Bladed diffuser and centrifugal compressor

Abstract

The present application provides a vane diffuser capable of improving static pressure recovery performance in the vane diffuser and a centrifugal compressor provided with the vane diffuser. A vane diffuser provided on the downstream side of an impeller of a centrifugal compressor, wherein the vane diffuser is provided with: a diffuser flow path forming portion that forms a diffuser flow path on the downstream side of the impeller and includes a hub side surface and a shroud side surface; and a plurality of diffuser blades that are provided at intervals in the circumferential direction of the impeller in the diffuser flow path, at least one of the plurality of diffuser blades being formed with at least one notch portion formed between either of the hub side surface and the shroud side surface, the at least one notch portion being formed with a one end of the notch portion at a position including one end of a leading edge portion of the diffuser blade, and the notch height of the notch portion becoming smaller as it goes toward the trailing edge portion side of the diffuser blade.

Description

Technical Field

[0001] The present invention relates to a vaned diffuser and a centrifugal compressor having the vaned diffuser.

[0002] This application claims priority based on Japan Patent Application No. 2021-180439 filed on November 4, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] Centrifugal compressors used in the compressor sections of turbochargers for vehicles, ships, and industries impart kinetic energy to fluids through the rotation of the compressor impeller, and achieve a pressure increase based on centrifugal force by discharging the fluid radially outward. Various studies have been conducted to improve the performance of these centrifugal compressors. One such study is improving the static pressure recovery performance (diffusion performance) of the vaned diffuser located downstream of the centrifugal compressor impeller.

[0004] For example, the centrifugal turbomachinery described in Patent Document 1 includes an impeller and a bladed diffuser with multiple diffuser blades disposed on the downstream side of the impeller. Patent Document 1 describes a technique in which an arc-shaped cross-section recessed in the blade thickness direction is provided on the negative pressure surface of the diffuser blade at a position closer to the leading edge than the throat position, thereby suppressing the development of the boundary layer on the negative pressure surface side of the blade and suppressing the reduction in efficiency and narrowing of the operating range of the centrifugal compressor.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-124624

[0008] In centrifugal compressors equipped with vane diffusers, the flow within the diffuser is easily stripped due to the aerodynamic interference between the impeller and the diffuser, and a strong adverse pressure gradient, making it difficult to achieve near-ideal flow within the diffuser. However, from the perspective of improving the performance of centrifugal compressors, there is a desire to further enhance static pressure recovery performance. Summary of the Invention

[0009] In view of the above, the object of at least one embodiment of the present invention is to provide a vaned diffuser capable of improving the static pressure recovery performance in a vaned diffuser, and a centrifugal compressor having the vaned diffuser.

[0010] In one embodiment of the present invention, a vane diffuser is disposed downstream of the impeller of a centrifugal compressor, wherein,

[0011] The leaf diffuser includes:

[0012] A diffuser flow path forming section forms a diffuser flow path on the downstream side of the impeller. The diffuser flow path forming section includes a hub side surface and a protective shield side surface facing the hub side surface across the diffuser flow path.

[0013] Multiple diffuser blades are spaced apart in the circumferential direction of the impeller in the diffuser flow path.

[0014] At least one of the plurality of diffuser blades has at least one cut-out between the hub side and the shield side, the at least one cut-out being formed at one end of the leading edge of the diffuser blade extending in the blade height direction, and the cut-out height of the cut-out decreasing toward the trailing edge of the diffuser blade.

[0015] A centrifugal compressor according to one embodiment of the present invention comprises:

[0016] impeller;

[0017] A housing configured to house the impeller for rotation; and

[0018] The bladed diffuser is disposed inside the housing on the downstream side of the impeller.

[0019] Invention Effects

[0020] According to at least one embodiment of the present invention, a louvered diffuser capable of improving the static pressure recovery performance in a louvered diffuser is provided, as well as a centrifugal compressor having the louvered diffuser. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view along the axial direction of one embodiment of a centrifugal compressor.

[0022] Figure 2 This is a schematic diagram showing the state of a leaf diffuser of one embodiment as viewed from the axial upstream side.

[0023] Figure 3 This is a schematic perspective view of a leaf diffuser according to one embodiment.

[0024] Figure 4 This is a schematic cross-sectional view of a leaf diffuser according to one embodiment.

[0025] Figure 5 This is a schematic cross-sectional view of a leaf diffuser, a comparative example.

[0026] Figure 6 This is an explanatory diagram used to illustrate the flow of fluid in a leafed diffuser of a comparative example.

[0027] Figure 7 This is an explanatory diagram used to illustrate the velocity loss within the diffuser flow path of the leaf diffuser in the comparative example.

[0028] Figure 8 It is used for explanation Figure 4 Explanation diagrams showing the entry angles of the louvered diffuser and the louvered diffuser of the comparative example.

[0029] Figure 9 It is used for explanation Figure 4 A diagram illustrating the flow of fluid in a leafed diffuser.

[0030] Figure 10 It is used for explanation Figure 4 A diagram illustrating the velocity loss within the diffuser flow path of a leaf diffuser.

[0031] Figure 11 This is a schematic cross-sectional view of a leaf diffuser according to one embodiment.

[0032] Figure 12 This is a schematic perspective view of the diffuser blades of a leaf diffuser according to one embodiment.

[0033] Figure 13 This is a schematic perspective view of the diffuser blades of a leaf diffuser according to one embodiment.

[0034] Figure 14 This is a schematic cross-sectional view of a leaf diffuser according to one embodiment.

[0035] Figure 15 This is a schematic cross-sectional view of a leaf diffuser according to one embodiment.

[0036] Figure 16 This is a schematic cross-sectional view of a leaf diffuser according to one embodiment.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1...Centrifugal compressor;

[0039] 2... Impeller;

[0040] 3...shell;

[0041] 4... Leaf diffuser;

[0042] 5... Diffuser flow path forming section;

[0043] 6, 6A, 6B... diffuser blades;

[0044] 7...Incision area;

[0045] 7A...Side cutout of the protective cover;

[0046] 7B...Side cutout of the wheel hub;

[0047] 21... Impeller blades;

[0048] 22...wheel hub;

[0049] 23...(the outer surface of the wheel hub);

[0050] 24...(the tip of the impeller blades);

[0051] 31...protective cover surface;

[0052] 32... Protective shield section;

[0053] 33... Fluid introduction path;

[0054] 34... Fluid inlet flow path forming section;

[0055] 35...vortex flow path;

[0056] 36...Vortex flow path forming section;

[0057] 50... Diffuser flow path;

[0058] 51... Wheel hub side;

[0059] 52...side of the shield;

[0060] 53... Hub sideflow path wall;

[0061] 54...side flow path wall of the protective cover;

[0062] 61...leading edge;

[0063] 62...posterior margin;

[0064] 63...pressure surface;

[0065] 64... Negative pressure surface;

[0066] 65... Wheel hub side end face;

[0067] 66...side end face of the protective cover;

[0068] 67... Inclined surface;

[0069] 67A... Side inclined surface of the protective cover;

[0070] 67B... Hub side slope surface;

[0071] 68...step section;

[0072] 68A...side step of the protective cover;

[0073] 68B...Rim side step section;

[0074] 71, 71A, 71B... one end;

[0075] 72, 72A, 72B...the other end;

[0076] 73...concave face;

[0077] 73A...Shield side concave curved face;

[0078] 73B...Concave curved surface on the side of the wheel hub;

[0079] 74A... Straight section of the protective cover side;

[0080] 74B...Straight section on the side of the wheel hub;

[0081] C...center of rotation;

[0082] CL... Blade thickness centerline;

[0083] The flow of fluids FL0, FL1...

[0084] L0, L1... curves;

[0085] R...direction of rotation;

[0086] SLA...speed loss zone;

[0087] T...throat;

[0088] TP...the throat area. Detailed Implementation

[0089] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. The dimensions, materials, shapes, and relative arrangements of the constituent components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0090] For example, expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" indicate relative or absolute configurations, not only in a strict sense, but also in a state of relative displacement by angle or distance with tolerance or to the extent that the same function can be obtained.

[0091] For example, expressions such as "same," "equal," and "homogeneous" that indicate the state of equality of things not only indicate a state of strict equality, but also indicate a state of difference in the degree to which the same function can be obtained due to the existence of tolerances.

[0092] For example, the descriptions of shapes such as quadrilaterals and cylindrical shapes not only refer to quadrilaterals and cylindrical shapes in a strict geometric sense, but also to shapes that include concave and convex parts, chamfered parts, etc., within the range where the same effect can be obtained.

[0093] On the other hand, expressions such as "possessing," "containing," or "having" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0094] It should be noted that for the same structure, sometimes the same reference numerals are used and the description is omitted.

[0095] (Centrifugal compressor)

[0096] Figure 1 This is a schematic cross-sectional view along the axial direction of one embodiment of a centrifugal compressor.

[0097] like Figure 1 As shown, the centrifugal compressor 1 of several embodiments includes an impeller 2, a housing 3 configured to house the impeller 2 as a rotatable structure, and a bladed diffuser 4 disposed inside the housing 3 on the downstream side of the impeller 2. It should be noted that the centrifugal compressor 1 of the present invention can be applied, for example, to turbochargers for automotive, marine, or industrial applications (e.g., for land-based power generation), other industrial centrifugal compressors, blowers, etc.

[0098] In the following description, the axial direction of impeller 2, that is, the direction of extension of the rotation center C of impeller 2, is sometimes referred to as ( Figure 1 The left-right direction is simply referred to as the axial direction. The upstream side of the flow of fluid flowing into the centrifugal compressor 1 in the axial direction ( Figure 1 The left side of the middle section is set as the upstream side of the axis, and its opposite side (downstream side) is set as the upstream side. Figure 1 The right side of the impeller 2 (centered on the center C) is designated as the downstream side of the axial direction. Sometimes the upstream side of the axial direction is called the shield side, and the downstream side is called the hub side. Additionally, the radial direction of the impeller 2, centered on the rotation center C, is sometimes simply referred to as the axial direction. The direction closest to the rotation center C in the radial direction is designated as the radial inner side, and the direction furthest from the rotation center C is designated as the radial outer side. Furthermore, the direction along the rotation direction of the impeller 2, centered on the rotation center C, is sometimes simply referred to as the circumferential direction.

[0099] In the following description, when referred to simply as the upstream side, it means the part or region related to the direction of flow that is upstream of the main flow direction of the fluid. Similarly, in the following description, when referred to simply as the downstream side, it means the part or region related to the direction of flow that is downstream of the main flow direction of the fluid.

[0100] (impeller)

[0101] like Figure 1 As shown, the impeller 2 includes a plurality of impeller blades 21 spaced apart circumferentially. The impeller 2 is supported by bearings (not shown) and the like so that it can rotate about a rotation center C. The impeller 2 is configured to guide fluid introduced axially from the axial upstream side relative to the impeller 2 radially outward by rotating about the rotation center C.

[0102] In the illustrated embodiment, the impeller 2 includes a hub 22 and the aforementioned plurality of impeller blades 21. The plurality of impeller blades 21 are vertically disposed on the outer surface 23 of the hub 22. Figure 1 In the axial section shown, the outer surface 23 of the hub 22 has an arc shape with a defined radius of curvature that increases in distance from the rotation center C as it moves from the upstream side of the axial direction toward the downstream side of the axial direction.

[0103] Each of the plurality of impeller blades 21 has its front end 24 positioned relative to the shroud surface 31, which is the inner surface of the housing 3, with a predetermined gap. That is, in several embodiments, the impeller 2 is configured as an open impeller, covering the outer periphery of the plurality of impeller blades 21 and without an annular shroud member (not shown) connected to the front end 24 of each of the plurality of impeller blades 21. It should be noted that in several embodiments, the impeller 2 of the centrifugal compressor 1 may not be an open impeller, but rather a closed impeller having the aforementioned annular shroud member.

[0104] (case)

[0105] like Figure 1 As shown, the housing 3 includes: a shield portion 32 having the shield surface 31 described above; a fluid inlet flow path forming portion 34 forming a fluid inlet flow path 33 for guiding fluid (e.g., air) introduced from the outside of the housing 3 to the impeller 2; and a vortex flow path forming portion 36 forming a vortex flow path 35 on the downstream side of the bladed diffuser 4.

[0106] The fluid inlet flow path 33 extends axially. The fluid inlet flow path 33 is formed at a position axially upstream of the impeller 2. The fluid inlet flow path forming portion 34 includes a fluid inlet flow path wall 341 defining the fluid inlet flow path 33. Fluid is guided from the outside of the housing 3 through the fluid inlet flow path 33 to the impeller 2 and compressed by the impeller 2. A vortex flow path 35 is formed on the outer peripheral side (radially outer side) of the impeller 2. The vortex flow path 35 is formed as a vortex extending circumferentially along the impeller 2. The vortex flow path 35... Figure 1 The cross-section shown has an arc shape along the axial direction. The vortex flow path forming part 36 includes a vortex flow path wall 361 that defines the vortex flow path 35.

[0107] (Leaf diffuser)

[0108] The bladed diffuser 4 includes a diffuser flow path forming section 5 that forms a diffuser flow path 50 on the downstream side of the impeller 2, and a plurality of diffuser blades 6 that are spaced apart in the circumferential direction of the impeller 2 in the diffuser flow path 50. A fluid inlet flow path 33, a diffuser flow path 50, and a vortex flow path 35 are formed inside the housing 3.

[0109] In the illustrated embodiment, the diffuser flow path 50 is formed as an annular shape extending circumferentially along the impeller 2. The downstream end (outer peripheral end) of the diffuser flow path 50 communicates with the vortex flow path 35. The vortex flow path 35... Figure 1 The cross-section shown is formed as a straight line extending radially. The fluid compressed by the impeller 2 is guided to the vortex flow path 35 through the flow path formed between adjacent diffuser blades 6 in the diffuser flow path 50.

[0110] The diffuser flow path forming section 5 includes a hub side surface 51 and a shield side surface 52 facing the hub side surface 51 across the diffuser flow path 50. The diffuser flow path forming section 5 has a hub-side flow path wall portion 53 with the hub side surface 51 and a shield-side flow path wall portion 54 with the shield side surface 52. The hub side surface 51 and the shield side surface 52 face the diffuser flow path 50. The hub side surface 51 defines the axial downstream side of the diffuser flow path 50, and the shield side surface 52 defines the axial upstream side of the diffuser flow path 50. The shield side surface 52 is located axially upstream of the hub side surface 51.

[0111] In the illustrated embodiment, the hub side 51 and the shield side 52 are each formed into annular shapes extending circumferentially along the impeller 2. The hub side 51 and the shield side 52 are respectively... Figure 1 The cross-section shown is formed as a straight line extending radially in the axial direction.

[0112] In the illustrated embodiment, the upstream end (inner peripheral end) of the shield side 52 is connected to the downstream end (outer peripheral end) of the shield surface 31. The downstream end (outer peripheral end) of the shield side 52 is connected to one end of the vortex flow path wall 361. The downstream end (outer peripheral end) of the hub side 51 is connected to the other end of the vortex flow path wall 361 located axially downstream of the aforementioned end.

[0113] It should be noted that, in Figure 1 In the diagram, the diffuser flow path forming section 5 is marked with a shading line different from other parts of the housing 3, such as the vortex flow path forming section 36, for convenience. However, the housing 3 may also be composed of multiple housing components connected at any point independent of the boundary position of the diffuser flow path forming section 5 and other parts of the housing 3. For example, the housing 3 may also include a compressor housing that houses the impeller 2 and a bearing housing that houses the bearing that supports the impeller 2 for rotation.

[0114] (Diffuser blades)

[0115] Figure 2 This is a schematic diagram showing the state of a leaf diffuser of one embodiment as viewed from the axial upstream side. Figure 3 This is a schematic perspective view of a leaf diffuser according to one embodiment.

[0116] like Figure 2 As shown, the plurality of diffuser blades 6 each have a radially inner end, i.e., a leading edge 61, a radially outer end, i.e., a trailing edge 62, a pressure surface 63 extending from the leading edge 61 to the trailing edge 62, and a negative pressure surface 64 extending from the leading edge 61 to the trailing edge 62. The leading edge 61, trailing edge 62, pressure surface 63, and negative pressure surface 64 each face the diffuser flow path 50. The negative pressure surface 64 is positioned on the opposite side from the pressure surface 63 relative to the blade thickness centerline CL passing through the center of the blade thickness of the diffuser blade 6.

[0117] In the illustrated embodiment, the trailing edge 62 of each of the plurality of diffuser blades 6 is positioned downstream of the leading edge 61 in the rotational direction R of the impeller 2. The plurality of diffuser blades 6 are respectively inclined such that they are located downstream of the leading edge 61 in the rotational direction R of the impeller 2. The pressure surface 63 of the diffuser blade 6 is located upstream of the impeller 2 in the rotational direction R, and the negative pressure surface 64 of the diffuser blade 6 is located downstream of the impeller 2 in the rotational direction R.

[0118] like Figure 3 As shown, in a pair of circumferentially adjacent diffuser blades 6, 6, the negative pressure surface 64 of the diffuser blade 6 located upstream in the rotation direction R of the impeller 2 faces the pressure surface 63 of the diffuser blade 6 located downstream in the rotation direction R of the impeller 2. The position where the flow path area between the pair of diffuser blades 6, 6 is minimized is called the throat T. Figure 3 In the diagram, a dashed line is used to represent an imaginary line extending from the other diffuser blade 6 to the first diffuser blade 6 along the region where the throat T exists. In the illustrated embodiment, the throat T is provided between the leading edge 61 of the other diffuser blade 6 and the negative pressure surface 64 of the first diffuser blade 6.

[0119] In the following description, the position corresponding to the throat T in the direction extending from the blade thickness centerline CL of diffuser blade 6 is referred to as the throat position TP. For example... Figure 3 As shown, the intersection of the blade thickness centerline CL of the aforementioned diffuser blade 6 and the straight line obtained by extending the aforementioned imaginary line that extends along the region where the throat T exists can also be set as the throat position TP of the aforementioned diffuser blade 6.

[0120] like Figure 1 , Figure 3 As shown, each of the multiple diffuser blades 6 also has an axial downstream end face, i.e., a hub-side end face 65, and an axial upstream end face, i.e., a shield-side end face 66. The hub-side end face 65 of each of the multiple diffuser blades 6 is connected to the hub side surface 51, and the shield-side end face 66 is connected to the shield side surface 52.

[0121] (Incision area)

[0122] Figure 4 This is a schematic cross-sectional view of a leafed diffuser according to one embodiment. Figure 4 And then Figure 11 , Figures 14-16 The diagram schematically shows a meridional section along the axial direction of the impeller 2 in the bladed diffuser 4. (See diagram for reference.) Figure 3 , Figure 4 As shown, at least one diffuser blade 6A among the plurality of diffuser blades 6 described above has at least one cutout 7 formed between the hub side 51 and the shield side 52.

[0123] In the following description, diffuser blade 6A is one of a plurality of diffuser blades 6 that has a notch 7 formed. Figure 3 As shown, cutouts 7 can be formed in two or more of the multiple diffuser blades 6 provided in the diffuser flow path 50, or cutouts 7 can be formed in all of the diffuser blades 6 provided in the diffuser flow path 50.

[0124] like Figure 4 As shown, at least one cutout 7 formed on the diffuser blade 6A has one end 71 at a position including one end 611 of the leading edge portion 61 extending along the blade height direction from the hub-side end face 65 of the diffuser blade 6A toward the shroud-side end face 66, and the cutout height of the cutout 7 decreases toward the trailing edge portion 62 of the diffuser blade 6A. The blade height direction of the diffuser blade 6A extends along the axial direction of the impeller 2.

[0125] At least one of the aforementioned cutout portions 7 has one end 72 formed on the trailing edge 62 side (downstream side) of the cutout portion 7 along the blade length direction of the blade thickness centerline CL of the diffuser blade 6A.

[0126] Each diffuser blade 6A includes an inclined surface 67 formed by at least one of the aforementioned cutouts 7. One end 671 of the inclined surface 67 is formed at one end 611 of the leading edge 61 of the diffuser blade 6A. The other end 672 of the inclined surface 67 is formed on the trailing edge 62 side (downstream side) of the diffuser blade 6A in the blade length direction. The gap (cutout height of the cutout 7) between the inclined surface 67 and either the hub side surface 51 or the shield side surface 52, which are opposite the cutout 7, decreases as it moves from one end 671 toward the other end 672.

[0127] In the illustrated embodiment, the at least one cutout 7 includes a shield-side cutout 7A formed between the diffuser blade 6A and the shield side surface 52, and a hub-side cutout 7B formed between the diffuser blade 6A and the hub side surface 51. The inclined surface 67 of the diffuser blade 6A includes a shield-side inclined surface 67A formed by the shield-side cutout 7A, and a hub-side inclined surface 67B formed by the hub-side cutout 7B.

[0128] For the shield-side cutout 7A, one end 71A of the shield-side cutout 7A is formed at the axial upstream end 611A, which includes the leading edge 61, and the other end 72A of the shield-side cutout 7A is formed on the trailing edge 62 side (downstream side) of the diffuser blade 6A in the blade length direction. Each diffuser blade 6A includes a shield-side inclined surface 67A formed by the shield-side cutout 7A. For the shield-side inclined surface 67A, one end 671A of the shield-side inclined surface 67A is formed at the axial upstream end 611A, and the other end 672A of the shield-side inclined surface 67A is formed on the trailing edge 62 side (downstream side) of the diffuser blade 6A in the blade length direction.

[0129] The gap (cut height of the side cut 7A) between the inclined surface 67A of the shield and the side surface 52 of the shield opposite the side cut 7A of the shield decreases as it moves from one end 671A toward the other end 672A. Figure 4 In the illustrated embodiment, the cut height of the shroud-side inclined surface 67A linearly decreases toward the trailing edge 62 of the diffuser blade 6A in at least a portion of the interval from one end 671A to the other end 672A (in the illustrated example, the interval from one end 671A to the other end 672A). In this case, the shroud-side inclined surface 67A is formed in such a linearly decreasing manner that it is easy to manufacture a diffuser blade 6A having the shroud-side inclined surface 67A.

[0130] For the hub-side cutout 7B, one end 71B of the hub-side cutout 7B is formed at the end 611, which includes the leading edge 61, i.e., the axially downstream end 611B. The other end 72B of the hub-side cutout 7B is formed on the trailing edge 62 side (downstream side) of the diffuser blade 6A in the blade length direction. Each diffuser blade 6A includes a hub-side inclined surface 67B formed by the hub-side cutout 7B. For the hub-side inclined surface 67B, one end 671B of the hub-side inclined surface 67B is formed at the axially downstream end 611B, and the other end 672B of the hub-side inclined surface 67B is formed on the trailing edge 62 side (downstream side) of the diffuser blade 6A in the blade length direction.

[0131] The gap (cut height of the wheel hub side cut 7B) between the inclined surface 67B of the wheel hub and the side surface 51 of the wheel hub, which is opposite the wheel hub side cut 7B, decreases as the wheel hub side slopes from one end 671B toward the other end 672B. Figure 4 In the illustrated embodiment, the hub-side inclined surface 67B, within at least a portion of the interval from one end 671B to the other end 672B (in the example shown, the interval from one end 671B to the other end 672B), has a cut height that linearly decreases toward the trailing edge 62 of the diffuser blade 6A. In this case, the hub-side inclined surface 67B is formed in such a linearly decreasing manner that it is easy to manufacture a diffuser blade 6A having the hub-side inclined surface 67B.

[0132] (Comparative example: leaf diffuser)

[0133] Figure 5 This is a schematic cross-sectional view of a comparative example of a leafed diffuser. Figure 5 The diagram schematically shows a meridional section along the axial direction of the impeller 2 in the bladed diffuser 04. Figure 5 As shown, the comparative example of the bladed diffuser 04 includes a diffuser flow path forming portion 5 that forms the diffuser flow path 50 described above and includes a hub side 51 and a shield side 52, and a plurality of diffuser blades 06 that are spaced apart in the circumferential direction of the impeller 2 in the diffuser flow path 50.

[0134] Each of the plurality of diffuser blades 06, unlike the diffuser blade 6A described above, does not have at least one of the aforementioned cutouts 7 (7A, 7B). The axial upstream end 0611A of the leading edge portion 061 of each of the plurality of diffuser blades 06 is connected to the upstream end (inner circumferential end) of the shield side end face 066, and the region of the shield side end face 066 including the upstream end of the shield side end face 066 is connected to the shield side surface 52. The axial downstream end 0611B of the leading edge portion 061 of each of the plurality of diffuser blades 06 is connected to the upstream end (inner circumferential end) of the hub side end face 065, and the region of the hub side end face 065 including the upstream end of the hub side end face 065 is connected to the hub side surface 51.

[0135] Figure 6 This is an explanatory diagram used to illustrate the flow of fluid in a leafed diffuser of a comparative example. Figure 7 This is an explanatory diagram used to illustrate the velocity loss within the diffuser flow path of the leaf diffuser in the comparative example.

[0136] In the comparative example of the leaf diffuser 04, such as Figure 6 As shown, the flow FL0 of the fluid that may flow in the diffuser flow path 50 abruptly bends towards the negative pressure surface 064 of the diffuser blade 06 near the shroud side of the leading edge 061 of the diffuser blade 06, becoming a low-energy fluid and flowing towards the pressure surface 063 of the adjacent diffuser blade 06. Due to the interference between the aforementioned low-energy fluid and the mainstream flow on the pressure surface 063 side of the adjacent diffuser blade 06, a large stripping occurs, thereby forming a velocity loss region SLA (see reference) between adjacent diffuser blades 06, 06 in the diffuser flow path 50. Figure 7 Due to the formation of the velocity loss region SLA, the velocity loss of the fluid within the diffuser flow path 50 increases, which may impair the static pressure recovery performance of the leaf diffuser 04.

[0137] (The effect of the incision)

[0138] Figure 8 It is used for explanation Figure 4 Explanatory diagrams showing the entry angles of the louvered diffuser and the comparative louvered diffuser. Figure 8 The diagram shows a graph with the span of the diffuser flow path 50 as the horizontal axis and the difference between the blade angle of the diffuser blades (6, 06) and the flow angle of the fluid, i.e., the entry angle, as the vertical axis. Regarding... Figure 8 The span is set as follows: Wheel hub side 51 is set to 0, and guard side 52 is set to 1. Regarding... Figure 8 The ideal entry angle is 0 degrees, preferably close to 0 degrees. Figure 8 The graph shows curve L0, which represents the relationship between the span and the entry angle of the leaf diffuser 04 in the comparative example, and curve L0, which represents the relationship between the span and the entry angle of the leaf diffuser 04 in the comparative example. Figure 4The curve L1 shows the relationship between the span of the leaf diffuser 4 and the angle of entry in the illustrated embodiment. (As shown...) Figure 8 As shown, the leaf diffuser 4 has diffuser blades 6A with at least one cutout 7 as described above, thus improving the entry angle compared to the leaf diffuser 04 of the comparative example. In particular, the entry angle near the shield side is effectively improved by the shield-side cutout 7A.

[0139] Figure 9 It is used for explanation Figure 4 A diagram illustrating the flow of fluid in a leafed diffuser. Figure 10 It is used for explanation Figure 4 A diagram illustrating the velocity loss within the diffuser flow path of a leaf diffuser.

[0140] Compared to the comparative example of the lobed diffuser 04, the lobed diffuser 4 improves the entry angle, thus improving the fluid flow within the diffuser flow path 50. In the lobed diffuser 4, as... Figure 9 As shown, the following situation can be suppressed: the flow FL1 of the fluid flowing in the diffuser flow path 50 bends towards the negative pressure surface 64 of the diffuser blade 6A near the shroud side of the leading edge 61 of the diffuser blade 6A, thereby causing the fluid to become a low-energy fluid and flow towards the pressure surface 63 of the adjacent diffuser blade 6A. Thus, as... Figure 10 As shown, it is possible to suppress the formation of the aforementioned velocity loss region SLA between adjacent diffuser blades 6A, 6A in the diffuser flow path 50 (see reference). Figure 7 ).

[0141] like Figure 1 As shown, several embodiments of the leaf diffuser 4 include a diffuser flow path forming section 5 that forms the diffuser flow path 50 described above, and a plurality of diffuser blades 6 described above. Figure 4 As shown, at least one diffuser blade 6A among a plurality of diffuser blades 6 has at least one cutout 7 (7A, 7B) formed between the hub side surface 51 and the shield side surface 52. The at least one cutout 7 (7A, 7B) is formed at one end 71 of the cutout 7 at a position including the leading edge 61 of the diffuser blade 6A, and the cutout height of the cutout 7 decreases as it moves toward the trailing edge 62 of the diffuser blade 6A.

[0142] According to the above structure, by forming a notch 7 in the diffuser blade 6A, the difference between the blade angle of the diffuser blade 6A and the flow angle of the fluid, i.e., the entry angle, can be improved, thereby improving the flow of fluid within the diffuser flow path 50. Specifically, by forming a notch 7 in the diffuser blade 6A, the flow of fluid near the leading edge 61 of the diffuser blade 6A can be prevented from bending towards the negative pressure surface 64 of the diffuser blade 6A, and the flow of the fluid as a low-energy fluid towards the pressure surface 63 of the adjacent diffuser blade 6B, thus preventing the formation of a velocity loss region (SLA). Therefore, according to the above structure, by forming a notch 7 in the diffuser blade 6A, the velocity loss of the fluid within the diffuser flow path 6A can be reduced, thereby improving the static pressure recovery performance of the bladed diffuser 4.

[0143] In several implementations, such as Figure 4 As shown, the other end 72 (72A, 72B) of at least one of the above-mentioned cut portions 7 (7A, 7B) is formed at a position on the leading edge 61 side of the throat position TP of the diffuser blade 6A.

[0144] like Figure 4 As shown, the other end 72A of the shield side cutout 7A (the other end 672A of the shield side inclined surface 67A) and the other end 72B of the hub side cutout 7B (the other end 672B of the hub side inclined surface 67B) are formed on the blade length direction along the blade thickness centerline CL of the diffuser blade 6A at a position closer to the leading edge 61 than the throat position TP of the diffuser blade 6A.

[0145] According to the above structure, by forming the other end 72 of the cut portion 7 at a position closer to the leading edge 61 than the throat position TP of the diffuser blade 6A, the velocity loss of the fluid in the diffuser flow path 50 caused by the cut portion 7 can be reduced, and the cut amount of the diffuser blade 6A can be made smaller. By making the cut amount of the diffuser blade 6A smaller, leakage from the pressure surface 63 to the negative pressure surface 64 of the diffuser blade 6A via the cut portion 7 can be suppressed, thereby improving the static pressure recovery performance in the leaf diffuser 4.

[0146] Furthermore, according to the above structure, the throat position TP of the diffuser blade 6A is not cut by the cut-out portion 7, so the throat area in the diffuser flow path 50 is maintained relative to the diffuser blade 6 without the cut-out portion 7. Therefore, even if the diffuser blade 6A has the cut-out portion 7, the throat area can be maintained, thereby suppressing changes in the flow characteristics of the centrifugal compressor 1.

[0147] like Figure 4 As shown, the blade thickness centerline CL (refer to) is drawn along the blade thickness centerline CL from the leading edge 61 of the diffuser blade 6A toward the throat position TP. Figure 2The blade length position of the leading edge 61 in the blade length direction is set to 0%, and the blade length position of the throat TP in the blade length direction is set to 100%.

[0148] In several implementations, such as Figure 4 As shown, the other end 72 (72A, 72B) of at least one of the aforementioned cutouts 7 (7A, 7B) is formed within a range of 30 to 70% of the blade length. The other end 672A of the shield side inclined surface 67A and the other end 672B of the hub side inclined surface 67B are also formed within a range of 30 to 70% of the blade length.

[0149] If the length of the cut portion 7 in the blade length direction is too short, it may be difficult to achieve the reduction effect of fluid velocity loss in the diffuser flow path 50 caused by the cut portion 7. Conversely, if the length of the cut portion 7 in the blade length direction is too long, leakage from the pressure surface 63 to the negative pressure surface 64 of the diffuser blade 6A via the cut portion 7 may increase. According to the above structure, by forming the other end 72 of the cut portion 7 within a range of 30-70% of the blade length, the reduction effect of fluid velocity loss in the diffuser flow path 50 caused by the cut portion 7 can be effectively achieved, and the cut amount of the diffuser blade 6A can be kept small. Therefore, the leakage via the cut portion 7 can be suppressed, thereby improving the static pressure recovery performance in the bladed diffuser 4.

[0150] In several implementations, such as Figure 4 As shown, at least one cutout 7 of the diffuser blade 6A includes a shield-side cutout 7A formed between the diffuser blade 6A and the shield side 52.

[0151] According to the above structure, by forming a shroud-side cutout 7A on the diffuser blade 6A, the entry angle on the shroud side (axial downstream side) can be improved, thereby improving the flow of fluid on the shroud side within the diffuser flow path 50. By improving the flow of fluid on the shroud side within the diffuser flow path 50, the velocity loss of the fluid on the shroud side within the diffuser flow path 50 can be reduced, thereby improving the static pressure recovery performance in the bladed diffuser 4.

[0152] In several implementations, such as Figure 4 As shown, at least one cutout 7 of the diffuser blade 6A includes a hub-side cutout 7B formed between the diffuser blade 6A and the hub side 51.

[0153] According to the above structure, by forming a hub-side cutout 7B in the diffuser blade 6A, the entry angle on the hub side (upstream side in the axial direction) can be improved, thereby improving the flow of fluid on the hub side within the diffuser flow path 50. By improving the flow of fluid on the hub side within the diffuser flow path 50, the velocity loss of the fluid on the hub side within the diffuser flow path 50 can be reduced, thereby improving the static pressure recovery performance in the bladed diffuser 4.

[0154] In several implementations, such as Figure 4 As shown, at least one cutout 7 of the diffuser blade 6A includes the aforementioned shield-side cutout 7A and the aforementioned hub-side cutout 7B.

[0155] According to the above structure, by forming the shroud-side cutout 7A and the hub-side cutout 7B on the diffuser blade 6A, the entry angles on the shroud side and hub side can be improved, thereby improving the fluid flow on the shroud side and hub side within the diffuser flow path 50. Compared to forming either the shroud-side cutout 7A or the hub-side cutout 7B on the diffuser blade 6A, the velocity loss of the fluid within the diffuser flow path 50 can be effectively reduced, thereby effectively improving the static pressure recovery performance of the leaf diffuser 4.

[0156] like Figure 4 As shown, the blade height position of the hub-side end face 65 in the blade height direction of the diffuser blade 6A is set to 0%, and the blade height position of the shroud-side end face 66 in the blade height direction is set to 100%. In several embodiments, such as Figure 4 As shown, the aforementioned side cutout 7A of the protective cover is formed in the range of 80-100% of the blade height.

[0157] If the length of the cut portion 7 in the blade height direction is too short, it may be difficult to achieve the reduction effect of fluid velocity loss in the diffuser flow path 50 caused by the cut portion 7. Conversely, if the length of the cut portion 7 in the blade height direction is too long, leakage from the pressure surface 63 to the negative pressure surface 64 of the diffuser blade 6A via the cut portion 7 may increase. According to the above structure, by forming the shroud-side cut portion 7A within the range of 80-100% of the blade height, the reduction effect of fluid velocity loss in the diffuser flow path 50 caused by the shroud-side cut portion 7A can be effectively achieved, and the cut amount of the diffuser blade 6A can be kept small. Therefore, the aforementioned leakage via the shroud-side cut portion 7A can be suppressed, thereby improving the static pressure recovery performance in the bladed diffuser 4.

[0158] In several implementations, such as Figure 4 As shown, the aforementioned hub-side cutout 7B is formed within a range of 0 to 20% of the blade height.

[0159] According to the above structure, by forming the hub-side cutout 7B within a range of 0-20% of the blade height, the velocity loss of the fluid in the diffuser flow path 50 caused by the hub-side cutout 7B can be effectively reduced, and the cutout amount of the diffuser blade 6A can be made smaller. Therefore, the aforementioned leakage through the hub-side cutout 7B can be suppressed, thereby improving the static pressure recovery performance in the bladed diffuser 4.

[0160] (Concave face)

[0161] Figure 11 This is a schematic cross-sectional view of a leaf diffuser according to one embodiment.

[0162] In several implementations, such as Figure 11 As shown, at least one of the above-mentioned cut portions 7 (7A, 7B) includes a concave curved surface 73 formed in such a way as to connect one end 71 of the cut portion 7 to the other end 72.

[0163] exist Figure 11 In the diagram, a hypothetical straight section 74A of the shield-side cutout 7A is indicated by a double-dotted line, representing the cut height of the shield-side cutout 7A that linearly decreases from one end 71A toward the other end 72A. The shield-side cutout 7A includes the aforementioned concave curved surface 73, i.e., the shield-side concave curved surface 73A, formed in a manner connecting one end 71A and the other end 72A. The shield-side concave curved surface 73A has a concave curved surface shape that is recessed axially upstream of the hypothetical straight section 74A.

[0164] like Figure 11 As shown, the inclined surface 67A of the shield side has a convex curved surface shape that protrudes axially upstream from one end 671A to the other end 672A in at least a portion of the interval from one end 671A to the other end 672A (in the example shown, the interval from one end 671A to the other end 672A). Figure 11 As shown, the inclined surface 67A of the shield side may also have a convex curved surface shape in which the rate of decrease of the cut height of the shield side cut portion 7A at predetermined intervals in the blade length direction gradually decreases from one end 671A toward the other end 672A.

[0165] exist Figure 11 In the diagram, a hypothetical straight section 74B of the hub-side cutout 7B is represented by a double-dotted line, indicating that the cut height of the hub-side cutout 7B decreases linearly from one end 71B towards the other end 72B. The hub-side cutout 7B includes the aforementioned concave curved surface 73, i.e., the hub-side concave curved surface 73B, formed in a manner connecting one end 71B and the other end 72B. The hub-side concave curved surface 73B has a concave curved surface shape that is recessed axially downstream than the hypothetical straight section 74B.

[0166] like Figure 11 As shown, the hub-side inclined surface 67B has a convex curved surface shape that protrudes axially downstream from at least a portion of the interval from one end 671B to the other end 672B (in the example shown, the interval from one end 671B to the other end 672B). Figure 11 As shown, the hub side inclined surface 67B may also have a convex curved surface shape in which the rate of decrease of the cut height of the hub side cut portion 7B gradually decreases at predetermined intervals in the blade length direction from one end 671B toward the other end 672B.

[0167] Based on the above structure, the velocity loss of the fluid within the diffuser flow path 50 can be reduced due to the cut portion 7 including the concave curved surface 73. Furthermore, compared to cases where one end 71 and the other end 72 are cut in a straight line, the cut portion 7 including the concave curved surface 73 allows for a smaller cut size. By reducing the cut size of the diffuser blade 6A, leakage from the pressure surface 63 to the negative pressure surface 64 of the diffuser blade 6A via the cut portion 7 can be suppressed, thus improving the static pressure recovery performance in the leaf diffuser 4.

[0168] In several implementations, such as Figure 4 , Figure 11 As shown, the diffuser blade 6A includes an inclined surface 67 formed by at least one of the above-mentioned cutouts 7, and a stepped portion 68 formed between the upstream ends 651 and 661 of either the hub-side end face 65 or the shield-side end face 66 of the diffuser blade 6A and the other end 672 of the inclined surface 67.

[0169] like Figure 4 , Figure 11 As shown, the diffuser blades 6A each include the aforementioned shroud-side inclined surface 67A and a shroud-side stepped portion 68A formed between the upstream end 661 of the shroud-side end face 66 and the other end 672A of the shroud-side inclined surface 67A. The shroud-side stepped portion 68A extends axially. The axial upstream end of the shroud-side stepped portion 68A is connected to the upstream end 661 of the shroud-side end face 66. The axial downstream end of the shroud-side stepped portion 68A is connected to the other end 672A of the shroud-side inclined surface 67A.

[0170] like Figure 4 , Figure 11As shown, the diffuser blades 6A each include the aforementioned hub-side inclined surface 67B and a hub-side stepped portion 68B formed between the upstream end 651 of the hub-side end face 65 and the other end 672B of the hub-side inclined surface 67B. The hub-side stepped portion 68B extends axially. The axial upstream end of the hub-side stepped portion 68B is connected to the other end 672B of the hub-side inclined surface 67B. The axial downstream end of the hub-side stepped portion 68B is connected to the upstream end 651 of the hub-side end face 65. The stepped portion 68 includes a shroud-side stepped portion 68A and a hub-side stepped portion 68B.

[0171] According to the above structure, by providing a step portion 68 in the diffuser blade 6A, the cut amount of the diffuser blade 6A can be reduced compared to the case where the inclined surface 67 is extended without providing the step portion 68. By reducing the cut amount of the diffuser blade 6A, leakage from the pressure surface 63 to the negative pressure surface 64 of the diffuser blade 6A via the cut portion 7 can be suppressed, thereby improving the static pressure recovery performance in the leaf diffuser 4. In addition, according to the above structure, by providing a step portion 68 in the diffuser blade 6A, the inclined surface 67 is supported by the step portion 68, thereby improving the vibration intensity of the diffuser blade 6A compared to the case where the step portion 68 is not provided.

[0172] Figure 12 and Figure 13 These are schematic perspective views of the diffuser blades of a leaf diffuser according to one embodiment.

[0173] In several implementations, such as Figure 12 As shown, the stepped portions 68 (68A, 68B) described above have a profile shape that protrudes towards the upstream side (radially inward) when viewed from one side in the blade height direction. In the illustrated embodiment, the upstream end 651 of the hub-side end face 65, the upstream end 661 of the shroud-side end face 66, the other end 672B of the hub-side inclined surface 67B, and the other end 672A of the shroud-side inclined surface 67A each have a profile shape that protrudes towards the upstream side (radially inward) when viewed from one side in the blade height direction. Figure 12 As shown, the aforementioned stepped portions 68 (68A, 68B) may also have an arc-shaped (e.g., semi-circular) profile that protrudes towards the upstream side (radially inward) when viewed from one side in the blade height direction. Furthermore, the upstream end 651 of the hub-side end face 65, the upstream end 661 of the shield-side end face 66, the other end 672B of the hub-side inclined surface 67B, and the other end 672A of the shield-side inclined surface 67A may also have an arc-shaped (e.g., semi-circular) profile that protrudes towards the upstream side (radially inward) when viewed from one side in the blade height direction.

[0174] According to the above structure, by setting the stepped portion 68 of the diffuser blade 6A to have a profile shape that protrudes towards the upstream side, the surface of the stepped portion 68 can be smoothed. By smoothing the surface of the stepped portion 68, the flow of fluid can be suppressed from being stripped from the diffuser blade 6A, thereby reducing the velocity loss of the fluid in the diffuser flow path 50 and improving the static pressure recovery performance in the leaf diffuser 4.

[0175] In several implementations, such as Figure 13 As shown, the aforementioned stepped portions 68 (68A, 68B), when viewed from one side in the blade height direction, have a rectangular outline shape including an upstream end face 681 (681A, 681B) extending along the blade height direction. One end of the upstream end face 681 (681A, 681B) of the aforementioned stepped portions 68 (68A, 68B) in the blade height direction is connected to a pressure surface 63 extending downstream in the blade length direction, and the other end of the upstream end face 681 (681A, 681B) in the blade height direction is connected to a negative pressure surface 64 extending downstream in the blade length direction.

[0176] Based on the above structure, by setting the step portion 68 of the diffuser blade 6A to a shape having the outline shape of the rectangular shape described above, the formation of the step portion 68 becomes easy, and thus the diffuser blade 6A is easy to manufacture.

[0177] Figure 14 This is a schematic cross-sectional view of a leaf diffuser according to one embodiment.

[0178] In several implementations, such as Figure 14 As shown, the other end 672 of the inclined surface 67 of each of the diffuser blades 6A can also be connected to the upstream end (inner circumferential end) 651, 661 of either the hub-side end face 65 or the shield-side end face 66 of the diffuser blade 6A. That is, the stepped portion 68 (68A, 68B) may not be formed in each of the diffuser blades 6A.

[0179] In the illustrated embodiment, the other end 672A of the inclined surface 67A on the shield side of each diffuser blade 6A is connected to the upstream end 661 of the shield side end face 66.

[0180] In addition, the other end 672B of the hub-side inclined surface 67B of each diffuser blade 6A is connected to the upstream end 651 of the hub-side end face 65.

[0181] Based on the above structure, it is also possible to reduce the velocity loss of the fluid in the diffuser flow path 50 caused by the above-mentioned cut-out portion 7.

[0182] Figure 15 and Figure 16These are schematic cross-sectional views of a leafed diffuser according to one embodiment. In several embodiments, such as... Figure 15 As shown, the diffuser blades 6A described above have the aforementioned shield-side cutout 7A and the aforementioned hub-side cutout 7B. The other end 72A of the shield-side cutout 7A is formed at a position closer to the rear edge 62 than the other end 72B of the hub-side cutout 7B.

[0183] like Figure 15 As shown, in the blade length direction along the blade thickness centerline CL of the diffuser blade 6A, the other end 72A of the shroud-side cutout 7A (the other end 672A of the shroud-side inclined surface 67A) is formed at a position closer to the trailing edge 62 than the other end 72B of the hub-side cutout 7B (the other end 672B of the hub-side inclined surface 67B). Therefore, the cut amount of the shroud-side cutout 7A (the volume of the cutout 7 from one end 71 to the other end 72) is larger than that of the hub-side cutout 7B. It should be noted that, as... Figure 15 As shown, the cut height at one end 71A of the side cutout 7A of the guard can also be formed to be the same size as the cut height at one end 71B of the side cutout 7B of the wheel hub.

[0184] When the impeller 2 of the centrifugal compressor 1 is configured as an open impeller, the velocity loss of the fluid on the shroud side within the diffuser flow path 50 becomes a problem. According to the above structure, by forming the other end 72A of the shroud-side cutout 7A at a position further along the trailing edge 62 than the other end 72B of the hub-side cutout 7B, the cut amount of the shroud-side cutout 7A can be made larger. This effectively reduces the velocity loss of the fluid on the shroud side within the diffuser flow path 50, thus improving the static pressure recovery performance in the vaned diffuser 4 for the centrifugal compressor 1 with the open impeller 2.

[0185] In several implementations, such as Figure 16 As shown, the diffuser blades 6A described above have the aforementioned shield-side cutout 7A and the aforementioned hub-side cutout 7B. The cutout height at one end 71A of the shield-side cutout 7A is greater than the cutout height at one end 71B of the hub-side cutout 7B.

[0186] like Figure 16 As shown, the gap between one end 671A of the guard side inclined surface 67A and the guard side surface 52 (the cut height at one end 71A) is formed to be larger than the gap between one end 671B of the hub side inclined surface 67B and the hub side surface 51 (the cut height at one end 71B). As a result, the cut amount of the guard side cut portion 7A (the volume of the cut portion 7 from one end 71 to the other end 72) is larger than that of the hub side cut portion 7B.

[0187] exist Figure 16In the illustrated embodiment, the diffuser blades 6A described above, within the range from one end 671A to the other end 672A of the inclined surface 67A on the shroud side along the blade length direction of the diffuser blade 6A, have a cut height on the shroud side cut 7A that is greater than the cut height on the hub side cut 7B at the corresponding blade length position. It should be noted that, as... Figure 16 As shown, the other end 72A of the shield side cutout 7A (the other end 672A of the shield side inclined surface 67A) can also be formed in the same position as the other end 72B of the hub side cutout 7B (the other end 672B of the hub side inclined surface 67B) in the blade length direction along the blade thickness centerline CL of the diffuser blade 6A.

[0188] According to the above structure, by making the cut height at one end 71A of the shroud-side cut 7A larger than the cut height at one end 71B of the hub-side cut 7B, the cut amount of the shroud-side cut 7A can be made larger. This effectively reduces the velocity loss of the fluid on the shroud side within the diffuser flow path 50, thus improving the static pressure recovery performance in the vaned diffuser 4 for the centrifugal compressor 1 equipped with the open impeller 2.

[0189] like Figure 1 As shown, the centrifugal compressor 1 in several embodiments includes the impeller 2 and the vaned diffuser 4 described above. According to the above structure, by forming a notch 7 in the diffuser blades 6A, the velocity loss of the fluid within the diffuser flow path 50 can be reduced, thus improving the static pressure recovery performance in the vaned diffuser 4. By improving the static pressure recovery performance in the vaned diffuser 4, the efficiency of the centrifugal compressor 1 can be improved.

[0190] The present invention is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations thereof.

[0191] The contents described in the above-described embodiments shall be understood as follows.

[0192] 1) In at least one embodiment of the present invention, a vane diffuser (4) is disposed downstream of the impeller (2) of a centrifugal compressor (1), wherein,

[0193] The leaf diffuser (4) comprises:

[0194] A diffuser flow path forming section (5) forms a diffuser flow path (50) on the downstream side of the impeller (2), and the diffuser flow path forming section (5) includes a hub side surface (51) and a shield side surface (52) opposite to the hub side surface (51) across the diffuser flow path (50); and

[0195] Multiple diffuser blades (6) are arranged circumferentially spaced in the diffuser flow path (50) of the impeller (2).

[0196] At least one diffuser blade (6A) among the plurality of diffuser blades (6) is formed with at least one cutout (7) between the hub side (51) and the shield side (52). The cutout (7) is formed at one end (71) of the leading edge (61) of the diffuser blade (6A) extending along the blade height direction, and the cutout height of the cutout (7) decreases as it moves toward the trailing edge (62) of the diffuser blade (6A).

[0197] According to the structure described in 1), by forming the aforementioned cutout (7) on the diffuser blade (6A), the difference between the blade angle of the diffuser blade (6A) and the flow angle of the fluid, i.e., the entry angle, can be improved, thereby improving the flow of fluid within the diffuser flow path (50). Specifically, by forming the aforementioned cutout (7) on the diffuser blade (6A), the following situation can be suppressed: the flow of fluid near the leading edge (61) of the diffuser blade (6A) bends towards the negative pressure surface (64) of the diffuser blade (6A), thereby causing the fluid to become a low-energy fluid and flow towards the pressure surface (63) of the adjacent diffuser blade (6B), forming a velocity loss region. Therefore, according to the structure described in 1), by forming the aforementioned cutout (7) on the diffuser blade (6A), the velocity loss of the fluid within the diffuser flow path (50) can be reduced, thereby improving the static pressure recovery performance in the bladed diffuser (4).

[0198] 2) In several embodiments, based on the leaf diffuser (4) described in 1) above,

[0199] The other end (72) of the at least one cut (7) is formed at a position closer to the leading edge (61) than the throat position (TP) of the diffuser blade (6A).

[0200] According to the structure described in 2), by forming the other end (72) of the cut portion (7) at a position closer to the leading edge (61) than the throat position (TP) of the diffuser blade (6A), the velocity loss of the fluid in the diffuser flow path (50) caused by the cut portion (7) can be reduced, and the cut amount of the diffuser blade (6A) can be made smaller. By making the cut amount of the diffuser blade (6A) smaller, leakage from the pressure surface (63) of the diffuser blade (6A) to the negative pressure surface (64) via the cut portion (7) can be suppressed, thereby improving the static pressure recovery performance in the bladed diffuser (4).

[0201] Furthermore, according to the structure described in 2), the throat position (TP) of the diffuser blade (6A) is not cut by the cut-out portion (7), so the throat area in the diffuser flow path (50) is maintained relative to the diffuser blade (6) without the cut-out portion (7). Therefore, even if the diffuser blade (6A) has the cut-out portion (7), the throat area can be maintained, thus suppressing changes in the flow characteristics of the centrifugal compressor (1).

[0202] 3) In several embodiments, based on the leaf diffuser (4) described in 1) or 2) above,

[0203] The at least one cutout (7) includes a shield-side cutout (7A) formed between the diffuser blade (6A) and the shield side (52).

[0204] According to the structure described in 3), by forming the aforementioned shroud-side cutout (7A) on the diffuser blade (6A), the entry angle on the shroud side (downstream side) can be improved, thereby improving the flow of fluid on the shroud side within the diffuser flow path (50). By improving the flow of fluid on the shroud side within the diffuser flow path (50), the velocity loss of fluid on the shroud side within the diffuser flow path (50) can be reduced, thereby improving the static pressure recovery performance in the bladed diffuser (4).

[0205] 4) In several embodiments, based on the leaf diffuser (4) described in 1) or 2) above,

[0206] The at least one cutout (7) includes a hub-side cutout (7B) formed between the diffuser blade (6A) and the hub side (51).

[0207] Based on the structure described in 4), by forming the hub-side cutout (7B) on the diffuser blade (6A), the entry angle on the hub side (upstream side in the axial direction) can be improved, thereby improving the flow of fluid on the hub side within the diffuser flow path (50). By improving the flow of fluid on the hub side within the diffuser flow path (50), the velocity loss of fluid on the hub side within the diffuser flow path (50) can be reduced, thereby improving the static pressure recovery performance in the bladed diffuser (4).

[0208] 5) In several embodiments, based on the leaf diffuser (4) described in 1) or 2) above,

[0209] The at least one cut portion (7) includes:

[0210] A side cutout (7A) is formed between the diffuser blade (6A) and the side surface (52) of the shield; and

[0211] A hub-side cutout (7B) is formed between the diffuser blade (6A) and the hub side surface (51).

[0212] According to the structure described in 5), by forming the aforementioned shield-side cutout (7A) and hub-side cutout (7B) on the diffuser blade (6A), the entry angles on the shield side and hub side can be improved, thereby improving the flow of fluid on the shield side and hub side within the diffuser flow path (50). According to the structure described in 5), compared to the case where either the shield-side cutout (7A) or the hub-side cutout (7B) is formed on the diffuser blade (6A), the velocity loss of the fluid within the diffuser flow path (50) can be effectively reduced, thereby effectively improving the static pressure recovery performance in the bladed diffuser (4).

[0213] 6) In several embodiments, based on the leaf diffuser (4) described in any one of 1) to 5) above,

[0214] The at least one cut portion (7) includes a concave curved surface (73) formed in such a way as to connect one end (71) of the cut portion (7) to the other end (72).

[0215] Based on the structure described in 6), the velocity loss of the fluid within the diffuser flow path (50) can be reduced due to the cut portion (7) including the concave curved surface (73). Furthermore, the cut portion (7) including the concave curved surface (73) allows for a smaller cut size compared to cases where one end (71) and the other end (72) are cut in a straight line. By reducing the cut size of the diffuser blades (6A), leakage from the pressure surface (63) to the negative pressure surface (64) of the diffuser blades (6A) via the cut portion (7) can be suppressed, thus improving the static pressure recovery performance in the leaf diffuser (4).

[0216] 7) In several embodiments, based on the leaf diffuser (4) described in any one of 1) to 6) above,

[0217] At least one of the plurality of diffuser blades (6) includes:

[0218] An inclined surface (67) formed by the at least one cutout (7) is formed at one end (671) of the leading edge (61); and

[0219] A stepped portion (68) is formed between the upstream end (651, 661) of either the hub-side end face (65) or the shield-side end face (66) of the at least one diffuser blade (6A) and the other end (672) of the inclined surface (67).

[0220] According to the structure described in 7), by providing the step portion (68) on the diffuser blade (6A), the cut amount of the diffuser blade (6A) can be reduced compared to the case where the inclined surface (67) is extended without providing the step portion (68). By reducing the cut amount of the diffuser blade (6A), leakage from the pressure surface (63) to the negative pressure surface (64) of the diffuser blade (6A) via the cut portion (7) can be suppressed, thereby improving the static pressure recovery performance in the bladed diffuser (4). Furthermore, according to the structure described in 7), by providing the step portion (68) on the diffuser blade (6A), the inclined surface (67) is supported by the step portion (68), thereby improving the vibration intensity of the diffuser blade (6A) compared to the case where the step portion (68) is not provided.

[0221] 8) In several embodiments, based on the leaf diffuser (4) described in 7) above,

[0222] When viewed from one side in the direction of blade height, the stepped portion (68) has a profile shape that protrudes towards the upstream side.

[0223] According to the structure described in 8), by setting the stepped portion (68) of the diffuser blade (6A) to have a profile shape that protrudes towards the upstream side, the surface of the stepped portion (68) can be made smooth. By making the surface of the stepped portion (68) smooth, the flow of fluid can be suppressed from being stripped from the diffuser blade (6A), thereby reducing the velocity loss of the fluid in the diffuser flow path (50) and improving the static pressure recovery performance in the bladed diffuser (4).

[0224] 9) In several embodiments, based on the leaf diffuser (4) described in 2) above,

[0225] When the blade length position of the leading edge portion (61) along the blade thickness center line from the leading edge portion (61) of the diffuser blade (6A) toward the throat position (TP) is set to 0%, and the blade length position of the throat position (TP) along the blade length direction is set to 100%, the other end (72) of the at least one cut portion (7) is formed in the range of 30% to 70% of the blade length position.

[0226] If the length of the cut portion (7) in the blade length direction is too short, it may be difficult to obtain the effect of reducing the velocity loss of the fluid in the diffuser flow path (50) caused by the cut portion (7). In addition, if the length of the cut portion (7) in the blade length direction is too long, the leakage from the pressure surface (63) to the negative pressure surface (64) of the diffuser blade (6A) through the cut portion (7) will increase. According to the structure of 9) above, by forming the other end (72) of the cut portion (7) in the range of 30 to 70% of the blade length, the effect of reducing the velocity loss of the fluid in the diffuser flow path (50) caused by the cut portion (7) can be effectively obtained, and the cut amount of the diffuser blade (6A) is smaller. As a result, the leakage through the cut portion (7) can be suppressed, and thus the static pressure recovery performance in the bladed diffuser (4) can be improved.

[0227] 10) In several embodiments, based on the leaf diffuser (4) described in 3) or 5) above,

[0228] When the blade height position of the diffuser blade (6A) on the hub side end face (65) in the blade height direction is set to 0%, and the blade height position on the shield side end face (66) in the blade height direction is set to 100%, the shield side cutout (7A) is formed in the range of 80% to 100% of the blade height position.

[0229] If the length of the cut (7) in the blade height direction is too short, it may be difficult to obtain the effect of reducing the velocity loss of the fluid in the diffuser flow path (50) caused by the cut (7). In addition, if the length of the cut (7) in the blade height direction is too long, the leakage from the pressure surface (63) to the negative pressure surface (64) of the diffuser blade (6A) through the cut (7) may increase. According to the structure of 10) above, by forming the shroud-side cut (7A) in the range of 80 to 100% of the blade height position, the effect of reducing the velocity loss of the fluid in the diffuser flow path (50) caused by the shroud-side cut (7A) can be effectively obtained, and the cut amount of the diffuser blade (6A) can be made smaller. As a result, the leakage through the shroud-side cut (7A) can be suppressed, and thus the static pressure recovery performance in the bladed diffuser (4) can be improved.

[0230] 11) In several embodiments, based on the leaf diffuser (4) described in 4) or 5) above,

[0231] When the blade height position of the diffuser blade (6A) on the hub side end face (65) in the blade height direction is set to 0%, and the blade height position on the shield side end face (66) in the blade height direction is set to 100%, the hub side cutout (7B) is formed in the range of 0 to 20% of the blade height position.

[0232] According to the structure described in 11), by forming the hub-side cutout (7B) within a range of 0 to 20% of the blade height, the velocity loss of the fluid in the diffuser flow path (50) caused by the hub-side cutout (7B) can be effectively reduced, and the cutout amount of the diffuser blade (6A) can be made smaller. As a result, the leakage through the hub-side cutout (7B) can be suppressed, thereby improving the static pressure recovery performance in the bladed diffuser (4).

[0233] 12) In several embodiments, based on the leaf diffuser (4) described in 5) above,

[0234] The other end (72A) of the side cutout (7A) of the guard is formed at a position closer to the rear edge (62) than the other end (72B) of the side cutout (7B) of the hub.

[0235] When the impeller (2) of the centrifugal compressor (1) is configured as an open impeller, the velocity loss of the fluid on the shroud side within the diffuser flow path (50) becomes a problem. According to the structure described in 12), by forming the other end (72A) of the shroud side cutout (7A) at a position further along the trailing edge (62) than the other end (72B) of the hub side cutout (7B), the cut amount of the shroud side cutout (7A) can be made larger. As a result, the velocity loss of the fluid on the shroud side within the diffuser flow path (50) can be effectively reduced, and therefore, for the centrifugal compressor (1) equipped with an open impeller (2), the static pressure recovery performance in the vaned diffuser (4) can be improved.

[0236] 13) In several embodiments, based on the leaf diffuser (4) described in 5) or 12) above,

[0237] The cut height at one end (71A) of the side cutout portion (7A) of the shield is greater than the cut height at one end (71B) of the side cutout portion (7B) of the hub.

[0238] According to the structure described in 13), by making the cut height at one end (71A) of the shield-side cut (7A) larger than the cut height at one end (71B) of the hub-side cut (7B), the cut amount of the shield-side cut (7A) can be made larger. As a result, the velocity loss of the fluid on the shield side in the diffuser flow path (50) can be effectively reduced, and therefore the static pressure recovery performance in the vaned diffuser (4) can be improved for the centrifugal compressor (1) equipped with an open impeller (2).

[0239] 14) The centrifugal compressor (1) according to at least one embodiment of the present invention comprises:

[0240] Impeller (2);

[0241] A housing (3) configured to house the impeller (2) so that it is rotatable; and

[0242] The bladed diffuser (4) described in any one of 1) to 13) above is disposed inside the housing (3) on the downstream side of the impeller (2).

[0243] According to the structure described in 14), by forming the cutout (7) in the diffuser blade (6A), the velocity loss of the fluid in the diffuser flow path (50) can be reduced, thereby improving the static pressure recovery performance in the vaned diffuser (4). By improving the static pressure recovery performance in the vaned diffuser (4), the efficiency of the centrifugal compressor (1) can be improved.

Claims

1. A vaned diffuser provided on a downstream side of an impeller of a centrifugal compressor, wherein the vaned diffuser includes: a diffuser flow passage forming portion that forms a diffuser flow passage on a downstream side of the impeller, the diffuser flow passage forming portion including a hub side surface and a shroud side surface that faces the hub side surface across the diffuser flow passage; and a plurality of diffuser vanes that are provided at intervals in a circumferential direction of the impeller in the diffuser flow passage, at least one of the plurality of diffuser vanes is formed with at least one notch portion formed between either one of the hub side surface and the shroud side surface, the at least one notch portion is formed with one end of the notch portion at a position including one end of a leading edge portion of the diffuser vane extending in a vane height direction, and a notch height of the notch portion becomes smaller as it goes toward a trailing edge portion side of the diffuser vane, the at least one notch portion includes: a shroud side notch portion formed between the diffuser vane and the shroud side surface; and a hub side notch portion formed between the diffuser vane and the hub side surface, the impeller is an open type impeller that does not have a ring-shaped shroud member covering outer peripheries of a plurality of impeller vanes and connected to leading ends of the plurality of impeller vanes respectively, and the other end of the shroud side notch portion is formed at a position closer to the trailing edge portion side than the other end of the hub side notch portion.

2. The vaned diffuser according to claim 1, wherein when a vane height position of a hub side end surface in the vane height direction of the diffuser vane is set to 0% and a vane height position of a shroud side end surface in the vane height direction is set to 100%, the shroud side notch portion is formed in a range of 80 to 100% of the vane height position.

3. The vaned diffuser according to claim 1, wherein when a vane height position of a hub side end surface in the vane height direction of the diffuser vane is set to 0% and a vane height position of a shroud side end surface in the vane height direction is set to 100%, the hub side notch portion is formed in a range of 0 to 20% of the vane height position.

4. The vaned diffuser according to claim 1, wherein a notch height at the one end of the shroud side notch portion is formed to be larger than a notch height at the one end of the hub side notch portion.

5. A vaned diffuser provided on a downstream side of an impeller of a centrifugal compressor, wherein the vaned diffuser includes: a diffuser flow passage forming portion that forms a diffuser flow passage on a downstream side of the impeller, the diffuser flow passage forming portion including a hub side surface and a shroud side surface that faces the hub side surface across the diffuser flow passage; and a plurality of diffuser vanes that are provided at intervals in a circumferential direction of the impeller in the diffuser flow passage, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ at least one of the plurality of diffuser vanes is formed with at least one cutout portion formed between either of the hub side surface and the shroud side surface, the at least one cutout portion is formed with one end of the cutout portion at a position including one end of a leading edge portion of the diffuser vane extending in a vane height direction, and a cutout height of the cutout portion becomes smaller as toward a trailing edge portion side of the diffuser vane, the at least one cutout portion includes: a shroud side cutout portion formed between the diffuser vane and the shroud side surface; and a hub side cutout portion formed between the diffuser vane and the hub side surface, the impeller is an open type impeller without a ring-shaped shroud member covering outer peripheries of a plurality of impeller vanes and connected to leading ends of the plurality of impeller vanes respectively, the cutout height at the one end of the shroud side cutout portion is formed larger than the cutout height at the one end of the hub side cutout portion.

6. The vaned diffuser according to claim 1 or 5, wherein the other end of the at least one cutout portion is formed at a position on the leading edge portion side from a throat position of the diffuser vane.

7. The vaned diffuser according to claim 1 or 5, wherein the at least one cutout portion includes a concave curved surface portion formed in a manner connecting the one end and the other end of the cutout portion.

8. The vaned diffuser according to claim 1 or 5, wherein at least one of the plurality of diffuser vanes includes: a slope surface formed by the at least one cutout portion, the slope surface being formed with one end of the slope surface at the one end of the leading edge portion; and a step portion formed between an upstream end of either of a hub side end surface and a shroud side end surface of the at least one diffuser vane and the other end of the slope surface.

9. The vaned diffuser according to claim 8, wherein the step portion has a profile shape projecting toward an upstream side when viewed from one side in the vane height direction.

10. The vaned diffuser according to claim 6, wherein when a vane length position of the leading edge portion in a vane length direction along a vane thickness center line from the leading edge portion of the diffuser vane toward a throat position of the diffuser vane is set to 0%, and a vane length position of the throat position in the vane length direction is set to 100%, the other end of the at least one cutout portion is formed in a range of 30 to 70% of the vane length position.

11. A centrifugal compressor, wherein the centrifugal compressor is provided with: an impeller; a casing configured to house the impeller so as to be rotatable; and the vaned diffuser according to any one of claims 1 to 10 is disposed inside the casing on a downstream side of the impeller.

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