Centrifugal Compressor and Supercharger

Abstract

The centrifugal compressor includes: a casing that houses an impeller; a diffuser flow path formed in a radially outer side of the casing than the impeller; and a scroll flow path formed in the casing, communicating with the diffuser flow path from the radially outer side, and the scroll flow path extends in the rotational axis direction and the rotational direction of the impeller with respect to the diffuser flow path, and the scroll flow path includes an inner diameter end located at the innermost side in the radial direction, and the inner diameter end is away from the diffuser flow path with respect to a midpoint of the maximum flow path width of the scroll flow path in the rotational axis direction.

Description

Technical Field

[0001] The present disclosure relates to a centrifugal compressor and a supercharger. This application claims the benefit of priority based on Japanese Patent Application No. 2020-204236 filed on December 9, 2020, and incorporates its content into this application. Background Art

[0002] In Patent Document 1, a centrifugal compressor including a compressor housing and a compressor impeller is disclosed. A diffuser flow path and a scroll flow path are formed in the compressor housing of Patent Document 1. An inner diameter end located at the innermost side in the radial direction is formed in the scroll flow path. The inner diameter end of the scroll flow path is located on the diffuser flow path side with respect to the midpoint of the maximum flow path width in the rotational axis direction of the compressor impeller.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 6347457 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] When the inner diameter end of the scroll flow path is located on the diffuser flow path side, the cross-sectional shape on the inner diameter side of the scroll flow path is a shape with a large curvature. Therefore, the change in the direction of the flow along the scroll flow path wall becomes large, and air is likely to peel off on the inner surface on the inner diameter side and the diffuser flow path side of the scroll flow path.

[0008] An object of the present invention is to provide a centrifugal compressor and a supercharger capable of suppressing peeling of air in the scroll flow path.

[0009] Solutions for Solving the Problems

[0010] To solve the above problems, the centrifugal compressor of the present disclosure includes: a housing that houses an impeller; a diffuser flow path formed in the housing on the radially outer side of the impeller; and a scroll flow path formed in the housing, communicating with the diffuser flow path from the radially outer side, and the scroll flow path extends along the rotational axis direction and the rotational direction of the impeller with respect to the diffuser flow path. The scroll flow path includes an inner diameter end located at the innermost side in the radial direction, and the inner diameter end is away from the diffuser flow path with respect to the midpoint of the maximum flow path width of the scroll flow path in the rotational axis direction.

[0011] Alternatively, the scroll flow path may include an inner diameter surface located on the radially inner side, and the inner diameter surface includes: a first curvature surface closer to the diffuser flow path than the inner diameter end; and a second curvature surface farther from the diffuser flow path than the inner diameter end, and the radius of curvature of the first curvature surface is equal to the radius of curvature of the second curvature surface.

[0012] Alternatively, in terms of the separation distance between the midpoint and the rotational axis direction of the inner diameter end, the middle part between the tongue part and the winding end part of the scroll flow path is larger in the extending direction of the scroll flow path, as compared with the tongue part and the winding end part of the scroll flow path.

[0013] Alternatively, the scroll flow path includes an inner diameter surface located on the radially inner side, and the inner diameter surface includes: a first curvature surface closer to the diffusion flow path than the inner diameter end; and a second curvature surface farther from the diffusion flow path than the inner diameter end. In the middle part, the radius of curvature of the first curvature surface is larger than that of the second curvature surface.

[0014] To solve the above problems, the supercharger of the present disclosure includes the above centrifugal compressor.

[0015] Advantageous Effects of the Invention

[0016] According to the present disclosure, peeling of the flow along the wall of the scroll flow path can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic cross-sectional view of the supercharger.

[0018] Figure 2 is a schematic cross-sectional view of the compressor scroll flow path of the present embodiment.

[0019] Figure 3 is a view showing the visualization of the flow velocity of the air flowing through the compressor scroll flow path.

[0020] Figure 4 is a graph showing the relationship between the azimuth angle from the winding start part to the winding end part of the compressor scroll flow path and the distance between the inner diameter end and the midpoint in the rotational axis direction.

[0021] Figure 5 is a schematic cross-sectional view of the compressor scroll flow path of the middle part. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying Figure 1 drawings. The specific dimensions, materials, numerical values, etc. shown in the embodiments are merely illustrative examples for easy understanding, and do not limit the present disclosure unless otherwise specifically stated. In addition, in this specification and the drawings, elements having substantially the same functions and structures are denoted by the same reference numerals, and repeated descriptions are omitted. Further, elements not directly related to the present disclosure are omitted from the drawings.

[0023] Figure 1 is a schematic cross-sectional view of the supercharger TC. Hereinafter, Figure 1 the direction of the arrow L shown will be described as the left side of the supercharger TC. The direction of the arrow R shown Figure 1 will be described as the right side of the supercharger TC. AsFigure 1 As shown, the supercharger TC includes a supercharger main body 1. The supercharger main body 1 includes a bearing housing 3, a turbine housing 5, and a compressor housing (housing) 7. The turbine housing 5 is connected to the left side of the bearing housing 3 by fastening bolts 9. The compressor housing 7 is connected to the right side of the bearing housing 3 by fastening bolts 11.

[0024] A bearing hole 3a is formed in the bearing housing 3. The bearing hole 3a penetrates the bearing housing 3 in the left - right direction of the supercharger TC. A part of the shaft 13 is received in the bearing hole 3a. A bearing 15 is received in the bearing hole 3a. In the present embodiment, the bearing 15 is a full - floating bearing. However, it is not limited thereto, and the bearing 15 may also be other bearings such as a semi - floating bearing or a rolling bearing. The shaft 13 is rotatably supported by the bearing 15. A turbine impeller 17 is provided at the left end portion of the shaft 13. The turbine impeller 17 is rotatably accommodated in the turbine housing 5. A compressor impeller (impeller) 19 is provided at the right end portion of the shaft 13. The compressor impeller 19 is rotatably accommodated in the compressor housing 7. In the present disclosure, the rotational axis direction, radial direction, and rotational direction of the shaft 13, turbine impeller 17, and compressor impeller 19 may be simply referred to as the rotational axis direction, radial direction, and rotational direction, respectively.

[0025] An air inlet 21 is formed in the compressor housing 7. The air inlet 21 opens on the right side of the supercharger TC. The air inlet 21 is connected to an air filter (not shown). A diffuser flow path 23 is formed by the opposing surfaces of the bearing housing 3 and the compressor housing 7. The diffuser flow path 23 is formed in a ring shape. The diffuser flow path 23 is formed in the compressor housing 7 at a position radially outside the compressor impeller 19. The diffuser flow path 23 communicates with the air inlet 21 via the compressor impeller 19 on the radially inner side. The air flowing in from the air inlet 21 via the compressor impeller 19 flows through the diffuser flow path 23. The diffuser flow path 23 pressurizes the air.

[0026] A compressor scroll flow path (scroll flow path) 25 is formed in the compressor housing 7. The compressor scroll flow path 25 is formed in a ring shape. The compressor scroll flow path 25 is located, for example, radially outside the diffuser flow path 23. The compressor scroll flow path 25 communicates with the diffuser flow path 23 on the radially outer side. The compressor scroll flow path 25 extends in the rotational axis direction and rotational direction with respect to the diffuser flow path 23. The compressor scroll flow path 25 communicates with an air inlet of an engine (not shown) and the diffuser flow path 23. When the compressor impeller 19 rotates, air is sucked into the compressor housing 7 from the air inlet 21. The sucked air is pressurized and accelerated while flowing between the blades of the compressor impeller 19. The pressurized and accelerated air is further pressurized in the diffuser flow path 23 and the compressor scroll flow path 25. The pressurized air is guided to the air inlet of the engine.

[0027] A centrifugal compressor CC is composed of such a compressor housing 7 and a bearing housing 3. In the present embodiment, an example in which the centrifugal compressor CC is mounted on a supercharger TC will be described. However, it is not limited thereto, and the centrifugal compressor CC may be installed in a device other than the supercharger TC or may be a single unit.

[0028] An outlet 27 is formed in the turbine housing 5. The outlet 27 opens on the left side of the supercharger TC. The outlet 27 is connected to an exhaust gas purification device (not shown). A communication flow path 29 and a turbine scroll flow path 31 are formed in the turbine housing 5. The communication flow path 29 is located radially outside the turbine impeller 17. The communication flow path 29 is formed in a ring shape. The communication flow path 29 communicates the outlet 27 and the turbine scroll flow path 31 via the turbine impeller 17.

[0029] The turbine scroll flow path 31 is located, for example, radially outside the communication flow path 29. The turbine scroll flow path 31 is formed in a ring shape. The turbine scroll flow path 31 communicates with a gas inlet (not shown). The exhaust gas discharged from the exhaust manifold of an engine (not shown) is guided to the gas inlet. The exhaust gas passes through the turbine scroll flow path 31 and the communication flow path 29 and is guided to the outlet 27 via the turbine impeller 17. The exhaust gas rotates the turbine impeller 17 during the process of flowing through the turbine impeller 17.

[0030] The rotational force of the turbine impeller 17 is transmitted to the compressor impeller 19 via the shaft 13. When the compressor impeller 19 rotates, as described above, the air is pressurized. In this way, the air is guided to the intake port of the engine.

[0031] Figure 2 is a schematic cross-sectional view of the compressor scroll flow path 25 of the present embodiment. As Figure 2 shown, the compressor scroll flow path 25 has side end portions 25a, 25a that are the maximum flow path widths Th in the rotational axis direction. The inner surface of the compressor scroll flow path 25 has an outer diameter surface 25b and an inner diameter surface 25c with the side end portions 25a, 25a as boundaries.

[0032] The outer diameter surface 25b is formed on the inner surface of the compressor scroll flow path 25 on the outer diameter side of the side end portions 25a, 25a. The outer diameter surface 25b has a curved surface shape that protrudes radially outward. The inner diameter surface 25c is formed on the inner surface of the compressor scroll flow path 25 on the inner diameter side of the side end portions 25a, 25a. The inner diameter surface 25c has a curved surface shape that protrudes radially inward.

[0033] Most of the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 is guided along the outer diameter surface 25b from a portion close to the diffusion flow path 23 to a portion away from the diffusion flow path 23. The air moving along the outer diameter surface 25b is guided from the outer diameter surface 25b to the inner diameter surface 25c and is guided along the inner diameter surface 25c from a portion away from the diffusion flow path 23 to a portion close to the diffusion flow path 23. Thus, most of the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 forms Figure 2 a swirling flow in the clockwise direction (the direction of arrow Ra in the figure) in the compressor scroll flow path 25.

[0034] In addition, a part of the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 moves to the right in the Figure 2 figure from the outlet end face 23a of the diffusion flow path 23 and is guided along the inner diameter surface 25c from a portion close to the diffusion flow path 23 to a portion away from the diffusion flow path 23. Thus, a part of the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 forms Figure 2 a swirling flow in the counterclockwise direction (the direction of arrow Rb in the figure) in the compressor scroll flow path 25.

[0035] The Figure 2 clockwise swirling flow and the counterclockwise swirling flow in the compressor scroll flow path 25 collide with each other at the following first curvature surface 25g of the inner diameter surface 25c to form a stagnation region (peeling region).

[0036] The outer diameter surface 25b has an outer diameter end 25d that is the outermost in the radial direction in the compressor scroll flow path 25. The inner diameter surface 25c has an inner diameter end 25e that is the innermost in the radial direction in the compressor scroll flow path 25.

[0037] In the radial direction, the distance from the side ends 25a, 25a to the outer diameter end 25d is shorter than the distance from the side ends 25a, 25a to the inner diameter end 25e. The flow path cross-sectional area on the outer diameter side of the compressor scroll flow path 25 that is closer to the side ends 25a, 25a is smaller than the flow path cross-sectional area on the inner diameter side of the compressor scroll flow path 25 that is closer to the side ends 25a, 25a.

[0038] The outer diameter end 25d is located at the same position as the inner diameter end 25e in the rotation axis direction. However, it is not limited thereto, and the outer diameter end 25d may also be located at a different position from the inner diameter end 25e in the rotation axis direction. The outer diameter end 25d is farther from the diffusion flow path 23 than the midpoint 25f of the maximum flow path width Th in the rotation axis direction.

[0039] The inner diameter end 25e is separated from the diffusion flow path 23 by the intermediate point 25f of the maximum flow path width Th in the direction of the rotation axis. The width Ei between the side end 25a near the diffusion flow path 23 and the inner diameter end 25e is larger than the width Mh between the side end 25a near the diffusion flow path 23 and the intermediate point 25f. That is, the separation distance in the rotation axis direction between the side end 25a near the diffusion flow path 23 and the inner diameter end 25e is larger than the separation distance in the rotation axis direction between the side end 25a near the diffusion flow path 23 and the intermediate point 25f. The inner diameter end 25e is located between the side end 25a separated from the diffusion flow path 23 and the intermediate point 25f in the rotation axis direction. The inner diameter end 25e is closer to the intermediate point 25f than the side end 25a separated from the diffusion flow path 23.

[0040] The inner diameter surface 25c includes a first curved surface 25g and a second curved surface 25h. The first curved surface 25g is closer to the diffusion flow path 23 than the inner diameter end 25e in the inner diameter surface 25c. The second curved surface 25h is farther from the diffusion flow path 23 than the inner diameter end 25e in the inner diameter surface 25c. The radius of curvature of the first curved surface 25g is equal to the radius of curvature of the second curved surface 25h. Here, equal means including the case of complete equality, the substantially equal case with manufacturing tolerances and errors. However, it is not limited thereto, and the radius of curvature of the first curved surface 25g may also be different from the radius of curvature of the second curved surface 25h.

[0041] As described above, in the compressor scroll flow path 25 of the present embodiment, with respect to the side ends 25a, 25a where the maximum flow path width Th is formed, the height on the outer diameter side (the distance to the outer diameter end 25d in the radial direction) is smaller than the height on the inner diameter side (the distance to the inner diameter end 25e in the radial direction). Therefore, compared with the case where the height on the outer diameter side and the height on the inner diameter side are equal with respect to the side ends 25a, 25a, the maximum outer diameter of the compressor scroll flow path 25 can be reduced. As a result, the maximum outer diameter of the compressor housing 7 can be reduced.

[0042] On the other hand, in the compressor scroll flow path 25 of the present embodiment, compared with the case where the height on the outer diameter side and the height on the inner diameter side are equal with respect to the side ends 25a, 25a, the height on the inner diameter side is larger and has a shape protruding toward the inner diameter side. The larger the height on the inner diameter side of the compressor scroll flow path 25, the larger the curvature of the inner diameter side of the cross-sectional shape of the flow path, and the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 is particularly likely to peel off on the first curved surface 25g, and the peeling region is likely to expand. The more the peeling region expands, the lower the performance of the centrifugal compressor CC.

[0043] The closer the inner diameter end 25e of the compressor scroll flow path 25 is to the diffusion flow path 23 relative to the midpoint 25f, the larger the angle α between the outlet end face 23a of the diffusion flow path 23 and the first curved surface 25g. The larger the angle α, the easier it is for the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 to peel off from the first curved surface 25g.

[0044] Therefore, in the present embodiment, the inner diameter end 25e of the compressor scroll flow path 25 is arranged to be away from the diffusion flow path 23 relative to the midpoint 25f. As a result, compared with the case where the inner diameter end 25e is located near the diffusion flow path 23 relative to the midpoint 25f, the angle α between the outlet end face 23a of the diffusion flow path 23 and the first curved surface 25g can be reduced. As a result, the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 is difficult to peel off from the first curved surface 25g, and the expansion of the peeling region can be suppressed.

[0045] In addition, when the radius of curvature of the first curved surface 25g and the second curved surface 25h are equal, the air flowing from the diffusion flow path 23 into the compressor scroll flow path 25 can smoothly move on the first curved surface 25g and the second curved surface 25h. As a result, the air is difficult to peel off on the first curved surface 25g and the second curved surface 25h, and the expansion of the peeling region can be suppressed.

[0046] Figure 3 It is a diagram visualizing the flow velocity of the air flowing in the compressor scroll flow path 25. Figure 4 It is a graph showing the relationship between the azimuth angle from the winding start portion to the winding end portion of the compressor scroll flow path 25 and the distance between the inner diameter end 25e and the midpoint 25f in the rotation axis direction. Figure 3 In, the plurality of curves shown in the compressor scroll flow path 25 represent the magnitude of the flow velocity of the air. The longer the curve, the faster the flow velocity. In Figure 4 In, the vertical axis represents the distance in the rotation axis direction with respect to the side end portion 25a near the diffusion flow path 23, and the horizontal axis represents the azimuth angle from the winding start portion to the winding end portion of the compressor scroll flow path 25.

[0047] As Figure 3 and Figure 4 shown, the winding start portion 25i of the compressor scroll flow path 25 is represented by the azimuth angle 0°, and the winding end portion 25j is represented by the azimuth angle 330°. In addition, a tongue portion 25k that separates the upstream portion and the downstream portion of the compressor scroll flow path 25 is formed in the compressor scroll flow path 25. The tongue portion 25k of the compressor scroll flow path 25 is approximately represented by the azimuth angle 15°. In addition, the compressor scroll flow path 25 has an intermediate portion 25m between the winding start portion 25i (tongue portion 25k) and the winding end portion 25j in the extending direction of the compressor scroll flow path 25. As Figure 4As shown, the middle part 25m is, for example, a range represented by azimuth angles of 60° to 210°. However, the range (azimuth angle) of the middle part 25m is not limited to this.

[0048] As Figure 4 shown, the separation distance in the rotational axis direction between the middle point 25f and the inner diameter end 25e varies along the extending direction (azimuth angle) of the compressor scroll flow path 25. The separation distance between the middle point 25f and the inner diameter end 25e in the rotational axis direction is the smallest at the tongue part 25k.

[0049] The separation distance in the rotational axis direction between the middle point 25f and the inner diameter end 25e gradually increases from the tongue part 25k toward the middle part 25m, and gradually decreases from the middle part 25m toward the winding end part 25J. In other words, with respect to the separation distance in the rotational axis direction between the middle point 25f and the inner diameter end 25e, it is larger at the middle part 25m than at the winding start part 25i (tongue part 25k) and the winding end part 25j of the compressor scroll flow path 25.

[0050] Figure 5 is a schematic cross-sectional view of the compressor scroll flow path 25 at the middle part 25m. Figure 5 In Figure 2 it, the cross-sectional shape of the flow path of the winding end part 25j is represented by a dashed line, and the cross-sectional shape of the flow path of the middle part 25m is represented by a solid line. In addition, the cross-sectional shape of the flow path of the winding end part 25j is the same as

[0051] As Figure 5 shown, the inner diameter end 125e of the compressor scroll flow path 25 at the middle part 25m is farther from the diffuser flow path 23 than the inner diameter end 25e of the compressor scroll flow path 25 at the winding end part 25j. That is, the separation distance in the rotational axis direction between the middle point 25f and the inner diameter end 125e at the middle part 25m is larger than the separation distance in the rotational axis direction between the middle point 25f and the inner diameter end 25e at the winding end part 25j.

[0052] Therefore, the radius of curvature of the first curvature surface 125g of the compressor scroll flow path 25 at the middle part 25m is larger than the radius of curvature of the first curvature surface 25g of the compressor scroll flow path 25 at the winding end part 25j.

[0053] In addition, the radius of curvature of the second curvature surface 125h of the compressor scroll flow path 25 at the middle part 25m is smaller than the radius of curvature of the second curvature surface 25h of the compressor scroll flow path 25 at the winding end part 25j. As a result, the radius of curvature of the first curvature surface 125g is larger than the radius of curvature of the second curvature surface 125h. In other words, the radius of curvature of the second curvature surface 125h is smaller than the radius of curvature of the first curvature surface 125g.

[0054] As Figure 3As shown, multiple curves shown within the compressor scroll flow path 25 extend relatively long in the middle portion 25m (particularly at azimuth angles of 60° to 150°) up to near the outer diameter end of the compressor scroll flow path 25. Thus, the flow velocity of the air flowing through the compressor scroll flow path 25 is the fastest in the middle portion 25m (particularly at azimuth angles of 60° to 150°). The faster the flow velocity of the air, the easier it is for the air to peel off from the first curvature surfaces 25g and 125g.

[0055] Therefore, in the present embodiment, in the middle portion 25m where the flow velocity of the air is the fastest, the radius of curvature of the second curvature surface 125h is decreased. By decreasing the radius of curvature, it is possible to Figure 5 more efficiently decelerate the clockwise swirling velocity of the air in the middle portion 25m compared to the case where the radius of curvature is large. As a result, it is possible to suppress the air that moves from the second curvature surface 125h to the first curvature surface 125g from peeling off on the first curvature surface 125g and expanding the peeling region.

[0056] As described above, one embodiment of the present disclosure has been described with reference to the accompanying drawings, but the present disclosure is of course not limited to this embodiment. Obviously, those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it should be understood that they also naturally belong to the technical scope of the present disclosure.

[0057] In the above embodiment, an example where the separation distance in the rotational axis direction between the intermediate point 25f and the inner diameter end 25e changes along the extending direction of the compressor scroll flow path 25 has been described. However, it is not limited thereto, and the separation distance in the rotational axis direction between the intermediate point 25f and the inner diameter end 25e may also be constant along the extending direction of the compressor scroll flow path 25.

[0058] Symbol Explanation

[0059] CC - Centrifugal compressor, TC - Turbocharger, 7 - Compressor housing (housing), 19 - Compressor impeller (impeller), 23 - Diffusion flow path, 25 - Compressor scroll flow path (scroll flow path), 25a - Side end portion, 25b - Outer diameter surface, 25c - Inner diameter surface, 25d - Outer diameter end, 25e - Inner diameter end, 25f - Intermediate point, 25g - First curvature surface, 25h - Second curvature surface, 25i - Winding start portion, 25j - Winding end portion, 25k - Tongue portion, 25m - Middle portion, 125e - Inner diameter end, 125g - First curvature surface, 125h - Second curvature surface.

Claims

1. A centrifugal compressor, characterized in that it comprises: a housing that houses an impeller; a diffuser flow path formed radially outside the impeller in the housing; and a scroll flow path formed in the housing, communicating with the diffuser flow path from the radial outside, and the scroll flow path extends along the rotation axis direction and the rotation direction of the impeller with respect to the diffuser flow path. The scroll flow path includes an inner diameter end at the innermost side in the radial direction, and the inner diameter end is away from the diffuser flow path with respect to the midpoint of the maximum flow path width of the scroll flow path in the rotation axis direction. Regarding the separation distance in the rotation axis direction between the midpoint and the inner diameter end, it is larger in the middle part between the tongue part and the winding end part of the scroll flow path in the extending direction of the scroll flow path with respect to the tongue part and the winding end part of the scroll flow path.

2. The centrifugal compressor according to claim 1, characterized in that the scroll flow path includes an inner diameter surface located radially inside; the inner diameter surface includes: a first curvature surface closer to the diffuser flow path than the inner diameter end; and a second curvature surface farther from the diffuser flow path than the inner diameter end; the radius of curvature of the first curvature surface is equal to the radius of curvature of the second curvature surface.

3. The centrifugal compressor according to claim 1, characterized in that the scroll flow path includes an inner diameter surface located radially inside; the inner diameter surface includes: a first curvature surface closer to the diffuser flow path than the inner diameter end; and a second curvature surface farther from the diffuser flow path than the inner diameter end; in the middle part, the radius of curvature of the first curvature surface is larger than the radius of curvature of the second curvature surface.

4. A supercharger, characterized in that, A centrifugal compressor according to any one of claims 1 to 3 is provided.

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