JP2005155884A - Orifice body for decompression and valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an orifice body for decompression and a valve capable of sufficiently reducing cavitation action. <P>SOLUTION: This orifice body for decompression is mounted in a pipe where the fluid flows, has at least one through hole, and allows the fluid passing through the through hole to generate pressure loss. This orifice body for decompression has a mesh body in a state of covering at least a part of a cross-section of the pipe in a contraction flow part. In this valve comprising a throttle part inserted into a pipe in a casing, and a cross-sectional area adjusting means for adjusting a cross-sectional area of a through hole of the throttle part, a mesh body is mounted in a state of covering at least a part of the cross-section of the pipe at the contraction flow part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure-reducing orifice body that is disposed in a fluid pipe and gives pressure loss to the fluid, and a valve that adjusts the pressure and / or flow rate of the fluid.

  As a pressure reducing orifice body, a pressure reducing orifice body having a through-hole through which a fluid passes is provided in the center. FIG. 10 is a photograph of the state of the flow in the vicinity of the pressure reducing orifice body when such a pressure reducing orifice body is used and the incompressible fluid fills the pipe and flows. FIG. 11 is an explanatory diagram showing the situation. Furthermore, FIG. 12 shows the static pressure distribution in the central axis of the fluid. The horizontal axis in FIG. 12 is the dimensionless position of the decompression orifice body in the axial direction by the inner diameter D of the through hole 2 shown in FIG.

  As shown in FIG. 11, the fluid ejected from the through hole 2 continues to expand gradually while surrounding fluid is involved. In the case shown in this example, as shown in FIG. 12, the expansion continues to a downstream of about 8 times the inner diameter D of the through hole. Thereafter, in the case of turbulent flow, a flow having a substantially uniform velocity distribution over the tube cross section. It becomes.

  As shown in FIGS. 11 and 12, the static pressure is lower than the surrounding pressure because the flow velocity is high in the contracted portion. Furthermore, since the shearing force of the flow is locally increased, many vortices are generated in this contracted portion as shown in FIG. Of the vortices that are generated, the vortex that is thread-like is called a vortex. Particularly in the periphery of the orifice, the amount of vortex generation is large due to the large shearing force. When the center static pressure of the vortex becomes lower than the water vapor pressure, water vapor and contained air are generated as bubbles. Furthermore, when the vortex collapses due to the turbulence of the flow, the pressure of the fluid is recovered and the static pressure becomes higher than the water vapor pressure, so that the bubbles collapse. When such bubbles are generated and extinguished, an impact occurs, and if this impact propagates to the fluid and piping, inconveniences such as noise and vibration occur. Furthermore, when bubbles disappear, the impact propagates to the inner wall of the pipe, which causes a problem of erosion of the inner wall of the pipe. Hereinafter, these inconveniences may be collectively referred to as a cavitation action.

  For the purpose of reducing such cavitation action, Patent Document 1 discloses an orifice plate in which the inner diameter of a central through hole provided near the center is larger than the inner diameters of a plurality of peripheral through holes provided near the periphery. Yes. Thus, by providing a plurality of through-holes consisting of a central through-hole and a peripheral through-hole, and making the inner diameters different between the central through-hole and the peripheral through-hole, the pressure recovery position of the jet flow from each hole can be It can be dispersed in the axial direction, and by using the flow from the peripheral through-hole as a buffer material, it is possible to reduce the vibration of the pipe and the noise associated therewith.

  However, the pressure reducing orifice body disclosed in Patent Document 1 can reduce the vortex generation in the wake portion in the jet flow ejected from the central through hole, but has a porous structure in which a plurality of peripheral through holes are arranged. Therefore, the amount of vortex generation around the orifice increases. Therefore, a sufficient reduction effect of the cavitation action cannot be obtained.

  In addition, the valve is inserted in the fluid piping in order to adjust the pressure and / or flow rate of the fluid. This valve is usually provided with a throttle section having a variable cross-sectional area. In such a valve, when the cross-sectional area of the throttle portion is reduced by the operation of an adjustment cock or the like, the throttle portion performs the same function as the through hole of the pressure-reducing orifice body, thereby causing a problem of cavitation action. Therefore, also in the valve, it is desired to reduce the cavitation action as in the pressure reducing orifice body.

JP 2001-124280 A

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide a pressure reducing orifice body and a valve capable of sufficiently reducing the cavitation action.

  In order to achieve the above object, the present invention provides a pressure reducing orifice body that is installed in a pipe through which a fluid flows, has at least one through hole, and generates a pressure loss in the fluid that passes through the through hole. A decompression orifice body is provided in which a mesh body is disposed so as to cover at least a part of a pipe cross section in a contracted flow portion.

  Most of the fluid ejected from the through-hole is generated and disappears at the contracted portion. Therefore, in the contracted flow portion, the cavitation action such as noise and resonance becomes the largest due to the impact accompanying the generation and disappearance of the vortex. At this time, if the mesh body is arranged at the above position, the vortex generated in the contracted portion can be reduced, and the generated bubbles can be made into micro bubbles of about 1 mm or less, for example. Therefore, it has an effect in reducing the impact generated when large bubbles are generated and disappear. Furthermore, since the fluid containing bubbles has a property of absorbing the impact by the contraction and expansion of the bubbles, the fluid that has passed through the through hole remains even if the impact occurs due to the generation and disappearance of the bubbles. The microbubbles that act as a buffer material can reduce such an impact. Therefore, it is effective in reducing cavitation effects such as noise, resonance, and erosion of the inner wall of the pipe.

  Moreover, in this invention, it is preferable that at least one part of the pipe cross section in the said flow reduction part is at least one part of the said through-hole. That is, it is preferable that the mesh body is disposed so as to cover at least a part of the through hole. This is because it is relatively easy to dispose the mesh body in the through hole.

  Furthermore, in the present invention, it is preferable that the through hole has a central through hole provided in a central portion of the decompression orifice body and a peripheral through hole provided around the central through hole. This is because the velocity distribution of the fluid that has passed through the through hole can be flattened, so that the effect of suppressing the generation of vortices can be obtained.

  Furthermore, in the present invention, the orifice diameter ratio of the pressure reducing orifice body is preferably within a range of 0.001 to 0.2. This is because, outside the above range, the effect of reducing the cavitation action may not be sufficiently obtained.

  Furthermore, in the present invention, the opening area ratio of the mesh body is preferably 0.1 or more and less than 0.95. If the opening area ratio of the mesh body is smaller than the above range, the pressure loss when the fluid passes through the opening portion of the mesh body may be excessive, and if it exceeds the above range, the mesh body is caused by the fluid flow. This is because there is a risk of damage.

  In order to achieve the above object, the present invention is a valve comprising a throttle portion inserted in a pipe in a housing and a cross-sectional area adjusting means for adjusting a cross-sectional area of a through hole of the throttle portion. Thus, a valve is provided in which a mesh body is disposed so as to cover at least a part of a pipe cross section in the contracted flow portion.

  In the present invention, when the cross-sectional area of the through hole of the throttle portion is reduced by the cross-sectional area adjusting means, a plurality of vortices are generated in the fluid ejected from the through hole of the throttle portion. Most of these vortices are generated and disappear at the contraction. Therefore, in the contracted flow portion, the cavitation action such as noise and resonance becomes the largest due to the impact accompanying the generation and disappearance of the vortex. At this time, if the mesh body is arranged at the above position, the vortex generated in the contracted portion can be reduced, and the generated bubbles can be made into micro bubbles of about 1 mm or less, for example. Therefore, it has an effect in reducing the impact generated when large bubbles are generated and disappear. Furthermore, since the fluid containing bubbles has a property of absorbing the impact by the contraction and expansion of the bubbles, even if the impact occurs due to the generation and disappearance of the bubbles in the fluid that has passed through the through-hole of the throttle portion, The remaining microbubbles act as a cushioning material and can reduce such an impact. Therefore, it is effective in reducing cavitation effects such as noise, resonance, and erosion of the inner wall of the pipe.

  Moreover, in this invention, it is preferable that the opening area ratio of the said mesh body is 0.1 or more and less than 0.95. If the opening area ratio of the mesh body is smaller than the above range, the pressure loss when the fluid passes through the opening portion of the mesh body may be excessive, and if it exceeds the above range, the mesh body is caused by the fluid flow. This is because there is a risk of damage.

  In the pressure reducing orifice body and valve of the present invention, it is possible to reduce the cavitation action from the action caused by microbubbles, and to prevent the occurrence of inconveniences such as noise, vibration and erosion of the inner wall of the pipe. Play.

  The pressure-reducing orifice body and valve of the present invention will be described below.

A. The decompression orifice body The present inventors observed the occurrence of cavitation action with a high-speed video camera in the decompression orifice body having a through hole near the radial center of the decompression orifice body, and generated cavitation noise. The following knowledge was acquired by measuring.

  From the photograph shown in FIG. 10, it can be seen that most of the vortex generated in the jet ejected from the through-hole formed in the decompression orifice body is generated and disappears in the contracted portion. Moreover, when the noise simultaneously recorded with the microphone was reproduced in synchronization with the image, it was found that the larger the vortex, the greater the generated noise.

  In addition, bubbles generated by vortices such as vortex yarn almost disappear at the end of the constricted part where the pressure of the jet that has passed through the through hole is restored. It is difficult to be crushed, and the impact caused by the disappearance of bubbles is difficult to occur. In addition, microbubbles that remain without disappearing flow away downstream, but fluids containing bubbles generally absorb shocks by the contraction and expansion of bubbles, so if a large amount of bubbles remain, cavitation It is thought that the action can be attenuated.

  The present invention has been completed based on the above knowledge, and by reducing the vortex generated in the fluid that has passed through the through-hole, it is possible to reduce the cavitation effect by making the bubble generated by the vortex into a microbubble. It is what.

  FIG. 1 is a schematic cross-sectional view in a plane including an axial direction in a pipe in which an example of the pressure reducing orifice body of the present invention is arranged, and FIG. 2 is a cross-sectional view taken along the line I-I shown in FIG. It is a schematic sectional drawing.

  In the example shown in FIG. 1, one through hole 2 is formed in the center of the pressure reducing orifice body 1. Further, the mesh body 3 is fixed to the mesh body fixing portion 4 and arranged at the downstream edge 1 b that is the outlet end of the decompression orifice body 1. By arranging the mesh body 3 in this way, the entire through-hole 2 is covered with the mesh body 3 as shown in FIG. Therefore, since the fluid flowing in the direction of the arrow shown in FIG. 1 passes through the through-hole 2 and further passes through the mesh body 3, the vortex generated in the fluid can be divided and reduced. The generated bubbles can be microbubbles.

  FIG. 13 is a photograph of the flow around the pressure-reducing orifice body of the fluid that fills the piping and uses the pressure-reducing orifice body of the present invention. From the photograph shown in FIG. 13, it can be seen that the generation of large vortices was not observed and a large amount of microbubbles were generated, so that the vortices generated in the fluid that passed through the through holes could be reduced. Furthermore, it has been found that the effect of reducing the generation rate of vortex yarn can be obtained.

  Hereinafter, the decompression orifice body of the present invention will be described in detail separately for a mesh body and a through hole.

1. First, the mesh body in the present invention will be described.

  The mesh body used for the pressure reducing orifice body of the present invention is disposed so as to cover at least a part of the pipe cross section in the contracted portion.

  Most of the fluid ejected from the through-hole is generated and disappears at the contracted portion. Therefore, in the contracted flow portion, the cavitation action such as noise and resonance becomes the largest due to the impact accompanying the generation and disappearance of the vortex. At this time, if the mesh body is arranged at the above position, the vortex generated in the fluid that has passed through the through hole can be divided and reduced, so that the bubble generated by the vortex can be a microbubble of about 1 mm or less, for example. . Therefore, generation | occurrence | production of a big bubble can be suppressed and it has an effect in the reduction of the impact which arises when a big bubble is generated and extinguished. Furthermore, since the fluid containing bubbles has a property of absorbing the impact by the contraction and expansion of the bubbles, the fluid that has passed through the through hole remains even if the impact occurs due to the generation and disappearance of the bubbles. The microbubbles that act as a buffer material can reduce such an impact. Therefore, it is effective in reducing cavitation effects such as noise, resonance, and erosion of the inner wall of the pipe.

  As long as the mesh body used in the present invention can reduce the vortex generated in the fluid that has passed through the through-hole as compared with the case of the conventional decompression orifice body in which the mesh body is not installed, the mesh body is particularly suitable. There is no limitation.

  FIG. 3 is a graph showing the influence of the opening area ratio β on the resistance coefficient K of the mesh body used in the present invention. As shown in FIG. 3, the resistance coefficient K decreases as the opening area ratio β increases. Since the pressure loss increases as the resistance coefficient K increases, the opening area ratio β needs to be a numerical value within an appropriate range. In consideration of FIG. 3, the lower limit value of the opening area ratio β of the mesh body used in the present invention is preferably 0.1 or more. Further, the opening area ratio β is more preferably 0.3 or more, and further preferably 0.4 or more. If the opening area ratio β is smaller than the above range, the pressure loss when the fluid passes through the opening of the mesh body may become excessive, which is not preferable.

On the other hand, the upper limit of the opening area ratio β can be increased to such an extent that the mesh body is not damaged. Specifically, for example, a single circular _orifice: mesh body downstream face (diameter d 0 (m)) _(diameter: d b (m), the line center _pitch: p b (m), the lines constituting sheared When disposing the breaking stress σ _b (Pa)), the opening area ratio β of the mesh body preferably satisfies the following formula (2) as a condition satisfying the following formula (1). Note that the fluid density flowing through the orifice body is ρ (kg / m ³ ), and the fluid cross-sectional average velocity at the orifice is v ₀ (m / s).

  If the safety factor is 5, the mesh body opening area ratio β preferably satisfies the following formula (3).

円形以外の形状のオリフィス体や、非均一メッシュ体については、同様の強度計算により開口面積比βの上限値を規定する必要がある。式（１）〜式（３）を勘案すると、例えば直径４０ｍｍ程度のオリフィス体にメッシュ体を配置する場合、上限値は０．９５以下であることが好ましく、さらには０．８以下であることが好ましい。開口面積比βが上記範囲より大きくなると、流れによりメッシュ体が破損する恐れがあるからである。

For orifice bodies other than circular shapes and non-uniform mesh bodies, it is necessary to define the upper limit of the opening area ratio β by the same strength calculation. Considering the formulas (1) to (3), for example, when the mesh body is arranged on an orifice body having a diameter of about 40 mm, the upper limit value is preferably 0.95 or less, and more preferably 0.8 or less. Is preferred. This is because if the opening area ratio β is larger than the above range, the mesh body may be damaged by the flow.

  Here, the opening area ratio β means an area occupied by the opening portion of the mesh body. Specifically, an area of a predetermined range of the mesh body is defined as a mesh area So, and mesh lines occupied in the mesh area So When the projected area is Sm, it can be obtained by β = (So−Sm) / So.

  Further, the orifice wire diameter ratio γ (mesh body wire diameter / through hole inner diameter), which is the ratio of the wire diameter of the mesh body to the through-hole diameter, is in the range of 0.001 to 0.2, and in particular, 0.002. It is preferable to be within the range of ~ 0.1. This is because if it is outside the above range, the effect of reducing the cavitation action may not be sufficiently obtained.

  The through-hole diameter means the inner diameter when the cross-sectional shape of the through-hole is circular, and when the cross-sectional shape of the through-hole is a shape other than a circular shape, the through-hole diameter is a circle having the same cross-sectional area. It means the inner diameter of the case.

  Such a mesh body should just be arrange | positioned so that at least one part of the piping cross section in a flow reduction part may be covered, but it is arrange | positioned especially in at least one part of the area | region which is coaxial with a through-hole and has the same shape. It is preferable. For example, as shown in FIG. 11, the fluid that has passed through the through-hole 2 generates vortices in the contracted portion, but in the present invention, the mesh body is the contracted-flow portion and has the same shape as that of the through-hole. It is because the generated vortex can be effectively divided and reduced by being arranged in at least a part of the region. Moreover, in this invention, it is preferable that at least one part of the pipe cross section in the said flow reduction part is at least one part of a through-hole. Therefore, it is particularly preferable that the mesh body is disposed so as to cover at least a part of the through hole. This is because it is relatively easy to dispose the mesh body in a part of the through hole, and the vortex generated in the fluid that has passed through the through hole can be more effectively divided and reduced.

  Here, being arranged so as to cover at least a part of the through hole means that, for example, as shown in FIGS. 4A and 4B, the through hole 2 has a single or plural through holes 2. The case where it arrange | positions in all the area | regions, and the case where it arrange | positions only to a part of through-hole 2 as shown in FIG.4 (c) may be sufficient.

  In the present invention, the pipe cross section in the contracted portion means, for example, the inner diameter region of the pipe 10 as shown in FIGS. 1 and 2, and the through hole 2 is included in the inner diameter region of the pipe 10. ing.

  When the mesh body is disposed so as to cover at least part of the through hole, the area of the through hole in which the mesh body is disposed has an effect of reducing the vortex generated in the fluid that has passed through the through hole. If it is, it will not specifically limit, Specifically, the area of the through-hole in which the mesh body is arrange | positioned with respect to the total cross-sectional area of a through-hole is in the range of 1%-100%, especially 10%-100 % Is preferable. Furthermore, if the area to be arranged is the same, it is more preferable that the area is arranged on the outer peripheral side of the through hole. If the portion where the mesh body is disposed in the through hole is in the above range, the effect of reducing the vortex can be sufficiently obtained, generation of large bubbles can be suppressed, and impact caused by generation and disappearance of bubbles can be reduced. be able to. In addition, since a sufficient amount of microbubbles can be present in the fluid, it is effective in reducing the cavitation action.

  Further, the number of mesh bodies to be arranged is not particularly limited as long as it can be arranged so as to cover at least a part of the pipe cross section in the contracted portion. As shown in FIG. 1, one sheet or a plurality of sheets may be used. It is determined appropriately in consideration of the state of the vortex generated, the shape of the through-hole to be formed, the pressure loss of the fluid, and the like. For example, as shown in FIG. 5, when a plurality of mesh bodies 3 are arranged in the axial direction of the decompression orifice body 1, the effect of reducing the vortex can be obtained more sufficiently.

  Furthermore, if the position which arrange | positions a mesh body is a contraction part, it will not be specifically limited. As described above, most of the fluid ejected from the through hole is generated and disappears at the contracted portion. Therefore, the cavitation action such as noise and resonance becomes the largest in the contracted portion. At this time, if a mesh body is arranged in the contracted flow portion, generation of large bubbles can be suppressed, so that an impact caused by generation and disappearance of large bubbles can be reduced. Furthermore, since a sufficient amount of microbubbles can remain in the contracted flow portion, even when an impact occurs due to the generation and disappearance of bubbles, the impact can be reduced by contraction of the microbubbles. Among them, in the present invention, it is preferable to arrange a mesh body around the orifice. This is because it has a sufficient effect by reducing the cavitation action.

  Note that, as described above, the contracted flow portion here means that when the fluid that has passed through the through hole from the upstream edge of the pressure reducing orifice body expands in the radial direction of the pipe, the expansion ends and the pressure is reduced. It means the section to the position to recover. Furthermore, the orifice peripheral portion is a section from the upstream edge of the pressure reducing orifice body to the downstream edge of the pressure reducing orifice body, and 0.5 times the inner diameter of the through hole from the downstream edge in the axial direction of the pressure reducing orifice body. It means a range that combines with the previous section. As will be described later, when there are a plurality of through holes and the inner diameters of the respective through holes are different, the area around the orifice is different for each through hole.

  Specifically, in the example shown in FIG. 11 and FIG. 12, the contracted flow portion is a position where the fluid that has passed through the through-hole 2 continues to contract from inertia and then gradually expands, and is about 8 times the inner diameter D of the through-hole. Thus, since the pressure recovers, the range from the upstream edge 1a of the pressure reducing orifice body 1 to the position about 8 times the through-hole inner diameter D is applicable.

  Specifically, as shown in FIG. 6, as an example of installing the mesh body around the orifice, the upstream edge 1a of the pressure reducing orifice body 1, the inside of the through hole 2, the downstream edge 1b of the pressure reducing orifice 1, The case where it provides in the area within 0.5 times the internal diameter of a through-hole from a downstream edge from the downstream edge 1b of the orifice body 1 for pressure toward the axial direction of the orifice body 1 for pressure reduction, etc. can be mentioned.

  Further, the method for fixing the mesh body to the decompression orifice body is not particularly limited as long as it can be stably fixed. Specifically, a method of fixing using a fixing tool or the like, or as shown in FIG. 1, a mesh body fixing portion 4 for fixing the mesh body 3 to the pressure reducing orifice body 1 is provided in advance, and the mesh body fixing portion 4 A method of fixing the mesh body 3 by arranging the mesh body 3 can be used.

2. Through hole Next, the through hole will be described.

  In the present invention, the number of through holes is not particularly limited as long as at least one through hole is formed in the pressure reducing orifice. For example, one may be used as shown in FIG. 7, or a plurality may be used as shown in FIG.

  In the case of providing a plurality of through holes, as shown in FIG. 8A, a central through hole 2a, which is a through hole located at the radial center of the pressure reducing orifice 1, is provided, and the periphery of the central through hole 2a is provided. When providing a plurality of peripheral through-holes 2b, which are through-holes located in the area, as shown in FIG. 8B, when arranging the peripheral through-holes 2b so as to form a plurality of circles, as shown in FIG. 8C. As shown in FIG. 8D, when the through holes 2 having various shapes are irregularly arranged, a circle is drawn concentrically around the central through hole 2a provided at the center of the pressure reducing orifice 1. For example, the peripheral through hole 2b can be provided. Furthermore, as shown in FIG. 9, the case where the several through-hole 2 is each communicating can be mentioned.

  In the present invention, it is particularly preferable to provide a central through hole at the center in the radial direction of the decompression orifice body and provide a plurality of peripheral through holes so as to be located around the central through hole. This is because the velocity distribution of the fluid that has passed through the through hole can be flattened, and the effect of suppressing vortex generation can be obtained.

  Further, as described above, when the through hole is composed of the central through hole and the peripheral through hole, the inner diameter of the central through hole is preferably larger than the inner diameter of the peripheral through hole. As a result, the pressure recovery position in the fluid that has passed through the central through hole is different from the pressure recovery position in the fluid that has passed through the peripheral through hole, so that the positions where noise and vibration due to cavitation are generated can be dispersed. This is because it is effective in reducing the action.

  Furthermore, in the through hole in the present invention, the cross-sectional shape is not particularly limited as long as it does not hinder the passage of fluid. Specifically, as shown in FIGS. 7 and 8, various shapes such as a circle, a rectangle, a star, a cross, and a special shape are possible.

  Further, the shape of the inner wall of the through hole is not particularly limited. For example, as shown in FIG. 14 (a), a straight pipe shape whose cross-sectional area does not change from the upstream edge 1a side to the downstream edge 1b side, as shown in FIGS. 14 (b) and (c), the upstream edge side to the downstream edge side. As shown in FIG. 14 (d), the inner diameter of the through hole 2 in the central portion in the axial direction is the upstream edge 1a side and the downstream edge 1b. The venturi tube shape etc. which are larger than the internal diameter of the side can be mentioned. Among them, the tapered tube shape, the flow nozzle shape, and the venturi tube shape as shown in FIGS. 14B, 14C, and 14D are preferable because the amount of vortex generation can be reduced. In particular, a flow nozzle shape as shown in FIG.

  Furthermore, as shown in FIG. 14A, the flow direction of the fluid passing through the through-hole 2 is changed as shown in FIG. 14E, not only in the case of a straight hole that does not change the flow direction. An oblique hole may be used.

B. Valve Next, the valve of the present invention will be described.

  FIG. 16 is a schematic view showing an example of the valve 20 of the present invention. As shown in FIG. 16, the valve 20 includes a pipe 22, a throttle portion 23, and a mesh body 25 in a housing 21. Both ends of the piping 22 are connected to piping outside the valve 20. The throttle portion 23 is inserted in the pipe 22. The throttle portion 23 has a through-hole having a variable cross-sectional area inside. The through hole of the throttle portion 23 is a portion where the cross-sectional area with respect to the fluid flow direction is the smallest in the valve 20. In this example, the mesh body 25 is fixed to the outlet end of the throttle portion 23. By arranging the mesh body 25 in this way, vortices generated in the fluid that has passed through the throttle portion 23 can be divided and reduced. Therefore, bubbles generated from the vortex can be made into microbubbles.

  An adjustment cock 24 is connected to the throttle portion 23. A handle portion of the adjustment cock 24 is disposed outside the housing 21. When the handle portion of the adjustment cock 24 is operated by the user, the cross-sectional area of the through hole of the throttle portion 23 changes, and the flow rate and pressure of the fluid passing through the valve 20 increase or decrease. The adjustment cock 24 corresponds to a cross-sectional area adjusting means.

  Hereinafter, the valve of the present invention will be described in detail for each of the mesh body, the through hole of the throttle portion, the cross-sectional area adjusting means, and the housing.

1. First, the mesh body in the present invention will be described.

  The mesh body used for the valve of the present invention is arranged so as to cover at least a part of the pipe cross section in the contracted portion.

  The mesh body of the present invention has an operation similar to that of the above-described pressure-reducing orifice body. Therefore, the position at which the mesh body is disposed in the contracted portion, the ratio of the area covered with the pipe cross section (opening area ratio), the ratio of the mesh body wire diameter to the through hole diameter (mesh body wire diameter / through hole diameter) The area of the through hole in which the mesh body is arranged is the same as that of the above-mentioned pressure reducing orifice.

2. Next, the through hole of the throttle part in the present invention will be described.

  In the present invention, one through hole of the throttle part is provided in the throttle part. The through hole of the throttle used for the valve of the present invention has a structure similar to that of the through hole 2 shown in FIG. Thereby, a vortex is generated in the fluid that has passed through the through hole of the throttle portion. In this case, the vortex generated in the fluid is divided and reduced by the mesh body fixed to the outlet end of the throttle portion. Therefore, bubbles generated from the vortex can be made into microbubbles. As a result, the cavitation action can be reduced.

  The through hole of the throttle portion in the present invention is common to the through hole of the pressure reducing orifice body in that the flow rate and pressure of the fluid are increased and decreased and the cavitation action is generated. The difference from the through hole of the decompression orifice body is that the cross-sectional area is variable and that one is formed in the valve.

  In the present invention, the contracted part is from the upstream edge of the through hole of the throttle part to a position about eight times the inner diameter of the through hole of the throttle part, and the mesh body covers at least a part of the contracted part. It suffices if they are arranged in such a manner. Further, in the present invention, the pipe cross section in the contracted part means, for example, a flow path in the throttle part, and the through hole of the throttle part is included in the flow path in the throttle part.

  The inner diameter Da of the through hole of the throttle part in the present invention is a hydraulic equivalent diameter expressed by Da = 4 × (cross-sectional area of the through hole of the throttle part) / (wetting edge length of the through hole of the throttle part). Defined. The cross-sectional area of the through hole in the throttle part and the wetting edge length of the through hole in the throttle part vary depending on the opening of the valve, but the inner diameter Da in the maximum opening state within the use condition range of the valve is set to The inner diameter.

3. Next, the cross-sectional area adjusting means in the present invention will be described.

  The cross-sectional area adjusting means in the present invention adjusts the cross-sectional area of the through hole of the throttle portion, and a cock or the like used for a normal valve can be used. For example, the adjustment cock 24 shown in FIG. 16 can be used, and an actuator that automatically changes the cross-sectional area of the through hole of the throttle portion by an actuator or the like may be used.

4). Case Next, the case in the present invention will be described.

  As the casing in the present invention, a casing used for a normal valve can be used, and the shape and the like are not particularly limited.

  As described above, in the valve of the present invention, the through hole of the throttle portion corresponds to the through hole of the orifice body, and the mesh body of the present invention corresponds to the mesh body of the pressure reducing orifice body. Therefore, the valve of the present invention can solve the same problems as those of the pressure reducing orifice body.

  In addition, this invention is not limited to embodiment mentioned above. The above-described embodiment is an exemplification, and it is the present invention that has substantially the same configuration as the technical idea described in the claims of the present specification and has the same effect. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(Example 1)
A pressure reducing orifice having a basic structure similar to that shown in FIG. 4A and having a mesh body disposed on the downstream edge so as to cover the entire central through hole was used under the conditions shown in Table 1 below. The pressure reducing orifice body was attached to a pipe having an inner diameter of 78 mm, and the noise when water passed through the pressure reducing orifice body was investigated. With respect to the orifice body for pressure reduction, the cross-sectional area of the through hole was 1257 mm ² and the average cross-sectional velocity of the orifice was 16.0 m / s.

  A microphone was installed at a position 10 mm away from the outer wall of the pipe, and cavitation noise was recorded. In addition, pressure measurement holes were provided in the tube wall at a position 160 mm upstream from the downstream edge of the pressure reducing orifice body and 800 mm away from the downstream side, and the pressure loss before and after passage of the fluid through the pressure reducing orifice body was also measured.

(Example 2)
Example 1 except that a pressure reducing orifice having a basic structure similar to that shown in FIG. 4B and having a mesh body disposed on the downstream edge so as to cover only the peripheral through hole under the conditions shown in Table 1 below. And the same.

(Example 3)
Except for using a pressure reducing orifice having a basic structure similar to that of FIG. 4B and having a mesh body disposed on the downstream edge so as to cover the entire central through hole and peripheral through hole under the conditions shown in Table 1 below. Was the same as in Example 1 above.

(Comparative Example 1)
As Comparative Example 1, as shown in FIG. 4A, the same procedure as in Example 1 was performed except that a pressure reducing orifice body having a single central through hole but not having a mesh body was used.

(Comparative Example 2)
As Comparative Example 2, as shown in FIG. 8 (a), it has the central through hole and a plurality of peripheral through holes provided in the periphery thereof, except that a pressure reducing orifice body without a mesh body was used. Same as Example 1.

(Evaluation)
Table 1 below shows the noise survey results of the orifices for pressure reduction in Examples and Comparative Examples. The mesh number shown in Table 1 represents the number of mesh divisions per inch. Furthermore, PCD in Comparative Example 2 in Table 1 is an abbreviation for pitch circle diamond, and indicates that the diameter of a circle formed by connecting the centers of the peripheral through holes is 70 mm.

  From the results shown in Table 1 above, it is clear that cavitation noise is reduced in Examples compared to Comparative Example 1 and Comparative Example 2. In both of the examples and the comparative examples, the pressure loss coefficient value, which is an index indicating the orifice pressure reduction capability, was in the range of 20 to 30 and was at a satisfactory level.

Example 4
Noise was investigated in the same manner as in Example 1 above. The inner diameter of the central through hole was changed within the range of φ30 mm, φ40 mm, the mesh body wire diameter of 340 to 1100 μm, and Mesh 5 to 16, and the mesh body was arranged close to the outlet of the central through hole.

(Evaluation)
FIG. 15 shows the test results. The horizontal axis represents the wire diameter ratio γ, and the vertical axis represents the noise reduction rate on the basis of the comparative example 1. The formula in FIG. 15 is an empirical formula obtained by the method of least squares. From this graph, it was found that the wire diameter ratio with the highest noise reduction rate was 0.0175. It can be seen that a noise reduction effect of approximately 1 dB or more can be obtained by setting 0.001 <γ.

In the pipe line in which an example of the decompression orifice object of the present invention is arranged, it is a schematic sectional view in the field including the axial direction. It is a schematic sectional drawing of the II arrow directional cross section shown in FIG. It is a graph which shows the influence of the opening area ratio which acts on the resistance coefficient of a mesh body. It is explanatory drawing which showed the example of arrangement | positioning of the mesh body in this invention. It is explanatory drawing which showed the example of arrangement | positioning of the mesh body in this invention. It is explanatory drawing which showed the example of arrangement | positioning of the mesh body in this invention. It is explanatory drawing which showed the example of the through-hole in this invention. It is explanatory drawing which showed the example of the through-hole in this invention. It is explanatory drawing which showed the example of the through-hole in this invention. It is the photograph which image | photographed the mode of the flow in the vicinity of the orifice for pressure reduction when the fluid filled the inside of a pipe line and flowed using the conventional orifice for pressure reduction. It is explanatory drawing which showed the mode of the flow of the vicinity of the pressure-reducing orifice body when the fluid was filled up and flowed in the pipe line using the conventional pressure-reducing orifice body. It is the graph which showed the change of the static pressure before and behind the through-hole of the fluid. It is the photograph which image | photographed the mode of the flow of the orifice body for pressure reduction when the fluid filled the inside of a pipe line and flowed using the orifice body for pressure reduction of this invention. It is explanatory drawing which showed the example of the shape of the inner wall of the through-hole in this invention. It is the graph which showed the result in Example 4. It is the schematic of the valve | bulb of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Orifice body for pressure reduction 2 ... Through-hole 3 ... Mesh body 10 ... Pipe 20 ... Valve 21 ... Housing 22 ... Pipe 23 ... Restriction part 24 ... Adjustment cock 25 ... Mesh body

Claims (7)

  In a pressure-reducing orifice body that is installed in a pipe through which a fluid flows and has at least one through hole and generates a pressure loss in the fluid that passes through the through hole, at least a part of the pipe cross section in the contracted portion is formed. An orifice body for pressure reduction, wherein a mesh body is disposed so as to cover.   The orifice body for decompression according to claim 1, wherein at least a part of a cross section of the pipe in the contracted flow part is at least a part of the through hole.   The said through-hole has a center through-hole provided in the center part of the said orifice body for pressure reduction, and the periphery through-hole provided in the circumference | surroundings of the said center through-hole. The orifice body for pressure reduction as described in 1.   4. The orifice body for pressure reduction according to claim 1, wherein an orifice wire diameter ratio of the orifice body for pressure reduction is within a range of 0.001 to 0.2. 5. .   The orifice body for decompression according to any one of claims 1 to 4, wherein an opening area ratio of the mesh body is 0.1 or more and less than 0.95. A valve provided with a throttle part inserted in a pipe in a housing, and a cross-sectional area adjusting means for adjusting a cross-sectional area of a through hole of the throttle part,
A valve characterized in that a mesh body is disposed so as to cover at least a part of a pipe cross section in a contracted flow portion. The valve according to claim 6, wherein an opening area ratio of the mesh body is 0.1 or more and less than 0.95.

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