JPS61250304A - Axial flow turbine - Google Patents

Abstract

PURPOSE:To greatly improve turbine efficiency by disposing an axial seal fin in a leak passage formed between a turbine turning part and a turbine stationary part and constituting said seal fin as that the clearance between the fin and the turbine turning part can be forcedly adjusted according to the turbine condition. CONSTITUTION:Axial seal fins 15 and 18 are disposed, respectively, in a clearance (leak passage) 10A formed between a turbine turning part which contains both an impeller 2 and a moving blade 3, and a diaphragm internal wheel 7A fixed to a casing 5 which surrounds the turbine turning part, and a clearance (leak passage) 12 formed between a turbine stationary part containing both stationary blades 8A and 8B, and the shroud 4 of the turbine turning part. Each of the seal fins 15 and 18 is engagingly inserted respectively into the ring-like grooves 16 and 19 of the internal wheel 7A and an external wheel 6A, supported movably in the axial direction by a plurality of shape memorizing alloy members 17 and 20 which are disposed inside respective grooves 16 and 19. Each of the shape memorizing alloy members 17 and 20 is disposed as to get long as a turbine runs at higher temperature.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an axial flow turbine such as a steam turbine, and more particularly to an axial flow turbine that prevents leakage of working fluid from a gap between a rotating part and a stationary part of the turbine. .

[Technical background of the invention and its problems]

An axial flow turbine is composed of a stationary part and a rotating part, and a gap is provided between them so that they do not come into contact with each other during operation. If this gap is too narrow, the risk of contact accidents will increase, and if it is too large, leakage loss due to the amount of working fluid leaking from this gap will increase, resulting in a large stage loss. Especially in a stage where the rotor blades are short and the flow path is narrow, the above leakage loss is
It accounts for nearly 173 of the stage loss, and it has become important to reduce this leakage loss in order to improve turbine performance.

Figure 8 shows a conventional axial flow turbine, in which a plurality of moving blades are fixed at a predetermined pitch in the circumferential direction at the tip of an impeller 2 that is integrally formed with a rotor 1. . A shroud 4 is attached to the tips of these movements 113. These rotor 1, impeller 2, drive 113, and shroud 4 constitute a turbine rotating section. On the other hand, on the side of the casing 5 that surrounds this rotating part, a turbine stationary part consisting of a diaphragm outer ring 6 on the Shizuoka side, a diaphragm inner ring 7 on the stator blade side, and a plurality of stator blades 8 between these is installed. .

High-temperature steam F, which is a working fluid, flows in the direction of the arrow in the flow path 9 formed by the outer ring 6, the inner ring 7, the outer periphery of the impeller 2, and the shroud 4, is accelerated by the static II 8, and rotates the rotor blade 3. . A gap formed between the inner ring 7, the rotor 1, and the impeller 2 is a leak passage 1 that bypasses a part of the flow passage 9.
0 and a part of the steam F flowing through the flow path 9 leaks into the leakage path 10 and flows out into the flow path 9 again as leaked steam FR. In order to reduce the amount of this leaked steam FR, radial seal fins 11 are provided protruding from the inner ring 7 in the gap between the inner circumferential surface of the inner ring 7 and the outer circumferential surface of the rotor 1. Similarly, a leak passage 12 is formed between the shroud 4 and the stationary part, bypassing a part of the flow passage 9.
In order to reduce leakage steam F1 leaking to the shroud 4, seal fins 13 are provided in a radial direction to protrude from the inner peripheral surface of the extension 6a of the outer ring 6 toward the shroud 4.

The leaked steam F0 reduces the stage efficiency, and the leaked steam FR disturbs the steam flow near the root of the movable m3, increasing loss. Therefore, in order to reduce these leaked steam m, it is desirable to make the clearance between the shroud 4 and the seal fin 13 and the clearance between the rotor 1 and the seal fin 11 as small as possible. however,
The above-mentioned clearance changes in the circumferential direction between when the zero-tar 1 is at rest and when it is rotating, and there is also some whirling due to eccentricity. Furthermore, since the rotating part warms up more easily than the stationary part, the difference in thermal expansion between the rotating part and the stationary part increases when the turbine is started, and the above-mentioned clearance changes significantly.

The clearance between the shroud 4 and the seal fin 13 and the clearance between the 0-taper 1 and the seal fin 11 are determined in consideration of the above-mentioned changes, so they are usually quite large values, especially when the turbine is large or at high temperatures. When the pressure is increased, the value becomes extremely large, resulting in a significant decrease in turbine efficiency.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an axial flow turbine that can sufficiently reduce steam m leaking from a gap between a rotating part of the turbine and a stationary part of the turbine, thereby improving turbine efficiency.

[Summary of the invention]

In order to achieve this object, the first invention of the present application provides for leakage that bypasses a part of the working fluid flow path between a turbine rotating part and a turbine stationary part fixed to the casing side surrounding this rotating part. In an axial flow turbine in which a passage is formed, the axial flow turbine is slidably supported in the axial direction with respect to the stationary part,
It is characterized by comprising: an axial seal fin that can protrude in the axial direction from the stationary part toward the rotating part within the leakage passage; and a drive means for moving and displacing the seal fin towards the rotating part. That is. Further, a second invention provides an axial flow turbine in which a leakage passage that bypasses a part of the working fluid flow path is formed between a turbine rotating part and a turbine stationary part fixed to a casing side surrounding the rotating part. In the turbine stationary part, the turbine stationary part is attached so as to be movable in the axial direction with respect to the casing via a stator blade attachment member, and between the attachment member and the casing, there is a space between which the thrust force applied to the stator blade during turbine operation is disposed. A biasing member is provided that biases the mounting member in a direction opposite to the force, and a seal fin that can protrude in the axial direction from one of the mounting member and the rotating portion to the other is fixed to one of the mounting members. That is.

[Embodiments of the invention]

An embodiment of an axial flow turbine according to the present invention will be described below with reference to FIGS. 1 to 7, in which the same parts as in FIG. 8 are denoted by the same reference numerals.

In FIG. 1, the turbine rotating section is similar to FIG.
A rotor 1, an impeller 2 integrally formed with the rotor 1, and a plurality of impellers installed at predetermined intervals along the circumferential direction at the tip of the impeller 2. 113, and an arc-shaped shroud 4 fixed to the free ends of these movements 13 by tenons 14. The turbine stationary part is similar to that shown in FIG. 8, and includes a casing 5 surrounding the rotating part, diaphragm outer rings 6A and 6B fitted and fixed to this casing, and a diaphragm inner ring 7A.

7B, a plurality of static plates 118A sandwiched between the outer rings 6A, 6B and the inner rings 7A, 7B and arranged annularly at predetermined intervals,
It is composed of 8B.

A flow path 9 for steam F is formed between the inner rings 7A, 7B and the outer rings 6A, 6B, and between the outer peripheral surface of the impeller 2 and the shroud 4. A gap 11i10A formed between the inner ring 7A, the rotor 1, and the impeller 2 forms a leak passage that bypasses a part of the flow path 9. Furthermore, the gap 12 formed between the shroud 4 and the stationary portion also forms a leakage passage that bypasses a portion of the flow path 9. Upstream leak passage 10
A ring-shaped axial seal fin 15 is provided between the inner ring 7A and the impeller 2 in the gap between the inner ring 7A and the impeller 2.
It protrudes axially towards. This seal fin 15 is fitted into a ring-shaped groove 16 of the inner ring 7A.
The inner ring 7A is slidably supported in the axial direction via a plurality of shape memory alloy members 17 therein. These shape memory alloy members 17 are arranged at equal angular intervals and are configured in a spring shape that contracts in a low temperature state when the turbine is stationary and expands in a high temperature state when the turbine is in steady operation. Also, the side surface of the upstream outer ring 6A in the leakage passage 12 and the shroud 4
A ring-shaped axial seal fin 18 also protrudes from the outer ring 6A toward the shroud 4 in the gap therebetween. This seal fin 18 is supported by a plurality of shape memory alloy members 20 in a groove 19 of the outer ring 6A so as to be slidable in the axial direction. These seal fins 18, grooves 19, and shape memory alloy members 20 have the same configurations as the seal fins 15, grooves 16, and shape memory alloy members 17 of the inner ring 7A, respectively.

An axial seal fin 21 protruding toward the impeller 2 is fixed to the side wall of the downstream inner ring 7B, and similarly the downstream outer ring 6
An axial seal fin 22 protruding toward the shroud 4 is fixed to the side wall of B.

According to the present invention configured in this way, both the shape memory alloy members 17 and 20 are contracted when the turbine is stationary;
A predetermined clearance is formed between the tips of the axial seal fins 15 and 18 and the impeller 2 and the shroud 4, and a predetermined clearance is formed between the tips of the fixed axial seal fins 21 and 22 and the impeller 2 and the shroud 4. A relatively large clearance is formed.

When the turbine is started in this state and high-temperature steam, which is the working fluid F, flows into the flow path 9, the rotor blades 3 are rotated and the entire turbine is heated. The thrust bearing of the rotor, which is the fixed point of the rotating part, is located upstream of the illustrated paragraph, and the fixed point of the stationary part is also located upstream, so thermal expansion of the rotor 1 causes impellers 2, 113113, and shroud 4 to are displaced downstream, and similarly, due to thermal expansion of the casing 5, the stator vane diaphragm outer rings 6A, 6B and the inner ring 7A.

7B and static 18A; 8B is also displaced downstream. However, the amount of thermal expansion in the axial direction is higher for rotor 1 than for casing 5.
Therefore, during steady operation, the axial clearance between the upstream outer ring 6A and the impeller 2 and the axial clearance between the upstream outer ring 6A and the impeller 2 are both larger than when the turbine is stopped. On the other hand, when the shape memory alloy members 17 and 20 reach a high temperature steady state of operation, they elongate and the axial seal fins 15, 18
are slid in the axial direction so as to further protrude from the inner ring 7A and outer ring 6A, respectively. Due to this sliding, the clearances between the seal fins 15, 18, the impeller 2, and the shroud 4 are sufficiently reduced to reduce the amount of leaking steam into the leak passages 10A and 12, respectively.

When the leaked steam is reduced in this way, the steam flow flowing around the flow path 9, that is, near the inner circumferential surface of the outer ring and the outer circumferential surface of the inner ring, is significantly less disturbed by the leaked steam, and vortex loss can be reduced.

Fig. 2 shows the relative positional relationship between the upstream outer ring 6A and the shroud 4 when the turbine is stopped and during steady operation, with the outer ring 6A as a reference.The solid line indicates the position when the turbine is stationary, and the broken line indicates the position when it is stopped. show. Also, since the axial clearance between the downstream inner ring 7B and the impeller 2 and the axial clearance between the downstream outer ring 6B and the shroud 4 are smaller during steady operation than when stopped, it is natural that the axial clearance between the impeller 2 and the shroud 4 will be smaller. The clearance with the fins 21 and the clearance between the shroud 4 and the axial seal fins 22 are both reduced, reducing the amount of leaked steam.

In this way, the axial seal fins 15.18 are displaced to the optimum position in response to changes in the condition of the turbine, and the leakage passage 10A is closed.
, 12 are sufficiently small, the radial seal fins shown in FIG. 8 can be omitted. Therefore, it is possible to prevent the so-called steam whirl phenomenon caused by the presence of the radial seal fins, and it is also possible to prevent accidents caused by contact with the radial seal fins due to whirling of the rotor. Furthermore, if a radial seal fin existed, it would be necessary to bury the tenon 14 so that it would not protrude from the outer peripheral surface of the shroud 4, but by omitting the radial seal fin, this is no longer necessary and the structure is simplified. At the same time, stress between the tenon and the shroud can also be reduced.

In the above embodiment, the downstream seal fins 21 and 22 are fixed, which is effective when the relative axial displacement between the rotating part and the stationary part is relatively small at high temperatures, but when it is large, A sufficient sealing effect cannot be achieved. Therefore, a modified example that improves this point will be described below.

In FIG. 3, downstream axial seal fins 23, 24
are axially connected to the inner ring 7B and outer ring 6B by the groove 25 and shape memory alloy member 26 of the downstream inner ring 7B and the groove 27 and shape memory alloy member 28 of the downstream outer ring 6B, respectively, similarly to the upstream seal fins 15 and 18. It is slidably supported.

These shape memory alloy parts [26, 28 are of the type that contract at low temperatures and expand at high temperatures like the upstream shape memory alloy members 15 and 18, but the axial seal fins 23
The seal fins 23 and 24 are attached in different ways, and when the temperature is low, the seal fins 23 and 24 are respectively projected in the direction toward the rotating part, and when the temperature is high, they are retracted in the opposite direction.

The other configurations are exactly the same as in FIG. 1.

With this configuration, even if the rotating part is displaced relatively largely downstream with respect to the stationary part at high temperatures, the downstream seal fins 23 and 24 also slide downstream at this time, so the seal The clearance between the fins 23, 24 and the rotating part can also be maintained in an optimum state at all times.

FIG. 4 shows a second embodiment of the present invention, in which the axial seal fin 18 is attached to the outer ring 6A in the axial direction by a filler 19 of the upstream outer ring 6A and a shape memory alloy member 20, just as in FIG. A gap measuring device 29 for measuring the gap between the shroud 4 and the seal fin 18 is fixed to the seal fin 18 . The outer ring 6A is bored with a steam inlet hole 30 for controlling the alloy member, which communicates with the outer ring 6A.
A low temperature steam supply pipe 32 and a high temperature steam supply pipe 33 are connected via a switching valve 31. These supply pipes 32 and 33 selectively supply low-temperature steam and high-temperature steam for controlling the alloy member to the inlet hole 30 via switching valves 31, respectively. The pressures of the low-temperature steam and high-temperature steam for controlling alloy members are both set to be higher than the outlet pressure of the static 18A.

The outer ring 6A is further provided with a vapor outlet hole 34 for controlling the alloy member, which communicates the groove 19 with the flow path 9. The controller 35 controls the switching valve 31 according to the output signal of the gap measuring device 29, and when the gap between the axial seal fin 18 and the shroud 4 is small, the low temperature steam supply pipe 32 is
When the temperature is large, the high temperature steam supply pipe 33 is connected to the inlet hole 3.
Connect to 0.

Next, this effect will be explained.

The gap measuring device 29 constantly measures the amount of gap between the seal fin 18 and the shroud 4 during turbine operation. The controller 35 communicates the high-temperature steam supply pipe 33 with the inlet hole 30 when the gap 11jiffi becomes too large, and the low-temperature steam supply pipe 32 with the inlet hole 30 when the gap 11jiffi becomes too small, in accordance with the output signal of the gap measuring device 29. , selector valve 3
Control 1.

Therefore, when the gap FIAW1 becomes too large, the shape memory alloy member 29 is heated and expanded by the high temperature steam, and the seal fin 18 is slid toward the shroud 4 side to reduce the gap, and conversely, the gap becomes too small. Sometimes the sealing fin 18 is cooled by low-temperature steam and contracts.
Slide in the opposite direction to increase the gap. In this way, the clearance between the seal fin and the shroud can always be controlled to an optimum value.

In this example, the gap between the seal fin and the shroud is measured and the shape memory alloy member is controlled according to this result, so the clearance between the seal fin and the shroud can be controlled with higher precision. can.

It goes without saying that such a configuration can also be adopted for the upstream inner ring, the downstream inner ring, and the outer ring.

Further, in this embodiment, a controller 35 is provided to automatically control the sliding of the seal fin 18 via the shape memory alloy member based on the output signal of the gap measuring device 29, but instead of this, the output signal of the measuring device 29 is It may be configured such that the information is displayed on a display and the switching valve 31 can be manually operated in accordance with the indication. Further, in FIGS. 1 to 4, a shape memory alloy member is used as a temperature deformable member that deforms depending on the temperature, but a material having a large coefficient of linear expansion such as an austenitic alloy or a bimetal may be used instead.

In each of the above embodiments, the upstream seal fin is the upstream inner ring,
The gap with the stationary part was controlled by making it slidable relative to the outer ring, but next, the upstream seal fin was fixed and the entire stator vane diaphragm was moved axially relative to the casing. An embodiment in which the gap is controlled by making it slidable will be described.

FIG. 5 shows a third embodiment of the present invention, in which an upstream Shizuoka diaphragm outer ring 6A is fitted into a groove 36 of the casing 5, and the outer ring 6A has a length of 36 in the axial direction. The axial length of the outer ring 6A is set to be larger than the axial length of the outer ring 6A by a predetermined amount so that the outer ring 6A can slide by a predetermined amount in the axial direction. Further, a key groove 37 is formed in the casing 5, and a key 38 fitted therein prevents the outer ring 6A from shifting. A shroud 4 is installed on the downstream side of this outer ring 6A.
An axial seal fin 39 protruding toward is fixed. Further, in the inwardly protruding portion 5a of the casing 5 that protrudes toward the shroud 4, a plurality of spring housing holes 40 are bored at approximately equal angular spacing in the circumferential direction.
Compression springs 41 are housed between the outer ring 6A and the downstream side surface of the outer ring 6A, and these springs 41 urge the outer ring 6A toward the upstream side in the axial direction.

An outer ring extension 6a is interposed between the shroud 4 and the casing inward projection 5a, and a radial seal fin 13 is protruded from this as in FIG. 7. In addition, the upstream inner ring 7A has an axial seal fin 4 protruding toward the impeller 2.
2 is permanently installed.

Next, the effect will be explained.

When the turbine starts and the temperature rises as the load increases, the gap between the axial seal fin 39 and the shroud 4 and the gap between the seal fin 42 and the impeller 2 decrease due to the difference in axial thermal expansion between the rotating part and the stationary part. will grow together. On the other hand, as the load increases, the stratoka applied to the stator 18A also increases, which moves the entire stator vane diaphragm 6A, 7A, 8A downstream against the biasing force of the spring 41, and the seal fins 39, 42. The gap between the shroud 4 and the impeller 2 is reduced.

FIG. 6 shows a modification of the third embodiment, in which axial seal fins 43 and 44 project from the impeller 2 and the shroud 4 toward the inner ring 7A and the outer ring 6A, respectively. . The other configurations are the same as in FIG. 5.

In Figures 5 and 6, radial seal fins 13 are also provided in addition to the axial seal fins to further prevent leakage of the working fluid, but contact accidents between the radial seal fins and steam whirl may occur. It may be desirable to omit the radial sealing fins if prevention is of particular concern.

In all of the above-described embodiments, the axial seal fins are parallel to the axial direction, but this need not necessarily be the case and they may be somewhat inclined.

FIG. 7 shows an example in which the axial seal fins are inclined, and the axial seal fins 44 are provided obliquely with respect to the axial direction on the inclined extension portion 6b of the upstream outer ring 6A, and the shroud 4
5 is also inclined so as to be substantially parallel to the inclined extension part 6b. The other configurations are the same as in FIG. 5.

〔Effect of the invention〕

As is clear from the above description, according to the invention, an axial seal fin is provided in the leakage passage between the turbine rotating part and the turbine stationary part, and the clearance with the axial seal fin is adjusted according to the state of the turbine. Since the configuration is configured to forcibly adjust, the amount of leakage of the working fluid can be reduced, and the turbulence in the flow of the working fluid due to the leaked fluid can be reduced, thereby reducing vortex loss. Therefore, the efficiency of the turbine can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of the axial flow turbine according to the present invention, FIG. 2 is a vertical cross-sectional view showing the turbine in FIG. 1 at low temperature and high temperature, and FIG. 7 is a longitudinal sectional view showing a third embodiment of the present invention and a modification thereof, respectively,
FIG. 8 is a longitudinal sectional view showing a conventional axial flow turbine. 1... Rotor, 2... Impeller, 3... Moving blade, 4...
...Shroud, 5...Casing, 6...Outer ring,
7... Inner ring, 8... Stationary blade, 9... Channel, 10.1
2...Leak passage, 15.18.39, 42.43.4
4... Axial seal fin, 17.20... Shape memory alloy member. Applicant's agent Inomata Seitaku 1st ha ward 5th 6th 2nd

Claims (1)

[Claims] 1. An axial flow system in which a leakage passage that bypasses a part of the working fluid flow path is formed between the turbine rotating part and the turbine stationary part fixed to the casing side surrounding the rotating part. In a turbine; an axial seal fin supported slidably in the axial direction with respect to the stationary part and capable of protruding in the axial direction from the stationary part toward the rotating part within the leakage passage; and the seal. An axial flow turbine comprising a drive means for moving and displacing the fins toward the rotating part. 2. The axial flow according to claim 1, wherein the driving means is a temperature deformable member that deforms according to the temperature within the turbine to drive the axial seal fin in the axial direction. turbine. 3. The axial flow turbine according to claim 2, wherein the temperature deformable member is a shape memory alloy member. 4. The driving means includes a temperature deforming member that changes according to temperature to move the seal fin in the axial direction, a gap measuring device that detects the amount of gap between the seal fin and the rotating part, and this measuring device. The axial flow turbine according to claim 1, further comprising means for changing the ambient temperature of the temperature deforming member in accordance with an output signal of the axial flow turbine. 5. In an axial flow turbine in which a leak passage that bypasses a part of the working fluid flow path is formed between a turbine rotating part and a turbine stationary part fixed to the casing side surrounding this rotating part; The section is mounted so as to be movable in the axial direction with respect to the casing via a stator vane mounting member, and between the mounting member and the casing, a thrust force is applied in a direction opposite to the thrust force applied to the stator vane during turbine operation. An axial flow turbine characterized in that a biasing member for biasing the mounting member is provided, and a seal fin that can protrude in the axial direction from one of the mounting member and the rotating part to the other is fixed to the one of the mounting members. . 6. The axial flow turbine according to claim 5, wherein the mounting member is an outer ring of a stator vane diaphragm, and the seal fin is fixed to the outer ring.