CN216199193U - Rotor shaft, rotor assembly and air cycle machine - Google Patents

Abstract

The application provides a rotor shaft, a rotor assembly and an air cycle machine. The rotor shaft comprises a reference shaft section (1), a first shaft section (2), a second shaft section (3) and a third shaft section (4), wherein the first shaft section (2) is configured to be assembled with an expansion impeller (8), the second shaft section (3) is configured to be assembled with a compression impeller (9), the third shaft section (4) is configured to be assembled with a wind impeller (10), the first shaft section (2) and the second shaft section (3) are arranged at two ends of the reference shaft section (1), two end faces of the reference shaft section (1) form an axial positioning face (17), the diameter of the reference shaft section (1) is D1, the diameter of the first shaft section (2) is D2, the diameter of the second shaft section (3) is D3, the diameter of the third shaft section (4) is D4, D1 > D2, D1 > D3 > D4. According to the rotor shaft, the positioning accuracy of the compression impeller, the expansion impeller and the wind impeller during installation can be improved.

Description

Rotor shaft, rotor assembly and air cycle machine

Technical Field

The application relates to the technical field of aircraft air conditioners, in particular to a rotor shaft, a rotor assembly and an air cycle machine.

Background

A compressed air circulating refrigeration system with air as a working medium adopts a turbine compressor to realize a compression process and an expander to realize an expansion process, and simultaneously the system also needs a fan to drive air to flow and take away heat of a heat exchanger. The expander, compressor and fan are combined into an air cycle machine comprising a rotor assembly and a stationary assembly, wherein the rotor assembly is supported for high speed rotational movement by a bearing system.

In order to assemble a structure including a compression impeller, an expansion impeller, and a wind impeller into a rotor assembly and allow the rotor assembly to reliably rotate at high speed, a journal shaft coupling the impellers is disclosed in the related art, a cylindrical tie rod passes through the journal shaft and all the impellers, and a clamping member applies a load to fix the compressor rotor, the turbine rotor, and the fan blades with respect to the tie rod. In the journal shaft, the structures of the compression impeller, the expansion impeller and the wind impeller are positioned through the clamping component, the positioning reference is inconsistent, and the positioning precision is not high.

SUMMERY OF THE UTILITY MODEL

Therefore, the technical problem that this application will be solved lies in providing a rotor shaft, rotor subassembly and air cycle machine, can improve the positioning accuracy when compression impeller, expansion impeller and wind impeller install.

In order to solve the above problems, the present application provides a rotor shaft, including a reference shaft section, a first shaft section, a second shaft section and a third shaft section, the first shaft section is configured to be assembled with an expansion impeller, the second shaft section is configured to be assembled with a compression impeller, the third shaft section is configured to be assembled with a wind impeller, the first shaft section and the second shaft section are disposed at two ends of the reference shaft section, end faces of two ends of the reference shaft section form axial positioning faces, a diameter of the reference shaft section is D1, a diameter of the first shaft section is D2, a diameter of the second shaft section is D3, a diameter of the third shaft section is D4, D1 > D2, and D1 > D3 ≧ D4.

Preferably, a fourth shaft section is arranged between the first shaft section and the reference shaft section, the fourth shaft section is configured to be provided with a thrust disc, the diameter of the fourth shaft section is D5, and D1 > D5 ≧ D2.

Preferably, the length of the reference shaft segment is L1, and L1/D1 is 1.1-2.0.

Preferably, L1/D1 is 1.69.

Preferably, the length of the second shaft section is L3, and L3/D3 is 1-7.4.

Preferably, L3/D3 is 1.53-5.4.

Preferably, the length of the fourth shaft section is L5, and L5/D5 is 0.3-2.5.

Preferably, L5/D5 is 0.5.

Preferably, a fifth shaft section is arranged between the second shaft section and the third shaft section, the fifth shaft section is configured to be provided with an axial positioning element, the diameter of the fifth shaft section is D6, and D3 is more than or equal to D6.

Preferably, a sixth shaft section is arranged between the second shaft section and the third shaft section, the sixth shaft section is configured to be mounted with a radial journal, the diameter of the sixth shaft section is D7, D3 ≧ D7.

Preferably, the two ends of the rotor shaft are provided with locking bolt holes, and locking bolt assemblies are installed in the locking bolt holes.

Preferably, a fourth shaft section is arranged between the first shaft section and the reference shaft section, a fifth shaft section and a sixth shaft section are arranged between the second shaft section and the third shaft section, the fifth shaft section and the second shaft section are sequentially arranged along the direction far away from the reference shaft section, the diameter of the fourth shaft section is D5, the diameter of the fifth shaft section is D6, the diameter of the sixth shaft section is D7, D1 > D5 > D2, and/or D1 > D3 > D6 > D7 > D4.

According to another aspect of the present application, there is provided a rotor assembly comprising a rotor shaft as described above.

Preferably, when the rotor shaft comprises a reference shaft section, a first shaft section, a second shaft section, a third shaft section, a fourth shaft section, a fifth shaft section and a sixth shaft section, the rotor assembly further comprises an expansion impeller, a compression impeller, a wind impeller, a thrust disc, an axial positioning element, a radial journal and an axial balancing element, wherein the expansion impeller is assembled on the first shaft section, the compression impeller is assembled on the second shaft section, the axial balancing element and the wind impeller are assembled on the third shaft section, the thrust disc is assembled on the fourth shaft section, the axial positioning element is assembled on the fifth shaft section, and the radial journal is assembled on the sixth shaft section.

According to another aspect of the present application, there is provided an air cycle machine including a rotor assembly as described above.

The application provides a rotor shaft, including the benchmark shaft segment, first shaft segment, second shaft segment and third shaft segment, first shaft segment is configured to the assembly inflation impeller, the second shaft segment is configured to the assembly compression impeller, the third shaft segment is configured to the assembly impeller, first shaft segment and second shaft segment set up the both ends at the benchmark shaft segment, the both ends terminal surface of benchmark shaft segment forms the axial positioning face, the diameter of benchmark shaft segment is D1, the diameter of first shaft segment is D2, the diameter of third shaft segment is D3, the diameter of fourth shaft segment is D4, D1 > D2, D1 > D3 is greater than or equal to D4. The rotor shaft utilizes the reference shaft section as a positioning reference, realizes axial positioning in the installation process of the expansion impeller, the compression impeller and the wind impeller, can realize uniform positioning reference, reduces positioning errors, improves positioning precision and improves the assembly precision of the rotor assembly.

Drawings

FIG. 1 is a schematic structural diagram of an air cycle machine according to an embodiment of the present application;

FIG. 2 is a schematic gas flow diagram of an air cycle machine according to an embodiment of the present application;

FIG. 3 is a schematic perspective view of a rotor shaft according to an embodiment of the present disclosure;

FIG. 4 is a cross-sectional structural schematic view of a rotor shaft of an embodiment of the present application;

FIG. 5 is a cross-sectional structural schematic view of a rotor assembly of an embodiment of the present application;

FIG. 6 is a cross-sectional structural schematic view of a rotor assembly of an embodiment of the present application;

FIG. 7 is an exploded view of a rotor assembly according to an embodiment of the present application;

FIG. 8 is a diagram of a sensor arrangement for a rotor assembly in an embodiment of the present application;

FIG. 9 is a graph of rotor movement at speed n for an air cycle machine according to an embodiment of the present application.

The reference numerals are represented as:

1. a reference shaft section; 2. a first shaft section; 3. a second shaft section; 4. a third shaft section; 5. a fourth shaft section; 6. a fifth shaft section; 7. a sixth shaft section; 8. an expansion impeller; 9. compressing the impeller; 10. a wind impeller; 11. a thrust plate; 12. a radial journal; 13. locking the bolt hole; 14. a locking bolt assembly; 15. an axial positioning member; 16. an axial balancing member; 17. an axial positioning surface; 18. an expansion shell; 19. compressing the shell; 20. a fan base; 21. and a bearing.

Detailed Description

With combined reference to fig. 1 to 9, according to an embodiment of the present application, the rotor shaft includes a reference shaft segment 1, a first shaft segment 2, a second shaft segment 3 and a third shaft segment 4, the first shaft segment 2 is configured to be assembled with an expansion impeller 8, the second shaft segment 3 is configured to be assembled with a compression impeller 9, the third shaft segment 4 is configured to be assembled with a wind impeller 10, the first shaft segment 2 and the second shaft segment 3 are disposed at both ends of the reference shaft segment 1, end faces of both ends of the reference shaft segment 1 form an axial positioning face 17, the reference shaft segment 1 has a diameter of D1, the first shaft segment 2 has a diameter of D2, the second shaft segment 3 has a diameter of D3, the third shaft segment 4 has a diameter of D4, D1 > D2, and D1 > D3 > D4.

The rotor shaft utilizes the reference shaft section 1 as a positioning reference, realizes axial positioning in the installation process of the expansion impeller 8, the compression impeller 9 and the wind impeller 10, can realize uniform positioning reference, reduces positioning errors, improves positioning precision and improves the assembly precision of a rotor assembly.

In this embodiment, each shaft segment and the reference shaft segment 1 are coaxially arranged, and each shaft segment is a cylindrical segment, so as to realize the installation and positioning of other components of the rotor assembly. Because each shaft section uses the reference shaft section 1 as a processing and mounting reference, the unification of the processing and mounting references is realized, parts required by positioning can be reduced, the mounting and positioning precision is improved, and the assembling precision of the rotor assembly is improved.

In one embodiment, a fourth shaft section 5 is arranged between the first shaft section 2 and the reference shaft section 1, the fourth shaft section 5 is configured to mount the thrust disk 11, the diameter of the fourth shaft section 5 is D5, D1 > D5 ≧ D2. The fourth shaft section 5 is arranged between the first shaft section 2 and the reference shaft section 1, so that the thrust disk 11 is arranged between the reference shaft section 1 and the expansion impeller 8, the axial installation accuracy of the thrust disk 11 can be positioned by using the reference shaft section 1, and meanwhile, the axial installation progress of the expansion impeller 8 can be positioned by using the thrust disk 11. As a preferred embodiment, D5 > D2, so that the thrust disk 11 is in clearance fit with the first shaft section 2 when passing through the first shaft section 2, which can reduce the installation and disassembly resistance of the thrust disk 11, reduce the installation and disassembly difficulty of the thrust disk 11, and improve the assembly efficiency of the thrust disk 11, without reducing the installation accuracy of the thrust disk 11 and the expansion impeller 8.

In one embodiment, the length of the reference shaft segment 1 is L1, and L1/D1 is 1.1 ~ 2.0.

Preferably, L1/D1 is 1.69.

The ratio is too small, the bearing 21 is difficult to arrange on the reference shaft section 1, and the wallpaper is too large, so that the axial size of the rotor shaft can be lengthened, the rigidity of the rotor shaft is reduced, and the high-speed operation of the rotor assembly is not facilitated.

In one embodiment, the second shaft section 3 has a length L3, L3/D3 ═ 1-7.4.

Preferably, L3/D3 is 1.53-5.4.

This ratio is too little, can lead to the axial length undersize of the second shaft section 3 that is used for installing compression impeller 9, is difficult to realize the assembly between compression impeller 9 and the rotor shaft, and this ratio is too big, then can lengthen the axial dimension of rotor shaft, reduces the rigidity of rotor shaft, is unfavorable for realizing the high-speed operation of rotor subassembly.

When the ratio is 1.53-5.4, the diameters of the shaft sections between the second shaft section 3 and the third shaft section 4 are the same, steps between the shaft sections are eliminated, and the processing difficulty of the rotor shaft is reduced.

In one embodiment, the length of the fourth shaft segment 5 is L5, and L5/D5 is 0.3-2.5.

Preferably, L5/D5 is 0.5.

This ratio is too little, then can lead to the axial length of fourth shaft section 5 too short, is unfavorable for realizing the fastening assembly between thrust dish 11 and the fourth shaft section 5 of rotor shaft, and this ratio is too big, then can lengthen the axial dimension of rotor shaft, reduces the rigidity of rotor shaft, is unfavorable for realizing the high-speed operation of rotor subassembly.

In one embodiment, a fifth shaft segment 6 is arranged between the second shaft segment 3 and the third shaft segment 4, the fifth shaft segment 6 is configured to mount an axial positioning member 15, the fifth shaft segment 6 has a diameter D6, and D3 ≧ D6.

In one embodiment, a sixth shaft segment 7 is disposed between the second shaft segment 3 and the third shaft segment 4, the sixth shaft segment 7 is configured to mount a radial journal 12, the sixth shaft segment 7 has a diameter D7, D3 ≧ D7.

In one embodiment, the rotor shaft has locking bolt holes 13 formed at both ends thereof, and locking bolt assemblies 14 are installed in the locking bolt holes 13.

In one embodiment, a fourth shaft segment 5 is disposed between the first shaft segment 2 and the reference shaft segment 1, a fifth shaft segment 6 and a sixth shaft segment 7 are disposed between the second shaft segment 3 and the third shaft segment 4, the fifth shaft segment 6 and the second shaft segment 3 are sequentially disposed along a direction away from the reference shaft segment 1, the diameter of the fourth shaft segment 5 is D5, the diameter of the fifth shaft segment 6 is D6, the diameter of the sixth shaft segment 7 is D7, D1 > D5 > D2, and/or D1 > D3 > D6 > D7 > D4.

When D1 > D3 > D6 > D7 > D4, the diameters of the shaft sections are sequentially reduced along the direction away from the reference shaft section 1, and in the process of installing the compression impeller 10, the inner cylindrical surface of the compression impeller 10 sequentially crosses the outer cylindrical surfaces of the third shaft section 4, the sixth shaft section 7 and the fifth shaft section 6 and then is in interference fit with the outer cylindrical surface of the second shaft section 3, so that the radial accurate positioning of the compression impeller 10 is realized. The compression impeller 10 is attached to the axial positioning surface 17 of the reference shaft section 1 at the end surface position, so that the axial accurate positioning of the compression impeller 10 is realized. The coaxiality of the cylindrical surface of the second shaft section 3 can be controlled with reference to the cylindrical surface of the reference shaft section 1, and is preferably 0.005 to 0.02mm, thereby facilitating control of the gap J02 between the compression impeller 10 and the compression housing 19.

When D6 is larger than D7 is larger than D4, the inner cylindrical surface of the axial positioning piece 15 passes through the outer cylindrical surfaces of the third shaft section 4 and the sixth shaft section 7 in sequence and then is in interference fit with the outer cylindrical surface of the fifth shaft section 6. The end face of the axial positioning piece 15 is attached to the end face of the compression impeller 10, so that on one hand, the axial displacement of the compression impeller 10 is limited, and on the other hand, the axial positioning of the axial positioning piece 15 is realized. The coaxiality of the cylindrical surface of the fifth shaft section 6 can be controlled by referring to the cylindrical surface of the reference shaft section 1, and the coaxiality is preferably 0.005-0.02 mm, so that the rotor shaft can meet the requirement of high-precision dynamic balance.

When D7 > D4, the inner cylindrical surface of radial journal 12 has passed through the outer cylindrical surface of third shaft segment 4 and then has interference fit with the outer cylindrical surface of sixth shaft segment 7. The end face of the radial journal 12 fits snugly against the end face of the axial positioning element 15. And controlling the coaxiality of the outer cylindrical surfaces of the fifth shaft section 6 and the sixth shaft section 7 respectively by referring to the cylindrical surface of the reference shaft section 1, wherein the coaxiality is preferably 0.005-0.02 mm. The radial journal 12 is supported by a bearing 21, the reference shaft section 1 is supported by another bearing 21, and the coaxiality of the outer cylindrical surfaces of the fifth shaft section 6 and the sixth shaft section 7 is controlled by referring to the cylindrical surface of the reference shaft section 1, so that the requirement of high-precision coaxiality of the bearing supporting part of the rotor shaft is favorably met.

The cylindrical surface of the axial balancing member 16 is fitted with the outer cylindrical surface of the fourth shaft section 5 in an interference fit. The end face of the axial balancing member 16 fits snugly against the end face of the radial journal 12. The inner cylindrical surface of the wind impeller 10 is in interference fit with the outer cylindrical surface of the fourth shaft section 5, and the end surface of the wind impeller 10 is fitted and assembled with the end surface of the axial balance piece 16, so that the wind impeller 10 is assembled. The coaxiality of the outer cylindrical surface of the fourth shaft section 5 can be controlled by referring to the cylindrical surface of the reference shaft section 1, and the coaxiality is preferably 0.005-0.02 mm, so that the control of the gap J03 between the wind impeller 10 and the fan seat 20 is facilitated.

D1 > D5 > D2 is favorable for interference fit assembly of the inner cylindrical surface of the thrust disc 11 and the outer cylindrical surface of the fourth shaft section 5 after the inner cylindrical surface of the thrust disc 11 crosses the outer cylindrical surface of the first shaft section 2, and meanwhile, the end surface of the thrust disc 11 is attached to and assembled with the axial positioning surface 17 of the reference shaft section 1, so that positioning assembly of the thrust disc 11 is realized. The coaxiality of the cylindrical surface of the first shaft section 2 can be controlled by referring to the cylindrical surface of the reference shaft section 1, and the coaxiality is preferably 0.005-0.02 mm, so that the requirement of high-precision dynamic balance of the rotor shaft can be met.

The inner cylindrical surface of the expansion impeller 8 is in interference fit with the outer cylindrical surface of the first shaft section 2. The end face of the expansion impeller 8 is attached to the end face of the thrust disc 11, and positioning and assembling of the expansion impeller 8 are achieved. The coaxiality of the outer cylindrical surface of the first shaft section 2 can be controlled with reference to the cylindrical surface of the reference shaft section 1, and is preferably 0.005-0.02 mm, thereby facilitating control of the gap J01 between the expansion impeller 8 and the expansion housing 18.

And the optical axis part of a locking bolt assembly 14 for locking the expansion impeller 8 is precisely guided and positioned through a positioning shaft hole section of a locking bolt hole 13 on the first shaft section 2, and is screwed into a shaft thread to realize the locking of the expansion impeller side. And the optical axis part of a locking bolt assembly 14 for locking the fan blade is precisely guided and positioned through a positioning shaft hole section of a locking bolt hole 13 on the third shaft section 4, and is screwed into shaft threads to realize the locking of the side of the fan blade. And respectively controlling the coaxiality of the positioning shaft hole section of the locking bolt hole 13 on the first shaft section 2 and the positioning shaft hole section of the locking bolt hole 13 on the third shaft section 4 by referring to the cylindrical surface of the reference shaft section 1, wherein the coaxiality is preferably 0.005-0.02 mm, so that the thread matching precision is controlled, and the rotor shaft can meet the high-precision dynamic balance requirement.

According to an embodiment of the application, the rotor assembly comprises a rotor shaft, which is the rotor shaft described above.

When the rotor shaft comprises a reference shaft section 1, a first shaft section 2, a second shaft section 3, a third shaft section 4, a fourth shaft section 5, a fifth shaft section 6 and a sixth shaft section 7, the rotor assembly further comprises an expansion impeller 8, a compression impeller 9, a wind impeller 10, a thrust disc 11, an axial positioning piece 15, a radial journal 12 and an axial balancing piece 16, wherein the expansion impeller 8 is assembled on the first shaft section 2, the compression impeller 9 is assembled on the second shaft section 3, the axial balancing piece 16 and the wind impeller 10 are assembled on the third shaft section 4, the thrust disc 11 is assembled on the fourth shaft section 5, the axial positioning piece 15 is assembled on the fifth shaft section 6, and the radial journal 12 is assembled on the sixth shaft section 7.

According to an embodiment of the present application, an air cycle machine includes a rotor assembly as described above.

In this embodiment, an air cycle machine is used to compress air, the gap cycle machine including a rotor assembly, a housing assembly, a bearing system, a dynamic and static seal system, and fasteners. The fastener assembles bearing system, static and dynamic sealing system and shell assembly into a static assembly, and the bearing system supports the rotor assembly to rotate at high speed.

The rotation power of the rotor component comes from the expansion work of the gas, the gas flows into the T01 and then is expanded by the expansion impeller 8 to do work, the temperature of the gas after the work is done is reduced, and the low-temperature gas flows out of the T02 and is conveyed to the area needing refrigeration. The expansion work drives the rotor assembly to rotate, and the compression impeller 9 in the rotating state sucks gas from the C01, compresses the gas by the compression impeller 9, and discharges the gas from the C02. At the same time, the fan wheel 10 in the rotating state sucks air from F01, discharges the air at F02, and drives the air flow.

Taking a cross section A01 perpendicular to the central axis of the rotor shaft, a pair of mutually perpendicular eddy current displacement sensors C1 and C2 are arranged on the cross section A01. And testing the surface displacement of the axial positioning piece 15 so as to monitor the rotary motion state of the rotor assembly, and taking the signal of C1 as an abscissa and C2 as an ordinate to obtain a motion trail diagram of the rotor in the rotary state.

Referring to fig. 9, it is a diagram showing the motion locus of the rotor when the rotor rotates at 52444RPM at high speed. As can be seen from the figure, the motion track of the rotor is smooth, so that the rotor assembly of the embodiment of the application has good running smoothness.

It is readily understood by a person skilled in the art that the advantageous ways described above can be freely combined, superimposed without conflict.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed. The foregoing is only a preferred embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present application, and these modifications and variations should also be considered as the protection scope of the present application.

Claims (15)

1. A rotor shaft is characterized by comprising a reference shaft section (1), a first shaft section (2), a second shaft section (3) and a third shaft section (4), wherein the first shaft section (2) is configured to be assembled with an expansion impeller (8), the second shaft section (3) is configured to be assembled with a compression impeller (9), the third shaft section (4) is configured to be assembled with a wind impeller (10), the first shaft section (2) and the second shaft section (3) are arranged at two ends of the reference shaft section (1), end faces of two ends of the reference shaft section (1) form an axial positioning face (17), the diameter of the reference shaft section (1) is D1, the diameter of the first shaft section (2) is D2, the diameter of the second shaft section (3) is D3, the diameter of the third shaft section (4) is D4, D1 > D2, D1 > D3D 4.

2. The rotor shaft according to claim 1, characterized in that a fourth shaft section (5) is arranged between the first shaft section (2) and the reference shaft section (1), the fourth shaft section (5) being configured to mount a thrust disc (11), the diameter of the fourth shaft section (5) being D5, D1 > D5 ≧ D2.

3. The rotor shaft according to claim 1, characterized in that the length of the reference shaft section (1) is L1, L1/D1 ═ 1.1-2.0.

4. The rotor shaft of claim 3 wherein L1/D1 is 1.69.

5. The rotor shaft according to claim 1, characterized in that the length of the second shaft section (3) is L3, L3/D3 ═ 1 to 7.4.

6. The rotor shaft of claim 5, wherein L3/D3 is 1.53-5.4.

7. The rotor shaft according to claim 2, characterized in that the length of the fourth shaft section (5) is L5, L5/D5 ═ 0.3-2.5.

8. The rotor shaft of claim 7 wherein L5/D5 is 0.5.

9. The rotor shaft according to claim 1, characterized in that a fifth shaft section (6) is arranged between the second shaft section (3) and the third shaft section (4), the fifth shaft section (6) being configured to mount an axial positioning member (15), the fifth shaft section (6) having a diameter D6, D3 ≧ D6.

10. The rotor shaft according to claim 1, characterized in that a sixth shaft section (7) is arranged between the second shaft section (3) and the third shaft section (4), the sixth shaft section (7) being configured for mounting a radial journal (12), the sixth shaft section (7) having a diameter D7, D3 ≧ D7.

11. The rotor shaft according to claim 1, characterized in that, the rotor shaft has locking bolt holes (13) opened at both ends, and locking bolt assemblies (14) are installed in the locking bolt holes (13).

12. Rotor shaft according to claim 1, characterized in that a fourth shaft section (5) is arranged between the first shaft section (2) and the reference shaft section (1), that a fifth shaft section (6) and a sixth shaft section (7) are arranged between the second shaft section (3) and the third shaft section (4), that the fifth shaft section (6) and the second shaft section (3) are arranged in sequence in a direction away from the reference shaft section (1), that the fourth shaft section (5) has a diameter D5, that the fifth shaft section (6) has a diameter D6, that the sixth shaft section (7) has a diameter D7, that D1 > D5 > D2, and/or that D1 > D3 > D6 > D7 > D4.

13. A rotor assembly, characterised by comprising a rotor shaft, the rotor shaft being as claimed in any one of claims 1 to 12.

14. The rotor assembly according to claim 13, characterized in that when the rotor shaft comprises a reference shaft section (1), a first shaft section (2), a second shaft section (3), a third shaft section (4), a fourth shaft section (5), a fifth shaft section (6) and a sixth shaft section (7), the rotor assembly further comprises an expansion impeller (8), a compression impeller (9), a wind impeller (10), a thrust disc (11), an axial positioning element (15), a radial journal (12) and an axial balancing element (16), the expansion impeller (8) is assembled on the first shaft section (2), the compression impeller (9) is assembled on the second shaft section (3), the axial balancing element (16) and the wind impeller (10) are assembled on the third shaft section (4), the thrust disc (11) is assembled on the fourth shaft section (5), the axial positioning element (15) is assembled on the fifth shaft section (6), the radial journal (12) is mounted on the sixth shaft section (7).

15. An air cycle machine comprising a rotor assembly, wherein the rotor assembly is as claimed in claim 13 or 14.

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