JP2007139143A - High pressure container integrity diagnosis method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high pressure container integrity diagnosis method having simple and inexpensive construction using one optical fiber for diagnosing the integrity of a high pressure container even when detecting multipoint deformation. <P>SOLUTION: The optical fiber 3, in which a plurality of Bragg gratings 2 having the same Bragg wavelength is discretely formed, is mounted in close contact with the high pressure container 1 so that the plurality of Bragg gratings are in different positions. After filling gas in the high pressure container 1, a light measuring device 4 connected to the end of the optical fiber 3 and having light injecting/emitting function is used for measuring the wavelength distribution of reflected lights from the Bragg gratings 2 in relation to an emitted light from the light measuring device 4. The integrity of the high pressure container 21 is diagnosed in accordance with the aging variation of the wavelength distribution. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-pressure vessel soundness diagnosis method and a high-pressure vessel soundness diagnosis device used for storing gas such as hydrogen used as fuel for a fuel cell.

  A high-pressure vessel used for storing gas such as hydrogen is deformed so that the high-pressure vessel expands outward at a high internal pressure when filling with gas, and is restored to its original shape as the internal pressure decreases when using gas. For this reason, the high pressure vessel is repeatedly deformed by repeated filling and releasing of gas, so that the material of the high pressure vessel deteriorates and the strength decreases when used for a long period of time, gas leakage, abnormal deformation, worst case There is a risk of bursting during gas filling. Therefore, when repeatedly filling and releasing the gas into the high-pressure vessel, it is necessary to diagnose whether the high-pressure vessel has sufficient strength, that is, the soundness of the high-pressure vessel. As one method of diagnosing the soundness of a high-pressure vessel, the amount of deformation of the high-pressure vessel at the time of gas filling is measured at the start of use (new), and then the amount of deformation at the time of gas filling and at the time of start of use. There is a method of comparing the amount of deformation. According to this method, the remaining life can be predicted according to the deformation amount of the high-pressure vessel at the time of gas filling, or the soundness of the high-pressure vessel can be diagnosed by determining that the life has been reached.

  As a method of diagnosing the soundness of a high-pressure vessel, the main body of a high-pressure vessel is made by simultaneously using an optical fiber in which a plurality of Bragg gratings having different Bragg wavelengths are discretely formed and a glass fiber impregnated with resin by a filament winding method. There is a method of forming a high-pressure container reinforced with a composite material by winding it around the outer surface of an aluminum cylinder-type container. The filament winding method is a molding method in which continuous reinforcing fibers such as glass fibers and carbon fibers are impregnated with a resin, wound around a molding die, and then cured and molded. Bragg gratings are gratings that are formed in the core of an optical fiber using ultraviolet rays so that their refractive indices are periodically different, and have the property of reflecting light in a narrow band of wavelengths, and the peak wavelength of this reflected light Is called the Bragg wavelength. According to this method, the optical fiber at each point is obtained by changing the wavelength of the reflected light from each of the two points of the circumferential winding of the optical fiber embedded in the glass fiber and the Bragg grating located at the two points of the spiral winding. Can be detected. By detecting the change in the shape of the high-pressure vessel with the wavelength change of the reflected light from the optical fiber by such a method, the soundness of the high-pressure vessel can be diagnosed (for example, see Non-Patent Document 1).

  In addition, as a method of monitoring the soundness of the concrete storage container, a Bragg grating is provided at an arbitrary position of the optical fiber, and the wavelength shift amount of the reflected light of the laser beam reflected by this Bragg grating is measured. There is a method of detecting the distortion of the storage container at the position of the Bragg grating from the shift amount (see, for example, Patent Document 1).

International SAMPE Symposium Exhib. Vol. 43, no. 1, P444-457 (1998) Japanese Patent Laid-Open No. 2001-133854 (page 3, FIG. 3)

  However, in the method for diagnosing the soundness of a high-pressure vessel or a storage vessel as described above, the Bragg grating needs to have different Bragg wavelengths at each measurement point in order to detect the distortion of the position where the Bragg grating is formed. . Therefore, when the conventional method is applied to a large-sized high-pressure vessel, a large number of Bragg gratings having different Bragg wavelengths must be formed in one optical fiber in order to increase the number of measurement points. Furthermore, there is a restriction that the wavelength change of the reflected light from the Bragg grating with respect to the deformation of the optical fiber accompanying the deformation of one high pressure vessel should not change beyond the Bragg wavelength of the Bragg grating located at another point. . This is because if it changes beyond the Bragg wavelength of the Bragg grating located at another point, it becomes difficult to determine which position the wavelength changes with respect to the deformation. For this reason, it is necessary to widen the wavelength interval of different Bragg wavelengths to some extent, and from the relationship between the wavelength interval of the Bragg wavelength and the emission wavelength width of the light source, the number of Bragg gratings having different Bragg wavelengths in one optical fiber is , About 40. Therefore, it is necessary to use a plurality of optical fibers in order to detect deformation at a large number of 40 points or more, and there is a problem that the structure is complicated and the cost is increased.

  The present invention has been made to solve the above-described problems. As a method for diagnosing the soundness of a high-pressure vessel, the present invention can be configured with a single optical fiber even when detecting deformation at multiple points. The present invention provides a method for diagnosing the health of a high-pressure vessel having a simple structure and a low cost.

  In the method for diagnosing the health of a high-pressure vessel according to the present invention, an optical fiber in which a plurality of Bragg gratings having the same Bragg wavelength are discretely formed is brought into close contact with the high-pressure vessel so that the plurality of Bragg gratings are at different positions. After the gas is filled into the high-pressure vessel, the wavelength distribution of the reflected light from the Bragg grating with respect to the light emitted from the optical measuring instrument having the light input / output function connected to the end of the optical fiber is measured with the optical measuring instrument. The soundness of the high-pressure vessel is diagnosed based on the change over time of the wavelength distribution.

  In the present invention, the number and position of the reflection peaks of the reflected light from the Bragg grating having the same Bragg wavelength after filling the gas into the high-pressure vessel are normal (at the start of use) and in use (gas filling and Since the soundness of the high-pressure vessel is diagnosed in comparison with the case after the discharge is repeatedly performed, a high-pressure vessel having a simple structure and a low-cost diagnostic method and a soundness diagnosis function can be provided.

Embodiment 1 FIG.
1 is a schematic diagram of a high-pressure vessel having a soundness diagnosis function according to Embodiment 1 of the present invention. In FIG. 1, a high-pressure vessel 1 is a high-pressure vessel to be subjected to soundness diagnosis, and an optical fiber 3 having a Bragg grating 2 having the same Bragg wavelength is in close contact with the outer wall of the high-pressure vessel 1. It is attached. In the present embodiment, four Bragg gratings 2 (2a, 2b, 2c and 2d) are formed, and are arranged at different positions on the outer wall of the high-pressure vessel 1, respectively. An optical measuring instrument 4 is connected to the end of the optical fiber 3. The optical measuring instrument 4 has a light source inside, makes the light from this light source incident on the optical fiber 3, and can measure the wavelength distribution of the reflected light from the Bragg grating 2 formed on the optical fiber 3. A computer 5 is connected to the optical measuring instrument 4, and the computer 5 controls the optical measuring instrument 4, stores the wavelength distribution measured by the optical measuring instrument 4, and is based on the temporal change of the wavelength distribution. The function of judging the soundness of the high-pressure vessel 1 is provided.

  Next, the operation of the soundness diagnosis method in the present embodiment will be described. Broadband light emitted from the optical measuring instrument 4 is guided to the optical fiber 3 and is incident on the Bragg gratings 2a, 2b, 2c and 2d. Each Bragg grating 2a, 2b, 2c and 2d reflects light of Bragg wavelength, and this reflected light is guided to the optical fiber 3 and enters the optical measuring instrument 4. In the optical measuring instrument 4, the wavelength distribution of the reflected light is measured, and this wavelength distribution is transmitted to the computer 5. The computer 5 stores the transmitted wavelength distribution and determines the soundness of the high-pressure vessel 1 based on the temporal change of the wavelength distribution.

  The soundness diagnosis method will be described in more detail. FIG. 2 is a characteristic diagram showing the wavelength distribution of the reflected light in the present embodiment. First, when the high-pressure vessel 1 is not filled with gas (when not filled), the high-pressure vessel 1 is not deformed, so the optical fiber 3 attached in close contact with the outer wall is also not deformed. The Bragg wavelengths of the Bragg gratings 2a, 2b, 2c and 2d are the same, and the peak wavelengths of the reflected light are observed as overlapped as shown in FIG. Next, when the high pressure vessel 1 is filled with gas (at the time of filling) and the internal pressure of the high pressure vessel 1 rises, the outer wall of the high pressure vessel 1 is deformed so as to expand outward. Since the deformation amount of the outer wall varies depending on the location, the deformation amount of the optical fiber 3 at each Bragg grating 2a, 2b, 2c, and 2d position also varies. As a result, since the amount of change in the Bragg wavelength of each Bragg grating 2a, 2b, 2c, and 2d varies depending on the location, the reflection peak of the reflected light that was one when not filled is separated, and FIG. A plurality of reflection peaks are observed as shown in FIG. FIG. 2B shows an example in which the amount of deformation at the positions of the Bragg gratings 2b and 2d is the same. In this case, the reflection peaks from the Bragg gratings 2b and 2d match.

The computer 5 monitors changes with time in the wavelength distribution of the reflected light observed by the optical measuring instrument 4. The Bragg wavelength of each Bragg grating 2 a, 2 b, 2 c and 2 d varies according to the internal pressure of the high-pressure vessel 1. For this reason, if the high-pressure vessel 1 is in a healthy state, the wavelength distribution of the reflected light observed by the optical measuring instrument 4 changes so as to satisfy a certain relationship determined by the internal pressure. In other words, when the wavelength distribution is as shown in FIG. 2B at the start of use, if the high-pressure vessel 1 is healthy, the gas filled in the high-pressure vessel 1 is discharged and then refilled. In addition, the same wavelength distribution as in FIG. 2B should be reproduced, and no deviation of the reflection peak occurs. Therefore, when the high-pressure vessel 1 is used for a long period of time, the wavelength distribution of the reflected light is observed after gas filling, and the computer 5 determines whether or not the wavelength distribution at this time is deviated from the wavelength distribution measured at the start of use. By monitoring, the soundness of the high-pressure vessel 1 can be determined. The following equation shows the peak wavelengths λ _2a , λ _2b , λ _2c and λ _2d (unit: nm) of the reflected light of each Bragg grating 2a, 2b, 2c and 2d and the internal pressure P (unit: MPa) of the high-pressure vessel 1 This shows the relationship.
λ _2a (nm) = 1545 (nm) + α ₁ (nm / MPa) × P (MPa)
λ _2b (nm) = 1545 (nm) + α ₂ (nm / MPa) × P (MPa)
λ _2c (nm) = 1545 (nm) + α ₃ (nm / MPa) × P (MPa)
λ _2d (nm) = 1545 (nm) + α ₄ (nm / MPa) × P (MPa)
Here, 1545 (nm) is the Bragg wavelength of the Bragg grating 2, and α ₁ , α ₂ , α ₃ and α ₄ (nm / MPa) are the internal pressures P (MPa) at the Bragg gratings 2a, 2b, 2c and 2d, respectively. ) With respect to the peak wavelength of the reflected light.

In the state shown in FIG. 2A, that is, in the non-filling state, P = 0, so that λ _2a = λ _2b = λ _2c = λ _2d = 1545 (nm). Next, in the state of FIG. 2B at the time of gas filling, since α ₂ = α ₄ , λ _2b = λ _2d , but for example, the outer wall of the high-pressure vessel 1 corresponding to the position of the Bragg grating 2b When the amount of deformation increases, that is, when the strength of the material constituting the outer wall deteriorates, α ₂ ≠ α ₄ and the peaks corresponding to the Bragg gratings 2b and 2d are separated as shown in FIG. As a result, the number of reflected peaks of reflected light changes from three to four. Thus, by measuring the change over time of the wavelength distribution of the reflected light, it is possible to detect that an unhealthy state has occurred in the high-pressure vessel 1.

  According to the present embodiment, an optical fiber formed with a plurality of Bragg gratings having the same Bragg wavelength is closely attached to a high-pressure vessel, and after filling the gas into the high-pressure vessel, a Bragg grating for light emitted from the optical measuring instrument The wavelength distribution of the reflected light from the light source is measured with an optical measuring instrument, and the soundness of the high-pressure vessel is diagnosed based on the change over time in the wavelength distribution. it can. As a result, it is possible to obtain a high-pressure vessel having a simple structure and a low-cost diagnostic method and a soundness diagnostic function.

  In the present embodiment, an example is shown in which four Bragg gratings are formed. However, in principle, the number of Bragg gratings is not limited. For this reason, even if the number of measurement points is increased, it is possible to configure with one optical fiber. However, when the arrangement of the optical fibers becomes complicated, it may be configured with two or more optical fibers. Furthermore, in the present embodiment, an example has been shown in which a change with time in the wavelength distribution of reflected light is detected by a combination of an optical measuring instrument and a computer. However, a single control having both functions of the optical measuring instrument and the computer is shown. An apparatus may be used.

Embodiment 2. FIG.
FIG. 3 is a schematic diagram of a cross section of the high-pressure vessel in the second embodiment. In Embodiment 1, the optical fiber is attached in close contact with the outer wall of the high-pressure vessel. However, in this embodiment, the outer wall of the high-pressure vessel is reinforced with a fiber-reinforced composite material, and the optical fiber is attached to the fiber-reinforced composite material. It is buried. In FIG. 3, in the high-pressure container 1 having an inner container 6 made of an aluminum alloy, the outside of the inner container 6 is reinforced with a fiber reinforced composite material 7, and the optical fiber 3 is embedded in the fiber reinforced composite material 7. As the fiber reinforced composite material, for example, a carbon fiber reinforced plastic material can be used. The high-pressure container having such a structure can be manufactured by a filament winding method. The optical fiber 3 is formed with four Bragg gratings 2a, 2b, 2c and 2d. An optical measuring instrument 4 is connected to the end of the optical fiber, and a computer 5 is connected to the optical measuring instrument 4.

  In the high-pressure vessel thus configured, the soundness of the high-pressure vessel can be diagnosed by the same method as in the first embodiment, and the optical fiber 3 can be protected by the fiber reinforced composite material 7. Moreover, since the optical fiber 3 is installed inside the outer wall, it is possible to detect an internal damage state in which no deformation appears to the outer wall, and the reliability of the high-pressure vessel is further improved.

  In the present embodiment, an example in which a carbon fiber reinforced plastic material is used as the fiber reinforced composite material has been described, but other fiber reinforced composite materials may be used.

It is a schematic diagram of a high-pressure vessel having a soundness diagnosis function according to Embodiment 1 of the present invention. It is a characteristic view which shows the wavelength distribution of the reflected light in Embodiment 1 of this invention. It is a schematic diagram of the cross section of the high pressure vessel in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure vessel 2, 2a, 2b, 2c, 2d Bragg grating 3 Optical fiber 4 Optical measuring instrument 5 Computer 6 Inner vessel 7 Fiber reinforced composite material

Claims (3)

An optical fiber in which a plurality of Bragg gratings having the same Bragg wavelength are discretely formed is closely attached to a high-pressure vessel so that the plurality of Bragg gratings are at different positions,
After filling the high pressure vessel with gas,
Measure the wavelength distribution of the reflected light from the Bragg grating with respect to the light emitted from the optical measuring instrument having a light incident / exit function connected to the end of the optical fiber,
Based on the change over time of the wavelength distribution,
A method for diagnosing the health of a high-pressure vessel, comprising diagnosing the health of the high-pressure vessel. An optical fiber closely attached to the high-pressure vessel;
A plurality of Bragg gratings having the same Bragg wavelength formed discretely in the optical fiber;
A function for measuring the wavelength distribution of the reflected light from the plurality of Bragg gratings, and an optical measuring instrument connected to the end of the optical fiber, and a health diagnostic measurement of the high-pressure vessel apparatus. 3. The health diagnostic apparatus for a high pressure container according to claim 2, wherein the high pressure container has a structure in which an outer surface is reinforced with a fiber reinforced composite material, and an optical fiber is embedded in the fiber reinforced composite material.

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