JP2013076341A - Seal structure of steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal structure of a steam turbine which can be manufactured by relative simple processing and suppress the generation of steam whirl.SOLUTION: The seal structure of the steam turbine includes: a casing 3; a turbine rotor 2 rotatably supported to the casing 3; a plurality of moving blades 11 provided on the turbine rotor 2; and a plurality of seal fins 7 and 8 provided on an inner periphery of the turbine casing 3 facing the moving blades 11. A groove portion 9 is formed between the adjacent seal fins 7 and 8 on the casing 3.

Description

  The present invention relates to a seal structure for a steam turbine.

  It is known that a labyrinth seal portion that prevents leakage of steam on the rotor shaft in a steam turbine generates a force that leads to unstable vibration due to the swirling flow. Unstable vibration caused by the force is called a steam whirl. As a countermeasure against the steam whirl, for example, a swirl prevention device for a fluid machine (for example, see Patent Document 1 below) or a labyrinth seal device (for example, the following) Patent Document 2) has been proposed.

  The above-described swirl flow prevention device for a fluid machine includes a protruding portion (swirl breaker) provided on the side surface of the diaphragm and facing the inlet side of the seal fin of the labyrinth seal, thereby increasing the resistance to steam. Thus, the generation of the swirling flow of steam is suppressed.

  In the labyrinth seal device described above, an inflow path (hole) for introducing steam is provided on one side of the labyrinth seal member, and an outflow port communicating with the inflow path is provided on the upstream side of the seal chamber. A reverse flow is generated to suppress the swirling flow of steam.

JP 2006-104952 A (see, for example, paragraphs [0065] to [0068], [FIG. 10], etc.) Japanese Patent Laid-Open No. 62-118008 (see, for example, FIGS. 1 to 4)

  In the above-described swirl flow preventing device for a fluid machine, the installation of the protruding portion causes anxiety of strength, and is not suitable as a countermeasure for steam whirl. In the above-described labyrinth seal device, the inflow path and the outflow port are produced by machining in the axial direction and the radial direction, and the machining is complicated.

  Therefore, in the conventional steam turbine seal structure, a structure that does not take measures against the steam whirl described above has been experimentally checked to prevent the occurrence of unstable vibration. In such a structure, unstable vibrations may occur during special operations such as overload, but this has been dealt with in operation. For this reason, there is a need for a seal structure for a steam turbine that can be manufactured by relatively simple processing and that can suppress the generation of steam whirl.

  In view of the above, the present invention has been made to solve the above-described problems, and provides a seal structure for a steam turbine that can be produced by relatively simple processing and that can suppress the occurrence of steam whirl. The purpose is to do.

The seal structure of the steam turbine according to the present invention that solves the above-described problems is as follows.
A casing, a rotor rotatably supported by the casing, a plurality of moving blades provided on the rotor, and a plurality of seal fins provided on an inner peripheral portion of the casing facing the moving blade. A steam turbine seal structure comprising:
A groove portion is formed between the adjacent seal fins in the casing.

The seal structure of the steam turbine according to the present invention that solves the above-described problems is as follows.
A seal structure for a steam turbine according to the invention described above,
The groove is a portion facing the first stage blade.

The seal structure of the steam turbine according to the present invention that solves the above-described problems is as follows.
A seal structure for a steam turbine according to the invention described above,
The groove is a portion facing the rotor blades in the second and subsequent stages.

  According to the seal structure of the steam turbine according to the present invention, since the groove portion is formed between the adjacent seal fins in the casing, the space between the adjacent seal fins is the case of the conventional steam turbine seal structure without the groove portion. Since it becomes substantially larger than that, the occurrence of steam whirl can be suppressed. In addition, the groove is only in the circumferential direction of the casing, and can be manufactured by relatively simple processing.

It is a figure for demonstrating the seal structure of the steam turbine which concerns on 1st Example of this invention, Comprising: The whole is shown to FIG. 1A, The expansion of the enclosure line I in FIG. 1A is shown. 1 is a longitudinal sectional view of a steam turbine having a steam turbine seal structure according to a first embodiment of the present invention. It is a principal part enlarged view of the steam turbine which comprises the seal structure of the steam turbine which concerns on 1st Example of this invention. It is a figure for demonstrating the seal structure of the steam turbine which concerns on 2nd Example of this invention, Comprising: The whole is shown to FIG. 4A, and the expansion of FIG. 4A is shown to FIG. 4B.

  The steam turbine seal structure according to the present invention will be described in each embodiment.

  The seal structure of the steam turbine according to the first embodiment of the present invention will be specifically described with reference to FIGS. 1A, 1B, 2, and 3. FIG.

  As shown in FIGS. 2 and 3, the steam turbine 1 includes a turbine rotor (rotary body) 2 and a casing (chamber compartment) 3 that accommodates the turbine rotor 2. Both ends of the turbine rotor 2 are supported by a bearing stand (not shown) via bearings (not shown). That is, the turbine rotor 2 is rotatably supported by the casing 3. The internal space of the casing 3 is partitioned into a high-pressure casing space 5 and an intermediate-pressure casing space 6 by a high-pressure dummy ring (stationary portion) 4. The high-pressure dummy ring 4 is an annular member and is fixedly attached to the inside of the casing 3.

  On the outer peripheral surface portion of the turbine rotor 2, a large number of blades 11 projecting radially outward at portions corresponding to the high-pressure casing space 5 and the medium-pressure casing space 6 along the axial direction L. Multiple stages can be attached at intervals.

A plurality of blade rings 13 are attached to the inside of the casing 3 along the axial direction L at portions corresponding to the high-pressure casing space 5 and the medium-pressure casing space 6.
A plurality of stationary blades 14 projecting radially inward are attached to each blade ring 13 along the axial direction L with a plurality of intervals.

  An annular high-pressure inlet 15 is provided on the medium-pressure compartment 6 side of the high-pressure compartment 5 and an annular high-pressure outlet 17 is provided on the opposite side in the axial direction. An annular medium-pressure inlet 19 is provided on the high-pressure compartment space 5 side of the intermediate-pressure compartment 6 and an annular medium-pressure outlet 21 is provided on the opposite side in the axial direction.

  The high-pressure inlet 15 communicates with the main steam pipe 23 and is formed such that steam supplied from a boiler (not shown) flows through the main steam pipe 23. The inflowing steam works in the high-pressure stage and is led out from the high-pressure outlet 17 through the high-pressure outlet pipe 25 as high-pressure exhaust steam. The high-pressure exhaust steam is introduced into the intermediate pressure inlet 19 through the intermediate pressure inlet pipe 27. The high-pressure exhaust steam introduced into the intermediate-pressure inlet 19 performs work at the intermediate-pressure stage and is exhausted from the intermediate-pressure outlet 21 through the intermediate-pressure exhaust pipe 29. An intermediate pressure side steam chamber 31 that communicates with the intermediate pressure inlet 19 is provided on the intermediate pressure chamber space 21 side. The intermediate pressure side steam chamber 31 is communicated with the high pressure outlet portion 17 by the connection flow path 33.

  As shown in FIGS. 1A and 1B, a shroud 12 is provided on the top of the first stage moving blade 11. On the inner peripheral surface of the casing 3 facing the first stage blade 11, two seal fins 7, 8 projecting in a ring shape in the circumferential direction are provided along the axial direction L with an interval L 2, A labyrinth seal structure is formed with the outer peripheral surface of the shroud 12. This suppresses the passage of steam between the shroud 12 and the casing 3. The height of the seal fin 7 is H1, and the height of the seal fin 8 is H2 (<H1).

  A groove portion 9 extending in the circumferential direction is provided between adjacent seal fins 7 and 8 on the inner peripheral surface of the casing 3. The groove portion 9 has a size of L1 (<L2) in the axial direction and a size (depth) of D1 in the radial direction. Thereby, the space comprised by the adjacent seal fins 7 and 8 and the groove part 9 becomes larger than the space comprised only by the adjacent seal fins 7 and 8, and generation | occurrence | production of a steam whirl can be suppressed. Further, the space surrounded by the seal fins 7 and 8 can be substantially increased without changing the radial size of the seal fins 7 and 8. That is, the same effect as when the seal fins 7 and 8 are enlarged in the radial direction can be obtained without reducing the strength of the seal fins 7 and 8. The axial dimension L1 of the groove 9 is set to such an extent that the strength for supporting the seal fins 7 and 8 is not lowered.

  As described above, according to the seal structure of the steam turbine according to the present embodiment, the inner peripheral surface of the casing 3 that faces the first stage moving blade 11, and between the adjacent seal fins 7 and 8. By forming the groove 9, the space formed between the adjacent seal fins 7 and 8 is substantially increased by the groove 9, and compared with the case of the conventional steam turbine seal structure without the groove, Occurrence can be suppressed. Moreover, since the groove part 9 exists only in the circumferential direction of the inner peripheral surface of the casing 3, it can be produced by a relatively simple process.

  Since the groove part 9 exists in the location which opposes the 1st stage (regulation stage) moving blade 11 with the highest pressure, generation | occurrence | production of a steam whirl can be suppressed effectively.

  The seal structure of the steam turbine according to the second embodiment of the present invention will be specifically described with reference to FIGS. 4A and 4B.

  The seal structure of the steam turbine according to the present embodiment is applied to a seal ring that is arranged to face the rotor blades in the second and subsequent stages. As shown in FIGS. 4A and 4B, a shroud 12 is provided at the top of the second and subsequent blades, and a ring-shaped seal ring 41 is attached to the inner peripheral portion of the casing 3 facing the shroud 12. It is done. A plurality of (four in the illustrated example) seal fins 42 projecting in a ring shape are provided on the inner peripheral surface of the seal ring 41 with an interval L4 along the axial direction L, and are separated from the outer surface of the shroud 12. It has a ring seal structure. This suppresses the passage of steam between the shroud 12 and the casing 3. The height of the seal fin 42 is H3.

  Between the adjacent seal fins 42 and 42 on the inner peripheral surface of the seal ring 41, a groove portion 43 extending in the circumferential direction is provided. The groove 43 has a size of L3 (<L4) in the axial direction and a size (depth) of D2 in the radial direction. Thereby, the space comprised by the adjacent seal fins 42 and 42 and the groove part 43 becomes larger than the space comprised only by the adjacent seal fins 42 and 42, and generation | occurrence | production of a steam whirl can be suppressed. Further, the space surrounded by the seal fins 42, 42 can be substantially increased without changing the size of the seal fins 42, 42 in the radial direction. That is, the same effect as when the seal fins 42 and 42 are increased in the radial direction can be obtained without reducing the strength of the seal fins 42 and 42. The axial size L3 of the groove 43 is set to such an extent that the strength for supporting the seal fins 42, 42 is not reduced.

  As described above, according to the seal structure of the steam turbine according to the present embodiment, the inner peripheral surface of the seal ring 41 facing the shroud 12 provided on the second and subsequent moving blades 11 and adjacent thereto. By forming the groove portion 43 between the seal fins 42, 42, the space between the adjacent seal fins 42, 42 is substantially increased by the groove portion 43, as compared with the conventional steam turbine seal structure having no groove portion. , The occurrence of steam whirl can be suppressed. In addition, the groove 43 is only in the circumferential direction of the seal ring 41 and can be manufactured by relatively simple processing.

  The present invention is a seal structure for a steam turbine, can be produced by relatively simple processing, and can suppress the occurrence of steam whirl, so that it can be used beneficially in the power generation industry and the like.

DESCRIPTION OF SYMBOLS 1 Steam turbine 2 Turbine rotor 3 Casing 4 High pressure dummy ring 5 High pressure casing space 6 Medium pressure casing space 7, 8 Seal fin 9 Groove part 11 Rotor blade 12 Shroud 13 Blade ring 14 Stator blade 15 High pressure inlet part 17 High pressure outlet part 19 Medium pressure inlet 21 Medium pressure outlet 23 Main steam pipe 25 High pressure outlet pipe 27 Medium pressure inlet pipe 29 Medium pressure exhaust pipe 31 Medium pressure side steam chamber 33 Connection flow path 41 Seal ring 42 Seal fin 43 Groove parts D1, D2 Groove depth H1-H3 Seal fin height (length)
L1, L3 Groove size in the axial direction L2, L4 Distance between adjacent seal fins

Claims (3)

A casing, a rotor rotatably supported by the casing, a plurality of moving blades provided on the rotor, and a plurality of seal fins provided on an inner peripheral portion of the casing facing the moving blade. A steam turbine seal structure comprising:
A seal structure for a steam turbine, wherein a groove is formed between adjacent seal fins in the casing. A steam turbine seal structure according to claim 1,
The seal structure for a steam turbine, wherein the groove portion is a portion facing the first stage moving blade. A steam turbine seal structure according to claim 1,
The seal structure for a steam turbine, wherein the groove is a portion facing the rotor blades in the second stage and thereafter.

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