JP7749974B2 - Impeller and centrifugal compressor - Google Patents

Description

This disclosure relates to an impeller and a centrifugal compressor.

Patent Document 1 discloses a compressor impeller having a hub and multiple blades attached to 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 varies from the root portion where the blade connects to the hub to the tip portion.

Patent No. 6372207

The thinner the blade thickness, the smaller the air resistance, improving 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 blades of the compressor impeller described in Patent Document 1 above have a varying rate of reduction in blade thickness from the root to the tip, but when considering the balance between blade strength and aerodynamic performance, there was room for improvement in the design of the blade thickness.

The purpose of this disclosure is to provide an impeller and centrifugal compressor that can achieve both blade strength and aerodynamic performance.

In order to solve the above problem, an impeller according to the present disclosure includes a hub provided on a shaft, and blades 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% along a spanwise length from a root portion to a tip portion ,
The blade thickness reduction rate gradually increases within a range of less than 40% along the spanwise length from the root to the tip, reaches a maximum value, and then gradually decreases from the position of the spanwise length at which the blade 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.

The blade thickness at 80% of the spanwise length from the root to the tip may be 1.2 times or more the blade thickness at the tip of the blade.

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

The blade thickness reduction rate may be continuous in the span direction.

To solve the above problem, the centrifugal compressor disclosed herein is equipped with the above impeller.

This disclosure makes it possible to achieve both blade strength and aerodynamic performance.

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

One embodiment of the present disclosure will be described below with reference to the accompanying drawings. Dimensions, materials, and other specific values shown in the embodiment are merely examples to facilitate understanding and, unless otherwise specified, do not limit the present disclosure. Note that in this specification and drawings, elements that have substantially the same function and configuration are designated by the same reference numerals to avoid redundant explanation, and elements that are not directly related to the present disclosure are not shown.

Figure 1 is a schematic cross-sectional view of the turbocharger TC. In the following description, the direction of arrow L in Figure 1 will be referred to as the left side of the turbocharger TC. The direction of arrow R in Figure 1 will be referred to as the right side of the turbocharger TC. As shown in Figure 1, the turbocharger TC comprises 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.

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 a semi-floating bearing, a rolling bearing, or other type of 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.

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 on its radially inner side via the compressor impeller 8. The surface of the inner surface of the compressor housing 6 that faces radially from the compressor impeller 8 is formed as the shroud surface 6a.

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 directed to the intake port of the engine.

These compressor housings 6 and bearing housing 2 constitute a centrifugal compressor CC. In this embodiment, an example in which the centrifugal compressor CC is mounted on a turbocharger TC will be described. However, this 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.

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). The turbine housing 4 is formed with a turbine scroll passage 14 and a communication passage 15. 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 is connected to a gas inlet (not shown). Exhaust gas discharged from an exhaust manifold (not shown) is introduced into the gas inlet. The communication passage 15 connects the turbine scroll passage 14 to 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.

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. The air is then guided to the engine intake port.

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

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.

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

The blades 17 are thin plate-shaped members molded integrally with the hub 16. Multiple blades 17 are arranged circumferentially spaced from one another on the outer peripheral surface 16c of the hub 16. 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 Figure 1) and are curved so as to be inclined in the circumferential direction of the hub 16.

The blades 17 include full blades 18 (long blades, full blades) and short blades 19 (half blades) that are shorter in axial length than the full blades 18. The full blades 18 and short blades 19 are arranged alternately in the circumferential direction. In this way, by arranging the short blades 19 between full blades 18, the air suction efficiency of the turbocharger TC is improved compared to when the same number of blades 17 are all full blades 18. Hereinafter, when simply referring to blades 17, it refers to both full blades 18 and short blades 19.

Figure 3 is an explanatory diagram illustrating the shape of the blade 17. In Figure 3, the meridian shape of the blade 17 of this embodiment is shown by a dot-dash line. The meridian shape is the 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 Figure 3, the left-right direction is the axial direction of the shaft 7, with the right side being the bottom surface 16b side of the hub 16 and the left side being the top surface 16a side of the hub 16. In Figure 3, the up-down direction is the span direction (blade length direction) of the blade 17, with the upper side being the shroud surface 6a side (hereinafter simply referred to as the tip side) and the lower side being the outer peripheral surface 16c side of the hub 16 (hereinafter simply referred to as the root side).

As shown in Figure 3, each 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). Note that the leading edge 17b, which is one axial end of the short blade 19, is located downstream in the flow direction from the leading edge 17b, which is one axial end of all blades 18.

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 path formed between the blades 17a.

As shown in Figure 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.

The blade surface 17d has a curved shape with the leading edge 17b and trailing edge 17c as its ends, and is traced by the continuous movement of the generating line 17e (shown by the dashed line in Figure 3) of the blade 17.

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.

The generating line 17e is a line connecting any point on the outer edge 17f and the 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 trajectory of this generating line 17e.

Figure 4 is a graph showing the blade thickness of the leading edge 17b of the blade 17. As shown in Figure 4, the blade 17 has a root portion 20 connected to the hub 16 (see Figure 2) and a tip portion 21 spaced apart from the hub 16 in the span direction. In Figure 3, the vertical axis represents the distance from the root portion 20 to each part (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. Note that in Figures 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 tip portion 21 of the blade 17.

The blade thickness at the root portion 20 of the blade 17 is greater than the blade thickness at the tip portion 21. The blade thickness at the tip portion 21 of the blade 17 is less than the blade thickness at the root portion 20. The blade thickness of the blade 17 decreases from the root portion 20 to the tip portion 21. The blade thickness of the blade 17 is thickest at the root portion 20 and thinnest at the tip portion 21. The rate of decrease in blade thickness 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 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.

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

As shown in Figure 5, the blade thickness of the blade 17 increases gradually from the tip 21 toward the root 20. The blade thickness 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.

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

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

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 Figure 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 Figure 4). Here, "equal" means both perfect equality and deviations from perfect equality within the range of allowable error (such as processing accuracy or assembly error).

The blade thickness reduction rate from the root 20 to the tip 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 20 toward the tip 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 its maximum value to a spanwise distance of 1.0.

Figure 7 is a graph showing the blade thickness near the tip 21 of the blade 17 at a position where m1/m2 (m3/m4) = 0.35. In Figure 7, 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.

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

The blade thickness at a spanwise distance of 0.85 at a position where m1/m2 (m3/m4) = 0.35 on blade 17 is at least 1.5 times the blade thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.8 is at least 1.8 times the blade thickness at a spanwise distance of 1.0. The blade thickness at a spanwise distance of 0.7 is at least 2.0 times the blade thickness at a spanwise distance of 1.0.

Figure 8 is a graph showing the blade thickness of the trailing edge 17c of the blade 17. In Figure 8, the vertical axis represents the spanwise distance, and the horizontal axis represents the blade thickness of the blade 17.

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

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 Figure 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 the blade 17 where m1/m2 (m3/m4) = 0.35 (see Figure 6). The thickness of the tip portion 21 at the trailing edge 17c of the blade 17 is equal to the thickness of the trailing edge 17c and the thickness of the tip portion 21 at the position of m1/m2 (m3/m4) = 0.35.

The blade thickness reduction rate from the root 20 to the tip 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 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.

Figure 9 is a graph showing the blade thickness near the tip 21 of the trailing edge 17c of the blade 17. In Figure 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.

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

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.

Figure 10 is a graph showing the relationship between the spanwise length of all blades 18 and the blade thickness reduction rate. In Figure 10, the vertical axis represents the blade thickness reduction rate in the spanwise direction of all blades 18. The horizontal axis represents the percentage of the length from the root 20 (% Span in the figure) when the total spanwise length of all blades 18 from the root 20 to the tip 21 is taken as 100%. Figure 10 shows the blade thickness distribution in the spanwise direction at multiple locations from the leading edge 17b to the trailing edge 17c.

As shown in Figure 10, the blade thickness reduction rate of all blades 18 changes at every location 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% along the spanwise length from the root portion 20 to the tip portion 21, reaching a maximum value. The blade thickness reduction rate of all blades 18 gradually decreases within a range of 40% or more along 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.

Figure 11 is a graph showing the relationship between the spanwise length of the short blades 19 and the blade thickness reduction rate. Although the blade thickness reduction rate of the short blades 19 is smaller than that of the full blades 18, the characteristics of the blade thickness reduction rate are similar to those of the full blades 18, so explanation will be omitted.

Figure 12 is a graph illustrating the relationship between the blade thickness reduction rate of the blade 17 and aerodynamic performance. In Figure 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.

In Figure 12, the solid line shows the aerodynamic performance of the centrifugal compressor CC of this embodiment, which is equipped with blades 17 whose blade thickness reduction rate is maximum when the spanwise length is less than 40%. The dashed line shows the aerodynamic performance of a centrifugal compressor as Comparative Example 1, which is equipped with blades whose blade thickness reduction rate is maximum when the spanwise length is less than 30%. The dashed line shows the aerodynamic performance of a centrifugal compressor as Comparative Example 2, which is equipped with blades whose blade thickness reduction rate is maximum when the spanwise length is 40% or more.

As shown by the solid and dashed lines in Figure 12, the aerodynamic performance of the centrifugal compressors of this embodiment and Comparative Example 1 exceeds standard 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 standard value B. As can be seen from Figure 12, by setting the maximum blade thickness reduction rate in a range where the spanwise length of the blade 17 is less than 40%, aerodynamic performance equal to or greater than standard value B can be obtained. On the other hand, if the maximum blade thickness reduction rate is set in a range where the spanwise length is 40% or greater, aerodynamic performance equal to or greater than standard value B cannot be obtained.

Figure 13 is a graph illustrating the relationship between the blade thickness near the tip 21 of the blade 17 and the aerodynamic performance. In Figure 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.

In Figure 13, the solid line shows the aerodynamic performance of the centrifugal compressor CC of this embodiment, which is equipped with blades 17 whose blade thickness at 80% of the span length is 1.2 times the blade thickness at the tip 21. The dashed line shows the aerodynamic performance of a centrifugal compressor as Comparative Example 1, which is equipped with blades whose blade thickness at 80% of the span length is 1.3 times the blade thickness at the tip. The dashed line shows the aerodynamic performance of a centrifugal compressor as Comparative Example 2, which is equipped with blades whose blade thickness at 80% of the span length is 1.1 times the blade thickness at the tip.

As shown by the solid and dashed lines in Figure 13, the aerodynamic performance of the centrifugal compressors of this embodiment and Comparative Example 1 exceeds standard 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 standard value B. As can be seen from Figure 13, aerodynamic performance equal to or greater than standard value B can be obtained by setting the blade thickness of the blade 17 at 80% of the length in the span direction to at least 1.2 times the blade thickness at the tip 21. On the other hand, if the blade thickness of the blade 17 at 80% of the length in the span direction is set to less than 1.2 times the blade thickness at the tip 21, aerodynamic performance equal to or greater than standard value B cannot be obtained.

As described above, the compressor impeller 8 of this embodiment has blades 17 whose blade thickness reduction rate is at its maximum within a range of less than 40% of the spanwise length. This allows the blade thickness on the tip end 21 side of the blade 17 to be thinner than blades whose blade thickness reduction rate is at its maximum within a range of 40% or more of the spanwise length. The thinner the blade thickness on the tip end 21 side of the blade 17, the smaller the air resistance, thereby improving aerodynamic performance.

On the other hand, within a range of less than 40% of the spanwise length, the blade thickness can be increased, ensuring the strength of the blade 17 and suppressing a decrease in the natural frequency of the blade 17. As a result, it is possible to achieve both the strength and aerodynamic performance of the blade 17.

In addition, in this embodiment, the blade thickness of the blade 17 at 80% of the length in the span direction is 1.2 times or more the blade thickness at the tip 21. This allows the blade thickness to be thinner as it approaches the tip 21 of the blade 17. The rotational speed of the rotating compressor impeller 8 increases as it approaches the tip 21 of the blade 17, and the contribution to aerodynamic performance also increases. Therefore, the thinner the blade thickness at the tip 21, the more aerodynamic performance can be improved.

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 in the span direction on the tip 21 side of the blade 17, 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 further improves aerodynamic performance.

Furthermore, in this embodiment, the blade thickness reduction rate of the blade 17 is continuous in the span direction. In other words, the blade thickness reduction rate of the blade 17 is not discontinuous in the span direction, and no bends are formed, thereby suppressing deterioration of aerodynamic performance.

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 a person skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present disclosure.

In the above embodiment, an example was described in which the blades 17 were applied to a compressor impeller 8. However, this is not limited to this, and the blades 17 may also be applied to a turbine impeller 9.

In the above embodiment, an example was described in which the blade thickness of the blade 17 at 80% of the length in the span direction is 1.2 times or more the blade thickness of the tip 21 of the blade 17. However, this is not limited to this, and the blade thickness of the blade 17 at 80% of the length in the span direction may be less than 1.2 times the blade thickness of the tip 21 of the blade 17.

In the above embodiment, an example was 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, this is not limited to this, and the blade thickness reduction rate may include a minimum value or may be discontinuous in the span direction.

CC Centrifugal compressor 8 Compressor impeller (impeller)
16 Hub 17 Blade 17b Leading edge 17c Trailing edge 17d Blade surface 17e Generator 17f Outer edge 17g Inner edge 18 Full blade 19 Short blade 20 Root portion 21 Tip portion

Claims (6)

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. a root thickness at the trailing edge of the blade is greater than a root thickness at the leading edge and less than a root thickness 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 . 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 . 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 . The blade thickness reduction rate has continuity in the span direction.
The impeller according to any one of claims 1 to 4 . A centrifugal compressor comprising the impeller according to any one of claims 1 to 5 .