Centrifugal compressor and centrifugal water chilling unit

Abstract

The invention relates to a compressor and an air conditioner, and belongs to the technical field of air conditioner compressors. The compressor comprises a shell, a main shaft, a motor, a first impeller, a second impeller, a backflow device and a sealing structure; wherein the main shaft is rotationally connected into the shell; the motor drives the spindle to rotate; the first impeller is coaxially connected to the main shaft; the second impeller is coaxially connected to the main shaft, and the second impeller and the first impeller are arranged at intervals; the second impeller is positioned in the shell; the backflow device is fixed in the shell and located between the first impeller and the second impeller. The sealing structure comprises a ring body and turbine blades, and the ring body is rotationally connected to the shell. The turbine blades are arranged on one side of the ring body and located on the inner side of the backflow device. A flow path is formed in the shell, and the turbine blades of the sealing structure are located in the flow path. According to the sealing structure, the turbine blades are arranged in the flow path on the inner side of the backflow device and rotate passively with backflow device outlet airflow pre-rotation as power, the inlet flow field of the second impeller is optimized by consuming pre-rotation, and the acting efficiency of the second impeller is improved.

Description

Technical Field

[0001] This application relates to the technical field of air conditioning compressors, and more particularly to a centrifugal compressor and a centrifugal chiller unit. Background Technology

[0002] Air conditioning systems utilize compressors to compress refrigerant. In multi-stage tandem centrifugal compressors, the uniformity of the inlet flow field of the secondary impeller directly affects the overall energy efficiency. To improve the working efficiency of the secondary impeller, a return flow device is typically installed before the secondary impeller to rectify and guide the inlet airflow. Leakage is reduced and aerodynamic losses are decreased by incorporating a gas-sealing tooth structure at the gap between rotating and stationary components. Existing technologies employ a tandem return flow device structure, which reduces gas separation through the tandem turbine blade arrangement, improves the turbine blade deswirl effect, reduces flow losses, and enhances return flow device efficiency. Another approach involves an active jet return flow device structure. This structure uses small holes in the suction surface of the return flow device turbine blades to expel air, eliminating the low-speed, low-energy zone formed on the suction surface, reducing airflow mixing losses, preventing secondary impeller inlet distortion, and thus improving compressor operating efficiency.

[0003] However, in the above-mentioned existing technical solutions, the reflux rectifier design and the gas seal tooth sealing structure are independent of each other and do not achieve effective coupling between the two. This results in the inability to fully utilize the pre-swirling airflow at the reflux outlet while optimizing the uniformity of the flow field at the inlet of the secondary impeller and the effect of suppressing gap leakage. As a result, the overall aerodynamic loss is difficult to further reduce, and the improvement of compressor energy efficiency is limited. Summary of the Invention

[0004] This invention at least partially solves one of the technical problems in the related art.

[0005] Therefore, this application aims to provide a compressor and air conditioner in which the sealing structure places the second blade in the airflow channel inside the first return valve, and passively rotates it with the pre-swirl of the airflow at the outlet of the first return valve as the driving force. This not only optimizes the inlet flow field of the second impeller and improves its working efficiency by consuming the pre-swirl, but also suppresses leakage in the static gap by means of dynamic sealing effect. No additional energy input is required, and the flow channel rectification and gap sealing coupling are realized, which effectively reduces the aerodynamic losses of the multi-stage centrifugal compressor and improves energy efficiency and operational stability.

[0006] To achieve the above objectives, the present invention provides a centrifugal compressor comprising: A main shaft, which is rotatably connected within the housing; The motor drives the main shaft to rotate; A first impeller is connected to the main shaft; The second impeller is connected to the main shaft and is spaced apart from the first impeller; A first reflux device is connected to the main shaft; The first reflux device includes a first blade, which is disposed on one side of the first reflux device; The second return valve is located inside the first return valve; The second return valve includes: A ring body, which is rotatably connected to the housing; The second blade is disposed on one side of the annulus and is located on the side facing the first reflux device; The first reflux device and the second reflux device are located between the first impeller and the second impeller; A diffuser channel is located between the first impeller and the first return flow device; An airflow channel is formed by the first return valve, the second return valve, and the second impeller, and the first blade and the second blade are located in the airflow channel.

[0007] In some embodiments, the gas / liquid in the airflow channel drives the second return valve to rotate as it passes through the second blade.

[0008] In some embodiments, the inner peripheral wall of the ring body is provided with threads; the helical direction of the threads is the same as the rotation direction of the second reflux device; the threads are close to the end peripheral wall of the second impeller.

[0009] In some embodiments, the second impeller includes a plurality of circumferentially spaced second blades; the thread is located near the outer edge of each second blade.

[0010] In some embodiments, multiple second blades are arranged at circumferential intervals along the annulus, and the spacing between any two adjacent turbine blades is the same.

[0011] In some embodiments, the reflux device includes a plurality of first blades, and the third blades are arranged circumferentially; in the airflow channel, the liquid / gas in the airflow channel first passes through the first blades and then through the second blades.

[0012] In some embodiments, a plurality of first blades and a plurality of second blades are staggered in the circumferential direction.

[0013] In some embodiments, the outer peripheral wall of the ring body and the inner wall of the housing are sealed and rotatably connected by a bearing.

[0014] This application also provides a centrifugal chiller unit, wherein the centrifugal chiller unit includes the centrifugal compressor described above.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the compressor according to an embodiment of this application; Figure 2 This is a front view of a compressor according to an embodiment of this application; Figure 3 yes Figure 2 A cross-sectional view along the AA direction; Figure 4 This is a schematic diagram of the sealing structure portion of the compressor according to an embodiment of this application; Figure 5 This is a front view of the sealing structure portion of a compressor according to an embodiment of this application; Figure 6 yes Figure 5 Cross-sectional view along the BB direction; Figure 7 This is an exploded view of the sealing structure portion of the compressor according to an embodiment of this application; Figure 8 This is a cross-sectional view of the sealing structure of a compressor according to an embodiment of this application; Figure 9 This is a cross-sectional view of the reflux device of a compressor according to an embodiment of this application; Figure 10 This is a schematic diagram of the sealing structure of a compressor according to an embodiment of this application.

[0017] In the above figures: 100, housing; 200, main shaft; 300, motor; 400, first impeller; 500, second impeller; 600, reflux device; 601, baffle; 602, third blade; 700, sealing structure; 701, ring; 702, turbine blade; 703, thread. Detailed Implementation

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0020] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0021] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0022] The present invention will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0023] In this application, the compressor includes a housing, a main shaft, a motor, a first impeller, and a second impeller. The motor drives the main shaft to rotate, which in turn drives the first and second impellers located inside the housing to rotate. The first impeller pressurizes the returning gas and liquid for the first time and delivers them to the second impeller, which then pressurizes the gas and liquid a second time and outputs them.

[0024] In the following, embodiments of this application will be described in detail with reference to the accompanying drawings.

[0025] Referring to all the accompanying drawings, in an illustrative embodiment of the compressor and air conditioner of the present invention, the compressor includes: a housing 100, a main shaft 200, a motor 300, and a first impeller 400. The main shaft 200 is rotatably connected within the housing 100. The motor 300 drives the main shaft 200 to rotate. The first impeller 400 is coaxially connected to the main shaft 200; the first impeller 400 is located within the housing 100. The motor 300 drives the first impeller 400 to rotate via the main shaft 200, and the first impeller 400 pressurizes and compresses the returning gas / liquid.

[0026] In some embodiments, the compressor further includes a second impeller 500, which is coaxially connected to the main shaft 200 and spaced apart from the first impeller 400; the second impeller 500 is located within the housing 100. The second impeller 500 is also driven by a motor 300 via the main shaft 200. The second impeller 500 further pressurizes the gas / liquid pressurized by the first impeller 400.

[0027] In some embodiments, the compressor further includes a first reflux device 600, which is fixed inside the housing 100. The first reflux device 600 is used to guide the flow field, adapt the power, and coordinate the sealing, thus ensuring the efficient operation of the entire machine.

[0028] In some embodiments, the compressor further includes a second reflux device 700, which includes an annulus 701 and a second blade 702. The annulus 701 is rotatably connected to the housing 100. The second blade 702 is disposed on one side of the annulus 701 and is located on the side facing the first reflux device 600.

[0029] In some embodiments, the first reflux 600 and the second reflux 700 are located between the first impeller 400 and the second impeller 500.

[0030] In some embodiments, a diffuser channel is formed within the housing 100, and the diffuser channel is located between the first impeller 400 and the first return valve 600.

[0031] In some embodiments, an airflow channel is formed within the housing 100, and the first return valve 600, the second return valve 700, and the second impeller 500 form the airflow channel, with the first blade 602 and the second blade 702 located within the airflow channel.

[0032] In this application, the compression of refrigerant by a compressor is used as an example, but it is not limited to other gases / liquids.

[0033] In this application, the second blade 702 is located inside the first return flow device 600 and within the airflow channel. This structure utilizes the pre-swirl of the airflow at the outlet of the first return flow device 600 as a power source. When the refrigerant flows through the second blade 702, it drives the entire second return flow device 700 to rotate passively. On one hand, the rotation of the second blade 702 consumes and reduces the degree of pre-swirl at the outlet of the first return flow device 600, converting the kinetic energy existing in the form of pre-swirl into the mechanical energy of the turbine. This reduces the pre-swirl of the airflow entering the second impeller 500, making the inlet flow field of the second impeller 500 more uniform, reducing flow separation and mixing losses, and improving the working efficiency of the second impeller 500.

[0034] On the other hand, the rotation of the second reflux valve 700 drives the ring body 701 to rotate synchronously. Utilizing the dynamic sealing effect at the side gap between the ring body 701 and the second impeller 500, leakage at the stationary gap is further suppressed, reducing leakage flow losses from the high-pressure side to the low-pressure side. This second reflux valve 700 requires no external energy input and is completely passively driven, achieving a coupled design of flow channel rectification optimization and gap sealing leakage suppression. This effectively reduces the overall aerodynamic losses of the multi-stage centrifugal compressor, improves the compressor's energy efficiency and operational stability, and is also simple and reliable in structure.

[0035] Understandably, the casing 100 has an inlet and an outlet, with the first impeller 400 located near the inlet and the second impeller 500 near the outlet. The inlet provides a stable path for the refrigerant, allowing the airflow to smoothly enter the first impeller 400 for initial compression; the outlet efficiently discharges the high-pressure refrigerant after compression by the two impellers, ensuring the continuity of fluid circulation throughout the machine.

[0036] In some embodiments, the direction from the first impeller 400 toward the second impeller 500 is the compressor's suction direction.

[0037] In some embodiments, the refrigerant is ensured to rotate the sealing structure 700 when it passes through the second blade 702.

[0038] Specifically, the second blade 702 is in the shape of an arc plate, and the line connecting the two ends of the arc plate is set at an angle to the direction of gas / liquid flow in the flow path, so as to ensure that the refrigerant can drive the second return valve 700 to rotate when passing through the second blade 702.

[0039] In some embodiments, the inner peripheral wall of the ring 701 is provided with a thread 703; along the suction direction, the helical direction of the thread 703 is the same as the rotation direction of the second return valve 700; the thread 703 is fitted onto the second impeller 500. Specifically, the thread 703 is close to the end peripheral wall of the second impeller 500. The helical direction of the thread 703 is the same as the rotation direction of the sealing structure 700 and it is fitted onto the second impeller 500. This design allows the thread 703 on the inner peripheral wall of the ring 701 to generate a pumping effect when the sealing structure 700 rotates under the drive of the refrigerant pre-swirling airflow, pushing the airflow at the gap back towards the direction of the refrigerant's arrival, resisting the pressure difference of the second impeller 500, and reducing leakage.

[0040] This method creates a dynamic sealing force that actively resists pressure differences, effectively suppressing leakage of high-pressure gas from the second impeller 500 side to the low-pressure side. The threaded 703 structure works in conjunction with the second blade 702. While the second blade 702 reduces pre-swirl to optimize the inlet flow field, the threaded 703 utilizes the same rotational power to further reduce leakage losses, achieving a dual-function coupling of rectification and sealing. Compared to traditional fixed gas seal teeth that passively reduce leakage through labyrinth throttling, the rotating threaded 703 seal in this solution significantly improves the sealing effect without increasing system complexity, reduces aerodynamic losses and efficiency degradation caused by leakage, improves the compressor's operational stability and overall energy efficiency under varying operating conditions, and maintains structural compactness and manufacturing economy.

[0041] It is worth noting that thread 703 is not connected to the second impeller 500. Thread 703 serves a guiding function for airflow / liquid and does not play a connecting role.

[0042] Understandably, since the first impeller 400, the second impeller 500, and the second reflux device 700 in this application all need to rotate, their structures are all shaft-like structures. In addition, the first reflux device 600 needs to guide the flow path, and the first reflux device 600 is also annular in structure.

[0043] In some embodiments, the second impeller 500 includes a plurality of circumferentially spaced third blades; a thread 703 is located near the outer edge of each third blade. The positions of the thread 703 and the third blades are further defined to ensure that the thread 703 is close to the edge of the second impeller 500, ensuring that the pumping airflow force generated by the rotation of the thread 703 can reverse the refrigerant, thereby preventing refrigerant leakage from the high-pressure side to the low-pressure side at the edge. This prevents refrigerant from flowing out from the edge of the third blades, ensuring that the refrigerant can be pushed towards the center of the second impeller 500 by the airflow reversed by the thread 703, so that the refrigerant flows out pressurized through the gaps between the third blades. This improves the interstage efficiency and overall energy efficiency of the compressor. This design makes full use of structural space, achieving better sealing while maintaining a compact compressor layout, contributing to improved performance stability and reliability of the compressor over a wide operating range.

[0044] In some embodiments, the thread 703 can be a single thread 703 or multiple threads 703.

[0045] It is understood that the thread 703 employs a multi-blade structure, but these blades are relatively thin and also guide airflow / liquid flow. Their principle is the same as that of this application, and they can also be considered as one type of the aforementioned multiple threads 703. Therefore, they fall within the scope of protection of this application.

[0046] In some embodiments, multiple second blades 702 are arranged at circumferential intervals along the annulus 701, with any two adjacent second blades 702 having the same spacing. This uniformly circumferentially distributed arrangement of the second blades 702 ensures that the sealing structure 700 experiences more balanced forces when driven by refrigerant, resulting in smooth rotation without significant vibration and avoiding eccentric loads and mechanical wear caused by blade asymmetry. The uniformly spaced blades can also more effectively capture the energy of the circumferentially distributed pre-swirling airflow at the outlet of the first return flow 600, improving energy conversion efficiency and allowing the turbine to more effectively reduce the degree of pre-swirling at the outlet. This improves the axisymmetry and uniformity of the inlet flow field of the second impeller 500, reducing additional losses caused by flow distortion.

[0047] Meanwhile, the uniform blade distribution helps stabilize the overall rotational speed of the second reflux unit 700, making the associated sealing effect more predictable and reliable. This design, without increasing structural complexity, improves the operational smoothness and durability of the passive rotating structure, further ensuring the optimized coupling effect of flow channel rectification and gap sealing, and effectively enhancing the overall aerodynamic performance and long-term operational reliability of the compressor.

[0048] In some embodiments, the first return flow device 600 includes a plurality of first blades 602, which are spaced circumferentially. In the flow path, the refrigerant first passes through the first blades 602 and then through the second blades 702. This design allows the refrigerant to undergo preliminary rectification and guidance by first passing through the first blades 602 of the first return flow device 600, forming an airflow with a certain pre-swirl angle. Subsequently, this pre-swirl airflow enters the second blades 702 as a driving energy source. The rectification effect of the first blades 602 provides a stable pre-swirl power input to the turbine, enabling the second blades 702 to adaptively adjust their speed according to the pre-swirl magnitude under operating conditions, achieving passive energy recovery and pre-swirl reduction. The greater the pre-swirl, the higher the turbine speed, and the stronger the pre-swirl reduction effect, thereby dynamically optimizing the uniformity of the inlet flow field of the second impeller 500.

[0049] This sequential flow order ensures coordination between turbine drive and rectification optimization, making the rotation of the second return valve 700 more reliable. Simultaneously, the synergy between the first blade 602 and the second blade 702 further reduces flow losses. This structure enables more refined interstage flow field management, improving the compressor's adaptability and energy efficiency under different loads.

[0050] In some embodiments, a plurality of first blades 602 and a plurality of second blades 702 are staggered in the circumferential direction.

[0051] In some embodiments, the first reflux 600 includes a baffle 601, which is annular and sleeves the main shaft 200. The baffle 601 is rotatably and sealingly connected to the main shaft 200. The two sides and outer peripheral wall of the baffle 601 are spaced apart from the housing 100 to form a section of a flow path. A first blade 602 is located on the side of the baffle 601 facing the second impeller 500. This baffle 601 structure effectively separates the interstage flow path, guiding the refrigerant to flow along a predetermined path. Simultaneously, its rotatable and sealed connection with the main shaft 200 reduces axial leakage. The first blade 602, located on the side of the baffle 601 facing the second impeller 500, brings the rectification effect closer to the inlet of the second impeller 500, further improving the guiding accuracy and pre-swirl control effect of the inlet airflow.

[0052] The flow path formed by the baffle 601 and the housing 100 ensures a smooth transition of the refrigerant to the second blade 702, providing uniform pre-swirl drive for the turbine. This design enhances the flow field guiding function of the first return flow 600, making the pre-swirl reduction by the second blade 702 more effective. The uniformity of the inlet flow field of the second impeller 500 is significantly improved, while the sealing connection of the baffle 601 helps suppress axial leakage channel losses. Overall, this improves the orderliness of interstage flow organization, reduces aerodynamic losses, and enhances the compressor's efficiency and operational stability.

[0053] In some embodiments, the first impeller 400 includes a plurality of fourth blades, which are spaced circumferentially and the distance between any two adjacent fourth blades is the same. When the first impeller 400 rotates, the first blades drive the refrigerant into the housing 100 and compress the refrigerant.

[0054] In some embodiments, the fourth blade is attached to the baffle 601 on the side facing the second impeller 500. This allows the refrigerant passing through the fourth blade to move radially along the baffle 601. The refrigerant moves past the edge of the baffle 601 to the side of the baffle 601 facing the second impeller 500. After being guided and slowed down by the first blade 602, the refrigerant moves to the second blade 702, where it is further slowed down and drives the second return valve 700 to rotate. Then, the refrigerant is further pressurized by the third blade before being output.

[0055] In some embodiments, the outer peripheral wall of the ring 701 is rotatably connected to the inner wall of the housing 100 via a bearing seal. The bearing further defines the rotatable connection between the outer peripheral wall of the ring 701 and the inner wall of the housing 100. This bearing connection provides low-friction rotatable support for the ring 701 while offering a reliable radial seal to prevent leakage of external gas flow. The use of bearings allows the second return valve 700 to rotate smoothly under refrigerant pre-swirl drive, reducing mechanical resistance losses and ensuring effective conversion and reduction of pre-swirl by the second blade 702, as well as stable dynamic sealing performance driven by the ring 701. The bearing seal connection also isolates moving and stationary parts, reducing wear risk and improving the long-term reliability of the second return valve 700. This design, while ensuring smooth passive rotation, maintains the sealing integrity of the compressor's internal flow path, further assisting the second blade 702 in optimizing the inlet flow field of the second impeller 500 and reducing gap leakage, effectively reducing overall aerodynamic losses and improving the compressor's energy efficiency, durability, and ease of maintenance.

[0056] Furthermore, the bearings are self-lubricating ceramic bearings. The use of self-lubricating ceramic bearings provides low-friction, highly reliable rotational support for the ring 701 of the second return converter 700, eliminating the need for an additional oil circuit system, simplifying the overall structure and reducing maintenance costs.

[0057] Furthermore, this application also provides a compressor, which includes a housing 100, a main shaft 200, a motor 300, and a first impeller 400. The main shaft 200 is rotatably connected within the housing 100. The motor 300 drives the main shaft 200 to rotate. The first impeller 400 is coaxially connected to the main shaft 200 and is located within the housing 100. The motor 300 drives the first impeller 400 to rotate via the main shaft 200, and the first impeller 400 pressurizes and compresses the returning gas / liquid.

[0058] In some embodiments, the compressor further includes a second impeller 500, which is coaxially connected to the main shaft 200 and spaced apart from the first impeller 400; the second impeller 500 is located within the housing 100. The second impeller 500 is also driven by a motor 300 via the main shaft 200. The second impeller 500 further pressurizes the gas / liquid pressurized by the first impeller 400.

[0059] In some embodiments, the compressor further includes a first reflux device 600, which is fixed inside the housing 100. The first reflux device 600 and a second reflux device 700 are located between the first impeller 400 and the second impeller 500. The first reflux device 600 is used to guide the flow field, adapt the power, and coordinate the sealing, thus ensuring the efficient operation of the entire machine.

[0060] In some embodiments, the compressor further includes a second reflux device 700, which includes a ring body 701 and a second blade 702. The ring body 701 is rotatably connected to the first reflux device 600. The second blade 702 is disposed on one side of the ring body 701 and is located inside the first reflux device 600.

[0061] In some embodiments, an airflow channel is formed within the housing 100, and the first return valve 600, the second return valve 700, and the second impeller 500 form the airflow channel, with the first blade 602 and the second blade 702 located within the airflow channel.

[0062] The second blade 702 is located inside the first return flow 600 and within the airflow channel. This structure utilizes the pre-swirl of the airflow at the outlet of the first return flow 600 as a power source. As the refrigerant flows through the second blade 702, it drives the entire second return flow 700 to rotate passively. On one hand, the rotation of the second blade 702 consumes and reduces the degree of pre-swirl at the outlet of the first return flow 600, converting the kinetic energy in the form of pre-swirl into the mechanical energy of the turbine. This reduces the pre-swirl of the airflow entering the second impeller 500, making the inlet flow field of the second impeller 500 more uniform, reducing flow separation and mixing losses, and improving the working efficiency of the second impeller 500.

[0063] On the other hand, the rotation of the second reflux valve 700 drives the ring body 701 to rotate synchronously. Utilizing the dynamic sealing effect at the side gap between the ring body 701 and the second impeller 500, leakage at the stationary gap is further suppressed, reducing leakage flow losses from the high-pressure side to the low-pressure side. This second reflux valve 700 requires no external energy input and is completely passively driven, achieving a coupled design of flow channel rectification optimization and gap sealing leakage suppression. This effectively reduces the overall aerodynamic losses of the multi-stage centrifugal compressor, improves the compressor's energy efficiency and operational stability, and is also simple and reliable in structure.

[0064] In some embodiments, the first return flow device 600 includes an annular baffle 601 fixed to the housing 100; an annular body 701 is coaxially sleeved on the main shaft 200, and the annular body 701 is sealed and rotatably connected to the baffle 601 and the main shaft 200. Further defining the first return flow device 600, it includes an annular baffle 601 fixed to the housing 100, and an annular body 701 coaxially sleeved on the main shaft 200, sealing and rotatably connected to both the baffle 601 and the main shaft 200. This design provides stable interstage separation and flow path guidance through the fixed baffle 601, and the annular body 701 directly forms a sealed rotating pair with the baffle 601 and the main shaft 200, achieving low-leakage dynamic and static isolation. The rotation of the annular body 701 driven by the turbine blades 702 maintains a sealed state relative to both the fixed baffle 601 and the rotating main shaft 200, ensuring that the turbine's pre-swirl reduction effect optimizes the inlet flow field of the second impeller 500, and enhancing the suppression of axial and radial leakage through the rotating sealing surface. This structure provides a more comprehensive sealing effect, reduces multi-path leakage losses, and the fixed installation of baffle 601 enhances the structural rigidity and flow field stability of the first return flow device 600. This design strengthens the reliability of interstage sealing, further reduces aerodynamic losses, and improves the energy efficiency and operational safety of the compressor under high pressure differential conditions.

[0065] Understandably, this solution only changes the connection position of the second return valve 700; the rest of the structure can be referred to above.

[0066] In addition, this application also provides a centrifugal chiller unit, characterized in that the centrifugal chiller unit includes a centrifugal compressor as described in any one of claims 1 to 9.

[0067] This compressor, through a passive rotary coupling design between the second reflux unit 702 and the annular body 701, optimizes the uniformity of the flow field between multi-stage impellers and suppresses gap leakage, significantly reducing aerodynamic losses and improving overall energy efficiency. In actual operation, this structure enables the compressor to maintain higher isentropic efficiency and stability over a wide variable frequency load range, reducing energy consumption and improving the air conditioner's cooling and heating performance and energy efficiency ratio. Simultaneously, its simple and reliable structure, requiring no additional drive source, helps reduce the overall manufacturing cost and maintenance difficulty of the air conditioner, enhancing the product's market competitiveness and user experience. The application of this compressor makes the air conditioner more energy-efficient and environmentally friendly, and operates more quietly and reliably.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A centrifugal compressor, characterized in that, It includes: A main shaft, which is rotatably connected within the housing; The motor drives the main shaft to rotate; A first impeller is connected to the main shaft; The second impeller is connected to the main shaft and is spaced apart from the first impeller; A first reflux device is connected to the main shaft; The first reflux device includes a first blade, which is disposed on one side of the first reflux device; The second return valve is located inside the first return valve; The second return valve includes: A ring body, which is rotatably connected to the housing; The second blade is disposed on one side of the annulus and is located on the side facing the first reflux device; The first reflux device and the second reflux device are located between the first impeller and the second impeller; A diffuser channel is located between the first impeller and the first return flow device; An airflow channel is formed by the first return valve, the second return valve, and the second impeller, and the first blade and the second blade are located in the airflow channel.

2. The centrifugal compressor according to claim 1, characterized in that, When the gas / liquid in the airflow channel passes through the second blade, it drives the second return valve to rotate.

3. The centrifugal compressor according to claim 1, characterized in that, The inner circumferential wall of the ring is provided with threads; the helical direction of the threads is the same as the rotation direction of the second reflux device; the threads are close to the end circumferential wall of the second impeller.

4. The centrifugal compressor according to claim 2, characterized in that, The second impeller includes a plurality of circumferentially spaced second blades; the thread is located near the outer edge of each second blade.

5. The centrifugal compressor according to claim 1, characterized in that, The second blades are arranged in multiple circumferentially along the ring body, and the spacing between any two adjacent turbine blades is the same.

6. The centrifugal compressor according to claim 4, characterized in that, The reflux device includes a plurality of first blades, and the third blades are arranged at circumferential intervals; in the airflow channel, the liquid / gas in the airflow channel first passes through the first blades and then through the second blades.

7. The centrifugal compressor according to claim 1, characterized in that, Multiple first blades and multiple second blades are staggered in the circumferential direction.

8. The centrifugal compressor according to claim 1, characterized in that, The outer peripheral wall of the ring is sealed to the inner wall of the housing by a bearing and is rotatably connected.

9. A centrifugal chiller unit, characterized in that, The centrifugal chiller unit includes a centrifugal compressor as described in any one of claims 1 to 8.

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