CN111237469A

CN111237469A - Fluid dynamic pressure type postposition isolation sealing device for dry gas sealing of turbine machinery

Info

Publication number: CN111237469A
Application number: CN202010152399.0A
Authority: CN
Inventors: 杨惠霞; 陈嘉懿; 张小明; 郑毅
Original assignee: Shanghai Haomi Sealing Technology Co Ltd
Current assignee: Shanghai Haomi Sealing Technology Co Ltd
Priority date: 2020-03-06
Filing date: 2020-03-06
Publication date: 2020-06-05

Abstract

The invention relates to a hydrodynamic pressure type postposition isolation sealing device for dry gas sealing of a turbomachine, which is arranged between a dry gas sealing component and a bearing box, and comprises a rotating component and a static component, wherein a lock nut is arranged on a main shaft, two ends of the rotating component are respectively clamped by the lock nut and a rotating part of the dry gas sealing component, the rotating component is sleeved outside the main shaft and rotates at a high speed along with the main shaft, the static component is arranged around the main shaft and is fixed with a shell, one end surface of the rotating component is attached to one end surface of the static component to form a sealing surface, the sealing surface is axially vertical to the main shaft, and a hydrodynamic pressure groove is arranged on the end surface of the rotating component. Compared with the prior art, the sealing device of the application is applied to the turbine machinery, can realize zero leakage of bearing side lubricating oil to dry gas sealing, and has extremely low loss of isolation gas.

Description

Fluid dynamic pressure type postposition isolation sealing device for dry gas sealing of turbine machinery

Technical Field

The invention relates to the technical field of mechanical sealing, in particular to a fluid dynamic pressure type rear-mounted isolation sealing device for dry gas sealing of a turbine machine.

Background

The turbo machinery comprises a turbo compressor (such as a centrifugal compressor and an axial flow compressor) and a turbo expander, which are high-speed rotating equipment and are key core equipment of devices such as petroleum and chemical engineering. At present, dry gas seal, namely dry running, gas lubrication and non-contact mechanical seal, is generally adopted by turbomachinery as shaft end seal. No matter the single-end face dry gas seal, the double-end face dry gas seal, the serial dry gas seal and the serial dry gas seal with the middle labyrinth are adopted, the rear isolation seal is needed to isolate the dry gas seal from the bearing box, and the condition that lubricating oil gas generated by the high-speed rotation of the main shaft in the bearing box pollutes the outer side seal of the dry gas seal through axial diffusion to cause failure of the dry gas seal is avoided.

The common sealing forms of the front and rear isolating seals are non-contact labyrinth seal (or comb seal) and split carbon ring seal. The labyrinth seal is realized by throttling and depressurizing, and has the advantages of non-contact, large working clearance and high reliability; but the defects are that the consumption of isolating gas is large, and the effect of plugging bearing lubricating oil gas is poor. The split carbon ring seal is also a throttling pressure reduction type seal, and is provided with a contact split carbon ring seal and a non-contact split carbon ring seal.

However, the contact carbon ring seal has a certain running-in period at the initial stage of use, the carbon ring has certain abrasion in the running-in period, the abrasion amount is related to the dew point of the isolation gas nitrogen, and the lower the dew point, the drier the nitrogen is, the larger the abrasion amount is. Carbon graphite powder from time to time running under wear may cause failure of the outer seal of the dry gas seal. The non-contact carbon ring seal has a large static leakage and the consumption of the barrier gas is very sensitive to the temperature at the carbon ring seal. For some special conditions, such as the bearing is too close to the dry gas seal axial distance; the position of the bearing oil drain port is unreasonable in design; the oil inlet pressure of the bearing is too high; the bearing box oil return port is too small, oil return flow is not smooth, and the labyrinth seal and the carbon ring seal are likely to have an isolation gas short circuit phenomenon, so that bearing lubricating oil or lubricating oil gas enters the outer side seal of the dry gas seal to pollute the dry gas seal, and the dry gas seal fails.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a hydrodynamic pressure type rear isolation sealing device for dry gas sealing of a turbine machine, which has good sealing effect.

In order to achieve the object of the present invention, the present application provides the following technical solutions.

In a first aspect, the present application provides a hydrodynamic rear isolation seal for a dry gas seal of a turbomachinery, the rear isolation sealing device is positioned between a dry gas sealing assembly and a bearing box in the turbine machinery, the turbine machine is provided with a main shaft rotating at high speed, the rear isolation sealing device comprises a rotating component and a static component, a lock nut is arranged on the main shaft, wherein, two ends of the rotating component are respectively clamped by the rotating parts of the locking nut and the dry gas sealing component, and the rotating component is sleeved outside the main shaft, and the static component is arranged around the main shaft and fixed with the shell of the turbine machine along with the high-speed rotation of the main shaft, one end face of the rotating component and one end face of the static component are jointed and form a sealing surface, the sealing surface is axially vertical to the main shaft, and the end surface of the rotating assembly is provided with a hydrodynamic groove. The rotating part of the dry gas seal assembly described in the application can be a compressing sleeve and other parts of the dry gas seal assembly, can be selected according to different actual equipment, and is the prior art.

In the application, when the turbine rotates at a high speed, the rotating assembly rotates at a high speed along with the main shaft under the clamping of the locking nut and the rotating part of the dry gas sealing assembly, and because the hydrodynamic pressure groove is arranged on the end face, which is attached to the static assembly, of the rotating assembly, a micron-sized gas film is formed between the rotating assembly and the static assembly (namely a sealing surface) when the rotating assembly rotates at a high speed, so that the lubricating and isolating effects on the sealing surface are achieved, and the sealed non-contact operation is realized. Because the rotating speed of the turbo machinery is very high, the rigidity of the extremely thin air film of the sealing surface is very high, the lubricating oil gas on the bearing side can be effectively isolated, and even if the air supply pressure of the isolation air is lower than the oil gas pressure of the bearing side, the zero leakage of the lubricating oil gas on the bearing side to the dry air seal can be ensured, so that the long-period stable operation of the dry air seal is ensured.

In a preferred scheme of the first aspect, the rotating assembly comprises a rotating ring, a shaft sleeve and a pressing sleeve, the shaft sleeve and the pressing sleeve are both annular and are sleeved outside the main shaft, wherein the shaft sleeve and the pressing sleeve are fixed through a hexagon socket head cap screw, the tail end of the shaft sleeve is abutted against a lock nut, the front end of the pressing sleeve is abutted against the rotating part of the dry gas sealing assembly, and the rotating ring is fixed with the shaft sleeve through a transmission pin and synchronously rotates.

In a preferred scheme of the first aspect, the axle sleeve includes first ring and the second ring of coaxial and integration setting, the tail end and the lock mother butt of second ring, the tail end integration of the front end of second ring and first ring are connected, the tail end of rotating ring and the laminating of the front end of second ring, and pass through the drive pin transmission, seal through the sealing washer, the internal diameter of rotating ring with the outer fringe butt of first ring.

In a preferred scheme of the first aspect, a groove is formed in a contact position of the tail end of the compression sleeve and the main shaft, the front end of the first ring is inserted into the groove and abutted against a groove wall, the bottom of the groove is fixed to the front end of the first ring through a hexagon socket head cap screw, and the tail end of the compression sleeve is abutted against the front end of the movable ring.

In a preferred version of the first aspect, a centering corrugated strip is provided between the inner diameter of the rotating ring and the outer edge of the first ring. Since the rotating ring rotates at a high speed during operation, the very small eccentricity causes additional vibrations, which affect the dynamic performance of the entire device. This application adds the centering ripple area between rotating ring and first ring, can eliminate the gap between the two to guarantee that rotating ring and main shaft are with the axle center, ensure its operating stability. Preferably, the centering corrugated strip is a commercially available tolerance strip of a high alloy material.

In a preferred version of the first aspect, an O-ring is provided between the sleeve and the main shaft.

In a preferred embodiment of the first aspect, a wear-resistant layer is attached to an end surface of the front end of the moving ring by spraying or surfacing, and a hydrodynamic groove is disposed on the wear-resistant layer, the hydrodynamic groove includes a middle annular groove, an outer dynamic groove and an inner dynamic groove, the middle annular groove and the moving ring are coaxially disposed, the outer dynamic groove and the inner dynamic groove are both communicated with the middle annular groove, an outer dam region without a groove is located between a root of the outer dynamic groove and an outer edge of the moving ring, and an inner dam region without a groove is located between a root of the inner dynamic groove and an axis of the moving ring. More preferably, the rotating component base material preferably recommends high-strength precipitation hardening stainless steel, and martensite stainless steel or dual-phase steel can be selected for working conditions with not very high rotating speed; the wear-resistant layer can be made of the hard alloy sprayed by supersonic flame and can also be made of the hard alloy subjected to surface overlaying.

In a preferable mode of the first aspect, the groove depth of the intermediate annular groove is 10 to 100 μm, and the groove depths of the outer dynamic pressure groove and the inner dynamic pressure groove are 3 to 20 μm.

In a preferable mode of the first aspect, the groove type of the outer dynamic pressure groove and the inner dynamic pressure groove is a one-way rotation groove type or a two-way rotation groove type, the one-way rotation groove type includes an arc groove or a spiral groove, and the two-way rotation groove type includes a U-shaped groove or a T-shaped groove. In the case of the unidirectional groove, the rotation directions of the outer dynamic pressure groove and the inner dynamic pressure groove are opposite (both viewed from the inside to the outside).

In a preferable scheme of the first aspect, a radial width of the outer dam region is 0.15 to 0.35 of a width of the sealing surface, and a radial width of the inner dam region is 0.1 to 0.3. When the width of the inner dam area or the outer dam area is too small, the film formed by the fluid dynamic pressure groove is too thick and is easy to leak inwards or outwards beyond the inner dam area or the outer dam area, so that the sealing performance is reduced; when the width of the inner dam area or the outer dam area is too large, the width of the hydrodynamic groove is small, an air film is not easy to form, and the service life and the performance of sealing are also influenced.

In a preferred version of the first aspect, the stationary assembly includes a spring seat, a spring, a push ring and a stationary ring, and the spring seat is fixed to the housing by a socket head cap screw; the end face of the tail end of the static ring is attached to the end face of the front end of the movable ring to form a sealing surface, the front end of the static ring is attached to the tail end of the push ring, the front end of the push ring is attached to the rear end of the spring, and the front end of the spring is attached to the end face of the bottom of the spring hole in the spring seat. And sealing rings are arranged at the matching positions of the push ring, the static ring and the spring seat. The joint of the end face of the static ring and the end face of the moving ring is realized by the axial pressing force of the spring and the gas pressure of the isolation gas. More preferably, the static ring is made of high-quality resin-impregnated carbon graphite or antimony-impregnated carbon graphite.

In a preferred embodiment of the first aspect, a through isolation air passage is provided in the spring seat, the push ring and the stationary ring, and an outlet of the isolation air passage in the stationary ring is located in a middle annular groove of the front end face of the east ring. The isolation gas firstly enters the middle annular groove through the isolation gas channel, and then the isolation gas in the middle annular groove area is respectively pumped outwards and inwards by utilizing the fluid dynamic pressure effect generated by the outer dynamic pressure groove and the inner dynamic pressure groove, so that a layer of micron-order gas film is formed between the sealing end faces, the lubrication and isolation effects are played on the sealing end faces, and the sealed non-contact operation is realized. Meanwhile, a small part of the isolation gas leaks to the inner diameter part through a small gap on the inner side groove area and the inner side dam area, and the isolation gas leaked from the inner diameter part is discharged to a high point together with the leakage gas sealed at the outer side of the dry gas seal through an annular passage between the spring and the pressing sleeve.

In a preferred aspect of the first aspect, a pin is provided between the spring seat and the push ring, and the pin prevents rotation between the spring seat and the push ring. More preferably, the push ring is provided with a limiting structure in the axial direction, so that the static assembly is convenient to mount, and the push ring and the O-shaped ring are prevented from being pushed out of the spring seat by the spring during assembly.

In a preferred arrangement of the first aspect, a pin is provided between the push ring and the stationary ring, and rotation between the push ring and the stationary ring is prevented by the pin. The arrangement ensures that the static ring and the push ring are kept static in the working state.

In a preferred scheme of the first aspect, the matching positions of the push ring and the stationary ring with the spring seat are provided with O-shaped rings, and the arrangement ensures that the isolation gas can only pass through the sealing surface of the isolation gas channel and cannot leak to other places, so that the sealing effect is ensured.

In a preferred aspect of the first aspect, the mating surface of the spring seat and the housing is provided with an O-ring.

In a preferred version of the first aspect, the rear end of the spring seat is flared, which arrangement facilitates the removal of lubricant.

In a preferred embodiment of the first aspect, the housing is provided with an oil slinger, and the lock nut is provided with an oil slinger, which can prevent or reduce the diffusion or splashing of the bearing-side lubricating oil to the rear isolation seal.

Compared with the prior art, the invention has the beneficial effects that:

(1) because the clearance between the static ring and the dynamic ring is extremely small, and the sealing pressure difference is low, the consumption of the isolating gas is extremely small, namely, the zero leakage of the lubricating oil gas at the bearing side to other turbine mechanical dry gas seals can be ensured only by the extremely low consumption of the isolating gas through the fluid dynamic pressure type rear isolating sealing device;

(2) even if the pressure of the isolation gas fluctuates and even the pressure of the isolation gas is lower than that of lubricating oil gas on the bearing side, the rear isolation sealing device can work normally, and the dry gas seal is ensured not to be polluted by the oil gas and fail.

Drawings

FIG. 1 is a schematic view of the construction of a seal of the present application;

FIG. 2 is a schematic view showing the shape of a one-way rotating groove type hydrodynamic groove provided at the front end of a rotating ring in the present application;

FIG. 3 is a schematic view showing the shape of another fluid dynamic pressure groove of a unidirectional rotation groove type provided at the leading end of a rotating ring in the present application;

fig. 4 is a schematic view showing the shape of a bidirectional rotating groove type hydrodynamic groove provided at the front end of the rotating ring in the present application.

In the drawing, 1 is a spring seat, 2 is a shaft sleeve, 3 is a transmission pin, 4 is a movable ring, 5 is a stationary ring, 6 is a spring seat, 7 is a spring, 8 is a pressing sleeve, 9 is an O-ring, 10 is an O-ring, 11 is a centering corrugated strip, 12 is a locking nut, 13 is a push ring, 14 is an O-ring, 15 is an O-ring, 16 is a pin, 17 is a pin, 18 is an inner hexagonal screw, 19 is an inner hexagonal screw, 20 is an O-ring, 21 is an inner hexagonal screw, 22 is a pin, 23 is a gasket, 24 is a main shaft, 25 is a housing, 26 is a first ring, 27 is a second ring, 28 is an oil retainer, 29 is an oil slinger, 30 is a middle annular groove, 31 is an outer dynamic pressure groove, 32 is an outer dam region, 33 is an inner dynamic pressure groove, and 34 is an inner dam region.

Detailed Description

Unless otherwise defined, technical or scientific terms used herein in the specification and claims should have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All numerical values recited herein as between the lowest value and the highest value are intended to mean all values between the lowest value and the highest value in increments of one unit when there is more than two units difference between the lowest value and the highest value.

While specific embodiments of the invention will be described below, it should be noted that in the course of the detailed description of these embodiments, in order to provide a concise and concise description, all features of an actual implementation may not be described in detail. Modifications and substitutions to the embodiments of the present invention may be made by those skilled in the art without departing from the spirit and scope of the present invention, and the resulting embodiments are within the scope of the present invention.

In the present description, all leading ends are the media side of fig. 1, i.e., the side where the dry gas seal assembly is located, and all trailing ends are the bearing side of fig. 1, i.e., the side where the bearing housing is located.

Examples

The following will describe in detail the embodiments of the present invention, which are implemented on the premise of the technical solution of the present invention, and the detailed embodiments and the specific operation procedures are given, but the scope of the present invention is not limited to the following embodiments.

Example 1

A fluid dynamic pressure type rear isolation sealing device for dry gas sealing of a turbine is structurally shown in figure 1, and the sealing device is arranged between a dry gas sealing assembly and a bearing box and consists of a rotating assembly and a static assembly.

The rotating assembly comprises a movable ring 4, a shaft sleeve 2, a pressing sleeve 8, a centering corrugated belt 11, a plurality of O-shaped rings, a driving pin 3, a plurality of inner hexagonal screws and the like, wherein the pressing sleeve 8 is connected with the shaft sleeve 2 into a whole through the inner hexagonal screws, specifically, the shaft sleeve 2 comprises a first ring 26 and a second ring 27 which are coaxially and integrally arranged, a groove is arranged at the tail end of the pressing sleeve 8 and is in contact with a main shaft 24, the front end of the first ring 26 is inserted into the groove and is abutted against the groove wall, the groove bottom of the groove is fixed with the front end of the first ring 26 through the inner hexagonal screws 19, the front end of the second ring 27 is integrally connected with the tail end of the first ring 26, the tail end of the movable ring 4 is attached to the front end of the second ring 27 and is driven through the driving pin 3 and is sealed through the O-shaped rings 10, the inner edge of the movable ring 4 is abutted against the outer edge of the first ring 26, the centering corrugated belt 11 is arranged between the, the front end of the pressing sleeve 8 abuts against the rotating part of the dry gas seal assembly and is kept in synchronous rotation by the pin 17. Through the axial compression of the dry gas sealing assembly and the lock nut 12, torque is transmitted to the shaft sleeve 2 and the compression sleeve 8, so that the shaft sleeve 2, the compression sleeve 8 and the main shaft 24 rotate together at a high speed. The sleeve 2 in turn transmits torque to the moving ring 4 via the drive pin 3, causing the moving ring 4 to rotate at high speed with the sleeve 2. The moving ring 4 is made of metal pieces, a high-hardness wear-resistant coating is sprayed or surfacing welded on the sealing end face, and micrometer-level fluid dynamic pressure grooves which are uniformly distributed along the circumferential direction are machined on the coating or surfacing layer in a special machining mode. The groove area is positioned in the middle of the sealing end face and consists of three parts: an intermediate annular groove 30, an outer dynamic pressure groove 31, an inner dynamic pressure groove 33; the inlet of the outer dynamic pressure groove 31 is communicated with the annular groove, and the outer dynamic pressure groove 31 is an outer dam region 32 without a groove outwards; the inlet of the inner dynamic pressure groove 33 communicates with the annular groove, the inner dynamic pressure groove 33 is further inward a non-groove inner dam 34, the outer dynamic pressure groove and the inner dynamic pressure groove of the hydrodynamic groove may be of a unidirectional rotation groove type, as shown in fig. 2 or fig. 3 as a spiral groove, and if of a unidirectional groove, the rotation directions of the outer dynamic pressure groove 31 and the inner dynamic pressure groove 33 are opposite (both viewed from inside to outside). The outer dynamic pressure grooves and the inner dynamic pressure grooves of the hydrodynamic grooves may also be of a bidirectional rotating groove type, such as T-shaped grooves shown in fig. 4. The groove depths of the middle annular groove 30, the outer dynamic pressure groove 31 and the inner dynamic pressure groove 33 are all in the order of mum; an O-ring 9 is provided between the sleeve 2 and the main shaft 24, and an O-ring 10 is provided between the rotating ring 4 and the second ring 27.

The static assembly is composed of a static ring 5 made of carbon graphite, a push ring 13, a spring 7, a plurality of O-shaped rings, a spring seat 6, a plurality of pins and a plurality of hexagon socket head cap screws, and the end face of the static ring 5 is attached to the end face of the movable ring 4 by means of axial pressing force of the spring 7 and gas pressure of isolation gas. Specifically, the spring seat 6 is fixed to the rear seal chamber 1 of the housing 25 by a socket head cap screw 18, and the O-rings 15 and 20 are provided therebetween. A push ring 13 and a static ring 5 are arranged in the spring seat 6, wherein the front end of the push ring 13 is attached to the rear end of a group of springs 7, the front end of each spring 7 is attached to the bottom of a spring hole in the spring seat 6, and meanwhile, a pin 16 is arranged between the push ring 13 and the spring seat 6 to prevent the push ring 13 and the spring seat 6 from rotating; the tail end of the push ring 13 is attached to the front end of the stationary ring 5 and is prevented from rotating by a pin 22, and meanwhile, an O-shaped ring 14 is arranged on the matching surfaces of the push ring 13, the stationary ring 5 and the spring seat 6. The tail end of the static ring 5 is jointed with the front end of the dynamic ring 4 to form a sealing surface.

In addition, the spring seat 6 is only arranged in the rear seal cavity 1 in the shell 25 and is fixed with the shell 25 through the hexagon socket head cap screw 21 and the gasket 23, the oil retainer 28 is arranged on the spring seat 6, the oil slinger 29 is arranged on the lock nut 12, and the tail end of the spring seat 6 is in a bell mouth shape, so that the lubricating oil on the bearing side is prevented or reduced from being diffused or splashed to the rear isolation seal part, and can be discharged in time.

When the turbomachinery works, the rotating ring 4 rotates at a high speed, the isolating gas enters the middle annular groove 30 area of the end surface of the rotating ring 4 through the isolating gas channel arranged on the parts such as the spring seat 6, the push ring 13, the static ring 5 and the like, and the isolating gas in the middle annular groove 30 area is respectively pumped outwards and inwards by utilizing the fluid dynamic pressure effect generated by the outer dynamic pressure groove 31 and the inner dynamic pressure groove 33, so that a layer of micron-scale gas film is formed between the sealing end surfaces, the lubricating and isolating effects are realized on the sealing end surfaces, and the sealed non-contact operation is realized. Because the rotating speed of the turbo machinery is very high, the rigidity of the extremely thin air film on the sealing end face is very high, the micron-level air films on the groove area and the dam area at the outer side can effectively isolate lubricating oil gas at the bearing side, and even if the air supply pressure of isolating air is lower than the oil gas pressure at the bearing side, zero leakage of the lubricating oil gas at the bearing side to dry air sealing can be ensured, so that the long-period stable operation of the dry air sealing is ensured. Meanwhile, a small part of the isolation gas leaks to the inner diameter part through the inner dynamic pressure groove and the minimum gap on the inner dam area, and is discharged to the air at a high point together with the leakage gas sealed at the outer side of the dry gas seal through the annular gap between the spring seat 6 and the pressing sleeve 8. From the view of fig. 1, the isolating gas enters the spring seat 6 from the point a, passes through the points B and C (both the points B and C are located in the isolating gas passage) in sequence to reach the position corresponding to the middle annular groove, forms a gas film between the static ring and the dynamic ring, and finally passes through the exhaust passage to be discharged from the point D. Because the end surface clearance is extremely small and the sealing pressure difference is low, the consumption of the isolating gas is extremely small, namely, the lubricating oil gas on the bearing side can be ensured to leak to the dry gas seal of other turbine machinery only by the extremely low consumption of the isolating gas by the fluid dynamic pressure type rear isolating sealing device. Even if the pressure of the isolation gas fluctuates and even the pressure of the isolation gas is lower than that of lubricating oil gas on the bearing side, the rear isolation sealing device can work normally, and the dry gas seal is ensured not to be polluted by the oil gas and fail.

The embodiments described above are intended to facilitate the understanding and appreciation of the application by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not limited to the embodiments herein, and those skilled in the art who have the benefit of this disclosure will appreciate that many modifications and variations are possible within the scope of the present application without departing from the scope and spirit of the present application.

Claims

1. A fluid dynamic pressure type rear isolation sealing device for dry gas sealing of turbine machinery is provided, which is positioned between a dry gas sealing component and a bearing box in the turbine machinery, the turbine machinery is provided with a main shaft rotating at high speed, it is characterized in that the rear isolation sealing device comprises a rotating component and a static component, a lock nut is arranged on the main shaft, wherein, two ends of the rotating component are respectively clamped by the rotating parts of the locking nut and the dry gas sealing component, and the rotating component is sleeved outside the main shaft, and the static component is arranged around the main shaft and fixed with the shell of the turbine machine along with the high-speed rotation of the main shaft, one end face of the rotating component and one end face of the static component are jointed and form a sealing surface, the sealing surface is axially vertical to the main shaft, and the end surface of the rotating assembly is provided with a hydrodynamic groove.

2. The hydrodynamic pressure type rear isolation seal device for dry gas seal of turbomachinery of claim 1, wherein said rotating assembly comprises a rotating ring, a shaft sleeve and a pressing sleeve, said shaft sleeve and pressing sleeve are both ring-shaped and are sleeved outside said main shaft, wherein said shaft sleeve and pressing sleeve are fixed by hexagon socket head cap screw, the tail end of said shaft sleeve is abutted with lock nut, the front end of said pressing sleeve is abutted with the rotating part of dry gas seal assembly, said rotating ring is fixed with said shaft sleeve by driving pin and rotates synchronously.

3. The hydrodynamic pressure type rear isolation seal for dry gas seal of turbomachinery of claim 2 wherein said sleeve comprises a first ring and a second ring coaxially and integrally provided, said second ring having a tail end abutting against said lock nut, said second ring having a tip end integrally connected to said first ring, said movable ring having a tail end fixed to said second ring via said driving pin, and an outer edge abutting against said first ring;

the tail end of the pressing sleeve is provided with a groove at the contact part with the main shaft, the front end of the first ring is inserted into the groove and is abutted against the groove wall, the groove bottom of the groove is fixed with the front end of the first ring through a hexagon socket head cap screw, and the tail end of the pressing sleeve is abutted against the front end of the movable ring.

4. The hydrodynamic rear isolation seal for dry gas seals in turbomachinery of claim 3 wherein a centering corrugated strip is provided between the inner diameter of said rotating ring and the outer edge of said first ring;

an O-shaped ring is arranged between the shaft sleeve and the main shaft.

5. The hydrodynamic pressure type rear-mounted isolation sealing device for dry gas sealing of turbomachinery according to claim 3, wherein a wear-resistant layer is attached to an end surface of a front end of the dynamic ring by means of spraying or build-up welding, and hydrodynamic pressure grooves are provided on the wear-resistant layer, the hydrodynamic pressure grooves include a middle annular groove, an outer dynamic pressure groove, and an inner dynamic pressure groove, the middle annular groove and the dynamic ring are coaxially arranged, the outer dynamic pressure groove and the inner dynamic pressure groove are both communicated with the middle annular groove, an outer dam region without a groove is provided between a root of the outer dynamic pressure groove and an outer edge of the dynamic ring, and an inner dam region without a groove is provided between a root of the inner dynamic pressure groove and an axis of the dynamic ring.

6. The hydrodynamic pressure type rear isolation seal for dry gas seal of turbomachinery according to claim 5, wherein the groove depth of said intermediate ring groove is 10 to 100 μm, and the groove depth of said outer dynamic pressure groove and said inner dynamic pressure groove is 3 to 20 μm;

the groove type of the outer dynamic pressure groove and the inner dynamic pressure groove is a unidirectional rotation groove type or a bidirectional rotation groove type;

the radial width of the outer dam area is 0.15-0.35 of the width of the sealing surface, and the radial width of the inner dam area is 0.1-0.3.

7. The hydrodynamic rear isolation seal for turbomachinery dry gas seal of claim 5 wherein said stationary component comprises a spring seat, a spring, a thrust ring and a stationary ring, said spring seat being fixed to the housing by a socket head cap screw; the end face of the tail end of the static ring is attached to the end face of the front end of the movable ring to form a sealing surface, the front end of the static ring is attached to the tail end of the push ring, the front end of the push ring is attached to the rear end of the spring, the spring seat is provided with a spring hole, and the front end of the spring is attached to the bottom end face of the spring hole.

8. The hydrodynamic pressure type rear isolation seal device for dry gas seal of turbomachinery as claimed in claim 7, wherein said spring seat, said thrust ring and said stationary ring are provided with a through isolation gas passage, and an outlet of the isolation gas passage in the stationary ring is located at a middle annular groove of a front end face of said movable ring.

9. The hydrodynamic rear isolation seal of claim 8 wherein a pin is provided between the spring seat and the thrust ring and prevents rotation between the spring seat and the thrust ring;

a pin is arranged between the push ring and the static ring, and the push ring and the static ring are prevented from rotating through the pin;

o-shaped rings are arranged at the matching positions of the push ring, the static ring and the spring seat;

and an O-shaped ring is arranged on the matching surface of the spring seat and the shell.

10. The hydrodynamic rear isolation seal of claim 7 wherein said spring seat has a flared end;

the oil slinger is arranged on the shell, and the oil slinger is arranged on the lock nut.