A Design Method for Expanding the Hole and Winding of the Head of a High-Pressure Hydrogen Storage Cylinder

Abstract

The present invention discloses a design method for hole-expanding winding of a high-pressure hydrogen storage cylinder head. The spiral winding angle and the thicknesses of the spiral winding layer and the circumferential winding layer of the cylinder section are pre-calculated using the grid theory. According to the results of the pre-calculation by the grid theory and combined with actual process experience, the pressure ratio between the circumferential and longitudinal directions of the winding layer is adjusted to give a hole-expanding winding ply design scheme that meets the burst pressure. Then, the hole-expanding winding ply design scheme is imported into the winding simulation software to confirm the feasibility of winding, and the ply winding scheme is adjusted according to the fiber stacking situation at the head. Next, the head thickness and angle that meet the winding process are exported and sorted out to establish a finite element model of the composite material and perform strength verification under the burst pressure. The winding design is repeatedly modified until the requirements are met. Finally, the winding scheme that meets the design requirements is output as G-code recognizable by the winding machine. The present invention has the advantages of enabling the head winding to meet the burst pressure requirements and achieving the purpose of lightweight design.

Description

Technical Field

[0001] The present invention relates to the technical field of composite pressure vessels, and particularly to a design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder. Background Technique

[0002] Fiber-reinforced composite materials have a series of advantages such as high specific strength, high specific stiffness, and designable properties. At present, fiber-wound pressure vessels have evolved from early all-metal pressure vessels (Type I), circumferentially fiber-reinforced metal-lined pressure vessels (Type II), all-fiber-wound metal-lined pressure vessels (Type III) to today's all-fiber-wound plastic-lined pressure vessels (Type IV). The use of reinforcing fibers has enabled pressure vessels to better meet the requirements of "light weight" and "reliability".

[0003] Among them, the Type IV gas cylinder mainly consists of a plastic liner, a metal joint, a carbon fiber winding layer, an outer protective layer, and a sealing structure. The liner does not bear the load and can serve as a mandrel during winding and prevent the storage medium from leaking. The composite winding layer is made by impregnating continuous carbon fibers with resin or using prepreg unidirectional tapes and winding them on the mandrel according to the ply design process, and then curing by heating. The composite winding layer serves as the main load-bearing component and provides strength for the Type IV gas cylinder. Therefore, the structural design of the composite winding layer has become the key and difficult point in the development of vehicle-mounted composite gas cylinders.

[0004] At present, the design and manufacturing process of Type IV high-pressure hydrogen storage cylinders is not yet mature, and there are disadvantages such as low precision, large test volume, cost waste, low design efficiency, and narrow application range. Although the traditional grid theory or laminate theory design methods are relatively reliable in calculating the cylinder section, it is difficult to accurately calculate the winding angle and winding layer thickness at the head, and there is a large error compared with the actual situation, which will cause the problem of insufficient winding thickness design at the head, resulting in the head failing first during blasting, thus posing a safety hazard; or the winding thickness design at the head is excessive, and it is impossible to quickly carry out lightweight design, resulting in material waste. Summary of the Invention

[0005] The purpose of the present invention is to provide a design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder that can make the head winding meet the blasting pressure requirements and achieve the purpose of lightweight design.

[0006] To achieve the above purpose, the present invention adopts the following technical scheme: A design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder, including the following steps:

[0007] Step (1): According to the physical properties of the carbon fiber material, the designed blasting pressure, and the liner structure, pre-calculate the helical winding angle, helical winding layer thickness, and circumferential winding layer thickness of the cylinder section using the grid theory;

[0008] Step (2): Calculate the burst pressure of the cylindrical section helical winding layer, the burst pressure of the cylindrical section circumferential winding layer, and the burst pressure ratio η of the burst pressure of the cylindrical section circumferential winding layer to the burst pressure of the cylindrical section helical winding layer based on the helical winding angle of the cylindrical section, the thickness of the cylindrical section helical winding layer, and the thickness of the cylindrical section circumferential winding layer obtained in step (1);

[0009] Step (3): Determine whether the burst pressure ratio η obtained in step (2) satisfies 0.6 ≤ η ≤ 0.7. If not, jump to step (4); if satisfied, jump to step (5);

[0010] Step (4): Readjust the thickness of the cylindrical section helical winding layer and the thickness of the cylindrical section circumferential winding layer, and recalculate the burst pressure of the adjusted cylindrical section helical winding layer, the burst pressure of the cylindrical section circumferential winding layer, and the burst pressure ratio η of the burst pressure of the cylindrical section circumferential winding layer to the burst pressure of the cylindrical section helical winding layer using the grid theory based on the adjusted thicknesses of the cylindrical section helical winding layer and the cylindrical section circumferential winding layer. Determine whether the adjusted burst pressure ratio η satisfies 0.6 ≤ η ≤ 0.7. If not, repeat step (4); if satisfied, jump to step (5);

[0011] Step (5): Design the hole-expanding winding layup scheme for the gas cylinder head according to the thicknesses of the cylindrical section helical winding layer and the cylindrical section circumferential winding layer that meet the requirements of the burst pressure ratio pre-calculated using the grid theory;

[0012] Step (6): According to the hole-expanding winding layup scheme of the gas cylinder head, use winding simulation software to analyze the rationality of winding and calculate and output the composite material thickness and winding angle corresponding to the parallel circle of the head;

[0013] Step (7): Import the calculation results obtained in step (6) into the modeling software to perform finite element modeling of the composite material;

[0014] Step (8): Perform finite element simulation calculations based on the composite material finite element model established in step (7) and check the first principal stress σ. Determine whether the calculated first principal stress σ satisfies σ ≤ σ b , σ b is the tensile strength in the fiber direction of the composite material; if not, readjust the hole-expanding winding layup scheme of the gas cylinder head and jump to step (6); if satisfied, output the G code recognizable by the winding machine for actual winding.

[0015] Furthermore, in the aforementioned method for hole-expanding winding design of a high-pressure hydrogen storage gas cylinder head, in step (1), the physical properties of the carbon fiber material for pre-calculation using the grid theory include: carbon fiber density, carbon fiber linear density, the bandwidth width after spreading a single bundle of yarn, fiber volume content, fiber developed strength, and the tensile strength in the fiber direction of the composite material.

[0016] Furthermore, for the aforementioned method for designing the hole-expanded winding of the head of a high-pressure hydrogen storage cylinder, in which: in step (1), the helical winding angle is calculated based on the geodesic winding angle, and the specific calculation formula is as follows:

[0017]

[0018] where α 0 is the helical winding angle, r 0 is the radius of the polar hole, and R is the radius of the inner liner cylinder section.

[0019] Furthermore, for the aforementioned method for designing the hole-expanded winding of the head of a high-pressure hydrogen storage cylinder, in which: in step (1), the specific calculation formula for the thickness of the helical winding layer of the cylinder section is as follows:

[0020]

[0021] where t α is the thickness of the helical winding layer of the cylinder section, R is the radius of the inner liner cylinder section, P b is the designed burst pressure, σ b is the tensile strength in the direction of the composite material fiber, K 1 is the strength utilization coefficient of the helical winding fiber, K1 ≤ 1, and α 0 is the helical winding angle;

[0022] The specific calculation formula for the thickness of the circumferential winding layer of the cylinder section is as follows:

[0023]

[0024] where t θ is the thickness of the circumferential winding layer of the cylinder section, R is the radius of the inner liner cylinder section, P b is the designed burst pressure, σ b is the tensile strength in the direction of the composite material fiber, K 2 is the strength utilization coefficient of the circumferential winding fiber, K2 ≥ 1, and α 0 is the helical winding angle.

[0025] Furthermore, for the aforementioned method for designing the hole-expanded winding of the head of a high-pressure hydrogen storage cylinder, in which: in step (2), the specific calculation formula for the burst pressure of the helical winding layer of the cylinder section is as follows:

[0026]

[0027] where P total-纵向 is the burst pressure of the helical winding layer of the cylinder section, t α is the thickness of the helical winding layer of the cylinder section, σ b is the tensile strength in the direction of the composite material fiber, and α 0is the spiral winding angle, and R is the radius of the inner liner section;

[0028] The specific calculation formula for the bursting pressure of the circumferential winding layer of the cylinder section is as follows:

[0029]

[0030] Among them, P total-环向 is the bursting pressure of the circumferential winding layer of the cylinder section, t α is the thickness of the spiral winding layer of the cylinder section, σ b is the tensile strength in the fiber direction of the composite material, α 0 is the spiral winding angle, R is the radius of the inner liner section, and t θ is the thickness of the circumferential winding layer of the cylinder section;

[0031] The specific calculation formula for the bursting pressure ratio η of the bursting pressure of the circumferential winding layer of the cylinder section to the bursting pressure of the spiral winding layer of the cylinder section is as follows:

[0032]

[0033] Among them, η is the bursting pressure ratio of the bursting pressure of the circumferential winding layer of the cylinder section to the bursting pressure of the spiral winding layer of the cylinder section, and P total-环向 is the bursting pressure of the circumferential winding layer of the cylinder section, and P total-纵向 is the bursting pressure of the spiral winding layer of the cylinder section.

[0034] Furthermore, in the aforementioned method for the design of hole-expanding winding of the high-pressure hydrogen storage cylinder head, where: in step (5), it is possible to check whether the bursting pressure ratio η of the hole-expanding winding ply arrangement of the cylinder head meets 0.6 ≤ η ≤ 0.7, and the specific calculation formula is as follows:

[0035] The longitudinal bursting pressure and circumferential pressure of the cylinder winding layer;

[0036]

[0037] P 环向缠绕-纵向 = 0

[0038]

[0039]

[0040] P total-纵向 = P 螺旋缠绕-纵向 + P 环向缠绕-纵向

[0041] P total-环向 = P 螺旋缠绕-环向 + P 环向缠绕-环向

[0042]

[0043] Among them, M is the number of reaming times, and t c is the thickness of a single layer of the composite material, and σ b is the tensile strength in the fiber direction of the composite material, and r 0 +i2b is the polar hole radius corresponding to the reaming winding, R is the radius of the inner liner cylinder section, is the number of layers of this reaming winding method, b is the width of the bandwidth used during winding after the yarn bundle is unwound, and N θ is the total number of circumferential winding layers, and η is the burst pressure ratio.

[0044] Furthermore, for the above-mentioned design method of reaming winding for the head of a high-pressure hydrogen storage cylinder, where: in step (5), the reaming winding layup scheme for the cylinder head is specifically: the reaming winding method is a reaming winding mode with a 2-fold bandwidth: the initial fiber is helically wound tangent to the polar hole at the polar hole, the first fiber is helically wound tangent to the polar hole circle plus 2-fold bandwidth, the second time, helical reaming winding is carried out at the polar hole circle plus 4-fold bandwidth, until after all the fiber helical reaming windings in the first row of the design scheme are completed, circumferential winding is carried out, and the fiber helical reaming windings and circumferential windings of all rows are carried out in the same way in turn.

[0045] Furthermore, for the above-mentioned design method of reaming winding for the head of a high-pressure hydrogen storage cylinder, where: in step (8), the physical properties of the composite material used for simulation analysis include: since the composite material layer can be regarded as an orthotropic single-layer thin plate, that is, it belongs to the plane stress state, only the in-plane stress of a single layer is considered, and the stress on a single layer can be ignored, so only the 5 engineering constants of E x , E y , v xy , v yz , G xy need to be measured. Also, since there is the following relationship among the first four items: Therefore, the actual number of independent engineering elastic constants that need to be measured is 4.

[0046] By implementing the above technical solutions, the advantages of the present invention are: (1) The grid theory is used to pre-calculate the helical winding angle, the thickness of the helical winding layer and the circumferential winding layer of the cylinder section. According to the results pre-calculated by the grid theory and combined with actual process experience, the pressure ratio between the circumferential and longitudinal directions of the winding layer is adjusted, so as to give a reaming winding layup design scheme for the cylinder head that meets the burst pressure requirements, thus making the winding of the cylinder head meet the burst pressure requirements and improving the safety of the cylinder; (2) The reaming winding method can also reduce the fiber accumulation at the polar hole when continuously winding at the same helical winding angle, thereby reducing the weight of the composite material in the high-pressure hydrogen storage cylinder and achieving the purpose of lightweight design; (3) It can accurately calculate the winding angle and the thickness of the winding layer at the head, avoiding the occurrence of insufficient winding thickness design at the head. Description of the Drawings

[0047] Figure 1 It is the inner liner structure of a type-IV composite material gas storage cylinder.

[0048] Figure 2 It is a schematic diagram of hole-expanding winding.

[0049] Figure 3 It is a schematic diagram for comparing the calculation methods of the head thickness.

[0050] Figure 4 It is a schematic diagram of the head thickness corresponding to the hole-expanding winding scheme.

[0051] Figure 5 It is a schematic diagram of the finite element model of the composite material for the hole-expanding winding scheme.

[0052] Figure 6 It is a schematic diagram of the stress values of the composite material layer under the working pressure and the burst pressure. Specific implementation manners

[0053] A design method for hole-expanding winding of the head of a high-pressure hydrogen storage gas cylinder includes the following steps:

[0054] Step (1): According to the physical properties of the carbon fiber material, the designed burst pressure, and the inner liner structure, pre-calculate the helical winding angle, the thickness of the helical winding layer, and the thickness of the circumferential winding layer of the cylinder section by using the grid theory;

[0055] Among them, the physical properties of the carbon fiber material used for the grid theory pre-calculation include: carbon fiber density, carbon fiber linear density, the bandwidth width after spreading a single bundle of yarn, fiber volume content, fiber developed strength, and the tensile strength in the fiber direction of the composite material;

[0056] Among them, the helical winding angle is calculated according to the geodesic winding angle, and the specific calculation formula is as follows:

[0057]

[0058] Among them, α 0 is the helical winding angle, r 0 is the polar hole radius, and R is the radius of the inner liner cylinder section;

[0059] Among them, the specific calculation formula for the thickness of the helical winding layer of the cylinder section is as follows:

[0060]

[0061] Among them, t α is the thickness of the helical winding layer of the cylinder section, R is the radius of the inner liner cylinder section, P b is the designed burst pressure, σ b is the tensile strength in the fiber direction of the composite material, and K 1is the strength utilization coefficient of helically wound fibers, K 1 ≤ 1, α 0 is the helical winding angle;

[0062] The specific calculation formula for the thickness of the circumferential winding layer of the cylinder section is as follows:

[0063]

[0064] where, t θ is the thickness of the circumferential winding layer of the cylinder section, R is the radius of the inner liner cylinder section, P b is the designed burst pressure, σ b is the tensile strength in the fiber direction of the composite material, K 2 is the strength utilization coefficient of circumferentially wound fibers, K 2 ≥ 1, α 0 is the helical winding angle;

[0065] Step (2): Calculate the burst pressure of the helical winding layer of the cylinder section, the burst pressure of the circumferential winding layer of the cylinder section, and the burst pressure ratio η of the burst pressure of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section according to the helical winding angle, the thickness of the helical winding layer of the cylinder section, and the thickness of the circumferential winding layer of the cylinder section obtained in step (1);

[0066] Among them, the specific calculation formula for the burst pressure of the helical winding layer of the cylinder section is as follows:

[0067]

[0068] where, P total-纵向 is the burst pressure of the helical winding layer of the cylinder section, t α is the thickness of the helical winding layer of the cylinder section, σ b is the tensile strength in the fiber direction of the composite material, α 0 is the helical winding angle, R is the radius of the inner liner cylinder section;

[0069] The specific calculation formula for the burst pressure of the circumferential winding layer of the cylinder section is as follows:

[0070]

[0071] where, P total-环向 is the burst pressure of the circumferential winding layer of the cylinder section, t α is the thickness of the helical winding layer of the cylinder section, σ b is the tensile strength in the fiber direction of the composite material, α 0 is the helical winding angle, R is the radius of the inner liner cylinder section, t θ is the thickness of the circumferential winding layer of the cylinder section;

[0072] The specific calculation formula for the burst pressure ratio η of the burst pressure of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section is as follows:

[0073]

[0074] Among them, η is the burst pressure ratio of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section, and P total-环向 is the burst pressure of the circumferential winding layer of the cylinder section, and P total-纵向 is the burst pressure of the helical winding layer of the cylinder section.

[0075] Step (3): Determine whether the burst pressure ratio η obtained in step (2) satisfies 0.6 ≤ η ≤ 0.7. If not, jump to step (4); if satisfied, jump to step (5);

[0076] Step (4): Readjust the thickness of the helical winding layer of the cylinder section and the thickness of the circumferential winding layer of the cylinder section, and based on the adjusted thickness of the helical winding layer of the cylinder section and the thickness of the circumferential winding layer of the cylinder section, re-precalculate the adjusted burst pressure of the helical winding layer of the cylinder section, the burst pressure of the circumferential winding layer of the cylinder section, and the burst pressure ratio η of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section using the grid theory. Determine whether the adjusted burst pressure ratio η satisfies 0.6 ≤ η ≤ 0.7. If not, repeat step (4); if satisfied, jump to step (5);

[0077] Step (5): Design the reaming winding layup scheme for the gas cylinder head according to the thickness of the helical winding layer of the cylinder section and the thickness of the circumferential winding layer of the cylinder section that meet the requirements of the burst pressure ratio pre-calculated by the grid theory;

[0078] Among them, the reaming winding layup scheme for the gas cylinder head is specifically as follows: The reaming winding method is a reaming winding mode with a 2-fold bandwidth: The initial fiber is helically wound tangent to the polar hole at the polar hole, the first fiber is helically wound tangent to the polar hole circle plus 2-fold bandwidth, and the second reaming winding is performed at the polar hole circle plus 4-fold bandwidth until all the fiber helical reaming windings in the first row of the design scheme are completed, and then circumferential winding is carried out. The fiber helical reaming winding and circumferential winding of all rows are carried out in the same way in turn;

[0079] Among them, it is possible to check whether the burst pressure ratio η of the reaming winding layup scheme for the gas cylinder head satisfies 0.6 ≤ η ≤ 0.7. The specific calculation formula is as follows:

[0080] Longitudinal burst pressure and circumferential pressure of the cylinder section winding layer;

[0081]

[0082] P 环向缠绕-纵向 = 0

[0083]

[0084]

[0085] P total-纵向 = P 螺旋缠绕-纵向 + P 环向缠绕-纵向

[0086] P total-环向 = P 螺旋缠绕-环向 + P 环向缠绕-环向

[0087]

[0088] where M is the number of reaming times, t c is the thickness of a single layer of the composite material, σ b is the tensile strength in the fiber direction of the composite material, r 0 + i2b is the polar hole radius corresponding to the reaming winding, R is the radius of the inner liner cylinder section, is the number of layers of this reaming winding method, b is the width of the tape used during winding after the yarn bundle is spread, N θ is the total number of circumferential winding layers, and η is the burst pressure ratio;

[0089] Step (6): According to the reaming winding ply scheme of the gas cylinder head, use winding simulation software to analyze the rationality of winding and calculate and output the composite material thickness and winding angle corresponding to the parallel circle of the head;

[0090] Step (7): Import the calculation results obtained in step (6) into the modeling software to perform finite element modeling of the composite material;

[0091] Step (8): Perform finite element simulation calculations based on the composite material finite element model established in step (7) and check the first principal stress σ, and determine whether the calculated first principal stress σ satisfies σ ≤ σ b , σ b is the tensile strength in the fiber direction of the composite material; if not satisfied, readjust the reaming winding ply scheme of the gas cylinder head and jump to execute step (6); if satisfied, output the G code recognizable by the winding machine for actual winding;

[0092] Among them, the physical properties of the composite material for simulation analysis include: Since the composite material layer can be regarded as an orthotropic single-layer thin plate, that is, it belongs to the plane stress state, only the in-plane stress of the single layer is considered, and the stress on the single layer can be ignored, so only the 5 engineering elastic constants of E x , E y , v xy , v yz , G xy need to be measured. Also, due to the following relationship among the first four items: Therefore, the number of independent engineering elastic constants that actually need to be measured is 4.

[0093] The following uses a specific embodiment to illustrate the high-pressure hydrogen storage cylinder head reaming winding design method of the present invention, specifically as follows:

[0094] 01. The physical properties of the carbon fiber material used in this example are: the density of carbon fiber is 1.8 g / cm 3 , the linear density of carbon fiber is 1.65 g / m, the bandwidth after spreading a single bundle of yarn is 5 mm, the number of roots is 2, the fiber volume content is 0.6, and the tensile strength in the fiber direction of the composite material is 2000 MPa.

[0095] The physical properties of carbon fiber can be provided by the supplier. The physical properties of the composite material can be calculated through the resin content used in the actual process, or the physical properties and thickness of the composite material can be obtained through tests on unidirectional composite laminates made of prepregs.

[0096] 02. This example uses a type-IV composite gas cylinder liner structure with equal polar holes at both ends (as Figure 1 shown), its polar hole radius is 32 mm, the outer diameter of the cylinder section is 175 mm, the total length of the cylinder section is 700 mm, and the ratio of the major axis to the minor axis of the head is 1.6:1;

[0097] Since both ends have an equal polar hole structure, the winding angle of the cylinder section is calculated according to the geodesic winding angle calculation formula:

[0098]

[0099] Among them, α 0 is the helical winding angle, r 0 is the polar hole radius, and R is the radius of the inner liner cylinder section;

[0100] Since under uniform internal pressure, except for local bending and shear stresses, the gas cylinder mainly bears membrane internal forces, and the ultimate tensile strength of the resin is much lower than that of the fiber, it can be regarded as a grid structure composed entirely of fibers;

[0101] Adopt the grid theory and according to the inner liner structure of the type-IV composite gas cylinder, pre-calculate the thickness of the helical winding layer and the circumferential winding layer required for the cylinder section when the hydrogen storage cylinder reaches the designed burst pressure of 157.5 MPa, and estimate the number of helical winding and circumferential winding layers according to the thickness of a single layer of the composite material.

[0102]

[0103]

[0104]

[0105]

[0106] 03. Calculate the burst pressure of the helical winding layer of the cylinder section, the burst pressure of the circumferential winding layer of the cylinder section, and the burst pressure ratio η of the burst pressure of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section according to the pre-calculated thickness in 02;

[0107]

[0108]

[0109]

[0110] Since there is no circumferential winding at the cylinder head of the gas cylinder and due to problems such as overlap and overhead of the helical winding layer caused by winding tension and winding sequence, the fiber strength at the cylinder head is lower than the strength of the multifilament measured in the test. If the winding is carried out completely according to the pre-calculated thickness in 02, the cylinder head will burst before the cylinder section; therefore, according to engineering experience, adjust the fiber strength utilization coefficient K 1 of the helical winding and the fiber strength utilization coefficient K 2 of the circumferential winding so that the pressure ratio ranges from 0.65 ± 0.5; where K 1 ≤ 1, K 2 ≥ 1;

[0111] 04. Modify K 1 , K 2 according to the engineering experience in 03, and then carry out the reaming winding design for the high-pressure hydrogen storage gas cylinder based on the thickness of the helical winding layer of the cylinder section and the thickness of the circumferential winding layer of the cylinder section obtained;

[0112] The reaming winding method (as shown in Figure 2 ) can eliminate problems such as the reduction of fiber strength caused by fiber accumulation, overhead, and porosity at the polar hole, and at the same time can achieve the purpose of reducing the weight of the composite hydrogen storage cylinder;

[0113] The reaming winding scheme is as follows:

[0114] [±11° ±17° ±24° ±32° ±40° ±49° ±60° ±79°] 1 ; [90°] 8 ;

[0115] [±11° ±17° ±24° ±32° ±40° ±49° ±60° ±79°] 1 ; [90°] 8 ;

[0116] [±11° ±17° ±24° ±32° ±40° ±49° ±60°] 1 ; [90°] 8 ;

[0117] [±11° ±17° ±24° ±32° ±40° ±49°] 1 ; [90°] 8 ;

[0118] [±11° ±17° ±24° ±32° ±40°] 1 ;

[0119] Calculate the longitudinal bursting pressure and circumferential pressure of the cylinder section winding layer respectively using the following formulas

[0120]

[0121]

[0122] P 环向缠绕-纵向 = 0 MPa

[0123]

[0124] P total-纵向 = P 环向缠绕-纵向 + P 螺旋缠绕-纵向 = 0 + 316.37 = 316.37 MPa

[0125] P total-环向 = P 环向缠绕-环向 + P 螺旋缠绕-环向 = 111.75 + 79.28 = 191.03 MPa

[0126]

[0127] Verify that the pressure ratio range is between 0.65 ± 0.5, meeting the empirical formula.

[0128] 05 Since the thickness and winding angle at the head change with the parallel circle radius, and there are large geometric deformations, material nonlinearities, and contact nonlinearities at the head under continuous pressure during the bursting test, it is difficult to calculate the bursting strength at the head using theoretical methods. Currently, finite element simulation software is often used for strength checking calculations; in finite element simulation calculations, how to accurately model the composite material thickness at the head is a difficult point because it directly affects the accuracy of the simulation calculations;

[0129] Currently, the main calculation methods for the thickness at the head are: single formula, plane method, double formula, etc.

[0130] Single formula:

[0131]

[0132] Among them, t cis the single-layer winding thickness of the cylinder section, R is the radius of the cylinder section, r is the radius of the parallel circle, and α 0 is the helical winding angle of the cylinder section.

[0133] Plane method:

[0134]

[0135]

[0136] Among them, T 0 = t 0 / r 0 and Y 0 = R / r 0 and B = b / r 0 and Y = r / r 0 are all dimensionless numbers.

[0137] Y w is

[0138] Dual-formula method:

[0139]

[0140]

[0141] Among them, b is the bandwidth used during winding after the yarn bundle is unwound;

[0142] As Figure 3 shown, these methods are relatively accurate in predicting the thickness at positions far from the polar hole area. However, due to problems such as slip, overhead, porosity, and fiber reorientation during winding, the predicted thickness results within a range of 1 bandwidth from the polar hole differ significantly from the actual thickness values.

[0143] 06. Since the calculation method described in 05 is inconsistent with the actual situation, in order to calculate the strength of the composite material of the head more accurately, according to the properties of carbon fiber reinforced composite materials in 01; the structural dimensions of the hydrogen storage cylinder in 02, and the reaming winding ply scheme in 03, a winding simulation software is used to calculate the thickness and winding angle of each layer, and the winding angle and thickness values of each layer are exported, as Figure 4 shown;

[0144] 07. According to the winding angle and thickness coordinate values of each layer in 06, the composite material is modeled layer by layer (as Figure 5 shown), and it is calculated whether it meets the strength under the actual working conditions (as Figure 6 shown);

[0145] According to Figure 6It can be seen that under 2.25 times the working pressure (157.5 MPa), the stresses of each reamed helical winding layer and the circumferential winding layer are less than the tensile strength of the composite material, which is 2000 MPa. When the pressure rises to 2.5 times the working pressure (175 MPa), the innermost circumferential winding layer exceeds the tensile strength of the composite material, which is 2000 MPa, and failure occurs.

[0146] After the calculation results meet the strength requirements, output the code file that can be used for winding by the winding machine to carry out the actual winding process.

[0147] The advantages of the present invention are as follows: (1) The grid theory is adopted to pre-calculate the helical winding angle and the thicknesses of the helical winding layer and the circumferential winding layer of the cylinder section. According to the results pre-calculated by the grid theory and combined with the actual process experience, the pressure ratio of the circumferential direction to the longitudinal direction of the winding layer is adjusted, so as to give a reamed winding ply design scheme for the gas cylinder head that meets the bursting pressure requirements, thereby enabling the winding of the gas cylinder head to meet the bursting pressure requirements and improving the safety of the gas cylinder; (2) The reamed winding method can also reduce the fiber accumulation at the polar hole when always winding at the same helical winding angle, thereby reducing the weight of the composite material in the high-pressure hydrogen storage gas cylinder and achieving the purpose of lightweight design; (3) It can accurately calculate the winding angle and the winding layer thickness at the head, avoiding the occurrence of insufficient winding thickness design at the head.

Claims

1. A design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder, characterized in that: It includes the following steps: Step (1): According to the physical properties of carbon fiber materials, the designed burst pressure and the liner structure, pre-calculate the helical winding angle, the thickness of the helical winding layer, and the thickness of the circumferential winding layer of the cylinder section using the grid theory; Step (2): Calculate the burst pressure of the helical winding layer of the cylinder section, the burst pressure of the circumferential winding layer of the cylinder section, and the burst pressure ratio η of the burst pressure of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section based on the helical winding angle, the thickness of the helical winding layer, and the thickness of the circumferential winding layer of the cylinder section obtained in Step (1); Step (3): Determine whether the burst pressure ratio η obtained in Step (2) satisfies 0.6 ≤ η ≤ 0.

7. If it does not satisfy, then jump to execute Step (4); if it satisfies, then jump to execute Step (5); Step (4): Re-adjust the thickness of the helical winding layer and the thickness of the circumferential winding layer of the cylinder section, and re-pre-calculate the adjusted burst pressure of the helical winding layer of the cylinder section, the burst pressure of the circumferential winding layer of the cylinder section, and the burst pressure ratio η of the burst pressure of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section using the grid theory based on the adjusted thickness of the helical winding layer and the thickness of the circumferential winding layer of the cylinder section. Determine whether the adjusted burst pressure ratio η satisfies 0.6 ≤ η ≤ 0.

7. If it does not satisfy, then repeat Step (4). If it satisfies, then jump to execute Step (5); Step (5): Design the expanding hole and winding layup scheme for the cylinder head according to the thickness of the helical winding layer and the thickness of the circumferential winding layer of the cylinder section pre-calculated by the grid theory and meeting the requirements of the burst pressure ratio; Step (6): According to the expanding hole and winding layup scheme of the cylinder head, use the winding simulation software to analyze the rationality of winding and calculate and output the composite material thickness and winding angle corresponding to the parallel circle of the head; Step (7): Import the calculation results obtained in Step (6) into the modeling software for finite element modeling of the composite material; Step (8): Perform finite element simulation calculations based on the composite material finite element model established in step (7) and check the first principal stress σ. Determine whether the calculated first principal stress σ satisfies σ ≤ σ b , σ b is the tensile strength in the fiber direction of the composite material; if not satisfied, readjust the hole expansion winding ply scheme of the gas cylinder head and jump to execute step (6); if satisfied, output the G code recognizable by the winding machine for actual winding.

2. A design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that: In Step (1), the physical properties of the carbon fiber material for pre-calculation using the grid theory include: carbon fiber density, carbon fiber linear density, the bandwidth width after spreading a single bundle of yarn, fiber volume content, fiber developed strength, and the tensile strength in the fiber direction of the composite material.

3. A design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that: In Step (1), the helical winding angle is calculated according to the geodesic winding angle, and the specific calculation formula is as follows: Among them, α 0 is the spiral winding angle, r 0 is the polar hole radius, and R is the radius of the inner liner section.

4. A design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder according to claim 3, characterized in that: In Step (1), the specific calculation formula for the thickness of the helical winding layer of the cylinder section is as follows: Among them, t α is the thickness of the helical winding layer of the cylinder section, R is the radius of the inner lining cylinder section, P b is the designed burst pressure, σ b is the tensile strength in the fiber direction of the composite material, K 1 is the coefficient of strength development of the helical winding fiber, K 1 ≤1, α 0 is the helical winding angle; The specific calculation formula for the thickness of the circumferential winding layer of the cylinder section is as follows: where t θ is the thickness of the circumferential winding layer of the cylinder section, R is the radius of the inner liner cylinder section, P b is the designed burst pressure, σ b is the tensile strength in the fiber direction of the composite material, K 2 is the strength utilization coefficient of the circumferential winding fibers, K 2 ≥ 1, α 0 is the helical winding angle.

5. A design method for expanding the hole and winding the head of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that: In Step (2), the specific calculation formula for the burst pressure of the helical winding layer of the cylinder section is as follows: Among them, P total-纵向 is the burst pressure of the helically wound layer of the cylinder section, t α is the thickness of the helically wound layer of the cylinder section, σ b is the tensile strength in the fiber direction of the composite material, α 0 is the helical winding angle, and R is the radius of the inner liner cylinder section; The specific calculation formula for the burst pressure of the circumferential winding layer of the cylinder section is as follows: Among them, P total-环向 is the burst pressure of the circumferential winding layer of the cylinder section, t α is the thickness of the helical winding layer of the cylinder section, σ b is the tensile strength in the fiber direction of the composite material, α 0 is the helical winding angle, R is the radius of the inner liner cylinder section, t θ is the thickness of the circumferential winding layer of the cylinder section; The specific calculation formula for the burst pressure ratio η of the burst pressure of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section is as follows: where η is the ratio of the burst pressure of the circumferential winding layer of the cylinder section to the burst pressure of the helical winding layer of the cylinder section, and p total-环向 is the burst pressure of the circumferential winding layer of the cylinder section, and P total-纵向 is the burst pressure of the helical winding layer of the cylinder section.

6. A method for the design of the hole expansion winding of the head of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that: In step (5), it is possible to check whether the burst pressure ratio η of the hole expansion winding ply scheme of the cylinder head meets 0.6 ≤ η ≤ 0.7, and the specific calculation formula is as follows: The longitudinal burst pressure and circumferential pressure of the winding layer of the cylinder section; P 环向缠绕-纵向 ＝0 P total-纵向 = P 螺旋缠绕-纵向 + P 环向缠绕-纵向 p total-环向 = P 螺旋缠绕-环向 + P 环向缠绕-环向 Among them, M is the number of reaming times, t c is the single-layer thickness of the composite material, σ b is the tensile strength in the fiber direction of the composite material, r 0 + i2b is the polar hole radius corresponding to the reaming winding, R is the radius of the inner liner section, is the number of layers of this reaming winding method, b is the bandwidth used during winding after the yarn bundle is unwound, N θ is the total number of circumferential winding layers, and η is the burst pressure ratio.

7. A method for the design of the hole expansion winding of the head of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that: In step (5), the hole expansion winding ply scheme of the cylinder head is specifically as follows: the hole expansion winding method is a hole expansion winding mode with a bandwidth of 2 times: the initial fiber helical winding is tangent to the polar hole at the polar hole, the first fiber helical hole expansion winding is tangent at the polar hole circle plus 2 times the bandwidth, and the second time, helical hole expansion winding is carried out at the polar hole circle plus 4 times the bandwidth, until the circumferential winding is carried out after all the fiber helical hole expansion windings of the first row of the design scheme are completed. The fiber helical hole expansion windings and circumferential windings of all rows are carried out in the same way in turn.

8. A method for the design of the hole expansion winding of the head of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that: In step (8), the physical properties of the composite material for simulation analysis include: since the composite material layer can be regarded as an orthotropic single-layer thin plate, that is, it belongs to the plane stress state, only the in-plane stress of the single layer is considered, and the stress on the single layer can be ignored, so only the five engineering elastic constants expressing the stiffness performance need to measure E x , E y , v xy , v yz , G xy . And because there are the following relationships among the first four items: Therefore, the number of independent engineering elastic constants that actually need to be measured is 4.

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