JP2014152696A - Labyrinth seal device, and turbomachine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a labyrinth seal device capable of effectively reducing a flow in a rotating direction at a labyrinth seal inlet to suppress unstable vibration of a rotating shaft, and reducing generation of vibration by contact with the rotating shaft and abrasion of a seal fin.SOLUTION: A labyrinth seal device 1 having a seal fin 11 disposed on an outer peripheral face of a rotating body and projecting to an outer peripheral side in the radial direction of the rotating body, and a seal ring 13 fixed to a stationary body enclosing the rotating body so as to face the seal fin, includes a projecting portion 14 formed on an inner peripheral face of the seal ring and projecting to an inner peripheral side in the radial direction of the seal ring, a plurality of flow straightening holes 15 formed in the radial direction and the circumferential direction of the projecting portion, penetrating through both axial side wall faces of the projecting portion, and reducing a speed component in the rotating direction of the rotating body, of a leakage flow passing through the holes, and the seal fin 11 disposed in opposition to an inner peripheral face of the projecting portion.

Description

  The present invention relates to a labyrinth seal device suitable for a high-speed, high-pressure turbo machine such as a steam turbine.

  In a turbo machine such as a steam turbine, a labyrinth seal is often provided between the rotating shaft and the casing in order to prevent the working fluid from leaking along the rotating shaft from the casing containing the rotating shaft.

The labyrinth seal generally has a plurality of seal fins in the axial direction of the rotating shaft, and a pressure loss gap is formed between these fins along the outer periphery of the rotating shaft.
The labyrinth seal exerts a pressure loss in the leakage flow flowing down in the seal due to the pressure loss gap, and exerts a sealing function by suppressing the leakage flow due to the pressure loss.

  In such a labyrinth seal, an unstable vibration of the rotating shaft may occur due to a leakage flow in the seal. Specifically, the leakage flow in the labyrinth seal is accompanied by a rotational flow in the same direction as the rotation of the rotation shaft due to the twisting effect caused by the rotation of the rotation shaft. This flow in the rotational direction forms a high-pressure portion on the upstream side in the rotational direction with respect to the rotational shaft displaced by vibration and generates an asymmetric pressure distribution. As the rotational speed of the rotating shaft increases, the flow velocity of the rotational flow increases. However, the pressure distribution generates a fluid force in a direction perpendicular to the vibration displacement of the rotating shaft with a strength corresponding to the flow velocity.

  For this reason, in a high-pressure turbomachine such as a steam turbine, a fluid force acting in a direction perpendicular to the vibration displacement of the rotating shaft during high-speed rotation acts to swing the rotating shaft in the rotating direction. As a result, the vibration stability of the rotating shaft is lowered and unstable vibration may occur.

  Such unstable vibration of the rotating shaft related to the labyrinth seal can be eliminated by suppressing the rotational flow. As a technique for suppressing the rotational flow, for example, a technique disclosed in Patent Document 1 is known.

  In the labyrinth seal of Patent Document 1, a spiral slit is provided on either the rotating body or stationary body at the entrance of the labyrinth seal, and a flow that opposes the rotational flow is generated by the leakage flow that passes through the slit, thereby suppressing the rotational flow. doing.

Japanese Unexamined Patent Publication No. 1-170702

  In the labyrinth seal structure disclosed in Patent Document 1 described above, the flow that opposes the rotational direction is generated by the leakage flow that flows through the groove and the flow in the rotational direction is suppressed. In order to generate | occur | produce, the rotation direction flow is suppressed only by a part of leak flow. In order to generate a flow that opposes the rotational direction using more leakage flow, it is necessary to narrow the gap between the rotating body and the stationary body. The fins may be worn.

  Accordingly, an object of the present invention is to more effectively reduce the rotational flow at the entrance of the labyrinth seal, to suppress unstable vibration of the rotating shaft, and to reduce vibration generation due to contact with the rotating shaft and wear of seal fins. It is in providing a labyrinth seal device.

  In order to achieve the above object, the present invention provides a seal fin that is provided on the outer peripheral surface of the rotating body and protrudes to the outer peripheral side in the radial direction of the rotating body, and a stationary body that contains the rotating body so as to face the seal fin. In a labyrinth seal device having a seal ring fixed to a protrusion, a protrusion formed on the inner peripheral surface of the seal ring and protruding toward the inner peripheral side in the radial direction of the rotating body is provided continuously in the radial direction and the peripheral direction of the protrusion. A rectifying hole that passes through both axial wall surfaces in the axial direction of the convex part and reduces the speed component in the rotational direction of the rotating body of the leakage flow that passes through the hole, and a seal fin provided facing the inner peripheral surface of the convex part It is characterized by having.

  According to the labyrinth seal device of the present invention, the labyrinth that suppresses the rotational flow that flows into the labyrinth seal, suppresses unstable vibration of the rotating shaft, and reduces vibration generation due to contact with the rotating body and wear of the seal fin. A sealing device can be provided.

It is sectional drawing which showed the principal part of the steam turbine schematically. It is a schematic diagram which shows the pressure distribution in the chamber of a labyrinth seal. It is an axial sectional view of the labyrinth seal concerning the 1st example of the present invention. It is an enlarged view of the cross section orthogonal to the axial direction of the rectification | straightening hole which concerns on 1st Example of this invention. It is a circumferential direction developed view of the labyrinth seal concerning the 1st example of the present invention. It is an axial sectional view of the labyrinth seal concerning the 2nd example of the present invention.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated using drawing.

  A first embodiment of the present invention will be described with reference to the drawings. In this embodiment, the present invention is applied to a labyrinth seal device used for a steam turbine.

  First, the main structure of a steam turbine to which the present invention is applied will be described.

  FIG. 1 is a cross-sectional view schematically showing an example of a main structure of a steam turbine to which the present invention is applied. In FIG. 1, 2 is a rotating shaft, 3 is a casing, 4 is a nozzle diaphragm inner ring, 5 is a diaphragm packing, 6 is a tip fin, 7 is a nozzle diaphragm outer ring, 8 is a moving blade, 9 is a nozzle, and 10 is a shaft packing. Show.

  The steam turbine 1 mainly includes a rotating shaft 2 that constitutes a rotating body together with the moving blades 8, and a casing 3 that is a stationary body, includes and holds the rotating shaft 2, and forms a flow path of the steam 16 that is a working fluid. Is provided. A plurality of moving blades 8 are fixed to the rotating shaft 2 in the circumferential direction, and a nozzle 9 is fixed to the plurality of casings 3 in the circumferential direction so as to oppose the upstream side of the moving blade 8 in the steam flow direction. . An annular nozzle diaphragm outer ring 7 is fixed to the inner peripheral side of the casing 3, and the outer peripheral end of the nozzle 9 is fixed to the inner peripheral side of the nozzle diaphragm outer ring 7. On the other hand, the inner peripheral side tip of the nozzle 9 is fixed by an annular nozzle diaphragm inner ring 4.

  In the steam turbine, a stage is formed by the moving blade 8 and the nozzle 9 that is installed facing the upstream side, and the stage is installed in a plurality of stages in the axial direction of the rotary shaft 2.

  The vapor 16 that is a working fluid is accelerated and sent to the moving blade 8 when passing through the nozzle 9, and the rotating shaft 2 rotates by being converted from velocity energy to kinetic energy by the moving blade 8. The rotating shaft 2 is connected to a generator (not shown), and an output is taken out as electric energy.

  A gap is provided between the rotating shaft 2 that is a rotating body and the casing 3 that is a stationary body so as not to hinder the rotation of the rotating shaft 2. In this gap, a part of the steam 16 flows out as a leakage flow from the high pressure side to the low pressure side, but the leaked steam is not effectively used for the rotational motion of the rotating shaft 2, This contributes to a decrease in turbine efficiency.

  Therefore, a sealing device such as a labyrinth seal is provided in a gap between the rotating shaft 2 that is a rotating body and the casing 3 that is a stationary body in order to prevent steam from flowing out. For example, the diaphragm packing 5 that prevents leakage of steam from the gap between the nozzle diaphragm inner ring 4 and the rotary shaft 2 provided on the inner peripheral side of the nozzle 9, and the leakage of steam from the gap between the moving blade 8 and the casing 3 are prevented. A labyrinth seal is used for the shaft packing 10 that prevents leakage of steam from the gap between the tip fin 6 and the rotary shaft 2 and the casing 3.

  The labyrinth seal has a plurality of seal fins protruding in the radial direction of the rotating body on at least one of the rotating body and the stationary body. A ring-shaped pressure loss gap (chamber 12) is formed along the outer periphery of the rotating shaft 2 between the plurality of seal fins provided along the rotating body axis direction. The labyrinth seal exerts a pressure loss in the leakage flow flowing down in the seal due to the pressure loss gap, and exhibits a sealing function by suppressing the leakage flow due to the pressure loss. However, the conventional labyrinth seal has the following problems.

  FIG. 2 is a schematic diagram for explaining the pressure distribution in the chamber of the labyrinth seal. As shown in FIG. 2, in general, in an axial flow turbomachine such as a steam turbine, when the rotating shaft 2 rotates, the leakage flow swirls in the rotating direction R of the rotating shaft 2 to generate a rotating flow RS. . When the rotation shaft 2 is eccentric (vibration displacement) in one direction, the chamber 12 is narrowed in the displacement direction. The rotational flow RS is blocked on the upstream side in the displacement direction of the rotary shaft 2 to generate a high-pressure portion. A fluid force is generated by this asymmetric pressure distribution, and the rotation shaft 2 is pushed in the rotation direction R. By repeating this, the rotating shaft 2 swings and causes unstable vibration.

  Based on the problems of the conventional labyrinth seal as described above, the labyrinth seal of this embodiment will be described with reference to FIGS.

  The present embodiment is an example in which the present invention is applied to a labyrinth seal used for the diaphragm packing 5 among the examples applied to a labyrinth seal used for a steam turbine.

  FIG. 3 is an axial sectional view of the labyrinth seal according to the first embodiment. FIG. 4 is an axial sectional view of the labyrinth seal according to the first embodiment of the present invention. FIG. 5 is a circumferential development of the labyrinth seal shown in FIG.

  In the labyrinth seal, as shown in FIG. 3, a seal ring 13 is provided on the inner peripheral side of the annular nozzle diaphragm inner ring 4. The seal ring 13 is a member assembled in a ring shape around the rotation shaft 2. On the inner peripheral surface of the seal ring 13, a convex portion 14 that protrudes toward the inner peripheral side in the radial direction of the rotation axis is formed. The convex portion 14 is formed in an annular shape by extending in the circumferential direction of the seal ring along the inner peripheral surface of the seal ring 13. The convex portion 14 is provided in a plurality of stages along the axial direction of the rotating shaft 2.

  On the other hand, the rotary shaft 2 is provided with seal fins 11 that protrude toward the outer peripheral side in the radial direction of the rotary shaft 2. The seal fin 11 is formed in an annular shape by extending in the circumferential direction of the rotation axis along the outer peripheral surface of the rotation shaft 2. A plurality of seal fins 11 are provided along the axial direction so as to face the seal ring 13. A plurality of these seal fins 11 are provided to face the convex portion 14. The length of the seal fin 11 is changed in accordance with the convex portion 14 so that the gap between the tip of the seal fin 11 and the seal ring 13 is equal.

  A ring-shaped chamber 12 is formed along the circumferential direction of the rotary shaft 2 between a plurality of seal fins 11 provided in the axial direction. In FIG. 3, an arrow with a symbol LS represents the flow direction of the leakage flow. Since the leakage flow that flows between the rotating shaft 2 and the seal ring 13 causes a pressure loss every time it passes through the chamber 12, the flow to the downstream side is suppressed.

  In the present embodiment, among the convex portions 14 provided in the seal ring 13, the first step convex portion 14 provided on the most upstream side in the leakage flow direction has a rectifying hole 15 penetrating the convex portion 14 in the rotation axis direction. A plurality are provided. Of the seal fins 11 provided on the rotating shaft 2 side, the first-stage seal fin 11 on the most upstream side in the leakage flow direction is provided so as to face the inner peripheral surface of the first-stage convex portion 14. It has been.

  FIG. 4 is an enlarged view in which a part of the rectifying hole 15 provided in the convex portion 14 is enlarged. As shown in FIG. 4, the first-stage convex portion 14 has a honeycomb structure when viewed from the rotation axis direction, and a plurality of hexagonal rectifying holes 15 are provided in the circumferential direction c and the radial direction r. ing. These straightening holes 15 are continuously provided so as to be substantially adjacent to each other in the circumferential direction c and the radial direction r.

  The direction in which the rectifying hole 15 penetrates the convex portion 14 is shown in FIG. The rectifying hole 15 penetrates both wall surfaces of the convex portion 14 in the rotation axis direction, and the direction in which the hole extends extends from the upstream side to the downstream side in the leakage flow direction so as to face the rotation direction of the rotation axis. Inclined in the direction opposite to the rotational direction R with respect to the axial direction of the rotary shaft 2.

  Next, the function and effect of the present invention will be described with reference to FIG.

  As shown in FIG. 5, in this embodiment, the leakage flow with the rotational flow RS flowing in from the most upstream side in the leakage flow direction of the labyrinth seal passes through the rectifying hole 15 and goes to the downstream side of the convex portion 14. Thus, it is ejected with a velocity component in the direction opposite to the rotation direction R. Therefore, the leakage flow with the rotation direction flow RS is converted into a flow with a flow in the direction opposite to the rotation direction R by passing through the rectifying hole 15. Since the flow direction of the leakage flow is converted by the rectifying hole 15, the rotational speed component of the rotational flow RS that causes unstable vibration is reduced, so that unstable vibration caused by the rotational flow is suppressed. Can do.

  Further, in this embodiment, a plurality of rectifying holes 15 communicating in the axial direction are provided in the convex portion 14, and the seal fin 11 is provided on the rotating shaft 2 side facing the convex portion 14 having the rectifying holes 15, The contact area with the rotating shaft 2 can be reduced.

  Since the convex portion 14 is composed of a porous structure in which a plurality of rectifying holes 15 are provided in the circumferential direction and the radial direction, the convex portion 14 is relatively free-cutting, so that the convex portion 14 is convex in a short time with little resistance when contacting the seal fin. Since the part 14 is scraped, risks such as vibration and wear of the seal fins can be reduced. By reducing the risk at the time of contact, the gap between the convex portion having the rectifying hole and the seal fin can be reduced, and a leakage flow higher than that of the conventional structure can flow into the rectifying hole 15.

  By these, the labyrinth seal of this invention can reduce risks, such as the vibration generation | occurrence | production at the time of contact, and abrasion of a seal fin, suppressing the rotation direction flow RS effectively.

  In addition, in the convex part of a present Example, although the rectification | straightening hole 15 was made into the hexagonal honeycomb structure like FIG. 4, the cross-sectional shape of the rectification | straightening hole 15 may be made into shapes, such as a triangle, a square, and a circle. Further, the holes of the rectifying holes 15 do not have to be uniform in size. Further, the axial distribution of the dimension of the rectifying hole 15 may not be constant. It may be narrowed or widened from the high pressure side toward the low pressure side.

  Further, the rectifying hole 15 may not be inclined in the direction opposite to the rotation direction R. The rectifying hole 15 may be provided so that the rotational flow RS becomes an axial flow. In addition, since the higher the pressure side, the greater the influence of the rotational flow on the unstable vibration, the rectifying hole 15 is provided in the first-stage convex portion 14 provided on the highest pressure side. It may be provided thereafter.

  Moreover, although the present Example demonstrated using the example which applied this invention to the labyrinth seal apparatus used for the diaphragm packing 5, when using a labyrinth seal apparatus for the shaft packing 10 and the chip fin 6, it is the same. Can be applied.

  Next, a second embodiment of the present invention will be described. FIG. 6 is an example of a configuration diagram showing the labyrinth seal 1 according to the second embodiment of the present invention. Constituent elements equivalent to those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the first embodiment described above, a gap is formed between the seal ring and the seal fin in order to prevent the rotating body and the casing from contacting each other. On the other hand, in this embodiment, the gap is made very small by providing the abradable layer 17 on the inner peripheral surface of the seal ring 13 including the rectifying hole 15 and the convex portion 14. In this embodiment, the seal fin 11 comes into contact with the abradable layer 17 before coming into contact with the rectifying hole 15 due to a difference in thermal expansion between the rotating shaft and the casing in the radial direction. Even if it contacts the abradable layer 17, vibrations and seal fin wear do not occur.

  As shown in FIG. 6, since the rectifying hole 15 is composed of a plurality of holes, even when the seal ring 13 is coated with the abradable layer 17, the flow path has a height higher than the thickness of the coating. Can be secured.

  Moreover, the clearance gap between the rectification | straightening hole 15 and the seal fin 11 can be made smaller than a 1st Example, and a leak flow can be more efficiently passed through a rectification | straightening hole. Even with the structure of the present embodiment, it is possible to suppress vibrations during contact and wear of the seal fins while effectively suppressing the rotational flow RS.

  In addition, in this embodiment, the gap between the rotating body and the casing, which greatly affects the sealing performance, is narrowed to make it difficult to leak, so that the amount of leakage can be effectively reduced. Therefore, the present embodiment can reduce the risk at the time of contact while effectively suppressing the rotational flow RS as in the first embodiment while ensuring the sealing performance.

  In addition, this invention is not limited to each above-mentioned Example, Various shape examples are included. Further, each of the above-described embodiments has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described.

  Moreover, although each above-mentioned Example demonstrated in the example of the steam turbine, it is not restricted to this, It can apply also to another turbomachine, for example, a centrifugal compressor etc.

1 Steam Turbine 2 Rotating Shaft 3 Casing 4 Nozzle Diaphragm Inner Ring 5 Diaphragm Packing 6 Tip Fin 7 Nozzle Diaphragm Outer Ring 8 Moving Blade 9 Nozzle 10 Shaft Packing 11 Seal Fin 12 Chamber 13 Seal Ring 14 Protrusion 15 Rectification Hole 16 Steam 17 Abradable Layer LS Leakage flow RS Rotational direction Flow R Rotational direction

Claims (10)

A labyrinth seal having seal fins provided on the outer peripheral surface of the rotating body and protruding outward in the radial direction of the rotating body, and a seal ring fixed to a stationary body containing the rotating body so as to face the seal fins A device,
A convex portion formed on the inner peripheral surface of the seal ring and protruding toward the inner peripheral side in the radial direction of the seal ring;
A plurality of rectifying holes provided in the radial direction and the circumferential direction of the convex portion, penetrating through both side wall surfaces in the axial direction of the rotating body of the convex portion, and reducing the velocity component in the rotating body rotating direction of the leakage flow passing through the hole;
A labyrinth seal device comprising: the seal fin provided to face the inner peripheral surface of the convex portion. The labyrinth seal device according to claim 1,
The straightening holes extend from the upstream side to the downstream side in the leakage flow direction so as to incline in the direction opposite to the rotation direction with respect to the axial direction of the rotation shaft, or from the upstream side to the downstream side in the leakage flow direction. The labyrinth seal device is characterized by extending along the rotation axis direction. The labyrinth sheet apparatus according to claim 1 or 2,
The convex portion is provided in a plurality of stages in the rotation axis direction,
The labyrinth seal according to claim 1, wherein the straightening hole is provided in the convex portion on the most upstream side in the leakage flow direction. The labyrinth seal device according to any one of claims 1 to 3,
The labyrinth seal device according to claim 1, wherein the convex portion has a honeycomb structure when viewed from the rotation axis direction. The labyrinth seal device according to any one of claims 1 to 4,
A labyrinth seal device, wherein an abradable layer is provided on an inner peripheral surface of the seal ring and the convex portion. A rotating body, a stationary body containing the rotating body, and a labyrinth seal device provided between the rotating body and the stationary body,
The labyrinth seal device is provided on an outer peripheral surface of the rotating body, and is fixed to a seal fin projecting outward in the radial direction of the rotating body and a stationary body containing the rotating body so as to face the seal fin. A turbomachine having a seal ring,
The labyrinth sealing device is
A convex portion formed on the inner peripheral surface of the seal ring and protruding toward the inner peripheral side in the radial direction of the seal ring;
A plurality of rectifying holes provided in the radial direction and the circumferential direction of the convex portion, penetrating through both side wall surfaces in the axial direction of the rotating body of the convex portion, and reducing the velocity component in the rotating body rotating direction of the leakage flow passing through the hole;
A turbomachine comprising: the seal fin provided to face the inner peripheral surface of the convex portion. The turbomachine according to claim 6,
The straightening holes extend from the upstream side to the downstream side in the leakage flow direction so as to incline in the direction opposite to the rotation direction with respect to the axial direction of the rotation shaft, or from the upstream side to the downstream side in the leakage flow direction. And a turbomachine characterized by extending along the direction of the rotation axis. A turbomachine according to claim 6 or 7,
The labyrinth seal device has a plurality of the convex portions in the rotation axis direction, and among the convex portions provided in a plurality of steps in the rotation axis direction, the rectifying hole is formed in the convex portion on the most upstream side in the leakage flow direction. A turbomachine characterized by comprising: A turbomachine according to any one of claims 6 to 8,
The turbo machine according to claim 1, wherein the convex portion has a honeycomb structure when viewed from the axial direction of the rotating body. A turbomachine according to any one of claims 6 to 9,
A turbomachine comprising an abradable layer provided on an inner peripheral surface of the seal ring and the convex portion.