JPH10318430A - Piping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent generation of high frequency vibration compounding a higher order acoustic mode, in a pipe in the downstream of a steam valve. SOLUTION: In a part opposed to a valve element 3, a valve seat 4 is provided inside a steam valve. In connection to this valve seat 4, an insert pipe 5 is provided, a downstream pipe 6 is connected thereto. A constitution is formed by holding an equal diameter in an outlet of the valve seat 4 and an inlet of the insert pipe 5 and by holding an equal diameter in an outlet of the insert pipe 5 and an inlet of the downstream pipe 6. An internal diameter of the insert pipe 5 is gradually increased along the axial direction. By this insert pipe 5, a high frequency vibration in a pipe compounding a higher order acoustic mode is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piping device suitable for preventing high-frequency vibration from being generated in a piping downstream of a steam valve through which high-pressure steam flows, for example.

[0002]

2. Description of the Related Art In piping such as a steam turbine through which high-pressure steam flows, a steam valve having a throttle element is used for flow rate adjustment. When the upstream pressure P1 and the downstream pressure P2 are before and after the throttle element of the steam valve, the pressure ratio P1 / P2
If the value exceeds a certain value, the flow velocity of the steam becomes supersonic at the throttle portion, and the flow is significantly disturbed by the shock wave generated at this time. In particular, in a steam valve in which high-pressure steam flows from a boiler, the downstream pipe may be damaged due to vibration caused by such a phenomenon.

Referring to the system shown in FIG. 11, high-temperature and high-pressure steam from a boiler (not shown) is supplied to an upstream pipe 21.
To reach the steam valve 22. The steam flowing to the steam valve 22 flows to the outlet of the steam valve 22 through a narrow flow path between the valve body 23 and the valve seat 24, and further flows to the downstream pipe 25. When the pressure ratio between the upstream side and the downstream side of the steam valve 22 becomes equal to or higher than the critical pressure determined by the type of fluid, the flow velocity becomes supersonic at the narrowest part of the flow path, and a shock wave is generated. The pressure fluctuation due to the shock wave is transmitted as disturbance of the flow from the valve seat 24 to the downstream side, and vibration is generated in the downstream pipe 5. Reference numeral 26 in the drawing indicates a pipe support that supports the downstream pipe 25.

[0004]

The vibration of the downstream pipe 5 caused by the above-mentioned shock wave is a coupled vibration between a higher-order acoustic mode and the pipe wall. This is the circumferential direction of the pipe 5, the radial direction,
Each has a vibration mode in the axial direction. The pipe support 26 conventionally used for vibration suppression is not installed in consideration of the vibration caused by such coupled vibration, and particularly, effectively suppresses the high-frequency vibration coupled with the higher-order acoustic mode. Can not.

[0005] In order to prevent the vibration of the piping coupled with the higher-order acoustic mode, appropriate measures must be adopted. Sex is impaired.

Accordingly, an object of the present invention is to provide a piping device which effectively prevents high-frequency vibration coupled with a higher-order acoustic mode from being generated in a piping downstream of a steam valve.

[0007]

In order to achieve the above object, the present invention relates to a piping apparatus in which a steam valve for controlling the amount of steam flowing into a downstream high-pressure device is provided in a pipe through which high-pressure steam flows. A vibration preventing element is provided at a connection portion of the steam valve with the downstream pipe so as to prevent vibration of the downstream pipe from being caused by disturbance of the high-speed fluid generated at the throttle section of the steam valve. It is.

In order to understand the coupled vibration between the higher-order acoustic mode of the fluid in the pipe and the vibration mode of the pipe wall, a detailed description will be given with reference to the drawings. As shown in FIG. 2A, the pressure fluctuation in the downstream pipe 25 at a point A immediately downstream of the steam valve 22 and at a point B significantly away from the steam valve 22 is caused by the throttle pressure ratio at the steam valve 22. When the (pressure ratio P1 / P2 between the upstream pressure P1 and the downstream pressure P2) is large, the frequency characteristic shown in FIG. 2B is exhibited. That is, the steam valve 2
The frequency characteristic of the pressure fluctuation at point A near 2 indicates a 1 / f characteristic that the pressure fluctuation decreases as the frequency increases, and is a random fluctuation.

On the other hand, at point B, which is far away from the steam valve 22, most of the frequency components of the pressure fluctuations observed near the steam valve 22 are attenuated and small, but the higher order of the fluid in the downstream pipe 25 is higher. The components of the primary and secondary modes of the coupled vibration between the acoustic mode (including the circumferential and radial vibration modes of the fluid in the pipe) and the vibration mode of the pipe wall do not attenuate, and maintain a large pressure fluctuation. ing.

This is, as shown in FIGS. 3A and 3B,
The primary (n = 1) and secondary (n = 2) modes of the circumferential vibration mode of the pipe wall are the circumferential primary (n = 1, m = 1) and secondary of the higher-order acoustic mode of the fluid in the pipe. (N = 1, m =
Mode 1) has a coupled relationship that stimulates each other. When the pressure in the pipe is high, the pipe wall expands, and when the pressure in the pipe is low, coupled vibration occurs in which the pipe wall shrinks and is transmitted to the downstream side without damping. It is because of that.

The frequency of the coupled vibration is expressed by equation (1) representing the frequency of the higher-order acoustic mode of the fluid in the pipe, and the frequency obtained from the solution of equation (2) in which the pipe wall vibration is approximated by a thin cylindrical shell. Are obtained as the vibration frequency in the case where they coincide with each other including the wave number in the axial direction.

[0012]

(Equation 1)

Here, Ca: sound velocity of the fluid in the pipe γi: radius of the pipe inner wall Umn: 2Jn (x) / 2x = 0 mth root Jn (x): n-order first-type Bessel function Kz: wave number in the pipe axis direction

[0014]

(Equation 2)

R: average pipe radius ρ: density of the pipe material E: Young's modulus of the pipe material Kz: wave number in the pipe axis direction h: wall thickness of the pipe n: mode in the pipe circumferential direction ν: Poisson's ratio of the pipe material

This coupled vibration mode is shown in FIGS.
As shown in (1), the vibration mode of the pipe wall and the pressure vibration mode of the fluid in the pipe (the thick part has a high pressure and the thin part has a low pressure) coincide with each other including the axial wavelength. The axial wavelength is represented by the following equation by the axial wave number kz.

(Axial wavelength) = 2π / kz

FIG. 5 shows that the fluid in the pipe is steam (sound speed 500 m /
Second), the axial wavelength of the coupled vibration is scheduled 40
This is an example in which the abscissa represents the inner diameter of a steel pipe having a thickness of.

As is apparent from the above description, the wavelength in the circumferential direction and the axial direction of the coupled vibration of the higher-order acoustic mode of the pipe and the vibration mode of the pipe wall to be suppressed by the present invention depend on the inner diameter of the pipe and the inside of the pipe. It has characteristics that depend on the sound speed of the fluid.

The source of vibration of the pipe is caused by the turbulence of the flow generated at the throttle portion of the steam valve. The vibration source of the steam valve is connected to the downstream pipe of the steam valve so that the vibration is not propagated from the steam valve to the downstream pipe. By installing a device for preventing vibration in the valve or by installing a device for preventing vibration integrally with the valve seat of the steam valve, it is possible to prevent piping vibration.

Further, the present invention is preferably configured such that the anti-vibration element extends along the axial direction and the inner diameter gradually increases.

Further, in the present invention, preferably, the vibration preventing element has an axial length larger than an inner diameter of the downstream pipe.

Further, in the present invention, preferably, the vibration preventing element has a cross-sectional shape different from the cross-sectional shape of the outlet of the steam valve or the cross-sectional shape of the inlet of the outlet-side pipe in an intermediate region thereof.

Further, the present invention is preferably configured such that the vibration preventing element has a cross-sectional center eccentric with respect to the center of the steam valve or the center of the downstream pipe in an intermediate region thereof.

Further, the present invention relates to a piping device in which a steam valve for controlling the amount of steam flowing into a downstream high-pressure device is interposed in a pipe through which high-pressure steam flows, and a vibration prevention is integrally provided with a valve seat of the steam valve. An element is provided to prevent generation of vibration in the downstream pipe due to disturbance of the high-speed fluid generated in the throttle section of the steam valve.

The present invention is also preferably configured such that the anti-vibration element gradually increases in inner diameter along the axial direction.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In FIG. 1, a steam valve 2 connected to an upstream pipe 1 on the inlet side accommodates a valve body 3 for adjusting the amount of steam therein. A valve seat 4 is provided at a position facing the valve body 3. Further, an insert pipe 5 which is a vibration preventing element is provided in connection with the valve seat 4.
Further, a downstream pipe 6 connected to the downstream high-pressure equipment at the other end is connected to the insert pipe 5. The outlet of the valve seat 4 has the same diameter as the inlet of the insert pipe 5, and the outlet of the insert pipe 5 and the inlet of the downstream pipe 6 have the same diameter. The insert tube 5 is configured such that the inner diameter gradually increases in the axial direction.

This embodiment has the above-described structure, and the valve seat 4
Since the inner diameter of the insert tube 5 extending from the outlet of the inner tube gradually increases along the axial direction, the coupled frequency continuously changes and attenuates without leaving a specific frequency component. The component of the coupled frequency of the side pipe 6 itself does not propagate from the steam valve 2 to the downstream pipe 6, and as a result, the vibration of the downstream pipe 6 can be suppressed.

(Embodiment 2) Another embodiment of the present invention will be described. In FIG. 6, an insert pipe 7 as a vibration preventing element has an axial length L longer than an inner diameter D of the downstream pipe 6. The outlet of the valve seat 4 and the inlet of the insert pipe 7 keep the same diameter, and the outlet of the insert pipe 7 and the inlet of the downstream pipe 6 keep the same diameter.

The present embodiment is configured as described above, and the inner diameter is gradually increased in the axial direction. Therefore, the coupled frequency changes continuously and attenuates without leaving a specific frequency component. The component of the coupled frequency of the downstream pipe 6 itself does not propagate from the steam valve 2 to the downstream pipe 6, and the downstream pipe 6
Vibration can be suppressed. Also, insert pipe 7
Since the length L in the axial direction is larger than the inner diameter of the downstream pipe 6, the disturbance of the flow generated in the steam valve 2 is not directly transmitted to the downstream pipe 6. As described above, all the specific frequency components are attenuated, and the flow disturbance due to the shock wave is small, so that the vibration of the downstream side pipe 6 can be surely suppressed.

(Embodiment 3) Another embodiment of the present invention will be described. In FIG. 7, the insert tube 8 of the present embodiment is formed in a circular shape with the outlet of the valve seat 4 and the inlet of the insert tube 8 maintaining the same diameter (see FIG. 7B). The inlet of the downstream pipe 6 has the same diameter and is formed in a circular shape (see FIG. 7D), but the intermediate region is formed in a square shape as shown in FIG. 7C.

In this embodiment, the insert tube 8 has the above-mentioned structure, and the cross-sectional shape of the insert tube 8 changes from a circular shape to a square shape, and further from a square shape to a circular shape as the inner diameter gradually increases. And the coupled frequency also changes continuously, so that a specific frequency component is attenuated without remaining, and the component of the coupled frequency of the downstream pipe 6 itself propagates from the steam valve 2 to the downstream pipe 6. No downstream piping 6
Vibration can be reliably suppressed.

(Embodiment 4) Another embodiment of the present invention will be described. In FIG. 8, an insert pipe 9 as a vibration preventing element is constituted by a pipe joint having a bent portion. The outlet of the valve seat 4 and the inlet of the insert pipe 9 keep the same diameter, and the outlet of the insert pipe 9 and the inlet of the downstream pipe 6 keep the same diameter. That is, the inner diameter of the insert pipe 9 having the bent portion gradually increases while reaching the downstream pipe 6.

The present embodiment has the above-described structure, and since the cross-sectional shape is changed by the insert tube 9 having the bent portion, the frequency of the higher-order acoustic mode changes at each stage, and the coupled frequency also changes continuously. Therefore, the above-described Embodiment-3
Similarly to the above, the specific frequency component is attenuated without remaining, whereby the vibration of the downstream pipe 6 can be surely suppressed.

(Embodiment-5) Further, another embodiment will be described. 9A, in the insert pipe 10 of the present embodiment, the outlet of the valve seat 4 and the inlet of the insert pipe 10 have the same diameter, and the outlet of the insert pipe 10 and the inlet of the downstream pipe 6 have the same diameter. However, as shown in FIG. 9B, the intermediate region is configured to have a cross-sectional center that is eccentric with respect to the centers of the steam valve 2 and the downstream pipe 6, and the cross-sectional shape is It changes continuously in the axial direction.

In this embodiment, the insert pipe 10 extending from the outlet of the valve seat changes its cross-sectional shape toward the downstream pipe 6, so that the coupled frequency changes continuously, and the specific frequency component is changed. Is attenuated without remaining,
The component of the coupled frequency is not transmitted from the steam valve 2 to the downstream pipe 6, and the vibration of the downstream pipe 6 can be suppressed.

(Embodiment-6) Further, another embodiment will be described. In FIG. 10, the insert pipe is not used in the present embodiment, and a part of the valve seat 11 is incorporated in the steam valve 2 as a vibration preventing element integrally formed. The valve seat 11 is configured so that the outlet thereof and the inlet of the downstream pipe 6 maintain the same diameter, and the inner diameter is gradually increased along the axial direction.

The present embodiment has the above configuration, and the valve seat 1
Since the inner diameter of the section connected to the first outlet pipe 6 is configured to gradually increase in the axial direction, the coupled frequency can be continuously changed, and the same effect as in the first embodiment can be obtained. Is possible.

[0040]

As described above, according to the present invention, the vibration preventing element is provided at the connection between the steam valve and the downstream pipe.
The turbulence of the flow becomes large at the throttle portion of the steam valve, and it is possible to prevent high-frequency vibration from being generated in the downstream pipe.

Therefore, according to the present invention, damage to the piping can be prevented, and the safety of a power plant or the like can be improved.

[Brief description of the drawings]

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

FIG. 2A is a diagram for explaining coupled vibration between a higher-order acoustic mode and a tube wall. (B) is a graph for explaining the characteristics of coupled vibration.

FIG. 3A is a diagram for explaining a tube wall vibration mode.
(B) is a figure for explaining a high-order sound mode.

FIGS. 4A and 4B are diagrams for explaining coupled vibration.

FIG. 5 is a characteristic diagram showing an axial wavelength distribution of coupled vibration in a pipe.

FIG. 6 is a cross-sectional view showing another embodiment of the present invention.

FIG. 7A is a sectional view of a piping device. (B) is sectional drawing which follows the AA line of (a). (C) is sectional drawing which follows the BB line | wire of (a). (D) is sectional drawing which follows CC line of (a).

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

FIG. 9A is a cross-sectional view of a piping device. (B) is sectional drawing which follows the DD line of (a).

FIG. 10 is a sectional view showing another embodiment of the present invention.

FIG. 11 is a sectional view showing an example of a conventional piping device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upstream piping 2 Steam valve 4,11 Valve seat 5,7,8,9,10 Insert pipe 6 Downstream piping

Claims (7)

[Claims] 1. A piping device in which a steam valve for controlling the amount of steam flowing into a downstream high-pressure device is interposed in a pipe through which high-pressure steam flows, wherein a vibration preventing portion is provided at a connection portion of the steam valve with the downstream pipe. A piping device, comprising: an element for preventing the downstream pipe from vibrating due to turbulence of a high-speed fluid generated in a throttle portion of the steam valve. 2. The piping apparatus according to claim 1, wherein the vibration preventing element is configured so that an inner diameter gradually increases along an axial direction. 3. The piping device according to claim 2, wherein the vibration preventing element has an axial length larger than an inner diameter of the downstream pipe. 4. The vibration-preventing element according to claim 1, wherein the vibration-preventing element has a cross-sectional shape different from an outlet cross-sectional shape of the steam valve or an inlet cross-sectional shape of the outlet-side pipe in an intermediate region thereof. Plumbing equipment. 5. The anti-vibration element is configured to have a cross-sectional center eccentric to a center of the steam valve or a center of the downstream pipe in an intermediate region thereof. The described piping device. 6. A piping device in which a steam valve for controlling an amount of steam flowing into a downstream high-pressure device is interposed in a pipe through which high-pressure steam flows, wherein a vibration preventing element is integrally provided with a valve seat of the steam valve. A piping device for preventing vibration of the downstream pipe from being caused by disturbance of the high-speed fluid generated in the throttle portion of the steam valve. 7. The piping device according to claim 6, wherein the vibration preventing element is configured so that the inner diameter gradually increases along the axial direction.