JP2009036372A - Control valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve element structure and a cavitation preventer structure for a butterfly valve for suppressing the occurrence of cavitation. <P>SOLUTION: This control valve comprises an approximately cylindrical valve body 2, and a valve element 3 arranged in the valve body 2 for opening/closing a flow path, wherein a valve seat 205 on which the valve element 3 is seated is located eccentric to the center of a valve rod 5 in the flowing direction of fluid and the center of the valve rod 5 is located at a double eccentric position eccentric to the direction perpendicular to the flow-down direction of the fluid and to the downstream side in the flow-down direction of the fluid. Around a nozzle-side edge portion 309 on the upstream-side face of the valve element 3, an upstream-nozzle-side raised portion 310 is formed which is raised toward the upstream side into a relatively large hill shape. The downstream-side face of the valve element is inclined around the valve rod 5 at 5-20° clockwise to a seal face where the valve seat 205 abuts on a valve element valve seat 302. An orifice-side edge portion of the valve element 3 is swollen outward in the radial direction, relative to the nozzle-side edge portion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cavitation breaker for preventing cavitation disposed on a path of piping through which a fluid flows, and in particular, the cavitation breaker has cavitation suppression and has a high differential pressure and high flow rate control. TECHNICAL FIELD The present invention relates to a control valve including an eccentric butterfly valve having high pressure and pressure controllability, and a cavitation preventing body having cavitation prevention arranged at a position immediately downstream of the eccentric butterfly valve.

  When a normal valve arranged on a piping path for fluid flow is used as a liquid phase fluid, if the differential pressure between the upstream side and the downstream side of the valve increases, the pressure immediately after the downstream side of the valve Tends to fall below the saturated vapor pressure, and cavitation is likely to occur. Cavitation occurs in the downstream area of the pressure drop point, also called the bena contractor, which is below the saturated vapor pressure, generating cavitation bubbles, and by collapsing the bubbles in the downstream area of the valve to generate impact pressure. In addition to causing noise and vibration, the inner surface of the valve body and piping may be damaged. This phenomenon occurs more conspicuously, especially when the valves arranged on the piping path are butterfly valves or ball valves, because the pressure recovery when these valves are used is large.

  There are various types of valves arranged on the piping path. Generally, control valves for controlling the flow rate and pressure add resistance to the flow of fluid to flow down, and the flow rate and pressure are controlled. The downstream pressure can be controlled. When the fluid passes through the valve, a contracted portion is generated at the valve portion, and the contracted flow contracted most immediately at the position immediately after the valve, thereby increasing the flow velocity in the region and reducing the pressure in the region. In addition to this, for example, in the case of a butterfly valve, a vortex flow is generated near the downstream surface of the valve body, and a low pressure portion is generated inside the vortex, so that a situation in which cavitation is likely to occur is created. In addition, the greater the pressure difference between the upstream side and downstream side of the valve, that is, the higher the differential pressure, the greater the pressure drop at the pressure drop point, making it more difficult to suppress the occurrence of cavitation and control the flow characteristics. become.

  It is known that cavitation is less likely to occur in a valve that is less likely to recover pressure because the amount of pressure drop in the bena contractor differs depending on the valve type and valve structure even if the pressure difference is the same. Pressure recovery is defined by a valve-specific value called a pressure recovery coefficient, and cavitation is less likely to occur as this value increases. For example, the values are about 0.8 for the globe valve, about 0.65 for the butterfly valve, and about 0.55 for the ball valve, and the globe valve is less prone to cavitation than the butterfly or ball valve.

  For this reason, the means that have been used to suppress cavitation in the past have been designed to select a valve type with a high pressure recovery coefficient and to obtain higher controllability among the valve types. The valve had a high pressure recovery coefficient value. In addition, as a means for suppressing cavitation, for example, the technique of Patent Document 1 disclosed by the present applicant can be cited. In the technique of Patent Document 1, by providing a plurality of comb teeth at predetermined positions on the surface of the valve body in the central butterfly valve, the fluid is changed into a fine jet flow, and cavitation generated on the downstream side of the valve body is dispersed. It is configured to suppress cavitation growth.

  In addition, as a means for suppressing the occurrence of cavitation, for example, as disclosed in Patent Document 2, a ball valve and a porous plate are provided side by side, and in addition to the pressure loss at the ball valve, the pressure at the porous plate There is a technique of suppressing cavitation by adding pressure loss and dispersing pressure loss. The valve of Patent Document 2 is provided with a cavitation resistance characteristic by providing a fluid buffering portion formed by penetrating a plurality of holes through which fluid can pass on either or both of the upstream side and the downstream side of the valve body. It is something that has

  On the other hand, the control valve has a flow control for its purpose, and the flow controllability depends on the flow characteristic specific to the valve. As a means of expressing the flow characteristics, there is an inherent flow characteristic that displays the flow rate relative to the valve opening as a percentage when the differential pressure before and after the valve is constant. A typical control characteristic is a large flow rate in a small valve opening region. There is a quick open characteristic in which the change of Cv appears, a Cv linear characteristic in which the Cv value and the valve opening degree change in direct proportion, or an equal percentage characteristic in which the flow rate% and the valve opening% change logarithmically. Varies greatly depending on the valve structure. For example, in the case of a normal center type butterfly valve, an equal percentage characteristic is exhibited at a valve opening of 60 ° or less, and an eccentric type butterfly valve exhibits a quick open characteristic in which the flow rate temporarily increases when the valve is opened. Therefore, there is a tendency that the controllable range tends to be narrow, and it is necessary to select a valve having a characteristic suitable for the intended use. Inherent flow characteristics are characteristics when the differential pressure before and after the valve is constant, but in the case of an actual piping line, depending on the relationship between the discharge pressure and flow rate of the centrifugal pump and the piping situation on the secondary side, The pressure and flow rate vary. Such a characteristic representing the flow rate with respect to the actual valve opening is referred to as an effective flow rate characteristic. Among them, when considering typical characteristics of the valve, typical effective flow characteristics (hereinafter simply referred to as effective flow characteristics) are often expressed using the characteristics of the centrifugal pump.

  The Cv linear characteristic is a property in which the flow rate% of the fluid passing through the valve is directly proportional to the valve opening degree% under the condition that the valve differential pressure of the valve is constant. The flow rate characteristic is an upwardly convex curve. When considering the flow rate% relative to the valve opening degree%, the flow rate changes greatly in the range where the valve opening degree is small, but the change in flow rate is gentle and the controllability improves in the range where the valve opening degree is large. Tend. For this reason, when the valve | bulb excellent in Cv linear characteristic requires true linearity, it is suitable for the use as a main valve of a large tank with constant level like a dam or a reservoir, for example. In addition, it is suitable when the pipe resistance is smaller than the resistance of the valve.

On the other hand, the inherent flow rate characteristic of the equal percentage characteristic is a characteristic in which the flow rate change with respect to the unit change amount of the valve opening is logarithmically proportional to the flow rate, and becomes a downward convex curve, but in the effective flow rate characteristic, Almost directly proportional. The valve controllability is relatively good in a wide range of usage scenes, and many of the conventional butterfly valves exhibit a flow rate characteristic close to an equal percentage characteristic. Valves with excellent equal percentage characteristics are generally used for a wide range of applications, and are suitable when there is a large pressure fluctuation in the piping system, and when the differential pressure change between the maximum and minimum flow rates is 3: 1 or more. ing.
JP-A-57-157866 Japanese Patent No. 61-256082

  According to the butterfly valve having a cavitation suppression function of Patent Document 1, in a region where the valve opening is small, cavitation is suppressed by dispersing the fluid into a fine jet flow by a plurality of comb teeth formed on the valve body surface. However, in the region where the valve opening is large, the effect of the comb teeth is reduced, so there is a problem that the cavitation suppression function becomes insufficient under conditions of high differential pressure and high flow velocity. .

  Further, in the valve having the fluid buffer portion of Patent Document 2, the cavitation suppression capability is determined by the capability of the fluid buffer portion. However, even if a plurality of fluid buffer portions such as perforated plates and orifices are provided, there is a problem that a sufficient cavitation suppression effect cannot be obtained under a high differential pressure. In the case of multiple stages, there arises a secondary problem that the size of the installation portion becomes very large. In addition, there is a problem that the flow rate range in which good control characteristics as a valve can be obtained becomes narrow. In other words, as described above, there has been no control valve that can control the flow rate and pressure with high accuracy under high differential pressure and can prevent the occurrence of cavitation.

  In addition, the conventional center type butterfly valve is relatively excellent in the equal percentage characteristic in the region of the valve opening of 60 ° or less, but there is a problem that the controllability is deteriorated at a high opening degree. However, there is a problem that the controllability deteriorates in the low valve opening range, there is no butterfly valve that exhibits a flow rate characteristic excellent in Cv linear characteristics, and there is no butterfly valve that can obtain a wide range of controllability.

  The present invention has been made in view of the above problems, and is capable of suppressing cavitation even if any valve body is disposed at a position immediately downstream of the valve body. The purpose is to provide a body.

  Further, according to the present invention, the valve body disposed immediately upstream of the cavitation prevention body is negatively generated in the downstream region of the valve body in an appropriate valve opening state of the valve body having an appropriate structure by using fluid analysis. Analyzing the pressure region, determining the tendency of cavitation to occur depending on the size of the negative pressure region, and deriving a valve body structure having a high degree of controllability, so that even a single valve body has cavitation suppression capability, and In addition, the flow rate and pressure can be controlled with high accuracy in a wide range of valve openings from low to high, and the valve body shape can be selected depending on the use of the flow characteristics at the intermediate opening of the valve. By combining the cavitation prevention body and the valve body shaped valve body, the cavitation can be prevented to a higher degree while being simple and compact, under the conditions of high differential pressure and high flow velocity. It is to St. provide a control valve that exhibits a high degree of controllability.

  In order to solve the above-mentioned problems, the control valve according to the present invention employs a substantially cylindrical valve body disposed on a piping path through which a fluid flows, and opening and closing of a flow path disposed in the valve body. And a valve seat on which the valve body is seated is in a position eccentric to the fluid flow direction with respect to the valve shaft center, and the center of the valve shaft is perpendicular to the fluid flow direction; In the control valve in the double eccentric position that is eccentric to the downstream side in the fluid flow direction, a relatively large hill-like bulge is formed around the nozzle edge on the upstream surface of the valve body toward the upstream side. An upstream nozzle-side raised portion is formed, and the downstream surface of the valve body is 5 ° to 20 ° clockwise with respect to the seal surface where the valve seat and the valve body valve seat abut around the valve shaft. Is provided, and the edge of the valve body on the orifice side is compared to the edge on the nozzle side. Characterized in that bulges radially outward.

  Cavitation prevention by arranging a plurality of perforated plates with a plurality of holes with a predetermined depth at equal pitches in the fully open state of the valve body at appropriate intervals in parallel with the fluid flow direction. The body is arranged to generate an overflow from each hole of the perforated plate, and the fluid is gently and evenly decompressed to prevent the occurrence of cavitation from low to high differential pressure. It is characterized by that.

  The holes formed in the plurality of perforated plates are each formed in a recess shape having a predetermined depth from the front and back surfaces of the perforated plate.

  The holes formed in the plurality of perforated plates are formed so as to penetrate the front and back of the perforated plate.

  The cavitation prevention body is detachably disposed at a position immediately downstream of the valve body.

  According to the present invention, a plurality of perforated plates formed by forming a plurality of holes having a predetermined depth at an equal pitch so that the cavitation prevention body is substantially parallel to the flow of fluid flowing down at an appropriate interval. When the fluid passes between the perforated plates, each hole in the direction perpendicular to the flow-down direction formed in each perforated plate causes the vortex of the fluid to flow. It becomes resistance, converts the kinetic energy of the vortex flow into thermal energy, can gently and evenly depressurize the fluid, and can be installed on an existing valve while being compact and low cost. There is an effect that cavitation can be prevented from occurring under a low differential pressure or a high differential pressure simply by disposing it immediately after the body.

  Further, the control valve of the present invention includes the valve body of the present invention on the upstream side, the cavitation prevention body of the present invention on the position immediately downstream thereof, and the valve body disposed on the position immediately upstream of the cavitation prevention body. Using a fluid analysis, analyze the negative pressure region generated in the downstream region of the valve body in an appropriate valve opening state of an appropriate structure, and determine the tendency of cavitation to occur in the size of the negative pressure region. By deriving a valve body structure with high controllability, even a single valve body has the ability to suppress cavitation, and the flow rate is highly accurate over a wide range of valve openings from low to high. By creating a valve body shape that can control the flow characteristics at the intermediate opening of the valve, and by combining the cavitation prevention body and the valve body of the valve body shape, Prevents cavitation more sophisticated, yet extract, there is an effect that it becomes possible to exert a high differential pressure and high flow rate conditions at a high degree of controllability also show.

  Embodiments of the present invention will be described in detail below. The control valve according to the present invention is arranged on a piping path through which a fluid flows, and prevents cavitation even under high differential pressure and high flow velocity, and can exhibit flow controllability and pressure controllability while preventing cavitation. A butterfly valve having a structure is characterized in that a valve body and a cavitation prevention body for preventing cavitation are provided inside the valve body. Here, the structure of the butterfly valve is not particularly limited, but it is preferable to select a valve body having good controllability and a valve body having cavitation suppression capability.

  The valve body has a cylindrical shape in which a flow path through which a fluid can flow is formed. The valve body has a valve body that is rotatably supported by a valve rod at an upstream position inside the valve body so that the valve body can be opened and closed. A cavitation prevention body for preventing cavitation is disposed at a position immediately downstream of the valve body in the fully opened state.

  The cavitation prevention body has a plurality of perforated plates formed with a plurality of holes having a predetermined depth of 1.5 d or more and 4 d or less, where d is a hole diameter of each hole provided in the perforated plate, and d is a hole diameter. Are arranged at a position immediately downstream of the valve body so as to be substantially parallel to the flow of fluid flowing down in the valve body with an appropriate interval therebetween. The intervals between the perforated plates are preferably set to 1d or more and 3d or less, where d is the diameter of each hole provided in the perforated plate. At this time, it is preferable that the perforated plate has a length in the fluid flow direction of 20d to 100d.

  The holes formed in the perforated plate may penetrate through the front and back surfaces of the perforated plate, or may be formed by being recessed at an appropriate depth from the plate surface of the perforated plate. May be. Furthermore, the perforated plate does not necessarily have to be flat, and for example, a suitable part of the perforated plate may be bent in a substantially vertical direction.

  The cavitation prevention body having the perforated plate configured as described above is such that when the nominal diameter of the pipe is D, the cavitation prevention body starts from the most downstream portion of the valve body in the fully opened state of the valve body. It is preferable to arrange so that the distance to the upstream side end portion is within 1D, and if this range is exceeded, the effect of preventing cavitation and the effect of reducing noise are reduced. Further, a valve having a valve body and a valve body can be configured such that a cavitation prevention body can be detachably disposed immediately downstream of the valve body. In this case, maintenance is easy. In addition, it is possible to replace only the cavitation prevention body.

  As described above, in the control valve that constitutes the cavitation prevention body, when the fluid passes between the perforated plates, each hole formed in each perforated plate in a direction perpendicular to the flow-down direction is the perforated plate. Constructed to prevent the occurrence of cavitation under low to high differential pressure by becoming the resistance of the fluid vortex, converting the kinetic energy of the vortex into thermal energy, and reducing the fluid gently and evenly Is done.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The control valve (1) of this embodiment is arranged on the piping path through which the fluid (F) flows, and has high flow controllability and pressure while preventing cavitation even under high differential pressure and high flow velocity. An eccentric butterfly valve having an anti-cavitation structure capable of exerting controllability, wherein the valve body (3) has a cavitation-inhibiting ability inside the valve body (2), and an anti-cavitation body for preventing cavitation (4 ).

  As shown in FIG. 1, the control valve (1) includes a substantially cylindrical valve body (2) and a valve body (2) at a position upstream of the valve body (2) so that the valve can be opened and closed. A valve body (3) rotatably supported by a valve rod (5) inserted through the body boss portion (301), and a downstream immediately downstream position that does not interfere with the opening / closing locus of the valve body (3). A cavitation prevention body (4) for preventing cavitation.

  1 and 3, the valve body (2) is formed by penetrating a cylindrical channel, and the upstream side opening of the valve body (2) is a seat ring made of an elastic sealing material such as rubber. (203) is detachably mounted, and the valve body valve seat (302) at the periphery of the valve body (3) contacts and closes the flow path (204) while setting the substantial diameter of the flow path (204). It has a seat (205) that can be used. The seat ring (203) is detachably fixed by an annular seat ring fixing body (206) in an opening on the upstream side of the flow path of the valve body (2). Since the control valve (1) of this embodiment is intended for control of flow rate and pressure, the valve seat (205) diameter is preferably set smaller than the nominal pipe diameter, and the valve seat (205) diameter is large. It is optimal that the length is about 80% of the nominal diameter of the pipe.

  In the valve main body (2), valve stem shaft support portions (213) and (215) extend outward in the diameter direction from the upstream outer peripheral surface. A mounting plate for attaching an actuator or the like for driving the valve stem (5) at the upper end in the radial direction of one of the valve stem support portions (213) having a plane perpendicular to the axial direction of the valve stem (5). A portion (208) is formed.

  Inside the valve body (2), the inner diameter increases toward the downstream side from the back side position on the nozzle side of the valve body (3) in the fully closed position to the center position of the valve rod (5), and the flow path (204) is formed. The valve rod (5) is formed to have a substantially constant inner diameter from a substantially central position of the valve stem (5) to a downstream position about the radius of the valve body (3). Furthermore, the flow path (204) inside the valve body (2) is located at the central position of the valve stem (5) from the downstream position to the valve rod (5) from the center to the outer periphery of the valve body (3). From the first to the downstream position, the inner diameter is gently reduced and the flow path (204) is narrowed. Then, the inside of the valve body (2) is from a downstream position from the center position of the valve stem (5) at a considerable distance from the center of the valve stem (5) to the outer peripheral edge of the valve body (3). The inner diameter is constant and the cavitation prevention body mounting space (210) for detachably mounting the cavitation prevention body (4) is formed up to the downstream end portion. An anti-reverse portion (211) projecting radially inward is formed at a position immediately downstream of the valve body (3) on the orifice side at the fully closed position of the valve body (3) inside the valve body (2). The reverse rotation of the valve body (3) is prevented.

  In the cavitation prevention body mounting space (210) formed in the downstream region inside the valve body (2), the outer shape having an outer diameter substantially equal to the inner diameter of the cavitation prevention body mounting space (210) is substantially cylindrical. The cavitation prevention body (4) is inserted from the downstream side of the valve main body (2), and is fixed to the valve main body (2) from the downstream end face thereof with a fixing screw (212).

  1 and 4 to 6, the cavitation prevention body (4) has a cylindrical shape having an outer diameter substantially equal to the inner diameter of the cavitation prevention body mounting space (210) and having a predetermined length. A cylindrical frame (401) is formed, and a plurality of perforated plates (402) disposed in parallel with each other inside the cylindrical frame (401). The perforated plate (402) is configured by appropriately bending a metal punching plate formed by penetrating a large number of holes (403) in the plate surface direction into a stepped shape that moves up and down in the height direction. .

  The punching plate forming each porous plate (402) has an appropriate size, for example, a thickness of 1.5 mm, a width of 84 mm, and a metal plate having an appropriate length, and a through hole (403) having a diameter of 3 mm is 5 mm in the vertical direction. A large number of holes are perforated at a pitch of 5 mm with a pitch of 60 ° in the lateral direction. The stepped portion formed by appropriately folding each porous plate (402) is formed by bending the punching plate at a height portion of 30 mm and the horizontal portion at a pitch of 5 mm. In the perforated plate (402), when the hole diameter of the hole (403) drilled in the punching plate is d, the length of the fluid (F) in the flow-down direction is preferably set to 20d to 100d. At this time, the pitch between the holes (403) is preferably about 1.5d to 4d, and the interval between the perforated plates (402) can be set to an appropriate value depending on the control target value. , D to 3d are appropriate, and if this range is exceeded, the control characteristics deteriorate.

  When the perforated plates (402) thus formed in a staircase shape are stacked in parallel with each other with respect to the horizontal diameter direction of the cylindrical frame (401), the shape in the vertical direction thereof is the cylindrical frame. It is formed to match the inner diameter of the body (401). The cavitation prevention body (4) accommodates a plurality of perforated plates (402) arranged in parallel with each other as described above in a cylindrical frame (401), and each perforated plate (402) is a valve main body (402). 2) It is comprised so that it may become substantially parallel to the flow of the fluid (F) which flows through the inside.

  The cavitation prevention body (4) should be fully open at a position immediately downstream of the valve body (3) at a position where it does not interfere with the valve body (3) when fully opened, preferably when the nominal diameter of the pipe is D. The valve body (2) is formed in the valve body (2) so that the upstream end of the cavitation prevention body (4) is located within the range from the position immediately after the downstream end of the valve body (3) to the distance 1D. The cavitation prevention body mounting space (210) is set, and the cavitation prevention body (4) is mounted inside the cavitation prevention body mounting space (210).

  According to the anti-cavitation body (4) configured as described above, the perforated plate (F) flowing through the valve body (2) is disposed in the cylindrical frame (401). 402), each through hole (403) formed in each perforated plate (402) in a direction perpendicular to the flow-down direction becomes resistance of the vortex of the fluid (F), and By converting kinetic energy into heat energy and reducing the pressure of the fluid (F) gently and evenly, the occurrence of cavitation can be prevented under low or high differential pressure.

  With reference to FIGS. 7 to 11, the cavitation prevention effect of the cavitation prevention body (4) configured as described above will be described using the simulation results of the fluid analysis model. However, the cavitation prevention body (40) as a fluid analysis model used here is a central portion of the cavitation prevention body (40) provided with a perforated plate (42) formed by penetrating a large number of holes (43) having a hole diameter d. FIG. 7 shows a perspective view of a longitudinal section, and FIG. 8 shows a transverse section of an appropriate portion of the cavitation prevention body (40) of FIG. In other words, the cavitation prevention body (40) of this model is formed in a cylindrical frame (41) having a length of 30d, and the inner diameter is divided into four equal parts in the height direction and spaced apart from each other. There are two horizontal plates (44a) (44b) (44c), and in the space of each step inside the cylindrical frame (41) defined by these horizontal plates (44a) (44b) (44c) A plurality of perforated plates (42) each having a through hole (43) having a depth of 30d and an appropriate height set to a height of d at a pitch of 1.2d are arranged in parallel at intervals of 1.2d. Is configured.

  FIG. 9 shows the result of analyzing the pressure distribution at the time when an appropriate amount of fluid (F) is allowed to pass through the anti-cavitation body (40) set as described above at an appropriate flow velocity and pressure. is there. As shown in FIG. 9, the fluid (F) flowing between the perforated plates (42) has a reduced pressure region, but each of the many holes (43) formed in each perforated plate (42). The region in (43) is at equal pressure.

  This is because, as shown in FIG. 10, the vortex of the fluid (F) flowing through the front and back surfaces of the perforated plate (42) is canceled by interference in the region in the hole (43), or the hole becomes a resistance, It was confirmed that kinetic energy was lost.

  In addition, all the holes (43) of the anti-cavitation body (40) of the above model are used to confirm the gentle pressure reduction effect of the fluid (F) pressure by the numerous holes (43) formed in the perforated plate (42). The cavitation suppression body (46) in which the perforated plate (42) is simply a plate (45) was set, and a simulation for comparison with the cavitation prevention body (40) was performed. The result is shown in FIG. FIG. 11 (A) shows the simulation result of the cavitation suppressing body (46) of the holeless plate (45), and FIG. 11 (B) shows the porous plate (42) in which a large number of holes (43) are formed. ) Shows a simulation result of the anti-cavitation body (40).

  As is clear from the comparison between FIGS. 11 (A) and 11 (B), in the cavitation suppression body (46) of (A), the central portion of the cavitation suppression body (46) in the flow direction of the fluid (F) has a wide range. The pressure is reduced in pressure, and a reduced pressure region is formed in a wide range extending from the downstream end to a strong reduced pressure region immediately after the downstream end. On the other hand, in the cavitation prevention body (40) of (B), although a relatively weak decompression region is generated in a narrow region near the downstream end, it is remarkably different from the cavitation suppression body (46) of (A). It was confirmed that the degree of decompression was small. 9 and 11 show that the darker the fluid color is, the stronger the pressure is reduced.

  From the above results, when the fluid (F) flows through the cavitation prevention body (4), the multi-porous plate (402) arranged in parallel with an appropriate interval therebetween. In each of the holes (403) of the large number of holes (403) formed in the cavitation preventive body ( 4) It is understood that the fluid (F) flowing through the inside is gradually depressurized toward the downstream, and cavitation is suppressed or prevented.

  Note that the shape of the perforated plate (402) can be configured in various forms as shown in FIGS. For example, as shown in FIGS. 12A and 12B, a large number of circular holes (403a) and (403b) penetrating on the front and back sides of a plate (402a) and (402b) having a predetermined thickness are formed at an equal pitch. May be configured. Alternatively, as shown in FIG. 12C, holes (403c) that are respectively recessed from the front and back sides of the plate (402c) may be drilled. In this case, the drilling position of the hole (403c) For example, the positions of the holes (403d) and (403f) formed in the front and back surfaces may be staggered as shown in (D) and (F). Further, the shape of the hole (403c) is not limited to a circular hole, and may be, for example, a cone shape or a semicircular shape as shown in (D), (E), or (F). Further, as shown in (B), an appropriate portion of the plate (402b) is formed in a step portion bent in a direction substantially perpendicular to the flow-down direction of the fluid (F), or as shown in (E). As described above, the plate (403e) may be formed in a wave shape in a direction substantially perpendicular to the flow-down direction of the fluid (F).

  Next, the structure of the valve body (3) of the present embodiment will be described in detail with reference to FIGS. The valve body (3) of this embodiment has a valve body valve seat (302) seated on a valve seat (205) formed inside the valve body (2) at the outer peripheral edge of the upstream surface. The valve body boss portion for allowing the valve rod (5) to be inserted into the downstream surface, that is, the back surface, is rotatably supported on the valve body (2) with the valve body (3) as the axis of rotation. (301) is formed, and is an eccentric butterfly valve having a substantially disc shape as a whole.

  The valve seat (205) is in a position eccentric in the flow direction of the fluid (F) with respect to the valve shaft center of the valve stem (5). Similarly, the valve body valve seat (302) is also positioned with respect to the valve shaft center. And is in a position to be seated on the valve seat (205) when fully closed. The center of the valve shaft is a double eccentric type that is eccentric in the direction perpendicular to the flow direction of the fluid (F) and the downstream side in the flow direction of the fluid (F).

  The valve body boss portion (301) is formed so that the valve body (3) can be opened and closed by contacting or separating from the valve seat (205) inside the valve body (2). The valve body (2) is rotatably supported by a valve rod (5) inserted through the valve body. The valve body boss portion (301) formed on the back surface of the valve body (3) includes an upper valve body boss portion (301a) having a substantially cylindrical shape extending in the valve axis direction on the upper and lower sides of the valve body (3) and a lower portion. It consists of a valve body boss part (301b).

  The valve stem (5) includes a relatively long upper valve rod (501) cut out from a long round rod and a relatively short lower valve rod (502). The lower end of the upper valve stem (501) is inserted into an upper valve body boss (301a) formed on the back surface of the valve body (3), and is integrally formed with the valve body (3) by a fixing pin (305). Fixed. The upper valve stem (501) is inserted into the upper valve stem shaft support (213) formed in the valve main body (2) from the lower part to the center part, and packing (in the vicinity of the upper end of the upper valve shaft support (213) ( 214). The upper end of the lower valve stem (502) is inserted into a lower valve body boss (301b) formed on the back surface of the valve body (3), and is integrally formed with the valve body (3) by a fixing pin (306). Fixed. The lower valve stem (502) is inserted from the upper part to the lower end part of the lower valve stem shaft support part (215) formed in the valve body (2), and the bearing spacer ( The lower valve stem shaft support portion (215) is sealed while being closed by the lower cover body (217) via 216).

  As shown in FIG. 27, the valve body valve seat (2302) in the conventional general double eccentric butterfly valve (2001) is arranged perpendicular to the piping direction, that is, the flow direction of the fluid (F). When the valve body (2003) is slightly opened from the fully closed state, the fluid (F) flows out at once. Therefore, there is a problem that it is difficult to perform delicate control at a low opening.

  On the other hand, in the valve body (3) of the present embodiment, as shown in FIG. 13, on the back surface of the valve body (3), the valve seat (205) and the valve body valve seat (302 ) Is inclined clockwise by 5 ° to 20 ° with respect to the sealing surface, and at a low opening, the unbalance torque when fully closed is lowered and the valve closing torque is reduced. Further, an upstream nozzle-side raised portion (310) that is relatively large and bulges toward the upstream side is formed around the nozzle-side edge portion (309) on the upstream surface of the valve body (3). The orifice side of the body (3) increases in thickness, and the orifice side edge (311) swells radially outward as compared to the nozzle side edge (309). As a result, even when the valve element (3) opens at a small opening, the gap between the valve body (2) and the inside of the valve body (2) is kept small, and the flow rate of the fluid (F) flowing out is limited, so that subtle control is possible even from a small opening However, it is possible to realize an equal percentage characteristic.

  In general, in the case of a control valve, control is performed with an intermediate opening of the valve. Therefore, the controllability increases as the valve torque at the intermediate opening decreases. In the valve body (3) of the present embodiment, the bearing fluid is almost eliminated by the dynamic fluid force acting on the valve body almost uniformly from the low opening to the high opening range, and the torque by the fluid (F) is low. As a result, the valve torque can be suppressed to about 1/5 at the maximum, and the controllability is remarkably improved even in the intermediate opening range.

  The double eccentric type valve element (3) expressing the equal percentage characteristic of the present embodiment configured as described above and the conventional central type butterfly valve (3001) valve element (3003) are respectively modeled. It is arranged inside the valve body (2), and the valves are opened to the same degree of opening, and an appropriate amount of fluid (F) is placed inside each valve body (2) at an appropriate flow rate and pressure. Passing from the left side to the right side, the pressure distribution at that time was analyzed. The results are shown in FIGS.

  FIG. 16 shows the result of analyzing the pressure distribution of the valve body (3) of this example, and FIG. 17 shows the pressure distribution of the valve body (3003) in the conventional central butterfly valve (3001). The result is shown. As is clear from these comparisons, on the back surface of the valve body (3003) of the conventional central butterfly valve (3001), there is a very strong negative pressure region, whereas the valve body of this embodiment ( In 3), there is almost no negative pressure area on the back surface of the valve body (3), and a part of the upstream side surface of the valve body (3) on the nozzle side and the edge of the valve body (3) on the orifice side It can be seen that only weak negative pressure regions are created around the part (311), and cavitation is generated and grows in the negative pressure region in the fluid (F). It is understood that the cavitation is suppressed in the valve body (3). In FIGS. 17 and 18, the darker the fluid color is, the stronger the pressure is reduced.

  The double eccentric type valve body (3) that expresses the equal percentage characteristic configured as described above and the cavitation prevention body (4) described above are combined and shown in FIGS. The control valve (1) was modeled and simulated using fluid analysis. The result is shown in FIG. As is clear from FIG. 18, the result of the fluid analysis of the control valve (1) of the present embodiment is that the negative pressure region is the smallest and the cavitation suppression effect by the double eccentric type valve body (3) that expresses the equal percentage characteristic. It is understood that there is a synergistic effect with the cavitation prevention effect by the cavitation prevention body (4) disposed immediately after the downstream side.

  Therefore, when the conventional butterfly valve, the conventional butterfly control valve, and the double eccentric type valve element (3) that expresses the equal percentage characteristic of this embodiment are used alone, the equality of this embodiment For each of the combination of the double eccentric type valve body (3) and the cavitation prevention body (4) that express the percentage characteristic, the differential pressure from the low differential pressure to the high differential pressure when the valve opening is fixed at 70 °. The noise characteristics with respect to the differential pressure up to the above were measured, the cavitation prevention effect and the noise reduction effect of the present invention were confirmed, and the results are summarized in the graph shown in FIG.

  As is clear from FIG. 19, even when the double eccentric type valve element (3) that expresses the equal percentage characteristic of the present embodiment is used alone, the noise reduction effect is significantly higher than that of the conventional type valve. It was confirmed that it was expressed. In other words, the double eccentric type valve element (3) that expresses the equal percentage characteristic can control the flow rate with high accuracy in a wide range of valve openings ranging from a low opening degree to a high opening degree. It was shown that cavitation can be prevented under a wide range of differential pressures from pressure to high differential pressure. Further, it can be said that the combined use of the valve body (3) of the present embodiment and the cavitation prevention body (4) of the present embodiment exhibits the cavitation prevention effect and the noise reduction effect more remarkably.

  In addition, the measured value of Cv value% with respect to valve opening% of the valve body (3) of Example 1 is shown in FIG. From the results, it can be seen that the valve body (3) of the present example approximately expresses the equal percentage characteristic. From this, the valve body (3) of the present example exhibits the equal percentage characteristic. It can be said that it is a double eccentric type. In the above description, the double eccentric type valve element (3) exhibiting the equal percentage characteristic has been described as an example of the valve element (3) of the present embodiment. However, the valve element of the present invention is not limited to this. Absent. Hereinafter, another embodiment relating to the valve body will be described.

  Hereinafter, an embodiment of a valve body (1003) disposed inside a valve body in a control valve of the present invention will be described in detail with reference to the drawings. Note that the description of the same configuration as that of the first embodiment is only an overview.

  Referring to FIGS. 20 to 22, another form of valve body (1003) in the present embodiment is a valve body valve seated on a valve seat formed inside the valve body at the outer peripheral edge of the upstream surface. It has a seat (1302). A valve body (1003) can be inserted into the downstream surface of the valve body (1003), i.e., the back surface, and a valve body for pivotally supporting the valve body with an axis of rotation of the valve body (1003). A boss portion (1301) is formed and has a substantially disc shape as a whole. This valve body (1003) is in a double eccentric position where the center of the valve shaft is eccentric to the direction perpendicular to the flow direction of the fluid (F) and the downstream side in the flow direction of the fluid (F). Is in a position that is eccentric in the fluid flow direction with respect to the valve shaft center of the valve stem (1005), and in the same way, the valve body valve seat (1302) is also in an eccentric position with respect to the valve shaft center. This is a double eccentric butterfly valve shaped to be seated on the valve seat when closed.

  The valve body (1003) is a valve stem inserted into the valve body boss portion (1301) so that the valve body (1003) can be opened and closed by abutting or separating from the valve seat inside the valve body. (1005) is rotatably supported with respect to the valve body. The valve body boss portion (1301) formed on the back surface of the valve body (1003) includes an upper valve body boss portion (1301a) formed in a substantially cylindrical shape extending in the valve axis direction on the upper and lower sides of the valve body (1003) and a lower portion. It consists of a valve body boss part (1301b).

  The back surface of the valve body (1003) is provided with an inclination of 5 ° to 20 ° clockwise with respect to the seal surface where the valve seat and the valve body valve seat (1302) abut on the valve shaft. At the opening, the unbalance torque when fully closed is reduced and the valve closing torque is reduced. Further, the upstream nozzle-side raised portion that protrudes in a hill shape toward the upstream side around the nozzle-side edge portion (1309) and the orifice-side edge portion (1311) around the upstream surface of the valve body (1003) (1310) and the upstream orifice side raised portion (1312) are formed. The size of the bulge of the upstream nozzle side bulge (1310) is set to be relatively small, and the bulge of the upstream orifice side bulge (1312) is set to be high instead. In addition, a downstream orifice-side raised portion (1314) is formed around the orifice-side edge portion (1313) of the downstream surface of the valve body (1003) so as to rise in a hill shape toward the downstream side. However, the edge portion (1313) on the orifice side swells thicker than the edge portion (1315) on the nozzle side. As a result, it is configured to be able to control by changing the flow characteristics at the low and medium opening, and even when the valve body (1003) is opened at a small opening, the gap between the inside of the valve body is kept small and the fluid flowing out ( The flow rate of F) can be limited, and a Cv linear percentage characteristic that can be finely controlled even from a small opening can be realized.

  FIG. 24 shows the measured value of the Cv value% with respect to the valve opening% of the double eccentric type valve element (1003) exhibiting the Cv linear percentage characteristic of Example 2 configured as described above. From the result, it was confirmed that the valve body of the present example approximately expresses the Cv linear percentage characteristic.

  In addition, the double eccentric type valve body (1003) that expresses the Cv linear percentage characteristic is used alone without a cavitation prevention body, and the differential pressure and torque can be adjusted within a valve opening range of 20 ° to 90 °. Measured, the torque for the differential pressure, that is, the torque / differential pressure was converted into a coefficient and summarized as a value for the valve opening in the graph shown in FIG. In FIG. 25, since the opening process and the closing process are almost the same graph, the double eccentric type valve body (1003) that expresses the Cv linear percentage characteristic has almost no bearing torque and fluid (F ) Shows that the torque is small. On the other hand, the graphs of the opening process and the closing process of the conventional valve in FIG. 26 are different from each other. From these results, it was confirmed that the double eccentric type valve body (1003) that expresses the Cv linear percentage characteristic has a small torque coefficient and high controllability.

Sectional drawing which shows the structure of the control valve of a present Example which combines the double eccentric type valve body which expresses an equal percentage characteristic, and a cavitation prevention body side by side Vertical sectional view of the control valve Rear view of the control valve Front view of the cavitation prevention body of the present embodiment (A) The figure which looked at the porous plate which comprises the same cavitation prevention body from the plate surface direction, (B) The figure which looked at the porous plate from the end surface direction Diagram showing the laminated structure of the same porous plate Perspective longitudinal sectional view showing the structure of a cavitation prevention body as a fluid analysis model Partial cross-sectional view showing the structure of a cavitation prevention body as a fluid analysis model Fluid pressure distribution diagram showing fluid analysis result of cavitation prevention body as fluid analysis model The figure which shows the state of the vortex which occurs on the front and back of the perforated plate (A) The figure which shows the simulation result of the cavitation suppression body of a plate without a hole, The figure which shows the simulation result of the cavitation prevention body of the perforated plate which formed many holes (B). (A)-(F) Sectional drawing which shows the main structures of the modification of a perforated plate The top view which shows the structure of the double eccentric type valve body which expresses the equal percentage characteristic of a present Example Rear view showing the structure of a double eccentric valve body that expresses the equal percentage characteristics Longitudinal sectional view showing the structure of a double eccentric valve body that expresses the equal percentage characteristics The figure which shows the result of having analyzed the pressure distribution of the double eccentric type valve body which expresses the equal percentage characteristic The figure which shows the result of having analyzed the pressure distribution of the valve body of the conventional center type butterfly valve The figure which shows the result of having analyzed the pressure distribution of the control valve of a present Example which combines the double eccentric type valve body which expresses the equal percentage characteristic of a present Example, and a cavitation prevention body. Graph showing the results of measuring the noise characteristics of each valve The top view which shows the structure of the double eccentric type valve body which expresses the Cv linear percentage characteristic of a present Example Rear view showing the structure of a double eccentric valve body that exhibits the Cv linear percentage characteristic Longitudinal sectional view showing the structure of a double eccentric valve body that exhibits the Cv linear percentage characteristic The graph which shows the value of Cv% with respect to the valve opening% of the double eccentric type valve body which expresses the equal percentage characteristic of a present Example. The graph which shows the value of Cv% with respect to the valve opening% of the double eccentric type valve body which expresses the Cv linear percentage characteristic of a present Example. The graph which shows the coefficient value of the torque / differential pressure with respect to the valve opening% of the double eccentric type valve body which expresses the Cv linear percentage characteristic of a present Example Graph showing coefficient value of torque / differential pressure against valve opening% of conventional valve The figure which shows the structure of the conventional common double eccentric butterfly valve

Explanation of symbols

1 Control valve 2 Valve body
201 Flange for piping
202 Piping flange
203 Seat ring
204 flow path
205 Valve seat
206 Seat ring fixing
207 Valve stem support
208 Mounting plate
209 Bolt hole
210 Cavitation prevention body wearing space
211 Reverse prevention part
212 Fixing screw
213 Upper valve stem shaft support
214 Packing
215 Lower valve stem support
216 Bearing spacer
217 Lower cover body 3 Valve body
301 Valve boss
301a Upper valve body boss
301b Lower valve boss
302 Valve seat
303 Cylindrical part
304 Cylindrical part
305 Pin for fixing
306 Pin for fixing
309 Nozzle edge
310 Upstream nozzle ridge
311 Orifice edge 4 Cavitation prevention body
40 Anti-cavitation body
41 Cylindrical frame
42 perforated plate
43 holes
44a horizontal plate
44b horizontal plate
44c horizontal plate
45 plates
46 Cavitation suppressor
401 Cylindrical frame
402 perforated plate
402a plate
402b plate
402c plate
403 holes
403a round hole
403b round hole
403c hole
403d hole
403e hole
403f Hole 5 Valve stem
501 Upper valve stem
502 Lower valve stem
1003 Disc
1301 Disc boss
1301a Upper valve boss
1301b Lower valve boss
1302 Valve seat
1303 Cylindrical part
1304 Cylindrical part
1309 Nozzle edge
1310 Upstream nozzle side ridge
1311 Orifice edge
1312 Uplift on the orifice side
1313 Orifice edge
1314 Downstream orifice-side ridge
1315 Nozzle edge
1005 Valve stem
2001 Conventional double eccentric butterfly valve
2302 Valve seat
3001 Conventional central butterfly valve
3003 Valve body F Fluid

Claims (5)

  A valve body having a substantially cylindrical valve body disposed on a piping path through which fluid flows and a valve body disposed in the valve body for opening and closing a flow path, and the valve seat on which the valve body is seated is a valve shaft Control that is eccentric in the fluid flow direction with respect to the center, and that the center of the valve shaft is in a double eccentric position that is eccentric to the direction perpendicular to the fluid flow direction and the downstream side in the fluid flow direction In the valve, an upstream nozzle-side raised portion that is relatively large and raised in a hill-like shape toward the upstream side is formed around the nozzle-side edge portion on the upstream surface of the valve body, and the downstream surface of the valve body However, an inclination of 5 ° to 20 ° is provided clockwise with respect to the seal surface where the valve seat and the valve body valve seat abut around the valve shaft, and the edge portion on the orifice side of the valve body is on the nozzle side. A control valve characterized by bulging outward in the radial direction as compared with the edge portion of the.   Cavitation prevention by arranging a plurality of perforated plates with a plurality of holes with a predetermined depth at equal pitches in the fully open state of the valve body at appropriate intervals in parallel with the fluid flow direction. The body is arranged to generate an overflow from each hole of the perforated plate, and the fluid is gently and evenly decompressed to prevent the occurrence of cavitation from low to high differential pressure. The control valve according to claim 1.   3. The control valve according to claim 2, wherein the holes formed in the plurality of perforated plates are formed in the shape of depressions having a predetermined depth from the front and back surfaces of the perforated plate.   The control valve according to claim 2, wherein the holes formed in the plurality of perforated plates are formed so as to penetrate the front and back of the perforated plate.   The control valve according to any one of claims 2 to 4, wherein the cavitation preventing body is detachably disposed at a position immediately downstream of the valve body.

Images