CN111946638A

CN111946638A - Multistage centrifugal compressor and refrigerating system

Info

Publication number: CN111946638A
Application number: CN202010980219.8A
Authority: CN
Inventors: 张晓锐; 钟瑞兴; 蒋楠; 亓静利
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2020-09-17
Filing date: 2020-09-17
Publication date: 2020-11-17

Abstract

The invention relates to a multistage centrifugal compressor and a refrigeration system. The Q impellers on the multistage centrifugal compressor comprise M first impellers and N second impellers; when Q is an even number, M is equal to N, each group of first impellers and each group of second impellers are distributed in a back-to-back mode under the condition that M is an even number, and under the condition that M is an odd number, two first impellers with the minimum grade, two second impellers with the maximum grade, the rest first impellers and the rest second impellers are distributed in a back-to-back mode; when Q is an odd number, M is greater than N by 1, when M is an even number, each group of first impellers, two second impellers with the largest level and the rest of the second impellers are distributed in a back-to-back mode with the second impellers with the largest level, and when M is an odd number, the two first impellers with the smallest level, the second impellers adjacent to the level and the rest of the first impellers are distributed in a back-to-back mode with the second impellers with the largest level.

Description

Multistage centrifugal compressor and refrigerating system

Technical Field

The invention relates to the technical field of refrigeration, in particular to a multistage centrifugal compressor and a refrigeration system.

Background

At present, in order to solve the problem that the compression ratio of a single centrifugal compressor cannot meet the industrial requirement, a plurality of impellers are usually integrated on the same centrifugal compressor, however, the axial force of the centrifugal compressor can be increased, and the stable operation of the centrifugal compressor is not facilitated.

Disclosure of Invention

Based on the above, the invention provides a multistage centrifugal compressor and a refrigeration system aiming at the problem of large axial force of the centrifugal compressor, and the problem of large axial force can be solved.

A multistage centrifugal compressor comprising: the motor and Q impellers are communicated, and two adjacent impellers in the level are communicated, wherein Q is an integer which is more than or equal to 4 and less than or equal to 8;

the impellers comprise M first impellers arranged on a first end of a rotor on the motor and N second impellers arranged on a second end of the rotor, M, N is an integer greater than 1, and the maximum level of the first impellers is smaller than the minimum level of the second impellers;

when Q is an even number, M is equal to N, the first impeller and the second impeller are respectively divided into a group in pairs according to the ascending order of the grade under the condition that M is an even number, each group of the first impeller and each group of the second impeller are distributed in a back-to-back mode, and under the condition that M is an odd number, the two first impellers with the minimum grade, the two second impellers with the maximum grade, the rest first impellers and the rest second impellers are distributed in a back-to-back mode;

when Q is an odd number, M is greater than N by 1, the first impellers are divided into a group in pairs according to the ascending order of the levels under the condition that M is an even number, each group of the first impellers, the two second impellers with the largest level and the rest of the second impellers and the second impellers with the largest level are distributed in a back-to-back mode, and under the condition that M is an odd number, the two first impellers with the smallest level, the second impellers adjacent to each other in the level and the rest of the first impellers and the second impellers with the largest level are distributed in a back-to-back mode.

In one embodiment, the level of the first impeller increases in steps in a direction from the first end to the second end;

the level of the second impeller decreases in steps in a direction from the first end to the second end.

In one embodiment, the ratio of the distance between two adjacent first impellers to the length of the smallest impeller in the two first impellers is 2-2.7;

the ratio of the distance between two adjacent second impellers to the length of the impeller with the smallest grade in the two second impellers is 2-2.7.

In one embodiment, the ratio of the length of any first impeller to the length of the first impeller of the next adjacent stage is 1.1-1.8;

the ratio of the length of any one second impeller to the length of the second impeller of the next adjacent level is 1.1-1.8.

In one embodiment, the volutes corresponding to each two adjacent impellers of any level are communicated through a vent pipe, and the vent pipe is provided with an air supplementing opening.

In one embodiment, the first end and the second end have the same diameter.

In one embodiment, the impeller is circumferentially secured to the rotor by a keyed connection.

In one embodiment, a first stop collar is arranged between any two adjacent first impellers;

the first impeller closest to the motor is abutted against the first step surface on the first end, and the first impeller farthest from the motor is axially fixed on the rotor by adopting a lock nut;

a second limiting sleeve is arranged between any two adjacent second impellers;

the second impeller closest to the motor is abutted against the second step surface on the second end, and the second impeller farthest from the motor is axially fixed on the rotor by adopting a locking nut.

In one embodiment, the ratio of the length of the first impeller farthest from the motor to the distance between the front face of the first impeller farthest from the motor and the end face of the first end is 3-4;

the ratio of the length of the second impeller farthest from the motor to the distance between the front face of the second impeller farthest from the motor and the end face of the second end is 3-4.

In one embodiment, at least one magnetic bearing is disposed on each of the first end and the second end.

A refrigeration system comprising a multistage centrifugal compressor as described in any one of the above.

According to the multistage centrifugal compressor and the refrigeration system, the number of the first impellers positioned on the first end of the motor rotor and the number of the second impellers positioned on the second end of the electronic rotor are determined according to the total number of the impellers, and the distribution mode of the first impellers and the second impellers is determined according to the specific number of the first impellers and the second impellers, so that the axial force generated by the impellers can be weakened to the greatest extent, and the stable operation of the multistage centrifugal compressor can be ensured.

Drawings

Fig. 1 is a schematic view of an internal structure of a multistage centrifugal compressor according to an embodiment of the present invention;

fig. 2 is a schematic view of a distribution manner of the first impeller and the second impeller under different numbers of impellers according to an embodiment of the present invention.

Wherein the reference numerals in the drawings are as follows:

100. a motor; 110. a rotor; 210. a first impeller; 220. a second impeller; 310. a first stop collar; 320. a second stop collar; 400. a magnetic suspension bearing; 500. a breather pipe 500; 600. a volute; a1, length of first impeller; a2, length of second impeller; b1, the distance between two adjacent first impellers; b2, a distance between two adjacent second impellers; d1, diameter of first end of rotor; d2, diameter of second end of rotor; c1, the distance between the front face of the first impeller farthest from the motor and the end face of the first end of the rotor; c2, the distance between the front face of the second impeller furthest from the motor and the end face of the second end of the rotor.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1, fig. 1 is a schematic structural diagram illustrating a multistage centrifugal compressor according to an embodiment of the present invention, and the multistage centrifugal compressor according to the embodiment of the present invention includes: the motor 100 and Q impellers, two adjacent impellers of rank are communicated, and Q is an integer greater than or equal to 4 and less than or equal to 8.

Wherein the impellers include M first impellers 210 provided on a first end of the rotor 110 on the motor 100 and N second impellers 220, M, N provided on a second end of the rotor 110 and being an integer greater than 1, the maximum level of the first impellers 210 being smaller than the minimum level of the second impellers 220.

Further, when Q is an even number, M is equal to N, and when M is an even number, the first impeller 210 and the second impeller 220 are respectively grouped into a group two by two according to the order of increasing levels, and each group of the first impeller 210 and each group of the second impeller 220 are distributed in a back-to-back manner, and when M is an odd number, the two first impellers 210 with the smallest levels, the two second impellers 220 with the largest levels, and the remaining first impellers 210 and the remaining second impellers 220 are distributed in a back-to-back manner.

When Q is an odd number, M is greater than N by 1, when M is an even number, the first impellers 210 are grouped into a group in pairs according to an increasing order of the levels, each group of the first impellers 210, the two second impellers 220 with the largest level, the remaining second impellers 220 and the second impeller 220 with the largest level are distributed in a back-to-back manner, and when M is an odd number, the two first impellers 210 with the smallest level, the second impellers 220 adjacent to each other in the level, the remaining first impellers 210 and the second impeller 220 with the largest level are distributed in a back-to-back manner. It will be appreciated that the maximum number of impellers is the same as the number of impellers, for example if the number of impellers is 8, the maximum number of impellers is 8.

It should be noted that, during the process of compressing the gas by the impeller, there is a pressure difference before and after the compression of the refrigerant gas, and the axial force generated by the pressure difference is directed to the back of the impeller. And the larger the grade the larger the axial force generated by the impeller, for example, the second stage impeller generates a greater axial force than the first stage impeller. Note that back-to-back means that the back portions of two adjacent impellers are opposed to each other.

As an example, as shown in fig. 2, the levels of the first impeller 210 increase gradually in a direction from the first end to the second end; the level of the second impeller 220 decreases in steps in a direction from the first end to the second end. Therefore, the internal structure of the multistage centrifugal compressor can be simplified, the production and the processing of the multistage centrifugal compressor are facilitated, the distance between two adjacent impellers in the grade can be reduced, the gas pressure loss can be reduced, and the operation capacity of the multistage centrifugal compressor is improved. The following description of the multistage centrifugal compressor with reference to fig. 2 is provided to reduce the axial force generated by the impeller according to the above description of the multistage centrifugal compressor:

referring to fig. 2(a), the first end and the second end of the rotor 110 are respectively provided with 2 first impellers 210 and 2 second impellers 220, and the 2 first impellers 210 and the 2 second impellers 220 are distributed in a back-to-back distribution manner. The back-to-back manner allows each of the 2 first impellers 210 and the 2 second impellers 220 to generate opposite axial forces, and can balance a part of the axial force generated by the first impeller 210 and a part of the axial force generated by the second impeller 220. Note that the arrows in fig. 2(a) represent the directions of the axial forces of the respective impellers.

Referring to fig. 2(b), the first end and the second end of the rotor 110 are respectively provided with 3 first impellers 210 and 2 second impellers 220, the first-stage first impeller 210 and the second-stage first impeller 210 are distributed in a back-to-back manner, the 2 second impellers 220 are installed in a back-to-back manner, and the third-stage first impeller 210 and the fifth-stage second impeller 220 are distributed in a back-to-back manner. The back-to-back distribution is such that the 2 second impellers 220 generate opposite axial forces between the first-stage first impeller 210 and the second-stage first impeller 210, which can balance a part of the axial forces. In addition, because the axial force of the fifth-stage second impeller 220 is greater than the axial force of the fourth-stage second impeller 220, the direction of the axial force generated by the two balanced second impellers 220 is the same as the axial force generated by the fifth-stage second impeller 220 itself, and at this time, because the third-stage first impeller 210 and the fifth-stage second impeller 220 are distributed in a back-to-back manner, the axial force generated by the third-stage first impeller 210 can counteract the balanced axial force between the fifth-stage second impeller 220 and the fourth-stage second impeller 220. Note that the arrows in fig. 2(b) represent the directions of the axial forces of the respective impellers.

Referring to fig. 2(c), the first end and the second end of the rotor 110 are respectively provided with 3 first impellers 210 and 3 second impellers 220, the first-stage first impeller 210 and the second-stage first impeller 210 are distributed in a back-to-back manner, the fifth-stage second impeller 220 and the sixth-stage second impeller 220 are installed in a back-to-back manner, and the third-stage first impeller 210 and the fourth-stage second impeller 220 are distributed in a back-to-back manner. The back-to-back distribution mode causes opposite axial forces to be generated between the first-stage first impeller 210 and the second-stage first impeller 210, between the fifth-stage second impeller 220 and the sixth-stage second impeller 220, and between the third-stage first impeller 210 and the fourth-stage second impeller 220, so that a part of the axial forces can be balanced. Note that the arrows in fig. 2(c) represent the directions of the axial forces of the respective impellers.

Referring to fig. 2(d), the first end and the second end of the rotor 110 are respectively provided with 4 first impellers 210 and 3 second impellers 220, the first-stage first impeller 210 and the second-stage first impeller 210, the first-stage third impeller and the fourth-stage first impeller 210 are distributed in a back-to-back manner, the sixth-stage second impeller 220 and the seventh-stage second impeller 220 are installed in a back-to-back manner, and the fifth-stage second impeller 220 and the seventh-stage second impeller 220 are distributed in a back-to-back manner. The back-to-back distribution causes opposite axial forces to be generated between the first-stage first impeller 210 and the second-stage first impeller 210, between the third-stage first impeller 210 and the fourth-stage first impeller 210, and between the seventh-stage second impeller 220 and the sixth-stage second impeller 220, so that a part of the axial forces can be balanced. In addition, the axial force of the fifth stage second impeller 220 may offset the balanced axial force between the seventh stage second impeller 220 and the sixth stage second impeller 220. Note that the arrows in fig. 2(d) represent the directions of the axial forces of the respective impellers.

Referring to fig. 2(e), the first end and the second end of the rotor 110 are respectively provided with 4 first impellers 210 and 4 second impellers 220, and the 4 first impellers 210 and the 4 second impellers 220 are distributed in a back-to-back distribution manner. The back-to-back approach may balance a portion of the axial force generated by the first impeller 210 with a portion of the axial force generated by the second impeller 220. Note that the arrows in fig. 2(e) represent the directions of the axial forces of the respective impellers.

As described above, in the multistage centrifugal compressor, by determining the number of the first impellers 210 located on the first end of the rotor 110 of the motor 100 and the number of the second impellers 220 located on the second end of the rotor 110 of the electronic motor according to the total number of the impellers, and by determining the distribution pattern of the first impellers 210 and the second impellers 220 according to the specific number of the first impellers 210 and the second impellers 220, the axial force generated by the impellers can be minimized, and the stable operation of the multistage centrifugal compressor can be ensured.

In some embodiments of the present invention, as shown in fig. 1, the ratio of the distance B1 between two adjacent first impellers 210 to the length of the smallest impeller a1 of the two first impellers 210 is 2-2.7, for example, the ratio B1/a1 may be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, etc. In this way, interference between two adjacent first impellers 210 due to a small distance therebetween can be avoided, and an increase in gas pressure loss due to a large distance between two adjacent first impellers 210 can also be avoided. Preferably, the ratio of the spacing B1 between two adjacent first impellers 210 to the length of the smallest impeller a1 of the two first impellers 210 is 2.3.

Similarly, in some embodiments of the present invention, as shown in fig. 1, the ratio of the distance B2 between two adjacent second impellers 220 to the length a2 of the smallest impeller of the two second impellers 220 is 2 to 2.7, for example, the ratio B2/a2 may be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, etc. In this way, it is possible to avoid interference between two adjacent second impellers 220 due to a small distance therebetween, and it is also possible to avoid an increase in gas pressure loss due to a large distance therebetween between two adjacent second impellers 220. Preferably, the ratio of the distance B2 between two adjacent second impellers 220 to the length a2 of the smallest impeller among the two first impellers 210 is 2.3.

In some embodiments of the present invention, as shown in fig. 1, the volutes 600 corresponding to each of two adjacent impellers of any level are communicated with each other through a vent pipe 500, and the vent pipe 500 is provided with an air supplement port. It should be noted that each impeller outer wall is covered with a volute 600, the volute 600 is provided with an air suction port communicated with the air suction port of the impeller and an air discharge port communicated with the air discharge port of the impeller, and the air duct 500 is communicated between the air discharge port and the air suction port of the two corresponding volutes 600. The air supplementing port is convenient for supplementing air, and the operation capacity of the multistage centrifugal compressor can be improved.

In some embodiments of the present invention, as shown in fig. 1, the diameter D1 of the first end of the rotor of the electric machine 100 is the same as the diameter D2 of the second end. In this way, the machining efficiency of the rotor 110, the first impeller 210, and the second impeller 220 can be improved, and the assembling efficiency of the first impeller 210 and the second impeller 220 can also be improved.

In some embodiments of the present invention, as shown in FIG. 1, the ratio of the length A1 of any first impeller to the length A1 of the adjacent next-level first impeller is 1.1-1.8, for example, the ratio may be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, etc. With this arrangement, the requirement that the length a1 of the first impeller of the current level is greater than the length a1 of the first impeller of the next level can be satisfied, and the installation of the first impellers 210 of the two adjacent levels can also be ensured. Preferably, the ratio between the length a1 of any first impeller and the length a1 of the adjacent first impeller of the next stage is 1.2.

Similarly, in some embodiments of the present invention, as shown in FIG. 1, the ratio of the length A2 of any second impeller to the length A2 of the adjacent second impeller of the next stage is 1.1-1.8, for example, the ratio may be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, etc. With this arrangement, the requirement that the length a2 of the second impeller of the current level is greater than the length a2 of the second impeller of the next level can be satisfied, and the installation of the first impellers 210 of two adjacent levels can also be ensured. Preferably, the ratio of the length a2 of any second impeller to the length a2 of the adjacent second impeller of the next stage is 1.2.

In some embodiments of the invention, the impeller is keyed to be circumferentially fixed to the rotor 110. Therefore, the impeller is convenient to mount and dismount, and the running stability of the multistage centrifugal compressor is improved.

Further, in some embodiments of the present invention, as shown in fig. 1, a first stop collar 310 is disposed between any two adjacent first impellers 210; the first impeller 210 closest to the motor 100 abuts against the first step surface on the first end, and the first impeller 210 farthest from the motor 100 is axially fixed to the rotor 110 by a lock nut (not shown in the drawings); each first impeller 210 can be limited in the axial direction of the rotor 110 by the cooperation of the first limiting sleeve 310 and the lock nut, so that the first impeller 210 is prevented from moving in the axial direction of the rotor 110.

Optionally, the fit between the first stop collar 310 and the rotor 110 is a clearance fit.

Optionally, a washer (not shown in the drawings) is disposed between the end surface of the first end of the rotor 110 and the head of the lock nut to enhance the locking strength of the lock nut.

Alternatively, as shown in fig. 1, the ratio between the length a1 of the first impeller farthest from the motor 100 and the distance C1 between the front surface and the end surface of the first end of the first impeller 210 farthest from the motor 100 is 3 to 4, for example, the ratio a1/C1 may be 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, etc. This ensures not only that the first impeller 210 farthest from the motor 100 is compressed, but also that the multistage centrifugal compressor is compact. Preferably, the ratio between the length a1 of the first impeller farthest from the motor 100 and the distance C1 between the front surface and the end surface of the first end of the first impeller 210 farthest from the motor 100 is 3.

Likewise, in some embodiments of the present invention, as shown in fig. 1, a second stop collar 320 is disposed between any two adjacent second impellers 220; the second impeller 220 closest to the motor 100 abuts against the second step surface on the second end, and the second impeller 220 farthest from the motor 100 is axially fixed to the rotor 110 by a lock nut (not shown in the drawings); each second impeller 220 can be limited in the axial direction of the rotor 110 by the cooperation of the second limiting sleeve 320 and the lock nut, so that the second impeller 220 is prevented from moving in the axial direction of the rotor 110.

Optionally, a washer (not shown in the drawings) is provided between the end surface of the second end of the rotor 110 and the head of the lock nut to enhance the locking strength of the lock nut.

Alternatively, as shown in fig. 1, the ratio between the length a2 of the second impeller farthest from the motor 100 and the distance C2 between the front surface and the end surface of the second end of the second impeller 220 farthest from the motor 100 is 3 to 4, for example, the ratio a2/C2 may be 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, etc. In this way, it is possible to ensure not only the second impeller 220 farthest from the motor 100 but also the structure of the multistage centrifugal compressor to be compact. Preferably, the ratio between the length a2 of the second impeller farthest from the motor 100 and the interval C2 between the front surface of the second impeller 220 farthest from the motor 100 and the end surface of the second end is 3.

In some embodiments of the present invention, as shown in fig. 1, at least one magnetic bearing 400 is disposed on each of the first and second ends of the rotor 110. Compared with an oil bearing, the magnetic suspension bearing 400 has the characteristics of simple structure and lower cost.

Optionally, a magnetic bearing 400 is disposed on each of the first and second ends of the rotor 110.

The operation of the multistage centrifugal compressor will be described by taking the multistage centrifugal compressor shown in fig. 1 as an example, wherein the arrows in fig. 1 represent the flowing direction of the refrigerant gas:

1. when the multistage centrifugal compressor is operated, refrigerant gas enters from the suction end of the first-stage first impeller 210;

2. through the high-speed rotation compression of the first-stage first impeller 210, the gas is discharged from the gas discharge end of the first-stage first impeller 210;

3. after being discharged, the gas flows to the suction end of the second-stage first impeller 210 through the gas outlet of the first-stage volute 600 corresponding to the first-stage first impeller 210;

4. after the high-speed rotation compression of the second-stage first impeller 210, the gas is discharged from the gas discharge end of the second-stage first impeller 210;

5. after being discharged, the gas flows to the suction end of the third-stage second impeller 220 through the gas outlet of the second-stage volute 600 corresponding to the second-stage first impeller 210;

6. through the high-speed rotation compression of the third-stage second impeller 220, the gas is discharged from the gas discharge end of the third-stage second impeller 220;

7. after being discharged, the gas flows to the suction end of the fourth-stage second impeller 220 through the gas outlet of the three-stage volute 600 corresponding to the third-stage second impeller 220;

8. through the high-speed rotation compression of the fourth-stage second impeller 220, the gas is discharged from the gas discharge end of the fourth-stage second impeller 220;

9. the gas is exhausted to the condenser of the unit through the exhaust port of the four-stage volute 600.

In summary, the multistage centrifugal compressor provided in the embodiment of the present invention has the following beneficial effects:

(1) the magnetic suspension shaft is adopted, and compared with an oil bearing, the bearing is simple in structure and low in cost;

(2) the whole structure adopts a double-cantilever structure, and the distribution mode of adjusting the impellers according to the number of the impellers is changed, so that the axial force can be better reduced;

(3) by adjusting the fitting size of the internal parts, the processing efficiency and the assembly efficiency can be improved, and the structure can be ensured to be compact under the premise of adopting a refrigerant with lower GWP (global warming potential), such as R1233zd (E) refrigerant.

In another aspect, an embodiment of the present invention further provides a refrigeration system including any one of the multistage centrifugal compressors described above.

In the refrigeration system as described above, by determining the number of the first impellers 210 located on the first end of the rotor 110 of the motor 100 and the number of the second impellers 220 located on the second end of the electronic rotor 110 according to the total number of the impellers, and by determining the distribution of the first impellers 210 and the second impellers 220 according to the specific numbers of the first impellers 210 and the second impellers 220, the axial force generated by the impellers can be weakened to the maximum extent, and the stable operation of the multistage centrifugal compressor can be ensured.

As an example, the refrigeration system may be an air conditioner.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A multistage centrifugal compressor, comprising: the motor and Q impellers are communicated, and two adjacent impellers in the level are communicated, wherein Q is an integer which is more than or equal to 4 and less than or equal to 8;

2. The multi-stage centrifugal compressor of claim 1, wherein the stages of the first impeller increase in series in a direction from the first end to the second end;

3. The multistage centrifugal compressor according to claim 2, wherein the ratio of the distance between two adjacent first impellers to the length of the smallest impeller of the two first impellers is 2-2.7;

4. The multistage centrifugal compressor of claim 2, wherein the ratio between the length of any one of the first impellers and the length of the first impeller of the next adjacent stage is 1.1-1.8;

5. The multistage centrifugal compressor according to any one of claims 1 to 4, wherein the volutes corresponding to each of two adjacent impellers of any one stage are communicated through a vent pipe, and the vent pipe is provided with an air supplement port.

6. The multi-stage centrifugal compressor of any one of claims 1-4, wherein the first end and the second end are the same diameter.

7. The multistage centrifugal compressor of any of claims 1 to 4, wherein the impeller is circumferentially fixed to the rotor by a keyed connection.

8. The multistage centrifugal compressor of claim 7, wherein a first stop collar is disposed between any adjacent two of the first impellers;

a second limiting sleeve is arranged between any two adjacent second impellers;

9. The multistage centrifugal compressor according to claim 8, wherein a ratio between a length of the first impeller farthest from the motor and a distance between a front face of the first impeller farthest from the motor and an end face of the first end is 3 to 4;

10. The multistage centrifugal compressor according to any of claims 1 to 4, wherein at least one magnetic bearing is provided on each of the first end and the second end.

11. A refrigeration system comprising a multistage centrifugal compressor according to any one of claims 1 to 10.