A TURBO COMPRESSOR PROVIDED WITH AN AXIAL BEARING COOLING ARRANGEMENT

Abstract

 The turbo compressor includes a drive shaft (3); an impeller (7.1) connected to an first axial end portion of the drive shaft (3); an electrical motor connected to a second axial end portion of the drive shaft (3); an axial bearing arrangement configured to limit an axial movement of the drive shaft (3) during operation, the axial bearing arrangement including an axial bearing plate (18) having an annular ring shape and facing towards the impeller (7.1); an inlet distributor (33) at least partially defining an inlet refrigerant flow path (P) ; and an axial bearing cooling arrangement including bypass openings (40) formed in the inlet distributor (33) and a bypass refrigerant flow path (43) defined by the inlet distributor (33) and the axial bearing plate (18), the bypass openings (40) being configured to derive a part of an inlet refrigerant flow, flowing into the inlet refrigerant flow path (P), into the bypass refrigerant flow path (43) so as to at least partially cool the axial bearing plate (18).

Description

Field of the invention

[0001] The present invention relates to a turbo compressor, and particularly to a refrigeration turbo compressor.

Background of the invention

[0002] As known, a refrigeration turbo compressor may include:

• a drive shaft including a first axial end portion and a second axial end portion opposite to the first axial end portion,
• a compression stage configured to compress a refrigerant and including an impeller connected to the first axial end portion of the drive shaft,
• an electrical motor connected to the second axial end portion of the drive shaft and configured to drive in rotation the drive shaft about a rotation axis,
• an axial bearing arrangement configured to limit an axial movement of the drive shaft during operation, the axial bearing arrangement including an axial bearing plate having an annular ring shape and facing towards the impeller,
• an inlet distributor at least partially defining an inlet refrigerant flow path configured to supply, and for example to axially supply, the compression stage with an inlet refrigerant flow, the inlet distributor being located adjacent the axial bearing plate, and
• a bearing sleeve located between the electrical motor and the axial bearing arrangement, the bearing sleeve having a longitudinal axis and surrounding the drive shaft, the bearing sleeve including:
  • a radial bearing part which is tubular and which is configured to rotatably support the drive shaft,
  • an outer sleeve part surrounding the radial bearing part, and
  • a cooling area formed in an outer circumferential surface the outer sleeve part and being intended for the passage of a refrigerant so as to dissipate heat from the bearing sleeve.

[0003] In operation, and particularly at the most critical running conditions of such a turbo compressor, the axial bearing plate facing towards the inlet distributor reaches a high temperature which leads to an important deformation of said axial bearing plate, and thus induce deformations of the gas films in the axial bearing arrangement when such an axial bearing arrangement is a gas axial bearing arrangement.

[0004] Such deformations of the axial bearing plate may lead to seizure of the axial bearing arrangement and to shortened lifetime of the turbo compressor.

[0005] In addition, deformations of the axial bearing plate may also lead to an instability of the axial bearing arrangement, which causes the generation of vibrations of the drive shaft and thus causes contacts of the latter with static parts of the turbo compressor leading to scratches or breaking of the drive shaft.

Summary of the invention

[0006] It is an object of the present invention to provide an improved turbo compressor which can overcome the drawbacks encountered in conventional turbo compressors.

[0007] Another object of the present invention is to provide a turbo compressor which is reliable, and which is particularly not subjected to the above-mentioned deformations.

[0008] According to the invention such a turbo compressor includes:

• a drive shaft having a longitudinal axis and including a first axial end portion and a second axial end portion opposite to the first axial end portion,
• a compression stage configured to compress a refrigerant, the compression stage including an impeller connected to the first axial end portion of the drive shaft,
• an electrical motor connected to the second axial end portion of the drive shaft and configured to drive in rotation the drive shaft about a rotation axis,
• an axial bearing arrangement configured to limit an axial movement of the drive shaft during operation, the axial bearing arrangement including an axial bearing plate having an annular ring shape and facing towards the impeller,
• an inlet distributor at least partially defining an inlet refrigerant flow path configured to supply, and for example to axially supply, the compression stage with an inlet refrigerant flow, the inlet distributor being located adjacent the axial bearing plate, and
• an axial bearing cooling arrangement configured to cool at least partially the axial bearing plate, the axial bearing cooling arrangement including bypass openings formed in the inlet distributor and a bypass refrigerant flow path at least partially defined by the inlet distributor and the axial bearing plate, the bypass openings being configured to derive a part of the inlet refrigerant flow into the bypass refrigerant flow path such that said derived part of the inlet refrigerant flow at least partially cools the axial bearing plate, the bypass refrigerant flow path being fluidly connected to the inlet refrigerant flow path downstream of the bypass openings such that the derived part of the inlet refrigerant flow returns, i.e. goes back, to the inlet refrigerant flow after having at least partially cooled the axial bearing plate.

[0009] Such a configuration of the axial bearing cooling arrangement, and particularly of the bypass openings, allows cooling the axial bearing plate with a derived part of the inlet refrigerant flow, and thus avoids or at least strongly reduces, even at the most critical running conditions of the turbo compressor, the thermal deformations of the axial bearing plate and thus of the axial bearing arrangement.

[0010] Therefore, the configuration of the turbo compressor according to the present invention avoids a seizure of the axial bearing arrangement and improves the stability of said axial bearing arrangement, and thus improves the reliability of the turbo compressor and increases the lifetime of the turbo compressor.

[0011] The turbo compressor may also include one or more of the following features, taken alone or in combination.

[0012] According to an embodiment of the invention, the bypass refrigerant flow path extends in parallel to the inlet refrigerant flow path.

[0013] According to an embodiment of the invention, the axial bearing arrangement is located adjacent the impeller.

[0014] According to an embodiment of the invention, the inlet distributor has an annular disc shape.

[0015] According to an embodiment of the invention, the bypass openings are circumferentially aligned around the longitudinal axis of the drive shaft.

[0016] According to an embodiment of the invention, the bypass refrigerant flow path extends at least partially along a surface of the axial bearing plate facing towards the inlet distributor.

[0017] According to an embodiment of the invention, the bypass refrigerant flow path is defined by the inlet distributor and the axial bearing plate.

[0018] According to an embodiment of the invention, the inlet distributor has a first axial surface facing toward the impeller and a second axial surface facing towards the axial bearing arrangement, each bypass opening extending through the inlet distributor thickness and emerging respectively in the first axial surface and in the second axial surface.

[0019] According to an embodiment of the invention, the bypass openings are angularly distributed around the longitudinal axis of the drive shaft.

[0020] According to an embodiment of the invention, the inlet distributor includes inlet flow guide members facing towards the impeller, the inlet flow guide members being angularly distributed around the longitudinal axis of the drive shaft and partially defining the inlet refrigerant flow path.

[0021] According to an embodiment of the invention, each of the inlet flow guide members extends radially towards the drive shaft.

[0022] According to an embodiment of the invention, each bypass opening is located between two respective adjacent inlet flow guide members.

[0023] According to an embodiment of the invention, each bypass opening emerges into the first axial surface of the inlet distributor between two respective adjacent inlet flow guide members.

[0024] According to an embodiment of the invention, the inlet flow guide members are provided on the first axial surface of the inlet distributor.

[0025] According to an embodiment of the invention, the inlet flow guide members are arranged such that each pair of adjacent inlet flow guide members is configured to radially guide a respective part of the inlet refrigerant flow towards a center area of the inlet distributor.

[0026] According to an embodiment of the invention, each of the inlet flow guide members has a triangular shape and has an apex oriented towards the drive shaft.

[0027] According to an embodiment of the invention, each of the inlet flow guide members has an arcuate cross sectional profile.

[0028] According to an embodiment of the invention, each inlet flow guide member radially converges towards the drive shaft.

[0029] According to an embodiment of the invention, the axial bearing cooling arrangement includes bypass flow guide members provided on the inlet distributor and facing towards the axial bearing arrangement, the bypass flow guide members being angularly distributed around the longitudinal axis of the drive shaft and partially defining the bypass refrigerant flow path.

[0030] According to an embodiment of the invention, each of the bypass flow guide members extends radially towards the drive shaft.

[0031] According to an embodiment of the invention, each bypass flow guide member radially converges towards the drive shaft.

[0032] According to an embodiment of the invention, each bypass flow guide member has a wing-shaped cross sectional profile.

[0033] According to an embodiment of the invention, each bypass flow guide member partially defines a bypass flow guide channel extending radially towards the drive shaft.

[0034] According to an embodiment of the invention, each bypass opening emerges into a respective bypass flow guide channel.

[0035] According to an embodiment of the invention, the turbo compressor includes a refrigerant inlet fluidly connected to inlet distributor and configured to supply the inlet distributor with refrigerant.

[0036] According to an embodiment of the invention, the axial bearing arrangement is an axial gas bearing arrangement.

[0037] According to an embodiment of the invention, the turbo compressor further includes a bearing sleeve located between the electrical motor and the axial bearing arrangement, the bearing sleeve having a longitudinal axis and surrounding the drive shaft, the bearing sleeve including:

• a radial bearing part which is tubular and which is configured to rotatably support the drive shaft,
• an outer sleeve part surrounding the radial bearing part and including an axial end face which faces towards the axial bearing arrangement and a contact surface which is located at the axial end face and which is configured to cooperate with the axial bearing arrangement.

[0038] According to an embodiment of the invention, the radial bearing part and the outer sleeve part are concentrically arranged.

[0039] According to an embodiment of the invention, the axial end face is planar and oriented perpendicularly with respect to the longitudinal axis of the bearing sleeve.

[0040] According to an embodiment of the invention, the bearing sleeve further includes an annular gap formed between the radial bearing part and the outer sleeve part and extending around the longitudinal axis of the bearing sleeve.

[0041] According to an embodiment of the invention, the bearing sleeve further includes a cooling area formed in an outer circumferential surface of the outer sleeve part and intended for the passage of a refrigerant so as to dissipate heat from the bearing sleeve.

[0042] According to an embodiment of the invention, the cooling area includes at least one annular cooling channel formed in the outer circumferential surface of the outer sleeve part and extending around the longitudinal axis of the bearing sleeve.

[0043] According to an embodiment of the invention, the axial bearing arrangement further includes:

• an additional axial bearing plate having an annular ring shape, and
• a spacer ring being clamped between the axial bearing plate and the additional axial bearing plate at radial outer portions of the axial bearing plate and the additional axial bearing plate, the spacer ring defining an axial distance between the axial bearing plate and the additional axial bearing plate.

[0044] According to an embodiment of the invention, the axial bearing plate and the additional axial bearing plate extend parallel to each other.

[0045] According to an embodiment of the invention, the additional axial bearing plate abuts against the contact surface of the bearing sleeve.

[0046] According to an embodiment of the invention, the axial bearing arrangement includes an axial bearing member arranged on the outer surface of the drive shaft, the axial bearing member extending substantially radially outwardly with respect to the drive shaft.

[0047] According to an embodiment of the invention, the axial bearing member extends into a space between radial inner portions of the axial bearing plate and the additional axial bearing plate.

[0048] According to an embodiment of the invention, the electrical motor includes a motor stator and a motor rotor, the motor rotor being connected to the second axial end portion of the drive shaft.

[0049] According to an embodiment of the invention, the radial bearing part includes a radial bearing surface configured to cooperate with the drive shaft.

[0050] According to an embodiment of the invention, the radial bearing part includes an additional radial bearing surface configured to cooperate with the drive shaft, the radial bearing surface and the additional radial bearing surface being axially offset with respect to each other.

[0051] According to an embodiment of the invention, the outer sleeve part and the radial bearing part are made in one piece.

[0052] According to an embodiment of the invention, the outer sleeve part and the radial bearing part are distinct from each other and are assembled together.

[0053] According to an embodiment of the invention, the inlet distributor includes an abutment surface against which abuts the bearing sleeve, and for example the contact surface of the sleeve part.

[0054] According to an embodiment of the invention, the bearing sleeve is axially immobilized with respect to the inlet distributor.

[0055] According to an embodiment of the invention, the inlet distributor may include a tubular part defining an inner housing in which are received the axial bearing plate, the additional axial bearing plate and the spacer ring.

[0056] According to an embodiment of the invention, the turbo compressor includes several compression stages configured to compress a refrigerant, each compression stage including an impeller connected to the first axial end portion of the drive shaft.

[0057] These and other advantages will become apparent upon reading the following description in view of the drawing attached hereto representing, as non-limiting example, an embodiment of a turbo compressor according to the invention.

Brief description of the drawings

[0058] The following detailed description of an embodiment of the invention is better understood when read in conjunction with the appended drawings being understood, however, that the invention is not limited to the specific embodiment disclosed.

Figures 1 and 2 are longitudinal section views of a turbo compressor according to the invention.

Figure 3 is an enlarged view of a detail of figure 1.

Figure 4 is a rear perspective view of an inlet distributor of the turbo compressor of figure 1.

Figure 5 is a front perspective view of the inlet distributor of figure 4.

Figure 6 is a longitudinal section view of the inlet distributor of figure 4.

Detailed description of the invention

[0059] Figures 1 to 6 represent a refrigeration turbo compressor 1 according to the invention, which may be for example a two-stage refrigeration turbo compressor.

[0060] The turbo compressor 1 includes an hermetic casing 2 and a drive shaft 3 which is rotatably arranged within the hermetic casing 2 and which extends along a longitudinal axis A. The drive shaft 3 includes a first axial end portion 4, a second axial end portion 5 opposite to the first axial end portion 4, and an intermediate portion 6 located between the first and second axial end portions 4, 5.

[0061] The turbo compressor 1 further includes one or several impeller(s) connected to the first axial end portion 4 of the drive shaft 3, and configured to compress a refrigerant.

[0062] According to the embodiment shown on the figures, the turbo compressor 1 includes two impellers 7.1, 7.2 arranged in a back-to-back configuration. The turbo compressor 1 further includes a refrigerant inlet 8 and a refrigerant outlet 9 respectively located upstream and downstream of the impeller 7.1 which belongs to a first compression stage, and an additional refrigerant inlet 10 and an additional refrigerant outlet 11 respectively located upstream and downstream of the impeller 7.2 which belongs to a second compression stage, the refrigerant outlet 9 being fluidly connected to the additional refrigerant inlet 10.

[0063] The turbo compressor 1 also includes an electrical motor 12 configured to drive in rotation the drive shaft 3 about the longitudinal axis A. The electrical motor 12 includes a motor stator 13 and a motor rotor 14. Advantageously, the motor rotor 14 is connected to the second axial end portion 5 of the drive shaft 3. To this end, the second axial end portion 5 may include an axial bore 15 within which is arranged the motor rotor 14. The motor rotor 14 may for example be firmly fitted, such as press-fitted or shrink fitted, within the axial bore 15. Further the motor rotor 14 may be a permanent magnet motor rotor.

[0064] The turbo compressor 1 further includes an axial bearing arrangement, also named thrust bearing arrangement, arranged between the impellers 7.1, 7.2 and the electrical motor 12 and configured to limit an axial movement of the drive shaft 3 during operation. The axial bearing arrangement is advantageously a gas axial bearing arrangement.

[0065] According to the embodiment shown on the figures, the axial bearing arrangement includes an axial bearing member 17 arranged on an outer surface of the intermediate portion 6 of the drive shaft 3 and extending radially outwardly with respect to the drive shaft 3.

[0066] The axial bearing arrangement also includes an axial bearing plate 18 and an additional axial bearing plate 19 each having an annular ring shape, and being arranged in parallel. The axial bearing plate 18 faces towards the impellers 7.1, 7.2, while the additional axial bearing plate 19 faces towards the electrical motor 12.

[0067] The axial bearing arrangement further includes a spacer ring 20 surrounding the axial bearing member 17, and being clamped between the axial bearing plate 18 and the additional axial bearing plate 19 at radial outer portions of the axial bearing plate 18 and the additional axial bearing plate 19. The spacer ring 20, the axial bearing plate 18 and the additional axial bearing plate 19 define a space in which extends the axial bearing member 17. The spacer ring 20 particularly defines an axial distance between the axial bearing plate 18 and the additional axial bearing plate 19, said axial distance being slightly greater than the width of the axial bearing member 17.

[0068] Advantageously, the turbo compressor 1 is configured so that gas refrigerant is introduced between the axial bearing member 17, the axial bearing plate 18 and the additional axial bearing plate 19 to form a gas axial bearing.

[0069] The turbo compressor 1 also includes a bearing sleeve 21, also named bearing housing, which extends along the intermediate portion 6 of the drive shaft 3 and which is located between the axial bearing arrangement and the electrical motor 12. The bearing sleeve 21 may be a one-piece bearing sleeve, or may be made from separated parts assembled together.

[0070] The bearing sleeve 21 particularly includes:

• a radial bearing part 22 which is tubular and which surrounds the intermediate portion 6 of the drive shaft 3, the radial bearing part 22 being configured to rotatably support the drive shaft 3,
• an outer sleeve part 23 surrounding the radial bearing part 22 and including an axial end face 24 facing towards the axial bearing arrangement, the axial end face 24 being planar and extending perpendicularly to a longitudinal axis of the bearing sleeve 21 which is substantially coincident with the longitudinal axis A of the drive shaft 3, and
• an annular gap 25 formed between the radial bearing part 22 and the outer sleeve part 23 and extending around the longitudinal axis of the bearing sleeve 21, the annular gap 25 facing towards the additional axial bearing plate 19.

[0071] The radial bearing part 22 and the outer sleeve part 23 are concentrically arranged, and the outer sleeve part 23 is connected to the radial bearing part 22 through a connecting part 26 which is away from the axial end face 24, and which is for example positioned substantially at a center of the axial length of the radial bearing part 22. The outer sleeve part 23 may be shorter than the radial bearing part 22 along the longitudinal axis of the bearing sleeve 21.

[0072] According to the embodiment shown of the figures, the bearing sleeve 21 further includes an additional annular gap 27 formed between the radial bearing part 22 and the outer sleeve part 23 and extending around the longitudinal axis of the bearing sleeve 21. Advantageously, the additional annular gap 27 faces towards the electrical motor 12, and the annular gap 25 and the additional annular gap 27 are separated by the connecting part 26.

[0073] According to the embodiment shown of the figures, the radial bearing part 22 includes a radial bearing surface 22.1 and an additional radial bearing surface 22.2 located on each side of the connecting part 26 and configured to respectively cooperate with a bearing portion 6.1 and an additional bearing portion 6.2 provided on the intermediate portion 6 of the drive shaft 3. The radial bearing surface 22.1 and the bearing portion 6.1 form a radial bearing 28, and particularly a radial gas bearing, while the additional radial bearing surface 22.2 and the additional bearing portion 6.2 define an additional radial bearing 29, and particularly an additional radial gas bearing.

[0074] The bearing sleeve 21 further includes a contact surface 30 located at the axial end face 24 of outer sleeve part 23, the additional axial bearing plate 19 abutting against the contact surface 30.

[0075] Advantageously, the bearing sleeve 21 further includes a cooling area 31 formed in an outer circumferential surface of the outer sleeve part 23. The cooling area 31 may for example include an annular cooling channel 32 formed in the outer circumferential surface of the outer sleeve part 23 and extending around the longitudinal axis of the bearing sleeve 21, the annular cooling channel 32 being intended for the passage of a refrigerant so as to dissipate heat from the bearing sleeve 21.

[0076] The turbo compressor 1 further includes an inlet distributor 33 fluidly connected to the refrigerant inlet 8, and at least partially defining an inlet refrigerant flow path P configured to supply, and for example to axially supply, the first compression stage with an inlet refrigerant flow. Advantageously, the inlet distributor 33 has an annular disc shape and is located adjacent the axial bearing plate 18.

[0077] Particularly, the inlet distributor 33 has a first axial surface 33.1 facing toward the impellers 7.1, 7.2 and a second axial surface 33.2 facing towards the axial bearing arrangement, and particularly facing towards the axial bearing plate 18.

[0078] According to the embodiment shown on the figures, the inlet distributor 33 includes inlet flow guide members 34 provided on and protruding from the first axial surface 33.1 of the inlet distributor 33 and facing towards the impellers 7.1, 7.2. The inlet flow guide members 34 partially define the inlet refrigerant flow path P and are particularly arranged such that each pair of adjacent inlet flow guide members 34 is configured to radially guide a respective part of the inlet refrigerant flow towards a center area of the inlet distributor 33.

[0079] As better shown on figure 5, the inlet flow guide members 34 are regularly angularly distributed around the longitudinal axis A of the drive shaft 3, and each inlet flow guide member 34 extends radially towards the drive shaft 3 and converges towards the drive shaft 3. Each inlet flow guide member 34 may have a triangular shape and have an apex oriented towards the drive shaft 3.

[0080] Advantageously, the bearing sleeve 21 is axially immobilized with respect to the inlet distributor 33. The turbo compressor 1 may therefore include a securing member 35 axially tightening the bearing sleeve 21 against the inlet distributor 33, and more particularly against an abutment surface 36 provided on the inlet distributor 33. The securing member 35 may be secured, for example by screwing, to the hermetic casing 2 or to the inlet distributor 33. Particularly, the contact surface 30 of the bearing sleeve 21 abuts against the abutment surface 36.

[0081] The inlet distributor 33 may for example include a tubular part 37 defining an inner housing 38 in which are received the axial bearing plate 18, the additional axial bearing plate 19 and the spacer ring 20.

[0082] The turbo compressor 1 further includes an elastic element 39 arranged between the axial bearing plate 18 and the inlet distributor 33. The elastic element 39 axially biases the axial bearing plate 18, the additional axial bearing plate 19 and the spacer ring 20 with a predetermined force, for example in the range of 1000 to 2000 N, against the contact surface 30 of the bearing sleeve 21. Advantageously, the elastic element 39 is an annular spring washer, preferably of the Belleville type, coaxially arranged with the bearing sleeve 21 and the drive shaft 3. The elastic element 39 is advantageously arranged in an annular recess formed in the second axial surface 33.2 of the inlet distributor 33, and is in contact with a radial outer portion of the axial bearing plate 18.

[0083] The elastic element 39 allows, notably when a thermal expansion occurs in the turbo compressor 1, an axial sliding of the axial bearing plate 18, of the additional axial bearing plate 19 and of the spacer ring 20 with respect to the inlet distributor 33, and thus avoids deformations of said parts which could lead to a shortened lifetime of the turbo compressor 1.

[0084] The turbo compressor 1 also includes an axial bearing cooling arrangement configured to cool at least partially the axial bearing plate 18.

[0085] As better shown on figures 3 to 6, the axial bearing cooling arrangement includes bypass openings 40 formed in the inlet distributor 33. The bypass openings are regularly angularly distributed around the longitudinal axis A of the drive shaft 3, and are advantageously circumferentially aligned around the longitudinal axis A of the drive shaft 3.

[0086] Each bypass opening 40 extends through the inlet distributor thickness and emerges respectively in the first axial surface 33.1 and in the second axial surface 33.2. Advantageously, each bypass opening 40 emerges in the first axial surface 33.1 of the inlet distributor 33 between two respective adjacent inlet flow guide members 34. According to the embodiment shown on the figures, each bypass opening 40 has a generally rectangular shape, but may have any other shape.

[0087] The axial bearing cooling arrangement further includes bypass flow guide members 41 provided on or recessed from the second axial surface 33.2 of the inlet distributor 33 and facing towards the axial bearing arrangement, and particularly towards the axial bearing plate 18. Advantageously, the bypass flow guide members 41 are angularly distributed around the longitudinal axis A of the drive shaft 3 and extend radially towards the drive shaft 3. According to the embodiment shown of the figures, each bypass flow guide member 41 partially defines a bypass flow guide channel 42 extending radially towards the drive shaft 3 and converging towards the drive shaft 3, and each bypass opening 40 emerges into a respective bypass flow guide channel 42.

[0088] The axial bearing cooling arrangement therefore includes a bypass refrigerant flow path 43 which is defined by the bypass flow guide channels 42 and the axial bearing plate 18, and which extends at least partially along the surface of the axial bearing plate 18 facing towards the inlet distributor 33 and the impellers 7.1, 7.2. Advantageously, the bypass refrigerant flow path 43 extends in parallel to the inlet refrigerant flow path P.

[0089] The bypass openings 40 are particularly configured to derive a part of the inlet refrigerant flow, flowing into the inlet refrigerant flow path P, into the bypass refrigerant flow path 43 such that said derived part of the inlet refrigerant flow flows into the bypass flow guide channels 42 and along the surface of the axial bearing plate 18 facing towards the impellers 7.1, 7.2 and thus at least partially cools the axial bearing plate 18. Further the bypass refrigerant flow path 43 is advantageously fluidly connected to the inlet refrigerant flow path P downstream of the bypass openings 40 through an annular gap 44 defined by the drive shaft 3 and an inner circumferential surface of the inlet distributor 33, such that the derived part of the inlet refrigerant flow returns to the inlet refrigerant flow after having at least partially cooled the axial bearing plate 18.

[0090] Such a configuration of the axial bearing cooling arrangement, and particularly of the bypass openings 40 and the bypass flow guide channels 42, allows cooling the axial bearing plate 18 with a derived part of the inlet refrigerant flow, and thus avoids or at least strongly reduces, even at the most critical running conditions of the turbo compressor, thermal deformations of the axial bearing plate 18 and thus of the axial bearing arrangement.

[0091] Therefore, the configuration of the turbo compressor 1 according to the present invention avoids a seizure of the axial bearing arrangement and improves the stability of said axial bearing arrangement, and thus improves the reliability of the turbo compressor 1 and increases the lifetime of the turbo compressor 1.

[0092] Further, as the derived part of the inlet refrigerant flow goes back to the inlet refrigerant flow after having at least partially cooled the axial bearing plate 18, such an axial bearing cooling arrangement has a very limited impact on the global performance of the turbo compressor.

[0093] Of course, the invention is not restricted to the embodiment described above by way of non-limiting example, but on the contrary it encompasses all embodiments thereof.

Claims

1. A turbo compressor (1) including:

- a drive shaft (3) having a longitudinal axis (A) and including a first axial end portion (4) and a second axial end portion (5) opposite to the first axial end portion, (4)

- a compression stage configured to compress a refrigerant, the compression stage including an impeller (7.1) connected to the first axial end portion (4) of the drive shaft (3),

- an electrical motor (12) connected to the second axial end portion (5) of the drive shaft (3) and configured to drive in rotation the drive shaft (3) about a rotation axis,

- an axial bearing arrangement configured to limit an axial movement of the drive shaft (3) during operation, the axial bearing arrangement including an axial bearing plate (18) having an annular ring shape and facing towards the impeller (7.1),

- an inlet distributor (33) at least partially defining an inlet refrigerant flow path (P) configured to supply the compression stage with an inlet refrigerant flow, the inlet distributor (33) being located adjacent the axial bearing plate (18), and

- an axial bearing cooling arrangement configured to cool at least partially the axial bearing plate (18), the axial bearing cooling arrangement including bypass openings (40) formed in the inlet distributor (33) and a bypass refrigerant flow path (43) at least partially defined by the inlet distributor (33) and the axial bearing plate (18), the bypass openings (40) being configured to derive a part of the inlet refrigerant flow into the bypass refrigerant flow path (43) such that said derived part of the inlet refrigerant flow at least partially cools the axial bearing plate (18), the bypass refrigerant flow path (43) being fluidly connected to the inlet refrigerant flow path (P) downstream of the bypass openings (40) such that the derived part of the inlet refrigerant flow returns to the inlet refrigerant flow after having at least partially cooled the axial bearing plate (18).

2. The turbo compressor (1) according to claim 1, wherein the bypass refrigerant flow path (43) extends at least partially along a surface of the axial bearing plate (18) facing towards the inlet distributor (33).

3. The turbo compressor (1) according to claim 1 or 2, wherein the inlet distributor (33) has a first axial surface (33.1) facing toward the impeller (7.1) and a second axial surface (33.2) facing towards the axial bearing arrangement, each bypass opening (40) extending through an inlet distributor thickness and emerging respectively in the first axial surface (33.1) and in the second axial surface (33.2).

4. The turbo compressor (1) according to any one of claims 1 to 3, wherein the inlet distributor (33) includes inlet flow guide members (34) facing towards the impeller (7.1), the inlet flow guide members (34) being angularly distributed around the longitudinal axis (A) of the drive shaft (3) and partially defining the inlet refrigerant flow path (P).

5. The turbo compressor (1) according to claim 4, wherein each bypass opening (40) is located between two respective adjacent inlet flow guide members (34).

6. The turbo compressor (1) according to any one of claims 1 to 5, wherein the axial bearing cooling arrangement includes bypass flow guide members (41) provided on the inlet distributor (33) and facing towards the axial bearing arrangement, the bypass flow guide members (41) being angularly distributed around the longitudinal axis (A) of the drive shaft (3) and partially defining the bypass refrigerant flow path (43).

7. The turbo compressor (1) according to claim 6, wherein each bypass flow guide member (41) radially converges towards the drive shaft (3).

8. The turbo compressor (1) according to claim 6 or 7, wherein each bypass flow guide member (41) partially defines a bypass flow guide channel (42) extending radially towards the drive shaft (3).

9. The turbo compressor (1) according to any one of claims 1 to 8, wherein the axial bearing arrangement is an axial gas bearing arrangement.

10. The turbo compressor (1) according to any one of claims 1 to 9, further including a bearing sleeve (21) located between the electrical motor (12) and the axial bearing arrangement, the bearing sleeve (21) having a longitudinal axis and surrounding the drive shaft (3), the bearing sleeve (21) including:

- a radial bearing part (22) which is tubular and which is configured to rotatably support the drive shaft (3),

- an outer sleeve part (23) surrounding the radial bearing part (22) and including an axial end face (24) which faces towards the axial bearing arrangement and a contact surface (30) which is located at the axial end face (24) and which is configured to cooperate with the axial bearing arrangement.

11. The turbo compressor (1) according to claim 10, wherein the bearing sleeve (21) further includes a cooling area (31) formed in an outer circumferential surface of the outer sleeve part (23) and intended for the passage of a refrigerant so as to dissipate heat from the bearing sleeve.

12. The turbo compressor (1) according to claim 11, wherein the cooling area (31) includes at least one annular cooling channel (32) formed in the outer circumferential surface of the outer sleeve part (23) and extending around the longitudinal axis of the bearing sleeve (21).

13. The turbo compressor (1) according to any one of claims 1 to 12, wherein the axial bearing arrangement further includes:

- an additional axial bearing plate (19) having an annular ring shape, and

- a spacer ring (20) being clamped between the axial bearing plate (18) and the additional axial bearing plate (19) at radial outer portions of the axial bearing plate (18) and the additional axial bearing plate (19), the spacer ring (20) defining an axial distance between the axial bearing plate (18) and the additional axial bearing plate (19).

Drawing