CENTRIFUGAL COMPRESSOR WITH SCROLL FLOW PATH

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of PCT Application No. PCT/JP2024/028233, filed on Aug. 7, 2024, which claims the benefit of priority from Japanese Patent Application No. 2023-137167, filed on Aug. 25, 2023. The entire contents of the above listed PCT and priority applications are incorporated herein by reference.

BACKGROUND

Field

The present disclosure relates to a centrifugal compressor.

Description of the Related Art

Japanese Unexamined Patent Publication No. 2012-211544 discloses a centrifugal compressor including a compressor cover. The compressor cover includes a flow path wall of a scroll flow path. The flow path wall of the scroll flow path is formed by a plurality of pieces. International Publication No. WO 2015/188028 discloses a turbine wheel and a turbine housing, although it is not a centrifugal compressor. In addition, Japanese Unexamined Patent Publication No. 2021-105385 discloses a blower including an impeller and scroll, although it is not a centrifugal compressor.

SUMMARY

In order to reduce a size of a centrifugal compressor, an outer diameter of a scroll flow path may be reduced. However, reducing the outer diameter of the scroll flow path leads to a reduction in a flow path cross-sectional area of the scroll flow path, resulting in a decrease in compression efficiency. On the other hand, if a wall thickness of the flow path wall forming the scroll flow path is reduced to maintain a flow path cross-section area, the structural integrity of the containment may be impaired.

Disclosed herein is an example centrifugal compressor includes a rotary shaft, a compressor impeller fixed to the rotary shaft, and a flow path wall forming a scroll flow path around the compressor impeller. The flow path wall includes an outer peripheral wall portion disposed outward from the rotary shaft in a radial direction thereof, and an inner peripheral wall portion disposed radially inward closer to the rotary shaft than the outer peripheral wall portion. The outer peripheral wall portion includes a thickened portion having a wall thickness greater than the inner peripheral wall portion opposed in the radial direction.

The outer peripheral wall portion of the scroll flow path that is disposed outward from the rotary shaft in the radial direction may be most likely to be affected by an operational anomaly of the compressor impeller. Conversely, the effect on the inner peripheral wall portion of the scroll flow path that is disposed inward in the radial direction may be limited as compared to that on the outer peripheral wall portion. Accordingly, by providing the thickened portion on the outer peripheral wall portion, the structural integrity of the containment property of the compressor impeller may be maintained. On the other hand, the inner peripheral wall portion may be made thinner than the thickened portion, which contributes to a reduction in size as compared to when a thickness of the inner peripheral wall portion is uniform, while still maintaining a sufficient flow path cross-sectional area for the scroll flow path. As a result, according to the centrifugal compressor, it may maintain the containment property in the scroll flow path and secure the sufficient flow path cross-sectional area for the scroll flow path.

In some examples, the flow path wall may include a connecting wall portion that connects the outer peripheral wall portion and the inner peripheral wall portion. The connecting wall portion may include a thickness change portion whose thickness changes continuously from the thickened portion to the inner peripheral wall portion. The connecting wall portion may connect the outer peripheral wall portion and the inner peripheral wall portion. In the event of an operational anomaly of the compressor impeller, the effect on the connecting wall portion may decrease gradually from the thickened portion to the inner peripheral wall portion. By providing the thickness change portion whose thickness changes continuously from the thickened portion to the inner peripheral wall portion, the wall thickness may be set with consideration for the magnitude of this effect.

In some examples, a discharge pipe that forms a discharge flow path communicating with the scroll flow path may be further provided. The thickened portion may be disposed on a side opposite to the discharge pipe with respect to the rotary shaft. According to the examples, the containment property of a portion far from the discharge flow path with respect to the rotary shaft may be maintained in the scroll flow path.

In some examples, a discharge pipe that forms a discharge flow path communicating with the scroll flow path and has a pipe axis extending in a tangential direction of the scroll flow path may be further provided. The flow path wall may include a rotation axis of the compressor impeller, and may include, in a cross-section along a plane parallel to the pipe axis, a first flow path wall portion disposed upstream in a flow direction of the scroll flow path, and a second flow path wall portion disposed downstream in the flow direction. The thickened portion may be disposed in a flow path region extending from the first flow path wall portion to the second flow path wall portion in the flow direction of the scroll flow path. The flow path region from the first flow path wall portion to the second flow path wall portion may be likely to be affected when the compressor impeller experiences an operational anomaly. According to the examples, by providing the thickened portion in the flow path region, the containment property may be maintained in at least a portion of the flow path region.

In some examples, the thickened portion may be provided over the entire flow path region. According to the examples, the containment property may be maintained over the entire flow path region.

In some examples, a ratio of a thickness of the thickened portion provided over the entire flow path region to a thickness of the inner peripheral wall portion opposing the thickened portion in the radial direction may be made constant. According to the examples, the containment property may be maintained to substantially the same degree over the entire flow path region.

In some examples, a compressor housing that houses the compressor impeller and includes a flow path wall, and a diffuser plate that is fixed to the compressor housing and forms a diffuser flow path may be further provided. A thickness of the diffuser plate may be made thinner than the thickness of the thickened portion. According to the examples, by making the diffuser plate thinner than the thickened portion, it may reduce the size of the centrifugal compressor, while maintaining the containment property.

In some examples, the thickness of the diffuser plate may be made greater than the wall thickness of the inner peripheral wall portion opposing the thickened portion in the radial direction.

In some examples, a compressor housing that houses the compressor impeller and has a flow path wall, and a diffuser plate that is fixed to the compressor housing and forms a diffuser flow path may be further provided. The flow path wall may include a connecting wall portion that connects the outer peripheral wall portion and the inner peripheral wall portion and is disposed to face the diffuser plate.

In some examples, the connecting wall portion may include a portion thinner than the diffuser plate.

In some examples, a compressor housing that houses the compressor impeller is provided, and the compressor housing includes a scroll portion having a flow path wall and a discharge pipe that is connected to the scroll portion and forms a discharge flow path communicating with the scroll flow path. The outer peripheral wall portion may include the thickened portion in the entire region along the scroll flow path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating an example centrifugal compressor.

FIG. 2 is a cross-sectional view along line II-II in FIG. 1.

FIG. 3 is a perspective view of an example compressor housing.

FIG. 4 is a plan view of the compressor housing illustrated in FIG. 3.

FIG. 5 is a cross-sectional view along line V-V in FIG. 4.

FIG. 6 is a cross-sectional view along line VI-VI in FIG. 4.

DETAILED DESCRIPTION

In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted.

In the following description, unless otherwise specified, the term “radial direction” is used with respect to a rotary shaft 12 or a rotation axis X. The “radial direction” is, for example, a centrifugal direction with respect to the rotary shaft 12 or the rotation axis X.

An example centrifugal compressor 1 will be described with reference to FIG. 1. The centrifugal compressor 1 is applied to an internal combustion engine of a vehicle or a ship, for example. The centrifugal compressor 1 is a type of rotating machine and includes a compressor 7. The centrifugal compressor 1 rotates a compressor impeller 8 using interactions of a rotor portion 13 and stator portion 14, compresses a gas such as air, and generates a compressed fluid such as compressed air. A motor 5 is configured by the rotor portion 13 and the stator portion 14.

The centrifugal compressor 1 may be connected to a turbocharger applied to an internal combustion engine of a vehicle or a ship, for example. In that case, the centrifugal compressor 1 sends compressed air to the compressor 7 of the turbocharger. By combining the centrifugal compressor 1 with the turbocharger, the centrifugal compressor 1 helps start up the turbocharger.

The centrifugal compressor 1 includes the rotary shaft 12 rotatably supported in a housing 2 and the compressor impeller 8 attached to an end portion of the rotary shaft 12. The housing 2 includes a motor housing 3 that houses the rotor portion 13 and the stator portion 14, and a compressor housing 6 that houses the compressor impeller 8. The compressor housing 6 is fixed to an end portion of the motor housing 3 (left side in the figure). The compressor housing 6 includes a suction pipe 9, a scroll portion 10, and a discharge pipe 11 (see FIGS. 2 and 3). In addition, an inverter, an inverter housing, and the like may be provided outside the motor housing 3.

The motor housing 3 includes an outer housing 31 that is cylindrical and open at one end, an inner housing 32 housed in the outer housing 31, and a lid portion 35 that closes the open end portion of the outer housing 31. The inner housing 32 includes a bearing support portion 17 that supports a bearing 20A, and the lid portion 35 includes a bearing support portion 18 that supports a bearing 20B.

The rotary shaft 12 is rotatably supported by the bearings 20A and 20B. The rotation axis X of the rotary shaft 12 can be described as the rotation axis X of the compressor impeller 8. The rotor portion 13 is attached to a center portion of the rotary shaft 12. The stator portion 14 is disposed around the rotary shaft 12, and is fixed to an inner surface of the inner housing 32 to surround the rotor portion 13. When an alternating current is applied to a coil of the stator portion 14 through a conductor, the rotary shaft 12 and the compressor impeller 8 rotate integrally with each other due to interactions of the rotor portion 13 and the stator portion 14. When the compressor impeller 8 rotates, the compressor impeller 8 sucks in outside air through the suction pipe 9, compresses the air through the scroll portion 10, and discharges it through the discharge pipe 11. The compressed air discharged from the discharge pipe 11 is supplied to the above-described internal combustion engine.

As shown in FIGS. 2 and 4, the scroll portion 10 includes a flow path wall 21 that forms a scroll flow path F1 around the compressor impeller 8. In the example illustrated in FIG. 2, the scroll flow path F1 surrounds more than half of the circumference of the compressor impeller 8. The scroll flow path F1 may surround the entire circumference of the compressor impeller 8. The inside of the discharge pipe 11 is a discharge flow path F2 communicating with (e.g., fluidly coupled with) the scroll flow path F1. The discharge flow path F2 is connected to an inlet Fa (upstream end portion) and an outlet Fb (downstream end portion) of the scroll flow path F1. The discharge pipe 11 extends linearly from the outlet Fb of the scroll flow path F1 and includes a linear pipe axis Xa. For example, the pipe axis Xa is a straight line extending from the outlet Fb of the scroll flow path F1 in a tangential direction of the scroll flow path F1. The discharge pipe 11 may be shaped to extend linearly from the outlet Fb of the scroll flow path F1 and then curve in the middle. In the case of a curved discharge pipe 11, the pipe axis Xa is also curved in the middle.

The scroll flow path F1 is a flow path that forms a generally spiral shape from the inlet Fa to the outlet Fb, and its flow path cross-sectional area gradually increases from the inlet Fa to the outlet Fb. The flow path wall 21 includes an outer peripheral wall portion 22 disposed on an outer side of the scroll flow path F1 in a radial direction D1, and an inner peripheral wall portion 23 disposed on an inner side of the scroll flow path F1 in the radial direction D1. Also, the inner peripheral wall portion 23 is a wall portion closer to the rotary shaft 12 than the outer peripheral wall portion 22 in the radial direction D1. In a flow direction D2 of the scroll flow path F1, a wall thickness Ta of the outer peripheral wall portion 22 is substantially constant, and a wall thickness Tb of the inner peripheral wall portion 23 is substantially constant. The flow direction D2 may be a circumferential direction of the compressor impeller 8.

In FIG. 2, the flow direction D2 of the scroll flow path F1 is a clockwise direction. The inlet Fa of the scroll flow path F1 is an upstream end portion in the flow direction D2, and the outlet Fb is a downstream end portion. The inlet Fa is provided with a tongue portion 6a.

For example, when the flow direction D2 is assumed to be a rotation direction centered about the rotation axis X, a straight line connecting the rotation axis X to the tongue portion 6a is an inlet intersection line L1, for example. Also, a straight line that is orthogonal to a center line of the discharge flow path F2 and intersects the rotation axis X is an outlet intersection line L2. In this case, in the scroll flow path F1, a portion that intersects the inlet intersection line L1 is the inlet Fa, and a portion that intersects the outlet intersection line L2 is the outlet Fb.

Also, when the inlet intersection line L1 is assumed to be disposed at 0° in the rotation direction, a rotation angle of the inlet intersection line L1 is 0°. For example, a straight line that indicates a position rotated 300°in the rotation direction from the inlet intersection line L1 is the outlet intersection line L2. In this case, in the scroll flow path F1, a portion that intersects the inlet intersection line L1 is the inlet Fa, and a portion that intersects the outlet intersection line L2 is the outlet Fb.

For example, the scroll flow path F1 includes an inlet region FB including the inlet Fa, an outlet region FC including the outlet Fb, and a flow path region FA between the inlet region FB and the outlet region FC. For example, the inlet region FB can be defined as a region from the inlet Fa to a position rotated 30° (rotation angle of 30°) in the rotation direction. The flow path region FA can be defined as a region from a position rotated 30° in the rotation direction to a position rotated 210° (rotation angle of 210°). The outlet region FC can be defined as a region from a position rotated 210° in the rotation direction to the outlet Fb. Also, the above description of the rotation angles is an example, and the inlet region FB, the outlet region FC, and the flow path region FA can be defined by different rotation angles depending on a shape and dimensions of the scroll flow path F1. For example, the inlet region FB can be defined as a region from the inlet Fa to a position rotated by a rotation angle of 20°, the flow path region FA can be defined as a region from a position rotated 30° in the rotation direction to a position rotated by a rotation angle of 200°, and the outlet region FC can be defined as a region from a position rotated 200° in the rotation direction to the outlet Fb.

Also, the inlet region FB, the outlet region FC, and the flow path region FA can be described on the basis of a reference plane Bs including the rotation axis X. For example, a plane that includes the rotation axis X and is parallel to the pipe axis Xa is assumed to be the reference plane Bs. The pipe axis Xa for assuming the reference plane Bs is a portion extending linearly from the outlet Fb of the scroll flow path F1, and is a portion that can be identified by ignoring the curved portion if it is curved in the middle. A region from the inlet Fa to the reference plane Bs is the inlet region FB. In addition, a region from the outlet Fb to the reference plane Bs is the outlet region FC. A region disposed on a side opposite to the discharge pipe 11 with respect to the reference plane Bs is the flow path region FA.

For example, FIG. 5 shows a cross-sectional view of the compressor housing 6 taken along the reference plane Bs. In the cross-section of the scroll flow path F1 shown in FIG. 5, two flow path portions, that is, a flow path portion on the inlet Fa side upstream in the flow direction D2, and a flow path portion on the outlet Fb side downstream in the flow direction D2, are shown. The flow path wall 21 includes a first flow path wall portion 21a that forms the flow path portion on the inlet Fa side and a second flow path wall portion 21b that forms the flow path portion on the outlet Fb side. The flow path region FA of the scroll flow path F1 (see FIG. 2) is a region from the first flow path wall portion 21a to the second flow path wall portion 21b.

As shown in FIG. 2, the outer peripheral wall portion 22 includes a thickened portion 22a having a wall thickness Ta thicker than the inner peripheral wall portion 23. The thickened portion 22a is disposed at least on a side opposite to the discharge pipe 11 with respect to the rotary shaft 12. The thickened portion 22a is provided, for example, in the flow path region FA. The thickened portion 22a is a portion having the wall thickness Ta greater than a wall thickness Tb of a portion (e.g., thin portion 23a) of the inner peripheral wall portion 23 disposed opposite thereto in the radial direction D1 (see FIG. 6). Also, in the example shown in FIG. 2, the thickened portion 22a is formed in the entire region along the scroll flow path F1.

For example, in the flow path region FA, the wall thickness Ta of the outer peripheral wall portion 22 is constant in the flow direction D2, and the wall thickness Tb of the inner peripheral wall portion 23 is constant in the flow direction D2. That is, the wall thickness Ta of the outer peripheral wall portion 22 of the flow path region FA is greater than the wall thickness Tb of the inner peripheral wall portion 23 over the entire flow direction.

For example, a ratio of the thickness of the thickened portion 22a provided over the entire flow path region FA to the thickness of the inner peripheral wall portion 23 opposing the thickened portion 22a in the radial direction D1 is constant. A ratio of the wall thickness Ta of the thickened portion 22a to the wall thickness Tb of the inner peripheral wall portion 23 can be, for example, 1. 1 times or more and 3 times or less. Also, the ratio of the wall thickness Ta to the wall thickness Tb can be 1. 3 times or more and 2 times or less.

For example, the wall thickness Ta of the outer peripheral wall portion 22 may not be constant in the flow direction D2, but may be provided to partially vary. Also, the wall thickness Tb of the inner peripheral wall portion 23 may not be constant in the flow direction D2, but may be provided to partially vary. In such an example, when the wall thickness Ta of a portion (target portion) of the outer peripheral wall portion 22 is greater than the wall thickness Tb of a portion of the inner peripheral wall portion 23 opposed in the radial direction D1, the target portion of the outer peripheral wall portion 22 is the thickened portion 22a. In addition, in such an example, when a wall thickness of any part (arbitrary part) of the outer peripheral wall portion 22 is greater than a wall thickness of a part of the inner peripheral wall portion 23 opposed in the radial direction D1, the outer peripheral wall portion 22 includes the thickened portion 22a over the entire flow path region FA.

As shown in FIGS. 5 and 6, the flow path wall 21 includes a connecting wall portion 24 that connects the outer peripheral wall portion 22 to the inner peripheral wall portion 23. The connecting wall portion 24 is disposed to face a diffuser plate 51. The connecting wall portion 24 includes a transition portion (e.g., thickness change portion 24a) whose thickness continuously changes from the thickened portion 22a of the outer peripheral wall portion 22 to the inner peripheral wall portion 23. For example, the thickness change portion 24a is provided so that its wall thickness gradually decreases from the thickened portion 22a to the inner peripheral wall portion 23. For example, the thickness change portion 24a is thickest at an outer portion connected to the thickened portion 22a, and thinnest at an inner portion connected to the inner peripheral wall portion 23. For example, the outer portion 24b (e.g., thick-walled portion) of the thickness change portion 24a connected to the thickened portion 22a is greater than a wall thickness Tc (thickness) of the diffuser plate 51, and the inner portion 24c (e.g., thin-walled portion) connected to the inner peripheral wall portion 23 is thinner than the wall thickness Tc (thickness) of the diffuser plate 51.

The thickened portion 22a is provided, for example, over the entire flow path region FA in the flow direction D2. The thickness change portion 24a is provided, for example, over the entire flow path region FA in the flow direction D2 to correspond to the thickened portion 22a. Also, the thickness change portion 24a may be provided partially or in a plurality of portions in the flow direction D2.

The diffuser plate 51 that forms a diffuser flow path F3 is fixed to the compressor housing 6. The diffuser plate 51 forms the diffuser flow path F3 between itself and the compressor housing 6. An impeller housing portion F4 that houses the compressor impeller 8, and the scroll flow path F1 are formed in the compressor housing 6. The diffuser flow path F3 is provided to allow communication between the impeller housing portion F4 and the scroll flow path F1. For example, the wall thickness Tc of the diffuser plate 51 is constant. Also, the wall thickness Tc of the diffuser plate 51 does not have to be constant.

For example, the wall thickness Ta of the thickened portion 22a of the outer peripheral wall portion 22 is greater than the wall thickness Tc of the diffuser plate 51. Additional information on the meaning of “the wall thickness Ta is greater than the wall thickness Tc” will be described. When the wall thickness Ta of the thickened portion 22a and the wall thickness Tc of the diffuser plate 51 are constant, it means that the wall thickness Ta of the thickened portion 22a is greater than the wall thickness Tc of the diffuser plate 51 in the entire region of the thickened portion 22a. When the wall thickness Ta of the thickened portion 22a and the wall thickness Tc of the diffuser plate 51 are not constant, for example, it means that, when a portion of the thickened portion 22a in which the wall thickness Ta is thickest is compared with a portion of the diffuser plate 51 in which the wall thickness Tc is thickest, the wall thickness Ta of the thickened portion 22a is greater than the wall thickness Tc of the diffuser plate 51.

For example, the wall thickness Tc of the diffuser plate 51 is greater than the wall thickness Tb of the inner peripheral wall portion 23. When the wall thickness Tc of the diffuser plate 51 and the wall thickness Tb of the inner peripheral wall portion 23 are constant, it means that the wall thickness Tc of the diffuser plate 51 is greater over the entire region than the wall thickness Tb of the inner peripheral wall portion 23. When the wall thickness Tc of the diffuser plate 51 and the wall thickness Tb of the inner peripheral wall portion 23 are not constant, for example, it means that, when a portion of the diffuser plate 51 in which the wall thickness Tc is thickest is compared with a portion of the inner peripheral wall portion 23 in which the wall thickness Tb is thinnest, the wall thickness Tc of the diffuser plate 51 is greater than the wall thickness Tb of the inner peripheral wall portion 23.

Next, operations and effects of the centrifugal compressor 1 illustrated in FIG. 2 will be described. The outer peripheral wall portion 22 disposed on an outer side of the rotary shaft 12 in the radial direction D1 is susceptible to an external effect or operational anomaly of the compressor impeller 8. Conversely, the effect on the inner peripheral wall portion 23 disposed on an inner side thereof in the radial direction D1 is limited as compared to the outer peripheral wall portion 22. The centrifugal compressor 1 includes the thickened portion 22a in the outer peripheral wall portion 22, and thus the outer peripheral wall portion 22 can be given additional strength to maintain the structural integrity of the containment property of the compressor impeller 8. On the other hand, a sufficient flow path cross-sectional area for the scroll flow path F1 may be achieved by adjusting the wall thickness Tb of the inner peripheral wall portion 23, which is thinner than the thickened portion 22a, which can contribute to a smaller size than when the thickness of the inner peripheral wall portion 23 is uniform. As a result, according to the centrifugal compressor 1, it may maintain the containment property in the scroll flow path F1 and to secure the sufficient flow path cross-sectional area for the scroll flow path F1.

For example, the flow path wall 21 includes the connecting wall portion 24 that connects the outer peripheral wall portion 22 to the inner peripheral wall portion 23. The connecting wall portion 24 includes, for example, the thickness change portion 24a whose thickness changes continuously from the thickened portion 22a to the inner peripheral wall portion 23. The susceptibility of the connecting wall portion 24 to an external effect gradually decreases from the thickened portion 22a to the inner peripheral wall portion 23. By providing the thickness change portion 24a whose thickness changes continuously from the thickened portion 22a to the inner peripheral wall portion 23, the wall thickness may be set with consideration for the magnitude of the effect.

For example, the centrifugal compressor 1 includes the discharge pipe 11, and the thickened portion 22a is disposed on the side opposite to the discharge pipe 11 with respect to the rotary shaft 12. As a result, the containment property of a portion far from the discharge flow path F2 with respect to the rotary shaft 12 can be maintained in the scroll flow path F1.

For example, the first flow path wall portion 21a disposed upstream in the flow direction D2 of the scroll flow path F1, and the second flow path wall portion 21b disposed downstream in the flow direction D2 are provided. The thickened portion 22a is disposed in the flow path region FA from the first flow path wall portion 21a to the second flow path wall portion 21b in the flow direction D2 of the scroll flow path F1. The flow path region FA from the first flow path wall portion 21a to the second flow path wall portion 21b may be configured to avoid a loss of structural integrity. For example, by providing the thickened portion 22a in the flow path region FA, the containment property can be maintained in at least a portion of the flow path region FA.

For example, the thickened portion 22a can be provided over the entire flow path region FA. As a result, the containment property can be maintained over the entire flow path region FA.

For example, the ratio of the thickness of the thickened portion 22a provided over the entire flow path region FA and the thickness of the inner peripheral wall portion 23 opposing the thickened portion 22a in the radial direction D1 can be constant. The containment property can be maintained to substantially the same degree over the entire flow path region FA.

For example, the thickness of the diffuser plate 51 is thinner than the thickness of the thickened portion 22a. By making the diffuser plate 51 thinner than the thickness of the thickened portion 22a, the size of the centrifugal compressor can be reduced while maintaining the containment property.

The centrifugal compressor is not limited to each of the above examples, and various other modifications are described herein. For example, each of the above examples may be combined with each other. The thickened portion can be provided over the entire scroll flow path. Also, the thickened portion can be provided in a portion or a plurality of locations of the flow path region of the scroll flow path. In addition, the thickened portion can be provided in a location deviating from the flow path region of the scroll flow path, for example, in an inlet region or an outlet region.

It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail.

Some additional examples are disclosed as follows, with continued reference to the drawings for convenience of description.

An example centrifugal compressor (1) includes: a rotary shaft (12); a compressor impeller (8) fixed to the rotary shaft (12); and a flow path wall (21) forming a scroll flow path (F1) around the compressor impeller (8). The flow path wall (21) includes: an outer peripheral wall (22) located on an outer side of the scroll flow path in a radial direction of the rotary shaft (12); and an inner peripheral wall (23) located on an inner side of the scroll flow path closer to the rotary shaft (12) than the outer peripheral wall (22) in the radial direction (D1). The outer peripheral wall (22) includes a thickened portion (22a) having a wall thickness greater than a wall thickness of a portion (23a) of the inner peripheral wall (23) that is opposite the thickened portion (22a) in the radial direction (D1).

In some examples, the flow path wall (21) may include a connecting wall portion (24) connecting the outer peripheral wall (22) to the inner peripheral wall (23). The connecting wall portion (24) may include a transition portion (24a) whose thickness changes continuously from the thickened portion (22a) to the inner peripheral wall (23).

In some examples, the centrifugal compressor (1) may include a discharge pipe (11) forming a discharge flow path (F2) fluidly coupled with the scroll flow path (F1). The thickened portion (22a) may be located opposite to the discharge pipe (11) with respect to the rotary shaft (12).

In some examples, the centrifugal compressor (1) may include a discharge pipe (11) forming a discharge flow path (F2) fluidly coupled with the scroll flow path (F1) and having a pipe axis (Xa) extending in a tangential direction of the scroll flow path (F1). The flow path wall (21) may include, in a cross-section along a plane that includes a rotation axis (X) of the compressor impeller (8) and is parallel to the pipe axis (Xa), a first flow path wall portion (21a) located upstream in a flow direction of the scroll flow path (F1), and a second flow path wall portion (21b) located downstream in the flow direction. The thickened portion (22a) may be located in a flow path region (FA) from the first flow path wall portion (21a) to the second flow path wall portion (21b) in the flow direction of the scroll flow path (F1).

In some examples, the thickened portion (22a) may be provided over the entire flow path region (FA).

In some examples, a ratio of the wall thickness of the thickened portion (22a) to the wall thickness of the inner peripheral wall (23) opposing the thickened portion (22a) in the radial direction (D1) in the flow path region (FA) may be constant.

In some examples, the centrifugal compressor may include a compressor housing (6) that houses the compressor impeller (8) and includes the flow path wall (21); and a diffuser plate (51) fixed to the compressor housing (6) to form a diffuser flow path. A thickness of the diffuser plate (51) may be thinner than the wall thickness of the thickened portion (22a).

In some examples, the thickness of the diffuser plate (51) may be greater than the wall thickness of the portion (23a) of the inner peripheral wall (23).

In some examples, the centrifugal compressor (1) may include a compressor housing (6) that houses the compressor impeller (8) and includes the flow path wall (21); and a diffuser plate (51) fixed to the compressor housing (6) to form a diffuser flow path (F3). The flow path wall (21) may connect the outer peripheral wall (22) to the inner peripheral wall (23) and may include a connecting wall portion (24) located to face the diffuser plate (51).

In some examples, the connecting wall portion (24) may include a thin-walled portion (24b) thinner than the diffuser plate (51).

In some examples, the centrifugal compressor (1) may include a compressor housing (6) that houses the compressor impeller (8). The compressor housing (6) may include a scroll portion including the flow path wall (21), and a discharge pipe (11) connected to the scroll portion (10) to form a discharge flow path (F2) communicating with the scroll flow path (F1). The outer peripheral wall (22) includes the thickened portion (22a) over an entire region along the scroll flow path (F1).

In some examples, the scroll flow path (F1) may surround more than half of a circumference of the compressor impeller (8).

Additionally, an example centrifugal compressor (1) includes a compressor impeller (8); a scroll flow path (F1) located around the compressor impeller (8); an outer peripheral wall (22) facing the scroll flow path (F1); and an inner peripheral wall (23) facing the scroll flow path (F1) and located between the compressor impeller (8) and the outer peripheral wall (22). The outer peripheral wall (22) includes a thickened portion (22a) facing a portion (23a) of the inner peripheral wall (23) in a radial direction of the compressor impeller (8). The thickened portion (23) has a wall thickness greater than a wall thickness of the portion (23a) of the inner peripheral wall (23).

In some examples, the outer peripheral wall (22) may extend along the scroll flow path (F1). The inner peripheral wall (23) extends along the scroll flow path (F1). A wall thickness of the outer peripheral wall (22) is greater than a wall thickness of the inner peripheral wall (23) in an entire region along the scroll flow path (F1).

In some examples, a ratio of the wall thickness of the outer peripheral wall (22) to the wall thickness of the inner peripheral wall (23) in the entire region along the scroll flow path (F1) may be constant.

In some examples, the centrifugal compressor (1) may include a connecting wall (24) connecting the thickened portion (22a) and the portion (23a) of the inner peripheral wall (23). The connecting wall (24) may include a transition portion (24a) whose thickness changes continuously from the thickened portion (22a) to the portion (23a) of the inner peripheral wall (23).

Next, an example centrifugal compressor (1) include a compressor impeller (8); a scroll flow path (F1) located around the compressor impeller (8); an outer peripheral wall (22) facing the scroll flow path (F1); an inner peripheral wall (23) facing the scroll flow path (F1) and located between the compressor impeller (8) and the outer peripheral wall (22); and a connecting wall (24) connecting the outer peripheral wall (22) and the inner peripheral wall (23), the connecting wall (24) including a transition portion (24a) whose thickness changes continuously from the outer peripheral wall (22) to the inner peripheral wall (23).

In some examples, the scroll flow path (F1) may partially surround a circumference of the compressor impeller (8).

In some examples, a wall thickness of the outer peripheral wall (22) may be greater than a wall thickness of the inner peripheral wall (23).

In some examples, a ratio of a thickness of the outer peripheral wall to a thickness of the inner peripheral wall opposing the outer peripheral wall in a radial direction (D1) of the compressor impeller (8) in the flow path region (FA) may be constant.