JP4387697B2 - Steam turbine seal device and steam turbine provided with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a seal device that reduces the leakage flow of steam at the blade tip of a steam turbine and a steam turbine using the seal device, and in particular, suppresses erosion due to drain (condensed moisture) in the steam, and adjusts the gap. The present invention relates to a steam turbine seal device that is easy to maintain and a steam turbine using the same.
[0002]
[Prior art]
The work efficiency of the steam turbine is affected by the amount of steam that flows through the blades (the blades), that is, actually rotates the blades (the blades). In other words, the sealing technology of how to reduce the steam leaking from the gap between the diaphragm outer ring and the blades affects the performance of the steam turbine. Therefore, a sealing technique for adjusting the steam flow that does not directly contribute to the rotation of the blades is positioned as an important technique for improving the performance of the turbine.
[0003]
As such steam turbine sealing technology for improving steam turbine efficiency, there is a technology for preventing leakage of working fluid by providing a honeycomb cell in a gap between a diaphragm and a wheel (turbine shaft) (for example, Patent Document 1). .
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-123803
[Problems to be solved by the invention]
However, when the wetness of steam is large, as represented by geothermal turbines, the inner surface of the seal ring holder is eroded by drainage (moisture) in the steam due to turbine operation for many years, and the gap between the seal ring holder and the wheel is increased. Inevitably increases the performance of the system.
[0006]
In a turbine having a conventional structure, it is necessary to remanufacture and replace the entire diaphragm inner and outer rings, so it is difficult to restore this gap to the original value.
[0007]
In addition, a method of fixing the seal ring holder as a separate member to the diaphragm by a fixing means is also used in the conventional steam turbine. However, since the separate diaphragm itself is a large member, the manufacturing cost is high. It is not easy to remove and install. Further, since the seal ring holder is a member located on the outer periphery of the rotating structure, it is necessary to accurately center the rotating structure, and it takes time to perform the centering operation at the turbine installation site. Also, it was not an easy task from the aspect of accuracy.
[0008]
The present invention has been made to solve the above-described problems, facilitates adjustment of the gap between the diaphragm and the blades, has excellent maintainability, has excellent corrosion resistance, and is used for long-term operation of a steam turbine. It is an object of the present invention to provide a steam turbine seal device capable of maintaining good turbine efficiency and a steam turbine using the same.
[0009]
[Means for solving the problems]
As described in claim 1, the steam turbine seal device according to the present invention includes a turbine wheel, blades implanted in the turbine wheel, seal fins provided at the tip of the blades, and a diaphragm outer ring. In a steam turbine including a diaphragm inner ring, and the diaphragm outer ring and a nozzle blade sandwiched between the diaphragm inner ring, a portion of the inner peripheral surface of the seal ring holder extending from the diaphragm outer ring is opposed to the blade tip. installing a removable ring segments, the seal fins and the ring segment and provided adjustable gap formed by Rutotomoni, .phi.A the seal ring holder upstream inner diameter, [phi] B and the ring segment inside diameter, the seal ring When the inner diameter on the downstream side of the holder is φC, the operating flow is φA <φB <φC Is characterized in that in accordance with the flow from the upstream side is configured to increase the inner diameter toward the downstream side. The steam turbine seal device according to the present invention includes, as described in claim 4, a turbine wheel, blades implanted in the turbine wheel, seal fins provided at the tip of the blades, and a diaphragm. In a steam turbine including an outer ring, a diaphragm inner ring, and a nozzle blade sandwiched between the diaphragm outer ring and the diaphragm inner ring, the blade faces the tip of the blade on the inner peripheral surface of a seal ring holder extended from the diaphragm outer ring. A detachable ring segment is installed in the portion, and a gap formed between the seal fin and the ring segment is provided to be adjustable, and a drain is provided upstream of the working fluid at a connection portion between the ring segment and the seal ring holder. A drain catch space is formed by providing a trapping gap. A drain hole for communicating the drain catch space and the outside of the diaphragm outer ring for discharging moisture circulated through the outer space to the outside of the diaphragm outer ring is provided. .
[0010]
The steam turbine according to the present invention, as described in claim 5, in which with a steam turbine seal device as claimed in any one of claims 4.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A steam turbine seal device of the present invention and a steam turbine using the same will be described below with reference to the drawings.
[0012]
FIG. 1 shows a first embodiment of a steam turbine seal device according to the present invention.
[0013]
One stage, which is the minimum unit of the steam passage section in the steam turbine, is composed of a nozzle 1 and blades (moving blades) 2. The nozzle 1 is held by a diaphragm inner ring 3 and a diaphragm outer ring 4. A seal ring holder 5 is extended from the diaphragm outer ring 4 so as to surround the outer periphery of the wheel 6.
[0014]
On the other hand, the blades 2 are implanted and fixed on the outer periphery of the wheel 6. A seal fin 7 is provided at the tip of the blade 2 in order to prevent vapor leakage from the gap between the seal ring holder 5 and the tip of the blade 2.
[0015]
Further, in the seal ring holder 5, a ring segment 11, which is a separate structure from the seal ring holder 5, is integrally installed on a surface facing the seal fin 7 at the tip of the blade 2. The ring segment 11 is fixed to the seal ring holder 5 by a fixing structure such as a dovetail groove provided on the inner peripheral surface of the seal ring holder 5. The ring segment 11 is usually composed of 4 to 8 parts in the circumferential direction of the inner periphery of the seal ring holder 5, and these ring segments 11 are respectively sealed along the circumferential direction of the seal ring holder 5. It is integrally fixed while being biased in the direction of the seal fin 7 by a leaf spring (not shown) installed between the ring holder 5 and the ring segment 11.
[0016]
The steam (arrow 14) circulated from the upstream is expanded and accelerated by flowing through the nozzle 1, and rotates the blade 2 to generate power. On the other hand, the moisture condensed by the steam is scattered to the outer peripheral side of the wheel 6 by centrifugal force and tends to flow through the gap between the seal ring holder 5 and the ring segment 11 as a leaked steam flow as indicated by an arrow 15. The condensed water gathers to form a water flow, and erosion proceeds by the water veins flowing on the wall surface. As a result, the gap between the blade 2 and the seal ring holder 5 is expanded.
[0017]
Therefore, in the steam turbine seal device of the first embodiment, when the ring segment 11 having a separate structure is installed on the inner peripheral surface of the seal ring holder 5, when the gap becomes wider than erosion, the eroded ring segment By replacing 11 with a new one, the gap can be easily returned to the original clearance, and the performance of the steam turbine can be restored.
[0018]
Since the ring segment 11 is a small member compared to the steam turbine body, the cost required for replacement is minimized. In addition, compared with a conventional steam turbine in which the seal ring holder 5 itself is replaced, the member cost is reduced and the centering is easy, so that the working time can be improved.
[0019]
FIG. 2 shows a second embodiment of the steam turbine seal device according to the present invention.
[0020]
In assembling the actual turbine, when the turbine rotor is assembled, the inner diameter of the ring segment 11 is adjusted in order to adjust the gap between the seal fin 7 of the blade 2 and the ring segment 11 to an appropriate value. During this adjustment process, a step may be formed in the steam flow direction between the inner surface of the seal ring holder 5 and the inner surface of the ring segment 11. If there is such a step, the flow of the condensed water to the downstream side is alienated, and the moisture stays in this gap to accelerate the erosion and corrosion of the seal fin 7.
[0021]
Therefore, in the steam turbine seal device of the second embodiment, the seal ring holder 5 upstream inner diameter φA, the ring segment 11 inner diameter φB, and the seal ring holder 5 downstream inner diameter φC are increased in this order.
[0022]
That is, the steam turbine seal device of the second embodiment is configured such that the inner diameter of each component increases as it goes downstream in the flow direction of moisture. That is, since the inner diameter φA of the upstream side of the seal ring holder 5, the inner diameter φB of the ring segment 11, and the inner diameter φC of the downstream side of the seal ring holder 5 are set to satisfy the relationship of φA <φB <φC, the water flow due to the step is excluded. It is possible to discharge moisture smoothly. Accordingly, the retention of moisture at the tip of the blade 2 is effectively prevented, and therefore it is possible to prevent the inner surface of the seal fin 7 and the seal ring holder 5 and the ring segment 11 from being eroded.
[0023]
FIG. 3 shows a third embodiment of the steam turbine seal device according to the present invention.
[0024]
During the operation of the steam turbine, the components of the steam turbine are heated to a high temperature by the high-temperature and high-pressure steam flowing through the passage portion constituted by the nozzle 1 and the blades (robot blades) 2. However, the passage portion is composed of the nozzle 1 and the blade 2 when the steam turbine is stationary and when the steam turbine is in operation due to the difference in thermal expansion coefficient and thermal conductivity due to the difference in material between the rotating portion (wheel side) and the stationary portion (nozzle side). The relative position changes in the turbine axial direction.
[0025]
Therefore, in the steam turbine seal device of the third embodiment, a slant structure is provided in which the inner surface of the ring segment 11 and the tip of the seal fin 7 are provided with an inclination S along the turbine axial direction. In general, the relative movement direction on the wheel side due to thermal expansion is the direction indicated by the arrow 16.
[0026]
According to the steam turbine seal device of the third embodiment, during operation of the turbine, as shown in FIG. 3, the ring segment 11 and the tip of the seal fin 7 at the blade tip have an inclination S in the same direction in the axial direction. Since the configuration is provided, when the wheel side moves relatively in the direction of the arrow 16, that is, in the direction approaching the nozzle 1, it is possible to control the gap between the operating blade and the segment small. Therefore, during the operation of the turbine, the minimum gap is maintained following the dimensional change due to thermal expansion, so that the turbine efficiency can be improved.
[0027]
FIG. 4 shows a fourth embodiment of a steam turbine seal device according to the present invention.
[0028]
In the steam turbine seal device of the fourth embodiment, the ring segment 11 is integrally fixed to the seal ring holder 5 by bolts 17 as fixing means. An adjustment shim 18 is mounted between the bolt 17 and the seal ring holder 5.
[0029]
According to the steam turbine seal device of the fourth embodiment, the inner diameter of the ring segment 11 can be finely adjusted by adjusting the number (thickness) of the adjustment shims 18. Therefore, the adjustment of the gap between the seal fin 7 and the ring segment 11 becomes extremely easy.
[0030]
As in the steam turbine seal device of the fourth embodiment, the inner diameter of the ring segment 11 can be easily adjusted, so that even when the gap increases due to erosion during the operation of the turbine, the ring segment 11 and Since it is possible to easily restore the optimal gap without replacing other components, the maintenance cost is greatly reduced. Note that a fixing means such as a bolt 17 may be provided in a combination of a dovetail groove and a leaf spring as shown in the first embodiment, and an adjustment shim 18 may be provided to adjust the gap.
[0031]
FIG. 5 shows a fifth embodiment of a steam turbine seal device according to the present invention.
[0032]
In the steam turbine seal device of the fifth embodiment, the ring segment 11 is arranged in the seal ring holder 5 as in the fourth embodiment. A seal fin 7 is installed at the tip of the blade.
[0033]
In the steam turbine seal device according to the fifth embodiment, a gap is provided at a connection portion between the ring segment 11 and the seal ring holder 5 and a drain catch space 19 for trapping moisture is installed. Further, the seal ring holder 5 is provided with a drain hole 21 which is a through hole that communicates the inner surface side of the seal ring holder 5 and the outside of the diaphragm outer ring 4. Further, the drain catch space 19 is provided on the upstream side of the steam flow, that is, on the front end side (nozzle 1 side) of the foremost seal fin 7a of the seal fin 7 for the purpose of capturing moisture.
[0034]
According to the steam turbine seal device having such a configuration, the condensed moisture hits the front row seal fin 7a, is scattered in the outer peripheral direction of the wheel 6 by centrifugal force, and is captured by the drain catch space portion 19 provided in advance. Furthermore, the trapped moisture is discharged to the outside through a drain hole 21 which is a through hole communicating with the outside. Accordingly, moisture does not stay in the gap formed by the seal fin 7 and the ring segment 11, and the erosion of the seal fin 7 and the ring segment 11 is prevented. It is possible to maintain good performance for a long time.
[0035]
Moreover, in the steam turbine seal device of the first to fifth embodiments, it is preferable that a material having corrosion resistance is disposed on the inner surface of the ring segment 11. This corrosion resistant material can effectively prevent erosion induced by moisture during turbine operation.
[0036]
In addition, the steam turbine which installed the steam turbine seal apparatus of these 1st Embodiment to 5th Embodiment improves operating efficiency, and since it is excellent in corrosion resistance, it maintains the performance stable also in long-term operation | movement favorably. Therefore, it is possible to provide a highly efficient and highly reliable steam turbine.
[0037]
【The invention's effect】
According to the steam turbine seal device of the present invention and the steam turbine using the same, a separate ring segment is provided on the inner surface of the seal ring holder so that moisture can smoothly pass through the wall surface, thereby preventing erosion of the seal ring holder. Therefore, it is possible to provide a highly efficient and reliable steam turbine. In addition, even when the ring segment is eroded, the restoration work can be easily and reliably performed by replacing the ring segment having a separate structure.
[Brief description of the drawings]
FIG. 1 is a structural diagram showing a first embodiment of a steam turbine seal device according to the present invention.
FIG. 2 is a structural diagram showing a second embodiment of a steam turbine seal device according to the present invention.
FIG. 3 is a structural diagram showing a third embodiment of a steam turbine seal device according to the present invention.
FIG. 4 is a structural diagram showing a fourth embodiment of a steam turbine seal device according to the present invention.
FIG. 5 is a structural diagram showing a fifth embodiment of a steam turbine seal device according to the present invention.
[Explanation of symbols]
1 Nozzle 2 Blade 3 Diaphragm inner ring 4 Diaphragm outer ring 5 Seal ring holder 6 Wheel 7 Seal fin 7a Front row fin 11 Ring segment 14 Arrow 15 indicating steam flow (during nozzle circulation) Arrow 16 indicating leaked steam flow (moisture) Arrow indicating movement direction 17 Bolt 18 Adjustment shim 19 Drain catch space 21 Drain hole

Claims (5)

A turbine wheel, a blade implanted in the turbine wheel, a seal fin provided at a tip of the blade, a diaphragm outer ring, a diaphragm inner ring, and a nozzle blade sandwiched between the diaphragm outer ring and the diaphragm inner ring In the steam turbine comprising: a detachable ring segment is installed at a portion of the inner peripheral surface of the seal ring holder that extends from the outer ring of the diaphragm that faces the tip of the blade, and is formed by the seal fin and the ring segment And the seal ring holder upstream inner diameter is φA, the ring segment inner diameter is φB, and the seal ring holder downstream inner diameter is φC,
φA <φB <φC
A steam turbine seal device configured to increase the inner diameter from the upstream side to the downstream side according to the flow of the working fluid.   The steam turbine seal device according to claim 1, wherein an inclination is provided on an inner peripheral surface of the ring segment so that an inner diameter of the ring segment gradually increases from the upstream side to the downstream side of the working fluid. .   The ring segment is fixed to the seal ring holder by a fixing unit, and the fixing unit is adjusted to adjust the gap between the seal fin at the tip of the moving blade and the ring segment. The steam turbine seal device according to Item 1. The steam turbine seal device according to any one of claims 1 to 3, wherein the ring segment is made of a corrosion-resistant material. A steam turbine comprising the steam turbine seal device according to any one of claims 1 to 4 .

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