High-pressure-ratio compression and expansion all-in-one machine

Abstract

The invention relates to a high-pressure-ratio compression and expansion all-in-one machine which comprises a motor, a slave motor, a rotor, compression equipment and expansion equipment, the compression equipment and the expansion equipment are both driven by the rotor, and the compression equipment comprises a compression volute, a first-stage compression impeller and a second-stage compression impeller, the first-stage compression impeller corresponds to the first-stage compression impeller, the second-stage compression impeller corresponds to the second-stage compression impeller, the second-stage compression impeller cover is located between the first-stage compression impeller and the second-stage compression impeller, and the second-stage compression impeller cover provides an impeller back effect for the first-stage compression impeller; a first flow channel connected with an outlet of the first-stage compression impeller and an inlet of the second-stage compression impeller is formed in the second-stage compression impeller cover; due to the design of the first flow channel formed in the second-stage compression wheel cover, gas subjected to first-stage compression can directly flow to the second-stage compression impeller through the flow channel, a complex external pipeline is not needed to guide the gas to flow between the two stages of compression impellers, the flowing path of the gas in the compression part is simplified, and the through-flow design difficulty is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of gas expansion and compression equipment, and in particular to a large pressure ratio compression and expansion integrated machine. Background Art

[0002] The compression-expansion machine driven by a high-speed permanent magnet synchronous motor has the advantages of high efficiency, high power density, and simple structure, and is gradually being promoted and applied. However, due to the centrifugal compression limiting the impeller linear speed, limited material strength, and differences in the physical properties of the working fluid, the pressure ratio of a single centrifugal impeller is limited.

[0003] The integrated compressor and expander is divided into a compression part, an expansion part and a drive motor part. According to the application requirements of the integrated compressor and expander, such as the rated cooling capacity of the rated temperature zone, the motor, compression part and expansion part, as well as other supporting structures are reasonably designed. During the design, sometimes there will be a situation where the pressure ratio of a single centrifugal impeller or expansion impeller cannot meet the requirements, and multi-stage compression and multi-stage expansion are required. Multiple integrated compressors and expanders or expanders or compressors are required to work with the integrated compressor and expander, and the system becomes complicated. If the multi-stage compression and / or multi-stage expansion can be set on the same integrated compressor and expander under power matching, the system structure can be simplified. This will lead to certain difficulties in the design of the flow-through part.

[0004] This patent provides a multi-stage compression and multi-stage expansion integrated compression and expansion machine structure, forming a multi-stage flow-through part structural arrangement, and achieving a large pressure ratio based on a single integrated compression and expansion machine. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a large pressure ratio compression and expansion integrated machine, aiming to solve one or more problems existing in the prior art.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a large pressure ratio compression and expansion integrated machine, comprising: a motor, a rotor extending from the motor at both ends of the motor housing, a compression device is arranged at one end of the motor housing, and an expansion device is arranged at the other end, the compression device and the expansion device are both driven by the rotor, the compression device comprises a compression volute, a primary compression impeller and a secondary compression impeller are arranged in the compression volute and are connected to the rotor in sequence from far to near, a primary compression wheel cover corresponding to the primary compression impeller and a secondary compression wheel cover corresponding to the secondary compression impeller are fixedly arranged in the compression volute, the secondary compression wheel cover is located between the primary compression impeller and the secondary compression impeller, the secondary compression wheel cover provides a wheel back effect for the primary compression impeller, a first flow channel connecting the primary compression impeller outlet and the secondary compression impeller inlet is formed in the secondary compression wheel cover, and the gas after the primary compression flows to the secondary compression impeller through the first flow channel.

[0007] Furthermore, the compression volute includes a first-stage compression volute and a second-stage compression volute, the first-stage compression volute and the second-stage compression volute together form an accommodating space for accommodating a first-stage compression impeller and a second-stage compression impeller, the first-stage compression volute and the second-stage compression volute are detachably and hermetically connected, the first-stage compression wheel cover and the first-stage compression impeller are both located in the first-stage compression volute and the first-stage compression wheel cover is fixedly connected to the first-stage compression volute, the second-stage compression wheel cover and the second-stage compression impeller are both located in the second-stage compression volute and the second-stage compression wheel cover is fixedly connected to the second-stage compression volute.

[0008] Furthermore, a compression wheel back is provided on a side of the secondary compression impeller away from the primary compression impeller.

[0009] Furthermore, the compression volute has a compression inlet and a compression outlet. The compression inlet is arranged on the first-stage compression volute and communicates with the first-stage compression impeller inlet. The compression outlet is arranged on the second-stage compression volute and communicates with the second-stage compression impeller outlet.

[0010] Furthermore, the expansion device includes an expansion volute, a primary expansion impeller and a secondary expansion impeller which are arranged in the expansion volute and connected to the rotor in sequence from near to far, a primary expansion wheel cover corresponding to the primary expansion impeller and a secondary expansion wheel cover corresponding to the secondary expansion impeller are fixedly arranged in the expansion volute; a primary expansion wheel back which is opposite to the primary expansion wheel cover is arranged on the side of the primary expansion impeller close to the motor housing, and a secondary expansion wheel back which is opposite to the secondary expansion wheel cover is arranged on the side of the secondary expansion impeller close to the motor housing, and the secondary expansion wheel back is located between the primary expansion impeller and the secondary expansion impeller, and the gas after the primary expansion enters the secondary expansion impeller through the secondary expansion wheel back.

[0011] Furthermore, the expansion volute has an expansion inlet and an expansion outlet, the expansion inlet is communicated with the inlet of the first-stage expansion impeller, and the expansion outlet is communicated with the outlet of the second-stage expansion impeller.

[0012] Furthermore, a plurality of through holes are provided on the back of the secondary expansion wheel to serve as channels for gas to flow from the primary expansion outlet to the secondary expansion inlet.

[0013] Furthermore, the output shaft of the rotor is a rotary stepped shaft, and the steps of the rotor provide axial positioning for the compression impeller and the expansion impeller.

[0014] Furthermore, it also includes a tie rod arranged at both ends of the rotor, both ends of the tie rod are provided with external threads, and both ends of the rotor are provided with threaded holes that cooperate with the tie rod. The tie rod is respectively fixed to the two ends of the rotor under the cooperation of the external thread and the threaded hole, and the first-stage compression impeller and the second-stage expansion impeller are both sleeved on the tie rod; a pre-tightening nut is threadedly connected on the tie rod, and under the action of the rotation and extrusion of the pre-tightening nut, the first-stage compression impeller and the second-stage expansion impeller are fixed on the rotor.

[0015] Furthermore, a primary fixing frame and a secondary fixing frame are fixedly arranged in the expansion shell, the primary expansion wheel cover is fixedly connected to the primary fixing frame, and the secondary expansion wheel cover is fixedly connected to the secondary fixing frame.

[0016] The large pressure ratio compression and expansion integrated machine described in the present invention has the beneficial effect that the design of the first flow channel formed in the second-stage compression wheel cover enables the gas compressed by the first stage to flow directly to the second-stage compression impeller through the flow channel, without the need for complex external pipeline connections to guide the gas to flow between the two-stage compression impellers, thereby simplifying the flow path of the gas inside the compression part and reducing the difficulty of flow design. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a cross-sectional view of the structure of a large pressure ratio compression and expansion integrated machine according to an embodiment of the present invention.

[0018] Explanation of the reference numerals in the accompanying drawings: 1. Motor; 11. Rotor; 2. Compression device; 21. Compression volute; 211. First-stage compression volute; 2111. First-stage compression wheel cover; 2112. First-stage compression impeller; 212. Second-stage compression volute; 2121. Second-stage compression wheel cover; 2122. Second-stage compression impeller; 2123. First flow channel; 2124. Compression wheel back; 22. Compression inlet; 23. Compression outlet; 3. Pull rod; 31. Pre-tightening nut; 4. Expansion device; 41. Expansion volute; 411. First-stage expansion impeller; 412. Second-stage expansion impeller; 413. First-stage expansion wheel cover; 414. Second-stage expansion wheel cover; 415. First-stage expansion wheel back; 416. Second-stage expansion wheel back; 42. Expansion inlet; 43. Expansion outlet; 44. First-stage fixing frame; 45. Second-stage fixing frame. DETAILED DESCRIPTION

[0019] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations therein are essentially used for illustration purposes rather than for limiting the present invention.

[0020] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0021] In order to further illustrate the principle and structure of the present invention, preferred embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, an embodiment of the present invention provides a large pressure ratio compression and expansion integrated machine, including: a motor 1, a rotor 11, a compression device 2 and an expansion device 4.

[0023] The motor 1 is used as a power source to provide power for the operation of the entire integrated machine. The rotor 11 extends from the motor 1 to both ends of the motor 1 housing, playing the role of connecting and transmitting power. A compression device 2 is provided at one end of the motor 1 housing, and an expansion device 4 is provided at the other end. The compression device 2 and the expansion device 4 are both driven by the rotor 11, so that the compression and expansion processes are completed simultaneously under the drive of a single motor 1.

[0024] The compression device 2 includes a compression volute 21, which provides installation space and a gas circulation channel for internal compression impellers and other components. A first-stage compression impeller 2112 and a second-stage compression impeller 2122 are arranged in the compression volute 21, which are connected to the rotor 11 in sequence from far to near. The first-stage compression impeller 2112 and the second-stage compression impeller 2122 are driven to rotate by the rotation of the rotor 11, thereby compressing the gas. A first-stage compression wheel cover 2111 corresponding to the first-stage compression impeller 2112 and a second-stage compression wheel cover 2121 corresponding to the second-stage compression impeller 2122 are also fixedly arranged in the compression volute 21, and a compression wheel back 2124 is arranged on the side of the second-stage compression impeller 2122 away from the first-stage compression impeller 2112. The secondary compression wheel cover 2121 is located between the primary compression impeller 2112 and the secondary compression impeller 2122. It plays an important role. On the one hand, it provides a wheel back function for the primary compression impeller 2112. On the other hand, a first flow channel 2123 is formed inside the primary compression impeller 2112 to connect the outlet of the primary compression impeller 2112 and the inlet of the secondary compression impeller 2122. The gas after primary compression can flow smoothly to the secondary compression impeller 2122 through the first flow channel 2123, ensuring the continuous flow of gas during the compression process and the effective implementation of multi-stage compression. The design of the first flow channel 2123 formed in the secondary compression wheel cover 2121 enables the gas after primary compression to flow directly to the secondary compression impeller 2122 through the flow channel, without the need for complex external pipeline connections to guide the gas to flow between the two-stage compression impellers. Traditional multi-stage compression equipment without such an integrated flow channel design requires additional pipes, valves and other components to realize the transition of the gas from the flow after primary compression to the secondary compression, which not only increases the number of components, but also easily causes leakage and pressure loss at the connection parts, increasing the complexity of the design of the flow part. However, this solution simplifies the flow path of the gas inside the compression part and reduces the difficulty of flow design by directly constructing the flow channel inside the second-stage compression wheel cover 2121.

[0025] Furthermore, the compression volute 21 includes a primary compression volute 211 and a secondary compression volute 212. The primary compression volute 211 and the secondary compression volute 212 together form a storage space for accommodating the primary compression impeller 2112 and the secondary compression impeller 2122, providing a stable installation and working environment for the two-stage compression impellers. The primary compression volute 211 and the secondary compression volute 212 are connected in a detachable sealed manner. During the installation of the equipment, the detachable design facilitates the assembly of various components. For example, during factory production or equipment maintenance, the primary compression volute 211 and the secondary compression volute 212 and their internal components can be separately installed and debugged, and then the two can be accurately docked and sealed, thereby improving the convenience of production and maintenance. The sealed connection ensures that the gas will not leak from the connection part of the volute during the compression process, maintains the pressure stability inside the system, and ensures the compression efficiency. The first-stage compression wheel cover 2111 and the first-stage compression impeller 2112 are both located in the first-stage compression volute 211, and the first-stage compression wheel cover 2111 is fixedly connected to the first-stage compression volute 211. The second-stage compression wheel cover 2121 and the second-stage compression impeller 2122 are both located in the second-stage compression volute 212, and the second-stage compression wheel cover 2121 is fixedly connected to the second-stage compression volute 212.

[0026] When actually manufacturing and installing the high-pressure ratio compression-expansion integrated machine, for the compression volute 21 part, first prepare the first-stage compression volute 211 and the second-stage compression volute 212. In the first-stage compression volute 211, accurately install the first-stage compression impeller 2112 and the corresponding first-stage compression wheel cover 2111, and firmly fix the first-stage compression wheel cover 2111 on the first-stage compression volute 211 by bolt connection or other suitable fixing methods to ensure that its position is stable and well sealed.

[0027] For the secondary compression volute 212, the secondary compression impeller 2122 and the secondary compression wheel cover 2121 are also installed inside and firmly fixed. During the installation process, special attention should be paid to the unobstructed first flow channel 2123 in the secondary compression wheel cover 2121 to ensure that it can accurately connect the outlet of the primary compression impeller 2112 and the inlet of the secondary compression impeller 2122.

[0028] Then, the first-stage compression volute 211 and the second-stage compression volute 212 are butt-jointed, and sealing materials such as sealing gaskets and sealants are used in conjunction with connecting parts such as bolts to achieve a detachable sealed connection.

[0029] Further, the compression inlet 22 is arranged on the primary compression volute 211, and the compression outlet 23 is arranged on the secondary compression volute 212. When the system is running, the gas enters the primary compression volute 211 from the outside through the compression inlet 22, and then enters the inlet of the primary compression impeller 2112 without any hindrance. The primary compression impeller 2112 rotates at a high speed driven by the rotor 11, and performs the first compression on the incoming gas to increase its pressure. The gas after the primary compression enters the secondary compression impeller 2122 through the first flow channel 2123 for further compression to achieve high pressure ratio compression. At this time, the secondary compression impeller 2122 is located in the secondary compression volute 212, and the compression outlet 23 is arranged on the secondary compression volute 212 and is connected to the outlet of the secondary compression impeller 2122. In this way, after the gas after the primary compression completes the second compression in the secondary compression impeller 2122, it can be smoothly discharged from the compression volute 21 through the compression outlet 23, enter the subsequent equipment or pipeline system connected to the compression outlet 23, and continue to participate in the entire workflow.

[0030] Furthermore, the expansion device 4 is mainly composed of an expansion volute 41 and components such as a primary expansion impeller 411 and a secondary expansion impeller 412 arranged inside the expansion volute 41. In the expansion volute 41, the primary expansion impeller 411 and the secondary expansion impeller 412 are sequentially connected to the rotor 11 from near to far. The rotor 11 serves as a power transmission component, driving the primary expansion impeller 411 and the secondary expansion impeller 412 to rotate synchronously. When the high-pressure gas enters the expansion device 4, it passes through the primary expansion impeller 411 and the secondary expansion impeller 412 in sequence. Under the rotation of the impeller, the gas expands and performs work externally.

[0031] Further, a first-stage expansion impeller 411 is provided with a first-stage expansion wheel back 415 opposite to the first-stage expansion wheel cover 413 on one side close to the motor 1 housing, and a second-stage expansion impeller 412 is provided with a second-stage expansion wheel back 416 opposite to the second-stage expansion wheel cover 414 on one side close to the motor 1 housing. Among them, the second-stage expansion wheel back 416 is located between the first-stage expansion impeller 411 and the second-stage expansion impeller 412, and the gas after the first-stage expansion can enter the second-stage expansion impeller 412 through the second-stage expansion wheel back 416. Compared with the traditional multi-stage expansion device 4, the flow of gas between the expansion impellers at each stage does not require complex external pipeline connections and steering devices, which reduces the number of components and avoids problems that easily lead to increased gas flow resistance, increased pressure loss, and increased leakage risk. The solution of this embodiment, by reasonably arranging the internal components and using the second-stage expansion wheel back 416 as a transition, allows the gas to flow naturally and smoothly between the two-stage expansion impellers, reduces the dependence of the flow-through part on the external complex pipeline, and thus simplifies the difficulty of the flow-through design.

[0032] Furthermore, the expansion volute 41 is provided with an expansion inlet 42 and an expansion outlet 43 . The expansion inlet 42 is communicated with the inlet of the first-stage expansion impeller 411 , and the expansion outlet 43 is communicated with the outlet of the second-stage expansion impeller 412 .

[0033] Furthermore, a second flow channel for gas to flow from the primary expansion outlet 43 to the secondary expansion inlet 42 is provided on the secondary expansion wheel back 416. Specifically, the second flow channel is a plurality of through holes provided on the secondary expansion wheel back 416, and the gas after primary expansion can enter the secondary expansion impeller 412 through the through holes of the secondary expansion wheel back 416.

[0034] Furthermore, the output shaft of the motor 1 rotor 11 described above adopts a rotary stepped shaft structure, and the design of the rotary stepped shaft structure provides precise axial positioning for the compression impeller and the expansion impeller. At the same time, by arranging the pull rod 3 at both ends of the rotor 11, and matching the corresponding threaded structure and the pre-tightening nut 31, the first-stage compression impeller 2112 and the second-stage expansion impeller 412 are reliably fixed, ensuring the stability and safety of the entire impeller system during high-speed rotation.

[0035] Specifically, the rotating stepped shaft structure of the rotor 11 has multiple steps, which provide a clear positioning reference for the impeller in the axial direction, so that the impeller can be accurately in the predetermined position during installation, ensuring that the gap between the impeller and other components such as the volute and wheel cover is uniform, thereby optimizing the flow performance of the gas and improving the compression and expansion efficiency.

[0036] The tie rods 3 at both ends of the rotor 11 are key components for fixing the impeller. Both ends of the tie rod 3 are provided with external threads, and threaded holes matching the external threads are provided at both ends of the rotor 11. During the installation process, the tie rod 3 is first installed at both ends of the rotor 11 through the matching of the external threads and the threaded holes, laying the foundation for the subsequent installation of the impeller. The first-stage compression impeller 2112 and the second-stage expansion impeller 412 are both sleeved on the tie rod 3. This sleeve arrangement allows the impeller to be initially positioned along the axial direction of the tie rod 3.

[0037] Subsequently, the pre-tightening nut 31 threaded on the tie rod 3 comes into play. During installation, a large pulling force is applied to the tie rod 3 with the help of special bolt tensioners and other tools, so that the tie rod 3 is subjected to the pre-tightening force. At this time, the pre-tightening nut 31 tightly fixes the first-stage compression impeller 2112 and the second-stage expansion impeller 412 on the rotor 11 under the action of rotational extrusion. The existence of the pre-tightening force can not only prevent the axial displacement of the impeller during operation and ensure the relative position of the impeller and other components remains stable, but also enable the impeller to better withstand various loads such as centrifugal force and gas force when rotating at high speed, thereby improving the overall rigidity and reliability of the impeller system, thereby ensuring the long-term stable operation of the compression and expansion machine.

[0038] In addition to the aforementioned structures such as the motor 1, the rotor 11, the compression device 2 and the expansion device 4, the high-pressure ratio integrated compression and expansion machine of the present invention also has corresponding designs in terms of refrigeration.

[0039] In the compression device 2, if intermediate cooling is required, an outlet can be provided on the first compression volute 211, and an inlet can be provided on the second compression volute 212. At the same time, the second compression wheel cover 2121 is deformed by the structure to cut off the first flow channel 2132 of the fluid after the first compression to the second compression impeller 2122. In this way, the high-temperature fluid after the first compression can be discharged, cooled by the external cooling device, and then returned to the inlet of the second compression volute 212, thus realizing the intermediate cooling process. This design helps to reduce the temperature of the gas during the compression process and improve the compression efficiency, which is of great significance in the refrigeration cycle that is more sensitive to temperature.

[0040] In the expansion device 4, when intermediate temperature control is required, an outlet structure corresponding to the primary expansion and an inlet structure corresponding to the secondary expansion can be provided on the expansion volute 41, and the second flow channel on the secondary expansion wheel back 416 can be cut off, and the fluid after the primary expansion can be exported through the outlet structure. For example, in some refrigeration applications, the temperature of the gas after the primary expansion may not meet the requirements of the subsequent process. By exporting it and adjusting the temperature through a processing device such as a heat exchanger, and then returning it to the inlet structure of the secondary expansion, the gas temperature during the expansion process can be accurately controlled, thereby optimizing the performance of the entire refrigeration cycle.

[0041] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high pressure ratio compression and expansion integrated machine, characterized in that: include: A motor, a rotor extending from the motor at both ends of the motor housing, a compression device being arranged at one end of the motor housing and an expansion device being arranged at the other end, both of which are driven by the rotor; the compression device comprises a compression volute, a primary compression impeller and a secondary compression impeller being arranged in the compression volute and connected to the rotor in sequence from far to near, a primary compression wheel cover corresponding to the primary compression impeller and a secondary compression wheel cover corresponding to the secondary compression impeller being fixedly arranged in the compression volute; The secondary compression wheel cover is located between the primary compression impeller and the secondary compression impeller. The secondary compression wheel cover provides a wheel back function for the primary compression impeller. A first flow channel connecting the primary compression impeller outlet and the secondary compression impeller inlet is formed in the secondary compression wheel cover. The gas compressed by the primary stage flows to the secondary compression impeller through the first flow channel.

2. The large pressure ratio compression and expansion integrated machine according to claim 1, characterized in that: The compression volute includes a first-stage compression volute and a second-stage compression volute, the first-stage compression volute and the second-stage compression volute together form an accommodating space for accommodating a first-stage compression impeller and a second-stage compression impeller, the first-stage compression volute and the second-stage compression volute are detachably and hermetically connected, the first-stage compression wheel cover and the first-stage compression impeller are both located in the first-stage compression volute, and the first-stage compression wheel cover is fixedly connected to the first-stage compression volute, the second-stage compression wheel cover and the second-stage compression impeller are both located in the second-stage compression volute, and the second-stage compression wheel cover is fixedly connected to the second-stage compression volute.

3. The large pressure ratio compression and expansion integrated machine according to claim 2, characterized in that: A compression wheel back is arranged on a side of the secondary compression impeller away from the primary compression impeller.

4. The large pressure ratio compression and expansion integrated machine according to claim 3, characterized in that: The compression volute has a compression inlet and a compression outlet. The compression inlet is arranged on the first-stage compression volute and communicates with the first-stage compression impeller inlet. The compression outlet is arranged on the second-stage compression volute and communicates with the second-stage compression impeller outlet.

5. The large pressure ratio compression and expansion integrated machine according to claim 1, characterized in that: The expansion device includes an expansion volute, a primary expansion impeller and a secondary expansion impeller which are arranged in the expansion volute and connected to the rotor in sequence from near to far, a primary expansion wheel cover corresponding to the primary expansion impeller and a secondary expansion wheel cover corresponding to the secondary expansion impeller are fixedly arranged in the expansion volute; a primary expansion wheel back which is opposite to the primary expansion wheel cover is arranged on the side of the primary expansion impeller close to the motor housing, and a secondary expansion wheel back which is opposite to the secondary expansion wheel cover is arranged on the side of the secondary expansion impeller close to the motor housing, and the secondary expansion wheel back is located between the primary expansion impeller and the secondary expansion impeller, and the gas after primary expansion enters the secondary expansion impeller through the secondary expansion wheel back.

6. The large pressure ratio compression and expansion integrated machine according to claim 5, characterized in that: The expansion volute has an expansion inlet and an expansion outlet. The expansion inlet is communicated with the inlet of the first-stage expansion impeller, and the expansion outlet is communicated with the outlet of the second-stage expansion impeller.

7. The large pressure ratio compression and expansion integrated machine according to claim 5, characterized in that: A plurality of through holes are provided on the back of the secondary expansion wheel to serve as channels for gas to flow from the primary expansion outlet to the secondary expansion inlet.

8. The large pressure ratio compression and expansion integrated machine according to claim 5, characterized in that: The output shaft of the rotor is a rotating stepped shaft, and the steps of the rotor provide axial positioning for the compression impeller and the expansion impeller.

9. The large pressure ratio compression and expansion integrated machine according to claim 8, characterized in that: It also includes a pull rod arranged at both ends of the rotor, both ends of the pull rod are provided with external threads, and both ends of the rotor are provided with threaded holes that cooperate with the pull rod. The pull rod is respectively fixed to the two ends of the rotor under the cooperation of the external thread and the threaded hole, and the first-stage compression impeller and the second-stage expansion impeller are both sleeved on the pull rod; a pre-tightening nut is threadedly connected on the pull rod, and under the action of the rotation and extrusion of the pre-tightening nut, the first-stage compression impeller and the second-stage expansion impeller are fixed on the rotor.

10. The large pressure ratio compression and expansion integrated machine according to claim 5, characterized in that: A primary fixing frame and a secondary fixing frame are fixedly arranged in the expansion shell, the primary expansion wheel cover is fixedly connected to the primary fixing frame, and the secondary expansion wheel cover is fixedly connected to the secondary fixing frame.

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