Low overpressure breather valve and design method thereof

Abstract

The invention relates to the technical field of breather valves, in particular to a low-overpressure breather valve which comprises a valve body, a valve seat arranged in the valve body and provided with an opening, a valve disc matched with the opening of the valve seat and a valve cover connected with the valve disc. The valve disc is movably connected relative to the valve seat in the longitudinal direction, and the shape of the inner wall of the valve cover is matched with the shape of the outer wall of the valve seat. The diameter and the height of the valve cover are set based on the relation among the inner circle area of the valve seat, the projection area of the valve cover and the airflow pressure difference proportionality coefficient, so that the overpressure value K of the breather valve meets 0 lt; k < 8%; through cooperation of the structural size of the valve cover, the theoretical design model and the internal flow resistance network, accurate control over the overpressure value of the breather valve is achieved, the problems that due to the fact that the overpressure interval of a traditional breather valve is too wide, unorganized emission of VOCs is difficult to control, and the setting pressure is too low are solved, the storage tank can operate under the higher and more stable pressure, and the storage tank can operate under the higher and more stable pressure. And the medium discharge loss is obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of breathing valve technology, and in particular to a low overpressure breathing valve and its design method. Background Technology

[0002] As a core safety and environmental protection device in the storage and transportation systems of industries such as petroleum and chemical, the breather valve of the storage tank plays an important role in regulating the pressure balance inside and outside the storage tank and preventing equipment damage or safety accidents caused by abnormal pressure.

[0003] However, traditional breather valves have long faced a series of prominent challenges in practical applications: in terms of environmental emissions, due to their wide opening pressure range during overpressure discharge, volatile organic compounds in the storage tank are prone to unorganized release during the discharge process, making it difficult to meet increasingly stringent environmental emission requirements.

[0004] Although there have been some attempts at technological improvements within the industry, a systematic solution is still lacking, especially in overpressure control, where precise design theories and methods are lacking. This results in low set pressures for breather valves, wide emission ranges, and limited VOCs control effectiveness. Therefore, there is an urgent need for an environmentally friendly breather valve that can fundamentally reduce overpressure, enable rapid valve opening and closing, and reduce media emissions, thereby improving the overall safety and environmental compliance of tank areas. Summary of the Invention

[0005] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0006] To address the shortcomings of existing technologies, one objective of this invention is to provide a low overpressure breathing valve.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a low overpressure breathing valve, comprising a valve body, a valve seat disposed inside the valve body and having an opening, a valve disc adapted to the opening of the valve seat, and a valve cover connected to the valve disc;

[0008] The valve disc is longitudinally movably connected to the valve seat, and the inner wall shape of the valve cover is adapted to the outer wall shape of the valve seat; the diameter D1 of the valve cover satisfies the following relationship: , , Where K is the overpressure value, and satisfies 0 <K<8%; The area of ​​the inner circle of the valve seat; The projected area of ​​the valve cover. The pressure difference between the bottom of the valve disc and the top of the valve cover when the valve disc just reaches its highest opening position. With the pressure inside the tank at this time The ratio of .

[0009] As a preferred embodiment of the low overpressure breathing valve of the present invention, wherein: the ratio coefficient Calculated using the following formula: , in, The flow resistance coefficient is the flow resistance coefficient of the airflow passing through the section surrounding the valve disc. The impact stabilization pressure coefficient; It is the total flow resistance coefficient of the airflow from the inlet to the outlet.

[0010] As a preferred embodiment of the low overpressure breathing valve of the present invention, wherein: the impact stagnation pressure coefficient The calculation formula is: , in, The impact efficiency coefficient ranges from 0.7 to 1.3. Let the impact efficiency function be used. , , For the characteristic impact depth, satisfying .

[0011] In a preferred embodiment of the low overpressure breathing valve of the present invention, the diameter D1 of the valve cover and the airfoil height h satisfy the following: ≤h≤ , ≤D1≤ .in, The thickness of the valve disc. H is the diameter of the valve disc, H is the maximum opening height of the valve disc, and D is the diameter of the valve body cavity.

[0012] This invention achieves precise control of the overpressure value K of the breather valve (K < 8%) by coordinating the valve cover structure dimensions with the theoretical design model and the internal flow resistance network. This solves the problems of difficult control of fugitive VOC emissions and low set pressure caused by the excessively wide overpressure range of traditional breather valves, enabling the storage tank to operate at higher and more stable pressures and significantly reducing media emission losses.

[0013] To address the shortcomings of existing technologies, another objective of this invention is to provide a design method for a low overpressure breathing valve.

[0014] To achieve the above objectives, the present invention adopts the following technical solution: The design method includes the following steps: Based on the force balance relationship and the inner circle area of ​​the valve seat Determine the target overpressure value K0 and the projected area of ​​the valve cover. as well as Design constraints; Establish a flow resistance network model of the internal flow of the breather valve and calculate the ratio coefficient. The correspondence between the valve cover diameter D1 and the airfoil height h; Based on the aforementioned correspondence, the undetermined coefficients in the algebraic relationship between the ratio and the valve cover diameter D1 and the airfoil height h are obtained through simulation or experimental optimization fitting, thereby determining the range of values ​​for D1 and h that satisfy K≤K0. The valve cover was manufactured according to the specified value range and tested for verification.

[0015] As a preferred embodiment of the design method for the low overpressure breathing valve of the present invention, wherein: in establishing the flow resistance network model of the internal flow of the breathing valve, the flow resistance network model decomposes the internal flow channel of the breathing valve into multiple flow resistance units connected in series and / or in parallel, including the inlet pipe section, the upstream section of the valve disc, the flow section around the valve disc, and the outlet pipe section, and calculates the flow resistance coefficient of each section using the Darcy-Weisbach formula and the Borda-Carnot formula.

[0016] As a preferred embodiment of the design method for the low overpressure breathing valve of the present invention, wherein: the flow resistance coefficient of the inlet pipe section is... The calculation formula is: , in, Let be the Darcy friction coefficient, which is taken as 0.02 for metal pipes; This refers to the length of the inlet pipe section; The diameter of the inlet pipe section; This refers to the cross-sectional area of ​​the inlet pipe section; This refers to the cross-sectional area of ​​the valve cavity's inner diameter. This represents the working fluid density.

[0017] As a preferred embodiment of the design method for the low overpressure breathing valve of the present invention, wherein: the flow resistance coefficient of the upstream section of the valve disc is... The calculation formula is: , This is the distance between the bottom surface of the valve disc and the valve seat when the valve disc reaches its maximum opening height. The thickness of the valve disc; This refers to the height of the valve cover airfoil; This refers to the inner diameter of the valve cavity; This represents the cross-sectional area of ​​the valve cavity's inner diameter.

[0018] As a preferred embodiment of the design method for the low overpressure breathing valve of the present invention, wherein: the flow resistance coefficient of the valve disc winding section is... The calculation includes the following steps: The airflow path is divided into path one, which is far from the outlet side, and path two, which is close to the outlet side. The flow resistance coefficient of path one is calculated separately. and the flow resistance coefficient of path two ; The total flow resistance is calculated using the parallel flow resistance formula: , Wherein, flow resistance coefficient The calculation formula is: ; Flow resistance coefficient The calculation formula is: ; The flow resistance is the resistance around the airflow as it passes through path one of the valve disc. The flow resistance coefficient is the radial flow path of the airflow through the valve disc. The flow resistance coefficient is the flow resistance coefficient of the airflow passing through the back pressure side of the valve disc; It is the flow resistance coefficient of the airflow from the back pressure side to the outlet pipe; The flow resistance is the resistance around the airflow as it passes through path two of the valve disc. It is the flow resistance coefficient of the airflow radially through path two of the valve disc.

[0019] As a preferred embodiment of the design method for the low overpressure breathing valve of the present invention, wherein: The calculation formula is: , The The calculation formula is: , in, The coefficient for flow loss due to necking; The expansion flow rate loss coefficient; This is the effective proportion coefficient of the flow in path two; This represents the area of ​​the annular gap.

[0020] As a preferred embodiment of the design method for the low overpressure breathing valve of the present invention, wherein: The calculation formula is: , The The calculation formula is: , As a preferred embodiment of the design method for the low overpressure breathing valve of the present invention, wherein: the flow resistance coefficient of the outlet pipe section is... The calculation formula is: ,

[0021] in, This refers to the length of the outlet pipe section; The diameter of the outlet pipe section; This refers to the cross-sectional area of ​​the outlet pipe section.

[0022] As a preferred embodiment of the design method for the low overpressure breathing valve described in this invention, wherein: In the simulation or experimental optimization, the computational fluid dynamics (CFD) simulation method is used to simulate the internal flow field of the breather valve. By changing the values ​​of D1 and h, parameterized analysis is performed to obtain simulation results of multiple overpressure values ​​K. In CFD simulations, local mesh refinement is applied to the area near the valve disc and valve cover, with the mesh size not exceeding [size missing]. , where t is the edge thickness of the valve cover, and steady-state simulation is performed using the k-ε turbulence model; In the experimental verification, multiple test valve covers with different D1 and h were made, and the opening pressure and full opening pressure were tested on the breathing valve test bench. The actual overpressure value K was measured and compared with the theoretical value for verification.

[0023] The design method of the low overpressure breathing valve of the present invention has the same beneficial effects as that of the low overpressure breathing valve, and will not be repeated here. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic cross-sectional view of the low overpressure breathing valve of the present invention in the critical opening state.

[0026] Figure 2 This is a schematic cross-sectional view of the low overpressure breathing valve of the present invention in its critical fully open state.

[0027] Figure 3 This is a schematic diagram illustrating the geometric parameters of the low overpressure breathing valve of the present invention.

[0028] Figure 4 This is a schematic diagram showing the flow resistance positions of each section of the low overpressure breathing valve of the present invention.

[0029] Figure 5 This is a schematic diagram illustrating the geometric parameters of the positive pressure section of the parallel breathing valve of the present invention.

[0030] Figure 6 This is a schematic diagram showing the geometric parameters of the negative pressure section of the parallel breathing valve of the present invention.

[0031] Figure 7 a is shown in the CFD calculation cloud diagram of the low overpressure breathing valve of the present invention.

[0032] Figure 8 b is shown in the CFD calculation cloud diagram of the low overpressure breathing valve of this invention.

[0033] Figure 9 c represents the CFD calculation cloud diagram of the low overpressure breathing valve of this invention.

[0034] Figure 10 d represents the CFD calculation cloud diagram of the low overpressure breathing valve of this invention.

[0035] Figure 11 e represents the CFD calculation cloud diagram of the low overpressure breathing valve of this invention.

[0036] Figure 12 f is the CFD calculation cloud diagram of the low overpressure breathing valve of the present invention.

[0037] Figure 13 g represents the CFD calculation cloud diagram of the low overpressure breathing valve of this invention. Detailed Implementation

[0038] To make the objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0041] Example 1

[0042] Reference Figures 1-4, which is the first embodiment of the present invention. This embodiment provides a low overpressure breather valve that can narrow the discharge range, increase the set pressure, and reduce VOC emissions from the source. It includes: a valve body 100, which is the main housing of the breather valve; a valve seat 200 disposed inside the valve body 100 and having an opening. The valve seat 200 is annular and has an upward opening for cooperating with the valve disc 300 to form a sealing surface. A valve disc 300 adapted to the opening of the valve seat 200. The valve disc 300 is a disc-shaped structure, and its bottom surface is adapted to the shape of the opening of the valve seat 200. It can move relative to the valve seat 200 in the longitudinal direction (i.e., the vertical direction) to achieve the opening and closing of the valve. And a valve cover 400 connected to the valve disc 300. The valve disc 300 is movably connected to the valve seat 200 in the longitudinal direction. The inner wall shape of the valve cover 400 is adapted to the outer wall shape of the valve seat 200. The valve cover 400 is fixedly connected above the valve disc 300 and moves together with the valve disc 300. The inner wall shape of the valve cover 400 is adapted to the outer wall shape of the valve seat 200, and an annular gap for gas flow is formed between them.

[0043] The diameter D1 and height h of the valve cover 400 satisfy the following relationship: , where K is the overpressure value and satisfies 0 < K < 8%. This is to strictly and quantitatively control the pressure response characteristics of the valve, so as to ensure that the working pressure of the breather valve when fully open does not exceed 1.1 times the set pressure.

[0044] is the inner circle area of the valve seat 200; is the projected area of the valve cover 400, expressed as: , where, is the pressure difference between the lower and upper sides of the valve disc 300 when the valve disc 300 just reaches the highest opening position and the tank pressure at this time.

[0045] Specifically, the overpressure value of the traditional breather valve (i.e., the pressure increase value of the valve from opening to fully open) is usually relatively high, resulting in a low set pressure of the valve and an overly wide opening pressure range. During the discharge process of the storage tank medium, the overly wide opening range will cause volatile organic compounds (VOCs) to start escaping at a relatively low pressure, making it difficult to control the fugitive emissions and不利于维持储罐的稳定微正压环境。

[0046] where, is the inner circle area of the valve seat 200, which is determined by the structural dimensions of the valve seat 200 and is a fixed value. The projected area of the valve cover 400 on the horizontal plane, the size of which is directly determined by the diameter of the valve cover 400. It should be noted that there is an unclear expression "不利于维持储罐的稳定微正压环境" in the original text. You may need to check and correct it according to the actual situation.This is a dimensionless proportionality coefficient. Its physical meaning is the ratio of the net pressure acting on the lower surface of the valve disc 300 (i.e., the pressure difference ΔP between the bottom of the valve disc 300 and the top of the valve cover 400) to the pressure Py inside the storage tank at that moment, when the valve disc 300 has just risen to its designed maximum opening position. It comprehensively reflects the various flow resistances generated when gas flows through the complex flow channel formed by valve disc 300, valve cover 400 and valve body 100, as well as the impact effect of airflow on valve disc 300.

[0047] Specifically, when valve disc 300 is in a critical open state, the pressure inside the tank... It only needs to overcome the gravity G of the valve disc 300 assembly (valve disc 300 + valve cover 400), that is When the valve disc 300 rises to its maximum opening height, gas can flow through the annular gap. At this time, the net lift force acting on the lower surface of the valve disc 300... × It still needs to be balanced with gravity G, that is Overpressure value is defined as follows: By simultaneously solving the above mechanical equilibrium equations and introducing coefficients... This allows us to derive the final formula for calculating the K value.

[0048] In summary, the low overpressure breathing valve of this embodiment, by establishing and applying a precise theoretical relationship between the key dimension of the valve cover 400 and the overpressure value K, realizes the active and quantitative design of the core performance parameter of the breathing valve—the overpressure value. This fundamentally solves the industry pain points of traditional breathing valves, such as wide emission range, low set pressure, and difficulty in VOCs control caused by excessively high overpressure values.

[0049] Example 2

[0050] Reference Figures 1-4 This is the second embodiment of the present invention. Unlike the previous embodiment, this embodiment provides a ratio coefficient. Impact stagnation pressure coefficient The formulas for the diameter D1 and height h of the valve cover 400 illustrate how the diameter D1 and height h of the valve cover 400, as key parameters in the design of low overpressure breathing valves, affect the internal flow resistance and impact pressure of the breathing valve.

[0051] Specifically, further, the ratio coefficient Calculated using the following formula: , in, The flow resistance coefficient is the flow rate of the airflow passing through the 300mm section around the valve disc. The impact stabilization pressure coefficient; It is the total flow resistance coefficient of the airflow from the inlet to the outlet.

[0052] Specifically, based on the previous structural and dimensional relationship, it further defines the specific method for the ratio coefficient η. By performing a refined fluid dynamics model of the gas flow process inside the breather valve, the theoretical prediction and calculation of the ratio coefficient η are realized, thus providing a reliable basis for the precise design of the valve cover 400 dimension.

[0053] in, : Represents the "flow resistance coefficient of the airflow passing through the flow section around valve disc 300". When valve disc 300 is open, the airflow mainly flows out through the annular gap between valve disc 300 and valve seat 200, bypassing valve disc 300. Since the outlet of the breather valve is usually located on one side of valve body 100, the airflow is not uniformly and symmetrically flowing in the valve cavity. This model equates the flow path bypassing valve disc 300 to two parallel air paths: Path one is a longer flow path far from the outlet side, where the airflow needs to bypass valve disc 300, flow through the back pressure zone, and then turn towards the outlet; Path two is a shorter flow path closer to the outlet side, where the airflow can flow directly to the outlet after bypassing valve disc 300.

[0054] This refers to the equivalent flow resistance coefficient of these two parallel paths, the calculation of which incorporates friction losses along the flow path through the annular gap, local losses from sudden contraction and expansion of the flow channel cross-section, etc. Furthermore, treating the flow section as a dual-path parallel flow, rather than a simple single channel, more realistically reflects the asymmetric flow caused by the offset of the breather valve outlet, thus... The calculations are more realistic.

[0055] : Represents the "impact stagnation pressure coefficient". This coefficient is used to quantify the impact effect of airflow on the lower surface of valve disc 300. When high-speed airflow impacts valve disc 300 from below, some dynamic pressure is converted into static pressure, generating an additional lift force on valve disc 300. This effect cannot be fully described by a flow resistance model based on pressure loss, so a separate coefficient Z is introduced for characterization. The calculation of Z considers the variation of impact efficiency with distance from valve disc 300, as well as the weighted effect of impact on the central cylindrical surface and annular surface of valve disc 300. The separate introduction of the impact stagnation pressure coefficient Z compensates for the deficiency of the pure flow resistance model in reflecting the physical mechanism of kinetic energy being directly converted into static pressure (i.e., generating additional force), thus giving the model's predicted η value, and consequently the predicted overpressure value K, higher accuracy.

[0056] This represents the "total flow resistance coefficient of airflow from inlet to outlet." It is equal to the sum of the coefficients of all flow resistance units that the airflow passes through within the breather valve, specifically including the flow resistance of the inlet pipe section. Flow resistance of valve disc 300 adjacent to the upstream cavity section The flow resistance of the valve disc 300 surrounding section mentioned above and the flow resistance of the outlet pipe section. .Right now .in, and The calculation takes into account friction loss along the straight pipe section and local losses due to sudden changes in pipe cross-section (such as sudden expansion); Then treat it as an equivalent straight pipe and calculate its friction loss.

[0057] By using the ratio coefficient The calculation formula allows designers to obtain a relatively accurate estimate during the valve design phase, based on the internal structural dimensions of the valve body 100 (such as the diameter, length, and cavity diameter of each pipe section) and the pre-set dimensions of the valve cover 400, by substituting a series of classic fluid dynamics formulas. Value. Then, this ratio coefficient can be... By substituting the overpressure value K into the main design formula, the overpressure performance of the valve cover with size 400 can be predicted or verified, or the valve cover size 400 that meets the target overpressure value can be solved in reverse. This shortens the product development cycle, reduces the trial production cost, and ensures the consistency and predictability of product performance, providing a solid theoretical tool for the precise design and performance optimization of low overpressure breathing valves.

[0058] Furthermore, the impact stagnation pressure coefficient The calculation formula is: , in, The impact efficiency coefficient ranges from 0.7 to 1.3. Let the impact efficiency function be used. , , in, For the characteristic impact depth, satisfying .

[0059] The core idea of ​​this formula is to extend this basic principle to engineering applications, specifically to non-ideal, non-uniform impact scenarios of the breather valve. During the opening of the breather valve and the upward impact of the airflow on the valve disc 300, the kinetic energy of the high-speed airflow is partially converted into static pressure (i.e., stagnation pressure) acting on the lower surface of the valve disc 300, thus generating an additional lift. This physical effect directly affects the force balance of the valve disc 300 at its maximum opening position, thereby affecting the overpressure value K. Ignoring or roughly estimating this effect in the design model will lead to deviations in the calculation of the comparison coefficient η and the final overpressure value K, making it difficult to achieve accurate low overpressure design.

[0060] Specifically, (Impact Efficiency Coefficient): This is an empirical correction coefficient, ranging from 0.7 to 1.3. It characterizes the efficiency reduction or enhancement when the ideal jet impact theory is applied to the actual complex valve cavity flow field. A value less than 1 indicates that the actual impact pressure is lower than the ideal theoretical value, which may be due to energy dissipation caused by factors such as airflow turbulence, diffusion, or non-perpendicular impact; a value greater than 1 may reflect a certain accumulation or enhancement effect of the valve cover structure on the flow field. This range is based on the fitting of CFD simulation and experimental data of a typical breather valve structure.

[0061] In the formula and These are weighting coefficients. It is the projected area of ​​the central cylindrical portion of valve disc 300. ,in The diameter of the valve disc is 300.

[0062] It is the projected area of ​​the 300mm annular portion of the valve disc. The sum of the areas of these two parts It is approximately equal to the total effective projected area of ​​the lower surface of the valve disc 300 subjected to airflow impact. This is because the central cylindrical portion of the valve disc 300 (height is...) The valve disc 300 and its outer annular portion (with a height reference of 0) are at different heights from the airflow nozzle, resulting in different impact efficiencies. Therefore, an area-weighted method is used to combine the impact effects of these two parts. The valve disc 300 is not a simple flat plate, but a combination of a central cylinder and an outer annular surface. The formula calculates the area and corresponding impact efficiency of each part separately (considering the height difference), and then performs an area-weighted average, which more accurately describes the influence of the actual geometry on the impact force than simplifying the valve disc 300 into a single flat plate.

[0063] Impact efficiency function Used to describe the impact efficiency as a function of impact distance The relationship between the distance between the impact point and the airflow outlet or the virtual impact source plane. When When the distance is very short, the jet has not yet fully developed, resulting in low impact efficiency. With... Increased size leads to improved impact efficiency. When When the velocity is too large, the jet diffuses excessively, the core velocity decreases, and the impact efficiency drops again. This functional form can better simulate this nonlinear trend of first increasing and then decreasing, because the airflow in the valve cavity is not an ideal free jet, but involves diffusion, turbulence, and three-dimensional effects. An efficiency function varying with distance is introduced. and empirical coefficient This is precisely to correct the deviation between theoretical and actual values, so that the model can be practical in engineering.

[0064] (Feature impact depth): This is the feature length parameter in the function, which determines the distance at which the efficiency reaches its peak.

[0065] Function independent variable: For the central cylindrical portion, the height of its lower surface from the reference plane is approximately... Therefore, use For the annular portion, its lower surface is essentially located on the reference plane (height is 0), therefore it uses... This reflects the difference in impact efficiency between the two structural parts due to their height difference.

[0066] Density and area terms: This is the density of the working medium (usually air). This is the projected area of ​​the valve cover (400). The formula is finally multiplied by... This is to normalize the impact pressure effect and convert it into a form consistent with the dimensions of the flow resistance coefficient R (i.e., the pressure loss coefficient), so as to be compatible with... Addition participation ratio coefficient The calculation.

[0067] In summary, this formula ultimately expresses the impact effect as a coefficient. Its dimensions are the same as the flow resistance coefficient. The similarity allows the impact force to be easily incorporated into the total flow resistance network model in the form of an "equivalent additional flow resistance". This approach achieves a seamless integration of the flow resistance loss model and the momentum impact model, enabling designers to quantify the crucial physical factor of airflow impact when applying low overpressure design theory. Combined with the flow resistance calculations in the previous embodiments, the η value of the breathing valve under specific structural dimensions can be predicted more comprehensively and accurately, thereby precisely controlling the overpressure value K.

[0068] Furthermore, the diameter D1 and height h of the valve cover 400 satisfy the following: ≤h≤ , ≤D1≤ .in The valve disc has a thickness of 300 mm. H is the diameter of valve disc 300, H is the maximum opening height of valve disc 300, and D is the inner diameter of valve body 100.

[0069] Specifically, if the height h of the valve cover 400 is too small or the diameter D1 is too large, it may interfere with the structure of the valve disc 300 or the inner cavity of the valve body 100, respectively, causing the valve to fail to open and close normally. Improper size selection may also affect the rationality of the internal flow channel, thereby threatening operational stability. Therefore, this embodiment clearly specifies... ≤h≤ , ≤D1≤ , the diameter D1 needs to satisfy ≤D1≤ . The setting of these boundary conditions directly stems from the mechanical structure of the breather valve, kinematic requirements, and flow channel space limitations. The lower limit of the height h≥ is the minimum size to ensure that the airfoil of the valve cover 400 can cross the valve disc to achieve the effect of converging air flow; the upper limit of the height h≤ is a constraint to prevent interference between the airfoil of the valve cover 400 and the lower cavity of the valve body 100. The lower limit of the diameter ≤D1 ensures that the valve cover 400 can completely cover the valve disc 300, which is the starting point for realizing its functions such as guiding air flow and changing the effective force-bearing area of the valve disc 300; the upper limit of the diameter D1≤ is a rigid condition to ensure that the valve cover 400 can move freely in the inner cavity of the valve body 100 without radial interference, and it is also the key to ensuring that gas can flow smoothly through the annular gap between the valve cover 400 and the valve body 100.

[0070] By setting these engineering boundary conditions, this embodiment anchors the abstract low overpressure design theory on the basis of engineering practice. In the actual design process, engineers first calculate multiple combinations of D1 and h based on performance goals and the aforementioned theoretical model, and then these solutions must be substituted into the constraint conditions of this embodiment for verification. Only when both ≤h≤ and ≤D1≤ are satisfied do the solutions have engineering significance, and then the optimal solution can be selected by comprehensively considering factors such as process and cost.

[0071] In summary, through the collaborative design of the diameter D1 and height h of the valve cover 400, the pressure change rate during the process of the breather valve from opening to fully open is precisely controlled, that is, the overpressure value K, thereby significantly narrowing the valve opening interval and increasing the set pressure.

[0072] The core lies in establishing a quantitative relationship between the key dimensions of the valve cover 400 and the overpressure value: the overpressure value K is determined by the formula and is controlled within the range of 0<K<8%. Among them, the area of the valve seat 200 is fixed, the projected area of the valve cover 400 is directly determined by D1, and the key coefficient is calculated through the flow model - this model comprehensively considers the flow resistance of the gas flowing around the valve disc 300 , the additional pressure effect generated by the air flow impacting the valve disc 300 , and the total system flow resistance .

[0073] During design, while satisfying the basic mechanical constraints ≤h≤ , ≤D1≤ On the premise that, by adjusting the combination of D1 and h to change , and then achieving the precise matching of the target overpressure value K. When the pressure in the tank reaches the set pressure , the valve disc 300 opens; as the pressure continues to rise slightly to , the valve disc 300 quickly reaches full open. Since the overpressure range is strictly controlled to be very narrow, the valve only opens and discharges in a very small high-pressure range, thus greatly reducing the medium discharge of the storage tank and achieving the dual purposes of source emission reduction and safe and precise control.

[0074] The remaining structures are the same as those in Embodiment 1.

[0075] Embodiment 3

[0076] Refer to Figures 1-4 , Figures 7-13 , for the third embodiment of the present invention. Different from the previous embodiment, this embodiment provides a design method for a low-overpressure breather valve. Specifically, the design method includes the following steps: S1: According to the force balance relationship and the inner circle area of the valve seat 200 , determine the design constraint relationship between the target overpressure value K0 and the projected area of the valve cover 400 and . According to the mechanical balance analysis of the valve disc 300 at two positions of critical opening and critical full open, the quantitative relationship between the overpressure value K and the inner circle area of the valve seat 200 , the projected area of the valve cover 400 and the proportionality coefficient η is derived: . Among them, the area of the valve seat 200 is pre-determined by basic parameters such as the nominal diameter of the valve. At the beginning of the design, a clear target overpressure value K0 (usually required 0 < K < 8%) needs to be set. This formula reveals the design essence: to achieve low overpressure (K ≤ K0), it is necessary to reasonably design the size of the valve cover 400 (determining ) and optimize the internal flow field (affecting ) so that the three satisfy the ≤ K0 constraint condition.

[0077] S2: Establish a flow resistance network model of the internal flow of the breather valve, and calculate the ratio coefficient and the diameter D of the valve cover 400 1、The correspondence between airfoil height h; this step is the core technical link of the design methodology, aiming to link the abstract coefficient η with the specific structural dimensions (diameter D1 and height h) of the valve cover 400 through a theoretical model. The model simplifies the complex three-dimensional gas flow inside the breather valve into a network composed of multiple flow resistance elements, assuming... The value is essentially determined by the ratio of the flow resistance of the local area (near valve disc 300) to the total flow resistance of the system.

[0078] S3: Determine the range of values ​​for D1 and h that satisfy K≤K0 through simulation or experimental optimization; their relationship with the constraints in S1. ≤K0 are combined. Because... It is a function of D1 Therefore, this inequality essentially defines a region in the two-dimensional plane that satisfies the target performance K≤K0.

[0079] S4: Manufacture the valve cover 400 according to the value range and conduct experimental verification. From the dimensional feasible range determined in S3, select one or more combinations with engineering convenience to manufacture the corresponding valve cover 400 prototype. Subsequently, conduct performance tests on the valve equipped with the valve cover 400 on a standard breather valve test platform to measure its overpressure value K. Compare the measured value with the target value K0 to verify the accuracy of the design. If the error is within an acceptable range, the design is complete; if there is a deviation, the test data can be fed back to the model in S2 for parameter correction and iterative optimization until the design requirements are met. This step is a key verification link connecting theoretical design and actual product, ensuring the reliability and effectiveness of the design scheme.

[0080] Furthermore, in establishing the flow resistance network model of the internal flow of the breathing valve, the flow resistance network model decomposes the internal flow channel of the breathing valve into multiple flow resistance units connected in series and / or in parallel, including the inlet pipe section, the upstream section of valve disc 300, the flow around valve disc 300, and the outlet pipe section, and uses the Darcy-Weisbach formula and the Borda-Carnot formula to calculate the flow resistance coefficient of each section.

[0081] In establishing the flow resistance network model of the internal flow of the breather valve, to accurately calculate the contrast coefficient η, a reasonable physical model of the gas flow process inside the breather valve must be performed. The method adopted in this embodiment is to decompose the entire flow path into several series and / or parallel flow resistance units. Specifically, the chambers and channels through which the airflow passes from the inlet flange to the outlet flange are divided into four main sections for modeling based on their geometric characteristics and flow functions: the inlet pipe section, the upstream section of valve disc 300, the flow around valve disc 300, and the outlet pipe section. This division method deconstructs the complex overall flow into a series of typical flow problems with relatively simple characteristics that are easy to describe theoretically.

[0082] For each flow resistance element, the flow resistance coefficient R is calculated based on classical incompressible fluid mechanics formulas. The Darcy-Weisbach formula is used to calculate the pressure loss along the pipe due to fluid viscosity and friction with the pipe wall in straight pipes or regular gaps; while the Borda-Carnot formula is used to calculate the local pressure loss caused by flow separation and vortex dissipation when the flow channel cross-section suddenly expands or contracts. By applying these formulas to each flow resistance element, analytical or semi-analytical relationships between the flow resistance coefficient R of each element and the corresponding flow channel geometry (such as diameter, length, gap height, etc.) can be derived. Finally, by synthesizing these elements based on their series and parallel connections, the total flow resistance of the system can be established. and the local flow resistance of valve disc 300 A complete functional relationship between the parameters and all key geometric parameters. This method directly applies engineering fluid mechanics theory to product design, laying a solid scientific foundation for the quantitative prediction of low overpressure performance.

[0083] Furthermore, the flow resistance coefficient of the inlet pipe section The calculation formula is: , in, Let be the Darcy friction coefficient, which is taken as 0.02 for metal pipes; This refers to the length of the inlet pipe section; The diameter of the inlet pipe section; This refers to the cross-sectional area of ​​the inlet pipe section; This refers to the cross-sectional area of ​​the valve cavity's inner diameter. This represents the working fluid density.

[0084] Specifically, the flow resistance coefficient for the inlet pipe section, a specific flow resistance unit. The detailed calculation formula and its principle.

[0085] When establishing the flow resistance network model of the internal flow of the breather valve, accurate modeling of the inlet pipe section is crucial, as it is the first section through which gas enters the valve body 100, and its flow losses directly affect the total flow resistance of the system. In this embodiment, the flow resistance coefficient of the inlet pipe section is... The following formula is used for calculation: , This formula has a clear physical meaning and source of composition, and it comprehensively considers the two main types of pressure loss in the inlet section: Friction loss along the friction path: from the formula The term is characterized. This part directly applies the core idea of ​​the Darcy-Weisbach formula. Among them, The Darcy friction coefficient is a dimensionless number whose value depends on the Reynolds number of the flow and the relative roughness of the pipe wall. For the stainless steel and other smooth metal pipes commonly used in breather valves, the flow is usually in the hydraulically smooth region or transition region. To simplify engineering calculations, empirical values ​​are typically used. =0.02. It is the length of the inlet straight pipe section. It is its inner diameter. This represents the length-to-diameter ratio of the pipe, which directly reflects the contribution of pipe length to friction loss.

[0086] Local expansion loss: from the formula This section characterizes the Borda-Carnot formula for sudden expansion of the cross-section. When gas flows from a cross-sectional area of... The inlet pipe flows into a valve cavity with a significantly larger cross-sectional area (its cross-sectional area is...). When D is the inner diameter of the valve cavity, the flow velocity drops abruptly, causing some kinetic energy to dissipate in the intense turbulent mixing, resulting in irreversible pressure loss. This term accurately captures the energy loss caused by this geometric abrupt change.

[0087] In the formula This is the density of the working fluid (usually air). Finally, the entire expression is multiplied by... This is to transform the loss coefficient into the standard flow resistance coefficient form with the square of the flow rate Q as the variable (i.e., satisfying...). This formula, based on fundamental principles and relying solely on the geometry of the inlet pipe section, the valve cavity size (D), and the physical properties of the fluid, achieves a reliable theoretical prediction of the inlet section flow resistance. It is a crucial foundation for building the accuracy of the entire flow resistance network model.

[0088] Furthermore, the flow resistance coefficient of the upstream section of valve disc 300 The calculation formula is:

[0089] in, The distance between the bottom surface of the valve disc 300 and the valve seat 200 when the valve disc 300 reaches its maximum opening height; The valve disc is 300mm thick; The valve cover has a 400 airfoil height; This refers to the inner diameter of the valve cavity; This represents the cross-sectional area of ​​the valve cavity's inner diameter.

[0090] Specifically, this relates to the flow resistance coefficient of the upstream segment of the valve disc 300 within the flow resistance network model. The calculation method.

[0091] When establishing the flow resistance network model, the upstream section of valve disc 300 refers to the valve cavity space located below valve disc 300 when valve disc 300 is opened to its maximum height H, i.e., the cylindrical region between the plane of valve seat 200 and the lower surface of valve disc 300. This flow channel is relatively regular, therefore its flow resistance coefficient is... The calculation can be simplified to a straight pipe friction loss model based on the Darcy-Weisbach formula.

[0092] The formula is constructed based on clear physical principles and geometric correspondences. The formula contains... This represents the calculated length of the equivalent straight pipe. Its structure is as follows: It is the initial distance between the bottom surface of the valve disc 300 and the upper surface of the valve seat 200 when the valve disc 300 is closed; It refers to the thickness of the valve disc 300 itself; This refers to the height of the valve cover at 400. When the valve disc at 300 rises to its maximum height... At that time, the actual distance between the lower surface of valve disc 300 and the plane of valve seat 200 is D is the diameter of this cylindrical cavity, i.e., the inner diameter of the valve cavity. Therefore, This is the length-to-diameter ratio of the equivalent flow channel. This is the Darcy friction coefficient (usually taken as 0.02). For fluid density, It is the cross-sectional area of ​​the valve cavity. The friction loss coefficient Combined with the velocity head expression, and converted into the standard flow resistance coefficient form. That is, the above is obtained. The calculation formula is as follows. This model reasonably simplifies the flow in the upstream cavity of the valve disc 300, attributing its resistance mainly to wall friction proportional to the flow length, thus contributing a precisely calculable component to the overall flow resistance network.

[0093] Furthermore, the flow resistance coefficient of the 300mm valve disc surrounding the flow section... The calculation includes the following steps: The airflow path is divided into path one, which is far from the outlet side, and path two, which is close to the outlet side. The flow resistance coefficient of path one is calculated separately. and the flow resistance coefficient of path two .

[0094] The total flow resistance is calculated using the parallel flow resistance formula: , Wherein, flow resistance coefficient The calculation formula is Flow resistance coefficient The calculation formula is ; The flow resistance around the airflow along path one of valve disc 300; The flow resistance coefficient is the flow path coefficient of the airflow radially through the valve disc 300. The flow resistance coefficient is the flow resistance coefficient of the airflow passing through the back pressure side of valve disc 300. It is the flow resistance coefficient of the airflow from the back pressure side to the outlet pipe; The flow resistance of the airflow through path two of valve disc 300; It is the flow resistance coefficient of the airflow radially through path two of valve disc 300.

[0095] Among them, the flow resistance coefficient of the most complex valve disc 300 flow section is... The calculation method.

[0096] Because the outlet of the breathing valve is usually located on the side of the valve body 100, the airflow is not symmetrical after the valve disc 300 is opened, resulting in a large error in the traditional single-channel model. This embodiment innovatively proposes a dual-path parallel flow channel model to accurately calculate the flow resistance in this section. The specific steps are as follows: First, based on the geometric symmetry of the flow, the path of the airflow around the valve disc 300 is divided into two parallel main paths. Path one is the airflow path away from the outlet side, where the airflow needs to bypass the valve disc 300, flow through the chamber (back pressure zone) on the back of the valve disc 300, and then turn towards the outlet; this path is longer. Path two is the airflow path closer to the outlet side, where the airflow can flow almost directly to the outlet after bypassing the valve disc 300; this path is shorter.

[0097] Calculate the flow resistance coefficient for path one separately. and the flow resistance coefficient of path two .in, The calculation comprehensively considers the local flow loss around the 300 annular gap of the valve disc, the friction loss that develops in the radial gap, the friction loss along the flow path in the back pressure chamber, and the local loss when turning from the back pressure zone to the outlet. The calculation mainly includes flow-around losses and radial friction losses. After obtaining... and Then, based on the calculation principle of flow resistance in parallel pipelines in fluid mechanics, the total flow resistance coefficient of the 300mm flow section around the valve disc was calculated. Calculated using the following formula: , This formula ensures that, under the same total pressure difference, the flow distribution of the two paths is inversely proportional to the square root of their flow resistance, conforming to the basic laws of parallel flow. Through this strategy of "breaking down the whole into parts, modeling in sections, and combining in parallel," this method can more realistically reflect the complex asymmetric flow inside the breather valve, thereby significantly improving the accuracy of predicting the flow resistance of the 300mm flow section around the valve disc, and even the flow resistance of the entire system.

[0098] Furthermore, The calculation formula is: , The calculation formula is: , in, The coefficient for flow loss due to necking; This is the flow loss coefficient for the expanded diameter; This is the effective proportion coefficient of the flow in path two; This represents the area of ​​the annular gap.

[0099] in, The calculation formula describes the overall loss of the airflow as it contracts from the valve cavity into the annular gap formed by the valve disc 300 and the valve cover 400, flows through the gap of length h, and then expands into the back pressure zone above the valve disc 300. Among these losses, It is the cross-sectional sudden shrinkage loss coefficient based on the Borda-Carnot formula; It is the friction loss along the flow path generated by the airflow over a length h in the annular gap, multiplied by This is to account for the increased flow velocity in this path caused by some traffic taking path two; It is the cross-sectional sudden expansion loss coefficient based on the Borda-Carnot formula. Area of ​​the annular gap .

[0100] For the radial flow resistance of path one The formula for calculating frictional losses during the airflow development from the center to the radial direction (annular gap inlet) below the valve disc 300 is derived from the Darcy-Weisbach formula in the radial flow coordinate system. In the formula, It is the characteristic height from the lower surface of valve disc 300 to the inlet section, and its cubic term reflects the combined effect of the radial flow cross-sectional area changing with radius on velocity distribution and friction loss. The item describes the radius of the inlet pipe. The radial integral effect from / 2 to the valve cavity radius D / 2. Similarly, the coefficient... Used to correct traffic allocation.

[0101] In the formula It is a geometric approximation of the path two flow ratio coefficient, where This is the diameter of the outlet pipe. This coefficient is based on the arc length of the outlet opening relative to the total circumference of the valve chamber. The proportion used to estimate the flow share directly to the outlet is a key coupling parameter connecting two paths. These formulas together constitute a refined physical description of the path-flow resistance.

[0102] Furthermore, The calculation formula is: , The calculation formula is: , The structure of this formula is similar to that of path one. The formula is similar, and it also includes the cross-sectional shrinkage loss. Friction loss along the annular gap and cross-sectional expansion loss The key difference lies in the correction factor for the friction loss term becoming... This is because the flow proportion coefficient *w* represents the share of the total flow through path two. Since the total flow rate *Q* is constant, the flow rate through path two is *w* × *Q*, and its velocity is higher. Therefore, under the same gap geometry, its frictional loss per unit length is greater. This portion of the loss was accurately amplified to reflect the impact of high flow rates.

[0103] The formula for calculating the radial flow resistance of path two is the same as that for path one. The formats are exactly the same, the only difference being that the flow allocation correction factor becomes... The reason is the same as above: the airflow in path two, during the radial flow stage below valve disc 300, has a higher velocity than the average velocity; therefore, the frictional loss caused by radial shear should also be proportional. Enlarge it.

[0104] By using the same physical model for two paths but different flow correction coefficients, this embodiment achieves differentiated modeling of asymmetric bipath flow within a unified theoretical framework. The coefficient w becomes the key parameter connecting the two paths and balancing the flow distribution, enabling the entire parallel model to consistently reflect the flow non-uniformity caused by the outlet bias.

[0105] Furthermore, the flow resistance coefficient of the outlet pipe section The calculation formula is: .

[0106] in, This refers to the length of the outlet pipe section; The diameter of the outlet pipe section; This refers to the cross-sectional area of ​​the outlet pipe section.

[0107] The outlet pipe section refers to the part of the pipeline connecting the valve cavity outlet flange to the outside atmosphere. The calculation of the flow resistance in this section is the final step in the flow resistance network model. The model is relatively simple and clear; the formula directly applies the core form of the Darcy-Weisbach formula, focusing on calculating the friction loss along the straight pipe section. It is the length of the outlet pipe section. It is its inner diameter. That is, its length-to-diameter ratio. The Darcy friction coefficient is usually taken as an empirical value of 0.02 for metal pipes. The fluid density is given. It is the cross-sectional area of ​​the outlet pipe. The formula combines the friction loss coefficient with the velocity head expression and transforms it into the standard flow resistance coefficient form.

[0108] Furthermore, in simulation or experimental optimization, computational fluid dynamics (CFD) simulation methods are used to simulate the internal flow field of the breather valve, by changing... Parametric analysis was performed on the values ​​of h to obtain simulation results for multiple sets of overpressure values ​​K.

[0109] In the CFD simulation, local mesh refinement was performed on the area near valve disc 300 and valve cover 400, with the mesh size not exceeding [value missing]. Where t is the edge thickness of the valve cover 400, and the k-ε turbulence model is used for steady-state simulation. In the experimental verification, multiple experimental valve covers 400 with different D1 and h are made, and the opening pressure and full opening pressure are tested on the breathing valve test bench. The actual overpressure value K is calculated and compared with the theoretical value for verification.

[0110] Specifically, in simulation or experimental optimization, to efficiently and systematically explore the relationship between the valve cover 400 dimensions and the overpressure value K and to verify the theoretical model, computational fluid dynamics (CFD) simulation is used as the core auxiliary method. In practice, firstly, a three-dimensional digital model of the breather valve is established based on the parameter range initially determined by the theoretical model. Then, the values ​​of the valve cover 400 diameter D1 and airfoil height h are systematically changed using parametric methods to generate a series of calculation examples. In the CFD simulation settings, to ensure calculation accuracy, especially to capture the complex flow separation and pressure gradients near the valve disc 300 and valve cover 400, local mesh refinement is required for these key areas. The refinement level requires the mesh size to be no larger than [value missing]. Where t is the thickness of the valve cover 400 edge, this requirement ensures the ability to analyze the fine effects of thin-walled structures on the flow field. The k-ε turbulence model, widely validated in engineering, is selected for steady-state simulation to balance computational accuracy and efficiency. By simulating each example, the flow field details under a given pressure difference can be directly obtained. Lift is obtained by integrating the surface pressure of the valve disc 300, and then combined with force balance calculations to determine the simulated overpressure value, thereby establishing a... The numerical mapping relationship between h and K is used to revise and enrich the theoretical model.

[0111] The calculations were divided into two groups: In group A, all examples had the same valve cover diameter D1 but different airfoil height h; in group B, all examples had the same valve cover airfoil height h but different diameter D1. The remaining geometric parameters are shown in the table below:

[0112] Reference Figures 7-13 For CFD calculation of cloud maps, corresponding to numbers a~g respectively.

[0113] Through fitting, the empirical parameter values ​​are obtained as follows:

[0114] Substituting the fitted empirical parameters into the calculation formula, the results are compared with the simulation results as follows:

[0115] The formula relates the valve disc airfoil length h to the valve disc thickness. When the dimensions are close, and the valve cover diameter With valve disc diameter The overpressure value calculated at close range has a relatively large error, while the error of the calculation results for other dimensions is within 10%.

[0116] To further verify the accuracy of the calculation formula, valve covers of different sizes were manufactured and divided into two groups for testing: in group A, all valve covers had the same diameter but different airfoil heights; in group B, all valve covers had the same airfoil height but different diameters.

[0117] Compare the overpressure values ​​obtained from the experiment with the overpressure values ​​calculated by the formula, and compare the specific dimensions of each valve cover with the corresponding results;

[0118] In experimental verification, physical testing is an indispensable final verification step. Based on several representative dimensional combinations obtained from CFD simulation and theoretical model optimization, multiple sets of physical test valve covers 400 were fabricated. Different valve covers 400 were assembled onto the same standard breathing valve body 100, and rigorous performance tests were conducted on a dedicated breathing valve test bench. The tests included accurately measuring the valve's opening and full-opening pressures, and calculating the actual overpressure value according to the definition. Finally, the experimental test values ​​were compared and analyzed with the theoretical predictions and CFD simulation values. If the three agree well (e.g., the error is within 10%), the theoretical model and design method are proven to be accurate and reliable, and the corresponding valve cover 400 dimensions are considered an effective design. If deviations exist, the experimental data can be used as the most realistic feedback to correct the empirical coefficients in the theoretical model, and the design can be iterated until satisfactory accuracy is achieved. This three-in-one closed-loop design verification process of "theory-simulation-experiment" greatly ensures the scientific rigor, reliability, and first-time success rate of the low overpressure breathing valve design.

[0119] Example 4

[0120] Reference Figures 5-6This is the fourth embodiment of the present invention. Unlike the previous embodiment, this embodiment provides a parallel low-overpressure breathing valve. Its structural feature is that the positive pressure discharge functional unit and the vacuum suction functional unit are arranged side-by-side within the same valve body, forming a compact dual-function breathing valve. This embodiment details how the low-overpressure design principles and methods of the present invention can be applied to the positive and negative pressure valve sections of this type of parallel structure, further demonstrating the wide applicability and engineering practicality of the present invention.

[0121] refer to Figure 5 (Schematic diagram of positive pressure valve section) and Figure 6 (Schematic diagram of negative pressure valve section) The parallel breather valve mainly includes a valve body, a positive pressure valve unit and a negative pressure valve unit arranged in parallel.

[0122] The positive pressure valve unit is used to open the vent when the pressure in the storage tank exceeds the set positive pressure setting value. Its core components include a positive pressure valve seat, a positive pressure valve disc, a positive pressure valve cover connected to the valve disc, and a positive pressure air inlet channel (composed of the first section A1 and the second section A2) and a positive pressure air outlet channel that communicate with the outside.

[0123] The negative pressure valve unit is used to open the intake when the vacuum degree in the storage tank exceeds the set negative pressure setting value. Its core components include a negative pressure valve seat, a negative pressure valve disc, a negative pressure valve cover connected to the valve disc, as well as a negative pressure intake channel (section C) and a negative pressure outlet channel (passing through section E and the shared section A1 in sequence).

[0124] The two valve units have independent airflow paths within the valve body, but can share some valve body structure and external interfaces. This embodiment aims to illustrate that, despite its more complex structure, the overpressure control theory and flow resistance network design method established in this invention, after adaptation, can still accurately guide this parallel breather valve to achieve low overpressure performance.

[0125] For positive pressure valve sections, the achievement of low overpressure performance still follows the formula: , in, The inner circle area of ​​the positive pressure valve seat. This represents the projected area of ​​the positive pressure valve cover.

[0126] The calculation of the proportionality coefficient η follows the flow resistance network model established in this invention: , Total flow resistance Based on its specific flow channel, it can be decomposed into: = + + + , The main difference from Example 1 lies in the flow resistance of the inlet pipe section. The calculation is required. Because parallel-structure inlet channels can be more complex, for example, consisting of two pipes of different diameters connected in series (e.g., ...). Figure 5 (As shown in segments A1 and A2), therefore, the flow resistance calculation requires segmented processing followed by summation: , in, , , and , These are the lengths and diameters of the first and second sections of the inlet, respectively. This represents the cross-sectional area of ​​the valve cavity. This calculation method is still entirely based on the Darcy-Weisbach and Borda-Carnot formulas, only with segmented superposition for specific flow channel geometry; its physical model and core formulas remain unchanged.

[0127] For the flow resistance of the valve disc winding section and impact stabilization pressure coefficient The calculation formula and model are completely consistent with those in Example 1. Only the corresponding geometric parameters of the positive pressure valve section need to be substituted.

[0128] For the negative pressure valve section, the principle of this invention also applies to the control of low overpressure (here referring to the increase in vacuum required to reach full opening) during its suction process. The formula for the overpressure value is: , in, The inner circle area of ​​the vacuum valve seat. This represents the projected area of ​​the vacuum valve cover.

[0129] The formula for calculating the proportionality coefficient η has the same form: , Total flow resistance Decomposed according to the airflow path of negative pressure intake. For example Figure 6 As shown, the airflow enters from the C-section inlet, bypasses the vacuum valve disc, and passes through the E-section and the shared... The segment flows out. Therefore: , , The flow resistance of each section is calculated as follows: Inlet section flow resistance (Corresponding to section C): , Outlet section flow resistance (Corresponding to section E, considered as a straight pipe section): , in, .

[0130] Shared outlet section flow resistance (Corresponding to segment A1, the calculation is the same as the first segment inlet of the positive pressure valve section). Flow resistance of the valve disc surrounding the flow section. With impact coefficient The calculation model and formula are the same as before; simply substitute the geometric parameters of the negative pressure valve section.

[0131] This embodiment demonstrates that the low overpressure design method provided by this invention is effectively applicable to all types of breathing valves, whether they are simple single-breathing valves, coaxial breathing valves, or more complex parallel breathing valves (including their positive and negative pressure valve sections). Its versatility is reflected in: Unified performance target formula: Overpressure value K all pass control.

[0132] Consistent modeling kernel: all coefficients η are derived from the formula based on the flow resistance network model. Solving the problem. Scalable flow resistance calculation: For any specific breather valve structure, simply decompose it into multiple standard flow resistance units (straight pipe sections, expansion / neck sections, bypass sections, etc.) according to its actual airflow path, and apply the corresponding classical formulas (Darcy's formula, Borda-Carnot formula, etc.) to calculate, thus constructing its customized flow resistance network model. The decomposition and combination of flow resistance units vary depending on the structure, but the underlying physical principles and calculation formulas are uniformly provided by this method.

[0133] Therefore, this embodiment not only discloses a specific implementation of a parallel breathing valve, but more importantly, through this example of a complex structure, it verifies the powerful adaptability and engineering practical value of the low overpressure design theory of this invention as a general calculation tool and methodology, which can guide the precise design and optimization of the low overpressure performance of breathing valves of various structural types.

[0134] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A low overpressure breathing valve, characterized in that: It includes a valve body (100), a valve seat (200) disposed inside the valve body (100) and having an opening, a valve disc (300) adapted to the opening of the valve seat (200), and a valve cover (400) connected to the valve disc (300). The valve disc (300) is longitudinally movably connected to the valve seat (200), and the inner wall shape of the valve cover (400) is adapted to the outer wall shape of the valve seat (200). The diameter D1 of the valve cover (400) satisfies the following relationship: ， ， Where K is the overpressure value, and satisfies 0 <K<8%, The inner circle area of ​​the valve seat (200) is... For the projected area of ​​the valve cover (400), The pressure difference between the bottom of the valve disc (300) and the top of the valve cover (400) when the valve disc (300) just reaches the highest opening position. With the pressure inside the tank at this time The ratio of .

2. The low overpressure breathing valve as described in claim 1, characterized in that: The ratio coefficient Calculated using the following formula: , in, The flow resistance coefficient is the flow resistance coefficient of the airflow passing through the section surrounding the valve disc. The impact stabilization pressure coefficient; It is the total flow resistance coefficient of the airflow from the inlet to the outlet.

3. The low overpressure breathing valve as described in claim 2, characterized in that: The impact stabilization pressure coefficient The calculation formula is: ， in, The impact efficiency coefficient ranges from 0.7 to 1.

3. Let the impact efficiency function be used. ， ， ， in, For the characteristic impact depth, satisfying .

4. The low overpressure breathing valve as described in any one of claims 1 to 3, characterized in that: The diameter D1 of the valve cover (400) and the airfoil height h satisfy the following: ≤h≤ , ≤D1≤ , in, The thickness of the valve disc (300) is... H is the diameter of the valve disc (300), H is the maximum opening height of the valve disc (300), and D is the inner diameter of the valve body (100).

5. A design method for a low overpressure breathing valve, characterized in that: Includes the following steps: Based on the force balance relationship and the inner circle area of ​​the valve seat (200) Determine the target overpressure value K0 and the projected area of ​​the valve cover (400). as well as Design constraints; Establish a flow resistance network model of the internal flow of the breather valve and calculate the ratio coefficient. The correspondence between the valve cover (400) diameter D1 and the airfoil height h; Based on the aforementioned correspondence, the ratio and the undetermined coefficients in the valve cover (400) diameter D1 and airfoil height h are obtained through simulation or experimental optimization fitting, thereby determining the range of values ​​for D1 and h that satisfy K≤K0; The valve cover (400) is manufactured according to the value range of D1 and h, and tested and verified.

6. The design method of the low overpressure breathing valve as described in claim 5, characterized in that: In the established flow resistance network model for the internal flow of the breathing valve, the flow resistance network model decomposes the internal flow channel of the breathing valve into multiple flow resistance units connected in series and / or in parallel, including the inlet pipe section, the upstream section of the valve disc, the flow section around the valve disc, and the outlet pipe section, and uses the Darcy-Weisbach formula and the Borda-Carnot formula to calculate the flow resistance coefficient of each section.

7. The design method of the low overpressure breathing valve as described in claim 6, characterized in that: The flow resistance coefficient of the inlet pipe section The calculation formula is: ， in, Darcy's coefficient of friction; This refers to the length of the inlet pipe section; The diameter of the inlet pipe section; This refers to the cross-sectional area of ​​the inlet pipe section; This refers to the cross-sectional area of ​​the valve cavity's inner diameter. The density of the working fluid.

8. The design method of the low overpressure breathing valve as described in claim 6, characterized in that: The flow resistance coefficient of the upstream section of the valve disc The calculation formula is: , This is the distance between the bottom surface of the valve disc and the valve seat when the valve disc reaches its maximum opening height. The thickness of the valve disc; This refers to the height of the valve cover airfoil; This refers to the inner diameter of the valve cavity; This represents the cross-sectional area of ​​the valve cavity's inner diameter.

9. The design method of the low overpressure breathing valve as described in any one of claims 6 to 8, characterized in that: The flow resistance coefficient of the valve disc surrounding section The calculation includes the following steps: The airflow path is divided into path one, which is far from the outlet side, and path two, which is close to the outlet side. The flow resistance coefficient of path one is calculated separately. and the flow resistance coefficient of path two ; The total flow resistance is calculated using the parallel flow resistance formula: , Wherein, flow resistance coefficient The calculation formula is: ; Flow resistance coefficient The calculation formula is: ; The flow resistance is the resistance around the airflow as it passes through path one of the valve disc. The flow resistance coefficient is the radial flow path of the airflow through the valve disc. The flow resistance coefficient is the flow resistance coefficient of the airflow passing through the back pressure side of the valve disc; It is the flow resistance coefficient of the airflow from the back pressure side to the outlet pipe; The flow resistance is the resistance around the airflow as it passes through path two of the valve disc. It is the flow resistance coefficient of the airflow radially through path two of the valve disc.

10. The design method of the low overpressure breathing valve as described in claim 9, characterized in that: The The calculation formula is: , The The calculation formula is: , in, The coefficient for flow loss due to necking; The expansion flow rate loss coefficient; This is the effective proportion coefficient of the flow in path two; This represents the area of ​​the annular gap.

11. The design method of the low overpressure breathing valve as described in claim 10, characterized in that: The The calculation formula is: , The The calculation formula is: 。 12. The design method of the low overpressure breathing valve as described in any one of claims 6, 7, 8, and 10, characterized in that: The flow resistance coefficient of the outlet pipe section The calculation formula is: , in, This refers to the length of the outlet pipe section; The diameter of the outlet pipe section; This refers to the cross-sectional area of ​​the outlet pipe section.

13. The design method of the low overpressure breathing valve as described in any one of claims 5, 6, 7, 8, and 10, characterized in that: In the simulation or experimental optimization, the computational fluid dynamics (CFD) simulation method is used to simulate the internal flow field of the breather valve. By changing the values ​​of D1 and h, parameterized analysis is performed to obtain simulation results of multiple overpressure values ​​K. In the CFD simulation, the local mesh is refined in the area near the valve disc (300) and valve cover (400), with the mesh size not exceeding [size missing]. , where t is the edge thickness of the valve cover (400), and steady-state simulation is performed using the k-ε turbulence model; In the experimental verification, multiple test valve covers (400) with different D1 and h were made, and the opening pressure and full opening pressure were tested on the breathing valve test bench. The actual overpressure value K was calculated and compared with the theoretical value for verification.

Images