A method of designing a combined valve core / valve seat

Abstract

The present application relates to a kind of combination valve core / valve seat design method, first determine the material parameters and process parameters of the product to be designed, then design the interference amount between the part size of the product to be designed, body and outer cylinder;Calculate whether gap appears between the body and outer cylinder of the product to be designed at working temperature, if appear, then increase interference amount;If no gap appears, then select elastic criterion or elastoplasticity criterion to carry out failure analysis of the product to be designed at ambient temperature, if failure, then reduce interference amount;If not failure, then judge whether holding force is enough, enough then complete calculation, otherwise increase interference amount.The present application guides the design of combination valve core / valve seat according to interference amount and yield relationship, can design combination valve core valve seat with wider working temperature range and larger interference amount, avoid gap between sleeve and outer cylinder at high temperature and improve the carrying capacity of cylinder.

Description

Technical Field

[0001] This invention belongs to the field of engineering mechanics and mechanical structure design, and relates to a design method for a combined valve core / seat. Background Technology

[0002] Control valves are commonly used in extreme conditions, such as high temperature, high pressure differential, and working media containing hard particles. These conditions easily lead to wear, erosion, or corrosion of the valve core, causing it to crack or break, thus weakening or even eliminating the valve's regulating capacity. Early valve cores were made of solid carbide, such as silicon carbide or tungsten carbide, which have high hardness and wear resistance. However, using solid carbide for the valve core has many drawbacks. First, the manufacturing and processing of carbide materials is very expensive. Second, large-sized parts are difficult to form due to limitations in equipment size and the length-to-diameter ratio. Finally, the probability of internal defects in carbide increases with volume, making the material more prone to fracture. Currently, composite valve core structures are mostly used, consisting of a carbide valve core and a steel valve stem, significantly reducing the amount of carbide used.

[0003] However, existing valve core assemblies have some shortcomings and defects. Most existing mechanical analyses of thick-walled cylinders under high-pressure conditions are limited to single-layer material cases. However, in high-pressure environments, to improve the pressure-bearing capacity of the structure, it is usually necessary to combine different materials to form a composite structure. How to guide the design of combined valve cores and seats based on interference fits and yield relationships, avoid gaps between the sleeve and outer cylinder at high temperatures, and improve the load-bearing capacity of the cylinder, is currently a major challenge in the engineering field.

[0004] In addition, current challenges in the engineering field include: Existing theories do not allow for plastic deformation of the outer cylinder, which severely restricts the selection of materials for the combined valve core and valve seat, especially making it difficult to select an outer cylinder material with a large coefficient of linear expansion. Due to limitations in expansion capacity, the operating temperature range for the combined valve core and seat is narrow. The interference fit given in the design of the combined valve core and valve seat is too conservative.

[0005] Therefore, it is urgent to conduct research on the design methods of combined valve cores and seats in order to overcome the above-mentioned problems. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a combined valve core / seat and its design method.

[0007] The solution of the present invention is as follows: A design method for a combined valve core / seat includes the following steps: Step 1: Determine the material and process parameters of the product to be designed. The product to be designed includes a body and an outer cylinder. When the product to be designed is a combined valve core, the body is a wear-resistant valve core; when the product to be designed is a combined valve seat, the body is a wear-resistant valve seat. Step 2: Design the component dimensions of the product to be designed, and the interference fit between the main body and the outer cylinder. Proceed to the third step; Step 3: Calculate the operating temperature Next, check if there is a gap between the product body and the outer cylinder. If there is, return to step two and increase the interference fit; if there is no gap, proceed to step four. Step 4: Select either the elasticity criterion or the elastoplastic criterion to perform failure analysis on the product under ambient temperature. If no failure occurs, proceed to Step 5; if failure occurs, return to Step 2 and reduce the interference fit. Step 5: Determine whether the holding force between the body and the outer cylinder is sufficient to overcome the force exerted on the body by the fluid under operating pressure at the operating temperature. With gravity If the gripping force is sufficient, the calculation is complete; otherwise, return to step three and increase the interference.

[0008] Preferably, in the third step, the operating temperature Lower interference satisfy:

[0009] like

[0010] This results in a gap between the product body and the outer cylinder. in, The outer diameter of the body. The coefficient of linear expansion of the bulk. For ambient temperature, The coefficient of linear expansion of the outer cylinder. > .

[0011] Preferably, in the fourth step, the elasticity criterion is selected to perform failure analysis on the product under ambient temperature, as follows: The criterion for determining whether the inner diameter of the outer cylinder corresponding to the body yields at ambient temperature is as follows:

[0012] If the above criteria are met, the system will not fail; otherwise, it will fail.

[0013] Preferably, in the fourth step, the elastoplastic criterion is selected to perform failure analysis on the product under ambient temperature, as follows: Calculate the outer diameter of the yielded region of the outer cylinder under ambient temperature. If the diameter is less than the outer diameter of the outer cylinder multiplied by the safety factor If the diameter is greater than the outer cylinder outer diameter × safety factor, it will not fail; If so, it will be ineffective; Calculate the outer diameter of the yielded region of the outer cylinder under ambient temperature. According to the outer diameter of the yielded region of the outer cylinder Calculate fitting pressure The system determines whether reverse yielding has occurred; if it has, the system fails; otherwise, it does not fail.

[0014] Preferably, the following equation can be used to solve the problem. :

[0015] in, The Poisson's ratio of the entity. The Young's modulus of the solid. The inner diameter of the body. To match the pressure, This refers to the pressure exerted on the inner wall of the body. The Poisson's ratio of the outer cylinder. The Young's modulus of the outer cylinder. The outer diameter of the outer cylinder. The outer diameter of the main body at the equilibrium position after the product to be designed is installed. The equilibrium position refers to the position where the outer diameter of the main body is equal to the inner diameter of the outer cylinder.

[0016] Preferred,

[0017] It represents the yield strength.

[0018] If the following conditions are met:

[0019] Then it is determined that reverse yielding will occur.

[0020] Preferably, in the fifth step, when the gripping force between the body and the outer cylinder... A grip is considered sufficient when the following formula is met:

[0021] Given that the coefficient of friction between the body and the outer cylinder is k, and the side contact area is S, then we have

[0022] Preferably, the assembly temperature of the product to be designed > Operating temperature >Ambient temperature .

[0023] A combined valve core designed using the aforementioned combined valve core / seat design method includes a wear-resistant valve core and a valve core outer cylinder. The wear-resistant valve core is interference-fitted into the valve core outer cylinder, and after installation, one end of the wear-resistant valve core protrudes from the valve core outer cylinder. The linear expansion coefficient of the valve core outer cylinder is greater than that of the wear-resistant valve core.

[0024] Preferably, the wear-resistant valve core material is hard alloy or ceramic, and the valve core outer cylinder material is austenitic stainless steel.

[0025] A combined valve seat designed using the aforementioned combined valve core / seat design method includes a wear-resistant valve seat and a valve seat outer cylinder; The wear-resistant valve seat is interference-fitted into the outer cylinder of the valve seat; the coefficient of linear expansion of the outer cylinder of the valve seat is greater than that of the wear-resistant valve seat.

[0026] Preferably, the wear-resistant valve seat material is hard alloy or ceramic, and the valve seat outer cylinder material is austenitic stainless steel.

[0027] The advantages of this invention compared to the prior art are: (1) The present invention guides the design of the combined valve core / seat based on the interference fit and yield relationship. It is a design method to avoid gaps between the sleeve and the outer cylinder at high temperatures and to improve the load-bearing capacity of the cylinder.

[0028] (2) The method of the present invention can design a combination valve core and valve seat with a wider operating temperature range and a larger interference fit. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the combined valve core and combined valve seat structure of the present invention; Figure 2 This is a sectional view of the combined valve core and combined valve seat; Figure 3 This is a schematic diagram showing the key dimensions of the combined valve core; Figure 4 This is a schematic diagram showing the key dimensions of the combined valve seat; Figure 5 for Figure 3 or Figure 4 Diagram of interference fit; Figure 6 for Figure 2 Sectional view of the combined valve core in the AA direction; Figure 7 for Figure 2 Sectional view of the combined valve seat in the middle BB direction; Figure 8 This is a schematic diagram of the mechanical model of the combined valve core; Figure 9This is a schematic diagram of the mechanical model of the combined valve seat; Figure 10 This is a schematic diagram showing the axial force on the valve core during operation. Figure 11 A flowchart illustrating the design method for combining valve core and valve seat. Detailed Implementation

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] like Figure 1 The diagram shows a schematic of the combined valve core 1 and the combined valve seat 2. The combined valve core 1 includes a valve core 11 and a valve core outer cylinder 12, and the combined valve seat 2 includes a valve seat 21 and a valve seat outer cylinder 22.

[0032] like Figure 2 The valve core 11 or valve seat 21 is connected to the corresponding outer cylinder portion by an interference fit. The valve core 11 or valve seat 12 is made of high-hardness, wear-resistant materials such as tungsten carbide (WC), which has a low coefficient of linear expansion. The valve core outer cylinder 12 and valve seat outer cylinder 22 are made of tough materials such as austenitic stainless steel, which have a higher coefficient of linear expansion. The coefficient of linear expansion of the valve core outer cylinder 12 is greater than that of the valve core 11. The coefficient of linear expansion of the valve seat outer cylinder 22 is greater than that of the valve seat 21.

[0033] like Figure 3 As shown, the key parameter of the combined valve core 1 is the outer diameter of the valve core 11. Valve core outer cylinder 12 inner diameter , outer diameter Size relationships are as follows: Figure 5 As shown, before assembly > Assembled at high temperature, and then cooled to achieve an interference fit. Due to geometric constraints, after assembly, the contact surfaces of the inner and outer parts expand under pressure to the same diameter. The valve core and valve core outer cylinder assembly are modeled as tightly connected without slippage, and the junction satisfies the conditions of radial displacement continuity and radial stress continuity.

[0034] like Figure 4 As shown, the key parameter of the combined valve seat 2 is the outer diameter of the valve seat 21. Valve seat outer cylinder 22 inner diameter , outer diameter Size relationships are as follows: Figure 5 As shown, before assembly > Assembled at high temperature, and then cooled to achieve an interference fit. Due to geometric constraints, after assembly, the contact surfaces of the inner and outer parts expand under pressure to the same diameter. The valve seat 21 and the valve seat outer cylinder 22 assembly are modeled as tightly connected without sliding, and the junction satisfies the conditions of continuous radial displacement and continuous radial stress.

[0035] like Figure 6 , 8 Since the axial force is not large, the vertical axial section of valve core 11 or valve seat 21 (respectively) Figure 2 Sections AA and BB can reflect the stress state after assembly. The stress state can be determined by, for example, Figure 7 , 9 The mechanical model diagram shown illustrates that the structural difference between the two lies in whether or not an internal diameter is present. Does the difference in force between the holes indicate internal pressure? Due to the significant pressure caused by the expansion of valve core 11 or valve seat 21, the corresponding outer cylinder undergoes plastic deformation starting from the inner wall. The boundary between the plastic zone and the elastic zone is located at the diameter... At the location; while the valve core 11 or valve seat 21, due to the selection of high-strength materials, will not yield. Therefore, from the inside out, the zones are elastic, plastic, and elastic, with the dividing line diameter being... , . Figure 10 This is a schematic diagram showing the axial force on the valve core during operation.

[0036] In theory, through Figure 11 The process, given the initial overshoot By continuously refining the values, a suitable value can be obtained.

[0037] The design method for a combined valve core / seat proposed in this invention is applicable to combined valve cores or combined valve seats. For ease of description, it is referred to as the product to be designed. The product to be designed includes a body and an outer cylinder. The specific steps are as follows: Step 1: Determine the material parameters and process parameters.

[0038] like Figure 1 Determine the physical property parameters of the product to be designed, including the coefficient of linear expansion. Young's modulus Poisson's ratio Yield strength In this invention, the characteristic parameters of the valve core and valve seat are represented by subscript 1, and the characteristic parameters of the outer cylinder are represented by subscript 2.

[0039] Specify the temperature. This includes the operating temperatures of the combined valve core 1 and valve seat 2. Assembly temperature Ambient temperature There is an assembly temperature. > Operating temperature >Ambient temperature .

[0040] Step 2: Design the dimensions of the parts.

[0041] If the product to be designed is a combination valve core, such as Figure 3 As shown, the key parameters of the combined valve core 1 include the inner diameter of the valve core 11. , outer diameter and the inner diameter of the outer cylinder 12 and outer diameter After the valve core 11 is combined with the outer cylinder 12, the outer diameter of the valve core 11 is... With the inner diameter of outer cylinder 12 Equal, diameter at equilibrium position .

[0042] If the product to be designed is a combination valve seat, such as Figure 4 As shown, the key parameters of the combined valve seat 2 include the inner diameter of the valve seat 21. , outer diameter and the inner diameter of the outer cylinder 22 and outer diameter After the valve seat 21 is combined with the outer cylinder 22, the outer diameter of the valve seat 21 is... With the inner diameter of the outer cylinder 22 Equal, diameter at equilibrium position .

[0043] Provide or adjust the interference fit. Based on the dimensions from step three, specify the ambient temperature. Below, the interference fit between the outer diameter of the main body and the inner diameter of the outer cylinder. First, an initial value is given. The interference is adjusted based on feedback from subsequent steps.

[0044] Step 3: Failure analysis at operating temperature. Calculate the failure rate at operating temperature. Next, check whether there is a gap between the valve core 11 or valve seat 21 and their respective outer cylinders 12 / 22.

[0045] Operating temperature interference:

[0046] Gap Judgment Criteria:

[0047] If yes, return to step two and increase the interference. If no, proceed to the next step.

[0048] Step 4: Failure analysis at ambient temperature. Select either the elastic criterion or the elastoplastic criterion as the design criterion.

[0049] If the elasticity criterion is chosen: determine whether the inner diameter of the outer cylinder 12 corresponding to the valve core 11 (the outer cylinder 22 corresponding to the valve seat 21) yields at ambient temperature, that is, whether the combined stress exceeds the yield strength. The judgment criteria are:

[0050] If the elastic-plastic criterion is chosen: calculate the outer diameter of the yielded region of the outer cylinder at ambient temperature. If the diameter is smaller than the outer diameter of the outer cylinder × Safety factor of fitting Then proceed to the next step. If the diameter is greater than the outer cylinder outer diameter × fitting safety factor, then... Then return to step three and reduce the interference. Solve for a given interference using the following equation. .

[0051]

[0052] in,

[0053] The criteria for determining whether the yield strength exceeds the limit are as follows:

[0054] Compression yield test. After reaching the plastic limit, there is a maximum constraint that determines whether the combined valve core or combined valve seat has reached a stable state. At the operating temperature, it is necessary to determine whether the outer cylinder has undergone compression yielding. If so, return to step two and reduce the interference fit by modifying the design dimensions.

[0055] The criteria for determining whether reverse yielding will occur are as follows:

[0056] Step 5: Grip Force Judgment. Determine the grip force between the valve core 11 or valve seat 21 and its respective outer cylinder at the operating temperature. Can it overcome the force exerted by the fluid on the valve core or valve seat under operating pressure? With gravity The combined force of the two forces, along with the safety factor N for holding the object.

[0057] Taking the combined valve core as an example, the gripping force is calculated to determine whether the gripping force between the valve core 11 and the outer cylinder 12 is sufficient at the operating temperature. The judgment criteria are as follows:

[0058] Given the coefficient of friction between the valve core and the outer cylinder is k, and the side contact area is S, then we have

[0059] If the gripping force is sufficient, complete the calculation. Otherwise, return to step three and increase the interference.

[0060] The combined valve core designed using the aforementioned combined valve core / seat design method includes a wear-resistant valve core and a valve core outer cylinder. The wear-resistant valve core is interference-fitted into the valve core outer cylinder, with one end of the wear-resistant valve core protruding from the valve core outer cylinder after installation. The linear expansion coefficient of the valve core outer cylinder is greater than that of the wear-resistant valve core. The wear-resistant valve core is made of hard alloy or ceramic, and for most wear-resistant and erosion-resistant applications, its HRC is required to be between 70 and 75. For applications with higher wear resistance requirements, its HRC is required to be between 75 and 80. The valve core outer cylinder is made of austenitic stainless steel.

[0061] The combined valve seat designed using the aforementioned combined valve core / seat design method includes a wear-resistant valve seat and a valve seat outer cylinder. The wear-resistant valve seat is interference-fitted into the valve seat outer cylinder. The linear expansion coefficient of the valve seat outer cylinder is greater than that of the wear-resistant valve seat. The wear-resistant valve seat material is hard alloy or ceramic, typically with a linear expansion coefficient of 11-17 × 10⁻⁶. -6 Between / ℃, the outer cylinder of the valve seat is made of austenitic stainless steel.

[0062] In this invention, the valve core or seat is made of high-hardness, wear-resistant materials such as hard alloys and ceramics, including tungsten carbide, silicon carbide, titanium nitride, and corundum. The outer cylinder is made of austenitic stainless steel or other materials with certain strength and toughness. The linear expansion coefficient of the outer cylinder is greater than that of the corresponding valve core or seat. Before installation, there is a certain interference fit between the inner diameter of the outer cylinder and the outer diameter of the valve core or seat. At high temperatures, this creates an installation gap. During the cooling process after installation, the outer cylinder contracts and clamps tightly to the valve core or seat, resulting in elastic deformation or even localized yielding deformation.

[0063] This invention also discloses a design method applicable to the material selection and interference fit design of interference-fitted combined valve cores. This method can quantitatively provide the relationship between material physical properties, interference fit, and yield zone, avoiding gaps between the sleeve and outer cylinder at high temperatures and improving the load-bearing capacity of the cylinder. By employing a special combined valve core and seat design method, this invention expands the range of material selection and component size design, enabling the combined valve core and seat to operate more stably in environments with strong corrosion, high abrasion, high pressure differential, and high temperature. The main body of this invention is made of elastic metal, exhibiting no significant yielding phenomenon. The outer cylinder is made of an alloy material that, after assembly, undergoes elastic deformation to yielding within a certain internal range. The main body and outer cylinder are connected by an interference fit. The linear expansion coefficient of the inner cylinder is less than that of the outer cylinder, allowing for assembly at high temperatures. This invention considers the elastic and elastoplastic deformation states of the assembly under high internal pressure loads, analyzes its stress distribution and deformation compatibility conditions, and derives relevant mathematical expressions and solution steps. Under normal temperature conditions where the outer cylinder does not yield, there is no gap between the main body and outer cylinder at the operating temperature. The internal pressure of the combined valve core is 0, while the internal pressure of the combined valve seat is not 0. The design method allows for a certain degree of yielding within the outer cylinder at normal temperature, with a boundary line at a certain diameter between the plastic and elastic regions. The boundary coefficient ζ between the plastic and elastic regions must be less than the boundary safety factor. .

[0064] The combined valve core and valve seat designed using this invention operate between 200-600℃.

[0065] The theoretical derivation and formulas of this invention can be used to guide the design and verification of valve core-thick-walled cylindrical assemblies, ensuring that their structural performance achieves the expected pressure-bearing and stability effects.

[0066] Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A design method for a combined valve core / seat, characterized in that, The steps include the following: Step 1: Determine the material and process parameters of the product to be designed. The product to be designed includes a body and an outer cylinder. When the product to be designed is a combined valve core, the body is a wear-resistant valve core; when the product to be designed is a combined valve seat, the body is a wear-resistant valve seat. Step 2: Design the component dimensions of the product to be designed, and the interference fit between the main body and the outer cylinder. Proceed to the third step; Step 3: Calculate the operating temperature Next, check if there is a gap between the product body and the outer cylinder. If so, return to step two and increase the interference fit. If no gap appears, proceed to step four; Step 4: Select either the elasticity criterion or the elastoplastic criterion to perform failure analysis on the product under ambient temperature. If no failure occurs, proceed to Step 5. If it fails, return to step two and reduce the interference. Step 5: Determine whether the holding force between the body and the outer cylinder is sufficient to overcome the force exerted on the body by the fluid under operating pressure at the operating temperature. With gravity If the gripping force is sufficient, the calculation is complete; otherwise, return to step three and increase the interference.

2. The design method of a combined valve core / seat according to claim 1, characterized in that, In the third step, the operating temperature Lower interference satisfy: like This results in a gap between the product body and the outer cylinder. in, The outer diameter of the body. The coefficient of linear expansion of the body is denoted as . For ambient temperature, The coefficient of linear expansion of the outer cylinder. > .

3. The design method of a combined valve core / seat according to claim 1, characterized in that, In the fourth step, the elasticity criterion is selected to perform failure analysis on the product under ambient temperature, as follows: The criterion for determining whether the inner diameter of the outer cylinder corresponding to the body yields at ambient temperature is as follows: If the above criteria are met, the system will not fail; otherwise, it will fail.

4. The design method of a combined valve core / seat according to claim 1, characterized in that, In the fourth step, the elastoplastic criterion is selected to perform failure analysis on the product under ambient temperature, as follows: Calculate the outer diameter of the yielded region of the outer cylinder under ambient temperature. If the diameter is less than the outer diameter of the outer cylinder multiplied by the safety factor If the diameter is greater than the outer cylinder outer diameter × safety factor, it will not fail; If so, it will be ineffective; Calculate the outer diameter of the yielded region of the outer cylinder under ambient temperature. According to the outer diameter of the yielded region of the outer cylinder Calculate fitting pressure The system determines whether reverse yielding has occurred; if it has, the system fails; otherwise, it does not fail.

5. The design method of a combined valve core / seat according to claim 4, characterized in that, Solve using the following equation : in, The Poisson's ratio of the entity. The Young's modulus of the solid. The inner diameter of the body. To match the pressure, This refers to the pressure exerted on the inner wall of the body. The Poisson's ratio of the outer cylinder. The Young's modulus of the outer cylinder. The outer diameter of the outer cylinder. The outer diameter of the main body at the equilibrium position after the product to be designed is installed. The equilibrium position refers to the position where the outer diameter of the main body is equal to the inner diameter of the outer cylinder.

6. The design method of a combined valve core / seat according to claim 4, characterized in that, It represents the yield strength.

7. If the following conditions are met: Then it is determined that reverse yielding will occur.

8. The design method of a combined valve core / seat according to claim 1, characterized in that, In the fifth step, when the gripping force between the main body and the outer cylinder... A grip is considered sufficient when the following formula is met: Given that the coefficient of friction between the body and the outer cylinder is k, and the side contact area is S, then we have 。 9. The design method of a combined valve core / seat according to claim 1, characterized in that, Assembly temperature of the product to be designed > Operating temperature >Ambient temperature .

10. A combined valve core designed using the combined valve core / seat design method according to any one of claims 1-7, characterized in that, It includes a wear-resistant valve core and a valve core outer cylinder. The wear-resistant valve core is interference-fitted into the valve core outer cylinder. After installation, one end of the wear-resistant valve core protrudes from the valve core outer cylinder. The linear expansion coefficient of the valve core outer cylinder is greater than that of the wear-resistant valve core.

11. The combined valve core according to claim 9, characterized in that: The wear-resistant valve core material is hard alloy or ceramic, and the valve core outer cylinder material is austenitic stainless steel.

12. A combined valve seat designed using the combined valve core / seat design method according to any one of claims 1-8, characterized in that, Includes a wear-resistant valve seat and a valve seat outer cylinder; The wear-resistant valve seat is interference-fitted into the outer cylinder of the valve seat; the coefficient of linear expansion of the outer cylinder of the valve seat is greater than that of the wear-resistant valve seat.

13. A combined valve seat according to claim 11, characterized in that: The wear-resistant valve seat material is hard alloy or ceramic, and the valve seat outer cylinder material is austenitic stainless steel.

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