Centrifugal compressor and turbocharger

Abstract

This centrifugal compressor is provided with a fluid introduction flow passage for introducing a fluid into a compressor inlet flow passage. An outlet part of the fluid introduction flow passage, wherein a flow passage wall surface of the fluid introduction flow passage includes: a first inclined surface which is positioned on a downstream side in an axial direction of an impeller with respect to an axial line of the fluid introduction flow passage, and is inclined toward the downstream side in the axial direction as approaching the compressor inlet flow passage; and a second inclined surface which is positioned on a downstream side in a rotation direction of the impeller with respect to an axial line of the fluid introduction flow passage, and is inclined toward the downstream side in the rotation direction as approaching the compressor inlet flow passage.

Description

Centrifugal compressors and turbochargers

[0001] The present disclosure relates to centrifugal compressors and turbochargers.

[0002] Patent Document 1 describes a technique for reducing pressure vibrations or acoustic loads on an open cavity by applying a curvature to the entire rear surface of the cavity so as to present a concave curved surface inside the cavity.

[0003] Special table 2019-510174 publication

[0004] Incidentally, for example, a centrifugal compressor of a turbocharger may be equipped with a compressor inlet passage that guides air to the impeller and a fluid introduction passage that introduces a fluid into the compressor inlet passage (for example, a bypass passage that returns a fluid from a scroll passage to the compressor inlet passage, or an EGR passage that returns engine exhaust gas to the compressor passage). In this case, noise is generated by vortices that are generated when the flow in the compressor inlet passage passes through the outlet of the fluid introduction passage (the opening of the fluid introduction passage on the compressor inlet passage side). In addition, because the direction of the flow in the compressor inlet passage changes depending on the flow rate of the centrifugal compressor, even if measures are taken only on one rear surface of the cavity, as described in Patent Document 1, the effect of noise reduction is limited.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a centrifugal compressor that can reduce noise generated at the outlet of a fluid introduction passage even when the flow rate changes, and a turbocharger including the centrifugal compressor.

[0006] In order to achieve the above object, a centrifugal compressor according to at least one embodiment of the present disclosure includes: an impeller; a compressor inlet passage that guides a fluid to the impeller; and a fluid introduction passage that connects to the compressor inlet passage in a direction intersecting an axis of the compressor inlet passage and introduces a fluid into the compressor inlet passage, wherein at an outlet portion of the fluid introduction passage, a passage wall surface of the fluid introduction passage includes: a first inclined surface that is located downstream in the axial direction of the impeller from the axis of the fluid introduction passage and inclined so as to move toward the downstream side in the axial direction as it approaches the compressor inlet passage; and a second inclined surface that is located downstream in the rotational direction of the impeller from the axis of the fluid introduction passage and inclined so as to move toward the downstream side in the rotational direction as it approaches the compressor inlet passage.

[0007] In order to achieve the above object, a centrifugal compressor according to at least one embodiment of the present disclosure comprises: an impeller; a compressor inlet flow path that guides a fluid to the impeller; and a fluid introduction flow path that is connected to the compressor inlet flow path in a direction intersecting an axis of the compressor inlet flow path and introduces a fluid into the compressor inlet flow path, wherein, with respect to an edge of the fluid introduction flow path on the compressor inlet flow path side, if the distance between the most upstream position in the axial direction of the impeller at the edge and the axis of the compressor inlet flow path is A1, the distance between the most downstream position in the axial direction at the edge and the axis is A2, the distance between the most upstream position in the rotational direction of the impeller at the edge and the axis is A3, and the distance between the most downstream position in the rotational direction at the edge and the axis is A4, A1 and A2 are different from each other, and A3 and A4 are different from each other.

[0008] In order to achieve the above object, a centrifugal compressor according to at least one embodiment of the present disclosure comprises: an impeller; a compressor inlet passage that guides a fluid to the impeller; and a fluid introduction passage that is connected to the compressor inlet passage in a direction intersecting an axis of the compressor inlet passage and introduces a fluid into the compressor inlet passage, and satisfies the following condition (A) or the following condition (B): Condition (A): In a cross section taken along the axial direction of the impeller, an angle formed between a passage wall surface of the compressor inlet passage and a passage wall surface of the fluid introduction passage on the upstream side of the axis of the fluid introduction passage in the axial direction is 90 degrees or less, and in a cross section perpendicular to the axial direction of the impeller, an angle formed between the passage wall surface of the compressor inlet passage and a passage wall surface of the fluid introduction passage on the upstream side of the axis of the fluid introduction passage in the rotational direction of the impeller is 90 degrees or less. Condition (B): In a cross section along the axial direction of the impeller, the flow path wall surface of the compressor inlet flow path includes a first convex portion at a position upstream in the axial direction of the outlet of the fluid introduction flow path, and in a perpendicular cross section along the axial direction of the impeller, the flow path wall surface of the compressor inlet flow path includes a second convex portion at a position upstream in the rotation direction of the impeller from the outlet of the fluid introduction flow path.

[0009] According to at least one embodiment of the present disclosure, there is provided a centrifugal compressor capable of reducing noise generated at the outlet of a fluid introduction passage even when the flow rate changes, and a turbocharger including the centrifugal compressor.

[0010] 1 is a partial cross-sectional view showing a schematic configuration of a turbocharger 2 according to an embodiment. FIG. 2 is a partially enlarged view showing an example of the shape of a connecting portion between a bypass passage 16 and a compressor inlet passage 40 in the centrifugal compressor 4 shown in FIG. 1 , showing a portion of a cross section (a cross section including the rotation axis of the impeller 6) along the axial direction in the vicinity of an end 24 of the bypass passage 16 on the compressor inlet passage 40 side. FIG. 3 is a view showing a portion of a cross section perpendicular to the axial direction at the position of the axis L1 of the bypass passage 16 of the centrifugal compressor 4 shown in FIG. 4 is a partially enlarged view showing another example of the shape of a connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in FIG. 2 is a partial cross-sectional view showing a portion of a cross section (a cross section including the rotation axis of the impeller 6) along the axial direction in the vicinity of an end 24 of the bypass passage 16 on the compressor inlet passage 40 side. FIG. 5 is a view showing a portion of a cross section perpendicular to the axial direction at the position of the axis L1 of the bypass passage 16 of the centrifugal compressor 4 shown in FIG. 8A is a diagram showing a comparison of noise levels among the embodiment shown in FIGS. 4 and 5 , the first comparative embodiment, and the second comparative embodiment, where a first comparative embodiment is a case where the outlet portion 16e of the bypass flow passage 16 has no inclined surface, and a second comparative embodiment is a case where the outlet portion 16e of the bypass flow passage 16 includes the first inclined surface 34 but does not include the second inclined surface 36. FIG. 8B is a partially enlarged view showing another example of the shape of the connection portion between the bypass flow passage 16 and the compressor inlet flow passage 40 in the centrifugal compressor 4 shown in FIG. 1 , showing a portion of a cross section (a cross section including the rotation axis of the impeller 6) along the axial direction near the end portion 24 of the bypass flow passage 16 on the compressor inlet flow passage 40 side. FIG. 8C is a diagram showing a portion of a cross section perpendicular to the axial direction at the position of the axis L1 of the bypass flow passage 16 of the centrifugal compressor 4 shown in FIG. 8A. FIG. 8D is a diagram for explaining details of the configuration shown in FIG. 8A. 9 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the rotation axis of the impeller 6) along the axial direction in the vicinity of an end 24 of the bypass passage 16 on the compressor inlet passage 40 side. Fig. 9 is a view showing a part of a cross section perpendicular to the axial direction at the position of the axis L1 of the bypass passage 16 of the centrifugal compressor 4 shown in Fig. 9.11 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in FIG. 1 , showing a part of a cross section (cross section including the rotation axis of the impeller 6) along the axial direction in the vicinity of an end 24 of the bypass passage 16 on the compressor inlet passage 40 side. 12 is a view showing a part of a cross section perpendicular to the axial direction at the position of the bypass passage 16 of the centrifugal compressor 4 shown in FIG. 11 . 13 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in FIG. 11 , showing a part of a cross section (cross section including the rotation axis of the impeller 6) along the axial direction in the vicinity of an end 24 of the bypass passage 16 on the compressor inlet passage 40 side. 14 is a view showing a part of a cross section perpendicular to the axial direction at the position of the bypass passage 16 of the centrifugal compressor 4 shown in FIG. 13 . 17 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in FIG. 1 , showing a part of a cross section (cross section including the rotation axis of the impeller 6) along the axial direction in the vicinity of an end 24 of the bypass passage 16 on the compressor inlet passage 40 side. 18 is a view showing a part of a cross section perpendicular to the axial direction at the position of the axis L1 of the bypass passage 16 of the centrifugal compressor 4 shown in FIG. 15. 19 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in FIG. 17, showing a part of a cross section perpendicular to the axial direction at the position of the axis L1 of the bypass passage 16. 20 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in FIG. 26.

[0011] Several embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the invention. For example, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express relative displacements with a tolerance or angle or distance to the extent that the same function is achieved. For example, expressions expressing the equality of things, such as "same," "equal," and "homogeneous," not only express strict equality, but also express tolerance or differences to the extent that the same function is achieved. For example, expressions expressing shapes such as a square or cylindrical shape not only express shapes such as a square or cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is achieved. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions that exclude the presence of other elements.

[0012] 1 is a partial cross-sectional view showing a schematic configuration of a turbocharger 2 according to one embodiment. As shown in Fig. 1, the turbocharger 2 includes a centrifugal compressor 4 and a turbine 12 including a turbine rotor 10 that shares a rotation axis 8 with an impeller 6 of the centrifugal compressor 4.

[0013] The centrifugal compressor 4 includes an impeller 6, a compressor inlet passage 40 that guides air to the impeller 6, a scroll passage 14 provided on the outer periphery of the impeller 6, a bypass passage 16 that bypasses the impeller 6 and connects the compressor inlet passage 40 to an outlet pipe 38 of the scroll passage 14, and a bypass valve 18 that can open and close a valve port 22 provided in the bypass passage 16. The bypass valve 18 is provided midway through the bypass passage 16, and a passage wall surface 26 of the bypass passage 16 is formed with a valve seat 27 against which the bypass valve 18 abuts. The opening and closing operation of the bypass valve 18 is controlled by an actuator 19, and the bypass valve 18 opens when the discharge pressure of the centrifugal compressor 4 excessively increases, thereby returning a portion of the compressed air flowing through the scroll passage 14 to the compressor inlet passage 40. That is, the bypass passage 16 is a fluid introduction passage that introduces a fluid (here, a portion of the compressed air compressed by the impeller 6) into the compressor inlet passage 40. In the illustrated exemplary embodiment, the compressor inlet flow passage 40 is formed by the compressor inlet pipe 37 that extends linearly along the rotational axis O1 of the impeller 6. The bypass flow passage 16 is connected to the compressor inlet flow passage 40 in a direction that intersects with the axis O1 of the compressor inlet flow passage 40 (an axis that coincides with the rotational axis O1 of the impeller 6).

[0014] Hereinafter, unless otherwise specified, "axial direction" means the axial direction of the impeller 6, "circumferential direction" means the circumferential direction of the impeller 6, and "radial direction" means the radial direction of the impeller 6. The axial direction of the impeller 6 coincides with the axial direction of the compressor inlet flow path 40 (axial direction of the compressor inlet pipe 37), the circumferential direction of the impeller 6 coincides with the circumferential direction of the compressor inlet flow path 40 (circumferential direction of the compressor inlet pipe 37), and the radial direction of the impeller 6 coincides with the radial direction of the compressor inlet flow path 40 (radial direction of the compressor inlet pipe 37).

[0015] Fig. 2 is a partially enlarged view showing an example of the shape of a connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet portion 16e of the bypass passage 16. Fig. 3 is a view showing a part of a cross section orthogonal to the axial direction at the position of the axis L1 of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 2.

[0016] 2 and 3 , at the outlet portion 16e of the bypass flow passage 16, the flow passage wall surface 26 of the bypass flow passage 16 includes a first inclined surface 28 and a second inclined surface 30. The outlet portion 16e of the bypass flow passage 16 refers to the end portion of the bypass flow passage 16 on the compressor inlet flow passage 40 side.

[0017] 2 , the first inclined surface 28 is located downstream in the axial direction from the axis L1 of the bypass flow passage 16, and is inclined toward the axial downstream side as it approaches the compressor inlet flow passage 40 (as it moves radially inward). In the illustrated exemplary embodiment, in a cross section along the axial direction, the first inclined surface 28 includes a straight line 28a that extends toward the axial downstream side as it approaches the compressor inlet flow passage 40, and the straight line 28a is inclined with respect to the axis L1 of the bypass flow passage 16. Note that the axis L1 of the bypass flow passage 16 means the axis of a pipe that constitutes the bypass flow passage 16.

[0018] 3 , the second inclined surface 30 is located downstream of the axis L1 of the bypass flow passage 16 in the rotation direction of the impeller 6, and is inclined toward the downstream side in the rotation direction of the impeller 6 as it approaches the compressor inlet flow passage 40 (as it moves radially inward). In the illustrated exemplary embodiment, in a cross section perpendicular to the axial direction, the second inclined surface 30 includes a straight line 30a that extends toward the downstream side in the rotation direction of the impeller 6 as it approaches the compressor inlet flow passage 40, and the straight line 30a is inclined with respect to the axis L1 of the bypass flow passage 16.

[0019] Under high flow rate operating conditions in the centrifugal compressor 4, the air flowing through the compressor inlet passage 40 flows along the axial direction as indicated by the arrow F in Figure 2, and the swirling component of the flow in the compressor inlet passage 40 in the rotational direction of the impeller 6 is relatively small. On the other hand, under low flow rate operating conditions in the centrifugal compressor 4, the influence of the rotation of the impeller 6 on the flow in the compressor inlet passage 40 becomes stronger, and the swirling component of the flow in the compressor inlet passage 40 in the rotational direction of the impeller 6 becomes relatively large.

[0020] 2 and 3, at the outlet portion 16e of the bypass flow passage 16, the flow passage wall surface 26 is provided with the first inclined surface 28 downstream in the axial direction from the axis L1 of the bypass flow passage 16. Therefore, under high flow rate operating conditions in the centrifugal compressor 4, even if a vortex is generated at a position P1 of an upstream edge of the outlet 16e1 in the axial direction (a leading edge of the outlet with respect to the axial flow) when the air (main flow) flowing in the compressor inlet flow passage 40 along the axial direction passes through the outlet 16e1 of the bypass flow passage 16, the pressure fluctuation caused by the vortex colliding with the vicinity of a position P2 of a downstream edge of the outlet 16e1 of the bypass flow passage 16 (a trailing edge of the outlet with respect to the axial flow) can be alleviated and the noise generated at the outlet 16e1 of the bypass flow passage 16 can be reduced compared to a case where the flow passage wall surface 26 of the bypass flow passage 16 is not inclined with respect to the axis L1 of the bypass flow passage 16. The outlet 16e1 of the bypass passage 16 is an opening on the compressor inlet passage 40 side of the bypass passage 16. The cross-sectional shape of the outlet 16e1 may be, for example, rectangular, or may be an oval shape such as circular or elliptical.

[0021] At the outlet 16 e of the bypass flow passage 16 , the flow passage wall surface 26 of the bypass flow passage 16 is provided with the second inclined surface 30 downstream of the axis L1 of the bypass flow passage 16 in the rotation direction of the impeller 6 . For this reason, under low flow rate operating conditions in the centrifugal compressor 4, when the swirling flow of air flowing through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at position P3 of the upstream edge of the outlet 16e1 in the rotation direction of the impeller 6 (the leading edge of the outlet 16e1 with respect to the swirling flow in the rotation direction of the impeller 6), the pressure fluctuation caused by the vortex colliding with the vicinity of position P4 of the downstream edge of the outlet 16e1 in the rotation direction of the impeller 6 (the trailing edge of the outlet 16e1 with respect to the swirling flow in the rotation direction of the impeller 6) can be mitigated and the noise generated at the outlet 16e1 of the bypass flow path 16 can be reduced compared to when the flow path wall surface 26 of the bypass flow path 16 is not inclined with respect to the axis L1 of the bypass flow path 16.

[0022] Therefore, according to the centrifugal compressor 4, it is possible to effectively reduce the noise generated at the outlet 16e1 of the bypass passage 16 even if the flow rate changes.

[0023] 1 and 2 , for example, when the area of ​​the outlet 16e1 of the bypass flow passage 16 is Sp and the flow passage area of ​​the bypass flow passage 16 at the position of the valve seat surface 27 (i.e., the flow passage area of ​​the valve port 22) is Sq, Sp≧Sq may be satisfied. Note that the area of ​​the outlet 16e1 of the bypass flow passage 16 refers to the area of ​​an opening formed in the flow passage wall surface 42 of the compressor inlet flow passage 40 at a position where the flow passage wall surface 26 of the bypass flow passage 16 connects, and refers to the area of ​​the opening defined by the position of the inner end of the first inclined surface 28 in the radial direction.

[0024] According to this configuration, it is possible to reduce the noise generated at the outlet 16e1 of the bypass flow path 16 while suppressing the effect on the performance of the centrifugal compressor 4 caused by providing the first inclined surface 28 and the second inclined surface 30.

[0025] 2 , for example, when the dimension of the first inclined surface 28 in the axial direction is E1 and the axial flow path width of the flow path portion 16u in the bypass flow path 16 adjacent to the upstream side of the first inclined surface 28 is E2, E1≧0.1×E2 may be satisfied. This makes it possible to effectively reduce noise generated at the outlet 16e1 of the bypass flow path 16.

[0026] 3 , for example, a direction perpendicular to both the axial direction and the axis L1 of the bypass flow passage 16 is defined as a first direction, and the dimension of the second inclined surface 30 in the first direction is defined as E3, and the flow passage width in the first direction of the flow passage portion 16u in the bypass flow passage 16 adjacent to the upstream side of the second inclined surface 30 is defined as E4. In this way, the relationship E3≧0.1×E4 may be satisfied. This makes it possible to effectively reduce noise generated at the outlet 16e1 of the bypass flow passage 16.

[0027] 2 and 3, for example, when the area of ​​the outlet 16e1 of the bypass passage 16 is Sp and the flow passage area of ​​the compressor inlet passage 40 at the position of the outlet 16e1 is Sv, Sp < 0.35 × Sv may be satisfied. If Sp / Sv exceeds 0.35 (i.e., if the size of the angular range in the circumferential direction in which the outlet 16e1 of the bypass passage 16 is present exceeds 60 degrees), the impact on the performance of the centrifugal compressor 4 becomes significantly large. Therefore, by satisfying Sp < 0.35 × Sv as described above, it is possible to reduce the noise generated at the outlet 16e1 of the bypass passage 16 while suppressing the impact on the performance of the centrifugal compressor 4.

[0028] Fig. 4 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet 16e of the bypass passage 16. Fig. 5 is a view showing a part of a cross section orthogonal to the axial direction at the position of the axis L1 of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 4.

[0029] In some embodiments, as shown in FIGS. 4 and 5 , at the outlet portion 16 e of the bypass flow passage 16 , the flow passage wall surface 26 of the bypass flow passage 16 includes a first inclined surface 34 and a second inclined surface 36 .

[0030] 4 , the first inclined surface 34 is located downstream in the axial direction from the axis L1 of the bypass flow passage 16, and is inclined toward the downstream side in the axial direction as it approaches the compressor inlet flow passage 40 (as it moves radially inward). In the illustrated exemplary embodiment, in a cross section along the axial direction, the first inclined surface 34 includes a curved convex curve 34 a that extends toward the downstream side in the axial direction as it approaches the compressor inlet flow passage 40.

[0031] 5 , the second inclined surface 36 is located downstream of the axis L1 of the bypass flow passage 16 in the rotation direction of the impeller 6, and is inclined toward the downstream side in the rotation direction of the impeller 6 as it approaches the compressor inlet flow passage 40 (as it moves radially inward). In the illustrated exemplary embodiment, in a cross section perpendicular to the axial direction, the second inclined surface 36 includes a curved convex curve 36a that extends toward the downstream side in the rotation direction of the impeller 6 as it approaches the compressor inlet flow passage 40.

[0032] In the centrifugal compressor 4 shown in FIGS. 4 and 5 , for the same reason as in the centrifugal compressor 4 shown in FIGS. 2 and 3 , the noise generated at the outlet 16e1 of the bypass flow path 16 can be effectively reduced even if the flow rate changes.

[0033] FIG. 6 shows test results comparing noise levels among the embodiment shown in FIGS. 4 and 5 , the first comparative embodiment, and the second comparative embodiment, where a first comparative embodiment is a case where there is no inclined surface at the outlet portion 16 e of the bypass flow path 16 (a case where the flow path wall surface 26 of the bypass flow path 16 is not inclined with respect to the axis L1 of the bypass flow path 16 at the outlet portion 16 e of the bypass flow path 16), and a second comparative embodiment is a case where the outlet portion 16 e of the bypass flow path 16 includes the first inclined surface 34 but does not include the second inclined surface 36.

[0034] As shown in Fig. 6, on the high flow rate side of the centrifugal compressor, the axial flow (main flow) is dominant in the compressor inlet passage 40, and therefore noise can be reduced as long as the first inclined surface 34 is provided, regardless of the presence or absence of the second inclined surface 36. On the other hand, on the low flow rate side of the centrifugal compressor, a swirling flow with a strong swirling component is formed in the compressor inlet passage 40, and therefore the effect of reducing the noise level in comparative embodiment 2, which is provided with only the first inclined surface 34, is limited, whereas the embodiment, which is provided with both the first inclined surface 34 and the second inclined surface 36, can significantly reduce the noise level.

[0035] 4 , for example, when the dimension of the first inclined surface 34 in the axial direction is E1 and the axial flow path width of the flow path portion 16u in the bypass flow path 16 adjacent to the upstream side of the first inclined surface 34 is E2, E1≧0.1×E2 may be satisfied. This makes it possible to effectively reduce noise generated at the outlet 16e1 of the bypass flow path 16.

[0036] 5 , for example, a direction perpendicular to both the axial direction and the axis L1 of the bypass flow passage 16 is defined as a first direction, and the dimension of the second inclined surface 36 in the first direction is defined as E3, and the circumferential flow passage width of the flow passage portion 16u in the bypass flow passage 16 adjacent to the upstream side of the second inclined surface 36 is defined as E4. In this way, the relationship E3≧0.1×E4 may be satisfied. This makes it possible to effectively reduce noise generated at the outlet 16e1 of the bypass flow passage 16.

[0037] Fig. 7 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet portion 16e of the bypass passage 16. Fig. 8A is a diagram showing a part of a cross section orthogonal to the axial direction at the position of the axis L1 of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 7. Fig. 8B is a diagram for explaining details of the configuration shown in Fig. 8A.

[0038] 7 and 8A , with respect to an edge 26e on the outlet 16e1 side of the bypass flow path 16 of the flow path wall surface 26, the distance A1 is defined as the distance between the most upstream position P1 in the axial direction of the edge 26e and the axis O1 of the compressor inlet flow path 40, the distance A2 is defined as the distance between the most downstream position P2 in the axial direction of the edge 26e and the axis O1, the distance A3 is defined as the distance between the most upstream position P3 in the rotational direction of the impeller 6 at the edge 26e and the axis O1 of the compressor inlet flow path 40, and the distance A4 is defined as the distance between the most downstream position P4 in the rotational direction of the impeller 6 at the edge 26e and the axis O1. Furthermore, in the embodiment shown in FIGS. 7 and 8A , the relationships A1<A2 and A3<A4 are satisfied. That is, A1 is smaller than A2, A3 is smaller than A4, there is a radial step between the most upstream position P1 and the most downstream position P2, and there is a radial step between the most upstream position P3 and the most downstream position P4.

[0039] 7 and 8A , the distances A1 and A2 are different from each other, so that a radial step is formed between the axial most upstream position P1 of the edge 26e of the flow path wall surface 26 of the bypass flow path 16 on the compressor inlet flow path 40 side and the axial most downstream position P2 of the edge 26e. Therefore, under high flow rate operating conditions of the centrifugal compressor 4, when the air (main flow) flowing axially through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at the position P1 of the axial upstream edge of the outlet 16e1 (the position of the leading edge of the outlet with respect to the axial flow), it is possible to suppress or avoid the vortex from colliding with the position P2 of the axial downstream edge of the outlet 16e1 of the bypass flow path 16 (the position of the trailing edge of the outlet with respect to the axial flow). This suppresses pressure fluctuations caused by the collision and reduces noise at the outlet 16e1 of the bypass flow path 16.

[0040] In the embodiment shown in FIGS. 7 and 8A, the distances A3 and A4 are different from each other, and therefore, for the edge 26e on the compressor inlet flow path 40 side of the flow path wall surface 26 of the bypass flow path 16, a step is formed in the radial direction between the upstream-most position P3 in the rotation direction of the impeller 6 at the edge 26e and the downstream-most position P4 in the rotation direction of the impeller 6 at the edge 26e. For this reason, under low flow rate operating conditions in the centrifugal compressor 4, when the swirling flow of air flowing through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at position P3 of the upstream edge of the outlet 16e1 in the rotational direction of the impeller 6 (the leading edge of the outlet 16e1 with respect to the swirling flow in the rotational direction of the impeller 6), it is possible to suppress or avoid the vortex from colliding with position P4 of the downstream edge of the axial direction of the outlet 16e1 of the bypass flow path 16 (the position of the trailing edge of the outlet 16e1 with respect to the swirling flow in the rotational direction of the impeller 6), and it is possible to suppress or avoid the pressure fluctuation caused by the collision and reduce noise at the outlet 16e1 of the bypass flow path 16.

[0041] 7 and 8A, it is possible to effectively reduce noise generated at the outlet 16e1 of the bypass passage 16 even when the flow rate changes. Moreover, since it is not necessary to increase the area of ​​the outlet 16e1 of the bypass passage 16, it is possible to reduce noise while suppressing the effect on the performance of the centrifugal compressor 4.

[0042] 7 and 8A , when the flow path width of the bypass flow path 16 in the axial direction at the position of the outlet 16e1 of the bypass flow path 16 is W1 and the flow path width of the bypass flow path 16 in the first direction (directions perpendicular to both the axial direction and the axis L1 of the bypass flow path 16) at the position of the outlet 16e1 of the bypass flow path 16 is W2, at least one of the following formulas (a) and (b) may be satisfied: |A1-A2|≧0.35×W1 (a1) |A3-A4|≧0.35×W2 (a2) That is, of the formulas (a1) and (a2), only the formula (a1) may be satisfied, only the formula (a2) may be satisfied, or both the formulas (a1) and (a2) may be satisfied. As the flow path widths W1 and W2 are larger, the flow along the circumferential direction in the compressor inlet flow path 40 penetrates deeper into the bypass flow path 16, and the range in which the flow circumferential flow is likely to collide with the flow path wall surface 42 of the bypass flow path 16 becomes wider. In this regard, by satisfying at least one of the above formulas (a1) and (a2), it is possible to effectively suppress the collision of vortices with the flow path wall surface 26 of the bypass flow path 16, and to suppress noise caused by vortex collision.

[0043] In some embodiments, as shown in Fig. 8B , when the flow path width of the bypass flow path 16 in the first direction (directions perpendicular to both the axial direction and the axis L1 of the bypass flow path 16) at the position of the outlet 16e1 of the bypass flow path 16 is W2, and the size of the angular range in the circumferential direction in which the outlet 16e1 of the bypass flow path 16 is located is θ, the following formula (b) may be satisfied. Formula (b): |A3 - A4| > W2 × tan(θ / 2)

[0044] As shown in Figure 8B, if L2 is an imaginary line extending from position P3 of the upstream edge of the impeller 6 in the rotation direction at the outlet 16e1 in a cross section perpendicular to the axial direction in the tangent direction of the circle constituting the flow path wall surface 42 of the compressor inlet flow path 40, when the above formula (b) is satisfied, position P4 of the downstream edge of the impeller 6 in the rotation direction at the outlet 16e1 in a cross section perpendicular to the axial direction will be radially outward from imaginary line L2. Therefore, even if a vortex is generated at position P3 of the upstream edge of the outlet 16e1 in the direction of rotation of the impeller 6 at the outlet 16e1 when the swirling flow of air flowing through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16 (the leading edge of the outlet 16e1 with respect to the swirling flow in the direction of rotation of the impeller 6), it is possible to suppress or avoid the vortex from colliding with position P4 of the downstream edge of the outlet 16e1 in the axial direction at the outlet 16e1 of the bypass flow path 16 (the trailing edge of the outlet 16e1 with respect to the swirling flow in the direction of rotation of the impeller 6), and noise caused by vortex collision can be effectively suppressed.

[0045] Fig. 9 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet 16e of the bypass passage 16. Fig. 10 is a view showing a part of a cross section orthogonal to the axial direction at the position of the axis L1 of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 9.

[0046] 9 and 10 , with respect to an edge 26e on the outlet 16e1 side of the bypass flow passage 16 of the flow passage wall surface 26, if A1 is the distance between a most upstream position P1 in the axial direction of the edge 26e and the axis O1 of the compressor inlet flow passage 40, A2 is the distance between a most downstream position P2 in the axial direction of the edge 26e and the axis O1, A3 is the distance between a most upstream position P3 in the rotational direction of the impeller 6 at the edge 26e and the axis O1 of the compressor inlet flow passage 40, and A4 is the distance between a most downstream position P4 in the rotational direction of the impeller 6 at the edge 26e and the axis O1, A1 and A2 are different from each other, and A3 and A4 are different from each other. In the embodiment shown in FIGS. 9 and 10 , A1 > A2 and A3 > A4 are satisfied. That is, A1 is larger than A2, A3 is larger than A4, there is a radial step between the most upstream position P1 and the most downstream position P2, and there is a radial step between the most upstream position P3 and the most downstream position P4.

[0047] 9 and 10 , the distances A1 and A2 are different from each other, so that a radial step is formed between the axial most upstream position P1 of the edge 26e of the flow path wall surface 26 of the bypass flow path 16 on the compressor inlet flow path 40 side and the axial most downstream position P2 of the edge 26e. Therefore, under high flow rate operating conditions of the centrifugal compressor 4, when the air (main flow) flowing axially through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at the position P1 of the axial upstream edge of the outlet 16e1 (the position of the leading edge of the outlet with respect to the axial flow) can be suppressed or avoided from colliding with the position P2 of the axial downstream edge of the outlet 16e1 of the bypass flow path 16 (the position of the trailing edge of the outlet with respect to the axial flow). This suppresses pressure fluctuations caused by the collision and reduces noise at the outlet 16e1 of the bypass flow path 16.

[0048] In the embodiment shown in FIGS. 9 and 10, the distances A3 and A4 are different from each other, and therefore, for the edge 26e of the flow path wall surface 26 of the bypass flow path 16 on the compressor inlet flow path 40 side, a step is formed in the radial direction between the upstream-most position P3 of the edge 26e in the rotation direction of the impeller 6 and the downstream-most position P4 of the edge 26e in the rotation direction of the impeller 6. For this reason, under low flow rate operating conditions in the centrifugal compressor 4, when the swirling flow of air flowing through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at position P3 of the upstream edge of the outlet 16e1 in the rotational direction of the impeller 6 (the leading edge of the outlet 16e1 with respect to the swirling flow in the rotational direction of the impeller 6), it is possible to suppress or avoid the vortex from colliding with position P4 of the downstream edge of the axial direction of the outlet 16e1 of the bypass flow path 16 (the position of the trailing edge of the outlet 16e1 with respect to the swirling flow in the rotational direction of the impeller 6), and it is possible to suppress or avoid the pressure fluctuation caused by the collision and reduce noise at the outlet 16e1 of the bypass flow path 16.

[0049] 9 and 10, noise generated at the outlet 16e1 of the bypass passage 16 can be effectively reduced even when the flow rate changes. Moreover, since there is no need to increase the area of ​​the outlet 16e1 of the bypass passage 16, noise can be reduced while suppressing the effect on the performance of the centrifugal compressor 4.

[0050] 9 and 10 , when the flow path width of the bypass flow path 16 in the axial direction at the position of the outlet 16e1 of the bypass flow path 16 is W1 and the flow path width of the bypass flow path 16 in the first direction at the position of the outlet 16e1 of the bypass flow path 16 is W2, at least one of the above formula (a1) and formula (a2) may be satisfied. That is, of the above formula (a1) and formula (a2), only the above formula (a1) may be satisfied, only the above formula (a2) may be satisfied, or both the above formulas (a1) and (a2) may be satisfied.

[0051] Fig. 11 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet portion 16e of the bypass passage 16. Fig. 12 is a view showing a part of a cross section orthogonal to the axial direction at the position of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 11.

[0052] In some embodiments, for example, as shown in FIG. 11 , in a section of the compressor inlet flow path 40 including a portion that connects to the bypass flow path 16, the distance R between the flow path wall surface 42 of the compressor inlet flow path 40 and the axis O1 of the compressor inlet flow path 40 may increase toward the downstream side in the axial direction. 11 and 12 , with regard to the edge 26e on the outlet 16e1 side of the bypass flow path 16 on the flow path wall surface 26, the distance between the most upstream position P1 in the axial direction at the edge 26e and the axis O1 of the compressor inlet flow path 40 is A1, the distance between the most downstream position P2 in the axial direction at the edge 26e and the axis O1 is A2, the distance between the most upstream position P3 in the rotational direction of the impeller 6 at the edge 26e and the axis O1 of the compressor inlet flow path 40 is A3, and the distance between the most downstream position P4 in the rotational direction of the impeller 6 at the edge 26e and the axis O1 is A4, the relationships A1<A2 and A3<A4 are satisfied.

[0053] 11 and 12 , it is possible to effectively reduce noise generated at the outlet 16e1 of the bypass passage 16 even when the flow rate changes. Moreover, since it is not necessary to increase the area of ​​the outlet 16e1 of the bypass passage 16, it is possible to reduce noise while suppressing the effect on the performance of the centrifugal compressor 4.

[0054] Fig. 13 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet portion 16e of the bypass passage 16. Fig. 14 is a view showing a part of a cross section orthogonal to the axial direction at the position of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 13.

[0055] In some embodiments, for example, as shown in FIG. 13 , in a section of the compressor inlet flow path 40 including the portion that connects to the bypass flow path 16, the distance R between the flow path wall surface 42 of the compressor inlet flow path 40 and the axis O1 of the compressor inlet flow path 40 may decrease toward the downstream side in the axial direction. In the exemplary embodiment shown in FIGS. 13 and 14 , with regard to the edge 26e on the outlet 16e1 side of the bypass flow path 16 on the flow path wall surface 26, if the distance between the most upstream position P1 in the axial direction at the edge 26e and the axis O1 of the compressor inlet flow path 40 is A1, the distance between the most downstream position P2 in the axial direction at the edge 26e and the axis O1 is A2, the distance between the most upstream position P3 in the rotational direction of the impeller 6 at the edge 26e and the axis O1 of the compressor inlet flow path 40 is A3, and the distance between the most downstream position P4 in the rotational direction of the impeller 6 at the edge 26e and the axis O1 is A4, then the relationships A1 > A2 and A3 > A4 are satisfied.

[0056] 13 and 14 , it is possible to effectively reduce noise generated at the outlet 16e1 of the bypass passage 16 even when the flow rate changes. Moreover, since it is not necessary to increase the area of ​​the outlet 16e1 of the bypass passage 16, it is possible to reduce noise while suppressing the effect on the performance of the centrifugal compressor 4.

[0057] Fig. 15 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet 16e of the bypass passage 16. Fig. 16 is a view showing a part of a cross section orthogonal to the axial direction at the position of the axis L1 of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 15.

[0058] In some embodiments, as shown in Figures 15 and 16, for example, in a cross section along the axial direction, the angle α formed between the flow path wall surface 42 of the compressor inlet flow path 40 and the flow path wall surface 26 of the bypass flow path 16 on the upstream side of the axis L1 of the bypass flow path 16 in the axial direction is less than 90 degrees, and in a cross section perpendicular to the axial direction, the angle β formed between the flow path wall surface 42 of the compressor inlet flow path 40 and the flow path wall surface 26 of the bypass flow path 16 on the upstream side of the axis L1 of the bypass flow path 16 in the rotation direction of the impeller 6 is less than 90 degrees. In the exemplary embodiment shown in FIGS. 15 and 16 , in a cross section along the axial direction, the angle formed by the flow path wall surface 42 of the compressor inlet flow path 40 and the flow path wall surface 26 of the bypass flow path 16 on the downstream side of the axis L1 of the bypass flow path 16 in the axial direction is 90 degrees, and in a cross section perpendicular to the axial direction, the angle formed by the flow path wall surface 42 of the compressor inlet flow path 40 and the flow path wall surface 26 of the bypass flow path 16 on the downstream side of the axis L1 of the bypass flow path 16 in the rotation direction of the impeller 6 is greater than 90 degrees.

[0059] In the embodiments shown in FIGS. 15 and 16 , the angle α is less than 90 degrees. Therefore, under high flow rate operating conditions of the centrifugal compressor 4, when the air (main stream) flowing through the compressor inlet flow path 40 in the axial direction passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at a position P1 of the upstream axial edge of the outlet 16e1 (the position of the leading edge of the outlet with respect to the axial flow) thereof, it is possible to suppress or avoid the vortex from colliding with a position P2 of the downstream axial edge of the outlet 16e1 of the bypass flow path 16 (the position of the trailing edge of the outlet with respect to the axial flow). This suppresses pressure fluctuations caused by the collision and reduces noise at the outlet 16e1 of the bypass flow path 16.

[0060] Furthermore, since the angle β is less than 90 degrees, under low flow rate operating conditions of the centrifugal compressor 4, when the swirling flow of air flowing through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at position P3 of the upstream edge of the outlet 16e1 in the rotation direction of the impeller 6 (the leading edge of the outlet 16e1 with respect to the swirling flow in the rotation direction of the impeller 6), it is possible to suppress or avoid the vortex from colliding with position P4 of the downstream edge of the outlet 16e1 of the bypass flow path 16 in the axial direction (the position of the trailing edge of the outlet 16e1 with respect to the swirling flow in the rotation direction of the impeller 6), and it is possible to suppress or avoid the pressure fluctuation caused by the collision and reduce noise at the outlet 16e1 of the bypass flow path 16.

[0061] Fig. 17 is a partially enlarged view showing another example of the shape of the connecting portion between the bypass passage 16 and the compressor inlet passage 40 in the centrifugal compressor 4 shown in Fig. 1, and shows a part of a cross section (a cross section including the axis O1 of the compressor inlet passage 40) along the axial direction in the vicinity of the outlet 16e of the bypass passage 16. Fig. 18 is a view showing a part of a cross section orthogonal to the axial direction at the position of the axis L1 of the bypass passage 16 in the centrifugal compressor 4 shown in Fig. 17.

[0062] In some embodiments, as shown in Figures 17 and 18, for example, in a cross section along the axial direction, the flow path wall surface 42 of the compressor inlet flow path 40 includes a first convex portion 43 at a position axially upstream of the outlet 16e1 of the bypass flow path 16, and in a cross section perpendicular to the axial direction, the flow path wall surface 42 of the compressor inlet flow path 40 includes a second convex portion 44 at a position upstream of the outlet 16e1 of the bypass flow path 16 in the rotation direction of the impeller 6.

[0063] In the illustrated exemplary embodiment, the first convex portion 43 includes a rounded convex curve 43a in a cross section along the axial direction, and the second convex portion 44 includes a rounded convex curve 44a in a cross section perpendicular to the axial direction. The distance between the first convex portion 43 and the outlet 16e1 of the bypass flow path 16 is smaller than the axial flow path width W1 of the bypass flow path 16 at the position of the outlet 16e1 of the bypass flow path 16. In the illustrated exemplary embodiment, the distance between the first convex portion 43 and the outlet 16e1 of the bypass flow path 16 is zero, and the first convex portion 43 is provided adjacent to the outlet 16e1 of the bypass flow path 16 upstream of the outlet 16e1 of the bypass flow path 16 in the axial direction. The distance between the second convex portion 44 and the outlet 16e1 of the bypass flow path 16 is smaller than the flow path width W2 of the bypass flow path 16 in the first direction at the position of the outlet 16e1 of the bypass flow path 16. In the illustrated exemplary embodiment, the distance between the second protrusion 44 and the outlet 16e1 of the bypass flow passage 16 is zero, and the second protrusion 44 is provided adjacent to the outlet 16e1 on the upstream side of the outlet 16e1 of the bypass flow passage 16 in the rotation direction of the impeller 6. The first protrusion 43 extends in the circumferential direction, and the second protrusion 44 extends in the axial direction. Furthermore, the upstream end of the first protrusion 43 in the rotation direction of the impeller 6 may be connected to the upstream end of the second protrusion 44 in the axial direction.

[0064] In the embodiment shown in Figures 17 and 18, in a cross section along the axial direction, the flow path wall surface 42 of the compressor inlet flow path 40 includes the first convex portion 43 at a position axially upstream of the outlet 16e1 of the bypass flow path 16.Therefore, under high flow rate operating conditions of the centrifugal compressor 4, when the air (main stream) flowing through the compressor inlet flow path 40 in the axial direction passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at a position P1 of the first convex portion 43 on the axial upstream side of the outlet 16e1, it is possible to suppress or avoid the vortex from colliding with a position P2 of the axial downstream edge of the outlet 16e1 of the bypass flow path 16 (the position of the trailing edge of the outlet with respect to the axial flow), and thereby it is possible to suppress pressure fluctuations caused by the collision and reduce noise at the outlet 16e1 of the bypass flow path 16.

[0065] Furthermore, in a cross section perpendicular to the axial direction, the flow path wall surface 42 of the compressor inlet flow path 40 includes the second convex portion 44 at a position upstream of the outlet 16e1 of the bypass flow path 16 in the rotation direction of the impeller 6. Therefore, under low flow rate operating conditions of the centrifugal compressor 4, when the swirling flow of air flowing through the compressor inlet flow path 40 passes through the outlet 16e1 of the bypass flow path 16, even if a vortex is generated at a position P3 of the second convex portion 44 on the upstream side of the outlet 16e1 in the rotation direction of the impeller 6, it is possible to suppress or avoid the vortex from colliding with a position P4 of the downstream edge in the axial direction of the outlet 16e1 of the bypass flow path 16 (the position of the trailing edge of the outlet 16e1 with respect to the swirling flow in the rotation direction of the impeller 6). This suppresses pressure fluctuations caused by the collision and reduces noise at the outlet 16e1 of the bypass flow path 16.

[0066] 2 or 4, in the cross section along the axial direction, the angle formed between the flow path wall surface 26 of the bypass flow path 16 and the flow path wall surface 42 of the compressor inlet flow path 40 is 90 degrees on the upstream side of the axis line L1 of the bypass flow path 16 in the axial direction. However, at the outlet portion 16e of the bypass flow path 16, the flow path wall surface 26 of the bypass flow path 16 may have an inclined surface that inclines toward the upstream side in the axial direction as it approaches the compressor inlet flow path 40 (as it moves radially inward).

[0067] Also, in the configuration shown in FIG. 3 or 5 , at the outlet portion 16 e of the bypass flow path 16, the flow path wall surface 26 of the bypass flow path 16 may have an inclined surface that is inclined toward the upstream side in the rotation direction of the impeller 6 with respect to the axis L1 in the rotation direction of the impeller 6 as it approaches the compressor inlet flow path 40 (as it moves radially inward).

[0068] In addition, in some of the above-described embodiments, the bypass flow path 16 is exemplified as a fluid introduction flow path that introduces a fluid into the compressor inlet flow path 40, but the fluid introduction flow path may also be, for example, an EGR flow path (exhaust gas recirculation flow path) that returns engine exhaust gas to the compressor inlet flow path.

[0069] The contents described in each of the above embodiments can be understood, for example, as follows.

[0070] (1) A centrifugal compressor according to at least one embodiment of the present disclosure (e.g., the above-described centrifugal compressor 4) includes: an impeller (e.g., the above-described impeller 6); a compressor inlet flow path (e.g., the above-described compressor inlet flow path 40) that guides a fluid to the impeller; and a fluid introduction flow path (e.g., the above-described bypass flow path 16 or an EGR flow path that returns exhaust gas from an engine to the compressor inlet flow path) that is connected to the compressor inlet flow path in a direction intersecting the axis of the compressor inlet flow path and that introduces a fluid into the compressor inlet flow path, wherein at an outlet portion of the bypass flow path (e.g., the above-described outlet portion 16e), a flow path wall surface of the bypass flow path (e.g., the above-described flow path wall surface 26) includes: a first inclined surface (e.g., the above-described first inclined surfaces 28 and 34) that is located downstream of the axis of the bypass flow path in the axial direction of the impeller and inclined toward the downstream side in the axial direction as it approaches the compressor inlet flow path; a second inclined surface (e.g., the above-mentioned second inclined surface 30, 36) that is located downstream of the axis of the bypass flow path in the rotation direction of the impeller and that inclines toward the downstream side in the rotation direction as it approaches the compressor inlet flow path.

[0071] Under high flow rate operating conditions in a centrifugal compressor, the fluid is guided into the compressor inlet passage and flows along the axial direction of the impeller, and the swirling component of the flow in the compressor inlet passage in the direction of the impeller rotation is relatively small. On the other hand, under low flow rate operating conditions in a centrifugal compressor, the influence of the impeller rotation on the flow in the compressor inlet passage becomes stronger, and the swirling component of the flow in the compressor inlet passage in the direction of the impeller rotation is relatively large.

[0072] In this regard, in the centrifugal compressor described in (1) above, at the outlet of the bypass passage, the flow path wall surface of the bypass passage is provided with the first inclined surface downstream in the axial direction from the axis of the bypass passage. Therefore, under high flow rate operating conditions of the centrifugal compressor, even if a vortex is generated at the position of the upstream edge of the outlet in the axial direction (the position of the leading edge of the outlet with respect to the axial flow) when air (main flow) flowing through the compressor inlet passage along the axial direction passes through the outlet of the bypass passage, pressure fluctuations caused by the vortex colliding with the vicinity of the position of the downstream edge of the outlet of the bypass passage (the position of the trailing edge of the outlet with respect to the axial flow) can be mitigated and noise generated at the outlet of the bypass passage can be reduced compared to a case where the flow path wall surface of the bypass passage is not inclined with respect to the axis of the bypass passage.

[0073] Furthermore, at the outlet portion of the bypass passage, a flow path wall surface of the bypass passage is provided downstream of the axis of the bypass passage in the rotation direction of the impeller. Therefore, under low flow rate operating conditions of the centrifugal compressor, even if a vortex is generated at the position of an upstream edge of the outlet in the rotation direction of the impeller (a leading edge of the outlet with respect to the swirling flow in the rotation direction of the impeller) when the swirling flow of air flowing through the compressor inlet passage passes through the outlet of the bypass passage, pressure fluctuations caused by the vortex colliding with the vicinity of the position of a downstream edge of the outlet in the rotation direction of the impeller (a trailing edge of the outlet with respect to the swirling flow in the rotation direction of the impeller) can be mitigated and noise generated at the outlet of the bypass passage can be reduced compared to a case where the flow path wall surface of the bypass passage is not inclined with respect to the axis of the bypass passage.

[0074] Furthermore, for example, in the embodiment shown in FIGS. 16 and 17 , the first convex portion 43 may be provided at a position slightly away from the outlet 16e1 of the bypass flow path 16 on the upstream side in the axial direction (for example, a position within the flow path width W1 from the outlet 16e1), and the second convex portion 44 may be provided at a position slightly away from the outlet 16e1 of the bypass flow path 16 on the upstream side in the rotation direction of the impeller 6 (for example, a position within the flow path width W2 from the outlet 16e1).

[0075] Therefore, according to the centrifugal compressor described in (1) above, the noise generated at the outlet of the bypass passage can be effectively reduced even if the flow rate changes.

[0076] (2) In some embodiments, in the centrifugal compressor described in (1) above, in a cross section along the axial direction, the first inclined surface includes a straight line (e.g., the above-mentioned straight line 28a), and in a cross section perpendicular to the axial direction, the second inclined surface includes a straight line (e.g., the above-mentioned straight line 30a).

[0077] According to the centrifugal compressor described in (2) above, it is possible to effectively reduce noise generated at the outlet of the bypass passage even when the flow rate changes.

[0078] (3) In some embodiments, in the centrifugal compressor described in (1) above, in a cross section along the axial direction, the first inclined surface includes a convex curve (e.g., the above-mentioned convex curve 34a), and in a cross section perpendicular to the axial direction, the second inclined surface includes a convex curve (e.g., the above-mentioned convex curve 36a).

[0079] According to the centrifugal compressor described in (3) above, it is possible to effectively reduce noise generated at the outlet of the bypass passage even when the flow rate changes.

[0080] (4) In some embodiments, in the centrifugal compressor according to any one of (1) to (3) above, when a dimension of the first inclined surface in the axial direction is E1 and a flow path width in the axial direction of a flow path portion of the bypass flow path adjacent to the upstream side of the first inclined surface is E2, E1≧0.1×E2 is satisfied.

[0081] According to the centrifugal compressor described in (4) above, it is possible to effectively reduce noise generated at the outlet of the bypass passage even when the flow rate changes.

[0082] (5) In some embodiments, in the centrifugal compressor according to any one of (1) to (4) above, when a direction perpendicular to each of the axial direction and the axis of the bypass flow passage is defined as a first direction, a dimension of the second inclined surface in the first direction is defined as E3, and a flow passage width in the first direction of a flow passage portion of the bypass flow passage adjacent to the upstream side of the second inclined surface is defined as E4, E3≧0.1×E4 is satisfied.

[0083] According to the centrifugal compressor described in (5) above, it is possible to effectively reduce noise generated at the outlet of the bypass passage even when the flow rate changes.

[0084] (6) A centrifugal compressor according to at least one embodiment of the present disclosure includes: an impeller (e.g., the above-described impeller 6); a compressor inlet flow path (e.g., the above-described compressor inlet flow path 40) that introduces a fluid to the impeller; and a fluid introduction flow path (e.g., the above-described bypass flow path 16 or an EGR flow path that returns engine exhaust gas to the compressor inlet flow path) that is connected to the compressor inlet flow path in a direction intersecting an axis of the compressor inlet flow path and introduces a fluid into the compressor inlet flow path, With respect to the edge (for example, the above-mentioned edge 26e) on the flow path wall surface of the fluid introduction flow path on the compressor inlet flow path side, if the distance between the most upstream position in the axial direction of the impeller at said edge (for example, the above-mentioned most upstream position P1) and the axis of the compressor inlet flow path is A1, the distance between the most downstream position in the axial direction at said edge (for example, the above-mentioned most downstream position P2) and the axis is A2, the distance between the most upstream position in the rotational direction of the impeller at said edge (for example, the above-mentioned most upstream position P3) and the axis is A3, and the distance between the most downstream position in the rotational direction at said edge (for example, the above-mentioned most downstream position P4) and the axis is A4, then A1 and A2 are different from each other, and A3 and A4 are different from each other.

[0085] Under high flow rate operating conditions in a centrifugal compressor, the fluid is guided into the compressor inlet passage and flows along the axial direction of the impeller, and the swirling component of the flow in the compressor inlet passage in the direction of the impeller rotation is relatively small. On the other hand, under low flow rate operating conditions in a centrifugal compressor, the influence of the impeller rotation on the flow in the compressor inlet passage becomes stronger, and the swirling component of the flow in the compressor inlet passage in the direction of the impeller rotation is relatively large.

[0086] In contrast, in the centrifugal compressor described in (6) above, the distances A1 and A2 are different from each other, so that a step is formed in the radial direction of the impeller between the most upstream position in the axial direction of the impeller at the edge of the passage wall surface of the fluid introduction passage on the compressor inlet passage side and the most downstream position in the axial direction of the impeller at the edge. Therefore, under high flow rate operating conditions of the centrifugal compressor, even if a vortex is generated at the position of the upstream edge of the impeller at the outlet in the axial direction of the outlet (the position of the leading edge of the outlet with respect to the axial flow) when the fluid flowing through the compressor inlet passage passes through the outlet of the fluid introduction passage, it is possible to suppress or avoid the vortex from colliding with the downstream edge of the impeller at the outlet in the axial direction of the fluid introduction passage (the trailing edge of the outlet with respect to the axial flow), thereby mitigating pressure fluctuations caused by the collision and reducing noise at the outlet of the fluid introduction passage.

[0087] In the centrifugal compressor described in (6) above, since the distances A3 and A4 are different from each other, a step is formed in the radial direction of the impeller at the edge of the wall surface of the fluid introduction passage on the compressor inlet passage side between the most upstream position of the edge in the direction of rotation of the impeller and the most downstream position of the edge in the direction of rotation of the impeller. Therefore, under low flow rate operating conditions in the centrifugal compressor, even if a vortex is generated at the position of the upstream edge of the outlet in the direction of rotation of the impeller (the position of the leading edge of the outlet with respect to the swirling flow in the direction of rotation of the impeller) when the fluid flowing through the compressor inlet passage passes through the outlet of the fluid introduction passage, it is possible to suppress or avoid the vortex from colliding with the downstream edge of the impeller in the axial direction at the outlet of the fluid introduction passage (the trailing edge of the outlet with respect to the swirling flow in the direction of rotation of the impeller), thereby mitigating pressure fluctuations caused by the collision and reducing noise at the outlet of the fluid introduction passage.

[0088] Therefore, the noise generated at the outlet of the fluid introduction passage can be effectively reduced even when the flow rate changes. Also, since there is no need to increase the area of ​​the outlet of the fluid introduction passage, the noise can be reduced while suppressing the effect on the performance of the centrifugal compressor.

[0089] (7) In some embodiments, in the centrifugal compressor described in (6) above, A1<A2 and A3<A4 are satisfied.

[0090] According to the centrifugal compressor described in (7) above, noise generated at the outlet of the fluid introduction channel can be more effectively reduced even when the flow rate changes, compared to when both A1>A2 and A3>A4 are satisfied.

[0091] (8) In some embodiments, in the centrifugal compressor described in (6) or (7) above, in a section of the compressor inlet passage including a connecting portion that connects to the fluid introduction passage, the distance between a passage wall surface of the compressor inlet passage and an axis of the compressor inlet passage (for example, the above-mentioned distance R) increases toward the downstream side in the axial direction.

[0092] According to the centrifugal compressor described in (8) above, it is possible to effectively reduce noise generated at the outlet of the fluid introduction passage even when the flow rate changes. Furthermore, since it is not necessary to increase the area of ​​the outlet of the fluid introduction passage, it is possible to reduce noise while suppressing the effect on the performance of the centrifugal compressor.

[0093] (9) In some embodiments, in the centrifugal compressor described in (6) or (7) above, in a section of the compressor inlet passage including a connecting portion that connects to the fluid introduction passage, the distance between a passage wall surface of the compressor inlet passage and an axis of the compressor inlet passage (for example, the above-mentioned distance R) decreases toward the downstream side in the axial direction.

[0094] According to the centrifugal compressor described in (9) above, it is possible to effectively reduce noise generated at the outlet of the fluid introduction passage even when the flow rate changes. Furthermore, since it is not necessary to increase the area of ​​the outlet of the fluid introduction passage, it is possible to reduce noise while suppressing the effect on the performance of the centrifugal compressor.

[0095] (10) In some embodiments, in the centrifugal compressor according to any one of (7) above, when a direction perpendicular to each of the axial direction and the axis of the fluid introduction channel is defined as a first direction, and a channel width of the fluid introduction channel in the first direction at the position of the outlet of the fluid introduction channel is W (for example, the above-mentioned W2), the following formula (a) is satisfied. Formula (a): |A3-A4|≧0.35×W

[0096] The flow in the compressor inlet passage along the circumferential direction of the impeller penetrates deeper into the fluid introduction passage, and the area where the flow collides with the passage wall surface of the fluid introduction passage tends to become wider as the passage width W increases. In this regard, by satisfying the above formula (a) as in the centrifugal compressor of (10) above, it is possible to effectively suppress the collision of vortices with the passage wall surface of the fluid introduction passage, and to suppress noise caused by vortex collision.

[0097] (11) In some embodiments, in the centrifugal compressor according to any one of (7) above, when a direction perpendicular to each of the axial direction and the axis of the fluid introduction channel is defined as a first direction, a channel width of the fluid introduction channel in the first direction at the position of the outlet of the fluid introduction channel is defined as W (for example, the above-mentioned W2), and a size of an angular range in the circumferential direction of the impeller in which the outlet of the fluid introduction channel exists is defined as θ, the following formula (b) is satisfied. Formula (b): |A3-A4|>W×tan(θ / 2)

[0098] If an imaginary line L2 is defined as an imaginary line extending from the upstream edge of the outlet of the fluid introduction passage in the direction of rotation of the impeller in a cross section perpendicular to the axial direction, in a tangential direction to a circle constituting the wall surface of the compressor inlet passage, and if the above formula (b) is satisfied, the downstream edge of the outlet in the direction of rotation of the impeller in the cross section perpendicular to the axial direction is located radially outward from the imaginary line L2. Therefore, even if a vortex is generated at the upstream edge of the outlet in the direction of rotation of the impeller (the leading edge of the outlet with respect to the swirling flow in the impeller rotation direction) when the swirling flow of the fluid flowing through the compressor inlet passage passes through the outlet of the fluid introduction passage, it is possible to suppress or avoid the vortex from colliding with the downstream edge of the outlet of the fluid introduction passage in the axial direction (the trailing edge of the outlet with respect to the swirling flow in the direction of rotation of the impeller), and noise caused by vortex collision can be effectively suppressed.

[0099] (12) A centrifugal compressor according to at least one embodiment of the present disclosure includes: an impeller (e.g., the above-described impeller 6); a compressor inlet flow path (e.g., the above-described compressor inlet flow path 40) that introduces a fluid to the impeller; and a fluid introduction flow path (e.g., the above-described bypass flow path 16 or an EGR flow path that returns engine exhaust gas to the compressor inlet flow path) that is connected to the compressor inlet flow path in a direction intersecting the axis of the compressor inlet flow path and introduces a fluid into the compressor inlet flow path, and satisfies the following condition (A) or the following condition (B): Condition (A): In a cross section along the axial direction of the impeller, the angle (e.g., the above-mentioned angle α) formed between the flow path wall surface of the compressor inlet flow path and the flow path wall surface of the fluid introduction flow path on the upstream side of the axis of the fluid introduction flow path in the axial direction is less than 90 degrees, and in a cross section perpendicular to the axial direction of the impeller, the angle (e.g., the above-mentioned angle β) formed between the flow path wall surface of the compressor inlet flow path and the flow path wall surface of the fluid introduction flow path on the upstream side of the axis of the fluid introduction flow path in the rotation direction of the impeller is less than 90 degrees. Condition (B): In a cross section along the axial direction of the impeller, the flow path wall surface of the compressor inlet flow path includes a first convex portion (e.g., the above-mentioned first convex portion 43) at a position upstream in the axial direction of the outlet of the fluid introduction flow path, and in a perpendicular cross section along the axial direction of the impeller, the flow path wall surface of the compressor inlet flow path includes a second convex portion (e.g., the above-mentioned second convex portion 44) at a position upstream in the rotation direction of the impeller from the outlet of the fluid introduction flow path.

[0100] Under high flow rate operating conditions in a centrifugal compressor, the fluid is guided into the compressor inlet passage and flows along the axial direction of the impeller, and the swirling component of the flow in the compressor inlet passage in the direction of the impeller rotation is relatively small. On the other hand, under low flow rate operating conditions in a centrifugal compressor, the influence of the impeller rotation on the flow in the compressor inlet passage becomes stronger, and the swirling component of the flow in the compressor inlet passage in the direction of the impeller rotation is relatively large.

[0101] In contrast, in a centrifugal compressor that satisfies the condition (A) or (B) of (12) above, under high flow rate operating conditions, when a fluid flowing through the compressor inlet passage passes through the outlet of the fluid introduction passage, even if a vortex is generated at the upstream axial edge of the impeller at the outlet (leading edge of the outlet with respect to the axial flow) it is possible to suppress or avoid the vortex from colliding with the downstream axial edge of the impeller at the outlet of the fluid introduction passage (trailing edge of the outlet with respect to the axial flow), thereby mitigating the pressure fluctuation caused by the collision and reducing noise at the outlet of the fluid introduction passage. Furthermore, in a centrifugal compressor that satisfies the condition (A) or (B) of (12) above, when the fluid flowing through the compressor inlet passage passes through the outlet of the fluid introduction passage under low flow rate operating conditions in the centrifugal compressor, even if a vortex is generated at the upstream edge of the outlet in the rotation direction of the impeller (the leading edge of the outlet with respect to the swirling flow in the rotation direction of the impeller), it is possible to suppress or avoid the vortex from colliding with the downstream edge of the outlet of the fluid introduction passage in the axial direction of the impeller (the trailing edge of the outlet with respect to the swirling flow in the rotation direction of the impeller), and it is possible to mitigate the pressure fluctuation caused by the collision and reduce the noise at the outlet of the fluid introduction passage.

[0102] Therefore, the noise generated at the outlet of the fluid introduction passage can be effectively reduced even when the flow rate changes. Also, since there is no need to increase the area of ​​the outlet of the fluid introduction passage, the noise can be reduced while suppressing the effect on the performance of the centrifugal compressor.

[0103] (13) In some embodiments, in the centrifugal compressor according to any one of (12) above, the condition (B) is satisfied, and in a cross section along the axial direction, the first convex portion includes a convex curve (for example, the above-mentioned convex curve 43a), and in a cross section perpendicular to the axial direction, the second convex portion includes a convex curve (for example, the above-mentioned convex curve 44a).

[0104] According to the centrifugal compressor described in (13) above, it is possible to effectively reduce noise generated at the outlet of the fluid introduction channel even when the flow rate changes. Furthermore, since it is not necessary to increase the area of ​​the outlet of the fluid introduction channel, it is possible to reduce noise while suppressing the effect on the performance of the centrifugal compressor. (14) In some embodiments, in the centrifugal compressor described in any of (12) above, the condition (B) is satisfied, and a distance between the first convex portion and the outlet of the fluid introduction channel is smaller than a channel width in the axial direction of the fluid introduction channel at the position of the outlet of the fluid introduction channel, and when directions perpendicular to the axial direction and an axis of the fluid introduction channel are defined as first directions, a distance between the second convex portion and the outlet of the fluid introduction channel is smaller than a channel width in the first direction of the fluid introduction channel at the position of the outlet of the fluid introduction channel.

[0105] According to the centrifugal compressor described in (14) above, by arranging each of the first convex portion and the second convex portion in the vicinity of the outlet of the fluid introduction flow path to the extent described in (14) above, it is possible to more effectively reduce noise generated at the outlet of the fluid introduction flow path.

[0106] (15) In some embodiments, the centrifugal compressor according to any one of (1) to (14) above further comprises a valve (for example, the above-mentioned bypass valve 18 or an EGR valve provided in the EGR flow path) provided midway through the fluid introduction flow path, and a valve seat (for example, the above-mentioned valve seat 27) against which the valve abuts is formed on a flow path wall surface of the fluid introduction flow path, and when the area of ​​the outlet of the fluid introduction flow path is Sp and the flow path area of ​​the fluid introduction flow path at the position of the valve seat is Sq, Sp≧Sq is satisfied.

[0107] According to the centrifugal compressor described in (15) above, it is possible to reduce noise generated at the outlet of the fluid introduction channel while suppressing the influence on the performance of the centrifugal compressor.

[0108] (16) In some embodiments, in the centrifugal compressor according to any one of (1) to (15) above, when a flow path area of ​​the outlet of the fluid introduction flow path is Sp and a flow path area of ​​the compressor inlet flow path at the position of the outlet is Sv, Sp<0.35×Sv is satisfied.

[0109] According to the centrifugal compressor described in (16) above, it is possible to reduce noise generated at the outlet of the fluid introduction channel while suppressing the influence on the performance of the centrifugal compressor.

[0110] (17) A turbocharger according to at least one embodiment of the present disclosure includes the centrifugal compressor according to any one of (1) to (16) above, and a turbine (e.g., the turbine 12 described above) connected to the centrifugal compressor.

[0111] According to the turbocharger described in (17) above, since it is equipped with the centrifugal compressor described in any one of (1) to (16) above, it is possible to effectively reduce noise generated at the outlet of the fluid introduction passage even when the flow rate changes.

[0112] 2 Turbocharger 4 Centrifugal compressor 6 Impeller 8 Rotating shaft 10 Turbine rotor 12 Turbine 14 Scroll passage 16 Bypass passage 16e1 Outlet 16e Outlet portion 16u Passage portion 18 Bypass valve 19 Actuator 22 Valve port 24 End portion 26, 42 Passage wall surface 26e End edge 27 Valve seat surface 28, 34 First inclined surface 28a, 30a Straight line 30, 36 Second inclined surface 34a, 36a, 43a, 44a Convex curve 37 Compressor inlet pipe 38 Outlet pipe 40 Compressor inlet passage 43 First convex portion 44 Second convex portion A1, A2, A3, A4, R Distance F Arrows L1, O1 Axis L2 Virtual line P1, P3 Most upstream position P2, P4 Most downstream position W1, W2 Channel width

Claims

1. The impeller and a compressor inlet flow path that guides fluid to the impeller; a fluid introduction flow path connected to the compressor inlet flow path in a direction intersecting an axis of the compressor inlet flow path and introducing a fluid into the compressor inlet flow path; Equipped with At the outlet portion of the fluid introduction channel, the channel wall surface of the fluid introduction channel is a first inclined surface located downstream in the axial direction of the impeller with respect to the axis of the fluid introduction passage, the first inclined surface inclining toward the downstream side in the axial direction as the first inclined surface approaches the compressor inlet passage; a second inclined surface located downstream of the axis of the fluid introduction passage in the rotation direction of the impeller, the second inclined surface inclining toward the downstream side in the rotation direction as it approaches the compressor inlet passage; A centrifugal compressor, including:

2. In a cross section along the axial direction, the first inclined surface includes a straight line, The centrifugal compressor according to claim 1 , wherein the second inclined surface includes a straight line in a cross section perpendicular to the axial direction.

3. In a cross section along the axial direction, the first inclined surface includes a convex curve. The centrifugal compressor according to claim 1 , wherein in a cross section perpendicular to the axial direction, the second inclined surface includes a convex curve.

4. 4. The centrifugal compressor according to claim 1, wherein, when a dimension of the first inclined surface in the axial direction is E1 and a flow path width in the axial direction of a flow path portion of the fluid introduction flow path adjacent to an upstream side of the first inclined surface is E2, E1≧0.1×E2 is satisfied.

5. 4. The centrifugal compressor according to claim 1, wherein a direction perpendicular to each of the axial direction and an axis of the fluid introduction flow path is defined as a first direction, a dimension of the second inclined surface in the first direction is defined as E3, and a flow path width in the first direction of a flow path portion of the fluid introduction flow path adjacent to an upstream side of the second inclined surface is defined as E4, and E3 ≥ 0.1 × E4 is satisfied.

6. The impeller and a compressor inlet flow path that guides fluid to the impeller; a fluid introduction flow path connected to the compressor inlet flow path in a direction intersecting an axis of the compressor inlet flow path and introducing a fluid into the compressor inlet flow path; Equipped with A centrifugal compressor wherein, with respect to an edge on an outlet side of the fluid introduction flow path at a flow path wall surface of the fluid introduction flow path, A1 is the distance between the most upstream position in the axial direction of the impeller at the edge and an axis of the compressor inlet flow path, A2 is the distance between the most downstream position in the axial direction at the edge and the axis, A3 is the distance between the most upstream position in the rotational direction of the impeller at the edge and the axis, and A4 is the distance between the most downstream position in the rotational direction at the edge and the axis.

7. The centrifugal compressor according to claim 6, wherein A1<A2 and A3<A4 are satisfied.

8. 8. The centrifugal compressor according to claim 6, wherein in a section of the compressor inlet passage including a connection portion that connects to the fluid introduction passage, a distance between a passage wall surface of the compressor inlet passage and an axis of the compressor inlet passage increases toward a downstream side in the axial direction.

9. 8. The centrifugal compressor according to claim 6, wherein in a section of the compressor inlet passage including a connection portion that connects to the fluid introduction passage, a distance between a passage wall surface of the compressor inlet passage and an axis of the compressor inlet passage decreases toward a downstream side in the axial direction.

10. 8. The centrifugal compressor according to claim 7, wherein a direction perpendicular to each of the axial direction and an axis of the fluid introduction channel is defined as a first direction, and a channel width of the fluid introduction channel in the first direction at a position of an outlet of the fluid introduction channel is defined as W, satisfying the following formula (a): Formula (a): |A3-A4|≧0.35×W

11. A direction perpendicular to each of the axial direction and the axis of the fluid introduction channel is defined as a first direction, and a channel width of the fluid introduction channel in the first direction at the position of the outlet of the fluid introduction channel is defined as W, and a size of an angular range in the circumferential direction of the impeller within which the outlet of the fluid introduction channel exists is defined as θ. The centrifugal compressor according to claim 7, which satisfies the following formula (b): Formula (b): |A3-A4|>W×tan(θ / 2)

12. The impeller and a compressor inlet flow path that guides fluid to the impeller; a fluid introduction flow path connected to the compressor inlet flow path in a direction intersecting an axis of the compressor inlet flow path and introducing a fluid into the compressor inlet flow path; Equipped with A centrifugal compressor that satisfies the following condition (A) or the following condition (B): Condition (A): In a cross section along the axial direction of the impeller, the angle formed by the flow path wall surface of the compressor inlet flow path and the flow path wall surface of the fluid introduction flow path on the upstream side of the axis of the fluid introduction flow path in the axial direction is less than 90 degrees, and in a cross section perpendicular to the axial direction of the impeller, the angle formed by the flow path wall surface of the compressor inlet flow path and the flow path wall surface of the fluid introduction flow path on the upstream side of the axis of the fluid introduction flow path in the rotation direction of the impeller is less than 90 degrees. Condition (B): In a cross section along the axial direction of the impeller, the flow path wall surface of the compressor inlet flow path includes a first convex portion at a position upstream in the axial direction of the outlet of the fluid introduction flow path, and in a cross section perpendicular to the axial direction of the impeller, the flow path wall surface of the compressor inlet flow path includes a second convex portion at a position upstream in the rotation direction of the impeller from the outlet of the fluid introduction flow path.

13. 13. The centrifugal compressor according to claim 12, wherein the condition (B) is satisfied, the first convex portion includes a convex curve in a cross section along the axial direction, and the second convex portion includes a convex curve in a cross section perpendicular to the axial direction.

14. the condition (B) is satisfied, and the distance between the first convex portion and the outlet of the fluid introduction channel is smaller than the axial flow channel width of the fluid introduction channel at the position of the outlet of the fluid introduction channel; 13. The centrifugal compressor according to claim 12, wherein a direction perpendicular to each of the axial direction and the axis of the fluid introduction channel is defined as a first direction, and a distance between the second convex portion and an outlet of the fluid introduction channel is smaller than a channel width of the fluid introduction channel in the first direction at a position of the outlet of the fluid introduction channel.

15. Further, a valve is provided in the fluid introduction channel, 2. The centrifugal compressor according to claim 1, wherein a valve seat with which the valve abuts is formed on a flow path wall surface of the fluid introduction flow path, and wherein, when a flow path area of ​​an outlet of the fluid introduction flow path is Sp and a flow path area of ​​the fluid introduction flow path at the position of the valve seat is Sq, Sp≧Sq is satisfied.

16. 2. The centrifugal compressor according to claim 1, wherein Sp<0.35×Sv is satisfied, where Sp is an area of ​​the outlet of the fluid introduction channel and Sv is a flow channel area of ​​the compressor inlet channel at the position of the outlet.

17. A turbocharger comprising the centrifugal compressor of claim 1 and a turbine coupled to the centrifugal compressor.