Oblique flow compressor and turbocharger

Abstract

This oblique flow compressor comprises an impeller and a casing that rotatably accommodates the impeller. The impeller includes: a hub having a surface including an inclined surface; and a plurality of blades provided on the surface of the hub. The casing includes a shroud part having a shroud surface facing the impeller via a gap in a radial direction. When a leading-edge position of the blade at a dimensionless meridional plane length position of a hub-side end of the blade is defined as 0% and a trailing-edge position of the blade is defined as 100%, a flow passage height, which is a length extending in a vertical direction from the surface of the hub to the shroud surface, is maximum in a portion on the leading-edge position side of a throat position + 10% of a tip-side end of the blade at the dimensionless meridional plane length position, and excluding the leading-edge position.

Description

Mixed flow compressor and turbocharger

[0001] The present disclosure relates to a mixed flow compressor and a turbocharger.

[0002] Conventionally, as a technology for improving the output of engines (internal combustion engines) such as automobile engines, turbochargers (superchargers) have been widely used, which compress the intake air drawn into the engine, increasing its density and supplying the engine with intake air that contains a lot of oxygen (see, for example, Patent Document 1).

[0003] A turbocharger, for example, comprises a mixed-flow compressor (centrifugal compressor) mounted on one side of a rotating shaft and a turbine mounted on the other side of the rotating shaft. The turbine rotor is rotated by the energy of exhaust gas sent from the engine, which rotates the impeller of the mixed-flow compressor, which rotates in conjunction with the rotation of the turbine rotor, thereby compressing the intake air and supplying it to the engine.

[0004] WO 2023 / 248534

[0005] According to the inventor's new findings, when the impeller of a mixed-flow compressor rotates at a relatively high speed, shock waves are generated near the throat on the suction surface side of the impeller blades, and an adverse pressure gradient caused by the shock waves may create a low-speed region downstream in the fluid flow direction. The occurrence of this low-speed region may cause pressure loss in the mixed-flow compressor, potentially reducing the efficiency of the mixed-flow compressor and a turbocharger equipped with the mixed-flow compressor. However, Patent Document 1 does not disclose the inventor's new findings.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure has an object to provide a mixed-flow compressor and a turbocharger that can suppress pressure loss due to shock waves generated near the throat.

[0007] A mixed-flow compressor according to at least one embodiment of the present disclosure is a mixed-flow compressor including an impeller and a casing configured to rotatably accommodate the impeller, wherein the impeller includes: a hub having a surface including an inclined surface that is inclined with respect to a central axis in a plane including a central axis; and a plurality of blades provided on the surface of the hub and arranged at intervals in the circumferential direction, the casing including a shroud portion that circumferentially surrounds the impeller and has a shroud surface that faces the impeller with a radial gap therebetween, and wherein, when a leading edge position of the blade at a dimensionless meridian plane length position of a hub-side end of the blade is defined as 0% and a trailing edge position of the blade is defined as 100%, a flow path height that is a length extending vertically from the surface of the hub to the shroud surface is configured to be maximum on the leading edge position side of a throat position + 10% of a tip-side end of the blade at the dimensionless meridian plane length position, and in a portion excluding the leading edge position.

[0008] A turbocharger according to at least one embodiment of the present disclosure includes: the mixed-flow compressor; and a turbine configured to drive the mixed-flow compressor.

[0009] According to at least one embodiment of the present disclosure, there is provided a mixed-flow compressor and a turbocharger that can suppress pressure loss due to shock waves generated near the throat.

[0010] Fig. 1 is a schematic cross-sectional view taken along the central axis of a turbocharger according to an embodiment of the present disclosure; Fig. 2 is a schematic cross-sectional view taken along the central axis of a mixed-flow compressor according to an embodiment of the present disclosure, showing a meridian plane cross-section of an impeller; Fig. 3 is a graph for explaining a flow path height in a mixed-flow compressor according to an embodiment of the present disclosure; Fig. 4 is an explanatory diagram for explaining shock waves generated in the vicinity of a throat of a mixed-flow compressor according to a comparative example; and Fig. 5 is a graph for explaining a radial length of a hub of an impeller in a mixed-flow compressor according to an embodiment of the present disclosure.

[0011] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0012] In the following embodiments, the mixed-flow compressor of the present disclosure will be described as being provided in a turbocharger, but the mixed-flow compressor of the present disclosure may also be an electric mixed-flow compressor, etc. Furthermore, the gas to be compressed by the mixed-flow compressor of the present disclosure does not need to be limited to air. In other words, the mixed-flow compressor of the present disclosure may be configured as a single mixed-flow compressor or in combination with mechanisms or devices other than a turbine, as long as it is capable of compressing and sending gas. Furthermore, there is no need to limit its use, etc.

[0013] (Mixed-flow compressor, turbocharger) Fig. 1 is a schematic cross-sectional view taken along the central axis of a turbocharger 10 according to one embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view taken along the central axis CA of a mixed-flow compressor 1 according to one embodiment of the present disclosure, showing a meridian plane cross-section of an impeller 2. As shown in Figs. 1 and 2 , the mixed-flow compressor 1 according to some embodiments includes the impeller 2 and a casing (compressor housing) 3 configured to rotatably house the impeller 2. The mixed-flow compressor 1 according to the present disclosure can be mounted on a turbocharger (supercharger) 10 for, for example, an automobile, a marine, or an industrial use (for example, land-based power generation).

[0014] 1, the turbocharger 10 includes a mixed-flow compressor 1 and a turbine 11 configured to drive the mixed-flow compressor 1. The turbine 11 includes a turbine rotor 12 that rotates using the energy of exhaust gas discharged from an engine (internal combustion engine) (not shown), and a turbine housing 13 configured to rotatably accommodate the turbine rotor 12.

[0015] 1 , the mixed-flow compressor 1 further includes a rotating shaft 14 to which the impeller 2 is attached, and a bearing 15 that rotatably supports the rotating shaft 14. In the turbocharger 10, the impeller 2 is coupled to one axial end of the rotating shaft 14, and the turbine rotor 12 is coupled to the other axial end of the rotating shaft 14. The bearing 15 rotatably supports the rotating shaft 14 between the impeller 2 and the turbine rotor 12. The turbocharger 10 may further include a bearing housing 16 that is disposed between the casing 3 and the turbine housing 13 and configured to house the rotating shaft 14 and the bearing 15.

[0016] The turbine 11 of the turbocharger 10 is configured to rotate a turbine rotor 12 by exhaust gas discharged from the engine. Exhaust gas generated by combustion in the engine is sent from the engine to the turbine 11, causing the turbine rotor 12 to rotate.

[0017] The impeller 2 is coaxially connected to the turbine rotor 12 via the rotary shaft 14, and is therefore driven to rotate about the central axis CA of the impeller 2 in conjunction with the rotation of the turbine rotor 12. The mixed-flow compressor 1 of the turbocharger 10 is configured so that, as the impeller 2 is driven to rotate about the central axis CA, air (intake air, gas) is drawn into the casing 3, the air is compressed, and the compressed air is sent to the engine. The compressed air sent from the mixed-flow compressor 1 to the engine is used for combustion in the engine.

[0018] The impeller 2 includes a hub 4 having a surface (outer peripheral surface) 41 and a back surface 42. Hereinafter, as shown in Fig. 2 , the direction in which the central axis CA of the impeller 2 extends will be referred to as the axial direction of the impeller 2, the direction perpendicular to the central axis CA will be referred to as the radial direction of the impeller 2, and the circumferential direction around the central axis CA will be referred to as the circumferential direction of the impeller 2. In the axial direction of the impeller 2, the side where the surface 41 of the hub 4 is located relative to the back surface 42 of the hub 4 (left side in Fig. 2) will be referred to as the front side, and the side where the back surface 42 is located relative to the surface 41 (right side in Fig. 2) will be referred to as the rear side.

[0019] 1, the turbine rotor 12 includes a hub 121 having a substantially truncated cone shape and a plurality of turbine blades 122 provided on the outer peripheral surface of the hub 121. The hub 121 and the plurality of turbine blades 122 are provided to be rotatable integrally with the rotating shaft 14 about a central axis CA. The turbine rotor 12 is configured to guide exhaust gas introduced from the outside in the radial direction of the turbine rotor 12 along the axial direction of the turbine rotor 12.

[0020] (Turbine Housing) A turbine scroll passage 131 for guiding exhaust gas discharged from the engine to the turbine rotor 12 and an exhaust gas discharge passage 132 for discharging exhaust gas that has passed through the turbine rotor 12 to the outside of the turbine housing 13 are formed inside the turbine housing 13. The turbine scroll passage 131 is provided on the outer periphery of the turbine rotor 12 and consists of a spiral passage extending along the circumferential direction of the turbine rotor 12. The exhaust gas discharge passage 132 extends along the axial direction of the turbine rotor 12.

[0021] The exhaust gas discharged from the engine is guided to the turbine rotor 12 through the turbine scroll passage 131, and drives the turbine rotor 12 to rotate. The exhaust gas that has driven the turbine rotor 12 to rotate is discharged to the outside of the turbine housing 13 through the exhaust gas discharge passage 132.

[0022] (Impeller) The impeller 2 of the mixed-flow compressor 1 is configured to guide air introduced along the axial direction of the impeller 2 to the radially outer side of the impeller 2. As shown in FIGS. 1 and 2 , the impeller 2 includes a hub 4 having a generally truncated cone shape and a plurality of blades (impeller blades) 5 provided around the hub 4. The surface 41 of the hub 4 includes an inclined surface 41A inclined with respect to the central axis CA in a plane including the central axis CA as shown in FIG. 2 . The inclined surface 41A is formed in a concave curve such that the radial distance (radial height) from the central axis CA increases toward the rear side (back surface 42 side) in the axial direction of the impeller 2. In the illustrated embodiment, the hub 4 includes a boss portion 43 that protrudes further forward in the axial direction of the impeller 2 than the plurality of blades 5. The surface 41 of the hub 4 includes a boss-side surface 41B that extends from the front end of the inclined surface 41A toward the front side in the axial direction of the impeller 2. The boss-side surface 41B is the outer peripheral surface of the boss portion 43.

[0023] The hub 4 is mechanically coupled to one axial side of the rotary shaft 14 and is therefore rotatable integrally with the rotary shaft 14 about the central axis CA of the impeller 2. In the illustrated embodiment, a through-hole 44 is formed in the hub 4, penetrating along the axial direction of the impeller 2 at a position including the central axis CA. The through-hole 44 is formed from a back surface 42, which is the rear end face of the hub 4, to a front end face 431 of the hub 4 (end face of the boss portion 43).

[0024] In the illustrated embodiment, the impeller 2 has a nut member 17 threaded onto one end 14A that is inserted through the through-hole 44 of the rotary shaft 14, and the hub 4 is clamped between the nut member 17 and another member by applying a rearward tightening force to the nut member 17. The other member may be the rotary shaft 14 or a collar attached to the rotary shaft 14.

[0025] Each of the plurality of blades 5 stands upright from the inclined surface 41A (surface 41) of the hub 4 and is arranged at intervals between the other blades 5 in the circumferential direction about the central axis CA. As shown in Fig. 2 , each of the plurality of blades 5 includes a leading edge LE located on the most upstream side in the flow direction of air guided to the impeller 2, a trailing edge TE located on the most downstream side, a hub-side end 51, and a tip-side end 52. Each of the plurality of blades 5 extends in the span direction between the hub-side end 51 and the tip-side end 52, between the leading edge LE and the trailing edge TE.

[0026] The hub end 51 is one end of the blade 5 in the span direction and is the end connected to the surface 41 of the hub 4. The tip end 52 is the other end of the blade 5 in the span direction and is the end located opposite to the hub end 51. In this specification, the span direction is the direction connecting the hub end 51 and the tip end 52 at each dimensionless meridian plane length position.

[0027] 2 , the tip end 52 of each of the plurality of blades 5 faces the shroud surface 31 across a clearance CL formed between the tip end 52 and the shroud surface 31. In other words, the impeller 2 is an open-type impeller that does not include an annular member covering the tip end 52.

[0028] 2, the casing 3 includes a shroud portion 30 having the above-described shroud surface 31. The shroud surface 31 includes an inclined surface 31A formed in a convex curve such that the distance from the central axis CA increases from the front side to the rear side in the axial direction of the impeller 2. A fluid introduction passage 32, a diffuser passage 33, and a scroll passage 34 are formed inside the casing 3.

[0029] The fluid introduction passage 32 is a passage for taking in air from outside the casing 3 and guiding the taken-in air (fluid) to the impeller 2. The fluid introduction passage 32 is provided forward of the impeller 2 in the axial direction of the impeller 2, and extends along the axial direction of the impeller 2. By driving the impeller 2 to rotate, air is taken in from outside the casing 3 into the fluid introduction passage 32, and the taken-in air flows through the fluid introduction passage 32 toward the rear side in the axial direction of the impeller 2 and is guided to the impeller 2.

[0030] The diffuser passage 33 and the scroll passage 34 are passages for guiding the compressed air (compressed fluid) that passes through the impeller 2 and is compressed by the impeller 2 to the outside of the mixed-flow compressor 1. The scroll passage 34 is provided on the outer periphery (outside in the radial direction) of the impeller 2 and is a spiral passage extending along the circumferential direction of the impeller 2. The diffuser passage 33 is provided between the scroll passage 34 and the impeller 2 in the radial direction of the impeller 2 and extends along the radial direction of the impeller 2. The diffuser passage 33 communicates with the scroll passage 34 at an outlet 331 provided at its downstream end (outer periphery end). The compressed air compressed by the impeller 2 flows into the diffuser passage 33, flows through the diffuser passage 33 toward the outside in the radial direction of the impeller 2, and is guided to the scroll passage 34.

[0031] (Definition of flow path height and dimensionless meridian plane length position) The length extending vertically from the surface 41 of the hub 4 to the shroud surface 31 on the meridian plane shown in Fig. 2 is defined as the flow path height h. The flow path height h is the length between the surface 41 of the hub 4 and the shroud surface 31 in a direction perpendicular to the tangent to the surface 41 of the hub 4 on the meridian plane shown in Fig. 2.

[0032] FIG. 3 is a graph illustrating the flow passage height h in the mixed-flow compressor 1 according to an embodiment of the present disclosure. The graph in FIG. 3 shows the distribution of the flow passage height h between the leading edge position 511 and the trailing edge position 512 at the dimensionless meridian plane length position m, with the horizontal axis representing the dimensionless meridian plane length position m at the hub-side end 51 of the blade 5 and the vertical axis representing the flow passage height h. In FIG. 3 , the leading edge position 511 at the dimensionless meridian plane length position m is defined as 0%, the trailing edge position 512 is defined as 100%, and each position on the dimensionless meridian plane length position m is expressed as a percentage. The intermediate position (50% dimensionless meridian plane length position) between the leading edge position 511 and the trailing edge position 512 at the dimensionless meridian plane length position m is designated MP.

[0033] In FIG. 2 , the throat position from the tip end 52 to the hub end 51 of the blade 5 is indicated by a two-dot chain line. In FIG. 3 , a throat position MT of the tip end 52 of the blade 5 at the dimensionless meridian plane length position m of the mixed-flow compressor 1 and a throat position MH of the hub end 51 of the blade 5 at the dimensionless meridian plane length position m of the mixed-flow compressor 1 are shown. The throat position MT is the position where the distance between the tip ends 52 of two adjacent blades 5 in the circumferential direction is smallest. The throat position MH is the position where the distance between the hub ends 51 of two adjacent blades 5 in the circumferential direction is smallest. In the illustrated embodiment, the throat position MT is located closer to the trailing edge TE than the throat position MH at the dimensionless meridian plane length position m at the hub end 51. The dimensionless meridian plane length position m of the throat position MT + 10% is located closer to the leading edge LE than the intermediate position MP.

[0034] A curve C1 shown in the graph of Fig. 3 shows an example of the distribution of the flow passage height h of the mixed-flow compressor 1. A curve C2 shown in the graph of Fig. 3 shows an example of the distribution of the flow passage height h of the mixed-flow compressor 01 according to the comparative example. The curve C2 indicates that the flow passage height h is maximum at the leading edge LE of the blade 5, is minimum at the trailing edge TE, and decreases monotonically from the leading edge LE to the trailing edge TE.

[0035] Figure 4 is an explanatory diagram illustrating shock waves generated near the throat of a mixed-flow compressor 01 according to a comparative example. The mixed-flow compressor 01 according to the comparative example has the same configuration as the mixed-flow compressor 1 except for the flow path height h. According to the inventor's new findings, as shown in Figure 4, when the impeller 2 rotates at a relatively high speed, shock waves (indicated by arrows in the figure) are generated near the throat on the suction surface side of the blades 5. The shock waves create an adverse pressure gradient, which may result in a low-speed area (LSA) downstream in the fluid flow direction. The occurrence of the low-speed area (LSA) may cause pressure loss in the mixed-flow compressor 01, potentially reducing the efficiency of the mixed-flow compressor 01.

[0036] In the mixed-flow compressor 1 according to some embodiments, as shown in FIG. 3 , the flow path height h is configured to be maximum on the leading edge position (0% dimensionless meridian plane length position) side of the throat position MT+10% of the tip side end 52 of the blade 5 at the dimensionless meridian plane length position m, excluding the leading edge position.

[0037] In the mixed-flow compressor 1 according to the embodiment shown in FIG. 3 , the flow path height h is maximum (a maximum within a range of 0% to 100%) at the dimensionless meridian plane length position m1. In the mixed-flow compressor 1 according to the embodiment shown in FIG. 3 , the flow path height h monotonically increases from the leading edge position to the dimensionless meridian plane length position m1 and monotonically decreases from the dimensionless meridian plane length position m1 to a predetermined position on the trailing edge side (the trailing edge in the illustrated example). Note that the predetermined position on the trailing edge side is not limited to the trailing edge, but is preferably as close to the trailing edge as possible. For example, the predetermined position on the trailing edge side may be the dimensionless meridian plane length position m1 + 50%, and more preferably the dimensionless meridian plane length position m1 + 80%.

[0038] 3, a region AR1 is formed near the throat position MT at the tip end 52, where the flow path height h is greater than that at the leading edge. The mixed-flow compressor 1 can increase the flow path area near the throat by relatively increasing the flow path height h near the throat, thereby reducing the fluid flow velocity near the throat and mitigating the strength of the shock waves. By mitigating the strength of the shock waves, the mixed-flow compressor 1 can suppress the occurrence of the low-speed region LSA and reduce pressure loss due to the low-speed region LSA.

[0039] 3, in the mixed-flow compressor 1 according to some embodiments, the flow passage height h is configured to be maximum on the leading edge side of the throat position MT of the tip end 52 of the blade 5 at the dimensionless meridian plane length position m. In this case, the flow passage height h near the throat of the mixed-flow compressor 1 can be increased, which reduces the flow velocity of the fluid near the throat and reduces the strength of shock waves generated under high-speed conditions.

[0040] In some other embodiments, the flow passage height h may be configured to be maximum on the trailing edge side of the throat position MT-10% and on the leading edge side of the throat position MT. Also, the flow passage height h may be configured to be maximum on the trailing edge side of the throat position MT and on the leading edge side of the throat position MT+10%.

[0041] (Radial Length of Hub) In the meridian plane shown in FIG. 2 , the radial length (hub radius) from the central axis CA of the surface 41 of the hub 4 is defined as the radial length R. FIG. 5 is a graph for explaining the radial length R of the hub 4 of the impeller 2 in the mixed-flow compressor 1 according to an embodiment of the present disclosure. The graph in FIG. 5 shows the distribution of the radial length R between the leading edge position 511 and the trailing edge position 512 of the dimensionless meridian plane length position m, with the horizontal axis representing the dimensionless meridian plane length position m at the hub-side end 51 of the blade 5 and the vertical axis representing the radial length R. In FIG. 5 , as in FIG. 3 , the leading edge position 511 of the dimensionless meridian plane length position m is defined as 0%, and the trailing edge position 512 is defined as 100%, and each position on the dimensionless meridian plane length position m is expressed as a percentage. The intermediate position (50% dimensionless meridian length position) between the leading edge position 511 and the trailing edge position 512 of the dimensionless meridian length position m is defined as MP.

[0042] 5 shows a throat position MT of the tip end 52 of the blade 5 at a dimensionless meridian plane length position m of the mixed-flow compressor 1, and a throat position MH of the hub end 51 of the blade 5 at the dimensionless meridian plane length position m of the mixed-flow compressor 1. In the illustrated embodiment, the throat position MT is located closer to the trailing edge TE than the throat position MH at the dimensionless meridian plane length position m at the hub end 51. The dimensionless meridian plane length position m of the throat position MT + 10% is located closer to the leading edge LE than the intermediate position MP.

[0043] A curve C3 shown in the graph of Fig. 5 shows an example of the distribution of the radial length R of the mixed-flow compressor 1. In the mixed-flow compressor 1 according to some embodiments, as shown in Fig. 5, the radial length R is configured to be smallest in a portion excluding the leading edge position (0% dimensionless meridian plane length position) of the tip-side end 52 of the blade 5 at the dimensionless meridian plane length position m relative to the throat position MT+10%.

[0044] In the mixed-flow compressor 1 according to the embodiment shown in FIG. 5 , the radial length R is minimum (a minimum within a range of 0% to 100%) at the dimensionless meridian plane length position m2. In the mixed-flow compressor 1 according to the embodiment shown in FIG. 5 , the radial length R monotonically decreases from the leading edge position to the dimensionless meridian plane length position m2 and monotonically increases from the dimensionless meridian plane length position m2 to a predetermined position on the trailing edge side (the trailing edge in the illustrated example). The predetermined position on the trailing edge side is not limited to the trailing edge, but is preferably as close to the trailing edge as possible. For example, the predetermined position on the trailing edge side may be the dimensionless meridian plane length position m2 + 50%, and more preferably the dimensionless meridian plane length position m2 + 80%.

[0045] 5, a region AR2 having a smaller radial length R than the leading edge position is formed near the throat position MT at the tip end 52. When the radial length at the leading edge position is defined as R0, the radial length R at the dimensionless meridian plane length position m2 preferably satisfies the condition of radial length R≧95% R0. If the radial length R is made too small, there is a risk of interference between adjacent blades 5.

[0046] In the mixed-flow compressor 1 according to the embodiment shown in Figure 5, a region AR2 having a smaller radial length R than the leading edge position is formed near the throat position MT at the tip end 52. By making the radial length R relatively small near the throat, the mixed-flow compressor 1 can increase the flow path area near the throat while suppressing an increase in the outer diameter of the blades 5. This reduces the fluid flow velocity near the throat and reduces the strength of the shock waves. By reducing the strength of the shock waves, the mixed-flow compressor 1 can suppress the occurrence of the low-speed region LSA and reduce pressure loss due to the low-speed region LSA.

[0047] Furthermore, if the outer diameter of the blades 5 were large, the centrifugal force acting on the impeller 2 would increase during rotation of the impeller 2, promoting plastic deformation in which the impeller 2 expands in the radial direction and contracts in the axial direction, which could reduce the tightening force (axial force) of the nut member 17. The mixed-flow compressor 1 according to the embodiment shown in Fig. 5 can increase the flow path area in the vicinity of the throat while preventing the outer diameter of the blades 5 from increasing, and therefore can prevent a reduction in the tightening force (axial force) of the nut member 17 due to plastic deformation during rotation of the impeller 2.

[0048] 5 , in the mixed-flow compressor 1 according to some embodiments, the radial length R is configured to be smallest on the leading edge side of the throat position MT of the tip end 52 of the blade 5 at the dimensionless meridian plane length position m. In this case, the radial length R in the vicinity of the throat of the mixed-flow compressor 1 can be reduced, and the flow path area in the vicinity of the throat can be increased while suppressing an increase in the outer diameter of the blade 5.

[0049] In some other embodiments, the radial length R may be configured to be smallest on the trailing edge side of the throat position MT-10% and on the leading edge side of the throat position MT. Also, the radial length R may be configured to be smallest on the trailing edge side of the throat position MT and on the leading edge side of the throat position MT+10%.

[0050] The mixed-flow compressor 1 according to the embodiment shown in Fig. 5 may have the configuration of the mixed-flow compressor 1 according to the embodiment shown in Fig. 3, or may not have the configuration of the mixed-flow compressor 1 according to the embodiment shown in Fig. 3. In other words, the mixed-flow compressor 1 according to the embodiment shown in Fig. 5 can be implemented independently.

[0051] 1 , a turbocharger 10 according to some embodiments includes the mixed-flow compressor 1 described above and the turbine 11 described above. By suppressing pressure loss due to shock waves generated near the throat of the mixed-flow compressor 1, it is possible to improve the efficiency of the mixed-flow compressor 1 and the turbocharger 10 including the mixed-flow compressor 1.

[0052] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only refer to shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also refer to shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0053] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0054] The contents of the above-described embodiments can be understood, for example, as follows.

[0055] 1) A mixed-flow compressor (1) according to at least one embodiment of the present disclosure is a mixed-flow compressor (1) including an impeller (2) and a casing (3) configured to rotatably accommodate the impeller (2), wherein the impeller (2) includes: a hub (4) having a surface (41) including an inclined surface (41A) inclined with respect to a central axis (CA) in a plane including the central axis (CA); and a plurality of blades (5) provided on the surface (41) of the hub (4) and arranged at intervals in the circumferential direction, and the casing (3) includes a shroud portion (30) that circumferentially surrounds the impeller (2) and has a shroud surface (31) facing the impeller (2) via a radial gap, When the leading edge position of the blade (5) at a dimensionless meridian plane length position (m) of the hub side end (51) of the blade (5) is defined as 0% and the trailing edge position of the blade (5) is defined as 100%, a flow path height (h) which is a length extending in a vertical direction from the surface (41) of the hub (4) to the shroud surface (31) is configured to be maximum on the leading edge position side of a throat position (MT) + 10% of a tip side end (52) of the blade (5) at the dimensionless meridian plane length position, and in a portion excluding the leading edge position.

[0056] According to the configuration 1), the flow path area near the throat of the mixed-flow compressor 1 can be increased by relatively increasing the flow path height (h) near the throat, thereby reducing the flow velocity of the fluid near the throat and mitigating the strength of shock waves generated under high-speed conditions. By mitigating the strength of the shock waves, the mixed-flow compressor 1 can suppress the occurrence of the low-speed area (LSA) and reduce pressure loss due to the low-speed area (LSA).

[0057] 2) In some embodiments, in the mixed-flow compressor (1) described in 1), a radial length (R) of the surface (41) of the hub (4) from the central axis (CA) is configured to be minimum on the leading edge position side of the throat position (MT) + 10% of the tip side end (52) of the blade (5) at the dimensionless meridian plane length position (m), and in a portion excluding the leading edge position.

[0058] According to the configuration 2), the radial length (R) near the throat of the mixed-flow compressor (1) is made relatively small, thereby making it possible to increase the flow path area near the throat while suppressing an increase in the outer diameter of the blades (5). If the outer diameter of the blades (5) were large, the centrifugal force acting on the impeller (2) during rotation would increase, promoting plastic deformation in which the impeller (2) expands in the radial direction and contracts in the axial direction, which could reduce the tightening force (axial force) of the nut member (17).

[0059] 3) In some embodiments, in the mixed-flow compressor (1) described in 2) above, the radial length (R) of the hub (4) is configured to be smallest on the leading edge position side of the throat position (MT) of the tip side end (52) of the blade (5) at the dimensionless meridian plane length position (m).

[0060] According to the configuration of 3) above, the radial length (R) of the mixed-flow compressor (1) near the throat can be reduced, so that the flow path area near the throat can be increased while preventing the outer diameter of the blades (5) from increasing.

[0061] 4) In some embodiments, in the mixed-flow compressor (1) according to any one of 1) to 3) above, the flow path height (h) is configured to be maximum on the leading edge position side of the throat position (MT) of the tip side end (52) of the blade (5) at the dimensionless meridian plane length position.

[0062] According to the configuration of 4) above, the flow path height (h) in the vicinity of the throat of the mixed-flow compressor (1) can be increased, so that the flow velocity of the fluid in the vicinity of the throat can be reduced, and the strength of the shock waves generated under high-speed conditions can be alleviated.

[0063] 5) A mixed-flow compressor (1) according to at least one embodiment of the present disclosure is a mixed-flow compressor (1) including an impeller (2) and a casing (3) configured to rotatably accommodate the impeller (2), wherein the impeller (2) includes: a hub (4) having a surface (41) including an inclined surface (41A) inclined with respect to a central axis (CA) in a plane including the central axis (CA); and a plurality of blades (5) provided on the surface (41) of the hub (4) and arranged at intervals in the circumferential direction, and the casing (3) includes a shroud portion (30) that circumferentially surrounds the impeller (2) and has a shroud surface (31) facing the impeller (2) via a radial gap, When the leading edge position of the blade (5) at the dimensionless meridian plane length position (m) of the hub side end (51) of the blade (5) is defined as 0% and the trailing edge position of the blade (5) is defined as 100%, the radial length (R) of the surface (41) of the hub (4) from the central axis (CA) is configured to be on the leading edge position side of a throat position (MT) + 10% of a tip side end (52) of the blade (5) at the dimensionless meridian plane length position (m), and to be minimum in a portion excluding the leading edge position.

[0064] According to the configuration of 5), the radial length (R) of the mixed-flow compressor (1) near the throat is relatively small, thereby preventing the outer diameter of the blades (5) from increasing and increasing the flow path area near the throat. This reduces the fluid flow velocity near the throat and reduces the strength of shock waves generated under high-speed conditions. By reducing the strength of the shock waves, the mixed-flow compressor (1) can suppress the occurrence of low-speed airflow (LSA) zones and reduce pressure loss due to the low-speed airflow (LSA) zones. Furthermore, if the outer diameter of the blades (5) were large, the centrifugal force acting on the impeller (2) would increase during rotation, promoting plastic deformation in which the impeller (2) expands radially and contracts axially, potentially reducing the tightening force (axial force) of the nut member (17).

[0065] 6) In some embodiments, in the mixed-flow compressor (1) described in 5) above, the flow path height (h) is configured to be maximum on the leading edge position side of the throat position (MT) of the tip side end (52) of the blade (5) at the dimensionless meridian plane length position.

[0066] According to the configuration of 6) above, the flow path height (h) in the vicinity of the throat of the mixed-flow compressor (1) can be increased, so that the flow velocity of the fluid in the vicinity of the throat can be reduced, and the strength of the shock waves generated under high-speed conditions can be alleviated.

[0067] 7) A turbocharger (10) according to at least one embodiment of the present disclosure includes: a mixed-flow compressor (1) according to any one of 1) to 6) above; and a turbine (11) configured to drive the mixed-flow compressor (1).

[0068] According to the configuration of 7) above, pressure loss due to shock waves generated near the throat of the mixed-flow compressor (1) can be suppressed, thereby improving the efficiency of the mixed-flow compressor (1) and the turbocharger (10) equipped with the mixed-flow compressor (1).

[0069] REFERENCE SIGNS LIST 1 mixed flow compressor 2 impeller 3 casing 4 hub 5 blade 10 turbocharger 11 turbine 12 turbine rotor 13 turbine housing 14 rotating shaft 15 bearing 16 bearing housing 31 shroud surface 32 fluid introduction passage 33 diffuser passage 34 scroll passage 41 surface 42 back surface 51 hub side end 52 tip side end LE leading edge R radial length TE trailing edge h passage height m dimensionless meridian plane length position

Claims

1. A mixed-flow compressor comprising an impeller and a casing configured to rotatably house the impeller, wherein the impeller comprises: a hub having a surface including an inclined surface that is inclined relative to a central axis in a plane including the central axis; and a plurality of blades provided on the surface of the hub and arranged at intervals in the circumferential direction, wherein the casing includes a shroud portion that circumferentially surrounds the impeller and has a shroud surface that faces the impeller with a radial gap between them, and wherein, when the leading edge position of the blade at the dimensionless meridian plane length position of the hub side end of the blade is defined as 0% and the trailing edge position of the blade is defined as 100%, the flow path height, which is the length extending vertically from the surface of the hub to the shroud surface, is configured to be maximum on the leading edge position side of the throat position of the tip side end of the blade at the dimensionless meridian plane length position + 10% and in a portion excluding the leading edge position.

2. A mixed-flow compressor according to claim 1, wherein the radial length of the surface of the hub from the central axis is configured to be minimum on the leading edge position side of the throat position + 10% of the tip side end of the blade at the dimensionless meridian plane length position, and in a portion excluding the leading edge position.

3. A mixed-flow compressor according to claim 2, wherein the radial length of the hub is configured to be smallest on the leading edge position side of the throat position of the tip-side end of the blade at the dimensionless meridian plane length position.

4. A mixed-flow compressor according to any one of claims 1 to 3, wherein the flow passage height is configured to be maximum on the leading edge position side of the throat position of the tip side end of the blade at the dimensionless meridian plane length position.

5. A mixed-flow compressor comprising an impeller and a casing configured to rotatably house the impeller, wherein the impeller comprises: a hub having a surface including an inclined surface that is inclined relative to the central axis in a plane including the central axis; and a plurality of blades provided on the surface of the hub and arranged at intervals in the circumferential direction, wherein the casing includes a shroud portion that circumferentially surrounds the impeller and has a shroud surface that faces the impeller with a radial gap between them, and wherein, when the leading edge position of the blade at the dimensionless meridian plane length position of the hub side end of the blade is defined as 0% and the trailing edge position of the blade is defined as 100%, the radial length of the surface of the hub from the central axis is on the leading edge position side of the throat position of the tip side end of the blade at the dimensionless meridian plane length position + 10%, and is minimum in a portion excluding the leading edge position.

6. A mixed-flow compressor according to claim 5, wherein the radial length of the hub is configured to be smallest on the leading edge side of the throat position of the tip-side end of the blade at the dimensionless meridian plane length position.

7. A turbocharger comprising: a mixed-flow compressor according to any one of claims 1 to 3, 5 and 6; and a turbine configured to drive the mixed-flow compressor.

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