Impeller of a centrifugal compressor and centrifugal compressor

Abstract

The impeller (6) of the centrifugal compressor of the present disclosure includes: a hub (18); a plurality of full blades (21) provided at intervals in the circumferential direction on the circumferential surface of the hub; and a plurality of splitter blades (22) respectively provided between adjacent full blades among the plurality of full blades on the circumferential surface of the hub. Further, when the blade height ratio, which is the ratio of the blade height (Hs) of the splitter blade to the blade height (Hf) of the full blade in the meridian plane of the impeller, is defined as Hs / Hf, the blade height ratio satisfies the relationship of Hs / Hf < 1 at least at the leading edge (22a) of the splitter blade. With such a configuration, by using the splitter blade, the flow along the circumferential surface of the hub toward the blade surface of the full blade can be blocked, the generation of secondary flow can be suppressed, and the interference with the leakage flow leaking from the gap on the front end side of the full blade can be effectively suppressed.

Description

Technical Field

[0001] The present disclosure relates to an impeller of a centrifugal compressor and a centrifugal compressor. Background Art

[0002] Conventionally, as a technique for increasing the output of engines such as automotive engines or marine engines, a turbocharger (supercharger) is often used. The turbocharger compresses the intake air sucked by the engine, increases the density, and supplies the intake air containing a large amount of oxygen to the engine.

[0003] For example, a turbocharger includes a rotating shaft, a centrifugal compressor (compressor) provided on one end side of the rotating shaft, and a turbine provided on the other end side of the rotating shaft. It is configured to rotate the impeller (turbine) of the turbine by the energy of the exhaust gas sent from the engine, and to rotate the rotating shaft, and thus rotate the impeller (compressor wheel) of the centrifugal compressor around the axis to compress the intake air and supply it to the engine.

[0004] In addition, the impeller of the centrifugal compressor is configured as follows: a hub (compressor hub) having a substantially frustoconical shape, which is coaxially connected to the rotating shaft; and a plurality of moving blades (compressor moving blades), which are spaced apart at a predetermined interval in the circumferential direction centered on the axis and extend from the outer circumferential surface of the hub toward the substantially radial outside of the axis center.

[0005] Here, in the case of having a plurality of moving blades having the same shape and the same size, there is a case where the flow velocity difference between the pressure surface side and the negative pressure surface side of the fluid (compressed air, etc.) of each moving blade becomes very large, and the impeller efficiency deteriorates.

[0006] Therefore, conventionally, in such an impeller, as the moving blade, a moving blade having the following configuration is often used: not only includes a plurality of full blades (long blades) arranged at a predetermined interval in the circumferential direction, but also includes a diverter blade (short blade, intermediate blade) arranged between the adjacent full blades in the circumferential direction, thereby improving the impeller efficiency.

[0007] However, in the airflow entering between adjacent full blades, for example, on both sides sandwiching the diverter blade, that is, the pressure surface side and the negative pressure surface side of the full blade, a flow velocity difference occurs in which the airflow on the negative pressure surface side becomes faster. Thus, even if there is a diverter blade and the flow path cross-sectional areas of the flow paths on both sides sandwiching the diverter blade are geometrically equal, there is a case where, since the flow velocity on the negative pressure surface side is faster than that on the pressure surface side, the flow rate increases, the flow rates of the respective flow paths become uneven, and the fluid cannot be evenly distributed. In this way, the flow rates of the flow paths become uneven and the fluid cannot be evenly distributed, thereby making the blade loads uneven, increasing the energy loss of the compressed air flowing through the flow path, and there is a case where the desired improvement effect of the impeller efficiency cannot be obtained.

[0008] Therefore, in the past, in order to improve the impeller efficiency, a large number of studies have been conducted on the shape, number, and arrangement of full blades and splitter blades.

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

[0010] In the impeller of this centrifugal compressor, by configuring the splitter blade as described above, the splitter blade is adapted to the complex internal flow of the centrifugal compressor, that is, the interference between the leading edge of the splitter blade and the leakage flow flowing beyond the front end of the full blade (through the front end gap) is suppressed, and the uniformization of flow rate distribution, high pressure ratio, and high efficiency (further improvement of impeller efficiency) are achieved.

[0011] In Patent Document 2, an impeller is disclosed, which includes a protrusion that protrudes from the outer peripheral surface of the hub between adjacent full blades (full blades) and splitter blades (half blades, first splitter blades) and extends along the flow direction of the fluid flowing radially outward between the adjacent full blades and splitter blades.

[0012] In this impeller, the protrusion functions as a second splitter blade, and functions to prevent the fluid flowing between the full blades and between the splitter blades from slipping by sandwiching the protrusion therebetween. As a result, a stronger force toward the radial outside of the impeller can act on the fluid, and the uniformization of flow rate distribution, high pressure ratio, and high efficiency can be achieved.

[0013] Prior Art Documents

[0014] Patent Documents

[0015] Patent Document 1: Japanese Patent Laid-Open No. 2011-80411

[0016] Patent Document 2: Japanese Patent Laid-Open No. 2017-44190 Summary of the Invention

[0017] Problems to be Solved by the Invention

[0018] On the other hand, the inventors of the present application have repeatedly conducted in-depth research and found that as Figure 8As shown, the air flow A2 entering the shaft side (inner side, hub 18 side) of the impeller 6 gradually flies outwards due to centrifugal force, gradually inclines relative to the direction of the shaft O1, and flows in a manner that rises along the wall surface (blade surface) of the moving blade 21 from the base end side of the moving blade 21 along the circumferential surface 18a of the hub 18. The air flow A2 rising along the wall surface of the moving blade 21 collides with the air flow A1 entering from the inlet side of the mainstream impeller 6 in the direction of the shaft O1, generating a secondary flow A3 that peels off from the wall surface of the moving blade 21 and flowing towards the outlet side of the impeller 6.

[0019] Furthermore, the inventor of the present application has discovered new insights such as the position (peeling line S) where peeling occurs to generate the secondary flow A3 hardly changes from the surge (low flow rate) side to the choking (maximum flow rate) side on the positive pressure side of the moving blade 21, the tendency becomes slightly more significant closer to the surge side with a higher pressure ratio, and a substantially same tendency also occurs on the negative pressure side of the moving blade 21. It has been found that the secondary flow A3 caused by such peeling has a great influence on the reduction of the impeller efficiency.

[0020] Therefore, based on such research results, there is a strong desire to develop a method for suppressing the generation of the secondary flow.

[0021] In view of the above situation, an object of the present disclosure is to provide an impeller of a centrifugal compressor and a centrifugal compressor that can suppress the generation of the secondary flow, and can more efficiently and effectively achieve uniform flow distribution, a high pressure ratio, and high efficiency compared with the prior art, and further improve the impeller efficiency.

[0022] Solution to the problem

[0023] An impeller of a centrifugal compressor according to one aspect of the present disclosure includes: a hub; a plurality of full blades provided at intervals in the circumferential direction on the circumferential surface of the hub; a plurality of splitter blades respectively provided between adjacent full blades among the plurality of full blades on the circumferential surface of the hub; when the blade height ratio, which is the ratio of the blade height (Hs) of the splitter blade to the blade height (Hf) of the full blade in the meridian plane of the impeller, is defined as Hs / Hf, at least at the leading edge of the splitter blade, the blade height ratio satisfies the relationship Hs / Hf < 1.

[0024] In addition, a centrifugal compressor according to one aspect of the present disclosure includes the impeller of the centrifugal compressor described above.

[0025] Effect of the invention

[0026] According to the impeller of a centrifugal compressor and the centrifugal compressor according to one aspect of the present disclosure, the generation of the secondary flow can be suppressed, and compared with the prior art, uniform flow distribution, a high pressure ratio, and high efficiency can be more efficiently and effectively achieved, and further improvement in the impeller efficiency can be realized. Description of the drawings

[0027] Figure 1 This is a diagram showing an example of a turbocharger equipped with the centrifugal compressor according to the first and second embodiments of the present disclosure.

[0028] Figure 2 This is a partial cross-sectional view showing an example of the centrifugal compressor and the impeller of the centrifugal compressor according to the first embodiment of the present disclosure.

[0029] Figure 3 This is a partial cross-sectional view showing a modified example of the centrifugal compressor and the impeller of the centrifugal compressor according to the first embodiment of the present disclosure.

[0030] Figure 4 This is a partial cross-sectional view showing a modified example of the centrifugal compressor and the impeller of the centrifugal compressor according to the first embodiment of the present disclosure.

[0031] Figure 5 This is a partial cross-sectional view showing a modified example of the centrifugal compressor and the impeller of the centrifugal compressor according to the first embodiment of the present disclosure.

[0032] Figure 6 This is a partial cross-sectional view showing an example of the centrifugal compressor and the impeller of the centrifugal compressor according to the second embodiment of the present disclosure.

[0033] Figure 7 This is a partial top view showing the moving blades and the convex portions of the centrifugal compressor and the impeller of the centrifugal compressor according to the second embodiment of the present disclosure.

[0034] Figure 8 This is a diagram showing the position (peeling line) where the fluid flowing between the moving blades of the impeller of the centrifugal compressor peels off from the blade surface.

[0035] Figure 9 This is a partial cross-sectional view showing an example of the centrifugal compressor and the impeller of the centrifugal compressor according to the first (second) embodiment of the present disclosure, and is a diagram showing the blade height, coating length, etc. Detailed Embodiment

[0036] (First Embodiment)

[0037] Hereinafter, with reference to Figures 1 to 5 , Figure 8 , Figure 9 , the impeller of the centrifugal compressor and the centrifugal compressor according to the first embodiment will be described.

[0038] Here, in the present embodiment, the case where the turbocharger includes the centrifugal compressor of the present disclosure has been described. However, the centrifugal compressor of the present disclosure may be, for example, an electric centrifugal compressor. In addition, it is not necessary to limit the fluid to be compressed to air. That is, the centrifugal compressor (and the impeller of the centrifugal compressor) of the present disclosure only needs to be able to compress and convey the fluid, and may be composed of a single centrifugal compressor, or may be composed in combination with mechanisms and devices other than the turbine. In addition, there is no need to limit its use, etc.

[0039] (Turbocharger)

[0040] The turbocharger 1 of the present embodiment is configured, for example, as Figure 1 shown, to rotate the impeller (turbine) 3 of the turbine 2 about the axis (rotation axis) O1 by using the energy of the exhaust gas G delivered from an engine such as an automotive engine or a marine engine, and further to rotate the rotating shaft 4 coaxially connected to the impeller 3, and further to rotate the impeller (compressor wheel) 6 of the centrifugal compressor (compressor) 5 coaxially connected to the rotating shaft 4, suck in air (intake air, fluid) A by the impeller 6 and compress it, and supply the compressed air gas A' to the engine.

[0041] (Turbine)

[0042] The turbine 2 includes an impeller 3 coaxially connected to the other end side of the rotating shaft 4 and a turbine shroud (turbine housing) 7 that houses the impeller 3.

[0043] The impeller 3 includes a substantially frustum-shaped turbine hub 8 coaxially connected to the rotating shaft 4; and turbine moving blades 9 extending radially outward from the outer peripheral surface of the turbine hub 8 toward the center of the axis O1.

[0044] On the radially outer side of the axis O1 of the impeller 3 of the turbine 2, an exhaust gas flow path R5 is provided. The exhaust gas flow path R5 is provided around the impeller 3 and is composed of a vortex flow path R3 for supplying the exhaust gas G discharged from the engine to the impeller 3 and a nozzle flow path R4 having an exhaust gas flow rate adjusting device such as nozzle blades 10.

[0045] In addition, on the rear side in the direction of the axis O1 of the impeller 3 (the exhaust gas G discharge port 11 side), a discharge flow path R6 (exhaust gas flow path R5) for receiving the exhaust gas G discharged from the outlet of the turbine moving blades 9 of the impeller 3 and discharging it to the outside is coaxially provided with the impeller 3. The discharge flow path R6 is composed of an exhaust diffuser 12.

[0046] In addition, in the turbocharger 1 of the present embodiment, the vortex flow path R3, the nozzle flow path R4, and the discharge flow path R6 (exhaust diffuser 12) are formed by the turbine shroud 7 that houses the impeller 3.

[0047] (Centrifugal compressor: Compressor)

[0048] The centrifugal compressor 5 of the present embodiment is configured as follows: An impeller (compressor wheel) 6 of the centrifugal compressor 5 is coaxially connected and provided at one end side of a rotating shaft 4 rotatably supported by bearing housings 15 and 16; A compressor housing 17 that houses the impeller 6.

[0049] The impeller 6 of the centrifugal compressor 5 includes: A substantially frustum-shaped compressor hub (hub) 18 coaxially connected to the rotating shaft 4; Compressor moving blades (impeller moving blades) 19 extending radially outward from the outer peripheral surface of the compressor hub 18 toward the center of the axis O1.

[0050] On the front side in the direction of the axis O1 of the impeller 6 (the air A suction port 20 side), an intake air flow path R1 is provided, and the intake air flow path R1 is used to supply air A to the impeller 6 by sucking it in as the impeller 6 rotates.

[0051] In addition, on the radially outer side of the center of the axis O1 of the impeller 6, a compressed air flow path (compressed gas flow path) R2 is provided, and the compressed air flow path R2 has a vortex chamber r2 for receiving the compressed air A' discharged from the impeller 6 and supplying it to the engine.

[0052] Moreover, in the turbocharger 1 of the present embodiment configured as described above, 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 vortex flow path R3 and the nozzle flow path R4 of the turbine 2, and the impeller 3 is rotationally driven using the energy of the exhaust gas G. By the rotation of the impeller 3, the rotating shaft 4 and the impeller 6 of the centrifugal compressor 5 are rotationally driven.

[0053] In addition, by the rotation of the impeller 6, air A is sucked in from the suction port 20 and flows through the intake air flow path R1, is supplied to the impeller 6 and compressed, and the compressed air A' is supplied to the engine through the compressed air flow path R2. The exhaust gas G after rotationally driving the impeller 3 of the turbine 2 flows through the discharge flow path R6 of the exhaust diffuser 12, and the pressure is restored and discharged to the outside.

[0054] (Impeller of centrifugal compressor)

[0055] On the other hand, the impeller 6 of the centrifugal compressor 5 of the present embodiment is configured as follows: A hub 18; A plurality of full blades 21 provided at intervals in the circumferential direction around the center of the axis (shaft) O1 on the circumferential surface 18a of the hub 18; A plurality of splitter blades 22 respectively provided between adjacent full blades 21 among the plurality of full blades 21 on the circumferential surface 18a of the hub 18.

[0056] Here, as described above ( Figure 8),The inventors of the present application repeatedly conducted in-depth research and found that the air flow A2 entering the shaft (O1, rotating shaft 4) side of the impeller 6 of the centrifugal compressor 5 gradually flies out toward the outer diameter side due to centrifugal force, gradually inclines with respect to the direction of the shaft O1, and rises along the blade surface (wall surface) of the moving blade 21 from the hub side (base end side) of the hub 18 of the moving blade 21 along the circumferential surface 18a of the hub, collides with the air flow A1 entering from the inlet side of the mainstream impeller 6, and generates a secondary flow A3 that peels off from the blade surface of the moving blade (21) and flows toward the outlet side.

[0057] In addition, the inventors of the present application found new insights such as the peeling line (boundary position) S that causes peeling and generates the secondary flow A3 hardly changes from the surge side to the choke side on the positive pressure surface side of the moving blade (21), this tendency becomes slightly more significant closer to the surge side with a higher pressure ratio, and a substantially same tendency also occurs on the negative pressure surface side of the moving blade (21). It was found that the secondary flow A3 caused by such peeling has a great influence on the reduction of the impeller efficiency.

[0058] Furthermore, it was found that in Figure 8 and Figure 9 in the meridian plane (meridian plane section) view of the impeller 6 shown, when the chord position at the leading edge 21a of the chord length L of the entire blade 21 is set to 0% and the chord position at the trailing edge 21b of the entire blade 21 is set to 100%, the peeling line S that causes peeling and generates the secondary flow A3 is formed into a concave curve shape (concave circular chord shape) that gradually extends from the base end 21c on the leading edge 21a side (position around approximately 0% to 5%) of the entire blade 21 toward the front end 21d side of the entire blade 21 and reaches the front end 21d at a position around approximately 70%.

[0059] In addition, it was also confirmed that the interference with the leakage flow leaking from the gap on the front end 21d side (tip side) of the entire blade 21, especially the interference with the leakage flow leaking from the gap on the leading edge 21a side of the entire blade 21, causes a further reduction in the impeller efficiency.

[0060] Based on the particularly remarkable achievements and insights of the inventors of the present application as described above, the impeller 6A (6) of the centrifugal compressor 5 of the present embodiment is as Figure 2 (refer to Figure 9 ) shown, and is configured such that when the blade height ratio, which is the ratio of the blade height (Hs) of the splitter blade 22A to the blade height (Hf) of the entire blade 21 on the meridian plane (meridian plane section) of the impeller 6, is defined as Hs / Hf, the blade height ratio satisfies the relationship of Hs / Hf < 1 at least at the leading edge 22a of the splitter blade 22A.

[0061] It should be noted that the meridian plane of the impeller 6 in the present disclosure refers to the cross-sectional shape obtained by overlapping the shape after the dynamic blade shape is rotationally projected along the central axis (O1) on the cross-section obtained by cutting the impeller 6 of the centrifugal compressor 5 along its central axis (O1), rather than simply maintaining the cross-section of only the part of the dynamic blades 19 (the full blades 21 and the splitter blades 22).

[0062] In addition, 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 respectively the length dimensions from the base ends 21c, 22c to the front ends 21d, 22d in the direction orthogonal to the center lines P1, P2 between the base ends 21c, 22c and the front ends 21d, 22d in the meridian plane of the impeller 6.

[0063] Furthermore, the blade height ratio Hs / Hf, which is the ratio of the blade height (Hs) of the splitter blade 22A to the blade height (Hf) of the full blade 21, is the ratio of the blade heights at the same chord position.

[0064] Moreover, in the impeller 6A of the centrifugal compressor 5 in the present embodiment, the splitter blade 22A is configured such that the blade height ratio satisfies the relationship Hs / Hf < 1 at least at its leading edge 22a. Thus, the splitter blade 22A with a blade height smaller than that of the full blade 21 can be used to block the airflow A2 flowing along the circumferential surface 18a of the hub 18 toward the blade surface (wall surface) of the full blade 21. As a result, the generation of the airflow A2 rising along the blade surface of the full blade 21 can be suppressed, and the generation of the secondary flow A3 can be suppressed by using the splitter blade 22A.

[0065] In addition, by configuring the blade height ratio to satisfy the relationship Hs / Hf < 1 at least at the leading edge 22a of the splitter blade 22A, the interference with the leakage flow leaking from the gap on the front end 22d side of the full blade 21 can be effectively suppressed.

[0066] Therefore, according to the impeller 6A of the centrifugal compressor 5 in the present embodiment and the centrifugal compressor 5 equipped with the impeller 6A, the generation of the secondary flow can be suppressed, and the interference with the leakage flow can be suppressed. Compared with the prior art, the uniformization of the flow rate distribution, the high pressure ratio, and the high efficiency can be achieved more efficiently and effectively, and the impeller efficiency can be further improved.

[0067] Here, as Figure 2 shown, the impeller 6A of the centrifugal compressor 5 in the present embodiment (and the centrifugal compressor 5 equipped with the impeller 6A) is preferably configured such that the blade height ratio satisfies the relationship Hs / Hf < 1 in all intervals 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.

[0068] In such a configuration, by using the splitter blade 22A with a blade height smaller than that of the full blade 21, interference with the leakage flow can be suppressed, the generation of the air flow A2 rising along the blade surface of the full blade 21 can be suppressed, and the generation of the secondary flow A3 can be suppressed by using the splitter blade 22A.

[0069] Furthermore, the impeller 6A of the centrifugal compressor 5 according to the present embodiment is more preferably configured such that, at least at the leading edge 22a of the splitter blade 22A, the blade height ratio satisfies the relationship of Hs / Hf ≤ 0.7.

[0070] In such a configuration, the generation of the secondary flow A3 can be suppressed, and interference with the leakage flow leaking from the gap on the front end 22d side of the full blade 21A can be more effectively suppressed.

[0071] Furthermore, the impeller 6A of the centrifugal compressor 5 according to the present embodiment is more preferably configured such that, in all intervals from the leading edge 22a to the trailing edge 22b of the splitter blade 22A, the blade height ratio satisfies the relationship of Hs / Hf ≤ 0.7.

[0072] In such a configuration, the generation of the secondary flow A3 can be further effectively suppressed, and interference with the leakage flow leaking from the gap of the front end 21d of the full blade 21 can be suppressed.

[0073] In addition, as Figure 3 (refer to Figure 8 、 Figure 9 ) shows, the impeller 6B(6) of the centrifugal compressor 5 according to the present embodiment may also 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)).

[0074] In such a configuration, for example, by forming the splitter blade 22B(22) in a manner that matches the separation line S, etc., the generation of the secondary flow A3 can be further effectively and efficiently suppressed, and interference with the leakage flow leaking from the gap on the front end 22d side of the full blade 21 can be suppressed.

[0075] In addition, based on the insights obtained from the in-depth research of the inventors of the present application, as described above, at the chord position in the meridional plane of the impeller 6(6A, 6B, 6C) of the centrifugal compressor 5 according to the present embodiment along the chord (chord length L) direction of the full blade 21, when the chord position at the leading edge 21a of the full blade 21 is set to 0%, the chord position at the trailing edge 21b of the full blade 21 is set to 100%, and further 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 front end 22d of the leading edge 22a of the splitter blade 22 is defined as Ct, as Figure 2 、 Figure 3 、Figure 4 (Refer to Figure 8 , Figure 9 ), it is more preferably configured to satisfy the relationship of Ch ≤ 30% and Ct ≥ 50%.

[0076] In such a configuration, it is also possible to form the splitter vane 22 according to the position of the separation line S that generates the secondary flow A3, effectively and efficiently suppress the generation of the secondary flow A3, and suppress the interference with the leakage flow leaking from the gap on the front end 21d side of the entire blade 21.

[0077] Furthermore, the impellers 6 (6C, 6D) of the centrifugal compressor 5 of the present embodiment may also be as Figure 4 , Figure 5 (Refer to Figure 8 , Figure 9 ), configured such that when the chord length L at the base end 22c of the splitter vane 22 (22C, 22D) is defined as Lh and the chord length L at the front end 22d of the splitter vane 22 is defined as Lt, the relationship of 2 × Lt ≤ Lh is satisfied. In other words, it may also be configured to have a blade leading edge shape in which the chord length Lh on the hub side is more than twice the chord length Lt on the tip side.

[0078] In this case, based on the insights obtained from the in-depth research of the inventors of the present application, it is also possible to form the splitter vane 22 according to the position of the separation line S that generates the secondary flow A3, still effectively and efficiently suppress the generation of the secondary flow A3, and suppress the interference with the leakage flow leaking from the gap on the front end 22d side of the entire blade 21.

[0079] Furthermore, as Figure 4 , Figure 5 (Refer to Figure 8 , Figure 9 ), the leading edge 22a of the splitter vane 22 (22C, 22D) may also have a concave curved portion 22e that is recessed in the meridional plane with respect to the straight line connecting the base end 22c and the front end 22d of the leading edge 22a.

[0080] In this case, based on the insights obtained from the in-depth research of the inventors of the present application, the splitter vane 22 can be formed according to the concave curved separation line S that generates the secondary flow A3. Thus, the generation of the secondary flow A3 can be further effectively and efficiently suppressed, and the interference with the leakage flow leaking from the gap on the front end 21d side of the entire blade 21 can be suppressed.

[0081] In addition, as Figure 5 (Refer to Figure 8 , Figure 9) As shown, the chord position Ch at the base end 22c of the leading edge 22a of the splitter vane 22 (22D) can also be set to satisfy the relationship Ch = 0%. In other words, it can also be configured such that the hub-side leading edge 22a of the splitter vane 22 extends to the leading edge 21a of the full vane 21 and is disposed at the same position (including substantially the same position).

[0082] In this case, it is possible to more effectively block the airflow along the circumferential surface 18a of the hub 18 toward the blade surface of the full vane 21, and it is possible to suppress the generation of the secondary flow A3 using the splitter vane 22.

[0083] (Second Embodiment)

[0084] Next, with reference to Figure 6 、 Figure 7 ( Figures 1 to 5 、 Figure 8 、 Figure 9 ), the impeller of the centrifugal compressor and the centrifugal compressor of the second embodiment will be described.

[0085] In the present embodiment, similar to the first embodiment, the case where the turbocharger 1 includes the centrifugal compressor 5 will be described. In addition, in the present embodiment, only the structure of the impeller 6 of the centrifugal compressor 5 is different from that of the first embodiment. Therefore, in the present embodiment, the same reference numerals are assigned to the same structures as those in the first embodiment, and their detailed descriptions are omitted.

[0086] (Impeller of Centrifugal Compressor)

[0087] As Figure 6 ( Figure 1 ) shows, in the centrifugal compressor 5 of the turbocharger 11 of the present embodiment, the impeller 6 (6E) is configured to include: a hub 18; a plurality of full vanes 21, which are circumferentially spaced apart on the circumferential surface 18a of the hub 18; and a plurality of splitter vanes 22, which are respectively disposed between adjacent full vanes 21 among the plurality of full vanes 21 on the circumferential surface 18a of the hub 18.

[0088] Here, the impeller 6 (6E) of the centrifugal compressor 5 of the present embodiment is not particularly limited, but as the splitter vane 22, it includes any one of the splitter vanes 22 described in the first embodiment (including modified examples of the first embodiment).

[0089] In addition, in the impeller 6 (6E) of the centrifugal compressor 5 of the present embodiment, a plurality of convex portions 25 are further provided. The plurality of convex portions 25 are a plurality of convex portions (for example, vortex generators: VG, etc.) each having at least one disposed between adjacent full vanes 21 (first full vane 21A, second full vane 21B), and are configured to protrude from the circumferential surface 18a of the hub 18.

[0090] As shown in Figure 6 and Figure 7 (refer to Figure 9 ), the convex portion 25 is arranged such that, at the chord position along the chord direction of the entire blade 21 in the meridian plane of the impeller 6 (6E), when the chord position at the leading edge 21a of the entire blade 21 is defined as 0%, the chord position at the trailing edge 21b of the entire blade 21 is defined as 100%, and the chord position at the upstream edge 25a of the convex portion 25 is defined as Cvl, the relationship Cvl ≤ 50% is satisfied. When the blade height of the entire blade 21 is defined as Hf and the height of the convex portion 25 in the meridian plane is defined as Hv, the relationship Hv ≤ 0.3×Hf is satisfied.

[0091] It should be noted that, similar to the first embodiment, the blade height Hf of the entire blade 21 and the height Hv of the convex portion 25 in the present disclosure are respectively the length dimensions in the direction orthogonal to the center lines P1 and P3 between the base ends 21c, 25c and the front ends 21d, 25d in the meridian plane of the impeller 6, from the base ends 21c, 25c to the front ends 21d, 25d.

[0092] In the case of having the convex portion 25 like this, with the convex portion 25 having a small height, the air flow along the circumferential surface 18a of the hub 18 towards the blade surface of the entire blade 21 (or the splitter blade 22) can be guided along the blade surface direction on the circumferential surface 18a of the hub 18, that is, towards the trailing edge 21b side of the entire blade 21, generating an air flow that is smoother towards the trailing edge 21b side of the entire blade 21 than the conventional air flow. Thus, it is difficult to generate an air flow that rises along the blade surface of the entire blade 21 (or the splitter blade 22), and the generation of the secondary flow A3 can be further suppressed.

[0093] Therefore, compared with the first embodiment, the impeller 6 of the centrifugal compressor 5 according to the present embodiment and the centrifugal compressor 5 having this impeller 6 can further suppress the generation of the secondary flow A3, and can suppress the interference with the leakage flow. Compared with the prior art, it can more efficiently and effectively achieve the uniformization of flow rate distribution, high pressure ratio, and high efficiency, and further improve the impeller efficiency.

[0094] Here, in the impeller 6 of the centrifugal compressor 5 of the present embodiment, the upstream edge 25a of the convex portion 25 preferably lies on the upstream side of the leading edge 22a of the splitter blade 22.

[0095] With such a configuration, with the convex portion 25 having a small height, the air flow along the circumferential surface 18a of the hub 18 towards the blade surface of the entire blade 21 (or the splitter blade 22) can be more effectively guided towards the direction along the blade surface side, generating an air flow that is smoother and neater than the conventional air flow. Therefore, the generation of the secondary flow A3 can be further suppressed.

[0096] As described above, the first and second embodiments of the impeller of the centrifugal compressor and the centrifugal compressor including the impeller of the present disclosure have been described. However, the impeller of the centrifugal compressor and the centrifugal compressor of the present disclosure are not limited to the above-described first and second embodiments, and can be appropriately modified without departing from the gist thereof.

[0097] For example, in the second embodiment, the impeller 6 of the centrifugal compressor 5 is configured to include the splitter vane 22 and the convex portion 25 of the first embodiment. However, the impeller 6 of the centrifugal compressor 5 may be configured without the splitter vane 22 and with a plurality of convex portions 25, with at least one convex portion 25 provided between adjacent full blades 21 and configured to protrude from the circumferential surface 18a of the hub 18.

[0098] In such a configuration, it is preferably configured that, at the chord position along the chord direction of the full blade 21 in the meridian 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 convex portion 25 is defined as Cvl, the relationship Cvl ≤ 50% is satisfied. When the blade height of the full blade 21 is defined as Hf and the height of the convex portion 25 in the meridian plane is defined as Hv, the relationship Hv ≤ 0.3 × Hf is satisfied.

[0099] Thereby, by means of the convex portion 25, the airflow along the circumferential surface 18a of the hub 18 toward the blade surface of the full blade 21 can be effectively guided to the direction along the blade surface, generating a smoother airflow than the conventional airflow. Thus, it is difficult to generate an airflow rising along the blade surface of the full blade 21, and the generation of the secondary flow A3 can be further suppressed. In addition, the interference with the leakage flow can be suppressed, and compared with the prior art, the uniformization of the flow rate distribution, the high pressure ratio, and the high efficiency can be achieved efficiently and effectively, and the impeller efficiency can be further improved.

[0100] In addition, as Figure 7 shown, it may also be configured that, when the circumferential pitch distance between the upstream edge 25a of the convex portion 25 and the suction surface of one of the adjacent full blades 21, the first full blade 21A, is defined as Pl1, and the circumferential pitch distance between the upstream edge 25a of the convex portion 25 and the pressure surface of the other of the adjacent full blades 21, the second full blade 21B, is defined as Pl2, the relationship Pl1 < Pl2 is satisfied.

[0101] In this case, the convex portion 25 can more efficiently and effectively guide the airflow A2 flowing toward the suction surface of the first full blade 21A to the direction along the blade surface (the trailing edge 21b side of the first full blade 21A), and a smoother and neater airflow than the conventional airflow can be appropriately generated.

[0102] Furthermore, at least one convex portion 25 provided between adjacent full blades 21 may also include a first convex portion 25A and a second convex portion 25B different from the first convex portion 25A. In other words, two or more convex portions 25 may be provided between blade pitches.

[0103] In this case, by using each convex portion 25, the air flow A2 along the circumferential surface 18a of the hub 18 toward the blade surface of the full blade 21 (or the splitter blade 22) can be guided to the side in the direction along the blade surface by the first convex portion 25A and the second convex portion 25B respectively, and a more orderly air flow than the conventional air flow can be generated more effectively. Thereby, it is difficult to generate an air flow rising along the blade surface of the full blade 21 (or the splitter blade 22), and the generation of the secondary flow A3 can be further suppressed.

[0104] In addition, at this time, the upstream edge 25a of the first convex portion 25A is preferably located more upstream than the upstream edge 25a of the second convex portion 25B. In other words, for two or more convex portions 25 (25A, 25B) arranged, it is preferable to arrange them in such a way that the convex portions 25 (25A, 25B) are at different positions in the flow direction.

[0105] In this case, by using each convex portion 25 (25A, 25B), the air flow A2 toward the blade surface can be guided to the side in the direction along the blade surface more effectively, and a more orderly air flow than the conventional air flow can be generated.

[0106] Furthermore, it is more preferable that the upstream edge 25a of the first convex portion 25A is arranged on the negative pressure surface side of the first full blade 21A more than the upstream edge 25a of the second convex portion 25B. In other words, it is preferable that a plurality of convex portions 25 (25A, 25B) arranged between blade pitches are arranged in multiple rows in the flow direction.

[0107] In this case, by using each convex portion 25 (25A, 25B), the air flow A3 along the circumferential surface 18a of the hub 18 toward the blade surface of the full blade 21 (or the splitter blade 22) can be guided to the side in the direction along the blade surface even more effectively, and a more orderly air flow than the conventional air flow can be generated.

[0108] Finally, the content described in the above embodiments (including modification examples) can be understood as follows, for example.

[0109] (1) The impellers (impellers 6, 6A to 6D) of a centrifugal compressor (centrifugal compressor 5) in one mode include: a hub (hub 18); a plurality of full blades (full blades 21) provided at intervals in the circumferential direction on the circumferential surface (circumferential surface 18a) of the hub; a plurality of splitter blades (splitter blades 22, 22A to 22D) respectively provided between adjacent full blades among the plurality of full blades on the circumferential surface of the hub; when the ratio of the blade height (Hs) of the splitter blade to the blade height (Hf) of the full blade in the meridian plane of the impeller, i.e., the blade height ratio, is defined as Hs / Hf, at least at the leading edge of the splitter blade, the blade height ratio satisfies the relationship of Hs / Hf < 1.

[0110] In this case, by using the splitter blade with a blade height smaller than that of the full blade, the flow along the circumferential surface of the hub toward the blade surface of the full blade can be blocked. Thus, the generation of secondary flow can be suppressed by the splitter blade.

[0111] In addition, by being configured such that at least at the leading edge of the splitter blade, the blade height ratio satisfies the relationship of Hs / Hf < 1, the interference with the leakage flow leaking from the gap on the front end side of the full blade can be effectively suppressed.

[0112] Therefore, the generation of secondary flow can be suppressed, and the interference with the leakage flow can be suppressed. Compared with the prior art, the uniformization of flow distribution, high pressure ratio, and high efficiency can be achieved more efficiently and effectively, and the impeller efficiency can be further improved.

[0113] (2) The impeller of a centrifugal compressor in another mode is the impeller of the centrifugal compressor in the above (1), wherein in all intervals from the leading edge (leading edge 22a) to the trailing edge (trailing edge 22b) of the splitter blade, the blade height ratio satisfies the relationship of Hs / Hf < 1.

[0114] In this case, by widely arranging the splitter blade with a blade height smaller than that of the full blade, in the overall operating range (wide range) represented by the relationship between the pressure ratio and the flow rate of the centrifugal compressor, the interference with the leakage flow can be effectively suppressed, and the generation of the air flow rising along the blade surface of the full blade can be suppressed. The generation of secondary flow can be suppressed by the splitter blade.

[0115] (3) The impeller of a centrifugal compressor in another mode is the impeller of the centrifugal compressor in the above (2), wherein in all intervals from the leading edge to the trailing edge of the splitter blade, the blade height ratio satisfies the relationship of Hs / Hf ≤ 0.7.

[0116] In this case, based on the research results (insight into the position of the separation line) of the inventors of the present application, since it is configured to satisfy the relationship of Hs / Hf ≤ 0.7, the generation of secondary flow can be more effectively suppressed, and the interference with the leakage flow leaking from the front end of the full blade can be suppressed.

[0117] (4) The impeller of the centrifugal compressor in another mode is the impeller of the centrifugal compressor in the above (1), wherein, at least at the leading edge of the splitter blade, the blade height ratio satisfies the relationship of Hs / Hf ≤ 0.7.

[0118] In this case, based on the results of the in-depth research by the inventors of the present application (insights on the position of the separation line), since it is configured to satisfy the relationship of Hs / Hf ≤ 0.7 at least at the leading edge of the splitter blade, the generation of secondary flow can be further effectively suppressed, and the interference with the leakage flow leaking from the gap at the front end of the full blade can be suppressed.

[0119] (5) The impeller of the centrifugal compressor in another mode is the impeller of the centrifugal compressor in the above (4), wherein the blade height ratio is configured to gradually increase from the leading edge to the trailing edge of the splitter blade.

[0120] In this case, for example, by forming the splitter blade in a manner that matches the separation line, the generation of secondary flow can be further effectively and efficiently suppressed, and the interference with the leakage flow leaking from the gap on the front end side of the full blade can be suppressed.

[0121] (6) The impeller of a centrifugal compressor in one mode includes: a hub; a plurality of full blades that are circumferentially spaced apart on the circumferential surface of the hub; a plurality of splitter blades that are respectively disposed between adjacent full blades among the plurality of full blades on the circumferential surface of the hub; at the chord position along the chord direction of the full blade in the meridian plane of the impeller, when defining the chord position at the leading edge of the full blade as 0%, the chord position at the trailing edge of the full blade as 100%, the chord position at the base end of the leading edge of the splitter blade as Ch, and the chord position at the front end of the leading edge of the splitter blade as Ct, the relationship of Ch ≤ 30% and Ct ≥ 50% is satisfied.

[0122] In the case of such a configuration, the splitter blade can also be formed according to the position of the separation line that generates secondary flow, the generation of secondary flow can be effectively and efficiently suppressed, and the interference with the leakage flow leaking from the front end side of the full blade can be suppressed.

[0123] (7) The impeller of the centrifugal compressor in another mode is the impeller of the centrifugal compressor in the above (6), wherein, when defining the chord length at the base end of the splitter blade as Lh and the chord length at the front end of the splitter blade as Lt, the relationship of 2 × Lt ≤ Lh is satisfied.

[0124] In this case, based on the insights obtained from the results of the in-depth research by the inventors of the present application, the splitter blade can also be formed according to the position of the separation line that generates secondary flow, and the generation of secondary flow can still be effectively and efficiently suppressed, and the interference with the leakage flow leaking from the front end side of the full blade can be suppressed.

[0125] (8) The impeller of another type of centrifugal compressor is the impeller of the centrifugal compressor described in (6) or (7) above, wherein the leading edge of the splitter blade has a curved surface that is recessed in the meridional plane with respect to the straight line connecting the base end (base end 22c) and the front end (front end 22d) of the leading edge.

[0126] In this case, based on the insights obtained from the in-depth research of the inventors of the present application, the splitter blade can be formed according to the concave curve (concave surface) separation line that generates secondary flow. Thus, the generation of secondary flow can be further effectively and efficiently suppressed, and the interference with the leakage flow leaking from the gap on the front end side of the entire blade can be suppressed.

[0127] (9) The impeller of another type of centrifugal compressor is the impeller of the centrifugal compressor described in (6) to (8) above, wherein the relationship of Ch = 0% is satisfied.

[0128] In this case, the airflow along the circumferential surface of the hub toward the blade surface of the entire blade can be blocked from the leading edge side of the entire blade, and the splitter blade can be used more effectively to suppress the generation of secondary flow.

[0129] (10) The impeller (impellers 6, 6E) of another type of centrifugal compressor is the impeller of the centrifugal compressor described in (1) to (9) above, and further includes a plurality of convex portions. The plurality of convex portions are at least one convex portion (convex portion 25) respectively provided between adjacent entire blades, and are configured to protrude from the circumferential surface of the hub. At the chord position along the chord direction of the entire blade in the meridional plane of the impeller, when the chord position at the leading edge of the entire blade is defined as 0%, the chord position at the trailing edge of the entire blade is defined as 100%, and the chord position at the upstream edge (upstream edge 25a) of the convex portion is defined as Cvl, the relationship of Cvl ≤ 50% is satisfied. When the blade height of the entire blade is defined as Hf and the height of the convex portion in the meridional plane is defined as Hv, the relationship of Hv ≤ 0.3 × Hf is satisfied.

[0130] In such a case, by using convex portions with a small height, the airflow along the circumferential surface of the hub toward the blade surface of the entire blade (or splitter blade) can be guided on the circumferential surface of the hub in the direction along the blade surface, that is, toward the rear end side of the entire blade, generating an airflow that is smoother toward the rear end side of the entire blade than the conventional airflow. Thus, it is difficult to generate an airflow that rises along the blade surface of the entire blade (or splitter blade), and the generation of secondary flow can be further suppressed.

[0131] Therefore, the generation of secondary flow can be further suppressed, and the interference with the leakage flow can be suppressed. Compared with the prior art, the uniformization of flow rate distribution, high pressure ratio, and high efficiency can be further efficiently and effectively achieved, and the impeller efficiency can be further improved.

[0132] (11) The impeller of the centrifugal compressor of another mode is the impeller of the centrifugal compressor of the above (10), wherein the upstream edge of the convex portion is located on the upstream side of the leading edge of the splitter blade.

[0133] With such a configuration, by using the convex portion with a small height, the air flow along the circumferential surface of the hub toward the blade surface of the full blade (or splitter blade) can be more effectively guided to the side along the blade surface direction, generating a smoother and more orderly air flow than the conventional air flow. Therefore, the generation of secondary flow can be further suppressed.

[0134] (12) The impeller of a centrifugal compressor of one mode includes: a hub; a plurality of full blades arranged at intervals in the circumferential direction on the circumferential surface of the hub; a plurality of convex portions, with at least one convex portion respectively arranged between adjacent full blades and configured to protrude from the circumferential surface of the hub; at the chord position along the chord direction of the full blade in the meridian plane of the impeller, when the chord position at the leading edge of the full blade is defined as 0%, the chord position at the trailing edge of the full blade is defined as 100%, and the chord position at the upstream edge of the convex portion is defined as Cvl, the relationship Cvl ≤ 50% is satisfied, and when the blade height of the full blade is defined as Hf and the height of the convex portion in the meridian plane is defined as Hv, the relationship Hv ≤ 0.3×Hf is satisfied.

[0135] In this case, by using the convex portion, the air flow along the circumferential surface of the hub toward the blade surface of the full blade can be effectively guided to the side along the blade surface direction, generating a smoother air flow than the conventional air flow. Therefore, it is difficult to generate an air flow rising along the blade surface of the full blade, and the generation of secondary flow can be further suppressed. In addition, the interference with the leakage flow can be suppressed, and compared with the prior art, the uniformization of flow rate distribution, high pressure ratio, and high efficiency can be achieved efficiently and effectively, further improving the impeller efficiency.

[0136] Therefore, the generation of secondary flow can be further suppressed, and the interference with the leakage flow can be suppressed. Compared with the prior art, the uniformization of flow rate distribution, high pressure ratio, and high efficiency can be achieved efficiently and effectively, further improving the impeller efficiency.

[0137] (13) The impeller of the centrifugal compressor of another mode is the impeller of the centrifugal compressor of the above (12), wherein when the circumferential pitch distance between the upstream edge of the convex portion and the suction surface of one side of the adjacent full blade (the first full blade 21A) is defined as Pl1, and the circumferential pitch distance between the upstream edge of the convex portion and the pressure surface of the other side of the adjacent full blade (the second full blade 21B) is defined as Pl2, the relationship Pl1 < Pl2 is satisfied.

[0138] In this case, the convex portion can be used to more efficiently and effectively guide the airflow flowing toward the negative pressure surface of the first full blade toward the direction along the blade surface (the rear end side of the first full blade), and appropriately generate an airflow that is smoother and neater than the conventional airflow.

[0139] (14) The impeller of another type of centrifugal compressor is the impeller of the centrifugal compressor in (13) above, wherein at least one convex portion provided between adjacent full blades includes a first convex portion (first convex portion 25A) and a second convex portion (second convex portion 25B) different from the first convex portion.

[0140] In this case, by using each convex portion, the airflow flowing along the circumferential surface of the hub toward the blade surface of the full blade (or splitter blade) can be guided toward the direction along the blade surface by the first convex portion and the second convex portion respectively, and an airflow that is neater than the conventional airflow can be generated more effectively. Thus, it is more difficult to generate an airflow rising along the blade surface of the full blade (or splitter blade), and the generation of secondary flow can be further suppressed.

[0141] (15) The impeller of another type of centrifugal compressor is the impeller of the centrifugal compressor in (14) above, wherein the upstream edge of the first convex portion is located more upstream than the upstream edge of the second convex portion.

[0142] In this case, by using each convex portion, the airflow toward the blade surface can be guided more effectively toward the direction along the blade surface, and an airflow that is neater than the conventional airflow can be generated.

[0143] (16) The impeller of another type of centrifugal compressor is the impeller of the centrifugal compressor in (14) or (15) above, wherein the upstream edge of the first convex portion is arranged more on the negative pressure surface side of the first full blade than the upstream edge of the second convex portion.

[0144] In this case, by using each convex portion, the airflow flowing along the circumferential surface of the hub toward the blade surface of the full blade can be guided even more effectively toward the direction along the blade surface, and an airflow that is neater than the conventional airflow can be generated.

[0145] (17) A type of centrifugal compressor includes the impeller of the centrifugal compressor in (1) to (16) above.

[0146] According to the centrifugal compressor in (17) above, the effects of the impeller of the centrifugal compressor described in (1) to (16) above can be obtained.

[0147] Description of Reference Numerals

[0148] 1 Turbocharger

[0149] 2 Turbine

[0150] 4 Rotating shaft

[0151] 5 Centrifugal compressor (compressor)

[0152] 6 Impeller

[0153] 6A - 6E Impellers

[0154] 18 Hub

[0155] 18a Peripheral surface

[0156] 21 Full blade (rotating blade)

[0157] 21A First full blade

[0158] 21B Second full blade

[0159] 21a Leading edge

[0160] 21b Trailing edge

[0161] 21c Base end

[0162] 21d Front end

[0163] 22 Splitter blade (rotating blade)

[0164] 22A - 22D Splitter blades

[0165] 22a Leading edge

[0166] 22b Trailing edge

[0167] 22c Base end

[0168] 22d Front end

[0169] 25 Protrusion

[0170] 25A First protrusion

[0171] 25B Second protrusion

[0172] 25a Upstream edge

[0173] A Air (fluid)

[0174] A’ Compressed air (compressed fluid, fluid)

[0175] A3 Secondary flow

[0176] O1 Axis (axial direction)

Claims

1. An impeller of a centrifugal compressor, comprising: a hub; A plurality of full blades, which are circumferentially spaced apart on the circumferential surface of the hub; A plurality of splitter blades, which are respectively arranged between adjacent full blades among the plurality of full blades on the circumferential surface of the hub; the impeller of the centrifugal compressor is characterized in that At the chord position along the chord direction of the full blade in the meridian plane of the impeller, Defining the chord position at the leading edge of the full blade as 0%, Defining the chord position at the trailing edge of the full blade as 100%, Defining the chord position at the base end of the leading edge of the splitter blade as Ch, When defining the chord position at the front end of the leading edge of the splitter blade as Ct, The relationship of Ch≤30% and Ct≥50% is satisfied.

2. The impeller of the centrifugal compressor according to claim 1, characterized in that, When defining the chord length at the base end of the splitter blade as Lh, When defining the chord length at the front end of the splitter blade as Lt, The relationship of 2×Lt≤Lh is satisfied.

3. The impeller of the centrifugal compressor according to claim 1, characterized in that, The leading edge of the splitter blade has a curved surface shape that is recessed in the meridian plane with respect to the straight line connecting the base end and the front end of the leading edge.

4. The impeller of the centrifugal compressor according to claim 1, characterized in that, The relationship of Ch = 0% is satisfied.

5. The impeller of a centrifugal compressor according to claim 1, characterized in that, It further comprises a plurality of convex portions, at least one of which is respectively arranged between the adjacent full blades and is configured to protrude from the circumferential surface of the hub, At the chord position along the chord direction of the full blade in the meridian plane of the impeller, Defining the chord position at the leading edge of the full blade as 0%, Defining the chord position at the trailing edge of the full blade as 100%, When defining the chord position at the upstream edge of the convex portion as Cvl, The relationship of Cvl≤50% is satisfied, When defining the blade height of the full blade as Hf and the height of the convex portion in the meridian plane as Hv, The relationship of Hv≤0.3×Hf is satisfied.

6. The impeller of the centrifugal compressor according to claim 5, characterized in that, The upstream edge of the convex portion is located upstream of the leading edge of the splitter blade.

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