CN111810253A - A kind of double-end dry gas sealing device for industrial steam turbine - Google Patents

Abstract

A double-end-face dry gas sealing device for an industrial steam turbine comprises a rotary sealing assembly and a static sealing assembly. The rotary sealing assembly comprises a shaft sleeve fixed on the shaft neck, a shaft shoulder is arranged in the middle of the shaft sleeve, two sides of the shaft shoulder are respectively provided with a movable ring, and a pneumatic pressure groove is formed in each movable ring. The static sealing assembly comprises a sealing sleeve fixed in the shell, and further comprises a pair of static rings and a pair of corrugated pipes which are respectively arranged on two sides of the shaft shoulder. Under the action of self elasticity, the corrugated pipe is pressed on the end face of the static ring on the same side to form a contact sealing structure. The static ring and the movable ring on the same side are arranged oppositely, and when the movable ring rotates along with the shaft of the steam turbine, a non-contact air film lubrication state is formed between the movable ring and the static ring. The dynamic ring and the static ring have self-adjusting capacity, so that stable air film lubrication non-contact sealing is formed between the dynamic ring and the static ring, high-pressure steam is sealed in the turbine, zero-leakage sealing of the steam in the turbine is realized, and the energy conversion efficiency of the steam turbine is greatly improved.

Description

A kind of double-end dry gas sealing device for industrial steam turbine

technical field

The invention relates to the technical field of mechanical seals, in particular to a double-end dry gas seal device for industrial steam turbines.

Background technique

Steam turbine is one of the main equipment of steam power plant, which is a kind of rotary power machine that converts the energy of steam into mechanical work. The working principle of the steam turbine is that steam with a certain pressure and temperature enters the steam turbine, expands rapidly in the nozzle to obtain a high flow speed, and then the high-speed flowing steam impels the rotor blades of the steam turbine to rotate and perform work, thereby obtaining mechanical energy. The steam turbine is mainly composed of a rotating part, a fixed part and a control part.

Industrial steam turbines are equipment that uses steam as the motive power and are mainly used in chemical, petroleum, mining, metallurgy, paper, textile, sugar and other industrial enterprises. Industrial steam turbines drive various types of pumps, fans, compressors, presses or drive generators to obtain low-cost power and electricity. In advanced industrial countries, primary energy has been fully utilized since steam turbines have been used in industry. Small heat (electricity) cogeneration (small back pressure machine) can make full use of waste, waste gas, waste heat to produce steam, or use rich steam and steam pressure difference, and then convert it into mechanical energy through power steam turbine to directly drive mechanical equipment to do work, also The variable speed operation of mechanical equipment can be realized by adjusting the speed of the steam turbine. Since the energy conversion links are reduced, the energy conversion efficiency is increased, and expensive industrial electricity is saved, therefore, the application of industrial steam turbines as motive power equipment in production can achieve the purpose of energy conservation and efficiency enhancement. In addition, the extraction and exhaust steam of industrial steam turbines can also be used in the industrial production process or external supply of enterprises and institutions, thereby realizing the cascade utilization of energy. It is one of the effective measures for energy conservation and consumption reduction in enterprises and institutions. , with significant advantages in comprehensive economic benefits.

Due to the high pressure and high temperature of the working medium, the current industrial steam turbine usually adopts the form of comb-tooth labyrinth seal or carbon ring seal at the shaft end. Since both labyrinth seals and carbon ring seals are radial non-contact seals, in order to avoid friction between the main shaft or the shaft sleeve and the sealing parts during the whole working process, the radial sealing gap is generally relatively large (static or dynamic) , resulting in a large amount of axial steam leakage. Especially the back pressure type steam turbine, the seal chamber pressure is higher, and its shaft end seal leakage is larger. The leakage of steam will cause energy loss. In addition, the leaked steam needs to be cooled by cooling water, and the amount of cooling water is also very large. According to statistics, for medium-sized steam turbine units, the annual steam leakage, cooling water consumption, and subsequent operation and maintenance costs are equivalent to operating costs of more than one million yuan.

Different from the dynamic and static seals of general machinery, there are many factors affecting the shaft end seal of industrial steam turbines, and the situation is complicated. Affected by the high temperature and high pressure of the steam in the engine, as well as the thermal expansion, jumping, winding deformation and other factors when the steam turbine shaft rotates at a high speed, the leakage problem of the shaft end of the industrial steam turbine has been a technical problem that the industry wants to solve but cannot be solved for a long time. From the perspective of energy saving and efficiency improvement, there is an urgent need for a new type of sealing device that has high reliability and can significantly reduce the leakage of shaft end seals.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies in the background technology, the present invention discloses a double-end dry gas sealing device for an industrial steam turbine, which adopts the following technical solutions:

A double-end dry gas sealing device for an industrial steam turbine, which is axially arranged between a casing and a bearing housing and radially between the casing and a journal of a steam turbine shaft, comprising a rotary seal assembly and a static seal assembly;

The rotary seal assembly includes a shaft sleeve fixed on the shaft journal, a shaft shoulder is arranged in the middle part of the shaft sleeve, and a moving ring is arranged on both sides of the shaft shoulder; the end faces on both sides of the shaft shoulder are sealing surfaces, and both sides The moving ring of the moving ring is sealed with the sealing surface on the same side, and rotates with the shaft sleeve; a plurality of circumferentially distributed pneumatic pressure grooves are arranged on the end face of the moving ring on the side away from the shaft shoulder;

The static sealing assembly includes a sealing sleeve fixed in the casing and sealingly connected to the casing, and also includes a pair of static rings and a pair of bellows respectively arranged on both sides of the shaft shoulder; wherein, the bellows is on the side away from the shaft shoulder The end face of the bellows is sealed with the sealing sleeve; the static ring is set between the bellows and the moving ring, and is floatingly connected to the sealing sleeve through the stop pin; under the action of its own elastic force, the end face of the bellows near the shoulder side is pressed against the static One end face of the ring forms a contact seal structure; the other end face of the stationary ring is opposite to the end face of the moving ring on the side away from the shaft shoulder. When the moving ring rotates with the turbine shaft, non-contact is formed between the moving ring and the stationary ring. The dry gas sealing structure is provided; the sealing sleeve is provided with a main sealing cavity at the position of the dry gas sealing structure, and the main sealing cavity is communicated with the external main sealing gas through a pipeline; the main sealing gas is the filtered steam outside the machine.

Preferably, the static seal assembly further includes a pair of damping sleeves for radially limiting the static ring and the bellows, and the outer ring sleeve surface of the damping sleeve is in contact with the inner sleeve surface of the sealing sleeve through a centering coil spring, The inner ring sleeve surface is respectively contacted and connected with the outer surface of the static ring and the bellows.

Preferably, a centering coil spring is set on both sides of the shaft shoulder; the centering coil spring is in contact with the inner ring surface of the moving ring on the same side, and the moving ring has a certain amount of floating; on the sealing surface of the shaft shoulder There is a flexible graphite ring for sealing the moving ring, and a drive pin in the axial direction; the moving ring is provided with a pin shaft hole corresponding to the drive pin, the diameter of the pin shaft hole is larger than the diameter of the drive pin, and the shaft shoulder The moving rings on both sides are driven to rotate by the transmission pin.

Preferably, a front compression sleeve is connected to the inner end of the shaft sleeve, and the front compression sleeve is pressed against the inner shaft shoulder of the journal; the outer end of the shaft sleeve is connected with a rear compression sleeve, and the rear compression sleeve is A flexible graphite ring is arranged between it and the shaft sleeve; the outer end of the rear compression sleeve is back-tightened by a main shaft nut screwed on the shaft journal.

Preferably, a labyrinth sleeve is arranged between the main shaft nut and the sealing sleeve, and a rear comb-shaped labyrinth sealing structure is arranged on the labyrinth sleeve; A venting cavity is arranged between the tubes, and the venting cavity is communicated with the atmosphere through a venting port.

Preferably, there is a rear air barrier cavity between the labyrinth sleeve and the spindle nut, the rear air barrier chamber is arranged in the middle of the rear comb-shaped labyrinth seal structure, and the rear air barrier chamber is connected to the outside through the pipeline. Rear isolation gas communication.

Preferably, the casing is provided with a front air isolation cavity on the inner side of the sealing sleeve to prevent the entry of steam in the machine, and a front isolation gas is introduced into the front air isolation cavity; the pressure of the front isolation gas is greater than that of the steam in the machine. pressure, and less than the pressure of the main seal gas.

Preferably, the inner and outer surfaces of the sealing sleeve are all multi-step surfaces; the outer surface of the sealing sleeve is sealed with the casing through multiple sealing rings, and the inner sleeve surface of the sealing sleeve is respectively connected to the outer surface of the labyrinth sleeve through the sealing ring. The sealing connection is sealed with one end of a pair of bellows away from the shaft shoulder through a flexible graphite ring.

Preferably, the pneumatic pressure groove is a one-way groove or a two-way groove; the groove depth of the one-way groove is 3-20 μm, and the width of the dam area of the pneumatic pressure groove is 0.25-0.75 times the width of the sealing surface.

Preferably, the material of the moving ring is silicon carbide, or silicon nitride, or a cemented carbide; the material of the static ring is graphite, or silicon carbide coated with a diamond-like film on the surface.

Due to adopting the above-mentioned technical scheme, compared with the background technology, the present invention has the following beneficial effects:

The invention realizes the quiet sealing between the casing and the sealing sleeve, the sealing sleeve and the bellows, and realizes the contact sealing between the bellows and the static ring, and the air film lubrication and non-contact sealing between the moving ring and the static ring. . The two-stage dry gas structure seals the high-pressure steam in the machine, which not only reduces energy consumption, but also improves the energy conversion efficiency of industrial steam turbines.

The dynamic ring and the static ring of the present invention have self-adjustment capabilities, and when the steam turbine shaft has thermal expansion, jumping, winding deformation, etc., a stable gas film can always be formed between the dynamic ring and the static ring, ensuring that the dry gas sealing structure can be Work reliably for long periods of time.

The invention adopts a double dry gas sealing structure. Under the same working conditions, the steam leakage of each dry gas sealing structure is only a few tenths to one percent of the existing sealing structure. The structure basically achieves zero leakage sealing. Since the steam no longer leaks, there is no need to set up an additional leakage steam cooling device, which greatly reduces the follow-up operation and maintenance costs of the industrial steam turbine, which can save nearly one million yuan in operating costs every year.

Dry gas seal was originally developed to solve the problem of high-speed centrifugal compressor shaft end seal, but in the steam turbine industry, it cannot be applied due to various factors. One of the important reasons is that industrial steam turbines are under complex working conditions. , it cannot guarantee a stable dry gas seal between the moving ring and the static ring. And the present invention, through long-term practical verification, stably realizes dry gas sealing between the dynamic ring and the static ring, and solves the technical problems that the industry has been trying to solve but cannot solve, and it is of great significance! In addition, the effect of the present invention in saving energy and improving efficiency is remarkable, and the economic value is huge.

Description of drawings

FIG. 1 is a schematic structural diagram of the present invention.

Figure 2 is a schematic diagram of the structure of the pneumatic pressure groove near the end of the moving ring outside the machine.

Figure 3 is a schematic diagram of the structure of the pneumatic pressure groove near the end of the moving ring in the machine.

In the figure: 1, journal; 2, casing; 3, shaft sleeve; 31, shaft shoulder; 4, front compression sleeve; 5, moving ring; 51, pneumatic pressure groove; 6, rear compression sleeve; 7, Spindle nut; 8. Bellows; 9. Static ring; 10. Sealing sleeve; 11. Damping sleeve; 12. Centering coil spring; 13. Labyrinth sleeve; 14. Transmission pin; 15. Stopping pin; 16. Flexible graphite; 17. Front comb-like labyrinth sealing structure; 18. Rear comb-like labyrinth sealing structure; 19. Main sealing cavity; 20. Front air barrier chamber; 21. Rear air barrier chamber;

Detailed ways

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principle of the present invention, and are not intended to limit the protection scope of the present invention.

It should be noted that, in the description of the present invention, terms indicating directions or positional relationships such as "inside" and "outside" are based on the relative indicated directions or positional relationships centered on the main body of the industrial steam turbine, which are only for the convenience of description. It is not intended to indicate or imply that the device or element must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention.

A double-end dry gas sealing device for an industrial steam turbine, as shown in Figure 1, is axially arranged between the casing 2 and the bearing housing (not shown in the figure), and radially between the casing 2 and the shaft of the steam turbine shaft. Between the necks 1, the rotary seal assembly and the static seal assembly are included, and the sealing structure formed between the rotary seal assembly and the static seal assembly is the main sealing structure of the present invention.

The rotary seal assembly includes a bushing 3 fixed on the journal 1 . Specifically, a front compression sleeve 4 is connected to the inner end of the shaft sleeve 3 by bolts, and the front compression sleeve 4 abuts against the inner shaft shoulder of the journal 1; The outer end of the compression sleeve 6 and the rear compression sleeve 6 is back-tightened by the main shaft nut 7 screwed on the journal 1, so that the shaft sleeve 3 is fixed on the journal 1 and rotates with the turbine shaft. A flexible graphite 16 ring is arranged between the rear compression sleeve 6 and the shaft sleeve 3, and the flexible graphite 16 ring not only has good sealing performance, but also has high temperature resistance. The axial sealing between the rear compression sleeve 6 and the shaft sleeve 3 is achieved by the flexible graphite 16 ring.

A shaft shoulder 31 is arranged in the middle part of the shaft sleeve 3 , and a moving ring 5 is arranged on each side of the shaft shoulder 31 . The end faces on both sides of the shaft shoulder 31 are both sealing faces, and flexible graphite 16 rings for sealing the moving ring 5 are respectively provided on the sealing faces on both sides of the shaft shoulder 31 , and a drive pin 14 in the axial direction is also provided. The movable ring 5 is provided with a pin shaft hole corresponding to the transmission pin 14 , and the transmission pin 14 is floatingly connected with the pin shaft hole of the movable ring 5 . The shaft shoulder 31 drives the moving rings 5 on both sides to rotate together with the steam turbine shaft through the transmission pin 14 .

The static sealing assembly includes a sealing sleeve 10 fixed in the inner cavity of the casing 2 and sealingly connected with the casing 2 . Since the main sealing structure penetrates the sealing sleeve 10, the sealing sleeve 10 has a longer axial dimension. In order to reduce the difficulty of processing and facilitate assembly and maintenance, the sealing sleeve 10 is formed by connecting three parts. The inner and outer surfaces of the sealing sleeve 10 are all multi-step surface structures, and the outer surface of the sealing sleeve 10 is sealedly connected with the casing 2 through multiple sealing rings.

The static seal assembly further includes a pair of static rings 9 and a pair of bellows 8 respectively arranged on both sides of the shaft shoulder 31 . A pair of static rings 9 and a pair of bellows 8 are symmetrically arranged with respect to the shaft shoulder 31, wherein the end face of the pair of bellows 8 on the side away from the shaft shoulder 31 is fixed on the inner stepped table surface of the sealing sleeve 10 by bolts, and is passed through flexible graphite. The 16 rings achieve a sealed connection with the sealing sleeve 10 . The static ring 9 is arranged between the bellows 8 and the moving ring 5 , and is floatingly connected to the sealing sleeve 10 through the stop pin 15 . In this embodiment, the bellows 8 is a high-temperature-resistant stainless steel bellows 8, which is not only resistant to high-temperature corrosion, but also has good elasticity. The bellows 8 is flexible and will generate a certain axial elastic force when it is pressed. Under the action of its own axial elastic force, the end face of the bellows 8 near the shoulder 31 is pressed against the end face of the same side of the static ring 9 to form a contact sealing structure between the bellows 8 and the static ring 9 . The other end face of the static ring 9 is arranged opposite to the end face of the moving ring 5 away from the shaft shoulder 31. Under the action of the axial elastic force of the bellows 8, a certain amount of space is maintained between the static ring 9 and the moving ring 5 on the same side. contact pressure.

The sealing sleeve 10 is provided with a main sealing cavity 19 at the position of the shaft shoulder 31 of the shaft sleeve 3 which communicates with the dry gas sealing structure. The main sealing cavity 19 communicates with the external main sealing gas through a pipeline. The main sealing gas can be high-pressure clean steam, or high-pressure nitrogen or instrument air, the pressure of which is greater than the pressure of the steam in the machine. A plurality of circumferentially distributed pneumatic pressure grooves 51 are provided on the end surface of the moving ring 5 on the side away from the shaft shoulder 31 . The pneumatic pressure groove 51 may be a unidirectional rotating groove, or a bidirectional rotating groove. It can be a one-way arc groove, a spiral groove, a triangular groove, or a two-way, such as a hammer-shaped two-way groove. In this embodiment, the pneumatic pressure groove 51 is a one-way spiral groove. Figure 2 shows a schematic diagram of the rotation direction of the one-way helical groove on the outer end face of the moving ring 5 close to the outer side of the turbine and the rotation direction of the turbine shaft when viewed from the X direction. Figure 3 shows a schematic diagram of the rotation direction of the one-way helical groove on the outer end face of the moving ring 5 close to the inner side of the turbine and the rotation direction of the turbine shaft when viewed from the Y direction. It can be seen from Figure 2 and Figure 3 that the rotating direction of the one-way spiral groove on the outer end face of the moving ring 5 close to the machine and the moving ring 5 near the outside of the machine is the same as that of the turbine shaft, and the one-way spiral groove automatically The inner part of the outer end surface of the ring 5 extends spirally in the outer radial direction, and is opened to the outer ring surface of the movable ring 5 . Along the direction of helical extension, the cross-sectional area of the one-way helical groove gradually increases. The groove depth of the one-way spiral groove is 12 μm, and the width of the dam area of the pneumatic pressure groove 51 is 0.5 times the width of the outer end face of the moving ring 5 . When the moving ring 5 rotates with the turbine shaft, the pressure of the main sealing gas is greater than that of the steam in the machine, and the main sealing gas enters the one-way spiral groove and produces a hydrodynamic pressure effect, so that the main sealing gas at the outer ring surface is pumped inward, As a result, a gas film of the order of microns is generated between the outer end face of the moving ring 5 and the inner end face of the static ring 9 to form a dry gas sealing structure. On the one hand, the main sealing gas blocks the leakage of steam and generates a gas film between the moving ring 5 and the static ring 9, and on the other hand cools the moving ring 5 and the static ring 9 to take away the heat generated by the dry gas sealing structure.

The dry gas sealing structure also plays the role of lubricating and isolating the sealing surface between the moving ring 5 and the static ring 9 . Due to the very high speed of the steam turbine shaft, the rigidity of the gas film is very large, and the opening force formed by the gas film is balanced with the axial elastic force of the bellows 8. Contact operation, and the sealing of the steam in the machine is realized. The amount of steam leaking out through the dry gas seal structure is only a few tenths to one percent of that of comb labyrinth seals or carbon ring seals under the same working conditions. In the present invention, two dry gas sealing structures are arranged inside and outside the main sealing structure, and the dry gas sealing structure located on the outer side seals the steam leaked from the inner dry gas sealing structure again, basically realizing zero leakage sealing of steam. . Since the steam no longer leaks, there is no need to set an additional leakage steam cooling device, so that the subsequent operation and maintenance costs of the industrial steam turbine are significantly reduced.

When the steam turbine shaft rotates at high speed, phenomena such as thermal expansion, jumping, and winding deformation will inevitably occur at the journal 1. The dry gas sealing structure requires a strict parallel relationship between the sealing surfaces of the movable ring 5 and the stationary ring 9 . Therefore, at least one of the moving ring 5 and the static ring 9 is guaranteed to have self-adjustment capability. To this end, a centering coil spring 12 is set on both sides of the shaft shoulder 31, and the centering coil spring 12 is in contact with the inner ring surface of the moving ring 5 on the same side; the diameter of the pin shaft hole is larger than the diameter of the transmission pin 14, preventing transmission The pin 14 restricts the floating of the movable ring 5; a certain gap is reserved between the movable ring seat and the outer ring surface of the movable ring 5. These measures make the moving ring 5 have a certain amount of floating, and realize the self-adjustment of the moving ring 5 .

In order to make the static ring 9 have the freedom of self-adjustment following the moving ring 5, a radially open long groove is provided on the outer ring surface of the static ring 9. The ring 9 rotates, but does not limit the floating of the static ring 9 . The bellows 8 exerts a certain axial force on the static ring 9 to ensure that the sealing surface of the static ring 9 does not detach from the sealing surface of the moving ring 5, and the bellows 8 itself has a certain universal flexibility to ensure that the bellows 8 is opposite to the static ring 9. The applied axial force is always perpendicular to the sealing surface of the moving ring 5, so that the static ring 9 always has the freedom of self-adjustment following the moving ring 5. In this way, when thermal expansion, jumping, winding deformation and other phenomena occur in the journal 1, a layer of parallel gas film is always formed between the moving ring 5 and the static ring 9, which can ensure the normal operation of the dry gas sealing structure.

When the steam turbine is working, the moving ring 5 rotates at a high speed with the steam turbine shaft, so it has high requirements on the strength of its material; due to long-term work in a high-temperature and high-pressure steam environment, the physical There are also high requirements for mechanical performance; in addition, during the starting and stopping process, the sealing surface between the moving ring 5 and the static ring 9 will have slight contact wear, so the surface tribological characteristics of the moving ring 5 and the static ring 9 are affected. There are also high demands. Therefore, the moving ring 5 can be made of high-hardness and high-wear-resistant materials such as silicon carbide, silicon nitride or cemented carbide with high strength, good tribological properties and relatively high hardness, or stainless steel can be used as the substrate. The surface is prepared by spraying or surfacing with a high-hardness wear-resistant coating. The static ring 9 can be prepared by using graphite with good self-lubrication, or silicon carbide with diamond-like carbon film (DLC) plated on the surface of silicon carbide. The use of DLC coating technology can improve the surface tribological properties of hard-to-hard friction pairs. Extending the service life of the moving ring 5 and the static ring 9 can greatly reduce the maintenance cost of the steam turbine.

Since the disturbance of the steam flow in the machine will cause tremors to the static ring 9 and the bellows 8, and even make the static ring 9 and the bellows 8 eccentrically unstable, the technical solution is further improved. The static sealing assembly also includes a pair of counter-static rings. 9. The damping sleeve 11 for the radial limit of the bellows 8. The damping sleeve 11 is made of a high temperature-resistant metal material. In this embodiment, the material of the damping sleeve 11 is stainless steel. The outer ring sleeve surface of each damping sleeve 11 is in contact with the inner sleeve surface of the sealing sleeve 10 through the two-stage centering coil spring 12 , and the inner ring sleeve surface is in contact with the outer surfaces of the static ring 9 and the bellows 8 respectively. It is worth noting here that the damping sleeve 11 is not fixed in the inner sleeve surface of the sealing sleeve 10 , but is in contact with the inner sleeve surface of the sealing sleeve 10 through the two-stage centering coil spring 12 . The two-stage centering coil spring 12 makes the damping sleeve 11 have a certain amount of floating. Therefore, although the damping sleeve 11 performs radial limit on the static ring 9 and the bellows 8, it does not prevent the static ring 9 from always having a follow-up ring. 5 degrees of freedom for self-adjustment.

In summary, the present invention realizes the sealing between the casing 2 and the sealing sleeve 10; realizes the sealing between the sealing sleeve 10 and the bellows 8 on the inner and outer sides; realizes the sealing between the bellows 8 on both sides and the static ring 9 on the same side The contact seal between the inner and outer sides; the non-contact sealing state of steam lubrication is formed between the inner and outer sides of the moving ring 5 and the static ring 9. The two-stage dry gas structure seals the high-pressure steam in the machine, which not only reduces energy consumption, but also improves the energy conversion efficiency of industrial steam turbines.

The dry gas seal has high requirements on the cleanliness of the gas at the high pressure end. Otherwise, the dirty high pressure end gas will contaminate the end face of the friction pair of the dry gas seal, and the bellows will lose its elasticity and compensation ability, resulting in premature failure of the seal. To this end, the casing 2 is provided with a front air isolation cavity 20 between the front comb-shaped labyrinth sealing structure 17 and the sealing sleeve 10 , and a front isolation gas is introduced into the front air isolation cavity 20 . It should be noted that the pre-comb-shaped labyrinth sealing structure 17 is a self-contained sealing structure of the existing steam turbine, which has a large amount of steam leakage, but is not affected by thermal expansion. The device only utilizes the existing structure to perform primary sealing on the steam in the engine.

The pre-isolation gas can be high-pressure and high-temperature steam drawn from the inlet of the steam turbine, or the externally drawn steam whose pressure and temperature meet the requirements. In this case, the pressure of the front isolation gas is required to be higher than the steam pressure in the machine, and the front isolation gas is returned to the machine through the front comb-shaped labyrinth sealing structure 17 to prevent the unfiltered visceral steam from contaminating the dry gas sealing structure. At the same time, the heat generated by the dry gas sealing structure is taken away. If the cleanliness of the steam medium itself in the steam turbine meets a certain quality standard, it can also be directly used as the front isolation gas to enter the front air isolation chamber 20 through the front comb-shaped labyrinth sealing structure 17. At this time, the front air isolation chamber 20 The external channel is closed.

In order to generate a pressure difference between the inside and outside of the dry gas seal, the casing 2 is provided with a main sealing cavity 19 at the position of the shaft shoulder 31, and the main sealing cavity 19 communicates with the main sealing gas through a pipeline. The main sealing gas is the external steam that has been filtered and whose pressure and temperature meet certain requirements. Since the pneumatic pressure groove 51 used in this embodiment is a one-way spiral groove with an outer high pressure, the main sealing air pressure entering the main sealing cavity 19 is greater than the front isolation air pressure entering the front air isolation cavity 20 . The main sealing gas can also be of the same source as the front insulation gas, but the front insulation gas entering the front gas insulation chamber 20 needs to be decompressed so as to generate a pressure difference between the inside and outside of the dry gas seal.

In order to prevent the lubricating oil in the bearing housing (not shown in the figure) from contaminating the dry gas sealing structure through diffusion, a labyrinth sleeve 13 is provided between the spindle nut 7 and the sealing sleeve 10, and the inner sleeve surface of the sealing sleeve 10 passes through the sealing ring. It is tightly connected with the outer surface of the labyrinth sleeve 13 . The labyrinth sleeve 13 is provided with a plurality of comb-shaped inner ring teeth, and forms a rear comb-shaped labyrinth seal structure 18 with the spindle nut 7 . The sealing sleeve 10 is provided with a venting cavity 22 between the rear comb labyrinth sealing structure 18 and the bellows 8 near the outer side, and the venting cavity 22 communicates with the atmosphere through the venting port. In this way, the rear comb labyrinth sealing structure 18 can seal off most of the lubricating oil gas in the casing 2, and a small amount of lubricating oil gas leaking from the rear comb labyrinth sealing structure 18 is emptied through the vent, preventing the lubricating gas from drying out. Contamination of hermetic structures. Similarly, a very small amount of steam leaking from the dry gas sealing structure is also vented through the venting port after entering the venting cavity 22 . Meanwhile, between the labyrinth sleeve 13 and the spindle nut 7 is provided with a rear air barrier cavity 21, the rear air barrier chamber 21 is arranged in the middle part of the rear comb-shaped labyrinth seal structure 18, and the rear air barrier cavity 21 passes through The pipeline is communicated with the external rear isolation gas. The rear isolation gas is nitrogen or instrument air. After the nitrogen or instrument air enters the air isolation chamber, the lubricating oil gas entering the rear comb labyrinth sealing structure is blocked. Excess nitrogen or instrument air enters the venting cavity 22 and is vented through the venting port.

The parts of the present invention that are not described in detail are prior art. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A kind of industry steam turbine uses the dry air sealing device of the double end, the axial is set up between casing and bearing box, radially between casing and journal of the steam turbine shaft, its characteristic is: comprises a rotary sealing component and a static sealing component;

the rotary sealing assembly comprises a shaft sleeve fixed on the shaft neck, a shaft shoulder is arranged in the middle of the shaft sleeve, and two movable rings are respectively arranged on two sides of the shaft shoulder; the end surfaces of two sides of the shaft shoulder are sealing surfaces, and the movable rings of the two sides are respectively connected with the sealing surfaces at the same side in a sealing way and rotate along with the shaft sleeve; a plurality of pneumatic pressure grooves distributed circumferentially are arranged on the end face of the movable ring on the side far away from the shaft shoulder;

the static sealing assembly comprises a sealing sleeve which is fixed in the shell and is in sealing connection with the shell, and also comprises a pair of static rings and a pair of corrugated pipes which are respectively arranged at two sides of the shaft shoulder; the end surface of the corrugated pipe, which is far away from the shaft shoulder, is in sealing connection with the sealing sleeve; the static ring is arranged between the corrugated pipe and the dynamic ring and is in floating connection with the sealing sleeve through a stop pin; under the action of self elasticity, the end face of the corrugated pipe close to one side of the shaft shoulder is pressed against the end face of one side of the static ring to form a contact sealing structure; the end face of the other side of the static ring is opposite to the end face of the side of the dynamic ring, which is far away from the shaft shoulder, and when the dynamic ring rotates along with the shaft of the steam turbine, a non-contact dry gas sealing structure is formed between the dynamic ring and the static ring; the sealing sleeve is provided with a main sealing cavity at the position of the dry gas sealing structure, and the main sealing cavity is communicated with the external main sealing gas through a pipeline; the main seal gas is the filtered off-machine steam.

2. The double-end-face dry gas seal assembly of claim 1, wherein: the static sealing assembly further comprises a pair of damping sleeves for radially limiting the static ring and the corrugated pipe, the outer ring sleeve surface of each damping sleeve is in contact connection with the inner sleeve surface of the sealing sleeve through a centering ring spring, and the inner ring sleeve surface of each damping sleeve is in contact connection with the outer surfaces of the static ring and the corrugated pipe respectively.

3. A double-ended dry gas seal assembly for an industrial steam turbine as claimed in claim 1 or claim 2 wherein: two sides of the shaft shoulder are respectively sleeved with a centering ring spring; the centering coil spring is contacted with the inner ring surface of the movable ring at the same side, and the movable ring has a certain floating amount; a flexible graphite ring for sealing the movable ring and a transmission pin in the axial direction are arranged on the sealing surface of the shaft shoulder; the rotating ring is provided with a pin shaft hole corresponding to the transmission pin, the diameter of the pin shaft hole is larger than that of the transmission pin, and the shaft shoulders drive the rotating rings on two sides to rotate through the transmission pin.

4. A double-ended dry gas seal assembly as claimed in claim 3 wherein: the inner side end of the shaft sleeve is connected with a front pressing sleeve which is propped against the shoulder part of the shaft neck at the inner side; the outer side end of the shaft sleeve is connected with a rear pressing sleeve, and a flexible graphite ring is arranged between the rear pressing sleeve and the shaft sleeve; the outer side end of the rear pressing sleeve is backed up by a spindle nut screwed on the shaft neck.

5. The double-end-face dry gas seal assembly of claim 4, wherein: a labyrinth sleeve is arranged between the main shaft nut and the seal sleeve, and a rear comb-shaped labyrinth seal structure is arranged on the labyrinth sleeve; the seal cover is provided with a vent cavity between the rear comb labyrinth seal structure and the corrugated pipe close to the outer side, and the vent cavity is communicated with the atmosphere through a vent hole.

6. The double-ended dry gas seal assembly of claim 5, wherein: a rear air-isolating cavity is arranged between the labyrinth sleeve and the spindle nut, the rear air-isolating cavity is arranged in the middle of the rear comb-shaped labyrinth sealing structure, and the rear air-isolating cavity is communicated with external rear isolating air through a pipeline.

7. The double-end-face dry gas seal assembly of claim 6, wherein: the inner side of the sealing sleeve of the shell is provided with a front air-isolating cavity for preventing steam in the shell from entering, and front isolating air is introduced into the front air-isolating cavity; the pressure of the front isolation gas is greater than the pressure of steam in the machine and less than the pressure of the main sealing gas.

8. A double-ended dry gas seal assembly for an industrial steam turbine as claimed in claim 5 or 6 or 7 wherein: the inner and outer sleeve surfaces of the sealing sleeve are multi-step surfaces; the outer sleeve surface of the sealing sleeve is in sealing connection with the machine shell through a plurality of sealing rings, and the inner sleeve surface of the sealing sleeve is in sealing connection with the outer sleeve surface of the labyrinth sleeve through the sealing rings and is in sealing connection with one end, far away from the shaft shoulder, of the pair of corrugated pipes through the flexible graphite ring.

9. The double-end-face dry gas seal assembly of claim 1, wherein: the pneumatic pressure groove is a one-way groove or a two-way groove; the depth of the one-way groove is 3-20 μm, and the width of the dam area of the pneumatic groove pressing is 0.25-0.75 times of the width of the sealing surface.

10. A double-ended dry gas seal assembly for an industrial steam turbine as claimed in claim 1 or 9 wherein: the movable ring is made of silicon carbide, silicon nitride or hard alloy; the static ring is made of graphite or silicon carbide with a diamond-like film plated on the surface.

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