JPH0942184A - Mixed flow type fluid machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the miniaturization of a mixed flow type fluid machine without impairing pump efficiency, cavitation performance and the stabilization of head discharge curve. SOLUTION: A mixed flow type fluid machine is composed of the first stage mixed flow impeller 2 and the second stage mixed flow impeller 3 which are axially concentric and accommodated in a casing 1, and provided with a rotating direction reversing mechanism for reversing the second stage mixed flow impeller 3 in an opposite rotating direction relative to the rotating direction of the first stage mixed flow impeller 2, and the outlet diameter of the second stage mixed flow impeller 3 is formed smaller than its inlet diameter. Since the second stage mixed flow impeller 3 is rotated in an opposite rotating direction, and the whole lift and discharge quantity are executed by two impellers having each different stage, the diameter of impeller can be lessened, and moreover a stable head curve can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drainage pump and a circulating water pump for circulating cooling water in a thermal power plant or a nuclear power plant, and is particularly suitable for downsizing and stabilizing a head curve. A mixed flow type fluid machine.

[0002]

FIG. 12 shows an example of a conventional mixed flow pump which is a mixed flow type fluid machine. The water sucked by the mixed flow pump is discharged from the discharge port 31 through the suction casing 21, the impeller 22, the guide blades 29, and the discharge casing 30. The impeller 22 is driven by a drive shaft 33 connected to an electric motor 32, which is a prime mover, and imparts energy to the suction flow to increase the pressure. The guide vanes 39 are static flow paths and have a function of converting circumferential residual components of the flow obtained by the impeller 22 into pressure. The demand for miniaturization of mixed flow pumps is increasing more than ever before. From the hydraulic point of view, in order to reduce the size of the hoop, measures such as rotating the impeller at high speed or increasing the blade outlet angle to increase the load on the impeller blade can be considered. There are such problems.

Since speeding up the impeller accelerates the occurrence of cavitation due to an increase in flow velocity, it is essential to improve cavitation performance and to take measures against erosion and vibration / noise increase due to cavitation, which is extremely difficult to realize. is there. When the load on the impeller blades is increased, an unstable portion is likely to occur in the pump head curve, which makes it difficult to operate in the low flow rate region. In addition, an excessive increase in load leads to an increase in loss due to flow separation, which lowers pump efficiency.

In the case of the mixed flow pump shown in FIG. 13, the first stage mixed flow impeller 2a and the second stage mixed flow impeller 2b, which are concentric with each other in the axial direction of the drive shaft 6, are housed in the casing 1a. , First
The second mixed flow impeller 2a and the first-stage straightening plate 4e are provided with a second
When the multi-stage mixed flow impeller 2b and the second-stage straightening plate 4f are used in multiple stages, the outer diameter of the casing 1a of the pump can be reduced, but the axial length becomes long, which often causes new problems in the pump structure. . Therefore, it is extremely difficult to solve these problems without sacrificing efficiency, cavitation performance, stability of the lift curve, structure, etc., and it has been extremely difficult to further downsize the conventional pump. .

[0005]

In the conventional mixed flow type fluid machine, when the impeller is rotated at a high speed for the purpose of downsizing, an unstable portion is likely to occur in the lift curve, which promotes the occurrence of cavitation. There is a problem that it becomes difficult to operate in the low flow rate range. Further, when the load on the impeller blades is increased, an excessive increase in load causes an increase in loss due to flow separation, which causes a problem that pump efficiency is reduced. Further, when the number of stages of the impeller is increased, the outer diameter can be reduced, but the axial length becomes long, which causes a new problem in the structure of the pump.

It is an object of the present invention to provide a mixed flow type fluid machine which can be miniaturized without sacrificing pump efficiency, cavitation performance and stabilization of a lift curve.

[0007]

To achieve the above object, a mixed flow type fluid machine according to the present invention comprises a first-stage mixed flow impeller and a second-stage mixed flow impeller which are coaxial with each other. In a mixed flow type fluid machine in which a casing is housed in a casing, a rotation direction reversing mechanism for reversing the second stage mixed flow impeller in a reverse rotation direction with respect to the rotation direction of the first stage mixed flow impeller is provided. The multi-stage mixed flow impeller is
The diameter of the outlet is smaller than the diameter of the inlet.

In a mixed flow type fluid machine in which a first-stage mixed flow impeller and a second-stage mixed flow impeller, which are coaxial with each other in the axial direction, are housed in a casing, the rotation direction of the first-stage mixed flow impeller On the other hand, a rotation direction reversing mechanism that reverses the second stage mixed flow impeller in the reverse rotation direction is provided, and the meridional flow passage of the second stage mixed flow impeller has a meridional flow path of the first stage mixed flow impeller. The structure may be formed such that it is continuous with the road and is formed outward so as to gradually separate from the center of the drive shaft toward the downstream side.

The rotation direction reversing mechanism includes a drive shaft and a drive hollow shaft having the drive shaft inserted therethrough, and connects the input shaft to the prime mover and the output shaft to the drive shaft and the other end of the drive hollow shaft. The first stage mixed flow impeller may be connected to one end of the drive shaft and the second stage mixed flow impeller may be connected to one end of the drive hollow shaft.

Further, the drive shaft may be rotatably supported by the drive hollow shaft and also supported by the bearing housing through the drive hollow shaft, and the bearing housing may be supported by the casing through the flow straightening vanes. .

A stationary guide vane may be installed between the first stage mixed flow impeller and the second stage mixed flow impeller.

The rotation direction reversing mechanism is installed between the first stage mixed flow impeller and the second stage mixed flow impeller, and has a drive shaft connected to the second stage mixed flow impeller. It may be configured to be connected to the prime mover via.

Further, the rotation direction reversing mechanism is provided between the first stage mixed flow impeller and the second stage mixed flow impeller, and is connected to the first stage mixed flow impeller and the second stage mixed flow vane. A configuration may also be adopted in which a vehicle and a prime mover connected to each other are arranged to face each other, and each prime mover is housed in a hub.

The rotating direction reversing mechanism is connected to the drive shafts of the first-stage mixed flow impeller and the second-stage mixed flow impeller and is provided to face each other, and a bevel gear orthogonal to the respective drive shafts. However, it may be configured to include a second bevel gear that meshes with each bevel gear and an input shaft of the second bevel gear, and the input shaft is connected to the prime mover.

Further, one of the first-stage mixed flow impeller and the second-stage mixed flow impeller may be constituted by movable blades.

Further in the turbo type fluid machine. It is configured by applying any one of the mixed flow type fluid machine technologies.

[0017]

In the normal mixed flow pump, the total head Hth of the single-stage pump obtained by the rotation of the impeller is obtained by the equation (1) from the change of the angular momentum. If there is no pre-turning at the impeller inlet, then Cu ₁ = 0, so the total head Hth is given by equation (2).

[0018]

[Equation 1]

[0019]

[Equation 2]

FIG. 5 shows the relative flow W ₁ -W at the blade inlet and outlet in the conical surface of the flow passages of the first stage mixed flow impeller and the second stage mixed flow impeller.
W ₄ is a diagram showing a. On the other hand, FIG. 6 shows a velocity triangle of the blades of the flow path shown by expanding the conical surface shown in FIG. FIG.
As shown in FIG. 6, the first-stage mixed flow impeller and the second-stage mixed flow impeller are provided, and the second-stage mixed flow impeller is rotated in a direction opposite to the rotation direction of the first-stage mixed flow impeller. When reversed, the reverse pre-turn Cu ₃ is applied to the inlet of the second stage mixed flow impeller.
The theoretical head in the case of such a counter-rotating pump is similarly obtained by the equation (3). There is no pre-turning at the pump inlet (C
u ₁ = 0), and there is no residual swirl at the pump outlet (Cu ₂ =
0), and Cu ₂ = Cu ₃ and U ₂ = U ₃ are set, (3)
Equation (4) is obtained from the equation.

[0021]

(Equation 3)

[0022]

(Equation 4)

That is, from the formulas (2) and (4), the circumferential component C of the second stage impeller inlet flow of the counter-rotating impeller is calculated.
Assuming that u ₃ is the same as the circumferential component Cu ₂ of the outlet flow of a normal single-stage impeller, the impeller outlet peripheral speed U ₂ is 1/2.
When the number of rotations is the same, the diameter of the impeller is halved, and the size can be greatly reduced. Alternatively, when the impeller diameter is the same, the circumferential component Cu ₂ of the impeller outlet flow can be set to 1/2. Since the blade load can be greatly reduced, an impeller with a stable lift curve can be easily obtained. In other words, by performing the work conventionally performed by the single-stage impeller by the two-stage impeller, the work amount per one-stage impeller can be reduced, so that the impeller can be downsized.
Also, since the work amount, that is, the load of the impeller can be reduced,
A stable lift curve can be obtained. Since the relative speed at the entrance of the second-stage impeller is reverse pre-turning, it becomes a large value, which may cause cavitation due to a decrease in static pressure.
Cavitation does not occur because the pressure is sufficiently increased by the step impeller.

Further, in principle, even if guide vanes are not provided,
Since the residual swirl component can be eliminated in the pump outlet flow, even if a two-stage impeller is applied, the axial length of the entire pump can be made equal to or shorter than that of the one-stage pump.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, a mixed flow type fluid machine in which a first-stage mixed-flow impeller 2 and a second-stage mixed-flow impeller 3 which are concentric in the axial direction are housed in a casing 1. A rotation direction reversing mechanism (reversing gear device) 15 for reversing the second-stage mixed flow impeller 3 in the reverse rotation direction with respect to the rotation direction of the second-stage mixed flow impeller 2 is provided. This is a configuration in which the diameter is formed smaller than the inlet diameter.

That is, the suction casing (casing) in which the suction bell mouth and the casing liner are integrated.
1, a first stage mixed flow impeller 2, a second stage mixed flow impeller 3,
It is composed of a concentric double drive hollow shaft 5 and a drive shaft 6 that apply a drive torque to the first-stage and second-stage mixed flow impellers 2 and 3, and a straightening vane (rectifying vane) 4a that supports the bearing housing 4b.
The rotation directions of the first-stage mixed-flow impeller 2 and the second-stage mixed-flow impeller 3 are set to be opposite to each other, and the blade shapes are as shown in FIG. It is set so that there is no pre-swirling component at the inlet of No. 2 and no residual swirling component at the outlet of the second stage mixed flow impeller 3. The outer diameter of the impeller is
The outer diameter is smaller than that of a normal single-stage impeller.

FIG. 2 shows a cross section taken along the line AA of the bearing housing. The drive hollow shaft 5 is an outer shaft, and a drive shaft 6 that rotates in a direction opposite to the drive hollow shaft 5 is inserted as an inner shaft. A bearing 7 is provided between the drive hollow shaft 5 and the drive shaft 6, and a bearing 8 is provided in the hollow portion between the drive hollow shaft 5 and the bearing housing 4b. Therefore, the drive shaft 6 is rotatably supported by the drive hollow shaft 5 by the bearing 7, and
The bearing housing 4b is rotatably supported by the bearing 8 through the bearing housing 4b, and the bearing housing 4b is supported by the casing 1 through the flow straightening vanes 4a. The drive hollow shaft 5 and the drive shaft 6 are, as shown in FIGS. 3 and 4, a double shaft joint 1 of an output shaft of a reversing gear device 15 connected to a prime mover 12 via a joint 16.
4 are connected to each other, and the power is transmitted to two shafts of a drive hollow shaft 5 and a drive shaft 6 which are concentric and have different rotation directions.

The reversing gear device 15 is formed of, for example, a planetary gear mechanism, and is an external gear sun gear 15a connected to the drive hollow shaft 5, and one surface is connected to the drive shaft 6 and the other surface is a joint 16. Sun gear 15b, which is an internal gear, which is connected to the prime mover 12 via
It is composed of a plurality of planetary gears 15c revolving around the sun gear 15b while meshing with b and rotating, and a carrier 15d pivotally supporting each planetary gear 15c. 5 is a structure in which 5 can be reversed in the reverse rotation direction.

In the counter-rotating mixed flow pump constructed as described above, when the impeller rotates, the velocity triangle at the inlet and outlet of the impeller becomes the shape shown in FIG. 6, and there is no residual swirl component at the outlet of the second stage impeller. It leaves the impeller at such a speed C ₄ .
At that time, the theoretical lift shown in equation (5) is obtained with the first-stage mixed flow impeller and the theoretical lift shown in equation (6) is obtained with the second-stage mixed flow impeller, so that at the pump outlet, The theoretical lift shown in equation (7), which is the sum of equations (5) and (6), is obtained.

[0030]

(Equation 5)

[0031]

(Equation 6)

[0032]

(Equation 7)

According to the present embodiment, the two-stage pump produces the same lift and discharge amount as compared with the normal single-stage pump, so that the load per single stage is reduced and the impeller diameter can be reduced. On the other hand, if the diameter of the impeller is the same as that of the conventional one, the impeller load is small, so that separation and stall are unlikely to occur in the impeller blade even in the low flow rate region, and the head curve is a downward-sloping curve without an unstable portion.

A second embodiment of the present invention is shown in FIG. First
Immediately after the two-stage mixed flow impeller 2, a second-stage mixed flow impeller 3 is installed,
And, the meridian flow passage shape is formed so that the central streamline thereof gradually becomes downstream and away from the center of the impeller drive shaft, and the meridional flow passage of the first stage mixed flow impeller and the second meridian flow passage are formed. It is a counter-rotating mixed flow pump configured such that the meridional flow path of the multi-stage mixed flow impeller is continuous. The maximum diameter of the first-stage mixed-flow impeller 2 is smaller than the maximum diameter of the second-stage mixed-flow impeller 3, and the load on the first-stage mixed-flow impeller 2 is reduced to prevent cavitation. Since it can be reduced, it is possible to realize a mixed flow pump having good cavitation performance. Since the pressure is increased by the first-stage mixed flow impeller 2 at the inlet of the second-stage mixed flow impeller 3, it is possible to suppress the occurrence of cavitation in the second-stage mixed flow impeller.

A third embodiment of the present invention is shown in FIG. First
The stationary guide vane 9 is installed between the stage mixed flow impeller 2 and the second stage mixed flow impeller 3. At this time, a part of the circumferential component of the impeller outlet generated in the first-stage mixed flow impeller 2 is decelerated from C ₂ to C ₃ by the stationary guide vanes 9a and 9b, etc. to recover pressure. Then, after that, it flows into the second stage mixed flow impeller 3. At this time, the stationary guide vane 9 shown in FIG.
The angle α ₃ in the velocity triangle at the inlet of the second-stage mixed flow impeller shown in FIG. as a result,
The inlet angle of the second stage mixed flow impeller blade is increased, and the blade length can be shortened, which facilitates the manufacture of the blade.

A fourth embodiment of the present invention is shown in FIG. The reversing gear device 25 is installed between the first stage mixed flow impeller 2 and the second stage mixed flow impeller 3, has a drive shaft 26 that is connected to the second stage mixed flow impeller 3, and drives the Prime mover 12 via shaft 26
It is connected to. That is, the reversing gear device 25 is built in the hub of the impeller. With such a configuration, it is not necessary to make the drive shaft 26 a hollow shaft, and the manufacture becomes easy.

The fifth embodiment of the present invention is shown in FIG. This embodiment is a tubular counter-rotating mixed flow pump. The reversing gear device 35 is installed between the first-stage mixed-flow impeller 2 and the second-stage mixed-flow impeller 3 and is connected to the first-stage mixed-flow impeller 2 and the prime mover 12 a and the second-stage mixed-flow vane. The prime mover 12b connected to the vehicle 3 is arranged to face each other, and each prime mover 12b
This is a configuration in which a and 12b are housed in the pump hub 34. The first-stage mixed-flow impeller 2 is driven by the installed prime mover 12a, the second-stage mixed-flow impeller 3 is driven by the prime mover 12b, and the rotation directions of the two original electric machines 12a and 12b are set to be opposite to each other. . Since the prime mover is built into the pump body, it can be made into a very compact shape.

The sixth embodiment of the present invention is shown in FIG. The reversing gear device 45 includes bevel gears 45a and 45b that are provided so as to be connected and connected to the drive shafts of the first-stage mixed flow impeller 2 and the second-stage mixed flow impeller 3 and face each other, and are orthogonal to the respective drive shafts. Second bevel gear 45 that meshes with each bevel gear 45a, 45b
c and the input shaft 46 of the second bevel gear 45c, and the input shaft 46 is connected to the prime mover 12. With this configuration, the total length of the mixed flow pump can be greatly shortened.

Further, as a seventh embodiment of the present invention, the first
It is possible to provide a small-sized mixed flow pump having the characteristics of the movable blade, which has a configuration in which either one of the first stage impeller and the second stage impeller is used as the movable vane.

Although the application to the mixed flow pump has been described in the above embodiments, the same technique can be applied to a turbo type fluid machine such as a mixed flow fan and a mixed flow compressor.

According to the present invention, since the total head and the work of the flow rate performed by the single-stage impeller are performed by the two-stage impeller, the impeller diameter can be reduced and the blade load can be set small. As a result, a stable pump head can be easily obtained.

[0042]

According to the present invention, the second stage mixed flow impeller is rotated in the reverse rotation direction with respect to the rotation direction of the first stage mixed flow impeller, and the total head and discharge amount are divided into two stages. Since it is performed by a car, the diameter of the impeller can be reduced and the load on the blade can be set small, so that there is an effect of obtaining a stable head curve.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a line AA of FIG.

FIG. 3 is an external view showing the entire apparatus of FIG.

FIG. 4 is a vertical cross-sectional view showing the rotation direction reversing mechanism of FIG.

5 is a perspective view showing a meridional flow path of the impeller of FIG. 1. FIG.

6 is a diagram showing a velocity triangle of the impeller of FIG.

FIG. 7 is a vertical cross-sectional view showing a second embodiment of the present invention.

FIG. 8 is a vertical cross-sectional view showing a third embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a fourth embodiment of the present invention.

FIG. 10 is a vertical cross-sectional view showing a fifth embodiment of the present invention.

FIG. 11 is a vertical sectional view showing a sixth embodiment of the present invention.

FIG. 12 is a vertical cross-sectional view of a vertical mixed flow pump showing a conventional technique.

FIG. 13 is a vertical cross-sectional view of a two-stage mixed flow pump showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suction casing 2 1st stage mixed flow impeller 3 2nd stage mixed flow impeller 4 Straightening plate 5 Drive hollow shaft 6,26,46 Drive shaft 7 Bearing 8 Bearing 9 Guide vane 10 Discharge casing 11 Discharge port 12 Prime mover 13 2 Heavy inversion mixed flow pump 14 Double joint 15, 25, 35, 45 Inversion gear device 16 Joint

Claims (10)

[Claims] 1. A first-stage mixed flow impeller and a second axial concentric fan shaft.
In a mixed flow type fluid machine in which a two-stage mixed flow impeller is housed in a casing, a rotation for reversing the second-stage mixed flow impeller in a reverse rotation direction with respect to a rotation direction of the first-stage mixed flow impeller. A mixed flow type fluid machine characterized in that a direction reversing mechanism is provided, and the second stage mixed flow impeller has an outlet diameter smaller than its inlet diameter. 2. A first-stage mixed-flow impeller coaxially concentric with the second
In a mixed flow type fluid machine in which a two-stage mixed flow impeller is housed in a casing, a rotation for reversing the second-stage mixed flow impeller in a reverse rotation direction with respect to a rotation direction of the first-stage mixed flow impeller. A direction reversing mechanism is provided, and the meridional flow passage of the second stage mixed flow impeller is continued to the meridional flow channel of the first stage mixed flow impeller, and gradually extends from the drive shaft center toward the downstream side. A mixed flow type fluid machine characterized in that it is formed so as to face away from one another. 3. The rotation direction reversing mechanism includes a drive shaft and a drive hollow shaft having the drive shaft inserted therethrough, the input shaft is connected to a prime mover, and the output shaft is connected to the drive shaft and the other end of the drive hollow shaft. The first stage mixed flow impeller is connected to one end of the drive shaft, and the second stage mixed flow impeller is connected to one end of the drive hollow shaft. The mixed flow fluid machine according to 1 or 2. 4. The drive shaft is rotatably supported by the drive hollow shaft and is also supported by the bearing housing via the drive hollow shaft, and the bearing housing is supported by the casing via the rectifying blades. The mixed flow type fluid machine according to claim 3, wherein: 5. The mixed flow type fluid machine according to claim 1, wherein a stationary guide vane is installed between the first stage mixed flow impeller and the second stage mixed flow impeller. 6. The rotation direction reversing mechanism has a drive shaft installed between the first stage mixed flow impeller and the second stage mixed flow impeller, and connected to the second stage mixed flow impeller. The mixed flow type fluid machine according to claim 1 or 2, which is connected to a prime mover via the drive shaft. 7. The rotating direction reversing mechanism is provided between the first stage mixed flow impeller and the second stage mixed flow impeller and is connected to the first stage mixed flow impeller and the second stage mixed flow. 2. The mixed flow type fluid machine according to claim 1, wherein the impeller and a prime mover connected to the impeller are arranged to face each other, and the prime movers are housed in a hub. 8. A bevel gear connected to the respective drive shafts of the first stage mixed flow impeller and the second stage mixed flow impeller and provided to face each other, and the respective drive shafts. 2. A second bevel gear, which is orthogonal to each other and meshes with each bevel gear, and an input shaft of the second bevel gear, the input shaft being connected to a prime mover. Two
The mixed flow fluid machine described. 9. The mixed flow fluid machine according to claim 1, wherein one of the first-stage mixed flow impeller and the second-stage mixed flow impeller is formed of movable blades. . 10. A turbo type fluid machine to which the technology of a mixed flow type fluid machine according to any one of claims 1 to 9 is applied.