Multi-stage electric centrifugal compressor

Abstract

A multi-stage electric centrifugal compressor (1) is configured to drive impellers arranged at both ends of a rotating shaft through an electric motor (10), and the multi-stage electric centrifugal compressor comprises: a rotating shaft (3); a low-pressure stage impeller (4) arranged on one side of the rotating shaft; a high-pressure stage impeller (5) arranged on the other side of the rotating shaft; a high-pressure stage casing (7) accommodating the high-pressure stage impeller; a connecting pipe (8) for supplying compressed gas compressed by the low-pressure stage impeller to the high-pressure stage casing; the high-pressure stage casing has a high-pressure stage inlet opening (71), the high-pressure stage inlet opening is opened in a direction intersecting the axis (CA) of the rotating shaft, and the connecting pipe includes a high-pressure stage side connecting portion (81) connected to the high-pressure stage inlet opening.

Description

Technical Field

[0001] The present disclosure relates to a multi-stage electric centrifugal compressor, which is configured such that impellers provided at both ends of a rotating shaft are driven by an electric motor. Background Art

[0002] Fuel cell vehicles, which generate electricity using fuel cells mounted on the vehicle and travel using electric motors, sometimes include electric centrifugal compressors. These compressors improve fuel cell efficiency by supplying compressed air to the fuel cell. Some electric centrifugal compressors have multi-stage systems that compress the volume of gas (e.g., air) in stages.

[0003] A multi-stage electric centrifugal compressor is constructed such that a low-pressure impeller provided on one side of a rotating shaft driven by an electric motor compresses gas to a first pressure, and a high-pressure impeller provided on the other side of the rotating shaft compresses the compressed air compressed by the low-pressure impeller to a second pressure higher than the first pressure (for example, Patent Document 1).

[0004] The multi-stage electric centrifugal compressor described in Patent Document 1 includes a low-pressure-stage casing that houses a low-pressure-stage impeller and a high-pressure-stage casing that houses a high-pressure-stage impeller. The high-pressure-stage casing has an inlet opening that opens toward the axis of the rotating shaft. Compressed air compressed by the low-pressure-stage impeller is introduced into the high-pressure-stage casing through the inlet opening and further compressed by the high-pressure-stage impeller.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-155696 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] To meet the performance requirements of fuel cell vehicles (low flow and high pressure), it is necessary to increase the output and air compression ratio of the electric motor of a multi-stage electric centrifugal compressor. This increases the complexity of the compressor's structure, leading to a tendency for the compressor to become larger. Therefore, miniaturization of the multi-stage electric centrifugal compressor is necessary.

[0010] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a multi-stage electric centrifugal compressor that can achieve miniaturization of the multi-stage electric centrifugal compressor.

[0011] Solutions for solving problems

[0012] The multi-stage electric centrifugal compressor disclosed herein is a multi-stage electric centrifugal compressor configured to drive impellers provided at both ends of a rotating shaft by an electric motor. The multi-stage electric centrifugal compressor includes:

[0013] the rotation axis;

[0014] a low-pressure stage impeller, which is arranged on one side of the rotating shaft;

[0015] a high-pressure stage impeller, which is arranged on the other side of the rotating shaft;

[0016] a high-pressure stage casing accommodating the high-pressure stage impeller;

[0017] a connecting pipe for supplying the compressed gas compressed by the low-pressure stage impeller to the high-pressure stage casing;

[0018] The high-pressure stage housing has a high-pressure stage inlet opening, which opens in a direction intersecting the axis of the rotating shaft.

[0019] The connecting pipe includes a high-pressure-stage side connecting portion connected to the high-pressure-stage inlet opening.

[0020] Effects of the Invention

[0021] According to at least one embodiment of the present invention, a multi-stage electric centrifugal compressor capable of achieving miniaturization and weight reduction is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure.

[0023] Figure 2 It is schematically shown as viewed from the axial high pressure stage side. Figure 1 A schematic cross-sectional view of the high-pressure stage connection portion of the connecting piping and the high-pressure stage shell cross section is shown.

[0024] Figure 3 Is used to illustrate Figure 1 An explanatory diagram of the shape of the high-pressure stage connection portion of the connecting piping shown.

[0025] Figure 4 This is a schematic diagram schematically showing the vicinity of connecting pipes in a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure.

[0026] Figure 5 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure.

[0027] Figure 6 The diagram is schematically shown as viewed from the high pressure stage side in the axial direction. Figure 5 A schematic cross-sectional view of a section of the high pressure stage casing is shown.

[0028] Figure 7 This is a schematic diagram schematically showing the vicinity of a high-pressure stage casing in a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure.

[0029] Figure 8 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure.

[0030] Figure 9 yes Figure 8 A schematic cross-sectional view of the area near the high-pressure stage side sleeve.

[0031] Figure 10 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure.

[0032] Figure 11 yes Figure 10 A schematic cross-sectional view of the area near the high-pressure stage side sleeve.

[0033] Figure 12 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure.

[0034] Figure 13 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0035] Several embodiments of the present disclosure are described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present disclosure and are merely illustrative examples.

[0036] For example, expressions indicating relative or absolute configurations such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" not only strictly indicate such configurations, but also indicate a state in which there is a tolerance, or a relative displacement at an angle or distance that can achieve the same degree of functionality.

[0037] For example, expressions such as “same,” “equal,” and “homogeneous” indicating that things are equal not only indicate a strictly equal state but also indicate a state with a tolerance or a difference to the extent that the same function can be achieved.

[0038] For example, expressions indicating shapes such as a quadrilateral or a cylinder not only indicate shapes such as a quadrilateral or a cylinder in a strict geometric sense, but also indicate shapes including concave and convex portions or chamfered portions as long as the same effect can be obtained.

[0039] On the other hand, expressions such as “having”, “includes” or “has” a constituent element are not exclusive expressions excluding the presence of other constituent elements.

[0040] It should be noted that the same configuration may be denoted by the same reference numerals and the description thereof may be omitted.

[0041] (Multi-stage electric centrifugal compressor)

[0042] Figure 1 1 is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. Figure 1 , a cross section of the multi-stage electric centrifugal compressor 1 along the axis CA of the rotating shaft 3 is schematically shown.

[0043] like Figure 1 As shown, the multi-stage electric centrifugal compressor 1 according to several embodiments of the present disclosure is configured such that impellers (a low-pressure stage impeller 4 and a high-pressure stage impeller 5 ) provided at both ends of a rotating shaft 3 are driven by an electric motor 10 .

[0044] like Figure 1 As shown, the multi-stage electric centrifugal compressor 1 comprises at least: a rotating shaft 3; a low-pressure stage impeller 4, which is arranged on one side of the rotating shaft 3 ( Figure 1 the high-pressure stage impeller 5, which is arranged on the other side of the rotating shaft 3 ( Figure 1 left side); a low-pressure stage casing 6, which is configured to accommodate the low-pressure stage impeller 4; a high-pressure stage casing 7, which is configured to accommodate the high-pressure stage impeller 5; a connecting pipe 8, which is used to supply the compressed gas compressed by the low-pressure stage impeller 4 to the high-pressure stage casing 7.

[0045] The following, such as Figure 1 As shown, the direction in which the axis CA of the rotating shaft 3 extends is defined as the axial direction X, and the direction perpendicular to the axis CA is defined as the radial direction Y. Figure 1 The right side of the middle) is set as the low-pressure side XL, and the opposite side of the low-pressure side XL ( Figure 1 The left side in the middle is set as the high-voltage stage side XH.

[0046] (Electric Motor)

[0047] The electric motor 10 mounted on the multi-stage electric centrifugal compressor 1 includes a rotating body 11 as a rotor and a motor stator 12 as a stator. The rotating body 11 includes at least a rotating shaft 3 and a rotor assembly 13 mounted on the outer circumference of the rotating shaft 3. The rotor assembly 13 includes a permanent magnet 14. The motor stator 12 includes a motor coil (stator coil) 121, which is configured to generate a magnetic field that rotates the rotating body 11 equipped with the permanent magnet 14 by power supplied from a power supply not shown. When the rotating body 11 is rotated by the magnetic field generated by the motor stator 12 (the power generated by the electric motor 10), the impellers (the low-pressure stage impeller 4 and the high-pressure stage impeller 5) mounted on the rotating shaft 3 rotate in conjunction with it.

[0048] The multi-stage electric centrifugal compressor 1 compresses gas introduced into the interior of the low-pressure stage casing 6 by rotating the low-pressure stage impeller 4, and pressurizes the gas to a first pressure. The compressed gas pressurized to the first pressure is guided into the interior of the high-pressure stage casing 7 via the connecting pipe 8. The multi-stage electric centrifugal compressor 1 further compresses the compressed gas introduced into the interior of the high-pressure stage casing 7 by rotating the high-pressure stage impeller 5, and pressurizes the compressed gas to a second pressure higher than the first pressure.

[0049] The multi-stage electric centrifugal compressor 1 further includes: a rotor assembly 13 mounted on the rotating shaft 3; a motor stator 12 arranged to surround the outer circumference of the rotor assembly 13; at least one bearing 15 rotatably supporting the rotating shaft 3; at least one bearing housing 16 configured to accommodate the at least one bearing 15; and a stator housing 17 configured to accommodate the electric motor 10 (motor stator 12). The at least one bearing housing 16 and the stator housing 17 are arranged between the low-pressure stage housing 6 and the high-pressure stage housing 7 in the axial direction X. The stator housing 17 is arranged adjacent to the at least one bearing housing 16 in the axial direction X. The motor stator 12 is supported by the stator housing 17 within the stator housing 17.

[0050] (Bearings, bearing housings)

[0051] In the illustrated embodiment, the at least one bearing 15 includes a low-pressure-stage bearing 15A, disposed between the low-pressure-stage impeller 4 and the rotor assembly 13 in the axial direction X; and a high-pressure-stage bearing 15B, disposed between the high-pressure-stage impeller 5 and the rotor assembly 13 in the axial direction X. The at least one bearing housing 16 includes a low-pressure-stage bearing housing 16A, configured to accommodate the low-pressure-stage bearing 15A; and a high-pressure-stage bearing housing 16B, configured to accommodate the high-pressure-stage bearing 15B. The low-pressure-stage bearing 15A is supported by a bearing support surface 161 formed within the low-pressure-stage bearing housing 16A. The high-pressure-stage bearing 15B is supported by a bearing support surface 162 formed within the high-pressure-stage bearing housing 16B.

[0052] The low-pressure-stage bearing housing 16A is positioned closer to the high-pressure-stage side XH than the low-pressure-stage housing 6 and closer to the low-pressure-stage side XL than the stator housing 17. The low-pressure-stage bearing housing 16A is mechanically connected to the low-pressure-stage housing 6 or the stator housing 17, which are positioned adjacent to the low-pressure-stage bearing housing 16A in the axial direction X, by fastening members such as fastening bolts. The high-pressure-stage bearing housing 16B is positioned closer to the low-pressure-stage side XL than the high-pressure-stage housing 7 and closer to the high-pressure-stage side XH than the stator housing 17. The high-pressure-stage bearing housing 16B is mechanically connected to the high-pressure-stage housing 7 or the stator housing 17, which are positioned adjacent to the high-pressure-stage bearing housing 16B in the axial direction X, by fastening members such as fastening bolts.

[0053] (Sleeve)

[0054] In the illustrated embodiment, the multi-stage electric centrifugal compressor 1 further comprises: a low-pressure-stage sleeve 18A mounted on the outer circumference of the rotating shaft 3 between the low-pressure-stage impeller 4 and the low-pressure-stage bearing 15A in the axial direction X; a high-pressure-stage sleeve 18B mounted on the outer circumference of the rotating shaft 3 between the high-pressure-stage impeller 5 and the high-pressure-stage bearing 15B in the axial direction X; and a pressure spring 19 for biasing the high-pressure-stage bearing 15B toward the low-pressure stage XL side. The rotating body 11 also includes the low-pressure-stage sleeve 18A and the high-pressure-stage sleeve 18B.

[0055] The low-pressure-stage bearing housing 16A has an inner surface (sleeve-facing surface) 163 that faces the outer circumferential surface of the low-pressure-stage sleeve 18A, and a locking surface 164 that extends radially inward from the low-pressure-stage-side XL end of the bearing support surface 161 and serves to lock the low-pressure-stage bearing 15A. The inner surface 163 has a smaller diameter than the bearing support surface 161. The high-pressure-stage bearing housing 16B has an inner surface (sleeve-facing surface) 165 that faces the outer circumferential surface of the high-pressure-stage sleeve 18A, and a locking surface 166 that extends radially inward from the high-pressure-stage-side XH end of the bearing support surface 162. The inner surface 165 has a smaller diameter than the bearing support surface 162. The aforementioned pressure spring 19 is positioned between the locking surface 166 and the high-pressure-stage bearing 15B to apply a predetermined pressure to the high-pressure-stage bearing 15B.

[0056] (Low-pressure stage casing, low-pressure stage impeller)

[0057] like Figure 1As shown, the low-pressure stage casing 6 is formed with a low-pressure stage inlet opening 61 for introducing gas from the outside of the low-pressure stage casing 6 into the interior, and a low-pressure stage outlet opening 62 for discharging gas from the interior of the low-pressure stage casing 6 to the outside. A supply flow path 63 is formed inside the low-pressure stage casing 6 to guide the gas introduced into the interior of the low-pressure stage casing 6 from the low-pressure stage inlet opening 61 toward the low-pressure stage impeller 4, and a swirl flow path 64 is formed to guide the gas that has passed through the low-pressure stage impeller 4 toward the low-pressure stage outlet opening 62. In the illustrated embodiment, the low-pressure stage inlet opening 61 opens toward the low-pressure stage side XL in the axial direction X. The low-pressure stage outlet opening 62 opens in a direction intersecting (e.g., perpendicular to) the axis CA.

[0058] exist Figure 1 In the illustrated embodiment, the low-pressure-stage impeller 4 includes a hub 41 mechanically connected to one side of the rotating shaft 3 and a plurality of impeller blades 43 disposed on the outer circumferential surface 42 of the hub 41. The low-pressure-stage impeller 4 is rotatable integrally with the rotating shaft 3 about the axis CA of the rotating shaft 3. The low-pressure-stage impeller 4 is a centrifugal impeller configured to guide gas delivered from the low-pressure-stage side XL in the axial direction X outward in the radial direction Y. Clearances are formed between the tips 44 of the plurality of impeller blades 43 and the convexly curved shroud surface 65 of the low-pressure-stage casing 6.

[0059] exist Figure 1 In the illustrated embodiment, the low-pressure-stage casing 6 is combined with another component (in the illustrated example, the low-pressure-stage bearing housing 16A) to form a low-pressure-stage impeller chamber 66 that rotatably accommodates the low-pressure-stage impeller 4. The low-pressure-stage impeller chamber 66 communicates with a supply flow path 63 located upstream in the gas flow direction and a vortex flow path 64 located downstream in the gas flow direction. The vortex flow path 64 has a vortex shape that surrounds the outer side of the low-pressure-stage impeller 4 in the radial direction Y. A shroud surface 65 partially defines the low-pressure-stage impeller chamber 66.

[0060] (High-pressure stage casing, high-pressure stage impeller)

[0061] like Figure 1 As shown, the high-pressure stage casing 7 is formed with a high-pressure stage inlet opening 71 for introducing gas from the outside of the high-pressure stage casing 7 into the interior, and a high-pressure stage outlet opening 72 for discharging gas from the interior of the high-pressure stage casing 7 to the outside. A supply flow path 73 is formed inside the high-pressure stage casing 7 for guiding the gas introduced into the interior of the high-pressure stage casing 7 from the high-pressure stage inlet opening 71 toward the high-pressure stage impeller 5, and a vortex flow path 74 is formed for guiding the gas that has passed through the high-pressure stage impeller 5 toward the high-pressure stage outlet opening 72. In the illustrated embodiment, the high-pressure stage outlet opening 71 and the high-pressure stage outlet opening 72 each open in a direction intersecting (e.g., perpendicular to) the axis CA.

[0062] exist Figure 1 In the illustrated embodiment, the high-pressure stage impeller 5 includes a hub 51 mechanically connected to the other side of the rotating shaft 3 and a plurality of impeller blades 53 provided on the outer peripheral surface 52 of the hub 51. The high-pressure stage impeller 5 is rotatable integrally with the rotating shaft 3 about the axis CA of the rotating shaft 3. The high-pressure stage impeller 5 is a centrifugal impeller configured to guide gas delivered from the high-pressure stage side XH in the axial direction X outward in the radial direction Y. Clearances are formed between the tips 54 of the plurality of impeller blades 53 and the convexly curved shroud surface 75 of the high-pressure stage casing 7.

[0063] exist Figure 1 In the illustrated embodiment, the high-pressure stage casing 7 is combined with another component (in the illustrated example, the high-pressure stage side bearing housing 16B) to form a high-pressure stage impeller chamber 76 that rotatably accommodates the high-pressure stage impeller 5. The high-pressure stage impeller chamber 76 communicates with a supply flow path 73 located upstream in the gas flow direction and a vortex flow path 74 located downstream in the gas flow direction. The vortex flow path 74 has a vortex shape that surrounds the outer side of the high-pressure stage impeller 5 in the radial direction Y. A shroud surface 75 partially defines the high-pressure stage impeller chamber 76.

[0064] Gas (e.g., air) guided from the outside of the low-pressure-stage casing 6 through the low-pressure-stage inlet opening 61 to the supply flow path 63 flows through the supply flow path 63 to the high-pressure-stage side XH, is then delivered to the low-pressure-stage impeller 4, and is compressed and pressurized to a first pressure by the rotation of the low-pressure-stage impeller 4. The compressed gas (e.g., compressed air) that has passed through the low-pressure-stage impeller 4 flows outward in the radial direction Y through the vortex flow path 64 before being discharged to the outside of the low-pressure-stage casing 6 through the low-pressure-stage outlet opening 62.

[0065] (Connecting pipes)

[0066] like Figure 1 As shown, the connecting piping 8 is formed into a tubular shape extending along its long side direction, and includes at least a high-pressure-stage side connecting portion 81 connected to the above-mentioned high-pressure-stage inlet opening 71 and a low-pressure-stage side connecting portion 82 connected to the low-pressure-stage outlet opening 62. In the illustrated embodiment, the high-pressure-stage side connecting portion 81 and the low-pressure-stage side connecting portion 82 extend in directions intersecting (orthogonal in the illustrated example) with respect to the axis CA of the rotating shaft 3. The connecting piping 8 also includes: an intermediate portion 83 extending along the axis CA of the rotating shaft; a low-pressure-stage side bending portion 84 having a bending shape connecting the low-pressure-stage side connecting portion 82 and the intermediate portion 83; and a high-pressure-stage side bending portion 85 having a bending shape connecting the high-pressure-stage side connecting portion 81 and the intermediate portion 83. In Figure 1 In FIG. 8 , the boundaries of the respective portions of the connecting pipe 8 are indicated by two-dot chain lines. The respective portions of the connecting pipe 8 may be constituted by separate components or may be integrally formed from a single material.

[0067] The compressed gas discharged from the low-pressure-stage outlet opening 62 of the low-pressure-stage casing 6 flows through the connecting pipe 8 from the low-pressure-stage side connection portion 82 toward the high-pressure-stage side connection portion 81. It is then guided to the supply flow path 73 through the high-pressure-stage inlet opening 71 of the high-pressure-stage casing 7. The compressed gas guided to the supply flow path 73 is delivered to the high-pressure-stage impeller 5, where it is compressed by the rotation of the high-pressure-stage impeller 5 and pressurized to a second pressure higher than the first pressure. The compressed gas that has passed through the high-pressure-stage impeller 5 flows outward in the radial direction Y through the vortex flow path 74 before being discharged from the high-pressure-stage outlet opening 72 to the exterior of the high-pressure-stage casing 7.

[0068] In the illustrated embodiment, the multi-stage electric centrifugal compressor 1 is configured as a multi-stage electric centrifugal compressor for fuel cell vehicles. Therefore, the multi-stage electric centrifugal compressor 1 further includes a compressed gas supply line 21 for supplying compressed gas, compressed by the high-pressure stage impeller 5, to the fuel cell 20. The fuel cell 20 is, for example, a solid oxide fuel cell (SOFC) and includes an air electrode 201, a fuel electrode 202, and a solid electrolyte 203 disposed between the air electrode 201 and the fuel electrode 202. Compressed gas discharged from the high-pressure stage outlet opening 72 of the high-pressure stage housing 7 is supplied to the fuel cell 20 via the compressed gas supply line 21 connecting the high-pressure stage outlet opening 72 and the air electrode 201 of the fuel cell 20. It should be noted that the present disclosure can also be applied to multi-stage electric centrifugal compressors other than fuel cell vehicles, for example, multi-stage electric centrifugal compressors for internal combustion engines, which pressurize combustion gas for delivery to an internal combustion engine such as an engine. That is, the compressed gas supply line 21 can also be configured to connect the high-pressure stage outlet opening 72 of the high-pressure stage housing 7 to the internal combustion engine (not shown).

[0069] like Figure 1 As shown, several embodiments of a multi-stage electric centrifugal compressor 1 include at least: a rotating shaft 3; a low-pressure stage impeller 4 disposed on one side (low-pressure side XL) of the rotating shaft 3; a high-pressure stage impeller 5 disposed on the other side (high-pressure side XH) of the rotating shaft 3; a high-pressure stage casing 7 that houses the high-pressure stage impeller 5; and a connecting pipe 8 for supplying compressed gas compressed by the low-pressure stage impeller 4 to the high-pressure stage casing 7. The high-pressure stage casing 7 has a high-pressure stage inlet opening 71 that opens in a direction intersecting (e.g., perpendicular to) the axis CA of the rotating shaft 3. The connecting pipe 8 includes a high-pressure stage-side connecting portion 81 connected to the high-pressure stage inlet opening 71.

[0070] According to the above configuration, the high-pressure stage inlet opening 71 of the high-pressure stage casing 7 opens in a direction intersecting the axis CA of the rotating shaft 3. A high-pressure-stage-side connection portion 81 of the connecting pipe 8 is connected to the high-pressure stage inlet opening 71. Therefore, compressed gas compressed by the low-pressure stage impeller 4 is supplied from the outer circumference (outer side in the radial direction Y) of the high-pressure stage casing 7 to the interior of the high-pressure stage casing 7 via the connecting pipe 8. In this case, the length of the connecting pipe 8 and the high-pressure stage casing 7 in the axial direction X can be shortened compared to a case where the compressed gas is introduced into the high-pressure stage casing 7 along the axial direction X of the rotating shaft 3. Consequently, the length of the multi-stage electric centrifugal compressor 1 in the axial direction X can be shortened, thereby achieving a reduction in size and weight of the multi-stage electric centrifugal compressor 1.

[0071] Figure 2 The diagram is schematically shown as viewed from the high pressure stage side in the axial direction. Figure 1 A schematic cross-sectional view of the high-pressure stage connection portion of the connecting piping and the high-pressure stage shell cross section is shown. Figure 3 Is used to illustrate Figure 1 An explanatory diagram of the shape of the high-pressure stage connection portion of the connecting piping shown.

[0072] In several embodiments, such as Figure 3 As shown, the flow path section (for example, flow path sections 813 and 814) of the above-mentioned high-pressure stage side connection portion 81 has a long side direction LD along a direction perpendicular to the axis CA of the rotating shaft 3, and includes convex curved portions 811 and 812 formed on both end sides of the long side direction LD.

[0073] In the illustrated embodiment, Figure 2 As shown, the high-pressure stage side connection portion 81 has an expansion area EA whose flow path cross-sectional area increases toward the high-pressure stage inlet opening 71. The expansion area EA is defined by the inner wall surface 810 of the high-pressure stage side connection portion 81. Figure 2 In the illustrated embodiment, the side where the high-pressure stage-side connection portion 81 connects to the high-pressure stage inlet opening 71 is the end point P2 of the expanded area EA, and the side opposite this end point is the starting point P1 of the expanded area EA. The flow path cross section 813 is the flow path cross section at the starting point P1 of the expanded area EA, and the flow path cross section 814 is the flow path cross section at the end point P2 of the expanded area EA.

[0074] According to the above configuration, the flow path cross section of the high-pressure-stage side connection portion 81 has a longitudinal direction LD perpendicular to the axis CA of the rotating shaft 3 and includes convexly curved portions 811 and 812 formed at both ends of the longitudinal direction LD. In this case, since the flow path cross section of the high-pressure-stage side connection portion 81 is an elliptical shape extending along the longitudinal direction LD, it is possible to prevent the high-pressure-stage side connection portion 81 from becoming larger in the axial direction X of the rotating shaft 3 and increase the flow path area of ​​the high-pressure-stage side connection portion 81. By increasing the flow path area of ​​the high-pressure-stage side connection portion 81, a desired amount of compressed gas can be supplied to the high-pressure stage casing 7. Furthermore, since the flow path cross section of the high-pressure-stage side connection portion 81 is an oblong shape, pressure loss of the compressed gas flowing through the high-pressure-stage side connection portion 81 can be reduced compared to a case where the flow path cross section has a polygonal shape, such as a rectangle.

[0075] In several embodiments, such as Figure 3 As shown, the flow path cross section (e.g., flow path cross sections 813 and 814) of the high-pressure-stage side connection portion 81 has a short-side direction SD along the axis CA of the rotating shaft 3. In this case, by forming the flow path cross section of the high-pressure-stage side connection portion 81 into a shape having a short-side direction SD along the axis CA, the length of the high-pressure-stage side connection portion 81 in the axial direction X of the rotating shaft 3 can be shortened, thereby achieving miniaturization and weight reduction of the multi-stage electric centrifugal compressor 1.

[0076] In several embodiments, such as Figure 3 As shown, the flow path cross-section of the high-pressure-stage side connection portion 81 (e.g., flow path cross-sections 813 and 814) further includes a straight portion 815 connecting the ends of the pair of convex curved portions 811 and 812. The straight portion 815 has a predetermined length L1 in the longitudinal direction LD and an equal length in the lateral direction SD. In this case, the flow path cross-section of the high-pressure-stage side connection portion 81 includes the straight portion 815, thereby increasing the velocity component of the compressed gas flowing through the high-pressure-stage side connection portion 81 toward the high-pressure-stage inlet opening 71, thereby allowing the compressed gas to flow smoothly from the high-pressure-stage inlet opening 71 into the high-pressure-stage impeller 5. This reduces the pressure loss of the compressed gas at the connection between the high-pressure-stage side connection portion 81 and the high-pressure-stage inlet opening 71.

[0077] In the illustrated embodiment, Figure 2 、 Figure 3As shown, the flow path cross section of the high-pressure stage-side connection portion 81 is formed so that the length in the longitudinal direction LD increases toward the high-pressure stage inlet opening 71. In the illustrated embodiment, the length in the longitudinal direction LD of flow path cross section 814 (end point P2 of expanded area EA) is greater than the length in the longitudinal direction LD of flow path cross section 813 (start point P1 of expanded area EA). In contrast, the length in the lateral direction SD varies little from start point P1 to end point P2 of expanded area EA, and the length in the longitudinal direction LD increases, thereby expanding the flow path cross-sectional area.

[0078] According to the above configuration, by forming the flow path cross-section of the high-pressure stage-side connection portion 81 so that the length in the longitudinal direction increases toward the high-pressure stage inlet opening 71, the compressed gas flowing along the inner wall surface 810 of the high-pressure stage-side connection portion 81 can be caused to flow directly along the inner wall surface 77 defining the supply flow path 73 of the high-pressure stage casing 7. By causing the compressed gas to flow along the inner wall surface 77 of the high-pressure stage casing 7, it is possible to suppress the compressed gas from separating from the inner wall surface 77, thereby reducing the pressure loss of the compressed gas in the supply flow path 73 of the high-pressure stage casing 7.

[0079] In several embodiments, such as Figure 2 As shown, the high-pressure stage inlet opening 71 is formed on the inner circumferential wall surface 772 that defines the outer periphery of the supply flow path 73. The inner wall surface 810 of the high-pressure stage side connection portion 81 smoothly connects to the inner circumferential wall surface 772 of the high-pressure stage housing 7. "Smoothly connected" here means that the boundary between the inner wall surface 77 and the inner circumferential wall surface 772 does not form a corner, but rather has a curvature. In the illustrated embodiment, the inner wall surface 810 has a convex curve. It should be noted that to reduce the pressure loss of the compressed gas at the connection between the high-pressure stage side connection portion 81 and the high-pressure stage inlet opening 71, the curvature of the portion connecting to the inner wall surface 77 of the inner circumferential wall surface 772 is preferably as large as possible. With this structure, the inner wall surface 810 of the high-pressure stage side connection portion 81 smoothly connects to the inner circumferential wall surface 772 of the high-pressure stage housing 7, thereby reducing the pressure loss of the compressed gas at the connection between the high-pressure stage side connection portion 81 and the high-pressure stage inlet opening 71.

[0080] In several embodiments, such as Figure 3As shown, the flow path cross section of the high-pressure stage-side connecting portion 81 is formed so that the maximum curvature of the convexly curved portions 811 and 812 increases toward the high-pressure stage inlet opening 71. In the illustrated embodiment, the maximum curvature R2 of the convexly curved portions 811 and 812 in flow path cross section 814 (end point P2 of the expanded area EA) is greater than the maximum curvature R1 of the convexly curved portions 811 and 812 in flow path cross section 813 (start point P1 of the expanded area EA). In the illustrated embodiment, the curvature of each of the convexly curved portions 811 and 812 in flow path cross section 813 is constant from the end connected to the straight portion 815 to one end in the longitudinal direction LD. In contrast, the curvature of each of the convexly curved portions 811 and 812 in flow path cross section 814 increases from the ends 816 and 818 connected to the straight portion 815 toward one end 817 and 819 in the longitudinal direction LD. In one embodiment, the maximum curvature R2 is more than twice the maximum curvature R1.

[0081] According to the above configuration, by forming the flow path cross-section of the high-pressure-stage side connection portion 81 so that the maximum curvature of the convex curved portions 811 and 812 increases toward the high-pressure-stage inlet opening 71, the compressed gas flowing through the high-pressure-stage side connection portion 81 can be smoothly guided to the high-pressure-stage inlet opening 71. As a result, the pressure loss of the compressed gas in the connection portion between the high-pressure-stage side connection portion 81 and the high-pressure-stage inlet opening 71 can be reduced.

[0082] In several embodiments, such as Figure 1 As shown, the connecting pipe 8 includes the high-pressure-stage connecting portion 81, the low-pressure-stage connecting portion 82, the intermediate portion 83, the low-pressure-stage bent portion 84, and the high-pressure-stage bent portion 85. Furthermore, at least the flow path cross-section of the low-pressure-stage connecting portion 82 is formed into a circular shape. In the illustrated embodiment, not only the low-pressure-stage connecting portion 82, but also the flow path cross-sections of the low-pressure-stage connecting portion 82 and the intermediate portion 83 are formed into a circular shape. Furthermore, at the high-pressure-stage bent portion 85, the flow path cross-section changes from a circular shape to an oblong shape.

[0083] The compressed gas delivered from the low-pressure stage casing 6 to the connecting pipe (8) has a swirling component. According to the above structure, by making the flow path cross-section of at least the low-pressure stage side connecting portion 82 in the connecting pipe 8 circular, the pressure loss of the compressed gas with a swirling component flowing in the connecting pipe 8 can be reduced. It should be noted that by making the flow path cross-section of the low-pressure stage side connecting portion 82 and the intermediate portion 83 circular, the pressure loss of the compressed gas with a swirling component flowing in the connecting pipe 8 can be further reduced.

[0084] Figure 4 This is a schematic diagram schematically showing the vicinity of connecting pipes in a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. Figure 4 , a cross section of the multi-stage electric centrifugal compressor 1 along the axis CA of the rotating shaft 3 is schematically shown.

[0085] In several embodiments, such as Figure 4 As shown, the multi-stage electric centrifugal compressor 1 further includes a cooling device 86 configured to perform heat exchange between the compressed gas in the connecting pipe 8 and a coolant (e.g., cooling water) for cooling the compressed gas. The compressed gas compressed by the low-pressure stage impeller 4 is cooled by the cooling device 86 and then supplied to the high-pressure stage impeller 5.

[0086] In the illustrated embodiment, the cooling device 86 includes a coolant circulation line 861 that circulates a coolant serving as a cooling medium, a coolant circulation pump 862 configured to transport the coolant, and a radiator 863 configured to cool the coolant. The coolant circulation line 861 includes a heat exchange section 864 that performs heat exchange between the compressed gas within the connecting pipe 8 and the coolant. The coolant circulation pump 862 is positioned upstream of the heat exchange section 864 in the coolant flow direction within the coolant circulation line 861 and transports the coolant to the downstream side. The radiator 863 is positioned upstream of the heat exchange section 864 in the coolant flow direction within the coolant circulation line 861 and cools the coolant, which has been heated by heat exchange with the compressed gas. As a result, the temperature of the coolant within the heat exchange section 864 is lower than the temperature of the compressed gas within the connecting pipe 8, which is the subject of heat exchange. It should be noted that the cooling device 86 only needs to be able to perform heat exchange between the compressed gas and the coolant in the connecting pipe 8 and is not limited to the illustrated embodiment.

[0087] According to the above-mentioned structure, the compressed gas flowing in the connecting pipe 8 is cooled by heat exchange between the compressed gas and the coolant in the cooling device 86. By using the cooling device 86 to lower the temperature of the compressed gas delivered to the high-pressure stage impeller 5, it is possible to suppress the high temperature of the compressed gas after passing through the high-pressure stage impeller 5. As a result, it is possible to achieve an improvement in the compression ratio in the high-pressure stage of the multi-stage electric centrifugal compressor 1. In addition, by suppressing the high temperature of the compressed gas after passing through the high-pressure stage impeller 5, it is possible to suppress the high temperature of the gas existing in the space 24 facing the back side 57 of the high-pressure stage impeller 5, thereby reducing the amount of heat input from the back side 57 of the high-pressure stage impeller 5 to the bearing 15 (particularly the high-pressure stage side grease-sealed bearing 15B). As a result, it is possible to suppress the deterioration of the bearing 15 due to heat, thereby improving the life and durability of the bearing 15.

[0088] In several embodiments, such as Figure 1As shown, the high-pressure stage casing 7 includes an inner wall surface 77 that defines a supply flow path 73 for guiding compressed gas supplied from the high-pressure stage inlet opening 71 to the high-pressure stage impeller 5. The inner wall surface 77 includes an inner end wall surface 771 on the opposite side (high-pressure stage side XH) from the high-pressure stage impeller 5, which defines the supply flow path 73, and an inner peripheral wall surface 772 on the outer peripheral side (outer side in the radial direction Y) of the supply flow path 73. The high-pressure stage casing 7 also includes a guide protrusion 78 that protrudes from the inner end wall surface 771 toward the high-pressure stage impeller 5. In the illustrated embodiment, the outer peripheral surface of the guide protrusion 78 is formed into a concave curved shape.

[0089] According to the above configuration, the compressed gas flowing through the supply flow path 73 of the high-pressure stage casing 7 can be guided to the high-pressure stage impeller 5 by the guide protrusion 78 protruding from the inner end wall surface 771 toward the high-pressure stage impeller 5. For example, the flow of the compressed gas flowing inward in the radial direction Y along the inner end wall surface 771 can be bent along the outer peripheral surface of the guide protrusion 78, thereby redirecting the flow toward the low-pressure stage side XL in the axial direction X. In this case, the compressed gas can be introduced axially to the high-pressure stage impeller 5 via the guide protrusion 78, thereby improving the efficiency of the multi-stage electric centrifugal compressor 1 compared to a case where the compressed gas is introduced to the high-pressure stage impeller 5 from the radially outer side.

[0090] Figure 5 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. Figure 6 The diagram is schematically shown as viewed from the high pressure stage side in the axial direction. Figure 5 A schematic cross-sectional view of the high pressure stage shell section is shown. Figure 5 , a cross section of the multi-stage electric centrifugal compressor 1 along the axis CA of the rotating shaft 3 is schematically shown.

[0091] In several embodiments, such as Figure 5 As shown, the inner circumferential wall surface 772 includes an inlet-side inner circumferential wall surface 773 in which the high-pressure stage inlet opening 71 is formed, and an opposite-side inner circumferential wall surface 774 located on the opposite side of the high-pressure stage inlet opening 71. The high-pressure stage housing 7 includes a swirl prevention plate 79 protruding from the opposite-side inner circumferential wall surface 774.

[0092] like Figure 6As shown, in a cross section of the high-pressure stage casing 7 viewed from the high-pressure stage side XH in the axial direction X, the position of the intersection P4 of the reference line RL passing through the center P3 of the high-pressure stage inlet opening 71 and the axis CA of the rotating shaft 3 and the inner peripheral wall surface 774 on the opposite side is set as the 0° position, the clockwise direction centered on the above-mentioned axis CA is set as the positive direction, and the circumferential angle of the rotating shaft 3 in the above-mentioned positive direction relative to the above-mentioned 0° position is defined as θ. The front end 791 of the above-mentioned anti-swirl plate 79 closest to the axis CA exists in the range of -90°≤θ≤90°. In the illustrated embodiment, the anti-swirl plate 79 has an outer surface (inclined surface) 792 that is inclined so that the width dimension becomes smaller as it approaches the front end 791.

[0093] exist Figure 6 In FIG. 5 , the tip 56 of the leading edge 55 of the high-pressure stage impeller 5 is shown as corresponding to the inlet of the high-pressure stage impeller 5. Figure 6 As shown, the compressed gas flowing in either the clockwise or counterclockwise direction along the inner circumferential wall surface 772 in the supply flow path 73 is bent along the outer surface 792 of the anti-swirl plate 79, thereby being diverted to flow toward the inlet of the high-pressure stage impeller 5. Assuming that the high-pressure stage casing 7 does not include the anti-swirl plate 79, the compressed gas flowing in the clockwise direction along the inner circumferential wall surface 772 in the supply flow path 73 collides with the compressed gas flowing in the counterclockwise direction along the inner circumferential wall surface 772 in the supply flow path 73, which may cause pressure loss in the supply flow path 73.

[0094] According to the above configuration, the swirl prevention plate 79 can suppress the collision of compressed gas flowing in one direction circumferentially of the rotating shaft 3 in the supply flow path 73 of the high-pressure stage casing 7 with compressed gas flowing in a direction opposite to the one circumferential direction in the supply flow path 73. Furthermore, the swirl prevention plate 79 guides the compressed gas flowing along the opposite inner peripheral wall surface 774 radially inward of the high-pressure stage impeller 5. This allows the compressed gas flowing in from the high-pressure stage inlet opening 71 to be smoothly guided to the high-pressure stage impeller 5. This reduces the pressure loss of the compressed gas in the supply flow path 73 of the high-pressure stage casing 7.

[0095] In several embodiments, such as Figure 6 As shown, the front end 791 of the anti-swirl plate 79 is located closer to the outer peripheral side of the rotating shaft 3 than the tip 56 of the leading edge 55 of the high-pressure stage impeller 5 (equivalent to the inlet of the high-pressure stage impeller 5).

[0096] If the front end 791 of the anti-swirl plate 79 is located further inwardly of the rotating shaft 3 than the tip 56 of the leading edge 55 of the high-pressure stage impeller 5, the radially inward velocity component of the compressed gas guided by the anti-swirl plate 79 and introduced into the high-pressure stage impeller 5 becomes larger, thereby potentially reducing the compression efficiency in the high-pressure stage impeller 5. According to the above configuration, the front end 791 of the anti-swirl plate 79 is located further outwardly of the rotating shaft 3 than the tip 56 of the leading edge 55 of the high-pressure stage impeller 5. Therefore, the radially inward velocity component of the compressed gas guided by the anti-swirl plate 79 and introduced into the high-pressure stage impeller 5 can be reduced. This can suppress a reduction in the compression efficiency in the high-pressure stage impeller 5.

[0097] like Figure 6 As shown, in a cross section of the high-pressure stage casing 7 viewed from the high-pressure stage side XH in the axial direction X, the distance between the front end 791 of the anti-swirl plate 79 and the axis CA of the rotating shaft 3 is defined as L2, and the radius of the tip 56 (the length from the axis CA) is defined as R3. If L2 is too large, the protruding length from the inner peripheral wall surface 774 on the opposite side of the anti-swirl plate 79 becomes smaller, making it difficult for the anti-swirl plate 79 to change the flow of the compressed gas. In addition, if L2 is too small, as described above, the radially inward velocity component of the compressed gas guided by the anti-swirl plate 79 and introduced into the high-pressure stage impeller 5 becomes larger, thereby potentially reducing the compression efficiency in the high-pressure stage impeller 5. Therefore, L2 preferably satisfies the condition of 1.5R3 ≤ L2 ≤ 2.5R3.

[0098] Each of the following embodiments of the multi-stage electric centrifugal compressor 1 can be implemented independently. For example, it can also be applied to a multi-stage electric centrifugal compressor in which the high-pressure stage inlet opening 71 opens toward the high-pressure stage side XH in the axial direction X. It should be noted that each of the following embodiments of the multi-stage electric centrifugal compressor 1 can combine the structures of each other, and can also combine the structures of the multi-stage electric centrifugal compressor 1 of the above-mentioned embodiments.

[0099] (Grease-packed bearings)

[0100] Figure 7 This is a schematic diagram schematically showing the vicinity of a high-pressure stage casing in a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. Figure 8 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. Figure 9 yes Figure 8 A schematic cross-sectional view of the area near the high-pressure stage side sleeve. Figure 10 This is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. Figure 11 yes Figure 10 A schematic cross-sectional view of the high-pressure stage side sleeve. Figure 7 、 Figure 8 as well as Figure 10 , a cross section of the multi-stage electric centrifugal compressor 1 along the axis CA of the rotating shaft 3 is schematically shown, and the above-mentioned connecting pipe 8 is omitted.

[0101] like Figure 5 、 Figure 8 、 Figure 10 As shown, several embodiments of a multi-stage electric centrifugal compressor 5 include: a rotating shaft 3; a low-pressure impeller 4 disposed on one side (low-pressure side XL) of the rotating shaft 3; a high-pressure impeller 5 disposed on the other side (high-pressure side XH) of the rotating shaft 3; at least one bearing 15 rotatably supporting the rotating shaft 3 and disposed between the high-pressure impeller 5 and the low-pressure impeller 4; and a bearing housing 16 that accommodates the at least one bearing 15. The at least one bearing 15 includes a high-pressure-stage-side grease-packed bearing 15B disposed between the high-pressure-stage impeller 5 and the electric motor 10 (rotor assembly 13). In other words, the high-pressure-stage-side bearing 15B is a grease-packed bearing pre-filled with grease. In the illustrated embodiment, the bearing housing 16 includes a high-pressure-stage-side bearing housing 16B that accommodates the high-pressure-stage-side grease-packed bearing 15B.

[0102] According to the above structure, the multi-stage electric centrifugal compressor 1 includes a high-pressure stage grease-sealed bearing 15B pre-filled with grease. In this case, since grease does not need to be supplied to the high-pressure stage grease-sealed bearing 15B, the structure of the components surrounding the high-pressure stage grease-sealed bearing 15B (for example, the high-pressure stage bearing housing 16B) can be simplified, thereby achieving a smaller and lighter multi-stage electric centrifugal compressor 1.

[0103] In several embodiments of the multi-stage electric centrifugal compressor 1, as Figure 5 、 Figure 8 、 Figure 10 As shown, the at least one bearing 15 further includes the aforementioned high-pressure-stage grease-packed bearing 15B and a low-pressure-stage grease-packed bearing 15A positioned between the low-pressure-stage impeller 4 and the electric motor 10 (rotor assembly 13). In other words, the low-pressure-stage bearing 15A comprises a grease-packed bearing pre-filled with grease. In the illustrated embodiment, the bearing housing 16 includes the aforementioned high-pressure-stage bearing housing 16B and the low-pressure-stage bearing housing 16A, which houses the low-pressure-stage grease-packed bearing 15A.

[0104] According to the above structure, the multi-stage electric centrifugal compressor 1 includes a low-pressure stage grease-sealed bearing 15A pre-filled with grease. In this case, since grease does not need to be supplied to the low-pressure stage grease-sealed bearing 15A, the structure of the components surrounding the low-pressure stage grease-sealed bearing 15A (for example, the low-pressure stage bearing housing 16A) can be simplified, thereby achieving a smaller and lighter multi-stage electric centrifugal compressor 1.

[0105] In order to suppress the thermal degradation of the high-pressure-stage side grease-sealed bearing 15B and the low-pressure-stage side grease-sealed bearing 15A, it is preferable to provide a mechanism for suppressing the transfer of heat from the back sides of the high-pressure-stage impeller 5 and the low-pressure-stage impeller 4 to these bearings 15A, 15B.

[0106] (Cooling passages for the bearing housing)

[0107] In several embodiments, such as Figure 5 As shown, the above-mentioned bearing housing 16 (high-pressure stage side bearing housing 16B) has a cooling passage 91 formed between the high-pressure stage side grease-sealed bearing 15B and the high-pressure stage impeller 5 in the axial direction X of the rotating shaft 3. In the illustrated embodiment, the cooling passage 91 is located on the outer peripheral side of the high-pressure stage side sleeve 18B. The cooling passage 91 extends along the circumference of the rotating shaft 3. The cooling passage 91 can be formed into a ring shape or an arc shape in a cross section along a direction perpendicular to the axis CA. It should be noted that in the illustrated embodiment, the cooling passage 91 is filled with gas (such as air), but the cooling passage 91 can also be filled with cooling water. The multi-stage electric centrifugal compressor 1 may also have a cooling water supply pipeline not shown in the figure for supplying cooling water to the cooling passage 91.

[0108] According to the above configuration, the bearing housing 16 (high-stage bearing housing 16B) includes a cooling passage 91 formed between the high-stage grease-packed bearing 15B and the high-stage impeller 5 in the axial direction X of the rotating shaft 3. Therefore, the cooling passage 91 can suppress the transfer of heat from the back surface 57 of the high-stage impeller 5 to the high-stage grease-packed bearing 15B. This prevents thermal degradation of the high-stage grease-packed bearing 15B, thereby improving the life and durability of the high-stage grease-packed bearing 15B.

[0109] It should be noted that the inner end of the cooling passage 91 in the radial direction Y is preferably located near the inner surface 165 of the high-pressure stage side bearing housing 16B. This can effectively prevent the heat from the gas existing in the space 24 facing the high-pressure stage impeller 5 and the back surface 57 of the high-pressure stage impeller 5 from passing through the high-pressure stage side sleeve 18B and the outer peripheral surface 181 (see FIG. Figure 9 ) and the gap 25 between the inner surface 165 (refer to Figure 9 ) is transmitted to the high-pressure stage side bearing housing 16B.

[0110] The above cooling passage can also be formed on the low pressure stage side. Figure 5 As shown, the above-mentioned bearing housing 16 (low-pressure side bearing housing 16A) has a cooling passage 92 formed between the low-pressure side grease-sealed bearing 15A and the low-pressure stage impeller 4 in the axial direction X of the rotating shaft 3. In the illustrated embodiment, the cooling passage 92 is located on the outer peripheral side of the low-pressure side grease-sealed bearing 15A. The cooling passage 92 extends along the circumference of the rotating shaft 3. The cooling passage 92 can be formed into a ring shape or an arc shape in a cross section along a direction perpendicular to the axis CA. It should be noted that in the illustrated embodiment, the cooling passage 92 is filled with gas (for example, air), but the cooling passage 92 can also be filled with cooling water. The multi-stage electric centrifugal compressor 1 may also have a cooling water supply pipeline, not shown, for supplying cooling water to the cooling passage 92.

[0111] According to the above configuration, the bearing housing 16 (low-pressure-stage bearing housing 16A) includes a cooling passage 92 formed between the low-pressure-stage grease-packed bearing 15A and the low-pressure-stage impeller 4 in the axial direction X of the rotating shaft 3. Therefore, the cooling passage 92 can suppress the transfer of heat from the back surface 57 of the low-pressure-stage impeller 4 to the high-pressure-stage grease-packed bearing 15A. This prevents thermal degradation of the low-pressure-stage grease-packed bearing 15A, thereby improving the life and durability of the low-pressure-stage grease-packed bearing 15A.

[0112] (Cooling passages for the high-pressure stage casing)

[0113] In several embodiments, such as Figure 7 As shown, the high-pressure stage casing 7 includes a high-pressure stage side cooling passage 70 formed on the outer circumferential side of the high-pressure stage impeller 5, closer to the swirl axis 3. A heat medium (e.g., coolant) at a lower temperature than the high-pressure stage casing 7 flows through the high-pressure stage side cooling passage 70, and heat is transferred from the compressed gas supplied to the high-pressure stage impeller 5 within the high-pressure stage casing 7 to the high-pressure stage side cooling passage 70 via the high-pressure stage casing 7. In the illustrated embodiment, the high-pressure stage side cooling passage 70 is formed between the radially inner surface forming the vortex flow path 64 and the shroud surface 65.

[0114] exist Figure 7In the illustrated embodiment, the high-pressure stage cooling passage 70 is formed in an annular shape extending along the circumference of the rotating shaft 3. It should be noted that the high-pressure stage cooling passage 70 may also be formed in an arc shape extending along the circumference of the rotating shaft 3. The high-pressure stage housing 7 further includes an inlet passage 701 for allowing coolant to flow into the high-pressure stage cooling passage 70 and an outlet passage 702 for discharging coolant from the high-pressure stage cooling passage 70. The inlet passage 701 connects a coolant inlet port 703 formed on the outer surface of the high-pressure stage housing 7 and the high-pressure stage cooling passage 70 so that coolant can flow. The outlet passage 702 connects a coolant outlet port 704 formed on the outer surface of the high-pressure stage housing 7 and the high-pressure stage cooling passage 70 so that coolant can flow.

[0115] In addition, Figure 7 In the illustrated embodiment, the multi-stage electric centrifugal compressor 1 includes a coolant supply line 705 for delivering coolant to the high-pressure stage cooling passage 70; a coolant storage device (coolant storage tank) 706 configured to store coolant; and a coolant circulation pump 707 configured to deliver coolant to the downstream side of the coolant supply line 705. The coolant storage device 706 is positioned upstream of the coolant circulation pump 707 in the coolant supply line 705. The downstream end of the coolant supply line 705 is connected to the coolant inlet 703 of the inlet passage 701. The coolant is delivered to the downstream side of the coolant supply line 705 by the coolant circulation pump 707, and the coolant flows into the high-pressure stage cooling passage 70 through the inlet passage 701. The coolant flowing into the high-pressure stage side cooling passage 70 flows through the high-pressure stage side cooling passage 70 along the circumferential direction of the rotating shaft 3, then passes through the outlet passage 702 and is discharged from the coolant outlet 704 to the outside of the high-pressure stage housing 7. It should be noted that the coolant discharged from the coolant outlet 704 to the outside of the high-pressure stage housing 7 may be cooled by a heat exchanger or the like, and then flows again into the high-pressure stage side cooling passage 70 through the inlet passage 701.

[0116] According to the above structure, the compressed gas supplied to the high-pressure stage impeller 5 in the high-pressure stage casing 7 can be cooled through the high-pressure stage side cooling passage 70, and the temperature increase of the compressed gas after passing through the high-pressure stage impeller 5 can be suppressed. As a result, the compression ratio in the high-pressure stage of the multi-stage electric centrifugal compressor 1 can be improved. In addition, by suppressing the temperature increase of the compressed gas after passing through the high-pressure stage impeller 5, the temperature increase of the gas existing in the space 24 facing the back side 57 of the high-pressure stage impeller 5 can be suppressed, thereby reducing the input heat from the back side 57 of the high-pressure stage impeller 5 to the bearing 15 (for example, the high-pressure stage side grease-sealed bearing 15B). As a result, the deterioration of the bearing 15 due to heat can be suppressed, thereby improving the life and durability of the bearing 15.

[0117] (Pressure relief vent)

[0118] In several embodiments, such as Figure 8 As shown, the high-pressure-stage bearing housing 16B (bearing housing 16) has a first pressure relief hole 93. The first pressure relief hole 93 includes a first inner opening 931 formed on the inner surface 165 of the high-pressure-stage bearing housing 16B, which faces the outer circumferential surface of the rotating body 11 including the rotating shaft 3, and a first outer opening 932 formed on the outer surface 168 of the high-pressure-stage bearing housing 16B. The first inner opening 931 is formed between the high-pressure-stage grease seal bearing 15B and the high-pressure-stage impeller 5 in the axial direction X of the rotating shaft 3.

[0119] like Figure 9 As shown, a space 24 is formed between the back surface 57 of the high-pressure-stage impeller 5 and the high-pressure-stage side surface 167 of the high-pressure-stage-side bearing housing 16B that faces the back surface 57. Furthermore, a gap 25 is formed between the outer peripheral surface 181 of the high-pressure-stage-side sleeve 18B and the inner surface 165 of the high-pressure-stage-side bearing housing 16B that faces the outer peripheral surface 181. This gap 25 communicates with the space 24.

[0120] In the illustrated embodiment, Figure 9 As shown, the outer peripheral surface 181 of the high-pressure stage side sleeve 18B has a first annular groove 182 for fitting a first sealing member (e.g., an annular seal ring) 22 and a second annular groove 183 for fitting a second sealing member (e.g., an annular seal ring) 23. The second annular groove 183 is formed on the low-pressure stage side XL ( axial direction X) in comparison with the first annular groove 182. Figure 9 The outer surfaces of the first and second sealing members 22 and 23 abut against the outer circumferential surface 181 of the high-pressure stage sleeve 18B, dividing the gap 25 into multiple sections. Furthermore, in the illustrated embodiment, the first inner opening 931 is located between the first and second annular grooves 182 and 183 in the axial direction X.

[0121] As the high-pressure stage impeller 5 rotates, the temperature and pressure of the gas in the space 24 increase. If the gas in the space 24 flows through the gap 25 and into the high-pressure stage grease-packed bearing 15B, the high-pressure stage grease-packed bearing 15B may be degraded by the heat.

[0122] According to the above structure, the high-pressure-stage bearing housing 16B (bearing housing 16) has a first pressure relief hole 93 having a first inner opening 931 formed on the inner surface 165 and a first outer opening 932 formed on the outer surface 168. The first inner opening 931 is formed between the high-pressure-stage grease seal bearing 15B and the high-pressure-stage impeller 5 in the axial direction X of the rotating shaft 3. In this manner, pressure leakage from the space 24 facing the back surface 57 of the high-pressure-stage impeller 5 can be released to the exterior of the high-pressure-stage bearing housing 16B (bearing housing 16) through the first pressure relief hole 93. In the illustrated example, high-temperature, high-pressure gas leaking from the space 24 into the gap 25 defined by the first and second seal members 22 and 23 is guided through the first inner opening 931 to the first pressure relief hole 93 by utilizing the pressure difference with the air outside the high-pressure-stage bearing housing 16B. The gas is then discharged to the exterior of the high-pressure-stage bearing housing 16B through the first outer opening 932. In this case, it is possible to suppress pressure leakage from the space 24 facing the back surface 57 of the high-pressure stage impeller 5 to the high-pressure stage side grease packing bearing 15B. This can suppress thermal degradation of the high-pressure stage side grease packing bearing 15B, thereby improving the life and durability of the high-pressure stage side grease packing bearing 15B.

[0123] The pressure relief hole mentioned above can also be formed on the low pressure side. Figure 8 As shown, the low-pressure-stage bearing housing 16A (bearing housing 16) has a second pressure relief hole 94. The second pressure relief hole 94 includes a second inner opening 941 formed on the inner surface 163 of the high-pressure-stage bearing housing 16B, which faces the outer circumferential surface of the rotating body 11 including the rotating shaft 3 (in the illustrated example, the outer circumferential surface 184 of the low-pressure-stage sleeve 18A); and a second outer opening 942 formed on the outer surface 169 of the low-pressure-stage bearing housing 16A. The second inner opening 941 is formed between the low-pressure-stage grease seal bearing 15A and the high-pressure-stage impeller 5 in the axial direction X of the rotating shaft 3. Similar to the first inner opening 931, the second inner opening 941 can also be formed in the axial direction X between two sealing members attached to the low-pressure-stage sleeve 18A.

[0124] According to the above configuration, the low-pressure-stage bearing housing 16A (bearing housing 16) includes a second pressure relief hole 94 having a second inner opening 941 formed on the inner surface 163 and a second outer opening 942 formed on the outer surface 169. The second inner opening 941 is formed between the low-pressure-stage grease-enclosed bearing 15A and the low-pressure-stage impeller 4 in the axial direction of the rotating shaft 3. In this manner, pressure leakage from the space facing the back surface 57 of the low-pressure-stage impeller 4 can be discharged to the exterior of the low-pressure-stage bearing housing 16A (bearing housing 16) through the second pressure relief hole 94. This prevents pressure leakage from the space facing the back surface of the low-pressure-stage impeller 4 from reaching the low-pressure-stage grease-enclosed bearing 15A. This prevents thermal degradation of the low-pressure-stage grease-enclosed bearing 15A, thereby improving the lifespan and durability of the low-pressure-stage grease-enclosed bearing 15A.

[0125] It should be noted that in several other embodiments, forced suction may be performed from the first pressure relief hole 93 or the second pressure relief hole 94. For example, the multi-stage electric centrifugal compressor 1 may also include a negative pressure source (not shown) and a pipe connecting at least one of the first pressure relief hole 93 or the second pressure relief hole 94 to the negative pressure source.

[0126] (Pressure application hole)

[0127] In several embodiments, such as Figure 10 As shown, the high-pressure-stage bearing housing 16B (bearing housing 16) has a first pressure application hole 95. The first pressure application hole 95 includes a third inner opening 951 formed on the inner surface 165 of the high-pressure-stage bearing housing 16B, which faces the outer circumferential surface 181 of the rotating body 11 including the rotating shaft 3, and a third outer opening 952 formed on the outer surface 168 of the high-pressure-stage bearing housing 16B. The third inner opening 951 is formed between the high-pressure-stage grease seal bearing 15B and the high-pressure-stage impeller 5 in the axial direction X of the rotating shaft 3. The multi-stage electric centrifugal compressor 1 has a pressure introduction line 26 configured to introduce pressure from a pressure source (e.g., the compressed gas supply line 21 or the surge tank 27) into the third inner opening 951.

[0128] like Figure 11 As shown, a space 24 is formed between the back surface 57 of the high-pressure-stage impeller 5 and the high-pressure-stage side surface 167 of the high-pressure-stage-side bearing housing 16B that faces the back surface 57. Furthermore, a gap 25 is formed between the outer peripheral surface 181 of the high-pressure-stage-side sleeve 18B and the inner surface 165 of the high-pressure-stage-side bearing housing 16B that faces the outer peripheral surface 181. This gap 25 communicates with the space 24.

[0129] In the illustrated embodiment, Figure 11 As shown, the outer peripheral surface 181 of the high-pressure stage side sleeve 18B has a first annular groove 182 for fitting a first sealing member (e.g., an annular seal ring) 22 and a second annular groove 183 for fitting a second sealing member (e.g., an annular seal ring) 23. The second annular groove 183 is formed on the low-pressure stage side XL ( axial direction X) closer to the first annular groove 182. Figure 11 The outer surfaces of the first and second sealing members 22 and 23 abut against the outer circumferential surface 181 of the high-pressure stage sleeve 18B, dividing the gap 25 into multiple sections. Furthermore, in the illustrated embodiment, the third inner opening 951 is located between the first and second annular grooves 182 and 183 in the axial direction X.

[0130] In the illustrated embodiment, the pressure introduction line 26 is configured to introduce pressure from the compressed gas supply line 21 and the pressure-surge tank 27 to the third outer opening 952, respectively. The gas in the pressure-surge tank 27 becomes high pressure compared to the space 24 due to the compressor 28. The pressure introduction line 26 comprises: a first pipe 261, one side of which is connected to the branch portion 211 of the compressed gas supply line 21, and the other side is connected to the third outer opening; a second pipe 262, one side of which is connected to the first pipe 261, and the other side is connected to the pressure-surge tank 27; and a switching device 263, which is configured to be able to switch the supply source of pressure to the third outer opening 952 to either the compressed gas supply line 21 or the pressure-surge tank 27. The switching device 263 may be as follows: Figure 10 The three-way valve shown as being provided at the connection between the first pipe 261 and the second pipe 262 may also be provided on the upstream side of the first pipe 261 relative to the connection with the second pipe 262, or on each of the second pipes 262 (e.g., an on-off valve). It should be noted that in other embodiments, the pressure introduction line 26 may also include a pipe having one side connected to the surge tank 27 and the other side connected to the third outer opening, configured to introduce pressure only from the surge tank 27 to the third outer opening 952. By introducing pressure from the compressed gas supply line 21 to the third outer opening 952, the capacity of the surge tank 27 can be reduced.

[0131] As described above, when the high-pressure stage impeller 5 rotates, the temperature and pressure of the gas in the space 24 increase. If the gas in the space 24 flows through the gap 25 and into the high-pressure stage grease-packed bearing 15B, the high-pressure stage grease-packed bearing 15B may be degraded by the heat.

[0132] According to the above configuration, the high-pressure-stage-side bearing housing 16B (bearing housing 16) includes a first pressure application hole 95. This first pressure application hole 93 has a third inner opening 951 formed in the inner surface 165 and a third outer opening 952 formed in the outer surface 168. The third inner opening 951 is formed between the high-pressure-stage-side grease-sealed bearing 15B and the high-pressure-stage impeller 5 in the axial direction of the rotating shaft 3. The multi-stage electric centrifugal compressor 1 includes the pressure introduction line 26. In this case, by introducing pressure from the pressure source to the third outer opening 952 via the pressure introduction line 26, the pressure within the gap 25 formed between the outer peripheral surface 181 and the bearing 165 can be made higher than the pressure within the space 24 facing the back surface 57 of the high-pressure-stage impeller 5. By making the pressure within the gap 25 higher than the pressure within the space 24, pressure leakage from the space 24 facing the back surface 57 of the high-pressure-stage impeller 5 can be suppressed. This can suppress thermal degradation of the high-pressure-stage grease-packed bearing 15B, thereby improving the life and durability of the high-pressure-stage grease-packed bearing 15B.

[0133] Furthermore, by making the pressure within gap 25 higher than the pressure within the space housing high-pressure-stage grease-sealed bearing 15B, it is possible to prevent grease sealed within high-pressure-stage grease-sealed bearing 15B from leaking through gap 25 or space 24 into the flow path through which compressed gas flows. This prevents grease from mixing with the compressed gas compressed by the multi-stage electric centrifugal compressor 1, allowing the multi-stage electric centrifugal compressor 1 to supply clean compressed gas to the fuel cell 20 and the like.

[0134] In the illustrated embodiment, Figure 10 As shown, the high-pressure-stage bearing housing 16B (bearing housing 16) has a third pressure relief hole 96. The third pressure relief hole 96 includes an inner opening 961 formed on the bearing support surface 162, closer to the high-pressure side (left side in the figure) than the high-pressure-stage grease-enclosed bearing 15B, and an outer opening 962 formed on the outer surface 168 of the high-pressure-stage bearing housing 16B. The inner opening 961 faces the space between the high-pressure-stage sleeve 18B and the high-pressure-stage grease-enclosed bearing 15B. With this structure, high-pressure gas leaking from the gap 25 defined by the first and second seal members 22 and 23 into the space between the high-pressure-stage sleeve 18B and the high-pressure-stage grease-enclosed bearing 15B is guided through the inner opening 961 to the third pressure relief hole 96 by utilizing the pressure difference with the air outside the high-pressure-stage bearing housing 16B. The gas can then be discharged to the outside of the high-pressure-stage bearing housing 16B through the outer opening 962. In this case, it is possible to suppress the pressure leakage from the gap 25 from flowing into the high-pressure stage-side grease-packed bearing 15B.

[0135] The pressure application hole mentioned above can also be formed on the low pressure side. Figure 10 As shown, the low-pressure-stage bearing housing 16A (bearing housing 16) has a second pressure application hole 97. This second pressure application hole 97 includes an inner opening 971 formed on the inner surface 163 of the high-pressure-stage bearing housing 16B, which faces the outer circumferential surface of the rotating body 11 including the rotating shaft 3 (in the illustrated example, the outer circumferential surface 184 of the low-pressure-stage sleeve 18A), and an outer opening 972 formed on the outer surface 169 of the low-pressure-stage bearing housing 16A. The inner opening 971 is formed between the low-pressure-stage grease seal bearing 15A and the low-pressure-stage impeller 4 in the axial direction X of the rotating shaft 3. Similar to the third inner opening 951, the inner opening 971 can also be formed in the axial direction X between two sealing members attached to the low-pressure-stage sleeve 18A.

[0136] In addition, the multi-stage electric centrifugal compressor 1 also has a pressure introduction line 29, which is configured to introduce pressure from a pressure source (for example, a compressed gas supply line 21 or a pressure-surge tank 27) to the outer opening 972. In the illustrated embodiment, the pressure introduction line 29 shares some equipment (piping or valves) with the above-mentioned pressure introduction line 26. That is, the pressure introduction line 29 has: a third pipe 291, one side of which is connected to the branch portion 264 of the first pipe 261, which is located between the connection portion with the second pipe 262 and the third outer opening 952, and the other side is connected to the outer opening 972; and a pressure reducing valve 292, which is arranged on the third left pipe 291. It should be noted that in several other embodiments, the pressure introduction line 29 may not share equipment with the pressure introduction line 26.

[0137] According to the above configuration, the low-pressure-stage bearing housing 16A (bearing housing 16) includes a second pressure application hole 97. This second pressure application hole 93 has an inner opening 971 formed in the inner surface 163 and an outer opening 972 formed in the outer surface 169. The inner opening 971 is formed between the low-pressure-stage grease-enclosed bearing 15A and the low-pressure-stage impeller 4 in the axial direction of the rotating shaft 3. The multi-stage electric centrifugal compressor 1 includes the pressure introduction line 29. In this case, by introducing pressure from the pressure source to the outer opening 972 via the pressure introduction line 29, the pressure in the gap facing the inner surface 163 can be made higher than the pressure in the space facing the back of the low-pressure-stage impeller. This suppresses pressure leakage from the space facing the back of the low-pressure-stage impeller, thereby improving the life and durability of the high-pressure-stage grease-enclosed bearing 15B.

[0138] Furthermore, by making the pressure within the gap facing the inner surface 163 higher than the pressure within the space housing the low-pressure-stage grease-sealed bearing 15A, it is possible to suppress leakage of the grease sealed within the low-pressure-stage grease-sealed bearing 15A into the flow path through which the compressed gas flows. This suppresses the mixing of grease into the compressed gas compressed by the multi-stage electric centrifugal compressor 1, thereby enabling the multi-stage electric centrifugal compressor 1 to supply clean compressed gas to the fuel cell 20 and the like.

[0139] In the illustrated embodiment, Figure 11 As shown, the low-pressure-stage bearing housing 16A (bearing housing 16) further includes a fourth pressure relief hole 98. This fourth pressure relief hole 98 has an inner opening 981 formed on the lower-pressure side (right side in the figure) of the bearing support surface 161 relative to the low-pressure-stage grease-packed bearing 15A, and an outer opening 982 formed on the outer surface 169 of the low-pressure-stage bearing housing 16A. The inner opening 981 faces the space formed between the low-pressure-stage sleeve 18A and the low-pressure-stage grease-packed bearing 15A. With this configuration, high-pressure gas leaking from the gap facing inner surface 163 into the space formed between low-pressure sleeve 18A and low-pressure grease-packed bearing 15A is guided through inner opening 981 to fourth pressure release hole 98 by utilizing the pressure difference with the air outside low-pressure-stage bearing housing 16A. The gas is then discharged to the outside of low-pressure-stage bearing housing 16A through outer opening 982. This prevents pressure leakage from the gap facing inner surface 163 from reaching low-pressure-stage grease-packed bearing 15A.

[0140] (Air cooling mechanism for electric motors)

[0141] Figure 12 as well as Figure 13 Each of the diagrams is a schematic structural diagram schematically showing the structure of a multi-stage electric centrifugal compressor according to one embodiment of the present disclosure. Figure 12 as well as Figure 13 , a cross section (half cross section) on one side relative to the axis CA of the rotating shaft 3 of the multi-stage electric centrifugal compressor 1 is schematically shown.

[0142] In several embodiments, such as Figure 12 、 Figure 13As shown, the stator housing 17 has an inner surface (inner circumferential surface) 171 that forms a motor housing 170 that accommodates the electric motor 10 (motor stator 12 and rotor assembly 13). The bearing housing 16 has an air inlet 30 for supplying air to the motor housing 170 and an air outlet 31 for discharging the air from the motor housing 170 to the outside of the bearing housing 16. The multi-stage electric centrifugal compressor 1 further includes an air inlet conduit 32 configured to supply air to the air inlet conduit 30 or to draw air from the air outlet conduit 31.

[0143] The air inlet hole 30 has a fourth inner opening 34 formed on the inner surface 33 of the bearing housing 16 facing the motor housing 170, and a fourth outer opening 35 formed on the outer surface 168 of the bearing housing 16. The air outlet hole 31 has a fifth inner opening 37 formed on the inner surface 36 of the bearing housing 16 facing the motor housing 170, and a fifth outer opening 38 formed on the outer surface 169 of the bearing housing 16. The inner surface 36 having the fifth inner opening 37 is located on the opposite side of the inner surface 33 having the fourth inner opening 34, across the electric motor 10, in the axial direction X of the rotating shaft 3. The fourth inner opening 34 is formed on the side closer to the electric motor 10 in the axial direction X of the rotating shaft 3 (on the high-pressure side XH in the illustrated example), while the fifth inner opening 37 is formed on the other side of the electric motor 10 in the axial direction X of the rotating shaft 3 (on the low-pressure side XL in the illustrated example). In the illustrated example, both the inner surface 33 and the inner surface 36 extend radially.

[0144] In the illustrated embodiment, the air inlet hole 30 is formed in the high-pressure stage side bearing housing 16B, and the air outlet hole 31 is formed in the low-pressure stage side bearing housing 16A. The motor stator 12 supported by the stator housing 17 in the motor housing 170 has a gap 170A with the rotor assembly 13. The above-mentioned motor housing 170 includes the gap 170A. In addition, the multi-stage electric centrifugal compressor 1 includes: a gas compressor 321 (for example, an electric fan) configured to blow air from the inlet side to the outlet side; and a power supply source 322 configured to supply power to the gas compressor 321. The gas compressor 321 rotates the fan, for example, by a fan motor driven by electricity supplied from the power supply source 322, thereby blowing air from the inlet side to the outlet side.

[0145] exist Figure 12 In the embodiment shown, the air introduction pipe 32 (32A) is configured to deliver air to the air introduction hole 30. Figure 12As shown, the air introduction pipe 32 ( 32A) includes a gas passage 323 through which air for cooling the motor housing portion 170 flows. One side of the gas passage 323 is connected to the outlet side of the gas compressor 321 , and the other side is connected to the fourth outer opening 35 .

[0146] In this case, by driving the gas compressor 321, air introduced from the inlet side of the gas compressor 321 is guided from one side to the other in the gas passage 323, and then delivered to the motor housing 170 through the air inlet hole 30. The air delivered to the motor housing 170 flows from the high-pressure stage side XH to the low-pressure stage side XL in the motor housing 170, passes through the aforementioned gap 170A, and is then discharged to the outside of the bearing housing 16 through the air discharge hole 31. It should be noted that the air discharged to the outside of the bearing housing 16 through the fifth outer opening 38 of the air discharge hole 31 may also be released to the atmosphere.

[0147] exist Figure 13 In the embodiment shown, the air introduction line 32 (32B) is configured to draw air from the air discharge hole 31. Figure 13 As shown, the air introduction pipe 32 ( 32B) includes a gas passage 324 through which air for cooling the motor housing 170 flows. One side of the gas passage 324 is connected to the inlet side of the gas compressor 321 , and the other side is connected to the fifth outer opening 38 .

[0148] In this case, by driving the gas compressor 321, air outside the bearing housing 16 is sucked into the air inlet hole 30 through the fourth outer opening 35. The air sucked into the air inlet hole 30 is transported to the motor housing 170 by the suction force of the gas compressor 321. In the motor housing 170, the air flows from the high-pressure stage side XH to the low-pressure stage side XL and passes through the gap 170A. Then, the air is discharged to the outside of the bearing housing 16 through the air discharge hole 31.

[0149] According to the above structure, air is forcibly introduced into the motor housing 170 from the fourth outer opening 35 through the air inlet hole 30 via the air inlet line 32. Furthermore, air is forcibly discharged from the motor housing 170 through the air outlet hole 31 to the outside of the bearing housing 16 via the air inlet line 32. The fifth inner opening 37 of the air outlet hole 31 is located on the opposite side of the rotating shaft 3 in the axial direction of the electric motor 10 relative to the fourth inner opening 34 of the air inlet hole 30. This allows air to be forcibly blown from one side of the motor housing 170 to the other side. The electric motor 10 housed in the motor housing 170 dissipates heat through heat exchange with the air, thereby being cooled (air-cooled). By using air to cool the rotor assembly 13 or motor coil 121 of the electric motor 10, which serves as a heat source, the temperature rise of the bearing 15 (for example, the high-pressure stage grease-filled bearing 15B) can be suppressed. This suppresses thermal degradation of the bearing 15, thereby improving the life and durability of the bearing 15.

[0150] It should be noted that in the above-described embodiment, the air inlet hole 30 is formed in the high-pressure-side bearing housing 16B, and the air outlet hole 31 is formed in the low-pressure-side bearing housing 16A. However, the air inlet hole 30 may be formed in the low-pressure-side bearing housing 16A, and the air outlet hole 31 may be formed in the high-pressure-side bearing housing 16B. The high-pressure-side bearing housing 16B is subject to a greater thermal influence than the low-pressure-side bearing housing 16A, so effective cooling of the high-pressure-side XH is necessary. Therefore, it is preferable to form the air inlet hole 30 in the high-pressure-side bearing housing 16B so that the upstream side of the air flow direction for cooling the electric motor 10 is on the high-pressure-side XH.

[0151] The present disclosure is not limited to the above-described embodiment, and includes modified embodiments of the above-described embodiment and appropriate combinations of these embodiments.

[0152] The contents described in the above-mentioned several embodiments can be understood as follows, for example.

[0153] 1) A multi-stage electric centrifugal compressor (1) according to at least one embodiment of the present disclosure is a multi-stage electric centrifugal compressor (1) configured to drive impellers (a low-pressure stage impeller 4 and a high-pressure stage impeller 5) provided at both ends of a rotating shaft (3) by an electric motor (10), and the multi-stage electric centrifugal compressor (1) comprises:

[0154] The rotating shaft (3);

[0155] a low-pressure stage impeller (4), which is arranged on one side of the rotating shaft (3);

[0156] a high-pressure stage impeller (5), which is arranged on the other side of the rotating shaft (3);

[0157] a high-pressure stage casing (7) accommodating the high-pressure stage impeller (5);

[0158] a connecting pipe (8) for supplying the compressed gas compressed by the low-pressure stage impeller (4) to the high-pressure stage casing (7);

[0159] The high-pressure stage housing (7) has a high-pressure stage inlet opening (71), which opens in a direction intersecting the axis (CA) relative to the rotating shaft (3).

[0160] The connecting pipe (8) includes a high-pressure stage side connecting portion (81) connected to the high-pressure stage inlet (71).

[0161] According to the structure 1) above, in the high-pressure stage casing (7), the high-pressure stage inlet opening (71) opens in a direction intersecting the axis (CA) of the rotating shaft (3), and the high-pressure stage side connection portion (81) of the connecting pipe (8) is connected to the high-pressure stage inlet opening (71). Therefore, the compressed gas compressed by the low-pressure stage impeller (4) is supplied from the outer peripheral side of the high-pressure stage casing (7) to the inside of the high-pressure stage casing (7) through the connecting pipe (8). In this case, the length of the connecting pipe (8) and the high-pressure stage casing (7) in the axial direction can be shortened compared to the case where the compressed gas is introduced into the high-pressure stage casing (7) along the axial direction of the rotating shaft (3). As a result, the length of the multi-stage electric centrifugal compressor (1) in the axial direction can be shortened, thereby achieving miniaturization and weight reduction of the multi-stage electric centrifugal compressor (1).

[0162] 2) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in 1) above,

[0163] The flow path cross section of the high-pressure stage side connection portion (81) has a long side direction (LD) along a direction orthogonal to the axis (CA) of the rotating shaft (3), and includes convex curved portions (811, 812) formed on both end sides of the long side direction LD.

[0164] According to the structure of 2) above, the flow path cross section of the high-pressure stage side connection part (81) has a long side direction (LD) along a direction perpendicular to the axis (CA) of the rotating shaft (3), and includes convex curved parts (811, 812) formed on both ends of the long side direction (LD). In this case, since the flow path cross section of the high-pressure stage side connection part (81) is an elliptical shape extending along the long side direction (LD), it is possible to suppress the high-pressure stage side connection part (81) from becoming larger in the axial direction of the rotating shaft (3), and increase the flow path area of ​​the high-pressure stage side connection part (81). By increasing the flow path area of ​​the high-pressure stage side connection part (81), a required amount of compressed gas can be supplied to the high-pressure stage housing (7). In addition, since the flow path cross section of the high-pressure stage side connection part (81) is an oval shape, it is possible to suppress the pressure loss of the compressed gas flowing in the high-pressure stage side connection part (81).

[0165] 3) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in 2) above,

[0166] The flow path cross section of the high-pressure stage side connection portion (81) has a short side direction (SD) along the axis (CA) of the rotating shaft (3).

[0167] According to the structure of 3) above, by forming the flow path cross section of the high-pressure stage side connection part (81) into a shape having a short side direction (SD) along the axis (CA), the length of the high-pressure stage side connection part (81) in the axial direction of the rotating shaft (3) can be shortened, thereby achieving miniaturization and lightweighting of the multi-stage electric centrifugal compressor (1).

[0168] 4) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in 2) or 3) above,

[0169] The flow path cross section of the high-pressure stage side connection portion (81) is formed so that the length in the longitudinal direction increases toward the high-pressure stage inlet opening (71).

[0170] According to the structure of 4), by forming the flow path cross section of the high-pressure stage side connection portion (81) so that the length in the longitudinal direction increases toward the high-pressure stage inlet opening (71), the compressed gas flowing along the inner wall surface (810) of the high-pressure stage side connection portion (81) can be made to flow directly along the inner wall surface (77) defining the supply flow path (73) of the high-pressure stage housing (7). By making the compressed gas flow along the inner wall surface (77) of the high-pressure stage housing (7), it is possible to suppress the compressed gas from being separated from the inner wall surface (77), thereby reducing the pressure loss of the compressed gas in the supply flow path (73) of the high-pressure stage housing (7).

[0171] 5) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in 4) above,

[0172] The flow path cross section of the high-pressure stage side connection portion (81) is formed so that the maximum curvature of the convex curved portion (811, 812) increases toward the high-pressure stage inlet opening (71) side.

[0173] According to the above-mentioned structure 5), by forming the flow path cross section of the high-pressure stage side connection part (81) so that the maximum curvature of the convex curved part (811, 812) increases toward the high-pressure stage inlet opening (71), the compressed gas flowing in the high-pressure stage side connection part (81) can be smoothly guided to the high-pressure stage inlet opening (71). As a result, the pressure loss of the compressed gas in the connection part between the high-pressure stage side connection part (81) and the high-pressure stage inlet opening (71) can be reduced.

[0174] 6) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 2) to 5) above,

[0175] A low-pressure stage casing (6) is provided, which accommodates the low-pressure stage impeller (4),

[0176] The low-pressure stage housing (6) has a low-pressure stage inlet opening (62) which opens in a direction intersecting the axis (CA) relative to the rotation shaft (3).

[0177] The connecting pipe (8) includes:

[0178] a low-pressure stage side connection portion (82), connected to the low-pressure stage outlet opening (62);

[0179] an intermediate portion (83) extending along the axis (CA) of the rotation shaft (3);

[0180] a low-pressure stage side bent portion (84) having a bent shape connecting the low-pressure stage side connecting portion (82) and the middle portion (83);

[0181] a high-pressure stage side bent portion (85) having a bent shape connecting the high-pressure stage side connecting portion (81) and the middle portion (83);

[0182] At least the flow path cross section of the low-pressure stage side connection portion (82) is formed in a circular shape.

[0183] According to the structure of 6) above, by making the flow path cross section of at least the low-pressure side connection portion (82) in the connecting pipe (8) circular, the pressure loss of the compressed gas with a swirling component flowing in the connecting pipe (8) can be reduced.

[0184] 7) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 2) to 6) above,

[0185] A cooling device (86) is further provided, which is configured to perform heat exchange between the compressed gas in the connecting pipe 8 and a cooling liquid for cooling the compressed gas.

[0186] According to the structure of 7) above, the compressed gas flowing in the connecting pipe (8) is cooled by heat exchange between the compressed gas and the coolant in the cooling device (86). By lowering the temperature of the compressed gas delivered to the high-pressure stage impeller (5), it is possible to suppress the temperature increase of the compressed gas after passing through the high-pressure stage impeller (5). As a result, it is possible to achieve an improvement in the compression ratio in the high-pressure stage of the multi-stage electric centrifugal compressor (1). In addition, by suppressing the temperature increase of the compressed gas after passing through the high-pressure stage impeller (5), it is possible to suppress the temperature increase of the gas existing in the space (24) facing the back side (57) of the high-pressure stage impeller (5), thereby reducing the amount of heat input from the back side (57) of the high-pressure stage impeller (5) to the bearing (15, especially the high-pressure stage side grease-sealed bearing 15B). As a result, it is possible to suppress the deterioration of the bearing (15) due to heat, thereby improving the life and durability of the bearing (15).

[0187] 8) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 1) to 7) above,

[0188] The high-pressure stage housing (7) comprises:

[0189] an inner wall surface (77) defining a supply flow path (73) for guiding the compressed gas supplied from the high-pressure stage inlet opening (71) to the high-pressure stage impeller (5), the inner wall surface (77) comprising: an inner end wall surface (771) defining a side of the supply flow path (73) opposite to the high-pressure stage impeller (5); and an inner peripheral wall surface (772) defining an outer peripheral side of the supply flow path;

[0190] A guide protrusion (78) protrudes from the inner end wall surface (771) toward the high-pressure stage impeller (5).

[0191] According to the structure of the above-mentioned 8), the compressed gas flowing in the supply flow path (73) of the high-pressure stage casing (7) can be guided to the high-pressure stage impeller (5) by the guide protrusion (78) protruding from the inner end wall surface (771) toward the high-pressure stage impeller (5). In this case, the compressed gas can be introduced into the high-pressure stage impeller (5) in the axial direction through the guide protrusion (78), so that the efficiency of the multi-stage electric centrifugal compressor (1) can be improved compared with the case where the compressed gas is introduced into the high-pressure stage impeller (5) from the radially outer side.

[0192] 9) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in 8) above,

[0193] The inner peripheral wall surface (772) includes an inlet-side inner peripheral wall surface (773) on which the high-pressure stage inlet opening (71) is formed, and an opposite-side inner peripheral wall surface (774) located on the opposite side to the high-pressure stage inlet opening (71).

[0194] The high-pressure stage casing (7) includes a swirl prevention plate (79) protruding from the opposite inner peripheral wall surface (774).

[0195] According to the structure of the above-mentioned 9), the swirl prevention plate (79) can suppress the collision of compressed gas flowing in one direction in the circumferential direction of the rotating shaft (3) in the supply flow path (73) of the high-pressure stage casing (7) with compressed gas flowing in the supply flow path (73) in the direction opposite to the above-mentioned one direction in the circumferential direction. In addition, the swirl prevention plate (79) guides the compressed gas flowing along the opposite inner peripheral wall surface (774) to the radial inner side where the high-pressure stage impeller (5) is located, thereby smoothly guiding the compressed gas flowing in from the high-pressure stage inlet opening (71) to the high-pressure stage impeller (5). As a result, the pressure loss of the compressed gas in the supply flow path (73) of the high-pressure stage casing (7) can be reduced.

[0196] 10) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in 9) above,

[0197] The front end (791) of the swirl prevention plate (79) is located on the outer peripheral side of the rotating shaft (3) compared to the tip (56) of the leading edge (55) of the high-pressure stage impeller (5).

[0198] Assuming that the front end (791) of the anti-swirl plate (79) is located on the inner circumference side of the rotating shaft (3) compared to the tip (56) of the leading edge (55) of the high-pressure stage impeller (5), the velocity component of the compressed gas guided by the anti-swirl plate (79) and introduced into the high-pressure stage impeller (5) toward the radial inner side becomes larger, and there is a possibility that the compression efficiency in the high-pressure stage impeller (5) is reduced. According to the structure of the above 10), the front end (791) of the anti-swirl plate (79) is located on the outer circumference side of the rotating shaft (3) compared to the tip (56) of the leading edge (55) of the high-pressure stage impeller (5), so that the velocity component of the compressed gas guided by the anti-swirl plate (79) and introduced into the high-pressure stage impeller (5) toward the radial inner side can be reduced. As a result, the reduction in the compression efficiency in the high-pressure stage impeller (5) can be suppressed.

[0199] 11) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 1) to 10) above comprises:

[0200] at least one bearing (15) which rotatably supports the rotating shaft (3) and is disposed between the high-pressure stage impeller (5) and the low-pressure stage impeller (4);

[0201] a bearing housing (16) housing the at least one bearing (15);

[0202] The at least one bearing (15) includes a high-pressure stage side grease-sealed bearing (15B) disposed between the high-pressure stage impeller (5) and the electric motor (10),

[0203] The bearing housing (16) has a cooling passage (91) formed between the high-pressure stage side grease-sealed bearing (15B) and the high-pressure stage impeller (5) in the axial direction of the rotating shaft (3).

[0204] According to the structure of 11) above, the multi-stage electric centrifugal compressor (1) includes a high-pressure stage side grease-sealed bearing (15B) in which grease is pre-sealed. In this case, since it is not necessary to supply grease to the high-pressure stage side grease-sealed bearing (15B), the structure of components surrounding the high-pressure stage side grease-sealed bearing (15B) (for example, the high-pressure stage side bearing housing 16B) can be simplified, thereby achieving miniaturization and weight reduction of the multi-stage electric centrifugal compressor (1).

[0205] Furthermore, according to the structure of 11) above, the bearing housing (16) has a cooling passage (91) formed in the axial direction of the rotating shaft (3) between the high-pressure stage side grease-sealed bearing (15B) and the high-pressure stage impeller (5). Therefore, the cooling passage (91) can suppress the transfer of heat from the back surface (57) of the high-pressure stage impeller (5) to the high-pressure stage side grease-sealed bearing (15B). As a result, the degradation of the high-pressure stage side grease-sealed bearing (15B) due to heat can be suppressed, thereby improving the life and durability of the high-pressure stage side grease-sealed bearing (15B).

[0206] 12) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 1) to 11) above,

[0207] The high-pressure stage casing (7) has a high-pressure stage side cooling passage (70) formed on the outer peripheral side of the rotating shaft (3) relative to the high-pressure stage impeller (5).

[0208] According to the structure of 12) above, the compressed gas supplied to the high-pressure stage impeller (5) in the high-pressure stage casing (7) can be cooled by the high-pressure stage side cooling passage (70), and the temperature increase of the compressed gas after passing through the high-pressure stage impeller (5) can be suppressed. As a result, the compression ratio in the high-pressure stage of the multi-stage electric centrifugal compressor (1) can be improved. In addition, by suppressing the temperature increase of the compressed gas after passing through the high-pressure stage impeller (5), the temperature increase of the gas in the space (24) facing the back side (57) of the high-pressure stage impeller (5) can be suppressed, thereby reducing the heat input from the back side (57) of the high-pressure stage impeller (5) to the bearing (15, such as the high-pressure stage side grease-sealed bearing 15B). As a result, the deterioration of the bearing (15) due to heat can be suppressed, thereby improving the life and durability of the bearing (15).

[0209] 13) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 1) to 12) above comprises:

[0210] at least one bearing (15) rotatably supporting the rotating shaft (3) and disposed between the high-pressure stage impeller (5) and the low-pressure stage impeller (4);

[0211] a bearing housing (16) housing the at least one bearing (15);

[0212] The at least one bearing (15) includes a high-pressure stage side grease-sealed bearing (15B) disposed between the high-pressure stage impeller (5) and the electric motor (10),

[0213] The bearing housing (16) has a first pressure relief hole (93), which has: a first inner opening (931) formed on the inner surface (165) of the bearing housing (16) opposite to the outer peripheral surface (181) of the rotating body (11) including the rotating shaft (3), and formed between the high-pressure stage side grease sealing bearing (15B) and the high-pressure stage impeller (5) in the axial direction of the rotating shaft (3); and a first outer opening (932) formed on the outer surface (168) of the bearing housing (16).

[0214] According to the structure of 13) above, the bearing housing (16) has a first pressure relief hole (93) having a first inner opening (931) formed on the inner surface (165) and a first outer opening (932) formed on the outer surface (168). The first inner opening (931) is formed between the high-pressure stage side grease seal bearing (15B) and the high-pressure stage impeller (5) in the axial direction of the rotating shaft (3). In this case, it is possible to suppress pressure leakage from the space (24) on the back side (57) facing the high-pressure stage impeller (5) to the high-pressure stage side grease seal bearing (15B). As a result, it is possible to suppress deterioration of the high-pressure stage side grease seal bearing (15B) due to heat, thereby improving the life and durability of the high-pressure stage side grease seal bearing (15B).

[0215] 14) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in 13) above,

[0216] The at least one bearing (15) further includes a low-pressure stage side grease-sealed bearing (15A) disposed between the low-pressure stage impeller (4) and the electric motor (10),

[0217] The bearing housing (16) has a second pressure relief hole (94), which has: a second inner opening (941) formed on the inner surface (163) of the bearing housing (16) opposite to the outer peripheral surface (184) of the rotating body (11) including the rotating shaft (3), and formed between the low-pressure stage side grease sealing bearing (15A) and the low-pressure stage impeller (4) in the axial direction of the rotating shaft (3); and a first outer opening (942) formed on the outer surface (169) of the bearing housing (16).

[0218] According to the structure of 14), the multi-stage electric centrifugal compressor (1) includes a low-pressure stage grease-sealed bearing (15A) pre-filled with grease. In this case, since it is not necessary to supply grease to the low-pressure stage grease-sealed bearing (15A), the structure of components surrounding the low-pressure stage grease-sealed bearing (15A) (e.g., the low-pressure stage bearing housing 16A) can be simplified, thereby achieving miniaturization and weight reduction of the multi-stage electric centrifugal compressor (1).

[0219] According to the structure of 14), the bearing housing (16) has a second pressure relief hole (94), and the second pressure relief hole (93) has a second inner opening (941) formed on the inner surface (163) and a second outer opening (942) formed on the outer surface (169). The second inner opening (163) is formed between the low-pressure grease-sealed bearing (15A) and the low-pressure impeller (4) in the axial direction of the rotating shaft (3). In this case, pressure leakage from the space facing the back of the low-pressure impeller (4) can be allowed to flow to the outside of the bearing housing (16) through the second pressure relief hole (94). In this case, pressure leakage from the space facing the back of the low-pressure impeller (4) can be suppressed from flowing to the low-pressure grease-sealed bearing (15A). As a result, deterioration of the low-pressure grease-sealed bearing (15A) due to heat can be suppressed, thereby improving the life and durability of the low-pressure grease-sealed bearing (15A).

[0220] 15) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 1) to 12) above comprises:

[0221] at least one bearing (15) which rotatably supports the rotating shaft (3) and is disposed between the high-pressure stage impeller (5) and the low-pressure stage impeller (4);

[0222] a bearing housing (16) housing the at least one bearing (15);

[0223] The at least one bearing (15) includes a high-pressure stage side grease-sealed bearing (15B) disposed between the high-pressure stage impeller (5) and the electric motor (10),

[0224] The bearing housing (16) has a first pressure application hole (95), and the first pressure application hole (93) has: a third inner opening (951) formed on the inner surface (165) of the bearing housing (16) opposite to the outer peripheral surface (181) of the rotating body (11) including the rotating shaft (3), and formed between the high-pressure stage side grease sealing bearing (15B) and the high-pressure stage impeller (5) in the axial direction of the rotating shaft (3); a third outer opening (932) formed on the outer surface (168) of the bearing housing (16),

[0225] The multi-stage electric centrifugal compressor (1) further includes a pressure introduction line (26) configured to introduce pressure from a pressure source (e.g., a compressed gas supply line 21 or a pressure stabilizing tank 27) into the third outer opening (95).

[0226] According to the structure of the above-mentioned 15), the bearing housing (16) has a first pressure application hole (95), and the first pressure application hole (95) has a third inner opening (951) formed on the above-mentioned inner surface (165) and a third outer opening (952) formed on the above-mentioned outer surface (168). The third inner opening (951) is formed between the high-pressure stage side grease sealing bearing (15B) and the high-pressure stage impeller (5) in the axial direction of the rotating shaft (3). The multi-stage electric centrifugal compressor (1) has the above-mentioned pressure introduction pipeline (26). In this case, the pressure from the above-mentioned pressure source is introduced into the third outer opening (95) through the pressure introduction pipeline (26), thereby making it possible to make the pressure in the gap (25) formed between the above-mentioned outer peripheral surface (181) and the above-mentioned (165) higher than the pressure in the space (24) facing the back side (57) of the high-pressure stage impeller (5). By making the pressure in the gap (25) higher than the pressure in the space (24), pressure leakage from the space (24) facing the back surface (57) of the high-pressure stage impeller (5) can be suppressed. As a result, thermal degradation of the high-pressure stage side grease-sealed bearing (15B) can be suppressed, thereby improving the life and durability of the high-pressure stage side grease-sealed bearing (15B).

[0227] Furthermore, by making the pressure in the gap (25) higher than the pressure in the space accommodating the high-pressure stage grease-sealed bearing (15B), it is possible to prevent the grease sealed in the high-pressure stage grease-sealed bearing (15B) from leaking through the gap (25) or the space (24) into the flow path where the compressed gas flows. Thus, it is possible to prevent the grease from mixing with the compressed gas compressed by the multi-stage electric centrifugal compressor (1), so that the multi-stage electric centrifugal compressor (1) can supply clean compressed gas to the fuel cell (20) and the like.

[0228] 16) In some embodiments, the multi-stage electric centrifugal compressor (1) as described in any one of 1) to 12) above has:

[0229] at least one bearing (15) which rotatably supports the rotating shaft (3) and is disposed between the high-pressure stage impeller (5) and the low-pressure stage impeller (4);

[0230] a bearing housing (16) housing the at least one bearing (15);

[0231] a stator housing (17) having an inner surface (171) forming a motor housing (170) for housing the electric motor (10), the stator housing (17) being arranged adjacent to the bearing housing (16);

[0232] The bearing housing (16) has:

[0233] An air inlet hole (30) having: a fourth inner opening (34) formed on an inner surface (30) of the bearing housing (16) facing the motor housing (170) and formed on an axial side closer to the rotating shaft (3) than the electric motor (10); and a fourth outer opening (35) formed on an outer surface (168) of the bearing housing (16);

[0234] An air discharge hole (31) has: a fifth inner opening (37) formed on an inner surface (30) of the bearing housing (16) facing the motor housing (170) and formed on the other side of the electric motor (10) in the axial direction of the rotating shaft (3); and a fifth outer opening (38) formed on an outer surface (169) of the bearing housing (16);

[0235] The multi-stage electric centrifugal compressor (1) further includes an air introduction pipe (32), which is configured to deliver air to the air introduction hole (30) or to draw air from the air discharge hole (31).

[0236] According to the structure of the above-mentioned 16), air is forcibly introduced into the motor housing (170) from the fourth outer opening (35) through the air inlet hole (30) through the air inlet pipe (32). In addition, air is forcibly discharged from the motor housing (170) through the air outlet hole (31) to the outside of the bearing housing (16) through the air inlet pipe (32). The fifth inner opening (37) of the air outlet hole (31) is located on the opposite side of the axial direction of the rotating shaft (3) with respect to the fourth inner opening (34) of the air inlet hole (30) of the electric motor (10). Thus, air can be forcibly blown from one side of the motor housing (170) to the other side. The electric motor (10) accommodated in the motor housing (170) dissipates heat through heat exchange with the air, thereby being cooled (air-cooled). By using air to cool the rotor assembly (13) or motor coil (121) of an electric motor (10) serving as a heat source, a temperature rise of a bearing (15, such as a high-pressure stage grease-sealed bearing 15B) can be suppressed. Thus, thermal degradation of the bearing (15) can be suppressed, thereby improving the life and durability of the bearing (15).

[0237] Description of Reference Numerals

[0238] 1 Multi-stage electric centrifugal compressor

[0239] 3 rotation axes

[0240] 4 Low-pressure stage impeller

[0241] 41 wheels

[0242] 42 outer surface

[0243] 43 impeller blades

[0244] 44 Front End

[0245] 5 High pressure stage impeller

[0246] 51 wheels

[0247] 52 outer surface

[0248] 53 impeller blades

[0249] 54 Front End

[0250] 6 Low-pressure stage housing

[0251] 61 Low pressure stage inlet opening

[0252] 62 Low pressure stage outlet opening

[0253] 63 Supply flow path

[0254] 64 vortex flow path

[0255] 65 shield surface

[0256] 66 Low pressure stage impeller chamber

[0257] 7 High pressure stage housing

[0258] 70 High pressure stage cooling passage

[0259] 71 High pressure stage inlet opening

[0260] 72 High pressure stage outlet opening

[0261] 73 Supply flow path

[0262] 74 vortex flow path

[0263] 75 shield surface

[0264] 76 High pressure stage impeller chamber

[0265] 8 Connect the pipes

[0266] 81 High-voltage side connection

[0267] 82 Low-voltage side connection

[0268] 83 middle part

[0269] 84 Low-pressure side bend

[0270] 85 High pressure stage side bend

[0271] 86 Cooling device

[0272] 10 Electric Motor

[0273] 11 Rotating body

[0274] 12 Motor stator

[0275] 13 Rotor assembly

[0276] 14 permanent magnets

[0277] 15 bearings

[0278] 15A low pressure side bearing

[0279] 15B high pressure stage side bearing

[0280] 16 Bearing housing

[0281] 16A low pressure stage side bearing housing

[0282] 16B high pressure stage side bearing housing

[0283] 161, 162 bearing support surface

[0284] 163, 165 inner surface

[0285] 164, 166 stop surface

[0286] 17 stator housing

[0287] 18A low-voltage side sleeve

[0288] 18B high pressure stage side sleeve

[0289] 19 Compression spring

[0290] 20 Fuel Cell

[0291] 201 Air Electrode

[0292] 202 fuel electrode

[0293] 203 Solid Electrolyte

[0294] 21 Compressed gas supply line

[0295] 22 First sealing component

[0296] 23 Second sealing component

[0297] 24 Space

[0298] 25 gap

[0299] 26, 29 pressure inlet pipeline

[0300] 27 Surge Tank

[0301] 28 compressor

[0302] CA (axis of rotation)

[0303] CB (high-voltage side connection) axis

[0304] X-axis

[0305] XH (axial) high pressure stage side

[0306] XL (axial) low-pressure side

[0307] Y Radial

Claims

1. A multi-stage electric centrifugal compressor, wherein an electric motor drives impellers disposed at both ends of a rotating shaft, the multi-stage electric centrifugal compressor comprising: the rotation axis; a low-pressure stage impeller, which is arranged on one side of the rotating shaft; a high-pressure stage impeller, which is arranged on the other side of the rotating shaft; a high-pressure stage casing accommodating the high-pressure stage impeller; a connecting pipe for supplying compressed gas compressed by the low-pressure stage impeller to the high-pressure stage casing; The high-pressure stage housing has a high-pressure stage inlet opening, which opens in a direction intersecting the axis of the rotating shaft. The connecting pipe includes a high-pressure stage side connecting portion connected to the high-pressure stage inlet opening, The flow path cross-section of the high-pressure stage side connection portion has a long side direction along a direction orthogonal to the axis of the rotating shaft, and includes convex curved portions formed on both end sides of the long side direction. The flow path cross-section of the high-pressure stage side connection portion has a short side direction along the axis of the rotating shaft.

2. The multi-stage electric centrifugal compressor according to claim 1, wherein: The flow path cross section of the high-pressure stage side connecting portion is formed so that the length in the longitudinal direction increases toward the high-pressure stage inlet opening side.

3. The multi-stage electric centrifugal compressor according to claim 2, wherein: The flow path cross section of the high-pressure stage side connecting portion is formed so that the maximum curvature of the convex curved portion increases toward the high-pressure stage inlet opening side.

4. The multi-stage electric centrifugal compressor according to claim 1, wherein: A low-pressure stage casing is provided for accommodating the low-pressure stage impeller. The low-pressure stage housing has a low-pressure stage outlet opening, which opens in a direction intersecting the axis with respect to the rotation shaft. The connecting pipe includes: a low-pressure stage side connecting portion connected to the low-pressure stage outlet opening; a middle portion extending along the axis of the rotation shaft; a low-pressure stage side bent portion having a curved shape connecting the low-pressure stage side connecting portion and the middle portion; a high-voltage-stage side bent portion having a curved shape connecting the high-voltage-stage side connecting portion and the middle portion; At least the flow path cross section of the low-pressure stage side connection portion is formed in a circular shape.

5. The multi-stage electric centrifugal compressor according to claim 1, wherein: A cooling device is further provided, the cooling device being configured to perform heat exchange between the compressed gas in the connecting pipe and a coolant for cooling the compressed gas.

6. The multi-stage electric centrifugal compressor according to claim 1, wherein: The high-pressure stage housing comprises: an inner wall surface defining a supply flow path for guiding the compressed gas supplied from the high-pressure stage inlet opening to the high-pressure stage impeller, the inner wall surface including: an inner end wall surface defining a side of the supply flow path opposite to the high-pressure stage impeller; and an inner peripheral wall surface defining an outer peripheral side of the supply flow path; A guide protrusion protrudes from the inner end wall surface toward the high-pressure stage impeller.

7. The multi-stage electric centrifugal compressor according to claim 6, wherein: The inner peripheral wall surface includes an inlet-side inner peripheral wall surface where the high-pressure stage inlet opening is formed, and an opposite-side inner peripheral wall surface located on the opposite side of the high-pressure stage inlet opening. The high-pressure stage casing includes a swirl prevention plate protruding from the opposite inner peripheral wall surface.

8. The multi-stage electric centrifugal compressor according to claim 7, wherein: The front end of the anti-swirl plate is located on the outer peripheral side of the rotating shaft relative to the tip of the leading edge of the high-pressure stage impeller.

9. The multi-stage electric centrifugal compressor according to claim 1, wherein: comprising: at least one bearing that rotatably supports the rotating shaft and is disposed between the high-pressure stage impeller and the low-pressure stage impeller; a bearing housing housing the at least one bearing; The at least one bearing includes a high-pressure stage side grease-filled bearing disposed between the high-pressure stage impeller and the electric motor, The bearing housing has a cooling passage formed between the high-pressure-stage grease-packed bearing and the high-pressure-stage impeller in the axial direction of the rotating shaft.

10. The multi-stage electric centrifugal compressor according to claim 1, wherein: The high-pressure stage casing includes a high-pressure stage side cooling passage formed on an outer peripheral side of the rotating shaft relative to the high-pressure stage impeller.

11. The multi-stage electric centrifugal compressor according to any one of claims 1 to 10, wherein: comprising: at least one bearing that rotatably supports the rotating shaft and is disposed between the high-pressure stage impeller and the low-pressure stage impeller; a bearing housing housing the at least one bearing; The at least one bearing includes a high-pressure stage side grease-filled bearing disposed between the high-pressure stage impeller and the electric motor, The bearing housing has a first pressure relief hole, which has: a first inner opening, which is formed on the inner surface of the bearing housing opposite to the outer peripheral surface of the rotating body including the rotating shaft, and is formed between the high-pressure stage side grease sealing bearing and the high-pressure stage impeller in the axial direction of the rotating shaft; and a first outer opening, which is formed on the outer surface of the bearing housing.

12. The multi-stage electric centrifugal compressor according to claim 11, wherein: The at least one bearing further comprises a low-pressure stage side grease-filled bearing disposed between the low-pressure stage impeller and the electric motor, The bearing housing has a second pressure relief hole, which has: a second inner opening, which is formed on the inner surface of the bearing housing opposite to the outer peripheral surface of the rotating body including the rotating shaft, and is formed between the low-pressure stage side grease sealing bearing and the low-pressure stage impeller in the axial direction of the rotating shaft; and a second outer opening, which is formed on the outer surface of the bearing housing.

13. The multi-stage electric centrifugal compressor according to any one of claims 1 to 10, wherein: comprising: at least one bearing that rotatably supports the rotating shaft and is disposed between the high-pressure stage impeller and the low-pressure stage impeller; a bearing housing housing the at least one bearing; The at least one bearing includes a high-pressure stage side grease-filled bearing disposed between the high-pressure stage impeller and the electric motor, The bearing housing has a first pressure application hole, which has: a third inner opening formed on the inner surface of the bearing housing opposite to the outer peripheral surface of the rotating body including the rotating shaft, and formed between the high-pressure stage side grease sealing bearing and the high-pressure stage impeller in the axial direction of the rotating shaft; a third outer opening formed on the outer surface of the bearing housing, The multi-stage electric centrifugal compressor further includes a pressure introduction line configured to introduce pressure from a pressure source into the third outer opening.

14. The multi-stage electric centrifugal compressor according to any one of claims 1 to 10, wherein: comprising: at least one bearing that rotatably supports the rotating shaft and is disposed between the high-pressure stage impeller and the low-pressure stage impeller; a bearing housing housing the at least one bearing; a stator housing having an inner surface forming a motor housing for housing the electric motor, the stator housing being arranged adjacent to the bearing housing; The bearing housing has: an air introduction hole having: a fourth inner opening formed on an inner surface of the bearing housing facing the motor housing portion and formed on an axial side of the rotating shaft relative to the electric motor; and a fourth outer opening formed on an outer surface of the bearing housing; an air discharge hole having: a fifth inner opening formed on an inner surface of the bearing housing facing the motor housing portion and formed on the other side of the electric motor in the axial direction of the rotating shaft; and a fifth outer opening formed on an outer surface of the bearing housing; The multi-stage electric centrifugal compressor further includes an air introduction pipe configured to deliver air to the air introduction hole or to draw air from the air discharge hole.

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