JPH07158599A - Noise reducing device for turbomachinery - Google Patents

Abstract

PURPOSE:To reduce the occurrence of phenomenon wherein the generation of noise is increased at a specified rotation speed by a method wherein a damping structure is arranged in a gap part in a radial direction between inner and outer casings. CONSTITUTION:A boiler water feed pump is provided with a multistage inner casing 3 having the flow passage of a rotating multistage impeller 2 located in a thick outer casing 1 being called barrel. When high speed fluid is collided with a diffuser, the inner casing 3 is excited. When the frequency of the fluid excitation force coincides with the natural frequency of the structure system of the inner casing 3, the inner casing 3 is resonated and high noise is generated. To prevent the occurrence of the resonance phenomenon, damping structures 10 and 11 formed of a laminate are arranged on an engagement part 4 between the outer and inner casings 1 and 3. This constitution prevents the occurrence of resonance of the inner casing 3 through absorption of energy during vibration of the inner casing 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double cylinder type turbomachine provided with an inner casing and a rotating centrifugal impeller in an outer casing such as a boiler feed pump or a high-pressure centrifugal compressor, and an outer casing-less turbomachine. The present invention relates to a noise reduction device for reducing fluid noise in a single-cylinder turbomachine.

[0002]

2. Description of the Related Art The structure of a boiler feed pump is shown in FIG. 5 as an example of a double casing casing type centrifugal rotating machine. In a thick outer casing 1 called a barrel, a multistage inner casing 3 that forms a flow path of a rotating multistage centrifugal impeller 2 is provided. The fitting portion 4 between the inner casing 3 and the outer casing 1 has a small gap. Except for the fitting portion 4 between the inner casing 3 and the outer casing 1, an annular gap 12 having a large gap is formed. Also, the inner casing 3
The contact surface portions 5a and 5b between the barrel 1 and the barrel 1 are in a metal contact state by water pressure. The inner casing 3 is provided with a diffuser 6 shown in FIG. 6, and the high-speed fluid discharged from the vanes 7 of the impeller 2 is pressure-recovered by the diffuser portion 6, and a high pressure is obtained by repeating this. There is. At this time, the high-speed fluid collides with the diffuser 6 and vibrates the inner casing 3. This vibration is transmitted to the outer casing 1 and emitted as sound. FIG. 7 shows how the noise level changes depending on the pump rotation speed. The noise level of the overall indicated by a circle in the figure becomes higher as the energy increases due to the increase in the rotation speed. In detail, the noise level fluctuates depending on the rotation speed. It can be seen that the 4NZ component (●: rotational frequency, Z: number of blades of the impeller) marked with a circle in the figure fluctuates significantly depending on the value of the rotational speed and peaks at a specific rotational speed. To reduce fluid noise, (1) reduce fluid excitation force, (2) reduce noise generated,
(3) It is effective to make the transmission characteristic of the force transmission path such as the casing low in sensitivity. As an example of (1), it is effective to separate the distance between the tip of the blade 7 of the impeller 2 and the diffuser 6 sufficiently, and the vibration force itself is reduced.
The noise level is reduced. However, this method is not preferable because it has a trade-off relationship with performance degradation. Further, it is of no use in solving the phenomenon that the noise increases at a specific rotation speed. In Japanese Patent Laid-Open No. 60-151530, there is a method of balancing the fluid exciting force generated from the impeller. on the other hand,
Various methods have been disclosed as to the soundproofing method for the sound radiated from the casing of (2). As described above, what has been publicly disclosed so far relates to (1) the method for reducing the fluid exciting force and (2) the soundproof method for the noise generated.

[0003]

The conventional fluid noise reduction method is to reduce the fluid excitation force and to prevent the generated noise, and the vibration characteristics of the force transmission path such as the casing are not taken into consideration. .

An object of the present invention is to provide a noise reducing device for a turbomachine, which has no influence on fluid performance, can reduce a phenomenon in which noise becomes large at a specific rotation speed, and is low in noise.

[0005]

In order to achieve the above object, a noise reduction device for a turbomachine according to the present invention comprises a damping structure at a fitting portion between an outer casing and an inner casing, and the outer casing and the inner casing. A damping structure is provided in the radial gap between the casing and a ring-shaped ring-shaped member that is fitted to the outer peripheral surface of the casing of a single-cylinder turbomachine with no outer casing so as to have a gap, and the gap The part is filled with a damping body.

[0006]

The operation of the double-barrel type turbomachine will be described as an example. The fluid force due to the high-speed fluid from the impeller colliding with the diffuser excites the inner casing. When the frequency of this fluid force exciting force matches the natural frequency of the structural system of the inner casing, the inner casing resonates, and as a result,
The noise is transmitted to the outer casing and makes a loud noise. However, in the present invention, since the damping structure is provided in the fitting portion between the outer casing and the inner casing, or the damping structure is provided in the radial gap between the casing and the inner casing. Even if the inner casing is vibrated by the fluid force, the damping structure absorbs energy, so that resonance of the inner casing can be avoided and the force transmitted to the outer casing is reduced. Therefore, the vibration level of the outer casing is lowered, and the emitted sound can be reduced.

In the single-cylinder turbomachine, the fluid force caused by the high-speed fluid impinging on the impeller impinges on the diffuser vibrates the casing. When the frequency of this fluid force exciting force and the natural frequency of the casing structure system match, the casing resonates, resulting in a large noise. However, in the present invention, since the annular member is provided on the outer peripheral surface of the casing and the damping structure is provided in the fitting portion clearance portion, even if the casing is vibrated by the fluid force, the damping structure is formed. Absorbs energy, so that resonance of the casing can be avoided, the vibration level of the annular member that radiates noise is lowered, and noise can be reduced.

With the above operation, it is possible to provide a low noise turbomachine in which the occurrence of noise peaks at a specific rotation speed is suppressed and the fluid performance is not affected.

[0009]

First, an embodiment of the present invention will be described with reference to FIG.

FIG. 1 is an explanatory view showing a noise reducing device for a boiler feed water pump of a double cylinder casing type centrifugal rotating machine according to an embodiment of the present invention.

In FIG. 1, the boiler feed pump is provided with a multi-stage inner casing 3 forming a flow path of a rotating multi-stage centrifugal impeller 2 in a thick outer casing 1 called a barrel. An enlarged view of the fitting portion 4 between the inner casing 3 and the outer casing 1 is shown in FIG. In this embodiment, the laminated plate 8 is provided in the radial gap of the fitting portion 4 between the inner casing 3 and the outer casing 1. Further, a laminated plate 9 is provided in the axial gap of the fitting portion 4 between the inner casing 3 and the outer casing 1. Similarly, the laminated plates 10 and 11 are also provided in other axial gaps.
Is provided.

As shown in FIG. 6, when the high-speed fluid from the impeller collides with the diffuser 6, the fluid force acts on the diffuser 6 and vibrates the inner casing 3. When the frequency of this fluid excitation force and the natural frequency of the structural system of the inner casing match, the inner casing resonates, and as a result, it is transmitted to the outer casing and a large noise is generated. FIG. 8 shows the relationship between noise and vibration transfer function. In (a), the size of the circle indicates the level of noise. (B) is a measured value of the vibration transfer function from the inner casing 3 to the outer casing, and the peak of the peak corresponds to the natural frequency. As is clear by comparing the two figures, the frequencies of the noise peak and the vibration transfer function peak are in good agreement. From this, it can be said that the reason why the noise increases at a specific rotation speed is that the inner casing 3 resonates.

Therefore, in this embodiment, the fitting portion 4 between the outer casing 1 and the inner casing 3 is provided with damping structures 8, 9 and 10, 11. Therefore, even if the inner casing 3 is vibrated by a fluid force, the damping structure absorbs energy, so that resonance of the inner casing 3 can be avoided and the force transmitted to the outer casing 1 is reduced. Therefore,
According to this embodiment, since the vibration level of the outer casing is lowered and the emitted sound can be reduced, the occurrence of noise peaks at a specific rotation speed is suppressed, and there is no effect on performance, A low-noise turbomachine can be provided.

FIG. 3 is an explanatory view showing a noise reducing device for a boiler feed water pump of a double cylinder casing type centrifugal rotating machine according to another embodiment of the present invention. In this embodiment shown in FIG. 3, a damping structure 13 in which the perforated plates shown in FIG. 4 are annularly laminated is provided in the annular gap 12 between the inner casing 3 and the outer casing 1. This laminated plate has a large number of holes, and when the inner casing vibrates, the squeeze film effect of the working fluid occurs, resulting in a large damping. Therefore, even if the inner casing 3 is vibrated by the fluid force, the damping structure 13 absorbs the vibration energy, so that the resonance of the inner casing 3 can be avoided and the force transmitted to the outer casing 1 is reduced. Further, in this embodiment, unlike the embodiment, it is not a fluid pressure seal portion, so that there is an advantage that it is not necessary to worry about occurrence of fretting due to relative movement. Therefore, according to the present embodiment, the vibration level of the outer casing is lowered, and the emitted sound can be reduced, so that the generation of noise peaks at a specific rotation speed is suppressed, and the influence on the performance is reduced. It is possible to provide a low-noise turbomachine.

Further, instead of the damping structure 13 in which the perforated plates are laminated in an annular shape in the embodiment of FIG. 3, a granular object may be packed in the annular gap portion 12 to form the damping structure 13.

FIG. 9 is an explanatory view showing a noise reducing device for a single cylinder casing type pump according to another embodiment of the present invention. In this embodiment shown in FIG. 9, an annular ring 17a is installed so as to surround the outer peripheral surface of the casing 16, and the ring 17a is supported by an elastic member 18 such as a leaf spring. When the casing 16 is vibrated by the fluid force of the pump to vibrate, the spring-mass system including the elastic member 18a and the ring 17a is vibrated, and as a result, the vibration of the entire pump casing is reduced and noise is generated. Can be suppressed.

FIG. 10 shows another embodiment of the noise reduction device. A ring-shaped ring 17b that surrounds the outer peripheral surface of the casing 16 is provided, a void is provided on the inner peripheral side of the ring 17b, and the void is filled with the particulate powder 20. Here, the granular powder 20 is a steel ball, a lead ball,
It may be composed of gravel or the like. When the casing 16 is vibrated by the fluid force of the pump to vibrate, the granular powder 20
Are vibrated, the particulate powders 20 collide with each other, and the vibration energy is dissipated. As a result, the vibration of the entire pump casing is reduced, and the generation of noise can be suppressed.

FIG. 11 shows another embodiment of the noise reduction device. A ring-shaped ring 17c that surrounds the outer peripheral surface of the casing 16 is installed, a void is provided on the inner peripheral side of the ring 17c, and a laminated plate 13 of perforated plates is provided in the void to inject viscous fluid. is there. With this structure, the vibration is damped by the viscous damper effect. As a result, the vibration of the entire pump casing is reduced, and the generation of noise can be suppressed.

Therefore, according to this embodiment, the vibration level of the outer casing is lowered and the emitted sound can be reduced, so that the generation of noise peaks at a specific rotation speed is suppressed and the performance is improved. It is possible to provide a low-noise turbomachine that is not affected by the above.

[0020]

According to the present invention, it is possible to provide a noise reducing device for a centrifugal rotating machine which has a reduced noise peak at a specific rotation speed and has no influence on performance, and which has low noise.

[Brief description of drawings]

FIG. 1 is a sectional view of a boiler feed pump according to an embodiment of the present invention.

FIG. 2 is a sectional view of a fitting portion between the outer casing and the inner casing of FIG.

FIG. 3 is a sectional view of a boiler feed pump according to another embodiment of the present invention.

FIG. 4 is an explanatory view of a porous laminated plate damper.

FIG. 5 is a sectional view of a conventional boiler feed pump.

FIG. 6 is an explanatory diagram of a fluid flow.

FIG. 7 is an explanatory diagram of a relationship between rotation speed and noise level.

FIG. 8 is an explanatory diagram showing a correlation between a vibration transfer function and noise.

[Explanation of symbols]

1 ... Outer casing, 2 ... Impeller, 3 ... Inner casing, 4
... Fitting part, 10 ... Other axial noise damping device, 11 ... Other axial noise damping device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiharu Ueyama 603, Kandachi-cho, Tsuchiura-shi, Ibaraki Hitate Works Co., Ltd. Tsuchiura factory

Claims (1)

[Claims] 1. A double-barrel type turbo rotating machine having an inner casing and a rotating centrifugal impeller inside the outer casing, wherein a damping structure is provided in a radial gap between the outer casing and the inner casing. A noise reduction device for a turbomachine, which is characterized by being provided.