Turbine wheel and turbine

Abstract

A turbine wheel comprising: a hub that has a hub surface; and at least one turbine blade that is provided standing upright on the hub surface, wherein the hub surface is configured such that, in a meridian plane view of the turbine wheel, the angle of inclination thereof relative to the axial direction of the turbine wheel in the location of connection with the trailing edge of the turbine blade is 7 degrees to 16 degrees.

Description

Turbine wheel and turbine

[0001] The present disclosure relates to a turbine wheel and a turbine including the turbine wheel.

[0002] A turbocharger includes, for example, a centrifugal compressor provided on one end side of a rotating shaft and a turbine provided on the other end side of the rotating shaft. The energy of exhaust gas (working fluid) sent from an engine rotates a turbine wheel, and the rotation of the turbine wheel rotates an impeller of the centrifugal compressor that rotates in conjunction with the rotation of the turbine wheel to compress intake air and supply it to the engine.

[0003] International Publication No. 2019 / 111370

[0004] In a turbine, in a diffuser passage which is an exhaust gas passage downstream of the turbine blades of a turbine wheel, pressure recovery may be performed by decelerating the exhaust gas that has passed through the turbine blades. If separation occurs in the flow of the exhaust gas in the diffuser passage, there is a risk that the pressure recovery performance will deteriorate.

[0005] Patent Document 1 discloses an invention in which the inner surface shape of a turbine casing forming a diffuser passage is gradually enlarged to suppress separation of the exhaust gas flow from the inner surface of the turbine casing and improve the exhaust gas pressure recovery performance in the diffuser passage.

[0006] The inventor has found that in a turbine, the working fluid that has passed through the turbine blades generates a flow toward the outside in the radial direction due to the swirling of the working fluid, causing separation of the working fluid flow on the inner peripheral side of the diffuser flow path and possibly deteriorating the pressure recovery performance of the working fluid.

[0007] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a turbine wheel capable of improving the pressure recovery performance by decelerating the working fluid that has passed through the turbine blades and a turbine including the turbine wheel.

[0008] A turbine wheel according to at least one embodiment of the present disclosure comprises a hub having a hub surface and at least one turbine blade erected on the hub surface, wherein the hub surface is configured such that, in a meridional view of the turbine wheel, the inclination angle with respect to the axial direction of the turbine wheel at the connection point with the trailing edge of the turbine blade is 7 degrees or more and 16 degrees or less.

[0009] A turbine according to at least one embodiment of the present disclosure comprises a turbine wheel and a turbine casing configured to rotatably house the turbine wheel.

[0010] According to at least one embodiment of the present disclosure, a turbine wheel and a turbine equipped with the turbine wheel are provided that can improve the pressure recovery performance by decelerating the working fluid that has passed through the turbine blades.

[0011] This is a schematic cross-sectional view along the axis of a turbocharger equipped with a turbine according to one embodiment of the present disclosure. This is a schematic diagram showing a meridional cross-section of a turbine wheel according to one embodiment of the present disclosure. This is a schematic diagram showing a meridional cross-section of a turbine wheel according to a comparative example. This is an explanatory diagram for explaining the flow of working fluid in the diffuser passage of a turbine equipped with a turbine wheel according to a comparative example. This is an explanatory diagram for explaining the flow of working fluid in the diffuser passage of a turbine equipped with a turbine wheel according to the embodiment shown in Figure 2. This is a graph for explaining the relationship between the turbine speed ratio, the static pressure recovery rate in the diffuser passage, and the inclination angle θ. This is a schematic diagram showing a meridional cross-section of a turbine wheel according to one embodiment of the present disclosure. This is a graph for explaining the relationship between the dimensionless meridional length position of the hub surface of the turbine wheel and the radius of curvature of the hub surface.

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

[0013] (Turbine) Figure 1 is a schematic cross-sectional view along the axis LA of a turbocharger 10 equipped with a turbine 1 according to one embodiment of the present disclosure. Figure 2 is a schematic view showing a meridional cross-section of a turbine wheel 2 according to one embodiment of the present disclosure. Figure 2 shows not only the turbine wheel 2 but also the shroud surface 33 of the turbine casing 3. As shown in Figures 1 and 2, the turbine 1 comprises a turbine wheel 2 and a turbine casing 3 configured to rotatably house the turbine wheel 2. The turbine 1 according to the present disclosure can be mounted, for example, on a turbocharger 10 for automobiles, marine or industrial use (e.g., stationary use).

[0014] In the following embodiments, the turbine 1 according to the disclosure will be described as a turbine mounted on a turbocharger 10 and operated by exhaust gas discharged from an internal combustion engine (exhaust gas turbine). However, the turbine 1 according to the disclosure is not limited to a turbine mounted on a turbocharger 10. Furthermore, the fluid (working fluid) for rotating the turbine wheel 2 of the turbine 1 according to the disclosure does not need to be limited to exhaust gas discharged from an internal combustion engine. In other words, the turbine 1 according to the disclosure only needs to be capable of rotating the turbine wheel 2 of the turbine 1 by the energy of the working fluid, and may be configured as a turbine 1 alone or in combination with other mechanisms or devices. Furthermore, there is no need to limit its application, etc.

[0015] (Turbocharger) The turbocharger 10, as shown in Figure 1, comprises a centrifugal compressor 11 and a turbine 1 configured to drive the centrifugal compressor 11. The centrifugal compressor 11 comprises an impeller 12 for compressing a combustion gas (e.g., air) that is directed to an internal combustion engine (not shown), and a compressor casing 13 configured to rotatably house the impeller 12.

[0016] In the illustrated embodiment, the turbine 1, as shown in Figure 1, comprises a rotating shaft 14 to which a turbine wheel 2 is attached, and a bearing 15 that rotatably supports the rotating shaft 14. In the turbocharger 10, the turbine wheel 2 is attached to one axial side of the rotating shaft 14, and the impeller 12 is attached to the other axial side of the rotating shaft 14. The bearing 15 is configured to rotatably support the rotating shaft 14 between the turbine wheel 2 and the impeller 12.

[0017] The turbocharger 10 may also include a bearing casing 16 positioned between the turbine casing 3 and the compressor casing 13, connected to the turbine casing 3 and the compressor casing 13, and configured to house the rotating shaft 14 and the bearing 15.

[0018] The turbine 1 (turbocharger 10) is configured to rotate the turbine wheel 2 using the energy of the exhaust gas discharged from the internal combustion engine. The impeller 12 is connected coaxially to the turbine wheel 2 via a rotating shaft 14, and therefore rotates in conjunction with the rotation of the turbine wheel 2. The centrifugal compressor 11 (turbocharger 10) is configured to draw fuel gas into the compressor casing 13 by rotating the impeller 12, compress the fuel gas, and send the compressed fuel gas to the internal combustion engine.

[0019] (Impeller) As shown in Figure 1, the impeller 12 includes a compressor hub 121 and a plurality of compressor blades 122 erected from the outer circumferential surface of the compressor hub 121. Each of the plurality of compressor blades 122 is spaced apart from the other compressor blades 122 in the circumferential direction around the axis LA. The outer circumferential surface of the compressor hub 121 is formed in a concave curve shape, where the distance from the axis LA increases as it moves toward the rear side of the compressor hub 121 in the axial direction of the impeller 12. The compressor hub 121 and the plurality of compressor blades 122 are provided to be rotatable integrally with the rotating shaft 14 about the axis LA. The impeller 12 is configured to guide the combustion gas introduced along the axial direction of the impeller 12 to the radially outer side of the impeller 12.

[0020] (Compressor Casing) Inside the compressor casing 13, a combustion gas introduction channel 131 and a compressed gas discharge channel 132 are formed. The combustion gas introduction channel 131 is a channel for taking in combustion gas from outside the compressor casing 13 and guiding the taken-in combustion gas to the impeller 12. The compressed gas discharge channel 132 is a channel for guiding the compressed gas compressed by the impeller 12 to the outside of the compressor casing 13.

[0021] The centrifugal compressor 11 rotates its impeller 12 to draw combustion gas from outside the compressor casing 13 into a combustion gas introduction channel 131, and guides it to the impeller 12 through the combustion gas introduction channel 131. The compressed gas compressed by the impeller 12 is guided to the outside of the compressor casing 13 through a compressed gas discharge channel 132. The compressed gas sent from the centrifugal compressor 11 to the internal combustion engine is used for combustion in the internal combustion engine. The exhaust gas generated by the combustion in the internal combustion engine is guided from the internal combustion engine to the turbine 1, which rotates the turbine wheel 2.

[0022] As shown in Figure 2 below, the direction in which the axis LA of the turbine wheel 2 extends is defined as the axial direction of the turbine wheel 2, the direction perpendicular to the axis LA is defined as the radial direction of the turbine wheel 2, and the circumferential direction around the axis LA is defined as the circumferential direction of the turbine wheel 2. Of the axial directions of the turbine wheel 2, the direction in which the hub surface 41 faces is defined as the first direction, and the direction in which the back surface 42 faces is defined as the second direction. The impeller 12 is positioned such that the outer circumferential surface of the compressor hub 121 faces the second direction.

[0023] (Turbine Casing) Inside the turbine casing 3, there is a scroll channel 31 for guiding the working fluid from outside the turbine casing 3 to the turbine wheel 2, a working fluid discharge channel 32 for guiding the working fluid that has passed through the turbine wheel 2 to the outside of the turbine casing 3, and a shroud surface 33. The scroll channel 31 is provided on the outer circumference side of the turbine wheel 2 and consists of a spiral-shaped channel that extends along the circumferential direction of the turbine wheel 2.

[0024] In the illustrated embodiment, the working fluid discharge channel 32 extends along the axial direction of the turbine wheel 2 and includes a diffuser channel 34 whose outer circumferential surface 341 widens radially outward from the turbine wheel 2 as it moves downstream in the direction of the working fluid flow. The shroud surface 33 is formed in a convex curved shape, with its distance from the axis LA decreasing as it moves toward the first direction described above. The shroud surface 33 is connected to the outer circumferential surface 341 of the diffuser channel 34. At least one of the shroud surface 33 or the outer circumferential surface 341 of the diffuser channel 34 surrounds the outer circumferential side of the boss portion 43 of the turbine wheel 2.

[0025] The exhaust gas (working fluid) discharged from the internal combustion engine is guided to the turbine wheel 2 through the scroll passage 31, causing the turbine wheel 2 to rotate. The exhaust gas that has rotated the turbine wheel 2 is discharged to the outside of the turbine casing 3 through the working fluid discharge passage 32, which includes the diffuser passage 34.

[0026] (Turbine Wheel) A turbine wheel 2 according to several embodiments, as shown in Figure 2, comprises a hub 4 having a hub surface 41 and a back surface 42, and at least one (multiple in the illustrated example) turbine blades 5 erected on the hub surface 41. Each of the plurality of turbine blades 5 is spaced apart from the other turbine blades 5 in the circumferential direction around the axis LA.

[0027] The hub 4 and the multiple turbine blades 5 are mounted to rotate integrally with the rotating shaft 14 about the axis LA. The turbine wheel 2 is configured to guide the working fluid (exhaust gas) introduced from the outside in the radial direction of the turbine wheel 2 in a first direction along the axial direction of the turbine wheel 2.

[0028] Each of the multiple turbine blades 5 includes a leading edge 51, a trailing edge 52, a hub-side end 53, and a tip-side end 54, as shown in Figure 2. The leading edge 51 is the edge of the turbine blade 5 located furthest upstream in the direction of the working fluid flow leading to the turbine wheel 2. The trailing edge 52 is the edge of the turbine blade 5 located furthest downstream in the direction of the working fluid flow leading to the turbine wheel 2. The boss portion 43 of the turbine wheel 2 is the portion of the hub 4 that protrudes downstream (first direction) in the direction of the working fluid flow from the trailing edge 52.

[0029] The hub end 53 is one end of the turbine blade 5 in the span direction and is the end connected to the hub surface 41. The tip end 54 is the other end of the turbine blade 5 in the span direction. In this specification, the span direction is the direction connecting the hub end 53 and the tip end 54 at each dimensionless meridional length position. Each of the plurality of turbine blades 5 extends along the span direction between the hub end 53 and the tip end 54 of the turbine blade 5.

[0030] Each of the multiple turbine blades 5 has a tip end 54 that faces the shroud surface 33, with a clearance CL formed between them. In other words, the turbine wheel 2 does not have an annular member that covers the multiple tip ends 54.

[0031] In a meridional view of the turbine wheel 2 as shown in Figure 2, let P1 be the connection point between the hub surface 41 and the leading edge 51 of the turbine blade 5 (leading edge connection point), let P2 be the connection point between the hub surface 41 and the trailing edge 52 of the turbine blade 5 (trailing edge connection point), and let θ be the inclination angle of the turbine wheel 2 with respect to the axial direction at the trailing edge connection point P2 of the hub surface 41.

[0032] In some embodiments of the turbine wheel 2, the inclination angle θ is configured to be between 7 degrees and 16 degrees in a meridional view of the turbine wheel 2 as shown in Figure 2.

[0033] Figure 3 is a schematic diagram showing a meridional cross-section of a turbine wheel 02 according to a comparative example. Figure 3 shows not only the turbine wheel 02 but also the shroud surface 33 of the turbine casing 3. The turbine wheel 02 according to the comparative example has the same configuration as the turbine wheel 2, except that the inclination angle θ is less than 7 degrees (0 degrees or more and 2 degrees or less in the illustrated example).

[0034] Figure 4 is an explanatory diagram illustrating the flow of working fluid in the diffuser channel 34 of a turbine 01 equipped with a turbine wheel 02 according to a comparative example. Figure 5 is an explanatory diagram illustrating the flow of working fluid in the diffuser channel 34 of a turbine 1 equipped with a turbine wheel 2 according to the embodiment shown in Figure 2. In Figures 4 and 5, respectively, the distribution of working fluid velocity in the diffuser channel 34 is shown, with the high-velocity region in the diffuser channel 34 being designated as HA and the low-velocity position in the diffuser channel 34 being designated as LA.

[0035] In the turbine 01 equipped with the turbine wheel 02 according to the comparative example, as shown in Figure 4, the working fluid that has passed through the turbine blades 5 generates a radially outward flow due to the swirling of the working fluid, which can cause flow separation of the working fluid on the inner circumference side of the diffuser passage 34. Flow separation of the working fluid occurs downstream of the boss portion 43 of the turbine wheel 02.

[0036] The turbine wheel 2 according to this disclosure has a larger inclination angle θ than the turbine wheel 02 according to the comparative example. As shown in Figure 5, the turbine 1 equipped with the turbine wheel 2 can generate a component inward in the radial direction of the turbine wheel 2 in the flow of the working fluid that has passed through the turbine blades 5, and this component can suppress the outward flow in the radial direction due to the swirling of the working fluid. By suppressing the outward flow in the radial direction of the working fluid that has passed through the turbine blades 5, flow separation of the working fluid on the inner circumference side of the diffuser flow path 34 can be suppressed, and the pressure recovery performance due to the deceleration of the working fluid in the diffuser flow path 34 can be improved.

[0037] Figure 6 is a graph illustrating the relationship between the velocity ratio U / C0 of turbine 1, the static pressure recovery rate Cp in the diffuser flow path 34, and the inclination angle θ. The velocity ratio U / C0 is a dimensionless parameter representing turbine efficiency and is the ratio of the turbine peripheral speed U to the theoretical adiabatic speed C0. The graph in Figure 6 shows approximate curves L1 to L5 that show the relationship between the velocity ratio U / C0 and the static pressure recovery rate Cp for each inclination angle θ. Approximate curve L1 shows the relationship between the velocity ratio U / C0 and the static pressure recovery rate Cp when the inclination angle θ is 0 degrees. Approximate curve L2 shows the relationship between the velocity ratio U / C0 and the static pressure recovery rate Cp when the inclination angle θ is 7 degrees. Approximate curve L3 shows the relationship between the velocity ratio U / C0 and the static pressure recovery rate Cp when the inclination angle θ is 10 degrees. Approximate curve L4 shows the relationship between the velocity ratio U / C0 and the static pressure recovery rate Cp when the inclination angle θ is 13 degrees. The approximation curve L5 shows the relationship between the velocity ratio U / C0 and the static pressure recovery rate Cp when the slope angle θ is 16 degrees.

[0038] As shown in Figure 6, when the inclination angle θ is 0 degrees, the static pressure recovery rate decreases when the velocity ratio is relatively large. In contrast, when the inclination angle θ is between 7 degrees and 16 degrees, the static pressure recovery rate is relatively large even when the velocity ratio is relatively large.

[0039] By setting the inclination angle θ of the turbine wheel 2 to 7 degrees or more and 16 degrees or less, a radially inward component can be generated in the flow of the working fluid that has passed through the turbine blades 5, and this component can suppress the radially outward flow caused by the swirling of the working fluid. By suppressing the radially outward flow of the working fluid that has passed through the turbine blades 5, flow separation of the working fluid on the inner circumference side of the diffuser flow path 34 can be suppressed, and the pressure recovery performance due to the deceleration of the working fluid in the diffuser flow path 34 can be improved.

[0040] Preferably, the turbine wheel 2 is configured such that, in a meridional view of the turbine wheel 2 as shown in Figure 2, the inclination angle θ is 10 degrees or more and 13 degrees or less. By setting the inclination angle θ of the turbine wheel 2 to 10 degrees or more and 13 degrees or less, the pressure recovery performance due to the deceleration of the working fluid in the diffuser flow path 34 can be improved compared to cases where the inclination angle θ is 7 degrees or more and less than 10 degrees or greater than 13 degrees and 16 degrees or less.

[0041] As shown in Figure 6, when the inclination angle θ is 10 degrees or 13 degrees, the static pressure recovery rate is larger when the velocity ratio is relatively large compared to when the inclination angle θ is 7 degrees or 16 degrees.

[0042] Figure 7 is a schematic diagram showing a meridional cross-section of a turbine wheel 2 according to one embodiment of the present disclosure. In some embodiments of the turbine wheel 2, as shown in Figures 2 and 7, the hub surface 41 described above has a connection range CR with the turbine blade 5, which extends from the connection position P1 with the leading edge 51 of the turbine blade 5 to the connection position P2 with the trailing edge 52 of the turbine blade 5, in a meridional view of the turbine wheel 2, and is composed of a plurality of arcs 6.

[0043] The plurality of arcs 6 include at least a first arc 61 passing through a connection position P1 with the leading edge 51 of the turbine blade 5 in the connection range CR and a second arc 62 passing through a connection position P2 with the trailing edge 52 of the turbine blade 5 in the connection range CR in the meridional plane view of the turbine wheel 2 as shown in FIGS. 2 and 7. The downstream end 611 of the first arc 61 is located between the connection positions P1 and P2 of the hub surface 41. The upstream end 621 of the second arc 62 is located between the connection positions P1 and P2 of the hub surface 41. The center of curvature CC1 of the first arc 61 and the center of curvature CC2 of the second arc 62 are located outside the turbine wheel 2 in the radial direction from the hub surface 41.

[0044] Each of the plurality of arcs 6 has a predetermined radius of curvature. Let the radius of curvature of the first arc 61 be R1 and the radius of curvature of the second arc 62 be R2.

[0045] As shown in FIG. 2, the plurality of arcs 6 may be constituted by the first arc 61 and the second arc 62. The downstream end 611 of the first arc 61 is connected to the upstream end 621 of the second arc 62.

[0046] As shown in FIG. 7, in addition to the first arc 61 and the second arc 62, the plurality of arcs 6 may include one or more intermediate arcs 63 provided between the first arc 61 and the second arc 62 and having a predetermined radius of curvature. The radius of curvature of the intermediate arc 63 is preferably larger than the radius of curvature R1 of the first arc 61 and smaller than the radius of curvature R2 of the second arc 62. The center of curvature of the intermediate arc 63 is preferably located outside the turbine wheel 2 in the radial direction from the hub surface 41.

[0047] In the turbine wheel 2 according to some embodiments, the above-described hub surface 41 is configured such that the radius of curvature ratio R2 / R1 of the radius of curvature R2 of the second arc 62 to the radius of curvature R1 of the first arc 61 satisfies the condition of R2 / R1≧5.

[0048] When the radius of curvature ratio R2 / R1 of the turbine wheel 2 satisfies the condition of R2 / R1 ≥ 5, the change in the inclination angle θ of the turbine wheel 2 with respect to the axial direction in the second arc 62 becomes relatively small. Therefore, it is possible to suitably suppress the flow of the working fluid passing through the turbine blades 5 from spreading radially outward due to swirling.

[0049] In the turbine wheel 2 according to some embodiments, the hub surface 41 described above is configured such that the radius of curvature ratio R2 / R1 of the radius of curvature R2 of the second arc 62 with respect to the radius of curvature R1 of the first arc 61 satisfies the condition of R2 / R1 ≤ 30.

[0050] When the radius of curvature ratio R2 / R1 of the turbine wheel 2 satisfies the condition of R2 / R1 > 30, the radius of curvature R1 of the first arc 61 becomes too small. Therefore, separation of the flow of the working fluid may occur near the leading edge 51 of the turbine blade 5, and the effect of improving the pressure recovery performance may decrease. On the other hand, when the radius of curvature ratio R2 / R1 of the turbine wheel 2 satisfies the condition of R2 / R1 ≤ 30, it is possible to suppress the radius of curvature R1 of the first arc 61 from becoming excessively small, and thus suppress the separation of the flow of the working fluid near the leading edge 51 of the turbine blade 5.

[0051] FIG. 8 is a graph for explaining the relationship between the dimensionless meridional plane length position m of the hub surface 41 of the turbine wheel 2 and the radius of curvature R of the hub surface 41. In FIG. 8, a graph with the dimensionless meridional plane length position m on the horizontal axis and the radius of curvature R of the hub surface 41 on the vertical axis is shown. The broken line L6 in FIG. 8 shows an example of the radius of curvature R of the hub surface 41 composed of a plurality of arcs 6 (61, 62) as shown in FIG. 2. The curve L7 in FIG. 8 shows an example of the radius of curvature R of the hub surface 41 composed of a plurality of arcs 6 (61, 62, 63) as shown in FIG. 7.

[0052] In some embodiments of the turbine wheel 2, as shown in Figure 8, when the dimensionless meridian length position m of the connection position P1 between the hub surface 41 and the leading edge 51 of the turbine blade 5 is set to 0%, and the dimensionless meridian length position m of the connection position P2 between the hub surface 41 and the trailing edge 52 of the turbine blade 5 is set to 100%, the upstream end 621 of the second arc 62 is configured to be in the range from 60% to 90% of the dimensionless meridian length position m. In this embodiment, it is preferable that the radius of curvature ratio R2 / R1 satisfies the condition R2 / R1 ≥ 5, and it is even more preferable that the radius of curvature ratio R2 / R1 satisfies the condition R2 / R1 ≤ 30.

[0053] The turbine wheel 2 is configured such that the upstream end 621 of the second arc 62 is located in the range from 60% to 90% of the dimensionless meridional length position m. This configuration makes the change in the inclination angle θ of the turbine wheel 2 with respect to the axial direction in the second arc 62 relatively small, effectively suppressing the outward radial spread of the working fluid flow that has passed through the turbine blade 5 due to swirling. If the upstream end 621 of the second arc 62 were located closer to the trailing edge 52 (trailing edge connection position P2) than the 90% position of the dimensionless meridional length m, the blade length of the turbine blade 5 formed in the second arc 62 would become too short. This could cause flow separation of the working fluid near the trailing edge 52 of the turbine blade 5, potentially reducing the effect of improving pressure recovery performance.

[0054] In addition, in some other embodiments of the turbine wheel 2, the radius of curvature ratio R2 / R1 may be configured to satisfy either 0 < R2 / R1 < 5 or R2 / R1 > 30. Furthermore, the upstream end 621 of the second arc 62 may be located on the trailing edge 52 (trailing edge connection position P2) side of the 90% position of the dimensionless meridional length position m. The upstream end 621 of the second arc 62 may be located on the leading edge 51 (leading edge connection position P1) side of the 60% position of the dimensionless meridional length position m.

[0055] In some embodiments of the turbine wheel 2, as shown in Figures 2 and 7, the boss portion 43 described above, that is, the portion of the hub 4 downstream in the direction of the working fluid flow from the connection position P2 with the trailing edge 52 of the turbine blade 5, is configured to be located at the same radial position as the tangent TL of the hub surface 41 at the connection position P2 with the trailing edge 52 of the turbine blade 5, or radially inward from the tangent TL.

[0056] In other words, the turbine wheel 2 is configured such that the portion of the hub 4 downstream of the connection point P2 with the trailing edge 52 of the turbine blade 5 (boss portion 43) in the direction of the working fluid flow does not have a protrusion that extends radially outward from the tangent line TL. Since the boss portion 43 of the turbine wheel 2 does not have such a protrusion, it is possible to suppress the obstruction of the working fluid flow that the boss portion 43 has passed through the turbine blade 5.

[0057] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances sufficient to achieve the same function. For example, expressions describing things being in an equal state such as "identical," "equal," and "homogeneous" shall not only describe states of being strictly equal, but also describe states where tolerances or differences exist to the extent that the same function is achieved. Furthermore, in this specification, expressions describing shapes such as quadrilaterals or cylindrical shapes shall not only describe geometrically precise quadrilaterals or cylindrical shapes, but also describe shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect is achieved. In addition, in this specification, expressions such as "equipment," "includes," or "possesses" a component are not exclusive expressions that exclude the existence of other components.

[0058] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0059] The contents described in some of the embodiments above can be understood, for example, as follows:

[0060] 1) A turbine wheel (2) according to at least one embodiment of the present disclosure comprises a hub (4) having a hub surface (41) and at least one turbine blade (5) erected on the hub surface (41), wherein the hub surface (41) is configured such that, in a meridional view of the turbine wheel (2), the inclination angle (θ) of the turbine wheel (2) with respect to the axial direction at the connection point (P2) with the trailing edge (52) of the turbine blade (5) is 7 degrees or more and 16 degrees or less.

[0061] According to the configuration described in 1) above, by setting the inclination angle (θ) of the turbine wheel (2) to 7 degrees or more and 16 degrees or less, a radially inward component can be generated in the flow of the working fluid that has passed through the turbine blade (5), and this component can suppress the radially outward flow caused by the swirling of the working fluid. By suppressing the radially outward flow of the working fluid that has passed through the turbine blade (5), flow separation of the working fluid on the inner circumference side of the diffuser passage (34) can be suppressed, and the pressure recovery performance due to the deceleration of the working fluid in the diffuser passage (34) can be improved.

[0062] 2) In some embodiments, the turbine wheel (2) described in 1) above is configured such that the hub surface (41) is such that, in a meridional view of the turbine wheel (2), the inclination angle (θ) of the turbine wheel (2) with respect to the axial direction at the connection point (P2) with the trailing edge (52) of the turbine blade (5) is 10 degrees or more and 13 degrees or less.

[0063] According to the configuration described in 2) above, by setting the inclination angle (θ) of the turbine wheel (2) to 10 degrees or more and 13 degrees or less, the pressure recovery performance due to the deceleration of the working fluid in the diffuser flow path (34) can be improved compared to the case where the inclination angle (θ) is 7 degrees or more and less than 10 degrees or greater than 13 degrees and 16 degrees or less.

[0064] 3) In some embodiments, the turbine wheel (2) described in 1) or 2) above, wherein the hub surface (41) is configured such that, in a meridional view of the turbine wheel (2), the connection range with the turbine blade (5) from the connection point (P1) with the leading edge (51) of the turbine blade (5) to the connection point (P2) with the trailing edge (52) of the turbine blade (5) is composed of a plurality of arcs (6), and in a meridional view of the turbine wheel (2), the radius of curvature of the first arc (61) among the plurality of arcs (6) that passes through the connection point (P1) with the leading edge (51) of the turbine blade (5) in the connection range is R1, and in a meridional view of the turbine wheel (2), the radius of curvature of the second arc (62) among the plurality of arcs (6) that passes through the connection point (P2) with the trailing edge (52) of the turbine blade (5) in the connection range is R2. The hub surface (41) is configured such that the ratio of the radius of curvature R2 of the second arc (62) to the radius of curvature R1 of the first arc (61), R2 / R1, satisfies the condition R2 / R1 ≥ 5.

[0065] According to the configuration described in 3) above, when the radius of curvature ratio R2 / R1 of the turbine wheel (2) satisfies the condition R2 / R1 ≥ 5, the change in the inclination angle (θ) of the turbine wheel (2) with respect to the axial direction in the second arc (62) becomes relatively small, so that the spread of the working fluid flow that has passed through the turbine blade (5) radially outward due to swirling can be effectively suppressed.

[0066] 4) In some embodiments, the turbine wheel (2) described in 3) above is configured such that the hub surface (41) satisfies the condition that the radius of curvature ratio R2 / R1 is R2 / R1 ≤ 30.

[0067] According to the configuration described in 4) above, if the radius of curvature ratio R2 / R1 of the turbine wheel (2) satisfies the condition R2 / R1 > 30, the radius of curvature R1 of the first arc (61) becomes too small, which may cause flow separation of the working fluid near the leading edge (51) of the turbine blade (5), potentially reducing the effect of improving pressure recovery performance. In contrast, if the radius of curvature ratio R2 / R1 of the turbine wheel (2) satisfies the condition R2 / R1 ≤ 30, it is possible to suppress the radius of curvature R1 of the first arc (61) from becoming excessively small, and consequently, to suppress flow separation of the working fluid near the leading edge (51) of the turbine blade (5).

[0068] 5) In some embodiments, the turbine wheel (2) described in 3) or 4) above, where the dimensionless meridional length position of the connection point (P1) between the hub surface (41) and the leading edge (51) of the turbine blade (5) is set to 0%, and the dimensionless meridional length position of the connection point between the hub surface (41) and the trailing edge (52) of the turbine blade (5) is set to 100%, the upstream end (621) of the second arc (62) is configured to be located in the range from 60% to 90% of the dimensionless meridional length position.

[0069] According to the configuration in 5) above, the turbine wheel (2) is configured such that the upstream end (621) of the second arc (62) is located in the range from the 60% to the 90% position of the dimensionless meridional length. This makes the change in the inclination angle (θ) of the turbine wheel (2) with respect to the axial direction in the second arc (62) relatively small, and thus effectively suppresses the outward spreading of the working fluid flow radially due to swirling after passing over the turbine blade (5). If the upstream end (621) of the second arc (62) is located further towards the trailing edge (52) than the 90% position of the dimensionless meridional length, the blade length of the turbine blade (5) formed on the second arc (62) becomes too short, which may cause flow separation of the working fluid near the trailing edge (52) of the turbine blade (5), potentially reducing the effect of improving pressure recovery performance.

[0070] 6) In some embodiments, the turbine wheel (2) described in any of 1) to 5) above, wherein the portion of the hub (4) downstream in the direction of the working fluid flow from the connection position (P2) with the trailing edge (52) of the turbine blade (5) (boss portion 43) is configured such that, in a meridional view of the turbine wheel (2), it is located at the same radial position as the tangent (TL) of the hub surface (41) at the connection position (P2) with the trailing edge (52) of the turbine blade (5), or radially inward from the tangent (TL).

[0071] According to the configuration in 6) above, the turbine wheel (2) is configured such that the portion of the hub (4) downstream in the direction of the working fluid flow (boss portion 43) from the connection point (P2) between the hub (4) and the trailing edge (52) of the turbine blade (5) does not have a protrusion that extends radially outward from the tangent (TL). Since the boss portion (43) of the turbine wheel (2) does not have the aforementioned protrusion, it is possible to suppress the obstruction of the flow of working fluid that has passed through the turbine blade (5) by the boss portion (43).

[0072] 7) A turbine (1) according to at least one embodiment of the present disclosure comprises a turbine wheel (2) as described in any of 1) to 6) above, and a turbine casing (3) configured to rotatably house the turbine wheel (2).

[0073] According to the configuration described in 7) above, the turbine (1) can improve the pressure recovery performance by reducing the working fluid in the diffuser flow path (34) formed within the turbine casing (3).

[0074] 1 Turbine 2 Turbine wheel 3 Turbine casing 4 Hub 5 Turbine blade 10 Turbocharger 11 Centrifugal compressor 12 Impeller 13 Compressor casing 14 Rotating shaft 15 Bearing 16 Bearing casing 31 Scroll passage 32 Working fluid discharge passage 34 Diffuser passage 41 Hub face 42 Back face 51 Leading edge 52 Trailing edge 53 Hub side end 54 Tip side end 121 Compressor hub 122 Compressor blade 131 Combustion gas introduction passage 132 Compressed gas discharge passage LA axis

Claims

1. A turbine wheel comprising a hub having a hub surface and at least one turbine blade erected on the hub surface, wherein the hub surface is configured such that, in a meridional view of the turbine wheel, the inclination angle with respect to the axial direction of the turbine wheel at the connection point with the trailing edge of the turbine blade is 7 degrees or more and 16 degrees or less.

2. The turbine wheel according to claim 1, wherein the hub surface is configured such that, in a meridional view of the turbine wheel, the inclination angle of the turbine wheel with respect to the axial direction at the connection point with the trailing edge of the turbine blade is 10 degrees or more and 13 degrees or less.

3. The hub surface is configured such that, in a meridional view of the turbine wheel, the connection range with the turbine blade, extending from the connection point with the leading edge of the turbine blade to the connection point with the trailing edge of the turbine blade, is composed of a plurality of arcs, and in a meridional view of the turbine wheel, the radius of curvature of the first arc among the plurality of arcs that passes through the connection point with the leading edge of the turbine blade in the connection range is R1, and in a meridional view of the turbine wheel, the radius of curvature of the second arc among the plurality of arcs that passes through the connection point with the trailing edge of the turbine blade in the connection range is R2, and the hub surface is configured such that the ratio of the radius of curvature of the second arc R2 to the radius of curvature of the first arc R1 satisfies the condition R2 / R1 ≥ 5.

4. The turbine wheel according to claim 3, wherein the hub surface is configured such that the radius of curvature ratio R2 / R1 satisfies the condition R2 / R1 ≤ 30.

5. The turbine wheel according to claim 3, wherein, when the dimensionless meridional length position of the connection point between the hub surface and the leading edge of the turbine blade is set to 0%, and the dimensionless meridional length position of the connection point between the hub surface and the trailing edge of the turbine blade is set to 100%, the upstream end of the second arc is configured to be in the range from 60% to 90% of the dimensionless meridional length position.

6. The turbine wheel according to claim 1 or 2, wherein the portion of the hub downstream in the direction of the working fluid flow from the connection point with the trailing edge of the turbine blade is configured such that, in a meridional view of the turbine wheel, it is located at the same radial position as the tangent to the hub surface at the connection point with the trailing edge of the turbine blade, or radially inward from the tangent.

7. A turbine comprising a turbine wheel according to claim 1 or 2, and a turbine casing configured to rotatably house the turbine wheel.

Images