Cage control valve

Abstract

To reduce cavitation in a cage control valve.SOLUTION: A cage control valve 10 comprises a valve body 11 having a flow path R through which liquid flows, and a cylindrical cage 12 provided midway along the flow path R, the cage 12 having a plurality of through holes 12A having a circular cross section and extending radially. The cage control valve is also provided with a plug 15 that is movable along a central axial direction of the cage 12. The plug 15 adjusts a flow rate of liquid by changing an opening of each of the plurality of through holes 12A depending on its position. Each of the plurality of through holes 12A has a first end through which liquid flows in and a second end through which liquid flows out, and is a tapered hole that gradually tapers from the first end to the second end.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cage regulator valve. [Background technology]

[0002] Patent Document 1 discloses a cage control valve that includes a valve box having a flow path through which a liquid flows, a cylindrical cage provided midway along the flow path and having a plurality of through holes with a circular cross section extending radially, and a plug configured to be movable along the central axis of the cage, which adjusts the flow rate of the liquid by changing the opening degree of each of the plurality of through holes depending on the position of the plug. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-020580 Summary of the Invention [Problem to be solved by the invention]

[0004] The cage control valve of Patent Document 1 has the disadvantage of being prone to cavitation. The occurrence of cavitation is caused by the liquid pressure recovery coefficient F L It is desirable to reduce cavitation because it leads to deterioration of the performance and erosion.

[0005] The present invention aims to reduce cavitation in a cage control valve. [Means for solving the problem]

[0006] The cage control valve of the present invention comprises a valve box having a flow path through which a liquid flows, a cylindrical cage provided midway along the flow path and having a plurality of radially extending through holes with a circular cross section, and a plug configured to be movable along the central axis of the cage, which adjusts the flow rate of the liquid by changing the opening degree of each of the plurality of through holes depending on the position of the plug, and each of the plurality of through holes has a first end through which the liquid flows in and a second end through which the liquid flows out, and is a tapered hole that gradually tapers from the first end to the second end. [Effects of the Invention]

[0007] The present invention reduces cavitation in cage control valves. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a cage regulator valve according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional perspective view of a main part of the cage control valve of FIG. [Figure 3] 3 is a cross-sectional view of a main part of the cage of the cage control valve of FIG. 1. FIG. [Figure 4] FIG. 4 is a graph showing the relationship between the taper angle θ and the capacity coefficient CV of the cage control valve when the taper angle θ is changed while the number of through holes in the cage is fixed. [Figure 5] FIG. 5 is a graph showing the relationship between the taper angle θ and the liquid pressure recovery coefficient FL of the cage regulating valve when the taper angle θ is changed while the number of through holes in the cage is fixed. [Figure 6] FIG. 6 is a graph showing the relationship between the taper angle θ and the capacity coefficient CV of the cage control valve when the taper angle θ is changed by setting a minimum spacing between the cages and varying the number of through holes. [Figure 7] Figure 7 is a visualization of the erosion distribution around the cage based on CFD analysis. [Figure 8]FIG. 8 is a diagram showing the relationship between the taper angle θ and the number of meshes where the erosion index obtained by the CFD analysis exceeds 1.0×10 7 . DETAILED DESCRIPTION OF THE INVENTION

[0009] A cage control valve according to an embodiment of the present invention will be described below with reference to the drawings. In the drawings, reference numerals may be used to denote only some of the elements.

[0010] As shown in FIG. 1, a cage control valve 10 according to one embodiment of the present invention includes a valve body 11, a cage 12 (see also FIG. 2), a gasket 13 (see also FIG. 2), a guide member 14 (see also FIG. 2), a plug 15 (see also FIG. 2), a top cover 16, a stem 17, and a seal member 18. The cage control valve 10 is configured to adjust the flow rate of a liquid, such as cold water or hot water. In the following description, the valve bottom 11A side of the valve body 11 is referred to as the lower side, and the side of the stem 17 that moves the plug 15 or the actuator (not shown) that moves the stem 17 up and down is referred to as the upper side. This up-down direction may not coincide with the vertical direction depending on the installation mode of the cage control valve 10. The central axes of the cage 12, gasket 13, guide member 14, communication passage R3, plug 15, and stem 17 are common to each other, forming a central axis C that is aligned in the up-down direction.

[0011] The valve box 11 is configured to be placed midway through a pipe that forms a liquid flow path, forming a flow path R through which liquid flows from the pipe. The flow path R includes a primary-side flow path R1, a secondary-side flow path R2, and a communication passage R3 that connects the primary-side flow path R1 and the secondary-side flow path R2. Liquid flowing from upstream of the flow path R flows into the primary-side flow path R1. The downstream end R11 of the primary-side flow path R1 is connected to the upstream end R21 of the secondary-side flow path R2 located below it via the communication passage R3. The liquid that flows into the primary-side flow path R1 flows through the communication passage R3, into the secondary-side flow path R2, and then flows out downstream of the flow path R. The valve box 11 includes an opening 11B that connects the downstream end R11 of the primary-side flow path R1 to the outside of the valve box 11. The opening 11B is closed by an upper cover 16.

[0012] The cage 12, the gasket 13, and the guide member 14 are disposed at the downstream end R11 of the primary flow path R1.

[0013] The cage 12 is formed in a hollow cylindrical shape. The cage 12 may have any cylindrical shape, and may alternatively have another cylindrical shape, such as a polygonal cylindrical shape. The cage 12 has a large number (e.g., 36) of through-holes 12A that connect the interior and exterior of the cage 12. The through-holes 12A are arranged in multiple rows (three rows in this example) along the vertical direction. The through-holes 12A constituting each row are aligned at equal intervals along the circumferential direction of the cage 12. The multiple rows are arranged so that the through-holes 12A are staggered. For example, two through-holes 12A aligned vertically (the through-holes 12A constituting the first and third rows from the top) and one through-hole 12A (the through-hole 12A constituting the second row from the top, i.e., the middle row) are aligned alternately and at equal intervals along the circumferential direction of the cage 12, with the latter through-hole 12A being positioned midway between the two through-holes 12A in the vertical direction. The arrangement of the through-holes 12A is not limited to this. For example, the through holes 12A in each row may be arranged spirally around the central axis C.

[0014] Each through hole 12A is formed in the same shape and is a circular hole with a circular cross section taken along a plane perpendicular to its central axis. Each through hole 12A is a tapered hole that gradually tapers from a first end, through which the liquid flows in, to a second end, through which the liquid flows out (see also Figure 3). This tapered hole tapers from the outside to the inside of the cage 12. The cage 12 is supported by an upward-facing ring-shaped support surface 11C on the inner surface that forms the downstream end R11 of the primary flow path R1 of the valve box 11.

[0015] The gasket 13 is sandwiched between the lower part of the cage 12 and the inner surface of the valve box 11 that forms the downstream end R11 of the primary flow path R1, and seals the gap.

[0016] The guide member 14 has a cylindrical shape with approximately the same cross-sectional shape as the cage 12. The guide member 14 presses the cage 12 from above against the support surface 11C by means of an upper cover 16 fixed to the valve box 11 so as to cover the opening 11B. This positions the cage 12. The guide member 14 and the cage 12 form a single cylindrical cage. A plug 15 is disposed inside this cage. The guide member 14 guides the vertical movement of the plug 15. The cage 12 and the guide member 14 may be integrally formed to form a single cage.

[0017] The plug 15 is configured to be movable along the direction of the central axis C of the cage 12, etc. The plug 15 closes or opens the numerous through holes 12A depending on its position. Specifically, the plug 15 changes the opening degree of each of the numerous through holes 12A depending on its position. For example, as the plug 15 gradually moves downward from its upper limit position, it gradually closes the through holes 12A in the first row from the top, then gradually closes the through holes 12A in the second row from the top, and then gradually closes the through holes 12A in the third row from the top (the bottom row). In this way, the opening degree (closure degree) of each through hole 12A changes depending on the position of the plug 15, and the flow rate of the liquid flowing through the flow path R1 is adjusted.

[0018] The plug 15 is connected to a stem 17 that is driven vertically by an actuator (not shown), and is moved vertically by this stem 17. The stem 17 passes through a through-hole 16A in the top cover 16. The gap between the stem 17 and the top cover 16 is sealed by an optional sealing member 18 disposed in the through-hole 16A, allowing the stem 17 to move vertically.

[0019] In the cage control valve 10, cavitation occurs in the liquid whose flow rate is to be controlled. This cavitation causes erosion and increases the liquid pressure recovery coefficient F of the cage control valve 10. L , the capacity coefficient C of the cage control valve 10 V It is related to the liquid pressure recovery coefficient F. L and the capacity coefficient C of the cage control valve 10 VThe larger the both, the better. Suppressing cavitation suppresses choked flow in the cage 12, and the liquid pressure recovery coefficient F of the cage control valve 10 L can be increased, but the capacity coefficient C V is not necessarily large.

[0020] The inventors of the present invention have found that by adjusting the taper angle θ (see FIG. 3) of the numerous through holes (tapered holes) 12A of the cage 12, the occurrence of cavitation and erosion and the liquid pressure recovery coefficient F L , capacity coefficient C V This point will be explained below. Note that the taper angle θ is the inclination angle of the inner surface of through hole 12A with respect to the central axis C1 of through hole (tapered hole) 12A, as shown in FIG.

[0021] The inventors of the present application have investigated the capacity coefficient Cv and the liquid pressure recovery coefficient F when the number of through holes (tapered holes) 12A is fixed at 12 per row, a total of 36, for the cage control valve 10 having the structure shown in Figures 1 and 2, and the taper angle θ is changed. L The change in the taper angle θ was determined through experiments and CFD (Computational Fluid Dynamics) analysis. When the taper angle θ was changed, the downstream end (the right end in Figure 3) of the through-hole (tapered hole) 12A was fixed. In other words, as the taper angle θ increased, the upstream end (the left end in Figure 3) of the through-hole 12A became larger.

[0022] The graphs of the above experiment and CFD results are shown in Figures 4 and 5. The error between the experiment results and the CFD analysis results is small, and the CFD analysis results for the taper angle θ, which was not adopted in the experiment results, are also considered to be reliable. In addition, the liquid pressure recovery coefficient F L The maximum value of is 1.

[0023] As shown in Fig. 4, the capacity coefficient Cv increases linearly when the taper angle θ is between 0 and 2 degrees, and remains approximately the same when the taper angle θ is greater than 2 degrees. Fig. 4 shows that a preferable capacity coefficient Cv is obtained when the taper angle θ is 0.8 degrees or greater, but a taper angle θ of 2 degrees or greater is more preferable.

[0024] As shown in Figure 5, the liquid pressure recovery coefficient F L The liquid pressure recovery coefficient F increases significantly when the taper angle θ is between 0 and 1 degree, and remains almost constant when the taper angle θ is 1 degree or more. From Fig. 5, it can be seen that when the taper angle θ is 0.8 degrees or more, the preferable liquid pressure recovery coefficient F L However, it is more preferable that the taper angle θ is 1 degree or more. L An increase in the pressure means that the cavitation has decreased, so if the through hole 12A is made into a tapered hole, the cavitation will decrease.

[0025] Next, for the cage control valve 10 having the structure shown in FIGS. 1 and 2, a rated travel is set to 29 mm, the vertical spacing between each through hole 12A and the through hole 12A in the row below (the spacing between the edges of the through holes 12A) is set to 0.75 mm or more, and the circumferential spacing (the spacing between the edges of the through holes 12A) is set to 1.0 mm or more. Figure 6 shows a graph of the change in capacity coefficient Cv of the cage control valve 10 with respect to the change in taper angle θ when the maximum number of through holes 12A are arranged. Note that, as mentioned above, increasing the taper angle θ increases the size of the upstream ends of the through holes 12A (the left end in FIG. 3). Furthermore, because the minimum spacing between the through holes 12A is set as described above, increasing the taper angle θ decreases the number of through holes 12A (the maximum number that can be arranged while ensuring that the spacing between the through holes 12A does not fall below the minimum spacing).

[0026] 6, as the taper angle θ increases, the number of through holes 12A decreases, and the capacity coefficient Cv gradually decreases. In particular, when the taper angle θ is greater than 3 degrees, the capacity coefficient Cv is less than half of that when the taper angle is 0 degrees. For this reason, it is preferable that the taper angle θ be 3 degrees or less, and more preferably 2 degrees or less.

[0027] Furthermore, the erosion caused by the taper angle θ was examined from the results of the CFD analysis. Fig. 7 shows a visualization of the erosion distribution around the cage 12 obtained by the CFD analysis. The evaluation of erosion resistance at the taper angle θ was carried out when the erosion index was 10 × 10 in the range of the enlarged view at the bottom of Fig. 7.7 The comparison was performed by comparing the number of larger meshes (fewer is better). The threshold value of the erosion index was set to 10 × 10 7 This is because damage due to erosion is predicted to occur above this value (Kenji Saito, Youn Chongho, “Prediction of cavitation erosion occurring in a control valve using computational fluid dynamics”, The 15th International Conference on Fluid Control, Measurements and Visualization (FLUCOME2019)).

[0028] The erosion index at each taper angle θ is 10×10 7 The number of meshes exceeding the threshold is shown in Figure 8. The number of meshes exceeding the threshold is relatively suppressed in the taper angle θ range of 0.8 to 4 degrees, but the rate of increase increases once the taper angle exceeds 5 degrees. In addition, the number of meshes exceeding the threshold is best suppressed in the range of 1 to 1.5 degrees.

[0029] From the above results, the capacity coefficient C V , liquid pressure recovery coefficient F L However, there is no taper angle that optimizes all of the erosion resistance performance, and when considering a preferable taper angle θ by taking all of these factors into consideration, the numerical range adopted for the taper angle θ is preferably 0.8 degrees to 3 degrees (including 0.8 degrees and 3 degrees; the same applies to ranges below), more preferably 0.8 degrees to 2 degrees, and even more preferably 1 degree to 1.5 degrees.

[0030] Furthermore, from the viewpoint of reducing cavitation, as mentioned above, it is at least preferable that the taper angle θ is 0 degrees, that is, that the through hole 12A is a tapered hole, as shown in FIG. 5, rather than a non-tapered hole.

[0031] Although the present invention has been described above with reference to the embodiments and modifications, the present invention is not limited to the above embodiments and modifications. For example, the present invention includes various modifications to the above embodiments and modifications that can be understood by a person skilled in the art within the scope of the technical concept of the present invention. The configurations listed in the above embodiments and modifications can be combined as appropriate within a range that does not cause inconsistencies.

[0032] The configurations disclosed in this specification are described below. (Appendix 1) a valve body having a flow path through which the liquid flows; a cylindrical cage provided midway along the flow path, the cage having a plurality of through holes with a circular cross section extending in a radial direction; a plug configured to be movable along a central axis of the cage, the plug adjusting the flow rate of the liquid by changing the opening degree of each of the plurality of through holes according to the position of the plug, Each of the plurality of through holes includes a first end through which the liquid flows in and a second end through which the liquid flows out, and is a tapered hole that gradually tapers from the first end toward the second end. Cage control valve. (Appendix 2) the first end is an opening on the outer periphery side of the cage, The second end is an opening on the inner circumferential side of the cage. 1. A cage control valve as described in Appendix 1. (Appendix 3) The taper angles of the plurality of through holes are within a range of 0.8 degrees to 3 degrees. 3. A cage control valve according to claim 1 or 2. (Appendix 4) The taper angles of the plurality of through holes are within a range of 0.8 degrees to 2 degrees. 3. A cage control valve according to claim 1 or 2. (Appendix 5) The taper angle of the plurality of through holes is within a range of 1 to 1.5 degrees. 3. A cage control valve according to claim 1 or 2. [Explanation of symbols]

[0033] 10...cage control valve, 11...valve body, 11A...valve base, 11B...opening, 11C...support surface, 12...cage, 12A...through hole (tapered hole), 13...gasket, 14...guide member, 15...plug, 16...top cover, 16A...through hole, 17...stem, 18...sealing member, C...central axis, C1...central axis, Cv...capacity coefficient, FL...liquid pressure recovery coefficient, R...flow path, R1...primary side flow path, R2...secondary side flow path, R3...communicating path, R11...downstream end, R21...upstream end, θ...taper angle.

Claims

1. a valve body having a flow path through which the liquid flows; a cylindrical cage provided midway along the flow path, the cage having a plurality of through holes with a circular cross section extending in a radial direction; a plug configured to be movable along a central axis of the cage, the plug adjusting the flow rate of the liquid by changing the opening degree of each of the plurality of through holes according to the position of the plug, each of the plurality of through holes includes a first end through which the liquid flows in and a second end through which the liquid flows out, and is a tapered hole that gradually tapers from the first end toward the second end; Cage control valve.

2. the first end is an opening on the outer periphery side of the cage, The second end is an opening on the inner circumferential side of the cage.

10. The cage regulating valve of claim 1.

3. The taper angle of the plurality of through holes is an angle in the range of 0.8 degrees to 3 degrees.

10. The cage regulating valve of claim 1.

4. The taper angle of the plurality of through holes is an angle in the range of 0.8 degrees to 2 degrees.

10. The cage regulating valve of claim 1.

5. The taper angle of the plurality of through holes is an angle in the range of 1 degree to 1.5 degrees.

10. The cage regulating valve of claim 1.

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