Centrifugal compressor

Abstract

In this centrifugal compressor, a casing has a diffuser part that forms an annular diffuser space, and an outer scroll part that forms a volute space which is connected with the diffuser space. The diffuser part has an annular plate that defines an edge on an axially first side of the diffuser space. The outer scroll part has: an inner surface that faces an axially second side and is positioned on the axially first side as compared to the annular plate; and a first annular groove that is recessed from the inner surface toward the axially first side. The annular plate has: a counter-flow passage lateral surface that faces the axially first side and comes into contact with the inner surface; a second annular groove that is recessed from the counter-flow passage lateral surface toward the axially second side; and a plurality of connection holes that connect the diffuser space and a space in the second annular groove. The first annular groove and the second annular groove together form an annular pressure equalization space.

Description

Centrifugal compressor

[0001] This invention relates to a centrifugal compressor. This application claims priority based on Japanese Patent Application No. 2025-026367, filed in Japan on February 21, 2025, the contents of which are incorporated herein by reference.

[0002] A centrifugal compressor generally comprises an impeller rotatable about an axis and a casing that houses the impeller. The impeller has a hub and a plurality of blades. The hub gradually widens in diameter from the first axis side to the second axis side in the axial direction in which the axis extends. The plurality of blades are mounted on the outer surface of the hub at intervals from each other in the circumferential direction with respect to the axis. The casing has a casing body and a diffuser. The casing body forms an impeller housing space that houses the impeller. The diffuser section is located on the outer circumference of the outlet edge of each of the plurality of blades, communicates with the impeller housing space, and forms an annular diffuser space about the axis. The casing body is further located on the outer periphery of the diffuser space, communicating with the diffuser space and forming a spiral-shaped volute space in which the spatial cross-sectional area gradually increases towards one side in the circumferential direction.

[0003] The following Patent Document 1 discloses the diffuser section of the centrifugal compressor described above. The diffuser space in this diffuser section is defined by a first side surface that expands radially outward and a second side surface that is spaced apart in the axial direction in which the axis extends with respect to this first side surface and expands radially outward. The diffuser section has an annular blade ring having this first side surface and a plurality of diffuser vanes provided on this blade ring. The plurality of diffuser vanes project from the first side surface toward the second side surface and are arranged at intervals in the circumferential direction. Among the plurality of diffuser vanes, the space between two adjacent diffuser vanes in the circumferential direction forms a diffuser flow path. The blade ring is fixed to the casing body. The casing body has a third side surface that faces the blade ring in the axial direction and an annular groove that is recessed from this third side surface to the side opposite to the blade ring. The annular groove of this casing body and the blade ring jointly form an annular duct. In the blade ring, communication holes are formed at positions between two adjacent diffuser vanes in the circumferential direction to communicate the diffuser space and the annular duct.

[0004] In the diffuser section described in this Patent Document 1, the pressure difference between the plurality of diffuser flow paths is suppressed by communicating the plurality of diffuser flow paths with each other through the communication holes and the annular duct. As a result, the centrifugal compressor provided with this diffuser section can operate stably.

[0005] U.S. Patent No. 10,473,115

[0006] Since the casing of the centrifugal compressor has a pressure-resistant structure due to the flow of compressed fluid inside, on the other hand, weight reduction is required for the casing of the centrifugal compressor.

[0007] Therefore, an object of the present disclosure is to provide a centrifugal compressor that can achieve stable operation and weight reduction of the casing.

[0008] A centrifugal compressor as one embodiment of the invention for achieving the above objective comprises an impeller rotatable about an axis and a casing housing the impeller. The impeller has a hub that gradually widens in diameter about the axis from the first axis side toward the second axis side in the axial direction in which the axis extends, and a plurality of blades attached to the outer surface of the hub at intervals from each other in the circumferential direction with respect to the axis. Each of the plurality of blades has an inlet edge that forms the end on the first axis side and an outlet edge that forms the radially outer end, located on the second axis side of the inlet edge and radially outward with respect to the axis. The casing includes an inner scroll section that forms an impeller housing space for housing the impeller; a diffuser section located on the outer circumference side of the outlet edge of each of the plurality of blades, communicating with the impeller housing space, and forming an annular diffuser space centered on the axis; and an outer scroll section located on the outer circumference side of the diffuser space, communicating with the diffuser space, and forming a volute space whose spatial cross-sectional area gradually increases toward one side in the circumferential direction. The diffuser section includes an annular plate that defines the edge on the first axis side of the diffuser space, and a plurality of diffuser vanes that protrude from the annular plate into the diffuser space and are spaced apart from each other in the circumferential direction. The outer scroll section has an inner surface facing the second axis side, located on the first axis side of the annular plate, extending radially with respect to the axis and in contact with the annular plate, and a first annular groove that recesses from the inner surface toward the first axis side and is annular around the axis. The annular plate has a side surface that faces the first axis and extends radially, contacting the inner surface; a second annular groove that recesses from the side surface towards the second axis and is annular around the axis; and a plurality of communication holes that connect the diffuser space and the space in the second annular groove at positions between the plurality of diffuser vanes. The first annular groove and the second annular groove work together to form an annular pressure equalization space centered on the axis.

[0009] In one aspect of this disclosure, a centrifugal compressor can be made to achieve stable operation while also reducing the weight of the casing.

[0010] This is a cross-sectional view of the main part of a centrifugal compressor according to one embodiment of the present disclosure. This is a front view of the diffuser section according to one embodiment of the present disclosure.

[0011] As shown in Figure 1, the centrifugal compressor in this embodiment comprises a rotating shaft 10, a shaft cap 11, an impeller 20, a casing 30, and a shaft sealing device 13.

[0012] The rotation axis 10 is cylindrical with the axis Ar as its center. In the following, the direction in which this axis Ar extends will be referred to as the axial direction Da. One side of this axial direction Da will be referred to as the first axis side Da1, and the other side as the second axis side Da2. The radial direction with respect to this axis Ar will simply be referred to as the radial direction Dr. The side of this radial direction Dr that approaches the axis Ar will be referred to as the radially inward Dri, and the side of this radial direction Dr that moves away from the axis Ar will be referred to as the radially outward Dr. The circumferential direction with respect to this axis Ar will simply be referred to as the circumferential direction Dc.

[0013] A rotation mechanism (not shown) that rotates the rotation shaft 10 around axis Ar is connected to the end of the second axis Da2 of the rotation shaft 10. An axis cap 11 is provided to cover the end of the first axis Da1 of the rotation shaft 10. This axis cap 11 is attached to the rotation shaft 10 by an axis cap connecting bolt 12.

[0014] The impeller 20 has a hub 21 and a plurality of blades 22. The hub 21 gradually widens in diameter around the axis Ar from the first axis side Da1 to the second axis side Da2. The plurality of blades 22 are attached to the outer surface of the hub 21 at intervals from each other in the circumferential direction Dc. Each of the plurality of blades 22 has an inlet edge 23, an outlet edge 24, and a tip 25. The inlet edge 23 faces the first axis side Da1 and forms the end of the first axis side Da1. The outlet edge 24 is located on the second axis side Da2 than the inlet edge 23 and radially outward Do with respect to the axis Ar, and faces radially outward Do and forms the end of radially outward Do. The tip 25 forms the end in the blade height direction. The first axial end Da1 of the tip 25 is connected to the radially outer end Do of the inlet edge 23, and the radially outer end Do of the tip 25 is connected to the first axial end Da1 of the outlet edge 24. This impeller 20 is of the open type.

[0015] The impeller 20 described above is mounted on the rotating shaft 10 in such a way that it cannot rotate relative to the shaft 10. Therefore, the impeller 20 can rotate integrally with the rotating shaft 10 around the axis Ar. Furthermore, the impeller 20 is restricted by the shaft cap 11 to prevent it from moving relative to the rotating shaft 10 on the first axis side Da1.

[0016] The casing 30 includes an inner scroll section 31, an outer scroll section 41, a rear support plate 49, a diffuser section 51, a plurality of connectors 61a, 61b, a plurality of sealing parts 62a, 62b, and one or more shims 63.

[0017] The inner scroll section 31 forms an impeller housing space Si that rotatably houses the impeller 20. This impeller housing space Si gradually widens in diameter around the axis Ar as it moves from the first axis side Da1 to the second axis side Da2. The outer circumferential edge of the impeller housing space Si, in other words, the inner circumferential surface 33 of the inner scroll section 31, faces the tips 25 of each of the multiple blades 22 at predetermined intervals. On this inner circumferential surface 33, the end of the second axis side Da2 is located radially outward Do compared to the outlet edges 24 of the multiple blades 22. The end of the impeller housing space Si on the first axis side Da1 is an inlet 32i through which fluid flows into the impeller housing space Si.

[0018] The inner scroll section 31 has an outer peripheral end face 34 and a flange 35. The outer peripheral end face 34 is connected to the end of the second axis Da2 of the inner peripheral surface 33 and faces radially outward Dr. Therefore, this outer peripheral end face 34 is located radially outward Dr than the exit edge 24 of each of the multiple vanes 22. The flange 35 protrudes radially outward Dr from the end of the first axis Da1 of the outer peripheral end face 34. This flange 35 extends radially outward Dr from the end of the first axis Da1 of the outer peripheral end face 34 and has a connecting surface 36 facing the second axis Da2.

[0019] The diffuser section 51 is located on the outer circumference of the outlet edge 24 of each of the multiple blades 22, communicates with the impeller housing space Si, and forms an annular diffuser space Sd with the axis Ar as the center.

[0020] The outer scroll portion 41 is located on the outer circumference side of the diffuser space Sd, communicates with the diffuser space Sd, and forms a volute space Sv in which the spatial cross-sectional area gradually increases towards one side in the circumferential direction Dc. The end of this volute space Sv in the circumferential direction Dc is a discharge port 32o through which the compressed fluid flows out. The outer scroll portion 41 has an inner surface 42, an outer surface 43, a first annular groove 45, and an inner circumferential end surface 46. The inner surface 42, outer surface 43, inner circumferential end surface 46, and first annular groove 45 are all located radially inward Dri from the volute space Sv. The inner surface 42 faces the second axis Da2 and extends radially Dr. The outer surface 43 is back-to-back with the inner surface 42 and faces the first axis Da1 and extends radially Dr. The inner circumferential end face 46 forms the end of the radially inner Dri of the outer scroll portion 41 and faces radially inner Dri. This inner circumferential end face 46 is connected to the end of the radially inner Dri of the inner surface 42 and the end of the radially inner Dri of the outer surface 43. The first annular groove 45 is recessed from the inner surface 42 toward the first axis Da1 and is annular around the axis Ar.

[0021] The rear support plate 49 is located on the second axis side Da2 relative to the impeller housing space Si, diffuser space Sd, and volute space Sv, and is disc-shaped with the axis Ar as its center. This rear support plate 49 is a component independent of the inner scroll section 31 and the outer scroll section 41. This rear support plate 49 is connected to the outer scroll section 41 by connecting bolts or the like. An axis seal device 13 is provided at the radially inner side Dri of the rear support plate 49 and at the position on the second axis side Da2 of the impeller 20. The axis seal device 13 is attached to the rear support plate 49. This axis seal device 13 suppresses the outflow of fluid from the first axis side Da1 to the second axis side Da2, with the axis seal device 13 as the reference point.

[0022] As shown in Figures 1 and 2, the diffuser section 51 includes an annular plate 52 and a plurality of diffuser vanes 58. The annular plate 52 is an annular plate centered on the axis Ar, and defines the edge Sd1 of the first axis Da1 in the diffuser space Sd. The edge Sd2 of the second axis Da2 in the diffuser space Sd is defined by a part of the back support plate 49. The plurality of diffuser vanes 58 protrude from the annular plate 52 into the diffuser space Sd and are spaced apart from each other in the circumferential direction Dc. These plurality of diffuser vanes 58 form a plurality of diffuser channels Sdp in the diffuser space Sd. Each of the plurality of diffuser channels Sdp is formed between two diffuser vanes 58 that are adjacent to each other in the circumferential direction Dc. The channel width of each diffuser channel Sdp widens towards the radially outward direction Doro. Furthermore, the aforementioned volute space Sv is formed on the first axis side Da1, with reference to the edge Sd2 of the second axis side Da2 in the diffuser space Sd.

[0023] The annular plate 52 has a flow path side surface 53, an anti-flow path side surface 54, a second annular groove 55, an inner circumferential end surface 56, and a plurality of communication holes 57. The flow path side surface 53 faces the second axis Da2 and extends radially in the Dr direction. This flow path side surface 53 is the surface that defines the edge Sd1 of the first axis Da1 in the diffuser space Sd. The anti-flow path side surface 54 is back-to-back with the flow path side surface 53 and faces the first axis Da1 and extends radially in the Dr direction. This anti-flow path side surface 54 is in contact with the inner surface 42 of the outer scroll portion 41. The inner circumferential end surface 56 forms the end of the radially inner Dri of the annular plate 52 and faces radially inward Dri. This inner circumferential end surface 56 is connected to the radially inner Dri end of the flow path side surface 53 and the radially inner Dri end of the anti-flow path side surface 54. The radial Dr position of the inner circumferential end face 56 of the annular plate 52 substantially coincides with the radial Dr position of the inner circumferential end face 46 of the outer scroll portion 41. The second annular groove 55 is recessed from the anti-flow channel side surface 54 toward the second axis Da2 and is annular around the axis Ar. Multiple communication holes 57 are arranged in the circumferential direction Dc and connect the diffuser space Sd with the space in the second annular groove 55. Each of the multiple communication holes 57 is formed between two diffuser vanes 58 that are adjacent to each other in the circumferential direction Dc. The first annular groove 45 and the second annular groove 55 work together to form an annular pressure equalization space Se centered on the axis Ar.

[0024] The annular plate 52 is a component independent of the rear support plate 49, the outer scroll section 41, and the inner scroll section 31. The annular plate 52 is connected to the outer scroll section 41 by a connecting bolt 61a, which is one of several connecting devices 61a, 61b. This connecting bolt 61a penetrates the annular plate 52 and is screwed into the outer scroll section 41 from the inner surface 42 of the outer scroll section 41. The inner scroll section 31 is a component independent of the rear support plate 49, the annular plate 52, and the outer scroll section 41. The inner scroll section 31 is connected to the outer scroll section 41 by a connecting bolt 61b, which is one of several connecting devices 61a, 61b. This connecting bolt 61b penetrates the flange 35 of the inner scroll section 31 and is screwed into the outer scroll section 41 from the outer surface 43 of the outer scroll section 41.

[0025] In this embodiment, one or more shims 63 are placed between the connecting surface 36 of the flange 35 in the inner scroll section 31 and the outer surface 43 of the outer scroll section 41. In this embodiment, the position of the inner scroll section 31 in the axial direction Da relative to the outer scroll section 41 can be easily adjusted by appropriately adjusting the number of shims 63. Therefore, in this embodiment, the gap between the tip 25 near the exit edge 24 of each of the multiple blades 22 and the inner circumferential surface 33 of the inner scroll section 31 can be easily adjusted. In this embodiment, the shims 63 are thin metal plates.

[0026] Furthermore, in this embodiment, a sealing component 62a is positioned between the inner circumferential end face 56 of the annular plate 52 and the outer circumferential end face 34 of the inner scroll portion 31. In addition, a sealing component 62b is positioned between the inner circumferential end face 46 of the outer scroll portion 41 and the outer circumferential end face 34 of the inner scroll portion 31. Therefore, in this embodiment, it is possible to suppress the fluid in the pressure equalization space Se from returning to the diffuser space Sd via the space between the inner circumferential end face 56 of the annular plate 52 and the outer circumferential end face 34 of the inner scroll portion 31. Furthermore, in this embodiment, it is possible to suppress the fluid in the pressure equalization space Se from flowing out of the casing 30 via the space between the inner circumferential end face 46 of the outer scroll portion 41 and the outer circumferential end face 34 of the inner scroll portion 31. Note that each of the sealing components 62a and 62b in this embodiment is an O-ring.

[0027] In this embodiment, multiple diffuser flow paths Sdp, which are spaces between multiple diffuser vanes 58, communicate with each other through communication holes 57 and a pressure equalization space Se. Therefore, in this embodiment, the pressure difference between the multiple diffuser flow paths Sdp can be suppressed, and as a result, stable operation of the centrifugal compressor becomes possible.

[0028] Incidentally, since compressed fluid flows through the outer scroll section 41, this outer scroll section 41 is a pressure-resistant structure. For this reason, the thickness between the groove bottom surface of the first annular groove 45 of the outer scroll section 41 and the outer surface 43 of the outer scroll section 41, which is back-to-back with the groove bottom surface, must be a predetermined thickness or greater to withstand the pressure of the fluid flowing into the first annular groove 45. For this reason, the thickness between the inner surface 42 and the outer surface 43 of the outer scroll section 41 is the aforementioned predetermined thickness or greater plus the groove depth of the first annular groove 45.

[0029] If the second annular groove 55 is not formed in the annular plate 52, and the pressure equalization space Se is formed only by the first annular groove 45 of the outer scroll portion 41, the groove depth of the first annular groove 45 will increase. In this case, the thickness between the inner surface 42 and the outer surface 43 of the outer scroll portion 41 will increase by the amount of the increased groove depth. Therefore, in this case, the outer scroll portion 41 will become heavier. On the other hand, in this embodiment, the second annular groove 55 of the annular plate 52 and the first annular groove 45 of the outer scroll portion 41 work together to form the pressure equalization space Se, so the groove depth of the first annular groove 45 is shallower than in the aforementioned case. Therefore, in this embodiment, the thickness between the inner surface 42 and the outer surface 43 of the outer scroll portion 41 is thinner than in the aforementioned case. Thus, in this embodiment, the weight of the outer scroll portion 41 can be reduced.

[0030] If the outer scroll section 41 becomes heavy, the back support plate 49 may not be able to support the outer scroll section 41. In this case, as shown in Figure 1, the outer scroll section 41 tilts as the outer scroll section 41 tilts with the radially outer end of the outer scroll section 41 as the pivot point, and the radially outer end of the outer scroll section 41 is displaced in the direction Dt toward the radially inner end of the outer scroll section 41 on the first axis side Da1. When the outer scroll section 41 tilts, the inner scroll section 31 also tilts in the same way, narrowing the clearance between the inner circumferential surface 33 of the inner scroll section 31 and the tip 25 of each of the multiple blades 22, which may damage the blades 22. For this reason, when the outer scroll section 41 becomes heavy, support or the like is needed to suppress this tilting of the outer scroll section 41.

[0031] In this embodiment, as described above, the weight of the outer scroll section 41 can be reduced, so the tilt of the outer scroll section 41 is suppressed. For this reason, in this embodiment, there is no need for supports or the like to suppress the tilt of the outer scroll section 41.

[0032] In this embodiment, an annular plate 52 is placed on the first axis Da1 with respect to the diffuser space Sd, and the edge Sd1 of the first axis Da1 of the diffuser space Sd is defined by the flow path side 53 of this annular plate 52. Suppose an annular plate 52 is placed on the second axis Da2 with respect to the diffuser space Sd, and the edge Sd2 of the second axis Da2 of the diffuser space Sd is defined by the flow path side 53 of this annular plate 52. In this case, the axial dimension Da between the edge Sd2 of the second axis Da2 of the diffuser space Sd and the outer surface of the portion in the casing 30 that exists on the second axis Da2 with respect to the diffuser space Sd will be increased by at least the thickness of the annular plate 52. Therefore, in this case, the axial dimension Da between the outer side of the portion located on the second axis side Da2 with respect to the diffuser space Sd in the casing 30 and the outer surface of the portion forming the diffuser space Sd in the casing 30 also increases by the thickness of the annular plate 52.

[0033] In this embodiment, the axial dimension Da between the edge Sd1 of the first axis Da1 of the diffuser space Sd and the outer surface 43 of the portion located on the first axis Da1 with respect to the diffuser space Sd in the casing 30 is increased by at least the thickness of the annular plate 52. However, since the position of the outer surface 43 of the portion located on the first axis Da1 with respect to the diffuser space Sd in the casing 30 is located on the second axis Da2 than the outer surface of the portion forming the volute space Sv in the casing 30, the axial dimension Da between the outer surface of the portion located on the second axis Da2 with respect to the diffuser space Sd in the casing 30 and the outer surface of the portion forming the diffuser space Sd in the casing 30 does not increase.

[0034] Therefore, in this embodiment, it is possible to suppress the increase in size of the casing 30.

[0035] In this embodiment, the connector 61b is removed to separate the inner scroll section 31 from the outer scroll section 41, and then the impeller 20 is removed. In this embodiment, since the outer peripheral end face 34 of the inner scroll section 31 is located radially outward Do from the outlet edge 24, the impeller 20 can be removed without interfering with the outer scroll section 41, even if process piping is connected to the outer scroll section 41. Once the impeller 20 is removed, the shaft seal device 13 located on the second side Da2 of the impeller 20's axis can be removed. Therefore, in this embodiment, the impeller 20 and the shaft seal device 13 can be easily removed, improving their maintainability.

[0036] This disclosure is not limited to the embodiments described above. Various additions, modifications, substitutions, and partial deletions are possible, provided that they do not depart from the conceptual idea and spirit of the present invention derived from the claims and their equivalents.

[0037] "Note" The centrifugal compressor in the above embodiments can be understood, for example, as follows:

[0038] (1) The centrifugal compressor in the first embodiment comprises an impeller 20 rotatable about an axis Ar, and a casing 30 housing the impeller 20. The impeller 20 has a hub 21 which gradually widens in diameter about the axis Ar from the first axis Da1 to the second axis Da2 in the axial direction Da to which the axis Ar extends, and a plurality of blades 22 which are attached to the outer surface of the hub 21 at intervals from each other in the circumferential direction Dc with respect to the axis Ar. Each of the plurality of blades 22 has an inlet edge 23 which forms the end of the first axis Da1, and an outlet edge 24 which is located on the second axis Da2 and radially outward Do with respect to the axis Ar, and forms the end of the radially outward Do. The casing 30 includes an inner scroll section 31 that forms an impeller housing space Si for housing the impeller 20, a diffuser section 51 located on the outer circumference side of the outlet edge 24 of each of the plurality of blades 22, communicating with the impeller housing space Si, and forming an annular diffuser space Sd centered on the axis Ar, and an outer scroll section 41 located on the outer circumference side of the diffuser space Sd, communicating with the diffuser space Sd, and forming a volute space Sv whose spatial cross-sectional area gradually increases toward one side in the circumferential direction Dc. The diffuser section 51 includes an annular plate 52 that defines the edge Sd1 of the first side Da1 of the axis in the diffuser space Sd, and a plurality of diffuser vanes 58 that protrude from the annular plate 52 into the diffuser space Sd and are provided spaced apart from each other in the circumferential direction Dc. The outer scroll portion 41 has an inner surface 42 that faces the second axis side Da2, is located on the first axis side Da1 of the annular plate 52, extends radially Dr with respect to the axis Ar and contacts the annular plate 52, and has a first annular groove 45 that is recessed from the inner surface 42 toward the first axis side Da1 and is annular around the axis Ar.The annular plate 52 has a non-flow channel side surface 54 that faces the first axis Da1 and extends radially Dr to contact the inner surface 42, a second annular groove 55 that is recessed from the non-flow channel side surface 54 toward the second axis Da2 and is annular around the axis Ar, and a plurality of communication holes 57 that connect the diffuser space Sd and the space in the second annular groove 55 at positions between the plurality of diffuser vanes 58. The first annular groove 45 and the second annular groove 55 work together to form an annular pressure equalization space Se centered on the axis Ar.

[0039] In this embodiment, the multiple diffuser flow paths Sdp, which are the spaces between the multiple diffuser vanes 58, communicate with each other through the communication holes 57 and the pressure equalization space Se. Therefore, in this embodiment, the pressure difference between the multiple diffuser flow paths Sdp can be suppressed, and as a result, stable operation of the centrifugal compressor becomes possible.

[0040] Incidentally, since compressed fluid flows through the outer scroll section 41, this outer scroll section 41 is a pressure-resistant structure. For this reason, the thickness between the groove bottom surface of the first annular groove 45 of the outer scroll section 41 and the outer surface 43 of the outer scroll section 41, which is back-to-back with the groove bottom surface, must be a predetermined thickness or greater to withstand the pressure of the fluid flowing into the first annular groove 45. For this reason, the thickness between the inner surface 42 and the outer surface 43 of the outer scroll section 41 is the aforementioned predetermined thickness or greater plus the groove depth of the first annular groove 45.

[0041] If the second annular groove 55 is not formed in the annular plate 52, and the pressure equalization space Se is formed only by the first annular groove 45 of the outer scroll portion 41, the groove depth of the first annular groove 45 will increase. In this case, the thickness between the inner surface 42 and the outer surface 43 of the outer scroll portion 41 will increase by the amount of the increased groove depth. Therefore, in this case, the outer scroll portion 41 will become heavier. On the other hand, in this embodiment, the second annular groove 55 of the annular plate 52 and the first annular groove 45 of the outer scroll portion 41 work together to form the pressure equalization space Se, so the groove depth of the first annular groove 45 will be shallower than in the aforementioned case. Therefore, in this embodiment, the thickness between the inner surface 42 and the outer surface 43 of the outer scroll portion 41 will be thinner than in the aforementioned case. Thus, in this embodiment, the weight of the outer scroll portion 41 can be reduced.

[0042] (2) The centrifugal compressor in the second embodiment is as follows: In the centrifugal compressor in the first embodiment, the annular plate 52 faces radially inward Dri with respect to the axis Ar and has an inner circumferential end face 56 that forms the end of the radially inward Dri. The inner scroll portion 31 faces radially outward Dr and has an outer circumferential end face 34 that faces the inner circumferential end face 56 in the radial direction Dr. The casing 30 has a sealing component 62a disposed between the inner circumferential end face 56 and the outer circumferential end face 34.

[0043] In this embodiment, it is possible to suppress the fluid in the pressure equalization space Se from returning to the diffuser space Sd via the space between the inner circumferential end face 56 of the annular plate 52 and the outer circumferential end face 34 of the inner scroll portion 31.

[0044] (3) The centrifugal compressor in the third aspect is the centrifugal compressor in the first aspect, wherein the inner scroll portion 31 and the outer scroll portion 41 are independent components of each other. The casing 30 has a connector 61b for connecting the inner scroll portion 31 and the outer scroll portion 41. The inner scroll portion 31 is located on the radially outer side Dro with respect to the outlet edge 24 and has an outer peripheral side end face 34 facing the radially outer side Dro. The outer scroll portion 41 faces the radially inner side Dri with respect to the axis Ar and has an inner peripheral side end face 46 facing the outer peripheral side end face 34 in the radial direction Dr.

[0045] In this aspect, after removing the connector 61b and separating the inner scroll portion 31 from the outer scroll portion 41, the impeller 20 is removed. At this time, in this aspect, since the outer peripheral side end face 34 of the inner scroll portion 31 is located on the radially outer side Dro with respect to the outlet edge 24, even if a process pipe is connected to the outer scroll portion 41, the impeller 20 can be removed without interfering with the outer scroll portion 41.

[0046] (4) The centrifugal compressor in the fourth aspect is the centrifugal compressor in the third aspect, wherein the annular plate 52 faces the radially inner side Dri and has an inner peripheral side end face 56 forming an end of the radially inner side Dri. A portion of the outer peripheral side end face 34 of the inner scroll portion 31 on the second side Da2 of the axis faces the inner peripheral side end face 56 of the annular plate 52 in the radial direction Dr. A portion of the outer peripheral side end face 34 of the inner scroll portion 31 on the first side Da1 of the axis faces the inner peripheral side end face 46 of the outer scroll portion 41 in the radial direction Dr. The casing 30 further includes a seal component 62a disposed between the inner peripheral side end face 56 of the annular plate 52 and the outer peripheral side end face 34 of the inner scroll portion 31, and a seal component 62b disposed between the inner peripheral side end face 46 of the outer scroll portion 41 and the outer peripheral side end face 34 of the inner scroll portion 31.

[0047] In this aspect, it is possible to suppress the fluid in the pressure equalizing space Se from returning into the diffuser space Sd through the space between the inner peripheral side end face 56 of the annular plate 52 and the outer peripheral side end face 34 of the inner scroll portion 31. Further, in this aspect, it is possible to suppress the fluid in the pressure equalizing space Se from flowing out of the casing 30 through the space between the inner peripheral side end face 46 of the outer scroll portion 41 and the outer peripheral side end face 34 of the inner scroll portion 31.

[0048] (5) The centrifugal compressor in the fifth aspect is the centrifugal compressor in the third aspect or the fourth aspect, wherein the outer scroll portion 41 has an outer surface 43 facing the first axial side Da1 and opposite to the inner surface 42. The inner scroll portion 31 has a connection surface 36 facing the second axial side Da2 at a position radially outside Dro from the outer peripheral side end face 34 and facing the outer surface 43 in the axial direction Da. The casing 30 has one or more shims 63 disposed between the connection surface 36 and the outer surface 43.

[0049] In this aspect, by appropriately adjusting the number of shims 63 disposed between the connection surface 36 of the inner scroll portion 31 and the outer surface 43 of the outer scroll portion 41, the position of the inner scroll portion 31 in the axial direction Da with respect to the outer scroll portion 41 can be easily adjusted. Therefore, in this aspect, the gap between the tip 25 near the outlet edge 24 of the impeller 22 and the inner peripheral surface 33 of the inner scroll portion 31 can be easily adjusted.

[0050] In the centrifugal compressor according to one aspect of the present disclosure, while aiming for stable operation, it is possible to reduce the weight of the casing.

[0051] 10: Rotating shaft 11: Shaft cap 12: Shaft cap connecting bolt 13: Shaft seal device 20: Impeller 21: Hub 22: Blades 23: Inlet edge 24: Outlet edge 25: Tip 30: Casing 31: Inner scroll section 32i: Inlet 32o: Outlet 33: Inner circumferential surface 34: Outer circumferential end face 35: Flange 36: Connection surface 41: Outer scroll section 42: Inner surface 43: Outer surface 45: First annular groove 46: Inner circumferential end face 49: Back support plate 51: Diffuser section 52: Annular plate 53: Flow path side 54: Anti-flow path side 55: Second annular groove 56: Inner circumferential end face 57: Communication hole 58: Diffuser vane 61a, 61b: Connector (or connecting bolt) 62a, 62b: Seal parts 63: Shim Si: Impeller storage space Sd: Diffuser space Sd1: Edge on the first side of the axis in the diffuser space Sd2: Edge on the second side of the axis in the diffuser space Sdp: Diffuser flow path Se: Pressure equalization space Sv: Volute space Ar: Axis Da: Axial direction Da1: First side of the axis Da2: Second side of the axis Dc: Circumferential direction Dr: Radial direction Dri: Inward radial direction Dr: Outward radial direction

Claims

1. An impeller rotatable about an axis, and a casing housing the impeller, the impeller having a hub that gradually widens in diameter about the axis from the first axis side toward the second axis side in the axial direction in which the axis extends, and a plurality of blades attached to the outer surface of the hub at intervals from each other in the circumferential direction with respect to the axis, each of the plurality of blades having an inlet edge forming the end on the first axis side, and an outlet edge located on the second axis side of the inlet edge and radially outward with respect to the axis, forming the radially outward end, the casing having an inner scroll portion that forms an impeller housing space housing the impeller, and a diffuser portion located on the outer circumference side of the outlet edge of each of the plurality of blades, communicating with the impeller housing space, and forming an annular diffuser space about the axis, The diffuser portion comprises an outer scroll portion located on the outer periphery of the diffuser space, communicating with the diffuser space, and forming a volute space whose cross-sectional area gradually increases toward one side in the circumferential direction, the diffuser portion comprising an annular plate defining the edge of the first axis side in the diffuser space, and a plurality of diffuser vanes projecting from the annular plate into the diffuser space and spaced apart from each other in the circumferential direction, the outer scroll portion comprising an inner surface facing the second axis side, located on the first axis side of the annular plate, extending radially with respect to the axis and in contact with the annular plate, and a first annular groove recessed from the inner surface toward the first axis side and annular around the axis, The annular plate has a reverse flow channel side facing the first axis and extending radially to contact the inner surface, a second annular groove recessed from the reverse flow channel side toward the second axis and annular around the axis, and a plurality of communication holes connecting the diffuser space and the space in the second annular groove at positions between the plurality of diffuser vanes, wherein the first annular groove and the second annular groove work together to form an annular pressure equalization space centered on the axis, a centrifugal compressor.

2. A centrifugal compressor according to claim 1, wherein the annular plate has an inner circumferential end face that faces radially inward with respect to the axis and forms the radially inward end, the inner scroll portion has an outer circumferential end face that faces radially outward and faces the inner circumferential end face in the radial direction, and the casing has a sealing component disposed between the inner circumferential end face and the outer circumferential end face.

3. A centrifugal compressor according to claim 1, wherein the inner scroll portion and the outer scroll portion are independent parts, the casing has a connector for connecting the inner scroll portion and the outer scroll portion, the inner scroll portion is located radially outward from the outlet edge and has an outer peripheral end face facing radially outward, and the outer scroll portion faces radially inward with respect to the axis and has an inner peripheral end face facing radially opposite the outer peripheral end face.

4. A centrifugal compressor according to claim 3, wherein the annular plate has an inner circumferential end face that faces radially inward and forms the radially inward end, the portion of the outer circumferential end face of the inner scroll portion on the second axis side faces the inner circumferential end face of the annular plate in the radial direction, the portion of the outer circumferential end face of the inner scroll portion on the first axis side faces the inner circumferential end face of the outer scroll portion in the radial direction, and the casing further comprises a sealing component disposed between the inner circumferential end face of the annular plate and the outer circumferential end face of the inner scroll portion, and a sealing component disposed between the inner circumferential end face of the outer scroll portion and the outer circumferential end face of the inner scroll portion.

5. A centrifugal compressor according to claim 3 or 4, wherein the outer scroll portion has an outer surface facing the first axis and back-to-back with the inner surface, the inner scroll portion has a connecting surface facing the second axis and facing the outer surface in the axial direction at a position radially outward from the outer peripheral end surface, and the casing has one or more shims disposed between the connecting surface and the outer surface.

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