Impeller and centrifugal compressor

Abstract

To achieve both strength and aerodynamic performance of a blade.SOLUTION: A compressor impeller includes a hub which is provided on a shaft, and a blade 17 which is provided on an outer peripheral surface of the hub in such a manner that a blade thickness reduction ratio is the maximum value in a range of less than 40% in a length in the span direction from a root 20 to a distal end 21.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a compressor impeller having a hub and a plurality of blades provided on the outer peripheral surface of the hub. The blades of the compressor impeller described in Patent Document 1 have a blade thickness reduction rate that changes from the root portion where the blade is connected to the hub to the tip portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6372207 Summary of the Invention [Problem to be solved by the invention]

[0004] The thinner the blade thickness, the smaller the air resistance, resulting in improved aerodynamic performance. However, the thinner the blade thickness, the lower the natural frequency of the blade and the higher the stress applied to the blade, resulting in a decrease in the strength of the blade. The compressor impeller blades described in Patent Document 1 vary their thickness reduction rate from the root to the tip, but considering the balance between blade strength and aerodynamic performance, there is room for improvement in the design of the blade thickness.

[0005] An object of the present disclosure is to provide an impeller and a centrifugal compressor that can achieve both blade strength and aerodynamic performance. [Means for solving the problem]

[0006] In order to solve the above problems, the impeller of the present disclosure includes a hub provided on a shaft, and blades provided on the outer peripheral surface of the hub, the blade thickness reduction rate of which is maximum within a range of less than 40% in the span direction length from the root portion to the tip portion.、 The thickness reduction rate gradually increases over a spanwise length of less than 40% from the root to the tip, reaches a maximum value, and then gradually decreases from the spanwise length where the thickness reduction rate reaches its maximum value to the tip. . the blade's trailing edge root thickness is greater than its leading edge root thickness and less than its intermediate root thickness between the leading and trailing edges; The root thickness at the midsection of the blade may be greater than the root thickness at the leading edge.

[0007] The blade thickness at 80% of the length in the span direction from the root to the tip may be 1.2 times or more the thickness of the blade at the tip.

[0008] The blade thickness reduction rate does not have to include a minimum value in the span direction.

[0009] The blade thickness reduction rate may have continuity in the span direction.

[0010] In order to solve the above problem, a centrifugal compressor of the present disclosure includes the above impeller. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to achieve both blade strength and aerodynamic performance. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of a turbocharger. [Figure 2] FIG. 2 is a perspective view of a compressor impeller. [Figure 3] FIG. 3 is an explanatory diagram for explaining the shape of the blade. [Figure 4] FIG. 4 is a graph showing the blade thickness at the leading edge of the blade. [Figure 5] FIG. 5 is a graph showing the blade thickness near the tip of the leading edge of the blade. [Figure 6] FIG. 6 is a graph showing the blade thickness at the meridional cross section at the position of m1 / m2 (m3 / m4)=0.35 of the blade. [Figure 7] FIG. 7 is a graph showing the blade thickness near the tip at the position where m1 / m2 (m3 / m4) = 0.35 of the blade. [Figure 8]FIG. 8 is a graph showing the blade thickness at the trailing edge of a blade. [Figure 9] FIG. 9 is a graph showing the blade thickness near the tip at the trailing edge of the blade. [Figure 10] FIG. 10 is a graph showing the relationship between the spanwise length of all blades and the blade thickness reduction rate. [Figure 11] FIG. 11 is a graph showing the relationship between the length of the short blade in the span direction and the blade thickness reduction rate. [Figure 12] FIG. 12 is a graph for explaining the relationship between the blade thickness reduction rate of the blade and the aerodynamic performance. [Figure 13] FIG. 13 is a graph for explaining the relationship between the blade thickness near the tip of the blade and the aerodynamic performance. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present disclosure will be described below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiment are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0014] FIG. 1 is a schematic cross-sectional view of a turbocharger TC. In the following description, the direction of arrow L shown in FIG. 1 will be referred to as the left side of the turbocharger TC. The direction of arrow R shown in FIG. 1 will be referred to as the right side of the turbocharger TC. As shown in FIG. 1, the turbocharger TC includes a turbocharger main body 1. The turbocharger main body 1 includes a bearing housing 2, a turbine housing 4, and a compressor housing 6. The turbine housing 4 is connected to the left side of the bearing housing 2 by a fastening bolt 3. The compressor housing 6 is connected to the right side of the bearing housing 2 by a fastening bolt 5.

[0015] A bearing hole 2a is formed in the bearing housing 2. The bearing hole 2a penetrates the turbocharger TC in the left-right direction. A bearing is disposed in the bearing hole 2a. In this embodiment, the bearing is a full-floating bearing. However, the bearing may be other bearings such as a semi-floating bearing or a rolling bearing. The shaft 7 is rotatably supported by the bearing. A compressor impeller (impeller) 8 is provided at the right end of the shaft 7. The compressor impeller 8 is rotatably housed in the compressor housing 6. A turbine impeller 9 is provided at the left end of the shaft 7. The turbine impeller 9 is rotatably housed in the turbine housing 4.

[0016] An intake port 10 is formed in the compressor housing 6. The intake port 10 opens to the right side of the turbocharger TC. The intake port 10 is connected to an air cleaner (not shown). A diffuser passage 11 is formed by the opposing surfaces of the bearing housing 2 and the compressor housing 6. The diffuser passage 11 pressurizes the air. The diffuser passage 11 is formed in an annular shape. The diffuser passage 11 communicates with the intake port 10 at its radially inner side via the compressor impeller 8. Of the inner surface of the compressor housing 6, the surface that faces the compressor impeller 8 in the radial direction is formed as a shroud surface 6a.

[0017] A compressor scroll passage 12 is provided in the compressor housing 6. The compressor scroll passage 12 is formed in an annular shape. The compressor scroll passage 12 is located, for example, radially outward of the shaft 7 relative to the diffuser passage 11. The compressor scroll passage 12 is connected to an intake port of the engine (not shown) and the diffuser passage 11. When the compressor impeller 8 rotates, air is drawn into the compressor housing 6 through the intake port 10. The drawn air is pressurized and accelerated as it flows between the blades of the compressor impeller 8. The pressurized and accelerated air is pressurized in the diffuser passage 11 and the compressor scroll passage 12. The pressurized air is led to the intake port of the engine.

[0018] The centrifugal compressor CC is configured by the compressor housing 6 and the bearing housing 2. In this embodiment, an example in which the centrifugal compressor CC is mounted on a turbocharger TC will be described. However, the present invention is not limited to this, and the centrifugal compressor CC may be incorporated into a device other than the turbocharger TC, or may be a standalone unit.

[0019] A discharge port 13 is formed in the turbine housing 4. The discharge port 13 opens to the left side of the turbocharger TC. The discharge port 13 is connected to an exhaust gas purification device (not shown). A turbine scroll passage 14 and a communication passage 15 are formed in the turbine housing 4. The turbine scroll passage 14 is formed in an annular shape. The turbine scroll passage 14 is, for example, located radially outward of the turbine impeller 9 relative to the communication passage 15. The turbine scroll passage 14 communicates with a gas inlet (not shown). Exhaust gas discharged from an exhaust manifold of the engine (not shown) is introduced into the gas inlet. The communication passage 15 connects the turbine scroll passage 14 with the discharge port 13 via the turbine impeller 9. The exhaust gas introduced from the gas inlet to the turbine scroll passage 14 is introduced to the discharge port 13 via the communication passage 15 and the turbine impeller 9. The exhaust gas introduced to the discharge port 13 rotates the turbine impeller 9 during its flow.

[0020] The rotational force of the turbine impeller 9 is transmitted to the compressor impeller 8 via the shaft 7. When the compressor impeller 8 rotates, the air is pressurized as described above, and the air is then guided to the intake port of the engine.

[0021] Fig. 2 is a perspective view of the compressor impeller 8. As shown in Fig. 2, the compressor impeller 8 has a hub 16 (wheel) and a plurality of vanes 17 (blades).

[0022] The hub 16 has a top surface 16a, a bottom surface 16b, an outer circumferential surface 16c, and a through hole 16d. The area of ​​the top surface 16a is smaller than the area of ​​the bottom surface 16b. The outer circumferential surface 16c is connected to the top surface 16a and the bottom surface 16b and extends radially outward from the top surface 16a toward the bottom surface 16b.

[0023] The through hole 16d penetrates from the top surface 16a to the bottom surface 16b. The shaft 7 is inserted into the through hole 16d. The end of the shaft 7 protrudes from the top surface 16a. A thread groove is formed on the end of the shaft 7 protruding from the top surface 16a. A hub 16 is provided on one end of the shaft 7 by fastening a nut to this thread groove. The hub 16 is a rotating body that rotates around the center of the through hole 16d as its axis of rotation.

[0024] The blades 17 are thin plate-shaped members molded integrally with the hub 16. A plurality of blades 17 are arranged on the outer peripheral surface 16c of the hub 16, spaced apart from one another in the circumferential direction. The circumferential gaps (inter-blade 17a) between adjacent blades 17 form flow paths for air (fluid). The blades 17 extend radially outward from the outer peripheral surface 16c of the hub 16 toward the shroud surface 6a (see FIG. 1) and are curved so as to be inclined in the circumferential direction of the hub 16.

[0025] The blades 17 include full blades 18 (long blades, full blades) and short blades 19 (half blades, half blades) that are shorter in the axial direction than the full blades 18. The full blades 18 and the short blades 19 are arranged alternately in the circumferential direction. By arranging the short blades 19 between the full blades 18 in this manner, the turbocharger TC has improved air suction efficiency compared to a case where the same number of blades 17 are all full blades 18. Hereinafter, when simply referring to blades 17, this refers to both the full blades 18 and the short blades 19.

[0026] FIG. 3 is an explanatory diagram for explaining the shape of the blade 17. In FIG. 3, the meridian shape of the blade 17 of this embodiment is shown by a dashed dotted line. The meridian shape is a shape obtained by rotating the outline of one blade 17 around the rotation axis of the hub 16 without changing the radial position of the hub 16 and projecting it onto a plane parallel to the rotation axis of the hub 16. In FIG. 3, the left-right direction is the axial direction of the shaft 7, the right side is the bottom surface 16b side of the hub 16, and the left side is the top surface 16a side of the hub 16. In FIG. 3, the up-down direction is the span direction (blade length direction) of the blade 17, the upper side is the shroud surface 6a side (hereinafter simply referred to as the tip side), and the lower side is the outer peripheral surface 16c side of the hub 16 (hereinafter simply referred to as the root side).

[0027] 3, the blade 17 has a leading edge 17b which is the upstream end in the flow direction of air passing through the compressor impeller 8 (hereinafter simply referred to as the flow direction). The leading edge 17b which is one axial end of the short blade 19 is located downstream in the flow direction of the leading edge 17b which is one axial end of the full blade 18.

[0028] The blade 17 has a trailing edge 17c, which is the end on the downstream side in the flow direction. The blade surface 17d is a curved surface formed between the leading edge 17b and the trailing edge 17c of the blade 17, facing the flow passage formed between the blades 17a.

[0029] 3, in the meridian shape, the leading edge 17b is approximately parallel to the radial direction of the shaft 7. The trailing edge 17c is approximately parallel to the axial direction of the shaft 7.

[0030] The blade surface 17d has a curved shape with leading edge 17b and trailing edge 17c as its end portions, and is traced by a locus obtained by continuously moving a generatrix 17e (shown by a broken line in FIG. 3) of the blade 17.

[0031] The blade 17 includes an outer edge 17f on the tip side between the leading edge 17b and the trailing edge 17c, and an inner edge 17g on the root side. Here, the length from the leading edge 17b to an arbitrary point on the outer edge 17f is defined as m1, and the length from the leading edge 17b to the trailing edge 17c on the outer edge 17f is defined as m2. Furthermore, the length from the leading edge 17b to an arbitrary point on the inner edge 17g is defined as m3, and the length from the leading edge 17b to the trailing edge 17c on the inner edge 17g is defined as m4.

[0032] The generating line 17e is a line connecting any point on the outer edge 17f and a corresponding point on the inner edge 17g. Specifically, the generating line 17e is a line connecting two points where m1 / m2 and m3 / m4 are equal. The blade surface 17d is a curved surface described by the movement locus of this generating line 17e.

[0033] Fig. 4 is a graph showing the blade thickness of the leading edge 17b of the blade 17. As shown in Fig. 4, the blade 17 has a root portion 20 connected to the hub 16 (see Fig. 2), and a tip portion 21 spaced apart from the hub 16 in the span direction. In Fig. 3, the vertical axis represents the distance from the root portion 20 to each portion (hereinafter referred to as the span direction distance) when the distance from the root portion 20 to the tip portion 21 is set to 1. The horizontal axis represents the blade thickness of the blade 17. In Figs. 4 to 9, the solid line represents the blade shape of the blade 17, and the dashed line represents an imaginary line connecting the root portion 20 and the tip portion 21 of the blade 17.

[0034] The thickness of the root portion 20 of the blade 17 is greater than the thickness of the tip portion 21. The thickness of the tip portion 21 of the blade 17 is less than the thickness of the root portion 20. The thickness of the blade 17 decreases from the root portion 20 to the tip portion 21. The thickness of the blade 17 is thickest at the root portion 20 and thinnest at the tip portion 21. The rate of decrease in thickness from the root portion 20 to the tip portion 21 of the blade 17 is not constant but varies.

[0035] Specifically, the blade thickness reduction rate of the blade 17 gradually increases from the root 20 toward the tip 21, reaches a maximum value (0.37) in the spanwise distance range of 0 to less than 0.4, and gradually decreases from the spanwise distance P at which it reaches its maximum value to a spanwise distance of 1.0.

[0036] Fig. 5 is a graph showing the blade thickness near the tip 21 of the leading edge 17b of the blade 17. In Fig. 5, the vertical axis represents the spanwise distance, and the horizontal axis represents the blade thickness at each location, where the blade thickness at the tip 21 is set to 1.

[0037] As shown in Figure 5, the blade thickness of the blade 17 gradually increases from the tip 21 toward the root 20. The blade thickness at a spanwise distance of 0.85 is 1.1 times or more the thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.8 is 1.2 times or more the thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.7 is 1.3 times or more the thickness at a spanwise distance of 1.0.

[0038] 6 is a graph showing the blade thickness of the cross section taken along the generatrix 17e at the position where m1 / m2 (m3 / m4)=0.35 of the blade 17. In FIG. 6, the vertical axis represents the spanwise distance, and the horizontal axis represents the blade thickness of the blade 17.

[0039] As shown in Figure 6, the blade thickness at root portion 20 of blade 17 is greater than the blade thickness at tip portion 21. The blade thickness at tip portion 21 of blade 17 is smaller than the blade thickness at root portion 20. The blade thickness of blade 17 decreases from root portion 20 to tip portion 21. The blade thickness of blade 17 is thickest at root portion 20 and thinnest at tip portion 21.

[0040] The blade thickness of the root portion 20 of the blade 17 at the position where m1 / m2 (m3 / m4) = 0.35 is greater than the blade thickness of the root portion 20 at the leading edge 17b (see FIG. 4). The blade thickness of the tip portion 21 of the blade 17 at the position where m1 / m2 (m3 / m4) = 0.35 is equal to the blade thickness of the tip portion 21 at the leading edge 17b (see FIG. 4). Here, "equal" means both a case where they are completely equal and a case where they deviate from being completely equal within the range of allowable error (such as processing accuracy or assembly error).

[0041] The blade thickness reduction rate from the root portion 20 to the tip portion 21 of the blade 17 is not constant but varies. Specifically, the blade thickness reduction rate of the blade 17 gradually increases from the root portion 20 toward the tip portion 21, reaches a maximum value (0.38) in the spanwise distance range of 0 to less than 0.4, and gradually decreases from the spanwise distance P at which it reaches the maximum value to a spanwise distance of 1.0.

[0042] 7 is a graph showing the blade thickness near the tip 21 of the blade 17 at the position where m1 / m2 (m3 / m4) = 0.35. In Fig. 7, the vertical axis represents the spanwise distance, and the horizontal axis represents the blade thickness at each location when the blade thickness at the tip 21 is set to 1.

[0043] As shown in Fig. 7, the thickness of blade 17 increases gradually from tip 21 toward root 20. The rate of increase in thickness near tip 21 at the position of blade 17 where m1 / m2 (m3 / m4) = 0.35 is greater than the rate of increase in thickness near tip 21 at leading edge 17b (see Fig. 5).

[0044] The blade thickness at a spanwise distance of 0.85 at the position where m1 / m2 (m3 / m4) = 0.35 of blade 17 is 1.5 times or more thicker than the blade thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.8 is 1.8 times or more thicker than the blade thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.7 is 2.0 times or more thicker than the blade thickness at a spanwise distance of 1.0.

[0045] 8 is a graph showing the blade thickness of the trailing edge 17c of the blade 17. In FIG. 8, the vertical axis represents the distance in the span direction, and the horizontal axis represents the blade thickness of the blade 17.

[0046] As shown in Figure 8, the blade thickness at root portion 20 of blade 17 is greater than the blade thickness at tip portion 21. The blade thickness at tip portion 21 of blade 17 is smaller than the blade thickness at root portion 20. The blade thickness of blade 17 decreases from root portion 20 to tip portion 21. The blade thickness of blade 17 is thickest at root portion 20 and thinnest at tip portion 21.

[0047] The thickness of the root portion 20 at the trailing edge 17c of the blade 17 is slightly larger than the thickness of the root portion 20 at the leading edge 17b (see FIG. 4). The thickness of the root portion 20 at the trailing edge 17c of the blade 17 is smaller than the thickness of the root portion 20 at the position of m1 / m2 (m3 / m4) = 0.35 of the blade 17 (see FIG. 6). The thickness of the tip portion 21 at the trailing edge 17c of the blade 17 is equal to the thickness of the tip portion 21 at the trailing edge 17c and at the position of m1 / m2 (m3 / m4) = 0.35.

[0048] The blade thickness reduction rate from the root portion 20 to the tip portion 21 of the blade 17 is not constant but varies. Specifically, the blade thickness reduction rate of the blade 17 gradually increases from the root portion 20 toward the tip portion 21, reaches a maximum value (0.37) in the spanwise distance range of 0 to less than 0.4, and gradually decreases from the spanwise distance P at which it reaches the maximum value to a spanwise distance of 1.0.

[0049] Fig. 9 is a graph showing the blade thickness near the tip 21 of the trailing edge 17c of the blade 17. In Fig. 9, the vertical axis represents the spanwise distance, and the horizontal axis represents the blade thickness at each location, where the blade thickness at the tip 21 is set to 1.

[0050] As shown in Fig. 9, the thickness of the blade 17 increases gradually from the tip portion 21 toward the root portion 20. The rate of increase in thickness near the tip portion 21 at the trailing edge 17c of the blade 17 is slightly larger than the rate of increase in thickness near the tip portion 21 at the leading edge 17b (see Fig. 5). The rate of increase in thickness near the tip portion 21 at the trailing edge 17c of the blade 17 is smaller than the rate of increase in thickness near the tip portion 21 at m1 / m2 (m3 / m4) = 0.35 (see Fig. 7).

[0051] The blade thickness at the trailing edge 17c of the blade 17 at a spanwise distance of 0.85 is at least 1.1 times the blade thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.8 is at least 1.2 times the blade thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.7 is at least 1.3 times the blade thickness at a spanwise distance of 1.0.

[0052] Fig. 10 is a graph showing the relationship between the spanwise length of all blades 18 and the blade thickness reduction rate. In Fig. 10, the vertical axis represents the blade thickness reduction rate in the spanwise direction of all blades 18. The horizontal axis represents the ratio of the length from the root portion 20 to the tip portion 21 of all blades 18 (%Span in the figure), assuming that the entire spanwise length from the root portion 20 to the tip portion 21 of all blades 18 is 100%. Fig. 10 shows the blade thickness distribution in the spanwise direction at multiple locations from the leading edge 17b to the trailing edge 17c.

[0053] As shown in Figure 10, the blade thickness reduction rate of all blades 18 varies from the leading edge 17b to the trailing edge 17c. The blade thickness reduction rate of all blades 18 gradually increases within a range of less than 40% in the spanwise length from the root portion 20 to the tip portion 21, and reaches a maximum value. The blade thickness reduction rate of all blades 18 gradually decreases within a range of 40% or more in the spanwise length from the root portion 20 to the tip portion 21. In this embodiment, the blade thickness reduction rate of all blades 18 does not include a minimum value in the spanwise direction. Furthermore, the blade thickness reduction rate of all blades 18 is continuous and not discontinuous in the spanwise direction.

[0054] 11 is a graph showing the relationship between the length in the span direction of the short blade 19 and the blade thickness reduction rate. Although the blade thickness reduction rate of the short blade 19 is smaller than that of the full blade 18, the characteristics of the blade thickness reduction rate are similar to those of the full blade 18, and therefore, description thereof will be omitted.

[0055] Fig. 12 is a graph for explaining the relationship between the blade thickness reduction rate and the aerodynamic performance of the blade 17. In Fig. 12, the vertical axis represents the aerodynamic performance (adiabatic efficiency) of the centrifugal compressor CC, and the horizontal axis represents the flow coefficient of the centrifugal compressor CC.

[0056] 12, the solid line indicates the aerodynamic performance of the centrifugal compressor CC of this embodiment equipped with the blade 17 whose blade thickness reduction rate is maximum when the spanwise length is less than 40%. The dashed line indicates the aerodynamic performance of the centrifugal compressor of Comparative Example 1 equipped with the blade whose blade thickness reduction rate is maximum when the spanwise length is less than 30%. The dashed line indicates the aerodynamic performance of the centrifugal compressor of Comparative Example 2 equipped with the blade whose blade thickness reduction rate is maximum when the spanwise length is 40% or more.

[0057] As shown by the solid line and the dashed-dotted line in Fig. 12, the aerodynamic performance of the centrifugal compressors of this embodiment and Comparative Example 1 exceeds the reference value B. On the other hand, as shown by the dashed line, the aerodynamic performance of the centrifugal compressor of Comparative Example 2 does not reach the reference value B. As can be seen from Fig. 12, by setting the maximum value of the blade thickness reduction rate in a range where the spanwise length of the blade 17 is less than 40%, it is possible to obtain aerodynamic performance equal to or greater than the reference value B. On the other hand, if the maximum value of the blade thickness reduction rate is set in a range where the spanwise length is 40% or more, it becomes impossible to obtain aerodynamic performance equal to or greater than the reference value B.

[0058] Fig. 13 is a graph for explaining the relationship between the blade thickness near the tip 21 of the blade 17 and the aerodynamic performance. In Fig. 13, the vertical axis represents the aerodynamic performance (adiabatic efficiency) of the centrifugal compressor CC, and the horizontal axis represents the flow coefficient of the centrifugal compressor CC.

[0059] 13, the solid line indicates the aerodynamic performance of the centrifugal compressor CC of this embodiment, which is equipped with a blade 17 in which the blade thickness at 80% of the length in the span direction is 1.2 times the blade thickness at the tip 21. The dashed line indicates the aerodynamic performance of a centrifugal compressor as Comparative Example 1, which is equipped with a blade in which the blade thickness at 80% of the length in the span direction is 1.3 times the blade thickness at the tip. The dashed line indicates the aerodynamic performance of a centrifugal compressor as Comparative Example 2, which is equipped with a blade in which the blade thickness at 80% of the length in the span direction is 1.1 times the blade thickness at the tip.

[0060] As shown by the solid line and the dashed-dotted line in Fig. 13, the aerodynamic performance of the centrifugal compressors of this embodiment and Comparative Example 1 exceeds the reference value B. On the other hand, as shown by the dashed line, the aerodynamic performance of the centrifugal compressor of Comparative Example 2 does not reach the reference value B. As can be seen from Fig. 13, by setting the blade thickness of the blade 17 at a position that is 80% of the length in the span direction of the blade 17 to be 1.2 times or more the blade thickness at the tip portion 21, it is possible to obtain aerodynamic performance that is equal to or greater than the reference value B. On the other hand, if the blade thickness of the blade 17 at a position that is 80% of the length in the span direction is set to be less than 1.2 times the blade thickness at the tip portion 21, it becomes impossible to obtain aerodynamic performance that is equal to or greater than the reference value B.

[0061] As described above, the compressor impeller 8 of this embodiment has the blade 17 whose blade thickness reduction rate is maximum within a range of less than 40% of the length in the span direction. This allows the blade thickness on the tip end 21 side of the blade 17 to be thinner than a blade whose blade thickness reduction rate is maximum within a range of 40% or more of the length in the span direction. The thinner the blade thickness on the tip end 21 side of the blade 17, the smaller the air resistance, and therefore the better the aerodynamic performance.

[0062] On the other hand, in the range of less than 40% of the length in the span direction, the blade thickness can be increased, which ensures the strength of the blade 17 and suppresses a decrease in the natural frequency of the blade 17. As a result, it is possible to achieve both strength and aerodynamic performance of the blade 17.

[0063] Furthermore, in this embodiment, the blade thickness of the blade 17 at a position that is 80% of the length in the span direction is 1.2 times or more the blade thickness at the tip portion 21. This allows the blade thickness to be thinner as it approaches the tip portion 21 of the blade 17. The rotation speed of the rotating compressor impeller 8 increases as it approaches the tip portion 21 of the blade 17, and the contribution to aerodynamic performance also increases. Therefore, the thinner the blade thickness at the tip portion 21, the more the aerodynamic performance can be improved.

[0064] Furthermore, in this embodiment, the blade thickness reduction rate in the span direction of the blade 17 does not include a minimum value. Because it does not include a minimum value, the blade thickness is small on the tip 21 side of the blade 17 in the span direction, and the change in blade thickness toward the tip 21 side is small. The small blade thickness and small change in thickness on the tip 21 side can further improve aerodynamic performance.

[0065] In this embodiment, the blade thickness reduction rate of the blade 17 is continuous in the span direction. That is, the blade thickness reduction rate of the blade 17 is not discontinuous in the span direction, and no bend is formed, thereby suppressing deterioration of aerodynamic performance.

[0066] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that various changes or modifications can be made within the scope of the present disclosure, and it is understood that these also fall within the technical scope of the present disclosure.

[0067] In the above embodiment, an example has been described in which the blades 17 are applied to the compressor impeller 8. However, the present invention is not limited to this, and the blades 17 may also be applied to the turbine impeller 9.

[0068] In the above embodiment, an example has been described in which the blade thickness of the blade 17 at the 80% position in the span direction is 1.2 times or more the blade thickness of the tip portion 21 of the blade 17. However, without being limited to this, the blade thickness of the blade 17 at the 80% position in the span direction may be less than 1.2 times the blade thickness of the tip portion 21 of the blade 17.

[0069] In the above embodiment, an example has been described in which the blade thickness reduction rate of the blade 17 does not include a minimum value and is continuous in the span direction. However, the present invention is not limited to this, and the blade thickness reduction rate may include a minimum value or may be discontinuous in the span direction. [Explanation of symbols]

[0070] CC centrifugal compressor 8 Compressor impeller (impeller) 16 Hub 17 Feather 17b leading edge 17c trailing edge 17d wing surface 17e busbar 17f outer edge 17g inner edge 18 All Feathers 19 Short feathers 20 Root 21 Tip

Claims

1. a hub provided on the shaft; a blade provided on an outer peripheral surface of the hub, the blade thickness reduction rate of which is maximum within a range of less than 40% in a span direction length from a root portion to a tip portion; Equipped with the blade thickness reduction rate gradually increases within a range of less than 40% in the spanwise length from the root portion to the tip portion, reaches the maximum value, and gradually decreases from the position in the spanwise length where the blade thickness reduction rate reaches the maximum value to the tip portion; Impeller.

2. The blade thickness at the root portion of the trailing edge of the blade is greater than the blade thickness at the root portion at the leading edge and less than the blade thickness at the root portion at an intermediate portion between the leading edge and the trailing edge; a root thickness at the intermediate portion of the blade is greater than a root thickness at the leading edge; The impeller of claim 1 .

3. a blade thickness of the blade at a position corresponding to 80% of the length in the span direction from the root portion to the tip portion is 1.2 times or more a blade thickness of the blade at the tip portion; 3. The impeller according to claim 1 or 2.

4. The blade thickness reduction rate does not include a minimum value in the span direction. The impeller according to any one of claims 1 to 3.

5. The blade thickness reduction rate has continuity in the span direction. An impeller according to any one of claims 1 to 4.

6. A centrifugal compressor comprising the impeller according to any one of claims 1 to 5.

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