JPS62118166A - Sealing device with gas-lubricated sliding seal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sole device having a gas-lubricated sliding seal, in which a recess extending radially in the form of a vane is formed on one of the two sealing surfaces. Regarding the format of

BACKGROUND OF THE INVENTION In the past, only labyrinth seals have been used to seal shafts exposed to extreme conditions, particularly high circumferential speeds, high pressures and high temperatures (such as occur in turbines, for example). This is because bushings and other sliding seals made of carbon materials that are in mechanical contact with the shaft cannot withstand such extreme conditions or have a short service life. be.

Other non-contact shaft sealing devices that cooperate with sealing liquids cannot be used at high temperatures. Additionally, it is necessary to take into account that labyrinth seals also experience relatively high tearing losses.

x 7 x -, Cranpa
c) special issue of ``Structural Components and Methods'', ``Gas Lubricated Seals'', January 1985, pages 80-81, gas lubricated sliding ring seals are disclosed. This sliding ring seal operates without contact above a certain rotational speed and has very low tearing losses.

Problem to be Solved by the Invention However, the known gas-lubricated sliding ring seals have the disadvantage that dry friction occurs at low rotational speeds (which necessarily occur at the start of movement or at switch-off). are doing. This is because the formation of a gas lubricant film is predicated on a predetermined rotational speed. Although such dry friction can be overcome to some extent by sliding a hard material (e.g. wolfram carbide) and a soft material (e.g. hard carbon) over each other, such hard materials cannot withstand harsh conditions, especially high temperatures. Therefore, such gas-lubricated sliding ring seals cannot be used where extreme loads occur, such as in turbines, for example.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve such a gas-lubricated sliding ring seal so that it is friction-free even in the low rotational speed range.

Means for Solving the Problems According to the present invention, which solves the problems described above, two sealing surfaces have a predetermined gap at the first position, and are connected to each other through a gas lubricating film at the second position. The first position is in a non-operating state and is in a rotational speed range in which a birostatic gas lubrication film has not yet formed.

Operation According to the invention, dry friction no longer occurs, so that by selecting the material of the reservoir of the two sliding rings with sealing surfaces, there is no need to take into account the unfavorable operating characteristics that lead to friction.

The selection of materials is made depending on the desired operating conditions.

In this way, it is possible to provide a sealing arrangement at circumferential speeds of up to 200 m/s, pressures of up to 250 bar, temperatures of up to 55°C, for example under operating conditions of a turbine. This sealing device has the necessary service life to avoid frequent replacement in turbines where disassembly costs for replacing parts are high.

When using a turbine and compressor,
The fact that the sliding ring is friction-free in the low speed range has the following special significance.

The turbine and partly also the compressor need to be rotated after being switched off. In other words, the turbine and compressor are rotated at low speeds in order to avoid temperature overlaps that could cause damage and thus distortion of the machine. Such rotations can last for a whole day on large machines, and can cause economically unacceptable levels of wear if the sealing surfaces of the sliding ring coolers are subjected to dry rubbing.

According to the present invention, care is taken to maintain a spacing such that the sealing surfaces do not come into contact with each other at a rotation speed that is not sufficient to form a gas lubricating film. When a predetermined rotational speed is exceeded, a hydrodynamic pressurization is produced by the pumping action of the radially extending vane-like recesses. In a speed range above this predetermined speed, the device according to the invention presses the two sealing surfaces together, so that the hydrodynamic pressure oyster
It acts to create a hydrostatic gas lubricant film between the two sealing surfaces. Such gas-lubricated films have a markedly low stability, and the sealing surface must provide the best surface properties. This allows them to slide around each other while maintaining a certain distance from each other. This significantly reduces the leakage rate compared to labyrinth seals. At lower rotational speeds, the sealing surfaces are again separated from each other by the device of the invention before the gas lubricant film is scraped off.

Embodiment According to an embodiment of the invention, the change in position of the sealing surface is obtained by a force acting on the sealing device from the outside. For this purpose, it is confirmed whether a hydrodynamic pressure key that acts on the formation of a gas lubricant film has been formed. This takes place at a predetermined rotational speed, which is dependent on the formation of the radially extending vane-like recesses, the diameter of the sliding ring and the nature of the gas or steam. This rotational speed is detected directly by a sensor (for example electronically detecting the rotating marking).

The position of the sealing surface is then changed via this sensor. The change in position of the sealing surface is effected by a mechanical, hydraulic or pneumatic force transmission device. Particularly in gas or steam turbines, gas under pressure or steam under high stress is used as energy transmission means and transmission medium.

A change in position in one direction, as well as a change in position in another direction, is obtained at a different pressure difference. Such regulating hysteresis can be caused structurally or is desired for safety reasons, for example in the event of rapid disconnection.

However, such hysteresis must always vary within conditions such that the gap between the two sealing surfaces is opened when the rotational speed is within the range where the gas lubricant film is scraped off.

In machines in which a given pressure of gas or steam is available at the same time as a given rotational speed, the change in the position of the sealing surface is preferably brought about by means of a pressure-detecting sensor; The pressure difference in the medium to be shut off is detected. Such means are
It is particularly suitable for a turbine in which the rotational speed of the turbine is increased to the rated rotational speed after the valve is opened as the pressure increases. When the pressure difference falls below the specified rotation speed,
The sealing surface is again brought to its first position. The sealing device can also be constructed in such a way that when a predetermined pressure difference is achieved, this pressure directly causes a change in the position of the sealing surface.

Another possibility for producing a change in the position of the sealing surface is provided by centrifugal force sensors which produce a change in position either directly or by means of auxiliary energy.

By providing a sealing steam or sealing gas device on the higher pressure side, the operational reliability and service life of the sealing device is increased.

This is because dirt particles are prevented from reaching the sealing surface (which has the best surface properties). The sealing vapor or sealing gas is preferably purified by means of a filter.

By providing an axial labyrinth seal on the high pressure side of the sealing device, the sealing gas or sealing steam device is regulated such that the pressure is slightly above the pressure of the medium to be sealed. This allows the unpurified portion of the medium to be sealed to be completely separated from the sealing surface. By providing the axial labyrinth seal on the low pressure side, the required amount of sealing gas or steam is significantly reduced in the operating range where a gap is maintained between the two noll surfaces.

The sealing device according to the invention is particularly suitable for turbines and compressors. This is because in the low speed range there is a low pressure that tends to break off, so that the gap between the sealing surfaces in this operating range is not adversely affected and, in particular, leakage losses can be reduced by using an additional labyrinth seal. This is because it decreases with use. During normal operation, by providing a sealing device, leakage losses are reduced and thus efficiency is increased.

When using sealing devices in turbines and compressors, it is advantageous to prevent the two sealing surfaces from moving into the second position, while there is a risk of a fluid film adhering to the sealing surfaces. In this connection, certain temperatures and condensate formations are measured. It is also possible to provide a time delay element in the machine in which the formation of a fluid film is reliably avoided after a predetermined time has elapsed since switching on.

Drains and holes for draining condensate may be additionally provided at all points where condensate collects.

When the sealing device according to the invention is installed in a turbine, it is advantageous if the sealing surfaces are made of a particularly heat-resistant hard material.

For example, steel can be used for the reservoir of the two sealing surfaces, by ensuring that the two sealing surfaces do not come into contact in any operating state.

As a safety measure in case of a malfunction, it is advantageous to provide an emergency layer on the sealing surface.

Embodiment Next, the structure of the present invention will be specifically explained with reference to an embodiment shown in the drawings.

A rotatable sliding ring 4, which is rigidly connected to the shaft 3, is provided with a sealing surface 1, which has a region with radially extending vane-like recesses. This wing-shaped recess forms a hydrodynamic pressure oyster when a predetermined rotational speed is reached. This pressure key acts so that the sol surface 2 and the range 1'' of the seal surface 1 slide against each other on the gas lubricating film. The sealing surface 2 of the connected sliding ring 6 seals the sliding ring 4 by the spring force of the spring 7 arranged uniformly on the outer circumference.
It can be applied to side 1 of The gas lubricating film is on the sealing surface 1.
and 2 are prevented from coming into contact with each other.

A valve (not shown) is opened by a sensor (not shown) in a rotational speed range in which a gas lubricant film is not formed. This causes gas under pressure or steam 10 at high pressure to flow into chamber 18 (in the direction of the arrow). The axial piston ring bushing 8 is then moved, and the projection 11 pulls the stationary sliding ring 6 against the spring force of the spring 7, thus opening the gap between the sealing surfaces 1 and 2. When the rotation speed exceeds a predetermined value, a sensor switches the valve to exhaust,
The pressure of the gas or steam 10 is lost. The barb 7 then presses the stationary sliding ring 6 against the rotatable sliding ring 4 again. Sealing member 19 that is not subject to dynamic loads or is subject to slight movement.
, 20.21 are for sealing the device.

The opening 15 is for supplying a sealing gas or a sealing vapor having the above-mentioned effect. One axial labyrinth seal 16 is located on the high-pressure side and is forwardly connected to the sealing device, and the other axial labyrinth seal 17 is located on the low-pressure side (rearly connected), the sealing action of which is as described above. Drainage channel 22 and hole 23 are for draining condensate.

FIG. 2 shows a variant embodiment in which the position of the sealing surface changes automatically as a result of changes in the pressure of the medium to be sealed.

A rotatable sliding ring 4, which is rigidly connected to the shaft 3, is provided with a sealing surface 1, which has a region with a radially extending vane-like recess 1'. These radially extending vane-shaped recesses 1' form a hydrodynamic pressure cage when a predetermined rotational speed is reached.

This pressure key acts in such a way that the sealing surface 2 and the area 1'' of the sealing surface 1 slide against each other on the gas lubricating film.

At this time, the sealing surface 2 of the sliding ring 6, which is connected to the casing 5 so as to be non-rotatable but movable in the axial direction.
However, the pressure is P1'.

It is applied against the sealing surface 1 of the sliding ring 4 by the pressure P1 acting on the ring 14 and the sliding ring 6 against the force of P2' and the spring 12. The gas lubricating film thereby prevents contact between the sealing surfaces 1 and 2. Under this normal operating condition, the leakage losses are so small that the pressure P1' does not fall significantly below the pressure P1. This is because the labyrinth seal 13 produces a large pressure difference only when gas flows through it. Force of pressure P1 and pressures P1' and P2
The force between the sealing surfaces 1'' and 2'' and the spring force of the spring 12 are about 9 degrees, so that the pressure between the sealing surfaces 1'' and 2'', P2', and the pressure of the gas lubricating film increases significantly as the distance between the two sealing surfaces decreases. This is achieved by rising and, on the other hand, increasing the distance between the two sealing surfaces and lowering it significantly.

The approximately 9-in-one state differs from the state in which the tab seal surface is switched from the first position to the second position when the seal is closed in the following points.

That is, due to the gas leaking through the gap between the seal surfaces 1 and 2 at the time of the pressure difference p1-p2, a large pressure significantly lower than the pressure P1 is generated due to the throttling action of the labyrinth seal 13. A drop occurs and the pressure P
A force of 1 compresses the sealing surfaces 1, 2 against the pressures P1' and P2/ and against the spring force of the spring 12.

When the seal is open (occupies the first position), the pressure P1 drops, for example when the turbine is switched off. The pressure P1' almost corresponds to the pressure P1 at this moment.

The pressure p2' of the gas lubricating film acts in conjunction with the spring force of the spring 12 to open the seal. At this time, the gap between the sealing surfaces 1 and 2 is opened again by displacing the ring 14, which is firmly connected to the sliding ring 6.

Sealing elements 19.21, which are not subjected to any dynamic loads or are allowed to move only slightly, are for sealing the device.

The opening 15 is for supplying a sealing gas or vapor having the same effect as described above. One axial labyrinth seal 16 is located on the high pressure side and is forwardly connected to the sealing device, and the other axial labyrinth seal 17
is located on the low pressure side (backward connection). The operation of these seals is as described above.

Effect As described above, the sealing device of the present invention does not cause dry friction even in the low rotation speed range and when no lubricating film is formed, so the materials for the two sliding rings with sealing surfaces are selected. This has the advantage that there is no need to take into consideration the unfavorable operating characteristics that cause friction. The sealing device of the invention can therefore also be used in turbines.

[Brief explanation of drawings]

FIG. 1 is a schematic partial vertical sectional view of a sealing device according to a first embodiment of the present invention, and FIG. 2 is a schematic partial vertical sectional view of a sealing device according to a second embodiment.

Claims (1)

[Claims] 1. A sealing device having a gas-lubricated sliding seal, in which a recess (1') extending in the shape of a vane in the radial direction is formed on one of the two sealing surfaces (1, 2). In this type, the two sealing surfaces (1, 2) are the first
have a predetermined gap at a position, and at a second position they slide relative to each other via a gas lubricating film, and when the first position is in a non-working state, hydrostatic gas lubrication is applied. A sealing device with a gas-lubricated sliding seal, characterized in that it is in a rotational speed range in which no membrane has yet formed. 2. The sealing device according to claim 1, wherein the change in position of the sealing surfaces (1, 2) is obtained by a force acting on the sealing device from the outside. 3. The sealing device according to claim 2, which is provided with a hydraulic force transmission device. 4. The sealing device according to claim 2, which is provided with a pneumatic force transmission device. 5. The sealing device according to claim 4, wherein the force is transmitted by gas under pressure or high-pressure steam. 6. One sealing surface (1) with a radially extending vane-like recess (1') is assigned to a rotatable sliding ring (4) connected to the shaft (3), and the other seal A stationary sliding ring (6) whose surface (2) is non-rotatably but movably axially connected to the casing (5)
an axial piston ring bushing, which is assigned to a stationary sliding ring (6) and which is pressed into a second position by a spring (7) uniformly distributed on the outer circumference, and which has a retaining member (9); (8) is movable in the axial direction by means of the drive medium (10), and the projection (11) acting as a driving member forces the stationary sliding ring (6) against the spring force of the spring (7). 6. A sealing device according to any one of claims 1 to 5, wherein the sealing device is brought into a second position. 7. When the sensor detects that the predetermined rotation speed has been reached,
the positions of the two sealing surfaces (1, 2) are changed;
A sealing device according to any one of claims 1 to 6. 8. Sealing device according to claim 1, wherein the position of the two sealing surfaces (1, 2) is changed by pressure changes in the medium to be severed. 9. When a first predetermined pressure difference between the higher pressure P1 range and the lower pressure P2 range is exceeded, the two sealing surfaces (1, 2) move from the first position to the second position. Move to the second position
below a predetermined pressure difference P1-P2, the sealing surface (1
, 2) again takes the first position.
Sealing device as described in section. 10. One sealing surface with a radially extending vane-like recess (1') is assigned to a rotatable sliding ring (4) connected to the shaft (3), and the other sealing surface (2)
) are assigned to an immovable sliding ring (6) which is connected non-rotatably but axially movable to the casing (5), and which immovable sliding ring (6) is distributed uniformly around the outer circumference. one half of the labyrinth seal (13) is placed in a ring (14) which is pressed into a first position by a spring (12) and which is connected to an immovable sliding ring (6); This labyrinth seal (13) is
Sealing surfaces (1, 2) on the side where high pressure P1 is created
is connected to the front side of the
), the force acting on the ring (14) and the sliding ring (6) due to the pressure P1 acts on the labyrinth seal (13) and the side of the sealing surface P1' and P2'
10. The sealing device according to claim 1, wherein the force of the spring (12) is also greater than the force of the spring (12). 11. Sealing device according to claim 7, wherein the change in position of the sealing surfaces (1, 2) is produced by a centrifugal force sensor. 12. The seal device according to any one of claims 1 to 11, wherein the seal on the higher pressure P1 side is provided with a sealing steam or sealing gas device. 13. The sealing device according to claim 12, wherein the sealing vapor or sealing gas is purified by a filter. 14. Any one of claims 1 to 13, wherein the space to be sealed by the sealing gas or sealing steam supply device (15) is sealed by an axial labyrinth seal (16). The sealing device according to item 1. 15. Sealing device according to one of the claims 1 to 14, characterized in that an axial labyrinth seal (17) is connected rearwardly to the sealing device on the low-pressure side of the sealing device. 16. The sealing device according to any one of claims 1 to 15, which is used as a sealing member in a turbine and a compressor. 17. The temperature of the sliding ring is measured by a sensor, and if the temperature of this sliding ring is too low, the two sealing surfaces (1
, 2) are prevented from moving into the second position. 18. The condensate adhering to the sliding ring seal is measured by a sensor, and while the condensate adhering to the sliding ring seal is being detected, the two sealing surfaces (1, 2)
17. A sealing device according to claim 16, wherein movement to the position is prevented. 19. As long as there is a risk of the formation of said condensate,
17. Sealing device according to claim 16, wherein the transition of the two sealing surfaces (1, 2) into the second position is prevented by a time delay element. 20. The sealing device according to claim 16, wherein a drainage groove (22) and a hole (23) for draining condensate are provided at a location where condensate adheres to the sealing device. 21. The sealing device according to any one of claims 1 to 20, wherein the sealing surfaces (1, 2) are made of a heat-resistant hard material. 22. The sealing device according to claim 21, wherein the sealing surfaces (1, 2) are provided with an emergency layer.