Compressor housing and centrifugal compressor

Abstract

The compressor housing is formed inside with: an inlet flow path including an inlet formed in the shroud surface; an outlet flow path including an outlet formed in an introduction surface on the front side of the shroud surface; a recirculation flow path connecting the inlet flow path and the outlet flow path; the intake introduction portion of the compressor housing includes a front side surface defining the front side of the outlet flow path, a rear side surface defining the rear side of the outlet flow path, and a front side introduction surface formed on the introduction surface at a position forward of the outlet, the front side surface, the rear side surface, and the front side introduction surface are each inclined rearward from the outer side in the radial direction toward the inner side, the rear side surface has a convex curved portion, and the front side introduction surface has an introduction surface side convex curved portion.

Description

Technical Field

[0001] The present disclosure relates to a compressor housing and a centrifugal compressor including the compressor housing. Background Art

[0002] A centrifugal compressor used in a compression section of a vehicle or marine turbocharger uses the rotation of an impeller to provide kinetic energy to a fluid and discharge the fluid radially outward, and uses centrifugal force to increase the fluid pressure. For such a centrifugal compressor, high pressure ratio and high efficiency are required in a wide operating range, and various efforts have been made for this.

[0003] A centrifugal compressor includes an impeller and a compressor housing that houses the impeller. The impeller guides a fluid (e.g., air) flowing in from the front side in the axial direction radially outward. Generally, the compressor housing has an intake introduction passage formed therein for guiding the fluid from the outside of the compressor housing to the front side in the axial direction of the impeller, an impeller chamber communicating with the intake introduction passage and housing the impeller, and a volute flow passage communicating with the impeller chamber and guiding the gas that has passed through the impeller to the outside of the compressor housing.

[0004] For such a compressor, it is required to widen the range of achieving a high pressure ratio in a wide operating range. However, at low flow rates where the intake flow rate of the compressor is small, an unstable phenomenon called surge occurs in which the fluid vibrates violently in the fluid flow direction. To avoid surge, the operating range of the compressor at low flow rates is limited. Therefore, methods for suppressing surge have been studied for the purpose of widening the low flow rate range.

[0005] Patent Document 1 discloses a centrifugal compressor in which a compressor housing includes a recirculation flow passage having one end connected to an impeller chamber housing the impeller and the other end connected to an intake introduction passage located upstream of the impeller chamber. In such a centrifugal compressor, even when the flow rate of the fluid (main flow) flowing from the outside of the compressor housing through the intake introduction passage to the impeller chamber is small, by allowing a part of the fluid in the impeller chamber to pass through the recirculation flow passage and the intake introduction passage and return to the impeller chamber again, it is possible to increase the flow rate of the fluid delivered to the inlet side of the impeller and suppress surge.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: International Publication No. 2011 / 099419 Summary of the Invention

[0009] Technical Problem to be Solved by the Invention

[0010] In a centrifugal compressor having a compressor housing formed with a recirculation flow path as described in Patent Document 1, if the degree of interference between the recirculation flow flowing out from the recirculation flow path into the intake introduction path and the main flow is large when they converge, the pressure loss caused by the interference between the recirculation flow and the main flow increases, and the efficiency of the centrifugal compressor may decrease. Therefore, a compressor housing is desired that can reduce the degree of interference between the recirculation flow and the main flow and thus suppress the generation of pressure loss of the fluid in the compressor housing.

[0011] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a compressor housing that can suppress the generation of pressure loss of the fluid in the compressor housing and improve the efficiency of the centrifugal compressor, and a centrifugal compressor having the compressor housing.

[0012] Technical solutions for solving technical problems

[0013] The compressor housing of the present disclosure is a compressor housing for rotatably accommodating an impeller of a centrifugal compressor, and includes:

[0014] A shroud portion including a shroud surface that faces the front end of the impeller blades of the impeller with a predetermined gap;

[0015] An intake introduction portion including an introduction surface formed on the front side of the shroud surface and defining an intake introduction path for guiding the intake air introduced from the intake port of the compressor housing toward the impeller blades;

[0016] An inlet flow path is formed inside the compressor housing, including:

[0017] An inlet opening formed on the shroud surface;

[0018] An outlet flow path including an outlet opening formed on the introduction surface;

[0019] A recirculation flow path connecting the inlet flow path and the outlet flow path;

[0020] The intake introduction portion includes, in a cross-section along the axis of the impeller:

[0021] A front side surface that defines the front side of the outlet flow path and is inclined rearward from the outer side in the radial direction toward the inner side;

[0022] A rear side surface that defines the rear side of the outlet flow path, is inclined rearward from the outer side in the radial direction toward the inner side, and has a convex curved surface portion formed as a convex curved surface at least in part;

[0023] The front-side inlet surface is formed at a position on the inlet surface that is closer to the front side than the outlet, slopes rearward from the outer side toward the inner side in the radial direction, and has an inlet surface side convex curved surface portion formed in a convex curved surface shape at least in part.

[0024] The centrifugal compressor of the present disclosure includes the compressor housing.

[0025] Effects of the Invention

[0026] According to at least one embodiment of the present disclosure, there is provided a compressor housing capable of suppressing the generation of pressure loss of the fluid in the compressor housing and improving the efficiency of the centrifugal compressor, and a centrifugal compressor including the compressor housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an explanatory diagram for explaining the structure of a turbocharger including a centrifugal compressor according to an embodiment.

[0028] Figure 2 It is a schematic cross-sectional view showing the compressor side of a turbocharger including a centrifugal compressor according to an embodiment, and is a schematic cross-sectional view including the axis of the centrifugal compressor.

[0029] Figure 3 It is an explanatory diagram for explaining the intake air introduction portion according to an embodiment.

[0030] Figure 4 It is an explanatory diagram for explaining the intake air introduction portion of a comparative example.

[0031] Figure 5 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction portion according to an embodiment.

[0032] Figure 6 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction portion of a comparative example.

[0033] Figure 7 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction portion of a comparative example.

[0034] Figure 8 It is an explanatory diagram for explaining the intake air introduction portion according to an embodiment.

[0035] Figure 9 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction portion according to an embodiment.

[0036] Figure 10 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction portion according to an embodiment.

[0037] Figure 11 is an explanatory diagram for explaining the rear side shown in Figure 10

[0038] Figure 12 is an explanatory diagram for explaining the intake air introduction part of an embodiment.

[0039] Figure 13 is an explanatory diagram for explaining the intake air introduction part of an embodiment. Detailed implementation mode

[0040] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative configurations, etc. of the constituent elements described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure thereto, but are merely illustrative examples.

[0041] For example, expressions indicating relative or absolute configurations such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such configurations, but also represent a state of relative displacement in such a way that there is a tolerance or an angle and distance that can achieve the same function.

[0042] For example, expressions indicating an equal state of things such as "identical", "equal", "homogeneous", etc. not only strictly represent an equal state, but also represent a state in which there is a tolerance or a difference in the degree that can achieve the same function.

[0043] For example, expressions indicating shapes such as a quadrilateral shape, a cylindrical shape, etc. not only represent shapes such as a quadrilateral shape and a cylindrical shape in a strictly geometric sense, but also represent shapes including concavo-convex portions, chamfered portions, etc. within a range that can achieve the same effect.

[0044] On the other hand, the expression of "including", "comprising", or "having" a constituent element is not an exclusive expression that excludes the existence of other constituent elements.

[0045] It should be noted that for the same structure, the same reference numerals will be used and the description will be omitted.

[0046] (Centrifugal compressor)

[0047] Figure 1 is an explanatory diagram for explaining the structure of a turbocharger equipped with a centrifugal compressor of an embodiment. Figure 2 is a schematic cross-sectional view schematically showing the compressor side of a turbocharger equipped with a centrifugal compressor of an embodiment, and is a schematic cross-sectional view including the axis of the centrifugal compressor.

[0048] As Figure 1 , Figure 2 ​As shown, a centrifugal compressor 1 according to some embodiments of the present disclosure includes an impeller 2 and a compressor housing 3 that rotatably houses the impeller 2. As Figure 2 shown, the compressor housing 3 includes at least: a shroud portion 4 that includes a shroud surface 41 that faces the front end 22 of the impeller blades 21 of the impeller 2 with a predetermined gap G; and an intake introduction portion 5 that includes an introduction surface (inner wall surface) 51 that defines an intake introduction passage 50 for guiding intake air (e.g., a fluid such as air) introduced from the intake port 31 of the compressor housing 3 toward the impeller blades 21.

[0049] The centrifugal compressor 1 can be applied, for example, to automotive, marine, or power generation turbochargers 10, other industrial centrifugal compressors, blowers, etc. In the illustrated embodiment, the centrifugal compressor 1 is mounted on the turbocharger 10. As Figure 1 shown, the turbocharger 10 includes a centrifugal compressor 1, a turbine 11, and a rotating shaft 12. The turbine 11 includes a turbine rotor 13 that is mechanically connected to the impeller 2 via the rotating shaft 12 and a turbine housing 14 that rotatably houses the turbine rotor 13.

[0050] In the illustrated embodiment, as Figure 1 shown, the turbocharger 10 further includes a bearing 15 that rotatably supports the rotating shaft 12 and a bearing housing 16 that is configured to house the bearing 15. The bearing housing 16 is disposed between the compressor housing 3 and the turbine housing 14 and is mechanically connected to the compressor housing 3 and the turbine housing 14 by fastening members such as fastening bolts.

[0051] Hereinafter, for example, as Figure 1 shown, the direction in which the axis of the centrifugal compressor 1, that is, the axis CA of the impeller 2 extends is defined as the axial direction X, and the direction orthogonal to the axis CA is defined as the radial direction Y. The upstream side in the suction direction of the centrifugal compressor 1 in the axial direction X, that is, the side where the intake port 31 is located relative to the impeller 2 (the left side in the figure) is defined as the front side XF. In addition, the downstream side in the suction direction of the centrifugal compressor 1 in the axial direction X, that is, the side where the impeller 2 is located relative to the intake port 31 (the right side in the figure) is defined as the rear side XR.

[0052] In the illustrated embodiment, as Figure 1 shown, the compressor housing 3 is formed with an intake port 31 for introducing a fluid (e.g., air) from the outside of the compressor housing 3 and an exhaust port 32 for discharging the fluid that has passed through the impeller 2 to the outside of the compressor housing 3. The turbine housing 14 is formed with an exhaust gas introduction port 141 for introducing exhaust gas into the inside of the turbine housing 14 and an exhaust gas discharge port 142 for discharging the exhaust gas that has passed through the turbine rotor 13 to the outside of the turbine housing 14.

[0053] AsFigure 1 As shown, the rotating shaft 12 has a length direction along the axial direction X. The rotating shaft 12 is mechanically connected to the impeller 2 on one side (front side XF) of the length direction, and is mechanically connected to the turbine rotor 13 on the other side (rear side XR) of the length direction. It should be noted that "along a certain direction" in the present disclosure includes not only a certain direction but also a direction inclined relative to a certain direction.

[0054] The turbocharger 10 rotates the turbine rotor 13 by using the exhaust gas introduced into the interior of the turbine housing 14 through the exhaust inlet 141 from an exhaust gas generating device (not shown) (for example, an internal combustion engine such as an engine). Since the impeller 2 is mechanically connected to the turbine rotor 13 via the rotating shaft 12, it rotates in conjunction with the rotation of the turbine rotor 13. The turbocharger 10 compresses the fluid introduced into the interior of the compressor housing 3 through the intake port 31 by rotating the impeller 2, and delivers the fluid to the fluid supply object (for example, an internal combustion engine such as an engine) through the discharge port 32.

[0055] (impeller)

[0056] like Figure 2 As shown, the impeller 2 includes a hub 23 and a plurality of impeller blades 21 provided on an outer surface 24 of the hub 23. The hub 23 is mechanically fixed to one side (front side XF) of the rotating shaft 12, so that the hub 23 and the plurality of impeller blades 21 are provided to be able to rotate integrally with the rotating shaft 12 around the axis CA of the impeller 2. The impeller 2 is housed in the compressor housing 3, and is configured to guide the fluid introduced from the front side XF in the axial direction X to the outside in the radial direction Y.

[0057] In the illustrated embodiment, the outer surface 24 of the hub 23 is formed into a concave curved shape that increases as the distance from the axis CA of the impeller 2 increases from the front side XF toward the rear side XR. The plurality of impeller blades 21 are arranged at intervals from each other in the circumferential direction around the axis CA. A gap G (interval) is formed between the front ends 22 of the plurality of impeller blades 21 and the shroud surface 41 that is convexly curved in a manner opposite to the front ends 22. The shroud surface 41 is formed into a convex curved shape that increases as the distance from the axis CA of the impeller 2 increases from the front side XF toward the rear side XR.

[0058] (Compressor housing)

[0059] In the illustrated embodiment, Figure 2 As shown, the compressor housing 3 includes a shroud portion 4 including the above-mentioned shroud surface 41, an intake air inlet portion 5 forming the above-mentioned intake air inlet passage 50, and a vortex portion 33, which forms a vortex-shaped vortex flow passage 34 for guiding the fluid passing through the impeller 2 to the outside of the compressor housing 3.

[0060] The intake introduction passage 50 and the scroll passage 34 are respectively formed inside the compressor housing 3. The intake introduction portion 5 has an introduction surface 51 that forms the intake introduction passage 50. The introduction surface 51 extends along the axial direction X toward the front side XF with respect to the shroud surface 41, and the above-mentioned intake port 31 is formed at the front side XF end thereof. The scroll passage 34 is formed so as to be located outside the impeller 2 in the radial direction Y, and surrounds the periphery of the impeller 2 housed in the compressor housing 3. The scroll portion 33 has an inner peripheral surface 35 that forms the scroll passage 34.

[0061] In addition, in the illustrated embodiment, as Figure 2 shown, the compressor housing 3 is formed with an impeller chamber 36 that is a space for rotatably housing the impeller 2 by combining with other members (in the illustrated example, the bearing housing 16) and a diffuser passage 37 of the centrifugal compressor 1 for guiding the fluid from the impeller 2 to the scroll passage 34. It should be noted that in some other embodiments, the impeller chamber 36 and the diffuser passage 37 may also be formed inside the compressor housing 3.

[0062] The above-mentioned shroud portion 4 is provided between the intake introduction portion 5 and the scroll portion 33. The shroud surface 41 of the shroud portion 4 forms the front side XF portion of the impeller chamber 36. The bearing housing 16 has an impeller chamber forming surface 161 that is disposed opposite to the shroud surface 41 at a position rearward of the shroud surface 41 in the rear side XR direction and forms the rear side XR portion of the impeller chamber 36.

[0063] The shroud portion 4 has a shroud side flow surface 42 that forms the front side XF portion of the diffuser passage 37 and connects the rear end 43 of the shroud surface 41 and one end 351 of the inner peripheral surface 35. The bearing housing 16 has a hub side flow surface 162 that is disposed opposite to the shroud side flow surface 42 at a position rearward of the shroud side flow surface 42 in the rear side XR direction. The hub side flow surface 162 is provided outside the impeller chamber forming surface 161 in the radial direction Y and connects the impeller chamber forming surface 161 and the other end 352 of the inner peripheral surface 35. In the cross-section along the axis CA as Figure 2 shown, the shroud side flow surface 42 and the hub side flow surface 162 respectively extend in a direction intersecting (orthogonal in the illustrated example) with the axis CA.

[0064] The outlet of the intake introduction passage 50 communicates with the inlet of the impeller chamber 36, and the outlet of the impeller chamber 36 communicates with the inlet of the diffuser passage 37. The fluid introduced into the inside of the compressor housing 3 through the intake port 31 flows toward the rear side XR in the intake introduction passage 50 and is then sent to the impeller 2. The fluid sent to the impeller 2 sequentially flows through the diffuser passage 37 and the scroll passage 34, and then is discharged to the outside of the compressor housing 3 from the discharge port 32 (refer to Figure 1 ).

[0065] Figure 3 This is an explanatory diagram for explaining the intake air introduction section of an embodiment. In Figure 3 and the following Figures 4 to 13 , cross-sections along the axis CA of the impeller 2 are schematically shown respectively.

[0066] As Figure 2 , Figure 3 shows, an inlet flow path 45 including an inlet 44 formed on the shroud surface 41, an outlet flow path 53 including an outlet 52 formed on the introduction surface 51, and a recirculation flow path 38 connecting the inlet flow path 45 and the outlet flow path 53 are formed inside the compressor housing 3. The inlet flow path 45 communicates with the impeller chamber 36 through the inlet 44, and the outlet flow path 53 communicates with the intake air introduction path 50 through the outlet 52. Therefore, the recirculation flow path 38 communicates with the impeller chamber 36 through the inlet flow path 45 and communicates with the intake air introduction path 50 through the outlet flow path 53. The impeller 2 of the centrifugal compressor 1 is driven to rotate, and a recirculation flow RF is generated due to the pressure difference between the inlet 44 and the outlet 52. The recirculation flow RF is introduced from the impeller chamber 36 into the inlet flow path 45 through the inlet 44, and after flowing through the inlet flow path 45, the recirculation flow path 38, and the outlet flow path 53 in sequence, it flows out to the intake air introduction path 50 through the outlet 52.

[0067] At low flow rates where the intake air flow rate of the centrifugal compressor 1 (the flow rate of the main flow MF flowing into the intake air introduction path 50 through the intake port 31 and flowing to the impeller 2) is small, an unstable phenomenon called surge occurs in which the fluid vibrates violently in the flow direction of the fluid. If surge occurs, a reverse flow flowing forward in the axial direction X, which is the direction opposite to the main flow MF, is generated near the shroud surface 41 of the impeller chamber 36, which may cause a decrease in the efficiency of the centrifugal compressor 1. An inlet flow path 45, a recirculation flow path 38, and an outlet flow path 53 are formed in the compressor housing 3 of the centrifugal compressor 1. In this case, a part of the fluid passing through the impeller chamber 36 passes through the recirculation flow path 38, the intake air introduction path 50, etc. as the recirculation flow RF and returns to the impeller chamber 36 again, which can increase the flow rate of the fluid delivered to the impeller 2, thereby suppressing the occurrence of surge. By suppressing the occurrence of surge at low flow rates, the centrifugal compressor 1 can achieve a high pressure ratio in a wide operating range from low flow rates to high flow rates.

[0068] Figure 4It is an explanatory diagram for explaining the intake air introduction portion of the comparative example. Inside the compressor housing 3A of the comparative example, an inlet flow path 45 including an inlet 44 formed in the shroud surface 41, a recirculation flow path 38A communicating with the inlet flow path 45 and extending forward along the axial direction X to the front side XF, and an outlet flow path 53A communicating with the front side XF of the recirculation flow path 38A and including an outlet 52A opening toward the front side XF are formed. In this case, the recirculation flow RF flowing from the impeller chamber 36 into the recirculation flow path 38A through the inlet flow path 45 flows toward the front side XF in the recirculation flow path 38A, and then, while maintaining its flow direction, flows out to the intake air introduction path 50 through the outlet 52A. The flow direction of the recirculation flow RF flowing out to the intake air introduction path 50 is opposite to the flow direction of the main flow MF flowing toward the rear side XR in the intake air introduction path 50. Therefore, the recirculation flow RF interferes with the main flow MF, and the pressure losses of the main flow MF and the recirculation flow RF increase, which may cause a decrease in the efficiency of the centrifugal compressor 1.

[0069] (Intake air introduction portion)

[0070] As Figure 3 shown, the compressor housing 3 of the centrifugal compressor 1 in some embodiments includes a shroud portion 4 including the above-mentioned shroud surface 41 and an intake air introduction portion 5 including the above-mentioned introduction surface 51. The above-mentioned inlet flow path 45, outlet flow path 53, and recirculation flow path 38 are formed inside the compressor housing 3. The above-mentioned intake air introduction portion 5 includes a front side surface 6 defining the front side XF in the outlet flow path 53, a rear side surface 7 defining the rear side XR in the outlet flow path 53, and a front side introduction surface 8 formed at a position on the above-mentioned introduction surface 51 closer to the front side XF than the outlet 52 in the sectional view along the axis CA of the impeller 2 as Figure 3 shown. The front side surface 6, the rear side surface 7, and the front side introduction surface 8 are each inclined toward the rear side XR from the outside in the radial direction Y toward the inside. In other words, the front side surface 6, the rear side surface 7, and the front side introduction surface 8 each have a shorter distance from the axis CA as they face the rear side XR. At least a part of the rear side surface 7 has a convex curved surface portion 71 formed in a convex curved surface shape. At least a part of the front side introduction surface 8 has an introduction surface side convex curved surface portion 81 formed in a convex curved surface shape.

[0071] In the illustrated embodiment, as Figure 2 shown, the recirculation flow path 38 is formed in a ring shape. It should be noted that the recirculation flow path 38 may also be formed in a shape other than a ring shape. In the illustrated embodiment, as Figure 3As shown, the intake introduction portion 5 further includes a rear-side introduction surface 9 formed at a position on the introduction surface 51 that is rearward of the flow outlet 52 at the rear-side XR. The rear-side introduction surface 9 is located at a position rearward of the rear-side surface 7 at the rear-side XR, and its front-side end 91 is smoothly connected to the rear-side end 72 of the rear-side surface 7 without a step. In addition, the rear-side introduction surface 9 is located at a position forward of the shroud surface 41 at the front-side XF, and its rear-side end 92 is smoothly connected to the front-side end 46 of the shroud surface 41 without a step.

[0072] According to the above structure, since the front-side surface 6 and the rear-side surface 7 that define the outlet flow path 53 are inclined rearwardly toward the inside from the outside in the radial direction Y, the outlet flow path 53 can turn the recirculation flow RF passing through the outlet flow path 53 in such a way that the velocity component toward the rear-side XR in the axial direction X increases and the velocity component toward the inside in the radial direction Y decreases. The recirculation flow RF flows toward the front-side XF in the axial direction X when passing through the recirculation flow path 38. The flow direction of the recirculation flow RF is changed to a direction toward the inside in the radial direction Y and the rear-side XR through the outlet flow path 53.

[0073] In addition, since at least a part of the rear-side surface 7 has a convex curved surface portion 71 formed in a convex curved surface shape, an inhalation effect of the recirculation flow RF due to the Coanda effect can be generated. Thereby, peeling of the recirculation flow RF flowing out to the intake introduction path 50 from the rear-side surface 7 can be suppressed, and thus turning of the recirculation flow RF at the outlet flow path 53 can be effectively performed.

[0074] By increasing the velocity component of the recirculation flow RF flowing out to the intake introduction path 50 toward the rear-side XR in the axial direction by using the above turning of the recirculation flow RF, generation of a countercurrent near the shroud surface 41 can be suppressed. And by decreasing the velocity component of the recirculation flow RF flowing out to the intake introduction path 50 toward the inside in the radial direction Y by using the above turning of the recirculation flow RF, interference between the main flow MF flowing toward the rear-side XR in the intake introduction path 50 and the recirculation flow RF flowing out to the intake introduction path 50 can be suppressed, and further pressure loss of the main flow MF and the recirculation flow RF can be reduced. Thus, according to the above structure, generation of pressure loss of the fluid in the compressor housing 3 can be suppressed and the efficiency of the centrifugal compressor 1 can be improved.

[0075] In addition, according to the above structure, the front-side introduction surface 8 is inclined rearwardly toward the inside from the outside in the radial direction Y and has an introduction surface-side convex curved surface portion 81 formed in a convex curved surface shape at least in a part. In this case, pressure loss caused by collision of the main flow MF flowing toward the rear-side XR in the intake introduction path 50 with the front-side introduction surface 8 can be suppressed.

[0076] In some embodiments, as Figure 3As shown, the above-mentioned front side surface 6 has a concave curved surface portion 61 formed in at least a part thereof. It should be noted that in the illustrated embodiment, the concave curved surface portion 61 is formed at a position of the front side surface 6 including the rear end side (the front side edge of the outflow port 52), and the convex curved surface portion 81 on the introduction surface side is formed at a position of the front side introduction surface 8 including the rear end side 82 (the front side edge of the outflow port 52). The rear end side of the concave curved surface portion 61 is connected to the rear end side of the convex curved surface portion 81 on the introduction surface side.

[0077] According to the above structure, since the recirculation flow RF passing through the outlet flow path 53 is guided by the concave curved surface portion 61, the turning at the outlet flow path 53 of the recirculation flow RF can be effectively performed. Thus, the inclination angle of the flow direction of the recirculation flow RF with respect to the flow direction of the main flow MF flowing toward the rear side XR along the axial direction X in the cross section can be made gentle along the axis CA. By making this inclination angle gentle, the interference between the main flow MF and the recirculation flow RF can be suppressed. Thus, the generation of the countercurrent near the shroud surface 41 can be effectively suppressed, and the pressure losses of the main flow MF and the recirculation flow RF caused by the interference between the main flow MF and the recirculation flow RF can be effectively suppressed.

[0078] Figure 5 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction portion of an embodiment. Figure 6 、 Figure 7 They are respectively explanatory diagrams for explaining the vicinity of the outlet flow path of the intake air introduction portion of a comparative example.

[0079] In some embodiments, as Figure 5 shown, the convex curved surface portion 71 of the above-mentioned rear side surface 7 is formed at a position of the rear side surface 7 including at least the rear end side 72. It should be noted that in the illustrated embodiment, the convex curved surface portion 71 of the rear side surface 7 is formed from the front end side 73 of the rear side surface 7 to the rear end side 72. The tangential direction of the convex curved surface portion 71 at the rear end side 72 is consistent with the extending direction of the rear side introduction surface 9 formed at a position on the introduction surface 51 that is more rearward than the outflow port 52 on the rear side XR. In Figure 5In this case, the tangent line of the convex curved surface portion 71 of the rear side end 72 is set as S1. The rear side introduction surface 9 extends along the axial direction X, which is the extending direction of the tangent line S1. In this situation, the convex curved surface portion 71 of the rear side surface 7 and the rear side introduction surface 9 can be smoothly connected without a step. Thus, the recirculation flow RF flowing along the convex curved surface portion 71 in the outlet flow path 53 can directly flow along the rear side introduction surface 9, and therefore, the turning of the recirculation flow RF at the outlet flow path 53 can be effectively performed. That is, the inclination angle of the flow direction of the recirculation flow RF with respect to the flow direction of the main flow MF flowing along the axial direction X toward the rear side XR in the cross section along the axis CA can be made gentle. In addition, by making the recirculation flow RF flow along the rear side introduction surface 9, the generation of a countercurrent near the shroud surface 41 can be effectively suppressed.

[0080] In the case where it is assumed that Figure 6 as shown, the tangent direction of the convex curved surface portion 71 passing through the rear side end 72 intersects with the extending direction of the rear side introduction surface 9, the recirculation flow RF flowing along the convex curved surface portion 71 in the outlet flow path 53 peels off from the rear side introduction surface 9. Thus, the recirculation flow RF flowing out to the intake introduction path 50 flows at a position radially Y inward of the space (peeling space) PS facing the rear side introduction surface 9 in the intake introduction path 50. Therefore, the degree of interference between the recirculation flow RF and the main flow MF becomes larger, and the possibility of an increase in the pressure losses of the main flow MF and the recirculation flow RF caused by the interference between the main flow MF and the recirculation flow RF increases. Also, the possibility of generating a countercurrent in the above peeling space PS and near the shroud surface 41 increases.

[0081] For example, as Figure 5 shown, the radius of curvature of the convex curved surface portion 71 in the rear side surface 7 is defined as R1, the radius of curvature of the concave curved surface portion 61 in the front side surface 6 is defined as R2, and the radius of curvature of the introduction surface side convex curved surface portion 81 in the front side introduction surface 8 is defined as R3.

[0082] In some embodiments, as Figure 5 shown, the above compressor housing 3 satisfies the relationship of R3 > R1. According to the above structure, by making the radius of curvature R1 of the convex curved surface portion 71 of the rear side surface 7 smaller than the radius of curvature R3 of the introduction surface side convex curved surface portion 81, the turning of the recirculation flow RF at the outlet flow path 53 can be effectively performed. That is, the inclination angle of the flow direction of the recirculation flow RF in the cross section along the axis CA with respect to the flow direction of the main flow MF flowing along the axial direction X toward the rear side XR can be made gentle. Thus, the generation of a countercurrent near the shroud surface 41 can be effectively suppressed, and the pressure losses of the main flow MF and the recirculation flow RF caused by the interference between the main flow MF and the recirculation flow RF can be effectively suppressed.

[0083] If it is assumed that Figure 6As shown, when the radius of curvature R1 of the convex curved surface portion 71 of the rear side surface 7 is equal to or greater than the radius of curvature R3 of the convex curved surface portion 81 on the introduction surface side, the degree of turning at the outlet flow path 53 of the recirculation flow RF is small. That is, the inclination angle of the flow direction of the recirculation flow RF along the axis CA with respect to the flow direction of the main flow MF flowing toward the rear side XR along the axial direction X in the cross section becomes steep. In this case, the degree of interference between the recirculation flow RF and the main flow MF increases, and the possibility of an increase in the pressure losses of the main flow MF and the recirculation flow RF due to the interference between the main flow MF and the recirculation flow RF increases. In addition, the possibility of a countercurrent occurring near the peeling space PS and the shield surface 41 increases.

[0084] In some embodiments, as Figure 5 shown, the compressor housing 3 described above satisfies the relationship R2 > R1. Assuming that the compressor housing 3 satisfies the relationship R2 ≤ R1 as Figure 7 shown, the inlet side flow path area on the side of the outlet flow path 53 opposite to the flow outlet 52 decreases sharply, and thus the pressure loss of the recirculation flow RF when passing through the outlet flow path 53 may increase. According to the above structure, by making the radius of curvature R2 of the concave curved surface portion 61 of the front side surface 6 larger than the radius of curvature R1 of the convex curved surface portion 71 of the rear side surface 7, the sharp reduction in the flow path area on the inlet side of the outlet flow path 53 can be alleviated, and thus the pressure loss of the recirculation flow RF passing through the outlet flow path 53 can be reduced.

[0085] In some embodiments, as Figure 5 shown, the compressor housing 3 described above satisfies the relationship R3 > R2 > R1. According to the above structure, by making the radius of curvature R3 of the convex curved surface portion 81 on the introduction surface side larger than the radius of curvature R1 of the convex curved surface portion 71 of the rear side surface 7, the interference when the main flow MF flowing in the intake introduction path 50 and the recirculation flow RF flowing out from the outlet flow path 53 into the intake introduction path 50 converge can be suppressed. Thereby, the pressure losses of the main flow MF and the recirculation flow RF can be reduced. In addition, by making the radius of curvature R2 of the concave curved surface portion 61 of the front side surface 6 larger than the radius of curvature R1 of the convex curved surface portion 71 of the rear side surface 7, the sharp reduction in the flow path area on the inlet side of the outlet flow path 53 can be alleviated, and thus the pressure loss of the recirculation flow RF passing through the outlet flow path 53 can be reduced. Thereby, according to the above structure, the main flow MF and the recirculation flow RF with low pressure losses in the intake introduction path 50 and the outlet flow path 53 can be delivered to the impeller 2, and thus the efficiency of the centrifugal compressor 1 can be effectively improved.

[0086] Figure 8 is an explanatory diagram for explaining an intake introduction portion of an embodiment.

[0087] In some embodiments, in Figure 8In the cross-section along the axis CA of the impeller 2 as shown, when the flow path width at the inlet 44 of the above-mentioned inlet flow path 45 is defined as t1 and the flow path width at the outlet 52 of the above-mentioned outlet flow path 53 is defined as t2, the relationship of t1 > t2 is satisfied. In this case, by making the flow path width t2 at the outlet 52 of the outlet flow path 53 larger than the flow path width t1 at the inlet 44 of the inlet flow path 45, the flow velocity of the recirculation flow RF passing through the outlet 52 of the outlet flow path 53 can be increased. By increasing the flow velocity of the recirculation flow RF introduced into the intake air introduction path 50, the inhibitory effect of the recirculation flow RF flowing backward near the shroud surface 41 can be increased.

[0088] Figure 9 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction part of an embodiment.

[0089] In some embodiments, the flow path width t of the above-mentioned outlet flow path 53 is as Figure 8 shown and is formed to be the same throughout the entire outlet flow path 53, that is, from the inlet side of the outlet flow path 53 to the outlet 52, or as Figure 9 shown and is formed to gradually decrease toward the outlet 52. In the Figure 9 embodiment shown, the flow path width t21 at the inlet side of the outlet flow path 53, that is, at the connection position of the outlet flow path 53 formed at the position including the front end 73 of the rear side surface 7 and the recirculation flow path 38, becomes the largest among the flow path widths t. In addition, the flow path width t2 at the outlet side of the outlet flow path 53, that is, at the outlet 52, becomes the smallest among the flow path widths t.

[0090] According to the above structure, by forming the flow path width t of the outlet flow path 53 to be the same throughout the entire outlet flow path 53 or to gradually decrease toward the outlet 52, the flow velocity of the recirculation flow RF passing through the outlet 52 of the outlet flow path 53 can be increased. By increasing the flow velocity of the recirculation flow RF introduced into the intake air introduction path 50, the inhibitory effect of the recirculation flow RF flowing backward near the shroud surface 41 can be increased. In addition, by forming the flow path width t of the outlet flow path 53 to be the same throughout the entire outlet flow path 53 or to gradually decrease toward the outlet 52, a sharp reduction in the flow path area on the inlet side of the outlet flow path 53 can be suppressed. Thereby, the pressure loss of the recirculation flow RF passing through the outlet flow path 53 can be suppressed.

[0091] In some embodiments, as Figure 9As shown, when the flow path length of the outlet flow path 53 is set to L1, the condition L1≥0 is satisfied. It should be noted that the flow path length L1 of the outlet flow path 53 is the length from the connection position of the outlet flow path 53 and the recirculation flow path 38 to the flow outlet 52. In this case, the length of the outlet flow path 53 can be made sufficiently large, so that the curved surface portions (for example, the convex curved surface portion 71 of the rear side surface 7 and the concave curved surface portion 61 of the front side surface 6) formed on the wall surface defining the outlet flow path 53 can be lengthened. By lengthening the above-mentioned curved surface portions, the turning of the recirculation flow RF can be promoted. In addition, a sharp reduction in the flow path area of the outlet flow path 53 can be suppressed, and further, the pressure loss of the recirculation flow RF passing through the outlet flow path 53 can be suppressed.

[0092] Figure 10 It is an explanatory diagram for explaining the vicinity of the outlet flow path of the intake air introduction portion of an embodiment. Figure 11 It is for Figure 10 an explanatory diagram for explaining the rear side surface shown.

[0093] In some embodiments, as Figures 9 to 11 shown, the rear end 82 on the rear side of the front side introduction surface 8 is located on the front side XF with respect to the front end 73 on the front side of the rear side surface 7. In this case, the length L1 of the outlet flow path 53 can be made sufficiently large, so that the curved surface portions (for example, the convex curved surface portion 71 of the rear side surface 7 and the concave curved surface portion 61 of the front side surface 6) formed on the wall surface defining the outlet flow path 53 can be lengthened. By lengthening the above-mentioned curved surface portions, the turning of the recirculation flow RF can be promoted.

[0094] As Figure 10 shown, the distance between the rear end 72 on the rear side of the rear side surface 7 and the axis CA of the impeller 2 is defined as d1, the distance between the front end 73 on the front side of the rear side surface 7 and the axis CA of the impeller 2 is defined as d2, and the distance between the rear end 82 on the rear side of the front side introduction surface 8 and the axis CA of the impeller 2 is defined as d3.

[0095] In some embodiments, as Figure 10 shown, the compressor housing 3 of the above satisfies the relationship d3>d1. According to the above structure, the distance d3 between the rear end 82 on the rear side of the front side introduction surface 8 and the axis CA is larger than the distance d1 between the rear end 72 on the rear side of the rear side surface 7 and the axis CA. In this case, the recirculation flow RF returns to the portion (area reduction portion) where the flow path area in the intake air introduction path 50 is reduced, so that the mixing of the recirculation flow RF and the main flow MF is promoted, and the uniformization of the velocity distribution of the fluid introduced into the impeller 2 can be achieved. Thereby, the generation of surging and the generation of reverse flow near the shroud surface 41 can be suppressed.

[0096] In some embodiments, as Figure 10As shown, the above-mentioned compressor housing 3 satisfies the relationship d3 ≤ d2. According to the above structure, the distance d2 from the front-side end 73 of the rear-side surface 7 to the axis CA is the same as or greater than the distance d3 from the rear-side end 82 of the front-side introduction surface 8 to the axis CA. In this case, it is possible to prevent the main flow MF flowing toward the rear side XR in the intake introduction passage 50 from facing the recirculation flow RF flowing out into the intake introduction passage 50. As a result, the interference between the main flow MF and the recirculation flow RF can be suppressed, and furthermore, the pressure losses of the main flow MF and the recirculation flow RF can be reduced.

[0097] In some embodiments, as Figure 10 shown, the above-mentioned compressor housing 3 satisfies the relationship d1 < d3 ≤ d2. According to the above structure, the distance d2 is the same as or greater than the distance d3. In this case, it is possible to prevent the main flow MF flowing toward the rear side XR in the intake introduction passage 50 from facing the recirculation flow RF flowing out into the intake introduction passage 50. As a result, the interference between the main flow MF and the recirculation flow RF can be suppressed, and furthermore, the pressure losses of the main flow MF and the recirculation flow RF can be reduced. In addition, the distance d3 is greater than the distance d1. In this case, the recirculation flow RF returns to the portion where the flow path area in the intake introduction passage 50 is reduced (area reduction portion), so the mixing of the recirculation flow RF and the main flow MF is promoted, and the uniformization of the velocity distribution of the fluid introduced into the impeller 2 can be achieved. As a result, the generation of surges and the generation of backflows near the shroud surface 41 can be suppressed.

[0098] In addition, according to the above structure, the distance d2 is greater than the distance d1. In this case, the rotational speed component of the recirculation flow RF can be reduced when passing through the outlet flow path 53. As a result, the interference between the main flow MF flowing toward the rear side XR in the intake introduction passage 50 and the recirculation flow RF flowing out into the intake introduction passage 50 can be suppressed, and furthermore, the pressure losses of the main flow MF and the recirculation flow RF can be reduced.

[0099] In some embodiments, as Figure 11 shown, the introduction surface side convex curved surface portion 81 of the above-mentioned front-side introduction surface 8 is formed at a position including at least the rear-side end 82 of the front-side introduction surface 8, and the imaginary circular arc VA including the introduction surface side convex curved surface portion 81 is configured to be tangent to the rear-side end 72 of the rear-side surface 7.

[0100] According to the above structure, since the imaginary arc VA including the inlet surface side convex curved surface portion 81 is configured to be tangent to the rear end 72 of the rear side surface 7, the main flow MF flowing along the inlet surface side convex curved surface portion 81 can flow along the rear side inlet surface 9 connected to the rear end 72 of the rear side surface 7. In addition, the recirculation flow RF that has passed through the outflow port 52 along the rear side surface 7 can flow along the rear side inlet surface 9. Thus, the inclination angle of the flow direction of the recirculation flow RF with respect to the flow direction of the main flow MF can be made gentle. By making this inclination angle gentle, the interference between the main flow MF and the recirculation flow RF can be suppressed. By suppressing the interference between the main flow MF and the recirculation flow RF, the pressure losses of the main flow MF and the recirculation flow RF can be effectively suppressed.

[0101] Figure 12 It is an explanatory diagram for explaining an intake air introduction part of an embodiment.

[0102] In some embodiments, as Figure 12 shown, the inner peripheral surface 381 forming the above-mentioned recirculation flow path 38 extends obliquely with respect to the axial direction of the impeller 2 in such a manner that the distance from the connection position 382 with the inlet flow path 45 to the connection position 384 with the outlet flow path 53 increases with respect to the axis CA of the impeller 2. In the illustrated embodiment, the distance between the front end 383 at the connection position 382 of the inner peripheral surface 381 with the inlet flow path 45 and the axis CA of the impeller 2 is defined as d4, and the distance between the rear end 385 at the connection position 384 of the inner peripheral surface 381 with the outlet flow path 53 and the axis CA of the impeller 2 is defined as d5. The above-mentioned distance d5 is larger than the above-mentioned distance d4. In addition, the recirculation flow path 38 is formed in such a manner that the distance between its axis CB and the axis CA of the impeller 2 gradually increases as it moves toward the front side XF.

[0103] According to the above structure, by making the inner peripheral surface 381 forming the recirculation flow path 38 increase the distance from the connection position 382 with the inlet flow path 45 to the connection position 384 with the outlet flow path 53 with respect to the axis CA of the impeller 2, the rotational speed component of the recirculation flow RF flowing in the recirculation flow path 38 can be reduced. By reducing the rotational speed component of the recirculation flow RF, the interference between the main flow MF flowing toward the rear side XR in the intake air introduction path 50 and the recirculation flow RF flowing out to the intake air introduction path 50 can be suppressed, and furthermore, the pressure losses of the main flow MF and the recirculation flow RF can be reduced.

[0104] Figure 13 It is an explanatory diagram for explaining an intake air introduction part of an embodiment.

[0105] In some embodiments, as Figure 13As shown, when the distance between the rear end 82 of the front-side inlet surface 8 and the axial direction of the impeller blade 21 parallel to the impeller 2 is defined as L, and the diameter of the leading edge 25 of the impeller blade 21 is defined as D, the relationship L≤0.5×D is satisfied. It should be noted that in the illustrated embodiment, the minimum length in the axial direction X between the rear end 82 of the front-side inlet surface 8 and the leading edge 25 of the impeller blade 21 is set as the above-mentioned L, and the maximum diameter of the shroud-side end 26 of the leading edge 25 of the impeller blade 21 is set as the above-mentioned D. According to the above structure, the relationship L≤0.5×D is satisfied. In this case, by arranging the outlet 52 of the outlet flow path 53 near the impeller blade 21, the recirculation flow RF can be returned near the leading edge 25 of the impeller blade 21. Thereby, the suppression effect of the countercurrent of the recirculation flow RF near the shroud surface 41 can be increased.

[0106] As Figure 2 shown, the centrifugal compressor 1 of some embodiments includes the above-mentioned compressor housing 3. In this case, by using the compressor housing 3, the generation of pressure loss of the fluid in the compressor housing 3 can be suppressed, and thus the efficiency of the centrifugal compressor 1 can be improved.

[0107] The present disclosure is not limited to the above embodiments, and also includes the solutions obtained by modifying the above embodiments and the solutions obtained by appropriately combining these embodiments.

[0108] The content described in the above-mentioned some embodiments can be understood as follows.

[0109] 1) The compressor housing (3) of at least one embodiment of the present disclosure is a compressor housing (3) for rotatably accommodating the impeller (2) of the centrifugal compressor (1), and includes:

[0110] A shroud portion (4) including a shroud surface (41) facing the front end (23) of the impeller blade (21) of the impeller (2) with a predetermined gap;

[0111] An air inlet portion (5) including an inlet surface (51) formed on the front side of the shroud surface (41) and defining an air inlet passage (50) for guiding the air introduced from the air inlet (31) of the compressor housing (3) toward the impeller blade (21);

[0112] Inside the compressor housing (3), there is formed:

[0113] An inlet flow path (45) including an inlet (44) formed on the shroud surface (41);

[0114] An outlet flow path (53) including an outlet (52) formed on the inlet surface (51);

[0115] A recirculation flow path (38) that connects the inlet flow path (45) and the outlet flow path (53);

[0116] The intake air introduction portion (5) includes, in a cross-section along the axis of the impeller (2):

[0117] A front side surface (6) that defines the front side (XF) in the outlet flow path (53), and is inclined from the outer side in the radial direction (Y) toward the inner side and toward the rear side (XR);

[0118] A rear side surface (7) that defines the rear side (XR) in the outlet flow path (53), is inclined from the outer side in the radial direction (Y) toward the inner side and toward the rear side (XR), and has a convex curved surface portion (71) formed in at least a part thereof;

[0119] A front side introduction surface (8) that is formed at a position on the introduction surface (51) that is more on the front side (XF) than the flow outlet (52), is inclined from the outer side in the radial direction (Y) toward the inner side and toward the rear side (XR), and has an introduction surface side convex curved surface portion (81) formed in at least a part thereof.

[0120] According to the structure of 1) above, since the front side surface (6) and the rear side surface (7) that define the outlet flow path (53) are each inclined from the outer side in the radial direction (Y) toward the inner side and toward the rear side (XR), the outlet flow path (53) can turn the recirculation flow (RF) that has passed through the outlet flow path (53) in such a way that the velocity component toward the rear side (XR) in the axial direction becomes larger and the velocity component toward the inner side in the radial direction becomes smaller. Since the rear side surface (7) has a convex curved surface portion (71) formed in at least a part thereof, an introduction effect of the recirculation flow (RF) due to the Coanda effect can be generated. As a result, peeling of the recirculation flow (RF) flowing out to the intake air introduction path (50) from the rear side surface (7) can be suppressed, and turning of the recirculation flow (RF) at the outlet flow path (53) can be effectively performed.

[0121] By using the turning of the above-mentioned recirculation flow (RF) to make the velocity component of the recirculation flow (RF) flowing out into the intake introduction passage (50) toward the rear side (XR) in the axial direction large, the generation of a countercurrent near the shroud surface (41) can be suppressed. Further, by using the turning of the above-mentioned recirculation flow (RF) to make the velocity component of the recirculation flow (RF) flowing out into the intake introduction passage (50) toward the inner side in the radial direction small, the interference between the main flow (MF) flowing toward the rear side (XF) in the intake introduction passage (50) and the recirculation flow (RF) flowing out into the intake introduction passage (50) can be suppressed, and furthermore, the pressure losses of the main flow (MF) and the recirculation flow (RF) can be reduced. Thus, according to the structure of the above 1), the generation of the pressure loss of the fluid in the compressor housing (3) can be suppressed, and the efficiency of the centrifugal compressor (1) can be improved.

[0122] Further, according to the structure of the above 1), the front-side introduction surface (8) is inclined from the outer side in the radial direction (Y) toward the inner side and toward the rear side (XR), and at least a part thereof has an introduction surface-side convex curved surface portion (81) formed in a convex curved surface shape. In this case, the pressure loss caused by the collision of the main flow (MF) flowing toward the rear side (XR) in the intake introduction passage (50) with the front-side introduction surface (8) can be suppressed.

[0123] 2) In some embodiments, according to the compressor housing (3) described in the above 1),

[0124] At least a part of the front-side surface (6) has a concave curved surface portion (61) formed in a concave curved surface shape.

[0125] According to the structure of the above 2), at least a part of the front-side surface (6) has a concave curved surface portion (61) formed in a concave curved surface shape. In this case, the recirculation flow (RF) passing through the outlet flow path (53) is guided by the concave curved surface portion (61), and thus the turning at the outlet flow path (53) of the recirculation flow (RF) can be effectively performed. Thereby, the generation of a countercurrent near the shroud surface (41) can be effectively suppressed, and the pressure losses of the main flow (MF) and the recirculation flow (RF) caused by the interference between the main flow (MF) and the recirculation flow (RF) can be effectively suppressed.

[0126] 3) In some embodiments, according to the compressor housing (3) described in the above 1) or 2),

[0127] The convex curved surface portion (71) of the rear-side surface (7) is formed at a position including at least the rear-side end (72) of the rear-side surface (7),

[0128] The tangential direction of the convex curved surface portion (71) of the rear side end (72) is identical to the extending direction of the rear side introduction surface (9) formed in the introduction surface (51) at a position on the rear side (XR) with respect to the outflow port (52).

[0129] According to the structure of item 3) above, the tangential direction of the convex curved surface portion (71) of the rear side end (72) is identical to the extending direction of the rear side introduction surface (9) formed in the introduction surface (51) at a position on the rear side (RF) with respect to the outflow port (52). In this case, the convex curved surface portion (71) of the rear side surface (7) and the rear side introduction surface (9) can be smoothly connected without a step. As a result, the recirculation flow (RF) flowing along the convex curved surface portion (71) in the outlet flow path (53) can flow along the rear side introduction surface (9), so that the turning of the recirculation flow (RF) at the outlet flow path (53) can be effectively performed, and the generation of a countercurrent near the shroud surface (41) can be effectively suppressed.

[0130] 4) In some embodiments, the compressor housing (3) according to any one of 1) to 3) above

[0131] When the radius of curvature of the convex curved surface portion (71) in the rear side surface (7) is defined as R1 and the radius of curvature of the introduction surface side convex curved surface portion (81) in the front side introduction surface (8) is defined as R3

[0132] The relationship of R3 > R1 is satisfied.

[0133] According to the structure of item 4) above, by making the radius of curvature R1 of the convex curved surface portion (71) of the rear side surface (7) smaller than the radius of curvature R3 of the introduction surface side convex curved surface portion (81), the turning of the recirculation flow (RF) at the outlet flow path (53) can be effectively performed. As a result, the generation of a countercurrent near the shroud surface (41) can be effectively suppressed, and the pressure losses of the main flow (MF) and the recirculation flow (RF) caused by the interference between the main flow (MF) and the recirculation flow (RF) can be effectively suppressed.

[0134] 5) In some embodiments, the compressor housing (3) according to item 2) above

[0135] When the radius of curvature of the convex curved surface portion (71) in the rear side surface (7) is defined as R1 and the radius of curvature of the concave curved surface portion (61) in the front side surface (6) is defined as R2

[0136] The relationship of R2 > R1 is satisfied.

[0137] According to the structure in 5) above, by making the radius of curvature R2 of the concave curved surface portion (61) of the front side surface (6) larger than the radius of curvature R1 of the convex curved surface portion (71) of the rear side surface (7), it is possible to alleviate the sharp reduction in the flow path area on the inlet side of the outlet flow path (53), and thus it is possible to reduce the pressure loss of the recirculation flow (RF) passing through the outlet flow path (53).

[0138] 6) In some embodiments, according to the compressor housing (3) described in 2) above,

[0139] In the case where the radius of curvature of the convex curved surface portion (71) in the rear side surface (7) is defined as R1, the radius of curvature of the concave curved surface portion (61) in the front side surface (6) is defined as R2, and the radius of curvature of the inlet surface side convex curved surface portion (81) in the front side inlet surface (8) is defined as R3,

[0140] The relationship of R3 > R2 > R1 is satisfied.

[0141] According to the structure in 6) above, by making the radius of curvature R1 of the convex curved surface portion (71) of the rear side surface (7) smaller than the radius of curvature R3 of the inlet surface side convex curved surface portion (81), it is possible to suppress the interference when the main flow (MF) flowing in the intake inlet path (50) merges with the recirculation flow (RF) flowing out from the outlet flow path (53) to the intake inlet path (50). Thereby, it is possible to reduce the pressure loss of the main flow (MF) and the recirculation flow (RF). In addition, by making the radius of curvature R2 of the concave curved surface portion (61) of the front side surface (6) larger than the radius of curvature R1 of the convex curved surface portion (71) of the rear side surface (7), it is possible to alleviate the sharp reduction in the flow path area on the inlet side of the outlet flow path (53), and thus it is possible to reduce the pressure loss of the recirculation flow (RF) passing through the outlet flow path (53). Thus, according to the structure in 6) above, it is possible to convey the main flow (MF) and the recirculation flow (RF) with less pressure loss in the intake inlet path (50) and the outlet flow path (53) to the impeller (2), and thus it is possible to effectively improve the efficiency of the centrifugal compressor (1).

[0142] 7) In some embodiments, according to the compressor housing (3) described in any one of 1) to 6) above,

[0143] In a cross-section along the axis (CA) of the impeller (2),

[0144] In the case where the flow path width at the flow inlet (44) of the inlet flow path (45) is defined as t1 and the flow path width at the flow outlet (52) of the outlet flow path (53) is defined as t2,

[0145] The relationship of t1 > t2 is satisfied.

[0146] According to the structure of the above (7), by making the flow path width t2 at the flow outlet 52 of the outlet flow path 53 larger than the flow path width t1 at the flow inlet 44 of the inlet flow path 45, the flow velocity of the recirculation flow RF passing through the flow outlet 52 of the outlet flow path 53 can be increased. By increasing the flow velocity of the recirculation flow RF introduced into the intake air introduction path 50, the inhibitory effect of the countercurrent of the recirculation flow RF near the shroud surface 41 can be increased.

[0147] 8) In some embodiments, according to the compressor housing 3 described in the above (7),

[0148] The flow path width t of the outlet flow path 53 is formed to be the same throughout the entire outlet flow path 53, or is formed to gradually decrease toward the flow outlet 52.

[0149] According to the structure of the above (8), by forming the flow path width t of the outlet flow path 53 to be the same throughout the entire outlet flow path 53 or to gradually decrease toward the flow outlet 52, the flow velocity of the recirculation flow RF passing through the flow outlet 52 of the outlet flow path 53 can be increased. By increasing the flow velocity of the recirculation flow RF introduced into the intake air introduction path 50, the inhibitory effect of the countercurrent of the recirculation flow RF near the shroud surface 41 can be increased. In addition, by forming the flow path width t of the outlet flow path 53 to be the same throughout the entire outlet flow path 53 or to gradually decrease toward the flow outlet 52, a sharp reduction in the flow path area on the inlet side of the outlet flow path 53 can be suppressed. Thereby, the pressure loss of the recirculation flow RF passing through the outlet flow path 53 can be suppressed.

[0150] 9) In some embodiments, according to the compressor housing 3 described in any one of the above (1) to (8),

[0151] The rear end 82 of the front side introduction surface 8 is located on the front side XF with respect to the front end 73 of the rear side surface 7.

[0152] According to the structure of the above (9), the rear end 82 of the front side introduction surface 8 is located on the front side XF with respect to the front side surface 73 of the rear side surface 7. In this case, the length of the outlet flow path 53 can be made sufficiently large, so that the curved surface portion (for example, the convex curved surface portion 71 of the rear side surface 7, etc.) forming the wall surface of the outlet flow path 53 can be lengthened. By lengthening the above-mentioned curved surface portion, the turning of the recirculation flow RF can be promoted.

[0153] 10) In some embodiments, for the compressor housing (3) according to any one of the above 1) to 9),

[0154] When the distance between the rear end (72) of the rear side surface (7) and the axis (CA) of the impeller (2) is defined as d1, and the distance between the rear end (82) of the front side inlet surface (8) and the axis (CA) of the impeller (2) is defined as d3,

[0155] The relationship d3 > d1 is satisfied.

[0156] According to the structure of the above 10), the distance d3 between the rear end (82) of the front side inlet surface (8) and the axis (CA) is larger than the distance d1 between the rear end (72) of the rear side surface (7) and the axis (CA). In this case, the recirculation flow (RF) returns to the part (area reduction part) where the flow path area in the intake inlet passage (50) is reduced, so the mixing of the recirculation flow (RF) and the main flow (MF) is promoted, and the uniformization of the velocity distribution of the fluid introduced into the impeller (2) can be achieved. Thereby, the generation of surging and the generation of backflow near the shroud surface (41) can be suppressed.

[0157] 11) In some embodiments, for the compressor housing (3) according to any one of the above 1) to 10),

[0158] When the distance between the front end (73) of the rear side surface (7) and the axis (CA) of the impeller (2) is defined as d2, and the distance between the rear end (82) of the front side inlet surface (8) and the axis (CA) of the impeller (2) is defined as d3,

[0159] The relationship d3 ≤ d2 is satisfied.

[0160] According to the structure of the above 11), the distance d2 between the front end (73) of the rear side surface (7) and the axis (CA) is the same as or larger than the distance d3 between the rear end (83) of the front side inlet surface (8) and the axis (CA). In this case, it is possible to prevent the main flow (MF) flowing toward the rear side (XR) in the intake inlet passage (50) and the recirculation flow (RF) flowing out to the intake inlet passage (50) from facing each other. Thereby, the interference between the main flow (MF) and the recirculation flow (RF) can be suppressed, and furthermore, the pressure losses of the main flow (MF) and the recirculation flow (RF) can be reduced.

[0161] 12) In some embodiments, for the compressor housing (3) according to any one of the above 1) to 11),

[0162] When the distance between the rear end (72) of the rear side surface (7) and the axis (CA) of the impeller (2) is defined as d1, the distance between the front end (73) of the rear side surface (7) and the axis (CA) of the impeller (2) is defined as d2, and the distance between the rear end (82) of the front side inlet surface (8) and the axis (CA) of the impeller (2) is defined as d3,

[0163] the relationship of d1 < d3 ≤ d2 is satisfied.

[0164] According to the structure of the above 12), the above distance d2 is the same as or larger than the above distance d3. In this case, it is possible to prevent the main flow (MF) flowing toward the rear side (XR) in the intake passage (50) from facing the recirculation flow (RF) flowing out into the intake passage (50). Thereby, the interference between the main flow (MF) and the recirculation flow (RF) can be suppressed, and further the pressure losses of the main flow (MF) and the recirculation flow (RF) can be reduced. In addition, the above distance d3 is larger than the above distance d1. In this case, the recirculation flow (RF) returns to the part where the flow path area in the intake passage (50) is reduced (area reduction part), so the mixing of the recirculation flow (RF) and the main flow (MF) is promoted, and the uniformization of the velocity distribution of the fluid introduced into the impeller (2) can be achieved. Thereby, the generation of surging and the generation of reverse flow near the shroud surface (41) can be suppressed.

[0165] In addition, according to the structure of the above 12), the above distance d2 is larger than the above distance d1. In this case, the rotational speed component of the recirculation flow (RF) can be reduced when passing through the outlet flow path (53). Thereby, the interference between the main flow (MF) flowing toward the rear side (XR) in the intake passage (50) and the recirculation flow (RF) flowing out into the intake passage (50) can be suppressed, and further the pressure losses of the main flow (MF) and the recirculation flow (RF) can be reduced.

[0166] 13) In some embodiments, according to the compressor housing (3) described in the above 10) or 12),

[0167] the convex curved surface portion (81) on the inlet surface side of the front side inlet surface (8) is formed at a position including at least the rear end (82) of the front side inlet surface (8),

[0168] The imaginary circular arc (VA) including the convex curved surface portion (81) on the inlet surface side is configured to be tangent to the rear end (72) of the rear side surface (7).

[0169] According to the structure of the above item 13), since the imaginary arc (VA) including the convex curved surface portion (81) on the inlet surface side is configured to be tangent to the rear end (72) on the rear side of the rear side surface (7), the main flow (MF) flowing along the convex curved surface portion (81) on the inlet surface side can flow along the rear side inlet surface (9) connected to the rear end (72) on the rear side of the rear side surface (7). In addition, the recirculation flow (RF) that has passed through the flow outlet (52) along the rear side surface (7) can flow along the rear side inlet surface (9). Thus, the inclination angle of the flow direction of the recirculation flow (RF) with respect to the flow direction of the main flow (MF) can be made gentle. By making this inclination angle gentle, the interference between the main flow (MF) and the recirculation flow (RF) can be suppressed. By suppressing the interference between the main flow (MF) and the recirculation flow (RF), the pressure losses of the main flow (MF) and the recirculation flow (RF) can be effectively suppressed.

[0170] 14) In some embodiments, the compressor housing (3) according to any one of the above items 10) to 13),

[0171] The inner peripheral surface (381) forming the recirculation flow path (38) extends axially with respect to the impeller (2) in such a manner that the distance from the connection position (382) with the inlet flow path (45) to the connection position (384) with the outlet flow path (53) becomes larger with respect to the axis (CA) of the impeller (2).

[0172] According to the structure of the above item 14), by making the inner peripheral surface (381) forming the recirculation flow path (38) have a larger distance from the connection position (382) with the inlet flow path (45) to the connection position (384) with the outlet flow path (53) with respect to the axis (CA) of the impeller (2), the rotational speed component of the recirculation flow (RF) flowing in the recirculation flow path (38) can be reduced. By reducing the rotational speed component of the recirculation flow (RF), the interference between the main flow (MF) flowing rearward (XR) in the intake introduction path (50) and the recirculation flow (RF) flowing out into the intake introduction path (50) can be suppressed, and further, the pressure losses of the main flow (MF) and the recirculation flow (RF) can be reduced.

[0173] 15) In some embodiments, the compressor housing (3) according to any one of the above items 1) to 14),

[0174] When the distance parallel to the axis of the impeller (2) between the rear end (82) of the front side inlet surface (8) and the impeller blade (21) is defined as L, and the diameter of the leading edge (25) of the impeller blade (21) is defined as D,

[0175] The relationship of L≤0.5×D is satisfied.

[0176] According to the structure of the above item 15), the relationship of L≤0.5×D is satisfied. In this case, by disposing the flow outlet (52) of the outlet flow path (53) near the impeller blade (21), the recirculation flow (RF) can be returned near the leading edge (25) of the impeller blade (21). Thereby, the suppression effect of the countercurrent of the recirculation flow (RF) near the shroud surface (41) can be increased.

[0177] 16) The centrifugal compressor (1) according to at least one embodiment of the present disclosure includes the compressor housing (3) described in any one of the above items 1) to 15).

[0178] According to the structure of the above item 16), by using the above compressor housing (3), the generation of the pressure loss of the fluid in the compressor housing (3) can be suppressed, and thus the efficiency of the centrifugal compressor (1) can be improved.

[0179] Description of Reference Numerals

[0180] 1 Centrifugal compressor;

[0181] 2 Impeller;

[0182] 3 Compressor housing;

[0183] 4 Shroud portion;

[0184] 5 Intake introduction portion;

[0185] 6 Front side;

[0186] 7 Rear side;

[0187] 8 Front side introduction surface;

[0188] 9 Rear side introduction surface;

[0189] 10 Turbocharger;

[0190] 11 Turbine;

[0191] 12 Rotating shaft;

[0192] 13 Turbine rotor;

[0193] 14 Turbine housing;

[0194] 15 Bearing;

[0195] 16 Bearing housing;

[0196] 21 Impeller blade;

[0197] 22 Front end;

[0198] 23 Hub;

[0199] 24 Outer surface;

[0200] 25 Leading edge;

[0201] 26 Shroud side end;

[0202] 31 Intake port;

[0203] 32 Discharge port;

[0204] 33 Vortex part;

[0205] 34 Vortex flow path;

[0206] 35 Inner peripheral surface;

[0207] 36 Impeller chamber;

[0208] 37 Diffusion flow path;

[0209] 38 Recirculation flow path;

[0210] 41 Shroud surface;

[0211] 42 Shroud side flow surface;

[0212] 43 Rear side end;

[0213] 44 Inlet;

[0214] 45 Inlet flow path;

[0215] 46 Front side end;

[0216] 50 Intake introduction path;

[0217] 51 Introduction surface;

[0218] 52 Discharge port;

[0219] 53 Outlet flow path;

[0220] 61 Concave curved surface part;

[0221] 71 Convex curved surface part;

[0222] 81 Introduction surface side convex curved surface part;

[0223] 82 Rear side end;

[0224] 141 Exhaust gas inlet;

[0225] 142 Exhaust gas outlet;

[0226] 161 Impeller chamber forming surface;

[0227] 162 Hub side flow surface;

[0228] CA Axis of the impeller;

[0229] Axis of the CB recirculation flow path;

[0230] MF Main flow;

[0231] PS Peeling space;

[0232] R1, R2, R3 Radius of curvature;

[0233] RF Recirculation flow;

[0234] S1 Tangent line;

[0235] VA Imaginary circular arc;

[0236] X Axial direction;

[0237] XF Front side (in the axial direction);

[0238] XR Rear side (in the axial direction);

[0239] Y Radial direction.

Claims

1. A compressor housing for accommodating an impeller of a centrifugal compressor in a rotatable manner, characterized in that, Comprising: A shroud portion including a shroud surface that faces the front end of the impeller blades of the impeller with a predetermined clearance; An intake introduction portion including an introduction surface that is formed on the front side of the shroud surface and defines an intake introduction path for guiding the intake air introduced from the intake port of the compressor housing toward the impeller blades; Inside the compressor housing, there are formed: An inlet flow path including an inlet formed in the shroud surface; An outlet flow path including an outlet formed in the introduction surface; A recirculation flow path that connects the inlet flow path and the outlet flow path; In a cross-section along the axis of the impeller, the intake introduction portion includes: A front side surface that defines the front side in the outlet flow path and is inclined rearward from the outer side in the radial direction toward the inner side; A rear side surface that defines the rear side in the outlet flow path, is inclined rearward from the outer side in the radial direction toward the inner side, and has a convex curved surface portion formed as a convex curved surface at least in part; A front side introduction surface that is formed on the front side of the introduction surface relative to the outlet, is inclined rearward from the outer side in the radial direction toward the inner side, and has an introduction surface side convex curved surface portion formed as a convex curved surface at least in part, The rear end on the rear side of the front side introduction surface is located on the front side of the front end on the front side of the rear side surface.

2. A compressor housing for rotatably accommodating an impeller of a centrifugal compressor, characterized in that, Comprising: A shroud portion including a shroud surface that faces the front end of the impeller blades of the impeller with a predetermined clearance; An intake introduction portion including an introduction surface that is formed on the front side of the shroud surface and defines an intake introduction path for guiding the intake air introduced from the intake port of the compressor housing toward the impeller blades; Inside the compressor housing, there are formed: An inlet flow path including an inlet formed in the shroud surface; An outlet flow path including an outlet formed in the introduction surface; A recirculation flow path that connects the inlet flow path and the outlet flow path; In a cross-section along the axis of the impeller, the intake introduction portion includes: A front side surface that defines the front side in the outlet flow path and is inclined rearward from the outer side in the radial direction toward the inner side; A rear side surface that defines the rear side in the outlet flow path, is inclined rearward from the outer side in the radial direction toward the inner side, and has a convex curved surface portion formed as a convex curved surface at least in part; A front side introduction surface that is formed on the front side of the introduction surface relative to the outlet, is inclined rearward from the outer side in the radial direction toward the inner side, and has an introduction surface side convex curved surface portion formed as a convex curved surface at least in part; When the distance between the rear end on the rear side of the rear side surface and the axis of the impeller is defined as d1, and the distance between the rear end on the rear side of the front side introduction surface and the axis of the impeller is defined as d3, The relationship d3 > d1 is satisfied.

3. A compressor housing for accommodating an impeller of a centrifugal compressor in a rotatable manner, characterized in that, Comprising: A shroud portion including a shroud surface that faces the front end of the impeller blades of the impeller with a predetermined clearance; An intake introduction part, which includes an introduction surface formed on the front side of the shroud surface and defining an intake introduction path for guiding the intake air introduced from the intake port of the compressor housing toward the impeller blades; Inside the compressor housing, there is formed: An inlet flow path, which includes an inlet formed on the shroud surface; An outlet flow path, which includes an outlet formed on the introduction surface; A recirculation flow path, which connects the inlet flow path and the outlet flow path; In a cross-section along the axis of the impeller, the intake introduction part includes: A front side surface, which defines the front side in the outlet flow path and is inclined rearward from the outer side in the radial direction toward the inner side; A rear side surface, which defines the rear side in the outlet flow path, is inclined rearward from the outer side in the radial direction toward the inner side, and has a convex curved surface part formed in at least a part thereof; A front side introduction surface, which is formed on the front side of the introduction surface closer to the front than the outlet, is inclined rearward from the outer side in the radial direction toward the inner side, and has an introduction surface side convex curved surface part formed in at least a part thereof; When the distance between the rear end of the rear side surface and the axis of the impeller is defined as d1, the distance between the front end of the rear side surface and the axis of the impeller is defined as d2, and the distance between the rear end of the front side introduction surface and the axis of the impeller is defined as d3, The relationship of d1 < d3 ≤ d2 is satisfied.

4. The compressor housing according to any one of claims 1 to 3, The front side surface has a concave curved surface part formed in at least a part thereof.

5. The compressor housing according to any one of claims 1 to 3, The convex curved surface part of the rear side surface is formed at a position including at least the rear end of the rear side surface, The tangential direction of the convex curved surface part passing through the rear end is consistent with the extending direction of the rear side introduction surface formed on the rear side of the outlet in the introduction surface.

6. The compressor housing according to any one of claims 1 to 3, When the radius of curvature of the convex curved surface part in the rear side surface is defined as R1 and the radius of curvature of the introduction surface side convex curved surface part in the front side introduction surface is defined as R3, The relationship of R3 > R1 is satisfied.

7. The compressor housing according to claim 4, When the radius of curvature of the convex curved surface part in the rear side surface is defined as R1 and the radius of curvature of the concave curved surface part in the front side surface is defined as R2, The relationship of R2 > R1 is satisfied.

8. The compressor housing according to claim 4, When the radius of curvature of the convex curved surface part in the rear side surface is defined as R1, the radius of curvature of the concave curved surface part in the front side surface is defined as R2, and the radius of curvature of the introduction surface side convex curved surface part in the front side introduction surface is defined as R3, The relationship of R3 > R2 > R1 is satisfied.

9. The compressor housing according to any one of claims 1 to 3, In a cross-section along the axis of the impeller, When the flow path width at the flow inlet of the inlet flow path is defined as t1 and the flow path width at the flow outlet of the outlet flow path is defined as t2, the relationship of t1 > t2 is satisfied.

10. The compressor housing according to claim 9, the flow path width of the outlet flow path is formed to be the same throughout the entire outlet flow path or is formed to gradually decrease toward the flow outlet.

11. The compressor housing according to any one of claims 1 to 3, when the distance between the front end of the rear side surface and the axis of the impeller is defined as d2 and the distance between the rear end of the front side inlet surface and the axis of the impeller is defined as d3, the relationship of d3 ≤ d2 is satisfied.

12. The compressor housing according to claim 2 or 3, the inlet surface side convex curved surface portion of the front side inlet surface is formed at a position including at least the rear end of the front side inlet surface, the imaginary circular arc including the inlet surface side convex curved surface portion is configured to be tangent to the rear end of the rear side surface.

13. The compressor housing according to claim 2 or 3, the inner peripheral surface forming the recirculation flow path extends axially inclined with respect to the axis of the impeller in such a manner that the distance from the connection position with the inlet flow path to the connection position with the outlet flow path increases.

14. The compressor housing according to any one of claims 1 to 3, when the distance between the rear end of the front side inlet surface and the axial parallel distance of the impeller blade with respect to the impeller is defined as L and the diameter of the leading edge of the impeller blade is defined as D, the relationship of L ≤ 0.5×D is satisfied.

15. A centrifugal compressor comprising the compressor housing according to any one of claims 1 to 14.

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