A method for partition reinforcement of the head of a type IV hydrogen storage cylinder

Abstract

The present invention provides a method for zoning and reinforcing the head of a Type IV hydrogen storage cylinder, which evenly distributes the thickness of carbon fibers in the head area and improves the stress state of the cylinder head area. The cylinder is composed of a carbon fiber layer at the pole mouth, a plastic liner, and a carbon fiber layer at the equator. The cylinder head area is divided in the height direction according to the longitudinal winding sand width, and the corresponding winding angle is calculated using the area height and the pole mouth radius as the hole expansion radius to form a set of layer expansion reinforcement schemes with winding angles. The number of hole expansion layers is calculated according to the pole mouth radius: the first sand width height expansion layer: the second sand width height expansion layer: the third sand width height expansion layer: ... the last sand width height expansion layer is ≈ 2:3:3:3:...:4:...:3:3:2. Each longitudinal fiber layer is cyclically and alternately wound to form a uniform reinforcement of the head surface. The present invention improves the rationality of the stress state in the head area, improves the bearing capacity of the cylinder, reduces the excess accumulation of carbon fibers at the pole mouth, and improves the hydrogen storage density.

Description

Technical Field

[0001] The present invention belongs to the technical field of gaseous high-pressure hydrogen storage cylinder molding, and in particular relates to a partition reinforcement method for a type IV hydrogen storage cylinder head. Background Art

[0002] Since carbon fiber is a highly brittle material, when the gas cylinder is subjected to internal pressure, the head portion is in a complex stress state under the combined effects of tension, bending, and shearing, which can easily cause low-pressure explosions at the head portion. Reinforcement of composite gas cylinders is the key to solving this problem. The head of a Type IV hydrogen storage cylinder is often structurally designed based on an isotension head. Under uniform internal pressure, when the fiber tension at any point on the isotension head is equal, it is an ideal isostrength structure head. In order to achieve higher hydrogen storage density, specific strength, and long life, the key to reducing the weight of the gas cylinder lies in reducing the weight of carbon fiber. In the design and analysis of the head profile of a Type IV hydrogen storage cylinder, the precise wall thickness of the head section is very critical, especially the head section with large thickness variations.

[0003] At present, the molding method of Type IV hydrogen storage cylinders mostly adopts a combination of longitudinal winding and hoop winding. Hoop winding can eliminate the hoop stress caused by the internal pressure of the cylinder, and longitudinal winding can provide longitudinal stress. Traditional layer design generally alternates hoop winding and longitudinal winding. There is no standard standard for the method of longitudinal winding expansion reinforcement in the head area. For 70MPa Type IV hydrogen storage cylinders, the traditional design method is used to form the head surface. Figure 1 The equatorial region of the seal is thinner, while the fiber is more densely packed at the end of the seal, resulting in a maximum thickness at the end of the seal being approximately twice the minimum thickness at the equator. This results in insufficient strength at the equator, resulting in a low hydraulic burst. More layers of carbon fiber are required to ensure strength in the equatorial region, which can lead to overweight cylinders and reduced hydrogen storage density.

[0004] At present, the reinforcement method for the head of a Type IV hydrogen storage cylinder with a working pressure of 70 MPa results in uneven carbon fiber accumulation in the cylinder head, with thinner carbon fibers at the equator and thicker carbon fibers at the mouth, which has the following disadvantages:

[0005] 1) The unevenness of the head surface can easily cause low-pressure explosion in the equatorial area;

[0006] 2) The carbon fiber is thickly deposited at the pole mouth, the volume content of the fiber inside and outside the fiber layer is different, the quality consistency of the inner and outer layers is very poor, and the volume in the resin system is difficult to evaporate outward and easily forms bubbles, resulting in low fiber strength.

[0007] 3) The circumferential stress at the pole mouth is relatively small, and the carbon fiber winding angle at the pole mouth is 90°. Excessive carbon fiber accumulates at the pole mouth, causing the gas cylinder to be overweight. Summary of the Invention

[0008] In response to the above shortcomings, the present invention designs a type IV hydrogen storage cylinder head zoning reinforcement method to solve the problem of evenly distributing the stacking thickness of carbon fiber on the cylinder head, improving the cylinder carrying capacity, achieving carbon fiber weight reduction, reducing costs, and increasing hydrogen storage density.

[0009] To solve the technical problem, the present invention adopts the technical solution

[0010] A method for reinforcing the head of a Type IV hydrogen storage cylinder by partitioning, the steps of which are as follows:

[0011] S1: Use the classical grid theory to design the thickness of the winding layer of the composite gas cylinder, and calculate the longitudinal h of the gas cylinder according to the formula fα and hoop fiber thickness h fθ Since the grid theory part considers the effect of numerical value, the above calculated thickness is the thickness of the fiber. The longitudinal h of the cylinder fα and hoop fiber thickness h fθ Divide by the fiber volume content to preliminarily complete the thickness design of the composite material layer

[0012]

[0013] Where, σ fα and σ fθ are the longitudinal and hoop winding fiber stresses, respectively, and the values ​​are taken as the fiber strength σ b ;h fα and h fθ are the longitudinal and hoop fiber thicknesses of the ply respectively, α is the longitudinal spiral winding angle; p b is the burst strength required for the cylinder, r is the radius of the inner liner;

[0014] S2: The head surface is divided into several areas to be reinforced by using the longitudinal sand width and circumferential equal height divisions. The sum of the height of each area and the pole radius is then used as the reinforcement expansion radius. The corresponding actual winding angle is then calculated simultaneously to form a set of winding angle ply expansion reinforcement winding process parameters;

[0015] S3: Calculate the circumferential blasting strength and longitudinal blasting strength of each layer, and superimpose them to obtain the circumferential blasting strength and longitudinal blasting strength of the existing ply. Check the ply strength against the blasting design index. If the strength index is met, the hole expansion ply optimization is completed. If the strength index is not met, appropriately increase the number of plies near the last sand width height hole expansion and the extreme mouth radius hole expansion until the design blasting pressure and circumferential / longitudinal stress ratio index are met. Complete the zoned hole expansion reinforcement ply design.

[0016]

[0017] where p α is the longitudinal winding blasting pressure, p θis the blasting pressure of the hoop winding, and the blasting strength of the cylindrical section is the smaller of the two:

[0018] p b =min{p α ,p θ}………………………………(3)

[0019] Circumferential blasting strength of composite layer p θ , longitudinal burst strength p α Given by the following formula

[0020]

[0021] Furthermore, the S1 fiber exerts strength σ b The value is based on 0.85 of the NOL ring tensile strength (0.85 is an empirical coefficient).

[0022] Furthermore, the S2 reinforcement is carried out in a ratio of the number of expansion layers of the pole radius: the number of expansion layers of the first sand width and height: the number of expansion layers of the second sand width and height: the number of expansion layers of the third sand width and height: ... the number of expansion layers of the last sand width and height ≈ 2:3:3:3:...:4:...:3:3:2, and each longitudinal fiber layer is alternately and symmetrically wound in a circular manner, thereby achieving uniform reinforcement of the head surface.

[0023] Beneficial effects obtained by the present invention

[0024] The present invention improves the rationality of the acceptance state of the head area and increases the carrying capacity of the gas cylinder; improves the fiber volume content inside and outside the fiber layer and increases the fiber strength; reduces the excess accumulation of carbon fibers at the pole port, reduces the weight of the gas cylinder, and increases the hydrogen storage density. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : Schematic diagram of the head structure of the Type IV hydrogen storage cylinder with a working pressure of 70 MPa of the present invention;

[0026] Figure 2 : Schematic diagram of traditional ply design;

[0027] Figure 3 : Schematic diagram of the supplementary zoning of the head area;

[0028] Among them: 1-carbon fiber layer at the pole mouth, 2-plastic liner, 3-carbon fiber layer at the equator, 4-carbon fiber layer at the pole mouth, 5-carbon fiber layer at the equator, 6-difference in carbon fiber thickness between the equator and the pole mouth, 7-pole mouth radius expansion position, 8-first sand width height expansion position, 9-second sand width height expansion position, 10-third sand width height expansion position, 11-fourth sand width height expansion position, 12-fifth sand width height expansion position, 13-last sand width height expansion position. DETAILED DESCRIPTION

[0029] This patented invention designs a type IV hydrogen storage cylinder head partition reinforcement method, which evenly distributes the carbon fiber thickness in the head area and improves the stress state of the cylinder head area. Figure 1 As shown, it is composed of a carbon fiber layer at the pole mouth (1), a plastic liner (2) and a carbon fiber layer at the equator (3). The cylinder head area is divided in the height direction according to the longitudinal winding sand width, and the corresponding winding angle is calculated using the area height and the pole mouth radius as the expansion radius to form a set of layer expansion reinforcement schemes with winding angles. According to the pole mouth radius, the number of expansion layers is as follows: the first sand width and height expansion layer: the second sand width and height expansion layer: the third sand width and height expansion layer: ... the last sand width and height expansion layer is ≈ 2:3:3:3: ...:4: ...:3:3:2. Each longitudinal fiber layer is cyclically and alternately wound to achieve uniform reinforcement of the head surface.

[0030] To make the objectives, features, and advantages of the technical solutions proposed by the present invention more clearly understood, the following will provide a clear and complete description of the embodiments of the technical solutions proposed by the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the proposed technical solutions, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0031] This patented invention designs a partition reinforcement method for the head of a Type IV hydrogen storage cylinder with a working pressure of 70MPa. Figure 1 The diagram shows the schematic diagram of the head structure of a Type IV hydrogen storage cylinder with a working pressure of 70 MPa, which consists of a carbon fiber layer (1) at the pole mouth, a plastic liner (2), and a carbon fiber layer (3) at the equator. The plastic liner (1) is used as a winding core mold, and the interface glue is evenly applied to the surface of the plastic liner (1) head and the barrel section. After the interface glue is semi-cured, the carbon fiber winding is solidified. Since the Type IV hydrogen storage cylinder requires the fiber layer to bear an internal pressure of 70 MPa, according to the safety factor of 2.3, the water explosion pressure is 161 MPa, and the cylinder layer design is designed according to 161 MPa. According to grid theory calculation, the thickness of the carbon fiber winding layer is about 23-25 ​​mm, which belongs to a thick arm pressure vessel. Only longitudinal winding can be used on the head surface. If a small expansion hole winding is used, it is easy to cause more fiber accumulation at the pole mouth and less fiber accumulation at the equator. A zoning reinforcement criterion for gas cylinder heads is defined. The gas cylinder head area is divided in the height direction according to the longitudinal winding sand width. The winding molding of the head surface is completed in a certain order and proportion, which effectively improves the head molding surface and makes it close to the isotension surface.

[0032] First, the thickness of the winding layer of the composite gas cylinder is calculated using the classical grid theory. During the design of the gas cylinder, the fiber rated strength σ b Performance is an important design parameter. According to past experience, the fiber performance strength σ b The value is based on 0.85 of the NOL ring tensile strength (0.85 is an empirical coefficient). At the same time, the thickness of the composite fiber layer is calculated by combining the design blasting pressure, carbon fiber mechanical properties, winding process parameters and fiber volume content. Using the classical grid theory, under the condition of balanced winding, refer to formula 1 to calculate the longitudinal h of the cylinder. fα and hoop fiber thickness h fθ Since the grid theory part takes numerical value into consideration, the above calculated thickness is the thickness of the fiber. fα and hoop fiber thickness h fθ Divide by the fiber volume content to preliminarily complete the thickness design of the composite material layer.

[0033]

[0034] Where, σ fα and σ fθ are the longitudinal and hoop winding fiber stresses, respectively, and the values ​​are taken as the fiber strength σ b ;h fα and h fθ are the longitudinal and hoop fiber thicknesses of the ply respectively, α is the longitudinal spiral winding angle; p b is the bursting strength required for the gas cylinder, and r is the radius of the inner liner.

[0035] The second one adopts longitudinal sand width and circumferential equal height partitioning for the head surface (see Figure 3 ), divided into several areas to be reinforced, the reinforcement expansion radius is then calculated as the sum of each area's height and the end radius. The corresponding actual winding angle is then simultaneously calculated to form a set of ply expansion and reinforcement winding process parameters. According to the end radius expansion layer number: first sand width height expansion layer number: second sand width height expansion layer number: third sand width height expansion layer number: ... final sand width height expansion layer number ≈ 2:3:3:3:...:4:...:3:3:2, alternating and symmetrical cyclic winding of the longitudinal fiber layers achieves uniform reinforcement of the end surface.

[0036] Thirdly, refer to Formula 2, Formula 3 and Formula 4 to calculate the circumferential blasting strength and longitudinal blasting strength of each layer, and superimpose them to obtain the circumferential blasting strength and longitudinal blasting strength of the existing ply. Check the ply strength against the blasting design index, and complete the hole expansion ply optimization when the strength index is met. If the strength index is not met, appropriately increase the number of plies near the last sand width height hole expansion and the extreme mouth radius hole expansion until the design blasting pressure and circumferential / longitudinal stress ratio index are met, and complete the zoned hole expansion reinforcement ply design.

[0037]

[0038] where p α is the longitudinal winding blasting pressure, p θ is the blasting pressure of the hoop winding, and the blasting strength of the cylindrical section is the smaller of the two:

[0039] p b =min{pα,pθ}……………………(3)

[0040] Circumferential blasting strength of composite layer p θ , longitudinal burst strength p α Given by the following formula

[0041]

[0042] The patent of this invention has been applied to the production process of Type IV hydrogen storage cylinders with a working pressure of 70MPa. The molded head surface is full and smooth, close to the isotensoid surface, and has passed the 196.7MPa water pressure blasting test. The weight of the carbon fiber is controlled within 55kg, and the hydrogen storage density reaches 5.7%.

Claims

1. A method for reinforcing the head of a type IV hydrogen storage cylinder by partitioning, characterized in that: The steps are as follows: S1: Use the classical grid theory to design the thickness of the winding layer of the composite gas cylinder, and calculate the longitudinal h of the gas cylinder according to the formula fα and hoop fiber thickness h fθ Since the grid theory does not consider the effect of numerical values, the above calculated thicknesses are all fiber thicknesses. The longitudinal h of the cylinder is fα and hoop fiber thickness h fθ Divide by the fiber volume content to preliminarily complete the thickness design of the composite material layer Where, σ fb is the longitudinal and circumferential winding fiber stress, which is taken as the fiber exerting strength σ b ;h fα and h fθ are the longitudinal and hoop fiber thicknesses of the ply respectively, α is the longitudinal spiral winding angle; p b is the burst strength required for the cylinder, r is the radius of the inner liner; S2: The head surface is divided into several areas to be reinforced by using the longitudinal sand width and circumferential equal height divisions. The sum of the height of each area and the pole radius is then used as the reinforcement expansion radius. The corresponding actual winding angle is then calculated simultaneously to form a set of winding angle ply expansion reinforcement winding process parameters; S3: Calculate the circumferential blasting strength and longitudinal blasting strength of each layer, and superimpose them to obtain the circumferential blasting strength and longitudinal blasting strength of the existing ply. Check the ply strength against the blasting design index. If the strength index is met, the hole expansion ply optimization is completed. If the strength index is not met, appropriately increase the number of plies near the last sand width height hole expansion and the extreme mouth radius hole expansion until the design blasting pressure and circumferential / longitudinal stress ratio index are met. Complete the zoned hole expansion reinforcement ply design. where p α is the longitudinal burst strength, p θ is the circumferential bursting strength, and the bursting strength of the cylindrical section is the smaller of the two: on b =min{p α ,p θ }………………………………(3) Circumferential blasting strength of composite layer p' θ , longitudinal burst strength p' α Given by the following formula 2. A method for reinforcing the head of a Type IV hydrogen storage cylinder according to claim 1, characterized in that: The S1 fiber exerts strength σ b The value is based on 0.85 of the NOL ring tensile strength.

Images