CN111828100A - A tandem dry gas sealing device for industrial steam turbines - Google Patents

Abstract

A series dry gas sealing device for an industrial steam turbine comprises two groups of rotary sealing components and two groups of static sealing components which are arranged in series. Each rotary seal assembly includes a rotating ring and a rotating ring seat disposed on a journal. Each group of static sealing components comprises a sealing sleeve fixed in the casing, and also comprises a static ring and a corrugated pipe which are coaxially arranged with the shaft sleeve. Under the action of self elasticity, the inner end face of the corrugated pipe is pressed against the outer end face of the static ring to form a contact sealing structure. The static ring is arranged between the corrugated pipe and the dynamic ring and is connected with the sealing sleeve in a floating mode through the stop pin. When the movable ring rotates along with the shaft of the steam turbine, the outer side end face of the movable ring and the inner side end face of the static ring form a non-contact air film lubrication state. Because the dynamic ring and the static ring have self-adjusting capacity, stable air film lubrication non-contact sealing is formed between the dynamic ring and the static ring, so that 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 tandem dry gas sealing device for industrial steam turbines

technical field

The invention relates to the technical field of mechanical seals, in particular to a tandem dry gas sealing 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 link is 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 saving 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 series dry gas sealing device for an industrial steam turbine, which adopts the following technical solutions:

A tandem 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 two sets of rotary seal assemblies and two sets of rotary seal assemblies arranged in series. Set of static seal components;

Each set of rotary seal assemblies includes a moving ring arranged on the journal, and a moving ring seat that seals and supports the inner end face of the moving ring and drives the moving ring to rotate together with the turbine shaft; There are multiple circumferentially distributed pneumatic pressure grooves;

Each group of static sealing assemblies includes a sealing sleeve fixed in the casing and sealingly connected to the casing, and also includes a static ring and a bellows coaxially arranged with the shaft sleeve; wherein, the outer end face of the bellows is in sealing connection with the sealing sleeve The static ring is arranged 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 inner end face of the bellows is pressed against the outer end face of the static ring to form a contact sealing structure; The inner end face of the static ring is arranged opposite to the outer end face of the moving ring. When the moving ring rotates with the steam turbine shaft, the outer end face of the moving ring and the inner end face of the stationary ring form a non-contact dry gas sealing structure;

A set of rotary seal assemblies and static seal assemblies close to the inside of the machine form a primary seal structure, and a set of rotary seal assemblies and static seal assemblies close to the outside of the machine form a secondary seal structure; the secondary seal structure is used for leakage to the primary seal structure The steam inside the machine is sealed for a second time.

As a preferred technical solution, the static seal assembly further includes a damping sleeve for radially limiting the static ring and the bellows, and the outer surface of the damping sleeve is in contact with the inner sleeve surface of the sealing sleeve through a centering coil spring, The inner sleeve surfaces are respectively contacted and connected with the outer surfaces of the static ring and the bellows.

As a preferred technical solution, a first bushing and a second bushing are arranged on the journal; the moving ring seat close to the inner side of the machine is connected to the inner end of the first bushing and abuts against the inner shaft of the journal shoulder; a pressing sleeve is connected to the outer end of the first bushing, and a flexible graphite ring is arranged between the pressing bush and the first bushing; the second bushing is pressed against the outer end of the pressing bush, and its The outer end is back-tightened by the main shaft nut screwed on the journal; a part of the inner end of the second shaft sleeve is sleeved on the first shaft sleeve and extends to the outer end face of the moving ring in the secondary sealing structure, used for the moving ring Axial limit; the moving ring seat close to the outside of the machine is connected to the first bushing through a key, and a part of its inner end extends to the outer end face of the moving ring in the primary sealing structure, which is used for the axial direction of the moving ring. limit.

As a preferred technical solution, a centering coil spring is sleeved on the first shaft sleeve; the centering coil spring is in contact with the inner ring surface of the moving ring, and the moving ring has a certain floating amount; the moving ring seat is provided with There is a support surface corresponding to the inner end face of the moving ring, a flexible graphite ring for sealing the inner end face of the moving ring is arranged on the support surface, and a transmission pin in the axial direction is also arranged; the moving ring is provided with a transmission pin. The corresponding pin shaft hole, the diameter of the pin shaft hole is larger than the diameter of the transmission pin, and the movable ring seat drives the movable ring to rotate together with the steam turbine shaft through the transmission pin.

As a preferred technical solution, an organic outer comb labyrinth sealing structure is arranged between the main shaft nut and the sealing sleeve; the sealing sleeve is provided with a venting cavity between the outer comb labyrinth sealing structure and the secondary sealing structure. , the venting cavity is communicated with the atmosphere through the venting port.

As a preferred technical solution, an air barrier cavity is provided between the labyrinth sleeve and the main shaft nut, the air barrier chamber is arranged in the middle part of the comb-shaped labyrinth seal structure outside the machine, and the air barrier cavity is communicated with the external barrier gas through a pipeline .

As a preferred technical solution, 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 a multi-channel sealing ring, and the inner sleeve surface of the sealing sleeve is connected to the labyrinth through the sealing ring respectively. The outer surface of the sleeve is sealed and connected with the outer end face of the bellows through the flexible graphite ring.

As a preferred technical solution, the casing is provided with a main sealing cavity on the inner side of the sealing sleeve for preventing the entry of steam in the machine, and a main sealing gas is introduced into the main sealing cavity; the main sealing gas meets certain quality standards. The medium inside the machine, or the steam outside the machine after filtering, and the pressure of the main sealing gas is greater than the pressure of the steam inside the machine.

As a preferred technical solution, the casing is provided with a leakage gas recovery cavity between the primary sealing structure and the primary sealing structure, and the leakage gas recovery cavity is communicated with an external leakage gas recovery device through a pipeline.

As a preferred technical solution, 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 of the width of the sealing surface times; 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 series-connected sealing structure seals the high-pressure steam in the machine, which not only reduces energy consumption, but also improves the energy conversion efficiency of the industrial steam turbine.

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.

In the figure: 1, journal; 2, casing; 3, first bushing; 4, second bushing; 5, moving ring; 51, pneumatic pressure groove; 6, moving ring seat; 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, stop pin; 16, flexible graphite ring; 17, machine Inner comb-like labyrinth sealing structure; 18. Comb-like labyrinth sealing structure outside the machine; 19. Main sealing cavity; 20. Air isolation cavity; 21. Leakage gas recovery cavity;

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 tandem 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 turbine shaft Between the necks 1, there are two sets of rotary seal assemblies and two sets of static seal assemblies arranged in series. The stationary seal assembly forms a secondary seal structure. The series combination of the primary sealing structure and the secondary sealing structure is the primary sealing structure of the present invention.

Each group of rotary seal assemblies includes a moving ring 5 arranged on the journal 1, and a moving ring seat 6 that seals and supports the inner end face of the moving ring 5 and drives the moving ring 5 to rotate with the turbine shaft. Specifically, the journal 1 is provided with a first bushing 3 and a second bushing 4 . The moving ring seat 6 close to the inner side of the machine is connected to the inner end of the first bushing 3 and abuts against the inner shoulder of the journal 1 . A pressing sleeve 23 is connected to the outer end of the first shaft sleeve 3 . The second shaft sleeve 4 is pressed against the outer end of the pressing sleeve 23, and its outer end is backed by the spindle nut 7 screwed on the journal 1, so that the first shaft sleeve 3 and the second shaft sleeve 4 are fixed on the shaft neck 1, and rotate with the turbine shaft. In order to limit the axial movement of the moving ring 5 to the outside, a part of the inner end of the second bushing 4 is sleeved on the first bushing 3 and extends to the outer end face of the moving ring 5 in the secondary sealing structure, so as to be used for the moving ring 5 the axial limit, but does not limit the floating of the moving ring 5. Similarly, the moving ring seat 6 near the outer side of the machine is connected to the first bushing 3 through a key, and a part of its inner side extends to the outer end face of the moving ring 5 in the primary sealing structure, for the shaft of the moving ring 5 To limit, but do not limit the floating of the moving ring 5. In order to prevent the leakage of steam in the machine from the gap between the journal 1 and the first shaft sleeve 3 , a flexible graphite ring 16 is provided between the pressing sleeve 23 and the first shaft sleeve 3 . The flexible graphite ring 16 not only has good sealing performance, but also has high temperature resistance. The movable ring seat 6 is provided with a support surface corresponding to the inner end face of the movable ring 5, and two flexible graphite rings 16 for sealing the inner end face of the movable ring 5 are provided on the support surface. The drive pin 14. 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 . When the moving ring seat 6 rotates with the steam turbine shaft, the moving ring seat 6 transmits the rotational torque to the moving ring 5 through the transmission pin 14, so that the moving ring 5 rotates together with the steam turbine shaft.

Each group of static sealing components includes a sealing sleeve 10 fixed in the inner cavity of the casing 2 and sealingly connected with the inner cavity of 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 of multi-step surface structure, and the outer surface of the sealing sleeve 10 is sealedly connected with the casing 2 through multiple sealing rings, so as to realize the sealing between the sealing sleeve 10 and the casing 2 .

Each group of static seal assemblies further includes a static ring 9 and a bellows 8 coaxially arranged with the first bushing 3 . 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 outer end surface of the bellows 8 is fixed on the sealing sleeve 10 by bolts, and is sealed with the inner surface of the sealing sleeve 10 through the flexible graphite ring 16 . 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 . Since the bellows 8 has elasticity, it has a certain axial elastic force when it is pressed. Under the action of its own axial elastic force, the inner end face of the bellows 8 is pressed against the outer end face of the static ring 9 to form a contact sealing structure between the bellows 8 and the static ring 9 . The inner end face of the static ring 9 is opposite to the outer end face of the moving ring 5 , under the action of the axial elastic force of the bellows 8 , a certain contact pressure is maintained between the static ring 9 and the moving ring 5 .

A plurality of circumferentially distributed pneumatic pressure grooves 51 are arranged on the outer end face of the moving ring 5, and the pneumatic pressure grooves 51 are opened on one side of the high-pressure steam in the machine. 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 high-pressure steam in the machine is located on the outer ring surface side of the moving ring 5, and the pneumatic pressure groove 51 is a one-way spiral groove. As shown in Figure 2, the direction of rotation of the one-way helical groove is the same as that of the turbine shaft, and the inner part of the outer end face of the automatic ring 5 of the one-way helical groove extends helically in the radial direction, and opens on the outer ring surface of the moving 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 helical groove is 15 μm, and the width of the dam area of the pneumatic pressure groove 51 is 0.7 times the width of the outer end face of the moving ring 5 . When the moving ring 5 rotates with the turbine shaft, the high-pressure steam enters the one-way helical groove and produces a hydrodynamic pressure effect, which pumps the high-pressure steam at the outer ring surface inward, so that the outer end face of the moving ring 5 and the static ring 9 A layer of micron-scale gas film is formed between the inner end faces of the ring, which lubricates and isolates the sealing surface between the moving ring 5 and the static ring 9. Due to the very high rotational 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, which not only realizes non-contact operation, but also realizes the sealing of the steam in the machine. . 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 this device, two dry gas sealing structures are arranged in series in the main sealing structure, and the secondary sealing structure located on the outer side seals the steam leaked from the primary sealing structure located on the inner side again. Zero leakage seal to steam inside the machine. Since the steam no longer leaks, there is no need to set an additional leakage steam cooling device, which greatly reduces the subsequent operation and maintenance costs of the industrial steam turbine.

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 sleeved on the first shaft sleeve 3, and the centering coil spring 12 is in contact with the inner ring surface of the moving ring 5; the diameter of the pin shaft hole is larger than the diameter of the transmission pin 14 to prevent the transmission pin 14 from moving Limitation of the floating of the ring 5; a certain gap is reserved between the moving ring seat 6 and the outer ring surface of the moving 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, and the static ring 9 is connected with the stop pin 15 through the long groove to prevent static 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 has no effect on 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 damping sleeve 11 for radially limiting the bellows 8 is made of a high-temperature-resistant metal material. In this embodiment, the material of the damping sleeve 13 is stainless steel. The outer ring sleeve surface of the damping ring sleeve 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 ring sleeve 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 axial swing. Therefore, although the damping sleeve 11 limits the static ring 9 and the bellows 8 in radial direction, it does not prevent the static ring 9 from always following. The freedom of the moving ring 5 for self-adjustment.

To sum up, the device 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 series-connected sealing structure seals the high-pressure steam in the machine, which not only reduces energy consumption, but also improves the energy conversion efficiency of the industrial steam turbine.

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 8 will lose its elasticity and compensation ability, resulting in premature failure of the seal. To this end, the casing 2 is provided with a main sealing cavity 19 on the inner side of the sealing sleeve 10 for preventing the entry of steam in the machine, and the main sealing gas is introduced into the main sealing cavity 19 . It should be noted that the main sealing cavity 19 is located between the primary sealing structure and the internal comb-shaped labyrinth sealing structure 17 . The comb-shaped labyrinth sealing structure 17 in the machine is a self-contained sealing structure of the existing steam turbine. The sealing structure 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 main sealing 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 main sealing gas is required to be greater than the steam pressure in the machine, and the main sealing gas is returned to the machine through the comb-shaped labyrinth sealing structure 17 in the machine, so as 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 in the steam turbine itself meets a certain quality standard, it can also be directly used as the main sealing gas to enter the main sealing cavity 19 through the comb-shaped labyrinth sealing structure 17 in the machine. At this time, the outer pipe of the main sealing cavity 19 is closed.

In order to prevent the lubricating oil in the bearing housing (outside the spindle nut 7, not shown in the figure) from contaminating the dry gas seal structure through diffusion, a labyrinth sleeve 13 is provided between the spindle nut 7 and the sealing sleeve 10. The labyrinth sleeve 13 The outer surface of the sealing sleeve 10 is connected with the inner sleeve surface of the sealing sleeve 10 through a sealing ring. The labyrinth sleeve 13 is provided with a plurality of comb-shaped inner ring teeth, and forms an external comb-shaped labyrinth seal structure 18 with the spindle nut 7 . The sealing sleeve 10 is provided with a venting cavity 22 between the external comb-shaped labyrinth sealing structure 18 and the secondary sealing structure, and the venting cavity 22 is communicated with the atmosphere through the venting port. In this way, the external comb-like labyrinth seal structure 18 can seal most of the lubricating oil gas, and a small amount of lubricating oil gas leaked from the external comb-like labyrinth seal structure 18 is vented through the venting port, thereby avoiding the contamination of the lubricating oil gas to the dry gas sealing structure . Similarly, a very small amount of steam leaking from the secondary sealing structure is also vented through the vent port after entering the low pressure chamber. Meanwhile, between the labyrinth sleeve 13 and the main shaft nut 7, there is an air barrier cavity 20, the air barrier chamber 20 is arranged in the middle part of the comb-shaped labyrinth seal structure 18 outside the machine, and the air barrier chamber 20 communicates with the outside air through a pipeline. . The isolation gas is nitrogen gas or instrument air. After the nitrogen gas enters the gas isolation chamber 20 , the lubricating oil gas entering the comb-shaped labyrinth seal structure 18 outside the machine is blocked. The excess nitrogen enters the low pressure chamber and is vented through the vent. In addition, the barrier gas can also cool the secondary seal structure.

In order to recover the steam leaked from the primary sealing structure, the casing 2 is provided with a leakage gas recovery cavity 21 between the primary sealing structure and the primary sealing structure, and the leakage gas recovery cavity 21 recovers the leakage gas from the outside through pipes. The device is connected, and the leaked steam is returned to the machine for reuse.

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. The utility model provides a serial-type dry gas sealing device for industrial steam turbine, axial setting is between casing and bearing box, radially between casing and the journal of steam turbine axle, characterized by: the sealing device comprises two groups of rotary sealing components and two groups of static sealing components which are arranged in series;

each group of rotary sealing components comprises a movable ring arranged on the shaft neck, and a movable ring seat which is used for sealing and supporting the end surface of the inner side of the movable ring and driving the movable ring to rotate along with the shaft of the steam turbine; a plurality of pneumatic pressure grooves distributed circumferentially are arranged on the outer side end surface of the movable ring;

each group of static sealing components comprises a sealing sleeve which is fixed in the casing and is in sealing connection with the casing, and also comprises a static ring and a corrugated pipe which are coaxially arranged with the shaft sleeve; the outer side end face of the corrugated pipe 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 surface of the inner side of the corrugated pipe is pressed on the end surface of the outer side of the static ring to form a contact sealing structure; the end face of the inner side of the static ring is opposite to the end face of the outer side of the dynamic ring, and when the dynamic ring rotates along with a shaft of the steam turbine, the end face of the outer side of the dynamic ring and the end face of the inner side of the static ring form a non-contact dry gas sealing structure;

the group of rotary sealing assemblies and the static sealing assemblies close to the inner side of the machine form a primary sealing structure, and the group of rotary sealing assemblies and the static sealing assemblies close to the outer side of the machine form a secondary sealing structure; the secondary sealing structure is used for carrying out secondary sealing on the steam in the machine leaked by the primary sealing structure.

2. The tandem dry gas seal device for an industrial steam turbine according to claim 1, wherein: the static sealing assembly further comprises a damping sleeve for radially limiting the static ring and the corrugated pipe, the outer sleeve surface of the damping sleeve is in contact connection with the inner sleeve surface of the sealing sleeve through a centering ring spring, and the inner sleeve surface is in contact connection with the outer surfaces of the static ring and the corrugated pipe respectively.

3. The tandem dry gas seal device for an industrial steam turbine according to claim 1 or 2, wherein: a first shaft sleeve and a second shaft sleeve are arranged on the shaft neck; the movable ring seat close to the inner side of the machine is connected to the inner side end of the first shaft sleeve and abuts against the shaft shoulder part of the inner side of the shaft neck; a compression sleeve is connected to the outer side end of the first shaft sleeve, and a flexible graphite ring is arranged between the compression sleeve and the first shaft sleeve; the second shaft sleeve is pressed against the outer side end of the pressing sleeve, and the outer side end of the second shaft sleeve is backed up by a main shaft nut screwed on the shaft neck; one part of the inner side end of the second shaft sleeve is sleeved on the first shaft sleeve and extends to the outer side end face of the movable ring in the secondary sealing structure for axially limiting the movable ring; the movable ring seat close to the outer side of the machine is connected to the first shaft sleeve through a key, and one part of the inner side end of the movable ring seat extends to the outer side end face of the movable ring in the primary sealing structure and is used for axially limiting the movable ring.

4. The tandem dry gas seal device for an industrial steam turbine according to claim 3, wherein: a centering ring spring is sleeved on the first shaft sleeve; the centering coil spring is contacted with the inner ring surface of the moving ring, and the moving ring has a certain floating amount; the movable ring seat is provided with a supporting surface corresponding to the end surface of the inner side of the movable ring, the supporting surface is provided with a flexible graphite ring for sealing the end surface of the inner side of the movable ring, and the movable ring seat is also provided with a transmission pin in the axial direction; 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 rotating ring seat drives the rotating ring to rotate along with the shaft of the steam turbine through the transmission pin.

5. The tandem dry gas seal device for an industrial steam turbine according to claim 3, wherein: an external comb labyrinth seal structure is arranged between the main shaft nut and the seal sleeve; the sealing sleeve is provided with a vent cavity between the comb-shaped labyrinth sealing structure and the secondary sealing structure outside the machine, and the vent cavity is communicated with the atmosphere through a vent hole.

6. The tandem dry gas seal device for an industrial steam turbine according to claim 5, wherein: an air isolating cavity is arranged between the labyrinth sleeve and the spindle nut, the air isolating cavity is arranged in the middle of the comb-shaped labyrinth sealing structure outside the machine, and the air isolating cavity is communicated with external isolated air through a pipeline.

7. The tandem dry gas seal device for an industrial steam turbine according to claim 5 or 6, 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 casing 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 the outer side end surface of the corrugated pipe through a flexible graphite ring.

8. The tandem dry gas seal device for an industrial steam turbine according to claim 1, 5 or 6, wherein: the inner side of the sealing sleeve of the shell is provided with a main sealing cavity for preventing steam in the shell from entering, and main sealing gas is introduced into the main sealing cavity; the main seal gas is an internal medium meeting a certain quality standard or external steam after filtration treatment, and the pressure of the main seal gas is greater than that of the internal steam.

9. The tandem dry gas seal device for an industrial steam turbine according to claim 8, wherein: the casing is provided with a leaked gas recovery cavity between the first-stage sealing structure and the second-stage sealing structure, and the leaked gas recovery cavity is communicated with an external leaked gas recovery device through a pipeline.

10. The tandem dry gas seal device for an industrial steam turbine according to claim 1 or 9, 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; 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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