CENTRIFUGAL COMPRESSOR IMPELLER AND CENTRIFUGAL COMPRESSOR

Abstract

Impeller (6, 6A, 6B, 6C) of a radial compressor (5), comprising: a hub (18); a plurality of full blades (21) arranged on a circumferential surface (18a) of the hub (18) at intervals in a circumferential direction; and a plurality of splitter blades (22, 22A, 22B, 22C, 22D), each of which is arranged between adjacent full blades (21) of the plurality of full blades (21) on the peripheral surface (18a) of the hub (18), wherein, with respect to a chord position along a chord direction of each full blade (21) on a meridional plane of the impeller (6, 6A, 6B, 6C), if the chord position at a leading edge (21a) of each full blade (21) is defined as 0%, the chord position at a trailing edge (21b) of each full blade (21) is defined as 100%, the chord position at a base end (22c) of a leading edge (22a) of each splitter blade (22, 22A, 22B, 22C, 22D) is defined as Ch, and the chord position at a tip end (22d) of the leading edge (22a) of each splitter blade (22, 22A, 22B, 22C, 22D) is defined as Ct, Ch ≤ 30% and Ct ≥ 50% are met.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a radial compressor impeller and a radial compressor. BACKGROUND

[0002] Traditionally, turbochargers (superchargers) are widely used as a technique to improve the performance of engines, such as automobile engines and marine engines, to compress intake air drawn into the engines and supply the oxygen-rich intake air with increased density to the engines.

[0003] A turbocharger, for example, includes a rotating shaft, a radial compressor (compressor) provided at one end of the rotating shaft, and a turbine provided at the other end of the rotating shaft, and is configured to rotate an impeller (turbine wheel) of the turbine by energy of exhaust gas from an engine, rotate the rotating shaft and thus an impeller (compressor wheel) of the radial compressor around the axis with the rotation of the turbine wheel to compress the intake air, and supply it to the engine.

[0004] The impeller of the radial compressor includes a substantially frustoconical hub (compressor hub) coaxially connected to the rotating shaft, and a plurality of rotor blades (compressor rotor blades) arranged at predetermined intervals in the circumferential direction around the axis and extending outwardly from the outer peripheral surface of the hub substantially in the radial direction.

[0005] Here, if the plurality of rotor blades have the same shape and size, the difference in the flow velocity of the fluid (compressed air, etc.) between the pressure side and the suction side of each rotor blade becomes very large, which may lead to poor impeller efficiency.

[0006] For this reason, conventionally, the impeller of this type often includes not only a plurality of full blades (long blades) arranged at predetermined intervals in the circumferential direction, but also splitter blades (short blades, intermediate blades) arranged between every two adjacent full blades in the circumferential direction as rotor blades in order to improve the impeller efficiency.

[0007] However, the flow velocity of the incoming flow between adjacent full blades can vary, for example, between opposite sides of each splitter blade, i.e., between the pressure and suction sides of the full blades, with a higher flow velocity on the suction side. As a result, even if splitter blades are provided such that the cross-sectional areas of flow passages (paths) on opposite sides of each splitter blade are geometrically equal, the flow rate on the suction side is higher than on the pressure side due to the higher flow velocity, causing an uneven flow rate between the passages and the inability to evenly distribute the fluid.The uneven flow rate between the passes and the inability to distribute the fluid evenly can cause uneven blade loading, which increases the energy loss of the compressed air flowing through the passes and prevents the desired improvement in impeller efficiency from being achieved.

[0008] For this reason, much research has been conducted on the shape, number and arrangement of solid blades and splitter blades to improve impeller efficiency.

[0009] For example, Patent Document 1 discloses a centrifugal compressor impeller in which the leading edge blade angle θ of the splitter blade at the inlet end varies in the height direction from the hub surface, the tip portion is inclined toward the suction side of the full blade at an inclination angle larger than that of the other portions, and the hub surface side portion is inclined toward the pressure side of the full blade at an inclination angle larger than that of the other portions.

[0010] In this centrifugal compressor impeller, by configuring the splitter blade as described above, the splitter blade is adapted to a complex internal flow of the centrifugal compressor, that is, the interference between the leading edge of the splitter blade and the leakage flow across the tip end of the full blade (through the tip gap) is suppressed, resulting in uniform flow distribution, high pressure ratio and high efficiency (that is, further improving the impeller efficiency).

[0011] Patent Document 2 discloses an impeller including a protrusion protruding from the outer peripheral surface of the hub between the adjacent full blade and splitter blade (first splitter blade) and extending along the flow direction of a fluid flowing radially outward between the adjacent full blade and splitter blade.

[0012] In this impeller, the protrusion acts as a second splitter blade to prevent the fluid flowing between the protrusion and the full blade or between the protrusion and the splitter blade from slipping off the side. This allows the impeller to exert a stronger radially outward force on the fluid, resulting in uniform flow distribution, a high pressure ratio, and high efficiency. Citation listPatent literature Patent Document 1: JP2011-80 411A Patent Document 2: JP2017-44 190A Patent Document 3: JP2008-196 381 A Patent Document 4: JP2004-44 473 A Patent document 5: WO 2005 / 054 681 A1 SUMMARYTask to be solved

[0013] On the other hand, the present inventors have carried out careful research and found that, as in Fig. As shown in Figure 8, the flow A2 entering the axis side (inner side, hub 18 side) of the impeller 6 is gradually directed outward by centrifugal force and gradually inclined with respect to the direction of the axis O1, and runs along the peripheral surface 18a of the hub 18 from the base side of the rotor blade 21 up the wall surface (blade surface) of the rotor blade 21. The flow A2 running up the wall surface of the rotor blade 21 collides with the main flow A1 entering in the direction of the axis O1 from the inlet side of the impeller 6 to generate a secondary flow A3, which separates from the wall surface of the rotor blade 21 and flows to the outlet side of the impeller 6.

[0014] Furthermore, the present inventors have found the following new findings: the position (separation line S) at which the separation occurs and the secondary flow A3 is generated remains almost unchanged from the pumping side (low flow rate side) to the throttling side (maximum flow side) on the pressure side of the rotor blade 21; this trend is slightly more prominent on the pumping side with higher pressure ratio; and the similar trend is observed on the suction side of the rotor blade 21 and found that the secondary flow A3 caused by these separations greatly affects the reduction of the impeller efficiency.

[0015] Therefore, based on such research results, the development of a technique for suppressing the generation of secondary flow was strongly desired.

[0016] In view of the above circumstances, an object of the present disclosure is to provide a centrifugal compressor impeller and a centrifugal compressor, whereby it is possible to suppress the generation of the secondary flow, achieve uniform flow distribution, high pressure ratio and high efficiency more efficiently and effectively compared with conventional ones, and further improve the impeller efficiency. Solution of the tasks

[0017] The centrifugal compressor impeller according to the present invention includes: a hub; a plurality of full blades arranged on a peripheral surface of the hub at intervals in a circumferential direction; and a plurality of splitter blades, each of which is arranged between adjacent full blades of the plurality of full blades on the peripheral surface of the hub. When a blade height ratio, which is a ratio of a blade height (Hf) of each full blade to a blade height (Hs) of each splitter blade on a meridional plane of the impeller, is defined as Hs / Hf, the blade height ratio preferably satisfies Hs / Hf < 1 at least at a leading edge of each splitter blade.

[0018] Further, a radial compressor according to one aspect of the present disclosure is provided with the radial compressor impeller described above. Beneficial effects

[0019] With the centrifugal compressor impeller and the centrifugal compressor according to one aspect of the present disclosure, it is possible to suppress the generation of the secondary flow, achieve uniform flow distribution, high pressure ratio and high efficiency more efficiently and effectively compared to conventional ones, and further improve the impeller efficiency. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing an example of a turbocharger equipped with the centrifugal compressor according to first and second embodiments of the present disclosure. Fig. 2 is a partial cross-sectional view showing an example of the centrifugal compressor and the centrifugal compressor impeller according to the first embodiment of the present disclosure. Fig. 3 is a partial cross-sectional view showing a modified example of the centrifugal compressor and the centrifugal compressor impeller according to the first embodiment of the present disclosure. Fig. 4 is a partial cross-sectional view showing a modified example of the centrifugal compressor and the centrifugal compressor impeller according to the first embodiment of the present disclosure. Fig. 5 is a partial cross-sectional view showing a modified example of the centrifugal compressor and the centrifugal compressor impeller according to the first embodiment of the present disclosure. Fig. 6 is a partial cross-sectional view showing an example of the centrifugal compressor and the centrifugal compressor impeller according to the second embodiment of the present disclosure. Fig. 7 is a partial plan view showing the centrifugal compressor and rotor blades and protrusions of the centrifugal compressor impeller according to the second embodiment of the present disclosure. Fig. Figure 8 is a diagram showing the position (parting line) where the fluid flowing between the rotor blades of the centrifugal compressor impeller separates from the blade surface. Fig. 9 is a partial cross-sectional view showing an example of the centrifugal compressor and the centrifugal compressor impeller according to the first (second) embodiment of the present disclosure, and showing the blade height, chord length, etc. DETAILED DESCRIPTION (First Embodiment)

[0020] Hereinafter, the radial compressor impeller and the radial compressor according to the first embodiment will be described with reference to the Fig. 1 to Fig. 5, Fig. 8 and Fig. 9 described.

[0021] In the present embodiment, the centrifugal compressor of the present disclosure is described as being provided in a turbocharger, but the centrifugal compressor of the present disclosure may be, for example, an electric centrifugal compressor, and the fluid to be compressed does not need to be limited to air. That is, the centrifugal compressor (and the centrifugal compressor impeller) of the present disclosure may be any centrifugal compressor capable of compressing and supplying a fluid, and may be configured by a centrifugal compressor alone or in combination with a mechanism or device other than a turbine. Furthermore, there is no need to limit the use or the like. (turbocharger)

[0022] For example, as in Fig. 1, a turbocharger 1 according to the present embodiment is configured to rotate an impeller 3 (turbine wheel) of a turbine 2 by energy of exhaust gas G from an engine such as an automobile engine or a marine engine about the axis (rotation axis) O1, rotate a rotary shaft 4 coaxially connected to the impeller 3, thus rotate an impeller (compressor wheel) 6 of a centrifugal compressor (compressor) 5 coaxially connected to the rotary shaft 4, to suck and compress the air (intake air, fluid) A through the impeller 6, and supply the compressed air A' to the engine. (Turbine)

[0023] The turbine 2 includes an impeller 3 coaxially connected to the other end of the rotating shaft 4, and a turbine cover (turbine casing) 7 accommodating the impeller 3.

[0024] The impeller 3 includes a substantially frusto-conical turbine hub 8 coaxially connected to the rotating shaft 4, and a plurality of turbine rotor blades 9 extending from the outer peripheral surface of the turbine hub 8 in the radial direction outwardly around the axis O1.

[0025] On the outer side of the impeller 3 of the turbine 2 in the radial direction around the axis O1, an exhaust passage R5 is provided, which consists of a spiral passage R3 arranged around the impeller 3 for supplying the exhaust gas G discharged from the engine to the impeller 3, and a nozzle passage R4 provided with a device for adjusting the exhaust gas flow rate, such as nozzle vanes 10.

[0026] Furthermore, on the rear side of the impeller 3 in the direction of the axis O1 (on the side of the exhaust gas G discharge port 11), a discharge duct R6 (exhaust gas duct R5) is provided coaxially with the impeller 3 to receive the exhaust gas G from the outlet of the turbine rotor blades 9 of the impeller 3 and discharge it to the outside. The discharge duct R6 consists of an exhaust gas diffuser 12.

[0027] In the turbocharger 1 according to this embodiment, the spiral passage R3, the nozzle passage R4 and the discharge passage R6 (exhaust gas diffuser 12) are formed by the turbine cover 7 which accommodates the impeller 3. (Central compressor: compressor)

[0028] The centrifugal compressor 5 according to the present embodiment includes an impeller (compressor wheel) 6 of the centrifugal compressor 5 coaxially connected to one end side of the rotary shaft 4 rotatably supported by bearing frames 15, 16, and a compressor cover 17 accommodating the impeller 6.

[0029] The impeller 6 of the radial compressor 5 includes a substantially frustoconical compressor hub (hub) 18 coaxially connected to the rotating shaft 4, and a plurality of compressor rotor blades (impeller rotor blades) 19 extending from the outer peripheral surface of the compressor hub 18 in the radial direction outwardly around the axis O1.

[0030] On the front side of the impeller 6 in the direction of the axis O1 (on the side of the suction port 20 for the air A), an intake duct R1 is provided to suck in the air A with the rotation of the impeller 6 and supply it to the impeller 6.

[0031] Further, on the outer side of the impeller 6 in the radial direction around the axis O1, a compressed air passage (compressed air passage) R2 having a spiral r2 is provided to receive the compressed air A' discharged from the impeller 6 and supply it to the motor.

[0032] In the turbocharger 1 according to the present embodiment having the above configuration, the exhaust gas G discharged from the engine is supplied from the radially outer side of the impeller 3 of the turbine 2 through the scroll passage R3 and the nozzle passage R4 of the turbine 2, and the energy of the exhaust gas G drives the impeller 3 to rotate. The rotation of the impeller 3 drives the rotary shaft 4 and the impeller 6 of the centrifugal compressor 5 to rotate.

[0033] With the rotation of the impeller 6, air A is sucked in from the intake port 20, flows through the intake passage R1, and is supplied to the impeller 6 while being compressed. The compressed air A' is then supplied to the engine through the compressed air passage R2. The exhaust gas G, which has driven the impeller 3 of the turbine 2, flows through the discharge passage R6 of the exhaust diffuser 12, recovers the pressure, and is discharged to the outside. (Impeller of the radial compressor)

[0034] The impeller 6 of the centrifugal compressor 5 according to the present invention includes a hub 18, a plurality of full blades 21 arranged on the circumferential surface 18a of the hub 18 at intervals in the circumferential direction around the axis (shaft) O1, and a plurality of splitter blades 22, each of which is arranged between adjacent full blades 21 of the plurality of full blades 21 on the circumferential surface 18a of the hub 18.

[0035] Here, as described above ( Fig. 8), the present inventors conducted careful research and found that the flow A2 entering the axis (O1, rotating shaft 4) side of the impeller 6 of the centrifugal compressor 5 is gradually directed outward by centrifugal force and gradually inclined with respect to the axis O1 direction, and along the peripheral surface 18a of the hub 18 from the hub side (base end side) of the rotor blade 21, the blade surface (wall surface) of the rotor blade 21 upwards. The flow A2 collides with the main flow A1 entering from the inlet side of the impeller 6 to generate a secondary flow A3, which separates from the blade surface of the rotor blade (21) and flows to the outlet side.

[0036] Furthermore, the present inventors have found the following new findings: the parting line (boundary position) S at which the separation occurs and the secondary flow A3 is generated remains almost unchanged from the pumping side to the throttling side on the pressure side of the rotor blade (21); this trend is slightly more prominent on the pumping side with higher pressure ratio; and the similar trend is observed on the suction side of the rotor blade (21), and found that the secondary flow A3 caused by these separations greatly influences the reduction of the impeller efficiency.

[0037] Furthermore, it was found that, in a meridional plane (meridional plane cross-section) of the impeller 6, which is Fig. 8 and Fig. 9, when the chord position along the chord length L at the leading edge 21a of the full blade 21 is defined as 0% and the chord position at the trailing edge 21b of the full blade 21 is defined as 100%, the parting line S where the separation occurs and the secondary flow A3 is generated is formed in a concave curved shape (concave arc shape) in which the line gradually extends from the base end 21c on the leading edge 21a side (approximately 0% to 5% position) of the full blade 21 to the tip end 21d side on the trailing edge 21b side of the full blade 21 and reaches the tip end 21d at approximately the 70% position.

[0038] In addition, it was confirmed that the impeller efficiency is reduced by interference with the leakage flow exiting through a gap on the tip end 21d (tip side) side of the full blade 21, particularly interference with the leakage flow exiting through a gap on the leading edge 21a side of the full blade 21.

[0039] Based on the above-described remarkable results and findings of the present inventors, as described in Fig. 2 (see Fig. 9), the impeller 6A (6) of the centrifugal compressor 5 according to the present embodiment is configured such that when a blade height ratio, which is a ratio of a blade height (Hf) of the full blade 21 to a blade height (Hs) of the splitter blade 22A on the meridional plane (meridional plane cross section) of the impeller 6, is defined as Hs / Hf, the blade height ratio satisfies Hs / Hf < 1 at least at the leading edge 22a of the splitter blade 22A.

[0040] The meridional plane of the impeller 6 in the present disclosure refers to a flow passage cross section of the impeller 6 of the centrifugal compressor 5 cut along the central axis (O1) and superimposed on a projection of the rotor blade rotated along the central axis (O1), not to a cross section of the rotor blade 19 (full blade 21, splitter blade 22) as it is.

[0041] The blade height Hf of the full blade 21 and the blade height Hs of the splitter blade 22A (22) in the present disclosure are each a length dimension from the base end 21c, 22c to the tip end 21d, 22d in the direction perpendicular to the center line P1, P2 between the base end 21c, 22c and the tip end 21d, 22d, in the meridional plane of the impeller 6.

[0042] Furthermore, the blade height ratio Hs / Hf, which is the ratio of the blade height (Hf) of the full blade 21 to the blade height (Hs) of the splitter blade 22A, is the blade height ratio at the same chord position.

[0043] In the impeller 6A of the centrifugal compressor 5 according to the present embodiment, since the splitter blade 22A is configured to satisfy the blade height ratio Hs / Hf < 1 at least at the leading edge 22a, the splitter blade 22A having a smaller blade height than the full blade 21 blocks the flow A2 along the circumferential surface 18a of the hub 18 to the blade surface (wall surface) of the full blade 21. Thus, it is possible to suppress the generation of the flow A2 running up the blade surface of the full blade 21 and thus the generation of the secondary flow A3 by the splitter blade 22A.

[0044] Further, when the blade height ratio Hs / Hf < 1 at least at the leading edge 22a of the splitter blade 22A, it is possible to effectively suppress interference with the leakage flow exiting through the gap on the tip end 22d side of the full blade 21.

[0045] Thus, with the impeller 6A of the centrifugal compressor 5 and the centrifugal compressor 5 including the same according to the present embodiment, it is possible to suppress the generation of the secondary flow and suppress interference with the leakage flow, achieve uniform flow distribution, high pressure ratio and high efficiency more efficiently and effectively compared with conventional ones, and further improve the impeller efficiency.

[0046] Here, the impeller 6A of the centrifugal compressor 5 (and the centrifugal compressors 5 including the same) according to the present embodiment is preferably configured so that the blade height ratio Hs / Hf < 1 in the entire section from the leading edge 22a to the trailing edge 22b of the splitter blade 22A, that is, at all chord positions from the leading edge 22a to the trailing edge 22b of the splitter blade 22A.

[0047] With this configuration, it is possible to suppress interference with the leakage flow by the splitter blade 22A having a smaller blade height than the full blade 21 and to suppress generation of the flow A2 running up the blade surface of the full blade 21 and thus generation of the secondary flow A3 by the splitter blade 22A.

[0048] Furthermore, the impeller 6A of the radial compressor 5 according to the present embodiment is preferably configured so that the blade height ratio Hs / Hf ≤ 0.7 satisfies at least at the leading edge 22a of the splitter blade 22A.

[0049] With this configuration, it is possible to suppress interference with the leakage flow exiting through the gap on the tip end 22d side of the full blade 21A, while more effectively suppressing the generation of the secondary flow A3.

[0050] Further, the impeller 6A of the centrifugal compressor 5 according to the present embodiment is preferably configured so that the blade height ratio Hs / Hf satisfies ≤ 0.7 in the entire section from the leading edge 22a to the trailing edge 22b of the splitter blade 22A.

[0051] With this configuration, it is possible to suppress the generation of the secondary flow A3 and more effectively suppress interference with the leakage flow exiting through the gap on the tip end 21d side of the full blade 21.

[0052] Furthermore, as in Fig. 3 (see Fig. 8 and Fig. 9), the impeller 6B (6) of the centrifugal compressor 5 according to the present embodiment may be configured such that the blade height ratio Hs / Hf gradually increases from the leading edge 22a to the trailing edge 22b of the splitter blade 22B (22C, 22D (22)).

[0053] With this configuration, for example, by forming the splitter blade 22B (22) in accordance with the parting line S, it is possible to suppress the generation of the secondary flow A3 and to suppress interference with the leakage flow exiting through the gap on the tip end 22d side of the full blade 21 more effectively and efficiently.

[0054] According to the invention, based on the findings obtained as a result of thorough research by the inventors as described above, the impeller 6 (6A, 6B, 6C) of the centrifugal compressor 5 according to the present invention is configured such that, with respect to the chord position along the chord (chord length L) direction of the full blade 21 on the meridional plane of the impeller 6, when the chord position at the leading edge 21a of the full blade 21 is defined as 0%, the chord position at the trailing edge 21b of the full blade 21 is defined as 100%, the chord position at the base end 22c of the leading edge 22a of the splitter blade 22 (22A, 22B, 22C) is defined as Ch, and the chord position at the tip end 22d of the leading edge 22a of the splitter blade 22 is defined as Ct, Ch ≤ 30%, and Ct ≥ 50 % are met, as in Fig. 2, Fig. 3 and Fig. 4 (see Fig. 8 and Fig. 9) is shown.

[0055] With this configuration, the splitter blade 22 can be formed in accordance with the position of the parting line S where the secondary flow A3 can be generated, so that it is possible to suppress the generation of the secondary flow A3 and effectively and efficiently suppress interference with the leakage flow exiting through the gap on the tip end 21d side of the full blade 21.

[0056] Furthermore, as in the Fig. 4 and Fig. 5 (see Fig. 8 and Fig. As shown in FIG. 9), the impeller 6 (6C, 6D) of the centrifugal compressor 5 according to the present embodiment may be configured such that, when a chord length L at the base end 22c of the splitter blade 22 (22C, 22D) is defined as Lh, and a chord length L at the tip end 22d of the splitter blade 22 is defined as Lt, 2 × Lt ≤ Lh is satisfied. In other words, the blade may have a leading edge shape such that the hub-side chord length Lh is twice or more than the tip-side chord length Lt.

[0057] In this case, similarly, based on findings obtained as a result of diligent research by the present inventors, the splitter blade 22 can be formed in accordance with the position of the parting line S where the secondary flow A3 can be generated, so that it is possible to suppress the generation of the secondary flow A3 and effectively and efficiently suppress interference with the leakage flow exiting through the gap on the tip end 22d side of the full blade 21.

[0058] Furthermore, as in Fig. 4 and Fig. 5 (see Fig. 8 and Fig. 9), the leading edge 22a of the splitter blade 22 (22C, 22D) may have a concave curved portion 22e which is concave with respect to a straight line connecting the base end 22c and the tip end 22d of the leading edge 22a on the meridional plane.

[0059] In this case, based on findings obtained as a result of diligent research by the present inventors, the splitter blade 22 can be formed in accordance with the concavely curved parting line S where the secondary flow A3 can be generated, so that it is possible to suppress the generation of the secondary flow A3 and suppress interference with the leakage flow exiting through the gap on the tip end 21d side of the full blade 21 more effectively and efficiently.

[0060] Furthermore, as in Fig. 4 and Fig. 5 shown (see Fig. 8 and Fig. 9), the chord position Ch at the base end 22c of the leading edge 22a of the splitter blade 22 (22D) can be adjusted to satisfy Ch = 0%. In other words, the leading edge 22a of the splitter blade 22 on the hub side can extend to the leading edge 21a of the full blade 21 so that their leading edges are aligned in the same position (including substantially the same position).

[0061] In this case, it is possible to block the flow along the peripheral surface 18a of the hub 18 toward the blade surface of the full blade 21 and to suppress the generation of the secondary flow A3 by the splitter blade 22 even more effectively. (Second embodiment)

[0062] Next, the centrifugal compressor impeller and the centrifugal compressor according to the second embodiment will be described with reference to the Fig. 6 and Fig. 7 described ( Fig. 1 to Fig. 5, Fig. 8 and Fig. 9).

[0063] In the present embodiment, as in the first embodiment, it is assumed that the centrifugal compressor 5 is provided in the turbocharger 1. This embodiment differs from the first embodiment only in the configuration of the impeller 6 of the centrifugal compressor 5. Therefore, in the present embodiment, the same configurations as those in the first embodiment are associated with the same reference numerals and will not be described in detail again. (Impeller of the radial compressor)

[0064] The impeller 6 (6E) of the radial compressor 5 of the turbocharger 1 according to the present embodiment includes, as shown in Fig. 6 ( Fig. 1), a hub 18, a plurality of full blades 21 arranged on the circumferential surface 18a of the hub 18 at intervals in the circumferential direction, and a plurality of splitter blades 22, each of which is arranged between adjacent full blades 21 of the plurality of full blades 21 on the circumferential surface 18a of the hub 18.

[0065] Here, the impeller 6 (6E) of the centrifugal compressor 5 of the present embodiment may include any of the splitter blades 22 described as the splitter blade 22 in the first embodiment (including modifications of the first embodiment), although there is no particular limitation.

[0066] In addition, the impeller 6 (6E) of the centrifugal compressor 5 of the present embodiment further includes a plurality of protrusions 25 (e.g., vortex generator VG) configured to protrude from the peripheral surface 18a of the hub 18, with at least one protrusion being arranged between each adjacent full blades 21 (first full blade 21A and second full blade 21B).

[0067] The projection 25 is provided such that, as in Fig. 6 and Fig. 7 (see Fig. 9), with respect to the chord position along the chord direction of the full blade 21 on the meridional plane of the impeller 6 (6E), when the chord position at the leading edge 21a of the full blade 21 is defined as 0%, the chord position at the trailing edge 21b of the full blade 21 is defined as 100%, and the chord position at the upstream edge 25a of the projection 25 is defined as Cvl, Cvl ≤ 50% is satisfied, and when a blade height of the full blade 21 is defined as Hf, and a height of the projection 25 on the meridional plane is defined as Hv, Hv ≤ 0.3 × Hf is satisfied.

[0068] As in the first embodiment, the blade height Hf of the full blade 21 and the height Hv of the projection 25 in the present disclosure are each a length dimension from the base end 21c, 25c to the tip end 21d, 25 in the direction perpendicular to the center line P1, P3 between the base end 21c, 25c and the tip end 21d, 25d in the meridional plane of the impeller 6.

[0069] When the protrusion 25 is provided, the protrusion 25 with a small height guides the flow along the peripheral surface 18a of the hub 18 to the blade surface of the full blade 21 (or splitter blade 22) in the direction along the blade surface on the peripheral surface 18a of the hub 18, that is, to the trailing edge 21b of the full blade 21, to generate a flow to the trailing edge 21b of the full blade 21 more smoothly than the conventional flow. As a result, the flow running up the blade surface of the full blade 21 (or splitter blade 22) is less likely to occur, and it is possible to further suppress the generation of the secondary flow A3.

[0070] Thus, with the impeller 6 of the centrifugal compressor 5 and the centrifugal compressor 5 including the same according to the present embodiment, it is possible to suppress the generation of the secondary flow A3 and more strongly suppress interference with the leakage flow, achieve uniform flow distribution, high pressure ratio and high efficiency more efficiently and effectively compared with conventional ones, and further improve the impeller efficiency than in the first embodiment.

[0071] Here, in the impeller 6 of the radial compressor 5 according to the present embodiment, the upstream edge 25a of the projection 25 is preferably arranged upstream of the leading edge 22a of the splitter blade 22.

[0072] With this configuration, the low-height protrusion 25 more effectively directs the flow along the peripheral surface 18a of the hub 18 toward the blade surface of the full blade 21 (or splitter blade 22) in the direction along the blade surface, creating a smoother and more organized flow than the conventional flow. Thus, it is possible to further suppress the generation of the secondary flow A3.

[0073] The centrifugal compressor impeller and the centrifugal compressor including the same according to the first and second embodiments of the present disclosure have been described above. However, the centrifugal compressor impeller and the centrifugal compressor of the present disclosure are not limited to the first and second embodiments, and various modifications may be applied as long as they do not deviate from the scope of the present disclosure.

[0074] For example, in the second embodiment, the impeller 6 of the centrifugal compressor 5 includes the projections 25 in addition to the splitter blades 22 of the first embodiment, but the impeller 6 may not include the splitter blades 22 but include the plurality of projections 25 configured to protrude from the peripheral surface 18a of the hub 18, with at least one projection 25 disposed between each adjacent full blade 21.

[0075] In this configuration, it is preferably configured such that, with respect to the chord position along the chord direction of the full blade 21 on the meridional plane of the impeller 6, when the chord position at the leading edge 21a of the full blade 21 is defined as 0%, the chord position at the trailing edge 21b of the full blade 21 is defined as 100%, and the chord position at the upstream edge 25a of the projection 25 is defined as Cvl, Cvl ≤ 50% is satisfied, and when a blade height of the full blade 21 is defined as Hf, and a height of the projection 25 on the meridional plane is defined as Hv, Hv ≤ 0.3 × Hf is satisfied.

[0076] In this case, the protrusion 25 effectively guides the flow along the peripheral surface 18a of the hub 18 toward the blade surface of the full blade 21 in the direction along the blade surface, generating a smoother flow than the conventional flow. As a result, the flow running up the blade surface of the full blade 21 is less likely to occur, and it is possible to further suppress the generation of the secondary flow A3. In addition, it is possible to suppress interference with the leakage flow, efficiently and effectively achieve uniform flow distribution, high pressure ratio, and high efficiency compared to conventional ones, and further improve the impeller efficiency.

[0077] Furthermore, as in Fig.7, it may be configured such that when a pitch distance along the circumferential direction between the upstream edge 25a of the protrusion 25 and the suction surface of a first full blade 21A, which is one of the adjacent full blades 21, is defined as Pl1, and a pitch distance along the circumferential direction between the upstream edge 25a of the protrusion 25 and the pressure surface of a second full blade 21B, which is the other of the adjacent full blades 21, is defined as Pl2, Pl1 < Pl2 is satisfied.

[0078] In this case, the protrusion 25 guides the flow A2 more efficiently and effectively to the suction surface of the first full blade 21A in the direction along the blade surface (toward the trailing edge 21b of the first full blade 21A) to appropriately produce a smoother and more organized flow than the conventional flow.

[0079] Furthermore, the at least one protrusion 25 disposed between adjacent full blades 21 may include a first protrusion 25A and a second protrusion 25B different from the first protrusion 25A. In other words, two or more protrusions 25 may be disposed between the blades.

[0080] In this case, each protrusion 25, the first protrusion 25A and the second protrusion 25B, guides the flow A2 along the peripheral surface 18a of the hub 18 toward the blade surface of the full blade 21 (or splitter blade 22) in the direction along the blade surface, more effectively generating a more organized flow than the conventional flow. As a result, the flow running up the blade surface of the full blade 21 (or splitter blade 22) is even less likely to occur, and it is possible to further suppress the generation of the secondary flow A3.

[0081] Furthermore, in this case, the upstream edge 25a of the first protrusion 25A is preferably located upstream of the upstream edge 25a of the second protrusion 25B. In other words, it is preferable that the two or more protrusions 25 (25A, 25B) are arranged at different positions in the flow direction.

[0082] In this case, each projection 25 (25A, 25B) more effectively guides the flow A2 to the blade surface in the direction along the blade surface to produce a more organized flow than the conventional flow.

[0083] Furthermore, the upstream edge 25a of the first protrusion 25A is preferably arranged closer to the suction surface of the first full blade 21A than the upstream edge 25a of the second protrusion 25B. In other words, it is preferable that the plurality of protrusions 25 (25A, 25B) are arranged between blades in multiple rows in the flow direction.

[0084] In this case, each projection 25 (25A, 25B) guides the flow A3 along the peripheral surface 18a of the hub 18 toward the blade surface of the full blade 21 (or splitter blade 22) more effectively in the direction along the blade surface to produce a more organized flow than the conventional flow.

[0085] Finally, the contents described in the above embodiments (including modifications) would be understood, for example, as follows.

[0086] (1) An impeller (impeller 6, 6A to 6D) of a centrifugal compressor (centrifugal compressor 5) according to one aspect includes: a hub (hub 18); a plurality of full blades (full blades 21) arranged on a peripheral surface (circumferential surface 18a) of the hub at intervals in a circumferential direction; and a plurality of splitter blades (splitter blades 22, 22A to 22D), each of which is arranged between adjacent full blades of the plurality of full blades on the peripheral surface of the hub. When a blade height ratio, which is a ratio of a blade height (Hf) of each full blade to a blade height (Hs) of each splitter blade on a meridional plane of the impeller, is defined as Hs / Hf, the blade height ratio satisfies Hs / Hf < 1 at least at a leading edge of each splitter blade.

[0087] In this case, the splitter blade, with a smaller blade height than the full blade, blocks the flow along the peripheral surface of the hub toward the blade surface of the full blade. Thus, it is possible to suppress the generation of secondary flow by the splitter blade.

[0088] Furthermore, when the blade height ratio Hs / Hf < 1 at least at the leading edge of the splitter blade, it is possible to effectively suppress interference with the leakage flow exiting through the gap on the tip end side of the full blade.

[0089] Accordingly, it is possible to suppress the generation of secondary flow and suppress interference with leakage flow, achieve uniform flow distribution, high pressure ratio and high efficiency more efficiently and effectively compared with conventional ones, and further improve the impeller efficiency.

[0090] (2) An impeller of a centrifugal compressor according to another aspect is the impeller described above (1), in which the blade height ratio Hs / Hf < 1 in the entire section from the leading edge (leading edge 22a) to a trailing edge (trailing edge 22b) of each splitter blade.

[0091] In this case, since the splitter blade is provided with a smaller blade height than the full blade over a wide range, it is possible to suppress the generation of the flow running up the blade surface of the full blade and thus the generation of the secondary flow by the splitter blade, while suppressing interference with the leakage flow over the entire operating range (wide range) indicated by the relationship between the flow rate and the pressure ratio of the centrifugal compressor.

[0092] (3) An impeller of a centrifugal compressor according to another aspect is the impeller described above (2), in which the blade height ratio Hs / Hf satisfies ≤ 0.7 in the entire section from the leading edge to a trailing edge of each splitter blade.

[0093] In this case, based on results of careful research (knowledge of the position of the parting line) by the present inventors, Hs / Hf ≤ 0.7 is satisfied, so that it is possible to suppress interference with the leakage flow exiting through the gap at the tip end of the full blade while more effectively suppressing the generation of the secondary flow.

[0094] (4) An impeller of a centrifugal compressor according to another aspect is the impeller described above (1), in which the blade height ratio Hs / Hf ≤ 0.7 satisfies at least at the leading edge of each splitter blade.

[0095] In this case, based on results of careful research (knowledge of the position of the parting line) by the present inventors, Hs / Hf ≤ 0.7 is satisfied at least at the leading edge of the splitter blade, so that it is possible to suppress interference with the leakage flow exiting through the gap at the tip end of the full blade while more effectively suppressing the generation of the secondary flow.

[0096] (5) An impeller of a centrifugal compressor according to another aspect is the impeller described above (4), in which the blade height ratio is configured to gradually increase from the leading edge to a trailing edge of each splitter blade.

[0097] In this case, for example, by forming the splitter blade in accordance with the parting line, it is possible to suppress the generation of the secondary flow and suppress interference with the leakage flow exiting through the gap on the tip end side of the full blade more effectively and efficiently.

[0098] (6) An impeller of a centrifugal compressor according to one aspect includes: a hub; a plurality of full blades arranged on a peripheral surface of the hub at intervals in a circumferential direction; and a plurality of splitter blades, each of which is arranged between adjacent full blades of the plurality of full blades on the peripheral surface of the hub. With respect to a chord position along a chord direction of each full blade on a meridional plane of the impeller, when the chord position at a leading edge of each full blade is defined as 0%, the chord position at a trailing edge of each full blade is defined as 100%, the chord position at a base end of a leading edge of each splitter blade is defined as Ch, and the chord position at a tip end of the leading edge of each splitter blade is defined as Ct, Ch ≤ 30% and Ct ≥ 50% are satisfied.

[0099] With this configuration, the splitter blade can be formed in accordance with the position of the parting line where the secondary flow can be generated, so that it is possible to suppress the generation of the secondary flow and effectively and efficiently suppress interference with the leakage flow exiting through the gap on the tip end side of the full blade.

[0100] (7) An impeller of a centrifugal compressor according to another aspect is the impeller described above (6), in which, when a chord length at the base end of each splitter blade is defined as Lh, and a chord length at the tip end of each splitter blade is defined as Lt, 2 × Lt ≤ Lh is satisfied.

[0101] In this case, similarly, based on findings obtained as a result of diligent research by the present inventors, the splitter blade can be formed in accordance with the position of the parting line where the secondary flow can be generated, so that it is possible to suppress the generation of the secondary flow and effectively and efficiently suppress interference with the leakage flow exiting through the gap on the tip end side of the full blade.

[0102] (8) An impeller of a centrifugal compressor according to another aspect is the impeller described above (6) or (7), in which the leading edge of each splitter blade has a curved surface shape that is concave with respect to a straight line connecting the base end (base end 22c) and the tip end (tip end 22d) of the leading edge on the meridional plane.

[0103] In this case, based on findings obtained as a result of diligent research by the present inventors, the splitter blade can be formed in accordance with the concave curved parting line (concave curved surface) where the secondary flow can be generated, so that it is possible to suppress the generation of the secondary flow and suppress interference with the leakage flow exiting through the gap on the tip end side of the full blade more effectively and efficiently.

[0104] (9) An impeller of a centrifugal compressor according to another aspect is the impeller described in any one of the above (6) to (8) in which Ch = 0% is satisfied.

[0105] In this case, it is possible to block the flow along the peripheral surface of the hub toward the blade surface of the full blade from the side of the leading edge of the full blade and more effectively suppress the generation of the secondary flow by the splitter blade.

[0106] (10) An impeller (impeller 6, 6E) of a centrifugal compressor according to another aspect is the impeller described in any one of (1) to (9) above, further including a plurality of protrusions (protrusions 25) configured to protrude from the peripheral surface of the hub, with at least one protrusion being disposed between each adjacent full blade. Regarding a chord position along a chord direction of each full blade on a meridional plane of the impeller, when the chord position at a leading edge of each full blade is defined as 0%, the chord position at a trailing edge of each full blade is defined as 100%, and the chord position at an upstream edge (upstream edge 25a) of each protrusion is defined as Cvl, Cvl ≤ 50%. If a blade height of each full blade is defined as Hf and a height of each projection on the meridional plane is defined as Hv, Hv ≤ 0.3 × Hf is satisfied.

[0107] In this case, the protrusion with a low height guides the flow along the peripheral surface of the hub toward the blade surface of the full blade (or splitter blade) in the direction along the blade surface on the peripheral surface of the hub, that is, toward the trailing edge of the full blade, to generate a flow toward the trailing edge of the full blade more smoothly than the conventional flow. As a result, the flow running up the blade surface of the full blade (or splitter blade) is less likely to occur, and it is possible to further suppress the generation of secondary flow.

[0108] Accordingly, it is possible to more effectively suppress the generation of secondary flow and suppress interference with leakage flow, achieve uniform flow distribution, high pressure ratio and high efficiency compared with conventional ones, and further improve the impeller efficiency.

[0109] (11) An impeller of a centrifugal compressor according to another aspect is the impeller described above (10), in which the upstream edge of each projection is arranged upstream of the leading edge of each splitter blade.

[0110] With this configuration, the low-height protrusion more effectively directs the flow along the peripheral surface of the hub toward the blade surface of the full blade (or splitter blade), creating a smoother and more organized flow than conventional flow. Thus, it is possible to further suppress the generation of secondary flow.

[0111] (12) An impeller of a centrifugal compressor according to one aspect includes: a hub; a plurality of full blades arranged on a circumferential surface of the hub at intervals in a circumferential direction; and a plurality of protrusions configured to protrude from the circumferential surface of the hub, wherein at least one protrusion is arranged between each adjacent full blade. With respect to a chord position along a chord direction of each full blade on a meridional plane of the impeller, when the chord position at a leading edge of each full blade is defined as 0%, the chord position at a trailing edge of each full blade is defined as 100%, and the chord position at an upstream edge of each protrusion is defined as Cvl, Cvl ≤ 50% is satisfied. If a blade height of each full blade is defined as Hf and a height of each projection on the meridional plane is defined as Hv, Hv ≤ 0.3 × Hf is satisfied.

[0112] In this case, the protrusion effectively guides the flow along the peripheral surface of the hub toward the blade surface of the full blade, creating a smoother flow than conventional flow. As a result, the flow running up the blade surface of the full blade is less likely to occur, and it is possible to further suppress the generation of secondary flow. In addition, it is possible to suppress interference with the leakage flow, achieve uniform flow distribution, high pressure ratio, and high efficiency efficiently and effectively compared to conventional ones, and further improve the impeller efficiency.

[0113] Accordingly, it is possible to more strongly suppress the generation of secondary flow and suppress interference with leakage flow, efficiently and effectively achieve uniform flow distribution, high pressure ratio and high efficiency compared with conventional ones, and further improve the impeller efficiency.

[0114] (13) An impeller of a centrifugal compressor according to another aspect is the impeller described above (12), in which, when a pitch distance along the circumferential direction between the upstream edge of each projection and a suction surface of a first full blade (first full blade 21A), which is one of the adjacent full blades, is defined as Pl1, and a pitch distance along the circumferential direction between the upstream edge of each projection and a pressure surface of a second full blade (second full blade 21B), which is the other of the adjacent full blades, is defined as Pl2, Pl1 < Pl2 is satisfied.

[0115] In this case, the protrusion directs the flow more efficiently and effectively to the intake surface of the first full blade in the direction along the blade surface (toward the trailing edge of the first full blade) to adequately produce a smoother and more organized flow than the conventional flow.

[0116] (14) An impeller of a centrifugal compressor according to another aspect is the impeller described above (13), in which the at least one projection arranged between the adjacent full blades includes a first projection (first projection 25A) and a second projection (second projection 25B) different from the first projection.

[0117] In this case, each protrusion, the first protrusion and the second protrusion, directs the flow along the peripheral surface of the hub toward the blade surface of the full blade (or splitter blade) in the direction along the blade surface, more effectively generating a more organized flow than the conventional flow. As a result, the flow running up the blade surface of the full blade (or splitter blade) is even less likely to occur, and it is possible to further suppress the generation of secondary flow.

[0118] (15) An impeller of a centrifugal compressor according to another aspect is the impeller described above (14), in which an upstream edge of the first projection is arranged upstream of an upstream edge of the second projection.

[0119] In this case, each protrusion directs the flow more effectively toward the blade surface in the direction along the blade surface to create a more organized flow than the conventional flow.

[0120] (16) An impeller of a centrifugal compressor according to another aspect is the impeller described above (14) or (15), in which an upstream edge of the first projection is arranged closer to the suction surface of the first full blade than an upstream edge of the second projection.

[0121] In this case, each protrusion still directs the flow along the peripheral surface of the hub toward the blade surface of the full blade more effectively in the direction along the blade surface to create a more organized flow than the conventional flow.

[0122] (17) A centrifugal compressor according to one aspect includes the impeller described in any one of the above (1) to (16).

[0123] With the radial compressor described in (17) above, it is possible to obtain the effects of the impeller described in any of (1) to (16) above. List of reference symbols 1 turbocharger 2 turbines 4 rotating shaft 5 radial compressors (compressors) 6 Wheel 6A to 6E wheel 18 Hub 18a circumferential surface 21 full blade (rotor blade) 21A First full bucket 21B Second full bucket 21a leading edge 21b trailing edge 21c base end 21d top end 22 Splitter blade (rotor blade) 22A to 22D Splitter Shovel 22a leading edge 22b trailing edge 22c base end 22d tip end 25 lead 25A First Lead 25B Second Lead 25a Upstream edge A Air (fluid) A' Compressed air (compressed fluid, fluid) A3 Secondary flow O1 axis (axial direction)

Claims

[1] Impeller (6, 6A, 6B, 6C) of a radial compressor (5), comprising: a hub (18); a plurality of full blades (21) arranged on a circumferential surface (18a) of the hub (18) at intervals in a circumferential direction; and a plurality of splitter blades (22, 22A, 22B, 22C, 22D), each of which is arranged between adjacent full blades (21) of the plurality of full blades (21) on the peripheral surface (18a) of the hub (18), wherein, with respect to a chord position along a chord direction of each full blade (21) on a meridional plane of the impeller (6, 6A, 6B, 6C), if the chord position at a leading edge (21a) of each full blade (21) is defined as 0%, the chord position at a trailing edge (21b) of each full blade (21) is defined as 100%, the chord position at a base end (22c) of a leading edge (22a) of each splitter blade (22, 22A, 22B, 22C, 22D) is defined as Ch, and the chord position at a tip end (22d) of the leading edge (22a) of each splitter blade (22, 22A, 22B, 22C, 22D) is defined as Ct, Ch ≤ 30% and Ct ≥ 50% are met. [2] Impeller (6, 6C, 6D) of a radial compressor (5) according to claim 1, wherein, when a chord length (L) at the base end (22c) of each splitter blade (22, 22C, 22D) is defined as Lh, and a chord length (L) at the tip end (22d) of each splitter blade (22, 22C, 22D) is defined as Lt, 2 × Lt ≤ Lh is satisfied. [3] The impeller (6, 6C, 6D) of a centrifugal compressor (5) according to claim 1 or 2, wherein the leading edge (22a) of each splitter blade (22, 22C, 22D) has a curved surface shape which is concave with respect to a straight line connecting the base end (22c) and the tip end (22d) of the leading edge (22a) on the meridional plane. [4] Impeller (6, 6A, 6B, 6C, 6D, 6E) of a radial compressor (5) according to one of claims 1 to 3, wherein Ch = 0% is satisfied. [5] Impeller (6, 6A) of a radial compressor (5) according to one of claims 1 to 4, wherein, when a blade height ratio, which is a ratio of a blade height (Hf) of each full blade (21) to a blade height (Hs) of each splitter blade (22, 22A) on a meridional plane of the impeller (6, 6A), is defined as Hs / Hf, wherein the blade height (Hf) of the full blade (21) and the blade height (Hs) of the splitter blade (22, 22A) are each a length dimension from a base end (21c, 22c) to a tip end (21d, 22d) in the direction perpendicular to a center line (P1, P2) between the base end (21c, 22c) and the tip end (21d, 22d), wherein the blade height ratio Hs / Hf is the ratio of the blade height (Hf) of the full blade (21) to the blade height (Hs) of the splitter blade (22, 22A) at the same chord position of the full blade (21) in the meridional plane of the impeller (6, 6a), the blade height ratio Hs / Hf < 1 is satisfied at least at the leading edge (22a) of each splitter blade (22, 22A). [6] Impeller (6, 6A) of a radial compressor (5) according to claim 5, wherein the blade height ratio Hs / Hf < 1 in an entire section from the leading edge (22a) to a trailing edge (22b) of each splitter blade (22, 22A). [7] Impeller (6, 6A) of a radial compressor (5) according to claim 6, wherein the blade height ratio Hs / Hf ≤ 0.7 in the entire section from the leading edge (22a) to the trailing edge (22b) of each splitter blade (22, 22A). [8] Impeller (6, 6A) of a radial compressor (5) according to claim 5, wherein the blade height ratio Hs / Hf ≤ 0.7 at least at the leading edge (22a) of each splitter blade (22, 22A). [9] The impeller (6, 6B) of a radial compressor (5) according to claim 8, wherein the blade height ratio Hs / Hf is configured to gradually increase from the leading edge (22a) to a trailing edge (22b) of each splitter blade (22, 22C, 22D). [10] Impeller (6, 6E) of a radial compressor (5) according to one of claims 1 to 9, further comprising a plurality of projections (25) configured to protrude from the peripheral surface (18a) of the hub (18), at least one projection (25) being arranged between each adjacent full blades (21, 21A, 21B), wherein, with respect to a chord position along a chord direction of each full blade (21) on a meridional plane of the impeller (6, 6E), if the chord position at the leading edge (21a) of each full blade (21) is defined as 0%, the chord position at the trailing edge (21b) of each full blade (21) is defined as 100%, and the chord position at an upstream edge (25a) of each projection (25) is defined as Cvl, Cvl ≤ 50 % is met, and if a blade height of each full blade (21) is defined as Hf, and a height of each projection (25) on the meridional plane is defined as Hv, Hv ≤ 0.3 × Hf is satisfied. [11] Impeller (6, 6A, 6B, 6C, 6D, 6E) of a radial compressor (5) according to claim 10, wherein the upstream edge (25a) of each projection (25) is arranged upstream of the leading edge (22a) of each splitter blade (22). [12] Radial compressor (5) comprising the impeller (6, 6A, 6B, 6C, 6D, 6E) according to one of claims 1 to 11.

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