A pressure self-reinforced seal structure for soft packing dynamic seal

Abstract

The application belongs to the technical field of sealing and discloses a pressure self-reinforcing sealing structure for soft packing dynamic sealing, which comprises a rotating hollow shaft dynamic sealing surface and a soft sealing packing assembly matched with the rotating hollow shaft dynamic sealing surface, the rotating hollow shaft dynamic sealing surface is provided with at least two groups of inclined wedge matched sealing structures, each group of the inclined wedge matched sealing structure is in the structural form of a cylindrical surface+an inclined surface, a cylindrical surface+ a curved surface or a cylindrical surface+an inclined surface+ a curved surface, the curved surface is a circular arc surface or an elliptical surface, the soft sealing packing assembly comprises a plurality of soft sealing packing rings, the inner contact surface shape of the soft sealing packing ring matched with the rotating hollow shaft dynamic sealing surface is consistent with or similar to the shape of the rotating hollow shaft dynamic sealing surface, the soft sealing packing ring is compressed and deformed under the action of assembly pressure and medium pressure, so that the soft sealing packing ring is completely attached to the rotating hollow shaft dynamic sealing surface to form inclined wedge matching, and the extrusion force and radial compression effect of the rotating hollow shaft dynamic sealing surface on the soft sealing packing ring increase with the increase of the medium pressure.

Description

Technical Field

[0001] This invention belongs to the field of trough-type solar thermal power generation and sealing technology, specifically relating to a pressure self-reinforcing sealing structure for soft packing dynamic seals. It is a soft packing dynamic seal for high-temperature medium-pressure rotating hollow shafts and can be applied to the sealing structure of high-temperature rotary joints in the industry. It is especially suitable for rotating hollow shafts with high-temperature medium-pressure media and is adapted to relevant application scenarios of soft packing dynamic seals. It can be applied to high-temperature rotary joints in solar thermal power generation, and is particularly suitable for planar rotary joints for flexible connection between solar thermal power collectors and pipelines. It is suitable for working environments with temperatures ≤700℃, pressures ≤8MPa, and media such as high-temperature molten salt, heat transfer oil, and water. Background Technology

[0002] In industrial production, the dynamic seal of rotating shafts is a critical aspect of equipment operation, especially the sealing of rotating hollow shafts under high temperature and medium pressure conditions, which has always been a challenging problem in the field of sealing technology. Soft packing dynamic seals are a common type of rotating shaft seal, and they are widely used in various industries due to their simple structure and easy replacement. However, the traditional soft packing dynamic seal structure has extremely poor adaptability under high temperature and medium pressure conditions.

[0003] For high-temperature rotating shaft seals, especially those with temperatures ≥350℃, traditional soft sealing materials such as rubber seals are no longer sufficient due to their inadequate high-temperature resistance. The industry has turned to soft sealing fillers suitable for high temperatures, such as flexible graphite, expanded vermiculite, and ceramic fibers. However, the sealing performance and resilience of these high-temperature soft sealing fillers are far lower than those of rubber seals. Currently, both domestically and internationally, soft-filled dynamic seals for high-temperature rotating shafts use packing or packing rings to directly seal the cylindrical surface of the rotating hollow shaft through compression deformation. This sealing method has many technical drawbacks: Firstly, the sealing reliability and service life are extremely poor. The direct sealing method of the cylindrical surface has extremely high requirements for the control of the compression amount of the packing. If the compression amount is too small, the medium will easily leak. If the compression amount is too large, it will increase the rotational torque of the rotating shaft, aggravate the wear of the packing and the shaft surface, and cause the sealing performance to decay rapidly. Generally, the replacement cycle of this type of sealing structure is no more than 3 months, which cannot meet the needs of long-term stable operation of industrial equipment. Secondly, the sealing effect is poor. Under high temperature conditions, soft sealing packing is prone to thermal shrinkage and thermal aging. Cylindrical surface seals cannot compensate for the deformation of the packing, which easily forms micro gaps on the sealing surface, leading to media leakage. For toxic, flammable, and high-temperature media (such as high-temperature molten salt), leakage will not only cause material loss, but also cause equipment corrosion, safety accidents and other problems. Third, it has poor adaptability. Traditional structures cannot adjust the sealing effect according to changes in working pressure. When the medium pressure fluctuates, the sealing performance fluctuates synchronously. Under medium-pressure conditions with pressure ≥4MPa, the leakage problem is particularly prominent.

[0004] The aforementioned problems are even more pronounced in the field of solar thermal power generation. Parabolic trough solar thermal power generation systems, with their advantages of excellent power generation quality, energy storage, environmental friendliness, and mature technology, have become an important direction for new energy development. To reduce costs and improve thermoelectric conversion efficiency, molten salt parabolic trough solar thermal power generation systems, using high-temperature molten salt as the heat transfer and storage medium, have become the mainstream development trend. In molten salt parabolic trough solar thermal power generation systems, the flexible connection between the high-temperature molten salt tank and the pipeline requires the use of planar rotary joints. Their operating environment is characterized by high temperature (conventional operating temperature 560℃, with future development directions exceeding 600℃), high pressure (conventional operating pressure 4MPa), and long service life (industry requirement 25-30 years). The rotary hollow shaft seal of the planar rotary joint has become the biggest technical bottleneck restricting the development and commercial application of this technology.

[0005] Currently, no effective soft-filler dynamic sealing solution has been proposed for the sealing problem of the planar rotary joint of the high-temperature molten salt tank in solar thermal power generation, both domestically and internationally. If a hard seal structure is adopted, although the sealing reliability can be improved, the hard seal has extremely high requirements for the dimensional accuracy and fit tolerance of the rotating hollow shaft, which makes it difficult to process and has high production costs. In addition, the hard seal structure is complex, and the assembly and maintenance are difficult, making it unsuitable for large-scale commercial applications.

[0006] Besides the concentrated solar power (CSP) industry, high-temperature rotary joints for roller conveyors in the metallurgical industry, high-temperature rotary joints for heat transfer oil in the papermaking industry, and high-temperature rotary joints for water media in the food industry all face problems such as poor reliability, short lifespan, and easy leakage of soft packing dynamic seals under high-temperature and medium-pressure conditions. Therefore, developing a pressure-reinforcing sealing structure for soft packing dynamic seals that adapts to high-temperature and medium-pressure media, features a rotating hollow shaft, self-reinforcing sealing effect with pressure, low processing and assembly difficulty, and long service life is key to solving the adaptation problem of soft packing dynamic seals under high-temperature and medium-pressure conditions, and is of great significance to promoting the technological development of the CSP industry. Summary of the Invention

[0007] In view of this, the present invention provides a pressure self-reinforcing sealing structure for soft packing dynamic seals. Addressing the technical problems of existing soft packing dynamic seal structures in high-temperature, medium-pressure rotating hollow shaft applications, such as poor sealing reliability, short lifespan, easy leakage, and inability to adjust sealing performance with pressure, as well as the high processing and assembly difficulty and cost of hard seal structures, the present invention provides a pressure self-reinforcing sealing structure for soft packing dynamic seals. The core objective of this invention is to achieve pressure self-reinforcing sealing by designing a "wedge" fit structure between the rotating hollow shaft dynamic sealing surface and the soft seal packing ring. This means that the higher the working pressure of the medium, the better the sealing effect, achieving zero leakage under high-temperature, medium-pressure conditions of 300℃~700℃ and 0~8MPa. Simultaneously, it reduces the requirements for machining accuracy and fit tolerances of the sealing structure, reduces processing and assembly difficulty, controls production costs, and adapts to the long-life (25~30 years) requirements of industries such as concentrated solar power generation, filling the technical gap in soft packing dynamic seals for high-temperature molten salt rotary joints in concentrated solar power generation both domestically and internationally.

[0008] The first aspect of the present invention is to provide a pressure self-reinforcing sealing structure for a soft-pack dynamic seal, applied to a rotating hollow shaft (6) in a high-temperature, medium-pressure medium medium, comprising a rotating hollow shaft dynamic sealing surface and a soft-seal packing assembly that mates with the rotating hollow shaft dynamic sealing surface. The rotating hollow shaft dynamic sealing surface is provided with at least two sets of wedge-fit sealing structures, each set of wedge-fit sealing structures being a cylindrical surface + inclined surface, a cylindrical surface + curved surface, or a cylindrical surface + inclined surface + curved surface structure, wherein the curved surface is an arc surface or an elliptical surface. The soft-seal packing assembly includes a plurality of soft-seal packing rings, the inner contact surface of which mates with the rotating hollow shaft dynamic sealing surface has a shape that is consistent with or similar to that of the rotating hollow shaft dynamic sealing surface. Under the action of assembly pressure and medium pressure, the soft-seal packing rings undergo compression deformation, thereby completely fitting with the rotating hollow shaft dynamic sealing surface to form a wedge fit. The extrusion force and radial compression effect of the rotating hollow shaft dynamic sealing surface on the soft-seal packing rings increase with the increase of the medium pressure.

[0009] Preferably, the wedge-fit sealing structure is a symmetrical or asymmetrical structure. The asymmetrical wedge-fit sealing structure can generate a thrust to one side on the rotating hollow shaft. The thrust is used to reduce the friction between the shoulder of the rotating hollow shaft and the end face of the bushing.

[0010] Preferably, the soft sealing packing assembly is also adapted to injectable soft sealing packing, which, after being injected, naturally forms a shape that is completely consistent with the dynamic sealing surface of the rotating hollow shaft and fits and seals.

[0011] Preferably, the soft sealing packing ring is made of high-temperature soft sealing packing material of flexible graphite, expanded vermiculite or ceramic fiber, and is suitable for high-temperature and medium-pressure working environments with temperatures ≤700℃ and pressures ≤8MPa.

[0012] Preferably, when applied to rotary joints with high working pressure of the medium and high sealing performance requirements, the dynamic sealing surface of the rotary hollow shaft adopts a structure of cylindrical surface + curved surface or cylindrical surface + inclined surface + curved surface; when applied to rotary joints with low working pressure of the medium and low sealing performance requirements, the dynamic sealing surface of the rotary hollow shaft adopts a structure of cylindrical surface + inclined surface.

[0013] Preferably, it also includes a rotary joint base structure, which includes a housing (1), a bushing bearing assembly, a spacer (7), a flange (9), and flange bolts (10). The bushing bearing assembly includes a first bushing bearing (2) and a second bushing bearing (8). The soft sealing packing assembly is disposed in the housing. The spacer is used to transmit assembly clamping force to the soft sealing packing ring. The flange and the flange bolts are used to axially fix the components in the housing. The bushing bearing assembly is used to support and position the rotating hollow shaft and withstand radial and axial external forces.

[0014] Preferably, the soft sealing packing ring includes a first soft sealing packing ring (3), a second soft sealing packing ring (4), and a third soft sealing packing ring (5). The first soft sealing packing ring (3) has a cylindrical surface fit with the dynamic sealing surface of the rotating hollow shaft, the second soft sealing packing ring (4) has an inclined surface fit with the dynamic sealing surface of the rotating hollow shaft, and the third soft sealing packing ring (5) has a curved surface fit with the dynamic sealing surface of the rotating hollow shaft. The wedge fit formed by the second soft sealing packing ring (4) and the third soft sealing packing ring (5) with the rotating hollow shaft is the main sealing fit structure, and the first soft sealing packing ring (3) is the auxiliary sealing fit structure.

[0015] Preferably, the number and circumferential arrangement of the wedge-fit sealing structures are adjusted according to the sealing requirements, shaft diameter, and working pressure of the rotary joint.

[0016] Preferably, the high-temperature medium-pressure medium is high-temperature molten salt, heat transfer oil or water, and the structure is adapted to a working temperature range of 300℃~700℃ and a working pressure range of 0~8MPa.

[0017] A second aspect of the invention is to provide the application of the pressure self-reinforcing sealing structure for soft packing dynamic sealing in the first aspect to a high-temperature rotary joint for solar thermal power generation, wherein the application to solar thermal power generation includes the application of the pressure self-reinforcing sealing structure for soft packing dynamic sealing in a planar rotary joint suitable for flexible connection of a high-temperature molten salt tank in a parabolic trough solar thermal power generation system.

[0018] The pressure self-reinforcing sealing structure for soft packing dynamic seals of the present invention, designed for rotating hollow shafts operating in high-temperature and medium-pressure media, has the following significant advantages compared to existing technologies: 1. Pressure-reinforced seal, ensuring high sealing reliability and achieving zero leakage. This invention achieves pressure-reinforced sealing through a wedge-fit structure. The higher the working pressure of the medium, the tighter the seal surface fits, resulting in a better sealing effect. This solves the problem of unstable sealing performance of traditional soft-pack dynamic seals under pressure fluctuations. Under high-temperature and medium-pressure conditions of 300℃~700℃ and 0~8MPa, it can achieve zero leakage for extended periods. Actual testing showed that under molten salt conditions in solar thermal power generation at 560℃ and 4MPa, the sealing structure operated continuously for 12 months without any leakage, demonstrating a sealing reliability far superior to traditional cylindrical surface sealing structures.

[0019] 2. Adaptable to high temperature and medium pressure operating conditions, filling a technological gap both domestically and internationally. The sealing structure of this invention is suitable for high-temperature and medium-pressure conditions with temperatures ≤700℃ and pressures ≤8MPa. The media include high-temperature molten salt, heat transfer oil, water, etc. It is especially suitable for planar rotary joints with flexible connections of high-temperature molten salt tanks in parabolic trough solar thermal power generation systems. It solves the technical bottleneck of sealing high-temperature molten salt rotary joints in the field of solar thermal power generation, fills the technical gap of soft packing dynamic sealing in this field at home and abroad, and promotes the commercial application of molten salt parabolic trough solar thermal power generation systems.

[0020] 3. Low processing and assembly difficulty, low production cost This invention employs a soft-filler dynamic sealing structure, which significantly reduces the requirements for dimensional accuracy and fit tolerances of the rotating hollow shaft compared to a hard-seal structure. The machining tolerance of the rotating hollow shaft can be relaxed to ±0.05mm, and the machining difficulty of the soft-seal packing ring is also lower. At the same time, the assembly process of the sealing structure is simple, requiring no special assembly equipment. Sealing assembly can be achieved simply by adjusting the preload of the flange bolts, which greatly improves production efficiency and reduces machining and assembly costs. Compared to a hard-seal structure, production costs are reduced by more than 60%.

[0021] 4. Long sealing life, low rotational torque, and high equipment operational stability. The soft-seal packing ring of this invention flexibly fits the rotating hollow shaft, resulting in significantly less wear than traditional cylindrical surface seals. Furthermore, the asymmetrical wedge-shaped fit effectively reduces end-face friction between the rotating hollow shaft and the bushing, lowering the rotational torque (by 30%–40% compared to traditional structures). The sealing structure has a design life of 25–30 years, meeting the long-life requirements of industries such as concentrated solar power generation, reducing the frequency of seal replacements, and lowering equipment maintenance costs.

[0022] 5. Highly adaptable and widely applicable, enabling online repair. The sealing structure of this invention can flexibly adjust the structural form of the rotating hollow shaft sealing surface and the number of wedge-fit sealing structures according to the working pressure and sealing requirements. It is suitable for high-temperature rotary joints in various industries such as solar thermal power generation, metallurgy, papermaking, and food. At the same time, it is compatible with injectable soft sealing filler, which can realize online replenishment of sealing filler and on-site repair of sealing surface without disassembling the rotary joint, greatly reducing equipment maintenance downtime and improving the continuous operation capability of the equipment.

[0023] 6. Uniform sealing force and minimal component wear. This invention uses spacers to uniformly transmit assembly clamping force, ensuring consistent compression of each soft-seal packing ring and uniform stress on the sealing surface. This avoids packing aging and shaft surface wear caused by localized stress concentration. At the same time, the pressure self-enhancing process is flexibly adjusted, and the tightness of the sealing surface changes automatically with the pressure, without rigid contact. This further reduces component wear and extends the service life of the sealing structure and the rotating hollow shaft. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the general-purpose rotary joint structure of the present invention; Figure 2 This is a schematic diagram of the rotating hollow shaft dynamic sealing surface structure of the present invention (a symmetrical structure of cylindrical surface + inclined surface + elliptical surface). Figure 3 This is a schematic diagram of the rotating hollow shaft dynamic sealing surface structure of the present invention (a symmetrical structure of cylindrical surface + inclined surface + arc surface). Figure 4 This is a schematic diagram of the rotating hollow shaft dynamic sealing surface structure of the present invention (a symmetrical structure of cylindrical surface + inclined surface); Figure 5 This is a schematic diagram of the rotating hollow shaft dynamic sealing surface structure of the present invention (an asymmetrical structure of cylindrical surface + inclined surface + elliptical surface).

[0025] Explanation of reference numerals in the attached figures: 1-Housing, 2-First shaft sleeve bearing, 3-First soft seal packing ring, 4-Second soft seal packing ring, 5-Third soft seal packing ring, 6-Rotating hollow shaft, 7-Spacer, 8-Second shaft sleeve bearing, 9-Flange, 10-Flange bolt. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The purpose of this invention is to provide a pressure-reinforced sealing structure for dynamic sealing of soft packing, applied to a rotating hollow shaft in high-temperature and medium-pressure media. It includes a soft-seal packing assembly and a matching rotary joint base structure. The structural design and fit of each part are as follows: The rotating hollow shaft is the core component of the sealing structure. Its dynamic sealing surface has at least two sets of wedge-shaped sealing structures, which can be designed as symmetrical or asymmetrical structures. Each set of wedge-shaped sealing structures has three specific forms: cylindrical surface + inclined surface, cylindrical surface + curved surface, and cylindrical surface + inclined surface + curved surface. The curved surface can be a circular arc surface or an elliptical surface. The radius of curvature of the curved surface is designed according to the shaft diameter and working pressure of the rotating hollow shaft; the larger the shaft diameter and the higher the working pressure, the smaller the radius of curvature of the curved surface. The symmetrical wedge-shaped sealing structure is suitable for working conditions where there are no special requirements for the axial thrust of the rotating shaft, and the sealing force is uniform. The asymmetrical wedge-shaped sealing structure can generate a directional thrust to one side of the rotating hollow shaft, which can effectively reduce the rotational friction between the shaft shoulder and the end face of the bushing, reduce rotational torque, and reduce component wear. The number and circumferential arrangement of the wedge-fit sealing structure can be flexibly adjusted according to the sealing requirements, shaft diameter, and working pressure of the rotary joint. When the shaft diameter is ≥100mm or the working pressure is ≥6MPa, the number of wedge-fit sealing structures can be increased to improve sealing reliability.

[0028] The soft sealing packing assembly is a sealing actuator, comprising several soft sealing packing rings and is also adapted to injectable soft sealing packing. In this embodiment, the soft sealing packing rings include a first soft sealing packing ring (3), a second soft sealing packing ring (4), and a third soft sealing packing ring (5). The first soft sealing packing ring (3) has a cylindrical surface fit with the dynamic sealing surface of the rotating hollow shaft, the second soft sealing packing ring (4) has a beveled surface fit with the dynamic sealing surface of the rotating hollow shaft, and the third soft sealing packing ring (5) has a curved surface fit with the dynamic sealing surface of the rotating hollow shaft. The wedge fit formed by the second soft sealing packing ring (4) and the third soft sealing packing ring (5) with the rotating hollow shaft is the main sealing fit structure, and the first soft sealing packing ring (3) is an auxiliary sealing fit structure.

[0029] The soft sealing packing ring is made of high-temperature resistant soft sealing packings such as flexible graphite, expanded vermiculite, and ceramic fiber. It is suitable for high-temperature and medium-pressure working conditions with temperatures ≤700℃ and pressures ≤8MPa. The shape of its inner contact surface that mates with the sealing surface of the rotating hollow shaft is the same as or similar to the shape of the sealing surface of the rotating hollow shaft. This ensures that under the action of assembly pressure and medium pressure, the soft sealing packing ring can undergo compression deformation and completely fit with the dynamic sealing surface of the rotating hollow shaft to form a tight wedge fit. Injectable soft sealing filler is a high-temperature self-leveling filler. After injection, it can flow naturally along the sealing surface of the rotating hollow shaft, forming a shape that is completely consistent with the sealing surface and fitting tightly. It is suitable for working conditions with extremely high sealing requirements or on-site repair, and can realize online replenishment of filler and seamless fitting of sealing surface. The number of soft-seal packing rings is configured according to the number of sets of wedge-fit sealing structures and sealing requirements. It includes at least three types of packing rings: cylindrical surface fit, inclined surface fit, and curved surface fit. These rings fit with the corresponding sealing surfaces of the rotating hollow shaft to form a double-layer sealing system of main seal and auxiliary seal.

[0030] The pressure self-reinforcing sealing structure for soft packing dynamic seals is based on the pressure self-reinforcing sealing principle derived from the mechanical characteristics of the wedge fit. Its working method and principle include: Assembly stage: Under the pre-tightening force of the flange bolts, the spacer transmits the axial assembly clamping force to the soft sealing packing ring. The soft sealing packing ring is compressed axially and expands radially, clamping with the dynamic sealing surface of the rotating hollow shaft to form an initial seal. At this time, the wedge fit structure has basic sealing capability. Working phase: When pressurized medium enters the rotary joint, the medium pressure acts on the end section of the soft sealing packing ring and the end section of the rotating hollow shaft, pushing the soft sealing packing ring and the rotating hollow shaft to produce a small displacement along the axial direction. This displacement will further reduce the fitting gap of the wedge fit structure, and the rotating hollow shaft dynamic sealing surface will generate greater extrusion force and radial compression on the soft sealing packing ring, making the soft sealing packing ring fit more tightly with the sealing surface. Pressure enhancement stage: The greater the working pressure of the medium, the greater the axial thrust, the stronger the squeezing force and radial compression of the wedge fit, the higher the tightness of the sealing surface, and the sealing effect is enhanced simultaneously, ultimately achieving zero leakage. Moreover, when the pressure fluctuates, the sealing structure can automatically adjust the tightness of the fit to ensure the stability of the sealing performance.

[0031] To balance sealing performance and processing costs, this invention determines the selection principle for the sealing surface of the rotary hollow shaft based on the working pressure and sealing performance requirements of the rotary joint. When applied to rotary joints with high working pressure (≥4MPa) and high sealing performance requirements (such as planar rotary joints for high-temperature molten salt tanks in solar thermal power generation), a sealing surface structure of cylindrical surface + curved surface or cylindrical surface + inclined surface + curved surface is selected. The arc structure of the curved surface can further enhance the pressure self-reinforcing effect of the wedge fit, ensuring zero leakage under high pressure. When applied to rotary joints with low working pressure (<4MPa) and low sealing performance requirements (such as rotary joints for high-temperature water media in the food industry), a sealing surface structure of cylindrical surface + inclined surface is selected. This structure has low processing difficulty and low production cost, and can meet the sealing requirements of low-pressure conditions.

[0032] The sealing structure of the present invention needs to be used in conjunction with the rotary joint base structure, which includes a housing 1, a bushing bearing assembly, a spacer 7, a flange 9, and flange bolts 10.

[0033] The housing 1 serves as the base of the rotary joint, used to install and fix all sealing and supporting components. Its inner wall has a packing installation groove to accommodate the installation and positioning of the soft-seal packing rings. The bushing bearing assembly includes a first bushing bearing 2 and a second bushing bearing 8, symmetrically arranged on both sides of the rotating hollow shaft 6. These provide radial and axial support and positioning for the rotating hollow shaft 6, withstand radial and axial external forces during equipment operation, ensure the coaxiality of the rotating hollow shaft 6, and prevent sealing surface gaps caused by shaft misalignment. Spacers 7 are placed between the soft-seal packing rings to evenly transmit assembly clamping force, ensuring consistent compression of each soft-seal packing ring and preventing seal failure due to excessive or insufficient local compression. Flanges 9 and flange bolts 10 are located at the ends of the housing 1, used to axially fix the rotating hollow shaft 6, soft-seal packing rings, spacers 7, bushing bearing assembly, and other components within the housing 1. Simultaneously, by adjusting the preload of the flange bolts 10, the initial compression of the soft-seal packing rings is controlled, thus adjusting the initial sealing effect.

[0034] Figure 1 The general-purpose rotary joint structure shown is the supporting base structure for the sealing structure of this invention. The housing 1 is an integral base, and the first bushing bearing 2, the first soft sealing packing ring 3, the second soft sealing packing ring 4, the third soft sealing packing ring 5, the spacer 7, and the second bushing bearing 8 are installed sequentially inside. The rotating hollow shaft 6 passes through the above components. The flange 9 and flange bolts 10 are located at the end of the housing 1 to achieve axial fixation. The first soft sealing packing ring 3 is a cylindrical surface mating packing ring, the second soft sealing packing ring 4 is a beveled surface mating packing ring, and the third soft sealing packing ring 5 is a curved surface mating packing ring. The three of them cooperate to form a sealing system. The spacer 7 is used to evenly transmit the preload force of the flange bolts 10. Figure 2 The dynamic sealing surface of the rotating hollow shaft 6 shown is a symmetrical structure of cylindrical surface + inclined surface + elliptical surface, which is a high sealing performance structure and is suitable for high temperature molten salt working conditions with pressure ≥4MPa. The radius of curvature of the elliptical surface is designed according to the shaft diameter. When the shaft diameter is 150mm, the radius of curvature of the elliptical surface is 20mm. The symmetrical structure makes the axial force of the rotating hollow shaft uniform and without directional thrust. Figure 3 The dynamic sealing surface of the rotating hollow shaft 6 shown is a symmetrical structure of cylindrical surface + inclined surface + arc surface, which is also suitable for working conditions with pressure ≥4MPa. The radius of curvature of the arc surface is 15mm (shaft diameter 150mm). The machining difficulty of the arc surface is slightly lower than that of the elliptical surface, which takes into account both sealing performance and machining convenience. Figure 4The dynamic sealing surface of the rotating hollow shaft 6 shown is a symmetrical structure of cylindrical surface + inclined surface, which is suitable for low-pressure and high-temperature working conditions with pressure <4MPa, such as heat transfer oil and high-temperature water medium. This structure has no curved surface machining, has the lowest machining difficulty, and low production cost. Figure 5 The dynamic sealing surface of the rotating hollow shaft 6 shown is an asymmetrical structure of cylindrical surface + inclined surface + elliptical surface. The radius of curvature of the elliptical surface is asymmetrically designed along the axial direction, with a radius of curvature of 25mm on the left and 20mm on the right (shaft diameter 150mm). It can generate a directional thrust to the left on the rotating hollow shaft 6, reduce the friction between the shoulder of the rotating hollow shaft 6 and the end face of the second bushing bearing 8, and reduce the rotational torque.

[0035] Example 1: Application of 560℃ / 4MPa High-Temperature Molten Salt Flat Rotary Joint Sealing in Parabolic Trough Solar Thermal Power Generation System This embodiment applies a planar rotary joint for the flexible connection between a high-temperature molten salt tank and a pipeline in a parabolic trough solar thermal power generation system. The rotating hollow shaft is the core component for conveying high-temperature molten salt. Specific application parameters include: The medium is a mixture of potassium nitrate and sodium nitrate in a high-temperature molten salt (mass ratio 60:40); the required operating temperature is 560℃ (long-term stable operating temperature), and the maximum instantaneous temperature is 580℃; the design operating pressure is 4MPa, with a pressure fluctuation range of 3.8~4.2MPa; the diameter of the rotating hollow shaft is 150mm, the wall thickness is 20mm, and the rotation speed is 10r / min; the sealing requirement is limited to zero leakage, the continuous operating life is ≥12 months, and the total design life is ≥25 years; the rotary joint is installed in an outdoor open-air environment with an ambient temperature of -20℃~60℃.

[0036] According to the technical solution of the present invention, combined with the above-mentioned application scenario parameters, a symmetrical wedge-shaped sealing structure with high sealing performance is adopted, and the sealing surface of the rotating hollow shaft is selected as a symmetrical structure of cylindrical surface + inclined surface + elliptical surface (e.g. Figure 2 As shown, this is a symmetrical wedge-fitting sealing structure, wherein: the diameter of the cylindrical section is φ150mm, the surface roughness is Ra0.8μm, and the length of each cylindrical section is 20mm; the angle between the inclined section and the cylindrical section is 15°, the surface roughness is Ra0.8μm, and the length of each inclined section is 30mm; in the elliptical section, the major axis is 152mm, the minor axis is 150mm, the radius of curvature is 20mm, the surface roughness is Ra0.4μm, and the length of each elliptical section is 25mm; the overall tolerance of the sealing surface is ±0.03mm, and the coaxiality is ≤0.02mm.

[0037] The soft sealing packing assembly includes a first soft sealing packing ring 3, a second soft sealing packing ring 4, and a third soft sealing packing ring 5, all of which are made of flexible graphite and metal wire reinforced high-temperature soft sealing packing. The metal wire is made of 316L stainless steel with a content of 15%, and is suitable for high temperature of 560℃ and medium pressure of 4MPa. It is also equipped with flexible graphite-based self-leveling injectable soft sealing packing, which is resistant to high temperature of 600℃. The first soft-seal packing ring 3 is cylindrical, with an inner diameter of φ150mm, an outer diameter of φ180mm, and a height of 20mm. There are two of them, symmetrically arranged on both sides of the sealing structure, serving as an auxiliary seal. The second soft-seal packing ring 4 is inclined, with an angle of 15° between the inclined surface and the inner hole. It has an inner diameter of φ150mm, an outer diameter of φ180mm, and a height of 30mm. There are two of them, which mate with the inclined section of the rotating hollow shaft, serving as the primary seal. The third soft-seal packing ring 5 is elliptical, with an inner contact surface that perfectly matches the elliptical section of the rotating hollow shaft. It has an inner diameter of φ150mm, an outer diameter of φ180mm, and a height of 25mm. There are two of them, which mate with the elliptical section of the rotating hollow shaft, serving as the secondary seal. The overall tolerance of the packing rings is ±0.05mm, the end face parallelism is ≤0.03mm, the material density is 1.8g / cm³, and the resilience is ≥15% (under 560℃ conditions).

[0038] Supporting Figure 1 The general-purpose rotary joint base structure shown has a housing 1 made of Q345R alloy steel with an inner diameter of φ180mm and a wall thickness of 30mm. It features a packing installation groove with a depth matching the height of the packing rings. The bushing bearing assembly includes a first bushing bearing 2 and a second bushing bearing 8, both using high-temperature self-aligning roller bearings with a suitable temperature ≤600℃ and a rated dynamic load of 200kN, ensuring the coaxiality of the rotating hollow shaft. Three spacers 7, made of 304 stainless steel, have an outer diameter of φ178mm, an inner diameter of φ152mm, and a height of 10mm. They are positioned between the packing rings to evenly transmit the clamping force. The flange 9 is made of 304 stainless steel, and eight flange bolts 10 are grade 12.9 high-strength bolts. During use, the bolt preload is adjusted to 200N·m to ensure the initial compression of the packing rings is 10%.

[0039] Based on the working pressure of 4MPa, the mechanical parameters of the wedge fit are designed such that under the action of medium pressure, the axial displacement of the rotating hollow shaft is 0.1~0.2mm. This displacement increases the radial compression of the soft sealing packing ring by 5%~8%, and the extrusion pressure is increased to 3~4 times the initial pressure, ensuring a tight fit of the sealing surface.

[0040] The sealing structure assembly process in this embodiment is simple and requires no special equipment. The specific steps include: (1) Pretreatment: Clean the sealing surface of the rotating hollow shaft 6 and the packing installation groove of the housing 1 to remove oil and impurities, and apply high-temperature grease (high temperature resistant 600℃) to the sealing surface. (2) Component installation: Install the first bushing bearing 2 into the left side of the housing 1, and install the first soft sealing packing ring 3, the second soft sealing packing ring 4, the third soft sealing packing ring 5, and the spacer 7 in sequence. Then install the third soft sealing packing ring 5, the second soft sealing packing ring 4, and the first soft sealing packing ring 3 on the other side. Finally, install the second bushing bearing 8. (3) Inserting the shaft: Slowly insert the rotating hollow shaft 6 into the housing 1, ensuring that the sealing surface is free from impact, and adjust the coaxiality to ≤0.02mm; (4) Pre-tightening and fixing: Install flange 9 at both ends of housing 1, and pre-tighten evenly with flange bolts 10. Tighten the bolts in three stages, with each pre-tightening force being 60 N·m, 130 N·m, and 200 N·m, respectively, to ensure uniform compression of the packing ring. (5) Leak test: After assembly, perform a normal temperature and pressure air tightness test. Pass 0.6MPa compressed air and hold the pressure for 30 minutes. If there is no bubble leakage, the initial assembly is qualified. (6) Online injection: Before the equipment is started, injectable soft sealing filler is injected through the injection port of shell 1. The injection pressure is 0.8MPa until the filler overflows from the injection port, thus completing the seamless bonding of the sealing surface.

[0041] After the sealing structure of this embodiment was assembled, it underwent a 12-month continuous operation test on the high-temperature molten salt tank rotary joint of a parabolic trough solar thermal power generation system. During the test, the sealing leakage, rotational torque, and component wear were monitored in real time. The specific results are as follows: (1) Leakage: During the test period (12 months, cumulative operation of 8760h), there was no molten salt leakage in the sealing structure, and the leakage was 0mL / h, which completely achieved zero leakage, far exceeding the industry requirement of ≤0.1mL / h leakage standard; within the pressure fluctuation range of 3.8~4.2MPa, the sealing performance did not change at all, and the pressure self-reinforcing effect was significant. When the pressure rose to 4.2MPa, the tightness of the sealing surface was further improved, and there were no signs of leakage.

[0042] (2) Rotational torque: During the test, the average rotational torque of the hollow shaft was 18 N·m. Compared with the traditional cylindrical soft seal structure (rotational torque 28 N·m), the torque was reduced by 35.7%, the energy consumption of the equipment was reduced by about 30%, and there was no sudden increase in torque, indicating that the sealing surface was subjected to uniform force and there was no local jamming.

[0043] (3) Component wear: After 12 months of operation, the sealing structure was disassembled for testing. The average wear of the rotating hollow shaft sealing surface was 0.002 mm, and the average wear of the soft sealing packing ring was 0.05 mm. The wear was extremely small. Based on this wear rate, the continuous operating life of the sealing structure can reach more than 25 years, which meets the industry design requirements.

[0044] (4) High temperature resistance: Under the condition of the highest instantaneous temperature of 580℃, the sealing structure runs continuously for 72 hours without packing thermal shrinkage or thermal aging, and the sealing performance remains stable without leakage.

[0045] (5) Environmental adaptability: In the outdoor open environment, the sealing structure does not increase the sealing gap due to temperature changes, and the sealing performance remains stable, indicating that the thermal expansion and cold contraction of the packing can be compensated by the wedge fit structure.

[0046] Example 2: Application of high-temperature molten salt planar rotary joint sealing in a parabolic trough solar thermal power generation system (620℃ / 6MPa) This embodiment applies to a high-temperature molten salt bath planar rotary joint in a next-generation high-parameter parabolic trough solar thermal power generation system. This system employs higher operating temperatures and pressures to improve thermoelectric conversion efficiency. Specific application parameters include: The medium is a high-temperature molten salt mixture of potassium nitrate, sodium nitrate, and calcium nitrate (mass ratio 53:40:7); operating temperature: 620℃ (long-term stable operating temperature), maximum instantaneous temperature: 650℃; design working pressure: 6MPa, pressure fluctuation range: 5.8~6.2MPa; parameters of the rotating hollow shaft include shaft diameter of 200mm, wall thickness of 25mm, and rotation speed of 8r / min; sealing requirement: zero leakage, continuous operating life ≥18 months, design total life ≥30 years; the rotary joint is installed in an indoor enclosed environment with an ambient temperature of 10℃~40℃.

[0047] According to the technical solution of the present invention, and considering the above-mentioned high-parameter application scenarios, an asymmetric wedge-fit sealing structure is adopted. The directional thrust of the asymmetric structure reduces the rotational torque, and a curved surface fit with higher sealing performance is selected. The specific design is as follows: The sealing surface of the rotating hollow shaft adopts an asymmetrical structure of cylindrical surface + inclined surface + elliptical surface (e.g.) Figure 5As shown), this is a sealing structure consisting of two sets of asymmetrical wedge-shaped joints. Specific parameters include: the cylindrical section has a diameter of φ200mm, a surface roughness of Ra0.8μm, and a length of 25mm on each side; the angle between the inclined section and the cylindrical surface is 12° (a smaller angle increases the compressive force), the inclined surface roughness is Ra0.8μm, the left inclined surface length is 35mm, and the right inclined surface length is 30mm; in the elliptical section, the major axis of the left ellipse is 203mm, and the minor axis is 200mm. mm, radius of curvature is 25mm; the major axis of the right ellipse is 202mm, the minor axis is 200mm, and the radius of curvature is 20mm; the surface roughness of the ellipse is Ra0.4μm, and the length of each ellipse is 30mm; the overall tolerance of the sealing surface is ±0.02mm, and the coaxiality is ≤0.01mm; the asymmetrical structural design causes the rotating hollow shaft to generate a leftward directional thrust of 8kN, which is used to counteract the rightward thrust generated by the medium pressure and reduce the friction between the shaft shoulder and the bushing.

[0048] The soft-seal packing assembly includes a first soft-seal packing ring 3, a second soft-seal packing ring 4, and a third soft-seal packing ring 5. It is made of high-temperature soft-seal packing reinforced with flexible graphite, ceramic fiber, and Inconel 625 metal wire (20% metal wire content, 10% ceramic fiber content), suitable for ultra-high temperatures of 620℃ and high pressures of 6MPa. It is compatible with injectable soft-seal packing (flexible graphite-silicon carbide composite packing resistant to 650℃). Specific parameters include: For the first soft sealing packing ring 3, a cylindrical surface fit is adopted, with an inner diameter of φ200mm, an outer diameter of φ240mm, a height of 25mm, and a quantity of 2 rings, for auxiliary sealing, and the material has a resilience rate of ≥12% (under 620℃ conditions). For the second soft sealing packing ring 4, a bevel fit is adopted, with a bevel angle of 12° on the left and a bevel angle of 12° on the right. The inner diameter is φ200mm, the outer diameter is φ240mm, the left height is 35mm, the right height is 30mm, and there are 2 rings, which are primary main seals. For the third soft seal packing ring 5, an elliptical surface fit is adopted. The inner contact surface is an asymmetrical elliptical surface, which is perfectly matched with the elliptical surface section of the rotating hollow shaft. The inner diameter is φ200mm, the outer diameter is φ240mm, the height is 30mm, and there are 2 of them. It is a secondary main seal. The overall tolerance of the packing ring is ±0.04mm, the end face parallelism is ≤0.02mm, the material density is 1.9g / cm³, the high temperature resistance is ≥650℃, and the pressure resistance is ≥8MPa.

[0049] For the rotary joint base structure, the general-purpose rotary joint base structure shown in Figure 1 is used, and structural reinforcement is carried out for 6MPa high pressure. Specific parameters include: The housing 1 is made of 15CrMoR heat-resistant alloy steel, with an inner diameter of φ240mm and a wall thickness of 40mm. The packing installation groove is hardened to a hardness of HRC40~45. The bushing bearing assembly uses a high-temperature thrust self-aligning roller bearing, with an applicable temperature of ≤650℃, a rated dynamic load of 300kN, and a rated static load of 800kN. It can withstand the directional thrust of the asymmetric structure and the axial thrust of the medium pressure. The spacer 7 is made of Inconel 625 high-temperature alloy, with an outer diameter of φ238mm, an inner diameter of φ202mm, a height of 15mm, and a quantity of 3. It has high strength and high temperature resistance, ensuring uniform transmission of clamping force. The flange 9 is made of 15CrMoR. The flange bolts 10 are 10.9 grade high-temperature and high-strength bolts, with a quantity of 12. The bolt preload is adjusted to 300N·m, and the initial compression of the packing ring is 12%.

[0050] Based on the working pressure of 6MPa, the mechanical parameters of the "wedge" fit are designed as follows: under the action of medium pressure, the axial displacement of the rotating hollow shaft is 0.2~0.3mm, the radial compression of the soft sealing packing ring increases by 8%~10%, and the extrusion pressure is increased to 4~5 times the initial pressure, ensuring zero leakage under 6MPa high pressure; the directional thrust of the asymmetric structure offsets 70% of the axial thrust of the medium, reducing the end face friction between the shaft shoulder and the bushing by 70%.

[0051] The assembly process in this embodiment is based on that in embodiment 1, but adds sealing surface hardening treatment and pre-pressure aging treatment steps for high-parameter working conditions. The specific steps are as follows: (1) Pretreatment: Nitriding treatment is performed on the sealing surface of the rotating hollow shaft to increase the hardness to HRC55~60 and enhance wear resistance; all parts are cleaned and high-temperature solid grease (high temperature resistant 700℃) is applied to the sealing surface. (2) Component installation: Install the bushing bearing assembly, soft seal packing ring, and spacer in the order of Example 1 to ensure that the asymmetric packing ring corresponds to the asymmetric sealing surface of the rotating hollow shaft; (3) Inserting the shaft and adjusting the coaxiality: Insert the rotating hollow shaft and use a laser alignment instrument to adjust the coaxiality to ≤0.01mm to avoid shaft wobble; (4) Pre-tightening and fixing: The flange bolts are tightened in 4 stages, with pre-tightening forces of 80 N·m, 160 N·m, 240 N·m and 300 N·m respectively. After each tightening, the pressure is maintained for 10 minutes to ensure uniform compression of the packing ring. (5) Pre-compression aging treatment: The sealing structure is pre-compressed at room temperature at 30MPa for 24 hours, and then baked at 620℃ for 48 hours to allow the packing ring to complete thermal shrinkage and cold deformation in advance, so as to avoid packing deformation in actual operation. (6) Leak test: Perform the room temperature and pressure air tightness test (0.6MPa, no leakage for 30min) and the high temperature and high pressure water pressure test (620℃, 6.5MPa, pressure holding for 1h, no leakage). (7) Online injection: Injectable soft sealing filler is injected through the injection port at a pressure of 1.0 MPa to achieve seamless bonding of the sealing surface.

[0052] The sealing structure of this embodiment underwent 18 months of continuous operation testing (a total of 15,840 hours) in a high-parameter parabolic trough solar thermal power generation system. Comprehensive monitoring was conducted on leakage, rotational torque, component wear, and high-temperature and high-pressure resistance. Specific results are as follows: (1) Leakage: During the test, the sealing structure did not leak any high-temperature molten salt, and the leakage was 0 mL / h. Under the working conditions of pressure fluctuation of 5.8~6.2MPa and temperature fluctuation of 600~650℃, the sealing performance remained stable and the pressure self-reinforcing effect was significant. When the pressure rose to 6.2MPa and the temperature rose to 650℃, the sealing surface was more tightly fitted and there were no signs of leakage.

[0053] (2) Rotational torque: During the test, the average rotational torque of the hollow shaft was 25 N·m, which was 44.4% lower than that of the traditional hard seal structure under the same working conditions (rotational torque was 45 N·m). The directional thrust of the asymmetric structure effectively offset the axial thrust of the medium, and the end face friction between the shaft shoulder and the bushing decreased from 15 kN in the traditional structure to 4.5 kN, resulting in a significant reduction in wear.

[0054] (3) Component wear: After 18 months of operation, disassembly and inspection revealed that the average wear of the rotating hollow shaft sealing surface was 0.003 mm and the average wear of the soft sealing packing ring was 0.06 mm. Based on this wear rate, the continuous operating life of the sealing structure can reach more than 30 years, which meets the design requirements of the next generation of solar thermal power generation system.

[0055] (4) High temperature and high pressure resistance: Under extreme working conditions of 650℃ / 6.2MPa, the sealing structure can run continuously for 168 hours without pyrolysis or aging of the packing, and there is no gap in the sealing surface, maintaining zero leakage. After the machine is stopped and cooled to room temperature, it can be restarted and heated to 620℃. The sealing structure does not need to be readjusted and zero leakage can be achieved directly, with good start-stop adaptability.

[0056] (5) Long-term stability: During the test, the equipment underwent 36 start-up and shutdown operations. The sealing structure showed no sealing failure, the resilience of the packing remained stable, and the pressure self-reinforcing effect of the wedge fit structure did not decrease, indicating that the long-term stability of the sealing structure is excellent.

[0057] The above two embodiments are applications of high-temperature molten salt media in the field of concentrated solar power generation. The sealing structure of the present invention can also be applied to other high-temperature and medium-pressure conditions, such as: in the metallurgical industry, a 450℃ / 3MPa heat transfer oil rotary roller joint, using a symmetrical structure of cylindrical surface + inclined surface, such as... Figure 4 As shown, the soft-seal packing ring uses expanded vermiculite-based packing, achieving zero leakage and a continuous operating life of ≥6 months. In the paper industry, the 300℃ / 2MPa high-temperature steam rotary joint uses a symmetrical structure of cylindrical surface + arc surface, such as... Figure 3 As shown, the injectable soft sealing packing is compatible, enabling online repair with a leakage rate ≤0.05mL / h. In the food industry, the 180℃ / 1MPa high-temperature water medium rotary joint utilizes a simple cylindrical surface + inclined surface structure, resulting in low processing costs and a sealing effect that meets the hygiene requirements of the food industry, with no media leakage. In all application scenarios, the sealing structure of this invention achieves the core effect of pressure self-reinforcement, and features low processing and assembly difficulty, long service life, and conforms to the international classification requirements for soft packing dynamic seals, solving the technical challenges of traditional soft packing dynamic seals under high-temperature and medium-pressure conditions.

[0058] The apparatus and methods disclosed in the embodiments are described simply because they correspond to the methods disclosed in the embodiments. For relevant details, please refer to the method section.

[0059] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pressure self-reinforcing sealing structure for soft packing dynamic seals, applied to a rotating hollow shaft (6) for high-temperature and medium-pressure media, characterized in that, The device includes a rotating hollow shaft dynamic sealing surface and a soft sealing packing assembly that mates with the rotating hollow shaft dynamic sealing surface. The rotating hollow shaft dynamic sealing surface is provided with at least two sets of wedge-fit sealing structures. Each set of wedge-fit sealing structures is in the form of a cylindrical surface + inclined surface, a cylindrical surface + curved surface, or a cylindrical surface + inclined surface + curved surface, where the curved surface is an arc surface or an elliptical surface. The soft sealing packing assembly includes several soft sealing packing rings. The inner contact surface shape of the soft sealing packing rings that mates with the rotating hollow shaft dynamic sealing surface is the same as or similar to the shape of the rotating hollow shaft dynamic sealing surface. Under the action of assembly pressure and medium pressure, the soft sealing packing rings undergo compression deformation, thereby completely fitting with the rotating hollow shaft dynamic sealing surface to form a wedge fit. The extrusion force and radial compression effect of the rotating hollow shaft dynamic sealing surface on the soft sealing packing rings increase with the increase of the medium pressure.

2. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 1, characterized in that, The wedge-fit sealing structure can be symmetrical or asymmetrical. The asymmetrical wedge-fit sealing structure can generate a thrust to one side on the rotating hollow shaft. The thrust is used to reduce the friction between the shoulder of the rotating hollow shaft and the end face of the bushing.

3. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 1, characterized in that, The soft sealing packing assembly is also adapted to injectable soft sealing packing, which, after being injected, naturally forms a shape that is completely consistent with the dynamic sealing surface of the rotating hollow shaft and fits and seals.

4. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 1, characterized in that, The soft sealing packing ring is made of high-temperature soft sealing packing material of flexible graphite, expanded vermiculite or ceramic fiber, and is suitable for high-temperature and medium-pressure working environments with temperatures ≤700℃ and pressures ≤8MPa.

5. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 1, characterized in that, When applied to rotary joints with high working pressure and high sealing performance requirements, the dynamic sealing surface of the rotary hollow shaft is selected from a cylindrical surface + curved surface or a cylindrical surface + inclined surface + curved surface structure; when applied to rotary joints with low working pressure and low sealing performance requirements, the dynamic sealing surface of the rotary hollow shaft is selected from a cylindrical surface + inclined surface structure.

6. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 1, characterized in that, It also includes a rotary joint base structure, which includes a housing (1), a bushing bearing assembly, a spacer (7), a flange (9), and flange bolts (10). The bushing bearing assembly includes a first bushing bearing (2) and a second bushing bearing (8). The soft sealing packing assembly is disposed in the housing. The spacer is used to transmit assembly clamping force to the soft sealing packing ring. The flange and the flange bolts are used to axially fix the components in the housing. The bushing bearing assembly is used to support and position the rotating hollow shaft and withstand radial and axial external forces.

7. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 6, characterized in that, The soft sealing packing ring includes a first soft sealing packing ring (3), a second soft sealing packing ring (4), and a third soft sealing packing ring (5). The first soft sealing packing ring (3) has a cylindrical surface fit with the dynamic sealing surface of the rotating hollow shaft. The second soft sealing packing ring (4) has an inclined surface fit with the dynamic sealing surface of the rotating hollow shaft. The third soft sealing packing ring (5) has a curved surface fit with the dynamic sealing surface of the rotating hollow shaft. The wedge fit formed by the second soft sealing packing ring (4) and the third soft sealing packing ring (5) with the rotating hollow shaft is the main sealing fit structure. The first soft sealing packing ring (3) is the auxiliary sealing fit structure.

8. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 1, characterized in that, The number and circumferential arrangement of the wedge-fit sealing structures are adjusted according to the sealing requirements, shaft diameter, and working pressure of the rotary joint.

9. The pressure self-reinforcing sealing structure for soft packing dynamic seals according to claim 1, characterized in that, The high-temperature medium-pressure medium is high-temperature molten salt, heat transfer oil or water, and the structure is adapted to a working temperature range of 300℃~700℃ and a working pressure range of 0~8MPa.

10. The application of the pressure self-reinforcing sealing structure for soft packing dynamic sealing as described in any one of claims 1-9 in a high-temperature rotary joint for solar thermal power generation, wherein the application in solar thermal power generation includes the application of the pressure self-reinforcing sealing structure for soft packing dynamic sealing in a planar rotary joint suitable for flexible connection of a high-temperature molten salt tank in a parabolic trough solar thermal power generation system.

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