JP2015190382A - compressor impeller, centrifugal compressor, and supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently enlarge the actuation area of a centrifugal compressor 29 onto a large flow rate side, and to promote improvement in compressor efficiency of the centrifugal compressor 29 in the actuation area of a small flow rate side.SOLUTION: A plurality of compressor blades 41 are integrally formed at an equal interval in a circumferential direction on a hub face 39h of a compressor disk 39; an inlet blade angle θm of a mid-span in each compressor blade 41 is set so as to be larger than an inlet blade angle θt of a tip end thereof; the inlet blade angle θm of the mid-span in each compressor blade 41 is set to 55-65 degrees; the inlet blade angle θt of the tip end in each compressor blade 41 is set to 50-60 degrees; and an inlet blade angle θh of a hub end in each compressor blade 41 is set to 30-40 degrees.

Description

  The present invention relates to a centrifugal compressor that compresses a fluid such as air using centrifugal force, a compressor impeller used in the centrifugal compressor, and the like.

  In recent years, various research and development have been conducted on centrifugal compressors used in superchargers, industrial machines, gas turbines, etc. The configuration of a general centrifugal compressor will be briefly described as follows (Patent Literature). 1 and Patent Document 2).

  A typical centrifugal compressor includes a compressor housing, and the compressor housing has a shroud inside. A compressor impeller is provided in the compressor housing so as to be rotatable around its axis (axis of the compressor impeller). The compressor impeller includes a compressor disk, and the hub surface of the compressor disk is radially outward from one axial side (one axial side of the compressor impeller) (radial direction of the compressor impeller). The outside). Furthermore, a plurality of compressor blades are integrally provided on the hub surface of the compressor disk at intervals in the circumferential direction (circumferential direction of the hub surface). Here, the tip (tip edge) of each compressor blade extends along the shroud of the compressor housing. The inlet blade angle of the compressor blade corresponds to the change in the span direction of the relative inflow angle of the fluid with respect to the compressor blade (the angle between the axial direction of the compressor impeller and the inflow direction of the fluid). It is set so as to gradually increase from the tip end to the tip end (see the broken line portion in FIG. 3).

JP 2011-80411 A JP 2009-150245 A

  By the way, in recent years, there is an increasing demand for improvement of the compressor efficiency of the centrifugal compressor in the operation region on the small flow rate side where the relative inflow angle of the fluid becomes large. In order to meet this demand, by increasing the inlet blade angle of the compressor blade, the incidence, which is the difference between the relative inlet angle of the fluid and the inlet blade angle of the compressor blade, is reduced, and fluid separation is suppressed. The method of doing is conceivable. On the other hand, when the inlet blade angle of the compressor blade is increased, the distance between two adjacent compressor blades is narrowed, the choke flow rate (choke margin) of the centrifugal compressor is reduced, and the operating range of the centrifugal compressor is increased. It becomes difficult to expand to the flow rate side. That is, there is a problem that it is not easy to promote the improvement of the compressor efficiency of the centrifugal compressor in the operation region on the small flow rate side while sufficiently expanding the operation region of the centrifugal compressor to the large flow rate side.

  Accordingly, an object of the present invention is to provide a compressor impeller, a centrifugal compressor, and the like having a novel configuration that can solve the above-described problems.

  The inventor of the present invention has repeated trial and error in order to solve the above-mentioned problems. As a result, the compressor blades maintain the blade shape, and the inlet blade angle of each compressor blade is changed from the hub end of the leading edge. By giving a predetermined distribution (change) over the tip end, the inlet blade angle of each compressor blade is gradually increased from the hub end of the leading edge to the tip end while suppressing a decrease in the choke flow rate of the centrifugal compressor. Compared with the case where it made it, the novel knowledge that the compressor efficiency of the centrifugal compressor in the small flow rate side can be improved was acquired, and it came to complete this invention (refer the below-mentioned Example). Here, “giving a predetermined change” means that the inlet blade angle of the midspan of each compressor blade is sufficiently larger than the average inlet blade angle, and the inlet blade angle at the tip end of each compressor blade is This means approaching the average inlet blade angle or making it smaller than the average inlet blade angle. The “average inlet blade angle” refers to the middle inlet blade angle between the minimum inlet blade angle and the maximum inlet blade angle.

  A first feature of the present invention is a compressor impeller for use in a centrifugal compressor that compresses a fluid using centrifugal force, a compressor disk having a hub surface extending radially outward from one side in the axial direction; A plurality of compressor blades integrally provided on the hub surface of the compressor disk at intervals in the circumferential direction thereof (circumferential direction of the hub surface). ) Is set to be larger than the inlet blade angle at the tip end.

  Here, in the specification and claims of the present application, “fluid” means that gas such as air is included, and “centrifugal compressor” is a supercharger such as a supercharger for vehicles. It is intended to include not only the centrifugal compressors used but also industrial centrifugal compressors, gas turbine centrifugal compressors, and the like. Further, “one axial direction” means one axial direction, and “axial direction” means the axial direction of the compressor impeller unless otherwise specified, and “radially outward”. Means the outside in the radial direction, “radial direction” means the radial direction of the compressor impeller unless otherwise specified, and “provided integrally” means being integrally formed. It is meant to include. Furthermore, “midspan” means the part at 50% span position with respect to the hub end, and “hub end” means the end of the compressor disk on the hub surface side, in other words, the span position reference. The “tip end” means the end opposite to the hub end, in other words, the portion at the 100% span position with respect to the hub end.

  According to the first feature, since the inlet blade angle of the midspan in each compressor blade is set to be equal to or larger than the inlet blade angle at the tip end, the inlet blade angle of the midspan of each compressor blade is set to the average inlet blade angle. And the inlet blade angle at the tip end of each compressor blade can be close to the average inlet blade angle or smaller than the average inlet blade angle. Thereby, the above-mentioned novel knowledge can be applied to the centrifugal compressor.

  According to a second aspect of the present invention, there is provided a centrifugal compressor that compresses a fluid using a centrifugal force, a compressor housing having a shroud on the inside thereof, a rotary housing provided in the compressor housing so as to be rotatable, The gist of the invention is that it includes a compressor impeller having features.

  According to the second feature, in addition to having the same effect as that of the first feature, the impeller is taken into the compressor housing by rotating the impeller around its axis (axis of the impeller). The fluid can be compressed. On the other hand, the compressed fluid (compressed fluid) is discharged to the outside of the compressor housing.

  According to a third aspect of the present invention, there is provided a supercharger that supercharges air supplied to the engine side using pressure energy of exhaust gas from the engine, and includes the centrifugal compressor according to the second aspect. The summary is as follows.

  According to the 3rd characteristic of this invention, there exists an effect | action similar to the effect | action by a 2nd characteristic.

  According to the present invention, since the above-mentioned novel knowledge can be applied to the centrifugal compressor, the inlet blade angle of each compressor blade is set to the leading edge while suppressing a decrease in the choke flow rate (choke margin) of the centrifugal compressor. The compressor efficiency of the centrifugal compressor in the operating region on the small flow rate side can be increased as compared with the case where it gradually increases from the hub end to the tip end. That is, according to the present invention, it is possible to promote the improvement of the compressor efficiency of the centrifugal compressor in the operating region on the small flow rate side while sufficiently expanding the operating region of the centrifugal compressor to the large flow rate side.

Fig.1 (a) is a front view of the compressor impeller which concerns on embodiment of this invention, FIG.1 (b) is a side view of the compressor impeller which concerns on embodiment of this invention. FIG. 2 is a diagram for explaining the inlet blade angles of the hub end, midspan, and tip end of the compressor blade. FIG. 3 is a diagram showing the relationship between the inlet blade angle of the compressor blade and the span position of the leading edge of the compressor blade in the embodiment (invention example) of the present invention and the conventional example. FIG. 4 is a sectional side view of the centrifugal compressor according to the embodiment of the present invention. FIG. 5 is a side sectional view of the supercharger for a vehicle according to the embodiment of the present invention. 6A is a front view of a compressor impeller according to a conventional example, and FIG. 6B is a side view of the compressor impeller according to the conventional example. FIG. 7A is a diagram showing the relationship between the flow rate and the compressor efficiency in the case of the invention example and the conventional example, and FIG. 7B is the relationship between the flow rate and the pressure ratio in the case of the invention example and the conventional example. FIG. FIG. 8A is a trajectory diagram showing the state of the flow field from the inlet side to the outlet side of the compressor impeller in the operating region on the small flow rate side, and FIG. 8B is the compression in the operating region on the large flow rate side. It is a trajectory diagram which shows the state of a flow field from the entrance side to the exit side of a machine impeller.

  Embodiments and examples of the present invention will be described with reference to FIGS. 1 to 8A and 8B. As shown in the drawings, “F” is the forward direction, “R” is the backward direction, “AD” is the axial direction, “BD” is the radial direction, “BDi” is the radially inner side, “BDo” "Is radially outward, and" CD "is the direction of rotation of the compressor impeller.

(Embodiment of the present invention)
As shown in FIG. 5, a vehicle supercharger (an example of a supercharger) 1 according to an embodiment of the present invention utilizes pressure energy of exhaust gas (an example of gas) from an engine (not shown). The air supplied to the engine is supercharged (compressed). And the specific structure of the supercharger 1 for vehicles is as follows.

  The vehicle supercharger 1 includes a bearing housing 3, and a pair of radial bearings 5 and a pair of thrust bearings 7 are provided in the bearing housing 3. The plurality of bearings 5 and 7 are provided with a rotor shaft (rotating shaft) 9 extending in the front-rear direction so as to be rotatable. In other words, the rotor shaft 9 is provided in the bearing housing 3 with the plurality of bearings 5. , 7 are rotatably provided.

  A radial turbine 11 that generates a rotational force (rotational torque) using the pressure energy of the exhaust gas is disposed on the rear side of the bearing housing 3, and the configuration of the radial turbine 11 is as follows. .

  A turbine housing 13 is provided on the rear side of the bearing housing 3, and the turbine housing 13 has a shroud 13 s inside. A turbine impeller 15 is provided in the turbine housing 13 so as to be rotatable around its axis C (the axis of the turbine impeller 15, in other words, the axis of the rotor shaft 9) C. Are concentrically and integrally connected to the rear end of the rotor shaft 9. The turbine impeller 15 includes a turbine disk 17, and a hub surface 17 h of the turbine disk 17 extends radially outward from the rear side (outside in the radial direction of the turbine impeller 15). Further, a plurality of turbine blades 19 are integrally formed on the hub surface 17h of the turbine disk 17 at equal intervals in the circumferential direction (circumferential direction of the hub surface 17h), and the tip (tip edge) 19t of each turbine blade 19 is The turbine housing 13 extends along the shroud 13s.

  An exhaust intake 21 for taking in exhaust gas into the turbine housing 13 is formed at an appropriate position of the turbine housing 13, and this exhaust intake 21 can be connected to an engine exhaust manifold (not shown). is there. Further, a spiral turbine scroll passage 23 is formed on the inlet side of the turbine impeller 15 in the turbine housing 13 (upstream side in the main flow direction of the exhaust gas). It communicates with the intake 21. Further, an exhaust discharge port 25 for discharging exhaust gas is formed on the outlet side of the turbine impeller 15 in the turbine housing 13 (downstream side in the main flow direction of the exhaust gas). The exhaust discharge port 25 is connected to the turbine impeller 15. It can be connected to an exhaust gas purification device (not shown) via a pipe (not shown).

  An annular heat shield plate 27 that shields heat from the turbine impeller 15 side is provided on the rear side surface of the bearing housing 3, and an outer edge portion 27o of the heat shield plate 27 is formed between the bearing housing 3 and the turbine housing. 13.

  A centrifugal compressor 29 that compresses air by using centrifugal force is disposed on the front side of the bearing housing 3. The configuration of the centrifugal compressor 29 is as follows.

  As shown in FIG. 4, a compressor housing 31 is provided on the front side of the bearing housing 3. The compressor housing 31 includes a housing main body 33 having a shroud 33 s inside, and an annular seal plate 35 provided on the rear side of the housing main body 33 and integrally connected to the front side portion of the bearing housing 3. It has.

  As shown in FIGS. 1A and 1B and FIG. 4, a compressor impeller 37 has a shaft center (an axis of the compressor impeller 37, in other words, a shaft of the rotor shaft 9) in the compressor housing 31. Center) The compressor impeller 37 is provided so as to be rotatable around C. The compressor impeller 37 is concentrically and integrally connected to the front end portion of the rotor shaft 9. The compressor impeller 37 includes a compressor disk 39 integrally connected to the front end portion of the rotor shaft 9, and the hub surface 39 h of the compressor disk 39 is arranged on the front side (in the axial direction of the compressor impeller 37). One side) extends outward in the radial direction (outside in the radial direction of the compressor impeller 37).

  A plurality of compressor blades 41 are integrally formed on the hub surface 39h of the compressor disk 39 at equal intervals in the circumferential direction (the circumferential direction of the hub surface 39h). A short blade (splitter blade) 43 having a cord length shorter than that of the compressor blade 41 is integrally formed between two adjacent compressor blades 41 on the hub surface 39 h of the compressor disk 39. In other words, the compressor blades 41 and the short blades 43 are alternately and integrally formed on the hub surface 39h of the compressor disk 39 at intervals in the circumferential direction. Here, the tip (tip edge) 41t of each compressor blade 41 and the tip 43t of each short blade 43 extend along the shroud 33s of the housing body 33, and the front edge 43a of each short blade 43 is compressed. It is located downstream of the leading edge 41a of the machine blade 41 in the main air flow direction. The plurality of short blades 43 may be omitted from the components of the compressor impeller 37.

  As shown in FIG. 4, on the inlet side of the compressor impeller 37 in the compressor housing 31 (upstream side in the main air flow direction), air intake as a fluid intake for taking air into the compressor housing 31 is provided. An inlet 45 is formed, and the air intake 45 can be connected to an air cleaner (not shown) for purifying air. An annular diffuser flow path 47 that pressurizes the compressed air is formed on the outlet side of the compressor impeller 37 in the compressor housing 31 (downstream side in the main air flow direction). Further, a spiral compressor scroll channel 49 is formed inside the compressor housing 31, and the compressor scroll channel 49 communicates with the diffuser channel 47. An air discharge port 51 for discharging the compressed air to the outside of the compressor housing 31 is formed at an appropriate position of the compressor housing 31, and the air discharge port 51 has a compressor scroll flow path. 49 and can be connected to an intake manifold (not shown) of the engine.

  Then, the characteristic part of the compressor impeller 37 which concerns on embodiment of this invention is demonstrated.

  As shown in FIGS. 1A, 1B, and 2, the midspan inlet blade angle (the angle formed between the axial direction and the blade thickness center line 41c of the midspan 41am of the leading edge 41a) in each compressor blade 41. θm is set to be not less than the inlet blade angle at the tip end (the angle formed between the axial direction and the blade thickness center line 41c of the tip end 41at of the leading edge 41a) θt. Further, the inlet blade angle θt at the tip end and the inlet blade angle θm at the midspan of each compressor blade 41 are determined from the inlet blade angle at the hub end (the axial direction and the blade thickness center line 41c at the hub end 41ah of the leading edge 41a). It is set larger than the angle formed by θh.

  Here, the midspan inlet blade angle θm of each compressor blade 41 is set to 55 to 65 degrees. If the angle is set to 55 degrees or more, and less than 55 degrees, the inlet blade angle θm of the midspan of the compressor blade 41 is made sufficiently larger than the average inlet blade angle Aθ (see FIG. 3). This is because it becomes difficult. The reason why the angle is set to 65 degrees or less is that when the angle exceeds 65 degrees, the compressor blade 41 maintains the blade shape, and the inlet blade angle θt at the tip end of the compressor blade 41 is set to the average inlet blade angle. This is because it becomes difficult to approach Aθ.

  The inlet blade angle θt at the tip end of each compressor blade 41 is set to 50 to 60 degrees. When the angle is less than 50 degrees, the compressor blade 41 maintains the blade shape, and the mid-span inlet blade angle θm of the compressor blade 41 is set to an average inlet blade. This is because it becomes difficult to make the angle sufficiently larger than the angle Aθ. The reason why the angle is set to 60 degrees or less is that when it exceeds 60 degrees, it becomes difficult to bring the inlet blade angle θt at the tip end of the compressor blade 41 close to the average inlet blade angle Aθ.

  The inlet blade angle θh at the hub end of each compressor blade 41 is set to 30 to 40 degrees. If the angle is less than 30 degrees, the compressor blade 41 maintains the blade shape, and the mid-span inlet blade angle θm of the compressor blade 41 is set to an average inlet blade. This is because it becomes difficult to make the angle sufficiently larger than the angle Aθ. The reason why the angle is set to 40 degrees or less is that if it exceeds 40 degrees, the space between the two adjacent compressor blades 41 becomes narrow, and it becomes difficult for the compressor blades 41 to maintain the blade shape. It is.

  In the compressor impeller 37 according to the embodiment of the present invention (compressor impeller according to the invention example), the relationship between the inlet blade angle of the compressor blade 41 and the span position of the front edge 41a of the compressor blade 41 is shown in FIG. As shown in FIG. That is, the compressor impeller 37 according to the embodiment of the present invention has a midspan inlet blade angle θm of the compressor blade 41 as compared with the compressor impeller 100 according to the conventional example (see FIGS. 6A and 6B). Is sufficiently large, and the inlet blade angle θt at the tip end of the compressor blade 41 is sufficiently small. Here, in the compressor impeller 100 according to the conventional example, the inlet blade angle of each compressor blade 41 is set so as to gradually increase from the hub end 41ah to the tip end 41at of the front edge 41a.

  As shown in FIG. 1B, the inlet blade angle (not shown) of each short blade 43 is set to gradually increase from the hub end 43ah to the tip end 43at of the front edge 43a.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  Exhaust gas taken into the turbine housing 13 from the exhaust inlet 21 flows from the inlet side to the outlet side of the turbine impeller 15 via the turbine scroll passage 23. Then, a rotational force (rotational torque) is generated using the pressure energy of the exhaust gas, and the compressor impeller 37 is rotated integrally with the turbine impeller 15 around its axis C (axis of the compressor impeller 37). Can be made. As a result, the air taken into the compressor housing 31 from the air inlet 45 is compressed, discharged from the air outlet 51 via the diffuser passage 47 and the compressor scroll passage 49, and supplied to the engine. The air can be supercharged. The exhaust gas flowing to the outlet side of the turbine impeller 15 is discharged from the exhaust discharge port 25 to the outside of the turbine housing 13 (normal operation of the vehicle supercharger 1).

  Since the midspan inlet blade angle θm of each compressor blade 41 is set to be equal to or larger than the tip end inlet blade angle θt, the midspan inlet blade angle θm of each compressor blade 41 is determined from the average inlet blade angle Aθ. The inlet blade angle θt at the tip end of each compressor blade 41 can be made close to the average inlet blade angle Aθ or smaller than the average inlet blade angle Aθ. Thereby, the above-mentioned novel knowledge can be applied to the centrifugal compressor 29 (specific action of the vehicle supercharger 1).

  Therefore, according to the embodiment of the present invention, the inlet blade angle of each compressor blade 41 extends from the hub end 41ah to the tip end 41at of the front edge 41a while suppressing a decrease in the choke flow rate (choke margin) of the centrifugal compressor 29. The compressor efficiency of the centrifugal compressor 29 in the operating region on the small flow rate side can be increased as compared with the case where it is gradually increased. That is, according to the embodiment of the present invention, the operating range of the centrifugal compressor 29, in other words, the operating range of the vehicle supercharger 1 is sufficiently expanded to the large flow rate side, while the operating range on the small flow rate side is increased. Improvement of the compressor efficiency of the centrifugal compressor 29, in other words, improvement of the efficiency of the vehicle supercharger 1 can be promoted.

  The present invention is not limited to the description of the above-described embodiment. For example, the technical idea applied to the centrifugal compressor 29 of the vehicle supercharger 1 is an industrial centrifugal compressor (not shown) or gas. You may apply to the centrifugal compressor for turbines (illustration omitted). The scope of rights encompassed by the present invention is not limited to the above-described embodiment.

(Example of the present invention)
As shown in FIGS. 1A and 1B and FIGS. 6A and 6B, the compressor impeller 37 according to the embodiment of the present invention is a compressor impeller according to an example of the invention, and the inlet of each compressor blade 41 is used. The compressor impeller 100 set so that the blade angle gradually increases from the hub end 41ah to the tip end 41at of the front edge 41a is a compressor impeller according to the conventional example. Of the plurality of constituent elements in the compressor impeller 100 according to the conventional example, those corresponding to the constituent elements in the compressor impeller 37 according to the invention example are denoted by the same reference numerals in the drawings.

  Then, a performance test is performed on a centrifugal compressor (not shown) using the compressor impeller 37 according to the invention example, and a centrifugal compressor (not shown) using the compressor impeller 100 according to the conventional example, and the test results are as follows. The relationship between the flow rate and the compressor efficiency and the relationship between the flow rate and the pressure ratio are summarized as shown in FIGS. That is, in the case of the invention example, the reduction in the choke flow rate of the centrifugal compressor is suppressed, and the compressor efficiency of the centrifugal compressor on the small flow rate side is increased compared to the case of the conventional example (specifically, the conventional example) 2% higher than in the case of 7A and 7B, N1, N2, and N3 indicate the rotational speed of the centrifugal compressor, and there is a relationship of N1 <N2 <N3 between N1 and N3.

  That is, the inventor of the present invention, based on the results of the performance test, the compressor blade 41 maintains the blade shape, and the inlet blade angle of each compressor blade 41 is changed from the hub end 41ah of the leading edge 41a to the tip end 41at. (See paragraph [0007]), the inlet blade angle of each compressor blade 41 is changed from the hub end 41ah of the leading edge 41a to the tip end while suppressing the reduction of the choke flow rate of the centrifugal compressor. As compared with the case where the pressure gradually increased over 41 at, new knowledge that the compressor efficiency of the centrifugal compressor on the small flow rate side can be increased was obtained. This new finding is thought to be due to the following reasons.

  That is, as shown in FIG. 8A, in general, in the operating region on the small flow rate side, a back flow region is generated near the tip 41t on the front edge 41a side of the compressor blade 41, and the front edge of the compressor blade 41 is The part on the chip 41t side on the 41a side is a part that does not contribute to work. On the other hand, as shown in FIG. 8B, in the operating region on the large flow rate side, the flow is forward from the inlet side to the outlet side of the compressor impeller, and the tip 41t side on the front edge 41a side of the compressor blade 41 This part becomes a part that takes in (inhales) a fluid having a flow rate higher than that of the flow on the hub side (hub surface 39h side). In consideration of the characteristics, a portion from the hub side to the midspan side on the front edge 41a side of the compressor blade 41 is a portion that sufficiently contributes to work in the operating region on the small flow rate side, and the front edge 41a of the compressor blade 41 This is probably because the portion on the side of the tip 41t is a portion that contributes to high-speed fluid intake (suction) in a large flow rate operating region. In other words, the role of the compressor blade 41 on the front edge 41a side of the compressor blade 41 according to the state of the flow field from the inlet side to the outlet side of the compressor impeller 37 in the operation region on the small flow rate side and the large flow rate side. This is considered to be due to the appropriate sharing in the span direction. 8A and 8B are obtained by numerical fluid analysis (CFD: Computational Fluid Dynamics analysis).

  1: vehicle supercharger (supercharger), 3: bearing housing, 9: rotor shaft, 11: radial turbine, 13: turbine housing, 15: turbine impeller, 29: centrifugal compressor, 31: compressor housing, 33: housing body, 33s: shroud, 35: seal plate, 37: compressor impeller, 39: compressor disk, 39h: hub surface, 41: compressor blade, 41a: leading edge, 41ah: hub end of leading edge, 41at: leading edge tip end, 41am: leading edge midspan (mean), 41t: tip, 43: short blade, 43a: leading edge, 43ah: leading edge hub end, 43at: leading edge tip end, 43t : Chip, 45: Air intake, 47: Diffuser flow path, 49: Compressor scroll flow path, 51: Air discharge port, Aθ: Average inlet blade angle, θh: Compressor block Raid hub blade inlet blade angle, θt: compressor blade tip blade inlet blade angle, θm: compressor blade midspan blade angle

Claims (5)

In a compressor impeller used in a centrifugal compressor that compresses a fluid using centrifugal force,
A compressor disk with a hub surface extending radially outward from one axial side;
A plurality of compressor blades that are integrally provided on the hub surface of the compressor disk at intervals in the circumferential direction thereof,
A compressor impeller characterized in that the midspan inlet blade angle of each compressor blade is set to be equal to or larger than the inlet blade angle at the tip end.   The compressor impeller according to claim 1, wherein an inlet blade angle of a mid span of each compressor blade is set to 55 to 65 degrees.   The compressor impeller according to claim 1 or 2, wherein an inlet blade angle at a tip end of each compressor blade is set to 50 to 60 degrees. In a centrifugal compressor that compresses fluid using centrifugal force,
A compressor housing having a shroud on the inside;
A centrifugal compressor provided with the compressor impeller according to any one of claims 1 to 3, which is rotatably provided in the compressor housing. In the supercharger that supercharges the air supplied to the engine side using the pressure energy of the exhaust gas from the engine,
A turbocharger comprising the centrifugal compressor according to claim 4.

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