Centrifugal compressor

Abstract

To reduce a volume of an air flow sound in a centrifugal compressor equipped with a casing treatment.SOLUTION: A centrifugal compressor includes: a compressor housing having an annular part equipped with an air introduction hole for introducing air toward an impeller and arranged inside the air introduction hole, and a spoke part for connecting an inner circumferential wall surface of the air introduction hole and the annular part; and a casing treatment having a cylindrical part provided more on an upstream side in an air introduction direction than the annular part in the air introduction hole, and a wing-like part extending toward a downstream side in the air introduction direction from the cylindrical part. The inside of the cylindrical part forms an air main flow passage. The wing-like part forms a sub-flow passage which engages with the annular part and branches from the main flow passage together with the annular part and the spoke part, and merges with the main flow passage again. The number of the spoke parts and the number of the wing-like parts are the same. An arrangement position along a circumferential direction of the annular part of the spoke part and an arrangement position along a circumferential direction of the annular part of the wing-like part are the same.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a centrifugal compressor. [Background technology]

[0002] 2. Description of the Related Art Conventionally, turbochargers equipped with a casing treatment that forms a sub-flow passage that branches off from a main flow passage that draws air into a centrifugal compressor and rejoins the main flow passage are known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-264339 A Summary of the Invention [Problem to be solved by the invention]

[0004] The casing treatment can increase the apparent air flow rate by recirculating the air drawn into the centrifugal compressor. This improves the torque of the turbocharger in the low rotation range. However, on the other hand, a turbocharger equipped with a casing treatment generates high-frequency airflow noise associated with the intake of air in the high rotation range. It is desirable for the turbocharger mounted on a vehicle to have low airflow noise. Patent Document 1 does not propose reducing the volume of the airflow noise.

[0005] Therefore, an object of the invention disclosed in this specification is to reduce the volume of airflow noise in a centrifugal compressor equipped with a casing treatment. [Means for solving the problem]

[0006] The above object is achieved by a centrifugal compressor comprising: a compressor housing which houses an impeller therein, which is provided with an air inlet hole for introducing air toward the impeller, and which includes an annular portion arranged inside the air inlet hole, and spoke portions connecting an inner circumferential wall surface of the air inlet hole and the annular portion; and a casing treatment which includes a cylindrical portion provided at the air inlet hole upstream of the annular portion in a direction in which the air is introduced, and a wing-like portion extending from the cylindrical portion toward a downstream side in the direction in which the air is introduced, wherein in the casing treatment, an inside of the cylindrical portion forms a main flow path for the air, the wing-like portion engages with the annular portion to form, together with the annular portion and the spoke portions, a secondary flow path which branches off from the main flow path and rejoins the main flow path, the number of spoke portions and the number of wing-like portions are the same, and the arrangement positions of the spoke portions along the circumferential direction of the annular portion and the arrangement positions of the wing-like portions along the circumferential direction of the annular portion are the same.

[0007] In the centrifugal compressor having the above-described configuration, a thickness dimension along the circumferential direction of the annular portion of the vane-like portion may be equal to or smaller than a thickness dimension along the circumferential direction of the annular portion of the spoke portion. Effect of the Invention

[0008] The invention disclosed in this specification can reduce the volume of airflow noise in a centrifugal compressor equipped with a casing treatment. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view taken along an axis line AX of a centrifugal compressor according to an embodiment. [Diagram 2] FIG. 2 is an enlarged view of the portion X in FIG. [Diagram 3] Fig. 3A is a side view of the insert ring, Fig. 3B is a plan view of the insert ring, and Fig. 3C is a cross-sectional view taken along line Y1-Y1 in Fig. 3B. [Figure 4] FIG. 4 is a schematic diagram showing how an insert ring is attached to an air inlet hole formed in a compressor housing. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of the connection portion between the spoke portion and the wing-like portion taken along a line corresponding to line Y2-Y2 in FIG. 3B. [Figure 6] FIG. 6 is a diagram showing a graph showing the volume of airflow noise generated by the centrifugal compressor of the embodiment together with a graph showing the volume of airflow noise generated by a centrifugal compressor of a comparative example. [Figure 7] 7A and 7B are side and plan views of the insert ring in the modified example. [Figure 8] FIG. 8 is a schematic diagram showing how an insert ring is attached to an air inlet hole formed in a compressor housing in a modified example. [Figure 9] FIG. 9 is an enlarged cross-sectional view of a connection portion between a spoke portion and a wing-like portion in a modified example, taken along a line corresponding to line Y3-Y3 in FIG. 7B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be illustrated to be completely consistent with the actual ones. Also, in some drawings, some details may be omitted.

[0011] (Embodiment) [Centrifugal Compressor] The centrifugal compressor 10 of this embodiment constitutes a part of a turbocharger. The turbocharger includes a turbine unit and the centrifugal compressor 10. The turbine unit and the centrifugal compressor 10 are connected by a connecting unit. The turbocharger is incorporated in an internal combustion engine. The turbine unit is located in an exhaust flow path, and the centrifugal compressor 10 is located in an intake flow path. FIG. 1 shows only the centrifugal compressor 10. The centrifugal compressor 10 includes a compressor housing 20 and an impeller 30.

[0012] <Compressor housing> The compressor housing 20 accommodates an impeller 30 therein. The compressor housing 20 includes an air inlet hole 21 that introduces air toward the impeller 30. The compressor housing 20 includes a scroll passage 22 that compresses the air introduced toward the impeller 30. The scroll passage 22 is formed on the radial outside of the impeller 30. The compressor housing 20 includes an annular portion 23 that is disposed inside the air inlet hole 21.

[0013] The annular portion 23 is disposed upstream of the impeller 30 in the air introduction direction. The annular portion 23 is connected to the inner circumferential wall surface 21a of the air introduction hole 21 via the spoke portions 24. A space is formed around the annular portion 23 supported by the spoke portions 24. This space forms a secondary flow path 25 that circulates air. The secondary flow path 25 will be described in detail later.

[0014] A plurality of spoke parts 24 are provided. The spoke parts 24 are arranged at equal intervals along the circumferential direction of the annular part 23. For example, when the spoke parts 24 are provided at two locations, the positions of the spoke parts 24 are spaced apart by 180 degrees in the circumferential direction. When the spoke parts 24 are provided at three locations, the positions of the spoke parts 24 are spaced apart by 120 degrees in the circumferential direction. When the spoke parts 24 are provided at four locations, the positions of the spoke parts 24 are spaced apart by 90 degrees in the circumferential direction. When the spoke parts 24 are provided at five locations, the positions of the spoke parts 24 are spaced apart by 72 degrees in the circumferential direction. When the spoke parts 24 are provided at six locations, the positions of the spoke parts 24 are spaced apart by 60 degrees in the circumferential direction. The number of spoke parts 24 is not limited to these. In this embodiment, the spoke parts 24 are provided at six locations as shown in FIG. 4. The thickness dimension of each spoke portion 24 along the circumferential direction of the annular portion 23 is t24, as shown in Fig. 4. The spoke portions 24 do not necessarily have to be disposed at equal intervals.

[0015] <Impeller> The impeller 30 is provided at one end of the rotating shaft member 11. The impeller 30 includes a cylindrical mounting portion 30a and impeller blades 30b formed around the mounting portion 30a. The impeller 30 is integrated with the rotating shaft member 11 by fixing the mounting portion 30a to the rotating shaft member 11. Although not shown, a turbine rotor including turbine blades is provided at the other end of the rotating shaft member 11. The turbine rotor is housed in a turbine housing and forms a turbine unit together with the turbine housing. A connecting unit is provided between the turbine unit and the centrifugal compressor 10 to connect them. The connecting unit is provided with a bearing portion. This bearing portion rotatably supports the rotating shaft member 11.

[0016] <Casing treatment> Next, the casing treatment 40 will be described. The casing treatment 40 forms a sub-flow passage 25 that branches off from the main flow passage 12 of the air introduced into the centrifugal compressor 10 and merges with the main flow passage 12 again. The casing treatment 40 is formed by fitting an insert ring 41 into an air introduction hole 21 formed in the compressor housing 20. As shown in Figs. 3A and 3B, the insert ring 41 has a cylindrical portion 41a and a plurality of wing-like portions 42. The insert ring 41 is attached to the air introduction hole 21 of the compressor housing 20 so that the upstream side shown in Fig. 3A coincides with the upstream side shown in Fig. 1. Note that Fig. 3B is a plan view of the insert ring 41, showing the insert ring 41 as viewed from the downstream side shown in Fig. 3A.

[0017] The axial direction of the cylindrical portion 41a coincides with the axis AX of the rotating shaft member 11. The cylindrical portion 41a has an inclined surface 41a1 on the peripheral portion located downstream in the air introduction direction. This inclined surface 41a1 is inclined upward from the radial outside of the cylindrical portion 41a toward the radial inside in the side view shown in FIG. 3A. The wing-like portion 42 is provided so as to protrude from this inclined surface 41a1 toward the downstream side in the air introduction direction. The wing-like portion 42 has a plate shape. The wing-like portion 42 is provided on the inclined surface 41a1 so that its thickness direction generally coincides with the circumferential direction of the cylindrical portion 41a. The wing-like portion 42 has a shape in which the dimensions in the direction along the air introduction direction are different between a portion located radially outside of the cylindrical portion 41a and a portion located radially inside of the cylindrical portion 41a. In the wing-like portion 42, the dimension along the air introduction direction of the portion located radially outward of the cylindrical portion 41a is longer than the dimension along the air introduction direction of the portion located radially inward of the cylindrical portion 41a. As a result, the wing-like portion 42 has a notch portion 42a formed by cutting out the radially inner side of the cylindrical portion 41a.

[0018] The thickness dimension of the cylindrical portion 41a of the wing-like portion 42 along the approximate circumferential direction is t42 as shown in FIG. 3B. The circumferential direction of the cylindrical portion 41a coincides with the circumferential direction of the annular portion 23 when the casing treatment 40 is attached to the compressor housing 20. The thickness dimension t42 of the wing-like portion 42 is set to be equal to or smaller than the thickness dimension t24 of the spoke portion 24. This suppresses the generation of vortexes. In this embodiment, the thickness dimension t42 of the wing-like portion 42 and the thickness dimension t24 of the spoke portion 24 are the same.

[0019] The number of wing-like portions 42 is the same as the number of spoke portions 24. The positions of the wing-like portions 42 along the circumferential direction of the annular portion 23 are the same as the positions of the spoke portions 24 along the circumferential direction of the annular portion 23. The spoke portions 24 in this embodiment are provided at six locations. Therefore, the number of wing-like portions 42 in this embodiment is six. The wing-like portions 42 are arranged at positions spaced apart by 60 degrees in the circumferential direction, similar to the spoke portions 24. Note that the spoke portions 24 may not be arranged at equal intervals. Even in this case, it is sufficient that the positions of the wing-like portions 42 along the circumferential direction of the annular portion 23 are the same as the positions of the spoke portions 24 along the circumferential direction of the annular portion 23.

[0020] The insert ring 41 is press-fitted into the air inlet hole 21 of the compressor housing 20 as indicated by an arrow 100b in Fig. 4. At this time, the insert ring 41 is fitted into the air inlet hole 21 so that the wing-like portion 42 is located downstream in the air inlet direction.

[0021] At this time, the position of each wing-like portion 42 along the circumferential direction of the annular portion 23 is made to coincide with the position of each spoke portion 24 along the circumferential direction of the annular portion 23. In other words, the insert ring 41 is fitted into the air inlet hole 21 so that the circumferential phase positions of each wing-like portion 42 and each spoke portion 24 coincide. As a result, as shown in FIG. 5, the notch portion 42a of the wing-like portion 42 is engaged with the spoke portion 24. The state in which the position of the spoke portion 24 and the position of the wing-like portion 42 coincide with each other may be a design value. For example, there are cases in which a slight positional deviation is recognized in a product. However, when this positional deviation is due to the processing accuracy or assembly accuracy of each part, the position of the spoke portion 24 and the position of the wing-like portion 42 coincide with each other and are considered to be in the same position.

[0022] The spoke portions 24 and the wing-like portions 42 joined to each other function as partitions that divide the sub-flow passages 25 in the circumferential direction. Therefore, a plurality of sub-flow passages 25 are formed in the circumferential direction. The spoke portions and the wing-like portions 42 are disposed at equal intervals in the circumferential direction of the annular portion 23. Therefore, the circumferential length of each of the sub-flow passages 25 is the same.

[0023] As described above, the thickness dimension t42 of the wing-like portion 42 and the thickness dimension t24 of the spoke portion 24 are the same. Therefore, the wing-like portion 42 and the spoke portion 24 are flush with each other at their joint portions.

[0024] By fitting the insert ring 41 into the air inlet hole 21, the inside of the cylindrical portion 41a of the insert ring 41 forms a part of the main flow path 12. The insert ring 41 fitted into the air inlet hole 21 forms a secondary flow path 25 together with the annular portion 23 and the spoke portions 24. In Figs. 1 and 2, the air passing through the main flow path 12 is indicated by an arrow 100a. A part of the air passing through the main flow path 12 branches off to the secondary flow path 25 side as indicated by an arrow 100a1 and merges with the main flow path 12. This increases the apparent flow rate of air sucked into the centrifugal compressor 10.

[0025] 2, a portion of the air passing through the main flow passage 12 flows toward the radial outside of the annular portion 23 on the downstream side of the annular portion 23. The air then flows toward the inclined surface 41a1 of the tubular portion 41a in the sub-flow passage 25. The air that collides with the inclined surface 41a1 flows toward the inside of the annular portion 23. The air that has flowed toward the inside of the annular portion 23 merges with the main flow passage 12 and flows through the main flow passage 12 again.

[0026] It is believed that separation of the airflow circulating through the secondary flow passage 25 and the generation of vortices increase the volume of the airflow noise. The centrifugal compressor 10 of the present embodiment suppresses separation of the airflow and reduces the vorticity of the flow field, that is, the strength of the vortex.

[0027] The number of spoke portions 24 and wing-like portions 42 that form the multiple secondary flow paths 25 is the same. The circumferential positions of the spoke portions 24 and the circumferential positions of the wing-like portions 42 are the same. As a result, no irregularities are formed inside the secondary flow paths 25, and the inner peripheral surface of the secondary flow paths 25 is formed smoothly. This suppresses separation of the airflow and reduces the vorticity of the flow field. As a result, an increase in the volume of the airflow sound of the air that flows into the secondary flow paths 25 and merges with the main flow path 12 is suppressed, and the airflow sound is reduced.

[0028] [effect] 6 shows a graph showing the volume of airflow noise in the centrifugal compressor 10 of the embodiment, together with a graph showing the volume of airflow noise in a centrifugal compressor of a comparative example. In each graph, the vertical axis shows turbo rotation speed (rpm), and the horizontal axis shows frequency (Hz). The volume of the airflow noise is shown by the size of the plotted points. In other words, the larger the size of the points plotted in each graph, the louder the airflow noise.

[0029] Comparative Example 1 has six spokes and eight wing-like portions. Therefore, the positions of the spokes and the positions of the wing-like portions are misaligned. As a result, there are irregularities in the secondary flow path. It is believed that the airflow separates due to the irregularities in the secondary flow path. As a result, the volume of the airflow sound in Comparative Example 1 is loud.

[0030] Comparative Example 2 has six spoke parts and six wing-like parts. In other words, the number of spoke parts and wing-like parts is the same. However, the circumferential positions of the spoke parts and the circumferential positions of the wing-like parts 42 are different. If the spoke parts and the wing-like parts are not in phase with each other, it is thought that a vortex will be generated when air passes through the secondary flow passage, causing the airflow noise to become louder. As a result, the volume of the airflow noise in Comparative Example 2 is louder.

[0031] In contrast, the present embodiment has the same number of spoke portions 24 and wing-like portions 42. In addition, the spoke portions 24 and wing-like portions 42 are arranged in the same circumferential position. As a result, the volume of airflow sound in the present embodiment is smaller than in Comparative Example 1 and Comparative Example 2.

[0032] In the centrifugal compressor 10 of this embodiment, the number of spoke portions 24 is the same as the number of wing-like portions 42. The positions of the spoke portions 24 along the circumferential direction of the annular portion 23 are the same as the positions of the wing-like portions 42 along the circumferential direction of the annular portion 23. This makes it possible to reduce the volume of airflow noise in the centrifugal compressor 10.

[0033] (Modification) Next, a modified example will be described with reference to Fig. 7A to Fig. 9. Fig. 7A is a side view of an insert ring 141 in the modified example. Fig. 7B is a plan view of the insert ring 141 in the modified example. Fig. 8 is a schematic diagram showing how the insert ring is attached to the air inlet hole 21 formed in the compressor housing 20 in the modified example. Components common to the above-described embodiment are given the same reference numbers in the drawings. Detailed descriptions of components given the same reference numbers are omitted.

[0034] As shown in Fig. 8, the compressor housing 20 has an annular portion 123 disposed inside the air inlet hole 21. The annular portion 123 is connected to the inner circumferential wall surface 21a of the air inlet hole 21 via spoke portions 124. A space is formed around the annular portion 23 supported by the spoke portions 124. This space forms a secondary flow path 25 for circulating air.

[0035] A plurality of spokes 124 are provided. However, unlike the spokes 24 in the above-described embodiment, the spokes 124 are arranged at unequal intervals along the circumferential direction of the annular portion 123.

[0036] 7A and 7B, the insert ring 141 includes a cylindrical portion 141a and wing-like portions 142. The number of wing-like portions 142 is the same as the number of spoke portions 124. The positions of the wing-like portions 142 along the circumferential direction of the annular portion 123 are the same as the positions of the spoke portions 124 along the circumferential direction of the annular portion 123.

[0037] The wing-like portions 142 may be disposed at any position along the circumferential direction of the annular portion 123, and the spoke portions 124 may be disposed at any position along the circumferential direction of the annular portion 123. In other words, the example shown in Figures 7A to 8 is merely one example of the arrangement of the wing-like portions 142 and the spoke portions 124, and other arrangement positions are also possible.

[0038] 7A and 7B, wing-like portion 142 of the modified example does not have notch portion 42a that is provided in wing-like portion 42 of the embodiment. Furthermore, the surfaces of annular portion 123 and spoke portions 124 that face insert ring 141 are flush with each other. Therefore, as shown in FIG. 9, wing-like portion 142 is in close contact with annular portion 123 and spoke portions 124.

[0039] Even with this modified example, the volume of airflow noise in the centrifugal compressor can be reduced.

[0040] The above-described embodiments are merely examples for implementing the present invention, and the present invention is not limited to these. Various modifications of these embodiments are within the scope of the present invention. Furthermore, it is self-evident from the above description that various other embodiments are possible within the scope of the present invention. [Explanation of symbols]

[0041] 10 Centrifugal compressor, 11 Rotating shaft member, 12 Main flow passage, 20 Compressor housing, 21 Air inlet hole, 21a Inner peripheral wall surface, 22 Scroll flow passage, 23 Annular portion, 24 Spoke portion, 25 Sub-flow passage, 30 Impeller, 40 Casing treatment, 41, 141 Insert ring, 41a, 141a Cylindrical portion, 41a1 Inclined surface, 42 Blade portion, 42a Notch portion

Claims

1. a compressor housing that houses an impeller therein, that has an air inlet hole that introduces air toward the impeller, and that has an annular portion disposed inside the air inlet hole, and spoke portions that connect an inner peripheral wall surface of the air inlet hole and the annular portion; a casing treatment including a cylindrical portion provided upstream of the annular portion in the air introduction direction in the air introduction hole, and a wing-like portion extending from the cylindrical portion toward a downstream side in the air introduction direction; having In the casing treatment, the inside of the cylindrical portion forms a main flow path of the air, and the wing-like portion engages with the annular portion to form a secondary flow path that branches off from the main flow path together with the annular portion and the spoke portion and rejoins the main flow path, the number of the spoke portions and the number of the wing-like portions are the same, and the positions of the spoke portions along the circumferential direction of the annular portion are the same as the positions of the wing-like portions along the circumferential direction of the annular portion. Centrifugal compressor.

2. a thickness dimension of the wing-like portion along the circumferential direction of the annular portion is equal to or smaller than a thickness dimension of the spoke portion along the circumferential direction of the annular portion; 2. The centrifugal compressor according to claim 1.

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