Impeller and motor integrated closed unit and supercritical carbon dioxide unit

Abstract

The invention belongs to the field of supercritical carbon dioxide, and discloses an impeller and motor integrated closed unit and a supercritical carbon dioxide unit. The impeller and motor integrated closed unit comprises a shell, a motor, an impeller and a sealing element; an air exhaust channel is arranged on the shell corresponding to the mounting cavity area, the pressure in the air exhaust channel is smaller than that in the motor cavity and that in the impeller cavity, a working medium in the motor cavity is different from that in the impeller cavity, and the density of the working medium in the motor cavity is smaller than that of the working medium in the impeller cavity; the motor is arranged in the motor cavity; the impeller is arranged on an output shaft of the motor; the sealing piece is arranged in the mounting cavity, a clearance space is formed between the sealing piece and the output shaft, and the air exhaust channel communicates with the clearance space. The wind resistance damage can be reduced, and the sealing complexity of the unit can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of supercritical carbon dioxide, and in particular to an impeller-motor integrated closed unit and a supercritical carbon dioxide unit. Background Art

[0002] The impeller-motor integrated sealed unit is a device that integrates the motor and impeller in a sealed housing. This design can improve the efficiency of the system, reduce space occupancy, and simplify the overall structure. The impeller-motor integrated sealed unit is used in the fields of fans, compressors, turbine generators, compressor-motor-turbine integrated units, etc. It can simplify the unit shaft end sealing system, improve the unit power density, achieve zero leakage of the working fluid in the unit, and avoid working fluid contamination. This technology has been applied in the fields of high-temperature gas-cooled reactor main helium fans, submarine compressors, magnetic levitation air compressors, organic Rankine cycle units, etc.

[0003] Rotor windage loss is an important factor affecting the efficiency of impeller-motor integrated closed units. In impeller-motor integrated closed units, the internal pressure of the motor is no longer normal pressure, but close to the process working fluid pressure, and the working fluid density increases significantly. The greater the working fluid density, the higher the rotor windage loss, the greater the difficulty of motor cooling, and the lower the unit efficiency. If applied to high-density working fluid units such as supercritical carbon dioxide units, the motor cavity can only maintain normal pressure or near normal pressure to prevent the working fluid density from increasing the rotor windage loss. However, when the motor cavity is at normal pressure, there is a huge pressure difference with the process fluid on the impeller side, which brings great difficulties to the design of the sealing system; under large pressure difference conditions, dry gas sealing is a conventional choice, but there are many problems such as complex sealing system and control requirements, high cost, and leakage, which limit its application scenarios.

[0004] Therefore, there is an urgent need for an impeller-motor integrated closed unit that can reduce the rotor wind resistance when applied to the field of supercritical carbon dioxide units and reduce the complexity of the unit sealing. Summary of the invention

[0005] The purpose of the present application is to provide an impeller-motor integrated closed unit and a supercritical carbon dioxide unit, which can not only reduce wind resistance damage but also reduce the complexity of unit sealing.

[0006] The technical solutions provided by this application are as follows:

[0007] On the one hand, a closed unit with an integrated impeller and a motor is provided, comprising:

[0008] A housing, comprising a motor cavity, a mounting cavity and an impeller cavity which are connected in sequence, an exhaust passage is provided on the housing corresponding to the mounting cavity area, the pressure in the exhaust passage is lower than the pressure in the motor cavity and the pressure in the impeller cavity, the working fluid in the motor cavity is different from the working fluid in the impeller cavity, and the density of the working fluid in the motor cavity is lower than the density of the working fluid in the impeller cavity;

[0009] A motor, disposed in the motor cavity;

[0010] An impeller is disposed in the impeller cavity, and the impeller is disposed on an output shaft of the motor;

[0011] A sealing member is arranged on the side wall of the installation cavity, a gap is formed between the sealing member and the output shaft, and the air extraction channel is communicated with the gap space.

[0012] In some embodiments, the working fluid in the motor cavity is helium.

[0013] In some embodiments, an air extraction device is further included, and the air extraction device is connected to the air extraction channel pipeline.

[0014] In some embodiments, a working fluid separation device is also included, which is arranged on the pipeline between the air pumping device and the air pumping channel, the outlet of the working fluid separation device is connected to the inlet of the impeller cavity or the compressor inlet, and the outlet of the air pumping device is connected to the motor cavity.

[0015] In some embodiments, when the impeller is a compressor impeller, the working fluid pressure in the motor cavity is not lower than the inlet working fluid pressure of the impeller cavity;

[0016] When the impeller is a turbine impeller, the working fluid pressure in the motor cavity is not lower than the working fluid pressure at the outlet of the impeller cavity.

[0017] In some embodiments, a vent is further provided on the housing between the air extraction channel and the impeller chamber, and the vent is communicated with the gap space.

[0018] In some embodiments, the working fluid pressure in the vent is higher than the working fluid pressure in the impeller chamber;

[0019] The working fluid pressure in the vent is higher than the working fluid pressure in the motor cavity.

[0020] In some embodiments, the number of the seals is three, the first seal is arranged between the impeller chamber and the vent, the second seal is arranged between the vent and the exhaust channel, and the third seal is arranged between the exhaust channel and the motor chamber.

[0021] In some embodiments, the vent is connected to the outlet of the impeller chamber; or;

[0022] The vent is connected to the compressor outlet; or;

[0023] The vent is communicated with an air supply system.

[0024] On the other hand, a supercritical carbon dioxide unit is also provided, comprising the impeller-motor integrated closed unit described in any of the above embodiments.

[0025] The technical effect of the present application is that the density of the working fluid in the motor cavity is lower than the density of the process working fluid in the impeller cavity. The working fluid with lower working fluid density is introduced into the motor cavity, which can not only reduce the windage loss of the unit, but also increase the pressure in the motor cavity, so as to reduce the pressure difference between the motor cavity and the impeller cavity, thereby reducing the difficulty of sealing between the motor cavity and the impeller cavity, so that the unit does not need to be sealed by dry gas sealing, simplifies the complexity of the unit sealing and auxiliary systems, improves the compactness of the unit sealing system, and reduces the cost of the sealing system; an exhaust channel is arranged between the impeller cavity and the motor cavity, so that the process working fluid leaked from the impeller cavity can flow toward the exhaust channel to form stream S1, and the working fluid helium leaked from the motor cavity can also flow toward the exhaust channel to form stream S2. Stream S1 and stream S2 are mixed to form stream S3 and flow out through the exhaust channel, so as to avoid the working fluid in the motor cavity from entering the impeller cavity, and avoid the working fluid in the impeller cavity from entering the motor cavity, so as to ensure the normal operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present application is further described in detail below with reference to the accompanying drawings and specific implementation methods:

[0027] Figure 1 This is a structural schematic diagram of an impeller-motor integrated closed unit provided in one embodiment of the present application;

[0028] Figure 2 It is a structural schematic diagram of an impeller-motor integrated closed unit provided in another embodiment of the present application.

[0029] Description of Figure Numbers:

[0030] 10. Casing; 11. Motor cavity; 12. Mounting cavity; 13. Impeller cavity; 14. Exhaust channel; 15. Gap space; 16. Vent; 20. Motor; 21. Output shaft; 30. Impeller; 40. Seal; 50. Exhaust device; 60. Working fluid separation device. DETAILED DESCRIPTION

[0031] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0032] In order to more clearly illustrate the application embodiments or technical solutions in the prior art, the specific implementation methods of the present application will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0033] In order to simplify the drawings, only the parts related to the present application are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0034] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0035] In this document, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0036] In the embodiments shown in the drawings, directional indications (such as up, down, left, right, front, and back, etc.) are not absolute but relative when describing the structure and movement of each component, and are not used to limit the direction of the product in actual use.

[0037] In addition, in the description of the present application, ordinal numbers, such as "first", "second", etc., are only used to distinguish and describe related objects, and cannot be understood as indicating or implying the relative importance or order between the related objects.

[0038] The present application provides an embodiment of an impeller-motor integrated sealed unit. The impeller-motor integrated sealed unit of this embodiment can be applied to the field of supercritical carbon dioxide units, and can also be applied to the field of low-density working fluid or low internal pressure sealed units. When the impeller-motor integrated sealed unit is applied to a supercritical carbon dioxide unit, the impeller-motor integrated sealed unit can form different power mechanisms according to different impeller types. For example, when the impeller is a compressor impeller, the impeller-motor integrated sealed unit is a compressor-motor integrated unit; when the impeller is a turbine impeller, the impeller-motor integrated sealed unit is a turbine-motor integrated unit; in addition, the compressor impeller and the turbine impeller can be arranged on both sides of the motor, respectively, and sealing systems such as seals and exhaust channels can be arranged, so that the impeller-motor integrated sealed unit forms a compressor-motor-turbine integrated unit.

[0039] like Figure 1 As shown, a working fluid different from the process working fluid in the impeller chamber 13 is introduced into the motor chamber 11 of the impeller-motor integrated closed unit of the present embodiment, and the density of the working fluid in the motor chamber 11 is less than the density of the process working fluid in the impeller chamber 13. For example, a process working fluid such as carbon dioxide and nitrogen is introduced into the impeller chamber 13, and helium or hydrogen with a smaller working fluid density can be introduced into the motor chamber 11. When the impeller-motor integrated closed unit is applied to a supercritical carbon dioxide unit, the pressure in the motor chamber 11 can be increased to reduce the difficulty of sealing between the motor chamber 11 and the impeller chamber 13. At the same time, the density of the helium or hydrogen in the motor chamber 11 is still relatively low at high pressure to reduce the windage loss of the rotor. In addition, a seal 40 and an exhaust channel 14 are provided between the impeller chamber 13 and the motor chamber 11 of the present application. The seal 40 can reduce the leakage of the working fluid in the impeller chamber 13 and the motor chamber 11. The pressure in the exhaust channel 14 is lower than the pressure in the motor chamber 11 and the pressure in the impeller chamber 13. The leaked working fluid in the motor chamber 11 flows toward the exhaust channel 14, and the leaked working fluid in the impeller chamber 13 also flows toward the exhaust channel 14. The leaked working fluid in the impeller chamber 13 and the motor chamber 11 can be sucked out of the unit by the exhaust channel 14 to prevent the working fluid in the motor chamber 11 from entering the impeller chamber 13, and at the same time prevent the working fluid in the impeller chamber 13 from entering the motor chamber 11, so that the unit can operate normally.

[0040] like Figure 1As shown, the impeller-motor integrated closed unit includes a housing 10, a motor 20, an impeller 30 and a seal 40. The housing 10 includes a motor cavity 11, a mounting cavity 12 and an impeller cavity 13 which are sequentially connected. An exhaust channel 14 is provided on the housing 10 corresponding to the mounting cavity 12. The pressure in the exhaust channel 14 is lower than the pressure in the motor cavity 11 and lower than the pressure in the impeller cavity 13. The working fluid in the motor cavity 11 is different from the working fluid in the impeller cavity 13, and the density of the working fluid in the motor cavity 11 is lower than the density of the working fluid in the impeller cavity 13. The motor 20 is arranged in the motor cavity 11; the impeller 30 is arranged in the impeller cavity 13, and the impeller 30 is arranged on the output shaft 21 of the motor 20; the seal 40 is arranged on the side wall of the mounting cavity 12, and a gap space 15 is formed between the seal 40 and the output shaft 21, and the exhaust channel 14 is connected to the gap space 15.

[0041] Specifically, the impeller 30 and the motor 20 are coaxially installed in the pressure-resistant housing 10, and a seal 40 is arranged between the impeller 30 and the motor 20. The seal 40 can be any one of a labyrinth seal, a honeycomb seal, and a carbon ring seal, or a combination thereof. In this embodiment, there are two seals 40, one seal 40 is arranged between the air extraction channel 14 and the impeller cavity 13 to reduce the leakage of the process medium in the impeller cavity 13, and the other seal 40 is arranged between the air extraction channel 14 and the motor cavity 11 to reduce the leakage of the medium in the motor cavity 11. One end of the seal 40 is connected to the inner side wall of the housing 10, and a gap space 15 is formed between the other end of the seal 40 and the output shaft 21. The gap space 15 connects the impeller cavity 13 and the motor cavity 11. The seal 40 can reduce the leakage of the impeller cavity 13 and the motor cavity 11. The working fluid in the impeller cavity 13 is the actual process working fluid, including but not limited to carbon dioxide, nitrogen, etc.; the working fluid in the motor cavity 11 is high-pressure and low-density, including but not limited to helium, hydrogen, etc. Helium and hydrogen still have a low density under high pressure to reduce wind resistance damage. Preferably, in this embodiment, high-pressure helium is introduced into the motor cavity 11. Because hydrogen is more dangerous, safety issues need to be considered when selecting hydrogen. Of course, hydrogen can also be introduced into the motor cavity 11 when safety is guaranteed.

[0042] An exhaust channel 14 is provided on the shell 10, and the exhaust channel 14 is located between the impeller cavity 13 and the motor cavity 11. One end of the exhaust channel 14 is connected to the gap space 15, and the other end can be connected to the exhaust device 50. The exhaust function of the exhaust device 50 can be achieved by a fan, an ejector, etc. When the exhaust device 50 is sucking, the pressure in the exhaust channel 14 is lower than the pressure in the motor cavity 11, and lower than the pressure in the impeller cavity 13. The process fluid leaked in the impeller cavity 13 and the process fluid leaked in the motor cavity 11 are both extracted from the exhaust channel 14 by the exhaust device 50 to prevent the process fluid leaked in the impeller cavity 13 from entering the motor cavity 11, and to prevent the process fluid leaked in the motor cavity 11 from entering the impeller cavity 13, so as to achieve normal operation of the entire unit.

[0043] In the impeller motor integrated closed unit of the present embodiment, a working fluid with a low working fluid density is introduced into the motor cavity 11, which can not only reduce the windage loss of the unit, but also increase the pressure in the motor cavity 11, so as to reduce the pressure difference between the motor cavity 11 and the impeller cavity 13, thereby reducing the sealing difficulty between the motor cavity 11 and the impeller cavity 13, so that the unit does not need to be sealed by dry gas sealing, simplifies the complexity of the unit sealing and auxiliary systems, improves the compactness of the unit sealing system, and reduces the cost of the sealing system; the impeller cavity 1 An exhaust passage 14 is provided between the impeller chamber 13 and the motor chamber 11, so that the process fluid leaking from the impeller chamber 13 can flow toward the exhaust passage 14 to form a process stream S1, and the working fluid helium leaking from the motor chamber 11 can also flow toward the exhaust passage 14 to form a working fluid stream S2. The process stream S1 and the working fluid stream S2 are mixed to form a stream S3, which is extracted through the exhaust passage 14, so as to prevent the working fluid in the motor chamber 11 from entering the impeller chamber 13, and to prevent the process working fluid in the impeller chamber 13 from entering the motor chamber 11, so as to ensure the normal operation of the unit.

[0044] In some embodiments, Figure 1 As shown, it also includes a working medium separation device 60, which is arranged on the pipeline between the exhaust device 50 and the exhaust channel 14, the outlet of the working medium separation device 60 is connected to the inlet of the impeller chamber 13 or the compressor inlet, and the outlet of the exhaust device 50 is connected to the motor chamber 11.

[0045] The process working fluid flow S1 in the impeller chamber 13 and the working fluid helium flow S2 in the motor chamber 11 are mixed and extracted from the exhaust channel 14 by the exhaust device 50, and then enter the working fluid separation device 60 for separation. The separated process working fluid returns to the compressor inlet or the inlet of the impeller chamber 13 for circulation, and the separated working fluid helium is sucked and pressurized by the exhaust device 50 and then re-enters the motor chamber 11 for circulation.

[0046] Specifically, when the impeller 30 is a compressor impeller, the inlet of the impeller chamber 13 is the compressor inlet, and the separated process fluid returns to the inlet of the impeller chamber 13, that is, returns to the compressor inlet. When the impeller 30 is a turbine impeller, the inlet of the impeller chamber 13 is the inlet of the turbine, and the separated process fluid returns to the compressor inlet of the supercritical carbon dioxide unit, not directly to the impeller chamber 13, and the process fluid enters the impeller chamber 13 after doing work in the compressor. The working fluid separation device 60 can be a condensing device. For example, the process working fluid carbon dioxide and helium exchange heat with the cooling medium in the condensing device, and the carbon dioxide is condensed into liquid and separated from the helium. The working fluid separation device 60 can also separate the process working fluid from the helium by pressure swing adsorption or membrane separation technology.

[0047] In some embodiments, when the impeller 30 is a compressor impeller, the working fluid pressure in the motor cavity 11 is not lower than the inlet working fluid pressure of the impeller cavity 13; when the impeller 30 is a turbine impeller, the working fluid pressure in the motor cavity 11 is not lower than the outlet working fluid pressure of the impeller cavity 13.

[0048] Specifically, when the impeller 30 is a compressor impeller, the impeller 30 performs work on the working fluid entering the impeller chamber 13, the working fluid pressure at the outlet of the impeller chamber 13 is greater than the working fluid pressure at the inlet of the impeller chamber 13, the working fluid pressure in the motor chamber 11 is not lower than the working fluid pressure at the inlet of the impeller chamber 13, and after the process working fluid is mixed with the helium gas in the motor chamber 11, the process working fluid pressure will not be lower than the working fluid pressure at the inlet of the impeller chamber 13, so that the separated process working fluid can be directly returned to the inlet of the impeller chamber 13 without the need for an additional pressurizing device to save costs. Of course, the working fluid pressure in the motor chamber 11 can also be lower than the working fluid pressure at the inlet of the impeller chamber 13. In this case, an additional pressurizing device is required to first pressurize the separated process working fluid and then allow the process working fluid to enter the compressor inlet.

[0049] When the impeller 30 is a turbine impeller, the working fluid entering the impeller chamber 13 does work on the impeller 30, the pressure of the process working fluid is reduced, the pressure of the process working fluid at the outlet of the impeller chamber 13 is less than the pressure of the process working fluid at the inlet of the impeller chamber 13, and the process working fluid at the outlet of the impeller chamber 13 enters the compressor again, so the inlet pressure of the compressor is equivalent to the outlet pressure of the impeller chamber 13. When the pressure of the working fluid in the motor chamber 11 is not lower than the pressure of the process working fluid at the outlet of the impeller chamber 13, the process working fluid separated by the working fluid separation device 60 can also be directly returned to the inlet of the compressor without the need for an additional pressurizing device, so as to save costs.

[0050] In some embodiments, Figure 2 As shown, a vent 16 is further provided on the housing 10 between the air extraction channel 14 and the impeller chamber 13 , and the vent 16 is communicated with the gap space 15 .

[0051] When the impeller 30 is a compressor impeller, the temperature of the process fluid leaking from the impeller chamber 13 is relatively low, and the leaked process fluid can be allowed to flow along the output shaft 21. Therefore, an air vent 16 may be provided between the exhaust channel 14 and the impeller chamber 13, or the air vent 16 may not be provided. However, if the air vent 16 is provided and a high-pressure process fluid is introduced, the sealing effect can be further improved.

[0052] When the impeller 30 is a turbine impeller, the temperature of the process fluid leaking from the impeller chamber 13 is relatively high. At this time, the leaked process fluid is not allowed to flow along the output shaft 21. Therefore, a vent 16 connected to the gap space 15 is provided between the exhaust channel 14 and the impeller chamber 13. High-pressure gas can be introduced into the vent 16 to prevent the process fluid in the impeller chamber 13 from flowing toward the exhaust channel 14.

[0053] The working medium pressure in the vent 16 is higher than the working medium pressure in the impeller chamber 13; the working medium pressure in the vent 16 is higher than the working medium pressure in the motor chamber 11. The process working medium is also introduced into the vent 16. The process working medium with a pressure higher than the highest pressure in the impeller chamber 13 enters the gap space 15 through the vent 16, forming a stream S4 flowing to the impeller chamber 13 and a reverse stream S5. The stream S4 seals the process working medium in the impeller chamber 13, i.e., the thermal cycle. After the reverse stream S5 is mixed with the stream S2, it flows to the working medium separation device 60 through the exhaust channel 14 to separate the process working medium from the working medium helium. The reverse stream S4 can improve the sealing effect of the motor chamber 11.

[0054] When the impeller 30 is a compressor impeller, the vent 16 can be connected to the outlet of the impeller chamber 13 to provide process fluid into the vent 16; when the impeller 30 is a turbine impeller, the vent 16 can be connected to the compressor outlet of the supercritical carbon dioxide unit, and the process fluid is provided by the compressor outlet; the vent 16 can also be connected to the air supply system, and the air supply system provides the process fluid entering the vent 16.

[0055] When the vent 16 is set, the number of seals 40 is three, the first seal 40 is set between the impeller chamber 13 and the vent 16, the second seal 40 is set between the vent 16 and the exhaust channel 14, and the third seal 40 is set between the exhaust channel 14 and the motor chamber 11 to improve the sealing effect and reduce leakage.

[0056] The present application also provides an embodiment of a supercritical carbon dioxide unit, including the impeller-motor integrated closed unit described in any of the above embodiments, the structure of the impeller-motor integrated closed unit is as follows: Figure 1 and Figure 2 When the impeller-motor integrated closed unit of the above embodiment is applied to a supercritical carbon dioxide unit, dry gas sealing is not required, the sealing form inside the unit is simple, the complexity of the unit sealing and auxiliary systems is simplified, the compactness of the unit sealing system is improved, the sealing system cost is reduced, the sealing system operation requirements are reduced, the unit operation flexibility is improved, the windage loss of the closed unit is reduced, and the unit efficiency is improved.

[0057] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0058] It should be noted that the above embodiments can be freely combined as needed. The above is only the preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present application, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. An impeller-motor integrated enclosed unit, characterized in that: include: A housing, comprising a motor cavity, a mounting cavity and an impeller cavity which are connected in sequence, an exhaust passage is provided on the housing corresponding to the mounting cavity area, the pressure in the exhaust passage is lower than the pressure in the motor cavity and the pressure in the impeller cavity, the working fluid in the motor cavity is different from the working fluid in the impeller cavity, and the density of the working fluid in the motor cavity is lower than the density of the working fluid in the impeller cavity; A motor, disposed in the motor cavity; An impeller is disposed in the impeller cavity, and the impeller is disposed on an output shaft of the motor; A sealing member is arranged on the side wall of the installation cavity, a gap is formed between the sealing member and the output shaft, and the air extraction channel is communicated with the gap space.

2. The impeller-motor integrated enclosed unit according to claim 1, characterized in that: The working medium in the motor cavity is helium.

3. The impeller-motor integrated enclosed unit according to claim 1, characterized in that: It also includes an air extraction device, which is connected to the air extraction channel pipeline.

4. The impeller-motor integrated enclosed unit according to claim 3, characterized in that: It also includes a working fluid separation device, which is arranged on the pipeline between the air extraction device and the air extraction channel, the outlet of the working fluid separation device is connected to the inlet of the impeller cavity or the compressor inlet, and the outlet of the air extraction device is connected to the motor cavity.

5. The impeller-motor integrated enclosed unit according to claim 1, characterized in that: When the impeller is a compressor impeller, the working fluid pressure in the motor cavity is not lower than the inlet working fluid pressure of the impeller cavity; When the impeller is a turbine impeller, the working fluid pressure in the motor cavity is not lower than the working fluid pressure at the outlet of the impeller cavity.

6. The impeller-motor integrated enclosed unit according to any one of claims 1 to 5, characterized in that: The shell is also provided with an air vent between the air extraction channel and the impeller chamber, and the air vent is communicated with the gap space.

7. The impeller-motor integrated sealed unit according to claim 6, characterized in that: The working fluid pressure in the vent is higher than the working fluid pressure in the impeller chamber; The working fluid pressure in the vent is higher than the working fluid pressure in the motor cavity.

8. The impeller-motor integrated sealed unit according to claim 6, characterized in that: There are three seals, the first seal is arranged between the impeller cavity and the air vent, the second seal is arranged between the air vent and the air extraction channel, and the third seal is arranged between the air extraction channel and the motor cavity.

9. The impeller-motor integrated enclosed unit according to claim 6, characterized in that: The vent is connected to the outlet of the impeller chamber; or; The vent is connected to the compressor outlet; or; The vent is communicated with an air supply system.

10. A supercritical carbon dioxide unit, characterized in that: A closed impeller-motor integrated unit comprising the impeller-motor integrated closed unit as described in any one of claims 1-9.

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