CN111765250B

CN111765250B - Supercritical carbon dioxide sealing device and method

Info

Publication number: CN111765250B
Application number: CN202010775165.1A
Authority: CN
Inventors: 洪先志; 唐大全; 包鑫; 周忠学
Original assignee: Chengdu Yitong Seal Co ltd
Current assignee: Chengdu Yitong Seal Co ltd
Priority date: 2019-11-08
Filing date: 2020-08-04
Publication date: 2022-03-18
Anticipated expiration: 2040-08-04
Also published as: CN110725955A; CN114508592A; CN114576362A; CN111765250A

Abstract

The invention relates to a sealing device and a method for supercritical carbon dioxide, the device at least comprises a static ring and a dynamic ring, the static ring (11) is movably arranged in a dynamic cavity which is formed by splicing a static ring seat (5) and a spring seat (8) and limits the moving range of the static ring (11), the static ring (11) is connected with the spring seat (8) through at least one spring (9) so as to transmit the opening force loaded by the spring (9), and the second end of the static ring (11) is provided with a labyrinth seal structure and is in clearance fit with a main shaft (1), so that the pressure difference formed by leaked gas before and after the static ring through the labyrinth seal structure generates a closing force on the static ring (11). According to the invention, the leakage gas flows between the dry gas sealing device and the labyrinth sealing structure, so that pressure difference is formed at two ends of the inner hole of the static ring, when the leakage amount is large enough, the higher the pressure difference at two ends of the inner hole of the static ring is, the static ring is pushed to approach the dynamic ring, and the dynamic ring and the static ring are contacted to realize the sealing of the leakage gas.

Description

Supercritical carbon dioxide sealing device and method

Technical Field

The invention relates to supercritical CO₂The technical field of sealing of cyclic power generation, in particular to a sealing device and a sealing method of supercritical carbon dioxide.

Background

In the prior art, supercritical CO₂The power generation is a novel power generation technology, and carbon dioxide in a supercritical state is used as a working medium to convert heat of a heat source into mechanical energy, wherein the heat source can be from a nuclear reactor, solar energy, geothermal energy, industrial waste heat, fossil fuel combustion and the like. Working medium of supercritical carbon dioxide under current energy and environment protection situationThe excellent characteristics make the system have good application prospect and research value. But the sealing structure adopted at present is dry gas sealing. The purpose of the safety seal is to avoid the condition that a large amount of high-pressure gas enters the bearing box to cause ultrahigh-pressure safety accidents. Supercritical CO₂The cycle power generation is a high-efficiency new energy power generation technology which is being researched and developed in various main countries, and a turbine compressor and an expander of the cycle power generation technology are hearts of the whole cycle power generation system. The turbo compressor and the expander can not stably and safely work and depend on the sealing performance of the shaft end. But major leakage of dry gas seal, especially of CO₂Entering the bearing housing can cause damage to the bearings.

For example, chinese patent document CN108612570A discloses a supercritical carbon dioxide impeller mechanical working medium replacement device and method using dry gas sealing, the device includes an impeller mechanical stator, a main shaft, a dry gas sealing, a stationary blade, a movable blade, a support bearing, an inlet section pipeline, an outlet section pipeline, a suction pipeline, a shut-off valve, a vacuum pump, an accident condition evacuation pipeline, a high-purity carbon dioxide gas source, a dry gas sealing pipeline, a main gas supply pipeline, and a regulating valve, and by controlling the on-off of valves on the pipelines of the device and the on-off of the vacuum pump, the air in the supercritical carbon dioxide impeller mechanical equipment is repeatedly sucked, inflated, and kept standing for circulation, and finally replaced by the high-purity supercritical carbon dioxide working medium. However, in supercritical CO₂When a large amount of leakage occurs, the invention still easily causes the damage of the bearing and increases the production cost of a workshop.

Chinese patent document CN106352094B discloses a static pressure gas labyrinth throttling regulation mechanism for a dynamic and static pressure type, wherein a third radial air inlet hole and an axial throttling hole are both arranged in a sealing static ring, the third radial air inlet hole is communicated with a labyrinth seal and is positioned in a comb tooth area of the labyrinth seal, the axial throttling hole is communicated with a pressure equalizing groove on the sealing end surface, and the other end of the axial throttling hole is tightly sealed by a countersunk head bolt; a second radial air inlet is processed in the labyrinth seal, a static pressure air cavity is formed between the periphery of the labyrinth seal and the inner gland as well as between the periphery of the labyrinth seal and the static ring, and the first radial air inlet and the second radial air inlet are both communicated with the static pressure air cavity; two sealing rings are arranged on the inner periphery of the labyrinth seal, gas entering the labyrinth seal can only flow into a third radial throttling hole, a third sealing ring is arranged between the outer periphery of the third radial throttling hole and the inner gland, and a first sealing ring is arranged between the static ring and the inner gland; and one end of the labyrinth seal, which is close to the outer gland, is provided with a regulating mechanism spring, and the labyrinth seal is enabled to axially slide along the peripheral surface of the static ring according to the pressure in the static pressure gas cavity, so that the static pressure regulation of the gas passing through the third radial gas inlet hole is realized. This patent document is purely driven by static pressure, with the aim of controlling the input pressure of the static pressure dry gas seal, which is basically achieved by the variation of the differential pressure through the variation of the number of different labyrinth teeth in the middle when the holes communicate with one another. The patent changes the tooth number of the labyrinth and adjusts the input pressure through the change of static pressure, thereby stabilizing the opening force of the static pressure type dry gas seal. However, this patent has a drawback in that dynamic pressure difference change cannot be achieved, and thus, a change in safety state after gas leakage or gas discharge cannot be timely coped with, and there is a delay.

Furthermore, on the one hand, due to the differences in understanding to the person skilled in the art; on the other hand, since the inventor has studied a lot of documents and patents when making the present invention, but the space is not limited to the details and contents listed in the above, however, the present invention is by no means free of the features of the prior art, but the present invention has been provided with all the features of the prior art, and the applicant reserves the right to increase the related prior art in the background.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a sealing device for supercritical carbon dioxide, which at least comprises a static ring and a dynamic ring and is characterized in that the static ring is movably arranged in a dynamic cavity which is formed by splicing a static ring seat and a spring seat and limits the moving range of the static ring, the static ring is connected with the spring seat through at least one spring so as to transmit the opening force loaded by the spring, and the second end of the static ring is provided with a labyrinth seal structure and is in clearance fit with a main shaft, so that the static ring is subjected to closing force by the pressure difference formed by leaked gas before and after the static ring through the labyrinth seal structure. The sealing device can be automatically adjusted, and can effectively prevent leaked CO when a system generates large leakage₂Mass entering bearingAnd a case protecting the bearing case to prevent the damage range from being enlarged.

Preferably, the first end of the stationary ring is provided with an abutting protrusion capable of abutting against the stationary ring seat and/or the spring seat, and the abutting protrusion is connected with the spring seat through at least one spring.

Preferably, the second end of the stationary ring seat is provided with the at least one first protrusion adapted to the abutting protrusion, the first protrusion is in sealing contact with the first end face of the stationary ring, and the first protrusion limits the dynamic moving range of the abutting protrusion in the dynamic cavity. Through the first protruding structure of quiet ring seat, can restrict the displacement range of quiet ring and form the passageway that allows the gas contact quiet ring of leaking, be favorable to gas pressure to realize the oppression to quiet ring.

Preferably, the contact surface of the stationary ring seat, which is in contact with the spring seat, is provided with at least one second protrusion, and the second protrusion is in contact with and embedded in a partial groove bottom of at least one groove of the spring seat, so that the rest part of the groove bottom of the groove is spliced with the contact surface of the stationary ring seat, which is close to the second end, to form the dynamic cavity. The static ring seat and the spring seat are embedded into a whole, and a space for the static ring to move is formed.

Preferably, the bottom depth of the groove is distributed in a stepped manner, the groove bottom of the groove at least comprises a first step and a second step, and the depth of the first step is smaller than that of the second step. The stepped structure is beneficial to the arrangement of the second bulges and the spring in different areas, and the operation is easier during the embedding.

Preferably, the groove bottom of the second step of the groove is provided with at least one spring connected with the abutting protrusion, so that the static ring moves and/or automatically resets relative to the spring seat in the dynamic cavity. When the pressure of CO2 on the leakage side disappears, the static ring moves to the side far away from the dynamic ring through the automatic resetting mechanism until the static ring returns to the original position, and the damage of a mechanical sealing structure caused by the contact of the static ring and the dynamic ring when the dynamic ring rotates is avoided.

Preferably, the sealing device is arranged in a sealing cavity which is arranged in the sealing cavity and takes the main shaft as the center, and the sealing device and at least one dry gas sealing device are arranged at intervals, so that the sealing cavity is divided into at least two cavities by the sealing device and the at least one dry gas sealing device, and one cavity is communicated with the exhaust port. So set up, be favorable to leaking gaseous safety to be got rid of, more be favorable to quiet ring to bear the influence of gas pressure through contacting leakage gas.

The invention also provides a sealing method of supercritical carbon dioxide, which is characterized by comprising the following steps: the static ring is connected with the spring seat through at least one spring so as to transmit the spring-loaded opening force, a labyrinth seal structure in clearance fit with the main shaft is arranged at the second end of the static ring, so that the pressure difference formed by leaked gas in the front and the back of the static ring through the labyrinth seal structure generates closing force on the static ring, the static ring moves to the moving ring until the static ring is in a sealing state in contact with the moving ring under the condition that the flow of the leaked gas is increased to the closing force larger than the opening force of the spring on the basis of the closing force, and the static ring moves to the return position on the basis of the opening force when the flow of the leaked gas is reduced to the condition that the closing force is smaller than the opening force of the spring.

Preferably, the method comprises: the static ring is movably arranged in a dynamic cavity which is formed by splicing a static ring seat and a spring seat and limits the moving range of the static ring in a sealing mode.

Preferably, the second end of quiet ring seat be provided with the protruding looks adaptation of butt at least one first arch, the first end of quiet ring be provided with can with quiet ring seat and/or spring holder butt protruding, first arch with the first terminal surface sealing contact of quiet ring, and first arch has been constituteed the protruding dynamic chamber at dynamic intracavity dynamic moving range of restriction butt with the recess that the bottom degree of depth of spring holder is cascaded distribution.

Preferably, the method further comprises: the second bulge of the static ring seat is embedded with the groove part of the first step in the groove, and the side surface of the second bulge and the step side wall of the second step are on the same axis to form a flat cavity wall, so that the spring can stretch along the axis, the static ring can move axially, and the static ring displacement caused by the inclination of the elastic direction is avoided.

Preferably, the method further comprises: at least one spring connected with the abutting protrusion is arranged on the groove bottom of the second step of the groove, so that the static ring moves and/or automatically resets relative to the spring seat in the dynamic cavity. When the pressure of CO2 on the leakage side disappears, the static ring moves to the side far away from the dynamic ring through the automatic resetting mechanism until the static ring returns to the original position, and the damage of a mechanical sealing structure caused by the contact of the static ring and the dynamic ring when the dynamic ring rotates is avoided.

Preferably, the method further comprises: the sealing device and at least one dry gas sealing device divide the sealing cavity into three chambers, wherein the chamber B is positioned between the sealing device and the dry gas sealing device, and the chamber C is adjacent to the bearing box. The chamber C is beneficial to diluting trace leakage gas and avoids entering a bearing box to damage a bearing.

Preferably, the end face of the static ring in sealing contact with the dynamic ring is provided with at least one sealing boss, and when the static ring moves to contact with the dynamic ring, the sealing boss is in sealing contact with the dynamic ring based on the pressure of the static ring. The sealing contact between the static ring and the dynamic ring is facilitated.

Preferably, a first sealing ring is arranged on the contact surface of the first bulge of the static ring seat and the static ring; a second sealing ring is arranged at the joint of the first end of the static ring seat and the inner wall of the sealing cavity; and the movable ring is hermetically connected with the main shaft through a third sealing ring.

The invention has the beneficial technical effects that: the sealing rings seal the plurality of gas channels, so that gas is promoted to be applied to the static ring only through the gas channels between the static ring seat and the main shaft.

The sealing device for supercritical carbon dioxide mainly comprises a moving ring and a static ring, wherein a labyrinth seal is arranged between the static ring and a main shaft. When the leakage is large, the leakage gas is throttled through the labyrinth seal, the leakage gas is accumulated between the dry gas seal and the labyrinth seal to form high pressure, so that the static ring is pushed to be close to the dynamic ring, and finally the dynamic ring and the static ring are contacted to realize the leakage gasAnd (4) sealing the body. The sealing device can be automatically adjusted, and can effectively prevent leaked CO when a dry gas sealing system generates large leakage₂A large amount of the oil enters the bearing box to protect the bearing box, thereby avoiding the expansion of the damage range. The sealing device of the supercritical carbon dioxide is also provided with an automatic resetting mechanism, and when the CO on the leakage side is leaked₂The pressure disappears, the static ring moves to one side far away from the dynamic ring through the automatic resetting mechanism until the static ring returns to the original position, and the damage of a mechanical sealing structure caused by the contact of the static ring and the dynamic ring when the dynamic ring rotates is avoided.

Drawings

FIG. 1 is a schematic cross-sectional view of the present invention in a sealed state;

FIG. 2 is a schematic cross-sectional view of the sealing condition at failure of the present invention;

FIG. 3 is a cross-sectional view of a spring seat in an embodiment of the present invention;

fig. 4 is a schematic sectional view of a stationary ring according to an embodiment of the present invention.

List of reference numerals

1: a main shaft; 2: a dry gas seal device; 3: sealing the cavity; 4: sealing the cavity; 5: a stationary ring seat; 6: a first sealing ring; 7: a second sealing ring; 8: a spring seat; 81: a first step; 82: a second step; 9: a spring; 10: a bearing housing; 11: a stationary ring; 12: a moving ring; 13: a fixing member; 14: a third sealing ring; 15: a bearing; 16: a discharge port; 17: an inner bore labyrinth passage; 111: an abutment projection; 112: and sealing the boss.

Detailed Description

The following detailed description is made with reference to the accompanying drawings.

The invention provides a sealing device for supercritical carbon dioxide, in particular to a sealing device for supercritical carbon dioxide for protecting a bearing box. The invention may also be a sealing system with a sealing means for supercritical carbon dioxide.

As shown in the solid line portion of the cross-sectional views of fig. 1 and 2, the sealing device of supercritical carbon dioxide of the present invention is disposed in the sealed chamber 4 of the dry gas sealing device. One side of the bearing box 10 is connected with a sealed cavity 4. Sealed cavityThe sealing cavity 3 of the body 4 is internally provided with a dry gas sealing device 2. The main shaft 1 penetrates the bearing housing 10 and the seal chamber 3. The dry gas sealing device 2 is sleeved on the outer side of the main shaft 1. A sealing means for supercritical carbon dioxide is arranged between the dry gas sealing means 2 and the bearing housing 10 for the leakage of CO₂Sealing to avoid CO₂Entering the bearing housing causes damage to the bearing. As shown in fig. 1 and 2, the dry gas seal 2 and the seal divide the seal chamber 3 into an a chamber, a B chamber, and a C chamber. The chamber a is located outside the dry gas seal 2. The B chamber is located between the dry gas seal 2 and the seal. The B chamber communicates with the discharge port 16. With the vent open, CO leakage is facilitated₂And (5) discharging gas. The chamber C is a chamber between the sealing device and the wall of the bearing box, and is favorable for buffering leaked gas. When the dry gas sealing device 2 works normally, the chamber A and the dry gas sealing device 2 bear all pressure of the process medium, the end face of the sealing device is in an open state, and the pressure of the chamber B and the pressure of the chamber C are close to each other. When dry gas sealing device 2 leaks partial CO₂When the gas is generated, the sealing device performs gas sealing, so that the cavity B and the cavity C form a gas pressure difference, the gas is prevented from entering the bearing box, and the bearing in the bearing box is protected.

The sealing device for supercritical carbon dioxide at least comprises a spring seat 8, a static ring 11 and a dynamic ring 12. The static ring 11 and the dynamic ring 12 are sleeved on the main shaft 1. The stationary ring 11 is arranged close to the leakage side of the dry gas seal 2. Preferably, the stationary ring 11 is mounted in the seal chamber 3 by means of a stationary ring seat 5. The static ring 11 is connected with the inner wall of the sealing cavity 3 in a sealing way. Wherein, the stationary ring seat 5 is a hollow structure sleeved on the outer side of the main shaft 1. The rotating ring 12 is disposed adjacent to the bearing housing 10. The rotating ring 12 is connected with the main shaft 1 in a sealing way. Preferably, a mechanical seal is arranged between the static ring 11 and the dynamic ring 12. Preferably, the rotating ring 12 is fixed on the main shaft 1 by a fixing member 13. The fixing member 13 is an anti-rotation pin.

As shown in the sectional views of fig. 1 to 2, the first end of the stationary ring seat 5 is in contact with the wall of the seal chamber 3 away from the main shaft. The contact surface of the second end of the static ring seat 5 and the static ring 11 is provided with at least one first bulge matched with the shape of the static ring 11. The cross section of the first bulge is rectangular. The side surface of the stationary ring seat 5 contacting with the spring seat is provided with at least one second protrusion for relatively engaging and relatively fixing with the spring seat 8.

As shown in fig. 3, the spring seat 8 is sleeved on the outer side of the main shaft 1 and is fixedly connected to the inner wall of the sealing cavity 3. The side of the spring seat 8 that is in contact with the stationary ring seat 5 is provided with at least one groove 83. Preferably, the groove bottoms of the grooves 83 are distributed in a stepped structure. Wherein, the first step 81 of the groove bottom in the groove 83 of the spring seat 8 is matched with the projection depth and projection width of the second projection of the stationary ring seat 5. Namely, after the spring seat 8 is spliced with the stationary ring seat 5, the side surface of the second protrusion is flush with the side wall of the second step 82 and forms a flat cavity wall. For example, the sides of the second protrusion are co-axial with the step sidewalls of the second step 82 to form a flat chamber wall. The axis is a line outside the spindle and parallel to the central axis of the spindle 1.

The second step 82 of the groove bottom in the recess of the spring seat 8 serves for the arrangement of at least one spring 9. The number of the springs 9 may be one or more than one. The depth value of the first step 81 may also be not smaller than the depth value of the second step 82. For example, the depth value of the first step 81 is equal to the depth value of the second step 82. The depth value of the first step 81 is larger than the depth value of the second step 82.

Preferably, the depth value of the first step 81 is smaller than the depth value of the second step 82. The length of the groove wall at the second end of the spring seat 8 is equal to the difference in depth between the first step 81 and the second step 82. For example, the depth value of the first step 81 is X₁The depth value of the second step 82 is X₂。X₁Less than X₂. The length of the groove wall of the second end of the spring seat 8 is X₃＝X₂—X₁. The advantage that so set up lies in, can be so that 8 and static ring seats 5 avoid the spring holder to shift through the concatenation reciprocal anchorage at the spring holder.

After spring holder 8 splices with quiet ring seat 5 relatively, the protruding embedding first recess 81 of second of quiet ring seat 5 for spring holder 8 and quiet ring seat 5 between form the developments chamber that holds quiet ring 11 and quiet ring shift space jointly, be favorable to quiet ring 11 to carry out appropriate removal under the effect of pressure.

When the second end of the stationary ring seat 5 is in contact with the main shaft 1, the first protrusion forms a passage between the second end of the stationary ring seat 5 and the main shaft 1, which allows a small amount of leaked gas to pass through. And a hole labyrinth passage 17 allowing leaked gas to enter and flow through the static ring 11 exists between the static ring seat 5 and the main shaft 1, so that the pressure difference is formed on two sides of the static ring 11.

As shown in fig. 4, the second end of the stationary ring 11 is provided with a labyrinth structure and is in clearance fit with the main shaft 1. The labyrinth seal structure can promote the accumulation of gas between the dry gas seal device and the labyrinth seal structure, resulting in higher pressure. The labyrinth seal structure of the static ring 11 adopts a helical tooth structure, the parameters of the helical tooth structure determine the front-back pressure difference which can be established under the given flow, and the diameter of the seal end surface of the static ring 11 and the matching diameter of the static ring seal ring 6 need to be determined according to the comprehensive design of the estimated leakage amount and the spring force.

An abutting projection 111 abutting against the spring 9 is provided on the outer side of the stationary ring 11. The first side step height of the abutment projection 111 is the same as the side height of the second projection of the stationary ring seat 5 in contact. So set up, be favorable to quiet ring 11 and quiet ring seat 5 no pressure butt. The stationary ring 11 of the present invention does not bear the pressure of the stationary ring seat 5 and the spring seat 8, and does not indicate that a gap exists between the abutment projection 111 of the stationary ring 11 and the stationary ring seat 5 and the spring seat 8. In fact, during the movement, the abutment projection 111 of the stationary ring 11 is in contact with the stationary ring seat 5 and the spring seat 8 in a sealed and movable manner, so as to avoid the stationary ring 11 causing the leakage gas to flow from the B chamber to the C chamber during the movement.

The second side step height of the abutment projection 111 is not less than the sum of the width of the second step 82 of the spring seat 8 and the groove wall thickness of the second end of the spring seat 8. The radial height of the stationary ring 11 is not less than the distance between the second end of the spring seat and the main shaft, which is beneficial to limiting the abutting protrusion 111 of the stationary ring 11 when the spring fails. The arrangement is also beneficial to ensuring that the abutting protrusion 111 of the static ring 11 moves in an allowable space without being influenced by the spring seat, and reducing the friction force between the static ring and the spring seat.

Preferably, the end surface of the stationary ring 11 in sealing contact with the moving ring 12 is provided with at least one sealing boss 112. The cross section of the sealing boss 112 is rectangular. When the stationary ring 11 moves towards and contacts the moving ring 12, the sealing boss 112 contacts the moving ring 12 first and bears the pressure between the stationary ring 11 and the moving ring 12, so that the mechanical seal between the stationary ring 11 and the moving ring 12 is realized.

Preferably, the plurality of springs 9 and the spring seat 8 constitute an automatic return mechanism of the stationary ring 11. The plurality of springs 9 are all installed on the spring seat 8, and the installation positions of the plurality of springs 9 correspond to the static ring 11. As shown in fig. 1, in the case where there is no leakage gas or a small amount of leakage gas in the B chamber, the stationary ring 11 is in contact with and sealed against the stationary ring seat 5 based on the elastic force of the spring, thereby preventing less leakage gas from flowing to the bearing housing. As shown in fig. 2, when there is a large amount of leakage gas in the B chamber and the pressure of the gas against the stationary ring 11 is larger than the elastic force of the spring 9, the stationary ring 11 moves toward the movable ring 12 under the pressure of the gas until it comes into contact with the movable ring 12. The spring 9 is now in the process of being gradually compressed. And a sealing structure is formed between the static ring 11 and the dynamic ring 12. At this time, the air pressure in the cavity B is buffered, and the static ring 11 and the dynamic ring 12 are sealed to avoid air leakage to the bearing box. Preferably, even though the stationary ring 11 and the moving ring 12 cannot form an absolute seal, that is, the gas leakage amount cannot be made absolutely zero. The C chamber is favorable for diluting trace leakage gas, so that the diluted gas concentration is safe concentration, and the bearing in the bearing box cannot be damaged. Therefore, the arrangement of the C-chamber is also beneficial for the protection of the bearing. When the CO on the leakage side₂The elastic force of the spring 9 is larger than the gas pressure of the chamber B, and the static ring 11 moves to the side far away from the dynamic ring 12 by the elastic force until the static ring returns to the original position, namely, returns to the working state of fig. 1.

In the invention, the flow of the leakage gas is increased, so that a pressure difference is formed before and after the static ring. In the case where the closing force by the pressure difference is larger than the opening force of the spring 9, the end surface of the abutment projection 111 seals against the stationary ring 5. At this time, the stationary ring 11 moves toward the movable ring 12 due to the closing force, and the stationary ring 11 comes into contact with the movable ring 12 to form a sealed state. The flow rate of the leaking gas is reduced so that the closing force generated by the pressure difference formed before and after the stationary ring is gradually reduced. Under the condition that the closing force generated by the pressure difference is smaller than the opening force of the spring 9, the end surface of the abutting protrusion 111 and the static ring seat 5 are in a relatively sealed state, and the static ring 11 moves to the return position to the static ring seat 5 based on the opening force. Compared with the prior art that the static ring is pushed by static pressure to form a dry gas sealing state, the static ring and the movable ring are pushed to be closed by utilizing the pressure difference formed by leaked gas, the quick response to the amount of the leaked gas is timely realized, and the delay phenomenon is avoided, which cannot be achieved by the prior art. The end face is closed through the pressure difference generated by the leakage flow, and the purpose of complete leakage prevention can be achieved; the sealing rate is 100%.

Preferably, the inner side of the static ring seat 5 is connected with the static ring 11 in a reciprocating rubber sealing mode. And a first sealing ring 6 is arranged on the contact surface of the first bulge of the static ring seat 5 and the static ring 11. A first sealing ring mounting groove is formed in the position, where the first sealing ring 6 is mounted, of the first protrusion of the static ring seat 5. And the first sealing ring 6 is arranged in the first sealing ring mounting groove. The first sealing ring 6 can seal a gap between the static ring seat 5 and the static ring 11, leakage of leakage gas to the direction of the bearing box is avoided, and meanwhile, the leakage gas can only enter the labyrinth sealing structure for sealing.

Preferably, the first end of the stationary ring seat 5 is provided with a second sealing ring 7 at the joint with the inner wall of the sealing cavity 3. And the first sealing ring 6 and the second sealing ring 7 are O-shaped rings. And a second sealing ring mounting groove is formed in the first end of the second static ring seat 5 at the position where the second sealing ring 7 is mounted. The second sealing ring 7 is arranged in the second sealing ring mounting groove and can avoid supercritical CO₂Is leaked. The second sealing ring 7 can seal a gap between the static ring seat 5 and the wall of the sealing cavity 3, and leakage of leaked gas to the direction of the bearing box is avoided.

Preferably, the rotating ring 12 is hermetically connected with the main shaft 1 through a third sealing ring 14. And a third sealing ring mounting groove is formed in the outer side of the main shaft 1 at the position where the third sealing ring 14 is mounted. And a third sealing ring 14 is arranged in the third sealing ring mounting groove. And the third sealing ring 14 is an O-shaped ring. The third seal ring 14 can seal the gap between the moving ring 12 and the main shaft 1, and prevent the leakage gas passing through the labyrinth seal of the stationary ring 1 from continuously leaking towards the bearing box.

The invention arranges three positions of a first sealing ring 6, a second sealing ring 7 and a third sealing ring 14 which are sequentially and progressively distant from the bearing boxSealing ring capable of effectively preventing CO₂Leakage is carried out between the main shaft 1 and the movable ring 12, so that leakage gas reaching the C chamber is very little and ignored, and the safety of the bearing box is protected.

Preferably, the clearance of the labyrinth seal of the stationary ring 11 is matched to the expected leakage Q. According to a theoretical calculation formula (Martin formula or Eggery formula) of the leakage amount of the labyrinth seal, the leakage amount is in direct proportion to the square of the clearance and in direct proportion to the shaft diameter and the pressure. With respect to both tooth type and tooth number. By adjusting the clearance, the shaft diameter and the pressure accordingly, the desired leakage Q can be obtained.

As shown in fig. 4, the fitting radius of the stationary ring 11 in sealing contact with the stationary ring seat 5 is Rb. The outer radius of the end face of the sealing boss 112 in sealing contact with the rotating ring 12 is Ro, and the inner radius is Ri. The friction force after the sealing end face is closed is related to the positive pressure of the sealing end face. The key point for reducing the friction force after the sealing end face is closed is to reduce the positive pressure of the sealing end face.

Positive end pressure Pc ═ K- λ Δ P

K＝(Rb²-Ri²)/(Ro²-Ri²)

Δ P is determined by the amount of leakage of the labyrinth seal. The leakage of the labyrinth seal is equal to the leakage Q of the dry gas seal. λ is constant, different media, and the value is different.

In the invention, the value range of K is 0.7-0.75, and the minimum end face positive pressure Pc is obtained on the premise of ensuring sealing, so that the friction force after the sealing end face is closed is reduced.

On the other hand, to reduce frictional heating, the radial width (Ro-Ri) of the seal face boss 112 is as narrow as possible. Preferably, the radial width (Ro-Ri) ranges from 2 mm to 3.5mm, and the friction force of the end face of the stationary ring 11 can be obviously reduced.

The invention enables the static ring 11 in a contact high-pressure running state to reduce abrasion and heat generation at high speed after the sealing end face is closed. The invention enables the load coefficient of the static ring 11 to be close to CO through the arrangement of the radiuses Rb, Ro and Ri of a plurality of end surfaces of the sealing device of the supercritical carbon dioxide₂Gas back pressure coefficient. Thus, the present inventionThe positive pressure on the end face with increased pressure is kept basically unchanged by the clear stationary ring 11, so that the increase of the friction force is not obvious.

The working process of the invention is as follows:

when supercritical CO₂When the dry gas seal generates large leakage, the flow value of the dry gas seal system is increased, and at the moment, an early warning module used for monitoring the leakage state of the system in the dry gas seal system generates an alarm. When the critical condition of chain shutdown is reached, the control module controls the unit to stop running based on the early warning information, and the main shaft 1 and the movable ring 12 also stop rotating. Due to large amount of leaked CO₂A high pneumatic pressure Fq is formed between the dry gas seal and the stationary ring 11. The high pneumatic pressure Fq pushes the stationary ring 11 closer to the moving ring 12. The static ring 11 compresses the spring 9 to generate elastic force Fs until the dynamic ring 12 contacts with the static ring 11, and sealing of leaked gas is completed. When the pressure of the dry gas sealing system is recovered to be normal, the air pressure Fq in the sealing cavity 3 is reduced, when the pressure of the sealing cavity 3 is reduced to be lower than the elastic force Fs of the spring 9, the static ring 11 is separated from the movable ring 12 based on the elastic force action of the spring 9 and returns to the original position where the static ring 12 is located under normal pressure, and the damage to mechanical sealing caused by high-speed rotation under the condition that the static ring 11 is in contact with the movable ring 12 when the dry gas sealing system works normally is avoided.

It should be noted that the above-mentioned embodiments are exemplary, and that those skilled in the art, having benefit of the present disclosure, may devise various arrangements that are within the scope of the present disclosure and that fall within the scope of the invention. It should be understood by those skilled in the art that the present specification and figures are illustrative only and are not limiting upon the claims. The scope of the invention is defined by the claims and their equivalents.

Claims

1. A sealing device for supercritical carbon dioxide at least comprises a static ring (11) and a dynamic ring (12), and is characterized in that the static ring (11) is movably and hermetically arranged in a dynamic cavity which is formed by splicing a static ring seat (5) and a spring seat (8) and limits the moving range of the static ring (11),

the stationary ring (11) is connected to the spring seat (8) via at least one spring (9) in order to transmit the opening force loaded by the spring (9),

the second end of the static ring (11) is provided with a labyrinth seal structure and is in clearance fit with the main shaft (1), so that the static ring (11) is closed by pressure difference formed by leaked gas in front of and behind the static ring through the labyrinth seal structure.

2. The sealing device for supercritical carbon dioxide according to claim 1,

the first end of stationary ring (11) is provided with the butt arch (111) that can with stationary ring seat (5) and/or spring holder (8) butt, butt arch (111) through at least one spring (9) with spring holder (8) are connected.

3. The sealing device for supercritical carbon dioxide according to claim 2,

the second end of the static ring seat (5) is provided with at least one first bulge matched with the abutting bulge (111),

the first projection is in sealing contact with a first end face of the stationary ring (11) and limits the dynamic range of movement of the abutment projection (111) within a dynamic cavity.

4. The supercritical carbon dioxide seal according to claim 3,

the contact surface of the static ring seat (5) which is in contact with the spring seat (8) is provided with at least one second bulge,

the second protrusion is contacted and embedded with part of the groove bottom of at least one groove (83) of the spring seat (8), so that the rest part of the groove bottom of the groove (83) is spliced with the contact surface of the static ring seat (5) adjacent to the second end to form the dynamic cavity.

5. The sealing device for supercritical carbon dioxide according to claim 4, characterized in that the depth of the bottom of the groove (83) is distributed in a step-like manner,

the groove bottom of the groove (83) comprises at least a first step (81) and a second step (82), wherein,

the depth of the first step (81) is smaller than the depth of the second step (82).

6. The supercritical carbon dioxide seal according to claim 5,

at least one spring (9) connected with the abutting bulge (111) is arranged at the bottom of the second step (82) of the groove (83),

so that the static ring (11) moves and/or automatically resets in the dynamic chamber relative to the spring seat (8).

7. A method of sealing supercritical carbon dioxide, the method comprising:

the stationary ring (11) is connected to the spring seat (8) via at least one spring (9) for transmitting an opening force loaded by the spring (9),

the second end of the static ring (11) is provided with a labyrinth seal structure which is in clearance fit with the main shaft (1), so that the pressure difference formed by the leaked gas before and after the static ring through the labyrinth seal structure generates closing force on the static ring (11),

under the condition that the flow rate of the leaked gas is increased to a closing force larger than the opening force of the spring (9), the static ring (11) moves towards the dynamic ring (12) based on the closing force until the static ring (11) is contacted with the dynamic ring (12) to form a sealing state,

in the case where the flow rate of the leaking gas is reduced to a closing force smaller than the opening force of the spring (9), the stationary ring (11) is moved to the stationary ring seat (5) to the return position based on the opening force.

8. The method of sealing supercritical carbon dioxide as claimed in claim 7, wherein the method comprises: the static ring (11) is movably arranged in a dynamic cavity which is formed by splicing the static ring seat (5) and the spring seat (8) and limits the moving range of the static ring (11) in a sealing mode.

9. The method for sealing supercritical carbon dioxide according to claim 7, characterized in that the second end of the stationary ring seat (5) is provided with at least one first protrusion adapted to an abutment protrusion (111),

the first end of the static ring (11) is provided with an abutting bulge (111) which can abut against the static ring seat (5) and/or the spring seat (8),

the first bulge is in sealing contact with the first end face of the static ring (11), and the first bulge and a groove (83) formed in the bottom of the spring seat (8) in a stepped distribution form a dynamic cavity for limiting the dynamic moving range of the abutting bulge (111) in the dynamic cavity.