Turbines and turbochargers

Abstract

This turbine T comprises: a turbine scroll flow passage; a turbine impeller 15 disposed further inside in a radial direction than the turbine scroll flow passage; and a blade body 15b that is inclined, from a hub 15a side to a shroud side, in the direction opposite to a rotation direction RD side of the turbine impeller 15, that has a leading edge LE which is provided to the turbine impeller 15 and has an inclination angle α1 of the turbine impeller 15 with respect to a center axis direction AD of greater than 0° and no greater than 45° when viewed in a radial direction.

Description

[Technical Field]

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2021-044156, filed on March 17, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] Turbines installed in turbochargers and the like include a type in which gas flows into the turbine wheel from the radially outer side. For example, Patent Document 1 discloses a radial turbine of this type in which gas flows in radially. Note that a turbine in which gas flows in a direction inclined relative to the radial direction is called a mixed-flow turbine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 128898 Summary of the Invention [Problem to be solved by the invention]

[0004] In turbines where gas flows into the turbine wheel from the outside in the radial direction, separation of the gas flow can occur at the gas inlet of the turbine wheel (i.e., the part of the turbine wheel into which the gas flows), depending on the operating conditions, and vortices can be generated. When separation of the gas flow occurs at the gas inlet of the turbine wheel, the efficiency of the turbine decreases.

[0005] An object of the present disclosure is to provide a turbine and a turbocharger that can improve the efficiency of the turbine. [Means for solving the problem]

[0006] In order to solve the above problems, the turbine of the present disclosure includes a turbine scroll passage, a turbine wheel arranged radially inward of the turbine scroll passage, and a turbine wheel inclined in the opposite direction to the rotation direction of the turbine wheel as it moves from the hub side to the shroud side, and the inclination angle with respect to the central axis direction of the turbine wheel when viewed in the radial direction is 10° to 30°. and has a linear shape and a blade body having a leading edge and provided on the turbine wheel, wherein, in the circumferential direction of the turbine wheel, the position of the hub-side end of the leading edge is located closer to the rotational direction than the position of the shroud-side end of the leading edge. The inclination angle is constant from the hub side to the shroud side. .

[0009] In order to solve the above problem, a turbocharger according to the present disclosure includes the above turbine. [Effects of the Invention]

[0010] According to the present disclosure, turbine efficiency can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a turbocharger according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view taken along the line AA in FIG. [Figure 3] FIG. 3 is a diagram of the portion enclosed by the dashed dotted line in FIG. [Figure 4] FIG. 4 is a side view illustrating a turbine wheel according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a graph showing the relationship between the leading edge inclination angle and the turbine efficiency difference. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for ease of understanding and, unless otherwise specified, do not limit the present disclosure. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

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

[0014] A protrusion 3a is provided on the outer peripheral surface of the bearing housing 3. The protrusion 3a is provided on the turbine housing 5 side. The protrusion 3a protrudes in the radial direction of the bearing housing 3. A protrusion 5a is provided on the outer peripheral surface of the turbine housing 5. The protrusion 5a is provided on the bearing housing 3 side. The protrusion 5a protrudes in the radial direction of the turbine housing 5. The bearing housing 3 and the turbine housing 5 are band-fastened by a fastening mechanism 9. The fastening mechanism 9 is, for example, a G-coupling. The fastening mechanism 9 clamps the protrusions 3a and 5a.

[0015] A bearing hole 3b is formed in the bearing housing 3. The bearing hole 3b penetrates the turbocharger TC in the left-right direction. A bearing is disposed in the bearing hole 3b. A shaft 13 is inserted into the bearing. The bearing supports the shaft 13 so that it can rotate freely. The bearing is a plain bearing. However, the bearing is not limited to this and may be a rolling bearing. A turbine wheel 15 is provided at the left end of the shaft 13. The turbine wheel 15 is rotatably housed in the turbine housing 5. A compressor wheel 17 is provided at the right end of the shaft 13. The compressor wheel 17 is rotatably housed in the compressor housing 7.

[0016] An intake port 19 is formed in the compressor housing 7. The intake port 19 opens to the right side of the turbocharger TC. The intake port 19 is connected to an air cleaner (not shown). A diffuser passage 21 is formed by the opposing surfaces of the bearing housing 3 and the compressor housing 7. The diffuser passage 21 pressurizes the air. The diffuser passage 21 is formed in an annular shape. The diffuser passage 21 communicates with the intake port 19 on its radially inner side via the compressor impeller 17.

[0017] A compressor scroll passage 23 is formed in the compressor housing 7. The compressor scroll passage 23 is formed in an annular shape. The compressor scroll passage 23 is located, for example, radially outward of the diffuser passage 21 on the shaft 13. The compressor scroll passage 23 is connected to an intake port of the engine (not shown) and the diffuser passage 21. When the compressor impeller 17 rotates, air is drawn into the compressor housing 7 through the intake port 19. The drawn air is pressurized and accelerated as it flows between the blades of the compressor impeller 17. The pressurized and accelerated air is pressurized in the diffuser passage 21 and the compressor scroll passage 23. The pressurized air is led to the intake port of the engine.

[0018] The turbine housing 5 is formed with an exhaust passage 25, an accommodation portion 27, and an exhaust passage 29. The exhaust passage 25 opens to the left side of the turbocharger TC. The exhaust passage 25 is connected to an exhaust gas purification device (not shown). The exhaust passage 25 communicates with the accommodation portion 27. The exhaust passage 25 is continuous with the accommodation portion 27 in the direction of the rotation axis of the turbine wheel 15. The accommodation portion 27 accommodates the turbine wheel 15. The exhaust passage 29 is formed radially outward from the turbine wheel 15. The exhaust passage 29 is formed in an annular shape. The exhaust passage 29 includes a turbine scroll passage 29a. The turbine scroll passage 29a communicates with the accommodation portion 27. In other words, the turbine wheel 15 is disposed radially inward from the turbine scroll passage 29a.

[0019] The exhaust flow path 29 communicates with an exhaust manifold of the engine (not shown). Exhaust gas discharged from the exhaust manifold of the engine (not shown) is guided to the exhaust flow path 25 via the exhaust flow path 29 and the housing portion 27. The exhaust gas guided to the exhaust flow path 25 rotates the turbine wheel 15 during the flow process.

[0020] The rotational force of the turbine wheel 15 is transmitted to the compressor impeller 17 via the shaft 13. When the compressor impeller 17 rotates, the air is pressurized as described above, and the air is then guided to the intake port of the engine.

[0021] Fig. 2 is a cross-sectional view taken along the line AA in Fig. 1. In Fig. 2, only the outer periphery of turbine wheel 15 is shown as a circle. As shown in Fig. 2, an exhaust flow path 29 is formed radially outside housing portion 27 (i.e., radially outside turbine wheel 15). Exhaust flow path 29 includes turbine scroll flow path 29a, a communication portion 29b, an exhaust inlet port 29c, and an exhaust introduction path 29d.

[0022] The communicating portion 29b is formed in an annular shape around the entire circumference of the accommodating portion 27. The turbine scroll passage 29a is located radially outward of the turbine wheel 15 with respect to the communicating portion 29b. The turbine scroll passage 29a is formed in an annular shape around the entire circumference of the communicating portion 29b (i.e., the entire circumference of the accommodating portion 27). The communicating portion 29b communicates between the accommodating portion 27 and the turbine scroll passage 29a. The turbine housing 5 is formed with a tongue portion 31. The tongue portion 31 is provided at the downstream end of the turbine scroll passage 29a, and separates the downstream portion from the upstream portion of the turbine scroll passage 29a.

[0023] The exhaust inlet 29c opens to the outside of the turbine housing 5. Exhaust gas discharged from an exhaust manifold of an engine (not shown) is introduced into the exhaust inlet 29c. An exhaust inlet passage 29d is formed between the exhaust inlet 29c and the turbine scroll passage 29a. The exhaust inlet passage 29d connects the exhaust inlet 29c and the turbine scroll passage 29a. The exhaust inlet passage 29d is formed, for example, in a linear shape. The exhaust inlet passage 29d guides the exhaust gas introduced from the exhaust inlet 29c to the turbine scroll passage 29a. The turbine scroll passage 29a guides the exhaust gas introduced from the exhaust inlet passage 29d to the accommodating section 27 via the communicating section 29b.

[0024] A bypass passage 33 is formed in the turbine housing 5. An inlet end OP of the bypass passage 33 opens to the exhaust passage 29 (specifically, the exhaust introduction passage 29d). An outlet end of the bypass passage 33 opens to the discharge passage 25 (see FIG. 1). The bypass passage 33 connects the exhaust introduction passage 29d and the discharge passage 25. A wastegate port WP (see FIG. 1) is formed at the outlet end of the bypass passage 33. A wastegate valve WV (see FIG. 1) that can open and close the wastegate port WP is disposed at the outlet end of the bypass passage 33. The wastegate valve WV is disposed in the discharge passage 25. When the wastegate valve WV opens the wastegate port WP, the bypass passage 33 causes a portion of the exhaust gas flowing through the exhaust introduction passage 29d to bypass the accommodation portion 27 (i.e., bypass the turbine wheel 15) and flow into the discharge passage 25.

[0025] In the turbine T, the flow rate of the exhaust gas flowing into the turbine wheel 15 is adjusted by controlling the opening and closing operation of the wastegate port WP. In this way, the turbine T is a variable displacement turbine. The bypass flow path 33 and the wastegate valve WV correspond to a flow rate adjustment mechanism that adjusts the flow rate of the exhaust gas flowing into the turbine wheel 15. However, as will be described later, the flow rate adjustment mechanism is not limited to the above example.

[0026] FIG. 3 is a diagram of the portion enclosed by the dashed dotted line in FIG. 1. As shown in FIG. 3, the turbine wheel 15 has a hub 15a and multiple blades 15b. Hereinafter, the central axial direction, circumferential direction, and radial direction of the turbine wheel 15 will also be simply referred to as the central axial direction, circumferential direction, and radial direction. The hub 15a is connected to the left end of the shaft 13 (see FIG. 1). The outer diameter of the hub 15a decreases toward the left side of the turbocharger TC. Multiple blades 15b are provided on the outer peripheral surface of the hub 15a. The multiple blades 15b are provided at intervals in the circumferential direction. The blades 15b are formed to extend radially outward from the outer peripheral surface of the hub 15a. The outer edges of the blades 15b include a leading edge LE and a trailing edge TE.

[0027] The leading edge LE is an edge portion of the blade body 15b on the upstream side in the flow direction of the exhaust gas. The leading edge LE is an edge portion of the blade body 15b on the turbine scroll passage 29a side. Exhaust gas flows into the leading edge LE from the turbine scroll passage 29a. In other words, the portion of the turbine wheel 15 where the leading edge LE is located corresponds to the exhaust gas inlet portion of the turbine wheel 15 (i.e., the portion of the turbine wheel 15 into which the exhaust gas flows). The leading edge LE is formed on the right end side of the blade body 15b. When viewed in the circumferential direction, the leading edge LE extends in the direction of the central axis of the turbine wheel 15. In the example of FIG. 3, the leading edge LE is inclined radially outward as it progresses in the direction of the central axis. However, when viewed in the circumferential direction, the leading edge LE may be parallel to the central axis direction.

[0028] The right end of the leading edge LE is the hub-side end P1 (i.e., the end on the hub 15a side). The left end of the leading edge LE is the shroud-side end P2 (i.e., the end on the shroud 27a side, which is the part of the turbine housing 5 that forms the accommodation portion 27). The leading edge LE extends from the hub-side end P1 to the shroud-side end P2.

[0029] The trailing edge TE is the edge of the blade body 15b on the downstream side in the flow direction of the exhaust gas. The trailing edge TE is the edge of the blade body 15b on the exhaust flow path 25 side. The exhaust gas flows out from the trailing edge TE toward the exhaust flow path 25. The trailing edge TE is formed on the left end side of the blade body 15b. When viewed in the circumferential direction, the trailing edge TE extends in the radial direction. Specifically, the trailing edge TE extends in the radial direction while twisting in the circumferential direction.

[0030] The portion of the outer peripheral edge of the blade body 15 b between the leading edge LE and the trailing edge TE extends along the shroud 27 a of the turbine housing 5 .

[0031] As shown by arrow FD in Fig. 3, exhaust gas flows radially into the turbine wheel 15 from the radially outer side. Thus, the turbine T is a radial turbine. However, the turbine T may also be a mixed-flow turbine in which exhaust gas flows in from the radially outer side in a direction inclined with respect to the radial direction.

[0032] Here, in a turbine T in which gas flows into the turbine wheel 15 from the radial outside, gas flow separation may occur at the exhaust gas inlet portion of the turbine wheel 15, causing vortices, depending on the operating conditions. In the turbine T, which is a variable geometry turbine, the operating conditions (specifically, the flow rate of exhaust gas flowing into the turbine wheel 15, etc.) vary over a wide range. Therefore, in the turbine T, which is a variable geometry turbine, gas flow separation is particularly likely to occur at the exhaust gas inlet portion of the turbine wheel 15. Such gas flow separation is a factor that reduces the efficiency of the turbine T. In the turbine T, which is a variable geometry turbine, there is a particularly high need to improve the efficiency of the turbine T.

[0033] Therefore, in the turbine T according to this embodiment, the shape of the blade body 15b of the turbine wheel 15 is devised to improve the efficiency of the turbine T. Hereinafter, the shape of the blade body 15b of the turbine wheel 15 will be described in detail with reference to Figs. 4 and 5.

[0034] 4 is a side view showing the turbine wheel 15 according to this embodiment. The leading edge LE of the blade body 15b of the turbine wheel 15 is inclined away from the rotation direction RD of the turbine wheel 15 as it progresses from the hub 15a side to the shroud 27a side. That is, in each blade body 15b, the circumferential position of the hub-side end P1 of the leading edge LE is closer to the rotation direction RD than the circumferential position of the shroud-side end P2 of the leading edge LE. In the example of FIG. 4, the rotation direction RD is counterclockwise when the turbine wheel 15 is viewed from the left side of the turbocharger TC (i.e., from the top in FIG. 4).

[0035] The leading edge LE has a linear shape. Specifically, the leading edge LE extends on a straight line connecting the hub-side end P1 and the shroud-side end P2. However, the shape of the leading edge LE is not limited to a linear shape. For example, a portion of the leading edge LE may be curved or bent.

[0036] The inventors conducted a flow analysis simulation to find that the efficiency of the turbine T varies depending on the inclination angle α1 of the leading edge LE with respect to the central axis direction AD of the turbine wheel 15 as viewed in the radial direction. The flow analysis simulation calculated the gas flow (e.g., direction, velocity, entropy, etc.) in the turbine wheel 15 and the efficiency of the turbine T when the inclination angle α1 was varied. In particular, the flow analysis simulation found that the efficiency of the turbine T improved when the leading edge LE was inclined toward the side opposite the rotation direction RD of the turbine wheel 15 as it progressed from the hub 15a side to the shroud 27a side, and when the inclination angle α1 was set within a specific range. As a result, in the turbine T according to this embodiment, the inclination angle α1 of the leading edge LE was set to be greater than 0° and equal to or less than 45°. This improves the efficiency of the turbine T.

[0037] FIG. 5 is a graph showing the relationship between the inclination angle α1 [deg] of the leading edge LE and the efficiency difference ΔE [%] of the turbine T. FIG. 5 is a graph obtained by a flow analysis simulation. The efficiency difference ΔE of the turbine T is the amount of change in the efficiency of the turbine T at each inclination angle α1 relative to the efficiency of the turbine T when the inclination angle α1 is 0°. In other words, the efficiency difference ΔE is obtained by subtracting the efficiency of the turbine T when the inclination angle α1 is 0° from the efficiency of the turbine T at each inclination angle α1. The efficiency of the turbine T is the ratio of the energy generated by the turbine T to the energy input to the turbine T.

[0038] 5, it can be seen that when the inclination angle α1 of the leading edge LE is greater than 0° and equal to or less than 45°, the efficiency of the turbine T is higher than when the inclination angle α1 is equal to or less than 0° or when the inclination angle α1 is greater than 45°. Note that when the inclination angle α1 is equal to or less than 0°, this corresponds to the case where the leading edge LE is parallel to the central axis direction AD or the case where the leading edge LE is inclined toward the rotation direction RD of the turbine wheel 15 as it moves from the hub 15a side to the shroud 27a side.

[0039] In a flow analysis simulation, it was observed that when the inclination angle α1 of the leading edge LE is greater than 0° and equal to or less than 45°, separation of the gas flow and the generation of vortices due to separation are suppressed in the portion of the turbine wheel 15 where the leading edge LE is located (i.e., the exhaust gas inlet portion of the turbine wheel 15). In other words, when the inclination angle α1 of the leading edge LE is greater than 0° and equal to or less than 45°, separation of the gas flow is suppressed, and as a result, it is thought that the efficiency of the turbine T is improved.

[0040] According to a flow analysis simulation, it is found that when the leading edge LE is inclined away from the rotation direction RD of the turbine wheel 15 as it moves from the hub 15a side to the shroud 27a side, the impact when the exhaust gas flowing in from the leading edge LE collides with the blade body 15b is alleviated and the generation of vortexes in the flow of the exhaust gas is suppressed. On the other hand, it is found that if the inclination angle α1 of the leading edge LE is excessively large, it becomes difficult for the exhaust gas flow to follow the blade body 15b after the exhaust gas flowing in from the leading edge LE collides with the blade body 15b, and gas flow separation is more likely to occur.

[0041] In the graph shown in Fig. 5, the efficiency difference ΔE of the turbine T is maximum when the inclination angle α1 is around 20°. As such, according to the graph shown in Fig. 5, it can be seen that the efficiency of the turbine T is particularly improved when the inclination angle α1 of the leading edge LE is equal to or greater than 10° and equal to or less than 30°.

[0042] In a flow analysis simulation, it was observed that when the inclination angle α1 of the leading edge LE is equal to or greater than 10° and equal to or less than 30°, separation of the gas flow and the generation of vortices due to separation are effectively suppressed in the portion of the turbine wheel 15 where the leading edge LE is located (i.e., the exhaust gas inlet portion of the turbine wheel 15). In other words, when the inclination angle α1 of the leading edge LE is equal to or greater than 10° and equal to or less than 30°, separation of the gas flow is effectively suppressed, and it is considered that the efficiency of the turbine T is effectively improved.

[0043] As described above, in the turbine T, the leading edge LE has a linear shape. This allows the inclination angle α1 to be optimized and the efficiency of the turbine T to be improved appropriately based on knowledge obtained from the flow analysis simulation.

[0044] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present disclosure.

[0045] Although the above describes an example in which the turbine T is a single scroll type (a type in which the number of turbine scroll passages 29a is one), the type of the turbine T is not limited to the above example. For example, the turbine T may be a double scroll type (a type in which two turbine scroll passages 29a are connected to the accommodating section 27 at different circumferential positions) or a twin scroll type (a type in which two turbine scroll passages 29a are arranged side by side in the axial direction).

[0046] In the above, an example has been described in which the bypass flow path 33 and the wastegate valve WV are used as a flow rate adjustment mechanism that adjusts the flow rate of exhaust gas flowing into the turbine wheel 15. However, the flow rate adjustment mechanism is not limited to the above example. For example, a mechanism including a plurality of variable nozzle vanes that can adjust the flow rate cross-sectional area of ​​the flow path upstream of the turbine wheel 15 may be used as the flow rate adjustment mechanism. The plurality of variable nozzle vanes are provided radially outward from the turbine wheel 15. The plurality of variable nozzle vanes are provided at intervals in the circumferential direction of the turbine wheel 15. As the variable nozzle vanes rotate, the flow rate cross-sectional area of ​​the flow path upstream of the turbine wheel 15 changes depending on the rotation angle of the variable nozzle vanes. This adjusts the flow rate of exhaust gas flowing into the turbine wheel 15. Note that the turbine T does not necessarily have to be provided with a flow rate adjustment mechanism. The turbine T may also be provided with both a flow rate adjustment mechanism including a wastegate valve WV and a flow rate adjustment mechanism including variable nozzle vanes.

[0047] In the above, an example has been described in which the turbine T is provided in the turbocharger TC. However, the turbine T may be provided in a device other than the turbocharger TC. [Explanation of symbols]

[0048] 15: Turbine impeller 15a: Hub 15b: Blade body 27a: Shroud 29a: Turbine scroll passage AD: Central axis direction LE: Leading edge RD: Rotation direction T: Turbine TC: Turbocharger α1: Inclination angle

Claims

1. a turbine scroll flow path; a turbine impeller disposed radially inward of the turbine scroll flow path; a blade body provided on the turbine wheel, the blade body having a leading edge with a linear shape, the leading edge inclining toward the opposite side to the rotation direction of the turbine wheel as it progresses from the hub side to the shroud side, and the inclination angle with respect to the central axis direction of the turbine wheel when viewed in the radial direction being between 10° and 30°; Equipped with In the circumferential direction of the turbine wheel, a position of an end portion of the leading edge on the hub side is located closer to the rotation direction than a position of an end portion of the leading edge on the shroud side, The inclination angle is constant from the hub side to the shroud side. Turbine.

2. A turbocharger comprising the turbine according to claim 1.

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