CENTRIFUGAL COMPRESSOR, REFRIGERATION HEAT PUMP UNIT

Description

BACKGROUND

This application claims benefit of Chinese Patent Application No. 202411146866.3, filed Aug. 20, 2024, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in their entirety are herein incorporated by reference.

BACKGROUND

This application relates to the technical field of refrigeration heat pumps, and specifically to a centrifugal compressor and a refrigeration heat pump unit with the centrifugal compressor. A multi-stage centrifugal compressor with multiple compression stages can provide a high compression ratio.

SUMMARY

This application aims to provide a centrifugal compressor and a refrigeration heat pump unit to at least solve or alleviate some of the problems existing in the related art.

A first aspect of this application provides a centrifugal compressor including a first compression chamber, a second compression chamber, a communication member, a first impeller, a second impeller, a third impeller and a first bypass pipe. The first compression chamber includes a first inlet portion that includes a first variable guide vane, and a first outlet portion. The second compression chamber includes a second inlet portion that includes a second variable guide vane, and a second outlet portion. The communication member allows the first outlet portion to communicate with the second inlet portion, or allows the second outlet portion to communicate with the first inlet portion. The first impeller is rotatably disposed inside the first compression chamber and disposed adjacent to the first variable guide vane. The second impeller is rotatably disposed inside the second compression chamber and disposed adjacent to the second variable guide vane. The third impeller is rotatably disposed inside the first compression chamber and located downstream of the first impeller. The first bypass pipe allows a discharge flow passage of the third impeller to communicate with an inlet of the third impeller.

The centrifugal compressor of one or more embodiments further includes a motor. The motor drives the first impeller, the second impeller and the third impeller. The first compression chamber and the second compression chamber are disposed opposite to each other at two ends of the motor.

In the centrifugal compressor of one or more embodiments, the motor includes a motor body and a motor shaft, the motor body is disposed between the first compression chamber and the second compression chamber, the motor shaft passes through the motor body and two ends thereof extend into the first compression chamber and the second compression chamber respectively, and the first impeller, the second impeller and the third impeller are all directly fixed to the motor shaft.

In the centrifugal compressor of one or more embodiments, the communication member allows the first outlet portion to communicate with the second inlet portion. The centrifugal compressor further includes a second bypass pipe that allows a discharge flow passage of the second impeller to communicate with an inlet of the second impeller.

In the centrifugal compressor of one or more embodiments, the communication member allows the first outlet portion to communicate with the second inlet portion. The centrifugal compressor further includes a second bypass pipe that allows the discharge flow passage of the second impeller to communicate with an inlet of the second variable guide vane.

In the centrifugal compressor of one or more embodiments, the communication member allows the first outlet portion to communicate with the second inlet portion. The centrifugal compressor further includes a fourth impeller and a second bypass pipe. The fourth impeller is rotatably disposed inside the second compression chamber, located downstream of the second impeller, and disposed adjacent to the second outlet portion. The second bypass pipe allows an outlet of the fourth impeller to communicate with an inlet of the fourth impeller.

A second aspect of this application provides a refrigeration heat pump unit including a refrigerant circuit formed by a centrifugal compressor, a condenser, a throttling device, and an evaporator.

The centrifugal compressor includes a first compression chamber, a second compression chamber, a first impeller, a second impeller, a third impeller and a first bypass pipe. The first compression chamber includes a first inlet portion that includes a first variable guide vane and communicates with an outlet of the evaporator, and a first outlet portion. The second compression chamber includes a second inlet portion that includes a second variable guide vane and communicates with the first outlet portion, and a second outlet portion that communicates with an inlet of the condenser. The first impeller is rotatably disposed inside the first compression chamber and disposed adjacent to the first variable guide vane. The second impeller is rotatably disposed inside the second compression chamber and disposed adjacent to the second variable guide vane. The third impeller is rotatably disposed inside the first compression chamber and located downstream of the first impeller. The first bypass pipe allows a discharge flow passage of the third impeller to communicate with an inlet of the third impeller.

In the refrigeration heat pump unit of one or more embodiments, the centrifugal compressor further includes a motor. The motor drives the first impeller, the second impeller and the third impeller. The first compression chamber and the second compression chamber are disposed opposite to each other at two ends of the motor.

In the refrigeration heat pump unit of one or more embodiments, the centrifugal compressor further includes a second bypass pipe that allows a discharge flow passage of the second impeller to communicate with an inlet of the second impeller, or allows the discharge flow passage of the second impeller to communicate with an inlet of the second variable guide vane.

The refrigeration heat pump unit of one or more embodiments further includes a first economizer, a second economizer, a first pipe and a second pipe.

The first economizer is connected between the condenser and the evaporator. The second economizer is connected between the condenser and the evaporator, and is connected in series with the first economizer. The first pipe allows an outlet of the first economizer to communicate with the inlet of the third impeller. The second pipe allows an outlet of the second economizer to communicate with the discharge flow passage of the third impeller. Two ends of the first bypass pipe are respectively connected to the first pipe and the second pipe.

The refrigeration heat pump unit of one or more embodiments further includes a control valve. The control valve is disposed on the first bypass pipe.

The throttling device includes a first throttling device, a second throttling device and a third throttling device. The first throttling device is located between the condenser and the second economizer. The second throttling device is located between the second economizer and the first economizer. The third throttling device is located between the first economizer and the evaporator.

A third aspect of this application provides a refrigeration heat pump unit including: a refrigerant circuit formed by a centrifugal compressor, a condenser, a throttling device, and an evaporator.

The centrifugal compressor includes a first compression chamber, a second compression chamber, a first impeller, a second impeller, a third impeller and a first bypass pipe. The first compression chamber includes a first inlet portion that includes a first variable guide vane, and a first outlet portion that communicates with an inlet of the condenser; The second compression chamber includes a second inlet portion that includes a second variable guide vane and communicates with an outlet of the evaporator, and a second outlet portion that communicates with the first inlet portion. The first impeller is rotatably disposed inside the first compression chamber and disposed adjacent to the first variable guide vane. The second impeller is rotatably disposed inside the second compression chamber and disposed adjacent to the second variable guide vane. The third impeller is rotatably disposed inside the first compression chamber and located downstream of the first impeller. The first bypass pipe allows a discharge flow passage of the third impeller to communicate with an inlet of the third impeller.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a refrigeration heat pump unit according to one or more embodiments of this application;

FIG. 2 shows a schematic diagram of a refrigeration heat pump unit according to one or more embodiments of this application;

FIG. 3 shows a schematic diagram of a refrigeration heat pump unit according to one or more embodiments of this application;

FIG. 4 shows a schematic diagram of a refrigeration heat pump unit according to one or more embodiments of this application;

FIG. 5 shows a schematic diagram of a refrigeration heat pump unit according to one or more embodiments of this application; and

FIG. 6 shows a schematic diagram of the refrigeration heat pump unit according to one or more embodiments of this application.

Reference numerals: 100 centrifugal compressor; 1 first compression chamber; 10 first inlet portion; 101 first variable guide vane; 11 first outlet portion; 2 second compression chamber; 20 second inlet portion; 201 second variable guide vane; 21 second outlet portion; 31 first impeller; 32 second impeller; 33 third impeller; 331 inlet of third impeller; 332 discharge flow passage of third impeller; 4 communication member; 5 first bypass pipe; 6 motor; 61 motor body; 62 motor shaft; 7 second bypass pipe; 321 inlet of second impeller; 322 discharge flow passage of second impeller; 34 fourth impeller; 341 inlet of fourth impeller; 342 outlet of fourth impeller; 1000 refrigeration heat pump unit; 81 condenser; 82 evaporator; 83 throttling device; 831 first throttling device; 832 second throttling device; 833 third throttling device; 84 economizer; 841 first economizer; 842 second economizer; 851 first pipe; 852 second pipe; 91 control valve.

DETAILED DESCRIPTION OF THE DISCLOSURE

It should be noted that working principles, features, advantages and the like of a centrifugal compressor and a refrigeration heat pump unit according to this application will be described below in an illustrative manner. However, it should be understood that all descriptions are only given for exemplification and therefore should not be understood as forming any limitation on this application.

In addition, for any single technical feature described or implicit in the embodiments mentioned herein, or any single technical feature shown or implicit in the drawings, this application still allows any combination or deletion between these technical features (or their equivalents) without any technical obstacles, thereby obtaining more other embodiments of this application that may not be directly mentioned herein.

In multi-stage centrifugal compressors provided in existing configurations, some compression stages are prone to enter a surge area, a stall area, or a high vibration noise area, thereby affecting an operating range of the compressor.

The centrifugal compressor and a refrigeration heat pump unit of the present disclosure aims to at least solve or alleviate some of these problems.

FIG. 1 is a schematic diagram of a refrigeration heat pump unit according to a one or more embodiments of this application. As illustrated in FIG. 1, the centrifugal compressor 100 having three and more compression stages, and a refrigeration heat pump unit 1000 having the centrifugal compressor 100, are shown with reference to generally the accompanying drawings, according to an exemplary embodiment. By a separate bypass of a compression stage without variable guide vanes (non-IGV-stage) separately, the compressor and unit can expand the stable operating range and reduce noise and vibration. Further, it is possible to optionally configure a single bypass for a high-pressure compression stage as well.

The centrifugal compressor 100 provided in some embodiments, as shown in FIG. 1, includes a first compression chamber 1, a second compression chamber 2, a communication member 4, a first impeller 31, a second impeller 32, a third impeller 33 and a first bypass pipe 5.

The first compression chamber 1 includes a first inlet portion 10 that includes a first variable guide vane 101, and a first outlet portion 11. The second compression chamber 2 includes a second inlet portion 20 that includes a second variable guide vane 201, and a second outlet portion 21. The communication member 4 allows the first outlet portion 11 to communicate with the second inlet portion 20.

The first impeller 31 is rotatably disposed inside the first compression chamber 1 and disposed adjacent to the first variable guide vane 101. The second impeller 32 is rotatably disposed inside the second compression chamber 2 and disposed adjacent to the second variable guide vane 201. The third impeller 33 is rotatably disposed inside the first compression chamber 1 and located downstream of the first impeller 31. The first bypass pipe 5 allows a discharge flow passage 332 of the third impeller to communicate with an inlet 331 of the third impeller.

Here, the discharge flow passage 332 of the third impeller refers to a flow passage between the outlet of the third impeller 33 and an inlet of a next stage impeller. It can be understood that an outlet of an impeller, a diffuser (not shown) and a volute (not shown) of the compression stage corresponding to the third impeller 33 are all included in the range of the discharge flow passage 332 of the third impeller described in this application. As a specific example, the first bypass pipe 5 allows an outlet of the volute of the compression stage corresponding to the third impeller 33 to communicate with the inlet 331 of the third impeller. In another specific example, the compression stage corresponding to the third impeller 33 does not have a separate volute, and the first bypass pipe 5 allows an outlet of the diffuser of the compression stage corresponding to the third impeller 33 to communicate with the inlet 331 of the third impeller.

The first bypass pipe 5 allowing a discharge flow passage 332 of the third impeller to communicate with an inlet 331 of the third impeller means that the first bypass pipe 5 connects the discharge flow passage 332 of the third impeller and the inlet 331 of the third impeller, or the first bypass pipe 5 connects the vicinity of the discharge flow passage 332 of the third impeller and the vicinity of the inlet 331 of the third impeller.

When the centrifugal compressor 100 in some embodiments is working, a refrigerant enters the first compression chamber 1 from the first inlet portion 10, leaves the first compression chamber 1 from the first outlet portion 11 after passing through the first impeller 31 and the third impeller 33, enters the second compression chamber 2 from the second inlet portion 20 after passing through the communication member 4, and leaves the second compression chamber 2 from the second outlet portion 21 after passing through the second impeller 32. It can be understood that after being accelerated and pressurized by each impeller, the refrigerant will enter the diffuser for diffusion and then pass through the next impeller. The diffuser can be considered as a part constituting the compression chamber.

The first inlet portion 10 of the first compression chamber 1 includes the first variable guide vane 101. The first variable guide vane 101 can adjust flow rates of the refrigerant entering the first impeller 31, that is, the compression stage corresponding to the first impeller 31 adjacent to the first variable guide vane 101 has the capacity to adjust the flow rates. Similarly, the second inlet portion 20 of the second compression chamber 2 includes the second variable guide vane 201. The second variable guide vane 201 can adjust flow rates of the refrigerant entering the second impeller 32, that is, a compression stage corresponding to the second impeller 32 adjacent to the second variable guide vane 201 has the capacity to adjust the flow rates. The compression stage corresponding to the first impeller 31 and the compression stage corresponding to the second impeller 32 are a compression stage with variable guide vanes (IGV-stage).

Different from the first impeller 31 and the second impeller 32, the third impeller 33 is located downstream of the first impeller 31, and no variable guide vane is disposed at the inlet 331 of the third impeller. Therefore, the compression stage corresponding to the third impeller 33 does not have the capacity to adjust the flow rates. The compression stage corresponding to the third impeller 33 is a compression stage without variable guide vanes (non-IGV-stage).

Compared with the compression stage with variable guide vanes (IGV-stage), the compression stage without variable guide vanes (non-IGV-stage) has a smaller operating range and is prone to enter a surge area or a stall area or an area with high vibration noise, thereby reducing the overall operating range of the centrifugal compressor 100. Specifically, in a high lift unloading condition, the compression ratio increases, the flow rate decreases, and a working point of the compression stage without variable guide vanes (non-IGV-stage) is prone to enter the surge area or the stall area or the area with high vibration noise. This disturbs a flow field of the compression stage without variable guide vanes (non-IGV-stage), resulting in a high noise, a high vibration, and a low operating efficiency of the centrifugal compressor 100.

In some embodiments, the first bypass pipe 5 allows the discharge flow passage 332 of the third impeller to communicate with the inlet 331 of the third impeller. In this way, when the working point of the compression stage corresponding to the third impeller 33 enters or is about to enter the surge area, the stall area or the area with high vibration noise, the refrigerant in the discharge flow passage 332 of the third impeller can be bypassed to the inlet 331 of the third impeller to increase the flow rate of the compression stage so that the working point thereof can be out of the surge area, the stall area or the area with high vibration noise. In this way, the overall operating range of the centrifugal compressor 100 is larger, especially the centrifugal compressor 100 can better correspond to a working condition of high compression ratio and low load.

In addition, in some embodiments, only the refrigerant in the discharge flow passage 332 of the third impeller is bypassed to the inlet 331 of the third impeller, that is, a single bypass, which is beneficial to improve the working efficiency of the centrifugal compressor 100 compared with the conventional manner of bypassing a refrigerant in a discharge port of a compressor.

It should be noted here that in some embodiments, the third impeller 33 is located downstream of the first impeller 31 and disposed adjacent to the first impeller 31, but this application is not limited thereto. As long as an impeller is disposed downstream of the first impeller 31 and does not have a variable guide vane disposed at the inlet, it is within the scope of the third impeller 33 described in this application. There is no particular limitation on the number of impellers in the first compression chamber 1 and the compression stage of the third impeller 33. For example, in some embodiments, one or more impellers are disposed at intervals between the first impeller 31 and the third impeller 33.

Continuing to refer to FIG. 1, the centrifugal compressor 100 provided in some embodiments further includes a motor 6. The motor 6 drives the first impeller 31, the second impeller 32 and the third impeller 33. The first compression chamber 1 and the second compression chamber 2 are disposed opposite to each other at two ends of the motor 6. Here, the first compression chamber 1 and the second compression chamber 2 being disposed opposite to each other specifically means that the first impeller 31 and the third impeller 33 in the first compression chamber 1, and the second impeller 32 in the second compression chamber 2 are disposed opposite to each other, so as to balance axial thrust and make a structure of the centrifugal compressor 100 more compact.

In some embodiments, there is only one motor 6 and it is located between the first compression chamber 1 and the second compression chamber 2, but this application is not limited thereto. In some embodiments, two motors 6 may be disposed between the first compression chamber 1 and the second compression chamber 2 to respectively drive the impeller in the first compression chamber 1 and the impeller in the second compression chamber 2. In some embodiments, one motor 6 may be disposed at one end of the first compression chamber 1, and another motor 6 may be disposed at one end of the second compression chamber 2, and the two motors 6 are staggered in the axial direction.

Continuing to refer to FIG. 1, in some embodiments, the motor 6 includes a motor body 61 and a motor shaft 62, the motor body 61 is disposed between the first compression chamber 1 and the second compression chamber 2, the motor shaft 62 passes through the motor body 61 and two ends thereof extend into the first compression chamber 1 and the second compression chamber 2 respectively, and the first impeller 31, the second impeller 32 and the third impeller 33 are all directly fixed to the motor shaft 62. That is, the first impeller 31, the second impeller 32 and the third impeller 33 are all directly driven by the motor 6, so that the centrifugal compressor 100 can provide a higher compression ratio.

In some embodiments, the first impeller 31, the second impeller 32 and the third impeller 33 are all directly fixed to the motor shaft 62, but this application is not limited thereto. In some embodiments, rotating shafts of the first impeller 31, the second impeller 32 and the third impeller 33 may be connected to the motor shaft 62 through driving wheels. Alternatively, the rotating shaft of the first impeller 31, the rotating shaft of the second impeller 32, the rotating shaft of the third impeller 33 and the motor shaft 62 may be partially coaxial or partially non-coaxial.

Some embodiments further provide the refrigeration heat pump unit 1000, as shown in FIG. 1, including a refrigerant circuit formed by a centrifugal compressor 100, a condenser 81, an economizer 84, a throttling device 83, and an evaporator 82. An outlet of the evaporator 82 communicates with the first inlet portion 10 of the first compression chamber 1, and an inlet of the condenser 81 communicates with the second outlet portion 21 of the second compression chamber 2.

It should be noted that the economizer 84 and the throttling device 83 in the illustrated embodiment are merely exemplary. It can be understood that an outlet of the economizer 84 may be connected to any compression stage of the centrifugal compressor 100 to supply air for the compression stage. In addition, the throttling device 83 may be disposed upstream and downstream of the economizer 84, and a specific type of the throttling device 83 may also be selected according to actual needs.

When the refrigeration heat pump unit 1000 in some embodiments is working, a refrigerant leaving from the evaporator 82 enters the centrifugal compressor 100 from the first inlet portion 10, passes through the first compression chamber 1 and the second compression chamber 2 in sequence, leaves the centrifugal compressor 100 from the second outlet portion 21, and enters the condenser 81. The refrigerant after heat exchange in the condenser 81 enters the evaporator 82 for heat exchange after passing through the economizer 84 and the throttling device 83.

In some embodiments, the refrigerant first enters the second compression chamber 2 and then enters the first compression chamber 1. That is, the second compression chamber 2 is a front compression chamber, and the first compression chamber 1 where the third impeller 33 is located is a rear compression chamber.

The centrifugal compressor 100 provided in some embodiments, as shown in FIG. 2, includes the second compression chamber 2, the first compression chamber 1, the communication member 4, the first impeller 31, the second impeller 32, the third impeller 33 and the first bypass pipe 5.

The second compression chamber 2 includes the second inlet portion 20 that includes the second variable guide vane 201, and the second outlet portion 21. The first compression chamber 1 includes the first inlet portion 10 that includes the first variable guide vane 101, and the first outlet portion 11. The communication member 4 allows the second outlet portion 21 to communicate with the first inlet portion 10.

The first impeller 31 is rotatably disposed inside the first compression chamber 1 and disposed adjacent to the first variable guide vane 101. The second impeller 32 is rotatably disposed inside the second compression chamber 2 and disposed adjacent to the second variable guide vane 201. The third impeller 33 is rotatably disposed inside the first compression chamber 1 and located downstream of the first impeller 31. The first bypass pipe 5 allows the discharge flow passage 332 of the third impeller to communicate with the inlet 331 of the third impeller.

When the centrifugal compressor 100 in some embodiments is working, a refrigerant enters the second compression chamber 2 from the second inlet portion 20, leaves the second compression chamber 2 from the second outlet portion 21 after passing through the second impeller 32, enters the first compression chamber 1 from the first inlet portion 10 after passing through the communication member 4, and leaves the first compression chamber 1 from the first outlet portion 11 after passing through the first impeller 31 and the third impeller 33.

In some embodiments, the compression stage corresponding to the third impeller 33 does not have the capacity to adjust the flow rates, that is, the compression stage is the compression stage without variable guide vanes (non-IGV-stage), and the working point of the compression stage corresponding to the third impeller 33 is prone to enter the surge area, the stall area or the area with high vibration noise. Therefore, the first bypass pipe 5 allows the discharge flow passage 332 of the third impeller to communicate with the inlet 331 of the third impeller. When the working point of the compression stage corresponding to the third impeller 33 enters or is about to enter the surge area, the stall area or the area with high vibration noise, the refrigerant in the discharge flow passage 332 of the third impeller can be bypassed to the inlet 331 of the third impeller to increase the flow rate of the compression stage so that the working point thereof can be out of the surge area, the stall area or the area with high vibration noise.

Some embodiments further provide the refrigeration heat pump unit 1000, as shown in FIG. 2, including the refrigerant circuit formed by the centrifugal compressor 100, the condenser 81, the throttling device 83, the economizer 84, and the evaporator 82. The outlet of the evaporator 82 communicates with the second inlet portion 20 of the second compression chamber 2, and the inlet of the condenser 81 communicates with the first outlet portion 11 of the first compression chamber 1.

When the refrigeration heat pump unit 1000 in some embodiments is working, a refrigerant leaving from the evaporator 82 enters the centrifugal compressor 100 from the second inlet portion 20, passes through the second compression chamber 2 and the first compression chamber 1 in sequence, leaves the centrifugal compressor 100 from the first outlet portion 11, and enters the condenser 81. The refrigerant after heat exchange in the condenser 81 enters the evaporator 82 for heat exchange after passing through the economizer 84 and the throttling device 83.

In some embodiments, referring to FIG. 3, differs in that, a second bypass pipe 7 that allows a discharge flow passage 322 of the second impeller to communicate with an inlet 321 of the second impeller is disposed in the centrifugal compressor 100 in some embodiments.

In some embodiments, the compression stage corresponding to the second impeller 32 belongs to the highest compression stage (specifically, the third compression stage), that is, the refrigerant passed through the highest compression stage is sent to the condenser 81 for heat exchange. Since the second impeller 32 corresponds to the highest compression stage, a operating flow rate of the second impeller 32 is small, and a working point is prone to enter the surge area, the stall area or the area with high vibration noise. Therefore, the second bypass pipe 7 allows the discharge flow passage 322 of the second impeller to communicate with the inlet 321 of the second impeller. When the working point of the compression stage corresponding to the second impeller 32 enters or is about to enter the surge area, the stall area or the area with high vibration noise, the refrigerant in the discharge flow passage 322 of the second impeller can be bypassed to the inlet 321 of the second impeller to increase the flow rate of the compression stage so that the working point thereof can be out of the surge area, the stall area or the area with high vibration noise. In some embodiments, as shown in FIG. 6, the refrigerant in the discharge flow passage 322 of the second impeller may be selectively bypassed to the upstream of the second variable guide vane 201. That is, the second bypass pipe 7 allows the discharge flow passage 322 of the second impeller to communicate with the inlet of the second variable guide vane 201 (not shown), and the inlet of the second variable guide vane 201 is disposed at the communication member 4.

That is, in some embodiments, considering that the compression stage without variable guide vanes (non-IGV-stage) is prone to surge or stall, and also considering that the rear compression stage (specifically the third compression stage corresponding to the second impeller 32) is more likely to surge or stall, or enter the area with high vibration noise than the front compression stage (specifically the first compression stage corresponding to the first impeller 31 and the second compression stage corresponding to the third impeller 33), separate bypass pipes (i.e., the first bypass pipe 5 and the second bypass pipe 7) are disposed for the compression stage without variable guide vanes (non-IGV-stage) and the rear compression stage (the third compression stage corresponding to the second impeller 32).

In some embodiments, referring to FIG. 4, a fourth impeller 34 is disposed downstream of the second impeller 32. A compression stage corresponding to the fourth impeller 34 belongs to the highest compression stage (specifically, a fourth compression stage). The second bypass pipe 7 allows an outlet 342 of the fourth impeller to communicate with an inlet 341 of the fourth impeller. When the working point of the compression stage corresponding to the fourth impeller 34 enters or is about to enter the surge area, the stall area or the area with high vibration noise, the refrigerant in the outlet 342 of the fourth impeller can be bypassed to the inlet 341 of the fourth impeller to increase the flow rate of the compression stage so that the working point thereof can be out of the surge area, the stall area or the area with high vibration noise.

In some embodiments, the fourth impeller 34 is located downstream of the second impeller 32 and disposed adjacent to the second impeller 32, but this application is not limited thereto. As long as a impeller is disposed downstream of the second impeller 32 and disposed adjacent to the second outlet portion 21 (that is, a impeller corresponding to the highest compression stage), it is within the scope of the fourth impeller 34 described in this application, and there is no particular limitation on the number of impellers in the second compression chamber 2. For example, in some embodiments, one or more impellers are disposed at intervals between the second impeller 32 and the fourth impeller 34.

In some embodiments, the first bypass pipe 5 is connected to an outlet pipe of the economizer.

The refrigeration heat pump unit 1000 in some embodiments, as shown in FIG. 5, includes the refrigerant circuit formed by the centrifugal compressor 100, the condenser 81, a first throttling device 831, a second economizer 842, a second throttling device 832, a first economizer 841, a third throttling device 833, and the evaporator 82. The outlet of the evaporator 82 communicates with the first inlet portion 10 of the first compression chamber 1, and the inlet of the condenser 81 communicates with the second outlet portion 21 of the second compression chamber 2. The first economizer 841 and the second economizer 842 are connected in series, and both are disposed between the condenser 81 and the evaporator 82. A first pipe 851 allows an outlet of the first economizer 841 to communicate with the inlet 331 of the third impeller, and a second pipe 852 allows an outlet of the second economizer 842 to communicate with the discharge flow passage 332 of the third impeller. Here, the discharge flow passage 332 of the third impeller includes an internal flow passage of the communication member 4. That is, the second pipe 852 may have one end to be communicated with the outlet of the economizer 842 and the other end to be communicated with the communication member 4. In this way, it is more beneficial to arrange pipelines.

Two ends of the first bypass pipe 5 are respectively connected to the first pipe 851 and the second pipe 852, so that the first bypass pipe 5 allows the discharge flow passage 332 of the third impeller to communicate with the inlet 331 of the third impeller. When the working point of the compression stage corresponding to the third impeller 33 enters or is about to enter the surge area, the stall area or the area with high vibration noise, the refrigerant in the discharge flow passage 332 of the third impeller can be bypassed to the inlet 331 of the third impeller to increase the flow rate of the compression stage so that the working point thereof can be out of the surge area, the stall area or the area with high vibration noise.

By disposing the first bypass pipe 5 as described above, it is possible to easily add the first bypass pipe 5 to some existing centrifugal compressors 100 to achieve a separate bypass of the compression stage without variable guide vanes (non-IGV-stage), thereby expanding the operating range of the centrifugal compressor 100 and enabling the centrifugal compressor 100 to operate stably under a low-load working condition. In addition, when it is not necessary to operate under a low-load working condition, the first bypass pipe 5 can be easily removed to save costs.

In some embodiments, the two ends of the first bypass pipe 5 are respectively connected to the first pipe 851 and the second pipe 852, so that there is no need to form an additional port on the centrifugal compressor 100, that is, the existing air supply port on the centrifugal compressor 100 is utilized, thereby achieving communication between the discharge flow passage 332 of the third impeller and the inlet 331 of the third impeller, but this application is not limited thereto. As long as the first bypass pipe 5 can achieve communication between the discharge flow passage 332 of the third impeller and the inlet 331 of the third impeller, it is within the scope of this application, and there is no particular limitation on specific disposing positions of the two ends of the first bypass pipe 5 on the centrifugal compressor 100. For example, in some embodiments, two additional ports may be added on the centrifugal compressor 100 for cooperative connection with the two ends of the first bypass pipe 5. In a specific example, one of the two additional ports above is located downstream of an air supply port connected to the first pipe 851, and the other is located upstream of an air supply port connected to the second pipe 852. In another specific example, one of the two additional ports above is located downstream of the air supply port connected to the first pipe 851, and the other is located downstream of the air supply port connected to the second pipe 852.

A control valve 91 is disposed on the first bypass pipe 5. Specifically, the control valve 91 is a precise envelope stability control valve (PESC valve), which can perform stepless adjustment according to the bypass flow rate determined by calculation. Of course, a specific type of the control valve 91 may be selected according to actual needs.

When the refrigeration heat pump unit 1000 in some embodiments is working, the refrigerant leaving from the evaporator 82 enters the centrifugal compressor 100 from the first inlet portion 10, passes through the first compression chamber 1 and the second compression chamber 2 in sequence, leaves the centrifugal compressor 100 from the second outlet portion 21, and enters the condenser 81. The refrigerant after heat exchange in the condenser 81 reaches the second economizer 842 after passing through the first throttling device 831. In the second economizer 842, a gaseous refrigerant is injected into the centrifugal compressor 100, and the gaseous refrigerant reaches the first economizer 841 after passing through the second throttling device 832. In the first economizer 841, a gaseous refrigerant is injected into the centrifugal compressor 100, and the gaseous refrigerant passes through the third throttling device 833 and enters the evaporator 82 for heat exchange.

In some embodiments, the two ends of the first bypass pipe 5 are respectively connected to the first pipe 851 and the second pipe 852, so that the first bypass pipe 5 allows the discharge flow passage 332 of the third impeller to communicate with the inlet 331 of the third impeller, but this application is not limited thereto. As long as it is possible to bypass the refrigerant in the discharge flow passage 332 of the third impeller to the inlet 331 of the third impeller, it is within the scope of the first bypass pipe 5 of this application. A specific connection method of the first bypass pipe 5 may be selected according to actual conditions.

The above embodiments are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application shall be included in the protection scope of this application.