Finite element analysis method for vibration characteristics of vertical low-temperature adiabatic cylinder system

Abstract

The application provides a vertical low-temperature adiabatic gas cylinder system vibration characteristic finite element analysis method, including the following steps: using Solidworks to construct three-dimensional models of vertical low-temperature adiabatic gas cylinder systems with different inner container wall thicknesses; importing the three-dimensional models of the vertical low-temperature adiabatic gas cylinder systems with different inner container wall thicknesses into ANSYS finite element analysis software respectively, setting material properties and contact according to actual conditions, and performing mesh division; setting loads and constraints according to actual vibration test conditions, calculating the first six order natural frequencies of the vertical low-temperature adiabatic gas cylinder systems with different inner container wall thicknesses in the ANSYS modal analysis module; using a harmonic response analysis module to calculate the resonance frequencies of the vertical low-temperature adiabatic gas cylinder systems with different inner container wall thicknesses in a standard frequency range, and providing a theoretical basis for the study of the vibration characteristics of the vertical low-temperature adiabatic gas cylinder system.

Description

Technical Field

[0001] This invention relates to the field of vibration characteristic analysis of industrial gas cylinders, and more specifically, to a finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system. Background Technology

[0002] Cryogenic insulated gas cylinders are capable of storing and transporting cryogenic liquids such as liquid oxygen, liquid nitrogen, and liquid argon under pressure. Compared to ordinary gas cylinders, they have a more complex structural design and higher production costs. During vehicle transportation, cryogenic insulated gas cylinders are subjected to continuous vibration, which can lead to vibration failure, resulting in structural strength or stiffness loss, and in extreme cases, even safety accidents. To effectively prevent the risk of vibration failure, vibration testing must be conducted during the product development and design phase to comprehensively evaluate the overall vibration resistance of the cylinder. However, it is worth noting that if vibration testing reveals failure, it will mean that additional time and funds will be needed to redesign and retest the cylinder.

[0003] The development of vehicle-mounted cryogenic insulated gas cylinders is still in its early stages, and there is limited research on their vibration characteristics. Hao Chaoyang et al. (Hao Chaoyang, Ding Hua, Li Muze, et al. Structural strength and vibration fatigue analysis of vehicle-mounted cryogenic insulated gas cylinders [J]. Cryogenics and Superconductivity, 2024, 52(06): 58-64+102.) studied the strength and fatigue of vehicle-mounted cryogenic insulated gas cylinders filled with liquid hydrogen under braking conditions based on ANSYS; Liu Rui et al. (Liu Rui, Chen Zuzhi, Huang Qianghua, et al. Numerical simulation analysis of the influence of filling amount and cylinder length on the resonance frequency of vehicle-mounted LNG cylinders [J]. Journal of Chemical Industry and Engineering, 2019, 70(11): 4486-4496.) simulated and calculated the natural frequencies of vehicle-mounted LNG cylinders with different filling rates and cylinder lengths based on ANSYS. Mir et al. (MIR O, SHAKOURIM, Ashory M R. Gas pressure and density effects on vibration of cylindrical pressure vessels: analytical, numerical and experimental analysis[J]. SN Applied Sciences, 2020, 2(1)) studied the natural frequencies and mode shapes of gas cylinders under different gases and internal pressures using modal tests and finite element software, respectively.

[0004] Current research mainly focuses on horizontal gas cylinders considering strap constraints, while studies on the vibration characteristics of vertical cryogenic insulated gas cylinders, especially under special vertical external frame constraints, are relatively insufficient. However, vertical cryogenic insulated gas cylinders are widely used in transportation processes; for example, live fish transport vehicles need to be equipped with vertical liquid oxygen cylinders to supply oxygen to the fish. To ensure the transportation safety of vertical cryogenic insulated gas cylinder systems in such vehicles, this invention proposes a finite element analysis method for the vibration characteristics of vertical cryogenic insulated gas cylinder systems, which can provide a theoretical basis for the study of the vibration characteristics of vertical cryogenic insulated gas cylinder systems. Summary of the Invention

[0005] The purpose of this invention is to construct a vertical cryogenic insulated gas cylinder system structure considering the external frame, and to analyze the vibration characteristics of this vertical cryogenic insulated gas cylinder system using the finite element analysis method. In order to solve the resonance problem that may occur during transportation, a finite element analysis method for the vibration characteristics of the vertical cryogenic insulated gas cylinder system is proposed.

[0006] The present invention is achieved by at least one of the following technical solutions.

[0007] A finite element method for vibration characteristic analysis of a vertical cryogenic insulated gas cylinder system includes the following steps:

[0008] S1. Construct a three-dimensional model of a vertical cryogenic insulated gas cylinder system with different inner wall thicknesses using three-dimensional modeling software.

[0009] S2. Construct the finite element model of the vertical cryogenic insulated gas cylinder system. Import the three-dimensional model of the vertical cryogenic insulated gas cylinder system into the finite element analysis software, set the material properties and contact according to the actual situation, and perform mesh generation to obtain the finite element model of the vertical cryogenic insulated gas cylinder system.

[0010] S3. Modal analysis under the influence of different inner liner wall thicknesses: Based on the actual vibration test conditions, loads and constraints are set, and the first six natural frequencies of the vertical cryogenic insulated gas cylinder system with different inner liner wall thicknesses are calculated in the modal analysis module of the finite element analysis software.

[0011] S4. Harmonic response analysis within the standard frequency range: The modal superposition method is used to perform harmonic response analysis on vertical cryogenic insulated gas cylinder systems with different inner wall thicknesses, and the resonant frequencies within the standard frequency range are analyzed.

[0012] S5. Compare the resonant frequencies of vertical cryogenic insulated gas cylinder systems with different inner wall thicknesses obtained in step S4 to determine the influence of inner wall thickness on the vibration characteristics of the vertical cryogenic insulated gas cylinder system.

[0013] Furthermore, the vertical cryogenic insulated gas cylinder system in step S1 includes a cryogenic insulated gas cylinder and a gas cylinder frame.

[0014] Furthermore, the three-dimensional model of the cryogenic insulated gas cylinder includes the upper and lower end caps of the outer shell, the outer shell cylinder, the upper and lower end caps of the inner liner, the inner liner cylinder, the upper and lower supports, the vibration isolation plate, the positioning cylinder, and the positioning sleeve.

[0015] Furthermore, the three-dimensional model of the gas cylinder frame includes a top component and a bottom component. The top component contains an axial support, and the bottom component contains radial supports and mounting holes.

[0016] Furthermore, the material properties in step S2 include density, elastic modulus, and Poisson's ratio.

[0017] Furthermore, the virtual mass method is used to equate the 50% liquid nitrogen filling the gas cylinder to the lower end cap of the inner liner and the lower half of the cylinder.

[0018] Furthermore, the calculation formula for the virtual mass method is as follows:

[0019]

[0020] Where, ρ e ρ represents the equivalent density. l ρ represents the density of the filling medium. in V represents the density of the gas cylinder liner, and m represents the effective volume of the gas cylinder. in This indicates the mass of the gas cylinder liner. This indicates the fill rate.

[0021] Furthermore, in step S2, the mesh generation is performed using the ANSYS Mesh module of the ANSYS finite element analysis software. The Hex Dominant method is used to mesh the inner liner and outer shell of the gas cylinder, while the remaining parts are automatically meshed. The mesh element type is Solid186 solid element.

[0022] Furthermore, the loads and constraints in step S3 are set through the Static Structural module, the nominal working pressure is evenly distributed on the inner liner of the gas cylinder, gravitational acceleration is added in the negative Y-axis direction, and fixed supports are set in the mounting holes at the bottom of the gas cylinder frame according to the actual vibration test conditions.

[0023] Furthermore, the natural frequencies in step S3 are obtained using the Modal module of ANSYS, where the frequency extraction order is set to the first six orders, and the Block Lanczos method is used to solve the modes.

[0024] Furthermore, the resonance frequency in step S4 is determined using the Harmonic Response module of ANSYS, employing the modal superposition method. The excitation acceleration is set to 0.5g, with acceleration directions perpendicular to and along the axis of the cryogenic insulated gas cylinder. The sweep frequency range and damping coefficient are set according to standard GB / T 24159-2022. The amplitude-frequency response curve is then obtained to analyze the resonance frequency.

[0025] The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system proposed in this invention has the following advantages compared with existing technologies:

[0026] This invention proposes a vertical gas cylinder outer frame and considers vertical cryogenic insulated gas cylinders with different inner wall thicknesses and the outer frame as a whole system. This approach not only overcomes the limitations of previous studies that only focused on a single gas cylinder without considering external constraint components or simplified models, but also more closely reflects actual working conditions, making the analysis results more accurate and comprehensive, and enabling a comprehensive analysis of the system composed of cryogenic insulated gas cylinders and outer frames.

[0027] This invention utilizes the finite element method, which can efficiently and accurately solve for the natural frequencies and resonant frequencies of a vertical cryogenic insulated gas cylinder system. Natural frequencies and resonant frequencies are crucial parameters for evaluating structural vibration characteristics, directly affecting the system's stability and safety under external excitations. This is especially important in dynamic environments such as vehicle transportation, where vertical cryogenic insulated gas cylinder systems may be subject to various complex excitations. Precise calculations can accurately identify potential vibration risk points, providing strong support for structural optimization.

[0028] The invention has a wide range of applications, not only applicable to the structural optimization design of vertical cryogenic insulated gas cylinder systems, but also providing a reference for the revision of relevant standards.

[0029] In summary, the finite element analysis method for vibration characteristics of vertical cryogenic insulated gas cylinder systems proposed in this invention can improve the accuracy and comprehensiveness of the analysis, and can provide a reference for the structural optimization design of vertical cryogenic insulated gas cylinder systems and the revision of relevant standards, so as to prevent structural resonance damage and ensure the safe transportation of gas cylinders. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. 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.

[0031] Figure 1Flowchart of the finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system as an example.

[0032] Figure 2 A schematic diagram of a three-dimensional model of a vertical cryogenic insulated gas cylinder system as an example;

[0033] Figure 3 A schematic diagram of the mesh generation for the finite element model of a vertical cryogenic insulated gas cylinder system as an example.

[0034] Figure 4 A schematic diagram of the natural frequency of a vertical cryogenic insulated gas cylinder system as an example.

[0035] Figure 5 This is a schematic diagram of the amplitude-frequency response curve of a vertical cryogenic insulated gas cylinder system as an example. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. However, the described embodiments are only a part of the embodiments of the present invention, and the implementation of the present invention is not limited thereto. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 As shown in the figure, this embodiment provides a finite element analysis method for the vibration characteristics of a vertical cryogenic insulated gas cylinder system, including the following steps:

[0038] S1, such as Figure 2 As shown, a three-dimensional model of a vertical cryogenic insulated gas cylinder system is constructed using Solidworks software. The model includes a cryogenic insulated gas cylinder and a cylinder frame. The three-dimensional model of the cryogenic insulated gas cylinder includes upper and lower end caps of the outer shell, outer shell cylinder, upper and lower end caps of the inner liner, inner liner cylinder, upper and lower supports, vibration isolation plate, positioning cylinder, and positioning sleeve. The three-dimensional model of the cylinder frame includes a top component and a bottom component. The top component includes an axial support, and the bottom component includes radial support and mounting holes. The three-dimensional model of the vertical cryogenic insulated gas cylinder system ignores non-pressure-bearing components such as valves and piping systems, as well as welds and chamfers.

[0039] As one embodiment, the main dimensions of the cryogenic insulated gas cylinder in this embodiment include: a nominal diameter of 450mm for the inner liner, a length of 1188mm for the inner cylinder, a nominal diameter of 504mm for the outer shell, and a length of 1348mm for the outer cylinder; the specifications of the gas cylinder frame are 600mm×600mm×1500mm.

[0040] S2. Construct the finite element model of the vertical cryogenic insulated gas cylinder system. Import the three-dimensional model of the vertical cryogenic insulated gas cylinder system into the ANSYS finite element analysis software. Set the material properties and contact according to the actual situation, and perform mesh generation to obtain the finite element model of the vertical cryogenic insulated gas cylinder system.

[0041] As one embodiment, the material properties include density, elastic modulus, and Poisson's ratio, as shown in Table 1. The inner and outer liner of the cryogenic insulated gas cylinder are both made of austenitic stainless steel 06Cr19Ni10 (S30408), the main body of the gas cylinder frame is made of carbon structural steel (Q235-B), and the vibration isolation plate is made of rubber material.

[0042] Table 1 Material Properties of Vertical Cryogenic Insulated Gas Cylinder System

[0043] structure Material <![CDATA[Density / kg·m -3 > Elastic modulus / GPa Poisson's ratio Cryogenic insulated gas cylinders (excluding vibration isolation plates) S30408 7930 193 0.29 Isolation board rubber 1500 0.08 0.48 Cylinder frame Q235-B 7850 210 0.274

[0044] The virtual mass method is used to represent the 50% liquid nitrogen filling the gas cylinder as equivalent to the lower end cap of the inner liner and the lower half of the cylinder body. This method ignores the influence of liquid sloshing and reduces the solid-liquid coupling problem to a simple solid dynamics problem, greatly simplifying the solution process. In this embodiment, the density of liquid nitrogen is 810 kg·m³. -3 The formula for calculating virtual mass is as follows:

[0045]

[0046] Where, ρ e ρ represents the equivalent density. l ρ represents the density of the filling medium. in V represents the density of the gas cylinder liner, and m represents the effective volume of the gas cylinder. in This indicates the mass of the gas cylinder liner. This indicates the filling rate (value is 50%).

[0047] The contact settings are as follows: the positioning cylinder of the lower support and the positioning sleeve use "No Separation" contact; the vibration isolation plate and the lower end cap of the outer shell use "Frictional" contact; and the connections of all other components use "Bonded" contact.

[0048] The mesh generation was performed using the ANSYS Mesh module, employing the Hex Dominant method to mesh the inner and outer shell of the gas cylinder. The remaining parts were automatically meshed. The mesh element type was Solid186. Figure 3 The diagram shown is a schematic of the grid division.

[0049] S3. Modal analysis under the influence of different inner liner wall thicknesses: Based on the actual vibration test conditions, loads and constraints are set, and the first six natural frequencies of the vertical cryogenic insulated gas cylinder system with different inner liner wall thicknesses are calculated in the ANSYS modal analysis module.

[0050] The loads and constraints are set via the Static Structural module. A nominal working pressure is uniformly distributed across the inner liner of the gas cylinder, i.e., a "Pressure" value of 2.3 MPa is added to the surface of the inner liner. Gravitational acceleration is also added in the negative Y-axis direction, i.e., the Y-axis acceleration is set to -9.81 m / s². 2 Then, the results from the Static Structural module are loaded into the Modal module in the form of prestress for modal analysis. Fixed supports are installed at the mounting holes at the bottom of the gas cylinder frame according to the actual vibration test conditions; specifically, "Fixed Support" constraints are added at two mounting holes on each side of the bottom.

[0051] The natural frequencies are calculated using ANSYS's Modal module. As an example, in "Analysis Settings," the "Max Modes to Find" value is 6, meaning the frequency extraction order is the first six. In "Solver Type," the "Direct" method is selected, which is equivalent to the classic Block Lanczos method for solving modes. Right-clicking "Solution" and then clicking "Solve" performs the calculation. The calculation results, i.e., the first six natural frequencies, are displayed in the "Tabular Data" window. (The summary is as follows...) Figure 4 As shown. By Figure 4 It can be found that the first six natural frequencies of the vertical cryogenic insulated gas cylinder system with this wall thickness are 26.52Hz, 26.75Hz, 35.11Hz, 42.87Hz, 48.50Hz, and 58.37Hz. Among them, the first three natural frequencies are in the range of 8-40Hz. According to the standard, we need to be wary of the resonant frequencies in this range. If resonance occurs during vehicle operation, it will cause large-amplitude vibration. Therefore, further harmonic response analysis is needed to determine the resonant frequencies.

[0052] S4. Harmonic response analysis within the standard frequency range: The modal superposition method is used to perform harmonic response analysis on vertical cryogenic insulated gas cylinder systems with different inner wall thicknesses, and the resonant frequencies within the standard frequency range are analyzed.

[0053] The resonant frequency is determined using the Harmonic Response module of ANSYS, employing the modal superposition method. The connection can be established by simply dragging and dropping the Harmonic Response module into the Solution of the Modal module to perform the modal superposition method.

[0054] The excitation acceleration is imported into Acceleration via Harmonic Response. When vibration is performed perpendicular to the axis of the cryogenic adiabatic gas cylinder, an input of 4900 mm / s is applied in the X-axis direction. 2 That is, 0.5g; when vibrating along the axis of the cryogenic insulated gas cylinder, the input in the Y-axis direction is 4900mm / s. 2 That is, 0.5g;

[0055] The sweep frequency range is set to 8-40Hz according to standard GB / T 24159-2022. In the Analysis Settings under Harmonic Response, the minimum range value "Range Minimum" is set to 8Hz, and the maximum range value "RangeMaximum" is set to 40Hz.

[0056] The damping setting is configured as 0.04 in DampingRatio under Analysis Settings in Harmonic Response.

[0057] Click Solve to perform the calculation. Add a Frequency Response to the Solution and select a point on the casing head for amplitude-frequency analysis. The amplitude-frequency response curve within the 8-40Hz range will be displayed. Figure 5 As shown, the amplitude-frequency response curve was analyzed to obtain the resonant frequency of the vertical cryogenic insulated gas cylinder system in the range of 8-40Hz. It was found that the amplitude increased to its maximum at a frequency of 26.8Hz, reaching 77185mm / s. 2 This indicates that when the vertical cryogenic insulated gas cylinder system vibrates with an acceleration of 0.5g perpendicular to the axis of the cylinder, it resonates at a frequency of 26.8Hz. This frequency falls within the range of 8-40Hz. Therefore, further structural optimization is needed to prevent resonance during vehicle operation, which could damage the cylinder system structure and cause a safety accident.

[0058] S5. Compare the resonant frequencies of vertical cryogenic insulated gas cylinder systems with different inner wall thicknesses obtained in step S4.

[0059] According to design requirements, the wall thickness of the cylinder liner is changed in Solidworks software. Steps S1 to S4 are repeated to obtain the resonant frequencies of vertical cryogenic insulated cylinder systems with different liner wall thicknesses. Comparative analysis reveals the influence of liner wall thickness on the vibration characteristics of the vertical cryogenic insulated cylinder system. This invention has a certain degree of universality in calculating the resonant frequency of vertical cryogenic insulated cylinder systems. By changing the filling medium, filling volume, cylinder length-to-diameter ratio, liner wall thickness, and outer frame constraint method, more natural frequencies and resonant frequencies under working conditions can be obtained. This provides a certain reference for the design of vertical cryogenic insulated cylinders, prevention of structural resonance damage during use, evaluation of vibration characteristics, and the formulation of standards.

[0060] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system, characterized in that, Includes the following steps: S1. Construct a three-dimensional model of a vertical cryogenic insulated gas cylinder system with different inner wall thicknesses using three-dimensional modeling software. The vertical cryogenic insulated gas cylinder system includes cryogenic insulated gas cylinders and cylinder frames; S2. Construct the finite element model of the vertical cryogenic insulated gas cylinder system. Import the three-dimensional model of the vertical cryogenic insulated gas cylinder system into the finite element analysis software, set the material properties and contact according to the actual situation, and perform mesh generation to obtain the finite element model of the vertical cryogenic insulated gas cylinder system. S3. Modal analysis under the influence of different inner liner wall thicknesses: Based on the actual vibration test conditions, loads and constraints are set, and the first six natural frequencies of the vertical cryogenic insulated gas cylinder system with different inner liner wall thicknesses are calculated in the modal analysis module of the finite element analysis software. S4. Harmonic response analysis within the standard frequency range: The modal superposition method is used to perform harmonic response analysis on vertical cryogenic insulated gas cylinder systems with different inner wall thicknesses, and the resonant frequencies within the standard frequency range are analyzed. S5. Compare the resonant frequencies of vertical cryogenic insulated gas cylinder systems with different inner wall thicknesses obtained in step S4 to determine the influence of inner wall thickness on the vibration characteristics of the vertical cryogenic insulated gas cylinder system.

2. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 1, characterized in that, The three-dimensional model of the cryogenic insulated gas cylinder includes the upper and lower end caps of the outer shell, the outer shell cylinder, the upper and lower end caps of the inner liner, the inner liner cylinder, the upper and lower supports, the vibration isolation plate, the positioning cylinder, and the positioning sleeve.

3. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 2, characterized in that, The three-dimensional model of the gas cylinder frame includes a top component and a bottom component. The top component contains an axial support, and the bottom component contains radial supports and mounting holes.

4. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 1, characterized in that, The material properties in step S2 include density, elastic modulus, and Poisson's ratio.

5. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 3, characterized in that, The virtual mass method is used to equate 50% of the liquid nitrogen filling the gas cylinder to the lower end cap of the inner liner and the lower half of the cylinder body.

6. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 5, characterized in that, The calculation formula for the virtual mass method is as follows: (1) in, Represents equivalent density. Indicates the density of the filling medium. This indicates the density of the gas cylinder liner. Indicates the effective volume of the gas cylinder. This indicates the mass of the gas cylinder liner. This indicates the fill rate.

7. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 1, characterized in that, In step S2, the mesh generation was performed using the ANSYS Mesh module of the ANSYS finite element analysis software. The HexDominant method was used to mesh the inner liner and outer shell of the gas cylinder, while the remaining parts were automatically meshed. The mesh element type was Solid186 solid element.

8. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 1, characterized in that, The loads and constraints in step S3 are set through the Static Structural module. The nominal working pressure is evenly distributed on the inner liner of the gas cylinder, and gravitational acceleration is added in the negative Y-axis direction. Fixed supports are set in the mounting holes at the bottom of the gas cylinder frame according to the actual vibration test conditions.

9. The finite element analysis method for vibration characteristics of a vertical cryogenic insulated gas cylinder system according to claim 1, characterized in that, The natural frequencies in step S3 are obtained using the Modal module of ANSYS, where the frequency extraction order is set to the first six orders, and the Block Lanczos method is used to solve the modes.

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