Piping device for multistage electric centrifugal compressor and multistage electric centrifugal compressor

Abstract

This piping device for a multistage electric centrifugal compressor comprises: a low-pressure stage-side connection part connected to a low-pressure stage outlet opening formed in a low-pressure stage housing for storing a low-pressure stage impeller; a high-pressure stage-side connection part connected to a high-pressure stage inlet opening formed in a high-pressure stage housing for storing a high-pressure stage impeller; an intermediate part extending along the center axis of a rotary shaft, the intermediate part including a gradually changing section that gradually changes from a first channel cross section having a circular channel cross section to a second channel cross section having a longitudinal direction along a direction intersecting the radial direction of the rotary shaft; a low-pressure stage-side curved part having a bent shape connecting the low-pressure stage-side connection part with the intermediate part and having a circular channel cross section; and a high-pressure stage-side curved part having a bent shape connecting the high-pressure stage-side connection part with the intermediate part and having a channel cross section conforming to the second channel cross section.

Description

Piping device for multi-stage electric centrifugal compressor and multi-stage electric centrifugal compressor

[0001] The present disclosure relates to a piping device for a multi-stage electric centrifugal compressor and a multi-stage electric centrifugal compressor including the piping device.

[0002] Fuel cell vehicles, which generate electricity using a fuel cell mounted on the vehicle body and run on the power of an electric motor, are sometimes equipped with electric centrifugal compressors. Electric centrifugal compressors improve the efficiency of the fuel cell by supplying compressed air to the fuel cell. Electric centrifugal compressors include multi-stage electric centrifugal compressors that compress the volume of gas (e.g., air) in stages.

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

[0004] Patent No. 7373076

[0005] The invention described in Patent Document 1 discloses a pipe for guiding a compressed fluid compressed in a low-pressure stage impeller to a high-pressure stage impeller. The pipe includes an intermediate section extending along the axis of a rotating shaft, and a low-pressure stage side curved section and a high-pressure stage side curved section connected to both ends of the intermediate section, and the flow path cross sections of the intermediate section, the low-pressure stage side curved section, and the high-pressure stage side curved section are circular.

[0006] If the flow path cross sections of the intermediate section, the low-pressure stage side curved section and the high-pressure stage side curved section are circular, separation occurs due to an increase in the flow curvature on the inner periphery of the compressed fluid flowing through the high-pressure stage side curved section, and there is a risk that pressure loss will occur due to the separation.

[0007] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a piping device for a multi-stage electric centrifugal compressor that can suppress pressure loss due to separation from the inner surface of a compressed fluid flowing through a curved portion on the high-pressure stage side, and a multi-stage electric centrifugal compressor including the piping device.

[0008] A piping device of a multi-stage electric centrifugal compressor according to at least one embodiment of the present disclosure is a piping device for connecting a low-pressure stage side and a high-pressure stage side of a multi-stage electric centrifugal compressor configured to drive impellers provided on both ends of a rotating shaft by an electric motor, the piping device comprising: a low-pressure stage side connecting part connected to a low-pressure stage outlet opening formed in a low-pressure stage housing that houses a low-pressure stage impeller provided on one side of the rotating shaft; a high-pressure stage side connecting part connected to a high-pressure stage inlet opening formed in a high-pressure stage housing that houses a high-pressure stage impeller provided on the other side of the rotating shaft; an intermediate part extending along a central axis of the rotating shaft, the intermediate part including a gradual change section in which a flow path cross section gradually changes from a first flow path cross section that is circular to a second flow path cross section having a longitudinal direction along a direction intersecting a radial direction of the rotating shaft; and a low-pressure stage side curved part having a curved shape that connects the low-pressure stage side connecting part and the intermediate part and having a circular flow path cross section. a high-pressure stage side curved portion having a curved shape connecting the high-pressure stage side connecting portion and the intermediate portion and having a flow path cross section along the second flow path cross section;

[0009] A multi-stage electric centrifugal compressor according to at least one embodiment of the present disclosure includes a piping device for the multi-stage electric centrifugal compressor.

[0010] According to at least one embodiment of the present disclosure, there is provided a piping device for a multi-stage electric centrifugal compressor that can suppress pressure loss due to separation from the inner surface of the compressed fluid flowing through a curved portion on the high-pressure stage side, and a multi-stage electric centrifugal compressor including the piping device.

[0011] FIG. 3 is a schematic configuration diagram illustrating a configuration of a multi-stage electric centrifugal compressor according to an embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view taken along the central axis of a rotating shaft of a piping device according to an embodiment of the present disclosure. FIG. 5 is a schematic cross-sectional view taken along the arrows A-B shown in FIG. 2. FIG. 6 is a schematic cross-sectional view taken along the arrows C-D shown in FIG. 2. FIG. 7 is a schematic cross-sectional view showing a modified example of a flow path cross section taken along the arrows C-D shown in FIG. 2. FIG. 8 is an explanatory diagram illustrating a swirling flow for each flow path cross-sectional shape. FIG. 9 is a schematic cross-sectional view taken along the central axis of a rotating shaft of a piping device according to a comparative example. FIG. 10 is an explanatory diagram illustrating a divergence angle. FIG. 11 is a schematic cross-sectional view taken along the central axis of a rotating shaft of a piping device according to an embodiment of the present disclosure. FIG. 12 is a schematic cross-sectional view taken along the central axis of a rotating shaft of a piping device according to an embodiment of the present disclosure.

[0012] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0013] In the following description, when simply referring to the upstream side, it refers to the upstream side along the main flow direction of the fluid in the part or area described in the direction. Similarly, in the following description, when simply referring to the downstream side, it refers to the downstream side along the main flow direction of the fluid in the part or area described in the direction.

[0014] (Multi-stage electric centrifugal compressor) Fig. 1 is a schematic diagram illustrating the configuration of a multi-stage electric centrifugal compressor 1 according to one embodiment of the present disclosure. In Fig. 1, the multi-stage electric centrifugal compressor 1 is illustrated in a cross section taken along a central axis CA of a rotating shaft 3. As shown in Fig. 1, the multi-stage electric centrifugal compressor 1 according to some 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 the rotating shaft 3 are driven by an electric motor 10.

[0015] As shown in FIG. 1 , the multi-stage electric centrifugal compressor 1 includes a rotating shaft 3, a low-pressure stage impeller 4 provided on one side (upper side in FIG. 1 ) of the rotating shaft 3, a high-pressure stage impeller 5 provided on the other side (lower side in FIG. 1 ) of the rotating shaft 3, a low-pressure stage housing 6 configured to accommodate the low-pressure stage impeller 4, a high-pressure stage housing 7 configured to accommodate the high-pressure stage impeller 5, and a piping device 8 for connecting the low-pressure stage side and the high-pressure stage side of the multi-stage electric centrifugal compressor 1.

[0016] 1 , the direction in which the central axis CA of the rotating shaft 3 extends is referred to as the axial direction X, and the direction perpendicular to the central axis CA is referred to as the radial direction Y. In the axial direction X, the side where the low-pressure stage impeller 4 is located relative to the high-pressure stage impeller 5 (upper side in FIG. 1 ) is referred to as the low-pressure stage side XL, and the side opposite to the low-pressure stage side XL (lower side in FIG. 1 ) is referred to as the high-pressure stage side XH.

[0017] (Electric Motor) The electric motor 10 mounted on the multi-stage electric centrifugal compressor 1 includes a rotating body 11 serving as a rotor and a motor stator 12 serving as a stator. The rotating body 11 includes at least a rotating shaft 3 and a rotor assembly 13 attached to the outer periphery 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 and is configured to generate a magnetic field that rotates the rotating body 11, on which the permanent magnet 14 is mounted, using power supplied from a power source (not shown). When the rotating body 11 rotates due to the magnetic field generated by the motor stator 12 (power generated by the electric motor 10), the impellers (low-pressure stage impeller 4 and high-pressure stage impeller 5) attached to the rotating shaft 3 rotate in conjunction with the magnetic field.

[0018] The multi-stage electric centrifugal compressor 1 rotates the low-pressure stage impeller 4 to compress the gas introduced into the low-pressure stage housing 6 and pressurize the gas to a first pressure. The compressed gas pressurized to the first pressure is guided into the high-pressure stage housing 7 through a piping device 8. The multi-stage electric centrifugal compressor 1 rotates the high-pressure stage impeller 5 to further compress the compressed gas introduced into the high-pressure stage housing 7 and pressurize the compressed gas to a second pressure higher than the first pressure.

[0019] The multi-stage electric centrifugal compressor 1 further includes a rotor assembly 13 attached to the rotating shaft 3, a motor stator 12 arranged to surround the outer periphery of the rotor assembly 13, at least one bearing 15 rotatably supporting the rotating shaft 3, at least one bearing housing 16 configured to house the at least one bearing 15, and a stator housing 17 configured to house 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 inside the stator housing 17.

[0020] (Bearings, Bearing Housing) In the illustrated embodiment, the at least one bearing 15 includes a low-pressure stage side bearing 15A arranged between the low-pressure stage impeller 4 and the rotor assembly 13 in the axial direction X, and a high-pressure stage side bearing 15B arranged 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 side bearing housing 16A configured to house the low-pressure stage side bearing 15A, and a high-pressure stage side bearing housing 16B configured to house the high-pressure stage side bearing 15B. The low-pressure stage side bearing 15A is supported by the low-pressure stage side bearing housing 16A. The high-pressure stage side bearing 15B is supported by the high-pressure stage side bearing housing 16B.

[0021] The low-pressure stage bearing housing 16A is arranged on the high-pressure stage side XH of the low-pressure stage housing 6 and on the low-pressure stage side XL of the stator housing 17. The low-pressure stage bearing housing 16A is mechanically connected to the low-pressure stage housing 6 and the stator housing 17, which are arranged 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 arranged on the low-pressure stage side XL of the high-pressure stage housing 7 and on the high-pressure stage side XH of the stator housing 17. The high-pressure stage bearing housing 16B is mechanically connected to the high-pressure stage housing 7 and the stator housing 17, which are arranged adjacent to the high-pressure stage bearing housing 16B in the axial direction X, by fastening members such as fastening bolts.

[0022] 1 , the low-pressure stage housing 6 is formed with a low-pressure stage inlet opening 62 for introducing gas from the outside of the low-pressure stage housing 6 into the inside, and a low-pressure stage outlet opening 61 for discharging gas from the inside of the low-pressure stage housing 6 to the outside. Inside the low-pressure stage housing 6, a supply passage 63 is formed for guiding gas introduced into the low-pressure stage housing 6 from the low-pressure stage inlet opening 62 to the low-pressure stage impeller 4, and a scroll passage 64 is formed for guiding gas that has passed through the low-pressure stage impeller 4 to the low-pressure stage outlet opening 61. In the illustrated embodiment, the low-pressure stage inlet opening 62 opens toward the low-pressure stage side XL in the axial direction X. The low-pressure stage outlet opening 61 opens in a direction intersecting (e.g., perpendicular to) the central axis CA.

[0023] 1 , the low-pressure stage impeller 4 has a hub 41 mechanically coupled to one side of the rotary shaft 3, and a plurality of impeller vanes 43 provided on an outer circumferential surface 42 of the hub 41. The low-pressure stage impeller 4 is rotatable integrally with the rotary shaft 3 about the central axis CA of the rotary shaft 3. The low-pressure stage impeller 4 is a centrifugal impeller configured to guide gas sent from the low-pressure stage side XL along the axial direction X to the outside in the radial direction Y. A gap (clearance) is formed between each of the tips 44 of the plurality of impeller vanes 43 and a convexly curved shroud surface 65 of the low-pressure stage housing 6.

[0024] 1 , the low-pressure stage housing 6 is combined with other members (in the illustrated example, a low-pressure stage bearing housing 16A) to form a low-pressure stage impeller chamber 66 that rotatably houses the low-pressure stage impeller 4. The low-pressure stage impeller chamber 66 communicates with a supply passage 63 located upstream in the gas flow direction, and a scroll passage 64 located downstream in the gas flow direction. The scroll passage 64 has a spiral shape that surrounds the outside of the low-pressure stage impeller 4 in the radial direction Y. The shroud surface 65 defines a portion of the low-pressure stage impeller chamber 66.

[0025] (High-Pressure Stage Housing, High-Pressure Stage Impeller) As shown in Fig. 1 , the high-pressure stage housing 7 is formed with a high-pressure stage inlet opening 71 for introducing gas from the outside of the high-pressure stage housing 7 into the interior, and a high-pressure stage outlet opening 72 for discharging gas from the inside of the high-pressure stage housing 7 to the outside. Inside the high-pressure stage housing 7, a supply passage 73 is formed for guiding the gas introduced into the high-pressure stage housing 7 from the high-pressure stage inlet opening 71 to the high-pressure stage impeller 5, and a scroll passage 74 is formed for guiding the gas that has passed through the high-pressure stage impeller 5 to the high-pressure stage outlet opening 72. In the illustrated embodiment, the high-pressure stage inlet opening 71 opens in a direction extending from the central axis CA. Each of the high-pressure stage outlet openings 72 opens in a direction intersecting (e.g., perpendicular to) the central axis CA. Note that in some other embodiments, the high-pressure stage inlet opening 71 may open in a direction intersecting (e.g., perpendicular to) the central axis CA.

[0026] 1 , the high-pressure stage impeller 5 has a hub 51 mechanically coupled to the other side of the rotary shaft 3, and a plurality of impeller blades 53 provided on an outer circumferential surface 52 of the hub 51. The high-pressure stage impeller 5 is rotatable integrally with the rotary shaft 3 about the central axis CA of the rotary shaft 3. The high-pressure stage impeller 5 is a centrifugal impeller configured to guide gas sent from the high-pressure stage side XH along the axial direction X to the outside in the radial direction Y. A gap (clearance) is formed between each of the tips 54 of the plurality of impeller blades 53 and a convexly curved shroud surface 75 of the high-pressure stage housing 7.

[0027] 1 , the high-pressure stage housing 7 is combined with other members (in the illustrated example, the high-pressure stage bearing housing 16B) to form a high-pressure stage impeller chamber 76 that rotatably houses the high-pressure stage impeller 5. The high-pressure stage impeller chamber 76 communicates with a supply passage 73 located upstream in the gas flow direction, and a scroll passage 74 located downstream in the gas flow direction. The scroll passage 74 has a spiral shape that surrounds the outside of the high-pressure stage impeller 5 in the radial direction Y. The shroud surface 75 defines a part of the high-pressure stage impeller chamber 76.

[0028] Gas (e.g., air) introduced into the supply passage 63 from outside the low-pressure stage housing 6 through the low-pressure stage inlet opening 62 flows through the supply passage 63 to the high-pressure stage side XH, and is then sent to the low-pressure stage impeller 4, where it is compressed by the rotation of the low-pressure stage impeller 4 and pressurized to a first pressure. 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 scroll passage 64, and is then discharged to the outside of the low-pressure stage housing 6 from the low-pressure stage outlet opening 61.

[0029] The compressed gas introduced into the supply passage 73 from outside the high-pressure stage housing 7 through the high-pressure stage inlet opening 71 flows through the supply passage 73 to the low-pressure stage side XL, and then is sent 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 through the scroll passage 74 toward the outside in the radial direction Y, and then is discharged from the high-pressure stage housing 7 through the high-pressure stage outlet opening 72.

[0030] In the illustrated embodiment, the multi-stage electric centrifugal compressor 1 is a multi-stage electric centrifugal compressor for a fuel cell vehicle. 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 a cathode 201, an anode 202, and a solid electrolyte 203 disposed between the cathode 201 and the anode 202. The 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 through the compressed gas supply line 21 connecting the high-pressure stage outlet opening 72 and the cathode 201 of the fuel cell 20. The present disclosure may also be applied to multi-stage electric centrifugal compressors other than those for fuel cell vehicles, for example, multi-stage electric centrifugal compressors for internal combustion engines that compress combustion gas to be sent to internal combustion engines such as internal combustion engines. That is, the compressed gas supply line 21 may be configured to connect the high-pressure stage outlet opening 72 of the high-pressure stage housing 7 to an internal combustion engine (not shown).

[0031] (Piping device) As shown in Fig. 1, the piping device 8 is formed in a tubular shape extending along its length. As shown in Fig. 1, the piping device 8 includes a low-pressure stage side connecting portion 81 connected to the above-mentioned low-pressure stage outlet opening 61, a high-pressure stage side connecting portion 82 connected to the above-mentioned high-pressure stage inlet opening 71, an intermediate portion 83, a low-pressure stage side curved portion 84, and a high-pressure stage side curved portion 85. The intermediate portion 83 extends along the central axis CA of the rotating shaft. The low-pressure stage side curved portion 84 has a curved shape connecting the low-pressure stage side connecting portion 81 and the intermediate portion 83. The high-pressure stage side curved portion 85 has a curved shape connecting the high-pressure stage side connecting portion 82 and the intermediate portion 83.

[0032] In the illustrated embodiment, the low-pressure stage side connection portion 81 extends in a direction intersecting (orthogonal in the illustrated example) the central axis CA of the rotating shaft 3. The high-pressure stage side connection portion 82 includes a radially extending portion 86 whose upstream end (one end) is connected to the high-pressure stage side curved portion 85 and which extends radially inward of the rotating shaft 3, and an inlet opening connection portion 87 having a curved shape that connects the downstream end (the other end) of the radially extending portion 86 to the high-pressure stage inlet opening 71. The radially extending portion 86 extends in a direction intersecting (orthogonal in the illustrated example) the central axis CA of the rotating shaft 3. In FIG. 1 , the boundaries between the various portions of the piping device 8 are indicated by two-dot chain lines. The various portions of the piping device 8 may be formed of separate members or may be integrally formed from a single material.

[0033] FIG. 2 is a schematic cross-sectional view taken along the central axis CA of the rotating shaft 3 of a piping device 8 according to an embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view taken along the arrows A-B shown in FIG. 2. FIG. 4 is a schematic cross-sectional view taken along the arrows C-D shown in FIG. 2. FIG. 5 is a schematic cross-sectional view showing a modified example of the flow path cross section taken along the arrows C-D shown in FIG. 2. In the piping device 8 according to some embodiments, as shown in FIG. 2, the intermediate portion 83 described above includes a gradual change section S1 in which the flow path cross section gradually changes from a circular first flow path cross section CS1 (see FIG. 3) toward the other side of the rotating shaft 3, i.e., the high-pressure stage side XH, to a second flow path cross section CS2 (see FIGS. 4 and 5) having a longitudinal direction LD that intersects with the radial direction of the rotating shaft 3.

[0034] In the embodiment shown in Fig. 4, the second flow path cross section CS2 is formed in an elliptical shape having a major axis LA and a minor axis SA. In the embodiment shown in Fig. 5, the second flow path cross section CS2 includes a pair of convex curved portions formed on both end sides in the longitudinal direction LD, and a pair of straight portions connecting the ends of the pair of convex curved portions.

[0035] The low-pressure stage side connecting portion 81 and the low-pressure stage side curved portion 84 each have a circular flow path cross section along the first flow path cross section CS1. The radially extending portion 86 and the high-pressure stage side curved portion 85 each have a flow path cross section along the second flow path cross section CS2. In the illustrated embodiment, the flow path cross sections of the second flow path cross section CS2 and the upstream end of the high-pressure stage side curved portion 85 have a short side direction (a direction perpendicular to the longitudinal direction LD in the flow path cross section) along the direction extending from the inner peripheral end to the outer peripheral end in the radial direction of the rotating shaft 3 on the inner surface of the intermediate portion 83 forming the second flow path cross section CS2. The flow path cross sections of the downstream end of the high-pressure stage side curved portion 85 and the radially extending portion 86 each have a short side direction along the direction extending from the low-pressure stage side XL end to the high-pressure stage side XH end in the axial direction of the rotating shaft 3.

[0036] FIG. 6 is an explanatory diagram illustrating the swirling flow for each flow path cross-sectional shape. FIG. 6 shows a flow path cross-section of the piping device 8. The swirl flow, which is a swirling component within the flow path cross-section of the main stream flowing through the piping device 8, is indicated by the symbol F1, and the separation vortex generated within the flow path cross-section is indicated by the symbol F2. As shown in FIG. 6, when the flow path cross-section is circular, pressure loss is unlikely to occur for the flow having the swirl flow F1. In contrast, when the flow path cross-section is elliptical or rectangular with rounded corners, separation vortex F2 occurs due to a sharp change in curvature at the corners for the flow having the swirl flow F1, which is likely to cause pressure loss due to separation from the inner surface of the piping device 8. When the flow path cross-section is elliptical, the separation vortex F2 generated by the continuous change in curvature is relatively smaller than when the flow path cross-section is rectangular with rounded corners, and pressure loss due to separation from the inner surface of the piping device 8 is small.

[0037] 7 is a schematic cross-sectional view taken along the central axis of the rotating shaft 3 of a piping device 8 according to a comparative example. In the piping device 8 according to the comparative example, the flow path cross sections of the intermediate section 83, the low-pressure stage side curved section 84, and the high-pressure stage side curved section 85 are each circular. In this case, a separation vortex F3 is generated in the high-pressure stage side curved section 85 with respect to the main flow flowing through the piping device 8, and pressure loss due to separation from the inner surface of the piping device 8 is likely to occur.

[0038] By providing the gradual change section S1 in the intermediate section 83 and making the section downstream of the gradual change section S1 including the high-pressure stage side curved section 85 have a flow path cross section having a longitudinal direction along the second flow path cross section CS2, it is possible to suppress separation at the high-pressure stage side curved section 85 from the mainstream flowing through the piping device 8, and reduce pressure loss due to separation. Furthermore, by providing the gradual change section S1 in the intermediate section 83 and making the section upstream of the gradual change section S1 including the low-pressure stage side curved section 84 have a circular flow path cross section along the first flow path cross section CS1, it is possible to suppress separation from the swirl flow upstream of the gradual change section S1, and reduce pressure loss due to separation.

[0039] In some embodiments, the second flow path cross section CS2 described above has a longitudinal direction LD that is aligned in a direction perpendicular to the radial direction of the rotating shaft 3. By forming the second flow path cross section CS2 in a cross-sectional shape that has the longitudinal direction LD that is aligned in a direction perpendicular to the radial direction of the rotating shaft 3, separation of the swirl flow downstream of the gradual-change section S1 that includes the high-pressure stage-side curved portion 85 can be relatively suppressed, and pressure loss due to the separation can be suppressed.

[0040] In some embodiments, the second flow path cross section CS2 described above is elliptical, as shown in Fig. 4. The radially extending portion 86 and the high-pressure stage side curved portion 85 each have an elliptical flow path cross section that conforms to the second flow path cross section CS2. By making the second flow path cross section CS2 elliptical, separation of the swirl flow downstream of the gradual change section S1 including the high-pressure stage side curved portion 85 can be relatively suppressed, and pressure loss due to the separation can be suppressed.

[0041] In some embodiments, as shown in Figure 4, the long axis LA of the elliptical second flow path cross section CS2 is at least twice as long as the short axis SA of the second flow path cross section CS2. Preferably, the long axis LA is at least 2.4 times and at most 4 times as long as the short axis SA.

[0042] By making the short axis SA of the second flow path cross section CS2 less than half the length of the long axis LA, separation at the high-pressure stage side curved section 85 from the main flow through the piping device 8 can be effectively suppressed, and the pressure loss due to such separation can be effectively reduced.

[0043] In some embodiments, the length L1 from the start point to the end point of the gradual-change section S1 (see FIG. 2) is four or more times the diameter D01 (see FIG. 3) of the first flow path cross section CS1. By making the length L1 of the gradual-change section S1 relatively long, that is, four or more times the diameter D01 of the first flow path cross section CS1, the change in shape of the flow path cross section in the gradual-change section S1 can be made gradual, thereby suppressing pressure loss in the gradual-change section S1.

[0044] In some embodiments, the divergence angle θ in the above-mentioned gradual change section S1 is 15° or less. By setting the divergence angle θ in the gradual change section S1 to 15° or less, the change in area of ​​the flow path cross section in the gradual change section S1 can be made gentler, thereby suppressing pressure loss in the gradual change section S1. FIG. 8 is an explanatory diagram for explaining the divergence angle θ. The divergence angle θ can be calculated using the following formula (1) when the length of the section in which the area changes is defined as L01 (corresponding to the length L1 from the start point to the end point of the gradual change section S1), the diameter of a virtual circle equivalent to the area at the start point of the section is defined as D01, and the diameter of a virtual circle equivalent to the area at the end point of the section is defined as D02. θ=tan ―１ ((D02-D01) / (2×L01))...Formula (1)

[0045] In some embodiments, the intermediate section 83 further includes an upstream section S2 having a flow path cross section along the first flow path cross section CS1 upstream of the gradual-change section S1, as shown in FIG. 2 . In this case, separation of the swirl flow in the upstream section S2 of the intermediate section 83 can be suppressed, thereby reducing pressure loss due to the separation. Note that in some other embodiments, a downstream section having a flow path cross section along the second flow path cross section CS2 may be included downstream of the gradual-change section S1, but it is preferable that the end point of the gradual-change section S1 is the downstream end of the intermediate section 83. Furthermore, in some other embodiments, the intermediate section 83 may not include the upstream section S2 or the downstream section, and the gradual-change section S1 may extend from the upstream end to the downstream end.

[0046] 1 , the above-described high-pressure stage side connecting portion 82 includes the above-described radial extending portion 86 and the above-described inlet opening connecting portion 87. The high-pressure stage side connecting portion 82 including the radial extending portion 86 and the inlet opening connecting portion 87 can be connected to the high-pressure stage inlet opening 71 that opens along the axial direction of the rotating shaft 3 without requiring a sudden expansion of the flow path cross section, and therefore separation that may occur due to a sudden expansion of the flow path cross section can be suppressed, and pressure loss due to the separation can be suppressed.

[0047] In some embodiments, the flow path area of ​​the inlet opening connection portion 87 is 1.5 times or less the flow path area of ​​the radially extending portion 86. Here, the comparison of the flow path areas of each portion may be performed by comparing the maximum flow path areas of each portion or by comparing the average flow path areas of each portion. The flow path area of ​​the inlet opening connection portion 87 is preferably 1.4 times or less, and more preferably 1.2 times or less, the flow path area of ​​the radially extending portion 86. By not making the flow path area of ​​the inlet opening connection portion 87 larger than the flow path area of ​​the radially extending portion 86, separation that may occur due to a sudden expansion of the flow path cross section can be suppressed, and pressure loss due to the separation can be suppressed.

[0048] 9 and 10 are schematic cross-sectional views taken along the central axis CA of the rotating shaft 3 of the piping device 8 according to an embodiment of the present disclosure. As shown in FIGS. 9 and 10 , the piping device 8 according to some embodiments further includes a bleed line 88 for guiding the compressed fluid flowing through the intermediate portion 83 to the cooling unit 9 (see FIG. 1 ) for cooling the electric motor 10 as a cooling medium. The cooling unit 9 may be any space capable of cooling the electric motor 10 by introducing compressed fluid therein. For example, the cooling unit 9 may be an internal space 9A formed inside the multi-stage electric centrifugal compressor 1 and accommodating the motor coil (stator coil) 121, or an internal space 9B formed on the outer periphery of the internal space 9A inside the multi-stage electric centrifugal compressor 1.

[0049] In some embodiments, the bleed line 88 described above includes a bleed hole 881 formed in the inner surface 831 upstream of the gradual change section S1 of the intermediate section 83 described above, as shown in Fig. 9 . In this case, the compressed fluid flowing upstream of the gradual change section S1 of the intermediate section 83 has a relatively high static pressure, so a sufficient differential pressure can be maintained with respect to the cooling section 9, and the amount of cooling air can be secured. The bleed hole 881 is preferably formed in the inner surface 832 on the outer circumferential side (outside in the radial direction of the rotating shaft 3) of the inner surface 831 upstream of the gradual change section S1 of the intermediate section 83 described above. Forming the bleed hole 881 in the inner surface 832 on the outer circumferential side of the intermediate section 83 makes it easier to layout the bleed line 88 than if the bleed hole 881 were formed on the inner surface on the inner circumferential side.

[0050] 10 , the bleed line 88 includes a bleed hole 882 formed on the inner surface 833 on the inner circumferential side of the downstream end of the gradual-change section S1 of the intermediate section 83. Note that, when the downstream section described above is located downstream of the gradual-change section S1 of the intermediate section 83, the bleed hole 882 may be formed on the inner surface on the inner circumferential side of the downstream section.

[0051] A boundary layer LPA (see FIG. 10 ) with a relatively low momentum may be formed downstream of the gradual-change section S1 of the intermediate portion 83 and on the inner circumferential side of the downstream end of the gradual-change section S1. The development of the boundary layer LPA can be suppressed by forming a bleed hole 882 on the inner surface 833 on the inner circumferential side and extracting the compressed fluid. By suppressing the development of the boundary layer LPA, separation of the main flow in the piping device 8 at the high-pressure stage side curved portion 85 can be suppressed, and the pressure loss due to the separation can be reduced.

[0052] 1, the multi-stage electric centrifugal compressor 1 according to some embodiments includes the above-described piping device 8. In this case, the pressure loss in the piping device 8 can be suppressed, and therefore the efficiency of the multi-stage electric centrifugal compressor 1 can be improved.

[0053] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0054] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0055] The contents of the above-described embodiments can be understood, for example, as follows.

[0056] 1) A piping device (8) for a multi-stage electric centrifugal compressor (1) according to at least one embodiment of the present disclosure is a piping device (8) for connecting a low-pressure stage side and a high-pressure stage side of the 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 includes: a low-pressure stage side connection part (81) connected to a low-pressure stage outlet opening (61) formed in a low-pressure stage housing (6) that houses the low-pressure stage impeller (4) provided on one side of the rotating shaft (3); and a high-pressure stage side connection part (82) connected to a high-pressure stage inlet opening (71) formed in a high-pressure stage housing (7) that houses the high-pressure stage impeller (5) provided on the other side of the rotating shaft (3); The rotary shaft (3) includes an intermediate section (83) extending along a central axis (CA) of the rotary shaft (3), the intermediate section (83) including a gradual-change section (S1) in which a flow path cross section gradually changes from a first flow path cross section (CS1) having a circular shape toward the other side to a second flow path cross section (CS2) having a longitudinal direction along a direction intersecting a radial direction of the rotary shaft (3); a low-pressure stage side curved section (84) having a curved shape connecting the low-pressure stage side connecting section (81) and the intermediate section (83) and having a circular flow path cross section; and a high-pressure stage side curved section (85) having a curved shape connecting the high-pressure stage side connecting section (82) and the intermediate section (83), and having a flow path cross section along the second flow path cross section (CS2).

[0057] According to the configuration 1), by providing a gradual change section (S1) in the intermediate section (83) and making the downstream side of the gradual change section (S1) including the high-pressure stage side curved section (85) have a flow path cross section having a longitudinal direction along the second flow path cross section (CS2), separation at the high-pressure stage side curved section (85) from the mainstream flowing through the piping device (8) can be suppressed, and pressure loss due to separation can be reduced. Furthermore, by providing a gradual change section (S1) in the intermediate section (83) and making the upstream side of the gradual change section (S1) including the low-pressure stage side curved section (84) have a circular flow path cross section along the first flow path cross section (CS1), separation from the swirl flow upstream of the gradual change section (S1) can be suppressed, and pressure loss due to separation can be reduced.

[0058] 2) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in 1), the second flow path cross section (CS2) is elliptical.

[0059] According to the configuration of 2) above, by making the second flow path cross section (CS2) elliptical, separation of the swirl flow downstream of the gradual change section (S1) including the high-pressure stage side curved portion (85) can be relatively suppressed, and pressure loss due to the separation can be suppressed.

[0060] 3) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in 2), the major axis (LA) of the second flow path cross section (CS2) has a length that is at least twice as long as the minor axis (SA) of the second flow path cross section (CS2).

[0061] According to the configuration of 3), by making the minor axis (SA) of the second flow path cross section (CS2) equal to or less than half the length of the major axis (LA), separation at the high-pressure stage side curved portion (85) with respect to the main flow through the piping device (8) can be effectively suppressed, and pressure loss due to the separation can be effectively reduced.

[0062] 4) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in any one of 1) to 3), the gradually changing section (S1) has a length that is four times or more the diameter (D01) of the first flow path cross section (CS1).

[0063] According to the configuration 4) above, by making the length of the gradual change section (S1) relatively long, at least four times the diameter (D01) of the first flow path cross section (CS1), the change in shape of the flow path cross section in the gradual change section (S1) can be made gradual, thereby suppressing pressure loss in the gradual change section (S1).

[0064] 5) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in any one of 1) to 4), the divergence angle (θ) in the gradually changing section (S1) is 15° or less.

[0065] According to the configuration of 5) above, by setting the expansion angle (θ) in the gradual change section (S1) to 15° or less, the change in area of ​​the flow path cross section in the gradual change section (S1) can be made gradual, thereby suppressing pressure loss in the gradual change section (S1).

[0066] 6) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in any one of 1) to 5), the intermediate section (83) further includes an upstream section (S2) having a flow path cross section along the first flow path cross section (CS1) upstream of the gradual change section (S1).

[0067] According to the above configuration 6), separation of the swirl flow in the upstream section (S2) of the intermediate portion (83) can be suppressed, and pressure loss due to the separation can be reduced.

[0068] 7) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in any one of 1) to 6), the second flow path cross section (CS2) has a longitudinal direction (LD) along a direction perpendicular to a radial direction of the rotating shaft (3).

[0069] According to the configuration of 7) above, by making the second flow path cross section (CS2) have a cross-sectional shape having a longitudinal direction (LD) along a direction perpendicular to the radial direction of the rotating shaft (3), separation of the swirl flow downstream of the gradual change section (S1) including the high-pressure stage side curved portion (85) can be relatively suppressed, and pressure loss due to the separation can be suppressed.

[0070] 8) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in any one of 1) to 7) above, the high-pressure stage side connection portion (82) includes: a radially extending portion (86) having one end connected to the high-pressure stage side curved portion (85) and extending inward in the radial direction of the rotating shaft (3); and an inlet opening connection portion (87) having a curved shape connecting the other end of the radially extending portion (86) and the high-pressure stage inlet opening (71).

[0071] According to the configuration of 8) above, the high-pressure stage side connection part (82) including the radial extending part (86) and the inlet opening connection part (87) can be connected to the high-pressure stage inlet opening (71) opening along the axial direction of the rotating shaft (3) without requiring a sudden expansion of the flow path cross section, and therefore separation that may occur due to a sudden expansion of the flow path cross section can be suppressed, and pressure loss due to the separation can be suppressed.

[0072] 9) In some embodiments, in the piping device (8) of the multi-stage electric centrifugal compressor (1) described in 8), the flow path area of ​​the inlet opening connection portion (87) is 1.5 times or less the flow path area of ​​the radial extension portion (86).

[0073] According to the configuration of 9) above, by not making the flow path area of ​​the inlet opening connection portion (87) larger than the flow path area of ​​the radially extending portion (86), separation that may occur due to a sudden expansion of the flow path cross section can be suppressed, and pressure loss due to the separation can be suppressed.

[0074] 10) In some embodiments, the piping device (8) for the multi-stage electric centrifugal compressor (1) according to any one of 1) to 9) above further includes an air bleed line (88) for guiding the compressed fluid flowing through the intermediate section (83) as a cooling medium to a cooling section (9) for cooling the electric motor (10), the air bleed line (88) including an air bleed hole (881) formed on an inner surface (831) of the intermediate section (83) upstream of the gradual change section (S1).

[0075] According to the configuration of 10) above, the compressed fluid flowing upstream of the gradual change section (S1) of the intermediate section (83) has a relatively high static pressure, so that a sufficient differential pressure can be maintained with respect to the cooling section (9), and the amount of cooling air can be secured.

[0076] 11) In some embodiments, the piping device (8) of the multi-stage electric centrifugal compressor (1) described in 10) above, wherein the bleed hole (881) is formed on the inner surface (832) on the outer circumferential side of the intermediate portion (83).

[0077] According to the configuration of 11), by forming the bleed holes (881) on the inner surface (832) on the outer circumferential side of the intermediate portion (83), the layout of the bleed lines (88) becomes easier than when the bleed holes (881) are formed on the inner surface on the inner circumferential side.

[0078] 12) In some embodiments, the piping device (8) for the multi-stage electric centrifugal compressor (1) according to any one of 1) to 9) above further includes an air bleed line (88) for guiding the compressed fluid flowing through the intermediate section (83) as a cooling medium to a cooling section (9) for cooling the electric motor (10), the air bleed line (88) including an air bleed hole (882) formed on an inner surface (833) of the intermediate section (83) downstream of the gradual change section (L1) or on an inner circumferential side of a downstream end of the gradual change section (L1).

[0079] According to the configuration of 12) above, a boundary layer (LPA) with a relatively low momentum may be formed downstream of the gradual change section (L1) of the intermediate portion (83) and on the inner peripheral side of the downstream end of the gradual change section (L1). By forming a bleed hole (882) on the inner surface (833) on the inner peripheral side and extracting the compressed fluid, the development of the boundary layer (LPA) can be suppressed. By suppressing the development of the boundary layer (LPA), separation of the main flow in the piping device (8) at the high-pressure stage side curved portion (85) can be suppressed, and pressure loss due to the separation can be reduced.

[0080] 13) A multi-stage electric centrifugal compressor (1) according to at least one embodiment of the present disclosure includes the piping device (8) of the multi-stage electric centrifugal compressor (1) described in any one of 1) to 12) above.

[0081] According to the configuration of 13), the pressure loss in the piping device (8) can be suppressed, and therefore the efficiency of the multi-stage electric centrifugal compressor (1) can be improved.

[0082] REFERENCE SIGNS LIST 1 Multi-stage electric centrifugal compressor 3 Rotating shaft 4 Low-pressure stage impeller 5 High-pressure stage impeller 6 Low-pressure stage housing 7 High-pressure stage housing 8, 08 Piping device 9 Cooling section 10 Electric motor 11 Rotating body 12 Motor stator 13 Rotor assembly 14 Permanent magnet 15 Bearing 15A Low-pressure stage side bearing 15B High-pressure stage side bearing 16 Bearing housing 16A Low-pressure stage side bearing housing 16B High-pressure stage side bearing housing 20 Fuel cell 21 Compressed gas supply line 61 Low-pressure stage outlet opening 62 Low-pressure stage inlet opening 71 High-pressure stage inlet opening 72 High-pressure stage outlet opening 81 Low-pressure stage side connecting portion 82 High-pressure stage side connecting portion 83 Intermediate portion 84 Low-pressure stage side curved portion 85 High-pressure stage side curved portion 86 Radial extension portion 87 Inlet opening connection 88 Bleed line 881, 882 Bleed holes CS1 First flow passage cross section CS2 Second flow passage cross section F1 Swirl flow F2, F3 Separated vortex LA Major axis LD Longitudinal direction LPA Boundary layer S1 Gradual change section S2 Upstream section SA Minor axis X Axial direction XH High pressure stage side XL Low pressure stage side Y Radial direction

Claims

1. A piping device for a multi-stage electric centrifugal compressor for connecting a low-pressure stage side and a high-pressure stage side of the multi-stage electric centrifugal compressor configured to drive impellers provided on both ends of a rotating shaft by an electric motor, comprising: a low-pressure stage side connecting part connected to a low-pressure stage outlet opening formed in a low-pressure stage housing that houses a low-pressure stage impeller provided on one side of the rotating shaft; a high-pressure stage side connecting part connected to a high-pressure stage inlet opening formed in a high-pressure stage housing that houses a high-pressure stage impeller provided on the other side of the rotating shaft; an intermediate part extending along the central axis of the rotating shaft, the intermediate part including a gradual change section in which the flow path cross section gradually changes from a first flow path cross section that is circular to a second flow path cross section having a longitudinal direction that is aligned along a direction intersecting the radial direction of the rotating shaft; and a low-pressure stage side curved part having a curved shape that connects the low-pressure stage side connecting part and the intermediate part and has a circular flow path cross section. a high-pressure stage side curved portion having a curved shape connecting the high-pressure stage side connecting portion and the intermediate portion, and having a flow path cross section along the second flow path cross section.

2. The piping device of a multi-stage electric centrifugal compressor according to claim 1, wherein the second flow passage cross section is elliptical.

3. The piping device of a multi-stage electric centrifugal compressor according to claim 2, wherein the major axis of the second flow passage cross section has a length at least twice as long as the minor axis of the second flow passage cross section.

4. The piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3, wherein the gradually changing section has a length that is four times or more the diameter of the first flow path cross section.

5. The piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3, wherein the divergence angle in the gradually changing section is 15° or less.

6. A piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3, wherein the intermediate section further includes an upstream section having a flow path cross section along the first flow path cross section, upstream of the gradually changing section.

7. A piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3, wherein the second flow path cross section has a longitudinal direction that is perpendicular to the radial direction of the rotating shaft.

8. A piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3, wherein the high-pressure stage side connecting portion includes: a radially extending portion having one end connected to the high-pressure stage side curved portion and extending radially inward of the rotating shaft; and an inlet opening connecting portion having a curved shape connecting the other end of the radially extending portion and the high-pressure stage inlet opening.

9. The piping device for a multi-stage electric centrifugal compressor according to claim 8, wherein the flow path area of ​​the inlet opening connecting portion is 1.5 times or less the flow path area of ​​the radially extending portion.

10. A piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3, further comprising an air bleed line for guiding the compressed fluid flowing through the intermediate section as a cooling medium to a cooling section for cooling the electric motor, the air bleed line including an air bleed hole formed on the inner surface of the intermediate section upstream of the gradual change section.

11. The piping device of a multi-stage electric centrifugal compressor according to claim 10, wherein the bleed hole is formed on the inner surface on the outer circumferential side of the intermediate portion.

12. A piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3, further comprising an air bleed line for guiding the compressed fluid flowing through the intermediate section to a cooling section for cooling the electric motor as a cooling medium, the air bleed line including an air bleed hole formed on the inner surface of the intermediate section downstream of the gradual change section or on the inner circumferential side of the downstream end of the gradual change section.

13. A multi-stage electric centrifugal compressor comprising the piping device for a multi-stage electric centrifugal compressor according to any one of claims 1 to 3.

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