Screw compressor sealing structure and sealing method

Abstract

The application discloses a screw compressor sealing structure and sealing method, and belongs to the technical field of compressors.The sealing structure comprises a compressor shell, a rotor, a shaft sealing assembly and a sealing pressure reduction assembly.The rotor is supported in the compressor shell through bearings.The shaft sealing assembly is located in the compressor shell.The shaft sealing assembly comprises a front sealing part and a main sealing part which are sequentially sleeved on the outside of the rotor.The sealing pressure reduction assembly is sealingly arranged on the outside of the connection part of the front sealing part and the main sealing part.The sealing method applies the sealing structure to realize the sealing of the shaft end of the screw compressor.The sealing pressure reduction assembly is sealingly arranged on the outside of the main sealing part and the front sealing part, process gas leaked from the front sealing part is led out and buffered, the gas pressure before the main sealing part is effectively reduced, the sealing gas of the main sealing part can seal the leaked gas without a large pressure and a large amount, the air tightness is effectively improved, and the sealing difficulty is reduced.

Description

Technical Field

[0001] This application belongs to the field of screw compressor technology, specifically relating to a screw compressor sealing structure and sealing method. Background Technology

[0002] Dry screw compressors, as important gas handling equipment in the petroleum, chemical, and environmental protection fields, play a crucial role in the treatment and utilization of process gases. To maintain the operating efficiency and ensure the safety of dry screw compressors, it is necessary to reduce leakage of process gases during compression. In existing technology, shaft seals are used to prevent process gases from leaking from the journal to the bearing section. While existing shaft seals can seal screw compressors under normal operating conditions, their sealing strength is insufficient under high-speed, high-pressure-ratio conditions, leading to sealing problems in the screw compressor. Summary of the Invention

[0003] Technical Problem: This application provides a sealing structure and sealing method for a screw compressor, aiming to solve the problem that existing screw compressors are not easy to seal under high speed and high pressure ratio conditions.

[0004] Technical solution: To achieve the above objectives, the technical solution adopted in this application is as follows.

[0005] This application provides a screw compressor sealing structure, including:

[0006] Compressor housing;

[0007] The rotor is supported within the compressor housing by bearings;

[0008] A shaft sealing assembly, located inside the compressor housing, comprising a front sealing portion and a main sealing portion sequentially sleeved on the outside of the rotor;

[0009] A sealing pressure reduction assembly is provided on the outside of the connection between the front sealing part and the main sealing part.

[0010] In some embodiments, the sealing pressure reduction assembly includes:

[0011] An annular sealing cavity, the annular sealing cavity sealingly surrounds the outside of the connection between the front sealing part and the main sealing part;

[0012] The adapter channel is located inside the compressor housing and includes a first end and a second end opposite to each other, the first end being in communication with the annular sealing cavity.

[0013] In some embodiments, the air pressure on the side of the main sealing part away from the front sealing part is P1, the air pressure between the front sealing part and the rotor is P2, and the air pressure in the annular sealing cavity is P3, satisfying: P1 > P3, P2 > P3.

[0014] In some embodiments, the sealing pressure reduction assembly further includes an additional sealing cavity having an air inlet connected to the second end, and the additional sealing cavity communicating with the annular sealing cavity through the transition channel.

[0015] In some embodiments, the additional sealing cavity is located inside the compressor housing or outside the screw compressor.

[0016] In some embodiments, the air pressure in the additional sealing cavity is P4, satisfying: P3 > P4.

[0017] In some embodiments, the additional sealing cavity further includes an air outlet, which is connected to the inlet of the screw compressor via a return pipe.

[0018] In some embodiments, the gas pressure at the inlet of the screw compressor is P5, satisfying: P4 > P5.

[0019] In some embodiments, the annular sealing cavity has opposing first and second sidewalls along the axial direction of the rotor, the first sidewall being connected to the front sealing portion and the second sidewall being connected to the main sealing portion.

[0020] In some embodiments, the rotor includes a male rotor and a female rotor, the female rotor is surrounded by a first annular sub-sealing cavity, the male rotor is surrounded by a second annular sub-sealing cavity, and the first annular sub-sealing cavity communicates with the second annular sub-sealing cavity.

[0021] In some embodiments, the front sealing portion includes a low-pressure side front sealing portion and a high-pressure side front sealing portion, the main sealing portion includes a low-pressure side main sealing portion and a high-pressure side main sealing portion, the low-pressure side main sealing portion and the low-pressure side front sealing portion are arranged adjacent to each other, the high-pressure side main sealing portion and the high-pressure side front sealing portion are arranged adjacent to each other, and the sealing pressure reducing assembly is surrounded on the outer side of the connection between the low-pressure side front sealing portion and the low-pressure side main sealing portion and on the outer side of the connection between the high-pressure side front sealing portion and the high-pressure side main sealing portion.

[0022] A sealing method for a screw compressor, using the screw compressor sealing structure described in any of the foregoing embodiments, includes the following steps:

[0023] Gas enters the screw compressor;

[0024] During the compression process, the exhaust side of the screw compressor uses a pre-sealing part to initially seal and reduce the pressure of the process gas leaking between the pre-sealing part and the rotor.

[0025] After passing through the pre-sealing section, most of the process gas flows into the lower-pressure annular sealing cavity for buffering.

[0026] The leaked process gas is further transferred to an additional sealing chamber with a lower pressure using a transfer channel;

[0027] The leaked process gas in the additional sealing chamber is fed back to the screw compressor inlet through the return pipe to form a return flow.

[0028] In some embodiments, the screw compressor is a single-stage screw compressor or a multi-stage screw compressor unit. When the screw compressor is a multi-stage screw compressor unit, only the last stage screw compressor is provided with a sealing pressure reduction component and connected to the inlet of the first stage screw compressor through the return pipe, or each stage screw compressor is provided with the sealing pressure reduction component and connected to the inlet of the first stage screw compressor through the return pipe.

[0029] Beneficial Effects: Compared with the prior art, the embodiments of this application provide a screw compressor sealing structure, including a compressor housing, a rotor, a shaft seal assembly, and a sealing pressure reduction assembly; the rotor is supported in the compressor housing by bearings; the shaft seal assembly is located in the compressor housing, and the shaft seal assembly includes a front seal portion and a main seal portion sequentially sleeved on the outside of the rotor; the sealing pressure reduction assembly is sealed around the outside of the connection between the front seal portion and the main seal portion. This application utilizes the sealing pressure reduction assembly sealed around the outside of the main seal portion and the front seal portion to draw out and buffer the process gas leaking from the front seal portion, effectively reducing the gas pressure before the main seal portion. This allows the sealing gas in the main seal portion to seal the leaking gas without requiring a large pressure and volume, effectively improving airtightness and reducing sealing difficulty.

[0030] Compared with the prior art, the embodiments of this application also provide a shaft sealing method for a screw compressor. It is understood that the shaft sealing method for the screw compressor applies the sealing structure of any of the above embodiments, and therefore the shaft sealing method has all the technical features and technical effects of the sealing structure, which will not be repeated here. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the overall cross-sectional structure of a dry screw compressor provided in an embodiment of this application;

[0033] Figure 2 This is a schematic diagram of the arrangement structure of the low-pressure side shaft seal of a dry screw compressor sealing structure provided in an embodiment of this application;

[0034] Figure 3 This application provides a schematic diagram of the arrangement structure of the high-pressure side shaft seal of a dry screw compressor sealing structure.

[0035] Figure 4 A vertical cross-sectional view of a sealing structure for a dry screw compressor provided in this application embodiment;

[0036] Figure 5 A horizontal cross-sectional view of a sealing structure for a dry screw compressor provided in this application embodiment;

[0037] Figure 6 A schematic diagram of the process gas recirculation flow of a single-stage screw compressor in a shaft sealing method for a dry screw compressor provided in this application embodiment;

[0038] Figure 7 A schematic diagram of the single-recirculation process flow of a two-stage screw compressor unit in a shaft sealing method for a dry screw compressor provided in this application embodiment;

[0039] Figure 8 This is a schematic diagram of the multi-recirculation process flow of a two-stage screw compressor unit in a shaft sealing method for a dry screw compressor provided in an embodiment of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1-Compressor housing, 2-Rotor, 21-Male rotor, 22-Female rotor, 3-Shaft sealing assembly, 31-Front seal, 311-Low-pressure side front seal, 312-High-pressure side front seal, 32-Main seal, 321-Low-pressure side main seal, 322-High-pressure side main seal, 33-Gap, 4-Sealing pressure-reducing assembly, 41-Annular sealing cavity, 411-First sidewall, 412-Second sidewall, 413-First annular sub-sealing cavity, 414-Second annular sub-sealing cavity, 42-Transfer channel, 421-First end, 422-Second end, 43-Additional sealing cavity, 431-Inlet, 432-Outlet, 44-Return pipe, 5-High-pressure side bearing assembly, 6-Low-pressure side bearing assembly, 7-Synchronous gear, X-Axial, Y-Radial. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0043] In the description of this application, it should be understood that the terms "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, and "at least one" can mean one, two, or more, unless otherwise explicitly specified. In the description of this application, "perpendicular" means completely perpendicular to 90° or almost completely perpendicular, for example, the range of included angles from 80° to 100° is considered perpendicular. Similarly, "parallel" means completely parallel or almost completely parallel, for example, the range of completely parallel angles from 10° is considered parallel.

[0044] This application provides a screw compressor sealing structure. The following provides a detailed description of each structure. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments.

[0045] The applicant notes that dry screw compressors, as important gas handling equipment in the petroleum, chemical, and environmental protection fields, have played a crucial role in the treatment and utilization of process gases. Currently, adapting to a wider variety of process gases, increasing compressed gas volume, improving pressure ratio, optimizing multi-stage design, and further improving safety are important development directions for dry screw compressor design.

[0046] A dry screw compressor has five main components: rotor, housing, bearings, shaft seal, and synchronous gears. Its normal operation and functionality depend on these five components. In actual operation, to maintain the compressor's efficiency and ensure its safety, it is necessary to minimize gas leakage during the compression process. During normal operation, process gas leakage includes leakage from the high-pressure chamber to the low-pressure chamber through the leakage triangle and meshing line in the working section of rotor 2; leakage from the high-pressure chamber to the low-pressure chamber through the gap between the rotor 2 tooth tip and the compressor housing 1; and leakage at the journal through the gap between the shaft and the compressor housing 1 to the bearing section and the outside. The shaft seal assembly 3 prevents process gas leakage from the journal to the bearing section. Besides ensuring exhaust pressure and machine operating efficiency, preventing leakage of toxic, flammable, explosive, or corrosive process gases is also a crucial role of the shaft seal assembly 3 in ensuring compressor safety.

[0047] However, to meet more demanding operating conditions, high-speed, high-pressure-ratio single-stage compressors or multi-stage compressor units may experience sealing difficulties in the second stage or higher compressor stages. For example, due to the large pressure ratio requirements, in the highest-stage compressor of a multi-stage screw compressor unit, the gas at the high-pressure end journal possesses significant potential energy due to its high pressure and temperature, and also significant kinetic energy due to its high speed. After secondary acceleration through the end face gap, it can penetrate the gap between the shaft seal and the shaft in a very short time, causing the seal to fail to a certain extent and resulting in the leakage of a certain amount of process gas. This poses a significant safety hazard, especially for flammable, explosive, or toxic and harmful media.

[0048] To address this issue, several existing methods exist in the design of dry screw compressors: using double-end dry gas seals, which ensures minimal leakage of process gas to the shaft end, but the gas pressure entering the dry gas seal should not be too high, requiring a long pre-seal to reduce the pressure in advance. Furthermore, the double-end dry gas seal itself is relatively large, resulting in a space-consuming and costly shaft sealing system; using multi-stage carbon ring seals to gradually reduce leakage pressure, but carbon ring seals still exhibit some leakage, failing to guarantee absolute safety, and consuming a large amount of sealing gas; increasing the sealing gas pressure, using sealing gas with a pressure higher than that leaking into the balance chamber, can theoretically provide an effective seal, but consumes a large amount of sealing gas, and in certain situations, requires additional pressurization equipment, such as in ship cabins where space is even more limited.

[0049] In view of this, embodiments of this application provide a screw compressor sealing structure to overcome at least one of the above-mentioned technical problems.

[0050] Please see Figure 1This application provides a screw compressor sealing structure, including a compressor housing 1, a rotor 2, a shaft sealing assembly 3, and a sealing pressure reducing assembly 4. The rotor 2 is disposed inside the compressor housing 1, and the shaft sealing assembly 3 is sleeved on the rotor 2. The shaft sealing assembly 3 includes a front sealing part 31 and a main sealing part 32 sequentially sleeved on the outside of the rotor 2. The front sealing part 31 includes a low-pressure side front sealing part 311 and a high-pressure side front sealing part 312. The main sealing part 32 includes a low-pressure side main sealing part 321 and a high-pressure side main sealing part 322. The low-pressure side main sealing part 321 and the low-pressure side front sealing part 311 are arranged adjacent to each other, and the high-pressure side main sealing part 322 and the high-pressure side front sealing part 312 are arranged adjacent to each other. The sealing pressure reducing assembly 4 is provided around the outside of the connection between the low-pressure side front sealing part 311 and the low-pressure side main sealing part 321, as well as the outside of the connection between the high-pressure side front sealing part 312 and the high-pressure side main sealing part 322.

[0051] Please continue reading. Figure 1 Furthermore, the screw compressor of this application also includes a high-pressure side bearing assembly 5, a high-pressure side main seal 322, a high-pressure side front seal 312, a compressor housing 1, a rotor 2, a low-pressure side front seal 311, a low-pressure side main seal 321, a low-pressure side bearing assembly 6, and a synchronous gear 7.

[0052] The gas duct that compresses the process gas is formed by the compressor housing 1 and the rotor 2. The dry screw compressor has two rotors 2: a male rotor 21 and a female rotor 22. A synchronous, contactless transmission between the rotor surfaces is achieved via a synchronous gear 7. The axial and radial forces acting on the rotor 2 are supported by the high-pressure side bearing assembly 5 and the low-pressure side bearing assembly 6. The sealing system ensures the continuous normal operation of the screw compressor and avoids the risk of leakage of flammable, explosive, or toxic gases. In a typical arrangement of dry screw compressor applications, a double-end dry gas seal is used as the main sealing part, and a comb-tooth seal or 1-3 carbon rings are used as the pre-sealing part 31. For example, in the embodiments of this application, in a high-pressure ratio single-stage dry screw compressor or a two-stage or higher-level compressor in a multi-stage dry screw compressor unit, the high-pressure side pre-sealing part 312 uses a three-carbon ring seal, the low-pressure side pre-sealing part 311 uses a comb-tooth seal, and both the low-pressure side main sealing part 321 and the high-pressure side main sealing part 322 use dry gas seals.

[0053] It should be noted that the screw compressors involved in this application are all dry screw compressors, which do not involve oil seals, and therefore there will be no lubricating oil or any other liquids; the gas passages are all dry. Dry gas sealing mainly utilizes the sealing gas to provide a higher pressure than the gas pressure between the main seal and the pre-seal section, thereby preventing the process gas inside the screw compressor from leaking out.

[0054] In this embodiment, since the pre-sealing part 31 and the main sealing part 32 are two separate components, sequentially fitted onto the rotor 2, in the prior art, the pre-sealing part 31 and the main sealing part 32 are directly embedded in the compressor housing 1 and fit against the compressor housing 1. Although there is a gap 33 at the connection between the two, the process gas will not leak out from the connection. It will only exert pressure on the main sealing part 32 due to the higher gas pressure. If the pressure of the process gas is greater than the sealing gas pressure of the main sealing part 32, gas leakage will occur. Therefore, the requirements for dry gas sealing are high. In this application, a sealing pressure reducing component 4 is provided at the connection between the pre-sealing part 31 and the main sealing part 32. The process gas leaking from the pre-sealing part 31 is introduced into the sealing pressure reducing component 4 through the gap 33 at the connection between the pre-sealing part 31 and the main sealing part 32. This reduces the process gas pressure between the pre-sealing part 31 and the main sealing part 32, thus reducing the difficulty of dry gas sealing. Only a small amount of sealing gas is needed to achieve sealing.

[0055] For further details, please refer to the following: Figure 2 , Figure 3 , Figure 4 and Figure 5 In some embodiments, the sealing and pressure-reducing assembly 4 includes an annular sealing cavity 41, which surrounds the outside of the connection between the front sealing portion 31 and the main sealing portion 32. The annular sealing cavity 41 surrounds the outside of the connection between the front sealing portion 31 and the main sealing portion 32 and communicates with the gap 33 at the connection between the front sealing portion 31 and the main sealing portion 32. The volume of the annular sealing cavity 41 is much larger than the volume between the front sealing portion 31 and the main sealing portion 32. Thus, after the process gas leaks through the front sealing portion 31, it flows into the annular sealing cavity 41 through the gap 33 between the front sealing portion 31 and the main sealing portion 32. Because the volume of the process gas increases instantaneously upon entering the annular sealing cavity 41, the pressure and leakage rate decrease rapidly. For leaking process gas with higher pressure, the main sealing portion 32 only requires a smaller amount of low-pressure sealing gas to ensure no leakage at the compressor shaft end.

[0056] Furthermore, the air pressure on the side of the main sealing part 32 away from the front sealing part 31 is P1, the air pressure between the front sealing part 31 and the rotor 2 is P2, and the air pressure in the annular sealing cavity 41 is P3, satisfying: P1 > P3, P2 > P3.

[0057] It should be noted that the flow of gas from high pressure to low pressure without obstruction is a natural phenomenon and is actively accomplished. In other words, the low-pressure chamber can generate suction to draw high-pressure gas into the low-pressure chamber. In this application, the gas pressure P3 in the annular sealing cavity 41 is simultaneously lower than the gas pressure P2 between the pre-sealing part 31 and the rotor 2 and the gas pressure P1 of the main sealing part 32. This allows leaked process gas to flow smoothly into the annular sealing cavity 41 through the gap at the connection between the pre-sealing part 31 and the main sealing part 32 after passing through the pre-sealing part 31, instead of flowing towards the higher-pressure main sealing part 32.

[0058] The purpose of the sealing pressure reduction component 4 in this application is to reduce the pressure of the leaking process gas before the main sealing part 32, thereby enabling the main sealing part 32 to ensure no leakage at the compressor shaft end with only a small amount of sealing gas, thus reducing the sealing difficulty of the main sealing part 32. To achieve this goal, the volume of the annular sealing cavity 41 is larger than the volume of the gap 33 between the front sealing part 31 and the main sealing part 32. Initially, there is no leaking process gas in the annular sealing cavity 41. Therefore, the pressure in the annular sealing cavity 41 is lower than the leaking process gas pressure of the front sealing part 31 and also lower than the sealing gas pressure at the main sealing part 32. This ensures that the leaking process gas flows smoothly into the annular sealing cavity 41, reducing the pressure between the front sealing part 31 and the main sealing part 32, thereby reducing the sealing difficulty of the main sealing part 32.

[0059] For further information, please refer to [link / reference]. Figure 2 , Figure 3 , Figure 4 and Figure 5 In some embodiments, the sealed pressure-reducing assembly 4 further includes a transition channel 42 and an additional sealing cavity 43. The transition channel 42 is located within the compressor housing 1 and includes a first end 421 and a second end 422 opposite to each other. The first end 421 communicates with the annular sealing cavity 41. The additional sealing cavity 43 has an air inlet 431 connected to the second end 422, and the additional sealing cavity 43 communicates with the annular sealing cavity 41 through the transition channel 42.

[0060] Specifically, the additional sealing cavity 43 is connected to the annular sealing cavity 41 through the transition channel 42, which further increases the capacity of the sealing pressure reduction assembly 4, thereby further increasing the capacity to contain leaked gas and increasing the pressure drop. This further reduces the gas pressure between the pre-sealing part 31 and the main sealing part 32 when the process gas leaks, and further reduces the sealing difficulty of the main sealing part 32.

[0061] Furthermore, depending on design requirements, the additional sealing cavity 43 can be located either inside the compressor housing 1 or outside the screw compressor. Located inside the compressor housing 1, it makes the dry screw compressor more streamlined and doesn't occupy external space. Especially in environments with limited space, such as ship cabins, the internal placement of the additional sealing cavity 43 effectively reduces its impact on cabin space. Located outside the compressor housing 1, it allows for further expansion of the additional buffer cavity's volume, improving its pressure reduction capacity.

[0062] It should be noted that the auxiliary sealing cavity 43 is relatively small in volume compared to the compressor housing 1, but is very large in volume compared to the annular sealing cavity 41. The annular sealing cavity 41 and the auxiliary sealing cavity 43 are connected by the transition channel 42, which can draw out the process gas in the annular sealing cavity 41 and has a good pressure reduction capability.

[0063] Furthermore, the air pressure inside the additional sealing cavity 43 is P4, which satisfies: P3 > P4.

[0064] It should be noted that the additional sealing cavity 43 is mainly designed to further increase the volume of the sealing and pressure-reducing assembly, thereby improving its pressure-reducing capacity. In this embodiment, limiting the pressure P4 in the additional sealing cavity 43 to be less than the pressure P3 in the annular sealing cavity is to ensure a positive pressure drop between the additional sealing cavity 43 and the annular sealing cavity 41, allowing leaked process gas to flow autonomously from the annular sealing cavity 41 into the additional sealing cavity 43, thus achieving a gradual pressure reduction.

[0065] In some embodiments, the additional sealing cavity 43 further includes an air outlet 432, which is connected to the inlet of the screw compressor via a return pipe 44.

[0066] Furthermore, the gas pressure at the inlet of the screw compressor is P5, which satisfies: P4 > P5.

[0067] It should be noted that the pressure P5 at the inlet of the screw compressor is limited to be less than the pressure P4 in the auxiliary sealing chamber 43, so as to achieve a positive pressure drop from the auxiliary sealing chamber 43 to the inlet of the screw compressor, which can ensure that the leaked process gas flows smoothly from the auxiliary sealing chamber 43 along the return pipe 44 to the inlet of the screw compressor.

[0068] Specifically, the outlet 432 is used to continuously draw out the process gas leaking from the auxiliary sealing chamber 43. The inlet of the screw compressor is the point of lowest pressure in the screw compressor. The outlet 432 and the inlet of the screw compressor are connected via a return pipe 44, thus connecting the auxiliary sealing chamber 43 to the inlet of the screw compressor. Specifically, for a single-screw compressor, the auxiliary sealing chamber 43 is connected to the compressor inlet via the return pipe 44. For a multi-stage screw compressor, the auxiliary sealing chamber 43 in the second or higher-stage compressor is connected to the inlet pipe of the first-stage compressor via the return pipe 44. Therefore, the initial pressure in the auxiliary sealing chamber 43 is the same as the pressure at the inlet of the screw compressor, which is the lowest pressure in the compressor or compressor unit. The process gas leaking from the exhaust end face of rotor 2 enters the gap 33 between the pre-seal part 31 and the main seal part 32 after passing through the pre-seal. The annular sealing cavity 41 causes the space of the gap 33 in the radial Y direction to suddenly increase. The radial Y direction is perpendicular to the axial X direction, and the width of the annular sealing cavity 41 along the axial X direction is greater than the width of the gap 33. Thus, the gas flows through the gap 33 and into the annular sealing cavity 41, forming a vortex in the annular seal. This prevents most of the leaked process gas from continuing to move in a straight line along the axial X direction towards the main seal part 32, and instead turns it to make annular curved motion in the space of the annular sealing cavity 41, thereby reducing the gas pressure of the leaked process gas and preventing the process gas from continuing to leak into the main seal part 32 to a certain extent.

[0069] At this time, due to the lower air pressure in the auxiliary sealing chamber 43, a portion of the process gas in the annular sealing chamber 41 is drawn to the lower pressure area through the transfer channel 42 and enters the larger auxiliary sealing chamber 43. The pressure of this portion of process gas is further reduced, and axial leakage stops. During the continuous operation of the screw compressor, this portion of process gas gradually increases and is then transported back to the inlet of the screw compressor through the return pipe 44 connected to the inlet 431 of the auxiliary sealing chamber 43, without being discharged to the outside. It is always confined within the compressor's gas path system, avoiding safety hazards caused by the leakage of flammable and explosive process gas.

[0070] Additionally, it should be noted that the process gas in the auxiliary sealing chamber 43 is drawn out through the return pipe 44 to the screw compressor inlet with a lower pressure to continue working. As the process gas is continuously drawn out, the auxiliary sealing chamber 43 is always kept in a low-pressure environment, which can further continuously draw out the process gas in the annular sealing chamber 41, making the gas pressure in the annular sealing chamber 41 lower, thereby maintaining a continuous pressure reduction of the process gas after passing through the pre-sealing section 31.

[0071] Please refer to the following: Figure 1 , Figure 2 and Figure 3In some embodiments, the annular sealing cavity 41 has a first sidewall 411 and a second sidewall 412 opposite to each other along the axial direction of the rotor 2. The first sidewall 411 is connected to the front sealing part 31, and the second sidewall 412 is connected to the main sealing part 32.

[0072] Specifically, the first sidewall 411 is connected to the outer wall of the front sealing part 31, and the second sidewall 412 is connected to the outer wall of the main sealing part 32. On the one hand, this ensures that the annular sealing cavity 41 has a larger width in the axial direction X compared to the front sealing part 31 and the main sealing part 32, thereby ensuring that it has a better pressure reduction capability. On the other hand, since a bearing assembly is set at the end of the main sealing part 32 away from the front sealing part 31 in the axial direction X, the bearing assembly inevitably contains liquids such as lubricating oil. The connection between the second sidewall 412 and the outer wall of the main sealing part 32 ensures that the annular sealing cavity 41 does not come into contact with the bearing assembly or even the gap between the main sealing part 32 and the bearing assembly. This effectively prevents the lubricating oil in the bearing assembly from overflowing into the annular sealing cavity 41, and prevents the lubricating oil from depositing in the annular sealing cavity 41 and continuing to flow into the auxiliary sealing cavity 43 through the transfer channel 42, or even eventually flowing into the inlet of the screw compressor, affecting the working performance of the sealing pressure reduction assembly 4, or even contaminating the gas in the screw compressor.

[0073] In some embodiments, the rotor 2 includes a male rotor 21 and a female rotor 22. The female rotor 22 is surrounded by a first annular sub-sealing cavity 413, and the male rotor 21 is surrounded by a second annular sub-sealing cavity 414. The first annular sub-sealing cavity 413 and the second annular sub-sealing cavity 414 are in communication. Since the distance between the male rotor 21 and the female rotor 22 is fixed, the radial depth (Y) and axial width (X) of the annular sealing cavity 41 are correspondingly increased. This not only expands the volume but also allows the two sealed annular sub-sealing cavities to communicate when they intersect, further expanding their volume.

[0074] This application also provides a sealing method for a screw compressor, using the screw compressor sealing structure of any of the foregoing embodiments, comprising the following steps:

[0075] S1: Gas enters the screw compressor;

[0076] S2: During the compression process, the exhaust side of the screw compressor uses the pre-sealing part 31 to initially seal and reduce the pressure of the process gas leaking between the pre-sealing part 31 and the rotor 2.

[0077] S3: After passing through the pre-sealing section 31, most of the process gas flows into the low-pressure annular sealing cavity 41 for buffering;

[0078] S4: The leaked process gas is further transferred to the lower-pressure additional sealing chamber 43 using the transfer channel 42;

[0079] S5: The leaked process gas in the additional sealing chamber 43 is fed into the screw compressor inlet through the return pipe 44 to form a return flow.

[0080] In this embodiment, because the annular sealing cavity 41 is relatively low, the process gas, after passing through the pre-sealing part 31, is drawn into the annular sealing cavity 41 through the gap 33 between the pre-sealing part 31 and the main sealing part 32, forming a vortex. This effectively prevents most of the process gas from continuing its linear movement along the axial direction X towards the main sealing part 32, instead directing it to make a circular curved movement within the space of the annular sealing cavity 41, thereby reducing its pressure and preventing process gas leakage to a certain extent. Then, the process gas in the annular sealing cavity 41 is drawn into the lower-pressure auxiliary sealing cavity 43 through the transfer channel 42, achieving further pressure reduction of the process gas. This reduces the pressure within the annular sealing cavity 41, allowing the process gas leaking from the pre-sealing part 31 to continue to be drawn out. As more and more process gas accumulates in the auxiliary sealing cavity 43, it is then introduced into the lower-pressure screw compressor inlet through the return pipe 44, achieving process gas return to the screw compressor and preventing external discharge, thus avoiding safety hazards caused by process gas leakage.

[0081] In some embodiments, the screw compressor is a single-stage screw compressor or a multi-stage screw compressor unit. When the screw compressor is a multi-stage screw compressor unit, only the last stage screw compressor is provided with a sealing pressure reduction component 4 and connected to the inlet of the first stage screw compressor through a return pipe 44, or each stage screw compressor is provided with a sealing pressure reduction component 4 and connected to the inlet of the first stage screw compressor through a return pipe 44.

[0082] Specifically, such as Figure 6 The diagram shows the process gas recirculation flow when the present invention is applied to a single-stage screw compressor. At this time, on the exhaust side of the screw compressor, i.e., the high-pressure side, the outlet 432 of the additional sealing chamber 43 is connected to the recirculation pipe 44 via a flange or connector. The recirculation pipe 44 recirculates the leaked process gas after pressure balancing by the sealing pressure reduction assembly 4, and connects to the compressor inlet via a flange.

[0083] like Figure 7The diagram shows a single-recirculation process flow for the process gas when applied to a two-stage screw compressor. In this case, on the exhaust side of the second-stage compressor, the outlet 432 of the additional sealing chamber 43 is connected to the return pipe 44 via a flange or connector. The return pipe 44 recirculates the leaked process gas after pressure balancing by the sealing pressure reducing assembly 4, and connects to the inlet of the first-stage compressor via a flange. This process is suitable for applications where the total exhaust pressure is high and the compressor is designed as a two-stage unit. It uses the process gas at the inlet of the first-stage compressor, which has the lowest pressure, to balance the pressure of the sealing pressure reducing assembly 4 on the exhaust side of the second-stage compressor, where the pressure is higher and there is a risk of sealing issues.

[0084] like Figure 8 The diagram shows a multi-recirculation process flow diagram of the process gas when the present invention is applied to a two-stage screw compressor. In this case, the outlets 432 of the auxiliary sealing chambers 43 on the exhaust sides of both the first and second stage compressors are recirculated through recirculation pipes 44, allowing the leaked process gas from the sealing pressure reduction assembly 4 to flow back. Both are connected to the inlet of the first stage compressor via flanges. This process is suitable for applications where a two-stage compressor unit is designed and both stages have sealing risks at their exhaust pressures. It uses the process gas at the inlet of the first stage compressor, which has the lowest pressure, to simultaneously balance the pressure of the sealing pressure reduction assembly 4 on both the higher-pressure first-stage exhaust side and the higher-pressure second-stage exhaust side.

[0085] Furthermore, since this invention targets a process gas compressor, nitrogen must be introduced into the compressor's gas passage before starting the compressor. At this time, the air in the sealing pressure-reducing assembly 4 is discharged and filled with nitrogen. Subsequently, when starting the compressor to compress the process gas, leaking process gas and nitrogen (used as a sealing and isolating gas) continuously enter and mix within the sealing pressure-reducing assembly 4, then flow back through the pipeline. Upon shutdown, the introduction of process gas stops first, then the compressor stops, and finally the nitrogen supply is shut off. At this point, the sealing pressure-reducing assembly 4 is refilled with nitrogen. Throughout the entire process, there is no mixing of process gas and air within the sealing pressure-reducing assembly 4, fully adapting to the design of existing compressor systems.

[0086] Using the following specific embodiments as examples, a simulation is performed on the secondary 178.5 sealing cavity of a marine BOG compressor unit to further illustrate and demonstrate the technical solution of this application.

[0087] In one embodiment, the annular sealing cavity 41 has a width a of 12 mm in the axial direction X and a depth b of 5 mm in the radial direction Y.

[0088] In the second embodiment, the annular sealing cavity 41 has a width a of 25 mm in the axial direction X and a depth b of 10 mm in the radial direction Y. An additional sealing cavity 43 with a larger volume is added, and the additional sealing cavity 43 is connected to the annular sealing cavity 41 through a plurality of 16 mm diameter transition channels 42.

[0089] Operating Condition 1: In the 14,000 cubic meter bunkering vessel project, unit 178.5 serves as the second stage of the unit, with an intake pressure of 0.35 GPaA, an intake temperature of 40℃, an exhaust pressure of 0.84 GPaA, and an exhaust temperature of approximately 150℃.

[0090] Taking the exhaust end of the male rotor 21 as an example, assume that the gas pressure leaking from the exhaust end face is 0.85 GPaA and the temperature is 160℃.

[0091] The additional sealing cavity 43 is connected to the intake pipe of the first-stage compressor via a flange and a return pipe 44, with a pressure of 0.101 GPaA and a temperature of -30℃.

[0092] The corresponding simulation result is as follows:

[0093]

[0094] Operating Condition 2: In the 174,000 cubic meter transport ship project, 178.5 serves as the second stage of the unit, with an intake pressure of 0.5 GPaA, an intake temperature of 40℃, an exhaust pressure of 1.3 GPaA, and an exhaust temperature of approximately 185℃.

[0095] Taking the exhaust end of the male rotor 21 as an example, assume that the gas pressure leaking from the exhaust end face is 1.4 GPaA and the temperature is 200℃.

[0096] The additional sealing cavity 43 is connected to the intake pipe of the first-stage compressor via a flange and a return pipe 44, with a pressure of 0.11 GPaA and a temperature of -30℃.

[0097] The corresponding simulation result is as follows:

[0098]

[0099] Operating Condition 3: 178.5 is the second stage of the unit, with an intake pressure of 0.45 GPaA, an intake temperature of 40℃, an exhaust pressure of 0.65 GPaA, and an exhaust temperature of approximately 110℃.

[0100] Taking the exhaust end of the male rotor 21 as an example, assume that the gas pressure leaking from the exhaust end face is 0.7 GPaA and the temperature is 110℃.

[0101] The additional sealing cavity 43 is connected to the intake pipe of the first-stage compressor via a flange and a return pipe 44, with a pressure of 0.11 GPaA and a temperature of -30℃.

[0102] The corresponding simulation result is as follows:

[0103]

[0104] Operating Condition 4: 178.5 is the first stage of the unit, with an intake pressure of 0.1 GPaA, an intake temperature of -30℃, an exhaust pressure of 0.38 GPaA, and an exhaust temperature of approximately 105℃.

[0105] Taking the exhaust end of the male rotor 21 as an example, assume that the gas pressure leaking from the exhaust end face is 0.38 GPaA and the temperature is 100℃.

[0106] The additional sealing cavity 43 is connected to the intake pipe of the first-stage compressor via a flange and a return pipe 44, with a pressure of 0.11 GPaA and a temperature of -30℃.

[0107] The corresponding simulation result is as follows:

[0108]

[0109] A comparison of the various embodiments shows that the annular sealing cavity 41 can reduce the pressure and temperature of the leaked process gas at the rotor exhaust end. Furthermore, by adding an additional sealing cavity 43 to the annular sealing cavity 41, the pressure and temperature of the leaked process gas at the rotor exhaust end can be further reduced.

[0110] In summary, the screw compressor sealing structure and method of this application, by setting a sealing pressure reducing component 4 at the connection between the main sealing part 32 and the pre-sealing part 31, can lead the leaked process gas outward, effectively reducing the gas pressure between the pre-sealing part 31 and the main sealing part 32, thereby reducing the gas pressure requirement of the sealing gas in the main sealing part 32 and reducing the sealing difficulty of the main sealing part 32. Furthermore, by setting a return pipe 44 to connect the sealing pressure reducing component 4 to the compressor inlet, the sealing pressure reducing component 4 can be connected to a low-pressure environment, which can greatly increase the volume of the sealing pressure reducing component 4 and effectively reduce the gas pressure of the leaked gas. Therefore, the sealing gas of the main seal does not need a large pressure and volume to seal the leaked gas, allowing it to return to the inlet through the pipe. Therefore, this application, without adding other equipment, uses a general shaft seal type and normal sealing gas volume to achieve the technical goal of solving the process gas leakage problem of high-speed, high-pressure-ratio screw compressors, ensuring safety while saving compressor operating costs.

[0111] The present application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of the present application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A screw compressor seal structure, characterized by, include: Compressor housing (1); Rotor (2), which is supported in the compressor housing (1) by bearings; Shaft sealing assembly (3), the shaft sealing assembly (3) is located inside the compressor housing (1), the shaft sealing assembly (3) includes a front sealing part (31) and a main sealing part (32) sequentially sleeved on the outside of the rotor (2), and there is a gap (33) between the front sealing part (31) and the main sealing part (32). A sealing pressure reducing assembly (4) includes an annular sealing cavity (41), a transfer channel (42), an additional sealing cavity (43), and a return pipe (44). The annular sealing cavity (41) is sealed around the outside of the connection between the front sealing part (31) and the main sealing part (32) and communicates with the gap (33). The volume of the annular sealing cavity (41) is larger than the volume of the gap (33). The transfer channel (42) is located inside the compressor housing (1). The additional sealing cavity (43) includes an air inlet (431) and an air outlet (432). The air inlet (431) communicates with the annular sealing cavity (41) through the transfer channel (42). The air outlet (432) is connected to the inlet of the screw compressor through the return pipe (44).

2. Screw compressor seal structure according to claim 1, characterized in that The air pressure on the side of the main sealing part (32) away from the front sealing part (31) is P1, the air pressure between the front sealing part (31) and the rotor (2) is P2, and the air pressure in the annular sealing cavity (41) is P3, satisfying: P1 > P3, P2 > P3.

3. Screw compressor seal structure according to claim 2, characterized in that The transfer channel (42) includes a first end (421) and a second end (422) opposite to each other. The first end (421) is connected to the annular sealing cavity (41), and the air inlet (431) is connected to the second end (422).

4. The screw compressor sealing structure according to claim 3, characterized in that, The air pressure in the additional sealing cavity (43) is P4, which satisfies: P3 > P4.

5. The screw compressor sealing structure according to claim 4, characterized in that, The gas pressure at the inlet of the screw compressor is P5, which satisfies the condition: P4 > P5.

6. The screw compressor sealing structure according to claim 1, characterized in that, The annular sealing cavity (41) has a first sidewall (411) and a second sidewall (412) opposite each other along the axial direction (X) of the rotor (2). The first sidewall (411) is connected to the front sealing part (31), and the second sidewall (412) is connected to the main sealing part (32).

7. The screw compressor sealing structure according to claim 1, characterized in that, The rotor (2) includes a male rotor (21) and a female rotor (22). The female rotor (22) is surrounded by a first annular sub-sealing cavity (413), and the male rotor (21) is surrounded by a second annular sub-sealing cavity (414). The first annular sub-sealing cavity (413) and the second annular sub-sealing cavity (414) are in communication.

8. The screw compressor sealing structure according to claim 1, characterized in that, The front sealing part (31) includes a low-pressure side front sealing part (311) and a high-pressure side front sealing part (312). The main sealing part (32) includes a low-pressure side main sealing part (321) and a high-pressure side main sealing part (322). The low-pressure side main sealing part (321) and the low-pressure side front sealing part (311) are arranged adjacent to each other. The high-pressure side main sealing part (322) and the high-pressure side front sealing part (312) are arranged adjacent to each other. The sealing pressure reducing assembly (4) is provided around the outer side of the connection between the low-pressure side front sealing part (311) and the low-pressure side main sealing part (321) and the outer side of the connection between the high-pressure side front sealing part (312) and the high-pressure side main sealing part (322).

9. A sealing method for a screw compressor, characterized in that, The method, employing the screw compressor sealing structure as described in any one of claims 1-8, comprises the following steps: Gas enters the screw compressor; During the compression process, the exhaust side of the screw compressor uses the pre-sealed part (31) to initially seal and reduce the pressure of the process gas leaking between the pre-sealed part (31) and the rotor (2); After passing through the pre-sealing section (31), most of the process gas flows into the annular sealing cavity (41) with lower pressure for buffering; The leaked process gas is further transferred to the additional sealing chamber (43) with a lower pressure using the transfer channel (42). The process gas in the additional sealing chamber (43) is fed into the screw compressor inlet through the return pipe (44) to form a return flow.

10. The screw compressor sealing method according to claim 9, characterized in that, The screw compressor is a single-stage screw compressor or a multi-stage screw compressor unit; when the screw compressor is a multi-stage screw compressor unit, only the last stage screw compressor is equipped with a sealing pressure reduction component (4) and is connected to the inlet of the first stage screw compressor through the return pipe (44), or, each stage screw compressor is equipped with the sealing pressure reduction component (4) and is connected to the inlet of the first stage screw compressor through the return pipe (44).

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