JP6774465B2 - Lid structure of accumulator for high-pressure hydrogen gas and accumulator for high-pressure hydrogen gas - Google Patents

Description

The present invention relates to a lid structure of a pressure accumulator for high-pressure hydrogen gas and a pressure accumulator for high-pressure hydrogen gas.

Fuel cell vehicles that can solve CO ₂ emission problems and energy problems are expected as new vehicles in the future. A pressure vessel called a pressure accumulator that accumulates hydrogen at a pressure of 80 MPa or more is installed in the hydrogen station for supplying hydrogen to the fuel cell vehicle.

There are roughly two types of pressure accumulators for high-pressure hydrogen gas. One is a cylinder type accumulator in which the end of the pipe is drawn to create a mirror part, as typified by a gas cylinder, and the other is a straight type accumulator with lids on both ends of the straight pipe. is there.

The cylinder-type accumulator has a shape in which the cross-sectional area inside the container decreases toward the gas outlet, and the base portion is sealed with a clasp having a screw structure having a small diameter. In this case, since the stress applied to the threaded portion of the base is reduced, there is no problem with pressure sealing. However, with accumulators for high-pressure hydrogen gas such as those for hydrogen stations, it is necessary to perform internal inspections on a regular basis after the start of use, and if the ends are squeezed as described above, the internal inspection of the accumulator becomes difficult. is there. Further, when a pressure accumulator including a steel container is manufactured, the steel container is usually heat-treated, but since it takes time for the cooling water to enter and discharge into the steel container, the heat treatment is performed. The cooling rate becomes slower and the steel structure becomes more variable. Further, since it is difficult to remove the scale and the decarburized layer generated on the surface of the steel container by the heat treatment, the inner surface is used as it is in the heat treatment, which causes deterioration of the fatigue characteristics of the steel container.

Therefore, in order to avoid the above problems, it is conceivable to use a straight type accumulator. If the structure is a straight pipe with a lid, the opening of the pipe is large, so that cooling during heat treatment becomes easy, and the structure of the steel material can be precisely controlled. In addition, the decarburized layer and scale generated during heat treatment can be easily removed by machining. Furthermore, by removing the lid, the internal surface inspection after use can be easily performed. In addition, since the straight type accumulator does not have a mirror portion that has been drawn, there is almost no variation due to processing, and a uniform container can be manufactured. As such a pressure accumulator for high-pressure hydrogen gas, for example, there are those described in Patent Document 1 and Non-Patent Document 1.

Japanese Unexamined Patent Publication No. 2015-158243

Japan Steel Works Technical Report, October 2015, No. 66, p. 149-150

However, when a straight pipe is used, since the cross section of the container is constant, all the internal pressure is received by the lid. Therefore, the lid structure of the accumulator for high-pressure hydrogen gas using a straight-shaped container is required to withstand extremely high stress.

As the lid structure of the straight type accumulator, a structure in which a flange is provided at the end of a straight container and the lid is bolted, or a structure in which the lid is screwed can be considered.

However, the lid structure using a flange has a problem that the container size becomes large and the cost increases because the flange is provided. On the other hand, in the lid structure by screwing, although the problem when the flange is used can be avoided, the stress applied to the screw portion is high and there is a possibility of fatigue fracture from the screw portion.

As described above, although the accumulator using the straight pipe has good container characteristics, there is a problem that the stress applied to the lid structure is high and fatigue fracture occurs.

The present invention has been made in view of the above circumstances, and an object of the present invention is to relieve stress applied to the lid structure of a pressure accumulator for high-pressure hydrogen gas provided with a straight-shaped steel container and prevent fatigue fracture. And.

The present invention has been made based on the above findings, and the gist structure thereof is as follows.

1. 1. It is a lid structure of a pressure accumulator for high-pressure hydrogen gas provided with a straight-shaped steel container constituting the pressure accumulator.
It has a small space that communicates with the accumulator and is not open to the outside of the accumulator for high-pressure hydrogen gas.
The ratio (S2 / S1) of the internal cross-sectional area S2 of the small space in the cross section perpendicular to the longitudinal direction of the steel container to the internal cross-sectional area S1 of the accumulator in the cross section perpendicular to the longitudinal direction of the steel container. , 0.4-0.8, lid structure of accumulator for high pressure hydrogen gas.

2. A disk-shaped first plug whose main surface faces the accumulator and seals between the inner peripheral surface of the steel container and the like.
A first gland nut having a thread on the outer peripheral surface and in contact with the other main surface of the first plug.
A disk-shaped second plug in which one main surface is in contact with the first gland nut and seals between the inner peripheral surface of the steel container.
It has a cylindrical shape with a thread on the outer peripheral surface, and includes a second gland nut that is in contact with the other main surface of the second plug.
The small space is defined by the first plug, the first gland nut, and the second plug.
The lid structure of the pressure accumulator for high-pressure hydrogen gas according to 1 above, wherein the pressure accumulator and the small space are communicated with each other by an opening provided in the first plug.

3. 3. A pressure accumulator for high-pressure hydrogen gas, comprising a straight-shaped steel container and having a lid structure according to 1 or 2 above at at least one end of the steel container.

4. The pressure accumulator for high-pressure hydrogen gas according to 3 above, which has a carbon fiber reinforced resin layer on the surface of the steel container.

5. The pressure accumulator for high-pressure hydrogen gas according to 3 or 4 above, wherein the steel container is made of a seamless steel pipe.

According to the lid structure of the accumulator for high-pressure hydrogen gas of the present invention, the stress applied to the lid structure is relaxed, and the accumulator using the straight-shaped steel container can be used at a higher pressure and a large cross section. be able to.

It is sectional drawing which shows the lid structure in one Embodiment of this invention. It is sectional drawing which shows the lid structure in the comparative example.

Next, the method of carrying out the present invention will be specifically described. The following description shows a preferred embodiment of the present invention, and the present invention is not limited to the following description.

[Lid structure]
The lid structure in one embodiment of the present invention is a lid structure of a pressure accumulator for high-pressure hydrogen gas provided with a straight-shaped steel container constituting the pressure accumulator, which communicates with the accumulator and is used for the high-pressure hydrogen gas. It has a small space that is not open to the outside of the accumulator. Since the small space communicates with the accumulator, when the accumulator is filled with hydrogen gas, the hydrogen gas is also introduced into the small space. Here, the “accumulation unit” refers to the internal space of the steel container, which is filled with hydrogen gas. Further, here, "not released to the outside" includes a case where it is cut off from the outside through a valve or the like.

Further, the ratio of the internal cross-sectional area S2 in the cross section perpendicular to the longitudinal direction of the steel container in the small space to the internal cross-sectional area S1 of the accumulator in the cross section perpendicular to the longitudinal direction of the steel container (S2 / S1). ) Is 0.4 to 0.8. By providing such a small space, the stress applied to the lid structure due to the pressure of the hydrogen gas filled in the accumulator can be reduced between the accumulator and the small space, for example, the first gland nut and the small space. It can be distributed in an appropriate distribution between the space and the outside of the accumulator, for example, at two locations of the second gland nut. The first plug and the first gland nut, and the second plug and the second gland nut have the same effect even if they are integrated. Therefore, the maximum value of the stress applied to the lid structure can be relaxed, and the accumulator can be used at a higher pressure and a large cross section. Further, by setting the ratio of the internal cross-sectional areas (S2 / S1) to 0.4 to 0.8, the stress distribution of the threaded portion can be made uniform. The reason why S2 / S1 is set to 0.8 or less is that when S2 / S1 is larger than 0.8, the maximum stress of the threaded portion is reduced, but the circumferential stress applied to the first gland nut itself due to the pressure is increased. This is because the gland nut may be significantly increased and deformed.

Further, in one embodiment of the present invention, the lid structure can include a first plug, a first gland nut, a second plug, and a second gland nut.

FIG. 1 is a schematic view showing an example of a lid structure using the plug and the gland nut, and shows a cross section of one end in the longitudinal direction of the pressure accumulator 1 for high-pressure hydrogen gas. The pressure accumulator 1 for high-pressure hydrogen gas includes a steel container 10 having a straight shape and a circular cross section, and the internal space of the steel container 10 constitutes a pressure accumulator portion 11.

A lid structure 20 is formed at the end of the steel container 10, and the lid structure 20 includes a first plug 21, a first gland nut 22, a second plug 23, and a second gland nut 24. ing.

The first plug 21 is a disk-shaped member having a pair of opposing main surfaces (flat circular surfaces), and the peripheral side surface thereof comes into contact with the inner peripheral surface of the steel container 10, whereby the first plug 21 is first. The plug 21 and the steel container 10 are sealed. One main surface of the first plug 21 faces the accumulator portion 11, and the first plug 21 has a structure that receives the pressure of the accumulator portion.

The first gland nut 22 is a cylindrical member having a thread on the outer peripheral surface, and is screwed with a screw provided on the inner peripheral surface of the steel container 10. The first gland nut 22 is in contact with the other main surface of the first plug 21, and has a function of supporting the first plug 21.

The second plug 23 is a disk-shaped member having a pair of opposing main surfaces (flat circular surfaces), and its peripheral side surface is in contact with the inner peripheral surface of the steel container 10. Further, one main surface of the second plug 23 is in contact with the first gland nut 22. The second plug 23 may have a screw on its peripheral side surface, in which case the screw can be screwed with a screw provided on the inner peripheral surface of the steel container 10.

The second gland nut 24 is a cylindrical member having a thread on the outer peripheral surface, and is screwed with a screw provided on the inner peripheral surface of the steel container 10. The second gland nut 24 is in contact with the other main surface of the second plug 23 and has a function of supporting the second plug 23.

Then, as shown in FIG. 1, a small space 25 is defined inside the lid structure 20 by the first plug 21, the first gland nut 22, and the second plug 23. The small space 25 communicates with the accumulator portion 11 by an opening 26 provided in the first plug 21. Therefore, when the accumulator portion 11 of the pressure accumulator 1 for high-pressure hydrogen gas is filled with hydrogen gas, the small space 25 is also filled with hydrogen gas.

The shape of the opening 26 is not particularly limited, and may be any shape such as a circle or a quadrangle. Further, the position of the opening is not particularly limited, but can be, for example, the center of the first plug 21. The size of the opening 26 (in the case of a circular opening, the diameter) is preferably smaller than the inner diameter of the first gland nut 22.

As described above, when two sets of plugs and gland nuts are used to form a lid structure provided with a small space 25, the pressure received by the first plug 21 from the accumulator portion 11 is partially due to the pressure received from the small space 25. Since they are offset, the stress applied to the threaded portion on the inner peripheral surface of the steel container screwed with the first gland nut 22 can be reduced by reducing the pressure applied to the first plug 21. Further, since the pressure applied to the second plug 23 is from the small space 25 having a cross-sectional area smaller than that of the accumulator portion 11, the load applied to the second plug 23 and the second gland nut 24 is also reduced. ..

When the above structure is adopted, the wall thickness of the first gland nut 22 may be adjusted so that the cross-sectional area of the small space 25 satisfies the above-mentioned conditions.

The screw shape of the gland nut is not particularly limited, and for example, it may be a screw specified by JIS, but it is preferable to use a shape that further reduces stress concentration. Examples of the shape for reducing the stress concentration include a screw having a large radius of curvature at the tip of the screw bottom (a shape in which the tip of a trapezoidal screw is rounded, etc.).

The material of the plug and the gland nut is not particularly limited, but it is preferably made of metal, and more preferably made of steel. As the steel, it is more preferable to use a steel having a tensile strength (TS) of 750 MPa or more. The steel may be, for example, a low alloy steel.

The wall thickness of the plug is not particularly limited, but from the viewpoint of increasing the strength and preventing deformation and buckling, the wall thickness of the first plug 21 and the second plug 23 is independently set to 35 mm or more. It is preferable to do so. On the other hand, from the viewpoint of facilitating quenching when manufacturing the plug, it is preferable that the wall thicknesses of the first plug 21 and the second plug 23 are independently set to 100 mm or less. Further, as with the plug, from the viewpoint of increasing the strength and preventing deformation and buckling, the wall thickness of the first gland nut 22 and the second gland nut 24 may be independently set to 20 mm or more. preferable.

The gland nut is not particularly limited, and a gland nut manufactured by any method can be used. For example, the inside of the steel material may be hollowed out to form a hollow cylinder, or a steel pipe may be processed. Further, as the steel pipe, any one such as an electric resistance welded steel pipe and a seamless steel pipe can be used, and among them, a gland nut made of a seamless steel pipe is preferably used. Gland nuts made of seamless steel pipes are superior to gland nuts manufactured by hollowing out in terms of toughness and other characteristics, and because they do not have welds, they are extremely suitable for sealing pressure accumulators for high-pressure hydrogen gas. it can.

Further, in the lid structure, a sealing member such as an O-ring can be used to prevent gas leakage. The arrangement of the seal members is not particularly limited, but for example, as shown in FIG. 1, an O-ring 27 can be provided between the members.

In the example shown in FIG. 1, the first plug 21, the first gland nut 22, and the second plug 23 are separate bodies, and these are joined via an O-ring to form a small space. Although 25 is defined, the structure is such that the first plug, the first gland nut, and the second plug are integrated, and a small space 25 communicating with the accumulator portion 11 may be formed inside the structure. it can.

[Pressure accumulator for high-pressure hydrogen gas]
The accumulator for high-pressure hydrogen gas according to one embodiment of the present invention is an accumulator for high-pressure hydrogen gas provided with a straight-shaped steel container constituting the accumulator, and has the lid structure at least one of the steel containers. It has at the end of. The steel container preferably has the lid structure at both ends thereof. The pressure accumulator for high-pressure hydrogen gas can be used as, for example, a pressure accumulator for a hydrogen station, but is not limited thereto and can be used for any purpose.

[Steel container]
Any steel can be used as the material of the steel container without particular limitation, but from the viewpoint of cost reduction, it is preferable to use a container made of low alloy steel, and in particular, chromium molybdenum steel JIS. It is preferable to use any one of SCM steel, nickel chrome molybdenum steel JIS SNCM steel, manganese chrome steel JIS SMnC steel, manganese steel JIS SMn steel, and boron-added steels N28CB, N36CB, N46CB, and ASME SA723. Above all, from the viewpoint of compatibility with material strength, it is more preferable to use chrome molybdenum steel or chrome molybdenum nickel steel, which can easily secure hardenability. For example, the chromium molybdenum steel (SCM435) has C: 0.33 to 0.38% by mass, Si: 0.15 to 0.35% by mass, Mn: 0.60 to 0.90% by mass, P: 0. 030% by mass or less, S: 0.030% by mass or less, Cr: 0.99 to 1.20% by mass, Mo: 0.15 to 0.30% by mass.

The steel container is not particularly limited as long as it has a straight shape, and a container manufactured by any method can be used. For example, the inside of the steel material may be hollowed out to form a container, or a steel pipe may be processed. Further, as the steel pipe, any one such as an electric resistance welded steel pipe and a seamless steel pipe can be used, and among them, a steel container made of a seamless steel pipe is preferably used. A steel container made of a seamless steel pipe is extremely suitable as a container for a pressure accumulator for high-pressure hydrogen gas because it is superior in characteristics such as toughness to a steel container manufactured by hollowing out and has no welded portion.

[Carbon fiber reinforced resin layer]
A carbon fiber reinforced resin layer can be provided on the surface of the steel container. The carbon fiber reinforced resin layer is a composite material in which carbon fiber is used as a reinforcing material and impregnated with a resin to improve the strength, and is called CFRP (carbon-fiber-reinforced plastic). By providing the carbon fiber reinforced resin layer, the pressure resistance and fatigue characteristics of the accumulator can be further improved. The carbon fiber reinforced resin layer can cover the entire or part of the outer peripheral surface of the steel container, but from the viewpoint of cost reduction, a type 2 accumulator in which carbon fibers are wound only in the circumferential direction of the container is used. Is preferable. When a carbon fiber reinforced resin layer is used, the steel container is referred to as a "liner".

The carbon fiber reinforced resin layer is a composite material in which carbon fiber is used as a reinforcing material and impregnated with a resin to improve the strength, and is called CFRP (carbon-fiber-reinforced plastic). The carbon fiber is not particularly limited, and any carbon fiber such as PAN type or pitch type can be used. The volume content of carbon fibers in the carbon fiber reinforced resin layer can be determined in accordance with Japanese Industrial Standards JIS K 7075 (1991), and is usually preferably in the range of 50% to 80%.

[Anti-corrosion layer]
When a carbon fiber reinforced resin layer is provided on the surface of the steel container, the outer peripheral surface of the steel container (liner) (between the carbon fiber reinforced resin layer and the steel container) is further prevented from electrolytic corrosion. It is preferable to provide an anticorrosive layer. As the anticorrosion layer, for example, a coating film or a glass fiber reinforced resin (GFRP) layer can be used. The coating film can be formed, for example, by powder coating. For the powder coating, a thermoplastic powder coating based on a vinyl chloride resin or the like, or a thermosetting powder coating based on a polyester resin, an acrylic resin, an epoxy resin or the like can be used. Above all, it is preferable to use a thermosetting powder coating material in consideration of heat and the like during hydrogen filling. Further, the glass fiber reinforced resin layer can be formed by winding the glass fiber reinforced resin. By providing the anticorrosion layer, even if cracks or the like occur in the carbon fiber reinforced resin layer which is the surface layer and moisture invades into the carbon fiber reinforced resin layer, it stays in the anticorrosion layer and therefore does not reach the surface layer of the liner. Is hard to corrode. Further, even if the surface layer of the liner should be reached, since the carbon fiber reinforced resin layer and the surface layer of the liner are separated from each other, electrolytic corrosion does not occur, the corrosion rate can be reduced, and the deterioration of the container can be suppressed.

Further, if the GFRP layer is wound on the carbon fiber reinforced resin layer, the GFRP is softer than the CFRP, so that it is possible to prevent scratches caused by pebbles and the like.

The screw bottom stress was analyzed by the finite element method (FEM) using the accumulator model. The accumulator model consists of a steel container made of low alloy steel, a type 1 accumulator that does not have a carbon fiber reinforced resin layer, and a steel container made of low alloy steel (liner) equivalent to the type 1 accumulator. ) And a type 2 accumulator provided with a carbon fiber reinforced resin layer formed by winding CFRP around the surface so as to have a thickness of 5 mm. The strength of the low alloy steel was set to tensile strength (TS): 894 MPa and yield strength (YP): 770 MPa using the stress-strain curve of SCM435 steel.

The dimensions of the steel container were length in the longitudinal direction: 1600 mm, inner diameter: 250 mm, and wall thickness: 60 mm. The lid structure has the structure shown in FIG. 1, and the wall thickness of the first plug 21 is 30 mm, the length of the first gland nut 22 is 60 mm, the wall thickness of the second plug 23 is 30 mm, and the second gland nut. The length of the 24 is 60 mm, and the outer periphery of the first gland nut 22, the second plug 23, and the second gland nut 24 has a screw.

The wall thickness of the gland nut, which is the thickness from the apex to the inner surface of the threaded portion of the gland nut, was compared with four types of wall thicknesses for the first gland nut 22 and fixed at 35 mm for the second gland nut 24. .. As for the strength of the material, the yield strength (YP) was set to 800 MPa. By changing the wall thickness of the first gland nut 22, an internal break in the cross section perpendicular to the longitudinal direction of the steel container in the small space with respect to the internal cross-sectional area S1 of the accumulator in the cross section perpendicular to the longitudinal direction of the container. The ratio of areas S2 (S2 / S1) was changed. The screw shape was a JIS trapezoidal screw with a pitch of 12 mm and a screw shoulder radius of curvature of 1 mm. Analysis of the thread bottom stress was performed on the female thread portion of the steel vessel where the vessel could be destroyed by fatigue. In addition, an analysis of the circumferential stress applied to the first gland nut, which changes by changing the wall thickness of the first gland nut 22, was also performed.

For comparison, analysis was also performed using a model with the structure shown in FIG. 2 without a small space. In this case as well, the wall thickness of the plug was set to 30 mm, and the wall thickness of the gland nut was set to 35 mm.

Using the above model, FEM analysis was performed under the condition of a maximum pressure of 82 MPa to obtain the maximum value of screw bottom stress. The results are shown in Table 1. When the maximum value of screw bottom stress can be reduced from 770 MPa, which is the material YP of the steel container, the fatigue characteristics are significantly improved. Here, it is considered good if the stress is equal to or less than the material YP. In the examples satisfying the conditions of the present invention, it was confirmed that the maximum value of the screw bottom stress could be reduced as compared with the material YP of the steel container, and the risk of fatigue fracture was reduced.

On the other hand, regarding the circumferential stress applied to the first gland nut, the circumferential stress increases sharply as the gland nut becomes thinner, so if the stress is 0.8 times or less of the material YP (800 MPa) of the gland nut. Good. In the embodiment satisfying the condition of the present invention, the maximum value of the circumferential stress applied to the first gland nut can be reduced to more than 0.8 times that of the material YP, and the risk of deformation of the first gland nut is reduced. It was confirmed that

By arranging a space having a cross-sectional area smaller than that of the accumulator portion adjacent to the pressure receiving portion in this way, a pressure accumulator that ensures safety with less stress generated at the screw bottom and less risk of fatigue failure is manufactured. be able to.

1 Accumulator for high-pressure hydrogen gas 10 Steel container 11 Accumulator 20 Lid structure 21 1st plug 22 1st gland nut 23 2nd plug 24 2nd gland nut 25 Small space 27 Seal member (O-ring)

Claims (4)

It is a lid structure of a pressure accumulator for high-pressure hydrogen gas provided with a straight-shaped steel container constituting the pressure accumulator.
It has a small space that communicates with the accumulator and is not open to the outside of the accumulator for high-pressure hydrogen gas.
A disk-shaped first plug whose main surface faces the accumulator and seals between the inner peripheral surface of the steel container and the like.
A first gland nut having a thread on the outer peripheral surface and in contact with the other main surface of the first plug.
A disk-shaped second plug in which one main surface is in contact with the first gland nut and seals between the inner peripheral surface of the steel container.
It has a cylindrical shape with a thread on the outer peripheral surface, and includes a second gland nut that is in contact with the other main surface of the second plug.
The small space is defined by the first plug, the first gland nut, and the second plug.
The pressure accumulator and the small space are communicated with each other by an opening provided in the first plug.
The ratio (S2 / S1) of the internal cross-sectional area S2 of the small space in the cross section perpendicular to the longitudinal direction of the steel container to the internal cross-sectional area S1 of the accumulator in the cross section perpendicular to the longitudinal direction of the steel container. , 0.4-0.8, lid structure of accumulator for high pressure hydrogen gas. Comprising a steel container straight shape, a lid structure according to claim 1 at least one end of the steel vessel, a pressure accumulator for high-pressure hydrogen gas. The pressure accumulator for high-pressure hydrogen gas according to claim 2 , which has a carbon fiber reinforced resin layer on the surface of the steel container. The pressure accumulator for high-pressure hydrogen gas according to claim 2 or 3 , wherein the steel container is made of a seamless steel pipe.

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