Centrifugal Compressors and Turbochargers

Abstract

To suppress a peeling region of a diffuser vane.SOLUTION: A centrifugal compressor comprises: a compressor housing; an annular diffuser flow path 23 formed in the compressor housing; a plurality of diffuser vanes 50 provided in the diffuser flow path 23, and arranged apart from each other in a circumferential direction of the diffuser flow path 23; and a vane flow path 61 that is formed between two adjacent diffuser vanes 50 separated in the circumferential direction, and in which an increase rate of a flow path cross-section area between the two diffuser vanes 50 is larger on a trailing edge 57 side than on a leading edge 55 side.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to centrifugal compressors and superchargers. [Background technology]

[0002] Patent Document 1 discloses a centrifugal compressor including a compressor housing and a compressor impeller. The compressor housing of Patent Document 1 is formed with a diffuser passage. A diffuser vane is provided in the diffuser passage. By providing the diffuser vane, the air flowing through the diffuser passage can be decelerated and the pressure can be increased. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-124715 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, in order to increase the deflection angle of the air flow in the diffuser vane, the negative pressure surface side of the diffuser vane is formed into a protruding shape.

[0005] However, as a result of investigations, the inventors of the present disclosure found that if the negative pressure surface side of the diffuser vane is shaped in a protruding shape, air becomes more likely to separate on the trailing edge side of the diffuser vane, and the separation area expands.

[0006] The present disclosure is based on the results of studies conducted by the above-mentioned inventors, and has an object to provide a centrifugal compressor and a turbocharger that are capable of suppressing separation regions of diffuser vanes. [Means for solving the problem]

[0007] In order to solve the above problems, a centrifugal compressor according to the present disclosure includes a housing, an annular diffuser passage formed in the housing, a plurality of diffuser vanes provided in the diffuser passage and spaced apart from each other in the circumferential direction of the diffuser passage, and a vane passage formed between two adjacent diffuser vanes spaced apart in the circumferential direction, in which an increase rate of a flow passage cross-sectional area between the two diffuser vanes is larger on the trailing edge side than on the leading edge side, and an outlet angle between a perpendicular line on an imaginary circle passing through the trailing edges of the plurality of diffuser vanes at the trailing edges and a flow direction of air flowing on the rear side of the trailing edge in the rotation direction of the impeller is smaller than an inflow angle between a perpendicular line on an imaginary circle passing through the leading edges of the plurality of diffuser vanes at the leading edges and a flow direction of air flowing on the rear side of the leading edge in the rotation direction of the impeller. Furthermore, the curvature of the leading edge side of the surface of the diffuser vane facing the front side in the impeller rotation direction is smaller than the curvature of the leading edge side of the surface of the diffuser vane facing the rear side in the impeller rotation direction. .

[0008] The diffuser vane may have a center line of its airfoil located aft of a straight line connecting the leading edge and the trailing edge in the rotational direction of the compressor impeller, and the trailing edge may have a circular or elliptical shape.

[0009] In order to solve the above problem, a turbocharger of the present disclosure includes the above centrifugal compressor. Effect of the Invention

[0010] According to the present disclosure, it is possible to suppress separation regions of the diffuser vane. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a turbocharger. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the diffuser vane of the present embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of the arrangement of a plurality of diffuser vanes provided in the diffuser flow passage. [Figure 4]FIG. 4 is a diagram for explaining the relationship between the diffuser vane and the separation region in the comparative example. [Diagram 5] FIG. 5 is a diagram for explaining the relationship between the diffuser vane and the separation region in this embodiment. [Figure 6] FIG. 6 is a diagram for explaining the width between two adjacent diffuser vanes. [Figure 7] FIG. 7 is a diagram for explaining the blade thickness of the diffuser vane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present disclosure will be described below with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiment are merely examples for ease of understanding, and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present disclosure are omitted from the drawings.

[0013] FIG. 1 is a schematic cross-sectional view of a turbocharger TC. In the following description, the direction of arrow L shown in FIG. 1 is the left side of the turbocharger TC. The direction of arrow R shown in FIG. 1 is the right side of the turbocharger TC. As shown in FIG. 1, the turbocharger TC includes a turbocharger body 1. The turbocharger body 1 includes a bearing housing 3, a turbine housing 5, and a compressor housing (housing) 7. The turbine housing 5 is connected to the left side of the bearing housing 3 by a fastening bolt 9. The compressor housing 7 is connected to the right side of the bearing housing 3 by a fastening bolt 11.

[0014] A bearing hole 3a is formed in the bearing housing 3. The bearing hole 3a penetrates the turbocharger TC in the left-right direction. The bearing hole 3a accommodates a part of the shaft 13. A bearing 15 is accommodated in the bearing hole 3a. In this embodiment, the bearing 15 is a full-floating bearing. However, the present invention is not limited to this, and the bearing 15 may be another bearing such as a semi-floating bearing or a rolling bearing. The shaft 13 is rotatably supported by the bearing 15. A turbine wheel 17 is provided at the left end of the shaft 13. The turbine wheel 17 is rotatably housed in the turbine housing 5. A compressor wheel 19 is provided at the right end of the shaft 13. The compressor wheel 19 is rotatably housed in the compressor housing 7.

[0015] An intake port 21 is formed in the compressor housing 7. The intake port 21 opens to the right side of the turbocharger TC. The intake port 21 is connected to an air cleaner (not shown). A diffuser passage 23 is formed by the opposing surfaces of the bearing housing 3 and the compressor housing 7. The diffuser passage 23 is located radially outside the compressor impeller 19. The diffuser passage 23 is formed in an annular shape. The diffuser passage 23 communicates with the intake port 21 via the compressor impeller 19 on the radially inner side. Air that flows in from the intake port 21 via the compressor impeller 19 flows through the diffuser passage 23. The diffuser passage 23 pressurizes the air.

[0016] In this embodiment, a diffuser vane 50 is provided in the diffuser passage 23. A plurality of diffuser vanes 50 are provided in the diffuser passage 23. The plurality of diffuser vanes 50 are arranged at equal intervals and spaced apart from one another in the circumferential direction of the diffuser passage 23. However, this is not limited thereto, and the plurality of diffuser vanes 50 may be arranged at unequal intervals in the circumferential direction of the diffuser passage 23. Details of the diffuser vanes 50 will be described later.

[0017] A compressor scroll passage 25 is formed in the compressor housing 7. The compressor scroll passage 25 is formed in an annular shape. The compressor scroll passage 25 is located, for example, radially outward of the shaft 13 than the diffuser passage 23. The compressor scroll passage 25 communicates with an intake port of an engine (not shown) and the diffuser passage 23. When the compressor impeller 19 rotates, air is sucked into the compressor housing 7 from the intake port 21. The sucked air is pressurized and accelerated in the process of flowing between the blades of the compressor impeller 19. The pressurized and accelerated air is pressurized in the diffuser passage 23 and the compressor scroll passage 25. The pressurized air is led to the intake port of the engine.

[0018] The centrifugal compressor CC is configured by the compressor housing 7 and the bearing housing 3. In this embodiment, an example in which the centrifugal compressor CC is mounted on a turbocharger TC will be described. However, the present invention is not limited to this, and the centrifugal compressor CC may be incorporated in a device other than the turbocharger TC, or may be a standalone unit.

[0019] A discharge port 27 is formed in the turbine housing 5. The discharge port 27 opens to the left side of the turbocharger TC. The discharge port 27 is connected to an exhaust gas purification device (not shown). A communication passage 29 and a turbine scroll passage 31 are formed in the turbine housing 5. The communication passage 29 is located radially outside the turbine wheel 17. The communication passage 29 is formed in an annular shape. The communication passage 29 communicates between the discharge port 27 and the turbine scroll passage 31 via the turbine wheel 17.

[0020] The turbine scroll passage 31 is located, for example, radially outward of the turbine wheel 17 with respect to the communicating passage 29. The turbine scroll passage 31 is formed in an annular shape. The turbine scroll passage 31 communicates with a gas inlet (not shown). Exhaust gas discharged from an exhaust manifold of an engine (not shown) is introduced to the gas inlet. The exhaust gas passes through the turbine scroll passage 31 and is introduced to the communicating passage 29. The exhaust gas is introduced to the discharge port 27 via the turbine wheel 17. The exhaust gas rotates the turbine wheel 17 while flowing through the turbine wheel 17.

[0021] The rotational force of the turbine wheel 17 is transmitted to the compressor wheel 19 via the shaft 13. When the compressor wheel 19 rotates, the air is pressurized as described above. In this manner, the air is guided to the intake port of the engine.

[0022] Fig. 2 is a schematic cross-sectional view of the diffuser vane 50 of this embodiment. As shown in Fig. 2, the diffuser vane 50 extends toward the front side in the rotation direction RD of the compressor impeller 19 as it moves radially outward. The diffuser vane 50 has a blade shape. The diffuser vane 50 has a pressure surface 51 and a suction surface 53. The pressure surface 51 is the surface of the diffuser vane 50 facing the rear side in the rotation direction RD. The suction surface 53 is the surface of the diffuser vane 50 facing the front side in the rotation direction RD.

[0023] A connecting end on the radially inner side between the pressure surface 51 and the suction surface 53 is a leading edge (front edge) 55 of the diffuser vane 50. A connecting end on the radially outer side between the pressure surface 51 and the suction surface 53 is a trailing edge (rear edge) 57 of the diffuser vane 50. The trailing edge 57 is located radially outward from the leading edge 55 and forward in the direction of rotation RD. The center line of the blade thickness (thickness) of the diffuser vane 50 is an airfoil center line (camber line) 59. The airfoil center line 59 protrudes rearward in the direction of rotation RD (toward the pressure surface 51) with respect to a straight line connecting the leading edge 55 and the trailing edge 57. The pressure surface 51 has a shape in which the center of curvature is located forward in the direction of rotation RD with respect to the pressure surface 51, and the curvature increases from the leading edge 55 to the trailing edge 57. The center of curvature of the suction surface 53 on the leading edge 55 side is located forward in the direction of rotation RD relative to the suction surface 53, and the center of curvature of the trailing edge 57 side is located rearward in the direction of rotation RD relative to the suction surface 53. In other words, the suction surface 53 has an inflection point. The suction surface 53 has a shape in which the curvature on the leading edge 55 side is smaller than the curvature of the leading edge 55 side of the pressure surface 51. In addition, the suction surface 53 has a shape in which the curvature on the trailing edge 57 side increases as it approaches the trailing edge 57.

[0024] The pressure surface 51 has a protruding portion 51a and an arc portion 51b. The protruding portion 51a is located on the leading edge 55 side with respect to the arc portion 51b. The protruding portion 51a is formed continuously from the leading edge 55 to the trailing edge 57 side. The protruding portion 51a has a curved shape. The arc portion 51b is formed continuously from the trailing edge 57 to the leading edge 55 side. In this embodiment, the arc portion 51b has an elliptical arc shape. However, this is not limited thereto, and the arc portion 51b may have an arc shape. The arc portion 51b is connected to the protruding portion 51a at a connection portion P1. The connection portion P1 is located on the pressure surface 51 at the position of the maximum blade thickness of the diffuser vane 50, or on the trailing edge 57 side of the position of the maximum blade thickness.

[0025] The region of the pressure surface 51 from the leading edge 55 to the connection portion P1 is the protruding region PR where the protruding portion 51a is formed. The protruding region PR (protruding portion 51a) protrudes rearward in the rotation direction RD with respect to a straight line connecting the leading edge 55 and the connection portion P1. The region of the pressure surface 51 from the trailing edge 57 to the connection portion P1 is the arc region AR where the arc region AR (arc portion 51b) protrudes rearward in the rotation direction RD with respect to a straight line connecting the trailing edge 57 and the connection portion P1. In this way, the diffuser vane 50 of this embodiment has a protruding shape protruding toward the pressure surface 51 side. Specifically, the diffuser vane 50 has a vane shape center line 59 located rearward in the rotation direction RD of the compressor impeller 19 with respect to a straight line connecting the leading edge 55 and the trailing edge 57.

[0026] The suction surface 53 has a recessed portion 53a and an arc portion 53b. The recessed portion 53a is located on the leading edge 55 side with respect to the arc portion 53b. The recessed portion 53a is formed continuously from the leading edge 55 to the trailing edge 57 side. The recessed portion 53a has a curved shape. The arc portion 53b is formed continuously from the trailing edge 57 to the leading edge 55 side. In this embodiment, the arc portion 53b has an elliptical arc shape. However, this is not limited thereto, and the arc portion 53b may have an arc shape. The arc portion 53b is continuous with the recessed portion 53a at a connection portion P2. The connection portion P2 is located on the suction surface 53 at the position of the maximum blade thickness of the diffuser vane 50, or on the trailing edge 57 side of the position of the maximum blade thickness.

[0027] The arc portion 53b is continuous with the arc portion 51b via the trailing edge 57. In this embodiment, the two arc portions 51b, 53b form a part of an ellipse, and have, for example, a semi-elliptical shape. However, without being limited thereto, the two arc portions 51b, 53b may form a part of a circle, and have, for example, a semi-circular shape. In this way, the arc portions 51b, 53b including the trailing edge 57 in this embodiment have an elliptical shape or a circular shape.

[0028] The region of the suction surface 53 from the leading edge 55 to the connection portion P2 is a recessed region CR where a recessed portion 53a is formed. The recessed region CR (recessed portion 53a) is recessed rearward in the direction of rotation RD with respect to a straight line connecting the leading edge 55 and the connection portion P2. The region of the suction surface 53 from the trailing edge 57 to the connection portion P2 is an arc region AR where an arc portion 53b is formed. The arc region AR (arc portion 53b) protrudes forward in the direction of rotation RD with respect to a straight line connecting the trailing edge 57 and the connection portion P2.

[0029] A circle centered on the rotation axis of the compressor impeller 19 and passing through the leading edge 55 of the diffuser vane 50 is a first imaginary circle VC1. A circle centered on the rotation axis of the compressor impeller 19 and passing through the trailing edge 57 of the diffuser vane 50 is a second imaginary circle VC2. The angle between a perpendicular line at the leading edge 55 (position where air flows in) on the first imaginary circle VC1 and the flow direction of air flowing on the pressure surface 51 side of the leading edge 55 is an inflow angle α1. The angle between a perpendicular line at a position on the second imaginary circle VC2 where the air flowing on the pressure surface 51 flows out and the flow direction of air flowing on the pressure surface 51 side of the trailing edge 57 is an outflow angle α2. Here, the difference between the inflow angle α1 and the outflow angle α2 is called a turning angle. In this embodiment, the outflow angle α2 is smaller than the inflow angle α1.

[0030] Fig. 3 is a diagram showing an example of the arrangement of the multiple diffuser vanes 50 provided in the diffuser flow passage 23. As shown in Fig. 3, the multiple diffuser vanes 50 are lined up in the rotation direction RD (circumferential direction) of the compressor impeller 19. Leading edges 55 of the multiple diffuser vanes 50 are located on a first imaginary circle VC1. Trailing edges 57 of the multiple diffuser vanes 50 are located on a second imaginary circle VC2.

[0031] The circumferential distance between two adjacent leading edges 55 is smaller than the circumferential distance between two adjacent trailing edges 57. In other words, the circumferential distance between two adjacent diffuser vanes 50 increases from the leading edge 55 toward the trailing edge 57. A vane flow passage 61 is formed between two adjacent diffuser vanes 50. The vane flow passage 61 is formed between the suction surface 53 and the pressure surface 51 of each of two adjacent diffuser vanes 50. The flow passage cross-sectional area of ​​the vane flow passage 61 gradually increases from the leading edge 55 toward the trailing edge 57.

[0032] The air that has flowed into the diffuser passage 23 flows through the vane passage 61. The air that flows through the vane passage 61 flows in at an inflow angle α1 on the leading edge 55 side of the diffuser vane 50, and flows out at an outflow angle α2 on the trailing edge 57 side. In the process of flowing through the vane passage 61, the flow direction of the air is changed from a direction along the rotation direction RD of the compressor impeller 19 to a direction approaching the radial direction of the compressor impeller 19. As a result, the air flowing through the diffuser passage 23 is efficiently decelerated, and the compressor efficiency is improved compared to a case in which the diffuser vane 50 is not provided. In addition, the diffuser vane 50 has a protruding portion 51a that protrudes rearward in the rotation direction RD on the pressure surface 51, thereby improving pressure (static pressure) recovery.

[0033] Fig. 4 is a diagram for explaining the relationship between the diffuser vane 50A and the separation region PeR in the comparative example. As shown in Fig. 4, the diffuser vane 50A in the comparative example has a pressure surface 51 and a negative pressure surface 53 that are generally planar. The pressure surface 51 of the diffuser vane 50A in the comparative example does not have the protruding portion 51a of the present embodiment. Moreover, the negative pressure surface 53 of the diffuser vane 50A does not have the recessed portion 53a of the present embodiment.

[0034] Flat portions PP are formed on the pressure surface 51 side and the suction surface 53 side near trailing edge 57 of diffuser vane 50A. The flat portion PP on the pressure surface 51 side has a plane that is bent forward in the direction of rotation RD relative to pressure surface 51. The flat portion PP on the suction surface 53 side has the same plane as suction surface 53. The arc portions 51b, 53b of this embodiment are not formed near trailing edge 57 of diffuser vane 50A of the comparative example.

[0035] The circumferential distance between the leading edges 55 of two adjacent diffuser vanes 50A is smaller than the circumferential distance between the trailing edges 57 of two adjacent diffuser vanes 50A. In other words, the circumferential distance between two adjacent diffuser vanes 50A increases from the leading edges 55 to the trailing edges 57.

[0036] The air passing between two adjacent diffuser vanes 50A moves along the rotation direction RD. Therefore, the air on the pressure surface 51 side of the air passing between two adjacent diffuser vanes 50A comes into contact with the pressure surface 51 and moves along the pressure surface 51. The air on the suction surface 53 side of the air passing between two adjacent diffuser vanes 50A comes into contact with the suction surface 53 near the leading edge 55 and moves along the suction surface 53. However, since the gap between two adjacent diffuser vanes 50A becomes larger from the leading edge 55 to the trailing edge 57 and the air moves toward the pressure surface 51, the air that was in contact with the suction surface 53 gradually separates from the suction surface 53. The region where the air separates from the suction surface 53 is the separation region PeR.

[0037] 5 is a diagram for explaining the relationship between the diffuser vane 50 and the separation region PeR in this embodiment. As shown in FIG. 5, a protrusion 51a is formed on the pressure surface 51 of the diffuser vane 50 in this embodiment. Therefore, air passing between two adjacent diffuser vanes 50 passes through the side closer to the negative pressure surface 53 than when the protrusion 51a is not formed. In other words, the protrusion 51a moves the air passing between two adjacent diffuser vanes 50 toward the negative pressure surface 53.

[0038] In this embodiment, a curved recess 53a is formed on the suction surface 53 of the diffuser vane 50. Therefore, the recess 53a can smoothly guide the air moved to the suction surface 53 side by the protrusion 51a along the suction surface 53 to the trailing edge 57 side.

[0039] Arc portions 51b, 53b are formed near trailing edges 57 of the pressure surface 51 and the suction surface 53. Arc portions 51b, 53b are semi-elliptical or semi-circular. Therefore, air flowing near the trailing edge 57 tends to flow along arc portions 51b, 53b, and the outflow angle α2 can be reduced, and the turning angle can be increased.

[0040] FIG. 6 is a diagram for explaining the width between two adjacent diffuser vanes 50. The width between two adjacent diffuser vanes 50 can be measured, for example, as the diameter of the inscribed circle of the two diffuser vanes. In FIG. 2 is the length of the airfoil centerline 59 from the leading edge 55 to the trailing edge 57 of the diffuser vane 50. m is the length from the leading edge 55 to any point on the airfoil centerline 59 of the diffuser vane 50. inis the width between the leading edges 55 of two adjacent diffuser vanes 50. Width is the width at any position from the leading edge 55 to the trailing edge 57 of two adjacent diffuser vanes 50. In Fig. 6, the dashed line indicates the width between two adjacent diffuser vanes 50A of the comparative example shown in Fig. 4, and the solid line indicates the width between two adjacent diffuser vanes 50 of the present embodiment shown in Fig. 5.

[0041] 6, the rate of increase in the width between two adjacent diffuser vanes 50A in the comparative example is constant from the leading edge 55 to the trailing edge 57. In other words, the rate of increase in the cross-sectional area of ​​the vane passage between two adjacent diffuser vanes 50A in the comparative example is constant from the leading edge 55 to the trailing edge 57. The cross-sectional area of ​​the vane passage can be measured as the product of the height of the diffuser vane in the direction of the central axis of rotation and the width of the vane passage, or the integral of the width of the vane passage over the height of the diffuser vane in the direction of the central axis of rotation.

[0042] On the other hand, the rate of increase in the width between two adjacent diffuser vanes 50 in this embodiment gradually increases from the leading edge 55 toward the trailing edge 57. In other words, the rate of increase in the flow path cross-sectional area of ​​the vane flow passage 61 between two adjacent diffuser vanes 50 in this embodiment gradually increases from the leading edge 55 toward the trailing edge 57. The rate of increase in the width between two adjacent diffuser vanes 50 in this embodiment is greater on the trailing edge 57 side than on the leading edge 55 side. In other words, the rate of increase in the flow path cross-sectional area of ​​the vane flow passage 61 in this embodiment is greater on the trailing edge 57 side than on the leading edge 55 side.

[0043] The width between the leading edges 55 of the two adjacent diffuser vanes 50 of this embodiment is the same as the width between the leading edges 55 of the two adjacent diffuser vanes 50A of the comparative example. However, the diffuser vane 50 of this embodiment has a protruding portion 51a. Therefore, at least in the protruding region PR, the width between the two adjacent diffuser vanes 50 of this embodiment is smaller than the width between the two adjacent diffuser vanes 50A of the comparative example. Therefore, the diffuser vane 50 of this embodiment can suppress the separation of air on the suction surface 53 compared to the diffuser vane 50A of the comparative example. As a result, as can be seen by comparing FIG. 4 and FIG. 5, the diffuser vane 50 of this embodiment can reduce the separation region PeR compared to the diffuser vane 50A of the comparative example.

[0044] Further, the diffuser vane 50 of the present embodiment has arc portions 51b, 53b. Therefore, in a part of the arc region AR, the width between two adjacent diffuser vanes 50 of the present embodiment is larger than the width between two adjacent diffuser vanes 50A of the comparative example. The width between the trailing edges 57 of the two adjacent diffuser vanes 50 of the present embodiment is larger than the width between the trailing edges 57 of the two adjacent diffuser vanes 50 of the comparative example. As a result, the diffuser vane 50 of the present embodiment can greatly decelerate the air flow on the trailing edge 57 side, compared to the diffuser vane 50A of the comparative example.

[0045] FIG. 7 is a diagram for explaining the blade thickness of the diffuser vane 50. In FIG. in is the blade thickness at the leading edge 55 of the diffuser vane 50 of this embodiment. t0 is the blade thickness at any position from the leading edge 55 to the trailing edge 57 of the diffuser vane 50 of this embodiment.

[0046] As shown in FIG. 7, the diffuser vane 50 of this embodiment is m / m 2 The maximum blade thickness is reached when m / m is 0.7 or more.2 When the maximum blade thickness is at a position where m / m is less than 0.7, air is likely to separate from the position of maximum blade thickness on the suction surface 53 toward the trailing edge 57, and the size of the separation region PeR shown in FIG. 5 approaches the size of the separation region PeR of the comparative example shown in FIG. 4. For this reason, in this embodiment, the position of maximum blade thickness of the diffuser vane 50 is set to be equal to or smaller than m / m. 2 For example, in this embodiment, the position of the maximum blade thickness of the diffuser vane 50 is set at a position where m / m 2 4. This makes it possible to make the size of the peeled region PeR of this embodiment shown in FIG. 5 smaller than the size of the peeled region PeR of the comparative example shown in FIG.

[0047] Although one embodiment of the present disclosure has been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such an embodiment. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure.

[0048] In the above embodiment, an example has been described in which the protrusion 51a is provided on the pressure surface 51. However, the present invention is not limited to this, and the protrusion 51a may be provided on the negative pressure surface 53 without providing the protrusion 51a on the pressure surface 51.

[0049] In the above embodiment, an example has been described in which the arc portions 51b, 53b are provided on the pressure surface 51 side and the suction surface 53 side of the trailing edge 57, and the trailing edge 57 has an elliptical or circular shape. However, the present invention is not limited to this, and the trailing edge 57 may have a flat surface portion on the pressure surface 51 side without the arc portion 51b. Also, the trailing edge 57 may have a flat surface portion on the suction surface 53 side without the arc portion 53b. [Explanation of symbols]

[0050] CC Centrifugal Compressor TC Turbocharger 7 Compressor housing (housing) 19 Compressor impeller 23 Diffuser passage 50 Diffuser Vane 51 Pressure Surface 51a Protrusion 51b Arc section 53 Suction surface 53a Recess 53b Arc section 55 Leading Edge 57 Trailing Edge 61 Vane passage

Claims

1. Housing and an annular diffuser passage formed in the housing; a plurality of diffuser vanes provided in the diffuser passage and spaced apart from one another in a circumferential direction of the diffuser passage; a vane flow passage formed between two adjacent diffuser vanes spaced apart in a circumferential direction, the increase rate of a flow passage cross-sectional area between the two diffuser vanes being larger on a trailing edge side than on a leading edge side; Equipped with an outflow angle between a perpendicular line at the trailing edge on an imaginary circle passing through the trailing edges of the plurality of diffuser vanes and a flow direction of air flowing on a rear side of the trailing edge in the rotation direction of the impeller is smaller than an inflow angle between a perpendicular line at the leading edge on an imaginary circle passing through the leading edges of the plurality of diffuser vanes and a flow direction of air flowing on a rear side of the leading edge in the rotation direction of the impeller, a curvature of a leading edge side of a surface of the diffuser vane facing a front side in a rotation direction of the impeller is smaller than a curvature of a leading edge side of a surface of the diffuser vane facing a rear side in a rotation direction of the impeller; Centrifugal compressor.

2. The diffuser vane has an airfoil center line located on the rear side in a rotation direction of the compressor impeller with respect to a straight line connecting the leading edge and the trailing edge, and the trailing edge has a circular or elliptical shape.

2. The centrifugal compressor according to claim 1.

3. A turbocharger comprising the centrifugal compressor according to claim 1 or 2.

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