Impeller for a centrifugal compressor, centrifugal compressor having the impeller and method of manufacturing the impeller

Abstract

The present application provides a kind of impeller of centrifugal compressor, centrifugal compressor with the impeller and the method for manufacturing the impeller.The impeller of centrifugal compressor of the present application has a plurality of blades, the plurality of blades include leading edge, trailing edge, pressure surface and negative pressure surface extending between leading edge and trailing edge, shroud side end and hub side end defining pressure surface and negative pressure surface with leading edge and trailing edge, pressure surface and negative pressure surface are all configured as the blade element connecting shroud side end and hub side end is linear, the outer diameter of trailing edge at shroud side end is greater than the outer diameter of hub side end, trailing edge is convex shape relative to the imaginary straight line connecting the shroud side end and hub side end of trailing edge.

Description

TECHNICAL FIELD

[0001] The present application relates to an impeller of a centrifugal compressor, a centrifugal compressor having the same, and a method of manufacturing the same. BACKGROUND

[0002] As a means for increasing the pressure ratio of a centrifugal compressor, a method of increasing the outer diameter of an impeller to increase the peripheral velocity is effective, but increasing the outer diameter of the impeller can adversely affect the mountability of the centrifugal compressor, and can become a cause of fatigue failure due to the increase in the peripheral velocity. Therefore, as disclosed in Patent Documents 1 and 2, a structure in which the outer diameter of the shroud side is larger than the outer diameter of the hub side is adopted as an effective means.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-221984

[0006] Patent Document 2: Japanese Patent Application Publication No. 2011-512479 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the case where the trailing edge of the impeller is in a straight shape connecting the shroud side end and the hub side end, as in the structure described in Patent Document 1, in the flow on the downstream side of the impeller, separation occurs on the shroud side on the large flow rate side, and the efficiency can decrease. On the other hand, in the case where a portion including a convex shape curved in the trailing edge is included, as in the structure described in Patent Document 2, although the possibility of separation occurring on the shroud side on the large flow rate side can be reduced, in order to manufacture such an impeller, a point cutting operation using the tip end of a cutting tool is generally required, and an increase in the cutting time can occur.

[0009] In view of the above, an object of at least one embodiment of the present application is to provide an impeller of a centrifugal compressor, a centrifugal compressor having the same, and a method of manufacturing the same, which can increase the pressure ratio, suppress a decrease in the efficiency on the large flow rate side, and achieve a shortening of the cutting operation time.

[0010] TECHNICAL MEANS FOR SOLVING THE PROBLEMS

[0011] To achieve the above object, the impeller of the centrifugal compressor of the present application has a plurality of blades including a leading edge, a trailing edge, a pressure surface and a suction surface extending between the leading edge and the trailing edge, a shroud side end and a hub side end defining the pressure surface and the suction surface together with the leading edge and the trailing edge, the pressure surface and the suction surface are each configured such that a blade element connecting the shroud side end and the hub side end is linear, the shroud side end of the trailing edge has an outer diameter larger than that of the hub side end, and the trailing edge has a convex shape with respect to an imaginary straight line connecting the shroud side end and the hub side end of the trailing edge.

[0012] Further, in the method of manufacturing an impeller of the present application, the impeller has a plurality of blades including a leading edge, a trailing edge, a pressure surface and a suction surface extending between the leading edge and the trailing edge, a shroud side end and a hub side end defining the pressure surface and the suction surface together with the leading edge and the trailing edge, the method includes a step of forming the plurality of blades, the step of forming the plurality of blades includes a step of line-cutting the pressure surface and the suction surface such that a blade element connecting the shroud side end and the hub side end is linear, and a step of forming the trailing edge by removing a portion of the blade such that the trailing edge has a convex shape with respect to an imaginary straight line connecting the shroud side end and the hub side end of the trailing edge.

[0013] Effects of the Invention

[0014] The impeller of the centrifugal compressor and the method of manufacturing the same according to the present application can increase a pressure ratio by making the outer diameter of the trailing edge of the shroud side end larger than that of the trailing edge of the hub side end. Further, since the trailing edge has a convex shape with respect to an imaginary straight line connecting the shroud side end and the hub side end of the trailing edge, it is possible to suppress the flow passing through the trailing edge on the large flow rate side from being deflected toward the hub side, to reduce the possibility of separation occurring on the shroud side, and thus to suppress the decrease in efficiency on the large flow rate side. Moreover, since the pressure surface and the suction surface are each configured such that a blade element connecting the shroud side end and the hub side end is linear, it is possible to line-cut the pressure surface and the suction surface, and thus to shorten the cutting operation time. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a cross-sectional view of a centrifugal compressor having an impeller according to an embodiment of the present application.

[0016] Figure 2 is a view showing a part of a blade provided on an impeller according to an embodiment of the present application.

[0017] Figure 3 is a view showing a part of a modified example of a blade provided on an impeller according to an embodiment of the present application.

[0018] Figure 4FIG. 1 is a view showing a part of another modification example of a blade provided on an impeller according to an embodiment of the present application.

[0019] Figure 5 FIG. 2 is a view for explaining a method of manufacturing an impeller according to an embodiment of the present application.

[0020] Figure 6 FIG. 3 is a view for explaining a flow of air in a centrifugal compressor having an impeller according to an embodiment of the present application. DETAILED DESCRIPTION

[0021] Hereinafter, an impeller of a centrifugal compressor according to an embodiment of the present application and a method of manufacturing the impeller will be described based on the drawings. The embodiment represents one aspect of the present application and does not limit the present application, and can be arbitrarily changed within the scope of the technical idea of the present application.

[0022] An impeller of a turbocharger will be described as an example of a centrifugal compressor. However, the centrifugal compressor of the present application is not limited to the centrifugal compressor of the turbocharger, and can be any centrifugal compressor that operates independently. In addition, in the following description, the fluid compressed by the centrifugal compressor is air, but can be any fluid.

[0023] <Structure of centrifugal compressor according to an embodiment of the present application>

[0024] As shown in FIG. 1, a centrifugal compressor 1 has a casing 2 and an impeller 3 provided inside the casing 2 so as to be rotatable about a rotational axis L. The impeller 3 has a plurality of blades 4 provided on a hub 5 at a predetermined interval in a circumferential direction. Only one blade 4 is depicted in FIG. 1. Figure 1 Each blade 4 has a leading edge 4a, a trailing edge 4b, a shroud side end 4c facing the casing 2, and a hub side end 4d connected to the hub 5. A pressure surface 8 and a negative pressure surface 9 of the blade 4 are respectively demarcated by the leading edge 4a, the trailing edge 4b, the shroud side end 4c, and the hub side end 4d in a manner extending between the leading edge 4a and the trailing edge 4b. Figure 1 <Structure of impeller of centrifugal compressor according to an embodiment of the present application>

[0025]

[0026] A part of the pressure surface 8 of the blade 4 is shown, and a blade element BE connecting the shroud side end 4c and the hub side end 4d is depicted on the pressure surface 8 in a dot-and-dash line. The pressure surface 8 is configured in a straight line shape. Although not shown in FIG. 1, the negative pressure surface 9 (refer to FIG. 2) is configured in a straight line shape. Figure 2 Figure 2 Figure 1 ​​) is also configured in the same manner as the pressure surface 8 to be linear with respect to the blade element connecting the shroud side end 4c and the hub side end 4d. In addition, a surface expressed by a locus of a line segment whose both ends are continuously moved on two curves in a three-dimensional space is called a line weave, but the pressure surface 8 and the negative pressure surface 9 correspond to the line weave, and the blade element corresponds to the line segment.

[0027] The trailing edge 4b is configured to have an outer diameter R 4c larger than an outer diameter R 4d of the hub side end 4d. In addition, the trailing edge 4b is convex with respect to an imaginary straight line IL connecting the shroud side end 4c and the hub side end 4d of the trailing edge 4b. The convex shape of the trailing edge 4b with respect to the imaginary straight line IL can be a curved convex shape as shown in Figure 2 , or a convex shape composed of two linear portions, i.e., a shroud side linear portion LP1 extending from the shroud side end 4c toward the hub side end 4d and a hub side linear portion LP2 extending from the hub side end 4d toward the shroud side end 4c as shown in Figure 3 . In the case where the convex shape is composed of two linear portions, as shown in Figure 4 , it is also possible to make the outer diameter of the shroud side linear portion LP1 constant. In addition, although not shown in the drawings, the convex shape can be composed of three or more linear portions.

[0028] <Method of manufacturing an impeller of a centrifugal compressor according to one embodiment of the present invention>

[0029] Next, a method of manufacturing the impeller 3 according to one embodiment of the present invention will be described. Except for the operation of forming the blade 4, the method is the same as a general method of manufacturing an impeller, and therefore, the operation of forming the blade 4 will be described in detail below.

[0030] As shown in Figure 5 , the pressure surface 8 of the blade 4 is cut by the cutting tool 10. At this time, the cutting tool 10 cuts the pressure surface 8 by line cutting of the side surface of the cutting tool 10 in a manner intersecting the shroud side end 4c and the hub side end 4d. Although not shown in the drawings, the negative pressure surface 9 (see FIG. 2) is also subjected to line cutting by the cutting tool 10. Thus, the blade element BE of the pressure surface 8 (and the negative pressure surface 9) becomes linear. Figure 1

[0031] Since the pressure surface 8 and the negative pressure surface 9 are formed by line cutting, the end edge 4b' of the trailing edge side of the blade 4 after the line cutting is linear with respect to the shroud side end 4c and the hub side end 4d. Therefore, after the pressure surface 8 and the negative pressure surface 9 are subjected to line cutting, the trailing edge 4b is formed by removing a portion of the blade 4 so that the trailing edge 4b is convex with respect to the imaginary straight line IL connecting the shroud side end 4c and the hub side end 4d. The removal of the portion of the blade 4 can be performed by any method, for example, by a lathe.​

[0032] Thus, after line cutting of the pressure surface 8 and the negative pressure surface 9, the blade 4 is formed by removing a part of the end edge 4b' of the trailing edge side of the blade 4, so that the cutting work can be shortened. Further, in the case where the convex shape of the trailing edge 4b is composed of two or more straight line portions as shown in Figure 3 and 4 , compared with the case where the trailing edge 4b is curved as shown in Figure 2 , the removal work of a part of the blade 4 becomes simple, the work time thereof can be shortened, so that the cutting work can be further shortened.

[0033] <Operation of centrifugal compressor of one embodiment of the present application>

[0034] Next, the operation of the centrifugal compressor 1 of one embodiment of the present application will be described. As shown in Figure 1 , the impeller 3 is rotated by the rotation of a turbine not shown. The air flowing into the centrifugal compressor 1 passes between the pressure surface 8 and the negative pressure surface 9 of the adjacent blade 4 after passing the leading edge 4a of the blade 4, and is compressed by the rotation of the impeller 3 during passing the trailing edge 4b of the blade 4.

[0035] As shown in Figure 6 , in the centrifugal compressor 100 which is a comparative example of the centrifugal compressor 1, the trailing edge 104b of the blade 104 is in a straight line shape connecting the shroud side end 104c and the hub side end 104d. In this structure, since the air flow F' passing the trailing edge 104 is inclined to the hub side, the air flow F' is deviated to the hub side, and as a result, a separation P is generated on the shroud side. Such a separation P has a tendency to be generated particularly on the large flow rate side.

[0036] In this regard, in the centrifugal compressor 1, since the trailing edge 4b has a curved convex shape, in the air flow F passing the trailing edge 4, the flow f on the shroud side is inclined to the hub side less than the air flow F' of the centrifugal compressor 100, and therefore, the air flow F is deviated to the hub side less than the air flow F' of the centrifugal compressor 100, and as a result, it is difficult to generate a separation P on the shroud side. Thus, particularly, it is possible to suppress the air flow F passing the trailing edge 4b on the large flow rate side from being deviated to the hub side, and it is possible to reduce the possibility of generating a separation P on the shroud side, and therefore, it is possible to suppress the decrease in the efficiency of the centrifugal compressor 1 on the large flow rate side.

[0037] In the centrifugal compressor 1 of Figure 6 , the trailing edge 4b has a curved convex shape Figure 2 , but even if the trailing edge 4b has a convex shape composed of two or more straight line portions Figure 3 or 4), the same effect can be obtained. Further, as shown in Figure 4In the structure in which the shroud-side linear portion LP1 including the trailing edge 4b has a certain outer diameter, as shown, compared with the structure in which the outer diameter of the trailing edge 4b decreases from the shroud-side end 4c toward the hub-side end 4d Figure 2 or 3), the portion (shroud-side linear portion LP1) in which the outer diameter of the impeller 3 is increased, and thus the pressure ratio can be increased, and the flow toward the shroud side can be further increased.

[0038] The content described in each of the embodiments described above is grasped as follows, for example.

[0039] [1] An impeller of a centrifugal compressor according to one embodiment includes a plurality of blades (4) including a leading edge (4a), a trailing edge (4b), a pressure surface (8) and a suction surface (9) extending between the leading edge (4a) and the trailing edge (4b), a shroud-side end (4c) and a hub-side end (4d) that define the pressure surface (8) and the suction surface (9) together with the leading edge (4a) and the trailing edge (4b),

[0040] the pressure surface (8) and the suction surface (9) are each configured such that a blade element (BE) connecting the shroud-side end (4c) and the hub-side end (4d) is linear,

[0041] an outer diameter (R 4c ) of the shroud-side end (4c) of the trailing edge (4b) is larger than an outer diameter (R 4d ) of the hub-side end (4d), and the trailing edge (4b) is in a convex shape with respect to an imaginary straight line (IL) connecting the shroud-side end (4c) and the hub-side end (4d) of the trailing edge (4b).

[0042] According to the impeller of the centrifugal compressor of the present application, the outer diameter of the trailing edge of the shroud-side end is larger than the outer diameter of the trailing edge of the hub-side end, and thus the pressure ratio can be increased. In addition, since the trailing edge is in a convex shape with respect to the imaginary straight line connecting the shroud-side end and the hub-side end of the trailing edge, the flow through the trailing edge can be prevented from being biased toward the hub side on the large flow rate side, and the possibility of separation occurring on the shroud side can be reduced, and thus the decrease in efficiency on the large flow rate side can be suppressed. In addition, since the pressure surface and the suction surface are each configured such that the blade element connecting the shroud-side end and the hub-side end is linear, the pressure surface and the suction surface can be line-cut, and thus the shortening of the cutting work can be achieved.

[0043] [2] An impeller of a centrifugal compressor according to another embodiment is the impeller of the centrifugal compressor according to [1], in which the trailing edge (4b) is in a convex shape curved with respect to the imaginary straight line (IL).

[0044] According to such a structure, the same advantageous effects as the impeller of the centrifugal compressor according to [1] can be obtained.

[0045] [3] Another centrifugal compressor impeller in the centrifugal compressor impeller of [1], the trailing edge (4b) includes at least two straight portions (LP1, LP2).

[0046] According to such a structure, compared with the case where the trailing edge is curved in a convex shape, the cutting time of the blade can be shortened.

[0047] [4] Another centrifugal compressor impeller in the centrifugal compressor impeller of [3], the at least two straight portions have a shroud side straight portion (LP1) extending from the shroud side end (4c) toward the hub side end (4d), and a hub side straight portion (LP2) extending from the hub side end (4d) toward the shroud side end (4c), the outer diameter of the shroud side straight portion (LP1) being constant.

[0048] According to such a structure, since the outer diameter of the shroud side straight portion is constant, compared with the structure where the outer diameter of the trailing edge decreases from the shroud side end toward the hub side end, the portion where the outer diameter of the impeller increases (the shroud side straight portion) increases, so the pressure ratio can be increased, and the flow toward the shroud side can be further increased.

[0049] [5] A centrifugal compressor having the impeller (3) of any one of [1] to [4].

[0050] According to the centrifugal compressor of the present application, the pressure ratio can be increased, the efficiency decrease on the large flow rate side can be suppressed, and the shortening of the cutting work at the time of manufacturing the impeller can be achieved.

[0051] [6] A method of manufacturing an impeller of a centrifugal compressor, the impeller (3) having a plurality of blades (4) including a leading edge (4a), a trailing edge (4b), a pressure surface (8) and a negative pressure surface (9) extending between the leading edge (4a) and the trailing edge (4b), a shroud side end (4c) and a hub side end (4d) defining the pressure surface (8) and the negative pressure surface (9) together with the leading edge (4a) and the trailing edge (4b),

[0052] the method including a step of forming the plurality of blades (4),

[0053] the step of forming the plurality of blades (4) includes a step of:

[0054] line-cutting the pressure surface (8) and the negative pressure surface (9) so that a blade element (BE) connecting the shroud side end (4c) and the hub side end (4d) becomes linear;

[0055] The trailing edge (4b) is formed by removing a portion of the blade (4) so that the trailing edge (4b) is convex with respect to an imaginary straight line (IL) connecting the shroud side end (4c) and the hub side end (4d) of the trailing edge (4b).

[0056] According to the method of manufacturing an impeller of a centrifugal compressor of the present application, the outer diameter of the trailing edge of the shroud side end is larger than the outer diameter of the trailing edge of the hub side end, whereby the pressure ratio can be increased. In addition, since the trailing edge is convex with respect to an imaginary straight line connecting the shroud side end and the hub side end of the trailing edge, the flow passing through the trailing edge on the large flow rate side can be inhibited from being deflected toward the hub side, the possibility of separation occurring on the shroud side can be reduced, and thus the decrease in efficiency on the large flow rate side can be inhibited. In addition, since the pressure surface and the negative pressure surface can be line-cut, the shortening of the cutting operation time can be achieved.

[0057] Explanation of Reference Numerals

[0058] 1: Centrifugal compressor

[0059] 3: Impeller

[0060] 5: Blade

[0061] 4a: Leading edge

[0062] 4b: Trailing edge

[0063] 4c: Shroud side end

[0064] 4d: Hub side end

[0065] 8: Pressure surface

[0066] 9: Negative pressure surface

[0067] BE: Blade element

[0068] IL: Imaginary straight line

[0069] R 4c : Outer diameter of trailing edge of shroud side end

[0070] R 4d : Outer diameter of trailing edge of hub side end

Claims

1. A method for manufacturing an impeller for a centrifugal compressor, wherein, The impeller has multiple blades, each blade including a leading edge, a trailing edge, a pressure surface and a negative pressure surface extending between the leading edge and the trailing edge, a protective cover side end and a hub side end that define the pressure surface and the negative pressure surface together with the leading edge and the trailing edge. The method includes the step of forming the plurality of blades. The steps for forming the plurality of blades include the following steps: The pressure surface and the negative pressure surface are wire-cut to make the blade element connecting the side end of the guard and the side end of the hub straight; The trailing edge is formed by removing a portion of the blade, such that the trailing edge becomes convex in the entire length from the shield side end to the hub side end relative to the imaginary straight line connecting the trailing edge to the shield side end. The plurality of blades each include: a portion from the trailing edge to the imaginary straight line that increases from the side end of the shield towards the side end of the hub; And the portion of the distance from the trailing edge to the imaginary straight line that increases from the hub side end to the shield side end; The outer diameter of the side end of the protective cover at the rear edge is greater than the outer diameter of the side end of the hub, and the angle formed by the side end of the protective cover and the rear edge is an obtuse angle.

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