JP2000154796A - Impeller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce axial thrust and to make an impeller compact and inexpensive by arranging the impeller between an impeller exit and a suction port and providing blades inclined so as to generate thrust in the advancing direction of fluid on an impeller exit side. SOLUTION: A plurality of blades 2 of an impeller 1 are twisted and inclined as the blades 2 approach to an impeller exit 6 side. Namely, as for front surfaces 2a of the blades 2, boundary lines F1 to F2 of an inside face of a front shroud 3 and the front surfaces 2a are located at the rear sides of boundary lines R1 to R2 of the inside of a rear shroud 4 and the front surfaces 2a in a rotating direction N. In the impeller 1, thrust T1 is generated in the direction opposite to an advancing direction of fluid by a pressure difference acting on the front and rear shrouds 3, 4. Because the front surface 2a and the rear surface become a pressure surface and a negative pressure surface, respectively, in each blade 2, force T2 caused by a pressure difference between both of the pressure surface and the negative pressure surface is generated from the front surface 2a to the rear surface. An axial component Ta of this force T2 is directed in the direction opposite to thrust T1 caused by a front and rear pressure difference of the impeller 1 and axial thrust T becomes one that Ta is subtracted from T1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impeller applied to a centrifugal fluid machine such as a centrifugal pump, a centrifugal compressor, and a centrifugal water turbine.

[0002]

2. Description of the Related Art Conventionally, centrifugal fluid machines such as centrifugal pumps, centrifugal compressors, centrifugal water turbines, etc.
As shown in FIG. 1, an impeller is used. The impeller 101 shown in these drawings has a plurality of blades 102 formed as so-called backward-facing blades. Each wing 102
The front shroud 103 and the rear shroud 104 are formed integrally with each other.
(In the case of a water turbine, an outflow port) is formed. Further, an outer periphery of the impeller 101 defines an impeller outlet 106 (an inflow port in the case of a water wheel) by each of the blades 102, the inner surface of the front shroud 103, and the inner surface of the rear shroud 104. Further, a spindle mounting hole 107 for fixing to a main shaft (not shown) of the centrifugal fluid machine is provided in the center of the impeller 101.
Are formed.

Here, in an impeller 101 used for a centrifugal pump, a centrifugal compressor, or the like, the outer surface area pressurized at a pressure close to the discharge pressure at an impeller outlet 106 is generally smaller than that of the front shroud 103. Since the rear shroud 104 is larger, the front shroud 103 and the rear shroud 1
The forces acting on 04 do not balance. Therefore, in the case of an impeller of a centrifugal pump or a centrifugal compressor, a direction (-Y) opposite to the direction Y of fluid flow (the direction of fluid suction, see FIG. 11).
Generates a thrust T1. Similarly, when the impeller 101 is applied as a runner of a centrifugal turbine, the outflow direction of fluid −Y
, A thrust T1 is generated. Therefore, various types of centrifugal fluid machines have a balance mechanism such as a balance ring or a thrust bearing in order to offset the thrust T1.

[0004]

On the other hand, in the impeller 101, as shown in FIG. 11, the inner surface of the front shroud 103 and the front surface 102a
F1 between the inner surface of the rear shroud 104 on the suction port 105 side and the blade front surface 102a.
It is necessary to keep away from the center axis A of the impeller 101 (that is, Df ≧ Dr). That is, the front surface 102 of the blade 102
12, the boundary (curve) F1- between the inner surface of the front shroud 103 and the front surface 102a, as shown in FIG.
F2 is located forward of the boundary (curve) R1-R2 between the inner surface of the rear shroud 104 and the front surface 102a in the rotation direction N. As a result, each blade 102
The end on the front shroud 103 side is the rear shroud 104
It is inclined so as to be located on the front side in the rotation direction N from the end on the side (see FIG. 13).

However, in this case, as shown in FIG. 13, the front surface 102a of each blade 102 serves as a pressure surface, and the rear surface 102b serves as a negative pressure surface. , A force T2 is generated. In the case of a centrifugal pump or a centrifugal compressor, the axial component Ta of the force T2 (the extending direction component of the central axis A) is opposite to the traveling direction Y of the fluid (-Y direction). In the water wheel, the fluid flows in the outflow direction -Y. In any case, the thrust Ta is in the same direction as the thrust T1 generated due to the pressure difference before and after the impeller 101, and the impeller 10
The axial thrust T generated at 1 increases as the sum of T1 and Ta. Therefore, a large-scale balance mechanism must be provided for the centrifugal fluid machine, and as a result,
The overall length and cost of the centrifugal fluid machine increase.

Accordingly, an object of the present invention is to provide an impeller capable of reducing axial thrust and realizing a compact and inexpensive centrifugal fluid machine.

[0007]

An impeller according to the present invention is applied to a centrifugal fluid machine, and discharges fluid sucked in an axial direction through a suction port from an impeller outlet in a radial direction. The impeller is provided between the impeller outlet and the suction port, and is provided with a blade that is inclined on an exit side of the impeller so as to generate a thrust in a fluid traveling direction.

[0008] When this impeller is applied to a centrifugal fluid machine such as a centrifugal pump or a centrifugal compressor, similarly to a general impeller, a pressure difference between the impeller and the centrifugal fluid machine before and after the impeller is reduced. As a result, a thrust is generated in a direction opposite to the direction in which the fluid travels (suction direction). On the other hand, the blades of the impeller were viewed, for example, such that the edge on the suction port side was parallel to the central axis of the impeller, and the front side of the impeller was lowered as approaching the impeller outlet side. In this case, it corresponds to the one that is gradually twisted so as to lean forward in the rotation direction N. Therefore, in this impeller, the thrust generated due to the inclined state of the blade is directed in the direction in which the fluid travels.

As a result, the thrust generated due to the pressure difference between the front and rear of the impeller and the thrust generated due to the inclined state of the blade are components in directions opposite to each other, and are the sum of the two. Axial thrust can be reduced. As a result, in a centrifugal fluid machine such as a centrifugal pump or a centrifugal compressor to which the impeller is applied, it is possible to simplify a balance mechanism for canceling the axial thrust,
A compact and inexpensive centrifugal fluid machine can be realized.

It is preferable that the suction port side of the blade is inclined in a direction opposite to the impeller outlet side. The blades of this impeller, for example, incline the suction port side in the same manner as the conventional one (in a state where thrust is generated in the direction in which the fluid moves in the opposite direction) and, as approaching the impeller outlet side, move the front side of the impeller. When viewed from below, it corresponds to one that is gradually twisted and bent so as to lean forward in the rotation direction N. Even with such a configuration, the axial thrust generated in the impeller can be reduced.

In this case, it is preferable that the blade is separated into an outlet side blade and a suction side blade. By employing such a configuration, it is possible to easily form a blade in which the suction port side and the impeller outlet side are inclined in opposite directions to each other.

Further, it is preferable that the blade is an intermediate blade disposed near the impeller outlet. In this configuration, an intermediate impeller (splitter vane) in which the impeller outlet side is inclined so as to generate a thrust in the traveling direction of the fluid is disposed between each impeller of a general impeller or the impeller according to the present invention. Equivalent to Even with such a configuration, the axial thrust generated in the impeller can be reduced.

[0013] The impeller according to the present invention described in claim 5 is:
In an impeller that is applied to a centrifugal turbine and flows out the fluid flowing in the radial direction from the inlet in the axial direction from the outlet, the impeller is disposed between the inlet and the outlet, and the inflow side is the anti-outflow of the fluid. A blade that is inclined to generate a thrust in the direction.

Even if such a configuration is adopted, the thrust generated due to the pressure difference between the front and rear of the impeller and the thrust generated due to the inclined state of the blade are components in directions opposite to each other. Therefore, the axial thrust, which is the sum (absolute value) of the two, can be reduced. Therefore, in the centrifugal turbine to which this impeller is applied, the balance mechanism for canceling out the axial thrust can be simplified, and a compact and inexpensive centrifugal turbine can be realized.

Also in this case, it is preferable that the outlet side of the blade is inclined in a direction opposite to the inlet side. Further, it is preferable that the blades are separated into an inlet-side blade portion and an outlet-side blade portion. Furthermore, the blade may be an intermediate blade disposed near the inlet.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an impeller according to the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a sectional view showing a first embodiment of an impeller according to the present invention. The impeller 1 shown in FIG. 1 is formed, for example, by casting stainless steel, and is applicable to a centrifugal fluid machine such as a centrifugal pump, a centrifugal compressor, and a centrifugal water wheel. Here, in order to simplify the description, the impeller 1 will be described as being used for an impeller such as a centrifugal pump or a centrifugal compressor.

The impeller 1 has a plurality of blades 2 formed as so-called backward-facing blades. Each blade 2 is formed integrally with a front shroud 3 and a rear shroud 4, and a suction port 5 is formed in the front shroud 3. Also,
On the outer peripheral portion of the impeller 1, an impeller outlet 6 is defined by each of the blades 2, the inner surface of the front shroud 3, and the inner surface of the rear shroud 4. That is, each blade 2 is arranged between the suction port 5 and the impeller outlet 6, and the fluid sucked in the axial and inward direction through the suction port 5 is radially and outwardly discharged from each impeller outlet 6. Discharge in the direction. Further, a spindle mounting hole 7 for fixing to a main spindle (not shown) of the centrifugal fluid machine is formed in the center of the impeller 1.

Here, as shown in FIGS. 1 and 2, the edge of the blade 2 included in the impeller 1 on the side of the suction port 5 is parallel to the central axis A of the impeller 1. That is, the intersection F1 between the inner surface of the front shroud 3 and the blade front surface 2a on the suction port 5 side,
Inner surface of rear shroud 4 and front surface 2 of blade at suction port 5 side
The line connecting the intersection a with the intersection a is a straight line parallel to the central axis A. (That is, Df = Dr).

The blades 2 are twisted and inclined in a direction of generating a thrust in a fluid traveling direction (suction direction) as approaching the impeller outlet 6 side. That is, regarding the front surface 2a of the blade 2, as shown in FIG. 2, the boundary (curve) F1-F2 between the inner surface of the front shroud 3 and the front surface 2a is the boundary line between the inner surface of the rear shroud 4 and the front surface 2a. (Curve) It is located behind R1-R2 in the rotation direction N. As a result, each blade 2
A state in which the end on the front shroud 3 side is located rearward in the rotation direction N from the end on the rear shroud 4 side, that is,
When the front shroud 3 is viewed with the lower side, it is inclined forward in the rotation direction N (see FIG. 3).

When the impeller 1 is applied to a centrifugal fluid machine such as a centrifugal pump or a centrifugal compressor, a difference between a pressure acting on the front shroud 103 and a pressure acting on the rear shroud 104 is obtained. , The thrust T1 is applied to the impeller 1 in the direction (−Y) opposite to the direction Y (suction direction) of the fluid.
Occurs. On the other hand, as shown in FIG. 3, the front surface 2a of each blade 2 serves as a pressure surface, and the rear surface 2b serves as a negative pressure surface.
A force T2 is generated from a to the rear surface 2b. This force T2
The axial component Ta (the component extending in the direction of the central axis A) is the traveling direction Y of the fluid in the case of a centrifugal pump or a centrifugal compressor.
Turn to. That is, the thrust Ta is directed in the opposite direction to the thrust T1 generated due to the pressure difference between the front and rear of the impeller 1, and the axial thrust T (absolute value) generated in the impeller 1 is from T1 to Ta.
Is subtracted.

As described above, of the thrusts acting on the impeller 1, the thrust generated due to the pressure difference before and after the impeller 1 and the thrust generated due to the inclined state of the blade 2 are mutually different. Since the components are in the opposite directions, the axial thrust, which is the sum of the two components, can be reduced. Thereby, in a centrifugal fluid machine such as a centrifugal pump or a centrifugal compressor to which the impeller 1 is applied, the tensile force acting on the main shaft to which the impeller 1 is attached can be reduced. Therefore, the reliability of the spindle can be improved, and the balance mechanism for canceling the axial thrust can be simplified.
A compact and inexpensive centrifugal fluid machine can be realized.

[Second Embodiment] FIGS. 4 and 5 show a second embodiment of the impeller according to the present invention. The impeller 11 shown in these drawings also has a plurality of blades 12 formed as so-called backward-facing blades, similarly to the impeller 1 shown in FIGS. The blades 12 incline the suction port 15 side in the same manner as in the prior art (to a state where thrust is generated in the counter-progression direction of the fluid), and as the blade approaches the impeller outlet 16 side, the fluid traveling direction Y (the suction direction). ) Is gradually twisted so as to generate a thrust. That is, the blade 12
Is inclined in a direction opposite to the impeller outlet 16 side, and a suction port for generating a thrust in a counter-moving direction (-Y, see FIG. 4) of the fluid with a boundary portion B as a boundary. It is divided into a side blade 18 and an outlet blade 19 that generates a thrust in the fluid traveling direction Y (see FIG. 4).

Referring to the front surface 18a of the suction-port-side blade portion 18, as shown in FIG. 5, the boundary (curve) F1-B between the inner surface of the front shroud 13 and the front surface 18a is defined by the inner surface and the front surface of the rear shroud 14. 18a (curve) R1-B
Than in the rotation direction N. As a result, the suction port side blade portion 18 of the blade 12 is in a state where the end on the front shroud 13 side is located forward in the rotation direction N from the end on the rear shroud 14 side, that is,
When the front shroud 13 is viewed downward, the rotation direction N
Will lean backwards toward.

On the other hand, regarding the front surface 19a of the outlet side blade portion 19, the boundary line (curve) B-F2 between the inner surface of the front shroud 13 and the front surface 19a is the boundary line (curve) between the inner surface of the rear shroud 14 and the front surface 19a. Curve) It is located rearward in the rotation direction N from B-R2. As a result, the outlet-side blade portion 19 of the blade 2 is in a state where the end on the front shroud 13 side is located rearward in the rotation direction N from the end on the rear shroud 14 side, that is, with the front shroud 3 down. When viewed, it tilts forward in the rotation direction N (see FIG. 3).

In this case, at the suction-port-side blade portion 18, the front surface 18a is caused by a pressure difference between the front surface 18a and the rear surface 18b.
The axial component of the force generated from the “a” toward the rear surface 18 b (the extending direction component of the central axis A) is opposite to the traveling direction Y of the fluid (−Y direction), and the front shroud 13 of the impeller 11 and the rear Thrust T1 generated due to pressure difference with shroud 14
And the same direction. On the other hand, as shown in FIG. 3, in the outlet-side blade portion 19, an axial component Ta of a force generated from the front surface 19 a toward the rear surface 19 b due to a pressure difference between the front surface 19 a and the rear surface 19 b. (Extension direction component of central axis A)
Is directed in the direction of travel Y of the fluid, and has a direction opposite to the thrust T1 generated due to the pressure difference between the front shroud 13 and the rear shroud 14 of the impeller 11. When the impeller 11 rotates, the pressure acting on the front surface 19a of the outlet-side blade portion 19 becomes larger than the pressure acting on the front surface 18a of the suction-side blade portion 18.

As a result, of the axial thrust acting on the impeller 11, the thrust T1 (see FIG. 3) generated due to the pressure difference between the front and rear of the impeller 11 and the suction port side blade 18
The thrust (referred to as Ta ') generated due to the tilted state is a component in the same direction. On the other hand, the thrust Ta generated due to the inclined state of the outlet-side blade portion 19 is a component in a direction opposite to the thrust T1 acting on the impeller 11, and
The absolute value is the thrust T generated at the suction-port-side blade 18.
It is larger than a '. Therefore, the axial thrust, which is the sum of T1, Ta 'and Ta, can be reduced as a result.
Thereby, even in a centrifugal fluid machine such as a centrifugal pump or a centrifugal compressor to which the impeller 1 is applied, the tensile force acting on the main shaft on which the impeller 1 is mounted can be reduced. Therefore,
Since the reliability of the main shaft can be improved and the balance mechanism for canceling the axial thrust can be simplified, a compact and inexpensive centrifugal fluid machine can be realized.

[Third Embodiment] FIGS. 6 and 7 show a third embodiment of the impeller according to the present invention. The impeller 21 shown in these drawings is equivalent to one obtained by separating the suction-side blade 18 and the outlet-side blade 19 of the blade 12 included in the impeller 11 shown in FIGS. I do. In other words, the impeller 21 moves in the opposite direction (-Y, FIG.
(See FIG. 6), and the suction-port-side blade portion 28 that generates a thrust is connected to the suction-port-side blade portion 28 through a slight gap C to generate a thrust in the fluid traveling direction (suction direction) Y (see FIG. 6). And an outlet-side blade portion 29. By adopting such a configuration, the blade 22 in which the suction port 25 side and the impeller outlet 26 side are inclined in opposite directions to each other can be easily formed. In consideration of pump efficiency and the like, the degree of inclination of the edge of the suction port side blade 28 on the side of the impeller outlet 26 and the edge of the outlet side blade 29 on the side of the suction port 25 are made as equal as possible. It is desirable that the gap C be as small as possible.

[Fourth Embodiment] FIGS. 8 and 9 show a fourth embodiment of the impeller according to the present invention. The impeller 31 shown in these drawings has a plurality of blades 32, and the impeller outlet 36 side is inclined so as to generate a thrust in the fluid traveling direction (suction direction) Y (see FIG. 9). And an intermediate blade 39 (splitter vane).
In this case, each of the blades 32 integrated with the front shroud 33 and the rear shroud 34 is the same as the conventional impeller shown in FIGS. 10 to 13 in the examples shown in FIGS. Like the impellers 1, 21, and 31, the blades may be inclined so as to generate a thrust in the traveling direction Y of the fluid.

As shown in FIG. 9, in this impeller 31,
Thrust Ta1 generated due to the inclined state of the intermediate blade 39
Is the thrust Ta2 generated due to the inclined state of the blade 32.
And the component in the opposite direction. Accordingly, thrusts T1, Ta1, and T3 generated due to the pressure difference between the front and rear of the impeller 31.
As a result, the axial thrust, which is the sum of a2, can be reduced. Accordingly, even in a centrifugal fluid machine such as a centrifugal pump or a centrifugal compressor to which the impeller 31 is applied, the tensile force acting on the main shaft to which the impeller 31 is attached can be reduced. Therefore, the reliability of the main shaft can be improved, and the balance mechanism for canceling the axial thrust can be simplified, so that a compact and inexpensive centrifugal fluid machine can be realized.

The impeller 1, 1 according to each of the above-described embodiments.
Each of 1, 1, 31 has been described as being applied to a centrifugal pump, a centrifugal compressor, and the like.
Any of 11, 21, 31 can be applied as it is as a runner of a centrifugal water turbine. In this case, the impeller outlet described above serves as an inlet of a runner through which fluid flows radially and inward, and the suction port serves as an outlet of a runner through which fluid flows out axially and outward. in this way,
When each impeller 1, 11, 21, 31 is applied to a centrifugal turbine, among the thrusts acting on the impeller, the thrust generated due to the pressure difference before and after the impeller, and the inclination state of the impeller The resulting thrusts are components in directions opposite to each other, so that the axial thrust, which is the sum of the two, can be reduced. Therefore, in the centrifugal water turbine to which the impellers 1, 11, 21 and 31 are applied, it is possible to simplify the balance mechanism for canceling the axial thrust, thereby realizing a compact and inexpensive centrifugal water turbine. Becomes possible.

[0032]

Since the impeller according to the present invention is configured as described above, the following effects are obtained. That is, it is possible to reduce the axial thrust by inclining the blade at the impeller outlet side so as to generate a thrust in the direction of fluid flow, and it is possible to realize a compact and inexpensive centrifugal fluid machine. Become.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of an impeller according to the present invention.

FIG. 2 is a schematic diagram illustrating an inclined state of a blade included in the impeller shown in FIG.

FIG. 3 is a schematic diagram for explaining a thrust acting on the impeller shown in FIG.

FIG. 4 is a sectional view showing a second embodiment of the impeller according to the present invention.

FIG. 5 is a schematic diagram illustrating an inclined state of a blade included in the impeller illustrated in FIG. 4;

FIG. 6 is a sectional view showing a third embodiment of the impeller according to the present invention.

FIG. 7 is a schematic diagram illustrating an inclined state of a blade included in the impeller illustrated in FIG. 6;

FIG. 8 is a schematic diagram illustrating an inclined state of a blade included in a fourth embodiment of the impeller according to the present invention.

FIG. 9 is a schematic diagram for explaining a thrust acting on the impeller shown in FIG.

FIG. 10 is a partially cutaway perspective view showing a conventional impeller.

11 is a sectional view of the impeller shown in FIG.

FIG. 12 is a schematic diagram illustrating an inclined state of a blade included in the impeller illustrated in FIG. 10;

FIG. 13 is a schematic diagram for explaining a thrust acting on a blade included in the impeller shown in FIG.

[Explanation of symbols]

1, 11, 21, 31 ... impeller, 2, 12, 22 ... blade, 2a ... blade front surface, 2b ... blade rear surface, 3, 13, 2
3,33 front shroud, 4,14,24,34 rear shroud, 5,15,25 inlet, 6,16,26,
36: impeller outlet, 18, 28: suction port side blade, 1
9, 29: exit side blade section, 39: middle blade, Y: traveling direction.

Claims (8)

[Claims] 1. An impeller, applied to a centrifugal fluid machine, for discharging fluid sucked in an axial direction through a suction port in a radial direction from an impeller outlet, wherein an impeller is provided between the impeller outlet and the suction port. An impeller, wherein the impeller includes an impeller, the impeller outlet side being inclined so as to generate a thrust in a traveling direction of the fluid. 2. The impeller according to claim 1, wherein the suction port side of the blade is inclined in a direction opposite to the impeller outlet side. 3. The impeller according to claim 2, wherein the blade is separated into an outlet-side blade and a suction-side blade. 4. The impeller according to claim 1, wherein the impeller is an intermediate impeller provided near an exit of the impeller. 5. An impeller, applied to a centrifugal turbine, for allowing fluid flowing radially from an inlet to flow out of an outlet in an axial direction, wherein the impeller is disposed between the inlet and the outlet. An impeller characterized in that the inlet has an impeller which is inclined so as to generate a thrust in a direction opposite to the outflow of the fluid. 6. The impeller according to claim 5, wherein the outlet side of the blade is inclined in a direction opposite to the inlet side. 7. The blade according to claim 6, wherein the blade is separated into an inlet-side blade and an outlet-side blade.
Impeller. 8. The impeller according to claim 5, wherein the blade is an intermediate blade provided near the inflow port.