Metal hard sealing structure of three-eccentric center butterfly valve and optimization design method of metal hard sealing structure

Abstract

The invention relates to a metal hard sealing structure of a three-eccentric center butterfly valve and an optimization design method of the metal hard sealing structure. The metal hard sealing structure comprises a valve body, a valve seat, a valve plate, a metal sealing ring and a valve plate gland. An annular groove is formed in the edge of the outer end face of the valve plate, the metal sealing ring is arranged in the annular groove, and the metal sealing ring is pressed and fixed through the valve plate gland. A metal hard sealing pair is formed between the metal sealing ring and the valve seat, and sealing surfaces between the metal sealing ring and the valve seat are matched conical surfaces; the valve plate is of an asymmetric structure; axial eccentricity b exists between the center line of the valve plate and the center line of the valve shaft, radial eccentricity a exists between the axial middle section of the metal sealing ring and the rotating center of the valve shaft, and an eccentric angle phi exists between the center line of the conical angle of the conical surface and the center line of the valve body. According to the three-eccentric butterfly valve, the size parameters and the material distribution of the valve internals are optimized, and the structural safety and the sealing performance of the three-eccentric butterfly valve are improved.

Description

Technical Field

[0001] The invention relates to a triple eccentric butterfly valve, in particular to a metal hard sealing structure of the triple eccentric butterfly valve and an optimization design method thereof. Background Art

[0002] The three-eccentric hard-sealed butterfly valve is an eccentric metal sealing structure. The sealing forms include metal-to-metal sealing, interchangeable metal sealing ring to metal sealing, stainless steel plate and graphite composite plate sealing ring to metal sealing, etc. The driving forms of the three-eccentric hard-sealed butterfly valve include electric, manual, worm gear drive, pneumatic, etc. The butterfly plate of the three-eccentric hard-sealed butterfly valve is installed in the diameter direction of the pipeline in the valve body. In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0° and 90°. When it rotates to 0°, the valve is fully closed; when it rotates to 90°, the valve is fully open.

[0003] The three-eccentric hard-sealed butterfly valve is resistant to wear, high temperature and corrosion, and is gradually replacing the cut-off valve and regulating valve, and is widely used in newly built nuclear power plants, coal chemical equipment and air separation equipment. At present, one-third of valve failures in the world are caused by sealing failures, and the sealing failure problem of the three-eccentric butterfly valve has always been a technical problem that needs to be solved urgently.

[0004] Under the action of fluid-solid coupling, the valve trim will produce large stress and deformation, which has a significant impact on the sealing performance of the triple-eccentric butterfly valve. The structural shape and dimensional parameters of the valve trim affect its stress distribution. Therefore, it is necessary to develop a metal hard seal structure for the triple-eccentric butterfly valve and propose a multi-objective optimization method that takes structural strength and sealing performance as the goals while improving the valve trim structural dimensional parameters and material distribution. Summary of the invention

[0005] The invention provides a metal hard seal structure of a triple eccentric butterfly valve and an optimization design method thereof, and optimizes the size parameters and material distribution of valve trims, thereby improving the structural safety and sealing performance of the triple eccentric butterfly valve.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A metal hard sealing structure of a three-eccentric butterfly valve comprises a valve body, a valve seat and a valve plate; the valve seat is arranged in the valve body, and the valve plate is driven to rotate by the valve shaft; the metal hard sealing structure also comprises a metal sealing ring and a valve plate pressure cover; the valve plate is provided with an annular groove at the edge of the outer end surface away from the valve shaft, the metal sealing ring is arranged in the annular groove, the outer edge of the metal sealing ring protrudes from the outer edge of the valve plate, and a valve plate pressure cover is arranged on the outer side of the valve plate to press and fix the metal sealing ring; a metal hard sealing pair is formed between the metal sealing ring and the valve seat, and the sealing surface between the metal sealing ring and the valve seat is a matching conical surface; the valve plate is an asymmetric structure; when the butterfly valve is in a fully closed state, the valve shaft, the metal sealing ring and the valve plate pressure cover are arranged in sequence along the liquid flow direction in the valve body, there is an axial eccentricity b between the center line of the valve plate and the center line of the valve shaft, there is a radial eccentricity a between the axial middle section of the metal sealing ring and the rotation center of the valve shaft, and there is an eccentric angle between the cone angle center line of the conical surface and the center line of the valve body

[0008] Furthermore, a graphite gasket is provided between the metal sealing ring and the valve plate, and the graphite gasket is provided in a mounting groove provided in the annular groove.

[0009] Furthermore, the valve plate gland and the valve body are connected by a plurality of screws evenly distributed along the circumferential direction.

[0010] Furthermore, viewed from one end close to the valve shaft, the vertical section of the conical surface has two characteristic points along the counterclockwise direction, namely, a large slope characteristic point located at the 0° coordinate, and a small slope characteristic point located at the 180° coordinate; correspondingly, the conical surface within ±45° of the 0° coordinate point is the large slope, and the conical surface within ±45° of the 180° coordinate point is the small slope; the upper conical surface connecting the large slope and the small slope is the upper transition surface, and the lower conical surface connecting the large slope and the small slope is the lower transition surface; the valve shaft is arranged parallel to the connection direction of the 90° coordinate point to the 270° coordinate point; viewed from above the valve plate, the opening direction of the valve plate is clockwise.

[0011] Furthermore, the asymmetric structure of the valve plate refers to a large slope structure on the side of the valve plate with a larger area bounded by the valve shaft, in which the material evenly transitions from the valve shaft to the edge of the valve plate, and a "small slope + plane" structure on the side of the valve plate with a smaller area bounded by the valve shaft; and corresponds to three valve plate structural parameters, namely, the height A of the large slope, the height B of the small slope, and the distance C from the lowest point of the small slope to the center line of the valve shaft.

[0012] Furthermore, the valve plate and the valve shaft are fixedly connected via a plurality of cylindrical pins arranged axially along the valve shaft, and a sealing packing is arranged between the valve shaft and the valve body.

[0013] An optimization design method for a metal hard seal structure of a triple eccentric butterfly valve comprises the following steps:

[0014] Step 1: 3D topology optimization of the valve plate;

[0015] 1) Establish the initial finite element model of the triple-eccentric butterfly valve, divide the hexahedron and tetrahedron mixed grid, and encrypt the grid near the sealing surface; determine the number of divided grids through the finite element grid independence experiment;

[0016] 2) The maximum equivalent stress of the valve plate does not exceed the allowable equivalent stress of its material as a constraint condition; set the optimized area and non-optimized area of ​​the valve plate; set boundary conditions including the fixed end faces of the flanges at both ends of the triple eccentric butterfly valve and the valve shaft being allowed to rotate, and set the positive fluid pressure as the load;

[0017] 3) Perform finite element simulation calculation on the equivalent stress of the valve plate, take the lightweight of the valve plate as the optimization goal, perform topological optimization on the valve plate, and determine the most reasonable valve plate material distribution plan after multiple iterations;

[0018] Step 2: Smooth the valve plate after 3D topology optimization, simplify the parameters that affect the strength of the valve plate, and use the three shape and size characteristic parameters determined after the valve plate material distribution as variables to participate in the next stage of response surface optimization;

[0019] Step three, using the equivalent stress distribution of the inner parts of the three-eccentric butterfly valve and the sealing pressure ratio on the sealing surface as indicators for evaluating the safety of the sealing structure and the sealing performance; using the central composite design method of the response surface method, taking the maximum equivalent stress and the maximum sealing pressure ratio of the sealing surface as the response values, the optimal parameter matching scheme including the valve plate structural parameters, the valve shaft diameter, and the valve seat thickness is obtained;

[0020] Step 4: Use finite element simulation analysis to verify the equivalent stress distribution of valve trim and the sealing pressure ratio on the sealing surface of the model before and after optimization.

[0021] Furthermore, the step three specifically includes the following process:

[0022] 1) Set the three shape and size characteristic parameters A, B, C after topology optimization, the valve shaft diameter D and the sealing surface width E as the optimized design parameter variables; set the maximum equivalent stress Y of the valve trim and the maximum sealing specific pressure X on the sealing surface as the multi-objective response values;

[0023] 2) Carry out single factor experiments to preliminarily determine the value range of design parameter variables;

[0024] 3) Use finite element simulation to provide experimental data samples, use Design-Expert software to perform experimental design and data analysis, use the central composite design method of the response surface method, and use the steepest climbing method to select new center points and directions in the experimental area to guide the selection of experimental points;

[0025] 4) The second-order design model is used to accurately approximate the optimal value of the response surface within the set investigation range, and the interaction terms and quadratic terms that have no significant impact on the response value are eliminated to obtain the optimal parameter matching solution.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The asymmetric valve plate structure obtained through 3D topology optimization is adopted, and the valve plate material is reasonably distributed on the basis of lightweight design to avoid the problem of uneven stress distribution caused by eccentricity of the valve shaft position and prevent stress concentration;

[0028] 2) The triple eccentric butterfly valve of the present invention adopts a metal sealing ring and a valve seat to form a sealing structure, and there is no interference when the valve is switched on and off, and the metal sealing ring and the valve seat can be separated or contacted instantly, thereby reducing the wear of the sealing surface, improving the sealing reliability, and adapting to the fluid medium environment of different temperatures;

[0029] 3) The present invention provides a multi-objective optimization method, which optimizes the material distribution and structural dimensions of valve trims at the same time; the maximum equivalent stress of the optimized lightweight valve trim is significantly reduced, and the sealing pressure ratio is within a reasonable range, ensuring long-term effective sealing performance;

[0030] 4) The present invention combines 3D topology optimization with the central composite design of the response surface method, uses finite element simulation experiments to provide experimental data samples, and uses Design-Expert software to perform professional experimental design and data analysis, which has high optimization efficiency and accurately approximates the optimal value of the response surface;

[0031] 5) Through finite element simulation analysis of the optimized three-eccentric butterfly valve model, it is proved that the stress distribution of the valve internals is reasonable after optimization, the maximum equivalent stress of the metal sealing ring is reduced by 62.86%, meeting the strength requirements; the maximum sealing pressure ratio is reduced by 60.52%, which is less than the allowable sealing pressure ratio, and a continuous circumferential sealing area is formed on the sealing surface, which has a good sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the triple eccentric butterfly valve of the present invention.

[0033] Figure 2 It is a schematic diagram of the metal hard seal structure of the triple eccentric butterfly valve of the present invention.

[0034] Figure 2a yes Figure 2 A partial enlarged view of .

[0035] Figure 3 It is a schematic structural diagram of the metal sealing ring of the present invention.

[0036] Figure 4It is a diagram of the evolution of the valve plate 3D topology optimization process described in the present invention.

[0037] Figure 5 It is a flow chart of the 3D topology optimization of the valve plate described in the present invention.

[0038] Figure 6 This is a rendering of the 3D topology optimization of the valve plate of the present invention.

[0039] Figure 7 It is the 3D topology optimization valve plate extraction parameter diagram of the present invention.

[0040] Figure 8 It is a flow chart of the response surface optimization central composite design described in the present invention.

[0041] Fig. 9 It is the stress distribution diagram of the main components of the three eccentric butterfly valves before optimization.

[0042] Fig.10 It is the stress distribution diagram of the main components of the optimized triple eccentric butterfly valve.

[0043] Fig.11 It is the sealing pressure distribution diagram of the sealing surface before optimization.

[0044] Fig.12 The sealing pressure distribution diagram of the optimized sealing surface.

[0045] Figure 1 Middle: 1-bearing 2-valve shaft 3-metal sealing ring 4-valve plate 5-cylindrical pin 6-valve plate gland 7-valve body 8-sealing packing 9-graphite gasket DETAILED DESCRIPTION

[0046] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0047] like Figure 1As shown, the metal hard sealing structure of a three-eccentric butterfly valve of the present invention comprises a valve body 7, a valve seat and a valve plate 4; the valve seat is arranged in the valve body 7, and the valve plate 4 is driven to rotate by the valve shaft 2; the metal hard sealing structure also comprises a metal sealing ring 3 and a valve plate gland 6; the valve plate 4 is provided with an annular groove at the edge of the outer end surface away from the valve shaft 2, the metal sealing ring 3 is arranged in the annular groove, the outer edge of the metal sealing ring 3 protrudes from the outer edge of the valve plate 4, and the valve plate gland 6 is arranged on the outer side of the valve plate 4 to press and fix the metal sealing ring 3; the metal sealing ring 3 and A metal hard seal pair is formed between the valve seats, and the sealing surface between the metal sealing ring 3 and the valve seat is a matching conical surface; the valve plate 4 is an asymmetric structure; when the butterfly valve is in a fully closed state, the valve shaft 2, the metal sealing ring 3 and the valve plate gland 6 are arranged in sequence along the liquid flow direction in the valve body 7, there is an axial eccentricity b between the center line of the valve plate 4 and the center line of the valve shaft 2, there is a radial eccentricity a between the axial middle section of the metal sealing ring 3 and the rotation center of the valve shaft 2, and there is an eccentric angle between the cone angle center line of the conical surface and the center line of the valve body 7

[0048] Furthermore, a graphite gasket 9 is provided between the metal sealing ring 3 and the valve plate 4, and the graphite gasket 9 is provided in a mounting groove provided in the annular groove.

[0049] Furthermore, the valve plate gland 6 and the valve body 7 are connected by a plurality of screws evenly distributed along the circumferential direction.

[0050] Furthermore, viewed from the end close to the valve shaft 2, the vertical section of the conical surface has two characteristic points along the counterclockwise direction, namely, a large slope characteristic point located at the 0° coordinate, and a small slope characteristic point located at the 180° coordinate; correspondingly, the conical surface within ±45° of the 0° coordinate point is the large slope, and the conical surface within ±45° of the 180° coordinate point is the small slope; the upper conical surface connecting the large slope and the small slope is the upper transition surface, and the lower conical surface connecting the large slope and the small slope is the lower transition surface; the valve shaft is arranged parallel to the connection direction of the 90° coordinate point to the 270° coordinate point; viewed from above the valve plate 4, the opening direction of the valve plate 4 is clockwise.

[0051] Furthermore, the asymmetric structure of the valve plate 4 refers to a large slope structure on the side of the valve plate 4 with a larger area bounded by the valve shaft 2, in which the material evenly transitions from the valve shaft to the edge of the valve plate, and a "small slope + plane" structure on the side of the valve plate 4 with a smaller area bounded by the valve shaft 2; and corresponds to three valve plate structural parameters, namely, the height A of the large slope, the height B of the small slope, and the distance C from the lowest point of the small slope to the center line of the valve shaft.

[0052] Furthermore, the valve plate 4 and the valve shaft 2 are fixedly connected via a plurality of cylindrical pins 5 arranged axially along the valve shaft 2 , and a sealing packing 8 is arranged between the valve shaft 2 and the valve body 7 .

[0053] The optimization design method of the metal hard seal structure of a triple eccentric butterfly valve described in the present invention comprises the following steps:

[0054] Step 1: 3D topology optimization of the valve plate;

[0055] 1) Establish the initial finite element model of the triple-eccentric butterfly valve, divide the hexahedron and tetrahedron mixed grid, and encrypt the grid near the sealing surface; determine the number of divided grids through the finite element grid independence experiment;

[0056] 2) Taking the maximum equivalent stress of the valve plate not exceeding the allowable stress of its material as the constraint condition, set the optimized area and non-optimized area of ​​the valve plate; set the boundary conditions including the flange end faces of both ends of the three-eccentric butterfly valve being fixed and the valve shaft being allowed to rotate, and set the positive fluid pressure as the load;

[0057] 3) Perform finite element simulation calculation on the equivalent stress of the valve plate, take the lightweight of the valve plate as the optimization goal, perform topological optimization on the valve plate, and determine the most reasonable valve plate material distribution plan after multiple iterations;

[0058] Step 2: Smooth the valve plate after 3D topology optimization, simplify the parameters that affect the strength of the valve plate, and use the three shape and size characteristic parameters determined after the valve plate material distribution as variables to participate in the next stage of response surface optimization;

[0059] Step three, using the equivalent stress distribution of the inner parts of the three-eccentric butterfly valve and the sealing pressure ratio on the sealing surface as indicators for evaluating the safety of the sealing structure and the sealing performance; using the central composite design method of the response surface method, taking the maximum equivalent stress and the maximum sealing pressure ratio of the sealing surface as the response values, the optimal parameter matching scheme including the valve plate structural parameters, the valve shaft diameter, and the valve seat thickness is obtained;

[0060] Step 4: Use finite element simulation analysis to verify the equivalent stress distribution of valve trim and the sealing pressure ratio on the sealing surface of the model before and after optimization.

[0061] Furthermore, the step three specifically includes the following process:

[0062] 1) Set the three shape and size characteristic parameters A, B, C after topology optimization, the valve shaft diameter D and the sealing surface width E as the optimized design parameter variables; set the maximum equivalent stress Y of the valve trim and the maximum sealing specific pressure X on the sealing surface as the multi-objective response values;

[0063] 2) Carry out single factor experiments to preliminarily determine the value range of design parameter variables;

[0064] 3) Use finite element simulation to provide experimental data samples, use Design-Expert software to perform experimental design and data analysis, use the central composite design method of the response surface method, and use the steepest climbing method to select new center points and directions in the experimental area to guide the selection of experimental points;

[0065] 4) The second-order design model is used to accurately approximate the optimal value of the response surface within the set investigation range, and the interaction terms and quadratic terms that have no significant impact on the response value are eliminated to obtain the optimal parameter matching solution.

[0066] The metal hard seal structure of a three-eccentric butterfly valve described in the present invention comprises a valve body, a metal sealing ring, a graphite gasket, a valve plate, a valve shaft (supported by a bearing 1) and a valve plate gland; the valve plate and the valve plate gland press and fix the metal sealing ring, and a metal hard seal pair is formed between the metal sealing ring and the valve seat in the valve body. The valve shaft drives the valve plate and the metal sealing ring to rotate under the action of the actuator to form different angle openings.

[0067] The metal hard sealing structure of a three-eccentric butterfly valve described in the present invention has a valve plate that has undergone 3D topology optimization. The valve plate has an asymmetric structure. The valve plate material is reasonably distributed on the basis of realizing a lightweight design of the valve plate, which effectively solves the problem of uneven stress distribution caused by the eccentric position of the valve shaft, prevents stress concentration, and can reduce the maximum equivalent stress by approximately 53.63%.

[0068] When the three-eccentric butterfly valve is closed, due to the area difference between the valve plate and the valve shaft on both sides, a closing torque can be generated under the action of the fluid medium pressure, thereby forming a sealing pressure ratio on the sealing surface to achieve automatic closing of the three-eccentric butterfly valve.

[0069] The valve plate is provided with a mounting groove a on one side of the contact surface with the metal sealing ring, and a graphite gasket is placed in the mounting groove to prevent leakage on the contact side between the metal sealing ring and the valve plate, thereby meeting the sealing requirements of high-temperature fluid media.

[0070] The valve plate and the valve plate gland are preferably connected by screws, which not only fix the metal sealing ring but also facilitate the removal and replacement of the metal sealing ring after pressure damage on the sealing surface. There is no need to replace the valve plate as a whole, which reduces maintenance costs while ensuring sealing reliability.

[0071] The sealing surface on the metal sealing ring is a conical surface, which is divided into four areas: large slope, small slope, upper transition surface and lower transition surface. When the valve is switched on and off, the metal sealing ring and the valve seat are separated or contacted instantly, which can reduce the wear on the sealing surface during switching and improve the sealing reliability.

[0072] The following embodiments are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0073] [Example]

[0074] In this embodiment, the metal hard seal structure of the triple eccentric butterfly valve Figure 1 , Figure 2 and Figure 2a As shown in the figure, it consists of a valve body (with a valve seat inside), a valve plate, a metal sealing ring, a valve plate gland and a graphite gasket. The valve shaft drives the valve plate to rotate in the valve body to form a maximum 90° angle opening. The metal sealing ring is fixed between the valve plate and the valve plate gland and is fixed by multiple screws evenly distributed around the circumference. A metal hard sealing pair with a conical surface is formed between the metal sealing ring and the valve seat. Under the action of a certain external torque, a sealing specific pressure is formed on the sealing surface to achieve reliable sealing. An installation groove is provided on the contact surface between the valve plate and the metal sealing ring, and a graphite gasket is placed in the installation groove to achieve effective sealing on the contact side between the valve plate and the metal sealing ring.

[0075] There is an axial eccentricity b between the center line of the valve plate and the center line of the valve shaft, a radial eccentricity a between the axial middle section of the metal sealing ring and the rotation center of the valve shaft, and an eccentricity angle between the center line of the cone angle of the conical surface and the center line of the valve body. The above three parameters are the three eccentric parameters. The semi-cone angle of the sealing surface is β (such as Figure 2 shown), Figure 2 The valve plate is shown in the closed state.

[0076] The sealing surface between the metal sealing ring and the valve seat (such as Figure 2a As shown) is a matching conical surface, such as Figure 3 As shown in the figure, the outer ring surface of the metal sealing ring can be divided into four curved surface areas: a large inclined surface near the 0° coordinate, a small inclined surface near the 180° coordinate, an upper transition surface near the 90° coordinate, and a lower transition surface near the 270° coordinate. The valve axis is parallel to the direction of the line connecting the 90° coordinate point and the 270° coordinate point.

[0077] Due to the above-mentioned conical surface, the sealing state of each area is different. When the valve is opened and closed, there is no interference between the valve trims, and the metal sealing ring and the valve seat can be separated or contacted instantly, which reduces the wear of the sealing surface and improves the sealing reliability.

[0078] In this embodiment, the optimization design process of the metal hard seal structure of the triple eccentric butterfly valve is as follows:

[0079] 1) Perform 3D topology optimization on the valve plate. Figure 5 As shown, based on the finite element simulation analysis, the initial finite element model of the valve plate is established, the hexahedron and tetrahedron mixed grid is divided, and the grid near the sealing surface is encrypted. The number of divided grids is determined through the finite element grid independence experiment.

[0080] The maximum equivalent stress of the valve plate does not exceed the allowable stress of its material as a constraint condition, and the optimization area and non-optimization area of ​​the valve plate are set; the boundary conditions such as the flange end faces of the two ends of the three-eccentric butterfly valve are fixed and the valve shaft is allowed to rotate are set; the positive fluid pressure is set to be a load of 4MPa; according to the finite element simulation calculation of the equivalent stress of the valve plate, the valve plate is topologically optimized with the lightweight design of the valve plate as the optimization goal. After multiple iterations (such as Figure 4 As shown), the material distribution of the valve plate is reasonably distributed.

[0081] For the valve plate after 3D topology optimization (the valve plate before and after optimization is as follows Figure 6 ) is smoothed to obtain the three valve plate structural parameters A, B, and C (as shown in Figure 7 These three valve plate structural parameters are also the main fixed dimensions of material distribution and will be involved in the next stage of response surface optimization.

[0082] 2) The central combination design method of the response surface methodology was adopted. Taking the working condition of 4 MPa forward medium pressure as an example, the response surface optimization central combination method was used to construct the functional relationship between the two response values ​​of the maximum equivalent stress Y of the valve trim and the maximum sealing pressure X of the sealing surface and the five parameters of the three valve plate structural parameters A, B, and C after topology optimization, the valve shaft diameter D, and the sealing surface width E. A regression model of the five parameters was established to obtain the optimal structural parameter combination of the butterfly valve.

[0083] Conduct a single factor experiment, and analyze the effect of a certain parameter change on the maximum equivalent stress Y of the valve trim and the maximum sealing pressure ratio of the sealing surface under the premise that other parameters remain unchanged. Then select the value range of the design parameter variable.

[0084] The central composite design method of the response surface method is to use finite element simulation experiments to provide experimental data samples, and use Design-Expert software to perform professional experimental design and data analysis. The simulation process is as follows Figure 8 shown.

[0085] By using the second-order design model, the optimal value of the response surface is accurately approximated within a smaller investigation range, and some interaction terms and quadratic terms that have no significant effect on the response value are eliminated. The maximum equivalent stress and maximum sealing pressure ratio are obtained after regression fitting as equations (1) and (2):

[0086] X=1643.98-3.22396A+1.96378B-7.56814C-8.59106D-41.0965E+0.031391AD-

[0087] 0.0694744BD+0.0497446CD+0.323856DE+0.0114375A 2 +0.0542528B2 +

[0088] 0.0133643C 2 -0.0403794D 2 +0.165746E 2 .

[0089] Formula (1)

[0090] Y=2629.61+0.163983A+4.77736B-12.9861C-10.4327D-83.8137E-0.0927872BD+

[0091] 0.0716765CD+0.0400125CE+0.620025DE+0.0362728B 2 +0.0228378C 2 -

[0092] 0.089871D 2 +0.404599E 2 .

[0093] Formula (2)

[0094] In order to verify the structural safety and sealing performance of the triple-eccentric butterfly valve after parameter optimization, the equivalent stress of the main valve internal components was simulated and compared under the same working conditions according to the structural parameter models before and after optimization. Fig. 9 and Fig.10 As shown in the figure. Before optimization, the maximum equivalent stress of the valve plate, valve shaft and metal sealing ring is greater than the allowable stress of their materials. After optimization, the maximum equivalent stress of the above components is less than the allowable stress of their materials, meeting the strength requirements. Among them, the maximum equivalent stress of the metal sealing ring is reduced by 62.86%.

[0095] Under the same working conditions, the sealing pressure ratios of the sealing surfaces before and after optimization are simulated and compared. Fig.11 and Fig.12 As shown in the figure. Although the sealing pressure ratio on the sealing surface before optimization can meet the short-term sealing requirements, its value is greater than the allowable sealing pressure ratio, and pressure loss will occur, which cannot meet the long-term sealing reliability requirements. After optimization, the maximum sealing pressure ratio of the sealing surface decreased by 60.52%, and its value was less than the allowable sealing pressure ratio, and a continuous circumferential sealing area was formed on the sealing surface, which has a good sealing effect.

[0096] Conclusion: The metal hard seal structure of the three-eccentric butterfly valve designed according to the optimization design method of the present invention has good structural safety and sealing performance. The optimization method optimizes the material distribution of the valve trim on the basis of realizing the lightweight design of the valve trim, obtains the optimal combination of structural parameters, and achieves the purpose of multi-objective optimization of structural strength and sealing performance.

[0097] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A metal hard seal structure of a three-eccentric butterfly valve, comprising a valve body, a valve seat and a valve plate; the valve seat is arranged in the valve body, and the valve plate is driven to rotate by the valve shaft; characterized in that: The metal hard sealing structure also includes a metal sealing ring and a valve plate pressure cover; the valve plate is provided with an annular groove at the edge of the outer end surface away from the valve shaft, the metal sealing ring is arranged in the annular groove, the outer edge of the metal sealing ring protrudes from the outer edge of the valve plate, and a valve plate pressure cover is arranged on the outer side of the valve plate to press and fix the metal sealing ring; a metal hard sealing pair is formed between the metal sealing ring and the valve seat, and the sealing surface between the metal sealing ring and the valve seat is a matching conical surface; the valve plate is an asymmetric structure; when the butterfly valve is in a fully closed state, the valve shaft, the metal sealing ring and the valve plate pressure cover are arranged in sequence along the liquid flow direction in the valve body, there is an axial eccentricity b between the center line of the valve plate and the center line of the valve shaft, there is a radial eccentricity a between the axial middle section of the metal sealing ring and the rotation center of the valve shaft, and there is an eccentric angle between the cone angle center line of the conical surface and the center line of the valve body.

2. The metal hard seal structure of a triple eccentric butterfly valve according to claim 1 is characterized in that: A graphite gasket is arranged between the metal sealing ring and the valve plate, and the graphite gasket is arranged in a mounting groove opened in the annular groove.

3. The metal hard seal structure of a triple eccentric butterfly valve according to claim 1 is characterized in that: The valve plate gland and the valve body are connected by a plurality of screws evenly distributed along the circumferential direction.

4. The metal hard seal structure of a triple eccentric butterfly valve according to claim 1 is characterized in that: Viewed from one end close to the valve shaft, the vertical section of the conical surface has two characteristic points along the counterclockwise direction, namely, a large slope characteristic point located at the 0° coordinate, and a small slope characteristic point located at the 180° coordinate; correspondingly, the conical surface within ±45° of the 0° coordinate point is the large slope, and the conical surface within ±45° of the 180° coordinate point is the small slope; the upper conical surface connecting the large slope and the small slope is the upper transition surface, and the lower conical surface connecting the large slope and the small slope is the lower transition surface; the valve shaft is arranged parallel to the connection direction of the 90° coordinate point to the 270° coordinate point; viewed from above the valve plate, the opening direction of the valve plate is clockwise.

5. A metal hard seal structure of a triple eccentric butterfly valve according to claim 1 or 4, characterized in that: The asymmetric structure of the valve plate refers to a large slope structure on the side of the valve plate with a larger area bounded by the valve shaft, in which the material evenly transitions from the valve shaft to the edge of the valve plate, and a "small slope + plane" structure on the side of the valve plate with a smaller area bounded by the valve shaft; and corresponds to three valve plate structural parameters, namely, the height A of the large slope, the height B of the small slope, and the distance C from the lowest point of the small slope to the center line of the valve shaft.

6. The metal hard seal structure of a triple eccentric butterfly valve according to claim 1, characterized in that: The valve plate and the valve shaft are fixedly connected via a plurality of cylindrical pins arranged along the axial direction of the valve shaft, and a sealing packing is arranged between the valve shaft and the valve body.

7. The optimization design method for the metal hard seal structure of the triple eccentric butterfly valve according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: 3D topology optimization of the valve plate; 1) Establish the initial finite element model of the triple-eccentric butterfly valve, divide the hexahedron and tetrahedron mixed grid, and encrypt the grid near the sealing surface; Determine the number of mesh divisions through finite element mesh independence experiments; 2) Taking the maximum equivalent stress of the valve plate not exceeding the allowable stress of its material as the constraint condition, set the optimized area and non-optimized area of ​​the valve plate; set the boundary conditions including the flange end faces of both ends of the three-eccentric butterfly valve being fixed and the valve shaft being allowed to rotate, and set the positive fluid pressure as the load; 3) Perform finite element simulation calculation on the equivalent stress of the valve plate, take the lightweight of the valve plate as the optimization goal, perform topological optimization on the valve plate, and determine the most reasonable valve plate material distribution plan after multiple iterations; Step 2: Smooth the valve plate after 3D topology optimization, simplify the parameters that affect the strength of the valve plate, and use the three shape and size characteristic parameters determined after the valve plate material distribution as variables to participate in the next stage of response surface optimization; Step three, using the equivalent stress distribution of the inner parts of the three-eccentric butterfly valve and the sealing pressure ratio on the sealing surface as indicators for evaluating the safety of the sealing structure and the sealing performance; using the central composite design method of the response surface method, taking the maximum equivalent stress and the maximum sealing pressure ratio of the sealing surface as the response values, the optimal parameter matching scheme including the valve plate structural parameters, the valve shaft diameter, and the valve seat thickness is obtained; Step 4: Use finite element simulation analysis to verify the equivalent stress distribution of valve trim and the sealing pressure ratio on the sealing surface of the model before and after optimization.

8. The optimization design method for the metal hard seal structure of a triple eccentric butterfly valve according to claim 7 is characterized in that: The step three specifically includes the following process: 1) Set the three shape and size characteristic parameters A, B, C after topology optimization, the valve shaft diameter D and the sealing surface width E as the optimized design parameter variables; set the maximum equivalent stress Y of the valve trim and the maximum sealing specific pressure X on the sealing surface as the multi-objective response values; 2) Carry out single factor experiments to preliminarily determine the value range of design parameter variables; 3) Use finite element simulation to provide experimental data samples, use Design-Expert software to perform experimental design and data analysis, use the central composite design method of the response surface method, and use the steepest climbing method to select new center points and directions in the experimental area to guide the selection of experimental points; 4) The second-order design model is used to accurately approximate the optimal value of the response surface within the set investigation range, and the interaction terms and quadratic terms that have no significant impact on the response value are eliminated to obtain the optimal parameter matching solution.

Images