DE19704968C2 - Container for storing compressed gas - Google Patents

Description

The invention relates to a container for storing compressed gas, the one has gas-tight metallic outer wall, which contains the cavity for receiving the Compressed gas encloses and at least one connection for a gas line for loading and / or unloading the container.

Explosive gases are transported in special containers, on the one hand Prevent volatilization of the stored gas, i.e. it must be tight, but it must be on the other hand, must also offer adequate protection against damage, so that the gas cannot be released suddenly when possible Pressure vessel is included in an accident, for example. Usually Containers for compressed gases consist of steel. For reasons of strength either spherical or cylindrical (with spherical end faces) prefers. As a rule, such containers either have a connection to each Loading and unloading the compressed gas or a common connection for loading and unloading the compressed gas. In the case of only one Afterwards, one speaks of compressed gas cylinders.

In order to keep the weight of the container as low as possible, the aim is to Make the wall thickness of the container as thin as possible. In terms of Tightness of such a container is not a problem. However, one comes across very quickly to the limits of what is permissible in terms of the required strength the container wall. In this context, it is known to be extremely thin-walled Pressurized gas container with an outer reinforcement by wrapping with high strength To provide fiber material or synthetic fiber fabrics. With a cylindrical or such a winding procedure is relatively simple  perform. However, the process encounters considerable application technology Problem once container shapes are chosen that are of this ideal spherical or Deviate from cylinder shape.

In vehicle technology, efforts have been underway for many years instead of Liquid fuels such as petrol and diesel fuel used today as a rule to use gaseous fuels. In this context, for example refer to motor vehicles that use hydrogen or natural gas are operated and due to these special fuels a comparatively Have low-emission exhaust gas. This is particularly true in urban areas Metropolitan areas in the inner city area are an important factor. Therefore in particular municipal utility vehicles as well as buses for the inner city Traffic equipped with appropriate internal combustion engines.

To the range of gas-powered motor vehicles in a sufficient To ensure order of magnitude, that carried by the respective motor vehicle Gas can be compressed to a relatively high pressure in order to be reasonable Volume can be accommodated. The required pressure is for example 150 or 250 bar or even more. This is an essential one Difference to the gas storage, which is only for the transport of liquid gas should be suitable. Natural gas powered buses are used usually a battery of cylindrically shaped compressed gas containers, that is Compressed gas cylinders. These can, for example, on the roof of such Vehicle are carried. Such training would be for passenger cars of a compressed gas storage hardly practicable, since it can be purely from pure optically would be rejected by buyers of such vehicles. It would be desirable if a container for storing compressed gas Would be available, not in terms of its external shape would be subject to usual restrictions, but a complex one Could have a shape structure, such as that used in today's conventional fuel tanks Vehicle technology available.

From the publication "Metal Foam - A Material with Perspectives" in Aluminum 70 (1994) No. 3/4 and from the publication "Possibilities for Production of components from foamed metals "in" Innovative and  economic components through powder metallurgy "(lectures on the occasion of the symposium on 25./26. November 1993 in Hagen; VDI Verlag) it is known to use metallic components to produce, in which foamed instead of solid metallic materials Metal materials are available. Techniques are known with which to target closed-pore or open-pore metal foams can be produced. The Production of metal foam can in principle be carried out in such a way that a metal powder is mixed with a blowing agent (e.g. titanium hydride) and about is formed into a semi-finished product by extrusion or axial hot pressing processed later in a thermal process to the desired component becomes. For this purpose, the prepared mixture of materials up to the solidus temperature of the metal heated, which also releases the blowing agent and the Foaming causes. If this process in a suitable z. B. made of ceramic or steel-made closed mold takes place, similar to that made by Metal casting workpieces of any shape can be produced. In this Context, it is known for construction components foamed from aluminum To manufacture vehicles. Also the foaming of aluminum pipes Aluminum foam for the production of high-strength lightweight construction elements for the Aircraft construction is known. So far, no use has been considered of metal foams in connection with the storage of compressed gases.

The object of the invention is therefore to propose a generic container, which is much larger in terms of its shape Offers scope for design and at the same time the safety risk of explosions reduced as much as possible due to damage to the container wall caused by the accident.

This problem is solved with a container of the type mentioned According to the invention by the characterizing features of claim 1. Advantageous developments of the invention are set out in claims 2 to 12 specified.

The invention is explained in more detail below with reference to FIGS. 1 and 2, each of which schematically shows two variants for a container according to the invention for storing compressed gas in the form of a sectional view.

A compressed gas container according to the invention has a gas-tight metallic outer wall 1 , which in the case of FIGS. 1 and 2 is provided with a connection 2 for a gas line for loading and unloading the container and encloses the cavity for receiving the compressed gas in a gas-tight manner. It is an essential characteristic of the present invention that an open-pore metal foam 3 is located in the cavity of the container. In the case of FIG. 1, the metal foam 3 fills the cavity at least for the most part of its volume. This means that in such a case there are partial areas 4 of the volume which are free of metal foam. For the functionality of the container according to the invention, it is advisable and, as a rule, also to strive for the entire surface of the cavity to be covered with the metal foam 3 . Another essential characteristic of the invention is that there is a material connection between the outer wall 1 and the open-pore metal foam 3 . This means that here there is not just a purely mechanical bond between two layers, as can be found, for example, in a double-walled pipe in which an outer pipe has merely been shrunk onto an inner pipe, so that there is a purely frictional connection. In the sense of the invention, it is always a composite material.

The entire cavity of the container is preferably filled with metal foam 3 , as shown in the variant in FIG. 2. The metallic outer wall 1 and the metal foam 3 expediently consist of a material of the same type or at least a related material. This ensures a good composite. In principle, however, it is also possible to connect different materials to one another in a container according to the invention. In this context, provision can also be made for the composite material to be provided as a soldered connection by switching on a third material layer, which is arranged between the metallic outer wall 1 and the metal foam 3 . In particular for reasons of strength, it is advantageous to use a steel material, preferably a deep-drawing steel, as the material for the outer wall 1 . This is desirable because not only can a high basic strength of the outer wall 1 be guaranteed, but because of such a material, hollow bodies with a complex shape structure, which deviates fundamentally from a spherical or cylindrical shape, such as in fuel tanks for a motor vehicle, without major problems , can be manufactured. Such a hollow body, produced for example by deep-drawing a sheet, could be used directly as a mold and foamed with metal foam and would then form the outer sheet metal skin of the container in the sense of a sandwich construction, the sheet metal skin being welded to the inner metal foam core. In this way, container shapes can be produced, the z. B. grant the same freedom in a motor vehicle, such as that offered by a conventional fuel tank for a vehicle. The degree of freedom would be even greater since there are no restrictions with regard to the necessary gradient for the filling of liquid fuels.

Instead of providing for the use of a sheet metal shape that becomes part of the container in the composition of a container according to the invention, the entire container can also be formed from a metal foam 3 , which is produced as integral foam. The integral foam has an increasing density in the direction of the outer wall 1 . There is a 100% material density in the vicinity of the outer surface, so that a gas-tight outer skin is guaranteed. A corrosion protection coating, preferably a plastic coating, is recommended for the outer surface of the outer wall 1 .

With regard to the thickness of the outer wall 1 and the structure of the metal foam 3 , the container according to the invention should be designed for loads such as are exerted by stored gases which are at a pressure of over 100 bar, in particular over 150 bar and preferably even over 250 bar arise.

The open-pore structure of the metal foam 3 , which at least for the most part fills the cavity enclosed by the outer wall 1 , ensures that the cavity is filled with compressed gas through the opening of the connection 2 and the compressed gas can later be removed again through this connection 2 . In the case of foaming with a closed-cell foam, the pore volume would not be accessible for gas absorption. If one were to produce a pressure vessel, as shown schematically in the outer form in FIGS. 1 and 2, without the foaming according to the invention, and fill it with compressed gas, the vessel would bulge very quickly, particularly on the flat sides, i.e. its shape would be inadmissible Change wise. By contrast, the open-pore metal foam 3 , which is materially connected to the outer wall 1 , ensures a highly effective inner support structure which counteracts bulging. Of course, this is most pronounced when the entire cavity is filled with metal foam 3 , as is the case in FIG. 2. There is an "area-wide" material connection between the opposing surfaces of the outer wall 1. This material connection of the metal foam 3 can absorb considerable tensile forces and prevents bulging. However, there is already a considerable support effect if the inner surface is covered with a sufficiently thick layer of the metal foam 3 , in particular if there is a bridge connection between the opposite flat sides at least in partial areas, as is the case in the central area in FIG. 1.

A great advantage of the metal foam filling of the cavity of an inventive Container is that this not only a large area of Tensile forces that counter the bulge is made possible, but that at the same time the volume to be made available for gas storage comparatively little reduced and the total weight of the container is increased comparatively little. It is particularly important that the Shape design of pressure vessel according to the invention almost no restrictions subject to. For example, shapes can be realized, as they are in conventional ones Fuel tanks for vehicles are already used today. But it could also, for. B. be remembered, pressure vessel of the bottom shape or the roof shape to adapt a motor vehicle and thus completely hide it visually without such as reducing the space available to accommodate people or luggage.

Another advantage of the invention is that the foaming of the Cavity of the container, in particular a complete foaming, a offers significant gain in operational safety if the container wall z. B. by Accident should be damaged. While a normal one Compressed gas container practically the entire contents if the container wall is torn open the gas filling flows out in a very short time, is due to the pore structure of the Metal foam ensures a considerable flow resistance, the one sudden leakage prevented. This makes the risk of explosion clear reduced. The rest is due to the supportive effect of the exterior wall connected metal foam prevents crack propagation in the outer wall.

Claims (12)

1. Container for storing compressed gas, with a gas-tight metallic outer wall ( 1 ) which encloses the cavity provided for storing the compressed gas and has at least one connection ( 2 ) for a gas line for loading and / or unloading the container, characterized in that that there is an open-pore metal foam ( 3 ) in the cavity, which is materially connected to the outer wall ( 1 ). 2. Container according to claim 1, characterized in that the metal foam ( 3 ) fills at least the major part of the cavity volume. 3. Container according to one of claims 1 to 2, characterized in that the entire inner surface of the cavity is covered with the metal foam ( 3 ). 4. Container according to claim 2, characterized in that the metal foam ( 3 ) completely fills the cavity volume. 5. Container according to one of claims 1 to 4, characterized in that the metallic outer wall ( 1 ) and the metal foam ( 3 ) consists of an identical or related material. 6. Container according to one of claims 1 to 5, characterized in that the outer wall ( 1 ) consists of a steel material, in particular a deep-drawing steel. 7. Container according to one of claims 1 to 6, characterized, that the outer shape of the container is different from the spherical or cylindrical shape a complex structure in the sense of a fuel tank for a motor vehicle having. 8. Container according to one of claims 1 to 7, characterized, that the container on its outer surface with a Corrosion protection coating, in particular a plastic coating, is provided. 9. Container according to one of claims 1 to 8, characterized, that the container in sandwich construction from an outer sheet metal skin and a so there is welded inner metal foam core. 10. Container according to one of claims 1 to 8, characterized, that the container in sandwich construction from an outer sheet metal skin and a inner metal foam core consists of a solder connection to the Sheet skin is connected. 11. Container according to one of claims 1 to 8, characterized in that the metal foam ( 3 ) is designed as an integral foam with increasing density in the direction of the outer wall ( 1 ). 12. Container according to one of claims 1 to 11, characterized in that the thickness of the outer wall ( 1 ) and the structure of the metal foam ( 3 ) are designed for a load by a pressure of the stored gas of at least 150 bar, in particular at least 250 bar is.