JP5734052B2 - Rotary shaft seal structure - Google Patents

Description

  The present invention relates to a rotary shaft seal structure having a rotary shaft and a seal disposed in the circumferential direction of the outer peripheral surface of the rotary shaft.

  In a rotary machine such as a gas turbine or a steam turbine, a labyrinth is used as one of the seal structures for a fluid that flows along the axial direction of the rotating shaft through a gap between the outer peripheral surface of the rotating shaft and a stationary portion provided on the outer peripheral side of the rotating shaft. A seal structure of a rotating shaft using a seal is widely known.

  Here, the labyrinth seal is to provide fins on the stationary part side, thereby forming a plurality of uneven gaps between the rotating shaft and the stationary part, and gradually reducing the leakage pressure at each stage to reduce the amount of leakage. It is to reduce.

  The seal structure of the rotating shaft using such a labyrinth seal is such that a labyrinth seal is provided between the rotating shaft and the stationary portion, and seal air is supplied to the seal portion. The seal air and the labyrinth seal rotate. The fluid flowing along the axial direction of the shaft is sealed. Such a seal structure of the rotating shaft is disclosed in Patent Document 1, for example.

JP 2003-343206 A

  In order to reduce the amount of fluid leakage in the labyrinth seal, it is preferable to reduce the clearance between the rotating shaft and the fins forming the labyrinth seal. However, in the conventional labyrinth seal, a metal material is used to form the labyrinth seal. Therefore, if the clearance is reduced in order to reduce the amount of fluid leakage, the rotating shaft and the fin may come into contact with each other and damage the rotating shaft. For this reason, there is a limit to improving the sealing performance by reducing the amount of clearance, that is, reducing the amount of fluid leakage, and it is necessary to secure a large clearance in consideration of manufacturing tolerances.

  By the way, since the labyrinth seal is a non-contact type seal, the amount of leakage of the sealing air from the labyrinth seal depends on the setting of the clearance of the labyrinth seal. Therefore, if the clearance is set larger, the amount of seal air leaked from the labyrinth seal increases.

  In other words, in a conventional rotary shaft seal structure using a labyrinth seal, there is a limit to reducing the clearance in order to prevent damage to the rotary shaft. For this reason, it is necessary to secure a large clearance, but in that case, the amount of leakage of seal air from the labyrinth seal increases, and the efficiency of the rotating machine may decrease.

  Thus, it is conceivable to reduce the amount of sealing air. However, if the amount of sealing air is small, sufficient performance as a sealing structure may not be exhibited. For example, when a labyrinth seal is used in a gas turbine and the clearance is large, the supply pressure of the seal air becomes insufficient when the gas turbine is started, and a back flow of fluid may occur in the labyrinth seal portion.

  In addition, when the labyrinth seal is a gas turbine bearing seal, if the backflow occurs, the lubricating oil is exposed to the surrounding high-temperature air and deteriorates, or the lubricating oil leaks to the outside. The amount may be insufficient.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rotating shaft sealing structure that can reduce the leakage amount of sealing air and can reliably exhibit the sealing ability.

In order to solve the above problems, in the present invention, there is provided a rotary shaft seal structure having a rotary shaft and a seal disposed in the circumferential direction of the outer peripheral surface of the rotary shaft, The opposing surfaces have both end surfaces positioned at both ends in the axial direction and an intermediate surface positioned between the both end surfaces and farther from the rotation shaft than the both end surfaces. A space is formed in the space, and fluid supply means for supplying a fluid from outside to the space is provided. The seal is pressed toward the rotating shaft, and the fluid supplied to the space is predetermined. It floats from the rotating shaft above the pressure.
Here, with respect to the pressing, for example, a pressing means such as a spring may be provided to press the seal toward the rotating shaft, and the seal is pressed toward the rotating shaft due to deformation or its own weight of the seal. Also good.

Thereby, the seal can be floated from the rotating shaft by supplying the fluid from the fluid supply means into the space. That is, a non-contact state between the rotating shaft and the seal can be created by supplying the fluid. Further, the floating amount of the seal can be controlled by adjusting the supply pressure and supply amount of the fluid.
That is, since the gap between the seal and the rotating shaft can be kept small by supplying the fluid into the space, the sealing ability can be surely exhibited even with a small amount of sealing air, and for example, sealing air or the like. The amount of leakage of the fluid can be kept small.

Moreover, the said seal | sticker is good for the surface facing the said rotating shaft to be formed with the material whose hardness is lower than the said rotating shaft.
Thereby, even when a seal and a rotating shaft contact, it can prevent that a rotating shaft is damaged by this contact. When the rotating shaft is low alloy steel, it is particularly preferable to use an elastic material as a material having a lower hardness than the rotating shaft. Examples of the elastic material include a viscoelastic body made of silicone rubber, fluororubber, and carbon nanotube.

The seal may be formed of an elastic material portion including a surface facing the rotation shaft and a high-rigidity material portion that reinforces the outer peripheral side of the elastic material portion.
Since the elastic material portion includes a surface facing the rotation shaft, the elastic material portion comes into contact with the rotation shaft when the seal and the rotation shaft are in contact with each other. Since the elastic material portion comes into contact with the rotating shaft, the contact can prevent the rotating shaft from being damaged.
In addition, by reinforcing the outside of the elastic material portion with a metal material, it is possible to prevent the elastic material portion from being deformed by introducing the fluid into the space portion and increasing the internal pressure of the space portion.

Moreover, the said seal | sticker is good to be comprised from the several segment divided | segmented into the circumferential direction of the said rotating shaft.
For example, the gravity applied to the seal in the direction of the rotation axis differs between the upper part and the lower part of the rotation axis. Therefore, when the seal is formed in, for example, one ring shape, the floating amount of the seal when the fluid is supplied to the space may vary depending on the position. Therefore, by forming the seal from a plurality of segments, the amount of floating from the rotating shaft of the entire seal can be made uniform by adjusting the appropriate fluid amount and fluid pressure for each segment.

Moreover, it is good to provide the urging means which urges | biases the said seal part to the said rotating shaft side.
Thereby, a seal | sticker and a rotating shaft can be made into the contact state at the time of the non-supply of the said fluid to the said space part.

The fluid supply means may include a nozzle that ejects the fluid into the space.
Thereby, by ejecting the fluid into the space by the nozzle, the temperature of the ejected fluid decreases in the space due to expansion. Therefore, by reducing the fluid temperature using the nozzle, it becomes possible to seal a substance that does not have heat resistance to the fluid temperature when the nozzle is not used.

At least a part of the intermediate surface may be an inclined surface whose distance from the rotation shaft increases toward the axially central side of the seal.
As a result, the pressure of the fluid introduced into the space is received in the direction away from the rotating shaft by the inclined surface, so that the seal can be lifted from the rotating shaft with a small amount of fluid.

The rotating shaft is a rotating shaft of a gas turbine, and the fluid can be sealed air.
As a result, it is possible to reduce the amount of seal air leakage at a location where a conventional labyrinth seal is used, such as a journal bearing of a gas turbine. Moreover, the seal air is supplied to the location where the labyrinth seal has been conventionally used. Therefore, by using seal air as the fluid, the existing gas turbine can be modified without newly providing a fluid supply system. In addition, it is not necessary to change the design of the newly installed gas turbine as compared with the conventional one, and the cost related to the design can be suppressed.

The rotating shaft may be a rotating shaft of a steam turbine, and the fluid may be steam, and may be applied to a ground seal of the steam turbine.
Gland seal steam is supplied to the ground seal portion of the steam turbine. Therefore, by using steam as the fluid, the existing steam turbine can be modified without newly providing a fluid supply system. In addition, it is not necessary to change the design of the newly-installed steam turbine as much as before, and the cost for the design can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the sealing structure of the rotating shaft which can exhibit the sealing capability reliably can be provided with few leaks of the fluid used for a seal | sticker.

It is sectional drawing which shows the cavity part of the rear part of the gas turbine last disk to which the sealing structure of the rotating shaft which concerns on an Example is applied. It is a schematic block diagram which shows the seal part 12 which concerns on an Example. It is a perspective view which shows one of the segments which comprise the seal part 12 which concerns on an Example. It is sectional drawing which shows one of the segments which comprise the seal part 12 which concerns on an Example, and its periphery. FIG. 6 is a cross-sectional view of another example showing one of the segments constituting the seal portion 12. It is sectional drawing of another example which shows the elastic material part which comprises a segment.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

First, the configuration of a gas turbine as an example to which the seal structure of the present invention is applied will be described with reference to FIG.
FIG. 1 is a cross-sectional view illustrating a cavity portion at the rear of a gas turbine final disk to which a rotary shaft seal structure according to an embodiment is applied.

  As shown in FIG. 1, the turbine 2 is disposed with a slight inclination in the direction of the turbine shaft 6 through a gap 10 and a rear end portion of a blade 2 a planted on the periphery of the disk 2 at the final stage of the gas turbine 1. An annular diffuser 4 is provided. One end side of the shaft seal air pipe 14 is opened in the cavity portion A surrounded by the exhaust side bearing portion 9 disposed on the outer peripheral surface of the diffuser 4 and the turbine shaft 6 on the inner peripheral side of the diffuser 4. Yes. Further, the compressed air is supplied to the cavity A from the shaft seal air pipe 14, and a part of the supplied compressed air can be supplied to the seal portion 7 via the seal portion 12 at the front end. It is configured as follows.

  In the configuration shown in FIG. 1, a shaft seal air pipe 14 is attached to the cavity portion A so that seal air having a pressure higher than the pressure PG of the high-temperature exhaust gas E / G can be sent. Therefore, components such as the bearing 8, the bearing oil drain 11, and the seal portion 7 that constitute the exhaust-side bearing portion 9 are isolated from the high-temperature exhaust gas E / G by the seal air.

  In the above configuration, the seal structure of the rotating shaft of the present invention is applied to the seal portion 7 and the seal portion 12.

Next, the outline of the structure of the seal structure of the present invention will be described with reference to FIG.
FIG. 2 is a schematic configuration diagram illustrating the seal portion 12 according to the embodiment.

  As shown in FIG. 2, a seal portion 12 is provided in the circumferential direction of the rotating shaft 6. The seal portion 12 includes eight segments 12a, 12b, 12c, 12d, 12e, 12f, 12g, and 12h arranged along the circumference of the rotation shaft 6. The segments 12a to 12h are arranged with a gap 13 having a width a. Here, the width a may be any width that can discharge seal air described later. Further, both end surfaces 23 a to 23 h that are opposed to the rotation shaft 6 of the segments 12 a to 12 h and are located at both ends in the axial direction are formed along the outer surface of the opposed rotation shaft 6.

Next, the structure of the segment which comprises the seal part 12 is demonstrated using FIG.3 and FIG.4.
FIG. 3 is a perspective view showing one of the segments constituting the seal portion 12 according to the embodiment, and FIG. 4 is a cross-sectional view showing one of the segments constituting the seal portion 12 according to the embodiment and the periphery thereof. . 3 and 4 show the segment 12a arranged on the upper side of the rotating shaft 6. FIG. Since the segments 12b to 12g have the same structure as the segment 12a except for the case specifically described below, only the segment 12a will be described and the description of the segments 12b to 12g will be omitted.

As shown in FIGS. 3 and 4, the segment 12 a includes an elastic material portion 22, a high-rigidity material portion 24, and a seal air supply means 26.
Moreover, the segment 12a is being fixed to the segment fixing | fixed part 13 of the exhaust side bearing part 9, as shown in FIG.

The elastic material portion 22 has heat resistance that can withstand the specifications of the gas turbine 1 such as silicone rubber, fluororubber, and viscoelastic body mainly composed of carbon nanotubes, and has, for example, Vickers hardness than the rotating shaft 6. It is made of an elastic material with low hardness.
In particular, a viscoelastic material containing carbon nanotubes as a main component has excellent heat resistance and can maintain viscoelasticity up to about 1000 ° C., so that it can be sufficiently used even in a severe environment of high temperature.
Note that a viscoelastic material mainly composed of carbon nanotubes (CNT) is prepared by, for example, depositing an iron catalyst on a silicon substrate by sputtering, preparing the catalyst by reactive ion etching with argon ions, and then superposing the catalyst on the substrate. It can be produced by compressing a CNT structure obtained by synthesizing CNTs by the growth method. In addition, the viscoelastic material mainly composed of CNT is described in the reference "Ming Xu, Don N. Futaba, Takao Yamada, Motoo Yumura and Kenji Hata," Carbon Nanotubes with Temperature-Invariant Viscoelasticity from -196 ° C to 1000 ° C, " Science, Vol. 330, No. 6009, pp. 1364-1368 (2010), Published online 3 December 2010. DOI: 10.1126 / science.1194865 ”.

  Further, the elastic material portion 22 has a surface facing the rotation shaft 6 located between both end surfaces 23a located at both ends in the axial direction of the rotation shaft and the both end surfaces 23a, and is farther from the rotation shaft than both end surfaces. By having the intermediate surface 25a, a space 28 is formed between the intermediate surface 25a and the rotating shaft 6, and the cross section has an Ω-like shape as shown in FIG.

  The high-rigidity material portion 24 is made of a high-rigidity material such as a metal material, and is attached to the outer peripheral side of the elastic material portion 22 by reinforcing the elastic material portion 22.

  The seal air supply means 26 is provided to supply seal air from the shaft seal air pipe 14 to the space 28. The sealing air means 26 is fixed to the segment fixing portion 13 so that the cavity 32 formed in the segment fixing portion 13 and the space portion 28 communicate with each other. The cavity 32 is provided with a supply path 34 through which sealing air is supplied from the shaft sealing air pipe 14. In this embodiment, the seal air from the shaft seal air pipe 14 is supplied to the space 28 from the seal air supply means 26, but the seal air from the shaft seal air pipe 14 is of a different system. Air may be supplied to the space 28 from the sealing air supply means 26.

  In FIG. 4, a coil spring 30 as an urging means is provided. The coil spring 30 presses the segment 12a toward the rotating shaft 6 side. In the coil spring 30, both end surfaces 23 a of the segment 12 a come into contact with the outer surface of the rotating shaft 6 when the seal air is not supplied to the space portion 28, and the air pressure in the space portion 28 and the space portion 28 are supplied when the seal air is supplied to the space portion 28. Considering the pressure receiving area of the air inside and the weight of the segment 12a, a coil spring having a spring force such that both end faces 23a of the segment 12a float from the outer surface of the rotating shaft 6 is adopted. For example, in segments such as the segments 12a and 12h located at the upper part of the rotary shaft 6, the rotation of the segments may be performed when the seal air is not supplied to the space portion 28 without providing the coil spring 30 by its own weight. The shaft facing surface may be in contact with the outer surface of the rotating shaft 6. In this case, the coil spring 30 may not be provided.

The operation of the seal structure of the rotary shaft of the present invention taking the seal portion 12 having the above configuration as an example will be described.
When the gas turbine 1 is not driven, that is, when the rotary shaft 6 is not rotated, or when the gas turbine 1 is started, that is, when the rotary shaft 6 is rotating at a low speed, the supply of the sealing air to the space 28 is interrupted or supplied. Make a trace amount. As a result, the segment 12 a is pressed in the direction of the rotating shaft 6 by the coil spring 30, and both end surfaces 23 a are in contact with the outer surface of the rotating shaft 6. The same applies to the segments 12b to 12h. When the segments 12a to 12h and the rotating shaft 6 are in contact with each other, the sealing portion 12 can surely perform sealing. Moreover, the rotating shaft 6 is non-rotating or rotating at a low speed, and both end surfaces 23a to 23h contacting the rotating shaft 6 of each segment 12a to 12h are formed of an elastic material having a lower hardness than the rotating shaft 6 as described above. Therefore, the rotating shaft 6 is not damaged by the contact between the segments 12a to 12h and the rotating shaft 6.

When the gas turbine 1 is driven and the rotary shaft 6 is in a high speed constant speed rotation state, the seal air from the shaft seal air pipe 14 is spaced from the seal air supply means 26 via the supply path 34 and the cavity 32. It is continuously introduced into the part 28. When the sealing air is continuously introduced into the space portion 28, the pressure inside the space portion 28 increases and the segment 12 a floats from the rotating shaft 6. The floating amount of the seal can be controlled by adjusting the supply pressure and supply amount of the seal air to the space 28 of the segment 12a. When the segment 12a rises, the seal air continuously supplied to the space 28 is discharged from the gap between the segment 12a and the rotary shaft 6 formed by the rise and the gap 13 between the segments. Since the pressure in the space portion 28 is reduced, the segments 12a are balanced in a state where a constant flying height is maintained from the rotating shaft 6. If the flying height is controlled so as to be as small as possible within the range where the segment 12a and the rotating shaft 6 do not come into contact with the rotation of the rotating shaft 6, the amount of sealing air used is reduced and the amount of leakage of the sealing air is reduced. This is preferable because it decreases. Further, the seal air discharged from the space portion 28 of the segment 12a is discharged outside the space portion 28 from the gap formed between the both end surfaces 23a and the rotary shaft 6 and the gap 13 between the segments by the rising of the segment 12a. Play a role. The same applies to the segments 12b to 12h.
With the above operation, when the rotating shaft 6 rotates at a constant speed, the gap between the segments 12a to 12h and the rotating shaft 6 can be kept small by supplying the sealing air into the space portion 28. The amount of leakage is small, and the sealing ability can be exhibited reliably.

Here, FIG. 5 is a cross-sectional view of another example showing one of the segments constituting the seal portion 12. 5, the same reference numerals as those in FIG. 4 have the same configurations as those in FIG.
When high-temperature air is used as the seal air and a substance that does not have heat resistance to the high temperature of the seal air is sealed by the seal portion 12, the seal air supply means is a nozzle 26 'as shown in FIG. A mechanism for ejecting seal air to the portion 28 is preferable. This is because, by ejecting the seal air into the space portion 28 by the nozzle, the temperature of the ejected seal air decreases in the space portion 28 due to expansion. In addition, 38 is a manifold for sealing air, 31 is a leaf | plate spring, and plays the same role as the coil spring 30 mentioned later.

Moreover, FIG. 6 is sectional drawing of another example which shows the elastic material part 22 which comprises the segment 23a. In FIG. 6, the same reference numerals as those in FIG. 4 have the same configurations as those in FIG.
In the elastic material portion 22 shown in FIG. 6, an inclined surface 27 a is formed on a part of the intermediate surface 25 a so that the distance from the rotation shaft 6 increases toward the axial center. By forming a part of the intermediate surface 25a as the inclined surface 27a, the pressure of the sealing air introduced into the space portion 28 is received in the direction away from the rotation axis by the inclined surface 27a, so that the elastic member 22 ( The segment 12a) can be levitated from the axis of rotation.

  According to the present embodiment described above, the sealing ability can be surely exhibited with a small supply amount of sealing air.

  Moreover, even if both end surfaces 23a-23h and the rotating shaft 6 contact by forming the both end surfaces 23a-23h which may contact the rotating shaft 6 with the elastic material whose hardness is lower than a rotating shaft, this contact It is possible to prevent the rotating shaft 6 from being damaged due to the above.

  In addition, by reinforcing the outer side of the elastic material portion 22 with the high-rigidity material portion 24, sealing air is introduced into the space portion 28, and the internal pressure of the space portion 28 is increased, so that the elastic material portion 22 is deformed. Can be prevented.

  Further, by forming the seal portion 12 from a plurality of (eight in this embodiment) segments 12a to 12h, for example, by adjusting the supply amount and supply pressure of the seal air for each segment, the rotation of the seal 12 as a whole. The flying height from the shaft can be made uniform.

  In the present embodiment, the case where the rotary shaft seal structure of the invention is applied to a gas turbine has been described. However, it can also be applied to a ground seal portion of a steam turbine. In this case, it is preferable to supply steam to the space instead of sealing air.

  The present invention can be used as a seal structure for a rotating shaft that has a small amount of seal air leakage and can reliably exhibit a sealing ability.

1 Gas turbine 6 Rotating shaft 12 Seal part (seal)
12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h Segment 22 Elastic material portion 24 Metal material portion 26 Seal air supply means (fluid supply means)
26 'nozzle (fluid supply means)
28 Space 30 Coil spring (biasing means)
31 Leaf spring (biasing means)

Claims (8)

A rotary shaft seal structure having a rotary shaft and a seal disposed in the circumferential direction of the outer peripheral surface of the rotary shaft,
The surface facing the rotation axis of the seal has both end surfaces located at both ends in the axial direction and an intermediate surface located between the both end surfaces and farther from the rotation axis than both end surfaces. And a space is formed between the rotary shaft and
Fluid supply means for supplying fluid from outside into the space part;
The seal is pressed toward the rotating shaft, and is configured such that the fluid supplied into the space portion floats from the rotating shaft at a predetermined pressure or higher .
The said seal is comprised from the some segment divided | segmented into the circumferential direction of the said rotating shaft, The sealing structure of the rotating shaft characterized by the above-mentioned.   2. The seal structure for a rotating shaft according to claim 1, wherein a surface of the seal facing the rotating shaft is made of a material having a hardness lower than that of the rotating shaft. The seal is
An elastic material portion including a surface facing the rotation axis;
The rotary shaft seal structure according to claim 1, wherein the rotary shaft seal structure is formed of a high-rigidity material portion that reinforces the outer peripheral side of the elastic material portion. Seal structure of the rotary shaft according to any one of claims 1-3, characterized in that it comprises a biasing means for biasing the seal to the rotating shaft side. The rotary shaft seal structure according to any one of claims 1 to 4 , wherein the fluid supply means includes a nozzle that ejects the fluid into the space. Wherein at least a portion of said intermediate surface, the rotating shaft according to any one of claims 1-5, wherein the is an inclined surface that distance increases with the rotary shaft toward the axial center side of the seal Seal structure. The rotating shaft is a rotating shaft of a gas turbine,
Seal structure of the rotary shaft according to any one of claims 1-6, wherein said fluid is a sealing air. The rotating shaft is a rotating shaft of a steam turbine,
The fluid is steam;
The rotary shaft seal structure according to any one of claims 1 to 6 , wherein the rotary shaft seal structure is applied to a ground seal of a steam turbine.

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