WO2024087826A1 - Outdoor unit and air conditioning system - Google Patents

Abstract

An outdoor unit (200) and an air conditioning system (10). The outdoor unit (200) comprises a multi-stage centrifugal compressor (230), and the multi-stage centrifugal compressor (230) comprises a compressor assembly and a first-stage impeller (233). The compressor assembly comprises a machine housing (231), a return channel (234), a reversing plate (237), and a vaneless diffuser (232); the machine housing (231) is internally provided with a cavity; the return channel (234), the reversing plate (237), and the vaneless diffuser (232) are all fixed in the cavity. The first-stage impeller (233) is rotatably arranged in the cavity, the vaneless diffuser (232) and the return channel (234) are respectively located on the two sides of the first-stage impeller (233) in the axial direction thereof, a diffusion channel (23A) is formed between the vaneless diffuser (232) and the return channel (234), and an air outlet of the first-stage impeller (233) is communicated with an air inlet of the diffusion channel (23A). The reversing plate (237) is arranged around the vaneless diffuser (232) by a circle, and an air inlet gap (23D) is formed between the reversing plate (237) and the peripheral wall surface of the vaneless diffuser (232). The multi-stage centrifugal compressor (230) effectively solves the technical problem of reduced energy efficiency of multi-stage centrifugal compressors.

Description

Outdoor unit and air conditioning system

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

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

Background technique

The interior of the air conditioner is generally provided 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.

Summary of the invention

On the one hand, an outdoor unit is provided, which includes a multi-stage centrifugal compressor. The multi-stage centrifugal compressor includes a compressor assembly and a first-stage impeller. The compressor assembly includes a casing, a returner, a reversing plate and a bladeless diffuser. The casing has a cavity inside, and the returner, the reversing plate and the bladeless diffuser are all fixed in the cavity. The first-stage impeller is rotatably arranged in the cavity, the bladeless diffuser and the returner 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 returner, and the air outlet of the first-stage impeller is connected to the air inlet of the diffusion channel. The reversing plate is arranged around the bladeless diffuser, and an air intake gap is formed between the reversing plate and the peripheral wall surface of the bladeless diffuser. The side edge of the reversing plate close to the returner extends in the direction close to the returner, and a reversing channel is formed between the returner, and the air inlet of the reversing channel is connected to the air outlet of the diffusion channel. The first end of the air intake gap is connected to 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.

On the other hand, an air conditioning system is provided, which includes an indoor unit and an outdoor unit. The outdoor unit includes a multistage centrifugal compressor. The multistage centrifugal compressor includes a compressor assembly and a first-stage impeller. The compressor assembly includes a casing, a returner, a reversing plate and a bladeless diffuser. The casing has a cavity inside, and the returner, the reversing plate and the bladeless diffuser are all fixed in the cavity. The first-stage impeller is rotatably arranged in the cavity, the bladeless diffuser and the returner are respectively located on both sides of the first-stage impeller along its axial direction, and a diffusion channel is formed between the bladeless diffuser and the returner, and the air outlet of the first-stage impeller is connected to the air inlet of the diffusion channel. The reversing plate is arranged around the bladeless diffuser, and an air intake gap is formed between the reversing plate and the peripheral wall surface of the bladeless diffuser. The edge of one side of the reversing plate close to the returner extends in the direction close to the returner, and a reversing channel is formed between the returner, and the air inlet of the reversing channel is connected to the air outlet of the diffusion channel. The first end of the air intake gap is connected to 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

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;

3 is a structural diagram of the internal refrigerant flow of the air-conditioning system in cooling mode according to some embodiments of the present disclosure;

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;

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

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

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

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

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

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

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

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

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

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

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

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

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;

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

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

Detailed ways

Some embodiments of the present disclosure will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments provided by the present disclosure are within the scope of protection of the present disclosure.

Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and other forms thereof, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open, 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" and the like are intended to indicate that specific 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 specific features, structures, materials or characteristics described may be included in any one or more embodiments or examples in any appropriate manner.

In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, 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.

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.

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

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

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.

FIG. 1 is a structural diagram of an air-conditioning system according to some embodiments of the present disclosure; FIG. 2 is another structural diagram of an air-conditioning system according to some embodiments of the present disclosure.

As shown in Fig. 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 connected to the indoor unit 100, and the two cooperate to adjust the indoor temperature.

As shown in Fig. 2, the indoor unit 100 includes a first housing 110 and a first heat exchanger 120, and the first heat exchanger 120 is disposed inside 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, and the second heat exchanger 220 and the multi-stage centrifugal compressor 230 are disposed inside the second housing 210. The first heat exchanger 120, the second heat exchanger 220, and the multi-stage centrifugal compressor 230 are connected in sequence to achieve the control of the indoor temperature.

The multi-stage centrifugal compressor 230 may be a two-stage centrifugal compressor, which can compress the gaseous refrigerant entering the two-stage centrifugal compressor twice, so that the gaseous refrigerant can be fully compressed to ensure smooth cooling or heating of the air-conditioning system 10.

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.

As shown in FIG3 , during summer cooling, the first heat exchanger 120 serves as the evaporator 121, and the second heat exchanger 220 serves as the condenser 221. The air inlet of the multistage centrifugal compressor 230 is connected to the air outlet of the evaporator 121, the exhaust port of the multistage 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.

Through the above arrangement, the liquid refrigerant entering the evaporator 121 will absorb the heat in the room, so that the indoor temperature is reduced and refrigeration is achieved. In addition, 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. In addition, 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.

FIG. 4 is a cross-sectional view of a multi-stage centrifugal compressor according to some embodiments of the present disclosure; and FIG. 5 is a simulation diagram of a multi-stage centrifugal compressor according to some embodiments of the present disclosure.

As shown in FIG4 , in order to compress the gaseous refrigerant entering the multistage centrifugal compressor 230, the multistage centrifugal compressor 230 includes a casing 231, a bladeless diffuser 232, a primary impeller 233, a returner 234 and a secondary impeller 235, wherein the bladeless diffuser 232, the primary impeller 233, the returner 234 and the secondary impeller 235 are sequentially installed in the casing 231. A pressure diffusion channel 23A, a reversing channel 23B and a reversing channel 23C are sequentially connected between the bladeless diffuser 232, the returner 234 and the casing 231. The air inlet of the pressure diffusion channel 23A is connected to the air outlet of the primary impeller 233, the air outlet of the reversing channel 23C is connected to the air inlet of the secondary impeller 235, and the reversing channel 23B is connected between the pressure diffusion channel 23A and the reversing channel 23C.

Through the above arrangement, the gaseous refrigerant discharged from the air outlet of the primary impeller 233 can pass through the pressure diffusion channel 23A, the reversing channel 23B, and the reflux channel 23C in sequence, enter the secondary impeller 235, and finally be discharged to the outside of the casing 231. When the gaseous refrigerant passes through the primary impeller 233 and the secondary impeller 235, the primary impeller 233 and the secondary impeller 235 rotate, and the centrifugal force generated during the rotation process is used to compress the gaseous refrigerant to obtain high-pressure gaseous refrigerant.

It is understandable that the function of the bladeless diffuser 232 is to convert the kinetic energy in the gaseous refrigerant discharged from the primary 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 primary impeller 233 so that the gaseous refrigerant can enter the secondary impeller 235 from the air inlet of the secondary impeller 235, thereby realizing the secondary compression of the gaseous refrigerant.

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. In this way, the gaseous refrigerant at the air outlet of the pressure diffuser channel 23A has a tendency to flow to 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.

In some embodiments, in order to eliminate the recirculation area shown in FIG5 , guide vanes may be added at the bend to reduce the recirculation phenomenon. However, this solution is complex and costly, and the effectiveness of this solution depends on the design of the guide vane angle. Under certain working conditions, this solution may even increase the recirculation area and deteriorate the performance of the entire machine.

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

To solve the above problems, as shown in Figures 6 and 7, some embodiments of the present disclosure provide a multi-stage centrifugal compressor 230. Compared with Figures 4 and 5, the multi-stage centrifugal compressor 230 provided in some embodiments of the present disclosure utilizes the two-stage refrigeration system air supplementation enthalpy increase technology to impact the reflux area by supplementing the gaseous refrigerant, thereby eliminating the reflux area and reducing the loss. It can be understood that this technology is mainly applied to a two-stage refrigeration centrifugal compressor system in series.

In some embodiments, as shown in Fig. 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 returner 234, and a vaneless diffuser 232. A cavity is formed inside the casing 231.

In some embodiments, as shown in FIG7 , the returner 234 and the bladeless diffuser 232 are fixed in the cavity. The primary impeller 233 is rotatably disposed in the cavity, the bladeless diffuser 232 and the returner 234 are respectively located on both sides of the axial direction of the primary impeller 233, and a diffusion channel 23A is formed between the bladeless diffuser 232 and the returner 234. The air outlet of the primary impeller 233 is connected to the air inlet of the diffusion channel 23A, and the air inlet of the primary impeller 233 is connected to the air outlet of the evaporator 121.

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

In some embodiments, as shown in FIG7 , the compressor assembly further comprises a reversing plate 237, which is fixed in the cavity and arranged around the vaneless diffuser 232. As shown in FIG8 , 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 in a direction close to 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 communicated with the air outlet of the diffuser channel 23A, and the air outlet of the reversing channel 23B is communicated with the air inlet of the return channel 23C. The first end of the air intake gap 23D is communicated with the air inlet of the reversing channel 23B, and the second end of the air intake gap 23D is communicated with the external gaseous refrigerant.

In this way, as shown in FIG7 , the low-pressure gaseous refrigerant discharged from the evaporator 121 can enter the first-stage impeller 233 through the air inlet of the first-stage impeller 233. Under the action of the first-stage impeller 233, the low-pressure gaseous refrigerant is converted into a high-speed gaseous refrigerant and enters the pressure diffusion channel 23A from the air outlet of the first-stage impeller 233. In the pressure diffusion channel 23A, the high-speed gaseous refrigerant is converted into a low-speed and high-pressure gaseous refrigerant and enters the reversing channel 23B, thereby achieving a first-stage compression. After passing through the reversing channel 23B, the gaseous refrigerant turns and enters the return channel 23C, and enters the second-stage impeller 235 through the return channel 23C. Under the action of the second-stage impeller 235, a second-stage compression is achieved, and finally discharged from the air outlet of the second-stage impeller 235 to the condenser 221, thereby compressing the gaseous refrigerant discharged from the evaporator 121.

FIG. 9 is a simulation diagram of a multi-stage centrifugal compressor provided by some embodiments of the present disclosure.

In some embodiments of the present disclosure, there is an air intake gap 23D between the reversing plate 237 and the peripheral wall surface of the bladeless diffuser 232. As shown in FIG9 , the air intake gap 23D can introduce the external gaseous refrigerant into the air inlet of the reversing channel 23B, so as to drive 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 reflux problem here, so that the gaseous refrigerant can flow smoothly in the diffuser channel 23A and the reversing channel 23B, thereby improving the energy efficiency of the multi-stage centrifugal compressor 230.

It is understandable that the bladeless diffuser 232, the primary impeller 233, the return flow device 234, the secondary impeller 235 and the partition 236 should be coaxially arranged. For example, by arranging a rotating shaft in the cavity, the rotating shaft passes through the bladeless diffuser 232, the primary impeller 233, the return flow device 234, the secondary impeller 235 and the partition 236 in sequence, and the rotating shaft is driven to rotate by a motor, so that the primary impeller 233 and the secondary impeller 235 are rotated.

FIG. 10 is an external structural diagram of a casing provided in some embodiments of the present disclosure.

In some embodiments, in order to make the air inlet of the primary impeller 233 communicate with the air outlet of the evaporator 121, as shown in Figures 6 and 10, the housing 231 is provided with an opening 2311, and the opening 2311 is communicated with the cavity. The air inlet of the bladeless diffuser 232 is communicated with the air outlet of the evaporator 121 through the opening 2311. The primary impeller 233 is arranged at the air inlet of the bladeless diffuser 232, so that the primary impeller 233 is communicated with the air outlet of the evaporator 121 through the air inlet of the bladeless diffuser 232.

Of course, a pipe can also be used to connect the air inlet of the primary impeller 233 to the air outlet of the evaporator 121. The pipe can pass through the side wall of the casing 231, and the first end of the pipe is connected to the air inlet of the bladeless diffuser 232, and further connected to the air inlet of the primary 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 primary impeller 233, for example, perpendicular to the axial direction of the primary impeller 233.

FIG. 11 is a structural diagram of an air conditioning system including an economizer according to some embodiments of the present disclosure.

In order to provide 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. In this way, the air conditioning system 10 can use the economizer 240 to provide gaseous refrigerant to the air intake gap 23D.

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 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.

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

In some embodiments, the economizer 240 is a heat exchange economizer. As shown in FIG. 11 , the economizer 240 is connected between the evaporator 121 and the condenser 221, and the 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 the economizer 240 is connected to the outlet of the condenser 221 through a connecting pipe. A first bypass passage is connected between the condenser 221 and the 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 the economizer 240. The first outlet 2403 of the economizer 240 is connected to the inlet of the evaporator 121, and the second outlet 2404 of the economizer 240 is connected to the second end of the 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 the economizer 240.

In this way, the flow rate of the 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 the refrigerant entering the economizer 240 from the first inlet 2401 and the refrigerant entering the economizer 240 from the second inlet 2402 can exchange heat. In this way, the refrigerant discharged from the second outlet 2404 of the economizer 240 can be a low-temperature gaseous refrigerant. Since the second outlet 2404 of the economizer 240 is connected to the second end of the air intake gap 23D, the low-temperature gaseous refrigerant can enter the reversing channel 23B through the air intake gap 23D. In this way, the refrigerant reflux problem at the air outlet of the expansion channel 23A (the air inlet of the reversing channel 23B) is improved, and the effect of air replenishment and enthalpy increase is achieved, so as to improve the energy efficiency of the multi-stage centrifugal compressor 230 and further improve the efficiency of the multi-stage centrifugal compressor 230.

It should be noted that the economizer 240 may also be of other types, for example, a plate heat exchanger may be used instead of the economizer. The plate heat exchanger is small in size and simple to control, but the refrigeration efficiency of the plate heat exchanger is lower than that of the economizer. The expansion valve 241 may be an electronic expansion valve.

In some embodiments, as shown in FIG8 , the air inlet gap 23D is arranged around the vaneless diffuser 232. In this way, the external gaseous refrigerant can enter the reversing channel 23B from the air outlet position of the diffuser channel 23A through the air inlet gap 23D arranged along the circumference of the vaneless diffuser 232. In this way, the gaseous refrigerant can enter various places of the air inlet of the reversing channel 23B along the circumference of the vaneless diffuser 232, so as to improve the refrigerant reflux problem at various places of the air outlet of the diffuser channel 23A in the circumference of the vaneless diffuser 232, thereby further improving the energy efficiency of the multi-stage centrifugal compressor 230.

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

In some embodiments, the intake gap 23D may also be provided along the circumference of the vaneless diffuser 232 and around a portion of the vaneless diffuser 232 .

On this basis, in order to facilitate the external gaseous refrigerant to enter the air intake gap 23D, as shown in FIG12 , the compressor assembly is further formed with an air duct 250, and the air duct 250 surrounds the bladeless diffuser 232. One end of the air duct 250 is connected to the second end of the air intake gap 23D, and the other end of the air duct 250 is connected to the external gaseous refrigerant.

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 surround 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.

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, thereby 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 second end of the air intake gap 23D to connect to the external gaseous refrigerant.

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

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

In some embodiments, the air guide portion may be a first groove 2371, the first groove 2371 is arranged around the vaneless diffuser 232, and the notch of the first groove 2371 faces the vaneless diffuser 232. The first groove 2371 and the vaneless diffuser 232 define the air duct 250. 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, and the second end of the air intake gap 23D is connected to the first groove 2371.

By providing a first groove 2371 on the reversing plate 237, the first groove 2371 and the bladeless diffuser 232 define an 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. 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.

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 bladeless 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 bladeless 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.

It should be noted that the fixed connection between the housing 231 and the reversing plate 237 can be formed in one piece, and the structure of the housing 231 and the reversing plate 237 formed in one piece is stable. In addition, during processing, the housing 231 and the reversing plate 237 can be processed at one time, which is conducive to improving production efficiency. Of course, the housing 231 and the reversing plate 237 can also be a split structure. In this case, the housing 231 and the reversing plate 237 are processed separately, and then a secondary process is performed to fix the two together, so that the difficulty of processing the housing 231 and the reversing plate 237 can be reduced.

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

In other embodiments, in order to form the above-mentioned air duct 250, as shown in FIG. 14, a new guide portion is provided, and the guide portion may 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 body 2323 , and the second groove 2312 and the body 2323 form an air duct 250 . The second groove 2312 is in communication with the air intake gap 23D.

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 an air duct 250, and the second groove 2312 is connected to the air intake gap 23D, so that external gaseous refrigerant can enter the second groove 2312 and finally enter the reversing channel 23B through the air intake gap 23D.

In order to make the second groove 2312 communicate with the air intake gap 23D, as shown in Figure 14, a first gap can be reserved between the surface where the second groove 2312 of the reversing plate 237 is located and the body 2323. In this way, the gaseous refrigerant in the air duct 250 can enter the air intake gap 23D through the first gap.

Alternatively, in order to connect the second groove 2312 with the air intake gap 23D, a second gap may be provided on the reversing plate 237, and the air duct 250 may be connected with the air intake gap 23D by the second gap, so that the gaseous refrigerant in the air duct 250 can enter the air intake gap 23D through the second gap.

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

In some other embodiments, to form the above-mentioned air duct 250, as shown in FIG15, the returner 234 is fixedly connected to the reversing plate 237. A third groove 2313 is provided on the housing 231, and the notch of the third groove 2313 faces the reversing plate 237. The third groove 2313 surrounds the vaneless diffuser 232, and the third groove 2313 and the reversing plate 237 define the air duct 250. The third groove 2313 is in communication with the intake gap 23D.

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 external gaseous refrigerant can enter the third groove 2313 and finally enter the reversing channel 23B through the air intake gap 23D.

The returner 234 and the commutator plate 237 are fixedly connected so that the two can be integrally formed. The integrally formed returner 234 and the commutator plate 237 have a stable structure. In addition, during processing, the returner 234 and the commutator plate 237 can be processed at one time, which is conducive to improving processing efficiency. Of course, the returner 234 and the commutator plate 237 can also be a split structure, and the returner 234 and the commutator plate 237 are processed separately, and then a secondary processing is performed to fix the two together, so that the difficulty of processing the returner 234 and the commutator plate 237 can be reduced.

FIG. 16 is a structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure; FIG. 17 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

In some embodiments, in order to allow the gaseous refrigerant entering the air duct 250 to enter the reversing channel 23B uniformly through the air intake gap 23D along the circumference of the air duct 250, as shown in FIG16, the multi-stage centrifugal compressor 230 further includes a first air intake pipe 238, and the first air intake pipe 238 is fixed to the outer wall of the casing 231. As shown in FIG17, the first air intake pipe 238 is tangent to the circumference of the air duct 250, the first end of the first air intake pipe 238 is connected to the air duct 250, and the second end of the first air intake pipe 238 is connected to the air duct 250. Along the flow direction of the gaseous refrigerant in the air duct 250, the ventilation cross-sectional area of the air duct 250 tends to decrease, and the first end of the first air inlet pipe 238 is connected to the largest ventilation cross-sectional area of the air duct 250.

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.

Since the ventilation cross-sectional area of the air duct 250 tends to decrease along the flow direction of the gaseous refrigerant in the air duct 250, the pressure of the gaseous refrigerant tends to increase during the flow of the gaseous refrigerant. This can improve the problem that the pressure of the gaseous refrigerant decreases as the gaseous refrigerant flows, and can also ensure that the gaseous refrigerant can enter the air intake gap 23D uniformly in the circumferential direction of the bladeless diffuser 232, ensuring the uniformity of the air intake in the circumferential direction of the reversing channel 23B, thereby further improving the backflow problem at the air inlet of the reversing channel 23B.

In some embodiments, in order to further achieve uniformity of air intake in the circumferential direction of the reversing channel 23B, the cross-sectional area of the air duct 250 decreases in equal proportion along the flow direction of the gaseous refrigerant in the air duct 250. That is, the cross-sectional area of the air duct 250 is reduced 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 by the above-mentioned comprehensive data.

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.

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

FIG. 18 is another structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure; FIG. 19 is yet another structural diagram of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

In other embodiments, in order to allow the gaseous refrigerant entering the air duct 250 to enter the reversing channel 23B uniformly through the air intake gap 23D along the circumference of the air duct 250, 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 in the radial direction of the first-stage impeller 233. As shown in FIG19, the first end of the second air intake pipe 239 is communicated with the air duct 250, and the second end of the second air intake pipe 239 is communicated with the external gaseous refrigerant.

FIG. 20 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure; FIG. 21 is yet another cross-sectional view of another multi-stage centrifugal compressor according to some embodiments of the present disclosure.

As shown in Fig. 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 Fig. 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 which are connected in sequence.

Along the axial direction of the bladeless diffuser 232, the edge of the first sub-surface 23211 away from the return flow device 234 (located above the axial direction of the bladeless 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 bladeless diffuser 232 in the first direction (the direction represented by the left arrow in Figure 21), toward the first end away from the second inlet pipe 239, and close to the axis of the bladeless diffuser 232.

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.

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.

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 After the air intake gap 23D, in the first direction, the farther the part of the air intake gap 23D is from the second air intake pipe 239, the smaller the resistance to the gaseous refrigerant. In this way, the pressure loss caused by the flow of the gaseous refrigerant in the first direction can be compensated. That is, the farther from the second air intake pipe 239, the smaller the pressure of the gaseous refrigerant in the air intake gap 23D. Thereby, the air intake of the air intake gap 23D between the first sub-surface 23211 and the vaneless diffuser 232 is uniform in the circumferential direction.

Similarly, since the second edge 2321B extends along the circumference of the bladeless diffuser 232 in the opposite direction to the first direction, toward the first end away from the second air inlet pipe, and toward the direction close to the axis of the bladeless diffuser 232. Therefore, after the gaseous refrigerant enters the air intake gap 23D, in the opposite direction of the first direction, the farther the part of the air intake gap 23D is from the second air intake pipe 239, the smaller the resistance to the gaseous refrigerant. In this way, the pressure loss caused by the flow of the gaseous refrigerant in the opposite direction of the first direction can be compensated. That is, the farther away from the second air intake pipe 239, the smaller the pressure of the gaseous refrigerant in the air intake gap 23D. Thereby ensuring that the air intake gap 23D between the second sub-surface 23212 and the bladeless diffuser 232 is evenly inhaled in the circumferential direction.

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.

It can be understood that the distance between the first edge 2321A and the axis of the vaneless diffuser 232 in the first direction is decreasing, and the distance between the second edge 2321B and the axis of the vaneless diffuser 232 in the opposite direction of the first direction is decreasing, and can be reduced in equal proportion, so that the intake uniformity of the intake gap 23D in the circumferential direction can be better achieved. Of course, the distance between the first edge 2321A and the axis of the vaneless diffuser 232 in the first direction is decreasing, and the distance between the second edge 2321B and the axis of the vaneless diffuser 232 in the opposite direction of the first direction is decreasing, and can also be reduced in a variable proportion.

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

In some embodiments, along the circumference of the vaneless diffuser 232, as shown in FIG21, the first sub-surface 23211 and the second sub-surface 23212 may each occupy half, that is, each occupy 180 degrees. In this way, the gaseous refrigerant moving along the first direction and along the opposite direction of the first and second directions can enter the reversing channel 23B more evenly along the circumference of the vaneless diffuser 232. Alternatively, along the circumference of the vaneless diffuser 232, the proportions occupied by the first sub-surface 23211 and the second sub-surface 23212 may not be equal, for example, the first sub-surface 23211 occupies 120 degrees, and the second sub-surface 23212 occupies 240 degrees, and of course, any other suitable proportions may also be used.

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

For example, in the case where the air duct 250 is composed of the second groove 2312 and the body 2323, in order to achieve uniform intake of the gaseous refrigerant entering the air duct 250 from the second air inlet pipe 239 in the circumferential direction of the primary impeller 233, as shown in FIG14 , the second air inlet pipe 239 is connected to the second groove 2312, the reversing plate 237 is arranged around the body 2323, and the first surface 2321 is 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 intake gap 23D through the second groove 2312, and finally enter the reversing channel 23B.

Those skilled in the art will understand that the disclosure scope of the present 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 the present application. The scope of the present application is limited by the appended claims.

Claims (18)

1. An outdoor unit includes a multi-stage centrifugal compressor; wherein the multi-stage centrifugal compressor includes:

   Compressor components, including:

   A casing, wherein the casing has a cavity inside;

   Reflux device;

   commutation 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; 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 connected to 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 connected to the second end of the air intake gap, and the air duct is connected to the external gaseous refrigerant.
4. The outdoor unit according to claim 3, wherein the multi-stage centrifugal compressor further comprises a first air inlet pipe, the first air inlet pipe is fixed to the outer wall of the casing and is tangent to the circumference of the air duct, a first end of the first air inlet pipe is communicated with the air duct, and a second end of the first air inlet pipe is communicated 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 point 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 comprises a second air inlet pipe, the second air inlet pipe is fixed to the outer wall of the casing and extends in the radial direction of the first-stage impeller, a first end of the second air inlet pipe is communicated with the air duct, and a second end of the second air inlet pipe is communicated with the external gaseous refrigerant;

   The air 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 away from the first end, 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 the opposite direction to the first direction, toward the first end of the second inlet pipe away from the first end, and close to the axis of the vaneless diffuser.
6. The outdoor unit according to claim 4, wherein the casing is fixedly connected to the reversing plate, 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 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, 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 primary impeller; the bladeless diffuser comprises:

   A protrusion surrounds the axis of the first-stage impeller, the reversing plate surrounds the protrusion and forms the air intake gap between the reversing plate and the protrusion, and the diffuser channel is formed between the protrusion and the return device; and

   The main body is fixedly connected to the protrusion and is located on a side of the protrusion away from the return device. 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, further comprising an economizer, wherein the economizer is communicated with 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 plate fixed in the cavity and located on a side of the returner away from the bladeless diffuser, the partition plate being arranged around the axis of the primary impeller and forming a return channel with the returner, the air inlet of the return 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 device. The air outlet of the return channel is connected to the air inlet of the secondary impeller.
10. An air conditioning system, comprising:

    Indoor unit; and

    An outdoor unit, the outdoor unit comprising a multi-stage centrifugal compressor, the multi-stage centrifugal compressor comprising:

    Compressor assembly, including:

    A casing, wherein the casing has a cavity inside;

    Reflux device;

    commutation 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 a reversing channel is formed 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 connected to 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 connected to the second end of the air intake gap, and the air duct is connected to the external gaseous refrigerant.
13. The air conditioning system according to claim 12, wherein the multi-stage centrifugal compressor further comprises a first air inlet pipe, the first air inlet pipe is fixed to the outer wall of the casing and is tangent to the circumference of the air duct, 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 point 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 comprises a second air inlet pipe, the second air inlet pipe is fixed to the outer wall of the casing and extends in the radial direction of the first-stage impeller, a first end of the second air inlet pipe is communicated with the air duct, and a second end of the second air inlet pipe is communicated with the external gaseous refrigerant;

    The air 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 a direction away from 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 a direction away from 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, 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 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 a 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, 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 bladeless diffuser comprises:

    A protrusion surrounds the axis of the first-stage impeller, the reversing plate surrounds the protrusion and forms the air intake gap between the reversing plate and the protrusion, and the diffuser channel is formed between the protrusion and the return device; and

    The main body is fixedly connected to the protrusion and is located on a side of the protrusion away from the return device. 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 comprises an economizer, and the economizer is communicated with 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 plate fixed in the cavity and located on a side of the returner away from the bladeless diffuser, the partition plate being arranged around the axis of the primary impeller and forming a return channel with the returner, the air inlet of the return 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 device. The air outlet of the return channel is connected to the air inlet of the secondary impeller.