WO2020049810A1

WO2020049810A1 - Centrifugal impeller and centrifugal fluid machine

Info

Publication number: WO2020049810A1
Application number: PCT/JP2019/021261
Authority: WO
Inventors: 洋平磯崎; 西岡　卓宏; 成瀬　友博; 道宏川下; 博青山; 洋平丹野
Original assignee: 株式会社日立インダストリアルプロダクツ
Priority date: 2018-09-04
Filing date: 2019-05-29
Publication date: 2020-03-12
Also published as: JP6995719B2; JP2020037900A

Abstract

Provided are a centrifugal impeller having a structure enabling an increase in peripheral speed thereof, and a centrifugal fluid machine provided with the same. A hollow part 112 is provided in a blade 102 of a centrifugal impeller of a centrifugal fluid machine constituted by a hub, a plurality of blades, and a shroud. The hollow part 112 is formed in the blade 102 in such a way that the hollowness of the blade 102 becomes minimum at a portion opposing a portion having a maximum curvature on the flow path side surface of the shroud and becomes higher with increasing distance from the portion having the maximum curvature on the flow path side surface of the shroud.

Description

Centrifugal impeller and centrifugal fluid machine

The present invention relates to a centrifugal impeller and a centrifugal fluid machine provided with the same.

では In a process centrifugal compressor, which is an example of a centrifugal fluid machine, the sucked working fluid is discharged after passing through a flow path provided in a single-stage or multi-stage impeller. In the process of the working fluid passing through the flow path of the impeller, rotational energy of the impeller is applied to the working fluid, and the working fluid is compressed. By increasing the peripheral speed by rotating the impeller at high speed, the amount of increase in fluid energy per unit weight (head) increases, and the number of impeller stages for satisfying the required head can be reduced. Furthermore, energy loss is reduced by reducing the number of impeller stages, and an improvement in compressor efficiency can be expected. In addition, by rotating the impeller at a high speed to increase the peripheral speed, it is possible to give the same amount of fluid energy as the conventional one using an impeller having a smaller outer diameter than the conventional one. In order to increase the peripheral speed by rotating the impeller at high speed, it is necessary to improve the limit peripheral speed of the impeller. By improving the peripheral speed of the impeller, the number of stages of the impeller and the outer diameter of the impeller can be reduced, and the centrifugal compressor for a process can be reduced in size and increased in efficiency.

向上 In improving the peripheral speed of the impeller, it is important to secure the structural strength during high-speed rotation. That is, the centrifugal stress generated in the impeller increases as the peripheral speed of the impeller increases, and when the rotation speed becomes excessive, excessive stress is generated in the shroud and the hub, and the impeller is damaged. As described above, the limit peripheral speed of the impeller is restricted by the structural strength. Therefore, in order to improve the limit peripheral speed of the impeller, it is necessary to provide a structure having high structural strength against centrifugal force. Conventionally, stress is suppressed by changing the dimensions of the hub and shroud of the impeller.

遠心 As a centrifugal compressor provided with an impeller capable of increasing the peripheral speed, for example, there is one described in Patent Document 1. In Patent Literature 1, a blade having high strength is provided by devising the shape of the blade so that the peripheral speed can be increased.

JP 2010-151126 A

Conventionally, the limit peripheral speed of the impeller has been improved from the viewpoint of changing the dimensions of the hub or shroud or devising the shape of the blade.
The present invention has been made by variously examining a method for improving the limit peripheral speed other than the conventional viewpoint.

An object of the present invention is to provide a centrifugal impeller having a structure capable of increasing the peripheral speed of the centrifugal impeller, and a centrifugal fluid machine including the same.

In the present invention, a hollow portion is provided in a blade of a centrifugal impeller of a centrifugal fluid machine including a hub, a plurality of blades, and a shroud.

According to the present invention, the centrifugal force generated in the centrifugal impeller decreases, and in particular, the stress generated in the hub decreases. As a result, the rotation speed of the centrifugal impeller at which the stress generated in the hub reaches the allowable limit stress increases, and the peripheral speed of the centrifugal impeller can be increased.
Problems, configurations, and effects other than those described above will be apparent from the following description of the embodiments.

1 is an external view of a centrifugal impeller according to one embodiment of the present invention. It is a figure which shows the shape which extracted one pitch of the blade in the centrifugal impeller shown in FIG. FIG. 3 is a diagram in which wing portions of the centrifugal impeller shown in FIGS. 1 and 2 are extracted, and is a diagram illustrating an example of a method of providing a hollow portion. FIG. 3 is a diagram in which a wing portion of the centrifugal impeller illustrated in FIGS. 1 and 2 is extracted, and is a diagram illustrating another example of a method of providing a hollow portion. FIG. 3 is a diagram in which a wing portion of the centrifugal impeller illustrated in FIGS. 1 and 2 is extracted, and is a diagram illustrating another example of a method of providing a hollow portion. It is a figure showing an example of a centrifugal fluid machine to which the centrifugal impeller of the present invention is applied.

Preferred embodiments for implementing the present invention will be described below with reference to the drawings.
First, before describing the embodiments of the present invention in detail, the background to the present invention will be described.

Conventionally, the peripheral speed of an impeller has been improved from the viewpoint of securing the structural strength at the time of high-speed rotation by changing the dimensions of a hub or a shroud, or devising the shape of the blade to obtain a high-strength blade. However, if the centrifugal force generated in the impeller can be reduced, the increase in the stress generated in the shroud and the hub can be suppressed even when the impeller is rotated at high speed, and damage to the impeller can be prevented. That is, the limit peripheral speed can be improved.

羽 The impeller is composed of a hub, a plurality of blades, and a shroud. The impeller is attached to the shaft by shrink fitting the hub to the shaft. There is a limit to the shrink fitting allowance when fixing the hub to the shaft due to reasons such as manufacturability.If the centrifugal force applied to the hub increases due to the high peripheral speed of the impeller, the hub expands and slides between the hub and the shaft. Occurs. Therefore, if the centrifugal force applied to the hub can be reduced, even if the impeller is rotated at a high speed, the expansion of the hub can be suppressed so that no slip occurs between the hub and the shaft. Can be improved. For example, it is conceivable to use a lightweight structural material in order to reduce the centrifugal force generated in the impeller.

On the other hand, in fields other than the centrifugal impeller, for example, blades of a gas turbine or a steam turbine have a hollow structure. In a gas turbine blade, the hollow portion is used as a cooling air passage for cooling the blade. In a steam turbine, a space is formed inside a stationary blade to collect droplets, and a moving blade is hollowed to reduce centrifugal force due to a longer blade. However, centrifugal impellers of centrifugal fluid machines often have thin blades from the viewpoint of improving the fluid performance, and as described in Patent Document 1, the blades are arranged in consideration of securing the strength of the blades. It has an actual structure.
Thus, the technical problem of the centrifugal impeller is different from the technical problem of the blade of the gas turbine or the steam turbine.
Further, the blades of a gas turbine or a steam turbine incorporate individually manufactured blades into a rotor or a casing, and the blades having a hollow structure are themselves manufactured by casting or bending. However, the centrifugal impeller integrally manufactures a hub, a plurality of blades, and a shroud, and it is difficult to make the blades hollow in such an impeller structure. From these facts, it has not been considered that the blade of the centrifugal impeller has a hollow structure like the blade of a gas turbine or a steam turbine.

However, in order to improve the peripheral speed limit of the centrifugal impeller, as described above, reducing the centrifugal force generated in the impeller reduces the stress generated in the hub and the like and the deformation of the shaft shrink fitting portion. It is effective for With the spread of 3D printers in recent years, it has become possible to design structures that have conventionally been difficult to process. For example, Japanese Patent Application Laid-Open No. 2016-37901 proposes that an impeller used for a turbocharger is formed by additive manufacturing. In this patent document, in order to reduce the inertial force while securing the required strength, as an impeller, a shell portion including a blade portion and a hub surface portion, a lattice-shaped skeleton and a space inside the shell portion are provided. A structure having a core portion having a lower density than the shell portion to be formed is adopted, and this structure is formed by additive manufacturing. This patent document 1 lowers the moment of inertia to improve the responsiveness as a turbocharger, but does not consider improving the peripheral speed limit or hollowing the blade portion.

The present invention focuses on the possibility of designing a centrifugal impeller having a hollow portion which has been difficult to process with the recent spread of 3D printers. By reducing the generated centrifugal force, the limit peripheral speed of the centrifugal impeller is improved.

According to the study of the present inventors, it is important to appropriately select a place where the hollow part is provided and the degree of hollowness when providing the hollow part for reducing the centrifugal force generated in the centrifugal impeller. The hollowness is a ratio of hollows in the blade (hollow volume per unit volume). Centrifugal force is calculated by the product of the square of the mass, the distance from the center of rotation, and the angular velocity. Therefore, the higher the hollowness is, and the more the hollow portion is provided at a position farther from the rotation center, the more the centrifugal force can be reduced.
However, when the degree of hollowness is increased in a portion where a high stress is generated, the stress in the portion where the hollow portion is provided is further increased, and the usable peripheral speed may be reduced. In an impeller for a centrifugal compressor, the axial length, inlet width, outlet width, and the like of the impeller greatly differ depending on specifications. Along with this, the distribution tendency of the stress when the centrifugal force is applied and the portion where the maximum stress occurs are different. Therefore, it is important to set the hollowness in consideration of the stress distribution tendency of various impellers having different specifications. In view of such points, in a preferred embodiment of the present invention, a structure of a centrifugal impeller for a centrifugal compressor in which a centrifugal force is reduced by providing a hollow portion while considering structural strength is proposed.

In centrifugal impellers for centrifugal compressors, high stress occurs in the blade section where the curvature of the surface of the shroud flow path side is maximum, but the stress decreases when the distance from the area where the curvature of the surface of the shroud flow path becomes maximum is reduced. I will do it. Therefore, in a portion where the curvature of the shroud flow path side surface is maximum, the strength margin of the blade is low, and it is difficult to set the hollowness high. On the other hand, as the distance from the portion where the curvature of the side surface of the shroud flow channel becomes maximum is increased, the strength margin of the blade is higher, and the hollowness can be set higher.

Therefore, the centrifugal impeller for a centrifugal compressor proposed in the embodiment of the present invention, the hollowness of the blade is minimized at a position where the curvature of the surface of the shroud flow path surface is maximum, and the shroud flow path surface is reduced. The higher the distance from the part where the curvature is maximized, the higher the setting. As a result, a rational weight reduction in consideration of the strength margin is achieved, and a centrifugal impeller with significantly reduced centrifugal force can be obtained while ensuring structural strength.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the configuration of a centrifugal impeller to which the present invention is applied will be described with reference to FIGS. FIG. 1 is an external view of a centrifugal impeller according to one embodiment of the present invention. FIG. 2 is a view showing a shape obtained by extracting one pitch of the blade in the centrifugal impeller shown in FIG.
As shown in FIGS. 1 and 2, a centrifugal impeller 100 to which the present invention is applied has a disc-shaped hub 101 having a shape in which a central portion on the blade inlet side protrudes, and is provided on the hub 101 in a circumferential direction. It is composed of a plurality of wings 102 arranged at intervals and a shroud 103 arranged to face the hub 101 with the wings 102 interposed therebetween. The hub 101, the wings 102, and the shroud 103 are molded as a single body by a layered manufacturing method using a 3D printer or the like. The centrifugal impeller 100 is fixed to a shaft (not shown) by shrink fitting at an inner diameter portion of the hub 101. In the centrifugal impeller 100, torque from a motor (not shown) is transmitted through a shaft at an inner diameter portion of the hub 101. A region surrounded by the hub 101, the blade 102, the shroud 103, the blade inlet side end 104, and the blade outlet side end 105 serves as a working fluid flow path 106 inside the centrifugal impeller 100. The working fluid flows in from the blade inlet side end 104 side, receives work from the centrifugal impeller 100 in the flow path 106, and is discharged from the blade outlet side end 105 side while being compressed.

Next, an example of a method of providing a hollow portion when the hollow portion is provided in the wing 102 will be described with reference to FIG. FIG. 3 is a diagram showing extracted blades 102 in the centrifugal impeller shown in FIGS. 1 and 2. FIG. 3 shows a shape in which the degree of hollowness of the blade is minimized at a position where the curvature of the side surface of the shroud flow channel is maximized, and is increased as the distance from the region where the curvature of the side surface of the shroud flow channel becomes maximum is increased.
Hereinafter, a portion where the curvature is maximum on the shroud flow path side surface 107 is referred to as a maximum shroud curvature portion 108, and a portion of the blade joined (opposed) to the maximum shroud curvature portion 108 is a wing portion 108a corresponding to the maximum shroud curvature portion. Called. The maximum shroud curvature portion 108 (the wing portion 108a corresponding to the maximum shroud curvature portion) is located at an intermediate portion between the blade inlet side end portion 104 and the blade outlet side end portion 105. Further, in the blade 102, a portion on the hub 101 side from a line (dotted line shown in the figure) connecting the midpoint of the blade inlet side end 104 and the midpoint of the blade outlet side end 105 along the blade surface 109. The side wing 110 and the shroud-side portion are referred to as shroud-side wings 111.

The wing 102 is provided with a hollow portion 112 as shown in FIG. In FIG. 3, the degree of hollowness is changed by changing the width of the hollow portion 112 in the thickness direction of the blade 102. Further, in order to maintain the strength of the blade 102, the hollow portion 112 is divided into a plurality in the direction from the blade inlet side end portion 104 to the blade outlet side end portion 105. The plurality of divided hollow portions 112 are provided radially with respect to the shroud channel side surface 107. In the present embodiment, the degree of hollowness of the wing becomes minimum near the wing portion 108a corresponding to the maximum shroud curvature, and the degree of hollowness of the wing 102 increases as the distance from the wing portion 108a corresponding to the maximum shroud curvature increases. That is, the width of the hollow portion 112 is minimum near the wing portion 108a corresponding to the maximum shroud curvature portion, and becomes wider as it goes away from the vicinity of the wing portion 108a corresponding to the maximum shroud curvature portion.

The shape of the hollow portion 112 is not limited to the shape shown in FIG. Since the centrifugal impeller of the present embodiment is manufactured by an additive manufacturing method using a 3D printer or the like, the hollow portion 112 can have various shapes. For example, the degree of hollowness may be changed between the hub-side wing 110 and the shroud-side wing 111. For example, the width of the hollow portion in the hub-side wing portion 110 may be reduced, and the width of the hollow portion in the shroud-side wing portion 111 may be increased. Alternatively, the width of the hollow portion may be increased toward the shroud side. Is also good. Further, the hollow portion 112 may be provided only in the shroud-side wing portion 111.

翼 The blade 102 provided with the hollow portion 112 is lighter in weight than a structure employing a solid blade, and the centrifugal force generated in the centrifugal impeller during rotation is reduced. As a result, the stress generated in the hub 101 that receives the centrifugal force in the wings 102 and the shroud 103 is reduced, so that the centrifugal impeller 100 can be rotated at a higher speed as compared with a structure employing solid wings. . That is, the number of rotations that reaches the allowable limit stress is higher than that of a structure having a solid blade, and the limit peripheral speed can be increased.

On the other hand, in the wing 102, although the stress generated during rotation generally rises compared to the case of using the solid wing due to the provision of the hollow portion 112, the maximum shroud curvature at which the maximum stress occurs when the solid wing is used is used. In the vicinity of the part corresponding wing 108a, the hollowness is low and the amount of increase in stress is small. That is, since the hollow portion is set in consideration of the stress distribution caused by the blade shape generated on the blade of the centrifugal impeller during rotation, occurrence of a strength problem in the vicinity of the hollow portion can be avoided. For this reason, the blade 102 does not become a bottleneck of strength, and the critical peripheral speed of the centrifugal impeller 100 is not defined from the stress generated in the blade 102. In addition, by radially dividing into a plurality of hollow portions and providing the hollow portions 112 on the blade 102, the size of the hollow portions can be set according to the gradient of the stress, and the stress can be optimized for each portion. Is possible.

Another advantage of the centrifugal impeller 100 of the present embodiment is that the reliability of the shrink-fit portion between the shaft and the centrifugal impeller inner diameter (hub) is improved. In the centrifugal impeller 100, the hollow portion 112 is provided in the blade 102 to reduce the centrifugal force, so that the amount of expansion of the centrifugal impeller inner diameter (hub) during rotation decreases. As a result, the interference required at the shrink fitting portion between the inner diameter of the centrifugal impeller and the shaft may be reduced. Further, the risk of slippage between the centrifugal impeller and the shaft is reduced, so that the peripheral speed limit can be improved.

利点 Advantages of adopting a hollow structure are that higher rigidity can be secured with the same mass and deformation can be suppressed as compared with a solid structure.

FIG. 4 shows another example of how to provide the hollow portion. In FIG. 4, when the hollow portion 212 is provided in the blade 202, the hollow portion 212 is provided only on the blade outlet side end portion 205 side. That is, the hollow part 212 is provided in the wing part between the wing part 208a corresponding to the shroud curvature maximum part and the wing outlet side end part 205. The hollow portion 212 may be provided on any of the wing portions on the wing inlet side end portion 204 side or the wing outlet side end portion 205 side. Whether the hollow portion 212 is provided on the blade inlet side end portion 204 side or the blade outlet side end portion 205 side depends on the result of the strength analysis. In general, from the viewpoint of reducing the centrifugal force, it is shown in FIG. As described above, it is preferable to provide the wing on the wing outlet side end 205 side distant from the rotation center. Also in this example, the hollowness of the wing 202 is minimized in the vicinity of the wing 208a corresponding to the maximum shroud curvature, and the hollowness of the wing 202 is increased as the distance from the wing 208a corresponding to the maximum shroud curvature is increased. Therefore, in this example, the hollowness of the wing increases as the distance from the rotation center increases. In the centrifugal impeller provided with the blades 202 shown in FIG. 4, the same effects as those of the centrifugal impeller provided with the blades 102 shown in FIG. 3 can be obtained.

FIG. 5 shows another example of how to provide the hollow portion. In FIG. 5, when the hollow portion 312 is provided in the wing 302, the hollow portion 312 is formed in a lattice shape. The other points are the same as those of the wing 102 shown in FIG. For example, the hollowness of the wing 302 becomes minimum near the wing portion 308a corresponding to the maximum shroud curvature portion, and the hollowness of the wing 302 increases as the distance from the wing portion 308a corresponding to the maximum shroud curvature portion increases. In the centrifugal impeller provided with the blade 302 shown in FIG. 5, the same effects as those of the centrifugal impeller provided with the blade 102 shown in FIG. 3 can be obtained. Further, by forming the hollow portion 312 in a lattice shape, the strength of the wing 302 can be increased.

<Configuration example of centrifugal fluid machine>
Next, a configuration example of a centrifugal fluid machine to which the centrifugal impeller of the present invention is applied will be described with reference to FIG. Examples of the centrifugal fluid machine include a centrifugal pump and a centrifugal compressor. FIG. 6 is a longitudinal sectional view showing the entire structure of the centrifugal compressor.
In FIG. 6, a centrifugal compressor 10 is formed in a cylindrical shape or the like to be a stationary portion (stator), and is rotatably provided in the casing 11 by being supported by

radial bearings

12, 13 and a thrust bearing 14. And a plurality of (five in FIG. 6) centrifugal impellers 16 mounted on the rotating shaft 15. The rotating shaft 15 and the centrifugal impeller 16 constitute a rotor 17. In the present embodiment, a single-shaft multi-stage centrifugal compressor in which a single rotating shaft 15 is provided with centrifugal impellers 16 in multiple stages will be described as an example. Can be similarly applied.

The casing 11 has a suction passage 18 for introducing a gas, which is a working fluid, to the first-stage centrifugal impeller 16, and a diffuser 19 for converting kinetic energy of gas discharged from each stage of the centrifugal impeller 16 into pressure energy. And a return flow path 20 for introducing the compressed gas from the diffuser 19 to the next-stage centrifugal impeller 16, and a discharge flow for discharging the gas discharged from the final-stage centrifugal impeller 16 to the outside of the casing 11. A road 21 and the like are provided.

駆動 A driving device (not shown) such as a motor is connected to the discharge side end of the rotating shaft 15, and the driving device drives the rotor 17 to rotate. Further, as the rotor 17 rotates, the gas is sucked from the suction flow channel 18, is sequentially compressed by the centrifugal impellers 16 in a plurality of stages, and is finally discharged from the discharge flow channel 21.

In the above-described configuration, the centrifugal impeller of the above-described embodiment is used as the centrifugal impeller 16.
By using the centrifugal impeller of the present invention described above, the number of stages of the centrifugal impeller of the centrifugal compressor and the outer diameter of the centrifugal impeller can be reduced, and the centrifugal compressor can be downsized and the efficiency can be improved.

Note that the present invention is not limited to the above-described embodiment, and includes various modifications.
For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described above. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of one embodiment can be added to the configuration of another embodiment. Further, for a part of the configuration of each embodiment, it is possible to add, delete, or replace another configuration.

記載 Also, in the description of the claims, a single citation is used for simplification of the citation relationship. However, the present invention includes a case where a multiple citation is used, and a case where a multiple citation is cited.

100: centrifugal impeller, 101: hub, 102, 202, 302: blade, 103: shroud, 104, 204: blade inlet side end, 105, 205: blade outlet side end, 106: flow path, 107: shroud Flow path side surface, 108, 208, 308: Shroud curvature maximum part, 108a, 208a, 308a: Shroud curvature maximum part corresponding wing part, 109: Blade surface, 110: Hub side wing part, 111: Shroud side wing part, 112, 212, 312: Hollow part

Claims

A centrifugal impeller of a centrifugal fluid machine including a hub, a plurality of blades, and a shroud,
A centrifugal impeller, wherein the wing has a hollow portion.
The centrifugal impeller according to claim 1,
The centrifugal cavity, wherein the hollow portion is provided such that the hollowness of a portion of the wing where maximum stress occurs when a solid wing is used as the wing is smaller than the hollowness of other portions. Impeller.
The centrifugal impeller according to claim 2,
The centrifugal impeller, wherein the hollow portion is provided so as to have a minimum hollowness at a portion of the blade facing a portion having a maximum curvature on the flow path side surface of the shroud.
The centrifugal impeller according to claim 3,
The centrifugal impeller is characterized in that the hollow portion is provided such that the hollowness of the blade increases with distance from a portion where the curvature is maximum on the flow path side surface of the shroud.
The centrifugal impeller according to claim 1,
The centrifugal impeller is characterized in that the hollow portion is provided by being divided into a plurality of portions, and is provided radially with respect to a flow path side surface of the shroud.
The centrifugal impeller according to any one of claims 1 to 5,
The centrifugal impeller, wherein the hub, the plurality of blades, and the shroud are integrally formed by additive manufacturing.
A rotary shaft, a centrifugal fluid machine including a centrifugal impeller shrink-fit to the rotary shaft,
A centrifugal fluid machine using the centrifugal impeller according to any one of claims 1 to 5 as the centrifugal impeller.
A rotary shaft, a centrifugal fluid machine including a centrifugal impeller shrink-fit to the rotary shaft,
A centrifugal fluid machine using the centrifugal impeller according to claim 6 as the centrifugal impeller.