JPH08284609A - Turbine active clearance control device - Google Patents

Abstract

PURPOSE: To prevent vibration and seal wear at low load and stabilize the motion of a seal segment at loading, concerning a turbine active clearance control device for the shaft seal between a rotary part and a stationary part of a steam or gas turbine. CONSTITUTION: A seal segment 1 is arranged on a stationary part 10 so as to seal between the upper stream side 12 and the lower stream side 13 against a rotary part 11. The seal segment 1 is provided with a passage 4 and a groove 5 so as to communicate together the upper stream 12 and the lower stream side 13, and provided with a pilot valve 2 through a spring 3. At low load, the pilot valve 2 is moved to the upper stream side 12 by the spring 3, and the segment is not in contact with a wall 10a by pressure in the groove 5, so as to enlarge the gap relative to the rotary shaft 11 and prevent vibration and wear. At loading, the valve 2 is pushed in the direction of the lower stream side 13 against the spring 3 by fluid pressure, the segment 1 comes in contact with the wall 10a, and hence the face is sealed and motion of the segment 1 is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine active clearance control device having a seal segment provided between a rotating part and a stationary part such as blades of steam turbines and gas turbines.

[0002]

2. Description of the Prior Art FIG. 5 is a cross-sectional view of a seal segment used between a rotating part and a stationary part of a conventional steam or gas turbine. In the figure, a seal segment 21 is provided between the stationary portion 10 and the rotating portion 11, and as the load increases, the pressure difference between the upstream side 12 and the downstream side 13 also increases, so that the radial force is increased. 26, the seal segment 21 is moved toward the inner diameter side against the seal surface frictional force 25 by the differential pressure of the spring reaction force 24.

As described above, when the turbine is started and stopped, the gap between the stationary portion 10 and the rotating portion 11 is increased to prevent vibrations due to contact and wear of the seal portion, and the seal segment 21 is moved to the inner diameter side 14 during load operation. By moving them, the gap between them is reduced to reduce the leakage of steam or gas.

[0004]

As described above, when the conventional steam or gas turbine is started or stopped, the gap between the stationary portion 10 and the rotating portion 11 is increased by the seal segment 21.
In order to prevent vibration and wear of the seal portion due to contact, and to reduce the gap by moving the seal segment 21 during load operation to reduce the leakage of steam or gas, as the load increases, the working fluid of steam or gas Increased pressure,
Therefore, by utilizing the fact that the differential pressure also increases, the seal segment is moved to adjust the radial gap.

However, in the conventional technique, the operation of the seal segment 21 is often unstable and has not come into widespread use. This seal segment 2
The cause of the unstable operation of No. 1 is that the seal surface frictional force 25 with the side surface of the stationary portion 10 is too large. That differential pressure to be force to move the seal segments 25 in the radial direction is also increased friction between the seal segment 21 and the side wall due to the axial force f ₁ to act also axial force f ₁ at the same time. Immediately after manufacturing, this contact surface is also smooth and the frictional force is not large, but the wear force 25 increases with use due to roughening of the contact surface.

For this reason, in order to overcome this frictional force and move the segment in the radial direction, a measure is taken to increase the acting force in the radial direction, but at present, it is a sufficient operating force against the frictional force. There is no such thing, and unstable operation has occurred, so it has not reached widespread use.

[0007]

In order to solve such a problem, the present invention provides a passage portion axially penetrating a seal segment provided between a rotating shaft of a turbine and a stationary portion. A valve mechanism is provided in the section, and this valve mechanism allows the seal segment to move when the load is low, and makes the gap between the seal segment and the rotary shaft large and makes the gap small during load operation.

That is, the present invention is provided between a rotary shaft of a turbine and a stationary part, is movable in a groove along the axial direction of the rotary shaft of the stationary part, and the rotary shaft is upstream of the fluid. Segment that axially seals between the downstream side and the downstream side; a passage portion that penetrates the seal segment in the axial direction and allows the fluid to flow from the upstream side to the downstream side; provided in the middle of the passage portion When the load is low at the time of starting and stopping, the fluid moves to the upstream side by the spring force to cause the fluid to flow into the downstream side of the passage portion, and the fluid pressure moves the seal segment to the upstream side in the groove. It is brought into non-contact with the downstream side wall surface in the groove, and during load operation, it moves to the downstream side against the spring force due to fluid pressure to close the passage, and at the same time the fluid pressure moves the seal segment to the downstream side. , The downstream in the groove It comprises a and a valve mechanism for contacting the wall surface, at the time of low load increases the gap between the seal segments and the rotating shaft, when the load operation is decreased by the same gap,
Provided is a turbine active clearance control device characterized by reducing the amount of steam or gas leakage.

[0009]

According to the present invention, when the turbine is started or stopped by such means, the pressure difference between the upstream side and the downstream side is small, and the valve mechanism is pushed to the upstream side by the spring force in the passage portion. The pressure flows from the upstream side to the downstream side, the pressure on the downstream side is almost the same on the upstream side, the pressing force of the seal segment on the downstream side wall surface in the groove is extremely small, and the seal segment easily operates in the radial direction. Therefore, when the turbine is started, the seal segment can be moved to the outer diameter side, and the gap between the rotary shaft and the stationary portion can be increased to reduce vibration due to contact and wear of the seal portion.

During load operation, the differential pressure increases as the load increases, and the differential pressure causes the seal segment to move inward in the groove. After that, the valve mechanism is pressed in the passage portion in the downstream direction, the passage of the fluid is closed, and the seal segment is brought into contact with the side wall surface on the downstream side in the groove by the fluid pressure to form the seal of the side wall portion and the rotary shaft. It is possible to reduce the gap between the stationary part and the amount of steam or gas leakage.

At the time of load drop, the valve mechanism moves upstream in the passage portion, the fluid flows into the groove downstream side of the seal segment, and its pressure rises, so the seal segment is pressed against the downstream side wall surface in the groove. The force decreases, and it can be easily moved to the original position in the radial outer direction by the acting force.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a turbine active clearance control device according to an embodiment of the present invention. In the figure, 10 is a stationary portion such as a turbine vane (nozzle) inner tip portion, 11 is a rotating portion such as a rotor blade outer diameter side tip portion, rotor shaft, and the like. Is provided. A passage 4 is provided in the seal segment 1 so as to penetrate from the upstream side 12 to the downstream side 13 in the axial direction, and a pilot valve 2 is provided via a spring 3. The downstream side of the passage 4 communicates with the groove 5 to reduce the contact area with the side wall 10a of the stationary portion 10.

In such a structure, the passage 4 for introducing the pressure P ₁ on the upstream side 12 to the downstream side 13 has the groove 5 provided to reduce the contact area between the side wall 10a of the stationary portion 10 and the seal segment 1. It can be made sufficiently larger than the volume, and the axial force f ₂ can be effectively reduced. If the volume of the passage 4 is excessively large, the sealing effect on the side surface disappears. Therefore, when the turbine load is low, that is, when the differential pressure is small, the seal segment 1 does not contact the wall 10a of the downstream side 13 and floats. In such a state, when the turbine load is increased and the radial operation of the seal segment 1 is completed, the pilot valve 21 is provided in the segment in order to generate the sealing effect of the side surface 10a.

When the pressure difference between the upstream side 12 and the downstream side 13 is small, the pilot valve 2 is pushed to the upstream side 12 by the spring 3, so that the pressure on the downstream side 13 is almost the same as that on the upstream side 12. The pressing force on the downstream side 13, that is, the axial force f ₂ is extremely small, so that the seal face friction force 6 is also small, and the seal segment 1 is easily actuated in the radial direction.

Therefore, when the turbine is started, the seal segment 1 moves to the inner diameter side 14 because the differential pressure increases due to the load increase due to the outer diameter side. Then, the pilot valve 2 is pressed toward the downstream side 13 to form a seal on the side wall portion of the downstream side 13.

When the load drops, the pilot valve 2 is on the upstream side 1
2 and the pressure in the groove 5 on the downstream side of the seal segment 1 rises, the pressing force against the side wall 10a on the downstream side 13 of the seal segment 1 decreases, and the frictional force 6 also decreases. 1 can be moved to the original position by the spring force 24 acting outward in the radius direction.

As described above, in this embodiment, the force in the axial direction is reduced as compared with the prior art, and the seal segment can be effectively moved in the radial direction. This effect is expressed by the formula: the conventional axial force is f ₁ , the contact area of the sealing surface is A ₁ (see FIG. 5), the axial force in this embodiment is f ₂ , the contact area is A ₂ , And the pressure difference between the upstream side 12 and the downstream side 13 is ΔP, f ₁ = A ₁ × ΔP, f ₂ = A ₂ × Δ
Since P and A ₁ > A ₂ , f ₁ > f ₂ and
The axial force f _{2 in} this embodiment is different from the conventional axial force f ₁
Can be made smaller.

FIG. 2 is an enlarged view of the vicinity of the pilot valve 2 in FIG. 1, showing the relationship of the area of the pressure introducing passage 4. In the figure, A ₀ , A ₁ , A _{2 to} A ₇ are the areas of the fluid passages, and the condition that the segments do not adhere to the downstream side when the load is low is A ₀ > (A ₁ + A ₂ )> A ₃ > A ₄ > A
₅ > A ₆ > (A ₇ + A ₈ ), the spring force causes (A
Set so that ₁ + A ₂ )> A ₃ .

FIG. 3 is a diagram showing the relationship between the area of the passage 4 and the pressure before and after the pilot valve 2, (a) showing the relationship between the passage area and the fluid flow direction, and (b) showing the upstream side. The distribution of the differential pressure between the downstream sides is shown.

FIG. 4 shows the relationship between pressure and load.
Shows the pressure before and after the pilot valve 2 moves to the downstream side when the load rises, and (b) shows the relationship between the pressure before and after the pilot valve moves to the upstream side when the load falls.

According to such an embodiment, since the difference between the differential pressure in the seal segment and the restoring force by the spring is small in the related art, the side face frictional force due to the axial force pressing the seal segment against the side face is overcome and the seal is obtained. Although the segment could not be moved effectively in the radial direction, the passage 4 was provided and the pilot valve 2 and the spring 3 were connected to the passage 4 as described above.
Since it is installed inside, the frictional force 6 between the seal segment 1 and the side surface of the stationary portion 10 is reduced when the turbine has a low load, vibration is prevented and wear of the seal portion is prevented, and the radial acting force is stabilized when the load is applied. It is possible to obtain a high sealing effect.

[0022]

As described above in detail, according to the present invention, the seal segment provided between the rotating shaft of the turbine and the stationary portion is provided with the passage portion penetrating in the axial direction,
A valve mechanism is provided in this passage, and this valve mechanism allows the seal segment to move when the load is low, makes the gap between the seal segment and the rotary shaft large, and makes it possible to reduce the gap during load operation. Therefore, the following effects can be obtained.

(1) When the turbine is started or stopped, and when the load is low, the radial gap between the segment and the rotating portion is large,
It prevents the seal part from contacting due to shaft vibration and wear of the seal part, and the shaft vibration is stable under high load, so there is no contact even if the gap becomes small, and the high sealing effect continues. Since it is obtained, it greatly contributes to the performance improvement.

(2) The conventional turbine shaft seal has not been widely used because of unstable operation of the segment, but in the present invention, the operation of the seal segment is stable, so that it is an effective means for the shaft seal. is there.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a turbine active clearance control device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of the vicinity of the pilot valve in FIG.

FIG. 3 is a diagram showing a relationship between a passage area and a differential pressure of a turbine active clearance control device according to an embodiment of the present invention, and FIG. 3A is a diagram showing a relationship between a fluid flow direction and an area of the passage. b) is a diagram showing a pressure distribution in a fluid flow direction.

FIG. 4 shows the relationship between the load and the differential pressure of the turbine active clearance control device according to the embodiment of the present invention,
(A) shows the load when the load rises, and (b) shows the load when the load falls and the pressure before and after the pilot valve, respectively.

FIG. 5 shows a cross-sectional view of a conventional turbine seal segment.

[Explanation of symbols]

 1 Seal Segment 2 Pilot Valve 3 Spring 4 Passage 5 Groove 6 Sealing Surface Friction Force 10 Stationary Part 11 Rotating Part 12 Upstream Side 13 Downstream Side

Claims (1)

[Claims] 1. A turbine is provided between a rotating shaft and a stationary part, is movable in a groove along the axial direction of the rotating shaft of the stationary part, and the rotating shaft is connected to a fluid upstream side and a downstream side. A seal segment that axially seals between the seal segment; and a passage part that penetrates the seal segment in the axial direction and allows the fluid to flow from the upstream side to the downstream side; When the load is low at the time of stop, the fluid moves to the upstream side by the spring force to flow the fluid into the downstream side of the passage portion, and the fluid pressure moves the seal segment to the upstream side in the groove, and the downstream in the groove. When not in contact with the side wall surface, the fluid pressure causes the fluid pressure to move to the downstream side against the spring force to close the passage while the fluid pressure causes the fluid pressure to move the seal segment to the downstream side. Contact with the downstream side wall surface of And a valve mechanism for reducing the amount of steam or gas leakage when the load is low and the gap between the rotary shaft and the seal segment is large when the load is low. Turbine active clearance control device.