DE102016208005B3 - Pressure vessel with outgassing channels and manufacturing process - Google Patents

Abstract

The technology disclosed herein relates to a pressure vessel 100 for storing fuel for a motor vehicle and a manufacturing method. The pressure vessel includes at least one fiber reinforced layer 120 surrounding a fuel storage volume. The fiber-reinforced layer 120 has a radially outer outer surface 122 and a radially inner surface 124 arranged inside. In the fiber reinforced layer 120, a plurality of outgassing channels 126 are provided. The outgassing channels 126 are configured to convey fuel from within the fiber reinforced layer to the outer surface 122. The outgassing channels begin at a distance from the inner surface of the fiber reinforced layer 120 and extend toward the outer surface 122.

Description

The technology disclosed herein relates to a pressure vessel for storing fuel for a motor vehicle. Such containers are known in the art. In particular, it is a pressure vessel with Ausgasungskanälen in the fiber reinforced layer. Further, the technology disclosed herein relates to a manufacturing method of such a pressure vessel.

Prior art pressure vessels include a liner and a fiber reinforced layer surrounding the liner. In order to achieve the most efficient use of space, the liner wall thicknesses are not designed arbitrarily thick. Therefore slow migration of the liner wall through small amounts of hydrogen over time is unavoidable and up to a certain upper limit also accepted in the legal regulations. The barrier effect of the externally adjoining fiber-reinforced layer can now again lead to accumulation of hydrogen between the liner and the fiber-reinforced layer. These accumulations can in turn reach high pressures at high tank pressures. If the liner is depressurized (eg, by rapid removal of hydrogen), the accumulations may expand and cause the liner to buckle.

Breather layers are known from the prior art, which are arranged between liner and fiber-reinforced layer. These breather layers are meant to cause the hydrogen collections to flow towards the bosses. In practice, this removal of hydrogen at high pressures takes place only to a small extent.

From the publication DE 10 2008 053 244 A1 goes out a pressure vessel, which has a liner for receiving the gaseous hydrogen. The liner surrounds a winding that gives the pressure vessel its dimensional stability. The winding of the pressure vessel is at least partially gas-permeable in such a way that the gases penetrating the liner can escape continuously through the winding from the pressure vessel. It should thus be avoided that accumulates hydrogen between the liner and the winding, which could lead to buckling of the liner due to high pressures in the pressure vessel after a rapid removal of hydrogen.

A disadvantage of the pressure vessel according to the DE 10 2008 053 244 A1 is that any dirt could penetrate into the holes revealed there. If, for example, water penetrates into these holes, ice formation can break up the winding. Furthermore, it can come to "extrusion". Extrusion is the effect that the plastic material of the liner "flows" through the high container pressure over a longer period of time and tries to adapt to its environment. Since the dimensionally stable envelope of the liner through the fiber reinforced layer at the in DE 10 2008 053 244 A1 revealed holes is interrupted, there is a flow of the liner material in the holes of the winding. This can adversely affect both the function of the liner and the Faserverbundarmierung. The safety of the pressure vessel is characterized in particular not given over the entire life.

It is a preferred object of the technology disclosed herein to reduce or eliminate the disadvantages of the prior art solutions. In particular, it is an object of the technology shown here to provide a weather-resistant pressure vessel system that reliably removes fuel gases that have diffused out of the container interior. The object is solved by the subject matter of patent claims 1 and 6. The dependent claims represent preferred embodiments.

The technology disclosed herein relates to a pressure vessel for storing gaseous fuel under ambient conditions. The pressure vessel can be used in a motor vehicle, which is operated for example with compressed ("compressed natural gas" = CNG) or liquefied (LNG) natural gas or with hydrogen. The pressure vessel may be, for example, a cryogenic pressure vessel (CcH2) or a high-pressure gas vessel (CGH2). High pressure gas containers are designed to hold fuel (e.g., hydrogen) at ambient temperatures substantially at a max. Operating pressure (also called maximum operating pressure or MOP) of about 350 barü (= overpressure relative to the atmospheric pressure), further preferably of about 500 barü and more preferably of about 700 barü store. A cryogenic pressure vessel is particularly suitable for storing the fuel at temperatures significantly below the operating temperature (meaning the temperature range of the vehicle environment in which the vehicle is to be operated) of the motor vehicle, for example at least 50 Kelvin, preferably at least 100 Kelvin or At least 150 Kelvin below the operating temperature of the motor vehicle (usually about -40 ° C to about + 85 ° C).

The pressure vessel disclosed herein may also include a liner for the pressure vessel for storing fuel disclosed herein. The liner may be made of a metal, a metal alloy or at least one plastic. Suitably, for example, a CcH2 container has a liner of aluminum or of an aluminum alloy, while a CGH2 container often uses plastic liners. The fuel is stored in the liner and the liner is usually responsible for the tightness of the pressure vessel. For example, if hydrogen is stored, the liner is usually designed to avoid hydrogen permeation. The liner can also serve as a winding and / or braided core. A metallic design can be load-bearing as well as, like a polymer liner, not load-bearing. Usually, the liner contour is chosen to be as thin as possible, since the strength of the fiber composite is much higher and thus a thinner overall wall thickness can be achieved. For example, the max. Thickness of the liner less than 30 mm, preferably less than 10 mm or 5 mm. Like the pressure vessel, the liner usually has an elongated, preferably cylindrical shape with generally curved end regions. The end regions and the idR cylindrical circumferential region M arranged therebetween are in particular advantageously integrally formed. In at least one of the pole caps of the liner, an opening is provided. It is also possible to form linerless pressure vessels with the technology disclosed herein.

The pressure vessel disclosed herein may further comprise a fuel diffusion layer (= breather layer) disposed between the liner and the fiber reinforced layer. The fuel diffusion layer is particularly suitable for transporting the fuel in the circumferential direction and / or in the axial direction (ie not in the radial direction through the fiber-reinforced layer explained below).

The pressure vessel includes at least one fiber reinforced layer surrounding a fuel storage volume of the pressure vessel. The fiber-reinforced layer may preferably completely surround a liner at least in regions. The fiber reinforced layer is often referred to as a laminate or armor. Hereinafter, the term "fiber-reinforced layer" is usually used. As a fiber reinforced layer i.d.R. Fiber-reinforced plastics (also abbreviated to FVK or FKV), for example carbon fiber reinforced plastics (CFRP) and / or glass fiber reinforced plastics (GRP). The fiber-reinforced layer suitably comprises reinforcing fibers embedded in a plastic matrix. In particular, matrix material, type and proportion of reinforcing fibers and their orientation can be varied so that the desired mechanical and / or chemical properties are established. Preferably, continuous fibers are used as reinforcing fibers, which can be applied by winding and / or braiding.

The fiber-reinforced layer has an outer surface (radially) arranged outside and an inner surface arranged further inwards (or farther towards the fuel storage volume) compared to the outer surface (radially). In the fiber-reinforced layer, a plurality or a plurality of Ausgasungskanäle are provided. They serve for degassing or degassing of the pressure vessel. Fuel accumulated in the fiber-reinforced layer or between the fiber-reinforced layer and the liner, which has diffused through the liner, is to be transported away via these outgassing channels in a substantially radial direction. Advantageously, therefore, the outgassing channels themselves essentially (preferably exactly) run in the radial direction. For example, deviations that occur due to manufacturing tolerances are not essential in this context. The outgassing channels are thus designed to convey diffused fuel from the interior of the fiber-reinforced layer to the outer surface. The outgassing channels begin at a distance from the inner surface and extend to the outer surface and open into it.

The outer surface of the fiber-reinforced layer itself may be protected by further measures, such as a protective film or other functional layers. Furthermore, it can also be a pressure vessel with several nested sub-volumes. Then the diffused fuel would continue to be usable. Such a system is for example in the German patent application with DE 10 2009 024 794 A1 disclosed, the contents of which. The multiple shells hereby incorporated by reference here. Also discloses the German patent application DE 10 2016 204 073 a multi-shell pressure vessel. The content of this document with respect to the multiple shells and with respect to the pressure control is hereby incorporated by reference here, but no liquid must be present in the outermost shell.

The inner ends of the Ausgasungskanäle each have a radial distance to the inner surface. In the region adjacent to the respective outgassing channel, the ratio of the radial distance to the total thickness D of the fiber-reinforced layer is preferably about 0.05 to about 0.5, preferably about 0.1 to about 0.25. The inner ends are the ends, which are provided in the fiber-reinforced layer. The inner ends could also be referred to as the ends of the outgassing channels facing the fuel storage volume.

The lateral or lateral distance b between two directly adjacent outgassing channels can be less than the total thickness D. the fiber-reinforced layer in the region of the directly adjacent outgassing channels.

The optimal geometry of the outgassing channels depends directly on the radial, axial and tangential permeation properties of the fiber-reinforced layer (= Faserverbundarmierung) and the radial permeation properties of the liner.

The outgassing channels can be designed as fuel-permeable pins or as fuel-permeable pipes.

The technology disclosed herein further relates to a method of manufacturing the pressure vessel disclosed herein. The method disclosed herein may include the step of introducing outgassing channels into the fiber reinforced layer that begin at a distance from the inner surface of the fiber reinforced layer and extend toward the outer surface.

During the manufacture of the fiber-reinforced layer, pins and / or tubes may be provided in the areas in which the outgassing channels are to be formed later.

The method disclosed herein may include the step of at least partially removing the pins and / or tubes after forming the fiber reinforced layer.

• – Aufbringen von Verstärkungsfasern auf einen Kern;
• – Einbringen von Stiften und/oder Rohren in den Bereichen, in denen später die Ausgasungskanäle ausgebildet werden sollen; und/oder
• – Aushärten eines Matrixmaterials.

The method disclosed herein may include at least one of the steps:

• - Applying reinforcing fibers to a core;
• - Inserting pins and / or pipes in the areas in which later the Ausgasungskanäle are to be formed; and or
• - curing a matrix material.

Further, the method disclosed herein may include the step of moving, preferably rotating, the pins during curing.

Further, the method disclosed herein may include the step of placing the pins and / or tubes spaced apart from the inner surface of the pressure vessel and extending toward the outer surface in the fiber reinforced layer, and wherein the pins are oriented substantially in the radial direction.

The technology disclosed herein will now be explained with reference to the figures. Show it:

1 a schematic perspective view of the disclosed here pressure vessel;

2 an enlarged view of detail A of 1 ;

3 schematically the result of a simulation with an outgassing channel disclosed herein in the fiber reinforced layer disclosed herein; and

4 schematically shows the result of a simulation with a fiber reinforced layer without the outgassing channel disclosed herein.

The 1 shows a perspective view of a pressure vessel 100 , The pressure vessel 100 is shown cut. Simplified, the pole cap area was omitted or cut away. The pressure vessel shown here 100 includes a liner 110 , The liner 110 is made of a fiber reinforced layer 120 surround. The pressure vessel 100 or here the fiber-reinforced layer 120 has an outer surface 122 on. The inner surface 124 (not in 1 shown) is here directly on the liner 110 on. In the embodiment shown here, the outgassing channels have openings or outer ends 127 on, for example, could be covered by a fuel-permeable layer.

The 2 shows an enlarged view of the detail A of 1 , The fiber reinforced layer 120 has a total thickness D that is greater than the length of the outgassing channels 126 or in particular as the radial length portion of the Ausgasungskanäle 126 , The outgassing channels 126 are arranged here essentially in the radial direction. The outgassing channels 126 have inner ends 125 spaced at a radial distance a from the inner surface 124 are arranged. The distance a is here about 10% of the total thickness D. Two directly adjacent outgassing channels 126 have a lateral distance b which is less than the total thickness D of the fiber-reinforced layer 120 , The radial distance a is chosen so that between the inner surface 124 the fiber reinforced layer 120 and the liner 110 accumulating fuel through the fiber reinforced layer 120 , here through the distance a, can diffuse through. In particular, the distance a is thus selected so that fuel diffusing through the liner does not flow, or only to a small extent, between the liner 110 and the fiber reinforced layer 120 can accumulate. Advantageously, on the one hand, a liner bumps can be avoided and, on the other hand, it can be ensured that no liquid or no soiling in the region between the inner surface 124 and the liner 110 arrives.

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

As mentioned above, ideally the geometry (especially the radial distance a and the lateral distance b) is tuned to the permeation properties of the fiber reinforced layer and the liner. In the case of a / D = 0.0678 and b / D = 0.67 is in the 3 and 4 the result of a simulation, each with and without outgassing channel shown. The letters A to E respectively show the lines of equal (hydrogen) concentration and / or equal (hydrogen) partial pressure. The concentration or the partial pressure is decreasing from A to E. It can clearly be seen how the permeability of the reinforcement through the outgassing channel is improved, even without the outgassing duct reaching down to the liner.

Even without simulation, this can easily be seen from the rate of gas permeation Q: Q is inversely proportional to the length of the permeation path. If the length of the permeation path is now substantially equal to the radial distance a (instead of the total thickness D), a clear increase in permeation results, which ideally reduces or prevents the accumulation of gas bubbles between the liner and the fiber composite reinforcement so that a liner bulge is reduced or even reduced is avoided.

Claims (10)

Pressure vessel ( 100 ) for storing fuel for a motor vehicle, comprising at least one fiber-reinforced layer ( 120 ) surrounding a fuel storage volume of the pressure vessel, wherein the fiber reinforced layer ( 120 ) an outer surface ( 122 ) and an inner surface ( 124 ), wherein in the fiber-reinforced layer ( 120 ) several outgassing channels ( 126 ) are provided, wherein the outgassing channels ( 126 ) are formed, fuel from the interior of the fiber-reinforced layer ( 120 ) to the outer surface ( 122 ), characterized in that the outgassing channels ( 126 ) spaced from the inner surface ( 124 ) and to the outer surface ( 122 ). Pressure vessel ( 100 ) according to claim 1, wherein inner ends ( 125 ) of the outgassing channels ( 126 ) to the inner surface ( 124 ) each have a radial distance (a), and wherein in the region of the respective outgassing channel ( 126 ) the ratio of the radial distance (a) to the total thickness (D) of the fiber-reinforced layer ( 120 ) is about 0.05 to about 0.5, preferably about 0.1 to about 0.25. Pressure vessel ( 100 ) according to claim 1 or 2, wherein between two directly adjacent outgassing channels ( 126 ) a lateral distance (b) is formed, which is smaller than the total thickness (D) of the fiber-reinforced layer ( 120 ) in the region of the directly adjacent outgassing channels ( 126 ). Pressure vessel ( 100 ) according to one of the preceding claims, further comprising at least one liner ( 110 ) and at least one fuel diffusion layer interposed between the liner ( 110 ) and the fiber reinforced layer ( 120 ) is arranged. Pressure vessel ( 100 ) according to one of the preceding claims, wherein the outgassing channels ( 126 ) are designed as fuel-permeable pins and / or tubes. Method for producing a pressure vessel, wherein during the production of the fiber-reinforced layer ( 120 ) Pins and / or tubes for the later formation of outgassing channels ( 126 ) are provided. The method of claim 6, and wherein the pins and / or tubes after formation of the fiber reinforced layer ( 120 ) are at least partially removed. A method according to claim 6 or 7, comprising the steps of: - applying reinforcing fibers to a core; Introduction of pins and / or tubes in the regions for the later formation of outgassing channels ( 126 ); and curing a matrix material.  Method according to one of claims 6 to 8, wherein the pins are moved during curing, preferably rotated. Method according to one of claims 6 to 9, wherein the pins and / or tubes spaced from the inner surface ( 124 ) of the pressure vessel beginning and to the outer surface ( 122 ) extending in the fiber reinforced layer ( 120 ), and wherein the pins are oriented substantially in the radial direction.

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