Turbines and superchargers

Abstract

The turbine (T) comprises: a housing (29) for housing a turbine impeller (15); an exhaust flow path (31) for connecting the housing (29) with an exhaust inlet (31c); a discharge flow path for connecting the housing (29) with an exhaust outlet; a bypass flow path (35) for connecting the exhaust flow path (31) with the discharge flow path in a manner that bypasses the housing (29); and a branching portion (BP) between the exhaust flow path (31) and the bypass flow path (35), which has a flow path cross-sectional area that is 0.6 times or more the flow path cross-sectional area of ​​the exhaust inlet (31c).

Description

Technical Field

[0001] The present disclosure relates to a turbine and a supercharger. This application claims the benefit of priority based on Japanese Patent Application No. 2021-048180, filed on March 23, 2021, the contents of which are incorporated herein by reference. Background Art

[0002] A turbine, such as one provided in a supercharger, has a housing portion that houses the turbine impeller. The housing portion communicates with an exhaust gas inlet via an exhaust gas flow path and communicates with an exhaust gas outlet via a discharge gas flow path. For example, some turbines include a bypass flow path, as disclosed in Patent Document 1. The bypass flow path connects the exhaust gas flow path and the discharge flow path, bypassing the housing portion.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-241898 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In turbines equipped with a bypass flow path, gas flow separation easily occurs at the branching portion between the exhaust flow path and the bypass flow path. Gas flow separation at the branching portion increases pressure loss in the turbine, significantly reducing turbine efficiency.

[0008] An object of the present disclosure is to provide a turbine and a supercharger capable of improving the efficiency of the turbine.

[0009] Solutions to Problems

[0010] In order to solve the above-mentioned problems, the turbine disclosed in the present invention comprises: a housing portion, which houses a turbine impeller; an exhaust flow path, which connects the housing portion with the exhaust inlet; a discharge flow path, which connects the housing portion with the exhaust nozzle; a bypass flow path, which connects the exhaust flow path with the discharge flow path in a manner that bypasses the housing portion; and a branch portion, which is a branch portion between the exhaust flow path and the bypass flow path, and has a flow path cross-sectional area that is greater than 0.6 times the flow path cross-sectional area of ​​the exhaust inlet.

[0011] Preferably, in the exhaust gas flow path closer to the exhaust gas inlet than the branch portion, the flow path cross-sectional area in an area of ​​60% or more closer to the exhaust gas inlet in the direction in which the exhaust gas flow path extends is 0.9 times or more of the flow path cross-sectional area of ​​the exhaust gas inlet.

[0012] In order to solve the above-mentioned problems, a supercharger according to the present disclosure includes the above-mentioned turbine.

[0013] Effects of the Invention

[0014] According to the present disclosure, the efficiency of a turbine can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic cross-sectional view of a supercharger according to an embodiment of the present disclosure.

[0016] Figure 2 yes Figure 1 Cross-sectional view at section AA.

[0017] Figure 3 This is a graph showing the distribution of the cross-sectional area ratio of the flow path cross-sectional area at each flow direction position of the exhaust flow path in the turbine according to the embodiment of the present disclosure to the flow path cross-sectional area of ​​the exhaust gas inlet.

[0018] Figure 4 It is a graph showing the relationship between the cross-sectional area ratio and the efficiency change.

[0019] Figure 5 This is a diagram showing entropy distribution obtained by flow analysis simulation in a comparative example.

[0020] Figure 6 This is a diagram showing entropy distribution obtained by flow analysis simulation in this embodiment. DETAILED DESCRIPTION

[0021] The following describes embodiments of the present disclosure with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples to facilitate understanding and do not limit the present disclosure unless otherwise specified. Furthermore, in this specification and the accompanying drawings, elements having substantially the same function and structure are denoted by the same reference numerals, and repeated descriptions are omitted. Elements not directly related to the present disclosure are also omitted from illustration.

[0022] Figure 1 This is a simplified cross-sectional view of the supercharger TC. Figure 1 The direction of arrow L shown is explained as the left side of the supercharger TC. Figure 1 The direction of arrow R shown is explained as the right side of the supercharger TC. Figure 1 As shown, supercharger TC includes a supercharger body 1. The supercharger 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 via a fastening mechanism 9. The compressor housing 7 is connected to the right side of the bearing housing 3 via fastening bolts 11. Supercharger 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 a bearing housing 3 and a compressor housing 7.

[0023] A protrusion 3a is provided on the outer circumferential surface of the bearing housing 3. The protrusion 3a is located on the turbine housing 5 side. The protrusion 3a protrudes radially from the bearing housing 3. A protrusion 5a is provided on the outer circumferential surface of the turbine housing 5. The protrusion 5a is located on the bearing housing 3 side. The protrusion 5a protrudes radially from the turbine housing 5. The bearing housing 3 and the turbine housing 5 are fastened together in a band-like manner 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.

[0024] A bearing hole 3b is formed in the bearing housing 3. The bearing hole 3b extends horizontally through the supercharger TC. A bearing is disposed in the bearing hole 3b. The rotating shaft 13 is inserted through the bearing. The bearing rotatably supports the rotating shaft 13. The bearing is a sliding bearing. However, this is not limited to a sliding bearing; the bearing may also be a rolling bearing. A turbine impeller 15 is disposed at the left end of the rotating shaft 13. The turbine impeller 15 is rotatably housed in the turbine housing 5. A compressor impeller 17 is disposed at the right end of the rotating shaft 13. The compressor impeller 17 is rotatably housed in the compressor housing 7.

[0025] An air intake port 19 is formed in the compressor housing 7. The air intake port 19 opens to the right of the supercharger TC. The air intake port 19 is connected to an air cleaner (not shown). A diffuser flow path 21 is formed by the opposing surfaces of the bearing housing 3 and the compressor housing 7. The diffuser flow path 21 boosts the air pressure. The diffuser flow path 21 is annular in shape. The diffuser flow path 21 communicates with the air intake port 19 radially inwardly via the compressor impeller 17.

[0026] A compressor scroll flow path 23 is formed in the compressor housing 7. The compressor scroll flow path 23 is formed in an annular shape. The compressor scroll flow path 23 is located, for example, at a position radially outside the rotating shaft 13 relative to the diffuser flow path 21. The compressor scroll flow path 23 is connected to the air intake and diffuser flow path 21 of the engine (not shown). If the compressor impeller 17 rotates, air is sucked into the compressor housing 7 from the air intake 19. The sucked air is pressurized and accelerated in the process of flowing between the blades of the compressor impeller 17. The pressurized and accelerated air is pressurized in the diffuser flow path 21 and the compressor scroll flow path 23. The pressurized air is guided to the air intake of the engine.

[0027] An exhaust gas outlet 25 is formed in the turbine housing 5. The exhaust gas outlet 25 opens on the left side of the supercharger TC. The exhaust gas outlet 25 is connected to an exhaust gas purification device (not shown). An exhaust flow path 27, a storage portion 29, and an exhaust flow path 31 are formed in the turbine housing 5. The exhaust flow path 27 connects the storage portion 29 with the exhaust gas outlet 25. The exhaust flow path 27 and the storage portion 29 are continuous in the direction of the rotation axis of the turbine impeller 15. The storage portion 29 stores the turbine impeller 15. The exhaust flow path 31 is formed radially outward of the turbine impeller 15. The exhaust flow path 31 is formed in an annular shape. The exhaust flow path 31 includes a turbine vortex flow path 31a. The turbine vortex flow path 31a is connected to the storage portion 29. In other words, the turbine impeller 15 is arranged radially inward of the turbine vortex flow path 31a.

[0028] The exhaust flow path 31 communicates with the 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 27 via the exhaust flow path 31 and the accommodating portion 29. The exhaust gas guided to the exhaust flow path 27 rotates the turbine impeller 15 as it flows through the exhaust flow path 31.

[0029] The rotational force of the turbine impeller 15 is transmitted to the compressor impeller 17 via the rotating shaft 13. When the compressor impeller 17 rotates, the air pressure is increased as described above. In this way, the air is guided to the air intake of the engine.

[0030] Figure 2 yes Figure 1 Cross-sectional view at section AA. Figure 2 In FIG. 1 , only the outer periphery of the turbine impeller 15 is shown as a circle. Figure 2 As shown, an exhaust flow path 31 is formed radially outside the housing 29 (i.e., radially outside the turbine impeller 15). The exhaust flow path 31 includes a turbine scroll flow path 31a, a communication portion 31b, an exhaust inlet 31c, and an exhaust inlet path 31d. The exhaust flow path 31 connects the housing 29 with the exhaust inlet 31c.

[0031] The communicating portion 31b is formed in an annular shape over the entire circumference of the housing portion 29. The turbine vortex flow path 31a is located radially outside the turbine impeller 15 relative to the communicating portion 31b. The turbine vortex flow path 31a is formed in an annular shape over the entire circumference of the communicating portion 31b (i.e., the entire circumference of the housing portion 29). The communicating portion 31b connects the housing portion 29 with the turbine vortex flow path 31a. A tongue portion 33 is formed in the turbine housing 5. The tongue portion 33 is provided at the downstream end of the turbine vortex flow path 31a, separating the downstream portion of the turbine vortex flow path 31a from the upstream portion.

[0032] The exhaust inlet 31c opens to the outside of the turbine housing 5. Exhaust gas discharged from the exhaust manifold of the engine (not shown) is introduced into the exhaust inlet 31c. An exhaust inlet passage 31d is formed between the exhaust inlet 31c and the turbine scroll flow path 31a. The exhaust inlet passage 31d connects the exhaust inlet 31c and the turbine scroll flow path 31a. The exhaust inlet passage 31d is formed, for example, in a straight line shape. The exhaust inlet passage 31d guides the exhaust gas introduced from the exhaust inlet 31c to the turbine scroll flow path 31a. The turbine scroll flow path 31a guides the exhaust gas introduced from the exhaust inlet 31d to the storage portion 29 via the connecting portion 31b.

[0033] The bypass flow path 35 is formed in the turbine housing 5. The inlet end of the bypass flow path 35 opens to the exhaust flow path 31 (specifically, the exhaust gas introduction path 31d). The outlet end of the bypass flow path 35 opens to the exhaust flow path 27 (see Figure 1 The bypass flow path 35 connects the exhaust flow path 31 (specifically, the exhaust gas introduction path 31d) and the exhaust flow path 27 in a manner that bypasses the storage portion 29. An exhaust gas bypass port WP (see Figure 1 A wastegate valve WV capable of opening and closing the wastegate port WP is disposed at the outlet end of the bypass flow path 35 (see Figure 1 The wastegate valve WV is disposed in the exhaust passage 27. When the wastegate valve WV opens the wastegate port WP, the bypass passage 35 allows a portion of the exhaust gas flowing through the exhaust inlet passage 31d to bypass the accommodating portion 29 (i.e., bypass the turbine impeller 15) and flow out to the exhaust passage 27.

[0034] In the turbine T, the flow rate of the exhaust gas flowing into the turbine impeller 15 is adjusted by controlling the opening and closing operation of the wastegate port WP. In this way, the turbine T is a variable capacity turbine.

[0035] In a turbine T equipped with a bypass flow passage 35, gas flow separation is prone to occur at the branch point BP between the exhaust flow passage 31 and the bypass flow passage 35 (i.e., the inlet end of the bypass flow passage 35). For example, when the exhaust bypass port WP is closed, a portion of the exhaust gas flowing in the exhaust inlet passage 31d flows from the branch point BP into the bypass flow passage 35 and then returns to the exhaust inlet passage 31d. In this case, gas flow separation may occur downstream of the branch point BP. Gas flow separation at the branch point BP increases pressure loss in the turbine T, significantly reducing the efficiency of the turbine T.

[0036] Therefore, in the turbine T of this embodiment, the cross-sectional area of ​​the exhaust gas flow path 31 (specifically, the exhaust gas inlet path 31d) is studied in order to improve the efficiency of the turbine T. Specifically, the cross-sectional area of ​​the exhaust gas flow path 31 is the area of ​​the cross-sectional area of ​​the flow path that is orthogonal to the flow direction FD of the exhaust gas (i.e., the extension direction of the exhaust gas flow path 31). Figures 2 to 5 , the flow path cross-sectional area of ​​the exhaust flow path 31 will be described in detail.

[0037] Hereinafter, the position in the exhaust gas flow direction FD in the exhaust gas flow path 31 is referred to as the flow direction position Pf. Figure 2 As shown, the flow direction position Pf of the exhaust gas inlet 31c is set to 0, and the flow direction position Pf of the branch portion BP is set to 1. The portion of the exhaust gas flow path 31 where the flow direction position Pf is greater than 0 and less than 1 corresponds to the portion closer to the exhaust gas inlet 31c than the branch portion BP. Figure 2 In the example, the flow direction position Pf of the branch portion BP is the position of the upstream end portion of the branch portion BP. However, as the flow direction position Pf of the branch portion BP, the position of a portion other than the upstream end portion of the branch portion BP may be used.

[0038] Figure 3 This is a graph showing the distribution of the cross-sectional area ratio of the flow path cross-sectional area at each flow direction position Pf of the exhaust flow path 31 to the flow path cross-sectional area of ​​the exhaust gas inlet 31 c in the turbine T of this embodiment. Figure 3 In FIG. 5 , the distribution of the cross-sectional area ratio in the present embodiment is indicated by a solid line, and the distribution of the cross-sectional area ratio in the comparative example is indicated by a dotted line.

[0039] like Figure 3 As shown, in both the present embodiment and the comparative example, the cross-sectional area ratio of the portion of the exhaust flow path 31 closer to the exhaust inlet port 31c than the branch portion BP decreases as the exhaust flow path 31 progresses downstream. In other words, the flow path cross-sectional area of ​​the portion of the exhaust flow path 31 closer to the exhaust inlet port 31c than the branch portion BP decreases as the exhaust flow path 31 progresses downstream.

[0040] Here, in the comparative example, at flow direction position Pf = 1, the cross-sectional area ratio is less than 0.6 (specifically, approximately 0.4). In other words, the flow path cross-sectional area of ​​the branch portion BP is less than 0.6 times the flow path cross-sectional area of ​​the exhaust gas inlet 31c. On the other hand, in the present embodiment, at flow direction position Pf = 1, the cross-sectional area ratio is greater than 0.6 (specifically, approximately 0.6). In other words, the flow path cross-sectional area of ​​the branch portion BP is greater than 0.6 times the flow path cross-sectional area of ​​the exhaust gas inlet 31c.

[0041] The following is a diagram showing the results of flow analysis simulations performed by the inventors. Figure 4 、 Figure 5 as well as Figure 6 In the flow analysis simulation, the flow conditions (eg, direction, velocity, entropy, etc.) of the gas in the exhaust flow path 31 and the efficiency of the turbine T are calculated.

[0042] Figure 4 This is a graph showing the relationship between the cross-sectional area ratio and the efficiency change. The cross-sectional area ratio is the ratio of the flow path cross-sectional area of ​​the branch portion BP to the flow path cross-sectional area of ​​the exhaust gas inlet 31c (i.e., the ratio of the flow path cross-sectional area at flow direction position Pf = 1 to the flow path cross-sectional area at flow direction position Pf = 0). The efficiency change [%] is the change in the efficiency of the turbine T at each cross-sectional area ratio relative to the efficiency of the turbine T at a cross-sectional area ratio of 0.4. In other words, the efficiency change [%] is obtained by subtracting the efficiency of the turbine T at a cross-sectional area ratio of 0.4 from the efficiency of the turbine T at each cross-sectional area ratio. 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.

[0043] according to Figure 4 The graph shows that the efficiency of the turbine T increases as the cross-sectional area ratio increases. In particular, it is shown that when the cross-sectional area ratio is 0.6 or greater, the efficiency of the turbine T improves by at least 0.8% compared to when the cross-sectional area ratio is 0.4. Therefore, in this embodiment, it is shown that the efficiency of the turbine T is significantly improved by setting the flow path cross-sectional area of ​​the branch portion BP to at least 0.6 times the flow path cross-sectional area of ​​the exhaust gas inlet 31c.

[0044] Figure 5 This is a diagram showing entropy distribution obtained by flow analysis simulation in a comparative example. Figure 6 This is a diagram showing entropy distribution obtained by flow analysis simulation in this embodiment. Figure 5 and Figure 6 In FIG, the density of hatching indicates the distribution of entropy near the branch portion BP in the exhaust flow path 31. Specifically, Figure 5 and Figure 6 In the graph, the denser the hatching (i.e., the narrower the intervals between the diagonal lines), the higher the entropy. Figure 5 and Figure 6 In FIG, the local gas flow direction near the branch portion BP is shown by an arrow.

[0045] When the right Figure 5 The comparative examples shown and Figure 6 When compared with the present embodiment shown in FIG. 1 , it can be seen that in the comparative example, compared with the present embodiment, the downstream side of the branch portion BP in the exhaust flow path 31 ( Figure 5 and Figure 6 Furthermore, it can be seen that, in the comparative example, unlike the present embodiment, separation of the gas flow and eddy flow occur at a position downstream of the branch portion BP in the exhaust flow path 31.

[0046] Here, it is considered that the efficiency of the turbine T varies depending on the size of the flow path cross-sectional area of ​​the branch portion BP. Specifically, if the flow path cross-sectional area of ​​the branch portion BP is too small, the flow velocity of the exhaust gas flowing in the exhaust flow path 31 (specifically, the exhaust inlet 31d) becomes excessively high at the branch portion BP. This easily causes separation of the gas flow and eddy flow near the branch portion BP (for example, at a location downstream of the branch portion BP in the exhaust flow path 31). For this reason, it is believed that in the comparative example (i.e., when the cross-sectional area ratio is approximately 0.4), separation of the gas flow and eddy flow occur near the branch portion BP. On the other hand, in the present embodiment (i.e., when the cross-sectional area ratio is 0.6 or greater), the flow path cross-sectional area of ​​the branch portion BP is larger than in the comparative example, resulting in a lower flow velocity of the exhaust gas at the branch portion BP. This suppresses separation of the gas flow and eddy flow near the branch portion BP, reduces pressure loss, and ultimately improves the efficiency of the turbine T.

[0047] Furthermore, from the perspective of improving the flow path efficiency to improve the turbine efficiency, it is preferable that the cross-sectional area ratio of the portion of the exhaust flow path 31 closer to the exhaust inlet 31c than the branch portion BP gradually decreases as it goes downstream. Specifically, in this embodiment, Figure 3 As shown in FIG, in the range where the flow direction position Pf is greater than or equal to 0 and less than or equal to 0.6, the cross-sectional area ratio is greater than or equal to 0.9. Figure 4 and Figure 5 As shown, the flow path efficiency and turbine efficiency are appropriately improved. Thus, from the perspective of improving the flow path efficiency to appropriately improve the turbine efficiency, it is preferable that the flow path cross-sectional area of ​​the exhaust gas inlet 31c is at least 0.9 times the flow path cross-sectional area of ​​the exhaust gas inlet 31c in the exhaust gas flow direction FD (i.e., the extension direction of the exhaust gas flow path 31) within a region of at least 60% on the exhaust gas inlet 31c side.

[0048] While the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it is self-evident that the present disclosure is not limited to such embodiments. It is obvious to those skilled in the art that various variations or modifications are conceivable within the scope of the claims, and it should be understood that such variations or modifications naturally fall within the technical scope of the present disclosure.

[0049] While the above description describes an example in which the turbine T is a single-scroll type (having a single turbine scroll flow path 31a), the type of turbine T is not limited to this example. For example, the turbine T may be a twin-scroll type (having two turbine scroll flow paths 31a connected to the housing 29 at different circumferential positions) or a twin-scroll type (having two turbine scroll flow paths 31a arranged side by side in the axial direction).

[0050] In the above description, an example in which the turbine T is provided in the supercharger TC has been described. However, the turbine T may be provided in a device other than the supercharger TC.

[0051] Explanation of symbols

[0052] 15 - turbine impeller, 25 - exhaust outlet, 27 - exhaust flow path, 29 - storage unit, 31 - exhaust flow path, 35 - bypass flow path, BP - branching unit, T - turbine, TC - supercharger.

Claims

1. A turbine, characterized in that: have: a housing portion for housing a turbine impeller; an exhaust flow path connecting the housing portion and the exhaust inlet; a discharge flow path connecting the storage portion and the exhaust outlet; a bypass flow path connecting the exhaust flow path with the discharge flow path in a manner bypassing the housing portion; as well as The branch portion is a branch portion between the exhaust flow path and the bypass flow path, and has a flow path cross-sectional area that is smaller than the flow path cross-sectional area of ​​the exhaust gas inlet and is 0.6 times or more of the flow path cross-sectional area of ​​the exhaust gas inlet.

2. The turbine according to claim 1, characterized in that In a portion of the exhaust flow path closer to the exhaust inlet than the branch portion, a flow path cross-sectional area in an area of ​​more than 60% closer to the exhaust inlet in the extending direction of the exhaust flow path is more than 0.9 times the flow path cross-sectional area of ​​the exhaust inlet.

3. A supercharger, characterized in that: A turbine according to claim 1 or 2.

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