JPH0223754B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a low-noise valve, and in particular to a valve that is slidably inserted into the cage to adjust the opening of a fluid control window provided on the peripheral wall of the cage. In a cage valve controlled by a valve plug, the generation of strong separation sound due to cavity resonance within the valve plug is prevented and noise is reduced.

[Prior Art] Conventionally, this type of cage valve has been constructed as shown in FIG. This will be briefly explained based on the figure. Reference numeral 1 denotes a valve body, and the inside thereof is partitioned into an upstream passage 3 and a downstream passage 4 by a partition wall 2.
Reference numeral 5 denotes an upper lid that is fitted into the upper open end of the valve body 1 and fixed with a plurality of bolts 6. Between the upper lid 5 and the partition wall 2, there is a seat formed in a cylindrical shape. A ring 7 and a cage 8 are arranged in a stacked manner. In this case, the seat ring 7 is fitted and fixed into a mounting hole 9 provided in the partition wall 2 via a packing 10, and the lower end opening communicates with the downstream passage 4. On the other hand, the cage 8 is inserted into the valve body 1 through the upper opening of the valve body 1, and the cage 8 is inserted into the valve body 1 through the upper opening of the valve body 1.
is pressed onto the seat ring 7.
A plurality of fluid control windows 11 are formed on the peripheral wall of the cage 8 so as to be equally spaced in the circumferential direction and have a shape according to desired flow characteristics and communicate the inside of the cage with the upstream passage 3 . In addition, in the inner hole of the cage 8,
A substantially cup-shaped valve plug 15 is slidably fitted to the lower end of a valve stem 14 that is slidably inserted into the through hole 13 of the upper lid 5 via a packing 12. An underwear seat 17 is provided at the lower end of the valve seat 17 to sit on a valve seat 16 provided at the upper end opening of the seat ring 7 when the valve seat 16 is fully closed. Further, an upper seating portion 19 is provided on the outer peripheral portion of the upper end of the valve plug 15 to sit on a valve seat 18 formed on the inner peripheral surface of the cage 8 . Valve plug 1
A cavity 20 provided inside the valve plug 5 and open to the bottom surface of the valve plug 15 forms a buffer chamber for equalizing the pressure acting on the bottom surface of the valve plug 15, thereby eliminating irregular and non-uniform pressure. The valve plug 15 is prevented from acting on the upper surface of the valve plug through the small hole 21 formed in the upper surface of the valve plug 15, thereby improving the balance state of the valve plug 15, in other words, stabilizing the valve stem force.

Note that 22 is a gasket interposed between the upper lid 5 and the cage 8.

With this configuration, when the valve stem 14 is moved up and down by the actuation of the drive unit by the automatic control device or by manual operation, the valve plug 5 moves integrally with the valve stem 14 and moves away from the cage from its outer peripheral wall. By changing the opening degree, that is, the opening area, of the fluid control window 11 of No. 8, the controlled fluid flows from the upstream flow path 3 through the fluid control window 11 and the seat ring 7 to the downstream flow path 4. flow rate is controlled.

[Problem that the invention seeks to solve]

However, when controlling the pressure and flow rate of a compressible fluid (air, steam, etc.) using a cage valve as described above, the pressure P ₁ in the upstream flow path 3 and the pressure in the downstream flow path 4 must be controlled. When the pressure ratio with P ₂ , that is, the valve pressure ratio P ₁ /P ₂ , exceeds the blockage point determined by the physical properties of the fluid and the jet enters the supersonic region, a strong separation sound is generated, as shown by the solid line in Figure 7. In some cases, the overall noise level may be significantly raised (about 10 _{dB )} so that the
(shows the case of 2.1MPa). This phenomenon occurs depending on the valve pressure ratio and valve lift. In other words, when the valve pressure ratio is in the range of about 2 to 7, the jet flow J (see Fig. 1)
This occurs in a valve lift range in which the length (up to the collision position, which is equal to the radius of the inner diameter of the cage 8) is about three times or more the jet diameter. Such a valve pressure ratio and valve lift range is also a range frequently used in normal valve use, and the problem is serious. Moreover, due to the mechanism of its generation, this separated sound occurs intermittently on the order of several seconds, and exhibits characteristics that are extremely unpleasant to recognize aurally.

The sound described here refers to the acoustic eigenmode that the valve plug cavity 20 originally has (this is determined from the eigenvalue by solving the wave equation in the cavity, and is generated in countless high-order modes). It is excited and generated as a result of one or more modes (existing) interfering with the jet, and 2 to 6 ^B
A cage-type valve with a large diameter generates an isolated sound on the order of several KHz, which is extremely unpleasant because it corresponds to the most sensitive band of hearing.

Next, the principle of generation of this separated sound will be described. As shown in FIG. 8, the jets J flowing into the cage 8 from each flow rate control window 11 collide at the center of the lower surface of the plug (C is the jet collision surface), but as a result, a broadband pressure wave (random acoustic wave) A is generated. This acoustic wave A naturally propagates into the plug cavity 20 adjacent to the top. Among these random acoustic waves, those that match the frequency of the plug cavity eigenmode actively excite the eigenmode of the cavity 20 (this is a so-called resonance phenomenon, and E indicates the excited cavity acoustic mode). Therefore, when the gas in the cavity 20 vibrates in its own unique posture, the pressure fluctuations stimulate the jet flow J. This stimulation is performed via acoustic waves B from the cavity 20 side. Originally, the jet J is sensitive to external stimuli, and is influenced depending on the flow conditions (Matsuha number of the jet and the ratio of the jet diameter to the jet length). As a result, the jet J takes a specific form and oscillates periodically. The pressure wave A propagates to the plug cavity 20 again due to the periodic collision phenomenon of the jet flow J in this manner. In this way, a feedback loop via acoustic waves is formed between the jet flow J and the valve plug cavity resonance mode, and a strong separation sound is generated.

In the case of a cage type valve, detailed research by the inventor of the present application has revealed that the jet flow J becomes vibrating and generates separation noise, particularly in the following two forms. FIG. 9 shows the region where the separated sound occurs for explanation. Note that here, d is the jet diameter, and l is the jet length.

Form (1) When the jet diameter is relatively large (3<l/d<4) and the valve pressure ratio is about 2 to 3 (region a in the figure). When a periodic stimulus is applied from the outside (ie, from the plug cavity side) to the shear layer where the jet and the surrounding gas mix, an organized large-scale vortex is formed. These vortices collide with each other at the center of the cage, generating pressure pulses (acoustic waves) that match the generation period of the vortices. In this case, the vortex generation frequency is = S _t ×
It is determined by U/d (where, is the frequency in KHz, S _t is the Stroh-Hal number, U is the jet speed m/S, and d is the jet diameter m), and is generated by taking S _t ≈0.3. In this case, the collision surface becomes a dipole sound source due to the jet jet form, and an acoustic mode that can be excited by the dipole sound source is selectively excited in the cavity, producing strong separated sound.

Form (2) When the diameter of the jet is small (l/d>4) (region b in the figure), the jet vibrates as if passing each other with the opposing jet in the section up to the collision surface. When the jet oscillates in this manner, a quadrupole sound source is also excited in the adjacent plug cavity in order to form a pressure field similar to a quadrupole sound source generated on the circular surface containing the jet. Only the eigenmodes of the eigenmodes are more likely to be excited, resulting in the growth of outstanding separated sound components.

Incidentally, in order to excite the acoustic eigenmode of the cavity 20, the collision position as an excitation source must necessarily be located at the center of the cage. Therefore, intermittent generation of separation sound appears due to the unsteadiness of moving from the center of the collision position to the periphery. When the diameter of the jet is very large or under conditions of high pressure ratio, the collision position is not stable at the center and no separation sound is generated.

Therefore, the problem we are trying to solve here is
This is about the separated sounds generated in areas a and b shown in FIG. If this component can be suppressed, the overall noise level in this area will be significantly reduced (approximately 10 dB)
This makes it possible to make the characteristics of the change in the noise level with respect to the pressure ratio monotonous, which is significantly advantageous from the standpoint of noise prediction.

Incidentally, there are known methods for preventing the generation of noise in cage type valves, such as Utility Model Publication No. 16968/1983 and Publication No. 23098/1989, but these all reduce the flowing energy of the controlled fluid. This has the disadvantage that when the downstream energy decreases, the valve capacity is reduced even though it is a large valve.

[Means for solving problems]

The low noise valve according to the present invention has been made to solve the above-mentioned problems, and its first purpose is to:
A valve comprising: a cylindrical cage having a fluid control window provided in a peripheral wall; and a cup-shaped valve plug slidably disposed within the cage and changing the opening degree of the fluid control window. The opening of the valve plug is closed by an acoustic resistance member that has air permeability and prevents transmission and reception of acoustic waves between the fluid to be controlled and the cavity within the valve plug.

A second object of the present invention is to provide a cylindrical cage having a fluid control window provided in a peripheral wall, and a cylindrical cage that is slidably disposed within the cage to change the opening degree of the fluid control window. In a valve equipped with a cup-shaped valve plug, the opening of the valve plug is controlled by an acoustic resistance member that has air permeability and prevents transmission and reception of acoustic waves between the controlled fluid and the cavity inside the valve plug. blocked,
In addition, the valve plug is filled with a noise-reducing filler.

[Effect]

In the present invention, the acoustic resistance member suppresses and prevents the exchange of acoustic waves between the controlled fluid and the valve plug cavity, thereby preventing the generation of separation sound.

In addition, in the present invention, the acoustic resistance member suppresses transmission and reception of acoustic waves, and the sound-deadening filling body suppresses resonance in the cavity within the valve plug, thereby further preventing the generation of separation sound and further increasing the sound-deadening effect. .

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a sectional view of the cage and valve plug used in the low-noise valve of the present invention, and FIG. 2 is a plan view of the acoustic resistance member. In these figures, the same constituent members and parts as in FIG. 6 are designated by the same reference numerals, and their explanations will be omitted. A valve seat 16 is formed below the fluid control window 11 on the inner circumferential wall of the cage 8, on which the lower seat portion 17 of the valve plug 15 is seated when the valve plug 15 is fully closed. This is by omitting the valve seat 16 of the seat ring 7 in the conventional structure shown in FIG. 6, and by fitting the lower end of the cage 8 into the mounting hole 9 of the partition wall 2, the seat ring 7 itself is eliminated. is possible. In other words, a part of the cage 8 constitutes a seat ring. Of course, the present invention is not limited to this, and it goes without saying that the cage shown in FIG. 6 may be used.

The lower end opening of the valve plug 15 is closed by an acoustic resistance member 30 that characterizes the present invention. This acoustic resistance member 30 is for cutting off the transmission and reception of acoustic waves between the jet flow flowing into the cage 8 from the fluid control window 11 and the valve plug cavity 20, and is shown in FIGS. As shown in the figure, it has sufficient air permeability because it is constructed of small-mesh wire mesh, porous plates, etc. This is necessary because the cavity 20 equalizes the pressure acting on the bottom surface of the valve plug 15 as described above, and prevents irregular and non-uniform pressure from acting on the top surface of the valve plug through the small hole 21. be done. In this case, the porous plate has a larger surface area that receives pressure than the wire mesh, and the cavity 2
In order to reduce the surface area of the surface, that is, the surface facing the inside of the cage 8, as much as possible, the shape of the small hole 31 is changed to a pyramidal shape as shown in FIG. It is desirable that they be kept close to each other. It is also desirable that the plate thickness be thin. The peripheral edge of the acoustic resistance member 30 is fixed to the lower end opening of the valve plug 15 by brazing or the like. The mounting position of the acoustic resistance member 30 is desirably such that the distance d from the lower end surface of the valve plug 15 is small;
0 and the inner surface of the cage from the resistance member 30 to the lower end of the valve plug 15.
This is to prevent resonance with unstable waves caused by collisions between jets, which has the same effect as the cavity 20.

Thus, according to the cage valve having such a configuration, the acoustic resistance member 30 prevents the propagation of periodic disturbances of high gain generated by the collision of the jet J to the cavity 20, so that the interaction between the jet J and the cavity 20 is prevented. A feedback loop system via acoustic waves is not formed between the valve plugs and, therefore, generation of separation noise due to the cavity within the valve plug can be suppressed or reduced.
Further, since the acoustic resistance member 30 has sufficient air permeability, the function of the cavity 20 as a buffer chamber is not deteriorated.

In fact, when we conducted an experiment using a cage valve with the above configuration, we found that the noise level of the cage valve was at a valve pressure ratio (P ₁ /P ₂ ) of about 2 to 7, as shown by the dashed line in Figure 7. It was confirmed that the noise was reduced by approximately 10 dB, and a low-noise cage valve could be obtained.

FIG. 4 is a sectional view of a cage and a valve plug showing another embodiment of the invention. This example is valve plug 1
5 is closed with an acoustic resistance member 30 similar to the above embodiment, and the cavity 20 is filled with a sound-deadening filler 35 made of a metal scrubber. The sound-absorbing filler 35 is not limited to a metal scrubber, but it is also possible to use short and small tube pieces 36 shown in FIG. Similarly to the acoustic resistance member 30, any material may be used as long as it does not reduce the function of the cavity 20 as a buffer chamber.

In such a configuration, the sound deadening filler 35
Since this directly suppresses and prevents the resonance of the cavity 20 due to fluid disturbance, this embodiment has the advantage of further reducing noise compared to the embodiment shown in FIG. The broken line in FIG. 7 shows the overall noise level due to the structure of this embodiment.

Although the present invention has been explained based on the theory for compressible fluids, the present invention is not limited to this and is applicable to incompressible fluids as well.

〔Effect of the invention〕

As explained above, the low noise valve according to the present invention has
Since the opening of the valve plug is closed with a breathable acoustic resistance member, it is possible to prevent the transmission and reception of acoustic waves between the jet flowing into the cage and the cavity inside the valve plug. A low-noise valve can be provided without generating separation sound. Also,
According to the present invention, the valve plug is filled with a sound-deadening filler to suppress the resonance of the cavity within the valve plug itself, thereby further improving the valve-muffling effect and realizing quiet operation. Moreover, as a result of suppressing the generation of separation sound, the noise level has a characteristic that changes monotonically over the entire pressure ratio, which is very advantageous from the standpoint of noise prediction.

In addition, it has a simple structure and is easy to manufacture.
It is possible to provide an inexpensive low-noise valve.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a cage and a valve plug showing one embodiment of a low noise valve according to the present invention, and FIGS.
The figures are a plan view and a sectional view of the acoustic resistance member, FIG. 4 is a sectional view of a cage and a valve plug showing another embodiment of the present invention, and FIG. 5 is a perspective view showing another embodiment of the sound-absorbing filling body. Figure 6 is a sectional view showing a conventional cage valve, Figure 7 is a diagram showing the relationship between valve pressure ratio and noise level, Figure 8 is a diagram showing the mechanism of separation sound generation, and Figure 9 is separation FIG. 3 is a diagram showing an area where sound is generated. 1... Valve body, 2... Partition wall, 3... Upstream flow path, 4
...Downstream flow path, 7...Seat ring, 8...Cage,
DESCRIPTION OF SYMBOLS 11... Fluid control window, 15... Valve plug, 20... Cavity, 30... Acoustic resistance member, 35... Sound deadening filling body.

Claims (1)

[Scope of Claims] 1. A cylindrical cage having a fluid control window provided in a peripheral wall, and a cup-shaped valve slidably disposed within the cage to change the opening degree of the fluid control window. In a valve equipped with a plug, having ventilation,
A low-noise valve characterized in that an opening of the valve plug is closed by an acoustic resistance member that prevents transmission and reception of acoustic waves between a controlled fluid and a cavity within the valve plug. 2. A valve comprising a cylindrical cage having a fluid control window provided on a peripheral wall, and a cup-shaped valve plug slidably disposed within the cage and changing the opening degree of the fluid control window. , has breathability,
The opening of the valve plug is closed by an acoustic resistance member that prevents transmission and reception of acoustic waves between the controlled fluid and the space inside the valve plug, and the valve plug is filled with a noise-reducing filler. Low noise valve.