Compressor cover, centrifugal compressor, turbocharger, method for manufacturing compressor cover and diffuser for centrifugal compressor

Abstract

An annular compressor cover forming a flow path wall of a diffuser flow path in a centrifugal compressor, wherein, where a position of a winding end of a screw flow path of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the compressor cover, a direction in which a fluid flows in the screw flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, and a distance between an outlet of the diffuser flow path and a central axis of an inner circumferential surface of the compressor cover is defined for each position in the circumferential direction as a diffuser radius, an average value of the diffuser radii in a range from a position of a tongue section of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 180° to 360° in the circumferential direction.

Description

Technical area

[0001] The present disclosure relates to a compressor cover, a centrifugal compressor, a turbocharger, a method of manufacturing a compressor cover, and a diffuser for a centrifugal compressor. State of the art

[0002] For example, the centrifugal compressor as described in PTL 1 includes an impeller, a scroll flow path formed on an outer peripheral side of the impeller, and a diffuser flow path that guides a fluid that has passed through the impeller to the scroll flow path. Citation listPatent literature

[0003] [PTL 1] Japanese Unexamined Patent Application Publication No. 2016-108994 Summary of the inventionTechnical problem

[0004] In the centrifugal compressor, since the scroll flow path on the outer peripheral side of the impeller has an asymmetric shape in a circumferential direction as shown in Fig. As shown in Figure 11, a local low-speed region may be formed in the scroll flow path, and thus, backflow may occur in the diffuser flow path. As a countermeasure against such a phenomenon, for example, if a diffuser radius, which is a distance between an outlet of the diffuser flow path and a rotation axis of the impeller, is reduced, a load on the diffuser flow path is reduced. Therefore, the formation of the local low-speed region and the occurrence of backflow in the diffuser flow path can be suppressed.

[0005] Meanwhile, when the diffuser radius is reduced, while it is possible to suppress the formation of the local low-speed region in the scroll flow path and the occurrence of backflow in the diffuser flow path to expand an operating range of the centrifugal compressor to a low flow rate side, pressure recovery at the diffuser flow path is suppressed, and compressor efficiency is reduced.

[0006] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a compressor cover, a centrifugal compressor, a turbocharger, a method of manufacturing a compressor cover, and a diffuser for a centrifugal compressor, which can realize a centrifugal compressor that can be operated with high efficiency in a wide operating range. Solution to the problem

[0007] To achieve the above object, a compressor cover according to at least one embodiment of the present disclosure is: an annular compressor cover forming a flow path wall of a diffuser flow path in a centrifugal compressor, wherein, when a position of a winding end of a scroll flow path of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the compressor cover, a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, and a distance between an outlet of the diffuser flow path and a center axis of an inner peripheral surface of the compressor cover for each position in the circumferential direction is defined as a diffuser radius, an average value of the diffuser radii in a range from a position of a tongue portion of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 180° to 360° in the circumferential direction.

[0008] To achieve the above object, a centrifugal compressor according to at least one embodiment of the present disclosure includes an impeller and the compressor cover described above.

[0009] To achieve the above object, a turbocharger according to at least one embodiment of the present disclosure includes the centrifugal compressor described above.

[0010] To achieve the above object, a method of manufacturing a compressor cover according to at least one embodiment of the present disclosure is: a method of manufacturing a compressor cover forming a flow path wall of a diffuser flow path in a centrifugal compressor, the method comprising: a step of manufacturing a molded intermediate article of the compressor cover, and a step of cutting an edge portion defining an outlet of the diffuser flow path in the intermediate molded article of the compressor cover while rotating the intermediate molded article of the compressor cover about a rotation axis eccentric from a center axis of an inner peripheral surface of the compressor cover.

[0011] To achieve the above object, a diffuser for a centrifugal compressor according to at least one embodiment of the present disclosure comprises: a casing sidewall section, and a hub sidewall portion facing the shroud sidewall portion and forming an annular diffuser flow path between the shroud sidewall portion and the hub sidewall portion, wherein, when a position of a coil end of the diffuser of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the compressor cover, a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, and a distance between an outlet of the diffuser flow path and the rotation axis of an impeller of the centrifugal compressor is defined for each position in the circumferential direction as a diffuser radius R, an average value of the diffuser radii in a range from a position of a tongue portion of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 180° to 360° in the circumferential direction. Advantageous effects of the invention

[0012] According to at least one embodiment of the present disclosure, a compressor cover, a centrifugal compressor, a turbocharger, a method of manufacturing a compressor cover, and a diffuser for a centrifugal compressor are provided, which can realize a centrifugal compressor that can be operated with high efficiency over a wide operating range. Brief description of the drawings Fig. 1 is a partial sectional view showing a schematic configuration of a turbocharger including a centrifugal compressor according to an embodiment. Fig. 2 is a diagram for describing a definition of a position in a circumferential direction. Fig. 3 is a diagram showing a change of a flow path cross section (cross section along an axial direction in a scroll flow path and a diffuser flow path) on a downstream side of an impeller every 60° from 0° to 360° in the circumferential direction for an example of the centrifugal compressor. Fig. 4 is a graph showing the change of the flow path cross section (cross section along the axial direction in the scroll flow path and the diffuser flow path) at a position of the impeller every 60° from 0° to 360° in the circumferential direction for a centrifugal compressor according to a comparative example. Fig. 5 is a graph showing a relationship between the position in the circumferential direction and a diffuser radius in each of the centrifugal compressor according to the embodiment and the centrifugal compressor according to the comparative example. Fig. 6 is a graph showing the relationship between the position in the circumferential direction and the diffuser radius in a centrifugal compressor according to another embodiment. Fig. 7 is a graph showing the relationship between the position in the circumferential direction and the diffuser radius in a centrifugal compressor according to still another embodiment. Fig. 8 is a diagram showing a position of an outlet of the diffuser flow path of the centrifugal compressor when viewed in an axial direction (position of an outer peripheral edge of a shroud side wall portion). Fig. 9 is a flowchart showing an example of a method for manufacturing a compressor cover of the centrifugal compressor. Fig. 10 is a diagram, when viewed in an axial direction, showing a position of an outer peripheral edge of a shell side wall portion of the compressor cover before and after cutting S13 in Fig. 9 shows. Fig. 11 is a diagram showing a radial flow velocity in a vicinity of a hub side wall surface on the downstream side of the impeller of a centrifugal compressor in the state of Technology shows.Description of embodiments

[0013] Some embodiments of the present disclosure will be described below with reference to the accompanying drawings. Dimensions, materials, shapes, relative arrangements, and the like of components described as embodiments or illustrated in the drawings are not intended to limit the scope of the invention, but are merely illustrative examples.

[0014] For example, an expression representing a relative or absolute arrangement, such as "in a certain direction", "along a certain direction", "parallel", "perpendicular", "center", "concentric" or "coaxial", does not strictly represent only such an arrangement, but also a tolerance or a state relatively displaced by an angle or a distance, as long as the same function can be obtained.

[0015] For example, expressions such as "identical," "equal," and "homogeneous," which indicate that things are in the same state, represent not only a strictly equal state, but also a state in which there is a tolerance or difference in the extent to which the same function can be obtained.

[0016] For example, an expression indicating a shape such as a square shape or a cylindrical shape represents not only a shape such as a square shape or a cylindrical shape in a geometrically strict sense, but also a shape including concave and convex portions, chamfer portions, or the like, to the extent that the same effects can be obtained.

[0017] However, an expression such as “comprising,” “possessing,” “provided with,” “containing,” or “having” a component is not an exclusive expression that excludes the presence of other components. (Schematic configuration of turbocharger)

[0018] Fig. 1 is a partial sectional view showing a schematic configuration of a turbocharger 2 including a centrifugal compressor 4 according to an embodiment.

[0019] As in Fig. 1, the turbocharger 2 includes the centrifugal compressor 4 and a turbine (not shown) connected to the centrifugal compressor 4 via a rotating shaft 8. The centrifugal compressor 4 includes an impeller 6 and a housing 14 that accommodates the impeller 6.

[0020] Hereinafter, an "axial direction" means an axial direction of the impeller 6 unless otherwise specified, a "radial direction" means a radial direction of the impeller 6 unless otherwise specified, and a "circumferential direction" means a circumferential direction of the impeller 6 unless otherwise specified. Furthermore, a side of the air inlet 13 of the centrifugal compressor 4 in the axial direction is referred to as a "front side," and a side opposite to the front side in the axial direction is referred to as a "rear side."

[0021] The casing 14 includes a tubular portion 16 that supplies air to the impeller 6 and forms an impeller receiving space 15 that receives the impeller 6, a scroll portion 20 that forms a scroll flow path 18 on an outer peripheral side of the impeller 6, and a diffuser portion 24 (diffuser) that forms an annular diffuser flow path 22 that connects the impeller receiving space 15 and the scroll flow path 18.

[0022] The diffuser portion 24 includes a shroud sidewall portion 26 formed on the outer peripheral side of the impeller 6 along a plane perpendicular to the axial direction, and a hub sidewall portion 28 positioned on a rear side of the shroud sidewall portion 26 and formed on the outer peripheral side of the impeller 6 along the plane perpendicular to the axial direction so as to face the shroud sidewall portion 26. The diffuser flow path 22 is formed between the shroud sidewall portion 26 and the hub sidewall portion 28. That is, the diffuser flow path 22 is defined by the shroud sidewall portion 26 and the hub sidewall portion 28.

[0023] In one exemplary form shown, the housing 14 includes an annular compressor cover 30 and an annular bearing housing 32. Furthermore, the tubular portion 16, the shroud sidewall portion 26 of the diffuser portion 24, and a portion of the scroll portion 20 are integrally formed to form the compressor cover 30. Furthermore, the hub sidewall portion 28 is configured by a portion of the bearing housing 32 for receiving a bearing (not shown) that supports the rotating shaft 8. The compressor cover 30 and the bearing housing 32 are secured to each other by a fastener such as a bolt (not shown).

[0024] Furthermore, as described in detail later, in the centrifugal compressor 4, a distance R between an outlet 22a of the diffuser flow path 22 and a center axis O1 of an inner peripheral surface 30a of a compressor cover changes according to a position in the circumferential direction. Hereinafter, the distance R between the outlet 22a of the diffuser flow path 22 and the center axis O1 of the inner peripheral surface 30a of the compressor cover 30 for each position in the circumferential direction is referred to as a "diffuser radius R."

[0025] The central axis O1 of the inner peripheral surface 30a of the annular compressor cover 30 coincides with a rotational axis O1 of the impeller 6, an axial direction of the compressor cover 30 coincides with the axial direction of the impeller 6 and an axial direction of the diffuser portion 24, a radial direction of the compressor cover 30 coincides with the radial direction of the impeller 6 and a radial direction of the diffuser portion 24, and a circumferential direction of the compressor cover 30 coincides with the circumferential direction of the impeller 6 and a circumferential direction of the diffuser portion 24. Furthermore, at each position in the circumferential direction, the diffuser radius R corresponds to a distance between the outlet 22a of the diffuser flow path 22 and the rotational axis O1 of the impeller 6.Furthermore, the outlet 22a of the diffuser flow path 22 means a boundary between the diffuser flow path 22 and the scroll flow path 18, and specifically, means an opening end formed in the diffuser flow path 22 at a position of an outer end 26a (hereinafter, it will be referred to as an outer peripheral edge 26a of the shroud side wall portion 26 in some cases) of the shroud side wall portion 26 in the radial direction. Furthermore, the diffuser radius R corresponds to a distance between the outer end 26a of the shroud side wall portion 26 and the center axis O1 in the radial direction. (Configuration example of diffuser flow path and screw flow path)

[0026] Some examples of configurations of the screw flow path 18 and the diffuser flow path 22 are described below.

[0027] Fig. 2 is a diagram for describing a definition of the position (angular position) in the circumferential direction.

[0028] As in Fig. 2, in the following description, a position of a coil end 18e of the scroll flow path 18 is defined as a position of 360° (i.e., 0°) in the circumferential direction, and a direction in which an exhaust gas (fluid) flows in the scroll flow path 18 in the circumferential direction is defined as a positive direction of the position in the circumferential direction. A position of a tongue portion 18t of the scroll flow path 18 in the circumferential direction may be approximately 60° (for example, a position between 45° and 75°). As known to those skilled in the art, the position of the tongue portion 18t of the scroll flow path 18 means a position of a tip end of a tongue-shaped protrusion formed at a position where a winding start portion 18a and a discharge portion 18b in the scroll flow path 18 are connected to each other.The direction in which the exhaust gas flows in the scroll flow path 18 in the circumferential direction coincides with a rotation direction of the impeller 6 (see . Fig. 1).

[0029] Fig. 3 is a diagram showing a change of a flow path cross section (cross section along the axial direction in the scroll flow path 18 and the diffuser flow path 22) on a downstream side of the impeller 6 every 60° from 60° to 360° in the circumferential direction for a centrifugal compressor 4A, which is an example of the centrifugal compressor 4.

[0030] As in Fig. 3, in the centrifugal compressor 4A, a flow path cross-sectional area of ​​the scroll flow path 18 gradually increases from 60° to 360° in the circumferential direction. Moreover, a position of the outlet 22a of the diffuser flow path 22 changes according to the position in the circumferential direction, and the position of the outlet 22a changes in the radial direction in the order of 60°, 120°, 180°, 240°, and 360° (0°) from an inner side to an outer side.

[0031] Fig. 4 is a diagram showing the change of the flow path cross section (cross section along the axial direction in the scroll flow path 18 and the diffuser flow path 22) on the downstream side of the impeller 6 every 60° from 60° to 360° in the circumferential direction for a centrifugal compressor 04 according to a comparative example.

[0032] As in Fig. 4, in the centrifugal compressor 04, the flow path cross-sectional area of ​​the scroll flow path 18 gradually increases from 60° to 360° in the circumferential direction. Furthermore, in the centrifugal compressor 04, a radial position of the outlet 22a of the diffuser flow path 22 is constant regardless of the position in the circumferential direction. That is, in the centrifugal compressor 04, the outlet 22a of the diffuser flow path 22 has a circular shape when viewed in an axial direction; in other words, the outer peripheral edge 26a of the shroud side wall portion 26 has a circular shape.

[0033] Fig. Fig. 5 is a graph showing a relationship between the position in the circumferential direction and the diffuser radius R in each of the centrifugal compressor 4A and the centrifugal compressor 04. In the Fig. In the graph shown in Figure 5, the position in the circumferential direction is shown on a horizontal axis, and the diffuser radius R is shown on a vertical axis.

[0034] As in Fig. 5, in the centrifugal compressor 04 according to the comparative example, the diffuser radius R is constant regardless of the position in the circumferential direction. In contrast, in the centrifugal compressor 4A, the diffuser radius R changes according to the position in the circumferential direction. Fig. In the exemplary centrifugal compressor 4A shown in Figure 5, the diffuser radius R decreases linearly in the circumferential direction from 0° to a position A1, is a constant value (= R1min) from position A1 to a position A2, and increases linearly from position A2 to 360°. In an example shown in the drawing, position A1 is a position of 0° or more and 60° or less in the circumferential direction, and position A2 is a position of 90° or more and 120° or less in the circumferential direction.

[0035] In the Fig. In the example shown in Figure 5, the diffuser radius R changes according to the position in the circumferential direction, and a minimum value R1min of the diffuser radius R is adopted in at least a part of a range from 0° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 45° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 60° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 90° to 180° in the circumferential direction.

[0036] In addition, as in Fig. 5, when the range from 90° to 180° in the circumferential direction is defined as a first range S1, in the centrifugal compressor 4A, the diffuser radius R in at least a part of the first range S1 in the circumferential direction is smaller than the diffuser radius R in at least a part of a range other than the first range S1 in the circumferential direction. The range other than the first range S1 in the circumferential direction means a range other than the range from 90° to 180° from a range from 0° to 360° in the circumferential direction, in other words, it means a range other than a position of 90° and a position of 180° from a range from 0° to 90° and a range from 180° to 360° in the circumferential direction.

[0037] In addition, as in Fig. 5, in the centrifugal compressor 4A, a maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than a maximum value R2max of the diffuser radius R in the region excluding the region S1 in the circumferential direction. Furthermore, in the centrifugal compressor 4A, an average value R1ave (not shown) of the diffuser radii R in the first region S1 in the circumferential direction is smaller than an average value R0ave (not shown) of the diffuser radii R in the region excluding the first region S1 in the circumferential direction.

[0038] Furthermore, in the centrifugal compressor 4A, an average value of the diffuser radii R in a range from the position of the tongue portion 18t of the scroll flow path 18 to 180° in the circumferential direction is smaller than an average value of the diffuser radii R in the range of 180° to 360° in the circumferential direction. Furthermore, an average value of the diffuser radii R in the first region S1 in the circumferential direction is smaller than an average value of the diffuser radii R in the range of 180° to 360° in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than a minimum value of the diffuser radius R in a range except the position of 180° among the range of 180° to 360° in the circumferential direction.Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the range from 180° to 360° in the circumferential direction. The minimum value R1min of the diffuser radius R in the range from 90° to 180° in the circumferential direction is smaller than a minimum value R1max of the diffuser radius R in the range from 180° to 360° in the circumferential direction.

[0039] Moreover, when the range from 270° to 360° in the circumferential direction is defined as a second range S2, in the centrifugal compressor 4A, the diffuser radius R in at least a part of the first range S1 in the circumferential direction is smaller than the diffuser radius R in at least a part of the range S2 in the circumferential direction. Moreover, in the centrifugal compressor 4A, the maximum value R1max of the diffuser radius R in the first range S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the second range S2 in the circumferential direction. Furthermore, in the centrifugal compressor 4A, the minimum value R1min of the diffuser radius R in the first range S1 in the circumferential direction is smaller than a minimum value R2min of the diffuser radius R in the second range S2 in the circumferential direction.Furthermore, in the centrifugal compressor 4A, an average value R1ave (not shown) of the diffuser radius R in the first region S1 in the circumferential direction is smaller than a minimum value R2ave (not shown) of the diffuser radius R in the second region S2 in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction. Furthermore, the diffuser radius R in at least a part of the first region S1 in the circumferential direction takes the minimum value R1min of the diffuser radius R in the range from 0° to 360° in the circumferential direction. That is, the diffuser radius R is minimized in at least a part of the first region S1 in the circumferential direction.

[0040] Furthermore, in the centrifugal compressor 4A, the average value of the diffuser radii R in the range from the position of the tongue portion 18t of the scroll flow path 18 to 180° in the circumferential direction is smaller than an average value of the diffuser radii R in the second region S2 in the circumferential direction. Furthermore, the average value of the diffuser radii R in the first region S1 in the circumferential direction is smaller than the average value of the diffuser radii R in the second region S2 in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction. In addition, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the second region S2 in the circumferential direction.In addition, the minimum value R1min of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction.

[0041] Furthermore, in the centrifugal compressor 4A, in at least a part of the range from 0° to 90° in the circumferential direction, the diffuser radius R decreases toward the positive direction in the circumferential direction, and in at least a part of a range from 180° to 270° in the circumferential direction, the diffuser radius R increases toward the positive direction in the circumferential direction.

[0042] An effect of the centrifugal compressor 4A is described below.

[0043] In the centrifugal compressor, in general, since the scroll flow path on the outer peripheral side of the impeller has an asymmetric shape in the circumferential direction, a local low-speed region (stall region) may be formed in the scroll flow path, and thus, backflow may occur in the diffuser flow path. Regarding this phenomenon, as a result of the present inventor's intensive investigation, it has been clarified that it is likely that backflow may occur in the diffuser flow path, particularly in the range of 90° to 180° in the circumferential direction (the above-described first region S1), as shown in Fig. 11. Furthermore, it was clarified that in the diffuser flow path, the backflow is unlikely to occur in the range of 270° to 360° (the second range S2 described above) in the circumferential direction.

[0044] Therefore, in the centrifugal compressor 4A as described above, the average value of the diffuser radii R in the range from the position of the tongue portion 18t of the scroll flow path 18 to 180° in the circumferential direction is smaller than the average value of the diffuser radii R in the range from 180° to 360° in the circumferential direction. Accordingly, it is possible to reduce a load on the diffuser flow path 22 in the range from the position of the tongue portion 18t to 180°, which is a range including a location where the stall region is likely to occur in the circumferential direction (range from 90° to 180°), more than the load on the diffuser flow path 22 in the range from 180° to 360° in the circumferential direction.Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of backflow in the diffuser flow path 22 and expand an operating range of the centrifugal compressor 4A toward a low flow rate side. Furthermore, compared to a case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path 22 in the range of 180° to 360° in the circumferential direction. Therefore, it is possible to suppress a decrease in compressor efficiency. Therefore, it is possible to realize the centrifugal compressor 4A that can operate with high efficiency in a wide operating range.

[0045] Furthermore, in the centrifugal compressor 4A as described above, the compressor cover 30 is configured such that the average value of the diffuser radii R in the first region S1 from 90° to 180° in the circumferential direction is smaller than the average value of the diffuser radii R in the range from 180° to 360° in the circumferential direction. Accordingly, it is possible to reduce a load on the diffuser flow path 22 in the first region S1 from 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction, more than the load on the diffuser flow path 22 in the range from 180° to 360° in the circumferential direction. Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of the backflow in the diffuser flow path 22 and to expand the operating range of the centrifugal compressor 4A to the low flow rate side.Furthermore, compared to the case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path 22 in at least a part of the area except the first area S1 in the circumferential direction. Therefore, it is possible to suppress the decrease in compressor efficiency. Therefore, it is possible to realize the centrifugal compressor 4A that can operate with high efficiency over a wide operating range.

[0046] Furthermore, in the centrifugal compressor 4A, the compressor cover 30 is configured such that the average value R1ave of the diffuser radii R in the first region R1ave from 90° to 180° in the circumferential direction is smaller than the average value R0ave of the diffuser radii R in the region excluding the first region S1 in the circumferential direction. Accordingly, it is possible to reduce the load on the diffuser flow path 22 in the first region S1 from 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction, more than the load on the diffuser flow path 22 in the region excluding the first region in the circumferential direction. Therefore, it is possible to enhance an effect of expanding the operating range of the centrifugal compressor 4A to the low flow rate side and an effect of suppressing the decrease in compressor efficiency.

[0047] Furthermore, in the centrifugal compressor 4A, the compressor cover 30 is configured such that the maximum value R1max of the diffuser radius R in the first region S1 from 90° to 180° in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the region excluding the first region S1 in the circumferential direction. Therefore, it is possible to enhance the effect of expanding the operating range of the centrifugal compressor 4A to the low flow rate side and the effect of suppressing the decrease in compressor efficiency.

[0048] Furthermore, in the centrifugal compressor 4A, the compressor cover 30 is configured such that the diffuser radius R in at least a part of the first range S1 from 90° to 180° in the circumferential direction is smaller than the diffuser radius R in at least a part of the second range S2 from 270° to 360° in the circumferential direction. Accordingly, it is possible to reduce the load on the diffuser flow path 22 in at least a part of the first region S1 from 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction, more than the load on the diffuser flow path 22 in at least a part of the second region S2 from 270° to 360°, which is a location where the stall region is unlikely to occur in the circumferential direction (region where the flow is normal).Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of backflow in the diffuser flow path 22 and expand the operating range of the centrifugal compressor 4A to the low flow rate side. Furthermore, compared to the case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path 22 in the second region S2 from 270° to 360° in the circumferential direction. Therefore, it is possible to suppress the decrease in compressor efficiency. Therefore, it is possible to realize the centrifugal compressor 4A that can operate with high efficiency in a wide operating range.

[0049] Furthermore, in the centrifugal compressor 4A, the compressor cover 30 is configured such that the average value R1ave of the diffuser radii R in the first region S1 from 90° to 180° in the circumferential direction is smaller than the average value R2ave of the diffuser radii R in the second region S2 from 270° to 360° in the circumferential direction. Accordingly, it is possible to reduce the load on the diffuser flow path 22 in the first region S1 from 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction, more than the load on the diffuser flow path 22 in the second region S2 from 270° to 360°, which is a location where the stall region is unlikely to occur in the circumferential direction (the region where the flow is normal).Therefore, it is possible to enhance an effect of expanding the operating range of the centrifugal compressor 4A to the low flow rate side and an effect of suppressing the decrease in compressor efficiency.

[0050] Furthermore, in the centrifugal compressor 4A, the compressor cover 30 is configured such that the maximum value R1max of the diffuser radius R in the first range S1 from 90° to 180° in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the second range from 270° to 360° in the circumferential direction. Therefore, it is possible to enhance the effect of expanding the operating range of the centrifugal compressor 4A to the low flow rate side and the effect of suppressing the decrease in compressor efficiency.

[0051] Furthermore, in the centrifugal compressor 4A, the compressor cover 30 is configured such that the minimum value R1min of the diffuser radius R in the first range S1 from 90° to 180° in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second range from 270° to 360° in the circumferential direction. Therefore, it is possible to enhance the effect of expanding the operating range of the centrifugal compressor 4A to the low flow rate side and the effect of suppressing the decrease in compressor efficiency.

[0052] Fig. Fig. 6 is a graph showing the relationship between the position in the circumferential direction and the diffuser radius R in a centrifugal compressor 4B according to another embodiment. Fig. In the graph shown in Figure 6, the position in the circumferential direction is shown on a horizontal axis, and the diffuser radius R is shown on a vertical axis.

[0053] In the Fig. In the exemplary centrifugal compressor 4B shown in Figure 6, the diffuser radius R decreases linearly in the circumferential direction from 0° to 60°, is a constant value (= R1max, R1min) from 60° to 180°, increases linearly from 180° to 270°, and is a constant value (= R2max, R2min) from 270° to 360°.

[0054] Even with the Fig. In the centrifugal compressor 4B shown in Fig. 6, the diffuser radius R changes according to the position in the circumferential direction, and the minimum value R1min of the diffuser radius R is adopted in at least a part of a range from 0° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 45° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 60° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 90° to 180° in the circumferential direction.

[0055] Even with the Fig. 6, when the range from 90° to 180° in the circumferential direction is defined as the first region S1, in the centrifugal compressor 4B, the diffuser radius R in at least a part of the first region S1 in the circumferential direction is smaller than the diffuser radius R in at least a part of the region other than the first region S1 in the circumferential direction.

[0056] Furthermore, in the centrifugal compressor 4B, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is also smaller than the maximum value R2max of the diffuser radius R in the region excluding the region S1 in the circumferential direction. Furthermore, the average value R1ave (not shown) of the diffuser radii R in the first region S1 in the circumferential direction is smaller than the average value R0ave (not shown) of the diffuser radii R in the region excluding the first region S1 in the circumferential direction.

[0057] Furthermore, in the centrifugal compressor 4B, the average value of the diffuser radii R in a range from the position of the tongue portion 18t of the scroll flow path 18 to 180° in the circumferential direction is smaller than the average value of the diffuser radii R in the range of 180° to 360° in the circumferential direction. Moreover, an average value of the diffuser radii R in the first region S1 in the circumferential direction is smaller than an average value of the diffuser radii R in the range of 180° to 360° in the circumferential direction. Moreover, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than a minimum value of the diffuser radius R in a range except the position of 180° among the range of 180° to 360° in the circumferential direction.Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the range from 180° to 360° in the circumferential direction. The minimum value R1min of the diffuser radius R in the range from 90° to 180° in the circumferential direction is smaller than a minimum value R1max of the diffuser radius R in the range from 180° to 360° in the circumferential direction.

[0058] Moreover, even in the centrifugal compressor 4B, when the range from 270° to 360° in the circumferential direction is defined as the second range S2, the diffuser radius R in at least a part of the first range S1 in the circumferential direction is smaller than the diffuser radius R in at least a part of the range S2 in the circumferential direction. Moreover, the maximum value R1max of the diffuser radius R in the first range S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the second range S2 in the circumferential direction. Moreover, the minimum value R1min of the diffuser radius R in the first range S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second range S2 in the circumferential direction.Furthermore, the average value R1ave (not shown) of the diffuser radii R in the first region S1 in the circumferential direction is smaller than the minimum value R2ave (not shown) of the diffuser radius R in the second region S2 in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction. Furthermore, the diffuser radius R in at least a part of the first region S1 in the circumferential direction takes the minimum value R1min of the diffuser radius R in the range from 0° to 360° in the circumferential direction.Furthermore, in at least a part of the range from 0° to 90° in the circumferential direction, the diffuser radius R decreases toward the positive direction in the circumferential direction, and in at least a part of the range from 180° to 270° in the circumferential direction, the diffuser radius R increases toward the positive direction in the circumferential direction.

[0059] Furthermore, in the centrifugal compressor 4B, the average value of the diffuser radii R in the range from the position of the tongue portion 18t of the scroll flow path 18 to 180° in the circumferential direction is smaller than the average value of the diffuser radii R in the second region S2 in the circumferential direction. Furthermore, the average value of the diffuser radii R in the first region S1 in the circumferential direction is smaller than the average value of the diffuser radii R in the second region S2 in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction. In addition, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the second region S2 in the circumferential direction.In addition, the minimum value R1min of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction.

[0060] According to the centrifugal compressor 4B, as with the centrifugal compressor 4A, it is possible to realize the centrifugal compressor which can be operated with high efficiency in the wide operating range.

[0061] Fig. Fig. 7 is a graph showing the relationship between the position in the circumferential direction and the diffuser radius R in a centrifugal compressor 4C according to still another embodiment. In the Fig. In the graph shown in Figure 7, the position in the circumferential direction is shown on a horizontal axis, and the diffuser radius R is shown on a vertical axis.

[0062] In the Fig. In the exemplary centrifugal compressor 4C shown in Figure 7, the diffuser radius R decreases in the circumferential direction from 0° to a position A3, increases from position A3 to a position A4, and decreases from position A4 to 360°. In an example shown in the drawing, position A3 is a position of 90° or more and 180° or less in the circumferential direction (more specifically, a position of 120° or more and 180° or less), and position A4 is a position of 270° or more and 360° or less in the circumferential direction (more specifically, a position of 300° or more and 360° or less). Fig. The graph shown in Figure 7 is configured by a smooth curve.

[0063] Even with the Fig. In the centrifugal compressor 4C shown in Fig. 7, the diffuser radius R changes according to the position in the circumferential direction, and the minimum value R1min of the diffuser radius R is adopted in at least a part of a range from 0° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 45° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 60° to 180° in the circumferential direction. Moreover, the diffuser radius R may adopt the minimum value R1min of the diffuser radius R in at least a part of a range from 90° to 180° in the circumferential direction.

[0064] Even with the Fig. 7, when the range from 90° to 180° in the circumferential direction is defined as the first region S1, in the centrifugal compressor 4C, the diffuser radius R in at least a part of the first region S1 in the circumferential direction is smaller than the diffuser radius R in at least a part of the region other than the first region S1 in the circumferential direction.

[0065] Furthermore, in the centrifugal compressor 4C, the minimum value R1min of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the region excluding the first region S1 in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the region excluding the first region S1 in the circumferential direction. Furthermore, the average value R1ave (not shown) of the diffuser radii R in the first region S1 in the circumferential direction is smaller than the average value R0ave (not shown) of the diffuser radii R in the region excluding the first region S1 in the circumferential direction.

[0066] Furthermore, in the centrifugal compressor 4C, the average value of the diffuser radii R in a range from the position of the tongue portion 18t of the scroll flow path 18 to 180° in the circumferential direction is smaller than the average value of the diffuser radii R in the range of 180° to 360° in the circumferential direction. Moreover, an average value of the diffuser radii R in the first region S1 in the circumferential direction is smaller than an average value of the diffuser radii R in the range of 180° to 360° in the circumferential direction. Moreover, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than a minimum value of the diffuser radius R in a range except the position of 180° among the range of 180° to 360° in the circumferential direction.Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the range from 180° to 360° in the circumferential direction. The minimum value R1min of the diffuser radius R in the range from 90° to 180° in the circumferential direction is smaller than a minimum value R1max of the diffuser radius R in the range from 180° to 360° in the circumferential direction.

[0067] Moreover, even in the centrifugal compressor 4C, when the range from 270° to 360° in the circumferential direction is defined as the second range S2, the diffuser radius R in at least a part of the first range S1 in the circumferential direction is smaller than the diffuser radius R in at least a part of the range S2 in the circumferential direction. Moreover, the maximum value R1max of the diffuser radius R in the first range S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the second range S2 in the circumferential direction. Moreover, the minimum value R1min of the diffuser radius R in the first range S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second range S2 in the circumferential direction.Furthermore, the average value R1ave (not shown) of the diffuser radii R in the first region S1 in the circumferential direction is smaller than the minimum value R2ave (not shown) of the diffuser radius R in the second region S2 in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction. Furthermore, the diffuser radius R in at least a part of the first region S1 in the circumferential direction takes the minimum value R1min of the diffuser radius R in the range from 0° to 360° in the circumferential direction.Furthermore, in at least a part of the range from 0° to 90° in the circumferential direction, the diffuser radius R decreases toward the positive direction in the circumferential direction, and in at least a part of the range from 180° to 270° in the circumferential direction, the diffuser radius R increases toward the positive direction in the circumferential direction.

[0068] Furthermore, in the centrifugal compressor 4C, the average value of the diffuser radii R in the range from the position of the tongue portion 18t of the scroll flow path 18 to 180° in the circumferential direction is smaller than the average value of the diffuser radii R in the second region S2 in the circumferential direction. Furthermore, the average value of the diffuser radii R in the first region S1 in the circumferential direction is smaller than the average value of the diffuser radii R in the second region S2 in the circumferential direction. Furthermore, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction. In addition, the maximum value R1max of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the maximum value R2max of the diffuser radius R in the second region S2 in the circumferential direction.In addition, the minimum value R1min of the diffuser radius R in the first region S1 in the circumferential direction is smaller than the minimum value R2min of the diffuser radius R in the second region S2 in the circumferential direction.

[0069] Fig. Fig. 8 is a diagram showing the position of the outlet 22a of the diffuser flow path 22 of the centrifugal compressor 4C when viewed in the axial direction (position of the outer peripheral edge 26a of the shroud side wall portion 26). Fig. In Fig. 8, the position of the outlet 22a of the diffuser flow path 22 of the centrifugal compressor 4C is shown by a solid line circle, and is shown by a one-dot chain line circle and a dashed line circle with reference to two circles C1 and C2, each centered on the center axis O1 (rotational axis of the impeller 6) of the inner peripheral surface 30a of the compressor cover 30. In Fig. 8, the position of the outlet 22a of the diffuser flow path 22 is shown with the central axis O1 as an origin, a direction from the origin to a position of 0° in the circumferential direction as a positive direction of an X coordinate, and a direction from the origin to a position of 90° as a positive direction of a Y coordinate.

[0070] As in Fig. As shown in Figure 8, the outlet 22a of the diffuser flow path 22 has a circular shape when viewed in the axial direction, and a center O2 of the circular shape defining the outlet 22a of the diffuser flow path 22 is eccentric from the center axis O1 (rotational axis of the impeller 6) of the inner peripheral surface 30a of the compressor cover 30 such that the center O2 is positioned within the range of 270° to 360° in the circumferential direction. The compressor cover 30 of the centrifugal compressor 4C can be easily manufactured by eccentric machining to be described below.

[0071] Fig. 9 is a flowchart showing an example of a method for manufacturing the compressor cover 30 of the centrifugal compressor 4C. Fig. 10 is a diagram, when viewed in an axial direction, showing the position of the outer peripheral edge 26a of the shroud side wall portion 26 of the compressor cover 30 before and after cutting S13 in Fig. 9 shows.

[0072] As in Fig. 9, at S11, a molded intermediate article of the compressor cover 30 is manufactured, for example, by casting. Here, the molded intermediate article of the compressor cover 30 is manufactured such that the outer peripheral edge 26a of the shell side wall portion 26 is cut at S12, as shown in Fig. 10 shown by a circle with a one-dotted dash line, has a cutting reserve (excess metal).

[0073] At S12, as in Fig. 10, the molded intermediate article of the compressor cover 30 is fixed (pivotally supported) by a device (not shown) so as to be rotated about the rotation axis O2 eccentric from the central axis O1.

[0074] At S13, cutting (eccentric machining) is performed to remove the above-described excess metal by rotating the formed intermediate article of the compressor cover 30 about the rotation axis O2 eccentric from the central axis O1 and contacting a cutting tool (not shown) with the outer peripheral edge 26a (see the circle with one-dot chain line in Fig. 10) of the casing side wall portion 26 of the molded intermediate article of the compressor cover 30. In this way, a finished product of the compressor cover 30 is produced. In the finished product of the compressor cover 30 produced in this way, as shown in Fig. 10, the outer peripheral edge 26a of the shroud sidewall portion 26 has a circular shape when viewed in the axial direction, and the center O2 of the circular shape defining the outer peripheral edge 26a is eccentric from the central axis O1 such that the center O2 is positioned within the range of 270° to 360° in the circumferential direction. That is, in the compressor cover 30 after S13 is performed, the outlet 22a of the diffuser flow path 22 has a circular shape when viewed in the axial direction, and the center O2 of the circular shape defining the outlet 22a of the diffuser flow path 22 is eccentric from the central axis O1 such that the center O2 is positioned within the range of 270° to 360° in the circumferential direction.

[0075] According to the centrifugal compressor 4C having the compressor cover 30 manufactured by the above manufacturing method, it is possible to realize the centrifugal compressor that can operate with high efficiency over a wide operating range, just like the centrifugal compressor 4A. Furthermore, the compressor cover 30 can be easily manufactured by eccentric machining.

[0076] The present disclosure is not limited to the above-described embodiments and includes a modification of the above-described embodiments and an appropriate combination of the embodiments.

[0077] For example, in the Fig.The graphs shown in Figure 6 show an example in which the diffuser radius R decreases and increases linearly with respect to the change in position in the circumferential direction. However, the diffuser radius R can change smoothly so that, for example, the diffuser radius R assumes a lower value in a range from 60° to 180° than in other ranges.

[0078] Furthermore, in some embodiments described above, the compressor cover 30 includes the tubular portion 16, the shroud sidewall portion 26 of the diffuser portion 24, and a portion of the scroll portion 20. However, a compressor cover to which the present disclosure is applicable may include at least one shroud sidewall portion of a diffuser portion, and may, for example, include only the shroud sidewall portion of the diffuser portion. In this case, a center axis of an inner peripheral surface of the compressor cover may be a center axis of an inner peripheral surface of the annular shroud sidewall portion and coincide with a rotational axis of an impeller.

[0079] Furthermore, in the centrifugal compressors 4A to 4C described above, a flow path area of ​​the scroll flow path 18 is substantially enlarged in the circumferential direction toward the positive direction. However, the flow path area of ​​the scroll flow path 18 may be locally reduced in a partial region in the circumferential direction toward the positive direction. In this case, a synergistic effect with the effect of suppressing the above-described backflow can be obtained by locally reducing the flow path area of ​​the scroll flow path 18 toward the positive direction in the circumferential direction in a region where the local backflow occurs in the circumferential direction (for example, in at least a part of the range from 90° to 180°).

[0080] The contents described in each embodiment are understood, for example, as follows. (1) A compressor cover (for example, the compressor cover 30 described above) according to at least one embodiment of the present disclosure is: an annular compressor cover forming a flow path wall (for example, the above-described shroud side wall portion 26) of a diffuser flow path (for example, the above-described diffuser flow path 22) in a centrifugal compressor (for example, the above-described centrifugal compressor 4 (4A to 4C)), wherein, when a position of a coil end (for example, the coil end 18 described above) of a scroll flow path (for example, the scroll flow path 18 described above) of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the compressor cover, a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, and a distance between an outlet (for example, the outlet 22a described above) of the diffuser flow path and a central axis (for example, the central axis O1 described above) of an inner peripheral surface of the compressor cover is defined for each position in the circumferential direction as a diffuser radius (for example, the diffuser radius R described above), an average value of the diffuser radii in a range from a position of a tongue portion of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 180° to 360° in the circumferential direction.

[0081] According to the compressor cover described in the above (1), it is possible to reduce a load on the diffuser flow path in the range from the position of the tongue portion to 180°, which is a range including a location where the stall region is likely to occur in the circumferential direction (range from 90° to 180°), more than the load on the diffuser flow path in other areas. Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of backflow in the diffuser flow path and expand an operating range of the centrifugal compressor to a low flow rate side. Furthermore, compared with a case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path in the range from 180° to 360° in the circumferential direction.Therefore, it is possible to suppress a decrease in compressor efficiency. Therefore, it is possible to realize a centrifugal compressor that can operate with high efficiency over a wide operating range.

[0082] (2) In some embodiments, in the compressor cover described in (1) above, an average value of the diffuser radii in a range of 90° to 180° in the circumferential direction is smaller than the average value of the diffuser radii in the range of 180° to 360° in the circumferential direction.

[0083] According to the compressor cover described in the above (2), it is possible to reduce a load on the diffuser flow path in the range of 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction, more than the load on the diffuser flow path in the range of 180° to 360° in the circumferential direction. Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of backflow in the diffuser flow path and expand the operating range of the centrifugal compressor to the low flow rate side. Moreover, compared with the case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path in at least a part of the region except the first region in the circumferential direction.Therefore, it is possible to suppress the decrease in compressor efficiency. Therefore, it is possible to realize the centrifugal compressor, which can operate with high efficiency over a wide operating range.

[0084] (3) In some embodiments, in the compressor cover described in (1) or (2) above, (for example, the maximum value R1max described above) a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in a range except a position of 180° from the range of 180° to 360° in the circumferential direction.

[0085] According to the compressor cover described in the above (3), it is possible to enhance the above-described effect of expanding the operating range of the centrifugal compressor to the low flow rate side and the above-described effect of suppressing the decrease in compressor efficiency.

[0086] (4) In some embodiments, in the compressor cover described in any one of (1) to (3) above, a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a maximum value of the diffuser radius in the range of 180° to 360° in the circumferential direction.

[0087] According to the compressor cover described in the above (4), it is possible to enhance the above-described effect of expanding the operating range of the centrifugal compressor to the low flow rate side and the above-described effect of suppressing the decrease in compressor efficiency.

[0088] (5) In some embodiments, in the compressor cover described in any one of (1) to (4) above, a minimum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in the range of 180° to 360° in the circumferential direction.

[0089] According to the compressor cover described in the above (5), it is possible to enhance the above-described effect of expanding the operating range of the centrifugal compressor to the low flow rate side and the above-described effect of suppressing the decrease in compressor efficiency.

[0090] (6) In some embodiments, in the compressor cover described in any one of (1) to (5) above, the average value of the diffuser radii in the range from the position of the tongue portion of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 270° to 360° in the circumferential direction.

[0091] According to the compressor cover described in the above (6), it is possible to reduce a load on the diffuser flow path in the range from the position of the tongue portion to 180°, which is a range including a location where the stall region is likely to occur in the circumferential direction (range from 90° to 180°), more than the load on the diffuser flow path in the range from 270° to 360°, which is a location where the stall region is unlikely to occur in the circumferential direction (range where the flow is normal). Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of the backflow in the diffuser flow path and expand the operating range of the centrifugal compressor to the low flow rate side.Furthermore, compared to the case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path in the range of 270° to 360° in the circumferential direction. Therefore, it is possible to suppress the decrease in compressor efficiency. Therefore, it is possible to realize a centrifugal compressor that can operate with high efficiency over a wide operating range.

[0092] (7) In some embodiments, in the compressor cover described in any one of (1) to (6) above, an average value of the diffuser radii in a range of 90° to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range of 270° to 360° in the circumferential direction.

[0093] According to the compressor cover described in the above (7), it is possible to reduce a load on the diffuser flow path in the range of 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction, more than the load on the diffuser flow path in the range of 270° to 360°, which is a location where the stall region is unlikely to occur in the circumferential direction (the region where the flow is normal). Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of the backflow in the diffuser flow path, and expand the operating range of the centrifugal compressor to the low flow rate side.Furthermore, compared to the case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path in the range of 270° to 360° in the circumferential direction. Therefore, it is possible to suppress the decrease in compressor efficiency. Therefore, it is possible to realize a centrifugal compressor that can operate with high efficiency over a wide operating range.

[0094] (8) In some embodiments, in the compressor cover described in any one of (1) to (7) above, a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in a range of 270° to 360° in the circumferential direction.

[0095] According to the compressor cover described in the above (8), it is possible to enhance the above-described effect of expanding the operating range of the centrifugal compressor to the low flow rate side and the above-described effect of suppressing the decrease in compressor efficiency.

[0096] (9) In some embodiments, in the compressor cover described in any one of the above (1) to (8), a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a maximum value of the diffuser radius in a range of 270° to 360° in the circumferential direction.

[0097] According to the compressor cover described in the above (9), it is possible to enhance the above-described effect of expanding the operating range of the centrifugal compressor to the low flow rate side and the above-described effect of suppressing the decrease in compressor efficiency.

[0098] (10) In some embodiments, in the compressor cover described in any one of (1) to (9) above, a minimum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in the range of 180° to 360° in the circumferential direction.

[0099] According to the compressor cover described in the above (10), it is possible to enhance the above-described effect of expanding the operating range of the centrifugal compressor to the low flow rate side and the above-described effect of suppressing the decrease in compressor efficiency.

[0100] (11) In some embodiments, in the compressor cover described in any one of (1) to (10) above, in at least a part of a range of 0° to 60° in the circumferential direction in a graph in which the position in the circumferential direction is shown on a horizontal axis and the diffuser radius is shown on a vertical axis, the diffuser radius decreases toward the positive direction in the circumferential direction.

[0101] According to the compressor cover described in (11) above, in at least a part of the range from 0° to 60° in the circumferential direction, it is possible to reduce a load on the diffuser flow path toward the first range from 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction. Therefore, it is possible to enhance an effect of expanding the operating range of the centrifugal compressor toward the low flow rate side.

[0102] (12) In some embodiments, in the compressor cover described in any one of (1) to (11) above, in at least a part of a range of 180° to 270° in the circumferential direction in a graph in which the position in the circumferential direction is shown on a horizontal axis and the diffuser radius is shown on a vertical axis, the diffuser radius towards the positive direction in the circumferential direction.

[0103] According to the compressor cover described in the above (12), in at least a part of the range from 180° to 270° in the circumferential direction, it is possible to increase a load for the diffuser flow path toward the range from 270° to 360° (toward the positive direction in the circumferential direction), which is the location where the stall region is unlikely to occur in the circumferential direction, to enhance a function of pressure recovery. Moreover, in at least a part of the range from 180° to 270° in the circumferential direction, it is possible to reduce a load for the diffuser flow path toward the range from 90° to 180° (toward a negative direction in the circumferential direction), which is the location where the stall region is likely to occur in the circumferential direction.Therefore, it is possible to enhance an effect of expanding the operating range of the centrifugal compressor to the low flow rate side and an effect of suppressing the decrease in compressor efficiency.

[0104] (13) In some embodiments, in the compressor cover described in any one of (1) to (12) above, the outlet of the diffuser flow path has a circular shape when viewed in an axial direction of the compressor cover, and a center (for example, the center O2 described above) of the circular shape defining the outlet of the diffuser flow path is eccentric from the central axis (for example, the center axis O1 described above) such that the center is positioned within a range of 270° to 360° in the circumferential direction.

[0105] According to the compressor cover described in (13) above, the effect described in (1) above can be achieved with a simple configuration in which a shape of the outlet of the diffuser flow path is defined by a circular shape when viewed in the axial direction. Therefore, the compressor cover capable of achieving the effect described in (1) above can be easily formed by eccentric machining.

[0106] (14) A centrifugal compressor (for example, the centrifugal compressor 4 (4A to 4C) described above according to at least one embodiment of the present disclosure comprises: a wheel (for example the wheel 6 described above); and the compressor cover (for example, the compressor cover 30 described above) described in any one of the above (1) to (13).

[0107] According to the centrifugal compressor described in the above (14), since it includes the compressor cover described in any one of the above (1) to (13), it is possible to realize a centrifugal compressor that can be operated in a wide operating range with high efficiency.

[0108] (15) A turbocharger according to at least one embodiment of the present disclosure comprises: the centrifugal compressor (for example, the above-described centrifugal compressor 4 (4A to 4C) described above) described in the above (14).

[0109] According to the turbocharger described in the above (15), since it includes the centrifugal compressor described in the above (1), it is possible to realize a turbocharger that can be operated in a wide operating range with high efficiency.

[0110] (16) A method of manufacturing a compressor cover according to at least one embodiment of the present disclosure is: a method of manufacturing a compressor cover (for example, the compressor cover 30 described above) forming a flow path wall (for example, the shroud sidewall portion 26 described above) of a diffuser flow path (for example, the diffuser flow path 22 described above) in a centrifugal compressor (for example, the centrifugal compressor 4 (4A to 4C) described above), the method comprising: a step of manufacturing a molded intermediate article of the compressor cover, and a step of cutting an edge portion (for example, the above-described outer peripheral edge 26a) defining an outlet of the diffuser flow path in the intermediate molded article of the compressor cover while rotating the intermediate molded article of the compressor cover about a rotation axis (for example, the above-described rotation axis O2) eccentric from a center axis (for example, the above-described center axis O1) of an inner peripheral surface of the compressor cover.

[0111] According to the method for manufacturing a compressor cover described in the above (16), a shape of the outlet of the diffuser flow path can be made circular when viewed in the axial direction of the compressor cover, and the compressor cover can be manufactured such that the center of the circular shape is eccentric from the center axis of the inner peripheral surface of the compressor cover. Therefore, by setting a direction in which the center of the circular shape is eccentric with respect to the center axis of the inner peripheral surface of the compressor cover, taking into account a location where backflow is likely to occur in the diffuser flow path, it is possible to easily manufacture a compressor cover that realizes a centrifugal compressor that can operate with high efficiency in a wide operating range.

[0112] (17) In some embodiments, in the method for manufacturing a compressor cover described in the above (16), when a position of a coil end (for example, the coil end 18e described above) of a scroll flow path (for example, the scroll flow path 18 described above) of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the compressor cover, and a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, in the step of cutting the edge portion, the edge portion is cut while rotating the molded intermediate article of the compressor cover around the rotation axis (for example, the above-described rotation axis O2) positioned within a range of 270° to 360° in the circumferential direction.

[0113] According to the method for manufacturing a compressor cover described in the above (17), for example, a compressor cover having the following effects can be easily manufactured by turning. According to the compressor cover manufactured by the method for manufacturing a compressor cover described in the above (14), it is possible to reduce a stress on the diffuser flow path in the range of 90° to 180°, which is the location where the stall region is likely to occur in the circumferential direction, more than the stress on the diffuser flow path in the range of 270° to 360°, which is a location where the stall region is unlikely to occur in the circumferential direction (region where the flow is normal).Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of backflow in the diffuser flow path, and to expand the operating range of the centrifugal compressor to the low-flow side. Furthermore, compared to the case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path in the range of 270° to 360° in the circumferential direction. Therefore, it is possible to suppress the decrease in compressor efficiency. Therefore, it is possible to provide a compressor cover that can realize the centrifugal compressor that can operate with high efficiency over a wide operating range.

[0114] (18) A diffuser (for example, the diffuser section 24 described above) for a centrifugal compressor according to at least one embodiment of the present disclosure comprises: a shroud sidewall portion (for example, shroud sidewall portion 26); and a hub sidewall portion (for example, the hub sidewall portion 28 described above) facing the shroud sidewall portion and forming an annular diffuser flow path (for example, the diffuser flow path 22 described above) between the shroud sidewall portion and the hub sidewall portion, wherein, when a position of a coil end (for example, the above-described coil end 18e) of a scroll flow path (for example, the above-described scroll flow path 18) of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the diffuser, a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, and a distance between an outlet (for example, the above-described outlet 22a) of the diffuser flow path and a rotation axis (for example, the above-described center axis O1) of an impeller (for example, the above-described impeller 6) of the centrifugal compressor is defined for each position in the circumferential direction as a diffuser radius (for example, the above-described diffuser radius R), an average value of the diffuser radii in a range from a position of a tongue portion of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 180° to 360° in the circumferential direction.

[0115] According to the diffuser for a centrifugal compressor described in the above (18), it is possible to reduce the load on the diffuser flow path in the range from the position of the tongue portion to 180°, which is a range including a location where the stall region is likely to occur in the circumferential direction (range from 90° to 180°), more than the load on the diffuser flow path in other areas. Therefore, it is possible to suppress the formation of the local low-speed region and the occurrence of backflow in the diffuser flow path, and expand the operating range of the centrifugal compressor toward the low-flow side. Furthermore, compared with a case where the diffuser radius R is uniformly reduced from 0° to 360°, it is possible to promote pressure recovery in the diffuser flow path in the range of 180° to 360° in the circumferential direction.Therefore, it is possible to suppress a decrease in compressor efficiency. Therefore, it is possible to provide a diffuser for a centrifugal compressor that can realize the centrifugal compressor operating at high efficiency over a wide operating range. List of reference symbols 2 turbochargers 4 (4A, 4B, 4C): Centrifugal compressor 6 Wheel 8 Rotating shaft 10 Turbine wheel 12 turbines 13 Air intake 14 housings 15 Wheel accommodation space 16 tubular section 18 Screw flow path 18a Winding start section 18b Submission section 18e winding end 18t tongue section 20 screw section 22 Diffuser flow path 22a Outlet 24 Diffuser section 26 Sheathing side wall section 26a Outer peripheral edge (outer end in radial direction) 28 Hub sidewall section 30 Compressor cover 30a inner peripheral surface 32 bearing housings QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2016-108994

[0003]

Claims

[1] Annular compressor cover forming a flow path wall of a diffuser flow path in a centrifugal compressor, wherein, when a position of a winding end of a scroll flow path of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the compressor cover, a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, and a distance between an outlet of the diffuser flow path and a center axis of an inner peripheral surface of the compressor cover for each position in the circumferential direction is defined as a diffuser radius, an average value of the diffuser radii in a range from a position of a tongue portion of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 180° to 360° in the circumferential direction. [2] The compressor cover according to claim 1, wherein an average value of the diffuser radii in a range of 90° to 180° in the circumferential direction is smaller than the average value of the diffuser radii in a range of 180° to 360° in the circumferential direction. [3] The compressor cover according to claim 1 or 2, wherein a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in a range other than 180° from the range of 180° to 360° in the circumferential direction. [4] The compressor cover according to any one of claims 1 to 3, wherein a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a maximum value of the diffuser radius in the range of 180° to 360° in the circumferential direction. [5] The compressor cover according to any one of claims 1 to 4, wherein a minimum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in the range of 180° to 360° in the circumferential direction. [6] The compressor cover according to any one of claims 1 to 5, wherein the average value of the diffuser radii in the range from the position of the tongue portion of the scroll flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range of 270° to 360° in the circumferential direction. [7] The compressor cover according to any one of claims 1 to 6, wherein an average value of the diffuser radii in a range of 90° to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range of 270° to 360° in the circumferential direction. [8] The compressor cover according to any one of claims 1 to 7, wherein a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in a range of 270° to 360° in the circumferential direction. [9] The compressor cover according to any one of claims 1 to 8, wherein a maximum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a maximum value of the diffuser radius in a range of 270° to 360° in the circumferential direction. [10] The compressor cover according to any one of claims 1 to 9, wherein a minimum value of the diffuser radius in a range of 90° to 180° in the circumferential direction is smaller than a minimum value of the diffuser radius in the range of 180° to 360° in the circumferential direction. [11] The compressor cover according to any one of claims 1 to 10, wherein in at least a part of a range of 0° to 60° in the circumferential direction in a graph in which the position in the circumferential direction is shown on a horizontal axis and the diffuser radius is shown on a vertical axis, the diffuser radius decreases toward the positive direction in the circumferential direction. [12] The compressor cover according to any one of claims 1 to 11, wherein in at least a part of a range of 180° to 270° in the circumferential direction in a graph in which the position in the circumferential direction is shown on a horizontal axis and the diffuser radius is shown on a vertical axis, the diffuser radius increases toward the positive direction in the circumferential direction. [13] The compressor cover according to any one of claims 1 to 12, wherein the outlet of the diffuser flow path has a circular shape when viewed in an axial direction of the compressor cover, and a center of the circular shape defining the outlet of the diffuser flow path is eccentric from the central axis so that the center is positioned within a range of 270° to 360° in the circumferential direction. [14] Centrifugal compressor, comprising: a wheel; and the compressor cover according to one of claims 1 to 13. [15] Turbocharger, comprising: the centrifugal compressor according to claim 14. [16] A method of manufacturing a compressor cover forming a flow path wall of a diffuser flow path in a centrifugal compressor, the method comprising: a step of manufacturing a molded intermediate article of the compressor cover; and a step of cutting an edge portion defining an outlet of the diffuser flow path in the intermediate molded article of the compressor cover while rotating the intermediate molded article of the compressor cover about a rotation axis eccentric from a center axis of an inner peripheral surface of the compressor cover. [17] A method for manufacturing a compressor cover according to claim 16, wherein, when a position of a winding end of a scroll flow path of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the compressor cover and a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, in the step of cutting the edge portion, the edge portion is cut while rotating the intermediate molded article of the compressor cover around the rotation axis positioned within a range of 270° to 360° in the circumferential direction. [18] Diffuser for a centrifugal compressor, the diffuser comprising: a casing sidewall section; and a hub sidewall portion facing the shroud sidewall portion and forming an annular diffuser flow path between the shroud sidewall portion and the hub sidewall portion, wherein, when a position of a winding end of a scroll flow path of the centrifugal compressor is defined as a position of 360° in a circumferential direction of the diffuser, a direction in which a fluid flows in the scroll flow path in the circumferential direction is defined as a positive direction of a position in the circumferential direction, and a distance between an outlet of the diffuser flow path and the rotation axis of an impeller of the centrifugal compressor for each position in the circumferential direction is defined as a diffuser radius, an average value of the diffuser radii in a range from a position of a tongue portion of the screw flow path to 180° in the circumferential direction is smaller than an average value of the diffuser radii in a range from 180° to 360° in the circumferential direction.

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