Tandem type dry gas sealing device and method suitable for supercritical carbon dioxide centrifugal pump

Abstract

The invention discloses a tandem type dry gas sealing device and method suitable for a supercritical carbon dioxide centrifugal pump. The tandem type dry gas sealing device comprises a rotor, an inner shaft sleeve, a first-stage moving ring, a second-stage moving ring, a first-stage static ring assembly, a second-stage static ring assembly and an atmosphere side comb tooth sealing assembly. The outer surface wall of the rotor is sleeved with the inner shaft sleeve and the atmosphere side comb tooth sealing assembly, the outer surface wall of the inner shaft sleeve is sleeved with the first-stage moving ring and the second-stage moving ring, the first-stage static ring assembly and the first-stage moving ring are oppositely arranged on the rotor, and the second-stage static ring assembly and the second-stage moving ring are oppositely arranged on the rotor. And dynamic pressure grooves are formed in the first-stage moving ring and the second-stage moving ring. The rotor rotates to drive the movable ring to rotate, a sealing medium flows into the movable pressure groove of the movable ring, a high-pressure area is formed to extrude the static ring to form a sealing gas film, and the effect of sealing a medium side working medium is achieved. The tandem type two-stage dry gas seal is adopted, the sealing requirement is met, meanwhile, the outer side linear speed is controlled by reducing the shaft diameter of each stage of dry gas seal, and then the adverse effect caused by the too large linear speed is reduced.

Description

Technical Field

[0001] The present invention relates to a shaft end sealing device in the fluid machinery industry, and in particular to a series dry gas sealing device and method suitable for a supercritical carbon dioxide centrifugal pump, belonging to the technical field of shaft end dry gas sealing of rotating machinery. Background Art

[0002] As the new power system puts forward the requirements of clean, low-carbon, flexible and efficient, the supercritical carbon dioxide circulation system has been favored by more and more scholars for its advantages such as high efficiency and flexibility. As an important component of it, the supercritical carbon dioxide centrifugal pump can compress the carbon dioxide working fluid and increase its outlet pressure for use. Since the supercritical carbon dioxide has a high pressure during operation, the leakage will increase when the traditional sealing device is used, which will affect the circulation efficiency and have an adverse effect on the system economy, and cannot meet the use requirements.

[0003] As a non-contact shaft end seal, dry gas seal has the advantages of less leakage, no need for additional sealing oil system, and strong pressure resistance compared to mechanical seal, making it the most suitable sealing device for supercritical carbon dioxide centrifugal pump. During the operation of dry gas seal, the sealing medium flows into the dynamic pressure groove, is squeezed and the pressure increases, and the static ring is squeezed to form a sealing gas film. Due to the effect of the sealing gas film, during the operation, the working fluid on the medium side is sealed to prevent leakage. At the same time, the sealing gas film isolates the friction between the dynamic ring and the static ring, reducing the energy loss caused by the friction of the sealing ring.

[0004] However, in the prior art, the dry gas seal is affected by the temperature of the sealing ring. The high-temperature medium coming from the medium side will heat the dry gas seal. When the temperature is too high, it will affect the performance of the O-ring, causing increased leakage in the sealing device. At the same time, it is affected by the outer linear speed of the first-stage dynamic ring and the first-stage static ring. When only a first-stage sealing device is used, the leakage is large and cannot meet the existing needs. It is required to propose a new dry gas sealing device to reduce the leakage rate. Summary of the invention

[0005] The purpose of the present invention is to provide a series dry gas sealing device and method suitable for a supercritical carbon dioxide centrifugal pump, aiming to solve the problem that the dry gas seal in the prior art is affected by temperature and linear velocity. When the high-temperature supercritical carbon dioxide medium flows out from the impeller leakage point, the medium is cooled to a certain extent, and two-stage sealing is used in series to ensure the sealing effect, reduce leakage, and thus improve the system circulation efficiency and economy.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A tandem dry gas sealing device suitable for a supercritical carbon dioxide centrifugal pump, comprising a rotor, an inner sleeve, a first-stage dynamic ring, a first-stage static ring assembly, a second-stage dynamic ring seat, a second-stage dynamic ring, a second-stage static ring assembly, a static ring support frame and an atmosphere-side comb seal assembly;

[0008] The inner sleeve and the atmosphere side comb seal assembly are sleeved on the outer wall of the rotor, the first stage dynamic ring is sleeved on the outer wall of the inner sleeve, the first stage static ring assembly is arranged on the rotor relative to the first stage dynamic ring through the second stage dynamic ring seat, the second stage dynamic ring is sleeved on the outer wall of the inner sleeve, and the second stage static ring assembly is arranged on the rotor relative to the second stage dynamic ring through the static ring support frame.

[0009] Dynamic pressure grooves are provided on the first-stage dynamic ring and the second-stage dynamic ring.

[0010] Furthermore, it also includes a rubber ring and a sleeve clamping piece. The rubber ring is sleeved on the outer wall of the rotor and arranged outside the comb seal assembly on the atmosphere side. The sleeve clamping piece is sleeved on the outer wall of the rotor and arranged outside the rubber ring.

[0011] Furthermore, the first-stage stationary ring assembly includes a first-stage stationary ring, a first-stage stationary ring push ring, a first-stage support ring, a first-stage stationary ring O-ring and a first-stage stationary ring seat. The central axes of the first-stage stationary ring, the first-stage stationary ring push ring, the first-stage stationary ring O-ring and the first-stage stationary ring seat coincide with each other. The first-stage stationary ring and the first-stage stationary ring push ring are in contact with each other. A first-stage support ring is arranged between the first-stage stationary ring push ring and the first-stage stationary ring seat. A first-stage stationary ring O-ring is arranged between the first-stage stationary ring push ring and the first-stage stationary ring. A first-stage stationary ring seat O-ring is arranged on the outer wall of the first-stage stationary ring seat. The first-stage stationary ring is arranged on the second-stage dynamic ring seat.

[0012] Furthermore, a plurality of arrangement holes for arranging the first-stage support ring are evenly arranged along the circumferential direction on the first-stage stationary ring seat.

[0013] Furthermore, the second-stage stationary ring assembly includes a second-stage stationary ring, a second-stage stationary ring push ring, a second-stage support ring, a second-stage stationary ring O-ring and a second-stage stationary ring seat. The central axes of the second-stage stationary ring, the second-stage stationary ring push ring, the second-stage stationary ring O-ring and the second-stage stationary ring seat coincide with each other. The second-stage stationary ring and the second-stage stationary ring push ring are in contact with each other. A second-stage support ring is arranged between the second-stage stationary ring push ring and the second-stage stationary ring seat. A second-stage stationary ring O-ring is arranged between the second-stage stationary ring push ring and the second-stage stationary ring. A second-stage stationary ring seat O-ring is arranged on the outer wall of the second-stage stationary ring seat. The second-stage stationary ring is arranged on the stationary ring support frame.

[0014] Furthermore, a plurality of arrangement holes for arranging the second-stage support ring are evenly arranged along the circumferential direction on the second-stage stationary ring seat.

[0015] Furthermore, the atmospheric side comb teeth seal assembly includes an atmospheric side comb teeth seal sleeve, an atmospheric side comb teeth seal seat and an atmospheric side comb teeth seal, and the atmospheric side comb teeth seal sleeve, the atmospheric side comb teeth seal seat and the atmospheric side comb teeth seal center axis coincide, and the atmospheric side comb teeth seal sleeve, the atmospheric side comb teeth seal and the atmospheric side comb teeth seal seat are sequentially sleeved on the outer wall of the rotor.

[0016] Furthermore, it also includes a first-stage sealing gas channel, a second-stage sealing gas channel, an exhaust gas channel and a comb-teeth sealing gas channel arranged on the volute of the centrifugal pump. After the carbon dioxide working medium is drawn out from the outlet of the centrifugal pump and filtered, it is divided into three streams and sent to the first-stage sealing gas channel, the second-stage sealing gas channel and the comb-teeth sealing gas channel respectively. After the working medium leaked from the first-stage dry gas seal and the second-stage dry gas seal is mixed with the gas discharged from the comb-teeth seal on the atmosphere side, it enters the exhaust gas channel and is discharged;

[0017] A sealing device is provided at the shaft end of the impeller, and the rotor is connected to the pump body through a bearing.

[0018] Furthermore, a rubber ring and a sleeve clamp are arranged on the outside of the atmosphere-side comb seal assembly, the radial dimension of the sleeve clamp matches the volute, and the sleeve clamp is bolted to the outside of the volute through the sleeve clamp;

[0019] The medium-side comb seal is arranged between the medium and the inner sleeve;

[0020] The rotation direction of the rotor is consistent with the arrangement direction of the dynamic pressure groove. When the rotor rotates counterclockwise, a dynamic ring with a counterclockwise deviation of the dynamic pressure groove is used. When the rotor rotates, supercritical carbon dioxide working fluid flows into the dynamic pressure groove and is then squeezed to form an air film, thereby achieving a sealing effect.

[0021] A sealing method comprises the following steps:

[0022] During the startup process, supercritical carbon dioxide medium is first introduced into the first-stage sealing gas channel, the second-stage sealing gas channel and the comb-tooth sealing gas channel. The supercritical carbon dioxide medium flows into the root of the dynamic pressure groove and is squeezed to form a high-pressure area. When the pressure is large enough, a sealing gas film is formed between the first-stage dynamic ring and the first-stage static ring, thereby achieving a sealing effect and keeping the first-stage dynamic ring and the first-stage static ring from contacting each other. Since the impeller and rotor of the centrifugal pump are in the high-pressure area, part of the working fluid will leak to the shaft end. The leaked working fluid will be initially filtered by the comb-tooth seal on the medium side and merge with the supercritical carbon dioxide entering the first-stage sealing gas channel, and flow into the first-stage dry gas seal. The working fluid leaked from the first-stage dry gas seal merges with the supercritical carbon dioxide entering the second-stage sealing gas channel and reaches the second-stage dry gas seal for secondary sealing. At this time, a trace amount of carbon dioxide working fluid will merge with the working fluid discharged from the comb-tooth seal on the end atmosphere side, and then be recovered from the mixed gas channel;

[0023] During operation, supercritical carbon dioxide with a lower temperature is introduced through the first-stage sealing gas channel and the second-stage sealing gas channel to cool the supercritical carbon dioxide on the medium side, thereby reducing the degree of deformation of the first-stage dynamic ring, the first-stage static ring, the second-stage dynamic ring, and the second-stage static ring.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] In the present invention, dynamic pressure grooves are provided on the first-stage dynamic ring and the second-stage dynamic ring, and the rotation direction of the rotor is consistent with the arrangement direction of the dynamic pressure grooves. When the rotor rotates counterclockwise, a dynamic ring with a counterclockwise deflection of the dynamic pressure grooves is used. When the rotor rotates, supercritical carbon dioxide working fluid flows into the dynamic pressure grooves and is squeezed to form an air film, thereby achieving a sealing effect, effectively avoiding the reduction in system efficiency and technical and economic efficiency caused by leakage of supercritical carbon dioxide working fluid.

[0026] Furthermore, the medium-side comb seal is arranged between the medium and the inner sleeve to perform the first layer of sealing and filtering on the supercritical carbon dioxide working medium leaking from the impeller.

[0027] During the startup process of the tandem dry gas sealing device for supercritical carbon dioxide centrifugal pump provided by the present invention, a certain amount of supercritical carbon dioxide medium is first introduced into the first-stage sealing gas channel, the second-stage sealing gas channel and the comb-tooth sealing gas channel. The supercritical carbon dioxide medium flows into the root of the dynamic pressure groove and is squeezed to form a high-pressure area. When the pressure is large enough, a sealing gas film is formed between the first-stage dynamic ring and the first-stage static ring, thereby achieving the sealing effect, and keeping the first-stage dynamic ring and the first-stage static ring from contacting each other, so that the sealing end surface will not be worn. Since the impeller and rotor of the centrifugal pump are in the high-pressure area, part of the working fluid will leak to the shaft end. The comb-tooth seal is used to perform the first sealing and filtering of the leaking working fluid. When the leaking working fluid reaches the first-stage dry gas seal, it merges with the supercritical carbon dioxide flowing in from the first-stage dry gas seal gas channel. The temperature of the leaking working fluid is relatively high, so it will be cooled, reducing the heating effect on the dry gas seal. The leaked fluid from the first-stage dry gas seal reaches the second-stage dry gas seal for secondary sealing, further reducing the leakage rate. At this time, a trace amount of carbon dioxide fluid will merge with the end comb seal part of the fluid, and then be recovered from the mixed gas channel. The use of a series dry gas seal arrangement helps to further reduce the leakage rate and improve the cycle efficiency and technical economy. During operation, the first-stage dynamic ring and the first-stage static ring are likely to produce thermal deformation due to the influence of the high temperature of the supercritical carbon dioxide on the medium side, which affects the sealing performance. Supercritical carbon dioxide with a lower temperature is introduced through the first-stage sealing gas channel to cool the supercritical carbon dioxide on the medium side, thereby reducing the deformation degree of the first-stage dynamic ring and the first-stage static ring. At the same time, the present invention adopts a series dry gas seal. While using two-stage sealing to meet the sealing requirements, the shaft diameter of each stage of the dry gas seal is reduced to reduce the outer line speed, thereby reducing the adverse effects caused by excessive line speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a structural schematic diagram of a series dry gas sealing device applicable to a supercritical carbon dioxide centrifugal pump of the present invention;

[0030] Figure 2 It is a structural schematic diagram of the tandem dry gas sealing device of the present invention;

[0031] Figure 3 is a schematic diagram of the first-stage sealing gas channel, the second-stage sealing gas channel and the mixed gas channel of the present invention;

[0032] Figure 4 is a cross-sectional view of the pump body AA of the present invention;

[0033] Figure 5 It is a schematic diagram of the dry gas seal dynamic pressure groove adopted in the present invention.

[0034] Description of reference numerals:

[0035] 1-inlet flange; 2-impeller bolts; 3-volute; 4-impeller; 5-tandem dry gas seal; 6-rotor; 7-pump body; 8-bearing; 9-medium side comb seal; 10-inner sleeve; 11-first stage moving ring; 12-first stage static ring; 13-first stage static ring push ring; 14-first stage support ring; 15-first stage static ring seat; 16-second stage moving ring seat; 17-second stage moving ring; 18-second stage static ring; 19-second stage static ring Push ring; 20-second-stage support ring; 21-second-stage stationary ring seat; 22-stationary ring support frame; 23-atmospheric side comb teeth sealing sleeve; 24-O-ring; 25-atmospheric side comb teeth sealing seat; 26-atmospheric side comb teeth seal; 27-rubber ring; 28-sleeve clamping piece; 29-first-stage sealing air channel; 30-second-stage sealing air channel; 31-mixed gas channel; 32-comb teeth sealing air channel; 33-sleeve clamping piece bolt; 34-dynamic pressure groove. DETAILED DESCRIPTION

[0036] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0037] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0041] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0042] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0043] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0044] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0045] In order to solve the problems of insufficient sealing performance, high temperature of dynamic and static rings, and excessive linear speed in the prior art, the present invention proposes a series dry gas sealing device suitable for supercritical carbon dioxide centrifugal pumps. The sealing device adopts two-stage dry gas sealing in series, while meeting the sealing performance, reduces the temperature of the dynamic and static rings by introducing the first-stage sealing gas, and limits the linear speed at the outer shaft diameter of the dynamic and static rings.

[0046] like Figure 1 to Figure 5 As shown, the present embodiment provides a tandem dry gas sealing device suitable for a supercritical carbon dioxide centrifugal pump, including a rotor 6, a medium-side comb seal 9, an inner sleeve 10, a first-stage dynamic ring 11, a first-stage static ring assembly, a second-stage dynamic ring seat 16, a second-stage dynamic ring 17, a second-stage static ring assembly, a static ring support frame 22, an atmosphere-side comb seal assembly, a rubber ring 27 and a sleeve clamp 28.

[0047] Among them, the inner sleeve 10 is sleeved on the outer wall of the rotor 6, the first-stage dynamic ring 11 is sleeved on the outer wall of the inner sleeve 10, the first-stage static ring assembly is arranged on the rotor 6 relative to the first-stage dynamic ring 11 through the second-stage dynamic ring seat 16, the second-stage dynamic ring 17 is sleeved on the outer wall of the inner sleeve 10, and the second-stage dynamic ring 17 is covered by the second-stage dynamic ring seat 16, the second-stage static ring assembly is arranged on the rotor 6 relative to the second-stage dynamic ring 17 through the static ring support frame 22, the atmospheric side comb teeth sealing assembly is sleeved on the outer wall of the rotor 6, the rubber ring 27 is sleeved on the outer wall of the rotor 6 and arranged on the outside of the atmospheric side comb teeth sealing assembly, and the sleeve pressing piece 28 is sleeved on the outer wall of the rotor 6 and arranged on the outside of the rubber ring 27.

[0048] The medium-side comb seal 9 is arranged between the medium and the inner shaft sleeve 10 to perform the first layer of sealing and filtering for the supercritical carbon dioxide working medium leaking from the impeller.

[0049] The first-stage stationary ring assembly includes a first-stage stationary ring 12, a first-stage stationary ring push ring 13, a first-stage support ring 14, a first-stage stationary ring O-ring and a first-stage stationary ring seat 15. The central axes of the first-stage stationary ring 12, the first-stage stationary ring push ring 13, the first-stage stationary ring O-ring and the first-stage stationary ring seat 15 coincide with each other. The first-stage stationary ring 12 and the first-stage stationary ring push ring 13 are in contact with each other. The first-stage support ring 14 is squeezed between the first-stage stationary ring push ring 13 and the first-stage stationary ring seat 15, so as to achieve the function of supporting the first-stage stationary ring 12. The first-stage stationary ring O-ring is arranged between the first-stage stationary ring push ring 13 and the first-stage stationary ring 12, and the first-stage stationary ring seat O-ring is arranged on the outer wall of the first-stage stationary ring seat 15. Arrangement holes are evenly arranged on the first-stage stationary ring seat 15 along the circumferential direction to facilitate the arrangement of the first-stage support ring 14. A total of 12 first-stage support rings 14 are arranged along the axial direction. When the air film stiffness between the first stage dynamic ring 11 and the first stage static ring 12 is large, the first stage static ring 12 is squeezed, thereby balancing the axial force by squeezing the first stage support ring 13. The first stage static ring 12 is arranged on the second stage dynamic ring seat 16.

[0050] The second-stage stationary ring assembly includes a second-stage stationary ring 18, a second-stage stationary ring push ring 19, a second-stage support ring 20, a second-stage stationary ring O-ring and a second-stage stationary ring seat 21. The central axes of the second-stage stationary ring 18, the second-stage stationary ring push ring 19, the second-stage stationary ring O-ring and the second-stage stationary ring seat 21 coincide with each other. The second-stage stationary ring 18 and the second-stage stationary ring push ring 19 are in contact with each other. The second-stage support ring 20 is squeezed between the second-stage stationary ring push ring 19 and the second-stage stationary ring seat 21, so as to achieve the function of supporting the second-stage stationary ring 18. A second-stage stationary ring O-ring is arranged between the second-stage stationary ring push ring 19 and the second-stage stationary ring 18, and a second-stage stationary ring seat O-ring is arranged on the outer wall of the second-stage stationary ring seat 21. Arrangement holes are evenly arranged on the second-stage stationary ring seat 21 along the circumferential direction to facilitate the arrangement of the second-stage support ring 20. A total of 12 second-stage support rings 20 are arranged along the axial direction. When the air film stiffness between the second stage dynamic ring 17 and the second stage static ring 18 is large, the second stage static ring 18 is squeezed, thereby balancing the axial force by squeezing the second stage support ring 20. The second stage static ring 18 is arranged on the static ring support frame 22.

[0051] The atmospheric side comb teeth seal assembly includes an atmospheric side comb teeth seal sleeve 23, an O-ring 24, an atmospheric side comb teeth seal seat 25 and an atmospheric side comb teeth seal 26, and the central axes of the atmospheric side comb teeth seal sleeve 23, the O-ring 24, the atmospheric side comb teeth seal seat 25 and the atmospheric side comb teeth seal 26 coincide, the atmospheric side comb teeth seal 26 and the atmospheric side comb teeth seal seat 25 are fixed by bolts, and the atmospheric side comb teeth seal sleeve 23 and the stationary ring support frame 21 are fixed by bolts. The O-ring 24 is arranged between the atmospheric side comb teeth seal sleeve 23 and the atmospheric side comb teeth seal seat 25. The atmospheric side comb teeth seal sleeve 23, the atmospheric side comb teeth seal 26 and the atmospheric side comb teeth seal seat 25 are sequentially sleeved on the outer wall of the rotor 6.

[0052] See also Figure 3 The volute 3 of the centrifugal pump is provided with a first-stage sealed gas channel 29, a second-stage sealed gas channel 30, an exhaust gas channel 31 and a comb-teeth sealed gas channel 32. The carbon dioxide working fluid is drawn out from the outlet of the centrifugal pump and filtered before being divided into three streams, which are respectively sent to the first-stage sealed gas channel 29, the second-stage sealed gas channel 30 and the comb-teeth sealed gas channel 32. After being treated by the first-stage dry gas seal and the second-stage dry gas seal, the gas and the exhaust gas at the comb-teeth seal are mixed and recovered from the exhaust gas channel 31. Supercritical carbon dioxide enters the centrifugal pump from the inlet flange 1, passes through the impeller bolts 2 and the impeller 4, and then flows out from the volute 3 to the next-stage equipment. During operation, part of the working fluid will leak through the gap between the rotor 6 and the impeller 4, and it is necessary to arrange a sealing device 5 to reduce the leakage rate. See Figure 4 The rotor 6 is connected to the pump body 7 through the bearing 8.

[0053] A rubber ring 27 and a sleeve clamp 28 are arranged on the outside of the atmosphere-side comb seal assembly. The axial width of the sleeve clamp 28 matches the volute 3 and is connected to the outside of the volute 3 via a sleeve clamp bolt 33 .

[0054] See also Figure 5 The first-stage dynamic ring 11 and the second-stage dynamic ring 17 are provided with dynamic pressure grooves 34. The rotation direction of the rotor 6 is consistent with the arrangement direction of the dynamic pressure grooves 34. When the rotor 6 rotates counterclockwise, a dynamic ring with the dynamic pressure grooves 34 deviated counterclockwise is used. The groove depth of the dynamic pressure grooves 34 is 0.5 to 50 μm. When the rotor 6 rotates, the supercritical carbon dioxide working medium flows into the dynamic pressure grooves 34 and is then squeezed to form an air film to achieve a sealing effect.

[0055] The tandem dry gas sealing method for a supercritical carbon dioxide centrifugal pump based on the device as described above provided by the present invention is as follows: during the startup process, a certain amount of supercritical carbon dioxide medium is first introduced into the first-stage sealing gas channel 29, the second-stage sealing gas channel 30 and the comb-tooth sealing gas channel 32. The supercritical carbon dioxide medium flows into the root of the dynamic pressure groove 34 and is squeezed to form a high-pressure area. When the pressure is large enough, a sealing gas film is formed between the first-stage dynamic ring 11 and the first-stage static ring 12, thereby achieving a sealing effect, and keeping the first-stage dynamic ring 11 and the first-stage static ring 12 from contacting each other, so that the sealing end faces will not be worn. Since the impeller 4 and the rotor 6 of the centrifugal pump are in the high-pressure area, part of the working fluid will leak to the shaft end. After the leaked working fluid is initially filtered by the comb seal 9 on the medium side, it will merge with the supercritical carbon dioxide entering the first-stage sealing gas channel 29. The temperature of the leaked working fluid is relatively high, so it will be cooled to reduce the heating effect on the dry gas seal. Then it flows into the first-stage dry gas seal (including the first-stage dynamic ring 11 and the first-stage static ring assembly). The working fluid leaked from the first-stage dry gas seal merges with the supercritical carbon dioxide entering the second-stage sealing gas channel 30 for a second heat exchange cooling, and then flows into the second-stage dry gas seal (including the second-stage dynamic ring 17 and the second-stage static ring assembly) for secondary sealing to further reduce the leakage rate. At this time, a trace amount of carbon dioxide working fluid will merge with the working fluid discharged from the comb seal 26 on the end atmosphere side, and then be recovered from the mixed gas channel 31. The use of a series dry gas seal arrangement helps to further reduce the leakage rate and improve the cycle efficiency and technical economy.

[0056] During operation, the first-stage dynamic ring 11 and the first-stage static ring 12 are likely to be thermally deformed due to the high temperature of the supercritical carbon dioxide on the medium side, which affects the sealing performance. Supercritical carbon dioxide with a lower temperature is introduced through the first-stage sealing gas channel 29 to cool the supercritical carbon dioxide on the medium side, thereby reducing the deformation of the first-stage dynamic ring 11 and the first-stage static ring 12.

[0057] At the same time, a tandem dry gas seal is adopted. While using two-stage seals to meet the sealing requirements, the shaft diameter of each stage of dry gas seal is reduced to reduce the outer line speed, thereby reducing the adverse effects caused by excessive line speed.

[0058] The present invention drives the dynamic ring to rotate by the rotation of the rotor, and the sealing medium flows into the dynamic pressure groove of the dynamic ring, forming a high-pressure area to squeeze the static ring to form a sealing gas film, thereby achieving the function of sealing the medium side working medium. Since a tandem dry gas seal is adopted, a comb seal and a rubber ring are arranged on the outer side of the shaft end to isolate the medium from the outside, so the leakage of the supercritical carbon dioxide centrifugal pump will be extremely small, effectively avoiding the reduction of system efficiency and technical economy caused by the leakage of supercritical carbon dioxide working medium.

[0059] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. However, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A series dry gas sealing device suitable for a supercritical carbon dioxide centrifugal pump, characterized in that: It comprises a rotor (6), an inner shaft sleeve (10), a first-stage dry gas seal, a second-stage dry gas seal, a second-stage stationary ring assembly, a stationary ring support frame (22) and an atmosphere-side comb seal assembly; The first-stage dry gas seal comprises a first-stage dynamic ring (11) and a first-stage static ring assembly, the second-stage dry gas seal comprises a second-stage dynamic ring seat (16) and a second-stage dynamic ring (17), the inner sleeve (10) and the atmosphere-side comb seal assembly are sleeved on the outer wall of the rotor (6), the first-stage dynamic ring (11) is sleeved on the outer wall of the inner sleeve (10), the first-stage static ring assembly is arranged on the rotor (6) relative to the first-stage dynamic ring (11) through the second-stage dynamic ring seat (16), the second-stage dynamic ring (17) is sleeved on the outer wall of the inner sleeve (10), and the second-stage static ring assembly is arranged on the rotor (6) relative to the second-stage dynamic ring (17) through the static ring support frame (22). Dynamic pressure grooves (34) are provided on the first-stage dynamic ring (11) and the second-stage dynamic ring (17).

2. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 1, characterized in that: It also includes a rubber ring (27) and a shaft sleeve pressing piece (28), wherein the rubber ring (27) is sleeved on the outer wall of the rotor (6) and arranged on the outer side of the comb seal assembly on the atmosphere side, and the shaft sleeve pressing piece (28) is sleeved on the outer wall of the rotor (6) and arranged on the outer side of the rubber ring (27).

3. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 1, characterized in that: The first-stage stationary ring assembly comprises a first-stage stationary ring (12), a first-stage stationary ring push ring (13), a first-stage support ring (14), a first-stage stationary ring O-ring and a first-stage stationary ring seat (15); the central axes of the first-stage stationary ring (12), the first-stage stationary ring push ring (13), the first-stage stationary ring O-ring and the first-stage stationary ring seat (15) coincide with each other; the first-stage stationary ring (12) and the first-stage stationary ring push ring (13) are in contact with each other; the first-stage support ring (14) is arranged between the first-stage stationary ring push ring (13) and the first-stage stationary ring seat (15); the first-stage stationary ring O-ring is arranged between the first-stage stationary ring push ring (13) and the first-stage stationary ring seat (15); and the first-stage stationary ring seat O-ring is arranged on the outer wall surface of the first-stage stationary ring seat (15); the first-stage stationary ring (12) is arranged on the second-stage moving ring seat (16).

4. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 3, characterized in that: A plurality of arrangement holes for arranging the first-stage support ring (14) are evenly arranged along the circumferential direction on the first-stage stationary ring seat (15).

5. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 1, characterized in that: The second-stage stationary ring assembly comprises a second-stage stationary ring (18), a second-stage stationary ring push ring (19), a second-stage support ring (20), a second-stage stationary ring O-ring and a second-stage stationary ring seat (21); the central axes of the second-stage stationary ring (18), the second-stage stationary ring push ring (19), the second-stage stationary ring O-ring and the second-stage stationary ring seat (21) coincide with each other; the second-stage stationary ring (18) and the second-stage stationary ring push ring (19) are in contact with each other; the second-stage support ring (20) is arranged between the second-stage stationary ring push ring (19) and the second-stage stationary ring seat (21); the second-stage stationary ring O-ring is arranged between the second-stage stationary ring push ring (19) and the second-stage stationary ring (18); and the second-stage stationary ring seat O-ring is arranged on the outer wall surface of the second-stage stationary ring seat (21); and the second-stage stationary ring (18) is arranged on a stationary ring support frame (22).

6. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 5, characterized in that: A plurality of arrangement holes for arranging the second-stage support ring (20) are evenly arranged along the circumferential direction on the second-stage stationary ring seat (21).

7. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 1, characterized in that: The atmospheric side comb teeth seal assembly comprises an atmospheric side comb teeth seal shaft sleeve (23), an atmospheric side comb teeth seal seat (25) and an atmospheric side comb teeth seal (26), wherein the central axes of the atmospheric side comb teeth seal shaft sleeve (23), the atmospheric side comb teeth seal seat (25) and the atmospheric side comb teeth seal (26) coincide with each other, and the atmospheric side comb teeth seal shaft sleeve (23), the atmospheric side comb teeth seal (26) and the atmospheric side comb teeth seal seat (25) are sequentially sleeved on the outer wall of the rotor (6).

8. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 1, characterized in that: It also includes a first-stage sealing gas channel (29), a second-stage sealing gas channel (30), an exhaust gas channel (31) and a comb-teeth sealing gas channel (32) arranged on the volute (3) of the centrifugal pump. After the carbon dioxide working medium is drawn out from the outlet of the centrifugal pump and filtered, it is divided into three streams and sent to the first-stage sealing gas channel (29), the second-stage sealing gas channel (30) and the comb-teeth sealing gas channel (32) respectively. After the working medium leaked from the first-stage dry gas seal and the second-stage dry gas seal is mixed with the gas discharged from the comb-teeth seal (26) on the atmosphere side, it enters the exhaust gas channel (31) and is discharged; A sealing device (5) is arranged at the shaft end of the impeller (4), and the rotor (6) is connected to the pump body (7) via a bearing (8).

9. The tandem dry gas sealing device for a supercritical carbon dioxide centrifugal pump according to claim 1, characterized in that: A rubber ring (27) and a shaft sleeve clamping piece (28) are arranged on the outside of the atmosphere-side comb seal assembly. The radial dimension of the shaft sleeve clamping piece (28) matches that of the volute (3) and is connected to the outside of the volute (3) via a shaft sleeve clamping piece bolt (33). The medium-side comb seal (9) is arranged between the medium and the inner shaft sleeve (10); The rotation direction of the rotor (6) is consistent with the arrangement direction of the dynamic pressure groove (34). When the rotor (6) rotates counterclockwise, a dynamic ring with the dynamic pressure groove (34) deflected counterclockwise is used. When the rotor (6) rotates, supercritical carbon dioxide working fluid flows into the dynamic pressure groove (34) and is squeezed to form an air film, thereby achieving a sealing effect.

10. A sealing method for the device as claimed in claim 8, characterized in that: The following steps are involved: During the startup process, supercritical carbon dioxide medium is first introduced into the first-stage sealing air channel (29), the second-stage sealing air channel (30) and the comb-teeth sealing air channel (32). The supercritical carbon dioxide medium flows into the root of the dynamic pressure groove (34) and is squeezed to form a high-pressure area. When the pressure is large enough, a sealing air film is formed between the first-stage dynamic ring (11) and the first-stage static ring (12), thereby achieving a sealing effect and keeping the first-stage dynamic ring (11) and the first-stage static ring (12) from contacting each other. Since the impeller (4) of the centrifugal pump is close to the rotor, the impeller (4) of the centrifugal pump is close to the rotor. (6) In the high-pressure area, part of the working fluid leaks toward the shaft end. The leaked working fluid is initially filtered by the comb seal (9) on the medium side and then merges with the supercritical carbon dioxide entering the first-stage sealing gas channel (29), flows into the first-stage dry gas seal, and the working fluid leaking from the first-stage dry gas seal merges with the supercritical carbon dioxide entering the second-stage sealing gas channel (30), reaches the second-stage dry gas seal, and performs secondary sealing. At this time, a trace amount of carbon dioxide working fluid will merge with the working fluid discharged from the comb seal (26) on the end atmosphere side, and then be recovered from the mixed gas channel (31); During operation, supercritical carbon dioxide with a relatively low temperature is introduced through the first-stage sealing gas channel (29) and the second-stage sealing gas channel (30) to cool the supercritical carbon dioxide on the medium side, thereby reducing the degree of deformation of the first-stage dynamic ring (11), the first-stage static ring (12), the second-stage dynamic ring (17), and the second-stage static ring (18).

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