Centrifugal Compressor

Abstract

To reduce fluid loss.SOLUTION: A centrifugal compressor 100 comprises: a rotating body 200 provided with a first impeller 220 facing in a first direction out of axial directions of a shaft 210, and a second impeller 230 separated from the first impeller 220 in the axial directions, and facing in a second direction opposite to the first direction; a housing 500 formed with a first impeller housing chamber 530 housing the first impeller 220, and a second impeller housing chamber 550 housing the second impeller 230; a scroll flow passage 570 communicating with a discharge port 572 opened to the outside of the housing 500, and the second impeller housing chamber 550; and a communication passage 540 having through holes 504a and 506d formed radially outside the scroll flow passage 570, and extending in an arc shape in a circumferential direction by avoiding the discharge port 572, and causing the first impeller housing chamber 530 and the second impeller housing chamber 550 to communicate with each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to centrifugal compressors. [Background technology]

[0002] Patent Document 1 discloses a multi-stage compressor in which a front impeller and a rear impeller are arranged back-to-back in the axial direction of a shaft. The multi-stage compressor described in Patent Document 1 can further compress a fluid compressed by the front impeller with the rear impeller.

[0003] The multi-stage compressor described in Patent Document 1 includes a front-stage housing in which a front-stage scroll passage is formed so as to surround the outer periphery of the front-stage impeller. The multi-stage compressor described in Patent Document 1 also includes a rear-stage housing in which a rear-stage scroll passage is formed so as to surround the outer periphery of the rear-stage impeller. And, on the outside of the front-stage housing and the rear-stage housing, a pipe is provided that connects a discharge port of the front-stage scroll passage of the front-stage housing to an intake port of the rear-stage impeller of the rear-stage housing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-193653 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the multi-stage compressor described in Patent Document 1, the compressed fluid is actually discharged from the discharge port of the rear-stage scroll passage. Therefore, a configuration in which the front-stage scroll passage is provided in the front-stage housing leads to an increase in fluid loss in the multi-stage compressor. Also, a configuration in which a pipe is provided outside the front-stage housing and the rear-stage housing to connect the discharge port of the front-stage scroll passage and the intake port of the rear-stage impeller leads to an increase in fluid loss in the multi-stage compressor.

[0006] An object of the present disclosure is to provide a centrifugal compressor capable of reducing fluid loss. [Means for solving the problem]

[0007] In order to solve the above problems, the centrifugal compressor of the present disclosure includes a rotor provided with a first impeller facing a first direction in the axial direction of a shaft and a second impeller spaced axially from the first impeller and facing a second direction opposite to the first direction, a housing in which a first impeller accommodating chamber for accommodating the first impeller and a second impeller accommodating chamber for accommodating the second impeller are formed, a scroll passage communicating with a discharge port opening to the outside of the housing and the second impeller accommodating chamber, and a communication passage formed radially outward of the scroll passage, having a through hole extending circumferentially in an arc shape avoiding the discharge port, and communicating between the first impeller accommodating chamber and the second impeller accommodating chamber.

[0008] The radial width of each of the through holes at both circumferential ends may be greater than the radial width of the central portion.

[0009] The communicating passage may have an upstream communicating passage connecting the first impeller accommodating chamber and the through hole, and a downstream communicating passage connecting the through hole and the second impeller accommodating chamber, and the through hole may have a gradually decreasing portion connected to the upstream communicating passage and whose circumferential width gradually decreases from the upstream communicating passage side toward the downstream communicating passage side, and a gradually increasing portion connected to the downstream communicating passage and whose circumferential width gradually increases from the upstream communicating passage side toward the downstream communicating passage side. Effect of the Invention

[0010] According to the present disclosure, fluid loss can be reduced. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a centrifugal compressor according to the present embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a split body according to the present embodiment. [Diagram 3] FIG. 3 is a view taken along the line III-III in FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of a divided body according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for ease of understanding, and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present disclosure are not illustrated.

[0013] 1 is a schematic cross-sectional view of a centrifugal compressor 100 according to this embodiment. As shown in FIG. 1, the centrifugal compressor 100 includes a rotor 200, a bearing 300, an electric motor 400, and a housing 500.

[0014] The rotating body 200 includes a shaft 210 , a first impeller 220 , and a second impeller 230 .

[0015] The shaft 210 has a cylindrical shape, and is rotatably supported by a bearing 300. An output shaft 410 of an electric motor 400 is attached to one end of the shaft 210. The shaft 210 is driven to rotate by the electric motor 400.

[0016] First impeller 220 is provided at the middle of shaft 210, and is provided between second impeller 230 and bearing 300. First impeller 220 has a hub 222 and blades 224. Hub 222 has a conical shape, and the outer diameter increases as it is separated from electric motor 400. Blades 224 are provided on the outer periphery of hub 222, and a plurality of blades 224 are formed in the circumferential direction of hub 222 (hereinafter simply referred to as the circumferential direction).

[0017] The first impeller 220 is formed integrally with the shaft 210. However, without being limited thereto, the first impeller 220 may be formed separately from the shaft 210 and may be, for example, press-fitted into the shaft 210.

[0018] The second impeller 230 is provided at the end of the shaft 210 opposite to the end connected to the electric motor 400. The second impeller 230 has a hub 232 and blades 234. The hub 232 has a conical shape, and the outer diameter increases as it approaches the first impeller 220. The blades 234 are provided on the outer periphery of the hub 232, and a plurality of blades 234 are formed in the circumferential direction of the hub 232.

[0019] The maximum outer diameter of the hub 232 and the blades 234 is smaller than the maximum outer diameter of the hub 222 and the blades 224. In other words, the maximum outer diameter of the second impeller 230 is smaller than the maximum outer diameter of the first impeller 220. However, without being limited thereto, the maximum outer diameter of the second impeller 230 may be equal to or larger than the maximum outer diameter of the first impeller 220.

[0020] Bottom surface 222a of hub 222 and bottom surface 232a of hub 232 face each other in the axial direction of shaft 210 (hereinafter simply referred to as the axial direction). In other words, first impeller 220 and second impeller 230 are provided back-to-back with each other. In this manner, rotating body 200 is provided with first impeller 220 facing a first direction in the axial direction of shaft 210, and second impeller 220 spaced apart from first impeller 220 in the axial direction and facing a second direction opposite to the first direction.

[0021] The second impeller 230 is formed integrally with the shaft 210. However, without being limited thereto, the second impeller 230 may be formed separately from the shaft 210 and may be press-fitted into the shaft 210, for example.

[0022] The bearing 300 is attached to the outer circumferential surface of the shaft 210, and is disposed between the first impeller 220 and the electric motor 400. A support 310 is disposed on the inner circumferential surface of the housing 500. The bearing 300 is attached to the housing 500 by the support 310. The bearing 300 axially supports the shaft 210 so as to be freely rotatable. In this embodiment, the bearing 300 is a rolling bearing, and a pair is provided in the housing 500. However, the present invention is not limited to this, and the bearing 300 may be a plain bearing.

[0023] The electric motor 400 is provided outside the housing 500, and drives the shaft 210 to rotate when power is supplied thereto.

[0024] In the housing 500, an intake port 510, an intake passage 520, a first impeller accommodating chamber 530, a communication passage 540, a second impeller accommodating chamber 550, a diffuser passage 560, and a scroll passage 570 are formed. The communication passage 540 communicates the first impeller accommodating chamber 530 and the second impeller accommodating chamber 550 within the housing 500. The communication passage 540 in this embodiment includes an upstream communication passage 542, an intermediate communication passage 544, and a downstream communication passage 546.

[0025] The housing 500 of this embodiment includes a first housing 502, a partition plate 504, and a second housing 506. The first housing 502, the partition plate 504, and the second housing 506 are axially connected to one another. The first housing 502, the partition plate 504, and the second housing 506 may be connected by a fastener (not shown), or may be connected by welding, adhesion, or the like.

[0026] The first housing 502 is disposed closer to the electric motor 400 than the partition plate 504 and the second housing 506. The partition plate 504 is disposed between the first housing 502 and the second housing 506, and is sandwiched between the first housing 502 and the second housing 506. The second housing 506 is disposed on a side farther away from the electric motor 400 than the first housing 502 and the partition plate 504.

[0027] An intake port 510, an intake passage 520, a first impeller accommodating chamber 530, and an upstream communication passage 542 are formed in the first housing 502. The intake port 510 is an inlet that opens to the outside of the first housing 502 and through which air flows in as a fluid.

[0028] The intake passage 520 is connected to the intake port 510 and the first impeller housing chamber 530. The intake passage 520 guides the air flowing in from the intake port 510 to the first impeller housing chamber 530.

[0029] The first impeller accommodating chamber 530 is an accommodating space that accommodates the first impeller 220. The first impeller accommodating chamber 530 has a shape that is slightly larger than the outer shape of the first impeller 220. The first housing 502 includes divided bodies 502a and 502b. The divided bodies 502a and 502b are arranged to be spaced apart from each other in the axial direction. The divided body 502a is arranged to face the outer circumferential surface of the blade 224 of the first impeller 220 in the axial and radial directions. The divided body 502b is arranged to face the bottom surface 222a of the hub 222 of the first impeller 220 in the axial direction. The first impeller accommodating chamber 530 and the upstream communication passage 542 are formed by the space between the divided bodies 502a and 502b.

[0030] The upstream communication passage 542 is formed on the radial outside of the first impeller housing chamber 530. The upstream communication passage 542 is formed in an annular shape. In this embodiment, in a cross section perpendicular to the central axis of the shaft 210, the upstream communication passage 542 has a circular cross-sectional shape centered on the central axis of the shaft 210 or a ring-shaped cross-sectional shape. In particular, along the central axis, the cross-sectional shape of the upstream communication passage 542 perpendicular to the central axis of the shaft 210 transitions from a ring-shaped cross-sectional shape to a circular shape along the direction from the back surface of the first impeller 220 toward the surface. In addition, the radius of the circle on the outer periphery of the upstream communication passage 542 also monotonically decreases along the direction from the back surface of the first impeller 220 toward the surface. The upstream communication passage 542 has a radial extension portion 542a extending in the radial direction of the shaft 210 (hereinafter simply referred to as the radial direction) and an axial extension portion 542b extending in the axial direction. The radially extending portion 542a communicates with the outer diameter end portion of the first impeller accommodating chamber 530, and extends radially outward from the first impeller accommodating chamber 530. The axially extending portion 542b extends in the axial direction from the radially extending portion 542a.

[0031] Partition plate 504 has a flat plate shape, and is disposed between first housing 502 and second housing 506. At least a portion of partition plate 504 is disposed between first impeller 220 and second impeller 230. Partition plate 504 separates the space between first impeller 220 and second impeller 230.

[0032] A divided body 502b is attached to the first impeller 220 side of the partition plate 504. The divided body 502b is supported by the partition plate 504. A through hole 504a is formed in the partition plate 504. The through hole 504a passes through the partition plate 504 in the axial direction. The through hole 504a communicates with an axially extending portion 542b of the upstream communication passage 542 in the axial direction.

[0033] The radial position of the through hole 504a is equal to the radial position of the axial extension portion 542b of the upstream communication passage 542. The radial width of the through hole 504a is equal to the radial width of the axial extension portion 542b of the upstream communication passage 542. Here, "equal" means that it is completely equal and that it is deviated from the completely equal within the range of the allowable error (machining accuracy, assembly error, etc.). Hereinafter, "equal" or "same" means that it is completely equal (same) and that it is deviated from the completely equal (same) within the range of the allowable error (machining accuracy, assembly error, etc.). The through hole 504a has a shape equal to a part of the annular axial extension portion 542b. The through hole 504a of this embodiment is formed in a C-shape. Therefore, in a cross section perpendicular to the central axis of the shaft 210, the range in which the through hole 504a is formed is wider than 180 degrees with the central axis of the shaft 210 as the center. In addition, in the cross section, the through hole 504a of the present embodiment is formed by one closed region. Although the through hole 504a of the present embodiment is C-shaped, in a cross section perpendicular to the central axis of the shaft 210, the cross-sectional shape of the through hole 504a may be formed by several closed regions distributed in the circumferential direction.

[0034] The second housing 506 includes division bodies 506a, 506b, and 506c. The division body 506a is disposed between the division bodies 506b and 506c and the partition plate 504. The division body 506c is disposed between the division body 506a and the division body 506b. The division body 506a supports the division body 506b with the division body 506c being spaced apart from the division body 506a in the axial direction. The division body 506b supports the division body 506a and the partition plate 504. The division bodies 506a, 506b, and 506c and the partition plate 504 form a downstream communication passage 546, a second impeller accommodating chamber 550, a diffuser passage 560, and a scroll passage 570.

[0035] FIG. 2 is a schematic cross-sectional view of the divided body 506a according to the present embodiment. As shown in FIG. 2, a through hole 506d is formed in the divided body 506a. The through hole 506d extends in an arc shape in the circumferential direction of the shaft 210. The through hole 506d is axially communicated with the through hole 504a. The through hole 504a has a shape similar to that of the through hole 506d and extends in an arc shape in the circumferential direction of the shaft 210. The radial position of the through hole 506d is equal to the radial positions of the through hole 504a and the axially extending portion 542b of the upstream communicating passage 542 (see FIG. 1). The radial width of the through hole 506d is equal to the radial width of the through hole 504a and the axially extending portion 542b of the upstream communicating passage 542. The through hole 506d is communicated with the upstream communicating passage 542 via the through hole 504a.

[0036] The through holes 504a and 506d have a C-shape. In a cross section perpendicular to the central axis of the shaft 210, the range in which the through holes 504a and 506d are formed is a range wider than 180 degrees with the central axis of the shaft 210 as the center. The through holes 504a and 506d have a constant width in the radial direction. However, this is not limited thereto, and the radial width of the through holes 504a and 506d may vary in the circumferential direction. The through holes 504a and 506d are formed radially outward of the scroll passage 570. Therefore, the through holes 504a and 506d are radially separated from the scroll passage 570 and do not communicate with the scroll passage 570. In addition, the through holes 504a and 506d are formed to avoid the discharge port (discharge hole) 572 through which the scroll passage 570 communicates with the outside of the housing 500. Therefore, the through holes 504a and 506d are separated from the discharge port 572 in the circumferential direction and do not communicate with the discharge port 572.

[0037] FIG. 3 is a view taken along the line III-III in FIG. 2. In FIG. 3, the through holes 504a and 506d are shown in a planar development. As shown in FIG. 3, one end of the through hole 504a is connected to the upstream communication passage 542, and the other end is connected to the through hole 506d. The upstream communication passage 542 connects the first impeller housing chamber 530 (see FIG. 1) and the through hole 504a. One end of the through hole 506d is connected to the through hole 504a, and the other end is connected to the downstream communication passage 546. The downstream communication passage 546 connects the through hole 506d and the second impeller housing chamber 550 (see FIG. 1). The through holes 504a and 506d form an intermediate communication passage 544 that communicates the upstream communication passage 542 and the downstream communication passage 546. That is, the through holes 504a and 506d constitute a part of the communication passage 540.

[0038] The through hole 504a has a gradually decreasing portion 504aa. The gradually decreasing portion 504aa has a tapered shape in which the circumferential flow path width gradually decreases from the upstream communicating passage 542 toward the downstream communicating passage 546. In this manner, the gradually decreasing portion 504aa is connected to the upstream communicating passage 542, and the circumferential width gradually decreases from the upstream communicating passage 542 toward the downstream communicating passage 546. Since the gradually decreasing portion 504aa has a tapered shape, the fluid flowing through the upstream communicating passage 542 can be smoothly introduced into the through hole 506d, and pressure loss can be reduced.

[0039] The through hole 506d has a parallel portion 506da and a gradually increasing portion 506db. The parallel portion 506da is disposed between the gradually decreasing portion 504aa and the gradually increasing portion 506db, and has a constant flow path width in the circumferential direction and the radial direction. However, this is not limited thereto, and the flow path width of the parallel portion 506da may change in the circumferential direction or the radial direction. The gradually increasing portion 506db has a tapered shape in which the flow path width in the circumferential direction gradually increases from the upstream communication passage 542 toward the downstream communication passage 546. In this way, the gradually increasing portion 506db is connected to the downstream communication passage 546, and the circumferential width gradually increases from the upstream communication passage 542 toward the downstream communication passage 546. Since the gradually increasing portion 506db has a tapered shape, the fluid flowing through the parallel portion 506da can be smoothly introduced into the downstream communication passage 546, and the pressure loss can be reduced.

[0040] Returning to FIG. 1, the downstream communication passage 546 has one end connected to the through hole 506d and the other end connected to the second impeller housing chamber 550. The downstream communication passage 546 is a flow passage that supplies air to the second impeller 230. The air that has been supplied toward one side of the central axis of the shaft 210 through the communication passage 540 is turned back at the communication passage 540 and is supplied to the second impeller 230 with a velocity component toward one side of the central axis of the shaft 210. That is, in the cross section of the downstream communication passage 546 on the other side of the central axis of the shaft 210, a ring-shaped flow passage cross section on the outer periphery side corresponding to the upstream side of the downstream communication passage 546 and a circular flow passage cross section corresponding to the downstream side of the downstream communication passage 546 are formed, and the circular flow passage cross section is inside the ring-shaped flow passage cross section. In addition, the second housing 506 is provided with a member that faces the second impeller 230 and expands in diameter toward one side of the central axis of the shaft 210. The member forms a part of the outer periphery of the downstream communication passage 546. The upstream communication passage 542, the through holes 504a, 506d, and the downstream communication passage 546 communicate between the first impeller accommodating chamber 530 and the second impeller accommodating chamber 550. The downstream communication passage 546 is formed in the space between the divided bodies 506b, 506c separated in the axial direction.

[0041] The second impeller accommodating chamber 550 is an accommodating space that accommodates the second impeller 230. The second impeller accommodating chamber 550 has a shape slightly larger than the outer shape of the second impeller 230. The divided body 506a is disposed facing the outer circumferential surface of the blade 234 of the second impeller 230 in the axial and radial directions. The partition plate 504 is disposed facing the bottom surface 232a of the hub 232 of the second impeller 230 in the axial direction. The second impeller accommodating chamber 550, the diffuser passage 560, and the scroll passage 570 are formed by the spaces between the divided body 506a and the partition plate 504.

[0042] The diffuser passage 560 is formed on the radially outer side of the second impeller accommodating chamber 550 and communicates with the second impeller accommodating chamber 550 in the radially outer side. The diffuser passage 560 has an annular shape, communicates with the second impeller accommodating chamber 550 on the radially inner side, and communicates with the scroll passage 570 on the radially outer side.

[0043] The scroll passage 570 has one end connected to the diffuser passage 560 and the other end connected to a discharge port 572 (see FIG. 2) that opens to the outside of the second housing 506. The scroll passage 570 is formed in an annular shape. The scroll passage 570 is located, for example, radially outward of the shaft 210 than the diffuser passage 560. The scroll passage 570 communicates between the outside of the housing 500 and the second impeller accommodating chamber 550 via the diffuser passage 560 and the discharge port 572.

[0044] When the shaft 210 rotates and the first impeller 220 rotates, air is drawn into the intake passage 520 from the intake port 510. The drawn air is pressurized and accelerated in the process of flowing between the blades 224 of the first impeller 220. The pressurized and accelerated air passes through the upstream communication passage 542, the through holes 504a, 506d, and the downstream communication passage 546 and is supplied to the second impeller 230. The air supplied to the second impeller 230 is further pressurized and accelerated in the process of flowing between the blades 234 of the second impeller 230. The pressurized and accelerated air is pressurized in the diffuser passage 560 and the scroll passage 570.

[0045] As described above, the centrifugal compressor 100 includes the upstream communication passage 542 having the radially extending portion 542a extending radially outward from the first impeller accommodating chamber 530 and the axially extending portion 542b extending axially from the radially extending portion 542a. This makes it possible to guide the fluid that has passed through the first impeller 220 toward the second impeller 230 without forming a scroll passage separate from the scroll passage 570 in the housing 500. In other words, a single scroll passage 570 can be formed in the housing 500.

[0046] Further, the partition plate 504 is formed with a through hole 504a, and the second housing 506 is formed with a through hole 506d. The through holes 504a and 506d form a part of a communication passage 540 that communicates the first impeller housing chamber 530 and the second impeller housing chamber 550. The through holes 504a and 506d are formed radially outward from the scroll passage 570. Here, the through holes 504a and 506d are formed in an arc shape to avoid the discharge port 572 that opens to the outside of the housing 500. This makes it possible to guide the compressed fluid that has passed through the first impeller 220 inside the housing 500 to the second impeller 230 without providing piping outside the housing 500. As a result, the fluid loss of the centrifugal compressor 100 can be reduced.

[0047] The through holes 504a and 506d are formed with a gradually decreasing portion 504aa where the circumferential width gradually decreases and a gradually increasing portion 506db where the circumferential width gradually increases. Therefore, the fluid flowing through the upstream communicating passage 542 can be smoothly introduced into the through hole 506d, and the fluid flowing through the through hole 506d can be smoothly introduced into the downstream communicating passage 546, thereby reducing pressure loss.

[0048] (Modification) FIG. 4 is a schematic cross-sectional view of a divided body 1506a according to a modified example. Components substantially the same as those of the centrifugal compressor 100 of the above embodiment are denoted by the same reference numerals and will not be described. The through hole 1506d of this modified example has a different shape from the through hole 506d of the above embodiment. The through hole 1504a of this modified example has a different shape from the through hole 504a of the above embodiment. That is, the intermediate communication passage 1544 of this modified example has a different shape from the intermediate communication passage 544 of the above embodiment. The configuration other than the intermediate communication passage 1544 is the same as that of the centrifugal compressor 100 of the above embodiment.

[0049] As shown in FIG. 4, the through holes 1504a and 1506d have a central portion CE and both ends ED in the circumferential direction. The through holes 1504a and 1506d have a shape in which the radial width changes in the circumferential direction. Specifically, the radial width of both ends ED in the circumferential direction of the through holes 1504a and 1506d is larger than the radial width of the central portion CE. The radial width of the through holes 1504a and 1506d gradually increases from the central portion CE toward both ends ED. In other words, the flow path cross-sectional area of ​​the through holes 1504a and 1506d gradually increases from the central portion CE toward both ends ED.

[0050] According to this modification, the flow path cross-sectional area of ​​the through holes 1504a and 1506d gradually increases from the center portion CE toward the end portions ED. This causes the flow velocity of the fluid flowing through the through holes 1504a and 1506d to become slower toward the end portions ED. As a result, the fluid loss of the fluid flowing from the through holes 1504a and 1506d into the downstream communication passage 546 can be reduced.

[0051] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure.

[0052] In the above embodiment, the through holes 504a and 506d have a gradually decreasing portion and a gradually increasing portion. However, the present invention is not limited to this, and the through holes 504a and 506d do not necessarily have to have a gradually decreasing portion and a gradually increasing portion. [Explanation of symbols]

[0053] 100 Centrifugal Compressor 200 Rotating Body 210 Shaft 220 First impeller 222 Hub 222a Bottom 224 Feather 230 Second impeller 232 Hub 232a Bottom 234 Feather 300 Bearings 310 Support 400 Electric Motor 410 Output shaft 500 Housing 502 1st Housing 504 Partition 504a Through hole 504aa Tapered section 506 Second Housing 506d Through hole 506da parallel part 506db Gradual increase 510 Air Intake 520 Intake passage 530 First Impeller Containment Room 540 Communication path 542 Upstream communication path 542a Radial extension 542b Axial extension 544 Intermediate connecting passage 546 Downstream communication passage 550 Second Impeller Containment Room 560 Diffuser passage 562 Inner diameter 564 Tapered section 566 Outer diameter part 570 Scroll flow passage 1504a Through hole 1506d Through hole 1544 Intermediate passage CE central part ED both ends

Claims

1. a rotor provided with a first impeller facing a first direction in an axial direction of a shaft, and a second impeller spaced apart from the first impeller in the axial direction and facing a second direction opposite to the first direction; a housing in which a first impeller accommodating chamber for accommodating the first impeller and a second impeller accommodating chamber for accommodating the second impeller are formed; a scroll passage communicating with a discharge port opening to the outside of the housing and with the second impeller accommodating chamber; a communication passage formed radially outward from the scroll passage, the communication passage having a through hole extending in a circumferential direction in an arc shape avoiding the discharge port, the communication passage communicating between the first impeller accommodating chamber and the second impeller accommodating chamber; A centrifugal compressor comprising:

2. The radial width of each of the circumferential ends of the through hole is greater than the radial width of the central portion of the through hole.

2. The centrifugal compressor according to claim 1.

3. the communication passage includes an upstream communication passage that connects the first impeller accommodating chamber and the through hole, and a downstream communication passage that connects the through hole and the second impeller accommodating chamber, the through hole has a gradually decreasing portion connected to the upstream communication passage and whose circumferential width gradually decreases from the upstream communication passage side toward the downstream communication passage side, and a gradually increasing portion connected to the downstream communication passage and whose circumferential width gradually increases from the upstream communication passage side toward the downstream communication passage side.

3. The centrifugal compressor according to claim 1 or 2.

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