Centrifugal compressor
Patent Information
- Application Number
- JP2023213861
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-12-19
- Publication Date
- 2026-02-17
AI Technical Summary
Existing centrifugal compressors face challenges in forming a compact discharge scroll that suppresses fluid separation during inflow, either leading to peeling issues when changing flow direction or requiring a large outer diameter without direction change.
The centrifugal compressor design includes a discharge scroll connected to the diffuser flow path radially, extending circumferentially with a constant radial interval and gradually narrowing axially, ensuring the flow direction is not altered, thus preventing separation and allowing for a compact design.
This configuration enables a compact discharge scroll that suppresses fluid separation and reduces stall and pressure loss, ensuring stable performance while minimizing the compressor's radial size.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a centrifugal compressor.
Background Art
[0002] As a type of centrifugal rotating machine, a multistage centrifugal compressor having a plurality of stages of impellers for compressing gas is known. The multistage centrifugal compressor successively compresses the gas sucked into the casing from the suction port with a plurality of stages of impellers and discharges it outside the casing from the discharge port. A discharge scroll is connected to the discharge port to keep the flow velocity of the gas discharged from the impeller through the diffuser flow path constant and reduce the pressure.
[0003] For example, Patent Document 1 describes a discharge volute (discharge scroll) formed such that the radial interval gradually widens as it goes downstream in the gas flow direction in the circumferential direction. This discharge volute is formed by fixing a volute piece having a gradually decreasing radial wall thickness dimension to the casing as it goes downstream in the gas flow direction in the circumferential direction.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] By the way, when forming the discharge scroll, in the radial direction, it is formed in a shape that changes the flow direction of the working fluid such as gas discharged from the diffuser flow path toward the outside in the radial direction so as to flow inward in the radial direction, or a shape that allows it to flow in without changing the flow direction. In the discharge scroll with a shape that allows it to flow in after changing the flow direction, peeling is likely to occur when the working fluid flows into the discharge scroll. On the other hand, in the discharge scroll with a shape that allows it to flow in without changing the flow direction, the discharge scroll is formed on the outside in the radial direction with respect to the diffuser flow path, and the outer diameter becomes too large as a centrifugal compressor. It is required to form a discharge scroll compactly while suppressing the separation of the flow at the time of inflow of the working fluid.
[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a centrifugal compressor capable of forming a discharge scroll compactly while suppressing the separation of the flow at the time of inflow of the working fluid.
Means for Solving the Problems
[0007] To solve the above problems, the centrifugal compressor according to the present disclosure includes a rotating shaft extending in the axial direction along which the central axis extends, and a casing having a suction port formed on the first side in the axial direction and a discharge port formed on the second side in the axial direction. The rotating shaft is disposed within the casing and has an impeller that compresses and discharges the working fluid supplied from the first side in the axial direction to the outside in the radial direction with respect to the central axis. The casing includes a diaphragm formed in a cylindrical shape extending in the axial direction so as to cover the impeller, an outer casing formed in a cylindrical shape extending in the axial direction so as to cover the diaphragm, a head that closes the openings at both ends in the axial direction of the outer casing, a diffuser flow path that guides the working fluid discharged from the impeller toward the outside in the radial direction, and a discharge scroll that guides the working fluid discharged from the impeller to the discharge port. The discharge scroll is connected to the diffuser flow path on the outside in the radial direction, extends in the circumferential direction around the central axis, and the discharge scroll is formed such that the radial interval when viewed from the axial direction is constant, and the axial interval gradually narrows as it approaches away from the discharge port in the circumferential direction.
Effect of the Invention
[0008] According to the centrifugal compressor of the present disclosure, it is possible to form a compact discharge scroll while suppressing the separation of the flow at the time of inflow of the working fluid.
Brief Description of the Drawings
[0009]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Embodiments for Carrying Out the Invention
[0010] Hereinafter, embodiments for carrying out the centrifugal compressor according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to only this embodiment.
[0011] (Configuration of Centrifugal Compressor) As shown in FIG. 1, the centrifugal compressor 1 in the present embodiment is a single-shaft multi-stage centrifugal compressor. The centrifugal compressor 1 mainly includes a rotating shaft 2 that rotates around a central axis O, and a casing 10 formed so as to surround the rotating shaft 2.
[0012] (Configuration of Rotating Shaft) The rotating shaft 2 extends in the axial direction Da. The rotating shaft 2 extends so as to penetrate the inside of the casing 10 along the central axis O. The rotating shaft 2 has a rotating shaft main body 21 and an impeller 22.
[0013] In the present embodiment, the direction in which the central axis O extends is defined as the axial direction Da. The axial direction Da of the rotating shaft 2 is along the horizontal plane. That is, the central axis O extends horizontally. The radial direction with respect to the central axis O is simply defined as the radial direction Dr. Also, the direction around the rotating shaft 2 centered on the central axis O is defined as the circumferential direction Dc.
[0014] The rotating shaft body 21 is formed in a columnar shape extending in the axial direction Da. The end of the rotating shaft body 21 on the first side Da1 in the axial direction Da is supported by the casing 10 so as to be rotatable around the central axis O by the journal bearing 32A and the thrust bearing 31. The end of the rotating shaft body 21 on the second side Da2 in the axial direction Da is supported by the casing 10 so as to be rotatable around the central axis O by the journal bearing 32B.
[0015] The impeller 22 is arranged on the outer side Dro in the radial direction Dr with respect to the rotating shaft body 21, with the central axis O as a reference. A plurality of impellers 22 are arranged spaced apart in the axial direction Da within the casing 10. In the present embodiment, for example, six impellers 22 are arranged at intervals in the axial direction Da.
[0016] Each impeller 22 compresses and discharges the working fluid (for example, gas) supplied from the first side Da1 in the axial direction Da to the outer side Dro in the radial direction Dr. Each impeller 22 has an impeller flow path 23 formed therein. The impeller flow path 23 has a gradually decreasing cross-sectional area as it goes from the inner side Dri in the radial direction Dr to the outer side Dro in the radial direction Dr. As a result, the working fluid flowing through the impeller flow path 23 while the impeller 22 is rotating is gradually compressed and becomes high pressure. Each impeller 22 may be a closed impeller having a cover or an open impeller not having a cover.
[0017] (Configuration of the casing) The casing 10 is formed so as to surround the rotating shaft body 21 and the plurality of impellers 22 from the outer side Dro in the radial direction Dr. The casing 10 includes an outer casing 11, a suction port 111, a discharge port 112, a plurality of diaphragms 15, and a head 17.
[0018] The outer casing 11 is formed in a cylindrical shape extending in the axial direction Da. The outer casing 11 is formed so as to cover the rotating shaft 2, the plurality of diaphragms 15, and the head 17 from the outer side Dro in the radial direction Dr. The outer casing 11 forms a suction port 111 and a discharge port 112.
[0019] The suction port 111 is formed on the first side Da1 of the external casing 11 in the axial direction Da. The suction port 111 allows the working fluid to flow into the external casing 11 from the outside.
[0020] The discharge port 112 is formed on the second side Da2 of the external casing 11 in the axial direction Da. The discharge port 112 discharges the working fluid compressed through all the impellers 22 inside the external casing 11 to the outside of the external casing 11. That is, the discharge port 112 is arranged away from the suction port 111 on the second side Da2 in the axial direction Da.
[0021] The plurality of diaphragms 15 are arranged inside the external casing 11 on the inner side Dri in the radial direction Dr. The plurality of diaphragms 15 are formed in a cylindrical shape extending in the axial direction Da as a whole so as to cover each stage of the impeller 22. Each diaphragm 15 is formed in a disc shape centered on the central axis O. The plurality of diaphragms 15 are laminated in the axial direction Da, and adjacent diaphragms 15 are fixed to each other by welding or bolts. The plurality of diaphragms 15 cover the periphery of the rotating shaft 2 by being fixed to each other, and form a casing flow path 40 inside that connects between the plurality of impellers 22. Further, the plurality of diaphragms 15, together with the rotating shaft 2, the head 17, the journal bearings 32A, 32B, and the thrust bearing 31, constitute a bundle. The bundle is housed inside the external casing 11. In the bundle, the plurality of diaphragms 15, the rotating shaft 2, the head 17, the journal bearings 32A, 32B, and the thrust bearing 31 are in a state where they can move together so as to be integrated.
[0022] Also, the plurality of diaphragms 15 have, as the casing flow path 40, an introduction flow path 41, a diffuser flow path 42, and a return flow path 43.
[0023] The introduction flow path 41 guides the working fluid from the outer side Dro in the radial direction Dr toward the inner side Dri in the radial direction Dr. The introduction flow path 41 changes the working fluid flowing toward the inner side Dri in the radial direction Dr into a flow toward the second side Da2 in the axial direction Da and guides it to the impeller 22. In this way, the introduction flow path 41 changes the flow direction of the working fluid toward the second side Da2 in the axial direction Da and guides it to the impeller flow path 23 of the impeller 22.
[0024] The diffuser flow path 42 extends from the inner side Dri in the radial direction Dr toward the outer side Dro. The end portion on the inner side Dri in the radial direction Dr in the diffuser flow path 42 is communicated with the end portion on the outer side Dro in the radial direction Dr of the impeller flow path 23. The diffuser flow path 42 guides the working fluid compressed by the impeller 22 from the inner side Dri in the radial direction Dr toward the outer side Dro in the radial direction Dr.
[0025] The return flow path 43 reverses the flow direction of the working fluid that has flowed from the inner side Dri in the radial direction Dr toward the outer side Dro in the radial direction Dr through the diffuser flow path 42. The return flow path 43 guides the working fluid flowing toward the outer side Dro in the radial direction Dr toward the inner side Dri in the radial direction Dr. One end (the first side Da1 in the axial direction Da) of the return flow path 43, which is upstream in the flow direction of the working fluid, is communicated with the diffuser flow path 42. The other end side (the second side Da2 in the axial direction Da) of the return flow path 43, which is downstream in the flow direction of the working fluid, is communicated with the next introduction flow path 41.
[0026] A pair of heads 17 are arranged so as to close the openings at both ends in the axial direction Da of the cylindrical outer casing 11. They are annular members centered on the central axis O. The pair of heads 17 are arranged inside the outer casing 11. The head 17 of the present embodiment has a first casing head 171 and a second casing head 172.
[0027] The first casing head 171 is arranged to close the opening on the first side Da1 in the axial direction Da of the outer casing 11. That is, the first casing head 171 is arranged adjacent to the plurality of diaphragms 15 on the first side Da1 in the axial direction Da. A suction scroll for taking in external working fluid into the casing flow path 40 through the suction port 111 is formed between the first casing head 171 and the first-stage diaphragm 15 arranged on the most first side Da1 in the axial direction Da among the plurality of diaphragms 15. The first casing head 171 is fixed to the integrated plurality of diaphragms 15 by bolts or the like. Thereby, the first casing head 171 is integrated with the diaphragm 15.
[0028] The second casing head 172 is arranged to close the opening on the second side Da2 in the axial direction Da of the outer casing 11. That is, the second casing head 172 is arranged adjacent to the plurality of diaphragms 15 on the second side Da2 in the axial direction Da. Therefore, the second casing head 172 is adjacent to the final-stage diaphragm 15 arranged on the most second side Da2 in the axial direction Da among the plurality of diaphragms 15. The second casing head 172 is fixed to the integrated plurality of diaphragms 15 by bolts or the like. Thereby, the second casing head 172 is integrated with the diaphragm 15.
[0029] (Configuration of the discharge scroll) Furthermore, the casing 10 of the centrifugal compressor 1 has a discharge scroll 50 and a flow path forming portion 57. The discharge scroll 50 guides the working fluid discharged from the final-stage impeller 22 among the plurality of impellers 22 to the discharge port 112. As shown in FIG. 2, the discharge scroll 50 is connected to the diffuser flow path 42 on the outer side Dro in the radial direction Dr. As shown in FIG. 3, the discharge scroll 50 extends in the circumferential direction Dc around the central axis O. The discharge scroll 50 is a spiral flow path formed in one turn in the circumferential direction Dc around the central axis O. The discharge scroll 50 is connected to the diffuser flow path 42 on the inner side Dri in the radial direction Dr over the entire circumference. The discharge scroll 50 is connected to the discharge port 112 on the outer side Dro in the radial direction Dr in a part of the circumferential direction Dc. The discharge scroll 50 is formed such that the interval in the radial direction Dr is constant when viewed from the axial direction Da. As shown in FIGS. 4 to 7, the discharge scroll 50 is formed such that the interval in the axial direction Da gradually narrows as it approaches the circumferential direction Dc away from the discharge port 112. That is, as shown in FIG. 4, the discharge scroll 50 has the widest interval in the axial direction Da at the position closest to the discharge port 112 in the circumferential direction Dc. Then, as shown in FIGS. 5 to 7, the discharge scroll 50 gradually narrows the interval in the axial direction Da as it moves away from the discharge port 112 in the circumferential direction Dc. The discharge scroll 50 of the present embodiment gradually narrows the interval in the axial direction Da so that the flow velocity of the working fluid flowing inside in the circumferential direction Dc becomes constant.
[0030] Also, as shown in FIG. 2, the discharge scroll 50 is formed by the space formed in the second casing head 172 and the outer casing 11. The discharge scroll 50 is surrounded by a scroll inner peripheral surface 51 on the inner side Dri in the radial direction Dr, a scroll outer peripheral surface 52 on the outer side Dro in the radial direction Dr, a first flow path forming surface 53 disposed on the second side Da2 in the axial direction Da, and a second flow path forming surface (flow path forming surface) 54 disposed on the second side Da2 in the axial direction Da.
[0031] The scroll inner peripheral surface 51 is located at the innermost side Dri in the radial direction Dr in the discharge scroll 50. The scroll inner peripheral surface 51 is a surface facing the outer side Dro in the radial direction Dr. The scroll inner peripheral surface 51 is formed by the second casing head 172. The scroll inner peripheral surface 51 is arranged on the outer side Dro in the radial direction Dr with respect to the diffuser flow path 42 when viewed from the circumferential direction Dc. The scroll inner peripheral surface 51 is arranged on the inner side Dri in the radial direction Dr with respect to the boundary between the second casing head 172 and the diaphragm 15 and the outer casing 11 when viewed from the circumferential direction Dc.
[0032] The scroll outer peripheral surface 52 is located at the outermost side Dro in the radial direction Dr in the discharge scroll 50. The scroll outer peripheral surface 52 is a surface facing the inner side Dri in the radial direction Dr. The scroll outer peripheral surface 52 faces the scroll inner peripheral surface 51 in the radial direction Dr. The interval between the scroll outer peripheral surface 52 and the scroll inner peripheral surface 51 in the radial direction Dr is constant at any position in the axial direction Da and the circumferential direction Dc. The scroll outer peripheral surface 52 is formed by the outer casing 11. The scroll outer peripheral surface 52 is arranged on the inner side Dri in the radial direction Dr with respect to the outer peripheral surface of the outer casing 11 in the radial direction Dr. The scroll inner peripheral surface 51 is arranged on the outer side Dro in the radial direction Dr with respect to the boundary between the second casing head 172 and the diaphragm 15 and the outer casing 11 when viewed from the circumferential direction Dc.
[0033] The first flow path forming surface 53 is located at the first side Da1 in the most axial direction Da in the discharge scroll 50. The first flow path forming surface 53 is a surface facing the second side Da2 in the axial direction Da. The first flow path forming surface 53 is formed by the outer casing 11 and the diaphragm 15. The first flow path forming surface 53 is formed in a planar shape so as to be integrally connected at the same position as the surface forming the diffuser flow path 42 in the axial direction Da.
[0034] The second flow path forming surface 54 is located on the second side Da2 of the discharge scroll 50 in the most axial direction Da. The second flow path forming surface 54 faces the first flow path forming surface 53 in the axial direction Da. The interval between the first flow path forming surface 53 and the second flow path forming surface 54 in the axial direction Da gradually increases in the circumferential direction Dc as the discharge port 112 approaches. The second flow path forming surface 54 is a surface facing the first side Da1 of the axial direction Da. The second flow path forming surface 54 is formed by the second casing head 172 and a flow path forming portion 57 described later. The second flow path forming surface 54 extends from the scroll inner peripheral surface 51 to the outer side Dro in the radial direction Dr.
[0035] The flow path forming portion 57 forms at least a part of the second flow path forming surface 54. The flow path forming portion 57 of the present embodiment forms a part of the second flow path forming surface 54 at a position overlapping the outer casing 11 in the radial direction Dr. That is, the flow path forming portion 57 forms a region on the outer side Dro in the radial direction Dr of the second flow path forming surface 54 instead of the outer casing 11. Note that the region on the inner side Dri in the radial direction Dr of the second flow path forming surface 54 is formed by the second casing head 172. The flow path forming portion 57 is fixed to the outer casing 11 on the outer side Dro in the radial direction Dr with respect to the second casing head 172. The flow path forming portion 57 is disposed in a recess 113 formed in the outer casing 11. The recess 113 is recessed from the inner peripheral surface of the outer casing 11 to the outer side Dro in the radial direction Dr. The recess 113 also forms a space for forming the discharge scroll 50 in the outer casing 11. The recess 113 is formed with a constant width in the axial direction Da. The flow path forming portion 57 is a surface forming the recess 113 and is disposed in contact with a space forming surface 114 facing the first side Da1 in the axial direction Da in the outer casing 11. As shown in FIGS. 4 to 7, the flow path forming portion 57 is formed such that the interval in the axial direction Da gradually increases as it moves away from the discharge port 112 in the circumferential direction Dc.
[0036] As shown in FIG. 4, at the position closest to the discharge port 112 in the circumferential direction Dc, the flow path forming portion 57 is in a non - arranged state. That is, at the position closest to the discharge port 112 in the circumferential direction Dc, the interval in the axial direction Da is formed to be the narrowest. Then, as shown in FIGS. 5 to 7, as the distance from the discharge port 112 increases in the circumferential direction Dc, the interval of the flow path forming portion 57 in the axial direction Da gradually becomes thicker. In this way, the flow path forming portion 57 forms the second flow path forming surface 54 together with the surface facing the second side Da2 in the axial direction Da in the second casing head 172.
[0037] (Function and effect) In the centrifugal compressor 1 with the above - described configuration, the working fluid discharged from the final - stage impeller 22 passes through the final - stage diffuser flow path 42 and flows into the discharge scroll 50. The discharge scroll 50 is connected to the final - stage diffuser flow path 42 on the outer side Dro in the radial direction Dr. Therefore, when the working fluid flows from the diffuser flow path 42 into the discharge scroll 50, the flow direction of the working fluid is not changed. As a result, the separation of the working fluid when flowing from the diffuser flow path 42 into the discharge scroll 50 can be suppressed. Further, the discharge scroll 50 has a constant interval in the radial direction Dr when viewed from the axial direction Da. That is, at any position in the circumferential direction Dc, the discharge scroll 50 has a constant interval in the radial direction Dr. Further, the discharge scroll 50 is formed such that the interval in the axial direction Da gradually narrows as it approaches the discharge port 112 in the circumferential direction Dc. Therefore, in the discharge scroll 50, the flow path area through which the working fluid flows from the diffuser flow path 42 to the discharge port 112 can be ensured by the change in the interval in the axial direction Da. As a result, while suppressing the expansion of the discharge scroll 50 in the radial direction Dr, the necessary performance can be ensured for the discharge scroll 50. In this way, the discharge scroll 50 can be formed compactly while suppressing the separation of the flow at the time of inflow of the working fluid.
[0038] In particular, the scroll inner peripheral surface 51 is disposed on the outer side Dro in the radial direction Dr with respect to the diffuser flow path 42. Therefore, when flowing from the diffuser flow path 42 into the discharge scroll 50, there is no need to change the flow direction of the working fluid from the outer side Dro to the inner side Dri in the radial direction Dr. Thus, the separation of the flow at the time of the inflow of the working fluid into the discharge scroll 50 can be suppressed with high precision.
[0039] Also, in the discharge scroll 50, the axial direction Da interval gradually narrows so that the flow velocity of the working fluid flowing inside in the circumferential direction Dc becomes constant. Therefore, while suppressing the expansion of the discharge scroll 50 in the radial direction Dr, it is possible to reduce the stall and pressure loss of the working fluid flowing through the discharge scroll 50. Thus, even with the compact discharge scroll 50, stable performance can be ensured.
[0040] Also, in the discharge scroll 50, the scroll inner peripheral surface 51 is formed by the second casing head 172, and the scroll outer peripheral surface 52 is formed by the outer casing 11. Therefore, the space on the inner side Dri in the radial direction Dr of the discharge scroll 50 is formed in the second casing head 172. On the other hand, the space on the outer side Dro in the radial direction Dr of the discharge scroll 50 is formed in the outer casing 11. By forming a part of the discharge scroll 50 in the outer casing 11 in this way, the size of the second casing head 172 in the radial direction Dr can be suppressed. As a result, the size of the outer casing 11 covering the second casing head 172 in the radial direction Dr can also be suppressed. Thereby, it is possible to form a discharge scroll 50 that can ensure stable performance while suppressing the size of the centrifugal compressor 1 in the radial direction Dr.
[0041] Also, a part of the second flow path forming surface 54 is formed by the flow path forming portion 57. And the flow path forming portion 57 is formed such that the interval in the axial direction Da gradually widens as it moves away from the discharge port 112 in the circumferential direction Dc. By disposing such a flow path forming portion 57 in the outer casing 11 or the second casing head 172, it is possible to easily form the discharge scroll 50 which is formed such that the interval in the axial direction Da gradually narrows as it approaches away from the discharge port 112 in the circumferential direction Dc.
[0042] In particular, as in the present embodiment, the flow path forming portion 57 is fixed in the recess 113 of the outer casing 11 on the outer side Dro in the radial direction Dr with respect to the second casing head 172. Therefore, the flow path forming portion 57 forms a region on the outer side Dro in the radial direction Dr of the second flow path forming surface 54 at a position overlapping the outer casing 11, instead of the outer casing 11. The outer casing 11 is not only large in size in the radial direction Dr but also a huge and heavy member that is very long in the axial direction Da, compared with the diaphragm 15 and the second casing head 172. Machining a three-dimensional recess 113 such that the interval in the axial direction Da changes in the circumferential direction Dc on the inner peripheral surface of such an outer casing 11 is a very difficult task. However, by disposing the flow path forming portion 57, the width of the recess 113 itself can be made constant in the axial direction Da. Therefore, the machining operation of the outer casing 11 can be facilitated and the discharge scroll 50 can be easily created.
[0043] Furthermore, the region inside Dri in the radial direction Dr of the second flow path forming surface 54 is formed by the second casing head 172. That is, in the second casing head 172, the flow path forming portion 57 is not arranged, and a part of the discharge scroll 50 is formed so as to be recessed from the outer peripheral surface of the second casing head 172. The second casing head 172 is not only a smaller member compared to the outer casing 11, but also the machining site is the outer peripheral surface instead of the inner peripheral surface. Therefore, even a three-dimensional recess in which the interval in the axial direction Da changes in the circumferential direction Dc can be formed relatively easily. Accordingly, the size of the flow path forming portion 57 can be suppressed, and the discharge scroll 50 can be created at a reduced cost.
[0044] (Other Embodiments) As described above, the embodiments of the present disclosure have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present disclosure are also included.
[0045] Note that the centrifugal compressor 1 is not limited to the structure in which the discharge scroll 50 is formed via the flow path forming portion 57. That is, the centrifugal compressor 1 may not have the flow path forming portion 57. In that case, the second flow path forming surface 54 may be formed by the outer casing 11 and the second casing head 172.
[0046] Also, the flow path forming portion 57 is not limited to the structure fixed to the outer casing 11 and forming a region on the outer side Dro in the radial direction Dr of the second flow path forming surface 54 instead of the outer casing 11. For example, the flow path forming portion 57 may be fixed to the second casing head 172. In that case, the flow path forming portion 57 may form a region on the inner side Dri in the radial direction Dr of the second flow path forming surface 54 instead of the second casing head 172. Furthermore, the flow path forming portion 57 may be fixed to both the outer casing 11 and the second casing head 172. In that case, the flow path forming portion 57 may form the entire region of the second flow path forming surface 54 instead of the outer casing 11 and the second casing head 172.
[0047] Further, the flow path forming portion 57 may have any structure as long as it can form at least a part of the second flow path forming surface 54. That is, the flow path forming portion 57 may be formed in a block-like solid structure or may be formed in a hollow structure. When the flow path forming portion 57 is formed in a hollow shape, for example, it may have a structure including a plate material forming a part of the second flow path forming surface 54 and a support member supporting this plate material on the space forming surface 114.
[0048] Also, the discharge scroll 50 is not limited to a structure formed as a space spanning the outer casing 11 and the second casing head 172. The discharge scroll 50 may be formed only in the outer casing 11 or may be formed only in the second casing head 172.
[0049] <Appendix> The centrifugal compressor 1 described in the embodiment is understood, for example, as follows.
[0050] (1) The centrifugal compressor 1 according to the first aspect includes a rotating shaft 2 extending in the axial direction Da in which the central axis O extends, and a casing 10 having a suction port 111 formed on the first side Da1 in the axial direction Da and a discharge port 112 formed on the second side Da2 in the axial direction Da. The rotating shaft 2 is disposed within the casing 10 and has an impeller 22 that compresses and discharges the working fluid supplied from the first side Da1 in the axial direction Da to the outside Dro in the radial direction Dr with respect to the central axis O. The casing 10 includes a diaphragm 15 formed in a cylindrical shape extending in the axial direction Da so as to cover the impeller 22, an outer casing 11 formed in a cylindrical shape extending in the axial direction Da so as to cover the diaphragm 15, a head 17 that closes the openings at both ends of the outer casing 11 in the axial direction Da, a diffuser flow path 42 that guides the working fluid discharged from the impeller 22 toward the outside Dro in the radial direction Dr, and a discharge scroll 50 that guides the working fluid discharged from the impeller 22 to the discharge port 112. The discharge scroll 50 is connected to the diffuser flow path 42 at the outside Dro in the radial direction Dr, extends in the circumferential direction Dc around the central axis O, has a constant interval in the radial direction Dr when viewed from the axial direction Da, and is formed such that the interval in the axial direction Da gradually narrows as it approaches away from the discharge port 112 in the circumferential direction Dc.
[0051] According to such a configuration, the working fluid discharged from the final-stage impeller 22 flows into the discharge scroll 50 through the diffuser flow path 42. The discharge scroll 50 is connected to the outside Dro in the radial direction Dr with respect to the diffuser flow path 42. Therefore, it is possible to suppress the separation of the working fluid when flowing from the diffuser flow path 42 into the discharge scroll 50. Further, in this discharge scroll 50, the interval in the radial direction Dr when viewed from the axial direction Da is constant. That is, at any position in the circumferential direction Dc, the discharge scroll 50 has a constant interval in the radial direction Dr. Further, the discharge scroll 50 is formed such that the interval in the axial direction Da gradually narrows as it approaches away from the discharge port 112 in the circumferential direction Dc. Therefore, in the discharge scroll 50, it is possible to secure the flow path area through which the working fluid flows from the diffuser flow path 42 to the discharge port 112 due to the change in the interval in the axial direction Da. As a result, while suppressing the expansion of the discharge scroll 50 in the radial direction Dr, it is possible to secure the necessary performance for the discharge scroll 50. In this way, it is possible to form the discharge scroll 50 compactly while suppressing the separation of the flow at the time of inflow of the working fluid.
[0052] (2) The centrifugal compressor 1 according to the second aspect is the centrifugal compressor 1 of (1), wherein the discharge scroll 50 has the interval in the axial direction Da gradually narrowing so that the flow velocity of the working fluid flowing through the inside thereof becomes constant in the circumferential direction Dc.
[0053] According to such a configuration, while suppressing the expansion of the discharge scroll 50 in the radial direction Dr, it is possible to reduce the stall and pressure loss of the working fluid flowing through the discharge scroll 50. In this way, even a compact discharge scroll 50 can secure stable performance.
[0054] (3) The centrifugal compressor 1 according to the third aspect is the centrifugal compressor 1 of (1) or (2), wherein the scroll inner peripheral surface 51 on the inner side Dri of the radial direction Dr of the discharge scroll 50 is formed by the head 17, and the scroll outer peripheral surface 52 on the outer side Dro of the radial direction Dr facing the scroll inner peripheral surface 51 in the radial direction Dr is formed by the outer casing 11.
[0055] According to such a configuration, the space on the inner side Dri of the radial direction Dr of the discharge scroll 50 is formed by the head 17. On the other hand, the space on the outer side Dro of the radial direction Dr of the discharge scroll 50 is formed by the outer casing 11. In this way, by forming a part of the discharge scroll 50 in the outer casing 11, the size of the head 17 in the radial direction Dr can be suppressed. As a result, the size of the outer casing 11 covering the head 17 in the radial direction Dr can also be suppressed. Thereby, it is possible to form a discharge scroll 50 that can ensure stable performance while suppressing the size of the centrifugal compressor 1 in the radial direction Dr.
[0056] (4) The centrifugal compressor 1 according to the fourth aspect is the centrifugal compressor 1 according to any one of (1) to (3), wherein the casing 10 has a flow path forming portion 57 that is disposed on the second side Da2 in the axial direction Da of the discharge scroll 50 and forms at least a part of the flow path forming surface facing the first side Da1 in the axial direction Da, and the flow path forming portion 57 is formed such that the interval in the axial direction Da gradually widens as it moves away from the discharge port 112 in the circumferential direction Dc.
[0057] According to such a configuration, by disposing the flow path forming portion 57 in the outer casing 11 or the head 17, it is possible to easily form the discharge scroll 50 formed such that the interval in the axial direction Da gradually narrows as it approaches away from the discharge port 112 in the circumferential direction Dc.
[0058] (5) The centrifugal compressor 1 according to the fifth aspect is the centrifugal compressor 1 of (4), wherein the flow path forming portion 57 is fixed to the outer casing 11 on the outer side Dro in the radial direction Dr with respect to the head 17, and forms a part of the flow path forming surface at a position overlapping the outer casing 11 in the radial direction Dr.
[0059] According to such a configuration, the flow path forming portion 57 forms, instead of the outer casing 11, a region on the outer side Dro in the radial direction Dr of the second flow path forming surface 54 at a position overlapping the outer casing 11. The outer casing 11 is not only large in size in the radial direction Dr but also a huge and heavy member that is very long in the axial direction Da compared to the diaphragm 15 and the head 17. Machining a three-dimensional recess 113 such that the interval in the axial direction Da changes in the circumferential direction Dc on the inner peripheral surface of such an outer casing 11 is a very difficult task. However, by arranging the flow path forming portion 57, the width of the recess 113 of the outer casing 11 itself can be made constant in the axial direction Da. Therefore, the machining operation of the outer casing 11 can be facilitated, and the discharge scroll 50 can be easily created.
Explanation of Reference Numerals
[0060] 1... Centrifugal compressor O... Central axis 2... Rotating shaft 21... Rotating shaft body 22... Impeller 23... Impeller flow path 10... Casing 11... Outer casing 111... Suction port 112... Discharge port 113... Recess 114... Space forming surface 15... Diaphragm 40... Casing flow path 41... Introduction flow path 42... Diffuser flow path 43... Return flow path 17... Head 171... First casing head 172…Second casing head 50…Discharge scroll 51…Inner peripheral surface of scroll 52…Outer peripheral surface of scroll 53…First flow path forming surface 54…Second flow path forming surface 57…Flow path forming portion 31…Thrust bearing 32A, 32B…Journal bearings Da…Axial direction Da1…First side Da2…Second side Dr…Radial direction Dro…Outer side Dri…Inner side Dc…Circumferential direction
Claims
1. a rotation axis extending in the axial direction of the central axis; a casing having an intake port formed on a first side in the axial direction and an exhaust port formed on a second side in the axial direction, the rotating shaft has an impeller disposed in the casing, which compresses and discharges the working fluid supplied from a first side in the axial direction outward in a radial direction relative to the central axis, The casing comprises: a diaphragm formed in a cylindrical shape extending in the axial direction so as to cover the impeller; an outer casing formed in a cylindrical shape extending in the axial direction so as to cover the diaphragm; a head for closing openings at both ends of the outer casing in the axial direction; a diffuser flow path that guides the working fluid discharged from the impeller toward an outer side in the radial direction; a discharge scroll that guides the working fluid discharged from the impeller to the discharge port, The discharge scroll is connected to the diffuser passage on the outer side in the radial direction, extending in a circumferential direction around the central axis, The radial spacing is constant when viewed from the axial direction, and the axial spacing is gradually narrowed as the distance from the discharge port increases in the circumferential direction, the casing has a flow path forming portion that is disposed on a second side in the axial direction of the discharge scroll and forms at least a part of a flow path forming surface that faces the first side in the axial direction, The flow path forming portion is formed so that the spacing in the axial direction gradually increases with increasing distance from the discharge port in the circumferential direction.
2. 2. The centrifugal compressor according to claim 1, wherein the axial spacing of the discharge scroll gradually narrows so that the flow velocity of the working fluid flowing inside the discharge scroll is constant in the circumferential direction.
3. 3. The centrifugal compressor according to claim 1, wherein the discharge scroll has an inner circumferential surface on the inside in the radial direction formed by the head, and an outer circumferential surface on the outside in the radial direction that faces the inner circumferential surface of the scroll and is formed by the outer casing.
4. 3. The centrifugal compressor according to claim 1, wherein the flow path forming portion is fixed to the outer casing at a radially outer side relative to the head, and forms a part of the flow path forming surface at a position overlapping with the outer casing in the radial direction.