portion is shown in FIG. FIG. 16 shows the result.

However, as shown in FIG. 16, when the temperature distribution is almost uniform and the axle 2 is heated by steam from the outer peripheral side, no imbalance occurs in the rotor. On the other hand, as shown in FIG. 18, for example, when the thermal conductivity has a typical temperature distribution when the upper half is large and the lower half is small, the temperature distribution becomes eccentric with respect to the rotation center of the rotor. The upper half has a relatively high temperature, the thermal expansion of the upper half is large, and the rotor as a whole becomes convex upward as shown in FIG. 17, causing imbalance.

Here, the imbalance caused by the non-uniformity of the thermal conductivity has been described, but the same applies to other physical property values in that the imbalance may occur.

Incidentally, since the internal steam temperature of the steam turbine changes according to its operation state (particularly the output to be generated), the steam imbalance changes according to the operation state. In particular, since the heat capacity of the rotor is much larger than that of steam, even if the temperature of the steam quickly becomes steady, it takes a considerably long time (several hours) for the temperature distribution inside the rotor to be steady. There is a problem that the imbalance continues and the vibration of the rotor becomes large.

However, at present, almost no countermeasures have been taken against such imbalance caused by the circumferential nonuniformity of the physical properties of the rotor.

In view of the foregoing, the present invention provides a vibration suppressing device that prevents imbalance that occurs transiently due to circumferential nonuniformity of the physical properties of a steam turbine rotor and the accompanying increase in vibration. The purpose is to:

[0020]

SUMMARY OF THE INVENTION The present invention is directed to a balance hole and / or a scoop in which a part of the steam at the blade outlet side, whose temperature has been reduced due to the heat drop due to the expansion of steam, flows back to the upstream side of the stage. Is arranged in the rotor in a non-uniform manner in the circumferential direction in response to the non-uniformity in the circumferential direction of the physical property value which causes deformation due to heat such as thermal conductivity in the turbine rotor, and the cooling action by the steam is performed. Are non-uniform in the circumferential direction.

The imbalance caused by the circumferential nonuniformity of the physical properties of the rotor is often reproducible with respect to the temperature change inside the turbine. It is often found at a very early stage, and with current vibration analysis technology,
It is not difficult to determine in which direction the rotor is unbalanced.

Therefore, by making the cooling effect of the steam non-uniform in the circumferential direction corresponding to the unbalance, the unbalance is caused by non-uniform temperature distribution due to non-uniformity of thermal conductivity, specific heat, specific gravity and the like. In this case, the temperature distribution can be made uniform, and imbalance can be eliminated.
In addition, when the imbalance is caused by non-uniform expansion of the rotor due to non-uniformity such as linear expansion coefficient,
Conversely, by making the temperature distribution non-uniform by the above-mentioned cooling, the elongation can be made uniform and the unbalance can be removed.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a view of the wheel of the turbine rotor 3 as viewed from the shell 7 side, and FIG. 2 is a view of the wheel 3 as viewed from the upstream side of the paragraph, that is, from the center portion 8 side. A plurality of balance holes 9a, 9b, 9c, 9d, 9e are formed at predetermined intervals in the circumferential direction to communicate with the rotor 8 and the central portion 8 of the rotor. On both surfaces of the wheel 3, scoop mounting grooves 20 extending in the circumferential direction on a radius line including the balance holes 9a,... Are formed. The scoop 10 is fixed only on the rear side of the rotor rotation direction R of 9a. on the other hand,
Scoop mounting groove 2 on the rotor center portion 8 side of the wheel 3
At 0, a scoop 10 is provided on the rear side of the rotor rotation direction R of each balance hole other than the balance hole 9a.

FIG. 3 is an enlarged sectional view of the wheel 3 including the scoop 10 and the balance hole 9, and FIG. 4 is a perspective view of the wheel 3. The scoop 10 has an opening at the balance hole 9a side, and the height gradually decreases. It has a box shape. FIG. 5 shows the relationship between the balance holes 9a, 9b,... And the scoop 10 expanded in the circumferential direction.

When the rotor 2 rotates in the direction of the arrow R, a dynamic pressure is applied to the scoop 10 on the side of the shell 7, and a pumping effect is generated due to the increase in the pressure, so that more cooling steam is caused to flow through the balance hole 9a. I do. On the other hand, the scoop 10 on the rotor central portion 8 side has balance holes 9b,.
The pumping effect acts on 9e in the opposite direction, and has the effect of suppressing the flow of cooling steam.

FIG. 6 is a diagram showing an expansion line in the well-known stage of the turbine. In the steam turbine, the nozzle 5 has a nozzle inlet pressure P _n1 to a nozzle outlet pressure P _n1.
The output is transmitted to the rotor by expanding to _n2 and further to the blade outlet pressure P #. Here, the degree of reaction is defined by blade heat drop hυ / total heat drop ht. Total heat drop h
t is the difference between the enthalpy at the nozzle inlet total pressure Pn and the enthalpy at the blade outlet pressure on the adiabatic line in consideration of the kinetic energy of the steam in the paragraph.

FIG. 7 is a diagram showing the distribution of the degree of reaction in the blade length direction. In a typical stage design of a steam turbine, the distribution of the degree of reaction is shown by the solid line in FIG. It has a positive distribution throughout. At this time, the nozzle outlet pressure P _n2 is higher than the blade outlet pressure Pυ over the entire area from the blade root to the blade tip, and the steam flows smoothly. However, when a paragraph design such as the reaction degree with cooling shown by the broken line in FIG. 7 is performed, the blade outlet pressure Pυ
_Has a pressure greater than the nozzle outlet pressure P _n2 in the blade route. Since this reversal of pressure is limited to a small area of the blade route, it does not reverse the entire flow in the paragraph, but produces a flow velocity of the steam flow near the blade route. Further, since the shell portion 7 and the central portion 8 are governed by the pressure at the blade route, in this case, the shell portion has a higher pressure than the central portion, expands inside the paragraph, and has a lower temperature. Flows through the balance holes 9a,... To the central portion as cooling steam, and cools the axle 2 and the wheel 3 in the central portion 8.

However, if the scoop 10 is mounted only on a specific balance hole as described above, the amount of steam passing through the balance hole will be uneven at each balance hole.

Therefore, for example, the temperature distribution becomes non-uniform due to the non-uniformity of the thermal conductivity, specific heat, specific weight, etc. of the rotor material in the circumferential direction. By allowing more cooling steam to flow through the balance hole close to the rotor, unbalance of the rotor and, consequently, vibration of the rotor can be suppressed. If the unbalance is caused by unevenness of the rotor elongation due to non-uniformity of the coefficient of linear expansion and the like, more cooling steam is circulated through the balance hole near the part where the elongation is large. And the imbalance can be eliminated.

That is, in the above embodiment, since there is much cooling steam from the balance hole 9a,
The cooling effect in the vicinity of “a” is large, and the imbalance generated in this vicinity can be removed.

Note that it is relatively easy to know at what angle the rotor becomes unbalanced transiently during the operation of the steam turbine by analyzing the vibration during the operation. Therefore, by calculating the angle of transient imbalance occurrence from the initial operation data of the steam turbine and applying this technology when disassembling the turbine for periodic inspection, etc., the rotor vibration is suppressed in subsequent operations. can do.

In the above embodiment, a scoop is provided only in a specific balance hole to make the flow of cooling steam non-uniform in the circumferential direction.
As shown in (1), the balance holes 9 themselves may be unevenly arranged in the circumferential direction. Further, as shown in FIG. 9, the area of each balance hole 9 may be made different, and as shown in FIG. 10, a part of the balance holes uniformly arranged in advance in the circumferential direction is closed by a closing member 21 so that the balance holes 9 are closed. May be made uneven in the circumferential direction.

However, in these embodiments, since the balance holes themselves become unbalanced, this amount needs to be separately corrected by a balance weight.

[0035]

As described above, according to the present invention, one or both of the balance hole and the scoop may be displaced in the circumferential direction of the rotor in response to the unbalance due to the circumferential nonuniformity of the physical properties of the turbine rotor. Since the cooling effect by the steam is uneven in the circumferential direction, it is possible to eliminate the imbalance caused by the unevenness of the physical properties of the turbine rotor due to the difference in the cooling effect. ,
The effect of suppressing the vibration of the rotor can be achieved.

[Brief description of the drawings]

FIG. 1 is a view of a balance hole and a scoop in a vibration suppression device of the present invention as viewed from a downstream side of a paragraph.

FIG. 2 is a view of a balance hole and a scoop in the vibration suppression device of the present invention as viewed from the upstream side of the paragraph.

FIG. 3 is an enlarged sectional view of a wheel including a scoop and a balance hole.

FIG. 4 is a perspective view of a scoop mounting portion.

FIG. 5 is a diagram showing a relationship between a balance hole and a scoop developed in a circumferential direction.

FIG. 6 is an expansion diagram in the paragraph of the turbine.

FIG. 7 is a diagram showing a distribution of a degree of reaction in a blade length direction.

FIG. 8 is a diagram showing another embodiment of the present invention.

FIG. 9 is a view showing still another embodiment of the present invention.

FIG. 10 is a diagram showing another embodiment of the present invention.

FIG. 11 is a diagram showing a schematic configuration of a first stage section of the general turbine.

FIG. 12 is a view taken in the direction of arrows AA in FIG. 11;

FIG. 13 is a diagram showing a relationship between a balance hole and a scoop in a conventional turbine developed in a circumferential direction.

FIG. 14 is a diagram showing an outer shape of a turbine rotor.

FIG. 15 is a diagram in which an axle portion of a rotor is simply modeled.

FIG. 16 is a temperature distribution diagram of a section taken along line DD in FIG. 15;

FIG. 17 is a modeling diagram showing a state where an axle portion is deformed.

FIG. 18 is a temperature distribution diagram of an EE section in FIG. 17;

[Explanation of symbols]

 Reference Signs List 1 rotor 2 axle 3 wheel 4 blade 7 shell 9a, 9a, ... 9e balance hole 10 scoop 21 closing member

Claims (1)

(57) [Claims] 1. A balance hole and / or a scoop for returning a part of the steam at the blade outlet side, whose temperature has been reduced by the heat drop due to the expansion of steam, to the upstream side of the stage, and / or a heat sink in the turbine rotor. Corresponding to the imbalance due to the circumferential non-uniformity of the physical property value that causes deformation due to heat, such as unevenly arranged in the circumferential direction on the rotor,
A rotor vibration suppression device for a steam turbine, wherein the cooling action of the steam is made uneven in the circumferential direction.