JP2014125986A - Seal device, and rotary machine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal ring of a rotary machine capable of reducing unnecessary leakage and improving turbine plant efficiency by minimizing reduction of the number of sheets of effective seal fins to a seal ring capable of preventing a blowing-through state of working fluid due to existence of a clearance gap of the entire butting faces while having an allowance in dimensional tolerance in manufacturing.SOLUTION: In a seal device of a rotary machine which includes an annular seal ring 10, and a plurality of seal fins 12 axially disposed on an inner peripheral face of the seal ring, and in which the seal ring is composed of a plurality of segment bodies 7a, 7b annularly connected, peripheral end portions opposed to the adjacent segment body, of the segment bodies 7a 7b are provided with segment body joining structures composed of continuous steps formed into the stair shape when observed from the radial direction.

Description

  The present invention relates to a seal device for preventing leakage of working fluid in a rotating machine.

  A large rotating machine such as a steam turbine or a gas turbine generally has a structure in which a rotating body is surrounded by a casing in order to seal a working fluid. However, for the convenience of assembly, the casing is usually manufactured in a vertically split state, and is assembled after the rotating body is sandwiched inside. At that time, the mating surface portions of the upper and lower half casings usually have a flange structure in which a part protrudes to the outside, and the internal airtightness is maintained by a bolt tightened through the flange portion. .

  By the way, generally there is a gap between the rotating body and the stationary body, but if the working fluid leaks from this gap, it leads to energy loss, and therefore a seal mechanism for minimizing the leakage is used. This seal mechanism also has a ring shape in the assembled state, but has a segment structure composed of segment bodies divided into two or four before assembly. However, unlike the case of the casing, it is common to assemble them simply by attaching smooth mating surfaces without fastening them by bolts because of problems with internal space and cost.

  However, when used under high-temperature working fluid in steam turbines, gas turbines, etc., individual segment bodies are manufactured with dimensions that take into account this amount of deformation because they undergo large thermal deformation that differs from that during manufacture and assembly during operation. Need to do. However, since it is very difficult to accurately predict the heat distribution during operation and to produce individual seal rings divided in dimensions as determined from the predicted values, usually some tolerance was allowed. Designed. Therefore, there is actually a gap at the joint between adjacent segment bodies, and it is considered that energy is lost due to leakage due to blow-through from the gap.

  As a countermeasure, for example, Japanese Patent Application Laid-Open No. 2008-298286 (Patent Document 1) proposes a fitting structure in which one of the mating surfaces with a seal ring has a convex shape and the other has a concave shape. With this structure, it is possible to avoid a state where the working fluid is blown out due to a gap in the entire abutting surface while allowing a margin in dimensional tolerance during manufacturing. Furthermore, Japanese Patent Laying-Open No. 2012-92829 (Patent Document 2) proposes a structure in which the same mechanism is applied also in the radial direction of the seal ring butting surface.

JP 2008-298286 A JP 2012-92829 A

  Certainly, the use of Patent Document 1 or 2 can avoid the working fluid blow-through state, but the number of effective seal fins in the axial direction that overlap in the gap portion of the abutting surface is at most about 1/3 of the design value. The point which falls to may occur. And this fall amount does not improve even if the number of steps of unevenness is increased.

  By the way, the normal seal device is provided with a plurality of seal fins, and adiabatic expansion / compression is performed while the working fluid passes between the space created between the fins and the extremely narrow gap at the tip of the fin. Is repeated, and the passage flow rate is reduced by gradually reducing the pressure while generating a moderate loss. A decrease in the number of effective seal fins not only causes a direct increase in the amount of leakage, but also places where a large pressure drop occurs locally. When there is a large pressure drop, the working fluid excessively adiabatically expands and a large static temperature drop occurs, which increases the possibility of causing an uneven temperature distribution that causes thermal strain.

  Accordingly, an object of the present invention is to increase the number of effective seal fins for a seal ring that can avoid a state where the working fluid is blown out due to a gap in the entire joint portion of the segment body while allowing a margin for dimensional tolerance during manufacture. An object of the present invention is to provide a sealing device for a rotary machine that can reduce unnecessary leakage and improve turbine plant efficiency by minimizing the decrease in the above.

  An object of the present invention is to provide a rotary device seal comprising an annular seal ring and a plurality of axially provided seal fins on the inner peripheral surface of the seal ring, wherein the seal ring is composed of a plurality of annularly connected segment bodies. In the apparatus, this is achieved by providing a joining structure composed of continuous steps formed in a step shape when viewed from the radial direction at the circumferential end portion joining the adjacent seal segment bodies of the segment body.

  According to the present invention, not only the working fluid is blown out due to a gap in the entire joint portion of the segment body while allowing a margin for dimensional tolerance at the time of manufacture, but also the overlap of the seal fins over the entire region. Therefore, it is possible to bring the seal value close to the planned value, so that a high sealing performance as close as possible can be exhibited, unnecessary leakage can be reduced, and the turbine plant efficiency can be improved.

It is sectional drawing which represents typically the basic structure of a general turbine paragraph. It is a schematic diagram at the time of seeing a general two division type seal ring from an axial direction. It is a schematic diagram at the time of seeing a general 4 division type seal ring from an axial direction. 1 is a perspective view schematically showing a first embodiment of the present invention. It is the schematic diagram which looked at the conventional seal ring edge part from the radial direction outer side. FIG. 3 is a schematic view of the end portion in the circumferential direction of the seal ring according to the first embodiment of the present invention as viewed from the outside in the radial direction. FIG. 3 is a schematic view of the end portion in the circumferential direction of the seal ring according to the first embodiment of the present invention as viewed from the outside in the radial direction. It is the schematic diagram which looked at the circumferential direction edge part of the seal ring which concerns on 2nd Example of this invention from the radial direction outer side.

  Hereinafter, the form for implementing the sealing apparatus of this invention is demonstrated in detail with reference to figures suitably.

  A first embodiment of the present invention will be described. In order to facilitate understanding of the present invention, first, a basic structure of a general rotary machine (example of a steam turbine) and a sealing device will be described with reference to FIGS. 1 to 3, and then the sealing device according to the present embodiment will be described. The structure will be described with reference to FIG. Further, differences between the related art relating to the seal ring structure and the present invention will be described in detail with reference to FIGS.

FIG. 1 is a cross-sectional view schematically showing a basic structure of a general steam turbine stage. Here, a set of components composed of the moving blade 2 connected to the rotor 1 and the stationary blade 3 attached between the diaphragm outer ring 4b and the inner ring 4a is called a paragraph, and usually the paragraph is a rotor. A plurality of sets are provided in one axial direction to constitute the entire turbine stage. And the confidentiality inside a turbine is maintained by making it the structure which surrounds the circumference | surroundings of a turbine stage with a single or multiple casing.
In order to prevent leakage of the working fluid from the gap between the rotor and the stationary body, a sealing device 9 such as a labyrinth seal is usually used. In the example of FIG. 1, the sealing device 9 is used on the inner peripheral side of the diaphragm inner ring 4 a and the inner peripheral side of the seal holder 6 at the shaft end portion of the rotor 1.

  A sealing device 9 disposed around a rotor that is a rotating body includes an annular seal ring 10. The seal ring 10 is generally configured by arranging segment bodies in a ring shape.

  FIG. 2 is a schematic view of a general two-divided seal ring as viewed from the rotation axis direction of the rotor 1. The seal ring 10 includes two semi-annular segment bodies 7a and 7b. The side surfaces in the axial direction of the segment bodies 7a and 7b usually have a concavo-convex shape, and the concavo-convex shape is fitted to the diaphragm inner ring 4a and the seal holder 6 at the shaft end to hold the seal ring 10. Moreover, generally the circumferential direction edge part of each segment body 7a, 7b is formed in the smooth plane, and the circumferential direction edge part which opposes in the junction part 11 of segment body 7a, 7b is put together. An annular seal ring 10 is formed.

  FIG. 3 is a schematic view of a general four-divided seal ring as viewed from the rotation axis direction of the rotor 1. The four-part seal ring is obtained by further dividing the two-part seal ring shown in FIG. 2 into two parts. The four-part seal ring includes four segment bodies 7 a, 7 b, 7 c, and 7 d, and these are arranged in an annular shape to constitute an annular seal ring 10.

  By the way, as described in the background art, when such a sealing device is used under a high-temperature working fluid, it is necessary to manufacture a seal ring with a dimension that takes into account the amount of thermal strain during operation. However, since it is very difficult to accurately predict the heat distribution during operation and to produce a seal ring with the dimensions obtained from the predicted values, the design is usually tolerated by some tolerance. Therefore, in practice, there is a gap between adjacent segment bodies, for example, in FIG. 2, between the butted surfaces of the opposed circumferential ends of the segment bodies 7a and 7b. This is considered to cause a loss.

  In particular, as illustrated in FIG. 1, the sealing device 9 is arranged in multiple stages at the shaft end portion of the rotor 1 to gradually reduce the pressure, thereby reducing the amount of leakage by eliminating a large pressure difference from the outside. . However, in the sealing devices 9 provided in multiple stages, the positions of the joint portions between the segment bodies forming the seal ring 10 are usually aligned in each seal ring. For this reason, when a gap flow occurs at the abutting surface having a planar shape of the segment body, a blow-out occurs over a plurality of stages of the sealing device, and the leakage amount is larger than expected due to a large pressure difference (or pressure ratio) generated at both ends. There is a risk of an increase.

  Furthermore, when the working fluid is greatly adiabatic expansion / static temperature drop due to this large pressure difference (or pressure ratio), local thermal strain is also promoted, which may further increase the amount of leakage.

  As a countermeasure against this, a structure has been proposed in which one of the facing butting surfaces of the segment bodies adjacent in the circumferential direction is fitted in a convex shape and the other in a concave shape. Certainly, with this structure, it is possible to avoid a state in which the working fluid is blown out due to a gap in the entire joint, while allowing a margin for dimensional tolerance during manufacture. However, even in this case, in the gap portion of the joint portion, there may occur a portion where the number of effective seal fins in the axial direction is reduced to about 1/3 of the design value at the maximum. And this fall amount does not improve even if the number of steps of unevenness is increased.

  Further, the reduction in the number of effective seal fins not only directly increases the leakage amount, but also causes a location where a large pressure drop occurs locally. When there is a large pressure drop, the working fluid excessively adiabatically expands and a large static temperature drop occurs, which increases the possibility of generating a non-uniform temperature distribution that causes further thermal strain.

  The present invention solves the above-described problems.

  A first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a perspective view schematically showing a first embodiment according to the present invention, and is a perspective view of the vicinity (partial display) of an arbitrary joint 11 of the seal ring 10 as seen from the inner peripheral side of the ring. is there. 4 is an example in which the structure of FIG. 4 is applied to the joint portion 11 of the two-part seal ring shown in FIG. 2 or the four-part seal ring shown in FIG. Is shown.

  A plurality of seal fins 12 projecting in the radial direction are provided on the inner peripheral surfaces of the segment bodies 7a and 7b in the rotational axis direction of the rotor, and a slightly wider space is formed between the fins and the fins in the radial direction. . The plurality of seal fins 12 and the space therebetween provide an effect as a sealing device.

  In the seal ring 10 of the present embodiment, the end portions in the circumferential direction of the opposing segment bodies 7a and 7b are formed to have stepped steps so as to be fitted during assembly. A joining structure that joins the adjacent segment body 7a is formed at the circumferential end of the segment body 7b. As a joining structure, stepped steps are formed by alternately providing axial surfaces 8a parallel to the rotational axis direction and circumferential surfaces 8b perpendicular to the axial direction in the rotational axis direction. The step-like step is continuously formed from one end of the segment body in the rotation axis direction to the other end.

  On the other hand, a joining structure is also formed at the circumferential end portion of the opposing segment body 7a so as to mesh with the circumferential end portion of the segment body 7b. This joint structure also has stepped steps formed by alternately providing axial surfaces parallel to the axial direction and circumferential surfaces perpendicular to the axial direction in the axial direction.

  In the example of FIG. 4, a case where there are three steps is shown, but this is not the case in actual manufacturing. In addition, the cut lengths of the steps in the axial direction or the circumferential direction do not need to be the same, and even if thermal distortion and manufacturing tolerances are taken into account, the dimensions are such that the seal fins overlap in the axial direction when fitted. If it is good. And it can be seen that such a configuration can avoid a state where the working fluid is blown out due to a gap in the entire abutting surface while allowing a margin in dimensional tolerance at the time of manufacture. This will be described next. .

  Next, with reference to FIGS. 5 and 6, the difference between the related art relating to the structure of the joint portion 11 of the seal ring 10 and the present embodiment will be described in detail. FIG. 5 is a view of a joint portion of a seal ring having a concavo-convex shape according to the prior art as viewed from the outside in the radial direction. FIG. 6 is a view of the joint portion of the seal ring showing the first embodiment according to the present invention as seen from the outside in the radial direction. Here, the solid line in FIGS. 5 and 6 represents the top of the seal fin 12, and the arrow with reference numeral 20 represents a part of the flow of the working fluid. In FIG. 5, the number of effective seals composed of overlapping seal fins in the gap 13 formed between the circumferential end of the segment body 7a and the circumferential end of the segment body 7b is planned (total number of seal fins). ) Shows a state in which the working fluid passes through a portion that is reduced to 1/3. And this fall amount does not improve even if the number of steps of unevenness is increased.

  On the other hand, in the seal ring of the present invention, as shown in FIG. 6, the number of effective seals that overlap when the gap portion 13 between the segment body 7a and the segment body 7b has, for example, a three-stage axially divided step shape. Falls only to 2/3 of the planned (all seal fins). In principle, the amount of reduction in the number of effective seals decreases as the number of stages increases. For example, in the four-stage equal division, the number of effective seals can be ensured to be 3/4 of the plan, 4/5 of the plan in the case of five-stage division, and N-1 / N in the N-stage.

  As described above, according to the seal ring structure of the present embodiment, not only does the working fluid blown out due to the clearance between the entire butted surfaces, while allowing a margin in dimensional tolerance during manufacturing, the overfilling of the seal fins can be avoided. Since the wrap can be brought close to the design value over the entire region, it is possible to exhibit high sealing performance as close as possible to the planned value. Thereby, unnecessary leakage can be reduced and turbine plant efficiency can be improved.

  The present embodiment is not limited to the two-part or four-part seal ring shown in FIG. 2 or 3, but can be applied to a seal ring that is divided into a plurality of parts.

  Moreover, it is applicable not only to a steam turbine but also to other rotating machines such as a gas turbine.

  Next, a second embodiment of the present invention will be described with reference to FIGS. For ease of explanation, the problems in the first embodiment are pointed out with reference to FIG. 7, and the improved structure (second embodiment) is described with reference to FIG.

  FIG. 7 is a view of the seal ring end portion according to the first embodiment of the present invention as viewed from the outside in the radial direction. The solid line represents the top of the seal fin 12, the dotted line represents the lower portion between the fins at the circumferential end of the seal ring, and the arrow with reference numeral 20a represents part of the flow of the working fluid. A thrust force due to an axial pressure difference is applied to the side surfaces of the segment bodies 7a and 7b. Therefore, the segment bodies 7a and 7b come into contact with any one of the circumferential surfaces of the steps formed in a stepped shape at the circumferential end 14. The position is indicated by reference numeral 30 in FIG. As shown in FIG. 7, the structure of Example 1 in which the segment bodies 7a and 7b are in contact with any one of the circumferential surfaces of the stepped end portion can prevent the working fluid from being blown out from the gap portion 13. It is possible to keep the number of effective fins high. However, at the circumferential end 14, there is a slightly larger space in the radial direction between the fins than the portion where the fins are present. There is a slight possibility of the working fluid leaking through that rather large space. This is indicated by the arrow 20a.

FIG. 8 is a view of the seal ring end portion according to the second embodiment of the present invention as viewed from the outside in the radial direction. The solid line represents the top of the seal fin 12. Further, in this embodiment, at the circumferential ends of the segment bodies 7a and 7b, the gap between the fins is processed so as to have the same radial height as the tip of the seal fin, and the leakage fluid flows between the fins. A weir 15 is provided to block the flow in the circumferential direction. Thereby, there is no wide space in the radial direction between the fins at the end in the circumferential direction, and unnecessary leakage can be reliably reduced. Here, an arrow with a reference numeral 20 represents a part of the flow of the working fluid, and shows that there is no wide flow path through which the working fluid can be easily passed. In addition, since the ground contact side surface position 30 can be determined in advance relatively easily by adjusting the axial dimension of the stepped joint, the leakage route indicated by 20a in FIG. 7 can be predicted to some extent. Therefore, in practice, it is not necessary to adjust the height of the end of the entire joint, and the weir 15 may be provided by processing only a portion having a large radial space on the assumed route.

  Therefore, according to the seal ring structure of the present embodiment, not only does the working fluid blow-through state due to the gap between the entire butted surfaces not only avoiding the dimensional tolerance at the time of manufacture, but also planning. High sealing performance close to the value can be exhibited. Thereby, unnecessary leakage can be reduced and turbine plant efficiency can be improved.

DESCRIPTION OF SYMBOLS 1 Rotor 2 Rotor blade 3 Stator blade 4a Diaphragm inner ring 4b Diaphragm outer ring 5 Inner casing 6 Seal holder 7a, b, c, d Segment body 9 Sealing device 10 Seal ring 12 Seal fin 15 Weir

Claims (4)

A rotary machine seal device comprising an annular seal ring and a plurality of axially provided seal fins on the inner peripheral surface of the seal ring, wherein the seal ring is composed of a plurality of annularly linked segment bodies. And
A seal device comprising a segment body joining structure comprising continuous steps formed in a step shape when viewed from the radial direction at an end in a circumferential direction facing an adjacent seal segment body of the segment body.   The segment body joining structure is formed by alternately providing an axial surface extending in the axial direction and a circumferential surface extending in the circumferential direction from one end to the other end in the axial direction of the seal ring. The sealing device according to claim 1.   3. The sealing device according to claim 1, wherein a weir having a radial height similar to that of a tip end portion of the seal fin is provided between the seal fins at a circumferential end portion of the segment body.   A rotary machine comprising the seal device according to any one of claims 1 to 3 between a rotary shaft and a stationary body.