Expansion machine and circulation system

Abstract

The utility model relates to the technical field of machinery, and discloses an expansion machine and a circulating system, the expansion machine comprises a shell, a rotating shaft, a high-pressure-stage driving assembly and a low-pressure-stage driving assembly, and the high-pressure-stage driving assembly and the low-pressure-stage driving assembly are both fixed with the rotating shaft; the high-pressure-stage driving assembly is used for driving the rotating shaft to rotate under the driving of a high-pressure working medium, the low-pressure-stage driving assembly is used for driving the rotating shaft to rotate under the driving of a low-pressure working medium, high-pressure circulation and low-pressure circulation share one rotating shaft, and the circulation system is simplified; the high-pressure-stage driving assembly is located between the high-pressure-stage inlet and the high-pressure-stage outlet, and the low-pressure-stage driving assembly is located between the low-pressure-stage inlet and the low-pressure-stage outlet. A high-pressure working medium enters the shell from the high-pressure-stage inlet, drives the rotating shaft to rotate through the high-pressure-stage driving assembly, and then is discharged from the high-pressure-stage outlet; a low-pressure working medium enters the shell from the low-pressure-stage inlet and drives the rotating shaft to rotate through the low-pressure-stage driving assembly, and then the low-pressure working medium is discharged from the low-pressure-stage outlet.

Description

Technical Field

[0001] The utility model relates to the technical field of machinery, in particular to an expander and a circulation system. Background Art

[0002] Rankine cycle system: The system uses low-boiling-point organic matter as the working fluid. The working fluid in the liquid storage tank is pressurized by the working fluid pump, and then absorbs heat in the evaporator to become saturated steam or superheated steam with high enthalpy value. After outputting mechanical work through the expander (or the expander drives the motor, outputs electrical energy, etc.), it becomes low-pressure steam, then enters the condenser to cool to saturated liquid or supercooled liquid, and finally returns to the liquid storage tank. Among them, the working fluid is the working medium, which is the working substance that realizes the conversion of heat and work; in the Rankine cycle system, it is the medium that flows in the system for heat exchange and work conversion.

[0003] The existing high-pressure Rankine cycle system and the low-pressure Rankine cycle system are used in combination. The two systems are designed independently and need to be equipped with independent expanders, condensers, working fluid pumps, evaporators, etc. The system is complex, the structure space is large, the volume is bloated, and it is not convenient to install and arrange. Utility Model Content

[0004] The utility model discloses an expander and a circulation system, which are used for a high-pressure Rankine circulation loop and a low-pressure Rankine circulation loop to share the expander, so as to simplify the circulation system.

[0005] In order to achieve the above object, the utility model provides the following technical solutions:

[0006] In a first aspect, an expander is provided, the expander comprising: a shell, a rotating shaft, a high-pressure stage drive assembly and a low-pressure stage drive assembly, wherein the high-pressure stage drive assembly and the low-pressure stage drive assembly are both fixed to the rotating shaft, the high-pressure stage drive assembly is used to drive the rotating shaft to rotate under the drive of a high-pressure working fluid to generate kinetic energy, and the low-pressure stage drive assembly is used to drive the rotating shaft to rotate under the drive of a low-pressure working fluid to generate kinetic energy, the high-pressure cycle and the low-pressure cycle share a rotating shaft, the mechanical kinetic energy recovered by the high-pressure stage drive assembly and the mechanical kinetic energy recovered by the low-pressure stage drive assembly are coupled and superimposed, and then output together through the rotating shaft, so that the high-pressure expander and the low-pressure expander are integrated into one, and the high-pressure expander The Rankine cycle loop and the low-pressure Rankine cycle loop share an expander to simplify the circulation system and eliminate redundant parts; the shell has a high-pressure stage inlet, a high-pressure stage outlet, a low-pressure stage inlet and a low-pressure stage outlet, wherein the high-pressure stage drive assembly is located between the high-pressure stage inlet and the high-pressure stage outlet, and the low-pressure stage drive assembly is located between the low-pressure stage inlet and the low-pressure stage outlet; the high-pressure working fluid enters the shell from the high-pressure stage inlet, drives the above-mentioned rotating shaft to rotate through the high-pressure stage drive assembly, and then the high-pressure working fluid is discharged from the high-pressure stage outlet; the low-pressure working fluid enters the shell from the low-pressure stage inlet, drives the above-mentioned rotating shaft to rotate through the low-pressure stage drive assembly, and then the low-pressure working fluid is discharged from the low-pressure stage outlet. The high-pressure stage inlet and the low-pressure stage inlet are isolated from each other to prevent the high-pressure working fluid and the low-pressure working fluid from mixing in advance.

[0007] Optionally, the high-pressure stage drive assembly and the low-pressure stage drive assembly are distributed along the axial direction and are respectively connected to the rotating shaft.

[0008] Optionally, the high-pressure stage inlet and the low-pressure stage inlet are both located between the high-pressure stage drive assembly and the low-pressure stage drive assembly, the high-pressure stage outlet is located on the side of the high-pressure stage drive assembly away from the low-pressure stage drive assembly, and the low-pressure stage outlet is located on the side of the low-pressure stage drive assembly away from the high-pressure stage drive assembly.

[0009] Optionally, the expander further includes an isolating member located between the high-pressure stage drive assembly and the low-pressure stage drive assembly, wherein the isolating member is fixed to the rotating shaft and is in rotational contact with the inner wall of the shell to isolate the high-pressure stage inlet from the low-pressure stage inlet.

[0010] Optionally, the high-pressure stage inlet is located on a side of the high-pressure stage drive assembly away from the low-pressure stage drive assembly, the low-pressure stage inlet is located on a side of the low-pressure stage drive assembly away from the high-pressure stage drive assembly, and the high-pressure stage outlet and the low-pressure stage outlet are both located between the high-pressure stage drive assembly and the low-pressure stage drive assembly.

[0011] Optionally, the high-pressure stage outlet and the low-pressure stage outlet are independent of each other and are arranged at intervals; or, the high-pressure stage outlet and the low-pressure stage outlet share one outlet.

[0012] Optionally, the high-pressure stage drive assembly includes a high-pressure stage nozzle structure and a high-pressure stage impeller axially located in sequence between the high-pressure stage inlet and the high-pressure stage outlet; the low-pressure stage drive assembly includes a low-pressure stage nozzle structure and a low-pressure stage impeller axially located in sequence between the low-pressure stage inlet and the low-pressure stage outlet; the high-pressure stage impeller and the low-pressure stage impeller have opposite rotation directions.

[0013] Optionally, the high-pressure stage drive assembly and the low-pressure stage drive assembly are distributed radially and connected to each other.

[0014] Optionally, the high-pressure stage inlet and the low-pressure stage inlet are axially located on the same side of the high-pressure stage drive assembly and the low-pressure stage drive assembly; the high-pressure stage outlet and the low-pressure stage outlet are axially located on the same side of the high-pressure stage drive assembly and the low-pressure stage drive assembly.

[0015] Optionally, the high-pressure stage outlet and the low-pressure stage outlet share one outlet.

[0016] Optionally, the high-pressure stage drive assembly includes a high-pressure stage nozzle structure and a high-pressure stage impeller which are axially located in sequence between the high-pressure stage inlet and the high-pressure stage outlet; the low-pressure stage drive assembly includes a low-pressure stage nozzle structure and a low-pressure stage impeller which are axially located in sequence between the low-pressure stage inlet and the low-pressure stage outlet; the high-pressure stage impeller is located at the periphery of the low-pressure stage impeller and is fixedly connected to the low-pressure stage impeller; the high-pressure stage nozzle structure is located at the periphery of the low-pressure stage nozzle structure and is fixedly connected to the low-pressure stage nozzle structure.

[0017] Optionally, the high-pressure stage impeller has the same rotation direction as the low-pressure stage impeller.

[0018] In a second aspect, a circulation system is provided, which comprises: a liquid storage tank, a high-pressure working fluid pump, a high-pressure evaporator, a low-pressure working fluid pump, a low-pressure evaporator, a high- and low-pressure condenser, and an expander as described in any of the above technical solutions; the liquid storage tank, the high-pressure working fluid pump, the high-pressure evaporator, the expander, and the high- and low-pressure condensers are connected end to end in sequence to form a high-pressure Rankine cycle loop; the liquid storage tank, the low-pressure working fluid pump, the low-pressure evaporator, the expander, and the high- and low-pressure condensers are connected end to end in sequence to form a low-pressure Rankine cycle loop; wherein the high-pressure evaporator is connected to the high-pressure stage inlet, the low-pressure evaporator is connected to the low-pressure stage inlet, and the high- and low-pressure condensers are respectively connected to the high-pressure stage outlet and the low-pressure stage outlet.

[0019] The advantages of the circulation system described are the same as those of the above-mentioned expander over the prior art, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of the circulation system provided in the embodiment of the present application;

[0021] Figure 2 A schematic diagram showing the structure of a first embodiment of an expander provided in an embodiment of the present application;

[0022] Figure 3 A schematic diagram showing the structure of a second implementation of an expander provided in an embodiment of the present application;

[0023] Figure 4 A schematic diagram showing the structure of a third implementation of an expander provided in an embodiment of the present application;

[0024] Figure 5 express Figure 4 Schematic diagram of the assembly of the medium and high pressure stage impeller 22a and the low pressure stage impeller 22b. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] refer to Figures 2 to 4The expander provided in the embodiment of the present application includes: a shell 40, a rotating shaft 30, a high-pressure stage drive component 20a and a low-pressure stage drive component 20b, wherein the high-pressure stage drive component 20a and the low-pressure stage drive component 20b are both fixed to the rotating shaft 30, and the rotating shaft 30 is rotatably connected to the shell 40 or the bracket in the shell 40 through a bearing 32 to realize rotational support, and the high-pressure stage drive component 20a is used to drive the rotating shaft 30 to rotate under the drive of the high-pressure working fluid to generate kinetic energy, and the low-pressure stage drive component 20b is used to drive the rotating shaft 30 to rotate under the drive of the low-pressure working fluid to generate kinetic energy. The high-pressure cycle and the low-pressure cycle share a rotating shaft 30, and the mechanical kinetic energy recovered by the high-pressure stage drive component 20a and the mechanical kinetic energy recovered by the low-pressure stage drive component 20b are coupled and superimposed, and then output together through the rotating shaft 30, and the kinetic energy is output through the power output device 31, so that the high-pressure expander and the low-pressure expander are integrated into one. Both the high-pressure expander and the low-pressure Rankine cycle loop require an independent control system. The high-pressure Rankine cycle loop and the low-pressure Rankine cycle loop share the expander, and only one set of control system is needed to realize control, so as to simplify the circulation system and eliminate redundant parts; the shell 40 has a high-pressure stage inlet 11a, a high-pressure stage outlet 12a, a low-pressure stage inlet 11b and a low-pressure stage outlet 12b, wherein the high-pressure stage drive component 20a is located between the high-pressure stage inlet 11a and the high-pressure stage outlet 12a, and the low-pressure stage drive component 20b is located between the low-pressure stage inlet 11b and the low-pressure stage outlet 12b; the high-pressure working fluid enters the shell 40 from the high-pressure stage inlet 11a, drives the above-mentioned rotating shaft 30 to rotate through the high-pressure stage drive component 20a, and then the high-pressure working fluid is discharged from the high-pressure stage outlet 12a; the low-pressure working fluid enters the shell 40 from the low-pressure stage inlet 11b, drives the above-mentioned rotating shaft 30 to rotate through the low-pressure stage drive component 20b, and then the low-pressure working fluid is discharged from the low-pressure stage outlet 12b. The high pressure stage inlet 11a and the low pressure stage inlet 11b are isolated from each other to prevent the high pressure working fluid and the low pressure working fluid from mixing in advance. In addition, the high pressure cycle and the low pressure cycle share a shell 40, which can also simplify the process and assembly difficulty.

[0027] refer to Figure 2 and Figure 3 In a specific embodiment, the high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b are distributed along the axial direction and are respectively connected to the rotating shaft 30. The high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b are respectively directly fixed on the rotating shaft 30, which can save radial space and reduce radial dimensions.

[0028] refer to Figure 2In a specific embodiment, the high-pressure stage inlet 11a and the low-pressure stage inlet 11b are both located between the high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b, the high-pressure stage outlet 12a is located on the side of the high-pressure stage drive assembly 20a away from the low-pressure stage drive assembly 20b, and the low-pressure stage outlet 12b is located on the side of the low-pressure stage drive assembly 20b away from the high-pressure stage drive assembly 20a. The high-pressure stage inlet 11a, the high-pressure stage outlet 12a, the low-pressure stage inlet 11b and the low-pressure stage outlet 12b are all independently arranged, and the high-pressure cycle and the low-pressure cycle have mutually isolated paths, respectively, with strong independence, and are easy to be independently controlled.

[0029] In a specific embodiment, the expander also includes an isolation member 33 located between the high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b. The isolation member 33 is fixed to the rotating shaft 30. The isolation member 33 is in rotational contact with the inner wall of the shell 40 to isolate the high-pressure stage inlet 11a from the low-pressure stage inlet 11b, thereby preventing the high-pressure working fluid and the low-pressure working fluid from mixing prematurely with a simple structure.

[0030] In a specific embodiment, the high-pressure stage inlet 11a is located on the side of the high-pressure stage drive assembly 20a away from the low-pressure stage drive assembly 20b, and the low-pressure stage inlet 11b is located on the side of the low-pressure stage drive assembly 20b away from the high-pressure stage drive assembly 20a. The high-pressure stage outlet 12a and the low-pressure stage outlet 12b are both located between the high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b. After the high-pressure working fluid passes through the high-pressure stage drive assembly 20a and the low-pressure working fluid passes through the low-pressure stage drive assembly 20b, the two can be mixed with each other, which can further simplify the structure.

[0031] In a specific embodiment, the high-pressure stage outlet 12a and the low-pressure stage outlet 12b are independent of each other and are spaced apart so that the high-pressure working fluid and the low-pressure working fluid can flow out independently; alternatively, the high-pressure stage outlet 12a and the low-pressure stage outlet 12b share one outlet, and the pressures of the high-pressure stage outlet 12a and the low-pressure stage outlet 12b are equivalent. After merging, the overall axial distance of the expander is slightly shortened, and the size of the expander is slightly reduced accordingly.

[0032] In a specific embodiment, the high-pressure stage driving assembly 20a includes a high-pressure stage nozzle structure 21a and a high-pressure stage impeller 22a which are sequentially located along the axial direction between the high-pressure stage inlet 11a and the high-pressure stage outlet 12a. After the high-pressure working fluid enters from the high-pressure stage inlet 11a, after passing through the high-pressure stage nozzle structure 21a, the high-pressure working fluid expands, reduces pressure and increases speed, pushes the high-pressure stage impeller 22a to rotate, drives the rotating shaft 30 to rotate, and then flows out through the high-pressure stage outlet 12a; the low-pressure stage driving assembly 20b includes a low-pressure stage nozzle structure 21b and a low-pressure stage impeller 22b which are sequentially located along the axial direction between the low-pressure stage inlet 11b and the low-pressure stage outlet 12b. After the low-pressure working fluid enters from the low-pressure stage inlet 11b, after passing through the low-pressure stage nozzle structure 21b, the low-pressure working fluid expands, reduces pressure and increases speed, pushes the low-pressure stage impeller 22b to rotate, drives the rotating shaft 30 to rotate, and then flows out through the low-pressure stage outlet 12b; refer to Figure 2 and Figure 3 The high-pressure working fluid and the low-pressure working fluid flow in opposite directions, and the high-pressure stage impeller 22a and the low-pressure stage impeller 22b rotate in opposite directions to ensure that the rotation direction of the rotating shaft 30 is consistent to achieve maximum torque output.

[0033] In a specific embodiment, the high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b are distributed radially and connected to each other to reduce the occupied axial space. The axial dimension of the expander is shortened, and its radial dimension does not change much, so that the expander structure is more compact and more convenient to install and use.

[0034] In a specific embodiment, the high-pressure stage inlet 11a and the low-pressure stage inlet 11b are axially located on the same side of the high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b; the high-pressure stage outlet 12a and the low-pressure stage outlet 12b are axially located on the same side of the high-pressure stage drive assembly 20a and the low-pressure stage drive assembly 20b, and the outlet pressures of the high-pressure stage outlet 12a and the low-pressure stage outlet 12b are similar and can be mixed with each other.

[0035] In a specific embodiment, the high-pressure stage outlet 12a and the low-pressure stage outlet 12b share one outlet, which makes the structure more compact.

[0036] In a specific embodiment, the high-pressure stage driving assembly 20a includes a high-pressure stage nozzle structure 21a and a high-pressure stage impeller 22a which are sequentially located along the axial direction between the high-pressure stage inlet 11a and the high-pressure stage outlet 12a. After the high-pressure working fluid enters from the high-pressure stage inlet 11a, it expands, reduces pressure and increases speed after passing through the high-pressure stage nozzle structure 21a, and pushes the high-pressure stage impeller 22a to rotate, drives the rotating shaft 30 to rotate, and then flows out through the high-pressure stage outlet 12a; the low-pressure stage driving assembly 20b includes a low-pressure stage nozzle structure 21b and a low-pressure stage impeller 22b which are sequentially located along the axial direction between the low-pressure stage inlet 11b and the low-pressure stage outlet 12b. After the low-pressure working fluid enters from the low-pressure stage inlet 11b, it expands, reduces pressure and increases speed after passing through the low-pressure stage nozzle structure 21b, and pushes the low-pressure stage impeller 22b to rotate, drives the rotating shaft 30 to rotate, and then flows out through the low-pressure stage outlet 12b; Figure 5 The high-pressure impeller 22a is located outside the low-pressure impeller 22b and is fixedly connected to the low-pressure impeller 22b. A collar 23 is also provided outside the high-pressure impeller 22a, and the three can be welded and fixed to each other. The high-pressure impeller 22a and the low-pressure impeller 22b are designed as an integrated type, which can simultaneously convert the energy of the high-pressure working fluid and the low-pressure working fluid into the kinetic energy of the rotating shaft 30, and then output the kinetic energy through the power output device 31. The integrated design of the high-pressure impeller 22a and the low-pressure impeller 22b can greatly shorten the axial size of the expander, and its radial size does not change much, thereby making the expander structure more compact and more convenient to install and use. The high-pressure nozzle structure 21a is located outside the low-pressure nozzle structure 21b and is fixedly connected to the low-pressure nozzle structure 21b, which can greatly shorten the axial size of the expander.

[0037] In a specific embodiment, the high-pressure stage working fluid and the low-pressure stage working fluid have the same flow direction, and the high-pressure stage impeller 22a and the low-pressure stage impeller 22b have the same rotation direction, ensuring that the overall rotating shaft 30 rotates in the same direction, thereby achieving maximum torque output.

[0038] Based on the same idea, refer to Figure 1, the embodiment of the present application also provides a circulation system including: a liquid storage tank 5, a high-pressure working fluid pump 1a, a high-pressure evaporator 2a, a low-pressure working fluid pump 1b, a low-pressure evaporator 2b, a high- and low-pressure condenser 4 and an expander 3 provided in the above embodiment; the liquid storage tank 5, the high-pressure working fluid pump 1a, the high-pressure evaporator 2a, the expander 3 and the high- and low-pressure condenser 4 are connected end to end in sequence to form a high-pressure Rankine cycle loop; the liquid storage tank 5, the low-pressure working fluid pump 1b, the low-pressure evaporator 2b, the expander 3 and the high- and low-pressure condenser 4 are connected end to end in sequence to form a low-pressure Rankine cycle loop; wherein the high-pressure evaporator 2a is connected to the high-pressure stage inlet 11a, the low-pressure evaporator 2b is connected to the low-pressure stage inlet 11b, and the high- and low-pressure condensers 4 are respectively connected to the high-pressure stage outlet 12a and the low-pressure stage outlet 12b. In addition to the advantages of the expander 3, in the circulation system, the high-pressure Rankine cycle loop and the low-pressure Rankine cycle loop share the liquid storage tank 5, the expander 3 and the high- and low-pressure condensers 4, which can further simplify the system structure and eliminate the redundant parts of the system. The high-pressure Rankine cycle loop and the low-pressure Rankine cycle loop can still be controlled independently.

[0039] At the same time, the circulation system can be equipped with a certain number of temperature sensors, pressure sensors, flow meters, expander speed sensors, vibration sensors and other sensors, as well as a certain number of valves, filters, and corresponding expander bypass branches can be set as needed. The circulation system can use organic refrigerants including R245fa, R1233zd, R1234yf, etc. as circulation fluids (high-pressure fluids and low-pressure fluids), and can also use alkanes such as cyclopentane as circulation fluids, but is not limited to these fluids.

[0040] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An expander, characterized in that: include: A housing, a rotating shaft, a high-pressure stage drive assembly and a low-pressure stage drive assembly, wherein the high-pressure stage drive assembly and the low-pressure stage drive assembly are both fixed to the rotating shaft, the high-pressure stage drive assembly is used to drive the rotating shaft to rotate under the drive of the high-pressure working medium, and the low-pressure stage drive assembly is used to drive the rotating shaft to rotate under the drive of the low-pressure working medium; The housing has a high-pressure stage inlet, a high-pressure stage outlet, a low-pressure stage inlet and a low-pressure stage outlet, wherein the high-pressure stage drive assembly is located between the high-pressure stage inlet and the high-pressure stage outlet, and the low-pressure stage drive assembly is located between the low-pressure stage inlet and the low-pressure stage outlet; Wherein, the high-pressure stage inlet and the low-pressure stage inlet are isolated from each other.

2. The expander according to claim 1, characterized in that The high-pressure stage driving assembly and the low-pressure stage driving assembly are distributed along the axial direction and are respectively connected to the rotating shaft.

3. The expander according to claim 2, characterized in that The high-pressure stage inlet and the low-pressure stage inlet are both located between the high-pressure stage drive assembly and the low-pressure stage drive assembly, the high-pressure stage outlet is located on the side of the high-pressure stage drive assembly away from the low-pressure stage drive assembly, and the low-pressure stage outlet is located on the side of the low-pressure stage drive assembly away from the high-pressure stage drive assembly.

4. The expander according to claim 3, characterized in that The expander also includes an isolating member located between the high-pressure stage drive assembly and the low-pressure stage drive assembly, wherein the isolating member is fixed to the rotating shaft and is in rotational contact with the inner wall of the shell to isolate the high-pressure stage inlet from the low-pressure stage inlet.

5. The expander according to claim 2, characterized in that The high-pressure stage inlet is located on the side of the high-pressure stage drive assembly away from the low-pressure stage drive assembly, the low-pressure stage inlet is located on the side of the low-pressure stage drive assembly away from the high-pressure stage drive assembly, and the high-pressure stage outlet and the low-pressure stage outlet are both located between the high-pressure stage drive assembly and the low-pressure stage drive assembly.

6. The expander according to claim 5, characterized in that The high-pressure stage outlet and the low-pressure stage outlet are independent of each other and are arranged at intervals; or, The high-pressure stage outlet and the low-pressure stage outlet share one outlet.

7. The expander according to any one of claims 3 to 6, characterized in that: The high-pressure stage drive assembly comprises a high-pressure stage nozzle structure and a high-pressure stage impeller which are sequentially located between the high-pressure stage inlet and the high-pressure stage outlet in the axial direction; The low-pressure stage drive assembly comprises a low-pressure stage nozzle structure and a low-pressure stage impeller which are sequentially located between the low-pressure stage inlet and the low-pressure stage outlet in the axial direction; The high-pressure stage impeller and the low-pressure stage impeller have opposite rotation directions.

8. The expander according to claim 1, characterized in that The high-pressure stage driving assembly and the low-pressure stage driving assembly are distributed radially and connected to each other.

9. The expander according to claim 8, characterized in that The high-pressure stage inlet and the low-pressure stage inlet are axially located on the same side of the high-pressure stage drive assembly and the low-pressure stage drive assembly; The high-pressure stage outlet and the low-pressure stage outlet are axially located on the same side of the high-pressure stage drive assembly and the low-pressure stage drive assembly.

10. The expander according to claim 9, characterized in that The high-pressure stage outlet and the low-pressure stage outlet share one outlet.

11. The expander according to claim 8, characterized in that The high-pressure stage drive assembly comprises a high-pressure stage nozzle structure and a high-pressure stage impeller which are sequentially located between the high-pressure stage inlet and the high-pressure stage outlet in the axial direction; The low-pressure stage drive assembly comprises a low-pressure stage nozzle structure and a low-pressure stage impeller which are sequentially located between the low-pressure stage inlet and the low-pressure stage outlet in the axial direction; The high-pressure stage impeller is located at the periphery of the low-pressure stage impeller and is fixedly connected to the low-pressure stage impeller; The high-pressure nozzle structure is located at the periphery of the low-pressure nozzle structure and is fixedly connected to the low-pressure nozzle structure.

12. The expander according to claim 11, characterized in that The high-pressure stage impeller and the low-pressure stage impeller have the same rotation direction.

13. A circulation system, characterized in that: include: A liquid storage tank, a high-pressure working fluid pump, a high-pressure evaporator, a low-pressure working fluid pump, a low-pressure evaporator, a high- and low-pressure condenser, and an expander according to any one of claims 1 to 12; The liquid storage tank, the high-pressure working fluid pump, the high-pressure evaporator, the expander and the high- and low-pressure condensers are connected end to end in sequence to form a high-pressure Rankine cycle loop; The liquid storage tank, the low-pressure working fluid pump, the low-pressure evaporator, the expander and the high- and low-pressure condensers are connected end to end in sequence to form a low-pressure Rankine cycle loop; The high-pressure evaporator is connected to the high-pressure stage inlet, the low-pressure evaporator is connected to the low-pressure stage inlet, and the high-pressure and low-pressure condensers are respectively connected to the high-pressure stage outlet and the low-pressure stage outlet.

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