JP2012087682A - Impeller of centrifugal fluid machine and designing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high pressure ratio without degrading the efficiency of a centrifugal compressor.SOLUTION: The impeller 2 of the centrifugal compressor 1 is equipped with a plurality of vanes 6 installed on a core plate 4 in the circular cascade arrangement. Each vane 6 has a base end part 11 continued to the core plate 4 without forming any void, an inlet edge 13 to designate the inlet of an inter-vane passage 7 formed by mutually adjoining vanes 6 in the circumferential direction, an outlet edge 14 to designate the outlet of each inter-vane passage 7, a boundary part 15 at which the vane angle α formed by each vane 6 with respect to the radial direction begins decreasing, an outlet side portion 16 ranging from the boundary part 15 to the outlet edge 14, and a central portion 17 positioned radially inside of the boundary part 15. The outlet side angle α1 as the vane angle α of the outlet side portion 16 is smaller than the close-to-boundary angle α24 as the vane angle α close to the boundary part 15 when viewing the whole of the outlet side portion 16.

Description

  The present invention relates to a centrifugal fluid machine that compresses or pumps fluid, and more particularly, to an impeller provided in the centrifugal fluid machine and a method for designing the impeller.

  In a centrifugal fluid machine including an impeller having a plurality of blades arranged in a circular cascade, for example, a centrifugal compressor, as a means for increasing the pressure ratio of the centrifugal compressor without increasing the peripheral speed of the impeller It is known that the angle formed between the radial direction of the impeller and the blade (backward angle) is reduced to reduce the angle formed by the outlet flow of the impeller and the radial direction (for example, patents). Reference 1). In order to reduce the backward angle, in the centrifugal compressor described in Patent Document 1, the backward angle of the blades is reduced and the pressure ratio of the centrifugal compressor is increased due to elastic deformation due to centrifugal stress during high-speed rotation. In addition, a slit is provided so that a part of the base end portion of the blade is not fixed to the core plate.

JP-A-9-112286

In the impeller of a centrifugal compressor, when a slit is provided between the base end of the blade near the impeller outlet and the core plate, the fluid flowing through the inter-blade channel formed by the blades adjacent in the circumferential direction Since it leaks from the slit, the compression work of the impeller is reduced, leading to a reduction in efficiency.
In addition, in an impeller with a large reduction ratio in the impeller so that the pressure ratio becomes high, backflow tends to occur inside the impeller during small flow operation, so the operating limit on the design point flow rate and small flow side is limited. The surge margin, which is determined by the difference from the surge point flow rate, is reduced, and surge is likely to occur.

This invention is made | formed in view of such a situation, The objective is to obtain a high pressure ratio, without reducing the efficiency of a centrifugal fluid machine. Furthermore, another object of the present invention is to obtain a high pressure ratio while preventing a decrease in surge margin of a centrifugal fluid machine.
Another object of the present invention is to facilitate the improvement of a centrifugal fluid machine.

  The invention according to claim 1 is an impeller of a centrifugal fluid machine provided with a plurality of blades arranged in a circular blade row on a core plate and rotating around a rotation center line, wherein each blade forms a gap. A base end portion that continues to the core plate, a distal end portion, an inlet edge that defines an inlet of a flow passage between blades formed by the blades adjacent in the circumferential direction, and an outlet of the flow passage between the blades. An outlet edge to be defined, a boundary part where a blade angle between the radial direction and the blade starts to decrease when going radially outward from the rotation center line, and an outlet side from the boundary part to the outlet edge And the outlet side angle, which is the blade angle of the outlet side portion, is close to the boundary portion in the whole of the outlet side portion. Feather smaller than the boundary nearest angle α24, which is the blade angle of It is a car.

According to this, when each blade is bisected in the radial direction by the boundary portion into the radially inner side portion from the boundary portion and the outlet side portion from the boundary portion to the outlet edge, the impeller The blades are formed so that the outlet side angle, which is the blade angle at the outlet side portion in the vicinity of the outlet, is smaller than the closest angle to the boundary, which is the blade angle closest to the boundary. As a result, when the peripheral speed is the same, a higher pressure ratio can be obtained as compared with the impeller of the base centrifugal compressor.
In addition, since each blade is connected to the core plate without a gap, a reduction in the efficiency of the centrifugal compressor is prevented as compared with a centrifugal compressor including an impeller in which a slit is provided between the blade and the core plate.

According to a second aspect of the present invention, in the impeller according to the first aspect, a proximal-side angle that is the outlet-side angle at the proximal-end portion and a distal-side angle that is the outlet-side angle at the distal end portion Are different.
According to this, in the exit side angle, the base end side angle and the tip end side angle are different, and accordingly, the tip end portion which is the side plate side end portion and the base end portion which is the core plate side end portion are each optimally angled. Since the blades can be formed so as to have, it is possible to make the flow uniform in the blade height direction and improve the efficiency of the centrifugal fluid machine.

The invention according to claim 3 is the impeller according to claim 1 or 2, wherein the tip portion includes a side plate that is continuous without a gap, and the tip portion is an inlet flow from the inlet to a throat portion of the flow path between the blades. In the path portion, the angle formed between the axial direction and the tip portion does not vary greatly locally in the fluid flow direction.
According to this, since there is no increase in the local flow area in the inlet flow path from the inlet of the flow path between the blades to the throat portion where the flow area in the flow path between the blades is minimized, A sudden deceleration of the flow can be avoided. As a result, it becomes difficult for the backflow in the vicinity of the leading edge near the inlet edge that causes a surge and in the vicinity thereof to occur, and the reduction of the surge margin can be prevented.

According to a fourth aspect of the present invention, in the impeller according to any one of the first to third aspects, the outlet side portion is between the position of about 90% of the outlet radius from the rotation center line and the outlet edge. This is a range of
According to this, in the outlet flow path portion formed by the outlet side portion of the flow path between the blades, the outlet side portion is in a range between the position of about 90% of the outlet radius and the outlet edge. The main flow of the fluid flowing out from the nozzle can be more reliably brought closer to the direction of the outlet blade angle, contributing to an increase in the pressure ratio.

The invention according to claim 5 is a method of designing an impeller according to claim 1 based on a base impeller of a base centrifugal fluid machine, wherein each base blade of the base impeller is located at a position of the boundary portion. A base corresponding part at a position corresponding to the base, a base outlet side part from the boundary corresponding part to the outlet edge, and a base center side part located radially inward from the boundary corresponding part, The blade angle distribution or load distribution at the center side portion of each blade is the same as the blade angle distribution or load distribution of the base center side portion, and the outlet side angle is the whole of the outlet side portion. In this design method, the blade angle distribution or the load distribution in the outlet side portion is determined so as to be smaller than the blade angle in the entire outlet side portion of each base blade.
According to this, the impeller of a base centrifugal fluid machine can be improved to the impeller described in claim 1 easily and at low cost.

The invention according to claim 6 is the design method according to claim 5, wherein the base end side angle that is the exit side angle at the base end portion of each blade and the exit side angle at the tip end portion. Unlike a certain front end side angle, the base end side angle and the front end side angle are a base base end side angle that is a blade angle at a base end portion in the base outlet side portion and a base blade angle at a front end portion. The blade angle distribution or the load distribution at the outlet side portion of each blade is determined so that the angle is smaller than the tip side angle and the base side angle is different from the tip side angle. .
According to this, the impeller of a base centrifugal fluid machine can be improved to the impeller described in claim 2 easily and at low cost.

The invention according to claim 7 is the design method according to claim 5 or 6, wherein the tip is in the axial direction and the tip in the inlet channel from the inlet to the throat of the channel between the blades. The blade angle distribution or the flow velocity distribution in the inlet channel portion is determined so that the axial angle formed by
According to this, the impeller described in claim 3 can be manufactured easily and at low cost.

According to the present invention, a high pressure ratio can be obtained without reducing the efficiency of the centrifugal fluid machine. Furthermore, according to the present invention, it is possible to obtain a high pressure ratio while preventing a decrease in the surge margin of the centrifugal fluid machine.
Further, according to the present invention, the centrifugal fluid machine can be easily improved.

It is a schematic sectional drawing of the principal part of the centrifugal compressor which shows 1st Embodiment of this invention and is equipped with an impeller. It is the schematic of the principal part when the impeller of FIG. 1 is seen from an axial direction. It is a principal part perspective view in the exit vicinity of the impeller of a centrifugal compressor which shows 2nd Embodiment of this invention. It is a principal part perspective view in the vicinity of the inlet_port | entrance of the impeller of a centrifugal compressor which shows 3rd Embodiment of this invention. It is a figure equivalent to FIG. 1 of the base centrifugal compressor at the time of designing 1st, 2nd embodiment of this invention. FIG. 6 is a view corresponding to FIG. 2 of the base centrifugal compressor of FIG. 5. FIG. 6 is a view corresponding to FIG. 3 of the base centrifugal compressor of FIG. 5.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
<First Embodiment>
1 and 2 are diagrams illustrating a first embodiment of the present invention.
Referring to FIG. 1, in a first embodiment of the present invention, an impeller 2 is provided in a centrifugal compressor 1 as a centrifugal fluid machine for compressing or pumping fluid. In addition to the impeller 2, the centrifugal compressor 1 includes a rotation shaft 3 that is driven to rotate by a driving device and rotates about a rotation center line L. The impeller 2 is provided on the rotation shaft 3 and rotates in the rotation direction R integrally with the rotation shaft 3 around the rotation center line L.

The centrifugal compressor 1 is based on a centrifugal compressor 51 (hereinafter referred to as “base centrifugal compressor 51” as a base centrifugal fluid machine) shown in FIGS. Is an improvement of a part of the shape of the blade 56 of the impeller 52, and the other parts are basically the same.
Therefore, for each of the following embodiments, both the compressors 1, 51 are described by describing the reference numerals attached to the members of the base centrifugal compressor 51 in addition to the reference numerals attached to the members of the centrifugal compressor 1. Are described in parallel. Further, with respect to the constituent members and the like of the base centrifugal compressor 51, from the viewpoint of clarifying the distinction from the constituent members and the like of the centrifugal compressor 1, a modifier “base” is attached as necessary.

Referring to FIGS. 1, 2, 5, and 6, an impeller 2, 52 that compresses and pumps fluid flowing into the centrifugal compressors 1, 51 is a core plate 4 fixed to a rotary shaft 3, 53. , 54 and a plurality of blades 6, 56 arranged on the core plates 4, 54 in a circular blade row at equal intervals in the circumferential direction, and the blades 6, 56 are sandwiched between the core plates 4, 54. The side plates 5 and 55 are arranged. The blades 6 and 56 adjacent to each other in the circumferential direction, the core plates 4 and 54, and the side plates 5 and 55 form the inter-blade flow passages 7 and 57 through which the fluid flows.
In the present invention, the axial direction is a direction parallel to the rotation center line L, and the radial direction and the circumferential direction are a radial direction and a circumferential direction around the rotation center line L, respectively.

Each blade 6, 56 forms a gap between the base end portions 11, 61 provided continuously to the core plates 4, 54 and the side plates 5, 55 without forming a gap between the blades 4, 54. The front end portions 12 and 62 that are connected to the side plates 5 and 55 without being formed, the inlet edges 13 and 63 where the fluid flowing through the inter-blade flow paths 7 and 57 starts to contact the vanes 6 and 56, and the inter-blade space It has outlet edges 14 and 64 through which the fluid flowing through the flow paths 7 and 57 flows away from the blades 6 and 56.
The base end portions 11 and 61 are fixed to the core plates 4 and 54 as a whole, and the distal end portions 12 and 62 are fixed to the side plates 5 and 55 as a whole. The inlet edges 13 and 63 define the inlets 7i and 57i of the flow paths 7 and 57 between the blades, and the outlet edges 14 and 64 are the outlets 7o and 57o of the flow paths 7 and 57 between the blades (also the outlets of the impellers 2 and 52). .).

Each blade 6 of the centrifugal compressor 1 further includes a boundary portion 15 that starts to decrease when a blade angle α, which is an angle formed between the radial direction and the blade 6, goes outward in the radial direction, and an outlet edge from the boundary portion 15. 14 has an outlet side portion 16 until reaching 14 and a central side portion 17 located radially inward from the boundary portion 15. And the exit flow path part 7b of the flow path 7 between blade | wings is formed with the exit side part 16, the core plate 4, and the side plate 5 of the blade | wings 6 adjacent in the circumferential direction.
On the other hand, each blade 56 of the base centrifugal compressor 51 further includes a boundary corresponding portion 65 at a position corresponding to the position of the boundary portion 15, an outlet side portion 66 from the boundary corresponding portion 65 to the outlet edge 64, and a boundary. And a center side portion 67 located radially inward of the corresponding portion 65.

The boundary portion 15 and the boundary corresponding portion 65 are located at about 90% of the exit radius from the rotation center line L. Each of the blades 6 and 56 is radially outward from the position of about 50% of the exit radius to the boundary 15 or the boundary corresponding portion 65 in the center side portions 17 and 67 with respect to the rotation center line L. It is formed so as to bend in the counter-rotating direction opposite to the rotating direction R.
Further, the outlet side portions 16 and 66 including the outlet edges 14 and 64 have a range from a position of about 90% of the outlet radius to the position of 100% (that is, the outlet edges 14 and 64) with respect to the rotation center line L. Part.

At the boundary portion 15, the degree of curvature in the counter-rotating direction decreases radially outward. On the other hand, each base blade 56 extends from the boundary corresponding portion 65 to the outlet edge 64 while being further curved in the counter-rotating direction as compared with the curved state at the boundary corresponding portion 65 as it goes radially outward.
Here, the exit radius is the radius of the exit edges 14 and 64 when the impeller 2 and 52 are centered on the rotation center line L. Further, “about” added to a numerical value means that the numerical value within a range of 1 to 2% of the numerical value to which this character is attached is included.

The center side angle α2, which is the blade angle α of the center side portions 17 and 67, is determined from the inlet side angle α21 at the inlet edges 13 and 63 toward the boundary portion 15 or the boundary corresponding portion 65 from the inlet edges 13 and 63 to the inlet side. It changes so as to become a boundary side angle α23 larger than the intermediate angle α22 through an intermediate angle α22 smaller than the angle α21.
Further, the outlet side angle α1 that is the blade angle α of the outlet side portion 16 is smaller than the boundary closest angle α24 that is the boundary side angle α23 in the immediate vicinity of the boundary portion 15 in the entire outlet side portion 16. In the entire outlet side portion 16, the outlet side angle α1 is smaller than the outlet side angle α5 that is the blade angle α in the entire outlet side portion 66 of the base blade 56 (see FIGS. 2 and 6). . Further, in the outlet side portion 16, the outlet side angle α 1 is the same from the base end portion 11 to the tip end portion 12.
Thus, the impeller 2 has the same blade shape as the base impeller 52 except for the outlet side portion 16, and the centrifugal compressor 1 and the base centrifugal compressor 51 have different outlet side angles α1 and α5.

Hereinafter, a method for designing the impeller 2 will be described.
In designing the shape of the blade 6 of the impeller 2, the blade angle distribution or load distribution in the center side portion 17 is determined so that the blade angle distribution or load distribution is the same as that of the center side portion 67 of the base centrifugal compressor 51. The blade angle distribution or the load distribution in the outlet side portion 16 is determined so that the outlet side angle α1 of the compressor 1 is smaller than the outlet side angle α5 of the base centrifugal compressor 51.

Next, the operation and effect of the first embodiment configured as described above will be described.
Each blade 6 of the impeller 2 includes a base end portion 11 that continues to the core plate 4 without forming a gap, a boundary portion 15 at which the blade angle α starts to decrease, an outlet side portion 16, and a center side portion 17. The outlet side angle α1 of the outlet side portion 16 is smaller than the boundary closest angle α24 closest to the boundary portion 15 in the entire outlet side portion 16.
With this structure, each blade 6 is bisected in the radial direction by the boundary portion 15 into a central side portion 17 radially inward of the boundary portion 15 and an outlet side portion 16 from the boundary portion 15 to the outlet edge 14. When exiting, the blades are set so that the outlet side angle α1 which is the blade angle α at the outlet side portion 16 near the outlet of the impeller 2 is smaller than the boundary closest angle α24 which is the blade angle α closest to the boundary portion 15. 6 is formed. As a result, in the case of the same peripheral speed, a higher pressure ratio can be obtained as compared with the impeller 52 of the base centrifugal compressor 51.
Further, since each blade 6 is connected to the core plate 4 without a gap, the efficiency of the centrifugal compressor 1 is reduced as compared with a centrifugal compressor including an impeller in which a slit is provided between the blade 6 and the core plate 4. Is prevented.

  The outlet side portion 16 is in the range between the position about 90% of the outlet radius from the rotation center line L and the outlet edge 14, so that the outlet flow formed by the outlet side portion 16 of the inter-blade flow path 7. In the passage portion 7b, the main flow of the fluid flowing out from the outlet 7o can be more reliably brought closer to the direction of the outlet side angle α1, contributing to an increase in the pressure ratio.

  Further, the blade angle distribution or load distribution at the center side portion 17 of each blade 6 is the same as the blade angle distribution or load distribution of the center side portion 67 of each base blade 56, and the outlet side angle α 1 of the outlet side portion 6. However, the blade angle distribution or the load distribution in the outlet side portion 16 is determined so that the entire outlet side portion 16 is smaller than the blade angle α5 in the entire outlet side portion 66 of each base blade 56. The impeller 52 of the base centrifugal compressor 51 can be improved to the impeller 2 of the centrifugal compressor 1 easily and at low cost.

Second Embodiment
Next, a second embodiment of the present invention will be described mainly with reference to FIG. The second embodiment is different from the first embodiment in the form of the outlet side angle α1, and the rest has basically the same configuration. Therefore, description of the same part is omitted or simplified, and different points will be mainly described. In addition, about the member same as the member of 1st Embodiment, or the corresponding member, the same code | symbol is used as needed.

In the second embodiment, the impeller 2 of the centrifugal compressor 1 has an outlet side angle smaller than the base outlet side angle α5 (see FIG. 2) in the entire outlet side portion 16 as in the first embodiment. It has α1. In the entire outlet side portion 16, the proximal side angle α11 that is the outlet side angle α1 on the core plate 4 side and the distal side angle α12 that is the outlet side angle α1 on the side plate 5 side are set differently. Yes. Further, the outlet side angle α1 changes smoothly and continuously between the base end portion 11 and the tip end portion 12 from the base end side angle α11 to the tip end side angle α12.
Further, in the embodiment shown in FIG. 3, the base end side angle α11 is set to be larger than the front end side angle α12, but both the angles α11 and α12 are set so as to satisfy the magnitude relationship of α11 <α12. Also good.

With reference to FIG. 3, FIG. 6, FIG. 7, the design method of the impeller 2 in 2nd Embodiment is demonstrated.
In designing the shape of the blade 6 of the impeller 2, the blade angle distribution or load distribution in the center side portion 17 is the same as the blade angle distribution or load distribution of the base center side portion 67 of the impeller 52 of the base centrifugal compressor 51. The base proximal end is determined, and the base proximal end angle α11 and the base distal end angle α12 of the base outlet side portion 16 of the centrifugal compressor 1 are the base outlet side angle α5 at the base proximal end portion 61 of each base blade 66. The outlet side portion 16 is set so as to be smaller than the side angle α51 and the base tip side angle α52, which is the outlet side angle α5 at the base tip portion 62, and so that the base side angle α11 and the tip side angle α12 are different. The blade angle distribution or load distribution at is determined.

According to the second embodiment, the base end side angle α11 and the front end side angle α12 are smaller than the base outlet side angle α5, so that the same operation and effect as the first embodiment can be achieved with respect to the pressure ratio. The following actions and effects are exhibited.
The proximal end portion α that is the outlet side angle α1 at the proximal end portion 11 and the distal end side angle α12 that is the outlet side angle α1 at the distal end portion 12 are different from each other. Since the blades 6 can be formed so as to have an optimum angle between the tip 11 and the tip 12 on the side plate side end, the blade 6 flows in the blade height direction, which is the direction from the base 11 to the tip 12. It is possible to improve the efficiency of the centrifugal compressor 1.

  Further, the blade angle distribution or load distribution in the center side portion 17 is determined so as to have the same blade angle distribution or load distribution as the center side portion 67 of the base centrifugal compressor 51, and the base of the outlet side portion 16 of the centrifugal compressor 1 is determined. The base end side angle α11 and the front end side angle α12 are different so that the end side angle α11 and the front end side angle α12 are smaller than the base base end side angle α51 and the base front end side angle α52 of each base blade 66, respectively. As described above, by determining the blade angle distribution or the load distribution in the outlet side portion 16, the impeller 52 of the base centrifugal compressor 51 can be easily improved to the impeller 2 of the centrifugal compressor 1 at low cost. .

<Third Embodiment>
Next, a third embodiment of the present invention will be described mainly with reference to FIG. This third embodiment is different from the first and second embodiments in a part of the shape of the central side portion 17 of the blade 6 and the other parts are basically the same as the first embodiment or the second embodiment. It has a configuration. Therefore, description of the same part is omitted or simplified, and different points will be mainly described. In addition, about the member same as the member of 1st Embodiment or 2nd Embodiment, or the corresponding member, the same code | symbol is used as needed.

  With reference to FIG. 4, first, a surge that defines a limit that can be stably operated on the small flow rate side of the centrifugal compressor will be described. One reason for this surge is that a backflow occurs at the tip 12 near the inlet edge 13 of the blade 6 of the impeller 2 and in the vicinity thereof. In order to increase the pressure ratio, this reverse flow is, as shown in FIG. 4, an axial blade angle that is an angle formed between the axial direction and the blade 6 locally at the tip 12 near the inlet edge 13 and in the vicinity thereof. In the inter-blade channel 7, an angle sudden change portion 12 a in which β changes greatly is provided, and in the inlet channel portion 7 a from the inlet 7 i to the throat portion 7 t where the channel area in the inter-blade channel 7 is minimized. It tends to occur when the reduction ratio is increased.

Therefore, in the third embodiment, as shown in FIG. 4, the impeller 2 includes an axial vane at the distal end portion 12 near the inlet edge 13 and the vicinity thereof in the inlet flow path portion 7 a that is a speed reduction region. The blades 6 are formed so that the angle β does not significantly change locally in the fluid flow direction, so that the sudden angle change portion 12a is not formed.
Here, “not greatly changing locally” means that the change rate of the axial vane angle β is smoothly continuous in the inlet channel portion 7a, the change rate does not change in a polygonal line, and the change rate is normal. Means no negative value.

Next, a method for designing the impeller 2 will be described.
In designing the shape of the blade 6 of the impeller 2, the inlet flow path is such that the tip end portion 12 near the inlet edge 13 of the impeller 2 and the axial blade angle β in the vicinity thereof do not significantly change locally in the fluid flow direction. The blade angle distribution or the flow velocity distribution at the center side portion 17 in the portion 7a is determined.

According to the third embodiment, with respect to the pressure ratio, the same operations and effects as the first and second embodiments are exhibited, and further the following operations and effects are exhibited.
In the inlet channel portion 7 a from the inlet 7 i to the throat portion 7 t of the inter-blade channel 7, the tip end portion 12 is not greatly changed locally in the fluid flow direction. In the inlet channel portion 7a from the seven inlets 7i to the throat portion 7t, there is no change in the local channel area, so that a local flow abrupt deceleration can be avoided. As a result, it becomes difficult to generate a backflow in the vicinity of the distal end portion 12 near the inlet edge 13 that causes a surge and in the vicinity thereof, and a reduction in surge margin can be prevented.

  Further, the tip portion 12 near the inlet edge 13 of the impeller 2 and the axial blade angle β in the vicinity thereof at the central side portion 17 in the inlet flow passage portion 7a are not greatly changed locally in the fluid flow direction. By determining the blade angle distribution or the flow velocity distribution, the impeller 2 of the centrifugal compressor 1 that can prevent the reduction of the surge margin can be manufactured easily and at low cost.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The impeller may not include the side plate 5.
In addition to the centrifugal compressor, the centrifugal fluid machine may be, for example, a centrifugal pump or a blower.

DESCRIPTION OF SYMBOLS 1,51 Centrifugal compressor 2,52 Impeller 4,54 Core plate 6,56 Blade | wing 7,57 Flow path between blades 7t Throat part 11,61 Base end part 12,62 Tip part 13,63 Inlet edge 14,64 Outlet Edge 15 Boundary portion 16, 66 Outlet side portion 17, 67 Center side portion α Blade angle α1, α5 Outlet side angle α24 Nearest boundary angle β Axial blade angle

Claims (7)

In an impeller of a centrifugal fluid machine, which includes a plurality of blades arranged in a circular blade row on a core plate and rotates around a rotation center line,
Each of the blades includes a base end portion connected to the core plate without forming a gap, a distal end portion, and an inlet edge that defines an inlet of a flow path between the blades formed by the blades adjacent in the circumferential direction, An outlet edge defining an outlet of the flow path between the blades, a boundary part where a blade angle formed between the radial direction and the blades starts to decrease when going radially outward from the rotation center line, and the boundary part from the boundary part It has an exit side part until it reaches the exit edge, and a center side part located radially inward from the boundary part,
An impeller characterized in that an outlet side angle which is the blade angle of the outlet side portion is smaller than a boundary closest angle which is the blade angle closest to the boundary portion in the entire outlet side portion. The impeller according to claim 1,
An impeller characterized in that a proximal-side angle that is the outlet-side angle at the proximal-end portion and a distal-end-side angle that is the outlet-side angle at the distal end portion are different. The impeller according to claim 1 or 2, wherein the tip portion includes a side plate continuous without a gap.
In the inlet channel portion from the inlet to the throat portion of the inter-blade channel, the tip portion is characterized in that the angle formed between the axial direction and the tip portion does not vary greatly locally in the fluid flow direction. Impeller. The impeller according to any one of claims 1 to 3,
The impeller is an impeller having a range between a position of about 90% of an exit radius from the rotation center line and the exit edge. A method for designing an impeller according to claim 1 based on a base impeller of a base centrifugal fluid machine comprising:
Each base blade of the base impeller includes a boundary corresponding portion at a position corresponding to the position of the boundary portion, a base outlet side portion from the boundary corresponding portion to the outlet edge, and more than the boundary corresponding portion. A base center side portion located radially inward,
The blade angle distribution or load distribution at the center side portion of each blade is the same as the blade angle distribution or load distribution at the base center side portion,
The blade angle distribution or the load distribution in the outlet side portion is determined so that the outlet side angle is smaller than the blade angle in the whole outlet side portion of each base blade in the entire outlet side portion. Design method characterized by The design method according to claim 5,
The base end side angle that is the exit side angle at the base end portion of each blade is different from the front end side angle that is the exit side angle at the front end portion, and
The base end side angle and the front end side angle are respectively smaller than a base base end side angle that is a blade angle at the base end portion in the base outlet side portion and a base front end side angle that is a blade angle at the front end portion. Thus, the blade angle distribution or the load distribution in the outlet side portion of each blade is determined so that the proximal side angle and the distal side angle are different. The design method according to claim 5 or 6,
In the inlet channel portion from the inlet to the throat portion of the inter-blade channel, the tip portion is configured so that the axial direction angle formed between the axial direction and the tip portion does not significantly change locally. A design method characterized in that a blade angle distribution or a flow velocity distribution in a section is determined.

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