A design method for pressure-bearing equipment to resist explosion loads

Abstract

The present invention discloses a design method for pressure-bearing equipment that resists explosion loads. The method first determines the working conditions, use requirements, explosion load types, explosion load impulses and main technical parameters of the pressure-bearing equipment, and then performs a preliminary design of the structural dimensions of the pressure-bearing equipment, and performs static strength verification. The finite element software is then used to perform elastic-plastic dynamic response analysis on the pressure-bearing equipment to obtain the distribution of plastic strain of the pressure-bearing equipment; the residual strength of the plastic strain concentration area of ​​the pressure-bearing equipment is calculated, and finally the residual strength of the pressure-bearing equipment is calculated, and the safety status verification standards for single use and multiple use of the pressure-bearing equipment are used to determine whether the explosion-proof performance of the pressure-bearing equipment meets the design requirements. The method of the present invention proposes a new calculation method for residual strength, and realizes the differentiated design of pressure-bearing equipment that resists single explosions and multiple explosions, which is highly targeted.

Description

Technical Field

[0001] The invention relates to the field of pressure-bearing equipment design, and in particular to a method for designing pressure-bearing equipment capable of resisting explosion loads. Background Art

[0002] Pressure vessels and pipelines are often used to store and transport flammable and explosive media such as natural gas and hydrogen. During their service, pressure equipment faces the threat of medium explosions or shock waves from explosions of other nearby pressure equipment. In some environments with high safety requirements, pressure equipment needs to be designed for intrinsic safety - even if a single or multiple explosions occur in the surrounding area, the pressure equipment will not be damaged. However, the existing conventional pressure equipment design method only analyzes and verifies the structure under static loads, lacks consideration of the explosion-proof performance of pressure equipment, and cannot meet the design requirements of pressure equipment that can resist explosion loads.

[0003] At present, relevant design methods for pressure-bearing equipment that resists explosion loads have also been developed. The design method proposed by the Atomic Weapons Establishment (AWE) of the United Kingdom stipulates that the dynamic response of pressure-bearing equipment that resists multiple explosion loads is strictly limited to the elastic range. This method is too conservative as a whole. The fact that a certain part of the structure enters the plastic deformation stage does not mean that the entire equipment loses its bearing capacity. Moreover, it is only applicable to the design of pressure-bearing equipment that resists multiple explosion loads, and does not consider the design requirements of pressure-bearing equipment that resists a single explosion load. In the explosion-proof design method of pressure-bearing equipment, the American Society of Mechanical Engineers (ASME) stipulates that strain classification and linearization should be performed on the parts with large structural strains under explosion loads, and the membrane strain, bending strain and peak strain should be calculated and checked separately. The design method of the Los Alamos National Laboratory (LANL) in the United States stipulates that the equivalent membrane strain and equivalent plastic strain of the structure should be calculated and checked with the specified allowable value. Although both of the above methods are applicable to the design of pressure-bearing equipment that resists single and multiple explosion loads, they do not distinguish between the design of pressure-bearing equipment that resists single and multiple explosion loads. In addition, there are also shortcomings such as high implementation difficulty, complex process, and difficulty for engineers to understand. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention proposes a method for designing pressure-bearing equipment capable of resisting explosion loads. The method has low implementation difficulty, short process, and is easy for engineers to understand.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for designing pressure-bearing equipment to resist explosion loads, the method comprising the following steps:

[0007] Step 1: Determine the working conditions and use requirements of the pressure-bearing equipment, determine the type of explosion load that the pressure-bearing equipment is subjected to, the magnitude of the explosion load impulse that needs to be resisted, and the main technical parameters;

[0008] Step 2: Conduct a preliminary design of the structural dimensions of the pressure-bearing equipment to determine the type and geometric shape of the pressure-bearing equipment; determine the structural dimensions of the pressure-bearing equipment according to the applicable design codes and standards; and conduct a static strength check on the preliminarily designed pressure-bearing equipment. If the static strength check fails, redesign the structural dimensions of the pressure-bearing equipment. If the static strength check passes, proceed to Step 3.

[0009] Step 3: Use finite element software to construct a numerical analysis model for the dynamic response of the pressure-bearing equipment under explosion loads, conduct an elastoplastic dynamic response analysis on the pressure-bearing equipment, and obtain the plastic strain distribution of the pressure-bearing equipment.

[0010] Step 4: Analyze the plastic strain distribution of the pressure-bearing equipment, select the area where the plastic strain of the pressure-bearing equipment is concentrated, and calculate the remaining strength S of the plastic strain concentrated area of the pressure-bearing equipment according to the following formula i :

[0011]

[0012] where l i is the maximum depth of the plastic zone in the i area along the wall thickness direction. When the plastic zone distribution along the wall thickness direction is discontinuous, l i takes the sum of the depths of the plastic zones along the wall thickness direction; t is the wall thickness value of the pressure-bearing equipment corresponding to the i area. When the pressure-bearing equipment does not produce a plastic zone under the given explosion load, S i = 1;

[0013] Step 5: Calculate the remaining strength S of the pressure-bearing equipment according to the following formula:

[0014] S = min(S i ), i = 1, 2, 3, … n

[0015] Step 6: When the pressure-bearing equipment is a single-use equipment and the remaining strength S satisfies 0 < S ≤ 1, or when the pressure-bearing equipment is a multi-use equipment and the remaining strength S satisfies S = 1, the designed pressure-bearing equipment passes the safety status check of the pressure-bearing equipment under explosion loads. Otherwise, return to Step 2 to redesign the pressure-bearing equipment.

[0016] Further, the specific content of Step 2 includes:

[0017] If the design pressure of the pressure-bearing equipment is not greater than 35 MPa, determine the geometric dimensions of the equipment according to the GB150 national standard, and conduct a static strength check on the structure of the pressure-bearing equipment according to the elastic failure design criterion.

[0018] If the design pressure of the pressure equipment is greater than or equal to 35MPa and less than 100MPa, or the design pressure of the pressure equipment is 0.1MPa-100MPa and requires fine design, the geometric dimensions of the pressure equipment shall be determined according to the JB4732 industry standard, and the static strength finite element analysis of the pressure equipment shall be carried out using the analytical design method, and stress classification and linearization verification shall be carried out on stress concentration areas.

[0019] Furthermore, in the step 1, the main technical parameters of the pressure equipment include design pressure, working pressure, geometric volume, material selection requirements, design temperature range, working temperature range, medium composition and medium characteristics.

[0020] Furthermore, when performing elastic-plastic dynamic response analysis on the pressure-bearing equipment, the explosion shock wave impulse = the original explosion shock wave impulse × the explosion safety factor; wherein the explosion safety factor is taken as 1.7-2.0.

[0021] Furthermore, when analyzing the elastic-plastic dynamic response of pressure-bearing equipment, the explosion load is realized by applying a corresponding pressure load related to time on the wall of the pressure-bearing equipment, or by combining the immersed boundary method and arbitrary Lagrangian-Euler to construct a fluid-solid coupling numerical analysis model of the dynamic response of the pressure-bearing equipment under the explosion flow field. The mechanical properties of the pressure-bearing equipment material in the model are described by the stress-strain constitutive relationship related to the strain rate.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention proposes a new calculation method for residual strength, and provides different design and safety verification criteria for pressure-bearing equipment that resists single and multiple explosion loads, thereby improving the pertinence of the design. Compared with the existing design method for pressure-bearing equipment that resists explosion loads, this method realizes the differentiated design of pressure-bearing equipment that resists single explosion and multiple explosions; at the same time, compared with the existing safety verification criteria based on strain classification and linearization, the safety verification criteria for pressure-bearing equipment in this method are easy to implement, have a short process, and are easy for engineers to understand. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart of a method for designing a pressure-containing equipment for resisting explosion loads according to the present invention.

[0025] Figure 2 Schematic diagram of the numerical analysis model of the dynamic response of the hydrogen storage cylinder under explosion load in the embodiment.

[0026] Figure 3 For Figure 2 The result diagram of the elastic-plastic dynamic response analysis of the hydrogen storage cylinder that has been constructed in .

[0027] Figure 4This is the plastic strain distribution diagram along the wall thickness direction of region 1 where the plastic strain is concentrated in Example 1. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] like Figure 1 As shown, the design method of pressure-bearing equipment for resisting explosion loads of the present invention comprises the following steps:

[0030] 1. Clarify the design requirements and conditions of pressure equipment

[0031] Determine the working conditions and use requirements of pressure equipment. Determine the type of explosion load that the pressure equipment is subjected to and the size of the explosion load impulse that needs to be resisted. Determine the main technical parameters, including design pressure, working pressure, geometric volume, material selection requirements, design temperature range, working temperature range, medium components, medium characteristics, equipment category, service life and other requirements.

[0032] 2. Preliminary design and verification of pressure equipment structural dimensions

[0033] Conduct preliminary design of the structural dimensions of the pressure-bearing equipment. Determine the type (e.g., spherical, cylindrical) and geometry of the equipment, and determine the main dimensions of the equipment, such as height, diameter, wall thickness, etc., based on applicable design specifications and standards.

[0034] If the design pressure of the pressure equipment is not greater than 35MPa, the geometric dimensions of the equipment shall be determined according to the national standard GB150, and the static strength of the pressure equipment structure shall be checked according to the elastic failure design criteria;

[0035] If the design pressure of the pressure equipment is greater than or equal to 35MPa and less than 100MPa, or the design pressure of the pressure equipment is 0.1MPa-100MPa and requires fine design, the geometric dimensions of the pressure equipment shall be determined according to the JB4732 industry standard, and the static strength finite element analysis of the pressure equipment shall be carried out using the analytical design method, and stress classification and linearization verification shall be carried out on stress concentration areas.

[0036] If the static strength check fails, the structural dimensions of the pressure-bearing equipment will need to be redesigned.

[0037] 3. Analysis of elastic-plastic dynamic response of pressure-bearing equipment under explosion load

[0038] Before conducting the elastic-plastic dynamic response analysis of pressure-bearing equipment, the corresponding explosion safety factor must be taken according to the design requirements. The ASME explosion-resistant design method for pressure-bearing equipment can be referred to, and a value of 1.7-2.0 is recommended. When conducting the dynamic response analysis of pressure-bearing equipment under explosion load, the explosion shock wave impulse = original explosion shock wave impulse × explosion safety factor.

[0039] The numerical analysis model of the dynamic response of pressure equipment under explosion load is constructed by using software such as LS-DYNA, ABAQUS, and AUTODYN. The explosion load can be achieved by applying a corresponding pressure load related to time on the wall of the pressure equipment, or by combining the immersed boundary method, arbitrary Lagrangian-Euler and other algorithms to construct a fluid-solid coupling numerical analysis model of the dynamic response of pressure equipment under explosion flow field. The mechanical properties of the pressure equipment material in the model are described by the stress-strain constitutive relationship related to the strain rate, that is:

[0040]

[0041] Where σ is stress, are strain and strain rate, respectively, and the material mechanical properties parameters in the above constitutive relationship are obtained at the corresponding temperature of the pressure equipment before the explosion load is applied. The stress-strain mechanical properties parameters related to the material strain rate can be obtained by conducting a Hopkinson bar dynamic loading test on the material sample, or by searching relevant literature.

[0042] 4. Safety status verification of pressure-bearing equipment under explosion load

[0043] Analyze the distribution of plastic strain of the pressure-bearing equipment obtained by simulation, select the area with concentrated plastic strain for residual strength calculation, where the residual strength of area i of the pressure-bearing equipment is expressed as S i Characterize it, which is defined as:

[0044]

[0045] In the formula, l i is the maximum depth of the plastic zone in region i along the wall thickness direction. When the plastic zone distribution along the wall thickness direction is discontinuous, l i Take the sum of the depths of the plastic zone along the wall thickness direction; t is the wall thickness of the pressure-bearing equipment corresponding to area i. When the pressure-bearing equipment does not produce a plastic zone under a given explosion load, S i =1.

[0046] Calculate the residual strength S of the pressure-bearing equipment, where S is defined as the residual strength S of each area i The minimum value of , that is:

[0047] S=min(S i ),i=1,2,3,…n

[0048] That is, when S = 1, the pressure-bearing equipment is safe; when 0 < S < 1, the pressure-bearing equipment is damaged, and its specific explosion resistance performance is characterized by the value of S. The larger the S value, the stronger the explosion resistance performance; when S = 0, the pressure-bearing equipment undergoes full yield, and it is considered that the pressure-bearing equipment completely loses the ability to resist the explosion load. According to the calculated remaining strength S value of the pressure-bearing equipment, the structure is checked.

[0049] Design the safety state check criteria for single-use and multiple-use pressure-bearing equipment, and stipulate:

[0050] The single-use equipment should meet the requirements: it does not rupture under a single explosion load, and 0 < S ≤ 1

[0051] The equipment for repeated use should meet the requirements: it can be reused under multiple explosion loads, and S = 1

[0052] Therefore, when the pressure-bearing equipment is a single-use equipment and the remaining strength S satisfies 0 < S ≤ 1, or when the pressure-bearing equipment is a multiple-use equipment and the remaining strength S satisfies S = 1, the designed pressure-bearing equipment passes the safety state check of the pressure-bearing equipment under the explosion load; otherwise, return to redesign the pressure-bearing equipment until the explosion resistance performance of the pressure-bearing equipment meets the design requirements, and the anti-explosion design of the pressure-bearing equipment is completed.

[0053] Embodiment

[0054] According to the steps of the design method of the present invention, design a single-layer hydrogen storage cylinder that can withstand a single explosion load and can resist an explosion shock wave impulse of not less than 10 4 MPa·s, the cylinder volume is 205L, and the design pressure is 50MPa.

[0055] 1. Define the design requirements and conditions of the pressure-bearing equipment

[0056] According to the working environment, determine the main technical parameters as shown in Table 1.

[0057] Table 1 Main technical parameters of the single-layer hydrogen storage cylinder to be designed

[0058]

[0059] 2. Preliminary design and check of the structural dimensions of the pressure-bearing equipment

[0060] According to the geometric volume of 205L of the single-layer hydrogen storage cylinder to be designed, the cylinder length is determined to be 2000mm, the inner diameter is 414.2mm, and the hemispherical head is selected as the head form.

[0061] Calculate the wall thickness of the cylinder according to the cylinder thickness calculation formula:

[0062]

[0063] In the formula, δ is the calculated thickness; p cTo calculate the pressure, take 50MPa; D i is the inner diameter of the cylinder; [σ] t is the allowable stress of the material, which is taken as 398MPa; φ is the welding joint coefficient, which is taken as 0.8.

[0064] According to the above formula, the thickness of the gas cylinder is 35.4mm.

[0065] After the structural dimensions are determined, according to the JB4732 standard, the analysis and design method is used to carry out static strength finite element analysis of the pressure-bearing equipment, and stress classification and linearization verification are carried out on stress concentration areas.

[0066] 3. Analysis of elastic-plastic dynamic response of pressure-bearing equipment under explosion load

[0067] The explosion safety factor is 2.0, and the explosion shock wave impulse is 10 when analyzing the dynamic response of pressure-bearing equipment under explosion load. 4 ×2.0=2×10 4 MPa·s.

[0068] According to the design parameters of the single-layer hydrogen storage cylinder mentioned above, the LS-DYNA software is used to construct a numerical analysis model of the dynamic response of the hydrogen storage cylinder under explosion load, as shown in the figure. Figure 2 As shown in the figure. The gas cylinder is discretized using Lagrangian units. The grids at key locations of the gas cylinder are refined. The middle of the gas cylinder is subjected to an explosion load, which is achieved by applying a pressure-time load curve in the middle of the outer wall. The internal pressure of the gas cylinder is achieved by applying a pressure boundary condition on the inner wall. Fixed boundary conditions are applied to the left and right heads of the gas cylinder.

[0069] The mechanical properties of the gas cylinder material in the model are described by the Johnson-Cook dynamic constitutive model, namely:

[0070]

[0071] Where, σ and ε are equivalent stress and equivalent plastic strain; A, B, n, C are material constitutive parameters; is the reference strain rate.

[0072] Relevant literature was searched to obtain the material parameters of 4130X steel, which are listed in Table 2. Where ρ is the material mass density, E is Young's modulus, and υ is Poisson's ratio.

[0073] Table 2. 4130X steel material parameters

[0074]

[0075] According to the established numerical analysis model, elastic-plastic dynamic response analysis is carried out, and the results are as follows: Figure 3 shown.

[0076] 4. Safety status verification of pressure-bearing equipment under explosion load

[0077] Analyze the distribution and size of the plastic strain of the gas cylinder obtained by simulation, and select the area where the plastic strain is concentrated for residual strength calculation, where the residual strength S of area i is i Calculated by the following formula:

[0078]

[0079] The area where the simulated plastic strain is concentrated is located at the center of the explosion surface, and this area is set as area 1. The distribution of plastic strain in this area along the wall thickness direction is as follows: Figure 4 As shown, the maximum depth of the plastic zone along the wall thickness direction is l 1 is 21.6 mm, and the residual strength S is obtained by substituting it into the above formula. 1 =0.39. The residual strength S of the cylinder is defined as the residual strength S of each area i The minimum value is S=0.39.

[0080] According to the calculated residual strength S value, the safety status of the structure is checked. According to regulations, the pressure-bearing equipment should meet the following requirements when subjected to a single explosion load:

[0081] Single explosion loading without rupture, 0 <S≤1

[0082] The gas cylinder has S=0.39 under single explosion loading, which meets the design requirements.

[0083] The main parameters of the designed single-layer hydrogen storage cylinder are shown in Table 3.

[0084] Table 3 Main parameters of designed single-layer hydrogen storage cylinders

[0085]

[0086] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A method for designing pressure-bearing equipment to resist explosion loads, characterized in that: The method includes the following steps: Step 1: Determine the working conditions and usage requirements of the pressure-bearing equipment, determine the type of explosion load borne by the pressure-bearing equipment, the magnitude of the explosion load impulse to be resisted, and the main technical parameters; Step 2: Conduct a preliminary design of the structural dimensions of the pressure-bearing equipment to determine the type and geometric shape of the pressure-bearing equipment; determine the structural dimensions of the pressure-bearing equipment according to the applicable design codes and standards; And conduct a static strength check of the preliminarily designed pressure-bearing equipment; If the static strength check fails, redesign the structural dimensions of the pressure-bearing equipment; If the static strength check passes, proceed to Step 3; Step 3: Use finite element software to construct a numerical analysis model of the dynamic response of the pressure-bearing equipment under explosion load, conduct an elastoplastic dynamic response analysis of the pressure-bearing equipment, and obtain the plastic strain distribution of the pressure-bearing equipment; Step 4: Analyze the distribution of plastic strain of pressure-bearing equipment, select the area where plastic strain of pressure-bearing equipment is concentrated, and calculate the residual strength S of the strain concentration area of ​​pressure-bearing equipment according to the following formula: i : In the formula, l i is the maximum depth of the plastic zone in region i along the wall thickness direction. When the plastic zone distribution along the wall thickness direction is discontinuous, l i Take the sum of the depths of the plastic zone along the wall thickness direction; t is the wall thickness of the pressure-bearing equipment corresponding to region i; when the pressure-bearing equipment does not produce a plastic zone under a given explosion load, S i =1; Step 5: Calculate the remaining strength S of the pressure-bearing equipment according to the following formula: S=min(S i ),i=1,2,3,…n Step 6: When the pressure-bearing equipment is a single-use equipment and the remaining strength S satisfies 0 < S ≤ 1, or when the pressure-bearing equipment is a multi-use equipment and the remaining strength S satisfies S = 1, the designed pressure-bearing equipment passes the safety status check of the pressure-bearing equipment under explosion load; Otherwise, return to Step 2 to redesign the pressure-bearing equipment.

2. The method for designing pressure-bearing equipment for resisting explosion loads according to claim 1, characterized in that: The specific content of Step 2 includes: If the design pressure of the pressure-bearing equipment is not greater than 35 MPa, determine the geometric dimensions of the equipment according to the national standard GB150, and conduct a static strength check of the pressure-bearing equipment structure according to the elastic failure design criterion; If the design pressure of the pressure-bearing equipment is greater than or equal to 35 MPa and less than 100 MPa, or the design pressure of the pressure-bearing equipment is 0.1 MPa - 100 MPa and fine design is required, determine the geometric dimensions of the pressure-bearing equipment according to the industry standard JB4732, conduct a static strength finite element analysis of the pressure-bearing equipment using the analytical design method, and conduct stress classification and linearization check on the stress concentration parts.

3. The method for designing pressure-bearing equipment for resisting explosion loads according to claim 1, characterized in that: In the specific content of Step 1, the main technical parameters of the pressure-bearing equipment include design pressure, working pressure, geometric volume, material selection requirements, design temperature range, working temperature range, medium components, and medium characteristics.

4. The method for designing pressure-bearing equipment to resist explosion loads according to claim 1, characterized in that: The explosion shock wave impulse during the elastoplastic dynamic response analysis of the pressure-bearing equipment = the original explosion shock wave impulse × explosion safety factor; where the explosion safety factor is taken as 1.7 - 2.

0.

5. The method for designing pressure-bearing equipment to resist explosion loads according to claim 1, characterized in that: During the elastoplastic dynamic response analysis of the pressure-bearing equipment, the explosion load is realized by applying a time-related corresponding pressure load on the wall surface of the pressure-bearing equipment, or a fluid-structure interaction numerical analysis model of the dynamic response of the pressure-bearing equipment under the explosion flow field is constructed by combining the immersed boundary method and the arbitrary Lagrangian-Euler method. The mechanical properties of the material of the pressure-bearing equipment in the model are described by a stress-strain constitutive relationship related to the strain rate.

Images