JP2020197133A - Rotary machine - Google Patents

Abstract

To provide a rotary machine which further reduces friction loss to achieve improvement of the efficiency.SOLUTION: A rotary machine includes: a rotating body R which may rotate around an axis O and has a first facing surface P1 spreading in a plane intersecting with the axis O; and a stationary body S having a second facing surface P2 which faces the first facing surface P1 and forming a passage F1 in which a fluid circulates. The first facing surface P1 has a retreat surface 63 which is provided continuing into an end edge at the radial outer side relative to the axis O in a circumferential direction and retreated from the first facing surface P1 in an axis O direction. The second facing surface P2 has an inclined surface 72 which inclines toward the retreat surface 63 relative to the axis O from the radial inner side to the outer side.SELECTED DRAWING: Figure 3

Description

The present invention relates to a rotating machine.

For example, a rotating machine such as a centrifugal compressor, a centrifugal pump, a generator, or a turbine includes a rotor as a rotating body that rotates around an axis, and a casing as a stationary body that covers the rotor from the outside. Friction resistance (disc friction loss) occurs between the rotating rotor and the stationary casing via the working fluid. In particular, in the case of a centrifugal compressor, it is known that the disc friction loss increases because the outer diameter of the impeller becomes large in order to obtain a high head with respect to the discharge flow rate.

As a technique for reducing such disc friction loss, the one described in Patent Document 1 below is known. In Patent Document 1, the space on the back side is divided into a plurality of fences by providing a plurality of fences on the back side of the impeller of the centrifugal compressor at intervals in the radial direction. As a result, the velocity distribution in each space is controlled, and it is said that the disc friction loss can be reduced.

Japanese Unexamined Patent Publication No. 3-11198

However, in the device described in Patent Document 1, the fluid flowing in the divided space is in contact with the inner surface of the casing which is a stationary body. Therefore, there is a friction loss between the back surface of the impeller and the casing. That is, there is still room for improvement in the apparatus described in Patent Document 1. Further, since the peripheral surface of the impeller has a higher peripheral speed than the other parts, the friction loss generated between the outer peripheral surface and the casing cannot be ignored.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a rotary machine having improved efficiency by further reducing friction loss.

The rotating machine according to one aspect of the present invention is rotatable around an axis and faces a rotating body having a first facing surface extending in a plane intersecting the axis and facing the first facing surface from the axis direction. The first facing surface is provided with a stationary body having a second facing surface forming a flow path through which the fluid flows with the first facing surface, and the first facing surface is a radial outer edge with respect to the axis. Has a receding surface that is continuously provided in the circumferential direction and recedes from the first facing surface in the axial direction, and the second facing surface becomes the receding surface from the inside to the outside in the radial direction. It has an inclined surface that is inclined with respect to the axis so as to face the axis.

In the above configuration, for example, when a fluid flows from the inside to the outside in the radial direction in the flow path between the first facing surface and the second facing surface, the retreating surface of the first facing surface and the second facing surface are opposed to each other. A part of the fluid is trapped in the space between the inclined surface of the surface. The trapped fluid forms a vortex in the space. Here, the fluid flowing through the flow path contains a circumferential velocity component accompanying the rotation of the rotating body. Therefore, the above vortex is also in a swirling state while including the circumferential velocity component. By interposing this vortex, the friction loss generated between the rotating body and the stationary body can be reduced.

In the rotating machine, the radially inner edge of the inclined surface may be located radially inside the radially inner edge of the retracting surface in the radial direction.

According to the above configuration, for example, when the fluid flows from the inner side in the radial direction to the outer side in the flow path, the fluid can be guided to the inclined surface starting from the position on the inner side in the radial direction from the receding surface. That is, the fluid guided by the inclined surface can be quickly guided between the inclined surface and the receding surface. Therefore, a vortex can be formed more stably between the inclined surface and the receding surface.

In the rotary machine, the radial inner edge of the inclined surface may be in the same position as the radial inner edge of the receding surface in the radial direction.

According to the above configuration, the radial inner edge of the inclined surface and the radial inner edge of the receding surface are at the same position in the radial direction. As a result, it is possible to secure a separation distance between the inclined surface and the receding surface. As a result, for example, even when the rotating body is displaced in a direction close to the stationary body, the possibility that the rotating body and the stationary body come into contact with each other can be reduced.

In the rotating machine, the radial inner edge of the inclined surface may be located radially outer than the radial inner edge of the receding surface in the radial direction.

According to the above configuration, the radial inner edge of the inclined surface is located radially outer than the radial inner edge of the receding surface. As a result, it is possible to secure a separation distance between the inclined surface and the receding surface. As a result, for example, even when the rotating body is displaced in a direction close to the stationary body, the possibility that the rotating body and the stationary body come into contact with each other can be reduced.

In the rotating machine, the inclined surface may have a curved surface shape that is convex toward a side away from the retracting surface.

According to the above configuration, since the inclined surface has a curved surface shape, the fluid can be guided more smoothly along the inclined surface. As a result, the vortex can be held more stably between the receding surface and the inclined surface.

In the rotating machine, the inclined surface is formed with a concave groove that is recessed in the axial direction and continuous in the circumferential direction from the inclined surface at a position corresponding to the radial inner edge of the retracting surface in the radial direction. You may be.

According to the above configuration, since the concave groove is formed on the inclined surface, the rotating body and the stationary body can come into contact with each other even when the rotating body is displaced in a direction close to the stationary body, for example. The sex can be reduced.

In the rotating machine, the rotating body has a plurality of the retracting surfaces arranged from the inside to the outside in the radial direction, and the more the retracting surface is located on the outer side in the radial direction, the more the axis line from the first facing surface. It may be receding in the direction.

According to the above configuration, since the plurality of receding surfaces are formed, a plurality of vortices can be formed from the inside to the outside in the radial direction. As a result, a plurality of vortices are interposed between the inclined surface and the receding surface. Each vortex contains a circumferential velocity component associated with the rotation of the rotating body. Therefore, according to the above configuration, the friction loss generated between the rotating body and the stationary body can be further reduced.

According to the present invention, it is possible to provide a rotating machine with improved efficiency by further reducing friction loss.

It is sectional drawing which shows the structure of the centrifugal compressor as a rotary machine which concerns on 1st Embodiment of this invention. It is an enlarged sectional view which shows the structure around the impeller of the centrifugal compressor which concerns on 1st Embodiment of this invention. It is an enlarged sectional view of the main part of the disk which concerns on 1st Embodiment of this invention. It is an enlarged sectional view of the main part of the cover which concerns on 1st Embodiment of this invention. It is an enlarged sectional view of the main part which shows the modification of the centrifugal compressor which concerns on 1st Embodiment of this invention. It is an enlarged sectional view of the main part which shows the further modification of the centrifugal compressor which concerns on 1st Embodiment of this invention. It is an enlarged sectional view of the main part of the centrifugal compressor which concerns on 2nd Embodiment of this invention. It is an enlarged sectional view of the main part of the centrifugal compressor which concerns on 3rd Embodiment of this invention. It is an enlarged sectional view of the main part which shows the modification of the centrifugal compressor which concerns on 3rd Embodiment of this invention. (Concave groove)

[First Embodiment]
The first embodiment of the present invention will be described with reference to FIGS. 1 to 4. In this embodiment, a multi-stage centrifugal compressor as a rotating machine will be described as an example. As a rotary machine, it is also possible to apply the configuration of the present embodiment to a single-stage centrifugal compressor, a centrifugal pump, a generator, and a turbine.

The centrifugal compressor 100 includes a rotating shaft 1 that rotates around an axis, a casing 3 as a stationary body S that forms a fluid flow path 2 by covering the circumference of the rotating shaft 1, and a rotation provided on the rotating shaft 1. It includes a plurality of impellers 4 as a body R.

The casing 3 has a cylindrical shape extending along the axis O. The rotating shaft 1 extends so as to penetrate the inside of the casing 3 along the axis O. Journal bearings 5 and thrust bearings 6 are provided at both ends of the casing 3 in the axis O direction, respectively. The rotary shaft 1 is rotatably supported around the axis O by the journal bearing 5 and the thrust bearing 6.

An intake port 7 for taking in air as a working fluid G from the outside is provided on one side of the casing 3 in the O-axis direction. Further, on the other side of the casing 3 in the axis O direction, an exhaust port 8 is provided to exhaust the working fluid G compressed inside the casing 3.

Inside the casing 3, an internal space is formed in which the intake port 7 and the exhaust port 8 are communicated with each other and the diameter is repeatedly reduced and expanded. This internal space accommodates a plurality of impellers 4 and forms a part of the above-mentioned fluid flow path 2. In the following description, the side on the fluid flow path 2 where the intake port 7 is located is referred to as an upstream side, and the side where the exhaust port 8 is located is referred to as a downstream side.

A plurality (six) impellers 4 are provided on the outer peripheral surface of the rotating shaft 1 at intervals in the axis O direction. As shown in FIG. 2, each impeller 4 includes a disk 41 having a substantially circular cross section when viewed from the axis O direction, a plurality of blades 42 provided on the upstream surface of the disk 41, and a plurality of these blades. It has a cover 43 that covers the 42 from the upstream side.

The disk 41 is formed so as to gradually expand its radial dimension from one side to the other side in the axis O direction when viewed from the direction intersecting the axis O, thereby forming a substantially conical shape. There is.

A plurality of blades 42 are arranged radially outward in the radial direction with the axis O as the center on the conical surface facing the upstream side of both sides of the disk 41 in the axis O direction. More specifically, these blades are formed of thin plates erected from the upstream side surface of the disc 41 toward the upstream side. These plurality of blades 42 are curved so as to go from one side in the circumferential direction to the other side when viewed from the axis O direction.

A cover 43 is provided on the upstream edge of the blade 42. In other words, the plurality of blades 42 are sandwiched by the cover 43 and the disc 41 from the axis O direction. As a result, a space is formed between the cover 43, the disk 41, and the pair of blades 42 adjacent to each other. This space forms a part (compressible flow path 22) of the fluid flow path 2 described later.

The fluid flow path 2 is a space that communicates the impeller 4 configured as described above with the internal space of the casing 3. In the present embodiment, it is assumed that one fluid flow path 2 is formed for each impeller 4 (for each compression stage). That is, in the centrifugal compressor 100, five continuous fluid flow paths 2 are formed from the upstream side to the downstream side corresponding to the five impellers 4 excluding the last-stage impeller 4.

Each fluid flow path 2 has a suction flow path 21, a compression flow path 22, a diffuser flow path 23, a return bend portion 24, and a guide flow path 25. Note that FIG. 2 shows only the one-stage impeller 4 of the fluid flow path 2 and the impeller 4.

In the first-stage impeller 4, the suction flow path 21 is directly connected to the intake port 7. By the suction flow path 21, external air is taken into each flow path on the fluid flow path 2 as a working fluid G. More specifically, the suction flow path 21 is gradually curved from the axis O direction to the radial outer side from the upstream side to the downstream side.

The suction flow path 21 in the impeller 4 of the second and subsequent stages communicates with the downstream end of the guide flow path 25 (described later) in the fluid flow path 2 of the previous stage (first stage). That is, the flow direction of the working fluid G that has passed through the guide flow path 25 is changed so as to face the downstream side along the axis O in the same manner as described above.

The compression flow path 22 is a flow path surrounded by a surface on the upstream side of the disk 41, a surface on the downstream side of the cover 43, and a pair of blades 42 adjacent to each other in the circumferential direction. More specifically, the cross-sectional area of the compressed flow path 22 gradually decreases from the inside to the outside in the radial direction. As a result, the working fluid G flowing through the compression flow path 22 while the impeller 4 is rotating is gradually compressed into a high-pressure fluid.

The diffuser flow path 23 is a flow path extending from the inside to the outside in the radial direction of the axis O. The radial inner end of the diffuser flow path 23 communicates with the radial outer end of the compression flow path 22.

The return bend portion 24 reverses the flow direction of the working fluid G flowing from the inside to the outside in the radial direction through the diffuser flow path 23 toward the inside in the radial direction. One end side (upstream side) of the return bend portion 24 is communicated with the diffuser flow path 23, and the other end side (downstream side) is communicated with the guide flow path 25. In the middle of the return bend portion 24, the outermost portion in the radial direction is the top portion.

The guide flow path 25 extends radially inward from the downstream end of the return bend portion 24. The radial outer end of the guide flow path 25 communicates with the return bend portion 24. The radial inner end of the guide flow path 25 communicates with the suction flow path 21 in the subsequent fluid flow path 2 as described above.

In the centrifugal compressor 100 configured as described above, a gap is formed between the casing 3 and the impeller 4 in order to realize smooth rotation of the impeller 4. More specifically, a gap is formed between the disc back surface 41A (first facing surface P1) facing the downstream side of the disc 41 and the casing back surface 3A (second facing surface P2) facing the disc back surface 41A. Has been done. This gap is the flow path F1. In the flow path F1, as shown by the arrow A in FIG. 2, the high-pressure fluid leaking from the compression flow path 22 on the rear stage side flows from the inside to the outside in the radial direction.

Further, there is a gap between the cover upstream surface 43B (first facing surface P1') facing the upstream side of the cover 43 and the casing upstream surface 3B (second facing surface P2') facing the cover upstream surface 43B. It is formed. This gap is the flow path F2. In the flow path F2, as shown by the arrow B in FIG. 2, the high-pressure fluid flowing through the diffuser flow path 23 flows from the outer side in the radial direction to the inner side.

Further, there is also a gap between the disc outer peripheral surface 41C facing the radial outer side of the disc 41 and the cover outer peripheral surface 43C of the cover 43 facing the radial outer side and the casing inner peripheral surface 3D which is the inner peripheral surface of the casing 3. Is formed. This gap is a flow path F3 (outer flow path). The flow path F3 communicates with the flow path F1 and the flow path F2.

Here, between the impeller 4 as the rotating body R and the casing 3 as the stationary body S, frictional resistance (disk friction loss) is generated via the fluid flowing through the flow path F1 and the flow path F2. Occurs. In particular, in the case of the centrifugal compressor 100, it is known that the disc friction loss increases because the outer diameter of the impeller 4 increases as the lift increases. Further, since the peripheral surface of the impeller 4 (the above-mentioned disk outer peripheral surface 41C and the cover outer peripheral surface 43C) has the highest circumferential velocity of the fluid, friction loss generated between these outer peripheral surfaces and the casing inner peripheral surface 3D also occurs. Needs to be reduced.

Therefore, in the present embodiment, as shown in FIGS. 3 and 4, a step recessed in the axis O direction is formed at the radial outer edge of the disk outer peripheral surface 41C and the cover outer peripheral surface 43C. More specifically, as shown in FIG. 3, the above-mentioned disc back surface 41A has a circular main surface 61 centered on the axis O and an annular receding surface 63 surrounding the outer peripheral side of the main surface 61. It has a stepped surface 62 that connects the surface 63 and the main surface 61 in the axis O direction. The retracting surface 63 is retracted in the axis O direction with respect to the main surface 61. More specifically, the retracting surface 63 is retracted in a direction away from the back surface 3A of the casing as compared with the main surface 61. The receding surface 63 is parallel to the main surface 61. Further, the receding surface 63 forms an annular shape continuous in the circumferential direction with respect to the axis O. The outer peripheral edge of the retracting surface 63 is connected to the outer peripheral surface 41C of the disc. The stepped surface 62 connects the edge on the outer peripheral side of the main surface 61 and the edge on the inner peripheral side of the receding surface 63 in the axis O direction.

Similarly, as shown in FIG. 3, the casing back surface 3A has a circular main surface 71 centered on the axis O, and an annular inclined surface 72 surrounding the outer peripheral side of the main surface 71. The inclined surface 72 is inclined with respect to the axis O so as to be directed toward the receding surface 63 side from the inside to the outside in the radial direction. Further, in the cross-sectional view including the axis O, the inclined surface 72 extends in a plane shape. The radial inner edge of the inclined surface 72 (inner edge t1) is located radially inside the radially inner edge of the receding surface 63. Further, the radial outer edge (outer edge t2) of the inclined surface 72 is located on one side of the receding surface 63 in the axis O direction. Therefore, the inclined surface 72, the stepped surface 62, and the receding surface 63 define a space V having a triangular cross-sectional view.

Further, as shown in FIG. 4, the cover upstream surface 43B has a circular main surface 61 ′ centered on the axis O and an annular receding surface 63 ′ surrounding the outer peripheral side of the main surface 61 ′. It has a stepped surface 62'that connects the retracting surface 63'and the main surface 61' in the axis O direction. The receding surface 63'is retracted in the axis O direction with respect to the main surface 61'. More specifically, the retracting surface 63'is retracted in a direction away from the casing upstream surface 3B as compared with the main surface 61'. The receding surface 63'is parallel to the main surface 61'. Further, the receding surface 63'forms an annular shape continuous in the circumferential direction with respect to the axis O. The outer peripheral edge of the retracting surface 63'is connected to the outer peripheral surface 43C of the cover. The step surface 62'connects the outer peripheral edge of the main surface 61' and the inner peripheral edge of the receding surface 63'in the axis O direction.

Similarly, as shown in FIG. 4, the casing upstream surface 3B has a circular main surface 71 ′ centered on the axis O and an annular inclined surface 72 ′ surrounding the outer peripheral side of the main surface 71 ′. ing. The inclined surface 72'is inclined with respect to the axis O so as to be toward the receding surface 63' side from the inside to the outside in the radial direction. Further, in the cross-sectional view including the axis O, the inclined surface 72'extends in a plane. The radial inner edge of the inclined surface 72'(inner edge t1') is located radially inside the radial inner edge of the receding surface 63'. Further, the radial outer edge (outer edge t2') of the inclined surface 72'is located on the opposite side of the receding surface 63 in the axis O direction. Therefore, the inclined surface 72', the stepped surface 62', and the receding surface 63' define a space V'in a triangular cross-sectional view.

In the above configuration, when the fluid flows from the inside to the outside in the radial direction in the flow path F1 between the disk back surface 41A as the first facing surface P1 and the casing back surface 3A as the second facing surface P2. , A part of the fluid is captured in the space V between the receding surface 63 and the inclined surface 72. The captured fluid forms a vortex in the space V. Specifically, as shown in FIG. 3, this vortex swirls from the inclined surface 72 through the receding surface 63 toward the stepped surface 62. Further, another vortex is also formed between the disk outer peripheral surface 41C and the casing inner peripheral surface 3D (that is, in the flow path F3). Here, the fluid flowing through the flow path F1 contains a circumferential velocity component accompanying the rotation of the rotating body R. Therefore, the above vortex is also in a swirling state while including the circumferential velocity component. By interposing this vortex, the velocity gradient between the rotating body R and the stationary body S can be made gentle. As a result, the friction loss generated between the rotating body R and the stationary body S can be reduced.

Further, in the above configuration, in the flow path F2 between the cover upstream surface 43B as the first facing surface P1'and the casing upstream surface 3B as the second facing surface P2', from the outside in the radial direction to the inside. When the fluid flows, a part of the fluid is captured in the space V'between the receding surface 63'and the inclined surface 72'. The trapped fluid forms a vortex within the space V'. Specifically, as shown in FIG. 4, this vortex swirls from the inclined surface 72', through the stepped surface 62', and toward the receding surface 63'. Further, another vortex is formed in the flow path F2. The vortex travels in the flow path F2 from the inside to the outside in the radial direction, then turns toward the upstream surface 3B of the casing, and swirls inward in the radial direction again. Here, the fluid flowing through the flow path F2 contains a circumferential velocity component accompanying the rotation of the rotating body R. Therefore, the above vortex is also in a swirling state while including the circumferential velocity component. By interposing this vortex, the velocity gradient between the rotating body R and the stationary body S can be made gentle. As a result, the friction loss generated between the rotating body R and the stationary body S can be reduced.

Further, according to the above configuration, the radial inner edge (inner edge t1) of the inclined surface 72 is located radially inside the radial inner edge of the receding surface 63. As a result, when the fluid flows from the inner side in the radial direction to the outer side in the flow path F1, the fluid can be guided to the inclined surface 72 starting from the position inside the receding surface 63 in the radial direction. That is, the fluid guided by the inclined surface 72 can be quickly guided between the inclined surface 72 and the receding surface 63 (space V). Therefore, a vortex can be formed more stably in this space V.

The first embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated. For example, in the first embodiment, the inner edge t1 of the inclined surface 72 (or the inner edge t1'of the inclined surface 72') is the radial inner end of the receding surface 63 (or the receding surface 63'). The configuration that is located radially inside the edge has been described. However, it is also possible to adopt the configuration shown in FIG. 5 or FIG. In the example of FIG. 5, the inner edge t1 is in the same position in the radial direction as the radial inner edge of the receding surface 63. Further, in the example of FIG. 6, the inner edge t1 is located radially outer of the radially inner edge of the receding surface 63. According to such a configuration, a sufficient separation distance between the inclined surface 72 and the retracting surface 63 can be secured. Thereby, for example, even when the rotating body R is displaced in a direction close to the stationary body S, the possibility that the rotating body R and the stationary body S come into contact with each other can be reduced. As a result, the centrifugal compressor 100 can be operated more stably. Although only the inclined surface 72 is shown in FIGS. 5 and 6, the inclined surface 72'can also have the same configuration as described above.

[Second Embodiment]
Next, the second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 7, in the present embodiment, the configuration of the inclined surface 72B is different from that of the first embodiment. The inclined surface 72B is inclined toward the receding surface 63 from the inside to the outside in the radial direction, and has a curved surface shape. More specifically, the inclined surface 72B has a curved surface shape that is convex on the side away from the receding surface 63. The radial inner edge of the inclined surface 72B and the radial outer edge of the main surface 71 are continuously connected. Similarly, the radial outer edge of the inclined surface 72B and the casing inner peripheral surface 3D are continuously connected. That is, no step or the like is formed in these connecting portions.

According to the above configuration, since the inclined surface 72B has a curved surface shape, the fluid can be guided more smoothly along the inclined surface 72B. As a result, the vortex can be more stably held between the receding surface 63 and the inclined surface 72B.

The second embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated. For example, in the second embodiment, the configuration in which the inclined surface 72B is provided on the back surface 3A of the casing as the second facing surface P2 has been described. However, similarly to the first embodiment, it is also possible to provide a curved surface similar to the inclined surface 72B on the casing upstream surface 3B as the second facing surface P2'. Even in this case, the same effect as described above can be obtained.

[Third Embodiment]
Subsequently, the third embodiment of the present invention will be described with reference to FIG. The same components as those of the above embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 8, in the present embodiment, a plurality (two) of the above-mentioned stepped surface 62 and the retracted surface 63 are provided. More specifically, the inner step surface 62A and the inner receding surface 63A located relatively inward in the radial direction form an inner space V1 similar to the space V described in the first embodiment. Further, an outer step surface 62B extending in parallel with the inner step surface 62A is connected to the radial outer edge of the inner receding surface 63A. An outer receding surface 63B extending in parallel with the inner receding surface 63A is connected to the outer stepped surface 62B. The outer receding surface 63B is retracted from the casing back surface 3A with respect to the inner receding surface 63A.

According to the above configuration, since the plurality of receding surfaces 63 are formed, vortices can be formed in the inner space V1 and the outer space V2 from the inner side to the outer side in the radial direction, respectively. As a whole, a plurality of vortices can be formed. As a result, a plurality of vortices are interposed between the inclined surface 72 and the receding surface 63. Each vortex contains a circumferential velocity component associated with the rotation of the rotating body R. Therefore, according to the above configuration, the friction loss generated between the rotating body R and the stationary body S can be further reduced.

The third embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated. For example, in the above embodiment, regarding an example in which two stepped surfaces 62 (inner stepped surface 62A and outer stepped surface 62B) and two receding surfaces 63 (inner receding surface 63A and outer receding surface 63B) are formed. explained. However, the number of stepped surfaces 62 and retracted surfaces 63 (that is, the number of steps) is not limited to two, and may be three or more. Further, in the third embodiment, a configuration in which a plurality of stepped surfaces 62 and a plurality of receding surfaces 63 are provided on the disc back surface 41A as the first facing surface P1 has been described. However, similarly to the first embodiment, it is possible to provide the cover upstream surface 43B as the first facing surface P1'with the same configuration as the plurality of stepped surfaces 62 and the plurality of receding surfaces 63. Even in this case, the same effect as described above can be obtained.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The same components as those of the above embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 9, the present embodiment is different from the configuration described in the third embodiment in that a plurality (two) recessed grooves 70R are formed on the inclined surface 72. .. Specifically, the concave groove 70R is formed at a position overlapping with the radial outer edge of each receding surface 63 in the radial direction. Each concave groove 70R has an annular shape centered on the axis O. Further, each concave groove 70R is recessed on the inclined surface 72 in a direction away from the retracting surface 63. The groove has a semi-circular cross-sectional shape.

According to the above configuration, since the concave groove 70R is formed on the inclined surface 72, for example, even if the rotating body R is displaced in a direction close to the stationary body S, the portion of the concave groove 70R is formed. Since the space is secured only, the possibility that the rotating body R and the stationary body S come into contact with each other can be reduced. As a result, the centrifugal compressor 100 can be operated more stably.

The fourth embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated. For example, in the fourth embodiment, the configuration in which the concave groove 70R is formed on the back surface 3A of the casing as the second facing surface P2 has been described. However, similarly to the first embodiment, it is also possible to provide the same configuration as the concave groove 70R on the casing upstream surface 3B as the second facing surface P2'. Even in this case, the same effect as described above can be obtained.

100 Centrifugal compressor (rotary machine)
1 Rotating shaft 2 Fluid flow path 3 Casing 3A Casing back surface 3B Casing upstream surface 3D Casing inner peripheral surface 4 Impeller 5 Journal bearing 6 Thrust bearing 7 Intake port 8 Exhaust port 10 Recess 11 Recessed side recess 21 Suction flow path 22 Compression flow path 23 Diffuser flow path 24 Return bend part 25 Guide flow path 41 Disk 41A Disk back surface 41C Disk outer peripheral surface 42 Blade 43 Cover 43B Cover upstream surface 43C Cover outer peripheral surface 50 Return vanes 61, 61', 71, 71'Main surfaces 62, 62' Step surface 63, 63'retract surface 62A Inner step surface 62B Outer step surface 63A Inner retreat surface 63B Outer retreat surface 72, 72'Inclined surface F1, F2, F3 Flow path O Axis line P1, P1'First facing surface P2, P2 ´ Second facing surface R Rotating body S Resting body t1, t1 ´ Inner edge t2, t2 ´ Outer edge V, V ´ Space V1 Inner space V2 Outer space

Claims (7)

A rotating body that is rotatable around an axis and has a first facing surface that extends in a plane that intersects the axis.
A stationary body having a second facing surface that faces the first facing surface from the axial direction and forms a flow path through which a fluid flows between the first facing surface and the first facing surface.
With
The first facing surface has a receding surface that is continuously provided in the circumferential direction on the outer edge in the radial direction with respect to the axis and recedes in the axial direction from the first facing surface.
The second facing surface is a rotary machine having an inclined surface that is inclined with respect to the axis line from the inside to the outside in the radial direction toward the retracting surface. The rotating machine according to claim 1, wherein the radially inner edge of the inclined surface is located radially inside the radially inner edge of the retracting surface in the axial direction. The rotary machine according to claim 1, wherein the radial inner edge of the inclined surface is located at the same position as the radial inner edge of the receding surface in the axial direction. The rotating machine according to claim 1, wherein the radially inner edge of the inclined surface is located radially outside the radially inner edge of the retracting surface in the axial direction. The rotary machine according to any one of claims 1 to 4, wherein the inclined surface has a curved surface shape that is convex toward a side away from the retracting surface. The inclined surface is formed with a concave groove that is recessed in the axial direction from the inclined surface and is continuous in the circumferential direction at a position corresponding to the radial inner edge of the receding surface in the radial direction. The rotary machine according to any one of 5 to 5. The rotating body has a plurality of the retracting surfaces arranged from the inside to the outside in the radial direction.
The rotary machine according to any one of claims 1 to 6, wherein the retracting surface located on the outer side in the radial direction is retracted in the axial direction from the first facing surface.

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