JP2020101169A - Centrifugal rotating machine - Google Patents

Abstract

To provide a centrifugal rotating machine which is further reduced in vibration.SOLUTION: A centrifugal rotating machine comprises: a rotating shaft 1 extending along an axial line O; an impeller 4 having a disc 41 fixed to the rotating shaft 1, and a cover 43 for covering a blade 42 arranged at the disc 41, being an impeller 4 for pressure-sending fluid flowing from one side in an axial line direction O to the outside of a radial direction; and a casing 3 for accommodating the impeller 4. An impeller flow passage 21 for pressure-sending the fluid is formed of a face of the disc 41 at an upstream side in the axial line O direction, and an internal peripheral face of the cover 43, an outside flow passage F is formed of an external peripheral face 43A of the cover 43, and an internal peripheral face 3A of the casing 3 opposing the external peripheral face 43A of the cover 43, the outside flow passage F is connected to the impeller flow passage 21 at an outlet 21B of the impeller flow passage 21, and a protrusion 9 protruding from the internal peripheral face 3A of the casing 3 is formed in the outside flow passage F.SELECTED DRAWING: Figure 2

Description

The present invention relates to a centrifugal rotating machine.

Generally, a centrifugal compressor has a rotating shaft extending along the axis, an impeller provided on the rotating shaft, and a casing that covers the impeller from the outside. Of these, the impeller may be of a type called a closed impeller. The closed impeller has a disc-shaped disc centering on the axis, a plurality of blades provided on the surface of one side of the disc, and a conical cover that covers the plurality of blades from one side. ing. A clearance (outer flow path) is provided between the outer peripheral surface of the cover and the inner peripheral surface of the casing.

When the centrifugal compressor is operated, the fluid flows in the flow passage defined by the blades. The fluid is compressed in the middle of flowing from the inlet side to the outlet side in the flow path and becomes a high pressure state. Here, on the outlet side of the flow path, a fluid having a higher pressure than on the inlet side flows, so that the fluid also flows into the outer flow path. As described above, when a large amount of fluid flows into the outer flow path, the compression efficiency of the centrifugal compressor is reduced. Therefore, a technique is known in which a seal portion is provided on the inner peripheral surface of the casing to prevent the fluid from flowing. For example, Patent Document 1 below discloses, as a specific example of the seal portion, a configuration in which a seal fin is provided on the inner peripheral surface of the casing on the inlet side of the impeller. By providing such a seal fin, the fluid flowing into the outer flow path is reduced.

International Publication No. 2016/043090

In the centrifugal compressor having the above configuration, when the rotor including the impeller is displaced in the radial direction in a state where the fluid leaks between the seal fin and the outer peripheral surface of the cover, a circumferential pressure distribution is generated on the rotor surface. .. Here, a swirl component (swirl flow component) accompanying the rotation of the impeller is added to the fluid flowing through the outer flow path. Due to the influence of this swirl component, an exciting force (seal exciting force) acting in a direction orthogonal to the displacement direction acts on the impeller. By continuously applying this seal excitation force, whirling vibration occurs in the rotor. That is, there is still room for improvement in the centrifugal compressor described in Patent Document 1 above.

The present invention has been made to solve the above problems, and an object thereof is to provide a centrifugal rotating machine in which vibration is further reduced.

A centrifugal rotating machine according to an aspect of the present invention is a rotating shaft extending along an axis, and an impeller for pumping a fluid flowing in from one side in the axial direction outward in a radial direction, and a disk fixed to the rotating shaft. And an impeller having a cover for covering the blades provided on the disc, and a casing for accommodating the impeller, the surface of the disc on the upstream side in the axial direction, and the inner peripheral surface of the cover. An impeller flow path for pumping a fluid is formed, and an outer flow path is formed by an outer peripheral surface of the cover and an inner peripheral surface of the casing facing the outer peripheral surface of the cover, and the outer flow path is the impeller flow. A projecting portion that is connected to the impeller channel at the outlet of the channel and that projects from the inner peripheral surface of the casing is provided in the outer channel.

According to the above configuration, the fluid flowing into the outer flow passage is guided by the protrusion provided on the inner peripheral surface of the casing. Therefore, even when the fluid contains the swirl component (swirl component), the swirl component can be reduced by being guided by the protrusion. Here, when the flow of the fluid containing the swirl component flows into the outer flow path, an excitation force (seal excitation force) acting in a direction orthogonal to the displacement direction acts on the impeller. The continuous application of the seal excitation force causes whirling vibrations on the rotary shaft and the impeller. However, with the above configuration, such a possibility can be reduced.

In the centrifugal rotating machine, a plurality of the protrusions may be formed at intervals in the circumferential direction.

According to the above configuration, since the plurality of protruding portions are formed at intervals in the circumferential direction, the swirl component can be uniformly reduced over the entire area in the circumferential direction of the outer flow path. As a result, the pressure distribution of the fluid in the outer flow path becomes uniform, so that the vibration generated in the impeller can be suppressed more effectively.

In the centrifugal rotating machine, the protrusion may be provided in a predetermined area on the inner peripheral surface of the casing.

In the centrifugal rotating machine, the protrusion may be provided at a position overlapping with the outlet of the impeller flow path in a radial direction with respect to the axis.

According to the above configuration, since the projecting portion is provided at a position that radially overlaps with the outlet of the impeller channel, the swirl component contained in the fluid that has flowed into the outer channel can be reduced immediately after the inflow. .. Here, the inventors performed CFD analysis on the excitation force due to the swirl component. As a result, it was found that the excitation force generated in the impeller cover was large. The excitation force generated in this cover is due to the fluid flowing into the outer flow path. Therefore, as in the above-described configuration, the swirl component is reduced by providing the protrusion at the inlet of the outer flow passage, that is, the position that overlaps the outlet of the impeller flow passage, and the exciting force generated in the cover is more positively reduced. be able to. Further, the closer to the outlet of the impeller flow path, the more swirl components are present, so the swirl components can be more effectively reduced. As a result, it is possible to further reduce the possibility that the impeller is displaced or excited due to the influence of the swirl component. Further, as compared with the configuration in which the protrusion extends over the entire area of the outer flow path, only the necessary and sufficient amount of swirl component is removed, and therefore the friction between the outer peripheral surface of the impeller cover and the fluid is reduced due to excessive reduction of the swirl component. It is also possible to avoid an increase in resistance.

In the centrifugal rotary machine, in the outer flow path, there is a step that is an annular step centered on the axis line on the outer peripheral surface of the cover, and the step is provided radially outward of the protrusion. May be.

According to the above configuration, since the step is provided on the outer peripheral surface of the cover, the fluid flowing out from the outlet of the impeller passes through the radially outer portion of the outer flow path. That is, a larger amount of fluid will flow along the inner peripheral surface of the casing provided with the protruding portion. As a result, more fluid is guided toward the protrusion provided on the inner peripheral surface of the casing. This makes it possible to more positively reduce the swirl component of the fluid flowing into the outer flow path.

In the centrifugal rotating machine, the protrusion may be provided over the entire inner surface of the casing in the outer flow path.

According to the above configuration, since the protrusion is provided over the entire area of the outer flow path, the swirl component of the fluid flowing into the outer flow path can be further reduced.

In the centrifugal rotating machine, the protruding portion may be curved from one side in the circumferential direction with respect to the axis toward the other side as it goes outward in the radial direction.

Here, a swirl component swirling from the other side in the circumferential direction toward one side (that is, toward the front side in the rotation direction of the impeller) is added to the fluid flowing into the outer flow path. According to the above configuration, the projecting portion is curved from one side in the circumferential direction to the other side in the radially outward direction from the inlet side. That is, the protrusion is curved in the direction opposite to the swirl component turning direction. Therefore, by this protrusion, the swirl component can be rectified in the opposite direction. As a result, it is possible to further reduce the possibility that the rotating shaft and the impeller are excited due to the influence of the swirl component.

In the centrifugal rotating machine, the protrusion may be twisted from one side in the circumferential direction with respect to the axis toward the other side with respect to the inner peripheral surface of the casing, as it goes from the outlet side to the inlet side. Good.

According to the above configuration, since the twist of the protrusion is small on the outlet side, the protrusion has a large angle with respect to the inner peripheral surface of the casing. Therefore, it is possible to more efficiently capture the flow of the fluid containing the swirl component that has flowed into the outer flow passage from the impeller outlet side (that is, the upstream side of the outer flow passage). Thereby, the swirl component can be further reduced.

The centrifugal rotary machine may further include a seal portion that seals a fluid leak between the inner peripheral surface of the casing and the outer peripheral surface of the cover at a radially inner end portion of the outer flow path. Good.

According to the above configuration, since the twist of the projecting portion is large on the impeller inlet side (that is, the downstream side of the outer flow path), the projecting portion has a small angle with respect to the inner peripheral surface of the casing. Therefore, the fluid guided by the protrusion flows near the inner peripheral surface of the casing. As a result, for example, when the seal portion is provided on the upstream side of the inner peripheral surface of the casing, the fluid is more positively flown toward the seal portion itself than the clearance between the seal portion and the outer peripheral surface of the impeller cover. be able to. That is, the flow to the seal portion on the inlet side of the impeller becomes a flow state (downflow) from the inner peripheral surface of the casing to the outer peripheral surface of the cover inward in the radial direction, so that the contraction effect at the seal portion becomes large. Thereby, the leak flow passing through the seal portion can be further reduced.

In the centrifugal rotating machine, the protruding portion may be twisted from the front side in the rotational direction of the impeller toward the rear side with respect to the inner peripheral surface of the casing as it goes inward in the radial direction.

According to the above configuration, the protruding portion is twisted toward the rear side in the rotational direction of the impeller (that is, the side opposite to the swirling direction of the swirl component included in the flow in the outer flow path). Therefore, the swirl component can be captured and reduced more efficiently.

In the centrifugal rotating machine described above, the protrusion may have a gradually decreasing dimension in the circumferential direction with respect to the axis, as the protrusion is separated from the inner peripheral surface of the casing.

According to the above configuration, the circumferential dimension of the projecting portion is gradually reduced to form a tapered shape. Accordingly, for example, even when the outer peripheral surface of the impeller comes into contact with the protruding portion, the contact area between the protruding portion and the outer peripheral surface can be suppressed to be small. As a result, damage to the impeller and generation of vibration can be suppressed.

A centrifugal rotating machine according to an aspect of the present invention is a rotating shaft extending along an axis, and an impeller for pumping a fluid flowing in from one side in the axial direction outward in a radial direction, and a disk fixed to the rotating shaft. And an impeller having a cover for covering the blades provided on the disc, and a casing for accommodating the impeller, the surface of the disc on the upstream side in the axial direction, and the inner peripheral surface of the cover. An impeller flow path for pumping a fluid is formed, and an outer flow path is formed by an outer peripheral surface of the cover and an inner peripheral surface of the casing facing the outer peripheral surface of the cover, and the outer flow path is the impeller flow. A step, which is an annular step centered on the axis, is provided on the outer peripheral surface of the cover in the outer flow path, the step being connected to the impeller flow path at the outlet of the path.

According to the above configuration, since the step is provided on the outer peripheral surface of the cover, the gap between the outer peripheral surface of the cover and the inner peripheral surface of the casing can be reduced. That is, it is possible to limit the amount of fluid flowing into the outer flow path. As a result, it is possible to reduce the excitation force applied to the impeller when a large amount of fluid flows into the outer flow path.

According to the present invention, it is possible to provide a centrifugal rotating machine in which vibration is further reduced.

It is a sectional view of a centrifugal compressor concerning a first embodiment of the present invention. It is a principal part expanded sectional view of the centrifugal compressor which concerns on 1st embodiment of this invention. It is a principal part expanded sectional view of the centrifugal compressor which concerns on 2nd embodiment of this invention. It is a perspective view of the impeller which concerns on 2nd embodiment of this invention. It is a principal part expanded sectional view of the centrifugal compressor which concerns on 3rd embodiment of this invention. It is the figure which looked at the impeller concerning a third embodiment of the present invention from the direction of an axis. It is a principal part expanded sectional view of the centrifugal compressor which concerns on 4th embodiment of this invention. It is the figure which looked at the impeller concerning a 4th embodiment of the present invention from the direction of an axis. It is explanatory drawing which shows the flow of the fluid in the sealing part which concerns on 4th embodiment of this invention. It is sectional drawing which shows the modification of the protrusion part which concerns on each embodiment of this invention.

[First embodiment]
A centrifugal compressor 100 (centrifugal rotating machine) according to a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a centrifugal compressor 100 is provided on a rotary shaft 1 that rotates around an axis O, a casing 3 that covers the periphery of the rotary shaft 1 to form a flow path 2, and a rotary shaft 1. Further, it is provided with a plurality of stages of impellers 4 and a projecting portion 9 provided on the casing 3.

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

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 direction of the axis O. Further, an exhaust port 8 through which the working fluid G compressed inside the casing 3 is exhausted is provided on the other side of the casing 3 in the axis O direction.

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 reduction and the diameter extension are repeated. The internal space accommodates the plurality of impellers 4 and forms a part of the flow path 2. In the following description, the side of the flow path 2 where the intake port 7 is located is called the upstream side, and the side where the exhaust port 8 is located is called the downstream side. Return vanes 50 are provided on the downstream side of each impeller 4 on the flow path 2.

The rotary shaft 1 is provided with a plurality of (six) impellers 4 on the outer peripheral surface thereof at intervals in the axis O direction. As shown in FIG. 2, each impeller 4 has a disc-shaped disc 41 centered on the axis O, a plurality of blades 42 provided on the upstream side surface of the disc 41, and a plurality of these blades 42 upstream. And a cover 43 that covers from the side.

When viewed from the direction intersecting the axis O, the disk 41 is formed so that its radial dimension gradually increases from one side toward the other side in the direction of the axis O, thereby forming a generally conical shape. There is. A plurality of blades 42 are arranged radially on the surface facing the upstream side (disk upstream surface 41A) of the both surfaces of the disk 41 in the direction of the axis O radially toward the outside in the radial direction with the axis O as the center. More specifically, these blades are formed by thin plates that are erected from the disc upstream surface 41A toward the upstream side. When viewed from the direction of the axis O, the plurality of blades 42 are curved from one side in the circumferential direction with respect to the axis O to the other side.

Of the both surfaces of the disk 41 in the direction of the axis O, the surface facing the downstream side (disk back surface 41B) extends in the radial direction with respect to the axis O. A gap extending in the direction of the axis O is formed between the disc back surface 41B and the casing 3 (casing facing surface 3B).

The upstream edge of the blade 42 is covered with a cover 43. 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 disc 41, and the pair of blades 42 adjacent to each other. This space forms an impeller flow path 21 as a part of the flow path 2 described above. In the following description, the radially inner end of the impeller passage 21 will be referred to as the inlet 21A, and the radially outer end thereof as the outlet 21B. The outer peripheral surface (cover outer peripheral surface 43A) of the cover 43 has a substantially conical shape by extending outward in the radial direction toward the other side in the direction of the axis O.

The cover outer peripheral surface 43A faces the inner peripheral surface of the casing 3 (casing inner peripheral surface 3A) with a gap. The casing inner peripheral surface 3A extends outward in the radial direction from one side in the axis O direction toward the other side, following the shape of the cover outer peripheral surface 43A. An outer flow path F is defined between the casing inner peripheral surface 3A and the cover outer peripheral surface 43A. In the following description, in the extending direction of the outer flow path F, the end side corresponding to the outlet 21B side of the impeller flow path 21 is simply referred to as “outlet side”, and the end side corresponding to the inlet 21A side is referred to. Sometimes called simply "entrance side".

An annular space centered on the axis O is formed inside the casing inner peripheral surface 3A in the radial direction. This space is a cavity C. A seal portion S is provided on one side (upstream side) of the cavity C in the axis O direction. The seal portion S is provided to seal fluid leakage between the casing 3 and the cover outer peripheral surface 43A. The seal portion S has a plurality of seal fins S1 and a base portion S2 that supports these seal fins S1.

Inside the outer flow path F, a plurality of protrusions 9 for guiding the flow of the fluid flowing into the outer flow path F are provided. The projecting portion 9 projects from the inner peripheral surface 3A of the casing to the other side in the direction of the axis O and extends from the outlet side toward the inlet side. In the outer flow path F, a plurality of protrusions 9 are arranged at intervals in the circumferential direction with respect to the axis O. Each protrusion 9 has a plate shape extending from the outlet side toward the inlet side. Further, in the present embodiment, the protruding portion 9 is provided at a position overlapping the outlet 21B of the impeller 4 in the radial direction with respect to the axis O. In other words, the protruding portion 9 is provided at a position overlapping the outlet 21B of the impeller 4 when viewed from the direction of the axis O. Further, in a sectional view including the axis O, the protruding portion 9 has a rectangular shape.

Next, the operation of the centrifugal compressor 100 according to this embodiment will be described. In operating the centrifugal compressor 100, first, the rotary shaft 1 is rotationally driven by a drive source such as an electric motor. The impeller 4 rotates with the rotation of the rotary shaft 1, and the working fluid G is introduced from the intake port 7 into the flow path 2. The working fluid G introduced into the flow path 2 is sequentially compressed while passing through the impeller flow path 21 in each impeller 4. The working fluid G that has been compressed to a high pressure state is pressure-fed to the outside through the exhaust port 8.

By the way, as shown by the broken line arrow in FIG. 2, in the outer flow path F, the high-pressure working fluid G may flow from the outlet 21B side of the impeller flow path 21. A swirl component (swirl flow component) accompanying the rotation of the impeller 4 is added to the fluid flowing through the outer flow path F. The swirl component swirls in the same direction as the rotation direction of the impeller 4. Due to the influence of the swirl component, the impeller 4 is subjected to an exciting force directed in a direction orthogonal to the displacement direction. If this exciting force is continuously applied, whirling vibration may occur in the rotary shaft 1 and the impeller 4.

However, according to the above configuration, the working fluid G flowing into the outer flow path F is guided by the protruding portion 9 provided on the inner peripheral surface of the casing 3 (casing inner peripheral surface 3A). In the outer flow path F, the projecting portion 9 extends from the outlet 21B side of the impeller 4 toward the inlet 21A side. Therefore, even when the working fluid G contains a swirl component, the swirl component can be reduced by being guided by the protrusion 9. As a result, it is possible to reduce the possibility that whirling vibration occurs in the rotary shaft 1 and the impeller 4.

Further, according to the above configuration, since the projecting portion 9 is provided at a position that overlaps the outlet 21B of the impeller 4 in the radial direction, the swirl component contained in the working fluid G that has flowed into the outer flow path F is not allowed to flow after the inflow. It can be reduced immediately. In particular, in the outer flow path F, since the swirl component is greater at a position closer to the outlet 21B of the impeller flow path 21, the swirl component can be more effectively reduced by the above configuration. As a result, it is possible to further reduce the possibility that the impeller 4 is displaced or excited due to the influence of the swirl component.

Further, as compared with the configuration in which the protruding portion 9 extends over the entire area of the outer flow path F, only the necessary and sufficient amount of swirl component is removed, so that the cover outer peripheral surface 43A of the impeller 4 due to the excessive reduction of the swirl component is formed. It is also possible to avoid an increase in frictional resistance with the working fluid G. If the swirl component is excessively reduced, the flow velocity of the working fluid G flowing in the outer flow passage F becomes too small. Therefore, the frictional resistance due to the working fluid G between the outer peripheral surface 43A of the impeller 4 and the inner peripheral surface 3A of the casing is reduced. May increase, and smooth rotation of the impeller 4 may be hindered. According to the above configuration, such a possibility can be reduced.

Further, according to the above configuration, since the plurality of protrusions 9 are formed at intervals in the circumferential direction, the swirl component can be uniformly reduced over the entire area of the outer flow path F in the circumferential direction. As a result, the pressure distribution of the fluid in the outer flow path F becomes uniform, so that the vibration generated in the rotating shaft 1 and the impeller 4 can be suppressed more effectively.

The first embodiment of the present invention has been described above. Note that various changes and modifications can be made to the above configuration without departing from the spirit of the present invention.

[Second embodiment]
Subsequently, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. The same components as those in the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIGS. 3 and 4, in the present embodiment, the position of the protruding portion 9B is different from that in the first embodiment, and a step 10 is provided on the outlet side of the protruding portion 9B in the outer peripheral surface 43A of the cover. 4 is a diagram showing only the impeller 4 extracted, and the casing 3 is attached to the centrifugal compressor according to the present embodiment so as to cover the outside of the impeller 4, and the impeller 4 and the casing 3 are attached. An outer flow path F is formed between The rotary shaft 1 is attached to the impeller 4 so as to penetrate the central hole, and the impeller 4 rotates together with the rotary shaft 1. The casing 3 is a case that covers the whole and is a member that does not rotate (stationary member). Since it is necessary to form a gap between the casing 3 and the impeller 4, the outer flow path F is inevitably formed.

Step 10 projects from the outer peripheral surface 43A of the cover toward one side in the direction of the axis O. Step 10 has an annular shape centered on the axis O. Further, step 10 faces the protruding portion 9B from the outlet side. More specifically, when viewed from the direction in which the outer flow path F extends, the protrusion 9B and the step 10 overlap each other. The cross section of step 10 is rectangular. In addition, the cross-sectional shape of step 10 may be a triangle or a trapezoid other than a rectangle.

According to the above configuration, since the step 10 is provided on the cover outer peripheral surface 43A of the impeller 4, the working fluid G flowing out from the outlet 21B of the impeller flow path 21 is blocked by the step 10, and thus the outer flow path is blocked. It passes through the radially outer portion of F. That is, a larger amount of fluid flows along the casing inner peripheral surface 3A provided with the protruding portion 9B. As a result, more fluid is guided toward the protrusion 9B. Thereby, the swirl component of the working fluid G flowing into the outer flow passage F can be more positively reduced. Therefore, it is possible to further reduce the possibility that vibration occurs in the rotary shaft 1 and the impeller 4.

The second embodiment of the present invention has been described above. Note that various changes and modifications can be made to the above configuration without departing from the scope of the present invention. For example, in the second embodiment, the configuration in which the protrusion 9B and the step 10 are provided has been described. However, the protruding portion 9B may not necessarily be provided, and it is possible to adopt a configuration in which only the step 10 is provided on the cover outer peripheral surface 43A of the impeller 4. According to this configuration, since the step 10 is provided on the cover outer peripheral surface 43A of the impeller 4, the gap between the cover outer peripheral surface 43A and the casing inner peripheral surface 3A can be reduced. That is, the amount of the working fluid G flowing into the outer flow path F can be limited. As a result, the exciting force on the impeller 4 that occurs when a large amount of working fluid G flows into the outer flow path F can be reduced.

[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. The same components as those in the above-described embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 5 or 6, in this embodiment, the shape of the protrusion 9C is different from that in each of the above-described embodiments. The protrusion 9C extends over the entire area of the outer passage F from the outlet 21B to the inlet 21A of the impeller passage 21. More specifically, the projecting portion 9C extends from the outlet 21B of the impeller flow passage 21 to the end of the cavity C on the other side in the axis O direction. The protrusion height of the protrusion 9C (the protrusion size from the casing inner peripheral surface 3A) is constant over the entire area in the extending direction. Further, as shown in FIG. 6, the projecting portion 9C is curved from one side in the circumferential direction with respect to the axis O toward the other side from the inlet side toward the outlet side. In other words, the protrusion 9C is curved in a curved shape that is convex toward the front side in the rotation direction of the impeller 4. Further, the protrusion 9C extends in a direction intersecting the radial direction (broken line in FIG. 6) with respect to the axis O.

According to the above configuration, since the protrusion 9C is provided over the entire area of the outer flow passage F, the swirl component of the working fluid G flowing into the outer flow passage F can be further reduced. As a result, it is possible to further reduce the possibility of vibration occurring in the rotary shaft 1 and the impeller 4.

Here, the swirl component swirling from the other side in the circumferential direction to the one side (that is, toward the front side in the rotational direction of the impeller) is added to the fluid flowing into the outer flow path F. According to the above configuration, the projecting portion 9C is curved from one side in the circumferential direction to the other side from the inlet side toward the outlet side. That is, the protrusion 9C is curved in a direction opposite to the swirling direction of the swirl component. Therefore, the swirl component can be rectified in the opposite direction by the protrusion 9C. As a result, it is possible to further reduce the possibility that the impeller 4 is displaced or excited due to the influence of the swirl component.

The third embodiment of the present invention has been described above. Note that various changes and modifications can be made to the above configuration without departing from the spirit of the present invention.

[Fourth Embodiment]
Subsequently, a fourth embodiment of the present invention will be described with reference to FIGS. 7 to 9. The same components as those in the above-described embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIGS. 7 and 8, in this embodiment, the shape of the protruding portion 9D is different from that in each of the above-described embodiments. The projecting portion 9D is twisted from one side in the circumferential direction with respect to the axis O toward the other side with respect to the end edge 91 on the casing inner peripheral surface 3A side from the outlet side toward the inlet side. More specifically, the end edge 91 linearly extends along the casing inner peripheral surface 3A, while the end edge 92 on the opposite side of the end edge 91 extends from the outlet side toward the inlet side. It is curved from one side to the other side along an arc centered on the edge 91. In other words, as shown in FIG. 8, the end edge 92 moves from the outlet side to the inlet side from the front side to the rear side in the rotation direction R of the impeller 4 (that is, the swirl included in the flow in the outer flow path). The component is twisted toward the opposite side of the turning direction). Therefore, the angle formed by the protrusion 9D and the casing inner peripheral surface 3A is larger on the outlet side and smaller on the inlet side.

According to the above configuration, since the twist of the protrusion 9D is small on the outlet side, the protrusion 9D has a large angle with respect to the casing inner peripheral surface 3A. Therefore, the flow of the working fluid G containing the swirl component that has flowed into the outer flow path F from the outlet side (that is, the upstream side of the outer flow path F) can be captured more efficiently. Thereby, the swirl component can be further reduced. Further, on the inlet side (that is, on the downstream side of the outer flow path F), since the protrusion 9D has a large twist, the protrusion 9D has a small angle with respect to the casing inner peripheral surface 3A. Therefore, the fluid guided by the projecting portion 9D flows in a region biased near the casing inner peripheral surface 3A. As a result, the flow to the seal fin S1 on the inlet side of the impeller 4 becomes a flow state (downflow) inward in the radial direction from the casing inner peripheral surface 3A to the cover outer peripheral surface 43A. Will grow. Therefore, rather than the clearance V1 between the seal fin S1 provided on the upstream side of the casing inner peripheral surface 3A and the impeller 4 (cover outer peripheral surface 43A), the working fluid G is more positively directed toward the seal fin S1 itself. It can be flushed (see Figure 9). In other words, the apparent clearance V2 of the seal fin S1 can be made smaller than the actual clearance V1. Thereby, the leak flow passing through the seal fin S1 can be further reduced.

The fourth embodiment of the present invention has been described above. Note that various changes and modifications can be made to the above configuration without departing from the spirit of the present invention. For example, as a modification common to each of the above-described embodiments, a configuration as shown in FIG. 10 can be adopted. In the example shown in the figure, the protruding portion 9 (9B, 9C, 9D) has a tapered shape in which the dimension in the circumferential direction gradually becomes smaller as the projection 9 (9B, 9C, 9D) is spaced radially inward from the inner peripheral surface 3A of the casing. According to this configuration, even when the outer peripheral surface of the impeller 4 (cover 43) contacts the protruding portion 9 (9B, 9C, 9D), for example, the protruding portion 9 (9B, 9C, 9D) and the outer peripheral surface are formed. The contact area can be kept small. As a result, damage to the impeller 4 and generation of vibration can be suppressed.

DESCRIPTION OF SYMBOLS 1 rotating shaft 2 flow path 3 casing 3A casing inner peripheral surface 4 impeller 5 journal bearing 6 thrust bearing 7 intake port 8 exhaust port 9 protrusion 10 step 21 impeller flow path 21A inlet 21B outlet 41 disk 42 blade 43 cover 43A cover outer peripheral surface 50 Return Vane 100 Centrifugal Compressor F Outer Flow Path O Axis S Seal Part S1 Seal Fin S2 Base G Working Fluid

Claims (12)

A rotation axis extending along the axis,
An impeller for pumping a fluid flowing in from one side in the axial direction to the outside in the radial direction, a disc fixed to the rotating shaft, and an impeller provided with a cover for covering the blade provided on the disc,
A casing accommodating the impeller,
Forming an impeller flow path for pumping the fluid by the surface of the disk on the upstream side in the axial direction and the inner peripheral surface of the cover;
An outer flow path is formed by the outer peripheral surface of the cover and the inner peripheral surface of the casing facing the outer peripheral surface of the cover,
The outer flow path is connected to the impeller flow path at the outlet of the impeller flow path,
A centrifugal rotating machine in which a protrusion that protrudes from the inner peripheral surface of the casing is provided in the outer flow path. The centrifugal rotating machine according to claim 1, wherein a plurality of the protruding portions are formed at intervals in the circumferential direction. The protrusion is provided in a predetermined region of the inner peripheral surface of the casing,
The centrifugal rotating machine according to claim 1 or 2. The centrifugal rotating machine according to any one of claims 1 to 3, wherein the projecting portion is provided at a position overlapping the outlet of the impeller flow path in a radial direction with respect to the axis. In the outer flow path, the outer peripheral surface of the cover has a step that is an annular step centered on the axis,
The centrifugal rotating machine according to any one of claims 1 to 3, wherein the step is provided radially outward of the protruding portion. The centrifugal rotating machine according to claim 1, wherein in the outer flow path, the protruding portion is provided over the entire inner peripheral surface of the casing. The centrifugal rotating machine according to any one of claims 1 to 6, wherein the projecting portion is curved from one side in the circumferential direction with respect to the axis toward the other side as it goes outward in the radial direction. 8. The protruding portion is twisted from one side in the circumferential direction with respect to the axis toward the other side with respect to the inner peripheral surface of the casing as it goes toward the inner side in the radial direction. The centrifugal rotating machine described in 1. 9. A seal portion for sealing fluid leakage between the inner peripheral surface of the casing and the outer peripheral surface of the cover at the radially inner end portion of the outer flow path. The centrifugal rotating machine according to one item. The centrifugal rotation according to claim 8 or 9, wherein the projecting portion is twisted from the front side in the rotation direction of the impeller toward the rear side with respect to the inner peripheral surface of the casing as it goes toward the inner side in the radial direction. machine. The centrifugal rotating machine according to any one of claims 1 to 10, wherein a dimension of the projecting portion in a circumferential direction with respect to the axis gradually decreases with increasing distance from an inner circumferential surface of the casing. A rotation axis extending along the axis,
An impeller for pumping a fluid flowing in from one side in the axial direction to the outside in the radial direction, a disc fixed to the rotating shaft, and an impeller provided with a cover for covering the blade provided on the disc,
A casing accommodating the impeller,
Forming an impeller flow path for pumping the fluid by the surface of the disk on the upstream side in the axial direction and the inner peripheral surface of the cover;
An outer flow path is formed by the outer peripheral surface of the cover and the inner peripheral surface of the casing facing the outer peripheral surface of the cover,
The outer flow path is connected to the impeller flow path at the outlet of the impeller flow path,
In the outer flow path, a step that is an annular step centered on the axis is provided on the outer peripheral surface of the cover,
Centrifugal rotating machine.

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