A method for calculating the inner container pressure value during fiber winding of a composite hydrogen storage cylinder

Abstract

The application discloses a kind of composite hydrogen storage cylinder fiber winding inner container pressure value calculation method.Fiber winding layer produces the outer pressure P 外 Including annular winding layer to cylinder inner container and the outer pressure produced by helical winding layer;The critical instability load value P cr Of inner container is first carried out pre-buckling analysis, and finally carries out post-buckling analysis on the basis of pre-buckling analysis, and the critical instability load of inner container is P cr ;Inner container pressure value P 充 When fiber winding P 充 =P 外 -P cr , the calculation of composite hydrogen storage cylinder fiber winding inner container pressure value can be completed.The application is suitable for various composite hydrogen storage cylinders, and parameters such as winding tension, winding angle, winding layer number, winding width and thickness can be easily changed, and then the pressure value of cylinder inner container under different winding modes is obtained.The critical instability load of cylinder inner container is determined by buckling analysis, so that the calculated inner container pressure value is closer to the actual value, the calculation is simple, the process is simple, and the engineering application is facilitated.

Description

Technical Field

[0001] This invention relates to the field of structural stability analysis and calculation of composite material hydrogen storage cylinders, and specifically to a method for calculating the inner liner pressure value when the cylinder is wound with fibers. Background Technology

[0002] With the increasing consumption of fossil fuels and the decreasing reserves of non-renewable resources, hydrogen energy is an ideal new energy source. As a clean energy source, it is a future trend in the automotive industry. Composite material hydrogen storage cylinders are an indispensable component of hydrogen fuel cell vehicles. Their production and manufacturing have strong design flexibility. Compared with metal-lined composite hydrogen storage cylinders, under the same pressure, volume and outer diameter, plastic liners are lighter, more fatigue-resistant and lower in cost. Therefore, plastic-lined composite hydrogen storage cylinders are gradually replacing metal liners and becoming the mainstay of composite hydrogen storage cylinder liners.

[0003] To prevent the fiber winding layer from loosening and affecting the cylinder's load-bearing capacity, a certain winding tension is generally applied to the fiber strip during fiber winding to ensure cylinder production quality. However, the inner wall of a hydrogen storage cylinder with a plastic liner is relatively thin. Due to the winding tension, compressive stress will inevitably be generated on the plastic liner during fiber winding, which is equivalent to the plastic liner bearing external pressure. Because of the low strength of plastic, the plastic liner is prone to instability and deformation. Therefore, a certain internal pressure needs to be applied to the plastic liner during fiber winding to balance the external pressure generated by the winding tension and ensure the stability of the plastic liner during fiber winding. Currently, the determination of the inner liner pressure during fiber winding of composite hydrogen storage cylinders with plastic liners is mostly based on experience, and no specific calculation method has been developed. Therefore, it is necessary to develop a specific calculation method for the inner liner pressure during fiber winding. Summary of the Invention

[0004] Based on the above background, the purpose of this invention is to provide a method for calculating the inner liner pressure value when fiber winding is performed on composite hydrogen storage cylinders. This method fully considers the external pressure generated on the inner liner by all winding layers at different winding angles under the action of winding tension. Through post-buckling analysis, the calculated inner liner pressure value is closer to reality and more accurate. Furthermore, it can be applied to various composite hydrogen storage cylinders, and it is convenient to change parameters such as winding tension, winding angle, number of winding layers, winding bandwidth and thickness, thereby obtaining the inner liner pressure value of the cylinder under different winding methods.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for calculating the inner liner pressure of a composite hydrogen storage cylinder when the liner is fiber-wound includes the following steps:

[0007] (1) The external pressure P generated by the fiber winding layer on the inner liner of the gas cylinder 外 Calculation:

[0008] The external pressure P generated by the fiber winding layer on the inner liner of the gas cylinder 外 This includes the external pressure exerted by the circumferential winding layer on the inner liner of the gas cylinder and the external pressure exerted by the helical winding layer on the inner liner of the gas cylinder;

[0009] (1.1) External pressure P generated by the circumferential winding layer on the inner liner of the gas cylinder 外1 Calculation:

[0010] Let the bandwidth of a certain circumferential winding layer be *a*, the tension of a single circumferential winding fiber be *F1*, the outer radius of the gas cylinder liner be *R*, and the external pressure exerted by the circumferential winding layer on the gas cylinder liner be *P*. 外1 If half of the inner liner model is used for analysis, the external pressure and winding tension generated by the circumferential winding layer on the inner liner of the gas cylinder are in equilibrium:

[0011]

[0012] Where F n Let a be the winding tension of the nth layer. n is the winding bandwidth of the nth layer, where n is the number of circumferential winding layers;

[0013] The external pressure exerted by the n-layer circumferential fiber winding on the inner liner of the gas cylinder:

[0014]

[0015] (1.2) External pressure P generated by the spiral winding layer on the inner liner of the gas cylinder 外2 Calculation:

[0016] Let the bandwidth of a certain spiral wound layer be b, the tension of a single spiral wound fiber be F2, the winding angle be α, and the external pressure exerted by the spiral wound layer on the inner liner of the gas cylinder be P. 外2 The external pressure exerted by the spiral winding layer on the inner liner of the gas cylinder is in equilibrium with the winding tension.

[0017]

[0018] Where F m Let b be the winding tension of the m-th layer. m α is the winding bandwidth of the m-th layer, where m is the number of helical winding layers. m Let m be the winding angle of the m-th layer;

[0019] The external pressure exerted by the m-layer spiral fiber winding on the inner liner of the gas cylinder:

[0020]

[0021] Therefore, the sum of the external pressures exerted on the inner liner of the gas cylinder by the n-layer circumferential fiber winding and the m-layer helical fiber winding under the winding tension, i.e., the external pressure P exerted by the fiber winding on the inner liner of the gas cylinder, is... 外 for:

[0022]

[0023] (2) Critical instability load value P of the inner liner cr Calculation:

[0024] (2.1) Characteristic buckling analysis

[0025] The model was built using ABAQUS finite element analysis software. The elastic modulus and Poisson's ratio were set, and the analysis step was set to Linear perturbation-Buckle. The buckling characteristic values ​​were extracted using the subspace method. The load values ​​applied to the outer surface of the inner liner were set, boundary constraints were set, and the mesh was generated using solid mesh C3D8R. The keywords were edited, and the command was added: *nodefile,global=yes,lastmode=1,U, and the calculation was submitted.

[0026] Furthermore, in step (2.1), the extracted buckling feature values ​​are the first 5-50.

[0027] Furthermore, in step (2.1), the extracted buckling feature values ​​are the first 10.

[0028] Further, in step (2.1), the load applied to the outer surface of the inner liner is 1 MPa.

[0029] (2.2) Post-buckling analysis

[0030] Based on the original settings of the characteristic buckling analysis, the original Linearperturbation-Buckle analysis step is replaced with the static-riks analysis step. The maximum load proportionality factor, initial arc length increment step, maximum arc length increment step, and maximum number of increment steps are set. Keywords are edited, and the command is added: *imperfection, file=job-qianququ, step=1,1,10e-2, where job-qianququ is the displacement file generated during the characteristic buckling analysis. Other parameter settings are consistent with the characteristic buckling analysis. After calculation, the load proportionality factor LPF and arc length increment ArcLength values ​​for each increment step are output and plotted as curves. By observing the changes in the curve slope, the critical instability load of the composite hydrogen storage cylinder liner is determined. Before cylinder instability, the load proportionality factor LPF and arc length increment ArcLength values ​​have a linear relationship. When the curve slope changes significantly, the load proportionality factor LPF at this point is the critical instability load P of the composite hydrogen storage cylinder liner. cr ;

[0031] (3) Calculate P 外 and P cr Afterwards, the inner liner filling pressure value P during fiber entanglement 充 for:

[0032] P 充 =P 外 -P cr (6)

[0033] This allows for the calculation of the inner liner pressure value when the composite hydrogen storage cylinder is fiber-wound.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1) This method fully considers the external pressure exerted on the inner liner by all winding layers at different winding angles under winding tension, which is closer to actual manufacturing practices than current methods that only consider the same winding angle. Therefore, the calculated inner liner pressure value is more suitable for engineering applications. 2) This method is applicable to various composite material hydrogen storage cylinders, allowing for easy modification of parameters such as winding tension, winding angle, number of winding layers, winding bandwidth, and thickness to obtain the inner liner pressure value under different winding methods. 3) The critical buckling load of the inner liner is determined through a combination of post-buckling analysis and theoretical calculations, making the calculated inner liner pressure value more realistic and accurate. 4) The calculation is simple, the process is straightforward, and it is convenient for engineering applications. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the external pressure generated by the circumferential winding layer.

[0037] Figure 2 This is a schematic diagram illustrating the external pressure generated by the helical winding layer;

[0038] Figure 3 This is a schematic diagram of the inner liner of a gas cylinder;

[0039] Figure 4 This is a diagram showing the results of the characteristic buckling analysis of the gas cylinder liner;

[0040] Figure 5 This is the LPF-Arc Length curve of the gas cylinder liner after buckling instability.

[0041] Wherein, 1 represents the winding layer; 2 represents the inner liner of the gas cylinder; 3 represents the cylinder opening; a represents the bandwidth of a certain circumferential winding layer; F1 represents the winding tension of a single circumferential fiber layer; R represents the outer radius of the inner liner of the gas cylinder; and P represents the outer radius of the inner liner of the gas cylinder. 外1 The external pressure exerted by the circumferential winding layer on the inner liner of the gas cylinder is given by: L, length of the inner liner section; b, bandwidth of a certain spiral winding layer; F2, tension of a single spiral winding fiber; α, winding angle; P. 外2 The external pressure exerted by the spiral winding layer on the inner liner of the gas cylinder; LPF is the load proportionality coefficient; Arc Length is the arc length increment. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings:

[0043] Due to the external pressure, the inner liner of the gas cylinder will undergo unstable deformation. Therefore, it is necessary to calculate the external pressure generated by the fiber winding layer on the inner liner of the gas cylinder under the action of winding tension.

[0044] First, analyze the external pressure exerted by the circumferential winding layer on the inner liner of the gas cylinder, such as... Figure 1 As shown, let the bandwidth of a certain circumferential winding layer be a, the tension of a single circumferential winding fiber be F1, the outer radius of the gas cylinder liner be R, and the external pressure on the gas cylinder liner be P. 外1 If half of the inner liner model is used for analysis, the external pressure and winding tension generated by the circumferential winding layer on the inner liner of the gas cylinder are in equilibrium:

[0045]

[0046] Where F n Let a be the winding tension of the nth layer. n R is the winding bandwidth of the nth layer, n is the number of circumferential winding layers, R is the outer radius of the inner liner of the gas cylinder, and P is the outer radius of the inner liner of the gas cylinder. 外1 This refers to the external pressure exerted by the circumferential winding layer on the inner liner of the gas cylinder.

[0047] The external pressure exerted by the n-layer circumferential fiber winding on the inner liner of the gas cylinder:

[0048]

[0049] Further analysis of the external pressure exerted by the spiral winding layer on the inner liner of the gas cylinder, such as... Figure 2 As shown, let the bandwidth of a certain spiral wound layer be b, the tension of a single spiral wound fiber be F2, the winding angle be α, and the external pressure on the inner liner be P. 外2 The external pressure exerted by the spiral winding layer on the inner liner of the gas cylinder is in equilibrium with the winding tension.

[0050]

[0051] Where F m Let b be the winding tension of the m-th layer. m Let P be the winding bandwidth of the m-th layer, m be the number of spiral winding layers, R be the outer radius of the inner liner of the gas cylinder, and P be the outer radius of the inner liner of the gas cylinder. 外2 α is the external pressure exerted by the spiral winding layer on the inner liner of the gas cylinder. m Let m be the winding angle of the m-th layer;

[0052] The external pressure exerted by the m-layer spiral fiber winding on the inner liner of the gas cylinder:

[0053]

[0054] Therefore, the sum of the external pressures exerted on the inner liner of the gas cylinder by the n-layer circumferential fiber winding and the m-layer helical fiber winding under the winding tension, i.e., the external pressure P exerted by the fiber winding on the inner liner of the gas cylinder, is... 外 for:

[0055]

[0056] Calculate P 外 Afterwards, the inner liner filling pressure value P during fiber entanglement 充 for:

[0057] P 充 =P 外 -P cr (6)

[0058] Where P 充 P is the liner filling pressure value when the fibers are wrapped. cr This represents the critical instability load value of the inner liner.

[0059] Critical instability load value P of the inner liner cr To determine the critical buckling load, a pre-buckling analysis (characteristic buckling analysis, used to prepare for post-buckling analysis) is first performed. After the pre-buckling analysis, the analytical solution of the critical buckling load is calculated using theoretical formulas and compared with the pre-buckling results to verify the accuracy of the finite element analysis. Finally, based on the pre-buckling analysis, a post-buckling analysis is performed to obtain the critical buckling load P of the inner liner. cr .

[0060] Characteristic buckling analysis (probability analysis):

[0061] A model was built using ABAQUS finite element analysis software. (See attached document.) Figure 3 Since the extension of the cylinder liner's neck does not affect the cylinder liner's buckling analysis, the modeling is simplified.

[0062] The elastic modulus and Poisson's ratio are set, and the analysis step is set to Linear perturbation-Buckle. The first 10 buckling eigenvalues ​​are extracted using the subspace method. The load state is set as an external pressure of 1 MPa applied to the outer surface of the inner liner. Boundary constraints are set according to the actual situation, and a solid mesh (C3D8R) is generated. Keywords are edited, and the command is added: *nodefile, global=yes, lastmode=1, U. The calculation is then submitted. This will yield a preliminary critical buckling load for the inner liner. Figure 3 The results obtained from the structure shown are as follows Figure 4 As shown, the result is P. cr =0.0186MPa.

[0063] Theoretical verification of characteristic buckling analysis:

[0064] The accuracy of the finite element simulation is verified using Lammer's formula, as shown in the following equation:

[0065]

[0066] Where E is the elastic modulus of the inner liner material, t is the inner liner wall thickness, L is the length of the inner liner section, and D is the outer diameter of the inner liner.

[0067] Will Figure 3 Substituting the relevant parameters of the structure into the above formula, we get P. 理论 =0.021MPa. It can be seen that, when comparing the results calculated by characteristic buckling with those calculated by theoretical formula, the results calculated by characteristic buckling are very close to those calculated by theoretical formula, with a relative error of only about 11%. This verifies the accuracy of the finite element simulation analysis.

[0068] To obtain more accurate calculation results, a post-buckling analysis based on the Riks arc length method was finally performed based on the characteristic buckling analysis.

[0069] Post-buckling analysis:

[0070] Based on the original settings of the characteristic buckling analysis, the original Linearperturbation-Buckle analysis step was replaced with the static-riks analysis step. The maximum load proportionality factor, initial arc length increment step, maximum arc length increment step, and maximum number of increment steps were set in the calculation stopping conditions according to the actual situation. Keywords were edited, and the command *imperfection, file=job-qianququ, step=1,1,10e-2 was added. job-qianququ is the displacement file generated during the characteristic buckling analysis. Other parameter settings are consistent with the characteristic buckling analysis. After the calculation is completed, the load proportionality factor LPF value and arc length increment Arc Length value for each increment step are output and plotted as a curve. By observing the change in the curve slope, the critical instability load of the composite hydrogen storage cylinder liner is determined. Before cylinder instability, the load proportionality factor LPF value and arc length increment Arc Length value have a linear relationship. When the curve slope changes significantly, the load proportionality factor LPF value at this point is the critical instability load P of the composite hydrogen storage cylinder liner. cr The critical instability load P of the composite material hydrogen storage cylinder liner was obtained. cr =0.0167MPa, which is less than the characteristic buckling value of 0.0186MPa.

[0071] The critical instability load P is obtained. cr Then, P cr Substituting into formula (6), we can obtain the inner liner pressure value when the composite hydrogen storage cylinder is fiber-wound. Thus, through finite element analysis and theoretical formula calculation, a complete method for calculating the inner liner pressure value when the composite hydrogen storage cylinder is fiber-wound is formed.

[0072] This invention fully considers the external pressure exerted on the inner liner by all winding layers at different winding angles under winding tension. This approach is closer to actual manufacturing practices than current methods that only consider the same winding angle, resulting in a more suitable calculated inner liner pressure for engineering applications. This method is applicable to various composite material hydrogen storage cylinders, allowing for adjustments to parameters such as winding tension, winding angle, number of winding layers, winding bandwidth, and thickness to obtain the inner liner pressure under different winding methods. The critical buckling load of the inner liner is determined through a combination of post-buckling analysis and theoretical calculations, making the calculated inner liner pressure more accurate and closer to reality. The calculation is simple, the process is straightforward, and it is easy to apply in engineering.

[0073] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for calculating the inner liner filling pressure of a composite hydrogen storage cylinder when the liner is fiber-wound, characterized in that, Includes the following steps: (1) The external pressure P generated by the fiber winding layer on the inner liner of the gas cylinder 外 Calculation: The external pressure P generated by the fiber winding layer on the inner liner of the gas cylinder 外 This includes the external pressure exerted by the circumferential winding layer on the inner liner of the gas cylinder and the external pressure exerted by the helical winding layer on the inner liner of the gas cylinder; (1.1) External pressure P generated by the circumferential winding layer on the inner liner of the gas cylinder 外1 Calculation: Let the bandwidth of a certain circumferential winding layer be *a*, the tension of a single circumferential winding fiber be *F1*, the outer radius of the gas cylinder liner be *R*, and the external pressure exerted by the circumferential winding layer on the gas cylinder liner be *P*. 外1 If half of the inner liner model is used for analysis, the external pressure and winding tension generated by the circumferential winding layer on the inner liner of the gas cylinder are in equilibrium: Where F n Let a be the winding tension of the nth layer. n is the winding bandwidth of the nth layer, where n is the number of circumferential winding layers; The external pressure exerted by the n-layer circumferential fiber winding on the inner liner of the gas cylinder: (1.2) External pressure P generated by the spiral winding layer on the inner liner of the gas cylinder 外2 Calculation: Let the bandwidth of a certain spiral wound layer be b, the tension of a single spiral wound fiber be F2, the winding angle be α, and the external pressure exerted by the spiral wound layer on the inner liner of the gas cylinder be P. 外2 The external pressure exerted by the spiral winding layer on the inner liner of the gas cylinder is in equilibrium with the winding tension. Where F m Let b be the winding tension of the m-th layer. m α is the winding bandwidth of the m-th layer, where m is the number of spiral winding layers. m Let m be the winding angle of the m-th layer; The external pressure exerted by the m-layer spiral fiber winding on the inner liner of the gas cylinder: Therefore, the sum of the external pressures exerted on the inner liner of the gas cylinder by the n-layer circumferential fiber winding and the m-layer helical fiber winding under the winding tension, i.e., the external pressure P exerted by the fiber winding on the inner liner of the gas cylinder, is... 外 for: (2) Critical instability load value P of the inner liner cr Calculation: (2.1) Characteristic buckling analysis The model was built using ABAQUS finite element analysis software. The elastic modulus and Poisson's ratio were set, and the analysis step was set to Linearperturbation-Buckle. The buckling characteristic values ​​were extracted using the subspace method. The load values ​​applied to the outer surface of the inner liner were set, boundary constraints were set, and the mesh was generated using solid mesh C3D8R. The keywords were edited, and the command was added: *nodefile,global=yes,lastmode=1,U, and the calculation was submitted. (2.2) Post-buckling analysis Based on the original settings of the characteristic buckling analysis, the original Linearperturbation-Buckle analysis step is replaced with the static-riks analysis step. The maximum load proportionality factor, initial arc length increment step, maximum arc length increment step, and maximum number of increment steps are set. Keywords are edited, and the command is added: *imperfection, file=job-qianququ, step=1,1,10e-2, where job-qianququ is the displacement file generated during the characteristic buckling analysis. Other parameter settings are consistent with the characteristic buckling analysis. After calculation, the load proportionality factor LPF and arc length increment ArcLength values ​​for each increment step are output and plotted as curves. By observing the changes in the curve slope, the critical instability load of the composite hydrogen storage cylinder liner is determined. Before cylinder instability, the load proportionality factor LPF and arc length increment ArcLength values ​​have a linear relationship. When the curve slope changes significantly, the load proportionality factor LPF at this point is the critical instability load P of the composite hydrogen storage cylinder liner. cr ; (3) Calculate P 外 and P cr Afterwards, the inner liner filling pressure value P during fiber entanglement 充 for: P 充 =P 外 -P cr (6) This allows for the calculation of the inner liner pressure value when the composite hydrogen storage cylinder is fiber-wound.

2. The method for calculating the inner liner pressure of a composite hydrogen storage cylinder when the fiber is wound, as described in claim 1, is characterized in that... In step (2.1), the extracted buckling feature values ​​are the first 5-50.

3. The method for calculating the inner liner pressure of a composite hydrogen storage cylinder when the fiber is wound, as described in claim 2, is characterized in that... In step (2.1), the extracted buckling feature values ​​are the first 10.

4. The method for calculating the inner liner pressure of a composite hydrogen storage cylinder when the fiber is wound, as described in claim 1, is characterized in that... In step (2.1), the load applied to the outer surface of the inner liner is 1 MPa.

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