CN111379744B

CN111379744B - Centrifugal rotary machine

Info

Publication number: CN111379744B
Application number: CN201911326761.5A
Authority: CN
Inventors: 岩崎真人; 川下伦平; 时政泰宪; 山下修一; 枡谷穰
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Compressor Corp
Priority date: 2018-12-25
Filing date: 2019-12-20
Publication date: 2022-03-29
Anticipated expiration: 2039-12-20
Also published as: JP7168441B2; CN111379744A; JP2020101169A; US20200200184A1

Abstract

A centrifugal rotary machine is provided with: a rotating shaft extending along an axis; an impeller that pressure-feeds a fluid flowing in from one side in an axial direction to an outer side in a radial direction, and that includes a disk fixed to a rotating shaft, and a cover that covers blades provided on the disk; and a casing that houses the impeller, wherein an impeller flow path for pressure-feeding a fluid is formed by a surface on an upstream side in an axial direction of the disk and an inner peripheral surface of the cover, 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, the outer flow path is connected to the impeller flow path at an outlet of the impeller flow path, and a protrusion protruding from the inner peripheral surface of the casing is provided in the outer flow path.

Description

Centrifugal rotary machine

Technical Field

The present invention relates to a centrifugal rotary machine.

Background

Generally, a centrifugal compressor includes a rotating shaft extending along an axis, an impeller provided on the rotating shaft, and a casing covering the impeller from outside. Among them, as the impeller, an impeller of a form called a closed impeller is sometimes used. The closed impeller includes a disk-shaped disk centered on an axis, a plurality of blades provided on one surface of the disk, and a conical cover covering the plurality of blades from one side. A gap (outer flow path) is provided between the outer peripheral surface of the cover and the inner peripheral surface of the housing.

When the centrifugal compressor is operated, the fluid flows through the flow path defined by the vanes. In the flow path, the fluid is compressed and brought into a high-pressure state while flowing from the inlet side toward the outlet side. Here, since the high-pressure fluid flows through the outlet side of the flow path as compared with the inlet side, the fluid is also likely to flow into the outer flow path. As a result, when a large amount of fluid flows into the outer flow path, the compression efficiency of the centrifugal compressor is reduced. For this reason, a technique is known in which a seal portion is provided on an inner peripheral surface of the housing to prevent the flow of the fluid. For example, international publication No. 2016/043090 discloses a structure in which a sealing fin is provided on the inner circumferential surface of a housing on the inlet side of an impeller as a specific example of a sealing portion. By providing the sealing fin as described above, the fluid flowing into the outer flow path is reduced.

In the centrifugal compressor having the above-described configuration, when the rotor including the impeller is displaced in the radial direction in a state where the fluid leaks between the seal fins and the outer peripheral surface of the cover, a pressure distribution in the circumferential direction is generated on the surface of the rotor. Here, a vortex component (a swirling flow component) accompanying the rotation of the impeller is added to the fluid flowing through the outer flow path. Due to the influence of the swirl component, an excitation force (seal excitation force) in a direction orthogonal to the displacement direction acts on the impeller. By continuously applying the seal excitation force, a whirling vibration is generated in the rotor. That is, in the centrifugal compressor described in international publication No. 2016/043090, there is still room for improvement.

Disclosure of Invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide a centrifugal rotary machine that further reduces vibration.

A centrifugal rotary machine according to one aspect of the present invention includes: a rotating shaft extending along an axis; an impeller that pressure-feeds a fluid flowing in from one side in an axial direction to an outer side in a radial direction, and that includes a disk fixed to the rotating shaft, and a cover that covers blades provided on the disk; and a casing that houses the impeller, and that forms an impeller flow path for pumping the fluid by a surface on the upstream side in the axial direction of the disk and an inner peripheral surface of the cover, and forms an outer flow path by an outer peripheral surface of the cover and an inner peripheral surface of the casing that faces the outer peripheral surface of the cover, the outer flow path being connected to the impeller flow path at an outlet of the impeller flow path, and the outer flow path being provided with a protruding portion that protrudes from the inner peripheral surface of the casing.

According to the above configuration, the fluid flowing into the outer flow path is guided by the protrusion provided on the inner circumferential surface of the housing. Therefore, even when the fluid contains a vortex component (swirl flow component), the vortex component can be reduced by being guided by the protrusion. Here, when the fluid flow containing the vortex component flows into the outer flow passage, an excitation force (seal excitation force) in a direction orthogonal to the displacement direction acts on the impeller. By continuously applying the seal excitation force, a whirling vibration is generated in the rotary shaft and the impeller. However, according to the above configuration, the possibility of the above-described situation can be reduced.

In the centrifugal rotary machine, the plurality of projections may be formed at intervals in the circumferential direction.

According to the above configuration, since the plurality of projections are formed at intervals in the circumferential direction, the swirl component can be reduced uniformly over the entire circumferential region of the outer flow passage. This makes the pressure distribution of the fluid in the outer flow path uniform, and therefore vibration generated in the impeller can be more effectively suppressed.

In the centrifugal rotary machine, the projection may be provided in a predetermined region of an inner peripheral surface of the casing.

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

According to the above configuration, since the protruding portion is provided at a position radially overlapping the outlet of the impeller flow passage, the vortex component included in the fluid flowing into the outer flow passage can be reduced immediately after the fluid flows into the outer flow passage. Here, the inventors performed CFD analysis on the excitation force due to the eddy current component. As a result, it was found that the excitation force generated in the shroud of the impeller was large. The exciting force generated in the cover is caused by the fluid flowing into the outer flow path. Therefore, by providing the protruding portion at the inlet of the outer flow passage, i.e., at a position overlapping the outlet of the impeller flow passage as in the above-described configuration, the eddy component is reduced, and the exciting force generated in the shroud can be more positively reduced. Further, the closer to the outlet of the impeller flow path, the more the swirl component is, and therefore the swirl component can be more effectively reduced. As a result, the possibility of displacement or excitation of the impeller due to the influence of the swirl component can be further reduced. Further, compared to a configuration in which the protrusion extends over the entire outer flow path, since only the swirl component is removed to a sufficient extent as necessary, it is possible to avoid an increase in the frictional resistance between the outer peripheral surface of the shroud of the impeller and the fluid due to an excessive decrease in the swirl component.

In the centrifugal rotary machine, the outer flow path may have a step, which is an annular step centered on the axis, on the outer peripheral surface of the cover, and the step may be provided radially outward of the protruding portion.

According to the above configuration, since the step is provided on the outer peripheral surface of the cover, the fluid flowing out of the outlet of the impeller passes through the radially outer portion of the outer flow path. That is, more fluid flows along the inner circumferential surface of the housing provided with the protruding portion. As a result, more fluid is guided toward the protrusion provided on the inner peripheral surface of the housing. This can more positively reduce the swirl component of the fluid flowing into the outer flow path.

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

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

In the centrifugal rotary machine, the projection may be curved from one side to the other side in a circumferential direction with respect to the axis line as the projection is directed to the radially outer side.

Here, a swirl component that turns from the other side in the circumferential direction to one side (i.e., to 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 protruding portion is curved from one side to the other side in the circumferential direction as going from the inlet side to the radially outer side. In other words, the protruding portion is curved toward the direction opposite to the turning direction of the vortex component. Therefore, the eddy component can be rectified in the opposite direction by the protrusion. As a result, the possibility of excitation of the rotary shaft and the impeller due to the influence of the eddy component can be further reduced.

In the centrifugal rotary machine, the protruding portion may be twisted from one side to the other side in the circumferential direction with respect to the axis line with reference to the inner circumferential surface of the casing toward the radially inner side.

According to the above structure, the twist of the protruding portion is small at the outlet side, and therefore the protruding portion has a large angle with respect to the inner peripheral surface of the housing. Therefore, the fluid flow containing the vortex component flowing into the outer flow passage from the impeller outlet side (i.e., the upstream side of the outer flow passage) can be more effectively captured. This can further reduce the eddy current component.

In the centrifugal rotary machine, a seal portion that seals leakage of fluid between the inner peripheral surface of the casing and the outer peripheral surface of the cover may be further provided at a radially inner end portion of the outer flow passage.

According to the above structure, the twist of the protruding portion is large at the impeller inlet side (i.e., the downstream side of the outer flow path), and therefore the protruding portion has a small angle with respect to the inner peripheral surface of the casing. Therefore, the fluid guided by the protruding portion flows in the vicinity of the inner peripheral surface of the housing. As a result, for example, in the case where the seal portion is provided on the upstream side of the inner peripheral surface of the casing, the fluid can be more actively caused to flow toward the seal portion itself than the gap between the seal portion and the outer peripheral surface of the casing of the impeller. That is, the liquid flow toward the seal portion on the inlet side of the impeller becomes a flow condition (downward flow) from the inner peripheral surface of the casing toward the outer peripheral surface of the cover toward the inside in the radial direction, and therefore the contraction flow effect of the seal portion is improved. This can further reduce leakage flow through the seal portion.

In the centrifugal rotary machine, the protruding portion may be twisted from a front side to a rear side in a rotation direction of the impeller with respect to the inner circumferential surface of the housing as the protruding portion faces the radially inner side.

According to the above configuration, the protruding portion is twisted toward the rear side in the rotation direction of the impeller (i.e., the side opposite to the rotation direction of the vortex component included in the liquid flow in the outer flow passage). Therefore, the eddy component can be captured and reduced more effectively.

In the centrifugal rotary machine, the projection may be gradually reduced in size in the circumferential direction with respect to the axis as it is separated from the inner circumferential surface of the casing.

According to the above structure, the dimension of the protruding portion in the circumferential direction is gradually reduced to take a shape with a thin tip. Thus, for example, even when the outer peripheral surface of the impeller contacts the protruding portion, the contact area between the protruding portion and the outer peripheral surface can be kept small. As a result, damage to the impeller and occurrence of vibration can be suppressed.

A centrifugal rotary machine according to one aspect of the present invention includes: a rotating shaft extending along an axis; an impeller that pressure-feeds a fluid flowing in from one side in an axial direction to an outer side in a radial direction, and that includes a disk fixed to the rotating shaft, and a cover that covers blades provided on the disk; and a casing that houses the impeller, and that forms an impeller flow path for pumping the fluid by a surface on the upstream side in the axial direction of the disk and an inner peripheral surface of the cover, and forms an outer flow path that is connected to the impeller flow path at an outlet of the impeller flow path by an outer peripheral surface of the cover and an inner peripheral surface of the casing that faces the outer peripheral surface of the cover, wherein the outer flow path is provided with a step that is an annular step centered on the axis on the outer peripheral surface of the cover.

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 housing can be reduced. That is, the amount of fluid flowing into the outer channel can be limited. As a result, the exciting force to the impeller generated when a large amount of fluid flows into the outer flow passage can be reduced.

According to the present invention, a centrifugal rotary machine with further reduced vibration can be provided.

Drawings

Fig. 1 is a sectional view of a centrifugal compressor according to a first embodiment of the present invention.

Fig. 2 is an enlarged sectional view of a main part of a centrifugal compressor according to a first embodiment of the present invention.

Fig. 3 is an enlarged sectional view of a main portion of a centrifugal compressor according to a second embodiment of the present invention.

Fig. 4 is a perspective view of an impeller according to a second embodiment of the present invention.

Fig. 5 is an enlarged sectional view of a main part of a centrifugal compressor according to a third embodiment of the present invention.

Fig. 6 is a view of an impeller according to a third embodiment of the present invention as viewed from the axial direction.

Fig. 7 is an enlarged sectional view of a main portion of a centrifugal compressor according to a fourth embodiment of the present invention.

Fig. 8 is a view of an impeller according to a fourth embodiment of the present invention as viewed from the axial direction.

Fig. 9 is an explanatory diagram showing a fluid flow in the seal portion of the fourth embodiment of the present invention.

Fig. 10 is a cross-sectional view showing a modification of the protruding portion according to each embodiment of the present invention.

Detailed Description

[ first embodiment ]

A centrifugal compressor 100 (centrifugal rotary machine) according to a first embodiment of the present invention will be described with reference to the drawings. As shown in fig. 1, the centrifugal compressor 100 includes a rotary shaft 1 that rotates about an axis O, a casing 3 that forms a flow path 2 by covering the periphery of the rotary shaft 1, a multi-stage impeller 4 provided on the rotary shaft 1, and a projection 9 provided on the casing 3.

The housing 3 is cylindrical and extends along the axis O. The rotary shaft 1 extends along the axis O so as to penetrate the inside of the housing 3. Journal bearings 5 and thrust bearings 6 are provided at both ends of the housing 3 in the axis O direction, respectively. The rotary shaft 1 is supported by these journal bearing 5 and thrust bearing 6 so as to be rotatable about the axis O.

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

An internal space is formed inside the housing 3, which communicates the intake port 7 and the exhaust port 8 and is repeatedly reduced in diameter and increased in diameter. The internal space accommodates a plurality of impellers 4 and constitutes a part of the flow path 2. In the following description, the side of the flow path 2 where the inlet port 7 is located is referred to as the upstream side, and the side where the outlet port 8 is located is referred to as the downstream side. The flow path 2 is provided with rotary blades 50 on the downstream side of the impellers 4.

A plurality of (6) impellers 4 are provided on the outer peripheral surface of the rotary shaft 1 at intervals in the axis O direction. As shown in fig. 2, each impeller 4 includes a disk 41 having a disk shape with the axis O as the center, a plurality of blades 42 provided on the surface of the disk 41 on the upstream side, and a cover 43 covering the plurality of blades 42 from the upstream side.

The disk 41 is formed in a substantially conical shape such that the radial dimension thereof gradually increases from one side to the other side in the direction of the axis O when viewed in the direction intersecting the axis O. The blades 42 are radially arranged in a plurality of rows radially outward from the axis O on the upstream side (the disk upstream surface 41A) of both surfaces of the disk 41 in the axis O direction. More specifically, these vanes are formed of thin plates provided standing from the disk 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 to the other side in the circumferential direction with respect to the axis O.

Of the two surfaces of the disk 41 in the direction of the axis O, the surface facing the downstream side (disk back surface 41B) widens in the radial direction with respect to the axis O. A gap that widens in the direction of the axis O is formed between the disk back surface 41B and the housing 3 (housing facing surface 3B).

The upstream end edge of the vane 42 is covered with a cover 43. In other words, the plurality of blades 42 are sandwiched between the cover 43 and the disk 41 in the direction of the axis O. Thereby, a space is formed between the cover 43, the disk 41, and the pair of blades 42 adjacent to each other. This space constitutes the impeller flow path 21 which is a part of the flow path 2. In the following description, the radially inner end of the impeller flow passage 21 is referred to as an inlet 21A, and the radially outer end is referred to as an outlet 21B. The outer peripheral surface of the cover 43 (cover outer peripheral surface 43A) extends radially outward toward the second side in the axis O direction, and has a substantially conical shape.

The cover outer peripheral surface 43A faces the inner peripheral surface of the housing 3 (the housing inner peripheral surface 3A) with a gap. The housing inner peripheral surface 3A extends radially outward from the first side toward the second side in the axis O direction so as to follow the shape of the cover outer peripheral surface 43A. An outer flow path F is defined between the inner surface 3A of the housing and the outer surface 43A of the cover. In the following description, in the extending direction of the outer flow path F, the end portion side corresponding to the outlet 21B side of the impeller flow path 21 may be simply referred to as "outlet side", and the end portion side corresponding to the inlet 21A side may be simply referred to as "inlet side".

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

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

Next, the operation of the centrifugal compressor 100 of the present embodiment will be described. When the centrifugal compressor 100 is operated, the rotary shaft 1 is first driven to rotate by a drive source such as a motor. The impellers 4 rotate with the rotation of the rotary shaft 1, and the working fluid G is introduced into the flow path 2 through the air inlet 7. The working fluid G introduced into the flow path 2 is sequentially compressed while passing through the impeller flow path 21 of each impeller 4. The working fluid G compressed to a high pressure is pressure-fed to the outside through the exhaust port 8.

However, as indicated by the broken-line arrows 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 vortex component (a swirling flow component) accompanying the rotation of the impeller 4 is added to the fluid flowing through the outer flow path F. The swirl component revolves in the same direction as the rotation direction of the impeller 4. Due to the influence of the swirl component, an exciting force in a direction orthogonal to the displacement direction acts on the impeller 4. By continuing to apply this excitation force, it is possible to generate whirling vibration 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 protrusion 9 provided on the inner peripheral surface of the housing 3 (the housing inner peripheral surface 3A). The protrusion 9 extends from the outlet 21B side toward the inlet 21A side of the impeller 4 in the outer flow path F. 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, the possibility of generating whirling vibration in the rotary shaft 1 and the impeller 4 can be reduced.

Further, according to the above configuration, since the protrusion 9 is provided at a position radially overlapping the outlet 21B of the impeller 4, the swirl component included in the working fluid G flowing into the outer flow path F can be reduced immediately after the working fluid G flows into the outer flow path F. In particular, the swirl component increases as the position in the outer flow path F is closer to the outlet 21B of the impeller flow path 21, and thus the swirl component can be more effectively reduced by the above-described configuration. As a result, the possibility of displacement or excitation of the impeller 4 due to the influence of the swirl component can be further reduced.

Further, compared to the configuration in which the protrusion 9 extends over the entire area of the outer flow path F, since only the swirl component is removed to a sufficient extent as necessary, it is possible to avoid an increase in the frictional resistance between the cover outer circumferential surface 43A of the impeller 4 and the working fluid G due to an excessive decrease in the swirl component. If the swirl component is excessively reduced, the flow velocity of the working fluid G flowing through the outer flow path F becomes excessively low, and the frictional resistance of the working fluid G between the cover outer circumferential surface 43A of the impeller 4 and the housing inner circumferential surface 3A increases, which may prevent smooth rotation of the impeller 4. According to the above configuration, the possibility of the above-described situation can be reduced.

Further, according to the above configuration, since the plurality of projections 9 are formed at intervals in the circumferential direction, the swirl component can be reduced uniformly over the entire circumferential region of the outer flow path F. This makes the pressure distribution of the fluid in the outer flow path F uniform, and therefore vibration generated in the rotary shaft 1 and the impeller 4 can be more effectively suppressed.

The first embodiment of the present invention has been described above. It is to be noted that various changes and modifications can be made to the above-described configuration without departing from the scope of the present invention.

[ second embodiment ]

Next, a second embodiment of the present invention will be described with reference to fig. 3 and 4. The same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in fig. 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 cover outer circumferential surface 43A on the outlet 21B side of the protruding portion 9B. Fig. 4 is a diagram showing only the impeller 4 taken out, and in the centrifugal compressor of the present embodiment, the casing 3 is attached so as to cover the outside of the impeller 4, and an outside flow path F is formed between the impeller 4 and the casing 3. A rotary shaft 1 is attached to the impeller 4 so as to penetrate a hole in the center, and the impeller 4 rotates together with the rotary shaft 1. The housing 3 is a housing covering the entire body, and is a non-rotating member (stationary member). Since a gap inevitably occurs between the casing 3 and the impeller 4, an outer flow path F is inevitably formed.

The step 10 protrudes from the cover outer peripheral surface 43A toward the first side in the axis O direction. The step 10 is annular and centered on the axis O. The step 10 faces the projection 9B from the outlet 21B side. The protruding portion 9B is disposed at a distance from the step 10. More specifically, the protrusion 9B and the step 10 overlap each other when viewed from the extending direction of the outer flow path F. In addition, the step 10 has a rectangular cross section. The cross-sectional shape of the step 10 may be a triangle or a trapezoid, instead of a rectangle.

According to the above configuration, since the step 10 is provided on the shroud outer peripheral surface 43A of the impeller 4, the working fluid G (broken line in fig. 3) flowing out from the outlet 21B of the impeller flow path 21 passes through the radially outer portion of the outer flow path F while being blocked by the step 10. That is, more fluid flows along the housing inner peripheral surface 3A provided with the protruding portion 9B. As a result, more fluid is directed toward the protrusion 9B. This can more positively reduce the swirl component of the working fluid G flowing into the outer flow path F. Therefore, the possibility of vibration occurring in the rotary shaft 1 and the impeller 4 can be further reduced.

The second embodiment of the present invention has been described above. It is to be noted that various changes and modifications can be made to the above-described configuration without departing from the scope of the present invention. For example, in the second embodiment, the configuration in which the protruding portion 9B and the step 10 are provided is described. However, the protrusion 9B is not necessarily provided, and only the step 10 may be provided on the cover outer circumferential surface 43A of the impeller 4. According to this configuration, since the step 10 is provided on the cover outer circumferential surface 43A of the impeller 4, the gap between the cover outer circumferential surface 43A and the casing inner circumferential 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 to the impeller 4 generated when a large amount of the 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 fig. 5 and 6. The same components as those in the above embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in fig. 5 or 6, the present embodiment is different from the above embodiments in the shape of the protruding portion 9C. The protrusion 9C extends in the outer flow path F over the entire region from the outlet 21B to the inlet 21A of the impeller flow path 21. More specifically, the protrusion 9C extends from the outlet 21B of the impeller flow path 21 to the end on the second side in the axis O direction of the cavity C. The protruding height of the protruding portion 9C (protruding dimension from the housing inner peripheral surface 3A) is constant in the entire region in the extending direction. Further, as shown in fig. 6, the protruding portion 9C is curved from the first side toward the second side in the circumferential direction with respect to the axis O as going from the inlet 21A side toward the outlet 21B side. In other words, the protruding portion 9C is curved in a curved shape that becomes convex toward the front side in the rotation direction of the impeller 4. In addition, the protruding portion 9C extends in a direction intersecting with a radial direction (a dashed line in fig. 6) with respect to the axis O.

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

Here, a swirl component that turns from the second side in the circumferential direction toward the first side (i.e., toward the front side in the rotation direction of the impeller) is added to the fluid flowing into the outer flow path F. According to the above configuration, the projection 9C is curved from the first side toward the second side in the circumferential direction as going from the inlet side toward the outlet 21B side. In other words, the protruding portion 9C is curved toward the direction opposite to the turning direction of the swirl component. Therefore, the eddy current component can be rectified in the opposite direction by the protrusion 9C. As a result, the possibility of displacement or excitation of the impeller 4 due to the influence of the swirl component can be further reduced.

The third embodiment of the present invention has been described above. It is to be noted that various changes and modifications can be made to the above-described configuration without departing from the scope of the present invention.

[ fourth embodiment ]

Next, a fourth embodiment of the present invention will be described with reference to fig. 7 to 9. The same components as those in the above embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in fig. 7 and 8, the present embodiment is different from the above-described embodiments in the shape of the protruding portion 9D. The protruding portion 9D is twisted from the first side toward the second side in the circumferential direction with respect to the axis O with reference to the end edge 91 on the side of the housing inner peripheral surface 3A as going from the outlet 21B side toward the inlet 21A side. More specifically, the end edge 91 extends linearly along the housing inner peripheral surface 3A, and the end edge 92 on the opposite side of the end edge 91 is curved from the first side to the second side along an arc centered on the end edge 91 as going from the outlet 21B side to the inlet 21A side. In other words, as shown in fig. 8, the end edge 92 is twisted from the front side to the rear side in the rotation direction R of the impeller 4 (i.e., the side opposite to the rotation direction of the swirl component included in the liquid flow in the outer flow path) as it goes from the outlet 21B side to the inlet 21A side. Therefore, the angle formed by the protrusion 9D and the housing inner peripheral surface 3A becomes larger toward the outlet 21B and smaller toward the inlet 21A.

According to the above structure, at the outlet 21B side, since the twist of the protruding portion 9D is small, the protruding portion 9D has a large angle with respect to the housing inner peripheral surface 3A. Therefore, the flow of the working fluid G including the vortex component flowing into the outer flow path F from the outlet 21B side (i.e., the upstream side of the outer flow path F) can be more effectively captured. This can further reduce the eddy current component. Further, at the inlet 21A side (i.e., the downstream side of the outer flow path F), since the twist of the protruding portion 9D is large, the protruding portion 9D has a small angle with respect to the housing inner peripheral surface 3A. Therefore, the fluid guided by the protruding portion 9D flows in the region near the housing inner peripheral surface 3A. As a result, the flow of the fluid toward the seal fins S1 on the inlet 21A side of the impeller 4 flows radially inward from the casing inner peripheral surface 3A toward the cover outer peripheral surface 43A (downward flow), and therefore the flow contracting effect of the fins S1 is improved. Therefore, the working fluid G can be caused to flow more positively toward the seal fin S1 itself, rather than toward the gap V1 between the seal fin S1 provided on the upstream side of the casing inner peripheral surface 3A and the impeller 4 (the cover outer peripheral surface 43A) (see fig. 9). In other words, the apparent gap V2 of the sealing fin S1 can be made smaller than the actual gap V1. This can further reduce leakage flow through the sealing fin S1.

The fourth embodiment of the present invention has been described above. It is to be noted that various changes and modifications can be made to the above-described configuration without departing from the scope of the present invention. For example, a configuration as shown in fig. 10 may be employed as a modification commonly used in the above embodiments. In the example of the figure, the projection 9(9B, 9C, 9D) has a tapered shape with a gradually decreasing circumferential dimension as it is spaced radially inward from the housing inner peripheral surface 3A. According to this configuration, even when the outer peripheral surface of the impeller 4 (the cover 43) contacts the protruding portions 9(9B, 9C, 9D), for example, the contact area between the protruding portions 9(9B, 9C, 9D) and the outer peripheral surface can be suppressed to be small. As a result, damage to the impeller 4 and vibration can be suppressed.

While the preferred embodiments of the present invention have been described and illustrated, they are merely illustrative of the present invention and should not be construed as being limitative. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

1. A centrifugal rotary machine, wherein,

the centrifugal rotary machine includes:

a rotating shaft extending along an axis;

an impeller that pressure-feeds a fluid flowing in from one side in an axial direction to an outer side in a radial direction, and that includes a disk fixed to the rotating shaft, and a cover that covers blades provided on the disk; and

a casing which houses the impeller,

an impeller flow path for pumping the fluid is formed by a surface of the disk on the upstream side in the axial direction and an inner peripheral surface of the cover,

an outer flow path is formed by an outer peripheral surface of the cover and an inner peripheral surface of the housing facing the outer peripheral surface of the cover,

the outer flow path is connected to the impeller flow path at an outlet of the impeller flow path,

a protruding portion protruding from an inner peripheral surface of the casing is provided in the outer flow path at a position close to an outlet side of the impeller flow path,

the protrusion is provided at a position overlapping the outlet of the impeller flow passage in a radial direction with respect to the axis.

2. A centrifugal rotary machine, wherein,

the centrifugal rotary machine includes:

a rotating shaft extending along an axis;

a casing which houses the impeller,

the outer flow path has a step, which is an annular step around the axis, on the outer peripheral surface of the cover,

the step is provided at a more radially outer side than the protruding portion.

3. A centrifugal rotary machine, wherein,

the centrifugal rotary machine includes:

a rotating shaft extending along an axis;

a casing which houses the impeller,

in the outer flow path, the protrusion is provided in an entire area of an inner peripheral surface of the housing.

4. Centrifugal rotary machine according to claim 3,

the protruding portion is curved from one side to the other side in the circumferential direction with respect to the axis as facing the radially outer side.

5. A centrifugal rotary machine, wherein,

the centrifugal rotary machine includes:

a rotating shaft extending along an axis;

a casing which houses the impeller,

the protruding portion is twisted from one side to the other side in the circumferential direction with respect to the axis with respect to the inner circumferential surface of the housing as the protruding portion faces the radially inner side.

6. A centrifugal rotary machine according to any one of claims 1 to 5,

the outer flow path further includes a seal portion at a radially inner end thereof for sealing leakage of fluid between the inner circumferential surface of the housing and the outer circumferential surface of the cover.

7. Centrifugal rotary machine according to claim 5,

the protruding portion is twisted from the front side to the rear side in the rotation direction of the impeller with respect to the inner peripheral surface of the housing as the protruding portion faces the radially inner side.

8. A centrifugal rotary machine according to any one of claims 1 to 5,

the projection gradually decreases in size in the circumferential direction with respect to the axis as it goes away from the inner circumferential surface of the housing.