JP2019148325A - Pressure accumulator and method for manufacturing pressure accumulator - Google Patents

Abstract

To provide a pressure accumulator that is excellent in pressure resistance.SOLUTION: A pressure accumulator includes a cylindrical container body; and a reinforcement cylinder body disposed on an outer peripheral side of the container body. The reinforcement cylinder body is made of a fiber-reinforced plastic. The cylindrical container body is cooled, and the hardened reinforcement cylinder body is disposed on the outer peripheral side of the container body and the reinforcement cylinder body is fitted on the outer peripheral side of the container body with temperature return of the container body.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an accumulator capable of accumulating gas at a high pressure and a method for manufacturing the accumulator.

  High-pressure hydrogen containers used for hydrogen stations and the like include type 1 (metal container), type 2 (metal liner hoop wrap type composite pressure vessel), type 3 (metal liner full wrap type composite pressure vessel) and type 4 (nonmetal liner). Full-wrap type composite pressure vessels) are known.

With the increase in hydrogen stations for FCVs (fuel cell vehicles), hydrogen accumulators capable of storing 100 MPa class high-pressure hydrogen are required.
In Type 1, high fatigue strength can be obtained by thickening the steel, but the weight is excessive.
In Type 3, since CFRP (carbon fiber reinforced plastic) is constructed by helical winding, the cost increases. Moreover, the helical winding of the head is not easy, and the tension of the helical winding cannot be secured. In addition, self-tightening is performed to eliminate the gap between the aluminum alloy and CFRP, but the variation due to the position of the residual stress due to self-tightening is large, which affects the variation in the fatigue test results. In addition, the strength of the neck may decrease, and the destruction position cannot be guaranteed (it is not known whether it is the trunk or the head).
Type 4 is lighter than Type 3 but difficult to helically wind like Type 3. Moreover, there is a concern about hydrogen leakage between the metal of the boss portion and the resin. Also, be careful of buckling due to high thermal insulation.
Type 2 is made of steel and FRP, and in addition to being reduced in weight, it is expected to reduce costs because CFRP is constructed by hoop winding. A type 2 pressure accumulator is used as one of the hydrogen pressure accumulators for storing high-pressure hydrogen.

Type 2 pressure accumulators consist of a steel liner and hoop-wrapped FRP.
The type 2 pressure accumulator is a composite container of hoop wraps. As a container construction method, (C) FRP is generally filament wound on the inner steel.
In the type 2 container, since the fiber is only the circumference (hoop), the liner shares the axial load generated by the internal pressure.
According to ASME CC2579 (see Non-Patent Document 1), the type 2 pressure accumulator is a liner in which the straight body of a metal liner is constructed and coated in the circumferential direction with carbon fiber reinforced plastic (CFRP) or glass fiber reinforced plastic (GFRP). This is a hydrogen pressure accumulator having an outer diameter of 1.52 m or less and a CFRP thickness of 6 mm or more.

It is common to use Cr—Mo steel for the metal liner.
Patent Document 1 discloses a high-pressure hydrogen storage FRP container in which the outer periphery of a Cr-Mo steel liner is reinforced with FRP. Patent Document 2 discloses a full-wrap aluminum liner composite container.
The steel liner that shares the load is stronger as a liner than the type 3 container that uses an aluminum liner that does not share the load, and the amount of expensive FRP used can be reduced by that amount, which contributes to reduction of hydrogen station construction costs. It is expected. Regarding the high-pressure hydrogen hoop wrap type compound pressure vessel, there is only an overseas technical standard as Non-Patent Document 1.

When FRP is applied, the resin is cured by winding the fibers regularly and at a constant load and interval in the circumferential direction, and heating from inside and outside in the furnace. (Filament winding (FW))
In the above method, as shown in FIG. 8, CFRP (carbon fiber reinforced plastic) is heated together with the liner in the furnace, and the CFRP is cured while the liner is expanded.

JP 2009-293799 A JP 2007-154927 A JP 2011-073191 A

ASME BPVC.VIII.3-2017, Part KG-511, Two Park Avenue New York, NY 10016 USA, July 1, 2017 Takayoshi Murakami Ph.D. Professor, Kyushu University Metal fatigue Fatigue and influence of inclusions (March 8, 1993, 1st edition) ASME BPVC.VIII.3-2017, Part KD-1310, Two Park Avenue New York, NY 10016 USA, July 1, 2017 Summary of the 3rd Hydrogen Safety Technology Seminar 2017 p62 Toshihiro Yamada, Tatsumi Takehana, Hiroshi Fukutomi, “Fatigue Properties of Unidirectional Carbon Fiber Reinforced Composite Materials for FRP Composite Containers”, Pressure Technology, Vol. 47, No. 3, (2009), pp.171-177.

However, it is difficult to harden CFRP having sufficient strength without gaps by a method of winding CFRP around a steel liner by filament winding.
That is, in filament winding, a resin liner is impregnated with a reinforcing fiber such as carbon fiber, filament winding is performed on a steel liner, and then heated to cure the resin. The steel liner shrinks due to cooling during production, but the carbon fiber + resin layer does not substantially shrink because the thermal expansion coefficient is smaller than that of the liner. When finished, the steel liner shrinks when cooled to room temperature. For this reason, as shown in FIG. 8, a gap will be generated between the steel liner and the CFRP.
Furthermore, since the resin generates heat during the heat curing, the temperature of the liner further increases, and the gap may become large.
As mentioned above, in order to obtain sufficient strength as a composite container for Type 2 pressure accumulators, it is essential to construct CFRP with as little gap as possible. It cannot be suppressed.

The expected gap can be calculated by {(liner outer surface maximum temperature−room temperature) × liner thermal expansion coefficient}.
In addition, in patent document 1, it does not touch the construction method which does not produce a clearance gap between FRP and steel liner which are the most important for ensuring safety. Further, in Patent Document 3, means for securing the adhesive strength between metal and CFRP is ensured and effective for eliminating the gap, but the target is a prepreg and not a resin impregnation method. Further, the adhesive strength alone cannot withstand high pressure hydrogen of 40 MPa or more, and it cannot be solved unless the gap can be physically reduced.

  The present invention has been made against the background of the above circumstances, and the outer peripheral surface and the inner peripheral surface of the cylindrical container main body and the reinforcing cylindrical body arranged on the outer peripheral side of the container main body are in contact with each other. It aims at providing the manufacturing method of the accumulator arranged in the state, and an accumulator.

  That is, among the pressure accumulators of the present invention, the first embodiment has a cylindrical container body and a reinforcing cylinder disposed on the outer peripheral side of the container body, and the reinforcing cylinder is made of fiber reinforced plastic. The container body is arranged such that the outer peripheral surface is in contact with the inner peripheral surface of the reinforcing cylinder.

  In another aspect of the present invention, the container body has a residual compressive stress on the outer peripheral side.

  The invention of another form of the pressure accumulator is the invention of the above form, wherein the fiber reinforced plastic uses a thermosetting plastic.

  According to another aspect of the invention of the pressure accumulator, in the aspect of the invention, the container body is disposed such that an outer peripheral surface thereof is in close contact with an inner peripheral surface of the reinforcing cylindrical body.

  In another form of the pressure accumulator, in the invention of the above form, the reinforcing cylinder has an average interlaminar shear strength of the inner peripheral surface larger than an average interlaminar shear strength of the outer peripheral surface.

  In another form of the pressure accumulator, in the above-mentioned form of the invention, the container body has a stress intensity that linearly increases as the pressure increases on the inner surface of the container body within a predetermined internal pressure range. Yes.

  In another aspect of the invention of the pressure accumulator, the range of the internal pressure is 0 to 150 MPa.

  In the invention of the other form of the pressure accumulator, the pressure is accumulated in the internal pressure range of 100 MPa or less.

  Of the invention of the pressure accumulator manufacturing method of the present invention, the first aspect is that the cylindrical container body is cooled, the cured reinforcing cylinder is disposed on the outer peripheral side of the container body, and the temperature of the container body is restored. The reinforcing cylinder is fitted to the outer peripheral side of the container body.

  The invention of the manufacturing method of the pressure accumulator of another form is the invention of the said form. In the invention of the said form, the said container main body is contacting the inner peripheral surface of the said reinforcement cylinder body in the state which temperature returned.

  In another form of the pressure accumulator according to the present invention, the interference ratio in the container main body before cooling is −1.07 to 2.67 in 1000 fractions.

  In another aspect of the invention of the pressure accumulator, in the aspect of the invention, in the cooling, the container body is cooled to a temperature lower than room temperature.

  The invention of the other form of the pressure accumulator cools the container body to -160 ° C to -190 ° C in the invention of the above form.

  According to the present invention, the cylindrical container main body and the reinforcing cylindrical body arranged on the outer peripheral side of the container main body can be in a state where the inner and outer peripheral surfaces of both are in contact with each other, and the performance as a pressure accumulating container is excellent. Effect.

It is a figure which shows the manufacturing method and pressure accumulator of the pressure accumulator of one Embodiment of this invention. Similarly, it is a figure explaining the construction example in the fitting of the container main body with respect to a reinforcement cylinder. Similarly, it is the II sectional view taken on the line of the front sectional view and front sectional view showing the state where the container main body was fitted to the reinforcing cylinder. It is a figure which shows the water pressure test result of the pressure accumulator obtained by the filament winding shaping | molding in an Example, and the pressure accumulator obtained by fitting. It is a graph which shows the interlayer shear strength of CFRP obtained by the hot charge method in an Example, and CFRP hardened completely. In an Example, it is a figure which shows the internal surface stress strength of the container main body at the time of changing an interference and applying an internal pressure to a pressure accumulator. In an Example, it is a figure which shows the distortion of the fiber direction of the CFRP inner surface at the time of changing an interference and applying an internal pressure to an accumulator. It is a figure explaining a filament winding shaping | molding method.

Hereinafter, an embodiment of the present invention will be described.
First, a reinforcing cylinder is formed from predetermined fibers and thermosetting plastic, and the plastic is thermoset. The type of fiber and the type of thermosetting plastic are not particularly limited, and an appropriate material can be selected for the present invention. In this embodiment, carbon fiber is preferably used as the fiber, and epoxy resin, phenol resin, urea resin, melamine resin, polyurethane, or the like can be used as the thermosetting plastic. Although it is not limited to specific resin as this invention, an epoxy resin and a phenol resin are desirable from a heat resistant viewpoint.

  As shown in FIG. 1, a cylindrical container body 1 is fitted on the inner peripheral side of the cured reinforcing cylinder 2.

The hardening method in the reinforcement cylinder 2 is not specifically limited, A heating temperature is determined according to the characteristic etc. of a plastic, and it heats. By this heating, a completely cured reinforcing cylinder 2 is obtained.
In the fitting, the container main body 1 is cooled, and the container main body 1 </ b> A having a reduced cylinder diameter is inserted into the reinforcing cylinder 2. At this time, the cylinder diameter of the container main body 1 </ b> A is reduced by cooling, and the cooled container main body 1 </ b> A can be easily fitted into the cured reinforcing cylinder 2. After the fitting, the container body 1A is expanded in diameter by returning to normal temperature, and the outer peripheral surface of the expanded container body 1B is in contact with or in close contact with the inner peripheral surface of the reinforcing cylinder 2, and further by interference. Press contact with the reinforcing cylinder 2.
Therefore, in this construction, the container body 1 and the reinforcing cylinder 2 are separately manufactured so that the outer diameter of the container body 1 is larger than that of the reinforcing cylinder 2 at room temperature. That is, it is manufactured so that the interference (ratio) is positive at room temperature. In the present invention, the relationship between the inner diameter of the hardened reinforcing cylinder 2 and the outer diameter of the container main body 1 has an interference ratio of −1.07 to 2.67 at 1000 fractions in the container main body 1. It is desirable to have. The interference is expressed by (outer surface diameter of container body−inner surface diameter of reinforcing cylinder), and the interference ratio is expressed by (interference / outer surface diameter of container × 1000).

  The cooling of the container body 1 can be determined in consideration of the outer diameter of the container body 1 and the inner diameter of the hardened reinforcing cylinder 2. In cooling the container body 1, the container body 1 is cooled to a temperature below room temperature. For example, the cooling temperature is preferably in the range of -190 ° C to -160 ° C. By setting the cooling temperature to −160 ° C. or less, the container body can be sufficiently reduced in diameter. On the other hand, when the temperature is lower than −190 ° C., cooling takes time and the productivity is inferior, so it is desirable to cool to the above temperature range. However, in the present invention, the cooling temperature is not limited to a specific temperature, and an appropriate temperature can be selected as long as the fitting can be easily performed.

The method for fitting the completely cured reinforcing cylinder 2 to the container body 1 is not particularly limited, and can be performed by an appropriate method.
An example of an insertion process is demonstrated based on FIG.
In the test, a steel liner for type 2 having an outer diameter of about 347 mm, a thickness of 29 mm, and a length of about 2700 mm was used.
The container main body installation cylinder 10 has an installation base 11 at the inner center lower portion, and is installed in a state where the container main body 1 is built on the installation base 11. On the inner peripheral surface of the container main body installation cylinder 10, a plurality of gas injection units 12 having injection ports for injecting gas toward the inner peripheral side are installed along the circumferential direction and at a plurality of height positions. A container body fixing tool can be arranged on the upper side of the container body installation cylinder 10, and when the container body 1 is installed, the container body fixing tool holds and fixes the container body 1 at the upper side on the lower side. Can do. A temperature data logger 13 that can automatically measure the temperature at regular intervals is attached to the outer surface of the mirror part of the container main body 1, and the temperature change of the container main body 1 can be recorded at intervals of one minute, for example.

  Further, in the vicinity of the container main body installation cylinder 10, there is a holding base 20 for standing and holding the completely hardened reinforcing cylinder 2, and a suspension for hanging the reinforcing cylinder 2 installed on the holding base 20. The tool 21 is located above the installation position of the reinforcing cylinder 2, and the hanging tool 21 and the reinforcing cylinder 2 can be connected via the connecting tool 22.

Next, construction contents will be described. In addition, the container main body 1 is installed in the container main body installation cylinder 10, the reinforcement cylinder 2 is hold | maintained at the holding stand 20, and the reinforcement cylinder 2 shall be connected with the hanger 21. As shown in FIG.
In the container main body installation cylinder 10, initially, nitrogen gas is irradiated from the gas injection unit 12 toward the container main body 1 to remove the gas on the container main body 1. Thereafter, liquid nitrogen is injected from the gas injection unit 12 to cool the container body 1. The temperature of the container body 1 can be measured with a temperature data logger. After confirming that the container main body 1 has reached, for example, −160 ° C. or lower, the reinforcing cylinder 2 is fitted to the container main body 1 by lifting it from the side where the temperature data logger 13 is not attached.
Then, in the container main body installation cylinder 10, the container main body 1 and the reinforcement cylinder 2 are returned to normal temperature in nitrogen atmosphere.
The container main body 1 and the reinforcing cylindrical body 2 are in a state where the outer peripheral surface of the container main body 1 is in contact with the inner peripheral surface of the reinforcing cylindrical body 2. Depending on the value of the interference, the outer peripheral surface of the container main body 1 and the inner peripheral surface of the reinforcing cylindrical body 2 are in close contact, and the container main body 1 is pressed against the reinforcing cylindrical body 2 so Stress is generated.

FIG. 3 shows a state where the container main body 1 </ b> B is fitted to the reinforcing cylinder 2. Lids 1C and 1C are attached to both ends of the container main body 1B so that the inside of the container main body 1B can be sealed. The outer peripheral surface of the container main body 1 and the inner peripheral surface of the reinforcing cylindrical body 2 are fitted with almost no gap. More desirably, there is no gap and the outer peripheral surface of the container body 1 is in close contact with the inner peripheral surface of the reinforcing cylinder 2.
As a method for confirming that there is no gap, a strain gauge is attached to both the container body 1B and the reinforcing cylinder 2, and it is examined whether the strain has linearity and reproducibility at low pressure.
For example, a strain gauge is attached to the outer surface of the specimen obtained by fitting, and water pressure is applied to the inside of the specimen placed in a vertical position. Data from strain gauges can be collected and the presence or absence of linearity and reproducibility can be confirmed for each measurement position.

  The obtained pressure accumulator is capable of accumulating high-pressure gas. For example, gas such as hydrogen can be favorably accumulated up to 100 MPa.

Next, with respect to the accumulator obtained by filament winding (FW) molding and the accumulator obtained by the fitting of this embodiment, a water pressure test is conducted in a vertically placed state, and the obtained strain response is shown. Comparison was made in 4 (a) and (b). The pressure range of the water pressure test was 0 to 150 MPa for FW molding, 0 to 60 MPa for fitting, and 3 cycles. In addition, the thickness of CFRP by filament winding (FW) molding and CFRP which is a reinforcing cylinder was set to 10 mm (the same applies hereinafter).
4 (a) and 4 (b) show both measured values and analytical values of strain. The analytical values are the strain values in the axial direction and circumferential direction of the CFRP outer surface, and 0 to 150 MPa in FW molding. FEM analysis was carried out in increments of 10 MPa each in the range of 0 to 50 MPa.
On the other hand, the measured value of strain was obtained by attaching a biaxial strain gauge to both ends and the center of the CFRP, and collecting and collecting the strain value at the time of pressure increase / decrease.

As shown in FIG. 4A, in the accumulator obtained by FW molding, when the internal pressure is applied, the rise of strain is poor, and a gap of about 0.2 mm is generated between the liner and the CFRP. I understand.
On the other hand, as shown in FIG. 4B, in the accumulator obtained by fitting, the strain from the low pressure has linearity, and the analysis value shows a good agreement. Therefore, it turns out that both a container main body and a reinforcement cylinder fulfill | perform load sharing.

In addition, an interlaminar shear strength test was performed on CFRP obtained by wrapping around a liner by FW molding and CFRP completely cured from the premise of fitting, and the results were compared. The test results are shown in FIG.
The CFRP obtained by wrapping around the liner by FW molding and the end portion of CFRP completely cured from the premise of fitting are cut into small pieces, and 4 × 8 from the inner surface and outer surface of the obtained CFRP. A test piece of x24 mm was collected.
The test was conducted based on ASTM D 2344, and the test environment was a temperature: 23 ± 2 ° C. and a relative humidity: (50 ± 5)% RH. The test speed was 1 mm / min, the indenter tip was R3, the support tip was R1.5, and the support span was 16 mm.

Comparing the test results, as shown in FIG. 5, the completely cured CFRP clearly has a larger interlaminar shear strength on the inner surface side. From the above, fitting is extremely effective as a construction method of a pressure accumulator that can express the characteristics of the composite container and has no gap.
In addition, the type 2 pressure accumulator subjected to CFRP by fitting has a positive interference ratio (interference) and contributes to an increase in life.

Fig. 6 shows FEM analysis of liner inner surface stress strength when applying an internal pressure in the range of 0 to 300 MPa to a pressure accumulator with an interference of -0.3 to +1.0 mm (analysis software: Ansys) It is.
The liner has an outer diameter of about 374 mm, a thickness of 29 mm, and an elastic-plastic body (two-line approximation), and the CFRP tube has a thickness of 10 mm and a fiber content of 60%.
The inner stress strength of the liner decreases as the interference increases.
That is, even if the same internal pressure is applied to the liner, the acting stress is reduced and the life is increased.
Here, it is known that there is a correlation between the fatigue limit (σw0) and the tensile strength (σB) of the metal material, and σw0 = 0.5 × σB. (See Non-Patent Document 2)
Since the liner material is SCM435 TKB (TS = σB = 770 MPa), the fatigue limit σw0 is 770 × 0.5 = 385, which is slightly less than 400 MPa.
The above value (400 MPa) is approximately equal to the liner inner surface stress intensity when the interference is 1 mm (corresponding to an interference ratio of 2.67) and an internal pressure of 100 MPa is applied.
Therefore, when the interference ratio exceeds 2.67, it is considered that the liner does not undergo fatigue failure when the hydrogen pressure accumulator is used.

On the other hand, FIG. 7 shows an FEM analysis of the strain in the fiber direction on the inner surface of the CFRP when an internal pressure is applied in the range of 0 to 300 MPa to a pressure accumulator having an interference of −0.3 to +1.0 mm (analysis software). : Ansys).
Here, the carbon fiber (T710SC) has a breaking strain of 1.7%, and according to ASME KD-1310, the upper limit of the strain at which the CFRP does not break is 0.4 when operating with respect to the breaking strain. In the case of a pressure test, it must be considered by multiplying by 0.67 (see Non-Patent Document 3).

Assuming that the operating pressure is 100 MPa and the pressure test is 150 MPa, the upper limits of the strain at which the CFRP does not break during operation and the pressure test are 0.68 and 1.12.
If the CFRP does not reach the upper limit of strain during operation, that is, if the interference is 1 mm or less (interference ratio is 2.67 or less), the CFRP will not fatigue. (Refer to FIG. 6 of Non-Patent Document 5 and Non-Patent Document 5)
On the other hand, if the interference exceeds 1 mm (interference ratio exceeds 2.67), the CFRP breaks during operation, and the pressure accumulator loses its characteristics as a composite container.
From the above, the upper limit value of the interference ratio is 2.67.
On the other hand, the lower limit of the interference ratio is qualitatively a value at which the liner does not come into contact with CFRP even when the operating pressure is reached, and the function as a composite container is not exhibited.
This is an interference that does not deviate to 100 MPa from the curve obtained with No CFRP (liner only) in FIG. 7, and the value is −0.4 mm, which corresponds to an interference ratio of −1.07.

  As described above, the present invention has been described based on the above embodiment, but the present invention is not limited to the content of the above embodiment, and is appropriate for the present embodiment without departing from the scope of the present invention. It can be changed.

1, 1A, 1B Container body 2 Reinforcing cylinder

Claims (13)

  It has a cylindrical container body and a reinforcing cylinder disposed on the outer peripheral side of the container body, the reinforcing cylinder is made of fiber reinforced plastic, and the container body is formed on the inner peripheral surface of the reinforcing cylinder. A pressure accumulator with the outer peripheral surface in contact.   The pressure accumulator according to claim 1, wherein the container body has a residual compressive stress on an outer peripheral side.   The pressure accumulator according to claim 1 or 2, wherein the fiber reinforced plastic uses a thermosetting plastic.   The pressure accumulator according to any one of claims 1 to 3, wherein the container body is disposed such that an outer peripheral surface thereof is in close contact with an inner peripheral surface of the reinforcing cylindrical body.   The pressure accumulator according to any one of claims 1 to 4, wherein the reinforcing cylinder has an average interlayer shear strength of an inner peripheral surface larger than an average interlayer shear strength of an outer peripheral surface.   The accumulator according to any one of claims 1 to 5, wherein the container main body has a stress intensity that linearly increases with an increase in pressure on the inner surface of the container main body within a predetermined internal pressure range. .   The accumulator according to claim 6, wherein the range of the internal pressure is 0 to 150 MPa.   The pressure accumulator according to any one of claims 1 to 7, wherein pressure is accumulated in an internal pressure range of 100 MPa or less.   A pressure accumulator that cools a cylindrical container body, places a cured reinforcing cylinder on the outer peripheral side of the container main body, and fits the reinforcing cylindrical body on the outer peripheral side of the container main body by returning the temperature of the container main body. Production method.   The pressure accumulator manufacturing method according to claim 9, wherein the container main body is in contact with the inner peripheral surface of the reinforcing cylindrical body in a state in which the temperature is restored.   The method for manufacturing a pressure accumulator according to claim 9 or 10, wherein an interference ratio in the container main body before the cooling is -1.07 to 2.67 at 1000 minutes.   The manufacturing method according to claim 9, wherein in the cooling, the container body is cooled to a temperature lower than room temperature.   The manufacturing method according to any one of claims 9 to 12, wherein the container body is cooled to -160 ° C to -190 ° C.

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