Compressor wheel of centrifugal compressor and centrifugal compressor

Abstract

A compressor wheel of a centrifugal compressor has a hub and a plurality of blades provided at intervals in the circumferential direction on the peripheral surface of the hub, wherein the plurality of blades are each configured as follows: in a case where an angle formed by the blade and a meridian length direction is defined as a blade angle, an imaginary line formed by a set of intermediate positions in a spanwise direction of the blade is defined as a spanwise intermediate line, a blade angle at a hub side end of the blade is defined as a hub side end blade angle, a blade angle on the spanwise intermediate line of the blade is defined as a spanwise intermediate blade angle, and a blade angle at a tip side end of the blade is defined as a tip side blade angle, a leading edge position to a trailing edge position of a dimensionless meridian length position at the hub side end of the blade has a first interval in which a difference of the tip side blade angle with respect to the hub side end blade angle is 10° or more, and on the trailing edge position side from an intermediate position of the leading edge position and the trailing edge position, a second interval in which a variation amount of a difference of the spanwise intermediate blade angle with respect to the hub side end blade angle falls within a range of ±2°.

Description

Technical Field

[0001] The present invention relates to a compressor impeller of a centrifugal compressor and a centrifugal compressor having the compressor impeller. Background Technology

[0002] In the past, as a technology to improve the output of engines (internal combustion engines) such as automobile engines, a turbocharger (turbocharger) has been widely used. It compresses the intake air drawn into the engine, increases its density, and supplies the engine with intake air containing more oxygen (for example, see Patent Document 1).

[0003] A turbocharger, for example, includes a centrifugal compressor located on one side of a rotating shaft and a turbine located on the other side of the rotating shaft. It is configured such that the turbine rotor is rotated by the energy of exhaust gas from the engine, and the compressor impeller of the centrifugal compressor, which rotates in conjunction with the rotation of the turbine rotor, is rotated to compress the intake air and supply it to the engine.

[0004] Previous technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2022 / 259490 Summary of the Invention

[0007] The technical problem to be solved by the invention

[0008] According to the inventor's novel insight, the load generated at each position along the dimensionless meridional length of the compressor impeller blades in a centrifugal compressor becomes a load corresponding to the blade angular gradient. Furthermore, when there is a relatively large difference in the blade angular gradient closer to the hub than the midpoint in the spanwise direction of the blade, a secondary flow is generated from the hub side towards the blade tip side. This low-speed region, resulting from the accumulation of high-loss fluid at the trailing edge of the blade, may lead to a decrease in the efficiency of the centrifugal compressor. Additionally, content related to the inventor's novel insight is not disclosed in Patent Document 1.

[0009] In view of the above, the object of at least one embodiment of the present invention is to provide a compressor impeller of a centrifugal compressor that can improve the efficiency of a centrifugal compressor and a centrifugal compressor having the compressor impeller.

[0010] means for solving technical problems

[0011] The compressor impeller of a centrifugal compressor according to at least one embodiment of the present invention includes a hub and a plurality of blades arranged at intervals along the circumferential direction on the circumferential surface of the hub, wherein...

[0012] The plurality of blades are respectively configured as follows:

[0013] In the case where the angle between the blade and the meridional plane is defined as the blade angle, the imaginary line formed by the set of intermediate positions in the spanwise direction of the blade is defined as the spanwise midline, the blade angle at the hub-side end of the blade is defined as the hub-side blade angle, the blade angle on the spanwise midline of the blade is defined as the spanwise mid-blade angle, and the blade angle at the tip-side end of the blade is defined as the tip-side blade angle,...

[0014] From the leading edge to the trailing edge of the dimensionless meridional length position at the hub-side end of the blade, there is a first interval in which the difference between the blade tip angle relative to the dimensionless meridional length position and the hub-side blade angle at the same position is 10° or more.

[0015] On the side closer to the trailing edge position than the midpoint between the leading edge position and the trailing edge position at the dimensionless meridional length position, there is a second interval where the variation of the spanwise intermediate blade angle relative to the difference between the dimensionless meridional length position and the hub-side end blade angle at the same position falls within ±2°.

[0016] The centrifugal compressor according to at least one embodiment of the present invention comprises:

[0017] The compressor impeller of the centrifugal compressor.

[0018] Invention Effects

[0019] According to at least one embodiment of the present invention, a compressor impeller of a centrifugal compressor capable of improving the efficiency of a centrifugal compressor and a centrifugal compressor having the compressor impeller are provided. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view along the central axis of a turbocharger of a centrifugal compressor according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic cross-sectional view along the central axis of a centrifugal compressor according to an embodiment of the present invention, and is a schematic cross-sectional view showing the meridional section of the compressor impeller.

[0022] Figure 3 This is a schematic perspective view of the compressor impeller of a centrifugal compressor according to an embodiment of the present invention.

[0023] Figure 4 This is a diagram showing the blade angular distribution of the compressor impeller of a centrifugal compressor according to an embodiment of the present invention.

[0024] Figure 5This is a diagram used to define the blade angles of long and short blades according to one embodiment of the present invention.

[0025] Figure 6 This is an explanatory diagram showing the relationship between the blade angle and the mid-arc line of a long blade according to an embodiment of the present invention.

[0026] Figure 7 This is an explanatory diagram used to illustrate the low-speed region generated in the fluid flowing in the compressor impeller of the centrifugal compressor involved in the comparative example.

[0027] Figure 8 This is an explanatory diagram illustrating the low-speed region generated in the fluid flowing in the compressor impeller of a centrifugal compressor according to an embodiment of the present invention.

[0028] Figure 9 This is an explanatory diagram illustrating the distribution of the radial length of the trailing edge of the blades of the compressor impeller of a centrifugal compressor according to an embodiment of the present invention.

[0029] Figure 10 This is an explanatory diagram illustrating the distribution of the throat width of the blades of the compressor impeller of a centrifugal compressor according to an embodiment of the present invention relative to the radial position. Detailed Implementation

[0030] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the constituent parts described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0031] In the following embodiments, the centrifugal compressor of the present invention is described as a centrifugal compressor provided with a turbocharger, but the centrifugal compressor of the present invention may also be an electric centrifugal compressor or the like. Furthermore, it is not necessary to limit the gas compressed by the centrifugal compressor of the present invention to air. That is, the centrifugal compressor of the present invention can be configured as long as it is capable of compressing and delivering gas; it may be a single centrifugal compressor unit or a combination thereof with a mechanism or device other than a turbine. Furthermore, its application is not limited.

[0032] (Centrifugal compressor, turbocharger)

[0033] Figure 1 This is a schematic cross-sectional view along the central axis CA of a turbocharger 10 of a centrifugal compressor 1 according to an embodiment of the present invention. Figure 2 This is a schematic cross-sectional view along the central axis CA of the centrifugal compressor 1 according to one embodiment of the present invention, and is a schematic cross-sectional view showing the meridional section of the compressor impeller 3. Figure 1 and Figure 2As shown, the centrifugal compressor 1 according to some embodiments includes a rotating shaft 2, a compressor impeller 3, and a housing (compressor housing) 4 configured to rotatably accommodate the compressor impeller 3. The centrifugal compressor 1 according to the present invention can be mounted, for example, on a turbocharger (turbocharger) 10 for automotive, marine, or industrial (e.g., land-based power generation) applications.

[0034] The rotating shaft 2 extends along the central axis CA of the compressor impeller 3 and is capable of rotating about this central axis CA. The compressor impeller 3 is mounted on the outer circumferential surface of the rotating shaft 2.

[0035] like Figure 1 As shown, the turbocharger 10 includes a centrifugal compressor 1 and a turbine 11 configured to drive the centrifugal compressor 1. The turbine 11 includes: a turbine rotor 12, which rotates by the energy of exhaust gas discharged from an exhaust-generating device such as an engine (internal combustion engine) or fuel cell (not shown); and a turbine housing 13 configured to rotatably house the turbine rotor 12.

[0036] like Figure 1 As shown, the centrifugal compressor 1 also includes a bearing 14 that rotatably supports the rotating shaft 2. In the turbocharger 10, the compressor impeller 3 is connected to one side of the axial direction of the rotating shaft 2, i.e., the direction in which the central axis CA extends, and the turbine rotor 12 is connected to the other side of the axial direction of the rotating shaft 2. The bearing 14 rotatably supports the rotating shaft 2 between the compressor impeller 3 and the turbine rotor 12. The turbocharger 10 may also include a bearing housing 15, which is disposed between the housing 4 and the turbine housing 13, and is configured to accommodate the rotating shaft 2 and the bearing 14.

[0037] (turbine)

[0038] The turbine 11 of the turbocharger 10 is configured to rotate the turbine rotor 12 by exhaust gas discharged from the exhaust gas generating device. Exhaust gas is supplied from the exhaust gas generating device to the turbine 11, causing the turbine rotor 12 to rotate.

[0039] (Turbine rotor)

[0040] like Figure 1 As shown, the turbine rotor 12 includes: a hub 121 in the shape of a generally frustum conical; and a plurality of turbine blades 122 disposed on the outer peripheral surface of the hub 121. The hub 121 or the plurality of turbine blades 122 are configured to rotate integrally with the rotating shaft 2 about a central axis CA. The turbine rotor 12 is configured to guide exhaust gas introduced from the radially outer side of the turbine rotor 12 along the axial direction of the turbine rotor 12.

[0041] (Turbine casing)

[0042] Inside the turbine housing 13 are formed a turbine vortex flow path 131 for guiding exhaust gas discharged from the aforementioned exhaust gas generating device to the turbine rotor 12, and an exhaust gas discharge flow path 132 for discharging exhaust gas that has passed through the turbine rotor 12 to the outside of the turbine housing 13. The turbine vortex flow path 131 is composed of a vortex-shaped flow path provided on the outer periphery of the turbine rotor 12 and extending circumferentially along the turbine rotor 12. The exhaust gas discharge flow path 132 extends axially along the turbine rotor 12.

[0043] The exhaust gas discharged from the exhaust gas generating device is guided to the turbine rotor 12 via the turbine vortex flow path 131, causing the turbine rotor 12 to rotate. The exhaust gas that drives the turbine rotor 12 to rotate is discharged to the outside of the turbine housing 13 via the exhaust gas discharge flow path 132.

[0044] The compressor impeller 3 is coaxially connected to the turbine rotor 12 via the rotating shaft 2, and thus rotates around the central axis CA of the compressor impeller 3 in conjunction with the rotation of the turbine rotor 12. The centrifugal compressor 1 of the turbocharger 10 is configured to draw air (supply gas, gaseous gas) into the interior of the housing 4, compress the air, and deliver the compressed air to the compressed air supply destination. Examples of compressed air supply destinations include, for example, exhaust gas generating devices such as engines (internal combustion engines) or fuel cells.

[0045] (Compressor impeller)

[0046] like Figure 2 As shown, the compressor impeller 3 includes a hub 5 having an outer peripheral surface 51 and a back surface 52. Hereinafter, as... Figure 2 As shown, the direction extending from the central axis CA of the compressor impeller 3 is defined as the axial direction of the compressor impeller 3, the direction orthogonal to the central axis CA is defined as the radial direction of the compressor impeller 3, and the circumferential direction around the central axis CA is defined as the circumferential direction of the compressor impeller 3. In the axial direction of the compressor impeller 3, the side of the outer circumferential surface 51 of the hub 5 relative to the back surface 52 of the hub 5 ( Figure 2 The left side of the middle is designated as the front side, and the side of the back surface 52 relative to the outer peripheral surface 51 is designated as the front side. Figure 2 The right side of the middle section is designated as the rear side.

[0047] Figure 3 This is a schematic perspective view of the compressor impeller 3 of a centrifugal compressor 1 according to an embodiment of the present invention. The compressor impeller 3 of the centrifugal compressor 1 is configured to guide air introduced along the axial direction of the compressor impeller 3 to the outer radial direction of the compressor impeller 3. Figure 2 and Figure 3As shown, the compressor impeller 3 has a hub 5 with a generally frustum-shaped shape and a plurality of blades (long blades 6) spaced circumferentially on the circumferential surface (outer circumferential surface 51) of the hub 5. In the illustrated embodiment, as... Figure 3 As shown, the compressor impeller 3 also includes a plurality of short blades 7 disposed on the circumferential surface of the hub 5 between adjacent blades 6. Furthermore, Figure 3 , Figure 5 , Figure 7 and Figure 8 The arrow (symbol N) in the diagram indicates the direction of rotation of the compressor impeller 3. Furthermore, several embodiments of the present invention can also be applied to compressor impellers 3 that do not have the short blades 7.

[0048] The outer peripheral surface 51 of the hub 5 includes, as shown in the figure Figure 2 The plane of the shown central axis CA has an inclined surface that is tilted relative to the central axis CA. The inclined surface is formed in a concave-bend shape, with the radial distance (radial height) from the central axis CA increasing as it moves toward the rearward side (back side 52 side) of the compressor impeller 3 in the axial direction. In the illustrated embodiment, the hub 5 includes a boss portion 53 that protrudes further forward toward the axial direction of the compressor impeller 3 than the plurality of blades 6.

[0049] The hub 5 is mechanically connected to one side of the rotating shaft 2 along its axial direction, and is therefore configured to rotate integrally with the rotating shaft 2 around the central axis CA of the compressor impeller 3. In the illustrated embodiment, a through hole 54 is formed in the hub 5, extending axially along the compressor impeller 3 at a position including the central axis CA. The through hole 54 is formed by extending from the rear end face 52 of the hub 5 to the front end face 531 of the hub 5 (the end face of the boss portion 53).

[0050] In the illustrated embodiment, a nut component 16 is screwed onto one end 2A of the compressor impeller 3, which is inserted through the through hole 54 into the rotating shaft 2. The hub 5 is clamped between the nut component 16 and another component by a tightening force applied to the rearward side by the nut component 16. This other component can be the rotating shaft 2 or a collar mounted on the rotating shaft 2. Alternatively, the compressor impeller 3 can be fixed to the rotating shaft 2 by a fixing structure other than that via the nut component 16.

[0051] Multiple blades 6 are erected from the outer peripheral surface 51 of the hub 5, and are spaced apart from other blades 6 in the circumferential direction around the central axis CA. Multiple short blades 7 are erected from the outer peripheral surface 51 of the hub 5, and are respectively arranged between adjacent blades 6 in the circumferential direction around the central axis CA. The leading edge 73 of the short blades 7 in the fluid flow path formed between adjacent blades 6 on the circumferential surface of the hub 5 is located further downstream than the leading edge 63 of the blades 6.

[0052] like Figure 2 As shown, the plurality of blades 6 each include a hub-side end 61, a tip-side end 62, a leading edge 63 located on the upstream side in the direction of air flow introduced into the compressor impeller 3, and a trailing edge 64 located on the downstream side. The plurality of blades 6 extend along the spanwise direction between the hub-side end 61 and the tip-side end 62, respectively, between the leading edge 63 and the trailing edge 64.

[0053] Hub end 61 is the end of one side of the blade 6 in the spanwise direction, and it is the end that connects to the outer peripheral surface 51 of the hub 5. Tip end 62 is the end of the blade 6 in the other side in the spanwise direction, and it is the end located on the side opposite to hub end 61. In this specification, the spanwise direction of the blade 6 refers to the direction connecting hub end 61 and tip end 62 at each dimensionless meridional length position.

[0054] like Figure 2 As shown, the plurality of short blades 7 each include a hub side end 71, a blade tip end 72, a leading edge 73 located on the upstream side in the direction of air flow introduced into the compressor impeller 3, and a trailing edge 74 located on the downstream side. The plurality of short blades 7 extend along the spanwise direction between the hub side end 71 and the blade tip end 72, between the leading edge 73 and the trailing edge 74.

[0055] The hub-side end 71 is the end of one side of the short blade 7 in the spanwise direction, and is the end that connects to the outer peripheral surface 51 of the hub 5. The blade-tip-side end 72 is the end of the short blade 7 in the other side in the spanwise direction, and is the end located on the side opposite to the hub-side end 71. In this specification, the spanwise direction of the short blade 7 refers to the direction connecting the hub-side end 71 and the blade-tip-side end 72 at each dimensionless meridional length position.

[0056] like Figure 2 As shown, the tip 62 of each of the multiple blades 6 and the tip 72 of each of the multiple short blades 7 are opposite to the shroud surface 41 through a gap CL formed between them. That is, the compressor impeller 3 is an open compressor impeller that does not include the annular component covering the tip 62, 72.

[0057] (case)

[0058] like Figure 2 As shown, the housing 4 includes a protective cover portion 40 having the aforementioned protective cover surface 41. The protective cover surface 41 includes an inclined surface 41A, which is formed in a convex curved shape with the distance from the central axis CA increasing as it moves from the front side to the rear side in the axial direction of the compressor impeller 3. Inside the housing 4, a fluid inlet flow path 42, a diffuser flow path 43, and a vortex flow path 44 are formed.

[0059] The fluid inlet flow path 42 is a flow path for drawing air from the outside of the housing 4 and guiding the drawn air (fluid) to the compressor impeller 3. The fluid inlet flow path 42 is located further forward of the compressor impeller 3 in the axial direction and extends along the axial direction of the compressor impeller 3. By driving the compressor impeller 3 to rotate, air is drawn from the outside of the housing 4 into the fluid inlet flow path 42, and the drawn air flows in the fluid inlet flow path 42 toward the rearward side of the compressor impeller 3 in the axial direction and is guided to the compressor impeller 3.

[0060] The diffuser flow path 43 and the vortex flow path 44 are flow paths used to guide compressed air (compressed fluid) that has passed through and been compressed by the compressor impeller 3 to the outside of the centrifugal compressor 1. The vortex flow path 44 is composed of a vortex-shaped flow path disposed on the outer peripheral side (radially outer side) of the compressor impeller 3 and extending circumferentially along the compressor impeller 3. The diffuser flow path 43 is disposed radially between the vortex flow path 44 and the compressor impeller 3 and extends radially along the compressor impeller 3. The diffuser flow path 43 communicates with the vortex flow path 44 at its downstream end (outer peripheral end). The compressed air compressed by the compressor impeller 3 flows into the diffuser flow path 43 and is guided to the vortex flow path 44 by flowing radially outward in the diffuser flow path 43.

[0061] (Definition of the position of the dimensionless meridian plane)

[0062] Figure 4 This is a diagram showing the blade angle distribution of the compressor impeller 3 of a centrifugal compressor 1 according to an embodiment of the present invention. Figure 4 In the diagram, the horizontal axis is set to the dimensionless meridional length position m on the hub side end 61 of blade 6, and the vertical axis is set to the blade angle β of blade 6 and short blade 7. The diagram shows the distribution of the blade angle β between the leading edge position 611 (M0) and the trailing edge position 612 (M1) at the aforementioned dimensionless meridional length position m. The blade angle β is the angle formed by each of blade 6 and short blade 7 with the meridional length direction; details will be described later. Figure 4 In the dimensionless meridional length position m, the leading edge position M0 of the dimensionless meridional length position m is defined as 0 (m=0), and the trailing edge position M1 is defined as 1 (m=1). The positions on the dimensionless meridional length position m are represented by their ratio to the trailing edge position M1. The midpoint between the leading edge position M0 and the trailing edge position M1 (50% of the dimensionless meridional length position, m=0.5) is set as MP. The same value for the dimensionless meridional length position m means that the compressor impeller 3 is visually identified in the meridional direction at the same position.

[0063] like Figure 2As shown, the imaginary line formed by the set of intermediate positions in the spanwise direction of blade 6 is defined as the spanwise midline SM. Furthermore, the blade angle β at the hub-side end 61 of blade 6 is defined as the hub-side blade angle β1, and the blade angle β on the spanwise midline SM of blade 6 is defined as the spanwise midline blade angle β2. The blade angle β at the tip-side end 62 of blade 6 is defined as the tip-side blade angle β3. Figure 4 The curve L1, represented by the solid line, represents an example of the blade angle distribution of the blade angle β1 at the hub side. Figure 4 The curve L2, represented by the solid line, represents an example of the blade angle distribution towards the middle blade angle β2. Figure 4 The curve L3, represented by the solid line, represents an example of the leaf angle distribution of the leaf tip angle β3. Figure 4 The curve L4, represented by the dotted line, represents an example of the blade angle distribution of the blade angle β on the hub side end 71 of the short blade 7. Figure 4 The curve L5, represented by the dotted line, represents an example of the leaf angle distribution of the leaf angle β on the leaf tip 72 of the short leaf 7.

[0064] (Definition of blade angle)

[0065] Figure 5 This is a diagram used to define the blade angle β of the long blade 6 and the short blade 7 according to one embodiment of the present invention. Figure 6 This is an explanatory diagram showing the relationship between the blade angle β and the arc S of the long blade 6 according to an embodiment of the present invention. Figure 5 This is a diagram unfolded on a plane along the meridional length direction at any spanwise position of the long blade 6. In this unfolded diagram, the vertical axis represents the rotation direction N of the long blade 6, and the horizontal axis represents the meridional length direction. On this plane, the angle β formed by the long blade 6 or the short blade 7 with the meridional length direction is defined as the blade angle. For example, the blade angle β at any position of the long blade 6 is the angle formed by the tangent of the blade surface at that arbitrary position with respect to the meridional length direction. Furthermore, if referring to... Figure 6 In a coordinate system defined by axial direction Z, radial direction R, and rotation angle θ around the axis, the blade angle β within a small interval between coordinate point 1 (Z1, R1, θ1) and coordinate point 2 (Z2, R2, θ2) is defined by the following equation (1).

[0066] tanβ=R2·dθ / dm……(1)

[0067] Here, dθ=θ2-θ1, dm=√{(Z2-Z1) 2 +(R2-R1) 2}, where S is an arc.

[0068] In some embodiments, the compressor impeller 3, such as Figure 4As shown, the aforementioned plurality of long blades 6 are configured such that, from the leading edge position M0 at the dimensionless meridional length position m at the hub-side end 61 of the long blade 6 to the trailing edge position M1, the difference between the blade tip angle β3 and the hub-side blade angle β1 at the same position (where m is the same value) relative to the dimensionless meridional length position is 10° or more, forming a first interval SE1. In the illustrated embodiment, the first interval SE1 is provided across the entire range from the leading edge position M0 to the trailing edge position M1 at the dimensionless meridional length position m, but it may also be provided within a portion of the range from the leading edge position M0 to the trailing edge position M1.

[0069] like Figure 4 As shown, the aforementioned plurality of long blades 6 are respectively configured such that, on the side further from the trailing edge position M1 than the middle position MP of the dimensionless meridional length position m in the hub-side end 61 of the long blade 6, there is a second interval SE2 in which the variation of the difference Δβ between the aforementioned spanwise intermediate blade angle β2 and the hub-side end blade angle β1 at the same position relative to the dimensionless meridional length position (m is the same) falls within ±2°. Specifically, the difference Δβ1 (Δβ) at any position included in the second interval SE2, relative to the difference Δβ0 (Δβ) at the reference position included in the second interval SE2, satisfies the condition Δβ0-2°≤Δβ1≤Δβ0+2°. This second interval SE2 is preferably an interval in which the variation of the aforementioned difference Δβ falls within ±1°.

[0070] The proportion of the second interval SE2 mentioned above from the leading edge position M0 to the trailing edge position M1 of the dimensionless meridian length position m is preferably 20% or more, and more preferably 40% or more.

[0071] Figure 7 This is an explanatory diagram used to illustrate the low-speed region LSA generated in the fluid flowing through the compressor impeller 03 of the centrifugal compressor 01 involved in the comparative example. Figure 8 This is an explanatory diagram illustrating the low-speed region LSA generated in the fluid flowing through the compressor impeller 3 of the centrifugal compressor 1 according to an embodiment of the present invention. The compressor impeller 03 involved in the comparative example occupies a smaller proportion from the leading edge position M0 to the trailing edge position M1 of the dimensionless meridional length position m of the second interval SE2 described above than the compressor impeller 3.

[0072] The load generated at each position along the dimensionless meridional length m of the long blade 6 corresponds to the blade angular gradient dβ / dm of the long blade 6. If the blade angular gradient dβ / dm is large, the aforementioned load increases. Assuming a significant difference in blade angular gradient dβ / dm exists at the midpoint between the hub end 61 and the blade 6 in the spanwise direction, a secondary flow is generated from the hub side of the long blade 6 towards the blade tip side. This secondary flow, passing through the low-speed region LSA (Lead-Stage Acid) caused by the relatively high fluid loss accumulated at the trailing edge 64, may lead to a decrease in the efficiency of the centrifugal compressor 1.

[0073] According to the inventors' new insights, by reducing the difference in blade angle gradient dβ / dm between the hub side and the center position of blade 6 in the spanwise direction, the generation of secondary flow or the expansion of low-speed region LSA can be suppressed. By setting the second interval SE2, the difference in blade angle gradient dβ / dm between the hub side end 61 and the center position of blade 6 in the spanwise direction can be made relatively small. Therefore, the blade load at the hub side end 61 and the center position of blade 6 in the spanwise direction can be made equal. By making the blade load at the hub side end 61 and the center position of blade 6 in the spanwise direction equal, the generation of secondary flow or the expansion of low-speed region LSA can be suppressed. Therefore, compared to the centrifugal compressor 01 of the comparative example, the efficiency of centrifugal compressor 1 can be improved.

[0074] In some implementations, such as Figure 4 As shown, the aforementioned long blades 6 are configured such that the midpoint MP and trailing edge M1 of the dimensionless meridional length position m at the hub-side end 61 of the blade 6 are included in the second interval SE2. The second interval SE2 includes the range from the midpoint MP of the dimensionless meridional length position m to the trailing edge M1. Figure 4 In the embodiment shown, the blade angles β1 and β2 of each long blade 6 gradually increase towards the trailing edge position M1 within the range from the middle position MP of the dimensionless meridional length position m to the trailing edge position M1. However, within the above range, the blade angle gradients dβ / dm of the blade angles β1 and β2 ...

[0075] According to the above structure, in the second interval SE2, which includes the intermediate position MP and the trailing edge position M1, the proportion from the leading edge position M0 to the trailing edge position M1 at the dimensionless meridional length position m is large. By increasing this proportion, the blade load at the hub end 61 and the intermediate position in the spanwise direction of the blade 6 can be made equal over a relatively wide range of the dimensionless meridional length. As a result, the generation of the aforementioned secondary flow or the expansion of the low-speed region LSA can be effectively suppressed, thus improving the efficiency of the centrifugal compressor 1.

[0076] In some implementations, such as Figure 4 As shown, each of the aforementioned long blades 6 is configured such that a second interval SE2 is also present between the leading edge 73 of the short blade 7 at the dimensionless meridional length position m at the hub-side end 61 of the blade 6 and the intermediate position MP. The aforementioned second interval SE2 may include the range from the leading edge 73 of the short blade 7 at the dimensionless meridional length position m to the intermediate position MP, or it may include a portion of that range. The leading edge 73 of the short blade 7 is located further towards the leading edge position M0 than the intermediate position MP. In the illustrated embodiment, the leading edge 73 of the short blade 7 is located further towards the leading edge position M0 than the 40% dimensionless meridional length position where m = 0.4; however, in other embodiments, the leading edge 73 of the short blade 7 may also be located further towards the intermediate position MP than the 40% dimensionless meridional length position.

[0077] By also providing a second interval SE2 between the leading edge 73 and the intermediate position MP of the short blade 7, the proportion of the second interval SE2 from the leading edge M0 to the trailing edge M1 along the dimensionless meridional length m can be increased. By increasing this proportion, the blade load at the hub end 61 and the intermediate position in the spanwise direction of the blade 6 can be made equal over a relatively wide range of the dimensionless meridional length. As a result, the generation of the aforementioned secondary flow or the expansion of the low-speed region LSA can be effectively suppressed, thus improving the efficiency of the centrifugal compressor 1.

[0078] (The shape of the trailing edge of a long leaf)

[0079] Figure 9 This is an explanatory diagram illustrating the distribution of the radial length of the trailing edge 64 of the long blades 6 of the compressor impeller 3 of a centrifugal compressor 1 according to an embodiment of the present invention. Figure 9 The diagram shows the distribution of the radial length of the trailing edge 64 in the meridional shape of the blade 6, with the axial direction of the compressor impeller 3 as the transverse axis and the radial length of the trailing edge 64 of the long blade 6 of the compressor impeller 3 (i.e., the radial distance of the trailing edge 64 from the central axis CA) as the longitudinal axis.

[0080] In some embodiments, the compressor impeller 3, such as Figure 9 As shown, the trailing edge 64 of the meridional plane shape of blade 6 includes a tip-side convex bend 641, a hub-side convex bend 642, and an inflection point 643. The tip-side convex bend 641 has a bend shape that protrudes inward in the radial direction of the compressor impeller 3. The hub-side convex bend 642 has a bend shape that protrudes outward in the radial direction of the compressor impeller 3.

[0081] The hub-side convex bend 642 is located at the blade tip side end 644, further away from the trailing edge 64 than the blade tip-side convex bend 641. The inflection point 643 is located between the blade tip-side convex bend 641 and the hub-side convex bend 642. The inflection point 643 is located at the central portion of the blade 6 in the spanwise direction. Here, the central portion of the blade 6 in the spanwise direction is a spanwise range from 40% to 60% of the spanwise direction, and the inflection point 643 is located within this spanwise range.

[0082] By setting an inflection point 643 at the center of the blade 6 in the spanwise direction of the trailing edge 64, the abrupt change in the radial length of the trailing edge 64 in the aforementioned central portion of the trailing edge 64 can be suppressed. This makes the difference in radial length between the hub end 61 and the middle position of the trailing edge 64 in the spanwise direction of the blade 6 relatively small, thereby making the blade load at these positions more uniform. This effectively suppresses the generation of secondary flow or the expansion of the low-speed region LSA, thus improving the efficiency of the centrifugal compressor 1.

[0083] In some embodiments of the compressor impeller 3, such as Figure 9 As shown, the trailing edge 64 of the meridional plane shape of the blade 6 is configured such that the radial gradient relative to the axial gradient is the largest in the aforementioned blade tip lateral convex bend 641.

[0084] By setting the gradient in the convex bend 642 on the hub side to a relatively small value, the abrupt change in the radial length of the trailing edge 64, which is closer to the hub side than the central portion of the trailing edge 64, can be suppressed. This makes the difference in radial length between the hub-side end 61 and the trailing edge 64 at the midpoint of the spanwise direction of the blade 6 relatively small, thereby making the blade load at these locations more uniform. This effectively suppresses the generation of secondary flow or the expansion of the low-speed region LSA, thus improving the efficiency of the centrifugal compressor 1.

[0085] In other embodiments, each of the plurality of blades 6 described above may have a constant radial length of trailing edge 64 extending from the hub side to the tip side.

[0086] (Width of the throat of a short leaflet)

[0087] Among the aforementioned multiple blades 6, the blade 6 whose suction surface 66 is separated from the pressure surface 75 of the short blade 7 by the first flow path 81 for fluid flow is defined as one side blade 6A, and the blade 6 whose pressure surface 65 is separated from the suction surface 76 of the short blade 7 by the second flow path 82 for fluid flow is defined as the other side blade 6B.

[0088] Figure 10This is an explanatory diagram illustrating the distribution of throat widths TH (TH1, TH2) at radial positions of the blades 6 of the compressor impeller 3 of a centrifugal compressor 1 according to an embodiment of the present invention. Figure 10 The diagram shows a graph where the radial length of blade 6, i.e., the radial distance of blade 6 from the central axis CA, is set as the horizontal axis, and the throat width TH (TH1, TH2) of the leading edge 73 of short blade 7 relative to adjacent blades 6 (one side blade 6A or the other side blade 6B) is set as the vertical axis. Figure 10 In the image, a single-dotted line indicates the throat width TH1 of the leading edge 73 of the short blade 7 relative to one side of the blade 6A (reference). Figure 5 The distribution of the blades is shown in solid lines, with the leading edge 73 of the short blade 7 representing the throat width TH2 of the blade 6B on the other side (reference). Figure 5 The distribution of ).

[0089] In some embodiments of the compressor impeller 3, such as Figure 10 As shown, at the midpoint of the spanwise direction of blade 6 (on the spanwise centerline SM), the throat width TH1 of the leading edge 73 of the short blade 7 relative to one side blade 6A is greater than the throat width TH2 of the leading edge 73 of the short blade 7 relative to the other side blade 6B. At the midpoint of the spanwise direction of blade 6, by making the throat width TH1 relative to one side blade 6A greater than the throat width TH2 relative to the other side blade 6B, the inflow of fluid into the second flow path 82 can be suppressed. Here, the second flow path 82 is more prone to generating the aforementioned secondary flow or low-speed region LSA compared to the first flow path 81. By suppressing the inflow of fluid into the second flow path 82, the generation of the aforementioned secondary flow or the expansion of the low-speed region LSA can be effectively suppressed, thus improving the efficiency of the centrifugal compressor 1. Furthermore, this embodiment can be implemented independently of the above-described embodiment.

[0090] In some embodiments of the compressor impeller 3, such as Figure 10 As shown, it is configured to be positioned further from the hub end 61 than the middle position in the spanwise direction of the blade 6. Figure 10 (Left side), the throat width TH2 of the leading edge 73 of the short blade 7 relative to the other blade 6B is greater than the throat width TH1 of the leading edge 73 of the short blade 7 relative to the other blade 6A.

[0091] Even when the throat width TH1 relative to one blade 6A and the throat width TH2 relative to the other blade 6B are reversed at the hub end 61 position further in the spanwise direction than the center position of the blade 6, the inflow of fluid into the second flow path 82 can be suppressed by making the throat width TH1 relative to one blade 6A larger than the throat width TH2 relative to the other blade 6B at the center position of the blade 6 in the spanwise direction. Alternatively, in some other embodiments, the throat width TH1 relative to one blade 6A and the throat width TH2 relative to the other blade 6B may not be reversed at the hub end 61 position further in the spanwise direction than the center position of the blade 6.

[0092] like Figure 1 and Figure 2 As shown, the centrifugal compressor 1 according to some embodiments includes the compressor impeller 3 described above. The centrifugal compressor 1 with compressor impeller 3 can suppress the generation of the secondary flow or the expansion of the low-speed region LSA, thus improving the efficiency of the centrifugal compressor 1.

[0093] In this specification, expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" that indicate relative or absolute configuration not only strictly indicate such configuration, but also indicate the state of relative displacement of angle or distance with tolerance or to the extent that the same function can be obtained.

[0094] For example, expressions such as "same," "equal," and "homogeneous" that indicate things are in the same state not only mean that they are the same in a strict sense, but also that there are differences in the degree to which they can achieve the same function.

[0095] Furthermore, in this specification, the description of shapes such as quadrilaterals or cylinders refers not only to shapes such as quadrilaterals or cylinders in a strict geometric sense, but also to shapes such as concave or convex parts or chamfered parts within the range where the same effect can be obtained.

[0096] Furthermore, in this specification, expressions such as "possessing," "including," or "having" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0097] The present invention is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments or appropriate combinations thereof.

[0098] The contents described in some of the above embodiments are as follows.

[0099] 1) The compressor impeller 3 of the centrifugal compressor 1 according to at least one embodiment of the present invention includes a hub 5 and a plurality of blades (long blades 6) arranged circumferentially at intervals on the circumferential surface 51 of the hub 5.

[0100] The plurality of blades 6 are respectively configured as follows:

[0101] In the case where the angle between the blade 6 and the meridional plane is defined as the blade angle β, the imaginary line formed by the set of intermediate positions in the spanwise direction of the blade 6 is defined as the spanwise midline SM, the blade angle at the hub-side end 61 of the blade 6 is defined as the hub-side blade angle β1, the blade angle on the spanwise midline SM of the blade 6 is defined as the spanwise midline blade angle β2, and the blade angle at the tip-side end 62 of the blade 6 is defined as the tip-side blade angle β3,...

[0102] From the leading edge position M0 to the trailing edge position M1 at the dimensionless meridional length position m at the hub-side end 61 of the blade 6, there is a first interval SE1 where the difference between the blade tip angle β3 and the hub-side end blade angle β1 at the same position relative to the dimensionless meridional length position is 10° or more.

[0103] In the second interval SE2, which is closer to the trailing edge position M1 than the intermediate position MP between the leading edge position M0 and the trailing edge position M1 of the dimensionless meridional length position m, the difference Δβ between the spanwise intermediate blade angle β2 and the hub-side blade angle β1 at the same position of the dimensionless meridional length position and the intermediate position m falls within ±2°.

[0104] Based on the structure described in 1) above, by setting the second interval SE2, the difference in blade angular gradient dβ / dm between the hub end 61 and the blade 6 at the midpoint of the spanwise direction can be made relatively small. This allows for equalization of the blade load at the midpoint of the spanwise direction between the hub end 61 and the blade 6. By equalizing the blade load at the midpoint of the spanwise direction between the hub end 61 and the blade 6, the generation of secondary flow or the expansion of the low-speed region LSA can be suppressed, thus improving the efficiency of the centrifugal compressor 1.

[0105] 2) In some embodiments, the compressor impeller 3 of the centrifugal compressor 1 according to 1) above, wherein,

[0106] The plurality of blades 6 are respectively configured as follows:

[0107] The intermediate position MP and the trailing edge position M1 of the dimensionless meridional length position m at the hub side end 61 of the blade 6 are included in the second interval SE2.

[0108] According to the structure in 2) above, in the second interval SE2, which includes the intermediate position MP and the trailing edge position M1, the proportion from the leading edge position M0 to the trailing edge position M1 at the dimensionless meridional length position m is large. By setting this proportion to be large, the blade load at the intermediate position in the spanwise direction of the hub end 61 and the blade 6 can be made equal over a relatively wide range of the dimensionless meridional length. As a result, the generation of the aforementioned secondary flow or the expansion of the low-speed region LSA can be effectively suppressed, thus improving the efficiency of the centrifugal compressor 1.

[0109] 3) In some embodiments, the compressor impeller 3 of the centrifugal compressor 1 according to 1) or 2) above, wherein,

[0110] The hub 5 has multiple short blades 7, which are respectively disposed on the circumferential surface 51 of the hub 5 between adjacent blades 6.

[0111] The plurality of blades 6 are respectively configured as follows:

[0112] The second interval SE2 also exists between the leading edge 73 of the short blade 7 at the dimensionless meridional length position m at the hub side end 61 of the blade 6 and the intermediate position MP.

[0113] Based on the structure described in 3), by also setting a second interval SE2 between the leading edge 73 position and the middle position MP of the short blade 7, the proportion of the second interval SE2 from the leading edge position M0 to the trailing edge position M1 from the dimensionless meridional length position m can be increased.

[0114] 4) In some embodiments, the compressor impeller 3 of the centrifugal compressor 1 according to any one of 1) to 3) above, wherein,

[0115] The second interval SE2 occupies more than 20% of the area from the leading edge position M0 to the trailing edge position M1 of the dimensionless meridian length position m.

[0116] Based on the structure described in 4) above, by setting the proportion of the second interval SE2 from the leading edge position M0 to the trailing edge position M1 of the dimensionless meridional length position m to a relatively large proportion of 20%, the blade load at the hub end 61 and the middle position of the blade 6 in the spanwise direction can be made equal over a relatively wide range of the dimensionless meridional length. This effectively suppresses the generation of the aforementioned secondary flow or the expansion of the low-speed region LSA, thus improving the efficiency of the centrifugal compressor 1.

[0117] 5) In some embodiments, the compressor impeller 3 of the centrifugal compressor 1 according to any one of 1) to 4) above, wherein,

[0118] The trailing edge 64 in the meridional plane shape of the blade 6 includes:

[0119] The tip-side convex bend 641 protrudes radially inward toward the inner side of the compressor impeller 3;

[0120] The hub-side convex bend 642 is located at the tip end 644 of the trailing edge 64 in the axial direction of the compressor impeller 3, further away from the blade tip-side convex bend 641, and protrudes radially outward from the compressor impeller 3; and

[0121] Inflection point 643 is located between the blade tip convex bend 641 and the hub convex bend 642, and is located at the center of the blade 6 in the spanwise direction.

[0122] According to the structure described in 5) above, by providing an inflection point 643 at the center of the blade 6 in the spanwise direction of the trailing edge 64, the abrupt change in the radial length of the trailing edge 64 in the aforementioned central portion of the trailing edge 64 can be suppressed. This makes the difference in radial length between the hub end 61 and the middle position of the trailing edge 64 in the spanwise direction of the blade 6 relatively small, thereby making the blade load at these positions more uniform. This effectively suppresses the generation of secondary flow or the expansion of the low-speed region LSA, thus improving the efficiency of the centrifugal compressor 1.

[0123] 6) In some embodiments, the compressor impeller 3 of the centrifugal compressor 1 according to 5) above, wherein,

[0124] The trailing edge 64 in the meridional plane shape of the blade 6 is configured as follows:

[0125] In the convex bend 641 at the blade tip, the radial gradient relative to the axial gradient is the largest.

[0126] According to the structure described in 6) above, by setting the gradient in the hub-side convex bend 642 to a relatively small gradient, the abrupt change in the radial length of the trailing edge 64, which is closer to the hub side than the central portion of the trailing edge 64, can be suppressed. This makes the difference in radial length between the hub-side end 61 and the trailing edge 64 at the midpoint of the spanwise direction of the blade 6 relatively small, thereby making the blade load at these positions more uniform. This effectively suppresses the generation of secondary flow or the expansion of the low-speed region LSA, thus improving the efficiency of the centrifugal compressor 1.

[0127] 7) In some embodiments, the compressor impeller 3 of the centrifugal compressor 1 according to any one of 1) to 6) above, wherein,

[0128] The hub 5 has multiple short blades 7, which are respectively disposed on the circumferential surface 51 of the hub 5 between adjacent blades 6.

[0129] When the blade 6 with suction surface 66 facing the short blade 7 across the first flow path 81 for fluid flow is defined as one side blade 6A, and the blade 6 with pressure surface 65 facing the short blade 7 across the second flow path 82 for fluid flow is defined as the other side blade 6B,

[0130] At the midpoint of the spanwise direction of the blade 6, the throat width TH1 of the leading edge 73 of the short blade 7 relative to the side blade 6A is greater than the throat width TH2 of the leading edge 73 of the short blade 7 relative to the other side blade 6B.

[0131] According to the structure described in 7) above, by making the throat width TH1 of one side blade 6A greater than the throat width TH2 of the other side blade 6B at the middle position in the spanwise direction of the blade 6, the inflow of fluid into the second flow path 82 can be suppressed. Here, the second flow path 82 is more prone to generating the aforementioned secondary flow or low-speed region LSA compared to the first flow path 81. By suppressing the inflow of fluid into the second flow path 82, the generation of the aforementioned secondary flow or the expansion of the low-speed region LSA can be effectively suppressed, thus improving the efficiency of the centrifugal compressor 1.

[0132] 8) In some embodiments, the compressor impeller 3 of the centrifugal compressor 1 according to 7) above is configured as follows:

[0133] More than the middle position of the blade 6 in the spanwise direction, closer to the hub side end 61, the throat width TH2 of the leading edge 73 of the short blade 7 relative to the other side blade 6B is greater than the throat width TH1 of the leading edge 73 of the short blade 7 relative to the one side blade 6A.

[0134] According to the structure described in 8), even if the throat width TH1 relative to one side blade 6A and the throat width TH2 relative to the other side blade 6B are reversed at the middle position of the blade 6 in the spanwise direction, the inflow of fluid into the second flow path 82 can be suppressed by making the throat width TH1 relative to one side blade 6A greater than the throat width TH2 relative to the other side blade 6B at the middle position of the blade 6 in the spanwise direction.

[0135] 9) The centrifugal compressor 1 according to at least one embodiment of the present invention comprises:

[0136] The compressor impeller 3 of the centrifugal compressor 1 as described in any one of 1) to 8) above.

[0137] Based on the structure described in 9), the centrifugal compressor 1 equipped with the compressor impeller 3 can suppress the generation of the secondary flow or the expansion of the low-speed region LSA, thus achieving an increase in the efficiency of the centrifugal compressor 1.

[0138] Symbol Explanation

[0139] 1-Centrifugal compressor, 2-Rotating shaft, 3-Compressor impeller, 4-Housing, 5-Hub, 6-Blade (long blade), 7-Short blade, 10-Turbocharger, 11-Turbine, 12-Turbine rotor, 13-Turbine housing, 14-Bearing, 15-Bearing housing.

Claims

1. A compressor impeller for a centrifugal compressor, comprising a hub and a plurality of blades spaced circumferentially on the circumferential surface of the hub, wherein, The plurality of blades are respectively configured as follows: In the case where the angle between the blade and the meridional plane is defined as the blade angle, the imaginary line formed by the set of intermediate positions in the spanwise direction of the blade is defined as the spanwise midline, the blade angle at the hub-side end of the blade is defined as the hub-side blade angle, the blade angle on the spanwise midline of the blade is defined as the spanwise mid-blade angle, and the blade angle at the tip-side end of the blade is defined as the tip-side blade angle,... From the leading edge to the trailing edge of the dimensionless meridional length position at the hub-side end of the blade, there is a first interval in which the difference between the blade tip angle relative to the dimensionless meridional length position and the hub-side blade angle at the same position is 10° or more. On the side closer to the trailing edge position than the midpoint between the leading edge position and the trailing edge position at the dimensionless meridional length position, there is a second interval where the variation of the spanwise intermediate blade angle relative to the difference between the dimensionless meridional length position and the hub-side end blade angle at the same position falls within ±2°.

2. The compressor impeller of the centrifugal compressor according to claim 1, wherein, The plurality of blades are respectively configured as follows: The middle position and the trailing edge position of the dimensionless meridional length position at the hub side end of the blade are included in the second interval.

3. The compressor impeller of the centrifugal compressor according to claim 1 or 2, comprising a plurality of short blades, wherein the plurality of short blades are respectively disposed on the circumferential surface of the hub between adjacent blades. The plurality of blades are respectively configured as follows: The second interval also exists between the leading edge position of the short blade at the dimensionless meridional length position at the hub side end of the blade and the middle position.

4. The compressor impeller of the centrifugal compressor according to claim 1 or 2, wherein, The second interval occupies more than 20% of the area from the leading edge to the trailing edge of the dimensionless meridian plane.

5. The compressor impeller of the centrifugal compressor according to claim 1 or 2, wherein, The trailing edge of the meridional plane shape of the blade includes: The blade tip has a convex bend that protrudes radially inward toward the inner side of the compressor impeller; The hub-side convex bend is located at the tip end of the compressor impeller's trailing edge in the axial direction, further away from the blade tip-side convex bend than the blade tip-side convex bend, and protrudes radially outward from the compressor impeller; and The inflection point is located between the convex bend of the blade tip and the convex bend of the hub, and is located at the center of the blade in the spanwise direction.

6. The compressor impeller of the centrifugal compressor according to claim 5, wherein, The trailing edge of the meridional plane shape of the blade is configured as follows: The radial gradient relative to the axial gradient is greatest in the convex bend of the blade tip.

7. The compressor impeller of the centrifugal compressor according to claim 1 or 2, comprising a plurality of short blades, wherein the plurality of short blades are respectively disposed on the circumferential surface of the hub between adjacent blades. In the case where the blade with the suction surface facing the short blade across the first flow path for fluid flow is defined as a one-side blade, and the blade with the pressure surface facing the short blade across the second flow path for fluid flow is defined as the other-side blade, At the midpoint of the spanwise direction of the blade, the throat width of the leading edge of the short blade relative to the blade on one side is greater than the throat width of the leading edge of the short blade relative to the blade on the other side.

8. The compressor impeller of the centrifugal compressor according to claim 7, wherein the impeller is configured as follows: At a position closer to the hub end than the middle position of the blade in the spanwise direction, the throat width of the leading edge of the short blade relative to the other blade is greater than the throat width of the leading edge of the short blade relative to the other blade.

9. A centrifugal compressor, comprising: The compressor impeller of the centrifugal compressor according to claim 1 or 2.

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