Outdoor unit and air conditioning system

Abstract

An outdoor unit (200) and an air conditioning system (10), the outdoor unit (200) comprising a multi-stage centrifugal compressor (230), the multi-stage centrifugal compressor (230) comprising a compressor assembly and a first-stage impeller (233). The compressor assembly comprises a machine shell (231), a backflow device (234), a reversing plate (237) and a vaneless diffuser (232), a cavity is formed in the machine shell (231), and the backflow device (234), the reversing plate (237) and the vaneless diffuser (232) are all fixed in the cavity. The first-stage impeller (233) is rotationally arranged in the cavity, the vaneless diffuser (232) and the backflow device (234) are located on the two sides of the first-stage impeller (233) in the axial direction of the first-stage impeller (233) respectively, a diffusion channel (23A) is formed between the vaneless diffuser (232) and the backflow device (234), and an air outlet of the first-stage impeller (233) communicates with an air inlet of the diffusion channel (23A). The reversing plate (237) is arranged around the vaneless diffuser (232), and an air inlet gap (23D) is formed between the reversing plate (237) and the peripheral wall face of the vaneless diffuser (232). The multi-stage centrifugal compressor (230) effectively solves the technical problem that the energy efficiency of a multi-stage centrifugal compressor is reduced.

Description

Outdoor unit and air conditioning system

[0001] This application claims priority to Chinese patent application No. 202222831486.6 filed on October 26, 2022, priority to Chinese patent application No. 202211316558.1 filed on October 26, 2022, and priority to Chinese patent application No. 202222831956.9 filed on October 26, 2022, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure relates to the field of centrifugal compressors, and in particular to an outdoor unit and an air-conditioning system. Background Art

[0003] The interior of the air conditioner is generally equipped with a two-stage centrifugal compressor, which can pressurize the gaseous refrigerant flowing through it, thereby ensuring the efficiency of the air conditioner's cooling or heating.

[0004] Summary of the Invention

[0005] In one aspect, an outdoor unit is provided, comprising a multi-stage centrifugal compressor. The multi-stage centrifugal compressor comprises a compressor assembly and a first-stage impeller. The compressor assembly comprises a casing, a return flow collector, a reversing plate, and a vaneless diffuser. The casing defines a cavity within which the return flow collector, the reversing plate, and the vaneless diffuser are fixed. The first-stage impeller is rotatably disposed within the cavity. The vaneless diffuser and the return flow collector are located on either side of the first-stage impeller in an axial direction, with a diffusion channel formed between the vaneless diffuser and the return flow collector. The air outlet of the first-stage impeller communicates with the air inlet of the diffusion channel. The reversing plate surrounds the vaneless diffuser and forms an air intake gap with the circumferential wall of the vaneless diffuser. An edge of the reversing plate proximal to the return flow collector extends toward the return flow collector, forming a reversing channel between the reversing plate and the return flow collector. The air inlet of the reversing channel communicates with the air outlet of the diffusion channel. The first end of the air intake gap is communicated with the air inlet of the reversing channel, and the second end of the air intake gap is used to communicate with the external gaseous refrigerant.

[0006] In another aspect, an air conditioning system is provided, comprising an indoor unit and an outdoor unit. The outdoor unit comprises a multi-stage centrifugal compressor. The multi-stage centrifugal compressor comprises a compressor assembly and a first-stage impeller. The compressor assembly comprises a casing, a return flow collector, a reversing plate, and a vaneless diffuser. The casing defines a cavity within which the return flow collector, the reversing plate, and the vaneless diffuser are fixed. The first-stage impeller is rotatably disposed within the cavity. The vaneless diffuser and the return flow collector are located on either side of the first-stage impeller along its axial direction, with a diffusion channel formed between the vaneless diffuser and the return flow collector. The air outlet of the first-stage impeller communicates with the air inlet of the diffusion channel. The reversing plate surrounds the vaneless diffuser and forms an air intake gap with the circumferential wall of the vaneless diffuser. An edge of the reversing plate proximal to the return flow collector extends toward the return flow collector, forming a reversing channel between the reversing plate and the return flow collector. The air inlet of the reversing channel communicates with the air outlet of the diffusion channel. The first end of the air intake gap is communicated with the air inlet of the reversing channel, and the second end of the air intake gap is used to communicate with the external gaseous refrigerant. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG1 is a structural diagram of an air conditioning system according to some embodiments of the present disclosure;

[0008] FIG2 is another structural diagram of an air conditioning system according to some embodiments of the present disclosure;

[0009] FIG3 is a structural diagram of internal refrigerant flow in an air-conditioning system in a cooling mode according to some embodiments of the present disclosure;

[0010] FIG4 is a cross-sectional view of a multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0011] FIG5 is a simulation diagram of a multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0012] FIG6 is an exploded view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0013] FIG7 is a cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0014] FIG8 is a partial enlarged view of the circle A in FIG7 ;

[0015] FIG9 is a simulation diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0016] FIG10 is a structural diagram of a housing according to some embodiments of the present disclosure;

[0017] FIG11 is a structural diagram of an air conditioning system including an economizer according to some embodiments of the present disclosure;

[0018] FIG12 is another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0019] FIG13 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0020] FIG14 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0021] FIG15 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0022] FIG16 is a structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0023] FIG17 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0024] FIG18 is another structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0025] FIG19 is yet another structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0026] FIG20 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure;

[0027] 21 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0028] The following will be combined with the accompanying drawings to clearly and completely describe some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, rather than all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0029] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and its other forms, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to indicate that the particular features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0030] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0031] When describing some embodiments, the expressions "coupled" and "connected" and their derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The term "coupled" indicates, for example, that two or more components are in direct physical or electrical contact. The term "coupled" or "communicatively coupled" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0032] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0033] The use of "adapted to" or "configured to" herein is intended to be open and inclusive language that does not exclude devices adapted or configured to perform additional tasks or steps.

[0034] Additionally, the use of “based on” is meant to be open and inclusive, as a process, step, calculation, or other action “based on” one or more stated conditions or values ​​may, in practice, be based on additional conditions or values ​​beyond those stated.

[0035] FIG1 is a structural diagram of an air-conditioning system according to some embodiments of the present disclosure; FIG2 is another structural diagram of an air-conditioning system according to some embodiments of the present disclosure.

[0036] As shown in Figure 1, some embodiments of the present disclosure provide an air conditioning system 10, including an outdoor unit 200 and an indoor unit 100. The outdoor unit 200 is in communication with the indoor unit 100, and the two cooperate to adjust the indoor temperature.

[0037] As shown in Figure 2, the indoor unit 100 includes a first housing 110 and a first heat exchanger 120, which is disposed within the first housing 110. The outdoor unit 200 includes a second housing 210, a second heat exchanger 220, and a multi-stage centrifugal compressor 230, which are disposed within the second housing 210. The first heat exchanger 120, the second heat exchanger 220, and the multi-stage centrifugal compressor 230 are sequentially connected to each other to control the indoor temperature.

[0038] The multi-stage centrifugal compressor 230 may be a two-stage centrifugal compressor that can compress the gaseous refrigerant entering the two-stage centrifugal compressor twice. This allows the gaseous refrigerant to be fully compressed, ensuring smooth cooling or heating of the air-conditioning system 10.

[0039] FIG3 is a structural diagram of the internal refrigerant flow of an air-conditioning system in a cooling mode according to some embodiments of the present disclosure.

[0040] As shown in Figure 3, during summer cooling, the first heat exchanger 120 functions as the evaporator 121, and the second heat exchanger 220 functions as the condenser 221. The air inlet of the multi-stage centrifugal compressor 230 is connected to the air outlet of the evaporator 121, the exhaust port of the multi-stage centrifugal compressor 230 is connected to the air inlet of the condenser 221, and the outlet of the condenser 221 is connected to the inlet of the evaporator 121.

[0041] Through the above-mentioned arrangement, the liquid refrigerant entering the evaporator 121 will absorb the heat in the room, causing the indoor temperature to drop and achieve cooling. Moreover, the liquid refrigerant will be converted into a gaseous refrigerant due to the absorption of heat, and then discharged from the air outlet of the evaporator 121 and enter the multi-stage centrifugal compressor 230. In the multi-stage centrifugal compressor 230, the gaseous refrigerant is compressed into a high-pressure gaseous refrigerant, and then discharged from the exhaust port of the multi-stage centrifugal compressor 230 to the condenser 221. In the condenser 221, the gaseous refrigerant condenses and releases heat, and the heat is discharged to the outside. And the gaseous refrigerant is converted into a liquid refrigerant and enters the evaporator 121 again, and this cycle is used to continuously cool the room.

[0042] FIG4 is a cross-sectional view of a multi-stage centrifugal compressor according to some embodiments of the present disclosure; FIG5 is a simulation diagram of a multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0043] As shown in Figure 4, to compress the gaseous refrigerant entering the multi-stage centrifugal compressor 230, the multi-stage centrifugal compressor 230 includes a casing 231, a vaneless diffuser 232, a first-stage impeller 233, a return flow collector 234, and a second-stage impeller 235. The vaneless diffuser 232, the first-stage impeller 233, the return flow collector 234, and the second-stage impeller 235 are sequentially mounted within the casing 231. A diffuser channel 23A, a reversing channel 23B, and a return flow channel 23C are sequentially connected between the vaneless diffuser 232, the return flow collector 234, and the casing 231. The air inlet of the diffuser channel 23A is connected to the air outlet of the first-stage impeller 233, the air outlet of the return flow channel 23C is connected to the air inlet of the second-stage impeller 235, and the reversing channel 23B is connected between the diffuser channel 23A and the return flow channel 23C.

[0044] Through the above arrangement, the gaseous refrigerant discharged from the air outlet of the first-stage impeller 233 can sequentially pass through the pressure diffuser channel 23A, the reversing channel 23B, and the return channel 23C, enter the second-stage impeller 235, and finally be discharged to the outside of the casing 231. As the gaseous refrigerant passes through the first-stage impeller 233 and the second-stage impeller 235, the first-stage impeller 233 and the second-stage impeller 235 rotate, and the centrifugal force generated during the rotation compresses the gaseous refrigerant to obtain high-pressure gaseous refrigerant.

[0045] It is understood that the function of the vaneless diffuser 232 is to convert the kinetic energy of the gaseous refrigerant discharged from the first-stage impeller 233 into pressure energy to more fully compress the gaseous refrigerant. The function of the return flow device 234 is to rectify the gaseous refrigerant discharged from the air outlet of the first-stage impeller 233 so that the gaseous refrigerant can enter the second-stage impeller 235 through the air inlet of the second-stage impeller 235, thereby achieving secondary compression of the gaseous refrigerant.

[0046] As shown in Figure 5, since the kinetic energy of the gaseous refrigerant is converted into static pressure energy in the pressure diffuser channel 23A, the flow rate of the gaseous refrigerant at the air outlet of the pressure diffuser channel 23A will be reduced, and the pressure will be increased. That is, a pressure difference will appear between the air outlet and the air inlet of the pressure diffuser channel 23A. This will cause the gaseous refrigerant at the air outlet of the pressure diffuser channel 23A to have a tendency to flow toward the air inlet of the pressure diffuser channel 23A, that is, a backflow phenomenon will occur. This will block the flow of the gaseous refrigerant in the pressure diffuser channel 23A, thereby reducing the working energy efficiency of the multi-stage centrifugal compressor 230.

[0047] In some embodiments, to eliminate the recirculation area shown in Figure 5, guide vanes can be added at the bend to reduce the backflow phenomenon. However, this solution is complex and costly, and its effectiveness depends on the design of the guide vane angle. Under certain operating conditions, this solution may even increase the recirculation area, deteriorating overall machine performance.

[0048] Figure 6 is an exploded view of another multi-stage centrifugal compressor in some embodiments of the present disclosure; Figure 7 is a cross-sectional view of another multi-stage centrifugal compressor in some embodiments of the present disclosure; Figure 8 is a partial enlarged view of circle A in Figure 7; Figure 9 is a simulation diagram of another multi-stage centrifugal compressor in some embodiments of the present disclosure.

[0049] To address the above issues, as shown in Figures 6 and 7 , some embodiments of the present disclosure provide a multi-stage centrifugal compressor 230. Compared to Figures 4 and 5 , the multi-stage centrifugal compressor 230 provided in some embodiments of the present disclosure utilizes two-stage refrigeration system air replenishment and enthalpy increase technology. By supplementing the gaseous refrigerant to impact the reflux area, it eliminates the reflux area and reduces losses. It is understood that this technology is primarily applied to a two-stage refrigeration centrifugal compressor system connected in series.

[0050] 6 , a multi-stage centrifugal compressor 230 includes a compressor assembly, a first-stage impeller 233, and a second-stage impeller 235. The compressor assembly includes a casing 231, a return flow device 234, and a vaneless diffuser 232. A cavity is formed inside the casing 231.

[0051] In some embodiments, as shown in FIG7 , the return flow device 234 and the vaneless diffuser 232 are fixed within the cavity. The primary impeller 233 is rotatably disposed within the cavity. The vaneless diffuser 232 and the return flow device 234 are located on either side of the primary impeller 233 in the axial direction, with a diffusion channel 23A formed between the vaneless diffuser 232 and the return flow device 234. The air outlet of the primary impeller 233 communicates with the air inlet of the diffusion channel 23A, and the air inlet of the primary impeller 233 communicates with the air outlet of the evaporator 121.

[0052] In some embodiments, the compressor assembly further includes a partition 236, which is fixed within the cavity and located on the side of the return flow device 234 away from the vaneless diffuser 232. The partition 236 is disposed around the primary impeller 233 and forms a return flow channel 23C with the return flow device 234. The secondary impeller 235 is rotatably disposed within the cavity and located between the partition 236 and the return flow device 234. The air inlet of the secondary impeller 235 is connected to the air outlet of the return flow channel 23C, and the air outlet of the secondary impeller 235 is connected to the condenser 221.

[0053] In some embodiments, as shown in Figure 7, the compressor assembly further includes a reversing plate 237, which is fixed within the cavity and arranged around the vaneless diffuser 232. As shown in Figure 8, an air intake gap 23D is formed between the reversing plate 237 and the peripheral wall surface of the vaneless diffuser 232. A side edge of the reversing plate 237 close to the returner 234 extends toward the returner 234, and a reversing channel 23B is formed between the reversing plate 237 and the returner 234. The air inlet of the reversing channel 23B is connected to the air outlet of the diffuser channel 23A, and the air outlet of the reversing channel 23B is connected to the air inlet of the return channel 23C. The first end of the air intake gap 23D is connected to the air inlet of the reversing channel 23B, and the second end of the air intake gap 23D is connected to the external gaseous refrigerant.

[0054] As shown in Figure 7, the low-pressure gaseous refrigerant discharged from the evaporator 121 can enter the primary impeller 233 through its air inlet. Under the action of the primary impeller 233, the low-pressure gaseous refrigerant is converted into high-speed gaseous refrigerant and enters the diffuser channel 23A from the air outlet of the primary impeller 233. Within the diffuser channel 23A, the high-speed gaseous refrigerant is converted into low-speed, high-pressure gaseous refrigerant and enters the reversing channel 23B, thereby achieving primary compression. After passing through the reversing channel 23B, the gaseous refrigerant turns and enters the return channel 23C, and then enters the secondary impeller 235 through the return channel 23C. Under the action of the secondary impeller 235, secondary compression is achieved, and the gaseous refrigerant is finally discharged from the air outlet of the secondary impeller 235 into the condenser 221, thereby compressing the gaseous refrigerant discharged from the evaporator 121.

[0055] FIG9 is a simulation diagram of a multi-stage centrifugal compressor provided by some embodiments of the present disclosure.

[0056] In some embodiments of the present disclosure, an air intake gap 23D is defined between the reversing plate 237 and the peripheral wall of the vaneless diffuser 232. As shown in FIG9 , the air intake gap 23D can introduce external gaseous refrigerant into the air inlet of the reversing channel 23B, thereby driving the gaseous refrigerant at the air outlet of the diffuser channel 23A (i.e., the air inlet of the reversing channel 23B) to flow along the reversing channel 23B, thereby improving the refrigerant backflow problem there, thereby allowing the gaseous refrigerant to flow smoothly within the diffuser channel 23A and the reversing channel 23B, thereby improving the energy efficiency of the multi-stage centrifugal compressor 230.

[0057] It is understood that the bladeless diffuser 232, the first-stage impeller 233, the return flow collector 234, the second-stage impeller 235, and the partition 236 should be coaxially arranged. For example, a rotating shaft can be provided in the cavity, passing through the bladeless diffuser 232, the first-stage impeller 233, the return flow collector 234, the second-stage impeller 235, and the partition 236 in sequence, and driven by a motor to rotate the rotating shaft, thereby rotating the first-stage impeller 233 and the second-stage impeller 235.

[0058] FIG10 is an external structural diagram of a casing provided in some embodiments of the present disclosure.

[0059] In some embodiments, to connect the air inlet of the first-stage impeller 233 to the air outlet of the evaporator 121, as shown in Figures 6 and 10, the housing 231 is provided with an opening 2311, which is connected to the cavity. The air inlet of the vaneless diffuser 232 is connected to the air outlet of the evaporator 121 through the opening 2311. The first-stage impeller 233 is disposed at the air inlet of the vaneless diffuser 232, so that the first-stage impeller 233 is connected to the air outlet of the evaporator 121 through the air inlet of the vaneless diffuser 232.

[0060] Of course, a pipe can also be used to connect the air inlet of the first-stage impeller 233 to the air outlet of the evaporator 121. The pipe can pass through the side wall of the casing 231, with the first end of the pipe connected to the air inlet of the vaneless diffuser 232 and further connected to the air inlet of the first-stage impeller 233. The second end of the pipe is connected to the air outlet of the evaporator 121. In this way, the flow direction of the gaseous refrigerant can be non-parallel to the axial direction of the first-stage impeller 233, for example, perpendicular to the axial direction of the first-stage impeller 233.

[0061] FIG11 is a structural diagram of an air conditioning system including an economizer according to some embodiments of the present disclosure.

[0062] To supply gaseous refrigerant to the multi-stage centrifugal compressor 230, as shown in FIG11 , the outdoor unit 200 provided in some embodiments of the present disclosure further includes an economizer 240 , which is connected to the second end of the air intake gap 23D. Thus, the air conditioning system 10 can utilize the economizer 240 to supply gaseous refrigerant to the air intake gap 23D.

[0063] Since the gaseous refrigerant discharged from the economizer 240 is a low-temperature gaseous refrigerant, discharging the low-temperature gaseous refrigerant into the reversing channel 23B can not only replenish the air to the multi-stage centrifugal compressor 230, but also reduce the operating temperature of the multi-stage centrifugal compressor 230 to improve the working efficiency of the multi-stage centrifugal compressor 230.

[0064] Of course, a separate device can also be provided to provide gaseous refrigerant to the multi-stage centrifugal compressor 230. The supplementary air source can also be provided separately, without having to be obtained from the refrigerant circulating in the air conditioning system 10. The separate supplementary air source device can be provided in the multi-stage centrifugal compressor 230.

[0065] In some embodiments, economizer 240 is a heat exchange type economizer. As shown in Figure 11, economizer 240 is connected between evaporator 121 and condenser 221. Economizer 240 has a first inlet 2401, a second inlet 2402, a first outlet 2403, and a second outlet 2404. The first inlet 2401 of economizer 240 is connected to the outlet of condenser 221 via a connecting pipe. A first bypass passage is connected between condenser 221 and economizer 240. One end of the first bypass passage is connected to the connecting pipe, and the other end of the first bypass passage is connected to the second inlet 2402 of economizer 240. The first outlet 2403 of economizer 240 is connected to the inlet of evaporator 121, and the second outlet 2404 of economizer 240 is connected to the second end of intake gap 23D. An expansion valve 241 is provided between the connection point between the connecting pipe and the first bypass passage and the first inlet 2401 of economizer 240.

[0066] In this way, the flow rate of refrigerant entering the economizer 240 through the first inlet 2401 of the economizer 240 can be controlled by adjusting the expansion valve 241, so that heat exchange occurs between the refrigerant entering the economizer 240 through the first inlet 2401 and the refrigerant entering the economizer 240 through the second inlet 2402. This ensures that the refrigerant discharged from the second outlet 2404 of the economizer 240 is a low-temperature gaseous refrigerant. Because the second outlet 2404 of the economizer 240 is connected to the second end of the air inlet gap 23D, the low-temperature gaseous refrigerant can enter the reversing channel 23B through the air inlet gap 23D. This improves the refrigerant backflow problem at the outlet of the diffuser channel 23A (the air inlet of the reversing channel 23B) and achieves the effect of air replenishment and enthalpy increase, thereby improving the energy efficiency of the multi-stage centrifugal compressor 230 and further improving the efficiency of the multi-stage centrifugal compressor 230.

[0067] It should be noted that economizer 240 can also be of other types. For example, a plate heat exchanger can be used instead of an economizer. Plate heat exchangers are compact and simple to control, but their cooling efficiency is lower than that of economizers. Expansion valve 241 can be an electronic expansion valve.

[0068] In some embodiments, as shown in FIG8 , an air inlet gap 23D is provided around the vaneless diffuser 232. Thus, external gaseous refrigerant can pass through the air inlet gap 23D provided circumferentially along the vaneless diffuser 232 and enter the reversing channel 23B from the air outlet of the diffuser channel 23A. This allows the gaseous refrigerant to enter various locations of the air inlet of the reversing channel 23B along the circumference of the vaneless diffuser 232, thereby improving the refrigerant backflow problem at various locations of the air outlet of the diffuser channel 23A along the circumference of the vaneless diffuser 232, thereby further improving the energy efficiency of the multi-stage centrifugal compressor 230.

[0069] 12 is another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0070] In some embodiments, the inlet gap 23D may also be provided along the circumference of the vaneless diffuser 232 , surrounding a portion of the vaneless diffuser 232 .

[0071] On this basis, to facilitate the entry of external gaseous refrigerant into the air intake gap 23D, as shown in FIG12 , the compressor assembly further forms an air duct 250, which surrounds the vaneless diffuser 232. One end of the air duct 250 communicates with the second end of the air intake gap 23D, and the other end of the air duct 250 communicates with the external gaseous refrigerant.

[0072] In this way, the external gaseous refrigerant can enter the air duct 250. Since the air duct 250 is arranged around the bladeless diffuser 232, the gaseous refrigerant can circumvent the bladeless diffuser 232. In addition, since the air duct 250 is connected to the second end of the air inlet gap 23D, the gaseous refrigerant in the air duct 250 can further enter the reversing channel 23B through the air inlet gap 23D.

[0073] Due to the existence of the air duct 250, when introducing the gaseous refrigerant, it is only necessary to open an opening connected to the outside of the air duct on the side wall of the air duct 250 so that the opening is connected to the external gaseous refrigerant, avoiding the need to add an air intake pipe to connect the second end of the air intake gap 23D. This can simplify the installation steps and facilitate the connection of the second end of the air intake gap 23D to the external gaseous refrigerant.

[0074] FIG. 13 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0075] In some embodiments, to form the above-mentioned air duct 250, as shown in Figure 13, the casing 231 is fixedly connected to the reversing plate 237, and a guide portion is provided on the side surface of the reversing plate 237 facing the bladeless diffuser 232, and the refrigerant can flow in the guide portion.

[0076] In some embodiments, the air guide may be a first groove 2371. The first groove 2371 is disposed around the vaneless diffuser 232, with the opening of the first groove 2371 facing the vaneless diffuser 232. The first groove 2371 and the vaneless diffuser 232 define the air duct 250. An air intake gap 23D is formed between the surface where the opening of the first groove 2371 is located and the vaneless diffuser 232, and a second end of the air intake gap 23D communicates with the first groove 2371.

[0077] By opening a first groove 2371 on the reversing plate 237, the first groove 2371 and the bladeless diffuser 232 define the air duct 250, and an air intake gap 23D is formed between the surface where the notch of the first groove 2371 is located and the bladeless diffuser 232, and the second end of the air intake gap 23D is connected to the first groove 2371, so that the external gaseous refrigerant can enter the first groove 2371 and finally enter the reversing channel 23B through the air intake gap 23D.

[0078] It can be understood that the air intake gap 23D is formed between the surface where the notch of the first groove 2371 is located and the vaneless diffuser 232, which means that the air intake gap 23D is formed between the part of the surface where the notch of the first groove 2371 is located close to the return flow device 234 and the vaneless diffuser 232, so that the air intake gap 23D can be connected to the first groove 2371 and the air intake of the reversing channel 23B.

[0079] It should be noted that the fixed connection between the housing 231 and the reversing plate 237 can be formed integrally. This integrally formed housing 231 and reversing plate 237 provide a stable structure. Furthermore, during processing, the housing 231 and reversing plate 237 can be completed in one step, which improves production efficiency. Of course, the housing 231 and reversing plate 237 can also be separate structures. In this case, the housing 231 and reversing plate 237 are processed separately and then a secondary process is performed to secure them together. This reduces the difficulty of processing the housing 231 and reversing plate 237.

[0080] FIG14 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0081] In other embodiments, in order to form the above-mentioned air duct 250, as shown in Figure 14, a new guide portion is provided, and the guide portion can be a second groove 2312. The second groove 2312 is formed between the reversing plate 237 and the inner wall of the casing 231, and the second groove 2312 surrounds the axis of the first-stage impeller 233. The bladeless diffuser 232 includes a protrusion 2322 and a body 2323, and the protrusion 2322 surrounds the axis of the first-stage impeller 233. The reversing plate 237 surrounds the protrusion 2322 and forms an air intake gap 23D with the protrusion 2322. A diffusion channel 23A is formed between the protrusion 2322 and the return flow device 234. The body 2323 is fixedly connected to the protrusion 2322 and is located on the side of the protrusion 2322 away from the return flow device 234. The notch of the second groove 2312 faces the main body 2323 , and the second groove 2312 and the main body 2323 form an air duct 250 . The second groove 2312 is in communication with the air intake gap 23D.

[0082] By setting a second groove 2312 between the casing 231 and the reversing plate 237, the main body 2323 and the second groove 2312 define the air duct 250, and the second groove 2312 is connected to the air intake gap 23D, so that the external gaseous refrigerant can enter the second groove 2312 and finally enter the reversing channel 23B through the air intake gap 23D.

[0083] To connect the second groove 2312 with the air inlet gap 23D, as shown in FIG14 , a first gap can be reserved between the surface of the reversing plate 237 where the second groove 2312 is located and the body 2323. Thus, the gaseous refrigerant in the air duct 250 can enter the air inlet gap 23D through the first gap.

[0084] Alternatively, in order to connect the second groove 2312 with the air inlet gap 23D, a second gap may be formed on the reversing plate 237, and the air duct 250 may be connected with the air inlet gap 23D through the second gap. In this way, the gaseous refrigerant in the air duct 250 can enter the air inlet gap 23D through the second gap.

[0085] FIG15 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0086] In yet other embodiments, to form the aforementioned air duct 250, as shown in FIG15 , the returner 234 is fixedly connected to the diverter plate 237. A third groove 2313 is defined in the housing 231, with the notch of the third groove 2313 facing the diverter plate 237. The third groove 2313 surrounds the vaneless diffuser 232, and the third groove 2313 and the diverter plate 237 define the air duct 250. The third groove 2313 communicates with the intake gap 23D.

[0087] By opening a third groove 2313 on the casing 231, an air duct 250 is formed between the third groove 2313 and the reversing plate 237, and the air intake gap 23D is connected to the third groove 2313, so that the external gaseous refrigerant can enter the third groove 2313 and finally enter the reversing channel 23B through the air intake gap 23D.

[0088] The returner 234 and the diverter plate 237 can be fixedly connected by being integrally formed. The integrally formed returner 234 and diverter plate 237 provide a stable structure. Furthermore, during processing, the returner 234 and the diverter plate 237 can be completed in one step, which helps improve processing efficiency. Of course, the returner 234 and the diverter plate 237 can also be separate structures, with the returner 234 and the diverter plate 237 being processed separately and then subsequently affixed to the structure through secondary processing. This can reduce the difficulty of processing the returner 234 and the diverter plate 237.

[0089] FIG16 is a structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure; FIG17 is another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0090] In some embodiments, to ensure that the gaseous refrigerant entering air duct 250 flows evenly through intake gap 23D along the circumference of air duct 250 and into reversing channel 23B, multi-stage centrifugal compressor 230 further includes a first intake pipe 238, as shown in FIG16 . First intake pipe 238 is secured to the outer wall of casing 231. As shown in FIG17 , first intake pipe 238 is tangential to the circumference of air duct 250. A first end of first intake pipe 238 communicates with air duct 250, while a second end of first intake pipe 238 communicates with the external gaseous refrigerant. As the gaseous refrigerant flows within air duct 250, the ventilation cross-sectional area of ​​air duct 250 decreases, with the first end of first intake pipe 238 communicating with the point where the ventilation cross-sectional area of ​​air duct 250 is greatest.

[0091] Since the first air inlet pipe 238 is tangent to the circumference of the air duct 250, the gaseous refrigerant entering the first air inlet pipe 238 can enter the air duct 250 through the first air inlet pipe 238 along the direction tangent to the air duct 250 and flow clockwise or counterclockwise (clockwise in Figure 17) along the air duct 250.

[0092] Furthermore, since the ventilation cross-sectional area of ​​air duct 250 decreases along the flow direction of the gaseous refrigerant within air duct 250, the pressure of the gaseous refrigerant increases as the gaseous refrigerant flows. This can alleviate the problem of the gaseous refrigerant's pressure decreasing as the gaseous refrigerant flows. It can also ensure that the gaseous refrigerant enters the air intake gap 23D uniformly around the circumference of the vaneless diffuser 232, ensuring uniform air intake around the reversing channel 23B, thereby further improving the backflow problem at the air inlet of the reversing channel 23B.

[0093] In some embodiments, to further achieve uniform air intake along the circumference of the reversing channel 23B, the cross-sectional area of ​​the air duct 250 decreases proportionally along the flow direction of the gaseous refrigerant within the air duct 250. That is, the cross-sectional area of ​​the air duct 250 decreases at a fixed ratio. It should be noted that the ratio can be determined based on the wind resistance of the air duct 250, or based on the initial velocity of the gaseous refrigerant entering the air duct 250 and the maximum ventilation cross-sectional area of ​​the air duct 250. Alternatively, it can be determined based on the above-mentioned combined data.

[0094] Of course, along the flow direction of the gaseous refrigerant in the air duct 250, the cross-sectional area of ​​the air duct 250 may also be reduced at a varying ratio.

[0095] In some embodiments, when the air duct 250 is composed of the first groove 2371 and the reversing plate 237, to ensure that the first air inlet pipe 238 is tangential to the circumference of the air duct 250, as shown in Figures 13 and 16, the first air inlet pipe 238 should be tangential to the circumference of the first groove 2371 and tangential to the side of the housing 231 where the bottom of the first groove 2371 is located. In this way, external gaseous refrigerant can enter the first groove 2371 through the first air inlet pipe 238, be discharged from the notch of the first groove 2371 into the air inlet gap 23D, and finally enter the reversing channel 23B.

[0096] FIG18 is another structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure; FIG19 is yet another structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0097] In other embodiments, to ensure that the gaseous refrigerant entering the air duct 250 can be uniformly distributed along the circumference of the air duct 250 through the air intake gap 23D and into the reversing channel 23B, as shown in FIG18 , the multi-stage centrifugal compressor 230 includes a second air intake pipe 239. The second air intake pipe 239 is fixed to the outer wall of the casing 231 and extends radially along the first-stage impeller 233. As shown in FIG19 , a first end of the second air intake pipe 239 communicates with the air duct 250, and a second end of the second air intake pipe 239 communicates with the external gaseous refrigerant.

[0098] FIG20 is another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure; FIG21 is another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

[0099] As shown in Figure 20 , an intake gap 23D is formed between the first surface 2321 of the vaneless diffuser 232 and the reversing plate 237. As shown in Figure 21 , along the circumference of the vaneless diffuser 232, the first surface 2321 includes a first sub-surface 23211 and a second sub-surface 23212 connected in sequence.

[0100] Along the axial direction of the vaneless diffuser 232, the edge of the first sub-surface 23211 away from the return flow device 234 (located above the axial direction of the vaneless diffuser 232 in Figure 21) is the first edge 2321A (bounded by the vertical dotted line in Figure 21, the left side is the first edge 2321A), and the first edge 2321A extends along the circumference of the vaneless diffuser 232 in the first direction (the direction represented by the left arrow in Figure 21), toward the first end away from the second air inlet pipe 239, and close to the axis of the vaneless diffuser 232.

[0101] Along the axial direction of the bladeless diffuser 232, the edge of the second sub-surface 23212 away from the return flow device 234 is the second edge 2321B (bounded by the vertical dotted line in Figure 21, the left side is the second edge 2321B), and the second edge 2321B extends along the circumference of the bladeless diffuser 232 in the opposite direction to the first direction (the direction represented by the right arrow in Figure 21), toward the first end away from the second air inlet duct, and close to the axis of the bladeless diffuser 232.

[0102] Since the second air inlet pipe 239 extends radially along the first-stage impeller 233, the external gaseous refrigerant can enter the air duct 250 through the second air inlet pipe 239 and flow in two opposite directions in the air duct 250 starting from the second end of the second air inlet pipe 239.

[0103] Furthermore, since the first edge 2321A extends along the circumference of the vaneless diffuser 232 in the first direction, in a direction away from the first end of the second air inlet pipe 239, and in a direction close to the axis of the vaneless diffuser 232, when the gaseous refrigerant enters the air inlet gap 23D, in the first direction, the farther the portion of the air inlet gap 23D is from the second air inlet pipe 239, the less resistance the gaseous refrigerant encounters. This can compensate for the pressure loss caused by the flow of the gaseous refrigerant in the first direction. That is, the farther away from the second air inlet pipe 239, the lower the pressure of the gaseous refrigerant in the air inlet gap 23D. This ensures that the portion of the air inlet gap 23D between the first sub-surface 23211 and the vaneless diffuser 232 is evenly inhaled in the circumferential direction.

[0104] Similarly, since the second edge 2321B extends along the circumference of the vaneless diffuser 232 in the opposite direction to the first direction, in a direction away from the first end of the second air inlet pipe and close to the axis of the vaneless diffuser 232, when the gaseous refrigerant enters the air inlet gap 23D, in the direction opposite to the first direction, the farther the portion of the air inlet gap 23D is from the second air inlet pipe 239, the less resistance the gaseous refrigerant encounters. This can compensate for the pressure loss caused by the flow of the gaseous refrigerant in the direction opposite to the first direction. That is, the farther away from the second air inlet pipe 239, the lower the pressure of the gaseous refrigerant in the air inlet gap 23D. This ensures that the portion of the air inlet gap 23D between the second sub-surface 23212 and the vaneless diffuser 232 is evenly inhaled in the circumferential direction.

[0105] In this way, with the cooperation of the first sub-surface 23211 and the second sub-surface 23212 , the intake uniformity of the intake gap 23D between the first surface 2321 and the vaneless diffuser 232 in the circumferential direction can be achieved.

[0106] It is understood that the distance between the first edge 2321A and the axis of the vaneless diffuser 232 in the first direction decreases, while the distance between the second edge 2321B and the axis of the vaneless diffuser 232 in the direction opposite to the first direction decreases. These distances may be proportionally reduced, thereby achieving better intake uniformity in the circumferential direction of the intake gap 23D. Of course, the distance between the first edge 2321A and the axis of the vaneless diffuser 232 in the first direction decreases, while the distance between the second edge 2321B and the axis of the vaneless diffuser 232 in the direction opposite to the first direction decreases. These distances may also decrease at varying ratios.

[0107] It should be noted that the first surface 2321 can be an arc surface or a plane, which is not specifically limited in the present disclosure.

[0108] In some embodiments, as shown in FIG21 , along the circumference of the vaneless diffuser 232, the first sub-surface 23211 and the second sub-surface 23212 can each occupy half, i.e., 180 degrees each. In this way, the gaseous refrigerant moving in the first direction and in the opposite directions of the first and second directions can enter the reversing passage 23B more evenly along the circumference of the vaneless diffuser 232. Alternatively, along the circumference of the vaneless diffuser 232, the first sub-surface 23211 and the second sub-surface 23212 can occupy unequal proportions, for example, the first sub-surface 23211 occupies 120 degrees and the second sub-surface 23212 occupies 240 degrees. Of course, any other suitable proportions are also acceptable.

[0109] In some embodiments, as shown in FIG20 , where the first surface 2321 is planar and the first sub-surface 23211 and the second sub-surface 23212 each occupy half of the circumference of the vaneless diffuser 232, assuming that the second inlet pipe 239 is located above in FIG20 , to ensure circumferential air intake uniformity in the air intake gap 23D, the portion of the first surface 2321 closest to the second inlet pipe 239 can be set at an angle of 0° with the axis of the first-stage impeller 233, and the portion of the first surface 2321 farthest from the second inlet pipe 239 can be set at an angle A with the axis of the first-stage impeller 233, with A being between 0° and 20°, for example, 12°, 13°, 14°, or 15°. In this way, air intake uniformity in the air intake gap 23D is ensured.

[0110] For example, when the air duct 250 is composed of the second groove 2312 and the body 2323, to achieve uniform intake of the gaseous refrigerant entering the air duct 250 from the second air inlet pipe 239 around the circumference of the first-stage impeller 233, as shown in FIG14 , the second air inlet pipe 239 is connected to the second groove 2312, and the reversing plate 237 is disposed around the body 2323, with the first surface 2321 located on the protrusion 2322. In this way, the external gaseous refrigerant can enter the second groove 2312 through the second air inlet pipe 239, then enter the air intake gap 23D through the second groove 2312, and finally enter the reversing channel 23B.

[0111] Those skilled in the art will understand that the disclosure scope of this application is not limited to the above specific embodiments, and certain elements of the embodiments may be modified and replaced without departing from the spirit of this application. The scope of this application is limited by the appended claims.

Claims

1. An outdoor unit comprising a multi-stage centrifugal compressor; wherein: The multi-stage centrifugal compressor comprises: Compressor assembly, including: a housing, wherein the housing has a cavity therein; Reflux device; commutator plate; and a vaneless diffuser, wherein the returner, the reversing plate and the vaneless diffuser are all fixed in the cavity; and A first-stage impeller is rotatably disposed in the cavity, the bladeless diffuser and the return flow device are respectively located on both sides of the axial direction of the first-stage impeller, and a diffusion channel is formed between the bladeless diffuser and the return flow device, and the air outlet of the first-stage impeller is connected to the air inlet of the diffusion channel; wherein, The reversing plate is arranged around the vaneless diffuser, and an air intake gap is formed between the reversing plate and the peripheral wall surface of the vaneless diffuser; The side edge of the reversing plate close to the returner extends in the direction close to the returner, and forms a reversing channel between the reversing channel and the returner; the air inlet of the reversing channel is connected to the air outlet of the diffuser channel; The first end of the air intake gap is communicated with the air inlet of the reversing channel, and the second end of the air intake gap is used to communicate with the external gaseous refrigerant.

2. The outdoor unit according to claim 1, wherein: The air intake gap surrounds the vaneless diffuser.

3. The outdoor unit according to claim 2, wherein: An air duct is formed on the compressor assembly. The air duct surrounds the bladeless diffuser and is communicated with the second end of the air intake gap. The air duct is communicated with the external gaseous refrigerant.

4. The outdoor unit according to claim 3, wherein: The multi-stage centrifugal compressor further includes a first air inlet pipe, which is fixed to the outer wall of the casing and is tangential to the circumference of the air duct, wherein a first end of the first air inlet pipe is in communication with the air duct, and a second end of the first air inlet pipe is in communication with the external gaseous refrigerant; Along the flow direction of the gaseous refrigerant in the air duct, the ventilation cross-sectional area of ​​the air duct tends to decrease, and the first end of the first air inlet pipe is connected to the position where the ventilation cross-sectional area of ​​the air duct is the largest.

5. The outdoor unit according to claim 3, wherein The multi-stage centrifugal compressor further includes a second air inlet pipe, which is fixed to the outer wall of the casing and extends radially along the first-stage impeller, wherein a first end of the second air inlet pipe is in communication with the air duct, and a second end of the second air inlet pipe is in communication with the external gaseous refrigerant; The intake gap is formed between the first surface of the vaneless diffuser and the reversing plate, and along the circumference of the vaneless diffuser, the first surface includes a first sub-surface and a second sub-surface connected in sequence; Along the axial direction of the vaneless diffuser, the first sub-surface extends away from the edge of the return flow device, along the circumference of the vaneless diffuser in a first direction, toward the first end of the second inlet pipe, and close to the axis of the vaneless diffuser; along the axial direction of the vaneless diffuser, the second sub-surface extends away from the edge of the return flow device, along the circumference of the vaneless diffuser in a direction opposite to the first direction, toward the first end of the second inlet pipe, and close to the axis of the vaneless diffuser. The outdoor unit according to claim 4, wherein: The casing is fixedly connected to the reversing plate, and a first groove is provided on the surface of the reversing plate facing the bladeless diffuser. The first groove surrounds the bladeless diffuser and forms the air duct together with the bladeless diffuser. The air intake gap is formed between the surface where the notch of the first groove is located and the bladeless diffuser, and the second end of the air intake gap is connected to the first groove.

7. The outdoor unit according to claim 5, wherein: The returner is fixedly connected to the reversing plate, and a second groove is formed between the reversing plate and the inner wall of the casing, and the second groove surrounds the axis of the first-stage impeller; the vaneless diffuser includes: A protrusion surrounds the axis of the first-stage impeller, the reversing plate surrounds the protrusion and forms the air intake gap with the protrusion, and the diffuser channel is formed between the protrusion and the return flow device; and The main body is fixedly connected to the protrusion and is located on the side of the protrusion away from the returner. The notch of the second groove faces the main body and forms the air duct with the main body. The second groove is connected to the second end of the air intake gap.

8. The outdoor unit according to any one of claims 1 to 7, wherein: The outdoor unit further includes an economizer connected to the second end of the air intake gap.

9. The outdoor unit according to any one of claims 1 to 8, wherein: The multi-stage centrifugal compressor further comprises: a partition fixed in the cavity and located on a side of the returner away from the vaneless diffuser, the partition being arranged around the axis of the first-stage impeller and forming a return flow channel with the returner, the air inlet of the return flow channel being connected to the air outlet of the reversing channel; and The secondary impeller is rotatably disposed in the cavity and is located between the partition plate and the return flow device. The air outlet of the return channel is communicated with the air inlet of the secondary impeller.

10. An air conditioning system comprising: Indoor unit; as well as An outdoor unit, the outdoor unit comprising a multi-stage centrifugal compressor, the multi-stage centrifugal compressor comprising: Compressor assembly, including: a housing, wherein the housing has a cavity therein; Reflux device; commutator plate; and a vaneless diffuser, wherein the returner, the reversing plate and the vaneless diffuser are all fixed in the cavity; and A first-stage impeller is rotatably disposed in the cavity, the bladeless diffuser and the return flow device are respectively located on both sides of the axial direction of the first-stage impeller, and a diffusion channel is formed between the bladeless diffuser and the return flow device, and the air outlet of the first-stage impeller is connected to the air inlet of the diffusion channel; wherein, The reversing plate is arranged around the vaneless diffuser, and an air intake gap is formed between the reversing plate and the peripheral wall surface of the vaneless diffuser; The side edge of the reversing plate close to the returner extends in the direction close to the returner, and forms a reversing channel between the reversing plate and the returner, and the air inlet of the reversing channel is connected to the air outlet of the diffuser channel; The first end of the air intake gap is communicated with the air inlet of the reversing channel, and the second end of the air intake gap is used to communicate with the external gaseous refrigerant.

11. The air conditioning system according to claim 10, wherein: The air intake gap surrounds the vaneless diffuser.

12. The air conditioning system according to claim 11, wherein: An air duct is formed on the compressor assembly. The air duct surrounds the bladeless diffuser and is communicated with the second end of the air intake gap. The air duct is communicated with the external gaseous refrigerant.

13. The air conditioning system according to claim 12, wherein: The multi-stage centrifugal compressor further includes a first air inlet pipe, which is fixed to the outer wall of the casing and is tangential to the circumference of the air duct, wherein a first end of the first air inlet pipe is in communication with the air duct, and a second end of the first air inlet pipe is in communication with the external gaseous refrigerant; Along the flow direction of the gaseous refrigerant in the air duct, the ventilation cross-sectional area of ​​the air duct tends to decrease, and the first end of the first air inlet pipe is connected to the position where the ventilation cross-sectional area of ​​the air duct is the largest.

14. The air conditioning system according to claim 12, wherein: The multi-stage centrifugal compressor further includes a second air inlet pipe, which is fixed to the outer wall of the casing and extends radially along the first-stage impeller, wherein a first end of the second air inlet pipe is in communication with the air duct, and a second end of the second air inlet pipe is in communication with the external gaseous refrigerant; The intake gap is formed between the first surface of the vaneless diffuser and the reversing plate, and along the circumference of the vaneless diffuser, the first surface includes a first sub-surface and a second sub-surface connected in sequence; Along the axial direction of the vaneless diffuser, the first sub-surface extends away from the edge of the return flow device, along the circumference of the vaneless diffuser in a first direction, toward the first end of the second inlet pipe, and close to the axis of the vaneless diffuser; along the axial direction of the vaneless diffuser, the second sub-surface extends away from the edge of the return flow device, along the circumference of the vaneless diffuser in a direction opposite to the first direction, toward the first end of the second inlet pipe, and close to the axis of the vaneless diffuser.

15. The air conditioning system according to claim 13, wherein: The casing is fixedly connected to the reversing plate, and a first groove is provided on the surface of the reversing plate facing the bladeless diffuser. The first groove surrounds the bladeless diffuser and forms the air duct together with the bladeless diffuser. The air intake gap is formed between the surface where the notch of the first groove is located and the bladeless diffuser, and the second end of the air intake gap is connected to the first groove.

16. The air conditioning system according to claim 14, wherein: The returner is fixedly connected to the reversing plate, and a second groove is formed between the reversing plate and the inner wall of the casing, and the second groove surrounds the axis of the first-stage impeller; the vaneless diffuser includes: A protrusion surrounds the axis of the first-stage impeller, the reversing plate surrounds the protrusion and forms the air intake gap with the protrusion, and the diffuser channel is formed between the protrusion and the return flow device; and The main body is fixedly connected to the protrusion and is located on the side of the protrusion away from the returner. The notch of the second groove faces the main body and forms the air duct with the main body. The second groove is connected to the second end of the air intake gap.

17. The air conditioning system according to any one of claims 10 to 16, wherein: The outdoor unit further includes an economizer connected to the second end of the air intake gap.

18. The air conditioning system according to any one of claims 10 to 17, wherein: The multi-stage centrifugal compressor further comprises: a partition fixed in the cavity and located on a side of the returner away from the vaneless diffuser, the partition being arranged around the axis of the first-stage impeller and forming a return flow channel with the returner, the air inlet of the return flow channel being connected to the air outlet of the reversing channel; and The secondary impeller is rotatably disposed in the cavity and is located between the partition plate and the return flow device. The air outlet of the return channel is communicated with the air inlet of the secondary impeller.

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