A graded labyrinth seal system for nitrogen pressurization of a fan shaft

Abstract

This application relates to a graded labyrinth seal system for nitrogen pressurization of a fan shaft, belonging to the technical field of fan equipment sealing. It includes at least two labyrinth seal systems located inside the shaft seal. The two labyrinth seal systems are arranged axially along the shaft, with an annular chamber surrounding the shaft between adjacent systems. An annular receiving chamber, called a gas distribution chamber, surrounds the annular chamber, with a radius larger than the annular chamber's radius. The gas distribution chamber has an inlet connected to a pressurized nitrogen source. The volume of the gas distribution chamber is at least three times the volume of the annular chamber. At least six pipes, evenly arranged around the shaft, connect the outer side of the annular chamber to the inner side of the gas distribution chamber. This application, by connecting at least two labyrinth seal systems in series, forms multiple sealing barriers. Combined with the stable nitrogen pressure from the gas distribution chamber, this effectively improves the reliability of the seal and ensures stable sealed operation of the fan shaft.

Description

Technical Field

[0001] This application relates to the technical field of fan equipment sealing, and in particular to a fan equipment sealing system. Background Technology

[0002] As a general-purpose mechanical device in industrial production, the core function of a fan is to drive the impeller through the rotation of its shaft, thereby conveying, pressurizing, or exhausting gas, providing stable gas power support for the production process, and ensuring the normal operation of various industrial devices. In industrial systems, the operating efficiency and reliability of the fan are directly related to the continuity and stability of the overall production process; therefore, high requirements are placed on the performance and fitting precision of each component of the fan.

[0003] During operation, the fan shaft needs to rotate continuously to drive the impeller. To prevent gas leakage from the shaft and to avoid external impurities affecting the internal operation of the equipment, a special shaft seal is usually fitted around the outer circumference of the shaft. In existing technology, a corresponding sealing structure is configured inside the shaft seal to achieve a seal. Currently, a common approach is to install a single labyrinth seal system inside the shaft seal. This non-contact structural design reduces frictional losses during shaft rotation, while the structure's own throttling effect prevents gas leakage.

[0004] Regarding the aforementioned technologies, the existing single labyrinth seal system used on the inner side of the fan shaft seal can only form a single sealing barrier. When facing high pressure conditions inside the fan or long-term operation scenarios, the throttling resistance of the single labyrinth seal system is limited, making it difficult to continuously resist the leakage pressure of the gas. This can easily lead to a gradual increase in gas leakage, eventually resulting in seal failure. This cannot meet the long-term requirements for fan seal reliability in industrial production, and thus affects the continuous and stable operation of the fan. Utility Model Content

[0005] In view of the shortcomings of the existing technology, one of the objectives of this utility model is to provide a graded labyrinth seal system for nitrogen pressurization of a fan shaft.

[0006] This application provides a graded labyrinth seal system for nitrogen-pressurized fan shafts, which adopts the following technical solution:

[0007] The staged labyrinth seal system for nitrogen pressurization of the fan shaft includes at least two labyrinth seal systems, which are located inside the shaft seal;

[0008] Two labyrinth sealing systems are arranged back and forth along the axis of rotation, and an annular chamber surrounding the axis of rotation is provided between two adjacent labyrinth sealing systems;

[0009] The annular chamber is surrounded by an annular receiving chamber, the radius of which is larger than that of the annular chamber. This annular receiving chamber is called the gas distribution chamber.

[0010] The gas distribution chamber is provided with an air inlet, which is connected to a pressurized nitrogen gas source;

[0011] The volume of the gas distribution chamber is more than three times the volume of the annular chamber;

[0012] The outer side of the annular cavity is connected to the inner side of the gas distribution chamber by at least six pipes evenly arranged around the rotating shaft.

[0013] By adopting the above technical solution, at least two labyrinth sealing systems are arranged axially along the shaft, and an annular chamber for filling with nitrogen is added between adjacent labyrinth sealing systems. Compared with a single labyrinth sealing system, this method can achieve a sealing effect by injecting high-pressure nitrogen into the annular chamber between multiple labyrinth systems to form an air curtain, based on the throttling and sealing of a single labyrinth sealing system. The sealing is achieved as follows: the first labyrinth sealing system initially throttles and depressurizes the gas, reducing the pressure and velocity of the leaking gas to achieve a preliminary seal; the leaking gas is blocked by the air curtain in the annular chamber, preventing the insufficiently depressurized gas from directly entering the next labyrinth sealing system; and finally, a small amount of gas that breaks through the air curtain is throttled and intercepted again by the downstream labyrinth sealing system, thereby achieving a staged seal.

[0014] Meanwhile, the gas distribution chamber surrounding the annular cavity with a volume more than three times that of the annular cavity can prevent insufficient or absent gas supply in certain areas of the annular cavity when nitrogen is directly injected into it. This avoids localized weak seals caused by insufficient nitrogen in certain areas of the annular cavity. The gas distribution chamber also serves as a nitrogen pressure stabilization and buffer space. When external nitrogen is injected, the gas distribution chamber buffers and stabilizes the pressure, and then the nitrogen is evenly delivered to the annular cavity through pipes evenly arranged around the rotating shaft. This ensures uniform nitrogen distribution in the annular cavity and avoids localized seal failures in the graded labyrinth sealing system.

[0015] Preferably, the labyrinth sealing system includes an annular groove surrounding the rotating shaft, and a single labyrinth sealing system includes at least two annular grooves, which are arranged sequentially along the axial direction of the rotating shaft, with a spacing of 5 to 10 mm between two adjacent annular grooves along the axial direction of the rotating shaft.

[0016] By adopting the above technical solution, a single labyrinth seal system contains at least two annular grooves arranged sequentially along the axis of rotation, ensuring that each labyrinth seal system can generate a basic throttling function, so that the gas can undergo multiple expansion and throttling processes when passing through a single labyrinth seal system, thereby enhancing the sealing capability of the single labyrinth seal system.

[0017] The spacing between adjacent annular grooves along the shaft axis is limited to 5–10 mm to ensure that each annular groove within a single labyrinth seal system can stably achieve a sealing effect and is compatible with nitrogen-assisted sealing. If the spacing is less than 5 mm, the flow resistance of nitrogen between the annular grooves adjacent to the annular chamber will be too high, affecting the sealing effect of the nitrogen gas curtain. If the spacing is greater than 10 mm, the space between adjacent annular grooves will be too large, and the leaked gas will experience pressure rebound between the two annular grooves. As a result, when the next annular groove intercepts the leak, the gas pressure has partially recovered, the throttling attenuation effect is greatly weakened, and a stable pressure gradient cannot be formed, thereby reducing the sealing performance of a single labyrinth seal system.

[0018] Preferably, the axial cross-section of the annular groove along the rotating shaft is trapezoidal, with the upper base of the trapezoid located away from the rotating shaft and the lower base of the trapezoid located close to the rotating shaft. The length of the upper base of the trapezoid is 5–10 mm, and the length of the lower base is 15–25 mm.

[0019] By adopting the above technical solution, the annular groove has a trapezoidal upper base at the part away from the rotating shaft and a trapezoidal lower base at the part close to the rotating shaft, forming an annular groove spatial structure that is narrower away from the rotating shaft and wider close to the rotating shaft. When gas leaks along the rotating shaft axis towards the outside of the sealing area, when it enters the wide space of the annular groove close to the rotating shaft from the narrow gap between adjacent annular grooves, it will experience a violent expansion due to the sudden expansion of the cross-section, resulting in a decrease in flow velocity and a significant drop in pressure. Conversely, when the gas flows from the wide space of the annular groove to the narrow gap of the next adjacent annular groove, it will experience a strong throttling due to the contraction of the channel cross-section. This trapezoidal cross-section ensures that the gas undergoes both expansion and throttling processes within each annular groove, significantly improving the sealing performance.

[0020] Preferably, two adjacent labyrinth sealing systems arranged front and back are respectively provided with half of the annular chamber, the gas distribution chamber and the pipe at the adjacent locations;

[0021] After the two labyrinth sealing systems are connected, the half-structures of the two labyrinth sealing systems are spliced ​​together to form the annular chamber, the gas distribution chamber, and the pipeline.

[0022] By adopting the above technical solution, two adjacent labyrinth sealing systems arranged front and back can reduce the processing difficulty of the overall labyrinth sealing system by setting half-structures of annular chambers, gas distribution chambers and pipes at adjacent locations and then connecting them to form a complete structure. In addition, during the assembly stage, it is only necessary to precisely connect the two labyrinth sealing systems with half-structures along the axis of rotation, which improves the convenience of assembly operations. At the same time, when a problem occurs in a certain labyrinth sealing system or a local structure, the corresponding component can be disassembled individually for repair or replacement, reducing maintenance costs.

[0023] Preferably, a one-way valve is provided on the outside of the shaft seal, one end of the one-way valve is connected to the air inlet, and the end of the one-way valve away from the air inlet is connected to a pressurized nitrogen source.

[0024] By adopting the above technical solution, the one-way valve limits the flow direction of nitrogen gas, which can effectively prevent the high-pressure nitrogen gas inside the gas distribution chamber and the labyrinth seal system from leaking in the reverse direction along the air inlet when the pressure of the external pressurized nitrogen gas source is unexpectedly reduced or interrupted. This avoids the risk of leakage of the medium inside the fan caused by the sudden loss of pressure of the gas source, which would cause the labyrinth seal system to lose its active positive pressure support instantly.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. Set up at least two labyrinth sealing systems arranged axially along the shaft, and add an annular chamber for filling with nitrogen between adjacent labyrinth sealing systems. Compared with a single labyrinth sealing system, it can form a gas curtain by injecting high-pressure nitrogen into the annular chamber between multiple labyrinth systems to achieve a preliminary seal, based on the throttling seal of a single labyrinth sealing system. The first labyrinth sealing system initially throttles and depressurizes the gas, reducing the pressure and velocity of the leaking gas to achieve a preliminary seal. The leaking gas is blocked by the gas curtain in the annular chamber, preventing the gas that has not been sufficiently depressurized from directly entering the next labyrinth sealing system. Finally, a small amount of gas that breaks through the gas curtain is throttled and intercepted again by the downstream labyrinth sealing system, thereby achieving a staged seal.

[0027] Meanwhile, the gas distribution chamber surrounding the annular chamber has a volume more than three times that of the annular chamber. This prevents insufficient or absent gas supply in certain areas of the annular chamber when nitrogen is directly injected into it, thus avoiding weak local seals caused by insufficient nitrogen in certain areas of the annular chamber. The gas distribution chamber also serves as a nitrogen pressure stabilization and buffer space. When external nitrogen is injected, the gas distribution chamber buffers and stabilizes the pressure, and then the nitrogen is evenly delivered to the annular chamber through pipes evenly arranged around the rotating shaft. This ensures uniform nitrogen distribution in the annular chamber and avoids local seal failure in the graded labyrinth sealing system.

[0028] 2. Each labyrinth seal system contains at least two annular grooves arranged sequentially along the axis of rotation, ensuring that each labyrinth seal system can generate a basic throttling function, allowing the gas to undergo multiple expansion and throttling processes as it passes through a single labyrinth seal system, thereby enhancing the sealing capability of the single labyrinth seal system.

[0029] The spacing between adjacent annular grooves along the shaft axis is limited to 5–10 mm to ensure that each annular groove within a single labyrinth seal system can stably achieve a sealing effect and is compatible with nitrogen-assisted sealing. If the spacing is less than 5 mm, the flow resistance of nitrogen between the annular grooves adjacent to the annular chamber will be too high, affecting the sealing effect of the nitrogen gas curtain. If the spacing is greater than 10 mm, the space between adjacent annular grooves will be too large, and the leaked gas will experience pressure rebound between the two annular grooves. As a result, when the next annular groove intercepts the leak, the gas pressure has partially recovered, the throttling attenuation effect is greatly weakened, and a stable pressure gradient cannot be formed, thereby reducing the sealing performance of a single labyrinth seal system.

[0030] 3. The annular groove has a trapezoidal upper base at the point away from the rotating shaft and a trapezoidal lower base at the point closer to the rotating shaft, forming an annular groove spatial structure that is narrower away from the rotating shaft and wider closer to the rotating shaft. When gas leaks axially towards the outside of the sealing area, it enters the wider space of the annular groove close to the rotating shaft from the narrow gap between adjacent annular grooves. Due to the sudden expansion of the cross-section, it undergoes a violent expansion, resulting in a decrease in flow velocity and a significant drop in pressure. Conversely, when the gas flows from the wider space of the annular groove to the narrow gap of the next adjacent annular groove, it undergoes a strong throttling due to the contraction of the channel cross-section. This trapezoidal cross-section ensures that the gas undergoes both expansion and throttling processes within each annular groove, significantly improving the sealing performance. Attached Figure Description

[0031] Figure 1 This is a front view of an embodiment of the present application showing the installation positions of the shaft seal and the check valve;

[0032] Figure 2 for Figure 1 The cross-sectional view along AA shows the internal structure of the staged labyrinth seal system for nitrogen pressurization of the fan shaft;

[0033] Figure 3 for Figure 2 The enlarged view of section B shows the cross-sectional structure of the annular groove.

[0034] Reference numerals in the attached drawings: 1. Shaft seal; 2. Labyrinth seal system; 3. Annular chamber; 4. Gas distribution chamber; 5. Air inlet; 6. Check valve; 7. Annular groove. Detailed Implementation

[0035] The following is in conjunction with the appendix Figure 1 -Appendix Figure 3 This application will be described in further detail.

[0036] This application discloses a graded labyrinth seal system for nitrogen pressurization of a fan shaft.

[0037] Reference Figure 1 and Figure 2A graded labyrinth seal system for nitrogen pressurization of a fan shaft includes at least two labyrinth seal systems 2. The labyrinth seal systems 2 are located inside the shaft seal 1 and provide a non-contact seal for the shaft. Depending on the sealing pressure requirements, three or more labyrinth seal systems 2 can be provided. In the graded labyrinth seal system for nitrogen pressurization of the fan shaft disclosed in this embodiment, two labyrinth seal systems 2 are used, and the two labyrinth seal systems 2 are arranged back and forth along the shaft axis. An annular chamber 3 surrounding the shaft is provided between two adjacent labyrinth seal systems 2, and the annular chamber 3 is also located inside the shaft seal 1.

[0038] An annular chamber 3 is surrounded by an annular receiving chamber, the radius of which is larger than that of the annular chamber 3. This annular receiving chamber is called the gas distribution chamber 4, and its volume is more than three times that of the annular chamber 3. The gas distribution chamber 4 is provided with an air inlet 5, which is connected to a pressurized nitrogen source. The inner side of the gas distribution chamber 4 passes through the annular chamber 3, and is connected to at least six pipes evenly arranged around the rotating shaft. In the staged labyrinth seal system for nitrogen pressurization of the fan shaft disclosed in this embodiment, the volume of the gas distribution chamber 4 is four times that of the annular chamber 3, and there are 12 pipes evenly arranged around the rotating shaft.

[0039] Two adjacent labyrinth sealing systems 2 arranged front to back each other are respectively provided with half-structures of annular chamber 3, gas distribution chamber 4 and pipe at their adjacent locations. After the two labyrinth sealing systems 2 are docked, the half-structures of the two labyrinth sealing systems 2 are spliced ​​together to form a complete annular chamber 3, gas distribution chamber 4 and pipe. Specifically, on the inner side of the shaft seal 1, two adjacent labyrinth sealing systems 2 arranged front to back along the axis of rotation each have half-structures of annular chamber 3, gas distribution chamber 4 and pipe prefabricated at their adjacent ends near each other. These half-structures are integrally molded with the corresponding labyrinth sealing system 2, and the contours and dimensions of each half-structure are mutually adapted to ensure precise matching when the two labyrinth sealing systems 2 are docked. When the two labyrinth sealing systems 2 are assembled and connected along the axis of rotation, the half-structure of the annular chamber 3 on one labyrinth sealing system 2 and the half-structure of the annular chamber 3 on the other labyrinth sealing system 2 are exactly spliced ​​together to form a complete annular chamber 3 surrounding the axis of rotation. At the same time, the half-structures of the gas distribution chambers 4 on the two labyrinth sealing systems 2 are spliced ​​together to form a complete annular receiving chamber, i.e., the gas distribution chamber 4. The half-structures of the pipes on the two labyrinth sealing systems 2 are also spliced ​​together to form a complete pipe.

[0040] Furthermore, a one-way valve 6 is provided on the outside of the shaft seal 1. One end of the one-way valve 6 is connected to the air inlet 5 of the gas distribution chamber 4, and the end of the one-way valve 6 away from the air inlet 5 is connected to a pressurized nitrogen source. The flow direction of the one-way valve 6 is unidirectional, from the outside of the shaft seal 1 to the inside of the gas distribution chamber 4. This one-way valve 6 can effectively prevent reverse leakage of nitrogen inside the gas distribution chamber 4 when there are pressure fluctuations or interruptions in the external nitrogen supply, ensuring the stability of the nitrogen seal and improving the system's anti-interference capability.

[0041] Reference Figure 2 and Figure 3 The labyrinth seal system 2 includes an annular groove 7 surrounding the rotating shaft. The annular groove 7 is formed inside the shaft seal 1. Each labyrinth seal system 2 includes at least two annular grooves 7, which are arranged sequentially along the axial direction of the rotating shaft. The distance between two adjacent annular grooves 7 is 5–10 mm, meaning the distance between two adjacent annular grooves 7 along the axial direction of the rotating shaft is 5–10 mm. When the distance between two adjacent annular grooves 7 is too small, the flow resistance of gas between the adjacent annular grooves 7 will be too large; when the distance between two adjacent annular grooves 7 is too large, it will weaken the sealing effect of a single labyrinth seal system 2. In this embodiment, the distance between two adjacent annular grooves 7 is 5 mm.

[0042] The annular groove 7 has a trapezoidal cross-section along the rotating shaft. The part of the annular groove 7 away from the rotating shaft is the upper base of the trapezoid, and the part of the annular groove 7 close to the rotating shaft is the lower base of the trapezoid. The length of the upper base of the trapezoid is less than the length of the lower base. Specifically, the length of the upper base of the trapezoid is 5-10 mm, and the length of the lower base is 15-25 mm. In this embodiment, the length of the upper base of the trapezoid is 5 mm, and the length of the lower base is 15 mm. The shorter length of the upper base of the trapezoid makes the space of the annular groove 7 wider near the rotating shaft and narrower away from the rotating shaft. When gas enters the annular groove 7 along the rotating shaft, the sudden expansion of the gap in the annular groove 7 causes expansion and decompression. When the gas is about to leave the annular groove 7, the contraction of the gap in the annular groove 7 causes throttling and pressurization. With multiple annular grooves 7, the sealing performance is further improved.

[0043] The implementation principle of this application embodiment is as follows:

[0044] When the blower is operating, at least two labyrinth systems are connected in series, forming multiple sealing barriers, which greatly improves the reliability of the seal. Simultaneously, pressurized nitrogen is injected into the inlet 5 of the gas distribution chamber 4 through the one-way valve 6 outside the shaft seal 1. The nitrogen is stored and buffered within the gas distribution chamber 4. Because the volume of the gas distribution chamber 4 is larger than that of the annular chamber 3, the gas distribution chamber 4 effectively absorbs and stabilizes any pressure fluctuations that may occur in the nitrogen. The pressure-stabilized nitrogen is then smoothly delivered to the annular chamber 3 between the two labyrinth sealing systems 2 through 12 pipes evenly distributed around the shaft, thus forming a stable and evenly distributed 360-degree annular air curtain around the shaft. This further prevents the leakage of the internal medium of the blower.

[0045] When a small amount of internal medium from the blower passes through the labyrinth seal system 2 along the shaft axis, it sequentially passes through multiple annular grooves 7 with specific trapezoidal cross-sections. Each time the gas enters a wider annular groove 7 from a narrow gap, it expands and depressurizes; then, just before flowing into the next narrow gap, it is pressurized again due to throttling. After multiple depressurization and pressurization cycles, the leakage rate and pressure of the gas are greatly reduced, ultimately forming a dynamically balanced seal with the externally injected nitrogen, thus achieving a highly efficient and long-term stable seal for the blower shaft.

[0046] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A step labyrinth seal system for a fan shaft pressurized with nitrogen, comprising a labyrinth seal system (2) located inside a shaft seal (1), characterized in that, Includes at least two labyrinth sealing systems (2); Two labyrinth sealing systems (2) are arranged back and forth along the axis of rotation, and an annular chamber (3) surrounding the axis of rotation is provided between two adjacent labyrinth sealing systems (2); The annular chamber (3) is surrounded by an annular receiving chamber, the radius of which is larger than that of the annular chamber (3). This annular receiving chamber is called the gas distribution chamber (4). The gas distribution chamber (4) is provided with an air inlet (5), and the air inlet (5) is connected to a pressurized nitrogen gas source; The volume of the gas distribution chamber (4) is more than three times the volume of the annular chamber (3); The outer side of the annular chamber (3) is connected to the inner side of the gas distribution chamber (4), and at least 6 pipes are evenly arranged around the rotating shaft.

2. The fan shaft nitrogen pressurized stepped labyrinth seal system of claim 1, wherein, The labyrinth sealing system (2) includes an annular groove (7) surrounding the rotating shaft. Each labyrinth sealing system (2) includes at least two annular grooves (7), and the annular grooves (7) are arranged sequentially along the axial direction of the rotating shaft. The distance between two adjacent annular grooves (7) along the axial direction of the rotating shaft is 5 to 10 mm.

3. The fan shaft nitrogen pressurized stepped labyrinth seal system of claim 2, wherein, The annular groove (7) has a trapezoidal cross section along the axis of rotation. The part of the annular groove (7) away from the axis of rotation is the upper base of the trapezoid, and the part of the annular groove (7) close to the axis of rotation is the lower base of the trapezoid. The length of the upper base of the trapezoid is 5-10 mm, and the length of the lower base of the trapezoid is 15-25 mm.

4. The fan shaft nitrogen pressurized stepped labyrinth seal system of claim 1, wherein, Two adjacent labyrinth sealing systems (2) are arranged in front and behind, and the annular chamber (3), the gas distribution chamber (4) and the pipe half structure are respectively set at the adjacent locations; After the two labyrinth sealing systems (2) are connected, the half-structures of the two labyrinth sealing systems (2) are spliced ​​together to form the annular chamber (3), the gas distribution chamber (4) and the pipeline.

5. The fan shaft nitrogen pressurized stepped labyrinth seal system of claim 1, wherein, The shaft seal (1) is provided with a one-way valve (6) on the outside. One end of the one-way valve (6) is connected to the air inlet (5), and the end of the one-way valve (6) away from the air inlet (5) is connected to a pressurized nitrogen source.

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