Bearing arrangements and cooling schemes for refrigerant compressor

Abstract

A refrigerant compressor may include an electric motor. The refrigerant compressor may include a rotatable shaft rotatable by the electric motor. The refrigerant compressor may include at least one compression stage driven by the shaft. The refrigerant compressor may include a first radial bearing assembly and a second radial bearing assembly. The first and second radial bearing assemblies may be configured as radial foil bearings. The refrigerant compressor may include an axial bearing assembly. The first and second radial bearing assemblies and the axial bearing assembly may be cooled using refrigerant and without the use of oil.

Description

BEARING ARRANGEMENTS AND COOLING SCHEMES FOR REFRIGERANT COMPRESSORRELATED APPLICATION(S)

[0001] This application claims the benefit of U.S. Provisional Application No.63 / 754,092, filed February 5, 2025, and U.S. Provisional Application No. 63 / 754,104, filed February 5, 2025, the entirety of which are herein incorporated by reference.BACKGROUND

[0002] Refrigerant compressors are used to circulate refrigerant in a chiller via a refrigerant loop. Refrigerant loops are known to include a compressor, a condenser, an expansion device, and an evaporator. The compressor compresses the fluid, which then travels to the condenser, which in turn cools and condenses the fluid. The refrigerant then goes to the expansion device, which decreases the pressure of the fluid, and to the evaporator, where the fluid is vaporized, completing a refrigeration cycle.SUMMARY

[0003] In some aspects, the techniques described herein relate to a refrigerant compressor, including: an electric motor; a rotatable shaft rotatable by the electric motor; at least one compression stage driven by the shaft; a first radial bearing assembly and a second radial bearing assembly, wherein the first and second radial bearing assemblies are configured as radial foil bearings; and an axial bearing assembly, wherein the first and second radial bearing assemblies and the axial bearing assembly are cooled using refrigerant and without the use of oil.

[0004] In some aspects, the techniques described herein relate to a refrigerant compressor, wherein the axial bearing assembly is configured as an axial magnetic bearing.

[0005] In some aspects, the techniques described herein relate to a refrigerant compressor, wherein the axial bearing assembly is configured as an axial foil bearing.

[0006] In some aspects, the techniques described herein relate to a refrigerant compressor, wherein the at least one compression stage includes a first compression stage arranged adjacent a first end of the shaft and a second compression stage arranged adjacent a second end of the shaft opposite the first end.

[0007] In some aspects, the techniques described herein relate to a refrigerant compressor, wherein the motor is cooled using refrigerant and without the use of oil.

[0008] In some aspects, the techniques described herein relate to a refrigerant compressor, further including: a housing surrounding the electric motor, the shaft, the first and second radial bearing assemblies, and the axial bearing assembly; a first wall adjacent a first impeller of the at least one compression stage and supporting a seal relative to the shaft, wherein, during operation of the refrigerant compressor, a leakage flow of refrigerant leaks over the seal and flows toward the axial bearing assembly, flows through gaps in the axial bearing assembly and then through gaps in the second radial bearing assembly.

[0009] In some aspects, the techniques described herein relate to a refrigerant compressor, further including: an inlet for a motor cooling flow of refrigerant; and a circumferential passageway surrounding a stator of the electric motor, wherein, during operation of the refrigerant compressor, the motor cooling flow circulates through the circumferential passageway to cool the stator and then merges with the leakage flow downstream of the stator, and a combined leakage flow and motor cooling flow flows through gaps in the first radial bearing assembly.

[0010] In some aspects, the techniques described herein relate to a refrigerant compressor, further including: an inlet for a motor cooling flow of refrigerant, the inlet arranged axially between the first wall and a second wall adjacent the axial bearing assembly; wherein,during operation of the refrigerant compressor, the motor cooling flow mixes with the leakage flow upstream of the axial bearing assembly, and a combined flow flows through gaps in the axial bearing assembly and then at least partially through gaps in the second radial bearing assembly; and a second seal supported relative to the shaft adjacent a second impeller of the at least one compression stage, wherein, during operation of the refrigerant compressor, a second leakage flow leaks over the second seal and flows through gaps in the first radial bearing assembly.

[0011] In some aspects, the techniques described herein relate to a refrigerant compressor, wherein a portion of the combined flow flows radially outside a stator of the electric motor to cool the stator.

[0012] In some aspects, the techniques described herein relate to a refrigerant compressor, further including: an inlet for a motor cooling flow of refrigerant; a circumferential passageway surrounding a stator of the electric motor, wherein, during operation of the refrigerant compressor, the motor cooling flow circulates through the circumferential passageway to cool the stator without intermixing with other refrigerant; a motor cooling outlet downstream of the circumferential passageway; and a reintroduction inlet fluidly coupled to the motor cooling outlet, the reintroduction inlet configured to introduce the motor cooling flow into a chamber axially between the first wall and a second wall adjacent the axial bearing assembly such that the motor cooling flow merges with the leakage flow.

[0013] In some aspects, the techniques described herein relate to a refrigerant system, including: a main refrigerant loop including a compressor, a condenser, an evaporator, and an expansion device; wherein the compressor includes: an electric motor; a rotatable shaft rotatable by the electric motor; at least one compression stage driven by the shaft; a first radial bearing assembly and a second radial bearing assembly, wherein the first and second radial bearing assemblies are configured as radial foil bearings; and an axial bearing assembly,wherein the first and second radial bearing assemblies and the axial bearing assembly are cooled using refrigerant from the main refrigerant loop and without the use of oil.

[0014] In some aspects, the techniques described herein relate to a refrigerant system, wherein the axial bearing assembly is configured as an axial magnetic bearing.

[0015] In some aspects, the techniques described herein relate to a refrigerant system, wherein the axial bearing assembly is configured as an axial foil bearing.

[0016] In some aspects, the techniques described herein relate to a refrigerant system, wherein the at least one compression stage includes a first compression stage arranged adjacent a first end of the shaft and a second compression stage arranged adjacent a second end of the shaft opposite the first end.

[0017] In some aspects, the techniques described herein relate to a refrigerant system, wherein the compressor includes: a housing surrounding the electric motor, the shaft, the first and second radial bearing assemblies, and the axial bearing assembly; and a first wall adjacent a first impeller of the at least one compression stage and supporting a seal relative to the shaft, wherein, during operation of the refrigerant compressor, a leakage flow of refrigerant leaks over the seal and flows toward the axial bearing assembly and further flows through gaps in the axial bearing assembly and then through gaps in the second radial bearing assembly.

[0018] In some aspects, the techniques described herein relate to a refrigerant system, wherein the motor is cooled using refrigerant from the main refrigerant loop and without the use of oil.

[0019] In some aspects, the techniques described herein relate to a method of operating a refrigerant compressor, including: rotating a shaft with an electric motor to drive at least one compression stage and compress refrigerant; supporting the shaft radially with a first radial bearing assembly and a second radial bearing assembly, wherein the first and second radial bearing assemblies are radial foil bearings; supporting the shaft axially with an axialbearing assembly; and cooling the first and second radial bearing assemblies and the axial bearing assembly using refrigerant and without the use of oil.

[0020] In some aspects, the techniques described herein relate to a method, wherein the axial bearing assembly is one of an axial magnetic bearing or an axial foil bearing.

[0021] In some aspects, the techniques described herein relate to a method, further including: establishing a leakage flow of refrigerant by leaking a portion of the refrigerant over a seal adjacent a first impeller of the at least one compression stage; directing the leakage flow through gaps in the axial bearing assembly and then through gaps in the second radial bearing assembly; establishing a motor cooling flow of refrigerant via an inlet fluidly coupled to a location within a refrigerant circuit; merging the motor cooling flow with the leakage flow; and directing a combined flow through gaps in the first radial bearing assembly and to an exit fluidly coupled to the refrigerant circuit.

[0022] In some aspects, the techniques described herein relate to a method, further including cooling a stator of the electric motor with the motor cooling flow via a circumferential passageway surrounding the stator before merging with the leakage flow.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 schematically illustrates a refrigerant system.

[0024] Figure 2 is a cross-sectional view of an example compressor including a hybrid bearing arrangement and exhibiting a first example cooling scheme.

[0025] Figure 3 is a cross-sectional view of an example radial foil bearing.

[0026] Figure 4 is a cross-sectional view of an example compressor including a hybrid bearing arrangement and exhibiting a second example cooling scheme.

[0027] Figure 5 is a cross-sectional view of an example compressor including a hybrid bearing arrangement and exhibiting a third example cooling scheme.

[0028] Figure 6 is a cross-sectional view of an example compressor including a bearing arrangement and exhibiting a cooling scheme.

[0029] Figure 7 is a cross-sectional view of an example axial foil bearing.DETAILED DESCRIPTION

[0030] Figure 1 illustrates a refrigerant system 10. The refrigerant system 10 includes a main refrigerant loop, or circuit, 12 in communication with a compressor 14, a condenser 16, an evaporator 18, and an expansion device 20. This refrigerant system 10 may be used in a chiller, for example. In that example, a cooling tower may be in fluid communication with the condenser 16. While a particular example of the refrigerant system 10 is shown, this application extends to other refrigerant system configurations, including configurations that do not include a chiller. Further, in Figure 1, a portion of the fluid leaving the condenser 16 may return to the compressor 14 through an economizer. An economizer is not required in all examples. The refrigerant system 10 may be an oil-free refrigerant system in one implementation. Further, the compressor 14 may be an oil-free compressor.

[0031] Figure 2 is a cross-sectional view of the compressor 14. The compressor 14 includes an inlet 22 and an outlet 24. The outlet 24 may be downstream of a volute. The compressor 14 includes an exterior housing assembly 25 (“housing 25”), which includes a plurality of housing sections that surround, among other components, an electric motor 26.

[0032] The electric motor 26 includes a stator 28 arranged radially outside of a rotor 30. The rotor 30 is connected to, or incorporated into, a shaft 32, which rotates to drive a first compression stage 34 and a second compression stage 36 of the compressor 14. In this example, the first compression stage 34 includes an impeller 38 connected adjacent an end of the shaft 32, and the second compression stage 36 includes an impeller 40 connected adjacent an opposite end of the shaft 32 as the first compression stage 34. Providing one impeller 38, 40adjacent each end of the shaft 32 serves to balance the shaft 32. While one impeller is arranged at each end of the shaft 32 in this example, this disclosure extends to arrangements with an equal number of compression stages adjacent each end of the shaft 32.

[0033] During operation of the compressor 14, the shaft 32 and impellers 38, 40 are rotatable together with one another by the electric motor 26 about an axis A to compress fluid, which here is refrigerant, F. Within the first and second compression stages 34, 36, fluid enters in a substantially axial direction, and is then turned and expelled radially from those stages. An interstage pipe attached to, or incorporated into, the housing 25 may fluidly couple fluid expelled from the first compression stage 34 to an inlet of the second compression stage 36.

[0034] In this disclosure, the shaft 32 is rotatably supported by a plurality of bearing assemblies. Specifically, in this disclosure, the shaft 32 is supported by two radial bearing assemblies 42, 44 and one axial bearing assembly 46. The radial bearing assemblies 42, 44 are spaced-apart from one another along the axis A. The radial bearing assemblies 42, 44 are provided by a first type of bearing assembly and the axial bearing assembly 46 is provided by a second type of bearing assembly in this implementation. In this way, the compressor 14 may be said to have a hybrid bearing arrangement.

[0035] The radial bearing assemblies 42, 44 are provided as foil bearings, in this example. With reference to Figure 3, an example configuration of the radial bearing assembly 42 is shown, and it should be understood that the radial bearing assembly 44 is configured substantially similarly. The bearing assembly 42 includes a top foil 48, which is a thin, smooth layer adjacent the shaft 32, and a series of bump foils 50, which are radially outward of the top foil 48, providing spring-like support and compliance relative to the top foil 48. Top foil 48 and bump foils 50 do not rotate with the shaft 32. Between the top foil 48 and bump foil 50, there are passages 52 that allow refrigerant to flow. The passages 52 extend along an entire axial length between the bearing sleeve 54, which is radially outward of the bump foils 50.During operation of the compressor 14, a thin film of refrigerant is provided radially between the top foil 48 and the shaft 32, which radially supports the shaft 32.

[0036] The axial bearing assembly 46 is an axial magnetic bearing in this example. The axial bearing assembly 46 includes an electromagnet 56 and a disc 58 projecting radially outward from the shaft 32. The disc 58 may be made of a ferromagnetic material. An axial position of the disc 58, and in turn the shaft 32, may be detected by one or more sensors. The electromagnet 56 surrounds the disc 58 and generates magnetic flux to adjust the axial position of the disc 58 and in turn the shaft 32. Gaps are maintained between the disc 58 and the surrounding electromagnet 56 to allow refrigerant to flow freely.

[0037] The foil bearings (i.e., first and second radial bearing assemblies 42, 44) of the compressor 14 exhibit a reduced axial dimension relative to other types of bearings, and the magnetic bearing (i.e., axial bearing assembly 46) exhibits a relatively high load capacity. Therefore, this disclosure provides a compressor 14 that strikes a unique balance between exhibiting a reduced axial dimension and a relatively high load capacity.

[0038] The compressor 14 is an oil-free compressor. In particular, oil is not used to cool any components of the compressor 14, including the motor 26 or bearing assemblies 42, 44, 46. With respect to the bearing assemblies 42, 44, 46, the gaps mentioned above permit the bearing assemblies 42, 44, 46 to be cooled using refrigerant. Example configurations of the compressor 14 that facilitate such cooling will now be described.

[0039] With respect to Figure 2, the motor 26 and bearing assemblies 42, 44, 46 are cooled with a combination of leakage flow Fl and motor cooling flow F2. With reference to the impeller 38, a wall 60 adjacent the impeller 38 radially surrounds the shaft 32 and supports one or more seals 62 relative to the shaft 32. The seal 62 may be one or more knife edge seals, in an example. A portion of the refrigerant F within the compressor 14 does not flow to the outlet of the first compression stage 34 and instead leaks over the seal 62 and enters the spacebetween the first and second compression stages 34, 36 containing the motor 26 and bearing assemblies 42, 44, 46. This portion of the refrigerant F is referred to as leakage flow Fl.

[0040] Downstream of the seal 62, the leakage flow Fl flows axially toward the axial bearing assembly 46, which is axially between another wall 64 radially surrounding the shaft 32 and the second radial bearing assembly 44. Some of the leakage flow Fl flows through the aforementioned gaps in the axial bearing assembly 46 and then some of the leakage flow F 1 proceeds to flow through gaps in the second radial bearing assembly 44, between the bearing sleeve and shaft 32. Some of the leakage flow Fl flows through one or more bypass channels 66 in a wall 68 supporting the bearing sleeve of second radial bearing assembly 44. The leakage flow Fl continues flowing axially and combines with the motor cooling flow F2 to flow along shaft 32 toward the first radial bearing assembly 42, where some of combined flow flows through the aforementioned gaps radially between the bearing sleeve and shaft 32, while some of the flow flows through one or more bypass channels 70 in a wall 72 supporting the bearing sleeve of first radial bearing assembly 42. Bypass channels 66, 70 may serve to balance pressure relative to the radial bearing assemblies 42, 44. The leakage flow then flows to an exit 74 dedicated to cooling flow. The exit 74 is fluidly coupled to a location within the refrigerant circuit 12. In an example, fluid flowing downstream of the exit 74 is directed to the inlet 22. The exit 74 is axially between the wall 72 and another wall 76 adjacent impeller 40 and supporting a seal 78 radially about the shaft 32.

[0041] The motor cooling flow F2 is established as refrigerant enters the housing 25 via an inlet 80. Upstream of the inlet 80, the inlet 80 is fluidly coupled to a location, other than the compressor 14, within the refrigerant circuit 12. Downstream of the inlet 80, the motor cooling flow F2 proceeds to circulate about the stator 28 by way of a circumferential passageway 82. In one example, an outer radial boundary of the circumferential passageway 82 is provided in part by a helical channel formed in an inner surface of housing 25. In thisexample, an outer surface of the stator 28 provides an inner radial boundary for the circumferential passageway 82. Downstream of the stator 28, the motor cooling flow F2 flows radially inward and merges with the leakage flow Fl. In an example, a mass flow rate ratio between Fl and F2 is substantially as follows: F1:F2 = 1:1. The relative proportions of Fl and F2 may vary depending on operating conditions, however.

[0042] Another cooling arrangement will now be described relative to another compressor 114, shown in Figure 4. The compressors 14, 114 include like components, except where described. The compressor 114 is labeled in Figure 4 with common reference numbers associated with like components relative to the compressor 14, preappended with a “1.”

[0043] As shown in Figure 4, an inlet 180 for motor cooling flow F2 is axially between walls 160, 164. While a particular location of the inlet 180 is shown in Figure 4, the motor cooling flow F2 could be introduced at any location downstream of the first compression stage 134 and upstream of the axial bearing assembly 146. The motor cooling flow F2 is directed toward the shaft 132 and mixes with the leakage flow Fl and continues to flow along the shaft 132. The combined flow flows through gaps in the axial bearing assembly 146. Some of the combined flow continues to flow along the shaft 132 and through gaps in the second radial bearing assembly 144. Some of the combined flow flows through bypass channels 166 and then flows radially outside of the stator 128 to cool the stator 128. A second leakage flow F3 flows over seal 178, through gaps in the first radial bearing assembly 144, and mixes with the flows Fl, F2. The combined flows Fl, F2, F3 are directed to exit 174, which is axially between the bearing assembly 142 and the motor 26, in this example. While the circumferential passageway 182 is present in Figure 4, the circumferential passageway 182 could be removed or replaced by one or more structures configured to facilitate heat transfer relative to the stator 128, such as turbulators or axially-extending channels. In an example, the mass flow rate ratios between Fl, F2, and F3 are substantially as follows: F1:F2 = 1:10; F1:F3 = 1:3. The relativeproportions of Fl, F2, and F3 may vary depending on operating conditions, however. Further, in a variation of this example, the stator 128 is cooled by a cooling jacket using fluid that does not intermix with the flows Fl, F2, or F3.

[0044] Another cooling arrangement will now be described relative to another compressor 214, shown in Figure 5. The compressors 14, 114, 214 include like components, except where described. The compressor 214 is labeled in Figure 5 with common reference numbers associated with like components relative to the compressors 14, 114, preappended with a “2.”

[0045] In the embodiment of Figure 5, the motor cooling flow F2 is established as refrigerant enters the housing 225 via an inlet 280. Downstream of the inlet 280, the motor cooling flow F2 proceeds to circulate about the stator 28 by way of a circumferential passageway 282. Again, while inlet 280 is shown in a particular location, the motor cooling flow F2 could be introduced at any location downstream of the first compression stage 234 and upstream of the axial bearing assembly 246. At a downstream end of the circumferential passageway 282, the motor cooling flow F2 exits the motor cooling outlet 285. The motor cooling outlet 285 is fluidly coupled to an inlet 287 configured to reintroduce the motor cooling flow F2 into a chamber axially between plates 260, 264. A valve or flow control orifice may be placed fluidly between outlet 285 and inlet 287. The motor cooling flow F2 then merges with the leakage flow Fl. In an example, the motor cooling flow F2 is not configured to intermix with any other refrigerant when the motor cooling flow F2 is within the circumferential passageway 282. When the motor cooling flow F2 combines with the leakage flow Fl, the combined flow continues substantially as the leakage flow Fl does in Figure 2, flowing through gaps in the axial bearing assembly 246, through gaps in the second radial bearing assembly 244, through gaps in the first radial bearing assembly 242, and ultimately out the outlet 274. In an example, a mass flow rate ratio between Fl and F2 is substantially asfollows: Fl :F2 = 1:10. The relative proportions of Fl and F2 may vary depending on operating conditions, however.

[0046] Another cooling arrangement will now be described relative to another compressor 314, shown in Figure 6. The compressors 14, 114, 214, 314 include like components, except where described. The compressor 314 is labeled in Figure 6 with common reference numbers associated with like components relative to the compressors 14, 114, 214, preappended with a “3.”

[0047] Figure 6 is a cross-sectional view of the compressor 314. Compressor 314 is similar to compressor 14, with the exception that axial bearing assembly 46, which is provided by a magnetic bearing assembly, is replaced with axial bearing assembly 346, which is a foil bearing assembly.

[0048] In particular, the shaft 332 is rotatably supported by two radial bearing assemblies 342, 344 and one axial bearing assembly 346. The bearing assemblies 342, 344, 346 are provided by a common type of bearing assembly. In a specific example, the bearing assemblies 342, 344, 346 are provided by foil bearings, with the first and second radial bearing assemblies 342, 344 being provided by radial foil bearings and the axial bearing assembly 346 being provided by an axial, or thrust, foil bearing. In this way, the compressor 314 may be said to have a foil bearing arrangement. Because the compressor 314 has a foil bearing arrangement, the compressor 314 may provide a cost savings relative to compressors with other types of bearings, without compromising speed or reliability, and without requiring a complex cooling system or pressurized gas supply system.

[0049] Radial bearing assemblies 342 and 344 may be configured as in Figure 3. An example implementation of the axial bearing assembly 346 is shown in Figure 7. An axial foil bearing may be incorporated into compressors 14, 114, 214 and used in place of the axial magnetic bearing assembly.

[0050] As shown in Figure 7, the axial bearing assembly 346 includes two sets of axial foil bearings 346A, 346B. The axial foil bearing 346A is mounted to the wall 368, and axial foil bearing 346B is mounted to wall 364. The axial foil bearings 346A, 346B are mounted on opposite axial sides of a disc 356 projecting radially outward from the shaft 332 and configured to rotate with the shaft 332. Axial foil bearing 346A includes a base plate 357 mounted directly to wall 368, one or more bump foils 358, and one or more top foils 359. The top foils 359 are arranged axially between bump foils 358 and disc 356. Axial foil bearing 346B is configured substantially the same as axial foil bearing 346A, reflected about a radially-extending line bisecting the disc 356. During operation of the compressor 314, bump foils and top foils remain stationary (i.e., they do not rotate with disc 356), and refrigerant is able to flow through radially-extending gaps formed by the top foils and the bump foils. During rotation of the disc 356, the axial bearing assembly 346 provides a thin lubricating film that axially supports the disc 356 and maintains an axial position of the shaft 332.

[0051] It should be understood that terms such as “upstream,” “downstream,” “axial,” “radial,” and “circumferential” are used above with reference to the normal operational attitude of the compressors 14, 114, 214, 314. Further, these terms have been used herein for purposes of explanation, and should not be considered otherwise limiting. Terms such as “generally,” “substantially,” and “about” are not intended to be boundaryless terms, and should be interpreted consistent with the way one skilled in the art would interpret those terms.

[0052] Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. In addition, the various figures accompanying this disclosure are not necessarily to scale, and some featuresmay be exaggerated or minimized to show certain details of a particular component or arrangement.

[0053] One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.

Claims

CLAIMS1. A refrigerant compressor, comprising:an electric motor;a rotatable shaft rotatable by the electric motor;at least one compression stage driven by the shaft;a first radial bearing assembly and a second radial bearing assembly, wherein the first and second radial bearing assemblies are configured as radial foil bearings; andan axial bearing assembly, wherein the first and second radial bearing assemblies and the axial bearing assembly are cooled using refrigerant and without the use of oil.

2. The refrigerant compressor as recited in claim 1, wherein the axial bearing assembly is configured as an axial magnetic bearing.

3. The refrigerant compressor as recited in claim 1, wherein the axial bearing assembly is configured as an axial foil bearing.

4. The refrigerant compressor as recited in claim 1, wherein the at least one compression stage includes a first compression stage arranged adjacent a first end of the shaft and a second compression stage arranged adjacent a second end of the shaft opposite the first end.

5. The refrigerant compressor as recited in claim 1, wherein the motor is cooled using refrigerant and without the use of oil.

6. The refrigerant compressor as recited in claim 1, further comprising:a housing surrounding the electric motor, the shaft, the first and second radial bearing assemblies, and the axial bearing assembly;a first wall adjacent a first impeller of the at least one compression stage and supporting a seal relative to the shaft,wherein, during operation of the refrigerant compressor, a leakage flow of refrigerant leaks over the seal and flows toward the axial bearing assembly, flows through gaps in the axial bearing assembly and then through gaps in the second radial bearing assembly.

7. The refrigerant compressor as recited in claim 6, further comprising:an inlet for a motor cooling flow of refrigerant; anda circumferential passageway surrounding a stator of the electric motor, wherein, during operation of the refrigerant compressor, the motor cooling flow circulates through the circumferential passageway to cool the stator and then merges with the leakage flow downstream of the stator, and a combined leakage flow and motor cooling flow flows through gaps in the first radial bearing assembly.

8. The refrigerant compressor as recited in claim 6, further comprising:an inlet for a motor cooling flow of refrigerant, the inlet arranged axially between the first wall and a second wall adjacent the axial bearing assembly;wherein, during operation of the refrigerant compressor, the motor cooling flow mixes with the leakage flow upstream of the axial bearing assembly, and a combined flow flows through gaps in the axial bearing assembly and then at least partially through gaps in the second radial bearing assembly; anda second seal supported relative to the shaft adjacent a second impeller of the at least one compression stage, wherein, during operation of the refrigerant compressor, a secondleakage flow leaks over the second seal and flows through gaps in the first radial bearing assembly.

9. The refrigerant compressor as recited in claim 8, wherein a portion of the combined flow flows radially outside a stator of the electric motor to cool the stator.

10. The refrigerant compressor as recited in claim 6, further comprising:an inlet for a motor cooling flow of refrigerant;a circumferential passageway surrounding a stator of the electric motor, wherein, during operation of the refrigerant compressor, the motor cooling flow circulates through the circumferential passageway to cool the stator without intermixing with other refrigerant; a motor cooling outlet downstream of the circumferential passageway; anda reintroduction inlet fluidly coupled to the motor cooling outlet, the reintroduction inlet configured to introduce the motor cooling flow into a chamber axially between the first wall and a second wall adjacent the axial bearing assembly such that the motor cooling flow merges with the leakage flow.

11. A refrigerant system, comprising:a main refrigerant loop including a compressor, a condenser, an evaporator, and an expansion device;wherein the compressor includes:an electric motor;a rotatable shaft rotatable by the electric motor;at least one compression stage driven by the shaft;a first radial bearing assembly and a second radial bearing assembly, wherein the first and second radial bearing assemblies are configured as radial foil bearings; andan axial bearing assembly, wherein the first and second radial bearing assemblies and the axial bearing assembly are cooled using refrigerant from the main refrigerant loop and without the use of oil.

12. The refrigerant system as recited in claim 11, wherein the axial bearing assembly is configured as an axial magnetic bearing.

13. The refrigerant system as recited in claim 11, wherein the axial bearing assembly is configured as an axial foil bearing.

14. The refrigerant system as recited in claim 11, wherein the at least one compression stage includes a first compression stage arranged adjacent a first end of the shaft and a second compression stage arranged adjacent a second end of the shaft opposite the first end.

15. The refrigerant system as recited in claim 11, wherein the compressor includes:a housing surrounding the electric motor, the shaft, the first and second radial bearing assemblies, and the axial bearing assembly; anda first wall adjacent a first impeller of the at least one compression stage and supporting a seal relative to the shaft, wherein, during operation of the refrigerant compressor, a leakage flow of refrigerant leaks over the seal and flows toward the axial bearing assembly and further flows through gaps in the axial bearing assembly and then through gaps in the second radial bearing assembly.

16. The refrigerant system as recited in claim 15, wherein the motor is cooled using refrigerant from the main refrigerant loop and without the use of oil.

17. A method of operating a refrigerant compressor, comprising:rotating a shaft with an electric motor to drive at least one compression stage and compress refrigerant;supporting the shaft radially with a first radial bearing assembly and a second radial bearing assembly, wherein the first and second radial bearing assemblies are radial foil bearings;supporting the shaft axially with an axial bearing assembly; andcooling the first and second radial bearing assemblies and the axial bearing assembly using refrigerant and without the use of oil.

18. The method as recited in claim 17, wherein the axial bearing assembly is one of an axial magnetic bearing or an axial foil bearing.

19. The method as recited in claim 17, further comprising:establishing a leakage flow of refrigerant by leaking a portion of the refrigerant over a seal adjacent a first impeller of the at least one compression stage;directing the leakage flow through gaps in the axial bearing assembly and then through gaps in the second radial bearing assembly;establishing a motor cooling flow of refrigerant via an inlet fluidly coupled to a location within a refrigerant circuit;merging the motor cooling flow with the leakage flow; anddirecting a combined flow through gaps in the first radial bearing assembly and to an exit fluidly coupled to the refrigerant circuit.

20. The method as recited in claim 19, further comprising cooling a stator of the electric motor with the motor cooling flow via a circumferential passageway surrounding the stator before merging with the leakage flow.

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