Centrifugal compressor impeller and centrifugal compressor

Abstract

An impeller (10) of a centrifugal compressor (4) is provided with a hub (14) and a plurality of blades (16) provided at intervals in a circumferential direction of the impeller (10) on an outer peripheral surface of the hub (14). In a meridian plane shape of the blades (16), as the coordinate axes with the origin at a tip end (30s) of a trailing edge (30) of the blades (16), an X-axis connecting the tip end (30s) and a base end (30h) of the trailing edge (30) and a Y-axis orthogonal to the X-axis are defined. When a direction from the tip end (30s) toward the base end (30h) along the X-axis is defined as a positive direction of the X-axis and a direction toward the outside in a radial direction of the impeller (10) along the Y-axis is defined as a positive direction of the Y-axis, the trailing edge (30) in the meridian plane shape of the blades (16) includes a first decrease section (30a) extending so that the Y-coordinate decreases as the X-coordinate increases, and a first increase section (30b) positioned between the first decrease section (30a) and the base end (30h) and extending so that the Y-coordinate increases as the X-coordinate increases.

Description

[Technical field]

[0001] The present disclosure relates to an impeller for a centrifugal compressor and a centrifugal compressor. [Background technology]

[0002] Patent Document 1 describes that in order to promote a high pressure ratio of the centrifugal compressor while maintaining the durability of the impeller of the centrifugal compressor, a protrusion is provided in a predetermined range of the trailing edge of the impeller blade, protruding radially outward from the maximum diameter part of the compressor disk. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-194091 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the impeller blades of a typical conventional centrifugal compressor, the trailing edge of the blade is formed parallel to the axial direction, and in this configuration, as shown in Fig. 12, a boundary layer develops downstream of the impeller near the wall surface on the shroud wall side facing the tip of the blade and near the wall surface on the hub wall side. Therefore, as shown in Fig. 13, the radial flow velocity near the wall surface on the shroud wall side and the radial flow velocity near the wall surface on the hub wall side are slower than the radial flow velocity in the mid-span region between the shroud wall and the hub wall. Therefore, there is a risk of increased loss due to flow separation and reduced operating range due to stall near the wall surface on the shroud wall side and near the wall surface on the hub wall side.

[0005] For example, when a stall occurs near the wall surface on the shroud wall side, the flow is biased toward the hub wall side, and when a stall occurs near the wall surface on the hub wall side, the flow is biased toward the shroud wall side. In either case, this leads to a decrease in performance in the diffuser and instability of the flow in the centrifugal compressor, resulting in a decrease in the efficiency of the centrifugal compressor.

[0006] Furthermore, the configuration described in Patent Document 1 can suppress an increase in centrifugal stress in the compressor disk compared to a case in which the outer diameter of the impeller is uniformly expanded from the base end to the tip end of the trailing edge of the blade. However, since it cannot suppress the bias of the flow in the blade span direction in the diffuser, there is a problem in terms of the efficiency of the centrifugal compressor.

[0007] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide an impeller for a centrifugal compressor that can realize a highly efficient centrifugal compressor, and a centrifugal compressor including the impeller. [Means for solving the problem]

[0008] In order to achieve the above object, an impeller of a centrifugal compressor according to at least one embodiment of the present disclosure includes: An impeller of a centrifugal compressor, Hub and A plurality of blades are provided on an outer peripheral surface of the hub at intervals in a circumferential direction of the impeller; Equipped with In the meridian shape of the blade, an X-axis connecting the tip and the base end of the trailing edge and a Y-axis perpendicular to the X-axis are defined as coordinate axes having an origin at the tip of the trailing edge of the blade, the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction toward the outside in the radial direction of the impeller along the Y-axis is defined as the positive direction of the Y-axis. The trailing edge of the wing in the meridian shape is a first decreasing section extending such that the Y coordinate decreases as the X coordinate increases; a first increasing section located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Includes.

[0009] In order to achieve the above object, a centrifugal compressor according to at least one embodiment of the present disclosure includes: an impeller of the centrifugal compressor; A casing that houses the impeller; Equipped with. Effect of the Invention

[0010] According to at least one embodiment of the present disclosure, there is provided an impeller for a centrifugal compressor capable of realizing a highly efficient centrifugal compressor, and a centrifugal compressor including the impeller. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a partial cross-sectional view of a turbocharger 2 according to one embodiment, showing a schematic cross section of a centrifugal compressor 4 of the turbocharger 2 along the axial direction of a rotary shaft 6. [Figure 2A] FIG. 2 is a meridian plane view showing an example of a meridian plane shape of the blade 16 for the trailing edge 30 of the impeller 10 in the turbocharger 2 shown in FIG. 1, and shows an enlarged view of the vicinity of the outlet of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2. [Figure 2B] FIG. 2B is a diagram showing X-axis and Y-axis as coordinate axes in the configuration shown in FIG. 2A. [Diagram 3] 13 is a diagram showing the distribution of radial flow velocities at the position of evaluation cross section A in the embodiment shown in FIGS. 2A and 2B, and the distribution of radial flow velocities at the position of evaluation cross section A in the comparative embodiment shown in FIG. [Figure 4A] FIG. 2 is a meridian plane view showing another example of the meridian plane shape of the blade 16 for the trailing edge 30 of the impeller 10 in the turbocharger 2 shown in FIG. 1, and shows an enlarged view of the vicinity of the outlet of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2. [Figure 4B] FIG. 4B is a diagram showing X-axis and Y-axis as coordinate axes in the configuration shown in FIG. 4A. [Diagram 5] 13 is a diagram showing the distribution of radial flow velocities at the position of evaluation cross section A in the embodiment shown in FIGS. 4A and 4B, and the distribution of radial flow velocities at the position of evaluation cross section A in the comparative embodiment shown in FIG. 12. [Figure 6] FIG. 13 is a graph showing the relationship between flow rate and pressure head for the embodiment shown in FIG. 2B, the embodiment shown in FIG. 4B, and the comparative embodiment shown in FIG. [Figure 7A]FIG. 2 is a meridian plane view showing another example of the meridian plane shape of the blade 16 for the trailing edge 30 of the impeller 10 in the turbocharger 2 shown in FIG. 1, and shows an enlarged view of the vicinity of the outlet of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2. [Figure 7B] FIG. 7B is a diagram showing X-axis and Y-axis as coordinate axes in the configuration shown in FIG. 7A. [Figure 8] 13 is a diagram showing the distribution of radial flow velocities at the position of evaluation cross section A in the embodiment shown in FIGS. 7A and 7B, and the distribution of radial flow velocities at the position of evaluation cross section A in the comparative embodiment shown in FIG. 12. FIG. [Figure 9A] FIG. 2 is a meridian plane view showing another example of the meridian plane shape of the blade 16 for the trailing edge 30 of the impeller 10 in the turbocharger 2 shown in FIG. 1, and shows an enlarged view of the vicinity of the outlet of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2. [Figure 9B] FIG. 9B is a diagram showing X-axis and Y-axis as coordinate axes in the configuration shown in FIG. 9A. [Figure 10] 1A to 1C are diagrams showing some examples of the meridian shape of the trailing edge 30 in the XY coordinate system. [Figure 11] FIG. 2 is a meridian plane view showing another example of the meridian plane shape of the blade 16 for the trailing edge 30 of the impeller 10 in the turbocharger 2 shown in FIG. 1, and shows an enlarged view of the vicinity of the outlet of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2. [Figure 12] FIG. 11 is a meridian plane view showing the vicinity of an outlet of an impeller in a centrifugal compressor according to a comparative example, illustrating the development of a boundary layer downstream of the impeller. [Figure 13] FIG. 13 is a diagram showing the distribution of radial flow velocity at the position of evaluation cross section A in the comparative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the 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 configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions excluding the presence of other elements.

[0013] FIG. 1 is a partial cross-sectional view of a turbocharger 2 according to one embodiment, and shows a schematic cross section of a centrifugal compressor 4 of the turbocharger 2 along the axial direction of a rotary shaft 6.

[0014] 1, the turbocharger 2 includes a centrifugal compressor 4 and a turbine 8 connected to the centrifugal compressor 4 via a rotating shaft 6. The centrifugal compressor 4 includes an impeller 10 and a casing 12 that houses the impeller 10.

[0015] Hereinafter, the axial direction of the impeller 10 (the axial direction of the rotating shaft 6) will be referred to simply as the "axial direction", the radial direction of the impeller 10 (the radial direction of the rotating shaft 6) will be referred to simply as the "radial direction", and the circumferential direction of the impeller 10 (the circumferential direction of the rotating shaft 6) will be referred to simply as the circumferential direction.

[0016] The impeller 10 includes a hub 14 fixed to the rotating shaft 6 and a plurality of blades 16 provided at intervals in the circumferential direction on the outer circumferential surface of the hub 14. The impeller 10 is connected to a turbine wheel 9 of the turbine 8 via the rotating shaft 6, and the impeller 10 and the turbine wheel 9 are configured to rotate integrally. The rotating shaft 6 is rotatably supported by a bearing (not shown).

[0017] The casing 12 includes a cylindrical shroud wall portion 20 that circumferentially surrounds the impeller 10 and defines an air passage 18 therein, a hub wall portion 24 that faces a part of the shroud wall portion 20 on the outer side of the impeller 10 in the radial direction and defines a diffuser passage 22 between the hub wall portion 24 and the shroud wall portion 20, and a scroll portion 28 that defines a scroll-shaped scroll passage 26 that connects to an outlet of the diffuser passage 22. The shroud wall portion 20 is configured to face a tip 16s of the blade 16 that connects a leading edge 29 of the blade 16 to a trailing edge 30 of the blade 16.

[0018] Fig. 2A is a meridian plane diagram showing a schematic example of a configuration of the outlet vicinity of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2 shown in Fig. 1, and shows a part of the meridian plane shape of the blade 16 of the impeller 10. Fig. 2B is a diagram in which coordinate axes and the like are added to the meridian plane diagram shown in Fig. 2A. The meridian plane shape of the blade 16 refers to the shape of a projection image of the blade 16 projected onto the meridian plane of the impeller 10 in the direction of rotation. The meridian plane refers to a cross section including the rotation axis C (see Fig. 1) of the impeller 10.

[0019] 2B, in this specification, in the meridian shape of the blade 16, the tip 30s of the trailing edge 30 of the blade 16 is defined as the origin of coordinate axes, an X-axis connecting the tip 30s and the base end 30h of the trailing edge 30, and a Y-axis perpendicular to the X-axis, the direction from the tip 30s to the base end 30h along the X-axis is defined as the positive direction of the X-axis, and the direction toward the outside in the radial direction along the Y-axis is defined as the positive direction of the Y-axis. Note that the tip 30s of the trailing edge 30 of the blade 16 means the end of the trailing edge 30 on the shroud wall 20 side, and the base end 30h of the trailing edge 30 of the blade 16 means the end of the trailing edge 30 on the hub 14 side.

[0020] As shown in Fig. 2B, in the meridian shape of the wing 16, the trailing edge 30 of the wing 16 includes a first decreasing section 30a that extends so that the Y coordinate decreases as the X coordinate increases, and a first increasing section 30b that is located between the first decreasing section 30a and the base end 30h and extends so that the Y coordinate increases as the X coordinate increases. The first decreasing section 30a extends so that the Y coordinate increases as the X coordinate increases. The first increasing section 30b extends so that the Y coordinate increases as the X coordinate increases.

[0021] In the example shown in FIG. 2B, the first decreasing section 30a and the first increasing section 30b are adjacent to each other, one end of the first decreasing section 30a is the tip 30s of the trailing edge 30, the other end of the first decreasing section 30a is connected to one end of the first increasing section 30b, and the other end of the first increasing section 30b is the base end 30h of the trailing edge 30. In addition, in the meridian shape of the blade 16, the trailing edge 30 of the blade 16 has a concave shape that is concave inward in the radial direction from the X axis. In the XY coordinate system shown in FIG. 2B, the trailing edge 30 of the blade 16 is formed in a curved shape that is convex downward. That is, in the XY coordinate system shown in FIG. 2B, each of the first decreasing section 30a and the first increasing section 30b is formed in a curved shape that is convex downward.

[0022] In the example shown in FIG. 2B , the minimum value Dm of the radial distance between the first decreasing section 30a and the rotation axis C (see FIG. 1 ) of the impeller 10 in the first decreasing section 30a and the first increasing section 30b (the smaller of the minimum value of the radial distance between the first decreasing section 30a and the rotation axis C and the minimum value of the radial distance between the first increasing section 30b and the rotation axis C) is smaller than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C. In the illustrated example, the minimum value Dm of the radial distance between the first decreasing section 30a and the rotation axis C corresponds to the minimum value of the radial distance between the first increasing section 30b and the rotation axis C, and corresponds to the minimum value of the radial distance between the trailing edge 30 and the rotation axis C. The distance Dh between the base end 30h and the rotation axis C corresponds to the maximum value of the outer diameter of the hub 14.

[0023] In addition, in the example shown in FIG. 2B , if the X-coordinate of the base end 30h of the trailing edge 30 is Xh, and the X-coordinate at which the distance from the rotation axis C in the first decreasing section 30a and the first increasing section 30b is the smallest (in the illustrated example, the X-coordinate of the boundary between the first decreasing section 30a and the first increasing section 30b) is Xm, then 0.2≦Xm / Xh≦0.8 is satisfied.

[0024] 2B, the minimum value Ya of the Y coordinate of the first decreasing section 30a is a negative value. The Y coordinate of the trailing edge 30 is 0 at each of the tip 30s and base end 30h of the trailing edge 30, and has a negative value in the range between the tip 30s and base end 30h.

[0025] Here, the effects achieved by the embodiment shown in FIGS. 2A and 2B will be described. Fig. 3 is a diagram showing the distribution of radial flow velocity at the position of evaluation cross section A (see Fig. 2B) in Fig. 2B and the distribution of radial flow velocity at the position of evaluation cross section A in the comparative embodiment shown in Fig. 12. In Fig. 3, the horizontal axis indicates the blade span direction position (axial position in the illustrated example) from the wall surface on the shroud wall portion 20 side to the wall surface on the hub wall portion 24 side, and the vertical axis indicates the radial flow velocity (more specifically, a value made dimensionless by dividing the radial flow velocity by the average peripheral speed of the impeller 10 at the outlet position of the impeller 10).

[0026] As shown in FIG. 3, in the above embodiment, the trailing edge 30 of the blade 16 includes the first decreasing section 30a and the first increasing section 30b. Therefore, compared to the configuration shown in FIG. 12, the relative flow velocity of the tip 30s side (shroud wall 20 side) of the trailing edge 30 to the flow velocity in the mid-span region between the shroud wall 20 and the hub 14, and the relative flow velocity of the base end 30h side (hub wall 24 side) of the trailing edge 30 to the flow velocity in the mid-span region can be increased. This makes it possible to uniformize the radial flow velocity at each position in the blade span direction and suppress the bias of the flow in the blade span direction. In addition, when considering the same flow rate, the flow velocity near the shroud wall 20 and the flow velocity near the hub wall 24 can be increased to suppress the occurrence of separation near the shroud wall 20 and separation near the hub wall 24, thereby suppressing the increase in loss due to separation and reducing the risk of a reduction in the operating range due to stall. This makes it possible to realize a centrifugal compressor 4 that is highly efficient and has a wide operating range. Also, compared to a case in which the outer diameter of the impeller 10 is uniformly enlarged from the base end 30h to the tip 30s of the trailing edge 30 of the blade 16, the weight of the impeller 10 can be reduced and an increase in centrifugal stress can be suppressed.

[0027] Furthermore, as explained using FIG. 2B, in the above embodiment, the minimum value Dm of the radial distance between the rotation axis C and the first decrease section 30a and the first increase section 30b is smaller than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C. Therefore, the weight of the impeller 10 can be reduced and the centrifugal stress generated in the impeller 10 can be reduced compared to the case where the minimum value Dm of the radial distance between the rotation axis C and the base end 30h of the trailing edge 30 and the rotation axis C in the first decrease section 30a and the first increase section 30b is larger than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C.

[0028] As described with reference to FIG. 2B, in the above embodiment, the minimum value Ya of the Y coordinate of the first decrease section 30a has a negative value, thereby enhancing the effect of uniforming the radial flow velocity at each position in the blade span direction.

[0029] As described with reference to FIG. 2B, in the above embodiment, by satisfying 0.2≦Xm / Xh≦0.8, the effect of uniforming the radial flow velocity at each position in the blade span direction can be enhanced.

[0030] Fig. 4A is a meridian plane diagram that shows a schematic example of a configuration of the outlet vicinity of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2 shown in Fig. 1, and shows a part of the meridian shape of the blades 16 of the impeller 10. Fig. 4B is a diagram in which coordinate axes and the like are added to the meridian plane diagram shown in Fig. 4A. The definitions of the X-axis and Y-axis are the same as those described above with reference to Fig. 2B.

[0031] Also in the centrifugal compressor 4 shown in FIG. 4B , in the meridian shape of the blade 16, the trailing edge 30 of the blade 16 includes a first decreasing section 30a extending such that the Y coordinate decreases as the X coordinate increases, and a first increasing section 30b located between the first decreasing section 30a and the base end 30h and extending such that the Y coordinate increases as the X coordinate increases.

[0032] In the example shown in Fig. 4B, the first decreasing section 30a and the first increasing section 30b are adjacent to each other, one end of the first decreasing section 30a is the tip 30s of the trailing edge 30, the other end of the first decreasing section 30a is connected to one end of the first increasing section 30b, and the other end of the first increasing section 30b is the base end 30h of the trailing edge 30. In addition, in the meridian shape of the blade 16, the trailing edge 30 of the blade 16 has a concave shape that is concave inward in the radial direction from the X-axis. The XY coordinate system shown in Fig. 4B system , the first decrease section 30a is formed in a curved shape including an upward convex curve 30a1 and a downward convex curve 30a2, and the first increase section 30b is formed in a curved shape including a downward convex curve 30b1 and an upward convex curve 30b2. The illustrated trailing edge 30 includes the curve 30a1, the curve 30a2, the curve 30b1, and the curve 30b2 in this order in the positive direction of the X-axis.

[0033] 4B, the minimum value Dm of the radial distance between the rotation axis C (see FIG. 1) in the first decreasing section 30a and the first increasing section 30b is smaller than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C. The minimum value Dm of the radial distance between the rotation axis C in the first decreasing section 30a and the first increasing section 30b corresponds to the minimum value of the radial distance between the first increasing section 30b and the rotation axis C, and corresponds to the minimum value of the radial distance between the trailing edge 30 and the rotation axis C. The distance Dh between the base end 30h and the rotation axis C corresponds to the maximum value of the outer diameter of the hub 14.

[0034] In addition, in the example shown in FIG. 4B , if the X-coordinate of the base end 30h of the trailing edge 30 is Xh, and the X-coordinate at which the distance from the rotation axis C in the first decreasing section 30a and the first increasing section 30b is the smallest (in the illustrated example, the X-coordinate of the boundary between the first decreasing section 30a and the first increasing section 30b) is Xm, then 0.2≦Xm / Xh≦0.8 is satisfied.

[0035] 4B, the minimum value Ya of the Y coordinate of the first decreasing section 30a is a negative value. The Y coordinate of the trailing edge 30 is 0 at each of the tip 30s and the base end 30h of the trailing edge 30, and has a negative value in the range between the tip 30s and the base end 30h.

[0036] 4B , the distance Ds between the tip 30s of the trailing edge 30 and the rotation axis C of the impeller 10 is greater than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C. In other words, the outer diameter of the impeller 10 at the position of the tip 30s of the trailing edge 30 is greater than the outer diameter of the impeller 10 at the position of the base end 30h of the trailing edge 30.

[0037] Here, the effects achieved by the configuration shown in FIGS. 4A and 4B will be described. Fig. 5 is a diagram showing the distribution of radial flow velocity at the position of evaluation cross section A (see Fig. 4B) in the embodiment shown in Fig. 4A and Fig. 4B, and the distribution of radial flow velocity at the position of evaluation cross section A in the comparative embodiment shown in Fig. 12. In Fig. 5, the horizontal axis indicates the blade span direction position from the wall surface on the shroud wall portion 20 side to the wall surface on the hub wall portion 24 side, and the vertical axis indicates the radial flow velocity (more specifically, a value made dimensionless by dividing the radial flow velocity by the average peripheral speed of the impeller 10 at the outlet position of the impeller).

[0038] As shown in Fig. 5, in the above embodiment, the trailing edge 30 of the blade 16 includes the first decreasing section 30a and the first increasing section 30b described above, so that the radial flow velocity at each position in the blade span direction can be made uniform and the flow deviation in the blade span direction can be suppressed compared to the configuration shown in Fig. 12. In addition, when considering the same flow rate, the flow velocity near the shroud wall 20 and the flow velocity near the hub wall 24 can be increased to suppress the occurrence of separation near the shroud wall 20 and separation near the hub wall 24, so that the increase in loss due to separation can be suppressed and the risk of narrowing of the operating range due to stall can be reduced. Therefore, a centrifugal compressor 4 with high efficiency and a wide operating range can be realized.

[0039] As described with reference to Fig. 4B, in the above embodiment, the distance Ds between the tip 30s of the trailing edge 30 and the rotation axis C of the impeller 10 is greater than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C. Therefore, by increasing the outer diameter of the impeller 10 at the tip 30s side (shroud wall 20 side) of the trailing edge 30 while maintaining the maximum outer diameter of the hub 14 of the impeller 10, the pressure head (pressure ratio) at the same rotation speed can be increased as shown in Fig. 6. By increasing the outer diameter of the impeller 10 on the shroud wall 20 side, the flow velocity on the shroud wall 20 side can be increased as shown in Fig. 5, so that stall on the shroud wall 20 side can be effectively suppressed.

[0040] Fig. 7A is a meridian plane diagram that shows a schematic example of a configuration of the outlet vicinity of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2 shown in Fig. 1, and shows a part of the meridian shape of the blades 16 of the impeller 10. Fig. 7B is a diagram in which coordinate axes and the like are added to the meridian plane diagram shown in Fig. 7A. The definitions of the X-axis and Y-axis are the same as those described above with reference to Fig. 2B.

[0041] In the centrifugal compressor 4 shown in FIG. 7B, in the meridian shape of the blade 16, the trailing edge 30 of the blade 16 includes a first decrease section 30a extending such that the Y coordinate decreases as the X coordinate increases, a first increase section 30b located between the first decrease section 30a and the base end 30h and extending such that the Y coordinate increases as the X coordinate increases, and a second decrease section 30c located between the first increase section 30b and the base end 30h and extending such that the Y coordinate decreases as the X coordinate increases. The first decrease section 30a extends linearly toward the negative direction of the Y axis as it moves toward the positive direction of the X axis. The first increase section 30b extends linearly toward the positive direction of the Y axis as it moves toward the positive direction of the X axis. The second decrease section 30c extends linearly toward the negative direction of the Y axis as it moves toward the positive direction of the X axis.

[0042] In the example shown in FIG. 7B, the first decreasing section 30a and the first increasing section 30b are adjacent to each other, and the first increasing section 30b and the second decreasing section 30c are adjacent to each other. One end of the first decreasing section 30a is the tip 30s of the trailing edge 30, and the other end of the first decreasing section 30a is connected to one end of the first increasing section 30b. The other end of the first increasing section 30b is connected to one end of the second decreasing section 30c, and the other end of the second decreasing section 30c is the base end 30h of the trailing edge 30. In addition, in the meridian shape of the blade 16, the trailing edge 30 of the blade 16 has a concave portion 32 that is recessed in the negative direction of the Y axis from the X axis, and a convex portion 34 that is located closer to the hub 14 than the concave portion 32 and protrudes in the positive direction of the Y axis from the X axis.

[0043] Also, in an example shown in FIG. 7B, the minimum value Dm of the radial distance from the rotation axis C (see FIG. 1) in the first decreasing section 30a and the first increasing section 30b is greater than the distance Dh between the proximal end 30h of the trailing edge 30 and the rotation axis C. Further, the minimum value Dm of the radial distance from the rotation axis C in the first decreasing section 30a and the first increasing section 30b corresponds to the minimum value of the radial distance between the first increasing section 30b and the rotation axis C. The distance Dh between the proximal end 30h and the rotation axis C corresponds to the maximum value of the outer diameter of the hub 14.

[0044] Also, in an example shown in FIG. 7B, let the X coordinate of the proximal end 30h of the trailing edge 30 be Xh, the X coordinate at which the distance from the rotation axis C is minimum in the first decreasing section 30a and the first increasing section 30b (in the illustrated example, the X coordinate of the boundary between the first decreasing section 30a and the first increasing section 30b) be Xm, and the X coordinate of the boundary between the first increasing section 30b and the second decreasing section 30c (the position where the Y coordinate of the trailing edge 30 is maximum) be Xb. Then, 0.5 < Xb / Xh < 1.0 is satisfied, 0 < Xm / Xh < 0.5, and 0.2 ≦ Xm / Xh ≦ 0.8 is satisfied.

[0045] Also, in an example shown in FIG. 7B, the minimum value Ya of the Y coordinate of the first decreasing section 30a has a negative value, and the maximum value Yb of the Y coordinate of the first increasing section 30b has a positive value.

[0046] Also, in an example shown in FIG. 7B, the distance Ds between the tip 30s of the trailing edge 30 and the rotation axis C of the impeller 10 is greater than the distance Dh between the proximal end 30h of the trailing edge 30 and the rotation axis C, and the maximum value Db of the radial distance between the first increasing section 30b and the rotation axis C is greater than the distance Dh. That is, the outer diameter of the impeller 10 at the position of the tip 30s of the trailing edge 30 is greater than the outer diameter of the impeller 10 at the position of the proximal end 30h of the trailing edge 30, and the outer diameter of the impeller 10 at the position of the boundary between the first increasing section 30b and the second decreasing section 30c is greater than the outer diameter of the impeller 10 at the position of the proximal end 30h of the trailing edge 30.

[0047] Here, the functions and effects of the configurations shown in FIGS. 7A and 7B will be described. Fig. 8 is a diagram showing the distribution of radial flow velocity at the position of evaluation cross section A (see Fig. 7B) in the embodiment shown in Fig. 7A and Fig. 7B, and the distribution of radial flow velocity at the position of evaluation cross section A in the comparative embodiment shown in Fig. 12. In Fig. 8, the horizontal axis indicates the blade span direction position from the wall surface on the shroud wall portion 20 side to the wall surface on the hub wall portion 24 side, and the vertical axis indicates the radial flow velocity (more specifically, a value made dimensionless by dividing the radial flow velocity by the average circumferential speed of the impeller 10 at the outlet position of the impeller).

[0048] As shown in Fig. 8, in the above embodiment, the trailing edge 30 of the blade 16 includes the first decreasing section 30a and the first increasing section 30b, so that the radial flow velocity at each position in the blade span direction can be made uniform and the flow deviation in the blade span direction can be suppressed compared to the configuration shown in Fig. 12. In addition, when considering the same flow rate, the flow velocity near the shroud wall 20 and the flow velocity near the hub wall 24 can be increased to suppress the occurrence of separation near the shroud wall 20 and separation near the hub wall 24, so that the increase in loss due to separation can be suppressed and the risk of the reduction in the operating range due to stall can be reduced. Therefore, a centrifugal compressor 4 with high efficiency and a wide operating range can be realized.

[0049] 7B, in the above embodiment, the distance Ds between the tip 30s of the trailing edge 30 and the rotation axis C of the impeller 10 is greater than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C, and the maximum value Db of the radial distance between the first increasing section 30b and the rotation axis C is greater than the distance Dh. Therefore, by increasing the outer diameter of the impeller 10 at the tip 30s side (shroud wall 20 side) of the trailing edge 30 and the outer diameter of the impeller at the base end 30h side (hub wall 24 side) of the trailing edge 30 while maintaining the maximum outer diameter of the hub 14 of the impeller 10, the average outer diameter of the impeller 10 can be increased to increase the pressure head (pressure ratio) at the same rotation speed. In addition, the flow velocity on the hub wall 24 side as well as the shroud wall 20 side can be increased to more effectively uniform the radial flow velocity at each position in the blade span direction.

[0050] Fig. 9A is a meridian plane view showing another example of the meridian plane shape of the blade 16 for the trailing edge 30 of the blade 16 of the impeller 10 in the turbocharger 2 shown in Fig. 1, and shows an enlarged view of the vicinity of the outlet of the impeller 10 in the centrifugal compressor 4 of the turbocharger 2. Fig. 9B is a diagram showing the X-axis and the Y-axis as coordinate axes in the configuration shown in Fig. 9A. The definitions of the X-axis and the Y-axis are the same as those described above with reference to Fig. 2B.

[0051] In the centrifugal compressor 4 shown in FIG. 9B, in the meridian shape of the blade 16, the trailing edge 30 of the blade 16 includes a first decrease section 30a extending so that the Y coordinate decreases as the X coordinate increases, a first increase section 30b located between the first decrease section 30a and the base end 30h and extending so that the Y coordinate increases as the X coordinate increases, a second decrease section 30c located between the first increase section 30b and the base end 30h and extending so that the Y coordinate decreases as the X coordinate increases, and a second increase section 30d extending so that the Y coordinate increases as the X coordinate increases. The first decrease section 30a extends in the negative direction of the Y axis as it moves in the positive direction of the X axis. The first increase section 30b extends in the positive direction of the Y axis as it moves in the positive direction of the X axis. The second decrease section 30c extends in the negative direction of the Y axis as it moves in the positive direction of the X axis. The second increasing section 30d extends in the positive direction of the X-axis and then in the positive direction of the Y-axis.

[0052] In an example shown in FIG. 9B, the second increasing section 30d and the first decreasing section 30a are adjacent to each other, the first decreasing section 30a and the first increasing section 30b are adjacent to each other, and the first increasing section 30b and the second decreasing section 30c are adjacent to each other. One end of the second increasing section 30d is the tip 30s of the trailing edge 30, and the other end of the second increasing section 30d is connected to one end of the first decreasing section 30a. The other end of the first decreasing section 30a is connected to one end of the first increasing section 30b, the other end of the first increasing section 30b is connected to one end of the second decreasing section 30c, and the other end of the second decreasing section 30c is the base end 30h of the trailing edge 30. Further, in the meridional plane shape of the blade 16, the trailing edge 30 of the blade 16 includes a concave-shaped portion 32 that is recessed in the negative direction of the Y-axis with respect to the X-axis, a convex-shaped portion 34 that is located on the base end 30h side (hub wall portion 24 side) with respect to the concave-shaped portion 32 and protrudes outward in the positive direction of the Y-axis with respect to the X-axis, and a convex-shaped portion 36 that is located on the tip 30s side (shroud wall portion 20 side) with respect to the concave-shaped portion 32 and protrudes in the positive direction of the Y-axis with respect to the X-axis. One end of the convex-shaped portion 36 is the tip 30s of the trailing edge 30, the other end of the convex-shaped portion 36 is connected to one end of the concave-shaped portion 32, the other end of the concave-shaped portion 32 is connected to one end of the convex-shaped portion 34, and the other end of the convex-shaped portion 34 is the base end 30h of the trailing edge 30. In the XY coordinate system shown in FIG. 9B, the concave-shaped portion 32 includes a curve convex downward, and each of the convex-shaped portion 34 and the convex-shaped portion 36 includes a curve convex upward.

[0053] Also, in an example shown in FIG. 9B, the minimum value Dm of the radial distance between the first decreasing section 30a and the first increasing section 30b and the rotation axis C (see FIG. 1) (the minimum value of the radial distance between the rotation axis C in the first increasing section 30b in the illustrated example) is larger than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C. Further, the distance Ds between the tip 30s of the trailing edge 30 and the rotation axis C of the impeller 10 is larger than the distance Dh between the base end 30h of the trailing edge 30 and the rotation axis C. Also, the maximum value Db of the radial distance between the first increasing section 30b and the rotation axis C is larger than the distance Dh. In the illustrated example, Dh < Dm < Db < Ds is satisfied.

[0054] In another example shown in FIG. 9B, let the X coordinate of the proximal end 30h of the trailing edge 30 be Xh, the X coordinate at which the distance from the rotation axis C is minimized in the first decreasing section 30a and the first increasing section 30b be Xm, the X coordinate of the boundary between the first increasing section 30b and the second decreasing section 30c (the position where the Y coordinate of the trailing edge 30 is maximized) be Xb, and the X coordinate of the boundary between the second increasing section 30d and the first decreasing section 30a be Xd. Then, 0.5 < Xb / Xh < 1.0 is satisfied, and 0 < Xd / Xh < 0.5 is satisfied. Also, like some examples of the meridian plane shape of the trailing edge 30 shown in FIG. 10, the trailing edge 30 may be formed so as to satisfy 0.2 ≦ Xm / Xh ≦ 0.8.

[0055] In another example shown in FIG. 9B, the minimum value Ya of the Y coordinate of the first decreasing section 30a (i.e., the minimum value of the Y coordinate of the first increasing section 30b) has a negative value, the maximum value Yb of the Y coordinate of the first increasing section 30b (i.e., the maximum value of the Y coordinate of the second decreasing section 30c) has a positive value, and the maximum value Yd of the Y coordinate of the second increasing section 30d (i.e., the maximum value of the Y coordinate of the first decreasing section 30a) has a positive value. In the illustrated example, Ya < Yd < Yb is satisfied.

[0056] According to the centrifugal compressor 4 shown in FIG. 9B, similar to the configuration shown in FIG. 7B, the radial flow velocity at each position in the blade span direction can be equalized to suppress the flow deviation in the blade span direction. Therefore, it is possible to suppress the increase in loss due to separation and reduce the risk of narrowing of the operating range due to stall, and a centrifugal compressor 4 with high efficiency and a wide operating range can be realized. Also, not only the shroud wall portion 20 side but also the hub wall portion 24 side The flow velocity can be increased to more effectively equalize the radial flow velocity at each position in the blade span direction.

[0057] FIG. 11 is a meridional plane view schematically showing an example of the configuration of the vicinity of the outlet of the impeller 10 in the centrifugal compressor 4 of the supercharger 2 shown in FIG. 1, and shows a part of the meridional plane shape of the blade 16 of the impeller 10. The definitions of the X-axis and the Y-axis in the configuration shown in FIG. 11 are the same as the above-described definitions explained with reference to FIG. 2B.

[0058] In the centrifugal compressor 4 shown in FIG. 11, in the meridian shape of the blade 16, the trailing edge 30 of the blade 16 includes a first decrease section 30a extending such that the Y coordinate decreases as the X coordinate increases, a first increase section 30b located between the first decrease section 30a and the base end 30h and extending such that the Y coordinate increases as the X coordinate increases, a second decrease section 30c located between the first increase section 30b and the base end 30h and extending such that the Y coordinate decreases as the X coordinate increases, and a second increase section 30d extending such that the Y coordinate increases as the X coordinate increases.

[0059] In the centrifugal compressor 4 shown in FIG. 11, the reference symbols common to the respective components of the centrifugal compressor 4 shown in FIG. 9A and FIG. 9B indicate the same components as those shown in FIG. 9A and FIG. 9B unless otherwise specified, and the description thereof will be omitted.

[0060] In the example shown in Fig. 11, the minimum value Ya of the Y coordinate in the first decreasing section 30a (i.e., the minimum value of the Y coordinate in the first increasing section 30b) is equal to or greater than 0, and satisfies Ya>0. That is, the trailing edge 30 is located radially outward of the X coordinate in the entire range except for the tip 30s and the base end 30h. Also, the minimum value Dm of the radial distance between the rotation axis C (see Fig. 1) in the first decreasing section 30a and the first increasing section 30b corresponds to the radial distance between the trailing edge 30 and the rotation axis C at the boundary between the first increasing section 30b and the second decreasing section 30c.

[0061] According to the configuration shown in FIG. 11, similarly to the configuration shown in FIG. 9B, the radial flow velocity at each position in the blade span direction can be uniformized to suppress the bias of the flow in the blade span direction. Therefore, it is possible to suppress the increase in loss due to separation and reduce the risk of the reduction in the operating range due to stall, and it is possible to realize a centrifugal compressor 4 with high efficiency and a wide operating range. In addition, it is possible to increase the flow velocity not only on the shroud wall 20 side but also on the hub wall 24 side, and to more effectively uniform the radial flow velocity at each position in the blade span direction. In addition, since the minimum value Ya of the Y coordinate of the first decrease section 30a is 0 or more, it is possible to increase the flow velocity and increase the pressure head compared to the case of Ya<0.

[0062] The present disclosure is not limited to the above-described embodiments, and includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0063] For example, in some of the embodiments described above, the first decreasing section 30a and the first increasing section 30b are adjacent to each other, but the first decreasing section 30a and the first increasing section 30b do not have to be adjacent to each other. For example, there may be a section with a constant Y coordinate between the first decreasing section 30a and the first increasing section 30b.

[0064] The contents described in each of the above embodiments can be understood, for example, as follows.

[0065] (1) The impeller (e.g., the impeller 10 described above) of a centrifugal compressor (e.g., the centrifugal compressor 4 described above) according to at least one embodiment of the present disclosure has a hub (such as hub 14 described above); A plurality of blades (e.g., the above-mentioned blade 16) provided at intervals in the circumferential direction of the impeller on the outer peripheral surface of the hub; Equipped with In the meridian shape of the blade, if coordinate axes having an origin at the tip (e.g., the above-mentioned tip 30s) of the trailing edge (e.g., the above-mentioned trailing edge 30) of the blade are defined as an X-axis connecting the tip and the base end of the trailing edge (e.g., the above-mentioned base end 30h) and a Y-axis perpendicular to the X-axis, and the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction along the Y-axis toward the outside in the radial direction of the impeller is defined as the positive direction of the Y-axis, then: The trailing edge of the wing in the meridian shape is a first decreasing section (for example, the first decreasing section 30a described above) that extends such that the Y coordinate decreases as the X coordinate increases; a first increasing section (for example, the first increasing section 30b described above) located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Includes.

[0066] According to the impeller of the centrifugal compressor described in (1) above, since the trailing edge of the blade includes the first decreasing section and the first increasing section, the relative flow velocity of the tip side (shroud wall side) of the trailing edge to the flow velocity of the mid-span region between the shroud wall and the hub facing the tip of the blade, and the relative flow velocity of the base end side (hub wall side) of the trailing edge to the flow velocity of the mid-span region can be increased. This makes it possible to uniformize the radial flow velocity at each position in the blade span direction and suppress the bias of the flow in the blade span direction. In addition, when considering the same flow rate, the flow velocity near the shroud wall and the flow velocity near the hub wall can be increased to suppress the occurrence of separation near the shroud wall and separation near the hub wall, thereby suppressing the increase in loss due to separation and reducing the risk of a narrowing of the operating range due to stall. This makes it possible to realize a centrifugal compressor that is highly efficient and has a wide operating range. Furthermore, compared to a case in which the outer diameter of the impeller is uniformly enlarged from the base end to the tip end of the trailing edge of the blade, the weight of the impeller can be reduced and an increase in centrifugal stress can be suppressed.

[0067] (2) In some embodiments, in the impeller of the centrifugal compressor described in (1) above, The first decreasing section and the first increasing section are adjacent to each other.

[0068] According to the impeller of the centrifugal compressor described in (2) above, a highly efficient centrifugal compressor can be realized.

[0069] (3) In some embodiments, in the impeller of the centrifugal compressor described in (1) or (2), The distance between the tip of the trailing edge and the rotation axis of the impeller is greater than the distance between the base end of the trailing edge and the rotation axis.

[0070] According to the centrifugal compressor impeller described in (3) above, by increasing the outer diameter of the impeller at the tip side (shroud wall side) of the trailing edge while maintaining the maximum outer diameter of the impeller hub, it is possible to increase the pressure head (pressure ratio) at the same rotation speed. In addition, by increasing the outer diameter of the impeller on the shroud wall side, it is possible to increase the flow velocity on the shroud wall side, thereby effectively suppressing stall on the shroud wall side.

[0071] (4) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (3) above, The trailing edge includes a second decreasing section (eg, second decreasing section 30c described above) between the first increasing section and the base end that extends such that the Y coordinate decreases as the X coordinate increases.

[0072] According to the impeller of the centrifugal compressor described in (4) above, a convex portion (e.g., the above-mentioned convex portion 34) that protrudes in the positive direction of the Y axis beyond the X axis can be formed on the hub side of the trailing edge. This increases the flow velocity near the hub wall, making it possible to more effectively uniform the radial flow velocity at each position in the blade span direction.

[0073] (5) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (4) above, The trailing edge includes a convex portion on the hub side that protrudes further in the positive direction of the Y axis than the X axis.

[0074] According to the impeller of the centrifugal compressor described above in (5), the flow velocity in the vicinity of the hub wall portion can be increased, and the radial flow velocity at each position in the blade span direction can be more effectively uniformed.

[0075] (6) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (5) above, The minimum value of the radial distance between the rotation axis in the first decreasing section and the first increasing section is greater than the distance between the base end and the rotation axis.

[0076] According to the centrifugal compressor impeller described in (6) above, the average flow velocity at the outlet of the impeller can be increased compared to a case in which the minimum value of the radial distance between the rotation axis in the first decrease section and the first increase section is smaller than the distance between the base end of the trailing edge and the rotation axis.

[0077] (7) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (5) above, The minimum value of the radial distance between the rotation axis in the first decreasing section and the first increasing section is smaller than the distance between the base end and the rotation axis.

[0078] According to the impeller of the centrifugal compressor described in (7) above, the weight of the impeller 10 can be reduced, and the centrifugal stress generated in the impeller can be reduced, compared to the case where the minimum value of the radial distance between the rotation axis in the first decrease section and the first increase section is larger than the distance between the base end of the trailing edge and the rotation axis.

[0079] (8) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (7), The minimum value of the Y coordinate in the first decreasing section has a negative value.

[0080] According to the impeller of the centrifugal compressor described above in (8), the effect of uniforming the radial flow velocity at each position in the blade span direction can be enhanced.

[0081] (9) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (6) above, The minimum value of the Y coordinate in the first decreasing section is equal to or greater than 0.

[0082] According to the impeller of the centrifugal compressor described above in (9), the flow velocity can be increased and the pressure head can be increased, compared to when the minimum value of the Y coordinate in the first decrease section is smaller than 0.

[0083] (10) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (9), Each of the first decreasing section and the first increasing section is formed in a straight line.

[0084] According to the impeller for a centrifugal compressor described above in (10), the manufacture of the impeller can be simplified.

[0085] (11) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (9), Each of the first decreasing section and the first increasing section is formed in a curved shape.

[0086] According to the impeller of the centrifugal compressor described above in (11), the concentration of centrifugal stress in the impeller can be suppressed.

[0087] (12) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (11), The trailing edge includes a second increasing section between the leading edge and the first decreasing section that extends such that the Y coordinate increases as the X coordinate increases.

[0088] According to the impeller of the centrifugal compressor described in (12) above, a convex portion (e.g., the above-mentioned convex portion 36) that protrudes in the positive direction of the Y axis beyond the X axis can be formed on the shroud wall at the trailing edge. This increases the flow velocity near the shroud wall, making it possible to more effectively uniform the radial flow velocity at each position in the blade span direction.

[0089] (13) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (12), The trailing edge includes a convex portion on a tip side of the trailing edge that protrudes in the positive direction of the Y axis beyond the X axis.

[0090] According to the impeller of the centrifugal compressor described above in (13), the flow velocity in the vicinity of the shroud wall can be increased, and the radial flow velocity at each position in the blade span direction can be more effectively uniformed.

[0091] (14) In some embodiments, in the impeller of the centrifugal compressor according to any one of (1) to (13), The first decrease section and the first increase section are adjacent to each other, If the X coordinate of the base end of the trailing edge is Xh, and the X coordinate at which the distance from the rotation axis in the first decreasing section and the first increasing section is the smallest is Xm, then 0.2≦Xm / Xh≦0.8 is satisfied.

[0092] According to the impeller of the centrifugal compressor described above in (14), the effect of uniforming the radial flow velocity at each position in the blade span direction can be enhanced.

[0093] (15) At least one embodiment of the centrifugal compressor according to the present disclosure comprises: An impeller of a centrifugal compressor according to any one of (1) to (14) above; A casing that houses the impeller; Equipped with.

[0094] According to the centrifugal compressor described in (15) above, since it is equipped with the impeller described in any one of (1) to (14) above, it is possible to realize a highly efficient centrifugal compressor having a wide operating range. [Explanation of symbols]

[0095] 2. Turbocharger 4. Centrifugal Compressor 6 Rotation Axis 8. Turbine 9. Turbine Wheel 10 Impeller 12 Casing 14. Hub 16 wings 16s tip 18 Air Flow Path 20 Shroud wall 22 Diffuser passage 24 Hub wall 26 Scroll passage 28 Scroll section 29 Leading Edge 30 Trailing edge 30a First Decline Section 30b First increasing section 30c 2nd Decline 30d Second increasing section 30a1,30a2,30b1,30b2 curve 30h proximal end 30s tip 32 Concave portion 34,36 Convex shape part

Claims

1. An impeller circumferentially surrounded by a shroud wall of a casing of a centrifugal compressor, Hub and A plurality of blades are provided on an outer peripheral surface of the hub at intervals in the circumferential direction of the impeller; Equipped with the blade has a tip that connects a leading edge of the blade with a trailing edge of the blade and faces the shroud wall of the casing; In the meridian shape of the blade, an X-axis connecting the tip and the base end of the trailing edge and a Y-axis perpendicular to the X-axis are defined as coordinate axes having an origin at the tip of the trailing edge of the blade, the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction toward the radial outside of the impeller along the Y-axis is defined as the positive direction of the Y-axis. The trailing edge of the wing in the meridian shape is a first decreasing section extending such that the Y coordinate decreases as the X coordinate increases; a first increasing section located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Including, one end of the first reduced section on the shroud wall side is the tip of the trailing edge, The one end of the first increasing section on the hub side is the base end of the trailing edge. Centrifugal compressor impeller.

2. 2. The impeller of a centrifugal compressor according to claim 1, wherein the first decreasing section and the first increasing section are adjacent to each other.

3. An impeller circumferentially surrounded by a shroud wall portion of a casing of a centrifugal compressor, Hub and A plurality of blades are provided on an outer peripheral surface of the hub at intervals in the circumferential direction of the impeller; Equipped with the blade has a tip that connects a leading edge of the blade with a trailing edge of the blade and faces the shroud wall of the casing; In the meridian shape of the blade, an X-axis connecting the tip and the base end of the trailing edge and a Y-axis perpendicular to the X-axis are defined as coordinate axes having an origin at the tip of the trailing edge of the blade, the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction toward the radial outside of the impeller along the Y-axis is defined as the positive direction of the Y-axis. The trailing edge of the wing in the meridian shape is a first decreasing section extending such that the Y coordinate decreases as the X coordinate increases; a first increasing section located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Including, An impeller for a centrifugal compressor, wherein a distance between the tip of the trailing edge and a rotation axis of the impeller is greater than a distance between the base end of the trailing edge and the rotation axis.

4. 4. The impeller of claim 3, wherein the trailing edge includes a second decreasing section between the first increasing section and the base end, the second decreasing section extending such that the Y coordinate decreases as the X coordinate increases.

5. The impeller of a centrifugal compressor according to claim 1 , wherein the trailing edge includes a convex portion on a hub side thereof that protrudes in a positive direction of the Y-axis beyond the X-axis.

6. An impeller circumferentially surrounded by a shroud wall portion of a casing of a centrifugal compressor, Hub and A plurality of blades are provided on an outer peripheral surface of the hub at intervals in the circumferential direction of the impeller; Equipped with the blade has a tip that connects a leading edge of the blade with a trailing edge of the blade and faces the shroud wall of the casing; In the meridian shape of the blade, an X-axis connecting the tip and the base end of the trailing edge and a Y-axis perpendicular to the X-axis are defined as coordinate axes having an origin at the tip of the trailing edge of the blade, the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction toward the radial outside of the impeller along the Y-axis is defined as the positive direction of the Y-axis. The trailing edge of the wing in the meridian shape is a first decreasing section extending such that the Y coordinate decreases as the X coordinate increases; a first increasing section located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Including, an impeller for a centrifugal compressor, wherein a minimum value of the radial distance between the rotation axis of the impeller in the first decrease section and the first increase section is greater than a distance between the base end and the rotation axis.

7. 6. The impeller of a centrifugal compressor according to claim 1, wherein a minimum value of the radial distance between the rotation axis of the impeller in the first decrease section and the first increase section is smaller than a distance between the base end and the rotation axis.

8. The impeller of a centrifugal compressor according to claim 1 , wherein a minimum value of the Y coordinate in the first decreasing section has a negative value.

9. An impeller circumferentially surrounded by a shroud wall portion of a casing of a centrifugal compressor, Hub and A plurality of blades are provided on an outer peripheral surface of the hub at intervals in the circumferential direction of the impeller; Equipped with the blade has a tip that connects a leading edge of the blade with a trailing edge of the blade and faces the shroud wall of the casing; In the meridian shape of the blade, an X-axis connecting the tip and the base end of the trailing edge and a Y-axis perpendicular to the X-axis are defined as coordinate axes having an origin at the tip of the trailing edge of the blade, the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction toward the radial outside of the impeller along the Y-axis is defined as the positive direction of the Y-axis. The trailing edge of the wing in the meridian shape is a first decreasing section extending such that the Y coordinate decreases as the X coordinate increases; a first increasing section located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Including, The minimum value of the Y coordinate in the first decreasing section is equal to or greater than 0.

10. The impeller of a centrifugal compressor according to claim 1 , wherein each of the first decrease section and the first increase section is formed in a straight line.

11. The impeller of a centrifugal compressor according to claim 1 , wherein each of the first decreasing section and the first increasing section is formed in a curved shape.

12. An impeller circumferentially surrounded by a shroud wall portion of a casing of a centrifugal compressor, Hub and A plurality of blades are provided on an outer peripheral surface of the hub at intervals in the circumferential direction of the impeller; Equipped with the blade has a tip that connects a leading edge of the blade with a trailing edge of the blade and faces the shroud wall of the casing; In the meridian shape of the blade, an X-axis connecting the tip and the base end of the trailing edge and a Y-axis perpendicular to the X-axis are defined as coordinate axes having an origin at the tip of the trailing edge of the blade, the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction toward the radial outside of the impeller along the Y-axis is defined as the positive direction of the Y-axis. The trailing edge of the wing in the meridian shape is a first decreasing section extending such that the Y coordinate decreases as the X coordinate increases; a first increasing section located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Including, the trailing edge including a second increasing section between the tip and the first decreasing section, the second increasing section extending such that a Y coordinate increases as an X coordinate increases.

13. An impeller circumferentially surrounded by a shroud wall portion of a casing of a centrifugal compressor, Hub and A plurality of blades are provided on an outer peripheral surface of the hub at intervals in the circumferential direction of the impeller; Equipped with the blade has a tip that connects a leading edge of the blade with a trailing edge of the blade and faces the shroud wall of the casing; In the meridian shape of the blade, an X-axis connecting the tip and the base end of the trailing edge and a Y-axis perpendicular to the X-axis are defined as coordinate axes having an origin at the tip of the trailing edge of the blade, the direction from the tip to the base end along the X-axis is defined as the positive direction of the X-axis, and the direction toward the radial outside of the impeller along the Y-axis is defined as the positive direction of the Y-axis. The trailing edge of the wing in the meridian shape is a first decreasing section extending such that the Y coordinate decreases as the X coordinate increases; a first increasing section located between the first decreasing section and the base end and extending such that the Y coordinate increases as the X coordinate increases; Including, the trailing edge includes a convex portion protruding in a positive direction of the Y-axis beyond the X-axis on a tip side of the trailing edge.

14. The first decrease section and the first increase section are adjacent to each other, 14. The impeller of a centrifugal compressor according to claim 1, wherein, when an X-coordinate of the base end of the trailing edge is Xh, and an X-coordinate at which a distance from a rotation axis of the impeller in the first decrease section and the first increase section is a minimum is Xm, a relationship of 0.2≦Xm / Xh≦0.8 is satisfied.

15. An impeller for a centrifugal compressor according to any one of claims 1 to 14; A casing that houses the impeller; A centrifugal compressor comprising:

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