Casing of centrifugal compressor, centrifugal compressor, and turbocharger

Abstract

To provide a casing of a centrifugal compressor which can inhibit pressure loss of a compressed gas flowing through a scroll passage of the centrifugal compressor, and to provide the centrifugal compressor including the casing and a turbocharger.SOLUTION: A casing of a centrifugal compressor includes a scroll part that forms a scroll flow path in which its spiral start and its spiral end merge. The scroll part includes: an outer-side wall surface that defines a radially outer side of the scroll flow path; and an inner-side wall surface that defines a radially inner side of the scroll flow path. The outer-side wall surface has, in an axially orthogonal cross-section, on the spiral start side of the scroll flow path: an outer-side concave arc section formed in a concave arc form that is recessed toward the radially outer side; an outer-side convex arc section formed in a convex arc form that protrudes toward the radially inner side on an upstream side of the scroll flow path relative to the outer-side concave arc section, and on the radially outer side; and an outer-side inflection point provided at a position where the outer-side concave arc section and the outer-side convex arc section are connected.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a casing of a centrifugal compressor, a centrifugal compressor including the casing, and a turbocharger.

Background Art

[0002] A turbocharger includes, for example, a centrifugal compressor provided on one end side of a rotating shaft and a turbine provided on the other end side of the rotating shaft. The energy of the exhaust gas sent from the engine rotates the turbine rotor, and the impeller of the centrifugal compressor that rotates together with the turbine rotor compresses the gas and supplies it to the engine. A scroll flow path for guiding the gas compressed by the impeller is formed in the casing of the centrifugal compressor (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, assuming the flow of gas flowing in the rotation direction of the impeller as shown in the invention described in Patent Document 1, the flow path shape of the scroll flow path has been widely determined so that the gradient of the acceleration and deceleration of this gas flow becomes appropriate.

[0005] When an unsteady pressure change such as a pressure pulsation occurs in a device arranged on the downstream side of the scroll flow path such as an engine, the gas in the scroll flow path is not limited to the flow toward the rotation direction of the impeller, and a reverse flow flowing in the direction opposite to the rotation direction of the impeller may occur. For this reason, in the prior art, it may not be possible to suppress the pressure loss generated in the gas flowing through the scroll flow path due to the above reverse flow.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a casing of a centrifugal compressor, a centrifugal compressor including the casing, and a turbocharger that can suppress the pressure loss of the compressed gas flowing through the scroll flow path of the centrifugal compressor.

Means for Solving the Problems

[0007] The casing of the centrifugal compressor according to at least one embodiment of the present disclosure is a casing of a centrifugal compressor configured to accommodate an impeller, a scroll portion that forms a scroll flow path through which the compressed gas that has passed through the impeller flows along the circumferential direction of the impeller, and the start and end of the scroll flow path merge, The scroll portion includes an outer wall surface that defines the outside in the radial direction of the scroll flow path, and an inner wall surface that defines the inside in the radial direction of the scroll flow path. The outer wall surface, in a cross-section orthogonal to the axial direction, has an outer concave arc portion formed in a concave arc shape that is concave toward the outside in the radial direction, an outer convex arc portion formed upstream of the scroll flow path with respect to the outer concave arc portion, and the outer convex arc portion is formed in a convex arc shape that protrudes toward the inside in the radial direction on the outside in the radial direction with respect to the outer concave arc portion, and an outer inflection point provided at the connection position between the outer concave arc portion and the outer convex arc portion, on the start side of the scroll flow path.

[0008] The centrifugal compressor according to at least one embodiment of the present disclosure includes the casing of the centrifugal compressor, and the impeller rotatably accommodated in the casing of the centrifugal compressor.

[0009] The turbocharger according to at least one embodiment of the present disclosure includes the centrifugal compressor.

Advantages of the Invention

[0010] According to at least one embodiment of the present disclosure, there are provided a casing of a centrifugal compressor capable of suppressing pressure loss of compressed gas flowing through a scroll flow path of the centrifugal compressor, a centrifugal compressor including the casing, and a turbocharger.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0012] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples.

[0013] In the following embodiments, the centrifugal compressor of the present disclosure will be described as being provided in a turbocharger. However, the centrifugal compressor of the present disclosure may be an electric centrifugal compressor or the like. Further, the gas to be compressed by the centrifugal compressor of the present disclosure need not be limited to air. That is, the centrifugal compressor of the present disclosure only needs to be capable of compressing and delivering a gas, and may be constituted by a centrifugal compressor alone or in combination with a mechanism or device other than a turbine. Further, it is not necessary to limit its use or the like.

[0014] (Centrifugal compressor, turbocharger) FIG. 1 is a schematic view of an internal combustion engine system 11 including a turbocharger 10 according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view along the axis LA of the turbocharger 10 according to an embodiment of the present disclosure. As shown in FIGS. 1 and 2, the centrifugal compressor 1 according to some embodiments includes an impeller 2 and a casing 3 configured to rotatably accommodate the impeller 2. The centrifugal compressor 1 according to the present disclosure can be mounted on, for example, an automotive, marine or industrial (e.g., for onshore power generation) turbocharger (supercharger) 10.

[0015] As shown in FIGS. 1 and 2, the turbocharger 10 includes a centrifugal compressor 1 and a turbine 12 configured to drive the centrifugal compressor 1. The turbine 12 includes a turbine rotor 14 that rotates by the energy of the exhaust gas discharged from the internal combustion engine 13 (engine, see FIG. 1) and a turbine housing 15 configured to rotatably accommodate the turbine rotor 14.

[0016] The turbocharger 10 further includes a rotating shaft 16 to which the impeller 2 is connected at one end side and the turbine rotor 14 is connected at the other end side, and a bearing 17 that rotatably supports the rotating shaft 16 between the impeller 2 and the turbine rotor 14. The turbocharger 10 may further include a bearing housing 18 disposed between the casing 3 and the turbine housing 15 and configured to accommodate the rotating shaft 16 and the bearing 17.

[0017] The turbine 12 (turbocharger 10) is configured to rotate the turbine rotor 14 by the energy of the exhaust gas discharged from the internal combustion engine 13. Since the impeller 2 is coaxially connected to the turbine rotor 14 via the rotating shaft 16, the impeller 2 rotates about the axis LA together with the turbine rotor 14 and the rotating shaft 16. The centrifugal compressor 1 (turbocharger 10) is configured to suck air (gas) into the casing 3, compress the air, and send the compressed air to the internal combustion engine 13 as the impeller 2 rotates about the axis LA.

[0018] The compressed air sent from the centrifugal compressor 1 to the internal combustion engine 13 is used for combustion in the internal combustion engine 13. The exhaust gas generated by the combustion in the internal combustion engine 13 is sent from the internal combustion engine 13 to the turbine 12 and rotates the turbine rotor 14.

[0019] Hereinafter, the direction in which the axis LA of the impeller 2 extends is defined as the axial direction of the impeller 2, the direction orthogonal to the axis LA is defined as the radial direction of the impeller 2, and the circumferential direction around the axis LA is defined as the circumferential direction of the impeller 2. Hereinafter, the axial direction, the radial direction, and the circumferential direction of the impeller 2 may be simply abbreviated as the axial direction, the radial direction, and the circumferential direction.

[0020] (Turbine rotor) As shown in FIG. 2, the turbine rotor 14 includes a hub 141 having a substantially truncated conical shape and a plurality of turbine blades 142 provided on the outer peripheral surface of the hub 141. The hub 141 and the plurality of turbine blades 142 are provided so as to be rotatable integrally with the rotating shaft 16 about the axis LA. The turbine rotor 14 is configured to guide the exhaust gas introduced from the outside in the radial direction of the turbine rotor 14 along the axial direction of the turbine rotor 14 to the front side of the turbine rotor 14.

[0021] (Turbine housing) Inside the turbine housing 15, a turbine scroll flow path 151 for guiding the exhaust gas discharged from the internal combustion engine 13 to the turbine rotor 14 and an exhaust gas discharge flow path 152 for discharging the exhaust gas that has passed through the turbine rotor 14 to the outside of the turbine housing 15 are formed. The turbine scroll flow path 151 is provided on the outer peripheral side of the turbine rotor 14 and is composed of a spiral flow path extending along the circumferential direction of the turbine rotor 14. The exhaust gas discharge flow path 152 extends along the axial direction of the turbine rotor 14.

[0022] The exhaust gas discharged from the internal combustion engine 13 is guided to the turbine rotor 14 through the turbine scroll flow path 151, and rotates the turbine rotor 14. The exhaust gas that has passed through the turbine rotor 14 is discharged to the outside of the turbine housing 15 through the exhaust gas discharge flow path 152.

[0023] (Impeller) As shown in FIG. 2, the impeller 2 includes a hub 21 having a substantially frustoconical shape and a plurality of impeller blades 23 provided on the outer peripheral surface 22 of the hub 21. Each of the plurality of impeller blades 23 is arranged at intervals in the circumferential direction around the axis LA. Since the hub 21 is fixed to one end side of the rotating shaft 16, the hub 21 and the plurality of impeller blades 23 are provided so as to be rotatable integrally with the rotating shaft 16 about the axis LA of the impeller 2. The impeller 2 is configured to guide the air introduced along the axial direction of the impeller 2 to the outside in the radial direction of the impeller 2. As shown in FIG. 3, a clearance is formed between the tip side ends (tips) 24 of the plurality of impeller blades 23 and a shroud surface 31 that curves convexly so as to face the tip side ends 24. That is, the impeller 2 is an open type impeller that does not include an annular member that covers the tip side ends 24.

[0024] (Casing) As shown in FIG. 2, the casing 3 includes a scroll portion 4 that forms a scroll flow path 40. The scroll flow path 40 is provided on the outer peripheral side of the impeller 2 along the circumferential direction of the impeller 2. The scroll flow path 40 is configured such that the compressed gas that has passed through the impeller 2 flows therethrough. The scroll flow path 40 is a spiral flow path that extends along the circumferential direction of the impeller 2. The casing 3 has the above-described shroud surface 31. Inside the casing 3, a gas introduction flow path 32, a diffuser flow path 33, and the above-described scroll flow path 40 are formed.

[0025] The gas introduction flow path 32 is a flow path for taking in air from the outside of the casing 3 and guiding the taken-in air (gas) to the impeller 2. The gas introduction flow path 32 is provided on one side (front side) in the axial direction of the impeller 2 rather than the impeller 2 and extends along the axial direction of the impeller 2. By rotating the impeller 2, air is taken into the gas introduction flow path 32 from the outside of the casing 3, and the taken-in air flows toward the other side (rear side) in the axial direction of the impeller 2 through the gas introduction flow path 32 and is guided to the impeller 2.

[0026] The diffuser flow path 33 is a flow path for guiding the air that has passed through the impeller 2 and been compressed by the impeller 2 to the scroll flow path 40. The diffuser flow path 33 is provided between the scroll flow path 40 and the impeller 2 in the radial direction of the impeller 2 and extends along the radial direction of the impeller 2. The diffuser flow path 33 communicates with the scroll flow path 40 at an outlet (communication port) 34 provided at its downstream end (outer peripheral end). The compressed air (compressed gas) compressed by the impeller 2 flows into the diffuser flow path 33, flows through the diffuser flow path 33 toward the outside in the radial direction of the impeller 2, and is guided to the scroll flow path 40.

[0027] FIG. 3 is a schematic perspective view of the scroll portion 4 in an embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view orthogonal to the axial direction of the centrifugal compressor 01 according to the comparative example. FIG. 5 is a schematic cross-sectional view orthogonal to the axial direction in the vicinity of the confluence portion 403 of the scroll flow path 40 of the centrifugal compressor 1 according to an embodiment of the present disclosure. As shown in FIGS. 3 to 5, the scroll flow path 40 is configured such that the start 401 and the end 402 of the scroll flow path 40 merge. In other words, the scroll flow path 40 has a confluence portion 403 of the start 401 and the end 402. The scroll flow path 40 extends along the rotation direction of the impeller 2 (the clockwise direction in FIGS. 4 and 5, one side in the circumferential direction) from the start 401 to the end 402. Hereinafter, the connection position with the confluence portion 403 of the start 401 is defined as the upstream end, the upstream side in the rotation direction of the impeller 2 is defined as the upstream side of the scroll flow path 40, and the downstream side in the rotation direction of the impeller 2 is defined as the downstream side of the scroll flow path 40.

[0028] In FIG. 3, a cross-section CS1 orthogonal to the axial direction of the impeller 2 of the scroll flow path 40, a cross-section CS2 along the axial direction of the impeller 2 of the start 401 of the scroll flow path 40 (a cross-section orthogonal to the circumferential direction), and a cross-section CS3 along the axial direction of the impeller 2 of the end 402 of the scroll flow path 40 (a cross-section orthogonal to the circumferential direction) are shown.

[0029] As shown in FIGS. 3 to 5, scroll portion 4 includes an outer wall surface 5 that defines the outside in the radial direction of scroll flow path 40 and an inner wall surface 6 that defines the inside in the radial direction of scroll flow path 40 in a cross section orthogonal to the axial direction of impeller 2. The outer wall surface 5 includes a first outer wall surface 5A that defines the outside in the radial direction of the start of winding 401 and a second outer wall surface 5B that defines the outside in the radial direction of the end of winding 402. The inner wall surface 6 includes a first inner wall surface 6A that defines the inside in the radial direction of the start of winding 401 and a second inner wall surface 6B that defines the inside in the radial direction of the end of winding 402. As shown in FIG. 3, the upstream end of the first outer wall surface 5A is connected to the second inner wall surface 6B.

[0030] When an unsteady pressure change such as a pressure pulsation generated in a device arranged on the downstream side of scroll flow path 40 (downstream side of end of winding 402) such as an engine (internal combustion engine 13) occurs, as shown in FIGS. 4 and 5, the gas in scroll flow path 40 is not limited to the flow toward the rotation direction of impeller 2, and a reverse flow flowing in the direction opposite to the rotation direction of impeller 2 may occur. As shown in FIGS. 4 and 5, the flow flowing backward through scroll flow path 40, that is, the flow flowing through scroll flow path 40 in the direction opposite to the rotation direction of impeller 2 (counterclockwise direction) is designated as FA, and the flow flowing forward through scroll flow path 40, that is, the flow flowing through scroll flow path 40 in the rotation direction of impeller 2 is designated as FB. These flows FA and FB may exist in scroll flow path 40 simultaneously. The above-mentioned flow FA tends to occur on the start of winding 401 side of scroll flow path 40.

[0031] In the casing 3 of the centrifugal compressor 1 according to some embodiments, as shown in FIG. 5, the above-mentioned outer wall surface 5 has an outer concave arc portion 51, an outer convex arc portion 52, and an outer inflection point 53 on the start of winding 401 side of scroll flow path 40 in a cross section orthogonal to the axial direction. In the illustrated embodiment, the above-mentioned first outer wall surface 5A has an outer concave arc portion 51, an outer convex arc portion 52, and an outer inflection point 53.

[0032] (Outer concave arc portion) The outer concave arc portion 51 is formed in a concave arc shape that is concave toward the outside in the radial direction in a cross section as shown in FIG. 5. In the embodiment shown in FIG. 5, the outer concave arc portion 51 is formed in a concave arc shape having a predetermined curvature and a curvature radius R1. In some embodiments, the outer concave arc portion 51 may be composed of a plurality of curves with different curvatures (curvature radii) such as a semi-elliptical shape.

[0033] (Outer convex arc portion) The outer convex arc portion 52 is formed on the upstream side of the scroll flow path 40 with respect to the outer concave arc portion 51 in a cross section as shown in FIG. 5. The outer convex arc portion 52 is formed in a convex arc shape that protrudes toward the inside in the radial direction on the outside in the radial direction with respect to the outer concave arc portion 51. In the embodiment shown in FIG. 5, the outer convex arc portion 52 is formed in a concave arc shape having a predetermined curvature and a curvature radius R2. In some embodiments, the outer convex arc portion 52 may be composed of a plurality of curves with different curvatures (curvature radii) such as a semi-elliptical shape.

[0034] In the illustrated embodiment, the upstream end 50 of the outer convex arc portion 52 is connected to the second inner wall surface 6B, and the downstream end of the outer convex arc portion 52 is connected to the upstream end of the outer concave arc portion 51. The outer convex arc portion 52 has an increasing distance from the scroll center CS in the scroll flow path 40 from the downstream end toward the upstream end. In the embodiment shown in FIG. 5, the scroll center CS is present on the axis LA.

[0035] (Outer inflection point) The outer inflection point 53 is an inflection point provided at the connection position between the outer concave arc portion 51 and the outer convex arc portion 52. Specifically, the outer inflection point 53 is provided at the connection position between the upstream end of the outer concave arc portion 51 and the downstream end of the outer convex arc portion 52.

[0036] The centrifugal compressor 01 according to the comparative example is different from the centrifugal compressor 1 shown in FIG. 5 in that the outer wall surface 5 described above does not have the outer convex arc portion 52 and the outer inflection point 53 as shown in FIG. 4.

[0037] FIG. 6 is an explanatory diagram for explaining the flow of the compressed gas in the vicinity of the confluence portion 403 of the scroll flow path 40 of the centrifugal compressor 01 shown in FIG. 4. FIG. 7 is an explanatory diagram for explaining the flow of the compressed gas in the vicinity of the confluence portion 403 of the scroll flow path 40 of the centrifugal compressor 1 shown in FIG. 5. As shown in FIG. 6, in the scroll flow path 40 of the centrifugal compressor 01, the flow FA that reverses at the start 401 of the scroll flow path 40 and passes through the confluence portion 403 has a relatively large curvature in the portion including the confluence portion 403. The flow FA is bent more than the flow FB that flows downstream through the scroll flow path 40 after passing through the confluence portion 403. As a result, the frictional loss generated between the flow FA and the flow FB becomes the pressure loss of the gas flowing through the scroll flow path 40.

[0038] Since the outer wall surface 5 of the centrifugal compressor 1 shown in FIG. 5 has an outer convex arc portion 52 on the start 401 side of the scroll flow path 40, the flow path cross-sectional area of the scroll flow path 40 (start 401) facing the outer convex arc portion 52 can be enlarged, and the flow rate of the flow FA flowing upstream through the scroll flow path 40 passing through the confluence portion 403 of the scroll flow path 40 can be increased. By enlarging the flow path cross-sectional area of the scroll flow path 40 (start 401) facing the outer convex arc portion 52, the flow FA passing through the confluence portion 403 can be decelerated. Further, the radius of curvature RF1 (see FIG. 5) of the portion including the confluence portion 403 of the flow FA of the centrifugal compressor 1 shown in FIG. 5 is larger than the radius of curvature RF2 (see FIG. 4) of the portion including the confluence portion 403 of the flow FA of the centrifugal compressor 01 according to the comparative example. In other words, in the centrifugal compressor 1 shown in FIG. 5, the curvature of the portion including the confluence portion 403 of the flow FA is smaller than that of the centrifugal compressor 01 according to the comparative example. As a result, the flow FA passing through the confluence portion 403 can be decelerated and the curvature can be made relatively small, so that the frictional loss between the flow FB flowing downstream through the scroll flow path 40 and the flow FA is suppressed.

[0039] FIG. 8 is an explanatory diagram for explaining the efficiency reduction in the scroll portion 4 of the centrifugal compressor 1 according to an embodiment of the present disclosure. A graph is shown with the horizontal axis representing time T and the vertical axis representing the ratio DE occupied by the vicinity of the confluence portion 403 in the efficiency reduction of the scroll portion 4. The period from time T0 to time T1 is the same period as one cycle of the internal combustion engine 13. In FIG. 8, the centrifugal compressor 01 according to the comparative example shown in FIG. 4 is indicated by a solid line, and the centrifugal compressor 1 according to the present embodiment shown in FIG. 5 is indicated by a dotted line. As shown in FIG. 8, in the centrifugal compressor 01 and the centrifugal compressor 1, the ratio DE becomes maximum during the period when the reverse flow FA occurs. The centrifugal compressor 1 has a smaller ratio DE than the centrifugal compressor 01. The centrifugal compressor 1 can reduce the pressure loss of the gas flowing through the scroll flow path 40 more than the conventional examples described in the comparative example and Patent Document 1.

[0040] According to the above configuration, since the outer wall surface 5 has the outer convex arc portion 52 on the starting side 401 of the scroll flow path 40, the flow path cross-sectional area of the scroll flow path 40 facing the outer convex arc portion 52 can be enlarged, and the flow rate of the flow FA flowing backward through the scroll flow path 40 passing through the confluence portion 403 of the scroll flow path 40 can be increased. Thereby, the flow FA passing through the confluence portion 403 can be decelerated and the curvature can be made relatively small, so that the frictional loss between the flow FB flowing forward through the scroll flow path 40 and the above flow FA is suppressed, and the pressure loss of the gas flowing through the scroll flow path 40 can be reduced more than before.

[0041] (Angular position) In the following embodiments, for example, in a cross section orthogonal to the axial direction as shown in FIG. 5, regarding the (circumferential) angular position θ around the scroll center CS in the above-described scroll flow path 40, the confluence portion 403 of the starting end 401 and the ending end 402 of the scroll flow path 40 is set to 0 degrees, and the angular position θ is defined so that the angle gradually increases from the confluence portion 403 toward the downstream side of the scroll flow path 40. Specifically, the connection position between the upstream end of the first outer wall surface 5A and the second inner wall surface 6B, which forms the outer peripheral end of the confluence portion 403, is set to 0 degrees.

[0042] In the centrifugal compressor 1 according to some embodiments, in the cross section as shown in FIG. 5, the above-described outer inflection point 53 is provided within the range where the above-described angular position θ ranges from 0 degrees to 30 degrees. The outer inflection point 53 is preferably provided within the range where the angular position θ ranges from 10 degrees to 30 degrees.

[0043] The inventors have found that due to the pressure pulsation generated in the device disposed downstream of the scroll flow path 40 such as the engine (internal combustion engine 13), a reverse flow FA occurs in the scroll flow path 40 from the angular position θ of 0 degrees to around 30 degrees.

[0044] According to the above configuration, by providing the outer inflection point 53, that is, the downstream end of the outer convex arc portion 52, within the range where the angular position θ ranges from 0 degrees to 30 degrees, the cross-sectional area of the scroll flow path 40 through which the reverse flow FA in the scroll flow path 40 passes can be enlarged, and the pressure loss of the compressed gas flowing through the scroll flow path 40 can be appropriately suppressed. Although the outer inflection point 53 may be provided in a range where the angular position θ exceeds 30 degrees, in this case, since the volume of the scroll flow path 40 is excessively enlarged, it is not preferable from the viewpoint of mountability on the engine (internal combustion engine 13).

[0045] In the centrifugal compressor 1 according to some embodiments, in the cross section as shown in FIG. 5, the radius of curvature R2 of the above-described outer convex arc portion 52 is smaller than the radius of curvature R1 of the outer concave arc portion 51 (R2 < R1). In this case, compared with the case where the radius of curvature R2 of the outer convex arc portion 52 is larger than the radius of curvature R1 of the outer concave arc portion 51 (R2 > R1), the bend of the outer convex arc portion 52 becomes steeper, and the cross-sectional area of the scroll flow path 40 facing the outer convex arc portion 52 can be enlarged. Thereby, the pressure loss of the compressed gas flowing through the scroll flow path 40 can be appropriately suppressed. In some embodiments, the radius of curvature R2 of the outer convex arc portion 52 may be made larger than the radius of curvature R1 of the outer concave arc portion 51.

[0046] Each of FIGS. 9 and 10 is a schematic cross-sectional view orthogonal to the axial direction in the vicinity of the confluence portion 403 of the scroll flow path 40 of the centrifugal compressor 1 according to an embodiment of the present disclosure. In the casing 3 of the centrifugal compressor 1 according to some embodiments, as shown in FIGS. 9 and 10, the inner wall surface 6 described above has an inner convex arc portion 61, an inner concave arc portion 62, and an inner inflection point 63 on the starting side 401 of the scroll of the scroll flow path 40 in a cross-section orthogonal to the axial direction. In the illustrated embodiment, the first inner wall surface 6A described above has an inner convex arc portion 61, an inner concave arc portion 62, and an inner inflection point 63.

[0047] (Inner convex arc portion) The inner convex arc portion 61 is formed in a convex arc shape that bulges outward in the radial direction in a cross-section orthogonal to the axial direction as shown in FIGS. 9 and 10. In the embodiment shown in FIGS. 9 and 10, the inner convex arc portion 61 is formed in a convex arc shape having a predetermined curvature and a radius of curvature R3. In some embodiments, the inner convex arc portion 61 may be composed of a plurality of curves with different curvatures (radii of curvature) such as a semi-elliptical shape.

[0048] (Inner concave arc portion) The inner concave arc portion 62 is formed upstream of the inner convex arc portion 61 in the scroll flow path 40 in a cross-section as shown in FIGS. 9 and 10. The inner concave arc portion 62 is formed in a concave arc shape that is concave inward in the radial direction on the inner side in the radial direction than the inner convex arc portion 61. In the embodiment shown in FIGS. 9 and 10, the inner concave arc portion 62 is formed in a concave arc shape having a predetermined curvature and a radius of curvature R4. In some embodiments, the inner concave arc portion 62 may be composed of a plurality of curves with different curvatures (radii of curvature) such as a semi-elliptical shape.

[0049] In the illustrated embodiment, the upstream end of the inner concave arc portion 62 is connected to the second inner wall surface 6B, and the downstream end of the inner concave arc portion 62 is connected to the upstream end of the inner convex arc portion 61. The inner concave arc portion 62 may be configured such that the distance from the scroll center CS in the scroll flow path 40 decreases as it goes from the downstream end to the upstream end. In the embodiment shown in FIGS. 9 and 10, the scroll center CS is present on the axis LA.

[0050] (Inner inflection point) The inner inflection point 63 is an inflection point provided at the connection position between the inner convex arc portion 61 and the inner concave arc portion 62. Specifically, the inner inflection point 63 is provided at the connection position between the upstream end of the inner convex arc portion 61 and the downstream end of the inner concave arc portion 62.

[0051] According to the above configuration, since the inner wall surface 6 has the inner concave arc portion 62 on the start-of-winding 401 side of the scroll flow path 40, the flow path cross-sectional area of the scroll flow path 40 facing the inner concave arc portion 62 can be enlarged, and the flow rate of the flow FA flowing backward through the scroll flow path 40 passing through the confluence portion 403 of the scroll flow path 40 can be increased. By enlarging the flow path cross-sectional area of the scroll flow path 40 (start-of-winding 401) facing the inner concave arc portion 62, the flow FA passing through the confluence portion 403 can be decelerated. Thereby, since the flow FA passing through the confluence portion 403 can be decelerated, the frictional loss between the flow FB flowing forward through the scroll flow path 40 and the above flow FA is suppressed, and the pressure loss of the gas flowing through the scroll flow path 40 can be reduced compared to the conventional case.

[0052] In the casing 3 of the centrifugal compressor 1 according to some embodiments, as shown in FIG. 9, the inner wall surface 6 described above has, in a cross section orthogonal to the axial direction, the inner convex arc portion 61, the inner concave arc portion 62, and the inner inflection point 63 described above on the start side 401 of the scroll flow path 40. The outer wall surface 5 described above does not have the outer convex arc portion 52 and the outer inflection point 53 described above in a cross section orthogonal to the axial direction. According to the above configuration, considering the law of conservation of angular momentum, the effect of decelerating the flow FA is small compared to the embodiment shown in FIG. 5. However, in the casing 3 of the centrifugal compressor 1 according to the present embodiment, since the outer wall surface 5 does not have the outer convex arc portion 52, the mountability to the engine (internal combustion engine 13) is not deteriorated.

[0053] In the casing 3 of the centrifugal compressor 1 according to some embodiments, as shown in FIG. 9, the inner wall surface 6 described above has, in a cross section orthogonal to the axial direction, the inner convex arc portion 61, the inner concave arc portion 62, and the inner inflection point 63 described above on the start side 401 of the scroll flow path 40. The outer wall surface 5 described above has, in a cross section orthogonal to the axial direction, the outer concave arc portion 51, the outer convex arc portion 52, and the outer inflection point 53 described above on the start side 401 of the scroll flow path 40. In the illustrated embodiment, the inner inflection point 63 is arranged on the upstream side of the scroll flow path 40 (the side where the angular position θ is closer to 0 degrees) than the outer inflection point 53. Note that the inner inflection point 63 may be arranged on the downstream side of the scroll flow path 40 than the outer inflection point 53.

[0054] In the centrifugal compressor 1 according to some embodiments, in a cross section as shown in FIGS. 9 and 10, the inner inflection point 63 described above is provided within the range where the angular position θ described above ranges from 0 degrees to 30 degrees. The inner inflection point 63 is preferably provided within the range where the angular position θ ranges from 10 degrees to 30 degrees.

[0055] The inventors have found that, due to the pressure pulsation generated in equipment arranged on the downstream side of the scroll flow path 40 such as an engine (internal combustion engine 13), a reverse flow FA occurs in the scroll flow path 40 from an angular position θ of 0 degrees to around 30 degrees.

[0056] According to the above configuration, by providing the inner inflection point 63, that is, the downstream end of the inner concave arc portion 62, within a range where the angular position θ extends from 0 degrees to 30 degrees, the cross-sectional area of the scroll flow path 40 through which the reverse flow FA in the scroll flow path 40 passes can be enlarged, and the pressure loss of the compressed gas flowing through the scroll flow path 40 can be appropriately suppressed. Note that the inner inflection point 63 may be provided in a range where the angular position θ exceeds 30 degrees. However, in this case, since the volume of the scroll flow path 40 is excessively enlarged, the forward flow FB in the scroll flow path 40 may be difficult to flow, which is not preferable.

[0057] In the centrifugal compressor 1 according to some embodiments, in the cross-section as shown in FIGS. 9 and 10, the radius of curvature R4 of the inner concave arc portion 62 described above is smaller than the radius of curvature R3 of the inner convex arc portion 61 (R4 < R3). In this case, compared with the case where the radius of curvature R4 of the inner concave arc portion 62 is larger than the radius of curvature R3 of the inner convex arc portion 61 (R4 > R3), the bend of the inner concave arc portion 62 becomes more acute, and the cross-sectional area of the scroll flow path 40 facing the inner concave arc portion 62 can be enlarged. Thereby, the pressure loss of the compressed gas flowing through the scroll flow path 40 can be appropriately suppressed. Note that in some embodiments, the radius of curvature R4 of the inner concave arc portion 62 may be made larger than the radius of curvature R3 of the inner convex arc portion 61.

[0058] The centrifugal compressor 1 according to some embodiments includes, as shown in FIG. 2, the above-described casing 3 and the above-described impeller 2 rotatably accommodated in the casing 3. The turbocharger 10 according to some embodiments includes, as shown in FIG. 1, the above-described centrifugal compressor 1. According to the above configuration, by reducing the pressure loss of the gas flowing through the scroll flow path 40, the efficiency of the centrifugal compressor 1 and the turbocharger 10 including the centrifugal compressor 1 can be improved.

[0059] In this specification, expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states where there are tolerances or relative displacements with angles or distances that can achieve the same function. For example, expressions indicating that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent states where there are tolerances or differences that can achieve the same function. Also, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent shapes such as a rectangular shape or a cylindrical shape in a strictly geometric sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. Also, in this specification, the expressions "comprising", "including", or "having" a component do not exclude the existence of other components.

[0060] The present disclosure is not limited to the above-described embodiments, and also includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0061] The content described in some of the above-described embodiments can be understood as follows, for example.

[0062] 1) The casing (3) of the centrifugal compressor (1) according to at least one embodiment of the present disclosure is a casing (3) of a centrifugal compressor (1) configured to accommodate an impeller (2), a scroll flow path (40) through which compressed gas passing through the impeller (2) flows along the circumferential direction of the impeller (2), and includes a scroll portion (4) forming a scroll flow path (40) where the start (401) and the end (402) of the scroll flow path (40) merge, the scroll portion (4) is an outer wall surface (5) defining the outer side in the radial direction of the scroll flow path (40), and including an inner wall surface (6) that defines the inner side in the radial direction of the scroll flow path (40); in a cross section orthogonal to the axial direction, the outer wall surface (5) has an outer concave arc portion (51) formed in a concave arc shape that is recessed toward the outer side in the radial direction, and an outer convex arc portion (52) formed on the upstream side of the scroll flow path (40) with respect to the outer concave arc portion (51), the outer convex arc portion (52) being formed in a convex arc shape that protrudes toward the inner side in the radial direction on the outer side in the radial direction with respect to the outer concave arc portion (51); and has an outer inflection point (53) provided at the connection position between the outer concave arc portion (51) and the outer convex arc portion (52) on the start side (401) of the scroll of the scroll flow path (40).

[0063] According to the configuration of 1) above, since the outer wall surface (5) has the outer convex arc portion (52) on the start side (401) of the scroll of the scroll flow path (40), the flow path cross-sectional area of the scroll flow path (40) facing the outer convex arc portion (52) can be enlarged, and the flow rate of the flow (FA) flowing backward through the scroll flow path (40) passing through the confluence portion (403) of the scroll flow path (40) can be increased. Thereby, the flow (FA) passing through the confluence portion (403) can be decelerated and the curvature can be made relatively small, so that the frictional loss between the flow (FB) flowing forward through the scroll flow path (40) and the flow (FA) is suppressed, and the pressure loss of the gas flowing through the scroll flow path (40) can be reduced more than before.

[0064] 2) In some embodiments, there is provided a casing (3) of the centrifugal compressor (1) described in 1) above, for the angular position (θ) around the scroll center (CS) in the scroll flow path (40), when the confluence portion (403) of the start (401) and the end (402) of the scroll of the scroll flow path (40) is defined as 0 degrees, and the angular position (θ) is defined so that the angle gradually increases toward the downstream side of the scroll flow path (40) from the confluence portion (403), The outer inflection point (53) is provided within a range where the angular position (θ) extends from 0 degrees to 30 degrees.

[0065] The inventors have found that due to the pressure pulsation generated in a device arranged on the downstream side of a scroll flow path such as an engine, a flow (FA) flowing backward through the scroll flow path (40) occurs when the angular position (θ) is from 0 degrees to around 30 degrees. According to the configuration of 2) above, by providing the outer inflection point (53), that is, the downstream end of the outer convex arc portion (52), within a range where the angular position (θ) extends from 0 degrees to 30 degrees, the cross-sectional area of the scroll flow path (40) through which the flow (FA) flowing backward through the scroll flow path (40) passes can be enlarged, and the pressure loss of the compressed gas flowing through the scroll flow path (40) can be appropriately suppressed. Although the outer inflection point (53) may be provided in a range where the angular position (θ) exceeds 30 degrees, in this case, since the volume of the scroll flow path (40) is excessively enlarged, it is not preferable from the viewpoint of mountability on the engine.

[0066] 3) In some embodiments, it is the casing (3) of the centrifugal compressor (1) described in 1) or 2) above, The radius of curvature (R2) of the outer convex arc portion (52) is smaller than the radius of curvature (R1) of the outer concave arc portion (51).

[0067] According to the configuration of 3) above, compared with the case where the radius of curvature (R2) of the outer convex arc portion (52) is larger than the radius of curvature (R1) of the outer concave arc portion (51) (R2 > R1), the bend of the outer convex arc portion (52) becomes steeper, and the cross-sectional area of the scroll flow path (40) facing the outer convex arc portion (52) can be enlarged. Thereby, the pressure loss of the compressed gas flowing through the scroll flow path (40) can be appropriately suppressed.

[0068] 4) In some embodiments, it is the casing (3) of the centrifugal compressor (1) described in any one of 1) to 3) above, The inner wall surface (6) is, in a cross-section orthogonal to the axial direction, An inner convex arc portion (61) formed in a convex arc shape that bulges outward in the radial direction, and An inner concave arc portion (62) formed on the upstream side of the scroll flow path (40) with respect to the inner convex arc portion (61), the inner concave arc portion (62) being formed in a concave arc shape that is recessed toward the inner side in the radial direction inside the inner convex arc portion (61) in the radial direction. An inner inflection point (63) provided at the connection position between the inner convex arc portion (61) and the inner concave arc portion (62), which is on the start (401) side of the scroll flow path (40).

[0069] According to the configuration of 4) above, since the inner wall surface (6) has the inner concave arc portion (62) on the start (401) side of the scroll flow path (40), the flow path cross-sectional area of the scroll flow path (40) facing the inner concave arc portion (62) can be enlarged, and the flow rate of the flow (FA) flowing backward through the scroll flow path (40) passing through the confluence portion (403) of the scroll flow path (40) can be increased. Thereby, the flow (FA) passing through the confluence portion (403) can be decelerated and the curvature can be made relatively small, so that the frictional loss between the flow (FB) flowing in the forward direction through the scroll flow path (40) and the above flow (FA) is suppressed, and the pressure loss of the gas flowing through the scroll flow path (40) can be reduced more than before.

[0070] 5) In some embodiments, it is the casing (3) of the centrifugal compressor (1) described in 4) above, Regarding the angular position (θ) around the scroll center (CS) in the scroll flow path (40), when the confluence portion (403) of the start (401) and the end (402) of the scroll flow path (40) is set to 0 degrees, and the angular position (θ) is defined so that the angle gradually increases toward the downstream side of the scroll flow path (40) from the confluence portion (403), The inner inflection point (63) is provided within the range where the angular position (θ) ranges from 0 degrees to 30 degrees.

[0071] According to the configuration of 5) above, by providing the inner inflection point (63), that is, the downstream end of the inner concave arc portion (62) within a range where the angular position (θ) extends from 0 degrees to 30 degrees, the cross-sectional area of the scroll flow path (40) through which the flow (FA) flowing backward in the scroll flow path (40) passes can be increased, and the pressure loss of the compressed gas flowing through the scroll flow path (40) can be appropriately suppressed. Although the inner inflection point (63) may be provided in a range where the angular position (θ) exceeds 30 degrees, in this case, since the volume of the scroll flow path (40) expands excessively, it is not suitable from the viewpoint of mountability on the engine.

[0072] 6) In some embodiments, it is the casing (3) of the centrifugal compressor (1) described in 4) or 5) above, The radius of curvature (R4) of the inner concave arc portion (62) is smaller than the radius of curvature (R3) of the inner convex arc portion (61).

[0073] According to the configuration of 6) above, compared with the case where the radius of curvature (R4) of the inner concave arc portion (62) is larger than the radius of curvature (R3) of the inner convex arc portion (61) (R4 > R3), the bend of the inner concave arc portion (62) becomes more abrupt, and the flow path cross-sectional area of the scroll flow path (40) facing the inner concave arc portion (62) can be increased. Thereby, the pressure loss of the compressed gas flowing through the scroll flow path (40) can be appropriately suppressed.

[0074] 7) The casing (3) of the centrifugal compressor (1) according to at least one embodiment of the present disclosure is A casing (3) of a centrifugal compressor (1) configured to be able to accommodate an impeller (2), A scroll flow path (40) through which the compressed gas passing through the impeller (2) along the circumferential direction of the impeller (2) flows, and a scroll portion (4) forming a scroll flow path (40) in which the start (401) and the end (402) of the scroll flow path (40) merge, The scroll portion (4) is An outer wall surface (5) defining the outer side in the radial direction of the scroll flow path (40), including an inner wall surface (6) that defines the inner side in the radial direction of the scroll flow path (40); in a cross section orthogonal to the axial direction, the inner wall surface (6) has an inner convex arc portion (61) formed in a convex arc shape that bulges toward the outer side in the radial direction, and an inner concave arc portion (62) formed on the upstream side of the scroll flow path (40) with respect to the inner convex arc portion (61), the inner concave arc portion (62) being formed in a concave arc shape that is concave toward the inner side in the radial direction on the inner side in the radial direction with respect to the inner convex arc portion (61); and has an inner inflection point (63) provided at the connection position between the inner convex arc portion (61) and the inner concave arc portion (62) on the start side (401) of the scroll of the scroll flow path (40).

[0075] According to the configuration of 7) above, since the inner wall surface (6) has the inner concave arc portion (62) on the start side (401) of the scroll of the scroll flow path (40), the flow path cross-sectional area of the scroll flow path (40) facing the inner concave arc portion (62) can be enlarged, and the flow rate of the flow (FA) flowing backward through the scroll flow path (40) passing through the confluence portion (403) of the scroll flow path (40) can be increased. As a result, the flow (FA) passing through the confluence portion (403) can be decelerated, so that the frictional loss between the flow (FB) flowing forward through the scroll flow path (40) and the flow (FA) is suppressed, and the pressure loss of the gas flowing through the scroll flow path (40) can be reduced more than before.

[0076] 8) In some embodiments, the casing (3) of the centrifugal compressor (1) described in 7) above, for the angular position (θ) around the scroll center (CS) in the scroll flow path (40), when the confluence portion (403) of the start (401) and the end (402) of the scroll of the scroll flow path (40) is defined as 0 degrees and the angular position (θ) is defined so as to gradually increase toward the downstream side of the scroll flow path (40) from the confluence portion (403), the inner inflection point (63) is provided within a range where the angular position (θ) ranges from 0 degrees to 30 degrees.

[0077] According to the configuration of 8) above, by providing the inner inflection point (63), that is, the downstream end of the inner concave arc portion (62) within the range where the angular position (θ) is from 0 degree to 30 degrees, the cross-sectional area of the scroll flow path (40) through which the flow (FA) flowing backward in the scroll flow path (40) passes can be enlarged, and the pressure loss of the compressed gas flowing through the scroll flow path (40) can be appropriately suppressed. When the inner inflection point (63) is provided in a range where the angular position (θ) exceeds 30 degrees, since the volume of the scroll flow path (40) expands excessively, there is a possibility that the flow (FB) flowing forward in the scroll flow path (40) becomes difficult to flow.

[0078] 9) In some embodiments, it is the casing (3) of the centrifugal compressor (1) described in 7) or 8) above, The radius of curvature (R4) of the inner concave arc portion (62) is smaller than the radius of curvature (R3) of the inner convex arc portion (61).

[0079] According to the configuration of 9) above, compared with the case where the radius of curvature (R4) of the inner concave arc portion (62) is larger than the radius of curvature (R3) of the inner convex arc portion (61) (R4 > R3), the bend of the inner concave arc portion (62) becomes more acute, and the flow path cross-sectional area of the scroll flow path (40) facing the inner concave arc portion (62) can be enlarged. Thereby, the pressure loss of the compressed gas flowing through the scroll flow path (40) can be appropriately suppressed.

[0080] 10) The centrifugal compressor (1) according to at least one embodiment of the present disclosure is the casing (3) of the centrifugal compressor (1) described in any one of 1) to 9) above, and the impeller (2) rotatably accommodated in the casing (3) of the centrifugal compressor (1).

[0081] According to the configuration of 10) above, by reducing the pressure loss of the gas flowing through the scroll flow path (40), the efficiency of the centrifugal compressor (1) can be improved.

[0082] 11) The turbocharger (10) according to at least one embodiment of the present disclosure is It is provided with the centrifugal compressor (1) described in the above item 10).

[0083] According to the configuration of the above item 11), by reducing the pressure loss of the gas flowing through the scroll flow path (40), the efficiency of the turbocharger (10) can be improved.

Explanation of Signs

[0084] 1 Centrifugal compressor 2 Impeller 3 Casing 4 Scroll part 5 Outer wall surface 5A First outer wall surface 5B Second outer wall surface 6 Inner wall surface 6A First inner wall surface 6B Second inner wall surface 10 Turbocharger 11 Internal combustion engine system 12 Turbine 13 Internal combustion engine 14 Turbine rotor 15 Turbine housing 16 Rotating shaft 17 Bearing 18 Bearing housing 31 Shroud surface 32 Gas introduction flow path 33 Diffuser flow path 40 Scroll flow path 50 Upstream end 51 Outer concave arc part 52 Outer convex arc part 53 Outer inflection point 61 Inner convex arc part 62 Inner concave arc part 63 Inner inflection point 401 Start of winding 402 End of winding 403 Confluence part CS Scroll center CS1, CS2, CS3 Cross-section LA Axis Radius of curvature of R1, R2, R3, R4 Time of T, T0, T1

Claims

1. A casing of a centrifugal compressor configured to accommodate an impeller, comprising a scroll passage through which compressed gas passing through the impeller flows along the circumferential direction of the impeller, the scroll passage forming a scroll portion where the start and end of the scroll passage merge, the scroll portion including an outer wall surface defining an outer side in the radial direction of the scroll passage, and an inner wall surface defining an inner side in the radial direction of the scroll passage, the outer wall surface having an outer concave arc portion formed in a concave arc shape recessed toward the outer side in the radial direction in a cross section orthogonal to the axial direction, an outer convex arc portion formed upstream of the outer concave arc portion in the scroll passage, the outer convex arc portion being formed in a convex arc shape convex toward the inner side in the radial direction on the outer side in the radial direction than the outer concave arc portion, and an outer inflection point provided at a connection position between the outer concave arc portion and the outer convex arc portion, on the start side of the scroll passage, the casing of the centrifugal compressor.

2. Regarding the angular position around the scroll center in the scroll passage, when the merging portion of the start and end of the scroll passage is defined as 0 degrees and the angular position is defined so that the angle gradually increases toward the downstream side of the scroll passage from the merging portion, the outer inflection point is provided within a range where the angular position ranges from 0 degrees to 30 degrees, the casing of the centrifugal compressor according to Claim 1.

3. The radius of curvature of the outer convex arc portion is smaller than the radius of curvature of the outer concave arc portion, the casing of the centrifugal compressor according to Claim 1 or 2.

4. The inner wall surface has an inner convex arc portion formed in a convex arc shape convex toward the outer side in the radial direction in a cross section orthogonal to the axial direction, an inner concave arc portion formed upstream of the inner convex arc portion in the scroll passage, the inner concave arc portion being formed in a concave arc shape recessed toward the inner side in the radial direction on the inner side in the radial direction than the inner convex arc portion, and an inner inflection point provided at a connection position between the inner convex arc portion and the inner concave arc portion, on the start side of the scroll passage, the casing of the centrifugal compressor according to Claim 1 or 2.

5. Regarding the angular position around the scroll center in the scroll flow path, when the confluence of the start and end of the scroll flow path is defined as 0 degrees and the angular position is defined such that the angle gradually increases toward the downstream side of the scroll flow path from the confluence, the inner inflection point is provided within a range where the angular position ranges from 0 degrees to 30 degrees. The casing of the centrifugal compressor according to claim 4.

6. The radius of curvature of the inner concave arc portion is smaller than the radius of curvature of the inner convex arc portion. The casing of the centrifugal compressor according to claim 4.

7. A casing of a centrifugal compressor configured to accommodate an impeller, comprising a scroll portion that forms a scroll flow path through which the compressed gas that has passed through the impeller flows along the circumferential direction of the impeller, and the start and end of the scroll flow path merge. The scroll portion includes an outer wall surface that defines the outer side in the radial direction of the scroll flow path, and an inner wall surface that defines the inner side in the radial direction of the scroll flow path. The inner wall surface, in a cross-section orthogonal to the axial direction, has an inner convex arc portion formed in a convex arc shape that protrudes toward the outer side in the radial direction, and an inner concave arc portion formed upstream of the inner convex arc portion in the scroll flow path, and is formed in a concave arc shape that concaves toward the inner side in the radial direction on the inner side in the radial direction rather than the inner convex arc portion. and has an inner inflection point provided at the connection position between the inner convex arc portion and the inner concave arc portion on the start side of the scroll flow path. The casing of the centrifugal compressor.

8. Regarding the angular position around the scroll center in the scroll flow path, when the confluence of the start and end of the scroll flow path is defined as 0 degrees and the angular position is defined such that the angle gradually increases toward the downstream side of the scroll flow path from the confluence, the inner inflection point is provided within a range where the angular position ranges from 0 degrees to 30 degrees. The casing of the centrifugal compressor according to claim 7.

9. The radius of curvature of the inner concave arc portion is smaller than the radius of curvature of the inner convex arc portion. The casing of the centrifugal compressor according to claim 7 or 8.

10. The casing of the centrifugal compressor according to any one of claims 1, 2, 7, or 8, and the impeller rotatably accommodated in the casing of the centrifugal compressor. Centrifugal compressor.

11. A turbocharger comprising the centrifugal compressor according to claim 10.

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