Pressure vessel and pressure vessel system

Abstract

According to the invention, the technology disclosed herein relates to a pressure vessel (10) comprising a woven wall (20) enclosing an interior space (30) in which an overpressure can be built up. The wall (20) has a coverage greater than 1 up to an overpressure corresponding to a predetermined threshold value and a coverage less than 1 in the case of an overpressure exceeding the predetermined threshold value. Thereby, gaseous fuel is expelled more slowly than in the case of a burst event. According to the invention, the technology disclosed herein also relates to a pressure vessel system comprising at least one such pressure vessel (10).

Description

TECHNICAL FIELD

[0001] The technology disclosed herein relates to a pressure vessel and to a pressure vessel system comprising at least one such pressure vessel. BACKGROUND

[0002] Pressure vessels are often used in motor vehicles or other mobile or stationary devices in order to supply the motor vehicles or other mobile or stationary devices with gaseous fuel. A possible failure case of such a pressure vessel is a burst, in which case a large amount of gaseous fuel can leak in a short time. SUMMARY

[0003] A preferred task of the technology disclosed herein is to reduce or eliminate at least one of the disadvantages of the prior known solutions or to propose an alternative solution. In particular, a preferred task of the technology disclosed herein is to reduce possible damage in the event of a failure of a pressure vessel. Further preferred tasks can result from the advantageous effects of the technology disclosed herein.

[0004] The technology disclosed herein relates to a pressure vessel, which comprises a woven wall, which encloses an interior space, in which an overpressure can be formed. The wall has a coverage greater than 1 up to an overpressure corresponding to a predetermined threshold value. The wall has a coverage less than 1 in the event of an overpressure exceeding the predetermined threshold value. With such an embodiment it is possible to achieve that, when the threshold value is exceeded, targeted inter-fiber ruptures are produced, whereby a leak occurs along the wall. This leads to a slower pressure equalization compared to a burst process. As a result, the consequences of an excessively high pressure are significantly reduced. This applies in particular in comparison with pressure vessels known from the prior art, in which a burst event usually occurs before the coverage can fall below the value of 1.

[0005] In particular, the wall can have one or more fibers, which are woven in a suitable manner in order to enclose the interior space. The wall is usually pressure-tight at least up to the threshold value, so that the wall can withstand the corresponding overpressure. The overpressure is usually defined as the pressure in the interior space minus the pressure outside the wall. The pressure outside the wall can be, for example, the normal ambient pressure, which is usually approximately 1 bar. This overpressure in the form of a pressure difference is usually important for the stability of the wall, so that, for example, a higher internal pressure can also be applied when a higher pressure is applied outside the wall.

[0006] The woven wall can in particular be composed of fibers, which are brought into the desired form in particular by weaving. This can be done, for example, by weaving on a preform.

[0007] In principle, when an overpressure is applied, the braided wall expands, more precisely the greater the overpressure, the stronger the expansion. In a typical pressure vessel, for example having an elongated shape with a circular, oval or similar cross section, this expansion can inter alia comprise an increase in length and an increase in diameter. Thereby, the coverage also changes, wherein in principle the coverage decreases in the case of an expansion of the wall. The coverage can be understood in principle as the ratio between the surface covered by the fibers (in the case of multiple coverages being considered) and the wall surface. Thus, when the coverage is 1, the entire surface of the wall is covered without multiple coverages occurring. When the coverage is greater than 1, multiple coverages occur, wherein, for example, when the coverage is 1.2, 20% of the surface can be covered twice. When the coverage is less than 1, parts of the wall are not covered by fibers, resulting in intermediate spaces. This can generally lead to an inter-fiber rupture, which in the present case is deliberately induced, so that the overpressure release proceeds more slowly and more controlled than in a burst event.

[0008] The wall can inter alia have a coverage of at least 1.05 or at least 1.1 without overpressure. It has been shown that in typical embodiments such a coverage leads to a coverage of less than 1 at the threshold values to be used in general, at an overpressure of 0, i.e. when the internal pressure and the external pressure are the same. For example, at the threshold value, the coverage can have a value of 1.

[0009] It can inter alia be provided that the wall has a coverage of at most 1.1, at most 1.15 or at most 1.2 without overpressure. In the case of such a maximum coverage, it has also been shown that a coverage of less than 1 occurs when the threshold value is exceeded at the threshold values to be used in general.

[0010] In particular, all the proposed lower limits of the coverage can be combined with all the proposed upper limits to corresponding intervals.

[0011] For example, the predetermined threshold value can be at least 1400 bar. This corresponds to an expected design of the pressure vessel. The predetermined threshold value can also be at least 1575 bar, which also corresponds to a typical design of the pressure vessel. If the threshold value is to be higher than the design pressure, the threshold value can for example have a value between 1500 bar and 1650 bar or between 1650 bar and 1800 bar.

[0012] In particular, the pressure vessel can be configured as a linerless pressure vessel. Thus, in particular, there is no liner between the wall and the interior space and generally also no other material, so that the gaseous fuel stored in the interior space is in direct contact with the wall. Thereby, the function of the targeted, slower release of gaseous fuel described above can be realized in an advantageous manner, since the absence of a liner prevents possible gas leaks.

[0013] The woven wall can in particular be configured as a barrier to permeation of gaseous fuel stored in the interior space. Thereby, in particular an additional liner can be dispensed with. For example, the woven wall can be made of fibers and / or impregnated with one or more thermoplastics and / or thermosets or other materials, whereby the wall itself already ensures against leakage of gaseous fuel, if possible with low leakage.

[0014] The woven wall can in particular be impregnated with one or more thermoplastics and / or one or more thermosets. Such materials can also be referred to as matrix materials. Thereby, the function as a barrier to permeation can be improved and / or the stability can be increased. In principle, elastomers or multilayer composites composed of the same or different plastic types can also be used as matrix materials for the wall, in particular for the fiber-reinforced plastic forming the wall.

[0015] The thermoplastics and / or thermosets or other materials mentioned in the previous section can in particular form, in part, a barrier to permeation of gaseous fuel stored in the interior space, in the case of a coverage of less than 1. Thus, initially a certain reduction of the coverage below 1 can still be tolerated, in particular until the already described fiber discontinuity occurs. After the occurrence of the fiber discontinuity, the stability of the wall is generally no longer sufficient at least locally to prevent leakage of gaseous fuel. As already described above, this is intended in the technology disclosed herein.

[0016] In particular, the wall can be woven from fibers, which, in the case of a coverage of less than 1, create intermediate spaces between the fibers. Such intermediate spaces can in particular constitute weak points for the already described case of leakage of gaseous fuel, at which gaseous fuel can leak out.

[0017] The intermediate spaces can in particular be covered with one or more thermoplastics and / or thermosets. The other materials already mentioned above can also be used accordingly.

[0018] The intermediate spaces can in particular be configured as defined breaking points. Thereby, in particular for the desired case of leakage of gaseous fuel, for example after the desired fiber discontinuity, the already described function can be supported.

[0019] The technology disclosed herein also relates to a pressure vessel system comprising a plurality of pressure vessels as described herein. With regard to the pressure vessels, all described variants can be used. In particular, the pressure vessel system can be used for supplying motor vehicles or other mobile or stationary devices with gaseous fuels, which can be used, for example, in gas-operated internal combustion engines or fuel cells.

[0020] The degree of coverage can be adjusted in the manufacture of the pressure vessel, in particular during the braiding process, wherein different factors can be influenced in a targeted manner. These factors include, for example, the number of braiding threads, the braiding thread thickness, the braiding speed or feed speed of the braiding core and / or the winding speed of the braiding loops on the braiding wheel. Additionally, mechanisms can also be used for influencing the degree of coverage, for example, the yarns are stretched before being laid, for example, by supplying compressed air.

[0021] The pressure vessel is used, in particular, for storing gaseous fuels under ambient conditions. The pressure vessel or pressure vessel system can be used, in particular, in motor vehicles operated using compressed natural gas (also referred to as CNG) or liquefied natural gas (also referred to as LNG) or using hydrogen. The pressure vessel system can be fluidically connected to at least one energy converter, which is provided for converting the chemical energy of the fuel into another energy form. In particular, the pressure vessel can be a composite-coated pressure vessel. For example, the pressure vessel can be a cryogenic pressure vessel or a high-pressure gas vessel. The high-pressure gas vessel is configured for storing the fuel durably at ambient temperature at a nominal operating pressure (also referred to as nominal working pressure or NWP) of at least 350 baru (= overpressure compared to atmospheric pressure) or at least 700 baru. The cryogenic pressure vessel is suitable for storing the fuel at the above-mentioned operating pressure also at temperatures which are significantly (for example, more than 50 K or more than 100 K) below the operating temperature of the motor vehicle.

[0022] In particular, in the pressure vessels disclosed herein, an overpressure valve can be dispensed with, since the effect is reduced for the case of overpressure and thus can be controlled more easily.

[0023] In other words, it has been recognized that in the event of a failure of the pressure vessel, usually the outer wall or wall of the pressure vessel fails, which can lead to a sudden leakage of the stored medium. The pressure equalization between the environment and the medium which occurs here can lead to a burst pressure wave and damage to the environment. For example, carbon fiber reinforced plastic (CFRP) is used as a material for the outer wall or wall. A common manufacturing method for pressure vessels is fiber winding or fiber braiding on a winding / braiding core. In the interior space of the pressure vessel, a liner can be provided which ensures the sealing and the permeation barrier for the pressure vessel, wherein such an embodiment is referred to as a type IV pressure vessel. Furthermore, there is also a type V pressure vessel in which the matrix material of the CFRP layers has such good permeation properties that a liner for the pressure vessel is no longer required.

[0024] For safety reasons, pressure vessels can be provided with an overpressure valve. However, it can also be desirable to dispense with such an overpressure valve. For example, in this case, the vessel wall can be overdesigned in order to also withstand particularly high overpressures, taking into account appropriate safety factors. Not only such overdesigning but also overpressure valves can generally be dispensed with by the technology disclosed here, since, as already mentioned, the consequences of overpressure can be more easily controlled.

[0025] For pressure vessels manufactured in a braiding process, the braiding structure can be adjusted in a targeted manner by machine process parameters and manufacturing process parameters. This means that, firstly, the number of braiding threads and the laying width for the individual braiding threads can be influenced in a targeted manner. The coverage of the braiding threads on the braiding core can thus be influenced. The coverage is 1 if the braiding core is completely covered by the threads and the braiding pattern has no "holes". If there are more or fewer braiding threads than are required for complete coverage, the coverage is greater or less than 1. If the machine process parameters and the manufacturing process parameters now remain constant and the diameter of the braiding threads is reduced or increased, the coverage increases or decreases. Due to the material elasticity of the pressure vessel wall or walls, the pressure vessel is subjected to a clearly measurable expansion in the axial and radial directions in the operating situation. Here, the pressure vessel is continuously expanded from the unpressurized state up to the burst situation, and the diameter increases in the process. For a braided pressure vessel, this means that the forces between the braiding threads continuously increase, so that the braid wants to reduce its coverage. As soon as the coverage reaches the value 1, high forces occur between the fibers, which cannot be borne by the matrix material alone, which has a very low strength compared to the fibers. Matrix breakage then occurs, which is also referred to as inter-fiber breakage.

[0026] In a V-shaped pressure vessel, in particular the matrix material has the task of keeping the pressure vessel sealed. In the case of inter-fiber breakage, this is no longer the case, and the stored gas can escape through the resulting cracks. The braided V-shaped pressure vessel should now be designed in such a way that the braid has a coverage greater than 1 in the operating range. At the same time, the braid should be designed in such a way that, when the actual burst / design pressure is reached, the pressure vessel has already expanded in such a way that the braid has a coverage less than 1 and leaks along the entire diameter due to inter-fiber breakage, which brings a smoother pressure equalization than a burst failure. BRIEF DESCRIPTION OF DRAWINGS

[0027] The technology disclosed here is now described with the aid of the drawings. Here:

[0028] Figure 1 A pressure vessel is shown;

[0029] Figure 2 A section of the wall is shown with a coverage of 1 ; and

[0030] Figure 3 A portion of the wall is shown in which the coverage is less than 1. DETAILED DESCRIPTION

[0031] Figure 1 The pressure vessel 10 is shown purely diagrammatically and is formed substantially by a wall 20 which surrounds an inner space 30. The inner space 30 is configured for storing gaseous fuel under high pressure, whereby the inner space 30 is under overpressure compared to the surrounding atmosphere. The wall 20 prevents the gaseous fuel from escaping. The wall is composed of woven fibers which are currently impregnated with a thermoset plastic. Such a thermoset plastic can also be referred to as a resin or as a resin.

[0032] The pressure vessel 10 has a length l and a diameter d. The length and the diameter relate to values which are variable depending on the overpressure applied in the inner space 30. For example, the pressure vessel 10 can be manufactured without an applied overpressure, whereby a relevant length l and a relevant diameter d result. If the overpressure in the inner space 30 increases, the length l and the diameter d increase. This also has an effect on the fibers of the wall 20, which will be explained below with reference to Figure 2 and Figure 3 The effect is explained.

[0033] The pressure vessel 10 also has other components, for example tank connection valves for filling and / or extracting gaseous fuel. However, these components are not shown in Figure 1 since they are not relevant for understanding the technology disclosed herein.

[0034] Figure 2 The fibers 22 of the wall 20 are shown in which the coverage is 1 or slightly more than 1. As shown, the fibers 22 here lie so close to one another that there is no intermediate space at all, so that the fibers 22 completely surround the inner space 30. In general, the pressure vessel 10 has a high stability in this state, which reliably holds the gaseous fuel in the inner space 30, in particular up to the design pressure.

[0035] Figure 3A portion of the wall 20 is shown in which the coverage is less than 1, which occurs, inter alia, when the overpressure in the interior space 30 exceeds a predetermined threshold. Due to the stretching of the length 1 and the diameter d of the pressure vessel 10 already described, intermediate spaces 24 are created between the individual fibers 22, which are not covered by the fibers 22. In that only the thermosetting plastic serves as matrix material, which resists possible leaks with little resistance for the gaseous fuel. In this case, inter alia, inter-fiber fractures usually occur, whereby the stability of the wall 20 is locally reduced at some points. In this case, the intermediate spaces 24 serve, inter alia, as defined breaking points, in which the gaseous fuel is purposefully discharged from the interior space 30, more precisely, inter alia, much slower than in a burst event. Thereby, the effects of overpressure beyond the design can be greatly reduced.

[0036] For the sake of readability, the term "at least one" has been partially omitted for simplicity. When a feature of the technology disclosed herein is described in the singular or in the indefinite article (e.g., the pressure vessel, the fiber, etc.), the plural is also disclosed (e.g., the at least one pressure vessel, the at least one fiber, etc.).

[0037] The above description of the present application is for illustrative purposes, and is not intended to limit the present application. Different changes and modifications can be made within the scope of the present application and its equivalents without departing from the present application.

[0038] List of reference signs

[0039] 10 pressure vessel

[0040] 20 wall

[0041] 22 fiber

[0042] 24 intermediate space

[0043] 30 interior space

[0044] 1 length

[0045] d diameter

Claims

1. A pressure vessel (10), - the pressure vessel comprises a braided wall (20) which encloses an interior space (30) in which an overpressure can be formed; - the wall (20) has a coverage of more than 1 up to an overpressure corresponding to a predetermined threshold value; and - the wall (20) has a coverage of less than 1 in the case of an overpressure exceeding the predetermined threshold value, the wall (20) is braided from fibers (22) between which an intermediate space (24) is created in the case of a coverage of less than 1, the intermediate space (24) is covered with one or more thermoplastics and / or thermosets, and the intermediate space (24) is configured to set a breaking point, whereby gaseous fuel is discharged from the interior space more slowly in the case of a targeted breaking between the fibers than in a burst event.

2. The pressure vessel (10) according to claim 1, wherein, The wall (20) has a coverage of at least 1.05 in the case of no overpressure.

3. The pressure vessel (10) of claim 1, wherein, The wall (20) has a coverage of at least 1.1 in the case of no overpressure.

4. The pressure vessel (10) of claim 1, wherein, The wall (20) has a coverage of at most 1.1 in the case of no overpressure.

5. The pressure vessel (10) of claim 1, wherein, The wall (20) has a coverage of at most 1.15 in the case of no overpressure.

6. The pressure vessel (10) of claim 1, wherein, The wall (20) has a coverage of at most 1.2 in the case of no overpressure.

7. The pressure vessel (10) according to any one of claims 1 to 6, wherein, The predetermined threshold value is at least 1400 bar.

8. The pressure vessel (10) according to any one of claims 1 to 6, wherein, The pressure vessel (10) is configured as a linerless pressure vessel (10).

9. The pressure vessel (10) according to any one of claims 1 to 6, wherein, The braided wall (20) is configured as a permeation barrier for gaseous fuel stored in the interior space (30).

10. The pressure vessel (10) according to any one of claims 1 to 6, wherein, The braided wall (20) is impregnated with one or more thermoplastics and / or thermosets.

11. The pressure vessel (10) of claim 10, wherein, The thermoplastics and / or thermosets partially form a permeation barrier for gaseous fuel stored in the interior space (30) in the case of a coverage of less than 1.

12. A pressure vessel system comprising a plurality of pressure vessels (10) according to any one of claims 1 to 11.

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